Technical Strategic Plan 2023 for Decommissioning of
the Fukushima Daiichi Nuclear Power Station of Tokyo
Electric Power Company Holdings, Inc.

October 18, 2023

Nuclear Damage Compensation andDecommissioning Facilitation Corporation

All rights reserved except for reference data. No part of this document may be reproduced,edited, adapted, transmitted, sold, republished, digitalized or used in any other way that violates
the Copyright Act for any purpose whatsoever without the prior written permission of Nuclear
Damage Compensation and Decommissioning Facilitation Corporation.

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Table of Contents
1. Introduction ................................................................................................................................... 9
1.1 Structures and systems toward the decommissioning of the Fukushima Daiichi Nuclear
Power Station....................................................................................................................... 10
1.2 The Technical Strategic Plan 2023 ...................................................................................... 12
2. Concept for reducing risks and ensuring safety in the decommissioning of the Fukushima
Daiichi NPS................................................................................................................................ 16
2.1 Basic policy for the decommissioning of the Fukushima Daiichi NPS ................................. 16
2.1.1 Risks management to be addressed in Phase 3-[1]...................................................... 16
2.1.1.1 Risk reduction .......................................................................................................... 17
2.1.1.2 Requirement for the further expansion of fuel debris retrieval in scale .................. 18
2.2 Concept of reducing risks caused by radioactive materials ................................................. 19
2.2.1 Quantitative identification of risks .................................................................................. 19
2.2.2 Risk reduction strategy .................................................................................................. 24
2.2.2.1 Interim targets of the risk reduction strategy........................................................... 24
2.2.2.2 Basic approach to risk reduction ............................................................................. 29
2.3 Approach to ensuring safety during decommissioning ........................................................ 30
2.3.1 Basic policy for ensuring safety based on the characteristics of Fukushima Daiichi NPS....................................................................................................................................... 30
2.3.1.1 Promulgating the “Safety First” principle that safety perspective comes first......... 32
2.3.1.2 Optimization of judgement with a safety assessment as its basis and ensuring
timeliness in decommissioning ............................................................................... 32
2.3.1.3 Ensuring safety by incorporating “the operator’s perspective” ............................... 33
2.3.1.4 ALARP judgment based on safety .......................................................................... 34
2.3.2 Preliminary implementation and utilization of the obtained information in the latterstages ............................................................................................................................ 35
2.3.3 Approach to address a temporary increase in risk level associated withdecommissioning operations ........................................................................................ 36
3. Technological strategies toward the decommissioning of the Fukushima Daiichi NPS ............ 38
3.1 Fuel debris retrieval .............................................................................................................. 38
3.1.1 Target ............................................................................................................................. 38
3.1.2 Progress ......................................................................................................................... 38
3.1.3 Key issues and technical strategies to realize them...................................................... 44
3.1.3.1 Fuel debris retrieval strategies in each Unit ............................................................ 45
3.1.3.2 Trial retrieval (Internal investigation and fuel debris sampling) .............................. 48
3.1.3.3 Gradual expansion of fuel debris retrieval .............................................................. 52
3.1.3.4 Further expansion of fuel debris retrieval in scale .................................................. 54
3.1.3.5 Continuation of accident analysis activities (clarification of events that occurred at
the time of the accident) ......................................................................................... 65
3.1.3.6 Progress of research and development for further expansion of fuel debris retrieval
in scale.................................................................................................................... 65
3.1.3.7 Issues in examining safeguards strategies ............................................................. 75
3.1.4 Summary of key technical issues .................................................................................. 75
3.2 Waste management.............................................................................................................. 77
3.2.1 Target ............................................................................................................................. 77
3.2.2 Progress ......................................................................................................................... 77
3.2.3 Key issues and technical strategies............................................................................... 83
3.2.3.1 Characterization ...................................................................................................... 84
3.2.3.2 Storage/management .............................................................................................. 85
3.2.3.3 Processing/Disposal ................................................................................................ 86
3.2.4 Summary of key technical issues .................................................................................. 88
3.3 Contaminated water and treated water management .......................................................... 90
3.3.1 Target ............................................................................................................................. 903

3.3.2 Progress ......................................................................................................................... 90
3.3.3 Key issues and technical strategies to realize them...................................................... 97
3.3.3.1 Control of contaminated water generation amount ................................................. 97
3.3.3.2 Treatment of stagnant water in buildings .............................................................. 100
3.3.3.3 Issues of contaminated water management considering the decommissioning
process such as fuel debris retrieval .................................................................... 102
3.3.3.4 Future efforts for the discharge of ALPS-treated water into the sea .................... 104
3.3.4 Key technical issues and future plans ......................................................................... 110
3.4 Fuel removal from spent fuel pools .................................................................................... 111
3.4.1 Target ........................................................................................................................... 111
3.4.2 Progress ....................................................................................................................... 111
3.4.3 Key issues and technical strategies to realize them.................................................... 114
3.4.3.1 Fuel removal from SFPs ........................................................................................114
3.4.3.2 Decision on future treatment and storage methods ...............................................117
3.4.4 Summary of key technical issues ................................................................................ 118
4. Analysis strategy for promoting decommissioning................................................................... 119
4.1 Significance of analysis on decommissioning .................................................................... 119
4.2 Current status and strategies for analysis .......................................................................... 121
4.2.1 Measures to strengthen analytical method and analysis structure ............................. 121
4.2.1.1 Measures to strengthen analysis structure ........................................................... 121
4.2.1.2 Discussion on analysis plans ................................................................................ 122
4.2.1.3 Development of analysis and evaluation methods ............................................... 124
4.2.1.4 Securing facilities for analysis ............................................................................... 125
4.2.1.5 Securing human resources for analysis ................................................................ 127
4.2.2 Improvement of the quality of analysis results............................................................. 129
4.2.3 Diversification of analytical techniques to increase sample size and volume ............. 131
4.2.3.1 Comprehensive evaluation by diversified analysis and measurement methods .. 131
4.2.3.2 Use of sample analysis and non-destructive assays ............................................ 131
4.2.3.3 Improvement in number of analyses ..................................................................... 133
5. Efforts to facilitate research and development for decommissioning of the Fukushima Daiichi
NPS.......................................................................................................................................... 134
5.1 Significance and the current status of research and development .................................... 134
5.2 Key issues and strategies................................................................................................... 136
5.2.1 R&D medium-and-long-term plan ................................................................................ 136
5.2.2 Initiatives for the Project of Decommissioning, Contaminated Water and Treated Water
Management ............................................................................................................... 137
5.2.3 Promotion of cooperation between decommissioning sites and universities/ researching
institutions ................................................................................................................... 141
6. Activities to support our technical strategy............................................................................... 146
6.1 Capabilities, organization, and personnel to proceed with decommissioning ................... 146
6.1.1 Ensuring the capability, organization and personnel that TEPCO should possess as theowner of the Fukushima Daiichi Nuclear Power Station............................................. 146
6.1.1.1 Significance and current status of decommissioning project management ......... 146
6.1.1.2 Capability an owner should possess..................................................................... 151
6.1.1.3 Initiatives related to organization .......................................................................... 155
6.1.1.4 Initiatives to recruit and develop personnel .......................................................... 156
6.1.2 Fostering the next generation responsible for the decommissioning of Fukushima
Daiichi NPS and promoting public understanding ...................................................... 158
6.1.2.1 Fostering the next generation who will be responsible for the futuredecommissioning of Fukushima Daiichi NPS ...................................................... 158
6.1.2.2 Dissemination of basic knowledge and promoting people's understanding ofdecommissioning and the radiation safety involved in decommissioning ........... 160
6.2 Strengthening international cooperation ............................................................................ 161
6.2.1 Significance and the current status of international cooperation................................. 161
6.2.1.1 Significance of international cooperation .............................................................. 161

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6.2.1.2 Current status of international cooperation ........................................................... 162
6.2.2 Key issues and strategies ............................................................................................ 163
6.2.2.1 Integrating and giving back wisdom and knowledge from around the world ........ 163
6.2.2.2 Maintaining and developing the international community’s understanding, interest
and cooperation in decommissioning ................................................................... 164
6.3 Local community engagement............................................................................................ 167
6.3.1 Significance and the current status of local community engagement ......................... 167
6.3.1.1 Basic concept ........................................................................................................ 167
6.3.1.2 Specific measures under the current situation...................................................... 168
6.3.2 Key issues and strategies ............................................................................................ 170
6.3.2.1 Communication issues and strategies .................................................................. 170
6.3.2.2 Issues and strategies related to the creation of a regional industrial and economic
base through decommissioning............................................................................ 171
List of Acronyms/Glossaries ......................................................................................................... 174
List of Attachment ......................................................................................................................... 178

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Table of Figures
Fig. 1 Decommissioning process as defined in the Mid-and-Long-term Roadmap..........................9
Fig. 2 Division of roles of related organizations responsible for decommissioning of the
Fukushima Daiichi NPS .........................................................................................................10
Fig. 3 Positioning of the Technical Strategic Plan based on the Reserve Fund ............................. 11
Fig. 4 Risk levels posed by major risk sources at the Fukushima Daiichi NPS..............................23
Fig. 5 Reduction of risks present in the Fukushima Daiichi NPS ...................................................24
Fig. 6 Risk reduction process for major risk sources and its progress (as of March 2023) ...........27
Fig. 7 ALARP centered on safety (conceptual diagram) .................................................................34
Fig. 8 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 3 ...
.........................................................................................................................................................42
Fig. 9 Scope of internal investigation for Unit 1 PCV (Outside the pedestal on the basement floorof the PCV from 0 to 215 degrees, pedestal opening and inside the pedestal) ...................43
Fig. 10 Results of the internal investigation for Unit 1 PCV ............................................................43
Fig. 11 Image of fuel debris retrieval system ..................................................................................44
Fig. 12 Conceptual drawing from retrieval to storage of fuel debris ...............................................44
Fig. 13 Work steps of trial retrieval (internal investigations and fuel debris sampling)...................49
Fig. 14 Conceptual drawing of telescopic device to complement robot arm ..................................52
Fig. 15 Example of the proposed partial submersion method (water injection to RPV) .................58
Fig. 16 Overview of the partial submersion method option (RPV filling and solidification) ............61
Fig. 17 Example of the submersion method (Shell structure) .........................................................63
Fig. 18 Research topics and key activities in analysis and estimation technologies for fuel debris
characterization ...................................................................................................................71
Fig. 19 Key technical issues and future plans on fuel debris retrieval (progress schedule) ..........76
Fig. 20 Summary of waste hierarchy at the NDA, and countermeasures at the Fukushima Daiichi
NPS .....................................................................................................................................82
Fig. 21 Procedure to reasonably select safe processing/disposal methods of solid waste ...........88
Fig. 22 Key technical issues and future plans on waste management (progress schedule) .........89
Fig. 23 Outline of contaminated water management ......................................................................91
Fig. 24 Progress of contaminated water management and changes in the amount ofcontaminated water generated ..........................................................................................92
Fig. 25 Conceptual drawing of discharge facilities..........................................................................96
Fig. 26 General view of discharge facilities.....................................................................................96
Fig. 27 Conceptual drawing of water sealing at the edge of the gaps between buildings .............98
Fig. 28 Depth distribution of the building penetrations....................................................................99
Fig. 29 Lowering of sub-drain and building water levels .................................................................99
Fig. 30 Conceptual drawing of water sealing at the edge of the gap between buildings ...............99
Fig. 31 Overview of the zeolite sandbag recovery task ................................................................101

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Fig. 32 ALPS-treated water analysis and evaluation structure .....................................................105
Fig. 33 Flow to select nuclides to be measured and evaluated ....................................................106
Fig. 34 Framework for discussion and implementation system for marine monitoring ................108
Fig. 35 Key technical issues and future plans on contaminated water/treated water management
and natural disaster preparedness (progress schedule) .................................................. 110
Fig. 36 Layout drawing of the Common Spent Fuel Storage Pool and dry cask at the Temporary
Cask Custody Area and the workflow ............................................................................... 112
Fig. 37 Storage status of spent fuel .............................................................................................. 112
Fig. 38 State of the collapsed rubble on the Unit 1 operating floor............................................... 113
Fig. 39 Fuel removal method from Unit 1 SFP.............................................................................. 113
Fig. 40 Fuel removal method from Unit 2 SFP.............................................................................. 114
Fig. 41 Key technical issues and future plans for fuel removal from SFPs (Progress schedule). 118
Fig. 42 Relationship between the purpose of the analysis, equipment required forcharacterization, and radiation dose rates of the analysis targets ................................... 119
Fig. 43 Three elements of the fuel debris analysis strategy .........................................................120
Fig. 44 Analysis implementation flow for solid waste at the Fukushima Daiichi NPS ..................123
Fig. 45 Construction and operation schedule for fuel debris retrieval and new analyticallaboratories........................................................................................................................127
Fig. 46 Role of Analysis Coordinating Committee and Analysis Support Team ...........................129
Fig. 47 An example flow of non-destructive assay in the handling process for retrieved fuel debris...........................................................................................................................................133
Fig. 48 Scope of studying decommissioning R&D and implementation entities ..........................134
Fig. 49 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPS .......135
Fig. 50 List of FY 2023 decommissioning R&D plans ...................................................................139
Fig. 51 RFI and project review ......................................................................................................141
Fig. 52 Research centers for Decommissioning in Fukushima ....................................................145
Fig. 53 Standard workflow of risk management ............................................................................148
Fig. 54 The 7th International Forum on the Decommissioning of the Fukushima Daiichi Nuclear
Power Station ....................................................................................................................163
Fig. 55 Structural drawing inside Reactor building .......................................................................177
Fig. 56 Structural drawing inside Reactor Pressure Vessel (RPV) ...............................................177

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Table Heading
Table 1 Major risk sources at the Fukushima Daiichi NPS ............................................................ 22
Table 2 Status of solid waste storage/management ...................................................................... 81
Table 3 Major initiatives for discharging ALPS-treated water into the sea..................................... 94
Table 4 Nuclides to be measured and evaluated and their quantification methods .................... 107
Table 5 Objective for analysis planning ........................................................................................ 123
Table 6 Personnel exchange between TEPCO and JAEA and accepting personnel from NFD to
TEPCO ............................................................................................................................ 128
Table 7 Relative comparison of principal specifications between the sample analysis in the facility
for analysis and the non-destructive assay outside the facility for analysis ................... 132
Table 8 Difference between “Making” and “Buying” ........................................................... 155

81. Introduction
The long-term approach to the decommissioning of the Fukushima Daiichi Nuclear Power Stationof Tokyo Electric Power Company Holdings, Inc. (hereinafter referred to as the “Fukushima Daiichi
NPS”) has proceeded under “the Mid-and-Long-term Roadmap towards the Decommissioning ofFukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc.”(hereinafter referred to as “Mid-and-Long-term Roadmap”), developed by the Japanese
Government. (Fig. 1)

Accident

Early period Phase 1● From the time theaccident occurred(March 2011)
To Step 2 was completed*(December 2011)● From Step 2 wascompleted(December 2011)
To the start of spent fuelremoval from the first
implementing unit
(November 2011)

Phase 2

● From the end of Phase
1 (November 2013)
To the start of fueldebris retrieval from thefirst implementing unit

Phase 3Phase 3ー①

Phase 3ー②

●From the end of Phase
2 (around 2023)
To the end of 2031

●From the end of Phase
3- ①
Through the end of
decommissioning (Target
period will be 30 to 40
years after Step 2)* Situation where “releases of radioactive material are controlled, and radiation levels are significantly reduced”.

Fig. 1 Decommissioning process as defined in the Mid-and-Long-term Roadmap

Decommissioning works have been steadily progressing, as shown by the facts that the imagesof the inside the pedestal was successfully captured for the first time during the internal
investigations of Unit 1 in March 2023, milestones in reducing the amount of stagnant water in thereactor building were achieved, and the discharge of ALPS-treated water into the sea started inAugust. Preparations to start the final phase of Phase 2 are currently underway including trial
retrieval of fuel debris in the second half of fiscal 2023. From Phase 3-[1] onward, the developmentof analytical methods and the securing of analytical personnel are also being promoted, based on
examination of retrieval methods for further expansion of fuel debris retrieval in scale and theformulated analysis plan.
Nuclear Damage Compensation and Decommissioning Facilitation Corporation (hereinafterreferred to as “NDF”) has supported efforts related to the decommissioning of the Fukushima
Daiichi NPS as an organization that conducts research and development, as well as provides
advice and guidance, required for decommissioning since 2014. This “Technical Strategic Plan for
Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station” (hereinafter referred toas the “Technical Strategic Plan”), as a part of these supports, has been compiled annually since2015 with the following objectives (Attachment 1).
Providing a solid technical basis for the Mid-and-Long-term Roadmap and contributing to its
smooth and steady implementation, and consideration of revisions

9Providing a basis for “The Policy for Preparation of Withdrawal Plan for Reserve Fund for
Decommissioning” (hereinafter referred to as “The Policy for Preparation of Withdrawal
Plan”)In addition, since the “Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi
NPS” (hereinafter referred to as “Target Map for Reducing Risks”) formulated by the Nuclear
Regulation Authority (NRA) takes the process of the Mid-and-Long-term Roadmap into
consideration, and thus the Technical Strategic Plan also contributes to achieving the targets set
forth in the Target Map for Reducing Risks.

1.1 Structures and systems toward the decommissioning of the Fukushima
Daiichi Nuclear Power Station
In order to safely and steadily conduct the decommissioning of the Fukushima Daiichi NPS, thegovernment, NDF, Tokyo Electric Power Company Holdings, Inc. (hereinafter referred to as the“TEPCO”), Japan Atomic Energy Agency (hereinafter referred to as “JAEA”.), and other researchand development organizations are working together on the efforts based on their roles. Fig. 2
shows the division of roles the related organizations responsible for decommissioning. Under sucha system, TEPCO, the operator of the decommissioning project, is working to strengthen the project
management system for steadily advancing the decommissioning work by systematically
implementing responses to various issues with a view to the medium-to long-term of thedecommissioning work (details in Chapter 6).
Nuclear Emergency Response Headquarters (Director: Prime Minister)
Nuclear Regulation Authority

 Decide the direction of decommissioning and contaminated water
treatment Approval of implementation plan,
pre-service inspection, welding
inspection, etc.
 Providing goals for risk reduction(Chairperson: Chief Cabinet Secretary)

Mid-and-Long-Term Roadmap

The Team for Countermeasures for Decommissioning
and Contaminated Water Treatment(Head of Team: Minister of Economy, Trade and Industry) Progress management of each countermeasure according toMid-and-Long-Term Roadmap

Progressmanagement

Apply forapproval

 Development of a mid-to-long-term strategy

Withdrawal plan

Technical  Tech. support for progress management of important
issues (in collaboration)
Strategic  R&D planning and progress management
plan  Strengthen international partnership Management of Reserve Fund for
Decommissioning

Share progressand challenges

Reserve Fund for
Decommissioning

Advice, guidance, recommendations,supervision and support
Reserverelated to project management, etc.

ReportDisburse-ment

Apply for reportJapan Atomic Energy Agency (JAEA),etc.
 R&D implementation

Approve

Nuclear Damage Compensation and Decommissioning Facilitation Corporation

Granting of
project budget

R&D organization

Minister of Economy, Trade and Industry
Presentation ofimportant issues

ReportTarget map for Reducing
Medium-term Risk

Monitoring, examination

Report on theoutcomeReportBidirectional dialogue

Local residents and communities

Organizations related to decommissioning

Council for the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station*

Tokyo Electric Power Company Holdings, Inc. (Fukushima Daiichi Decontamination and Decommissioning Engineering Company)
 Contaminated water and ALPS-treated water management, fuel removal from SFP, fuel debris retrieval, waste management, etc.
 Through TEPCO's management reform, the funds required for decommissioning should be reserved
responsibly (Implementation of the 4th special business plan)Mid-and-Long-term Detailed measures for facility safety and protection of nuclear fuel material
Decommissioning Action Plan
(Development of implementation plan for specified nuclear facility)* In response to the ALPS-treated water disposal policy decided on April 13, 2021, “Council for the Decommissioning of TTEPCO’s Fukushima Daiichi NPS toward steady implementation of basic policy on ALPS-treatedwater disposal” was founded.

Fig. 2 Division of roles of related organizations responsible for decommissioning of the
Fukushima Daiichi NPS
From the financial aspect, to ensure the decommissioning work in the immediate future,decommissioning work is being implemented in accordance with the Reserve Fund for10

Decommissioning established by partially revised the Nuclear Damage Compensation Facilitation
Corporation Act passed in May 2017. The main steps in this process are as follows.
① TEPCO sets aside the amount of money determined by the NDF and approved by the
Minister of Economy, Trade and Industry every year.
② The NDF and TEPCO jointly prepare a Withdrawal Plan for Reserve Fund.
③ TEPCO withdraws the Reserve Fund based on the Withdrawal Plan approved by the
Minister of Economy, Trade and Industry.
Under this Reserve Fund system, NDF assumes the roles and responsibilities of appropriate
management of funds related to decommissioning, management of proper implementation
structures, and steady work management, as an organization to manage and oversee TEPCO's
decommissioning activities. Specifically, prior to the formulation of the Withdrawal Plan, NDF
presents the work targets and major works to be incorporated in the Withdrawal Plan to TEPCO
according to the Policy fir Preparation of Withdrawal Plan based on the Technical Strategic Plan.
Through the process of jointly preparing the Withdrawal Plan with TEPCO, NDF supports the properand steady implementation of decommissioning, as well as assesses the appropriateness of
TEPCO's efforts from the perspective of project execution by examining and presenting the works

Government

to be included in the Plan (Fig. 3).
Mid-and-Long-Term Roadmap*
Proposals for Revise* Continually revised based on on-site progress,in the past revised once every several years
Mid-and Long-term R&D Plan, Next R&D Plan
(The Government-led R&D program on
Decommissioning and Contaminated Water Management)

NDF

Strategic Plan (annual)
The Policy for Preparation ofWithdrawal Plan for Reserve Fund for
Decommissioning (annual)

Feedback

TEPCO

Withdrawal Plan for Reserve Fundfor Decommissioning (annual)

Planning from
Mid-and-long-term aspect

Jointly created with NDF and approved by METI
• Contaminated water management PG• Spent Fuel removal PG• Fuel debris retrieval PG• Waste management PG• General management of the site PG• ALPS-treated water management PG• Facility maintenance/Operational Management

Mid-and-Long-term
Decommissioning Action Plan(annual)On-site work

Engineering

Feedback

R&D

Promotion of Decommissioning project

Fig. 3 Positioning of the Technical Strategic Plan based on the Reserve Fund11

1.2 The Technical Strategic Plan 2023
The Technical Strategic Plan 2023 consists of six chapters and characteristically features below:


Unit 1; Investigation and evaluation for the integrity of the pedestal

Unit 2; Preparatory works related to trial retrieval (internal investigation and fuel debris
sampling)

Unit 3; Examination of selecting the retrieval methods toward further expansion of fueldebris retrieval in scaleEfforts toward the discharge of ALPS-treated water into the seaEnhancement of analysis system

Including the above, the major changes in the Technical Strategic Plan 2023 are as follows. The
accomplishment of the efforts to date for the Fukushima Daiichi NPS are shown in Attachment 2.
Chapter 2Concept for reducing risks and ensuring safety in the decommissioning of
the Fukushima Daiichi NPS

The SED assessment1 has been reviewed in terms of the Hazard Potential and Requiring
Level for Safety Management based on the radioactivity levels and management status ofeach risk source as at the end of March 2023. The most notable changes since the end of
March 2022 include decreasing of Hazard Potential as the progress of the transfer work of
the ALPS slurry stored in the HIC, which exceeded the standard for integrated absorbed
dose, and the review of Requiring Level for Safety Management for “contaminatedstructures in buildings, etc.” in light of the newly identified on-site conditions.



For some time, the immediate target has been to reduce the “Requiring Level for Safety
Management” of risk sources and bring them into “region of sufficiently stable management”.
To clarify the direction of its specific measures, the Technical Strategic Plan 2023 presents
how “Requiring Level for Safety Management” can be reduced from each perspective bybreaking down “Requiring Level for Safety Management” into two components (acomponent related to the containment of the facility and a component related to the longterm stability of risk sources).

Chapter 3

Technological strategies toward decommissioning of the Fukushima
Daiichi NPS(1) Fuel debris retrievalThis section stated that, as a result of the internal investigation of Unit 1 conducted in March
2023, a great deal of information was obtained, including the height of deposits outside thepedestal and the status of deposits and fallen objects located at the bottom of the pedestal.

1

A method based on the Safety and Environmental Detriment score (SED) developed by the Nuclear
Decommissioning Authority (NDA) to express the magnitude of risk (risk level) for radioactive materials. For
details, refer to Attachment 5.

12With regard to “Further expansion of fuel debris retrieval in scale”, the Technical Strategic
Plan 2022 described the study processes, the overview and examples of issues of the two
methods discussed (partial submersion method and submersion method), and the policy
for further action, based on the studies of the methods until the first half of 2022. In theTechnical Strategic Plan 2023, the description was completely revised, and the six factorsthat make it difficult to retrieve fuel debris, which should be taken into account whenproceeding with the evaluation of retrieval methods were identified, as well as the issues
and action policies for each of these factors were described in each of partial submersion
method (water injection into RPV), partial submersion method option (RPV filling andsolidification) and submersion method (shell method).

As this selection of retrieval methods is an extremely important decision that will determine
the success or failure of decommissioning over the medium-to long-term, it is necessary for
TEPCO, the government and NDF to cooperate in the study process. Therefore, this section
states that "The Sub-committee for Evaluation of Fuel Debris Retrieval Method" has been
established from February 2023 to perform expert and intensive studies and evaluations on
the technical feasibility of each method, business continuity of the project2.

In the Technical Strategic Plan 2022, the issues for each technical requirement werecomprehensively described as the Section 3.1.2.6, there were duplicated descriptions withthe previous section. The Technical Strategic Plan 2023 describes research anddevelopment items regarding further expansion of fuel debris retrieval in scale currently
being implemented in the Project of Decommissioning, Contaminated water and Treatedwater Management.

(2) Waste management
This section states that, since the studies on analysis have progressed, which is an
important element in advancing waste management, TEPCO formulated an analysis planin March 2023 with the aim of characterizing of solid waste and optimizing its
storage/management to review processing/disposal methods for solid waste.

Based on this analysis plan and other materials, new targets for analysis were set, and new
actionpoliciesaredescribed

accordingtothefieldsof“characterization”,“storage/management” and “processing/disposal”.
(3) Contaminated water and treated water management
As the prospect for reducing the amount of contaminated water generated to 100 m3/day orless to the average rainfall by the end of 2025 is becoming clear, and the reduction of theamount of stagnant water in reactor buildings to about half of that at the end of 2020 has
been achieved, in the Technical Strategic Plan 2023, new target (about 50 to 70 m3/day by

2

Indicators for determining whether decommissioning is a sustainable project over the long term. Examples arecosts, processes, availability of workers, and social receptivity.

13

the end of FY 2028) has been set and the policy for efforts to achieve this has been newly
added.


The Technical Strategic Plan 2022 describes what needs to be done towards the start ofdischarging ALPS-treated water into the sea, as well as the strategies for issues to beaddressed after the start of discharging. The Technical Strategic Plan 2023 summarizes theresults of the efforts that have been made toward the discharge of ALPS-treated water (e.g.
establishment of a cross-checking system, selection of 29 nuclides to be measured andevaluated) and describes the issues and policies to be addressed in the future.

(4) Fuel removal from spent fuel poolRegarding the removal of high-dose equipment, the Technical Strategic Plan 2022
described its significance and stated that the removal plan and process of high-dose
equipment should be fully considered in the design of fuel handling facilities. Considering
the progress of the plan, the issues and the need for action of site bunker capacity wereadded.

For the dry storage of spent fuel on high ground, the Technical Strategic Plan 2022 statedthat studies should be conducted with reference to overseas findings, including handling offuel with damaged cladding tubes. The Technical Strategic Plan 2023 describes the issues
and policies to be taken when studying the application of concrete casks (which have been
stored overseas but not in Japan), which were newly announced in the Mid-and-Long-term
Decommissioning Action Plan 2023.

Chapter 4 Analysis strategy for promoting decommissioningPrevious Technical Strategic Plans have mainly stated the analysis of fuel debris. Given thefact that studies on analysis have progressed and analysis plans have been drawn up, thescope of analysis has been expanded to include other than fuel debris, and the issues andaction policies are described.

The descriptions of the studies of analysis plans and the development of analysis/evaluation
methods are enhanced as new items, and the activity policies of the “Analysis Coordination
Meeting” and “Analysis Support Team” are also stated as new efforts to secure humanresources.

Chapter 5Efforts to facilitate research and development

Regard to the implementation structure for the Project of Decommissioning, Contaminatedwater and Treated water Management, the Technical Strategic Plan 2022 included points tobe noted and necessary initiatives (RFI (Request for Information), project review) with aview to shifting from the International Research Institute for Nuclear Decommissioning(hereinafter referred to as “IRID”)-centered structure to a new structure. In the Technical14

Strategic Plan 2023, it is stated that the new structure, based on the needs of TEPCO, hasbeen shifted to a system in which research institutions, manufacturers and others are themain implementers.


In order to continue and further strengthen the good practices of the functions performed by
IRID, specific measures being undertaken by the NDF such as RFIs and specific details of
project reviews are stated.

Chapter 6

Activities to support our technical strategy(1) Capacity, organization and human resources to facilitate decommissioning
In the Technical Strategic Plan 2022, the key items to be strengthened by TEPCO were

described: Safety and Operators’ Perspectives, promulgation of “Safety First”, and Owner's
engineering capabilities (project management capability, engineering capability based onsafety and operators’ perspectives). The Technical Strategic Plan 2023 describes the needto expand “Investigation capability at the upstream side of the project” as a capability thatowners should have, considering the progress of TEPCO's studies.
For “coexistence of reconstruction and decommissioning”, this section includes theconsideration of integrating and reorganizing Fukushima Daini NPS and its head office
functions into the Fukushima Daiichi Decontamination and Decommissioning Engineering
Company, which is being promoted by TEPCO.

(2) Strengthening international cooperation
In Subsection 6.2.2.1, “Integrating and giving back wisdom and knowledge from around theworld”, the previous descriptions are summarized in 3 strategies (Specifically, (1) strengthen
cooperation with counterparts, (2) expand the scope of information gathering, and (3) returnresults).

In Subsection 6.2.2.2, “Maintaining and developing the international community’sunderstanding, interest and cooperation in decommissioning”, 2 strategies ((1) approach toexperts; (2) approach to the general public) are described to gain international
understanding based on the experience obtained from the response to ALPS-treated water.

(3) Local community engagement

In relation to the creation of regional industrial and economic infrastructure, the “Mediumto-Long-Term Outlook in the Decommissioning” has been prepared since September 2020
with the aim of increasing the participation of local companies. From FY2022 the candidate
work orders involving local companies have been clearly indicated in the “Medium- to-LongTerm Outlook in the Decommissioning”. This section states that it is necessary to continue
and expand measures to facilitate the participation of local companies.

15

2. Concept for reducing risks and ensuring safety in thedecommissioning of the Fukushima Daiichi NPS
2.1 Basic policy for the decommissioning of the Fukushima Daiichi NPS<Basic policy for the decommissioning of the Fukushima Daiichi NPS>
Continuously and quickly reduce the risks arising from the radioactive materials caused by theaccident that do not exist in normal nuclear power plants

The Fukushima Daiichi NPS has the necessary safety measures required by the NRA in place
for the matters for which measures should be taken and it is being maintained in a state with acertain level of stability.
However, there are still enormous risks at the Fukushima Daiichi NPS because fuel debris andspent fuel still remain in the reactor buildings damaged by the accident, part of the status of the
NPS has not yet been sufficiently ascertained, and the site has radioactive contaminated water andenormous amounts of extraordinary radioactive wastes. If left unaddressed, these risks may
increase due to aging degradation of the facilities and other factors. Quickly and swiftly reducing
these risks is an urgent matter for the NPS.
Accordingly, the basic policy for the decommissioning of the Fukushima Daiichi NPS is “tocontinuously and quickly reduce the risks arising from the radioactive materials caused by theaccident that do not exist in normal nuclear power plants” by taking measures specifically designed
to reduce risks. Generally, the following measures are effective for reducing risks at facilities wherean accident has occurred; ① Improving the containment functions of the damaged facilities; ②
Changing the properties and form of the contained radioactive materials to be more stable; and ③
Strengthening monitoring and control over the equipment to better prevent or mitigate theoccurrence or propagation of abnormalities. In order to achieve these measures in an integrated
way, in addition, ④ Collecting radioactive materials from the damaged facilities or insufficient
containment conditions and placing them in more robust storage is effective.
Since the accident, these diverse measures for risk reduction have been taken with careful
preparations aimed at preventing accidents and radioactive exposure of workers (Attachment 3).
2.1.1 Risks management to be addressed in Phase 3-[1]In Phase 3-[1], several processes for risk reduction will be carried out in parallel according to themilestones in the Mid-and-Long-term Roadmap.


Aim to complete fuel removal from the spent fuel pools of Units 1 to 6.

Undertake trial retrieval of fuel debris and promote gradual expansion of fuel debris retrieval.



Minimize and stably maintain the amount of contaminated water generated.

Eliminate the temporary storage of rubble etc., as a waste management measure.

Regarding fuel debris retrieval, preparation of methods for further expansion of fuel debris
retrieval in scale, which will be full-scale decommissioning work, will be promoted. Even though16more than about twelve years have passed since the declaration of the cold shutdown state andthe current state of temperature and pressure inside the PCVs is stable, conditions may changewith the start of fuel debris retrieval. As the retrieval progresses, the risks attributable to fuel debris
will decrease. However, risks that were previously perceived as small may become relatively large,or unknown risks may become newly apparent. In preparation for these risks, to effectively respondto risks toward further expansion of fuel debris retrieval in scale, it is necessary to improve theability to observe conditions inside the PCVs where changes in these risks are likely to occur.
Therefore, despite the high degree of difficulty, consideration should be given to expanding the typeand number of monitoring targets, while taking into account the current purpose of the monitoring
parameters and the number of monitoring devices in the PCVs and difficulties in on-site operation.
For example, the dust concentration in the PCVs is expected to increase with fuel debris retrieval
work in the case of further expansion of fuel debris retrieval in scale. If the dust concentration in
the PCVs can be measured in a phase of preceding trial retrieval and gradual expansion of fueldebris retrieval, and the correlation between the location and scale of the retrieval operations andthe dust concentration can be determined, it is possible to reduce the uncertainty associated withretrieval operations and improve work efficiency while maintaining an appropriate safety margin.
Once the condition inside the PCVs can be observed from a more multifaceted perspective, it isexpected to provide a basis for whether or not the facilities being considered are required for further
expansion of fuel debris retrieval in scale, contributing to the optimization of resources.
In addition to promoting the design, manufacture, and installation of systems related to theretrieval methods, it is also important to secure and train operators and maintenance personnel,
develop a management framework, and establish a rational analysis framework for retrieved fueldebris.。
2.1.1.1 Risk reduction
2.1.1.1.1 Further measures to reduce the migration of radioactive materials from PCVs Gaseous and dusty radioactive materials
Toward fuel debris retrieval, containment ability should be further enhanced by reducing the
migration of gaseous and dusty radioactive materials that are prone to migration from PCVs.
Specifically, the effectiveness of the reduction in the amount of dust transferred outside the PCV
should be observed by PCV pressure equalization (slightly negative pressure) and an enhanced
dust concentration monitoring function in the PCVs, as shown in 2.1.1.
 Liquid radioactive materials
The migration of liquid radioactive materials, which are almost as easily migrated as gaseousand dusty radioactive materials, should be controlled without fail. Specifically, drainage of the waterretained in the suppression chamber (hereinafter referred to as “S/C”) and other systems thatTEPCO is currently undertaking should be accelerated to minimize the amount of PCV water.

17

In proceeding with the above, the tests available with the current system configuration, such asreactor water injection shutdown tests and nitrogen supply reduction tests, should be actively
performed in accordance with the “concept of preliminary implementation and utilization of theobtained information in the latter stages” described in 2.3.2, to assess the feasibility, anddetermine areas and difficulty of the issue.
2.1.1.1.2 Preparation for long-term risks to the integrity of reactor pressure vessels (RPVs),
primary containment vessels (PCVs), and reactor buildings containing fuel debris
The reactor pressure vessels (hereinafter referred to as “RPVs”) and the PCVs were directly
affected by the accident. It has been found that the molten fuel damaged the bottom of the RPVs
and the PCVs were partially damaged by overheating and overpressure.
At the PCV bottom, the effects due to contact with the molten core materials and their heat also
occurred. In the pedestal of Unit 1 PCV, exposure of inner wall reinforcement and inner-skirt wasobserved. For this reason, prudent approaches should be taken to maintain the long-term integrity,
including the containment performance of RPVs and PCVs and the strength of reactor buildings,
against threats of corrosion of metal materials, deterioration of containment performance, anddegradation in strength of the affected concrete structural materials.
To achieve that, it is necessary to verify the damage condition inside the PCVs in a focusedmanner and proceed with an integrity assessment based on the latest information on the PCVinterior, assuming long-term risks that may occur in the future, such as earthquakes and aging
degradation (Attachment 4). Given the limited information on damage conditions, this evaluation
always involves uncertainty. Still, it is necessary to make diligent efforts to update the evaluation
data and incorporate the latest in-core information for reducing uncertainty.
2.1.1.2 Requirement for the further expansion of fuel debris retrieval in scale
The following is required to conduct safe and reliable fuel debris retrieval toward the phase of
the further expansion of fuel debris retrieval in scale:Ensure that trial retrieval will be carried out while obtaining knowledge so that it can be utilized
in subsequent gradual expansion of fuel debris retrieval and further expansion of fuel debris
retrieval in scale.

Proceed with designing, manufacturing, and installing systems related to retrieval methods.

Establish a system for securing, training and managing operators and conduct necessary
training.



Since preliminary work for retrieval requires operations in the high-dose reactor building, due
to the prolonged work it is important to improve the on-site environment and ensure exposure
control and the long-term availability of workers.

In preparation for hardware, it is necessary to proceed with environmental improvements inthe surrounding area, such as dismantling and removing exhaust stacks and radioactive
waste disposal buildings.

18



Moreover, the organizations concerned need to discuss and develop an analysis plan,
facilities for analysis, and an analysis framework for analyzing the retrieved fuel debris
rationally.



It is important to facilitate waste storage that does not hinder the above operations.

Specific initiatives for the above are discussed in Chapters 3 and 4.

2.2 Concept of reducing risks caused by radioactive materials
2.2.3 Quantitative identification of risks
The term “risk” has various meanings depending on the field or situation in which it is used. In
general, in the context of appropriate risk management, “risk” can be understood as an expectation
value of the negative impact of an event. In other words, the magnitude of a risk (risk level) posedby a subject (risk source) can be expressed as the product of the level of impact and the Requiring
Level for Safety Management of an event.
The Technical Strategic Plan uses a method based on the Safety and Environmental Detrimentscore (hereinafter referred to as “SED”) developed by the Nuclear Decommissioning Authority(hereinafter referred to as “NDA”) to express the magnitude of risk (risk level) for radioactive
materials. The risk level expressed by SED is given by the calculation formula below.

Risk Level expressed by SED = “Hazard Potential” × “Requiring Level for Safety Management”(Formula 1)“Hazard Potential” here, is an index of the impact of the event, namely, the impact of internal
exposure in the event of human intake of radioactive material contained in the risk source. It canbe expressed as the product of Inventory, which is the amount of radioactive material contained in
the risk source (taking account of toxicity of the radioactive material), and factors that depend on
the form of the risk source and the time allowable until the manifestation of the risk. “Requiring
Level for Safety Management” is an index of the likelihood that an event will occur. It is determinedby factors that depend on the integrity and other aspects of the facility and on the
packaging/monitoring status of the risk source (Attachment 5). The name of this “Requiring Level
for Safety Management” was “Safety Management” until the Technical Strategic Plan 2022, andalthough the name has been revised in the Technical Strategic Plan 2023, the definition and otherdetails remain unchanged. This revision was made to explicitly indicate that a higher level of safetycontrol measures is required when the facility containing the risk source has inadequate integrity,
packing/ monitoring conditions, etc., or when the risk source itself is highly reactive.
The major risk sources of the Fukushima Daiichi NPS are listed in Table 1, and Fig. 4 shows therisk level in each risk source as at the end of March 2023. In addition, Fig. 5 shows the risk level ofthe Fukushima Daiichi NPS and their changes over time as the sum of these risk sources.

19

In Fig. 4, Hazard Potential and Requiring Level for Safety Management are reviewed based on
the radioactivity levels and management status of each risk source as at the end of March 2023.
In particular, the most notable changes since the end of March 2022 include the transfer of Hazard
Potential level of “ALPS slurry (to be transferred to other HICs)” to 'ALPS slurry' resulting from theprogress of the transfer of ALPS slurry stored in HICs that exceeded the standard for integrated
absorbed dose, and a review of the Requiring Level for Safety Management for “contaminatedstructures in buildings, etc.” considering the retention of hydrogen that entered into the system
connected to the PCV at the accident. Regarding the latter, as a result of piping integrity
assessment under the assumption that a hydrogen explosion should occur, Requiring Level for
Safety Management were increased based on the fact that the S/C of Unit 3 and the high-pressure
coolant injection system (hereinafter referred to as 'HPCI') exceeded the elastic deformation range.
However, the evaluation is based on conditions that do not take into account the attenuation of thepressure wave from the hydrogen explosion caused by the contained water in S/C. It is unlikelythat the S/C will immediately leak water from these systems, even if the elastic deformation range
is exceeded, it must undergo plastic deformation to rupture 3 . Because the PCV internal
investigation of Unit 1 revealed the partial loss of concrete in pedestals, TEPCO will evaluate theeffects on the Requiring Level for Safety Management of fuel debris and contaminated structuresin buildings in the future, referring to the ongoing seismic evaluation of pedestals.
In the Mid-and Long-term Roadmap, management of these risk sources is broadly classified into
the following three major categories. They are prioritized and the most appropriate measures arebeing taken.
①

Relatively high risks given high priority (stagnant water in buildings and fuel in SFPs)②

Immediate risk unlikely, but risk may grow when handling with haste (fuel debris), and③

Increased risk unlikely in the future, but appropriate decommissioning efforts are required(solid waste such as sludge generated by the decontamination device).

In Fig.4, above ① is represented in pink, ② in yellow, and ③ in green, with the risk sources inthe “sufficiently stable management” region (in pale blue area) are shown in light blue 4 . In
considering the station-wide risk reduction strategy for the Fukushima Daiichi NPS, the abovementioned SED is a quantitative indicator of risks attributable to radioactive materials at a certain
time, and is an effective method for prioritizing risk sources for risk reduction. In considering risk
reduction strategies for the Fukushima Daiichi NPP as a whole, the SED described above quantifies
the risk caused by radioactive materials over a certain time cross-section and is an effective method
3

Tokyo Electric Power Company Holdings Inc., “Response based on the hydrogen retention event at the Unit 1
RCW (Evaluation of the impact of hydrogen retention event)”, The 10th Technical meeting on the review of theimplementation plan for specific nuclear facilities, Material 2-1, June 5, 20231
4
In Fig. 4, for the risk level that the major risk sources at the Fukushima Daiichi NPS, the “sufficiently stable
management” region” is defined to encompass Likelihood of Occurring of risk sources stored in facilities thatwere safely designed and used before the accident and were not affected by the accident, such as theCommon Spent Fuel Storage Pool and Dry Cask Temporary Custody Facility, and in facilities designed for longterm storage after the accident, such as sorption vessels..

20

for determining the priority of measures for risk sources. Major risk sources identified at the
Fukushima Daiichi NPS are shown in Table 1. In addition, the overall decommissioning work overthe long term includes waste that existed before the accident and the risk sources that have low
hazard potential but are not adequately controlled in a stable manner. These issues have also beenpresented since the Technical Strategic Plan 2019. In particular, regarding the facilities containing
risk sources that were not expressly considered before, investigations and examinations are being
conducted in consideration of external events such as earthquakes, tsunamis, and rainwater. Once
information on the risk sources has been identified through investigation and review, those thathave been determined to be prioritized and addressed in the same manner as major risk sources
will be evaluated for risk levels in the future. (Attachment 6).
As events that were not anticipated have occurred during the long period of the decommissioning
work, it is important to identify unexpected risks. Although it is not easy to identify such risks, whenan unexpected event occurs, analyzing the event to clarify causes that had not been anticipated
before provides a clue for risk identification.
At the event of total-β contamination leakage in the rubble temporary storage area5 reported on
March 25, 2021, leakage of radioactive materials occurred from a container whose contents were
not identified. It has so far been assumed that solid content such as rubble would not immediatelytransfer radioactive materials to the environment due to container damage. However, subsequent
analysis suggested that corrosion of the inner surface of the container caused leakage6. In light ofthis event, however, it is important for risk identification to understand physicochemical state andits changes over time, in addition to the location of the risk sources and radioactivity. At the time ofthe earthquake on February 13, 20217, with its epicenter off the coast of Fukushima Prefecture,
lowering of the PCV water levels at Units 1 and 3, and sliding of tanks on site exceeding the sliding
amount evaluated at the time of tank installation were observed. At the time of the earthquake on
March 16, 2022, with its epicenter off the coast of Fukushima Prefecture, a lowering of the PCV
water levels at Units 1 and 3 was observed and the over-turning of containers in the temporarystorage area was confirmed8. For the PCVs for which the current state is not well-understood,
understanding the damage condition by internal investigation and assessment of the situation at
the accident, and estimation of aging by monitoring/evaluation are useful for risk identification.
Regarding external events such as natural disasters, it is necessary to thoroughly evaluate in

5

Tokyo Electric Power Company Holdings Inc., “Report on the accident event of the drainage at the shallow draft
wharf and storage management of rubble,” study group on monitoring and assessment of specified nuclear
facilities meeting (90th), Material 4, April 19, 2021
6
Tokyo Electric Power Company Holdings Inc., “Judgment of Item 10, Article 18 of the 1F Regulation (An event of
a high activity alert on the PSF monitor at the shallow draft wharf drainage),” Meeting of the Secretariat of theTeam for Countermeasures for Decommissioning and Contaminated Water/Treated Water (90th), Material 3-6,
May 27, 2021
7
Tokyo Electric Power Company Holdings Inc., “Additional system inspection and seismic evaluation in responseto the earthquake on February 13 at the Fukushima Daiichi Nuclear Power Station,” study group on monitoring
and assessment of specified nuclear facilities meeting (90th), Material 5-1-3, May 19, 2021
8
Tokyo Electric Power Company Holdings Inc., “Condition of the Fukushima Daiichi Nuclear Power Station after
the earthquake on March 16,” study group on monitoring and assessment of specified nuclear facilities meeting(the 99th), Material 1-1, April 18, 2022

21

advance the consequences of and the necessity of countermeasures against beyond-design-basis
events in existing/new systems.
Although none of the above events resulted in significant consequences, it is important tocarefully analyze the events using methods such as root cause analyses, and to identify risks that
had not been anticipated to in order help prevent the occurrence of significant consequences. For
this purpose, TEPCO needs to make efforts to learn from the unexpected events as describedabove.

Table 1 Major risk sources at the Fukushima Daiichi NPS
Fuel debris
Spent fuelContaminatedwater, etc.

Fuel in SFPs
Fuel in the Common
Spent Fuel Storage Pool
Fuel in dry casks

Fuel debris in RPVs/PCVs in Units 1 to 3
Fuel assemblies stored in the spent fuel pools (SFPs) in Units 1 and 2
Fuel assemblies stored in the Common Spent Fuel Storage Pool
Fuel assemblies stored in dry casks

Stagnant water in

Contaminated water accumulated in the reactor buildings of Units 1 tobuildings

3, process main building and high-temperature incinerator building,and sludge containing α-nuclides at the bottom of buildings of Units 1
to 3

Zeolite sandbags

Zeolite, etc. in sandbags placed on the basement floors of the process
main building and high-temperature incinerator building

Secondarywaste
generated bywater
treatment

Stored water in welded

Strontium-treated water and ALPS-treated water, etc. stored in welded

tanks

tanks

Residual water inConcentrated saltwater and sludge containing α-nuclides left at theflanged tanks

bottom of flanged tanks

Waste sorption vessels,

Spent sorption vessels, etc. generated from various contaminatedetc.

water treatment systems such as a cesium sorption apparatus

ALPS slurry

Slurry and waste absorbents generated during treatment by the multinuclide removal equipment and added multi-nuclide removal
equipment, and stored in high integrity containers (HIC)

ALPS slurry

ALPS slurry stored in HICs whose accumulated absorbed doses(to be transferred to

exceeded the criterion value of 5,000kGy (accumulated absorbed

other HIC)

dose with confirmed HIC’s structural integrity against drop) or
evaluated to be close to the criterion value among the HICs affectedby beta irradiation, which are planned to be transferred to other HICs.

Sludge generated at the

Flocculated

decontamination device

decontamination systemsludgeConcentrated liquid

Concentrated liquid waste generated by evaporative concentration ofwaste, etc.

concentrated

salt

generated

water

with

duringfurthertheoperation

volumeofreduction

thebyconcentration, and carbonate slurry collected from the concentrated
Rubble, etc.

Solid waste storage
facility
Soil-covered temporarystorage, etc.
Outdoor storage, etc.

liquid waste
Rubble (30 mSv/h and above) stored in the solid waste storage facility
Rubble stored in the soil-covered temporary storage facility andcontainers (1-30 mSv/h), fallen trees stored in the temporary storage
pool
Rubble stored in outdoor sheet-covered storage (0.1-1 mSv/h), rubble
stored in outdoor storage (below 0.1 mSv/h), fallen trees stored in
outdoor storage

22

Contaminated structures, etc., in thebuildings

Structures, pipes, components, and other items (shield plugs, standby
gas treatment system pipes, etc.) inside the reactor buildings andPCVs/RPVs that are contaminated with radioactive materials
dispersed due to the accident; and activated materials generated fromoperation before the accident

The Technical Strategic Plan 2023
Region of sufficiently
stable management

Region of sufficiently
stable management

Hazard Potential (logarithmic scale)(March 2023)

Fuels incommonpool

Hazard Potential (logarithmic scale)(Reference)The Technical Strategic Plan 2022

Fuel debris

Contaminatedstructures in bldgs.

Unit 1
ALPS Unit 3
slurryUnit 2

Fuels indry casks

Rubble instoragefacility

Waste
absorption
Fuels incolumns Waste Unit 2
SFPs
sludgeConcentrated
ALPSUnit 1
liquid waste,slurryetc. (to be transferred to other HICs)
Stagnant water inbuildings
Zeolitesandbags
Stored waterin welded tanks Residual waterin flanged tanks
Color-code for the
Soil coveredrisk sources based
temporarystorage, etc.
on the Mid-andOutdoor
storage, etc.

Long-term
Roadmap *Fuels indry casks

Rubble instoragefacility(March 2022)

Fuel debris

Contaminatedstructures in bldgs. Unit 1
ALPS Unit 3
slurryUnit 2
Waste
Unit 2 Fuels inabsorption
Waste
SFPs
columnssludgeConcentrated
ALPS Unit 1
liquid waste,slurryetc. (to be transferred to other HICs)

Stored waterin welded tanks

Zeolitesandbags

Stagnant waterin bldgs

Residual waterin flanged tanks

Soil covered
temporarystorage, etc.
Outdoorstorage, etc.

Requiring Level for Safety Management(logarithmic scale)Requiring Level for Safety Management(logarithmic scale)*

Fuels incommonpool

Risk sources that are “relatively high risks given high priority” are shown in pink, those that are “immediaterisk unlikely, but risk may grow when handling with haste” are shown in yellow, those that are “increased risk
unlikely in the future, but appropriate decommissioning efforts are required” are shown in green, and thosethat are in the “sufficiently stable management” region are shown in light blue.
The red letters present risk sources that have changed significantly from the evaluation of the TechnicalStrategic Plan 2022 (as of March 2022), the origin of the arrow indicates the location reported in the TechnicalStrategic Plan 2022. ALPS slurry (to be transferred to other HICs) was moving downward because Hazard
Potential of shifted ALPS slurry (green) has decreased as the progress of the transfer operation. Note that
there is little variation in the ALPS slurry (green) on a logarithmic scale, since the shifted percentage of the
Hazard Potential of ALPS slurry (green) to the original ALPS slurry (green) is small. For the “contaminatedstructure in buildings”, Requiring Level for Safety Management increased, reflecting the retaining hydrogenthat flowed into the system connected to the PCV at the accident.

Fig. 4 Risk levels posed by major risk sources at the Fukushima Daiichi NPS

23

0

1

2

3

4

5

6

7

8

Risk level (Linear scale)

Risk level(Logarithmic scale)

Risk level (Linear scale)

Fuel removal from
Unit 4 SPF started

9 10 11 12

Years after the accident

Mid-and-Long-term
Roadmap Phase 2

Mid-and-Long-term
Roadmap Phase 1

Risk level in the rightgraph is multiplied by 10

0.5

1
1.5
2
Year after the accident

Fuel debris
燃料デブリ

*1

*2

プール内燃料
Fuel in SFPs

2.5

3

4

5

6
7
8
9
10
Year after the accident

燃料デブリ
Fuel debris

Contaminated
汚染水等
water, etc.

プール内燃料
Fuel in SFPs

11

12

Contaminated water, etc.
汚染水等

The risk level was high due to fuel debris right after the accident, however, it became significantly lower because thehazard potential was decreased a lot by attenuation of the radioactive materials inside the fuel debris during the one
year after the accident.
In the evaluation eight years after the accident, as a result of incorporating the insight that the rise in the watertemperature after cooling shutdown was slower than expected, the risk associated with fuel in SFPs is lower thanpreviously estimated, because the time margin before the risk becomes apparent is increased.

Fig. 5 Reduction of risks present in the Fukushima Daiichi NPS
2.2.2 Risk reduction strategy
2.2.2.1 Interim targets of the risk reduction strategy
As indicated by Formula 1, measures to reduce the risk level assessed by SED include reducing
the impact of radioactive materials on the public presented by “Hazard Potential” and reducing“Requiring Level for Safety Management”.
Hazard Potential can be expressed as the product of the Inventory, which is the amount ofradioactive materials contained in the risk source, and factors related to the ease of releasedepending on differences in the properties of the risk sources, such as gas, liquid and solid, andthe time allowable until the risk becomes apparent in the event of loss of safety functions. Examplesof reduction of the “Hazard Potential” include the decrease in inventory and decay heat associatedwith radioactive decay, and changing the form of liquid and gas into a less moveable form. Treating
contaminated water to change it into secondary waste is an example of form change.
“Requiring Level for Safety Management” can be expressed as the product of two factors: one
pertaining to the sufficiency of the containment function of the facility that contains the risk sources(containment performance), and the other pertaining to the long-term stability and handleability of
the risk source, such as its characteristics (degradation and activity level), packing, and monitoring
conditions. As a method to reduce the likelihood of an event expressed in “Requiring Level for24

Safety Management”, the first is to improve the containment performance of the facilities that
contain risk sources. Measures to improve the containment performance include transferring therisk sources to more sound facilities on higher ground that are less susceptible to tsunamis, as well
as repairing damaged parts of existing storage facilities. The second is to improve the long-term
stability by reducing uncertainty in handling risk sources and by enabling long-term and stable
management based on the characteristics of risk sources. To this end, it is important to obtainsufficient information by investigating the distribution of risk sources, identifying theircharacterization through analysis and measurement, and improving monitoring conditions, and toreflect this information appropriately in methods of collection and storage according to thecharacteristics of risk sources. Such efforts to reduce uncertainty in the handling of risk sources
also help to keep the temporary increase in risk levels associated with risk reduction measures,such as source recovery operation, to a low level.
Of the various risk reduction measures, reduction of in the likelihood of occurrence of an event
expressed by this “Requiring Level for Safety Management” is generally considered to be easily
realized from an engineering perspective. Consequently, the interim target of the risk reduction
strategy in decommissioning of the Fukushima Daiichi NPS, which is implemented under the basic
policy of “to continuously and quickly reduce the risks arising from the radioactive materials causedby the accident and that do not exist in normal nuclear power plants” (refer to Section 2.1), is tobring “Requiring Level for Safety Management” into the “Sufficiently stable management” region(the pale blue area) as shown in Fig. 4 with the above measures. Even within “Sufficiently stable
management” region, to further lower “Requiring Level for Safety Management” leads to achieve astate that secures passive safety, i.e., a state in which dynamic measures such as water injection
or nitrogen injection are not required to maintain a stable state.
Fig. 6 shows the process to bring major risk sources into the “Sufficiently stable management”
region as the interim target, and representing the decommissioning work progress along thisprocess.
Fig. 6(a) shows the outline flow of the decommissioning work to date and the future plans torepresent the overall decommissioning process in a comprehensive way. Using the coloring in Fig.
4 to indicate the risk level of each risk source, Fig. 6(a) also shows the flow of risk reduction. Basedon this flow, it is possible to visualize how the risk sources have changed compared with the timeof the accident by applying it to fuel debris, spent fuel, and Cs-137 released during the accident.
The number of spent fuel assemblies as an indicator to make the work progress easier to see in
Fig. 6(b), and for Cs-137, the estimated radioactivity (Bq) common to various risk sources as anindicator in Fig. 6(c) both indicate the progress of the decommissioning work by representing thestatus of transition to the “Sufficiently stable management” region in a pie chart format. Fig. 6(b)has made no progress since Technical Strategic Plan 2022. Fig. 6(c) incorporates theincrease/decrease in Cs-137 due to the decrease in the stagnant water in buildings, the increasein waste sorption vessels, the increase in the storage volume in solid waste storage, and theincrease of attenuation in FY 2022. Fig. 6(d) shows the transition of Requiring Level for Safety25Management corresponding to risk sources and their treatment process indicated in the flow
graphically by risk source category. The Requiring Level for Safety Management shown is divided
into two components, one for containment performance and the other for long-term stability, whichcorrespond to the methods for reducing the Requiring Level for Safety Management describedabove9. This will help determine whether containment performance or long-term stability measures
should be prioritized to bring the risk source into the “Sufficiently stable management” region. In
addition, in the processing process that is the scope of a future or ongoing study in the flow, theblue and orange arrows in Fig. 6 (d) indicate what needs to be improved to bring the Requiring
Level for Safety Management into the Sufficiently Stable Management region (in the pale blue areain the graphs). The containment performance related to the Requiring Level for Safety Managementof retrieved fuel debris in Fig. 6(d -1) and secondary waste generated by water treatment after
stabilization treatment in Fig. 6(d -4) is equivalent to that of facilities, such as dry casks and solid
waste storage facilities. The long-term stability is assumed to be in a state where appropriate
storage and management can be achieved, considering the reactivity of the risk sources. This is
an assumption at present, and it may change depending on the progress of future studies.
Specific risk reduction strategies for each source are detailed in Chapter 3.

9Of the Requiring Level for Safety Management indicators shown in Attachment 5, the FD-related components
are mapped to containment performance, and the WUD-related components to long-term stability. In Fig. 6(d),the Likelihood of Occurring shown is divided into two components, one for containment performance and theother for long-term stability, by using the logarithm of the Likelihood of Occurring of each risk source (FD ×
WUD) 4. The heights of the blue and orange bars represent the logarithm of how many times the product ismultiplied by the component related to containment performance and other component related to long-term
stability when multiplying the Hazard Potential by Likelihood of Occurring. The representative risk source isindicated if the risk source consists of multiple risk sources.

26Color-coding is the same as in Fig. 3

Arrows show the shifting/processing flow of risk sources.
Dotted lines indicate the scope of future studies and being studied.
Category

Risk source

Sufficiently stable
management condition

Processing

Reducing risks by processing

Fuel debris

Fuel debris inside
PCV

Retrieve

Temporary storage
for fuel debris

Storage for fuel debris

Spent fuelSpent fuel pool

RemoveCommon Spent
Fuel Storage PoolDry cask

Purify Cs/Sr

Stored water inwelded tanks(Sr-treated water)

Removemultinuclide

Water
filtering*１※2
Cs-137
released during
the accident

Stagnant water inbuildings

Residual water inflanged tanks

SludgeFiltered water
Concentrateby evaporation(Operation stopped)*１

Stored water inwelded tanks(ALPS-treated water)*2
Concentrated liquid
waste, etc.

Dehydrate/stabilize

ALPS slurry

Solid waste
storage facility(Incl. ALPS slurry to be（高線量HIC含む）
transferred
to other HICs)

Temporary storageof used columns(Sorption columns)

Decontaminate(Operation stopped)

Waste sludge
Collect/stabilize
Zeolite sandbags

Contaminatedstructures in bldgs

Dismantle/
RemoveOutdoor storage, etc.

Reducevolume, etc.

Rubbles, Felled trees, etc.

*１ Connect the arrow from
“Remove multi-nuclide”*２ Connect the arrow from
“Water filtering”

Soil-covered, etc.

Discharge into theenvironment(a) Risk reduction process
Residual water in the buildings
Additional
事故時に放出されたCs-137
and ALPS slurryattenuation(FY2022)(to be transferred to other HICs)

AttenuatedSpent fuelstored in SFP

Environmental
discharge

ContaminatedStructures inbuildings, etc.

Solid waste
storage facility

Fuel transported toCommon Spent Fuel
Storage Pool after theaccident

Sorptioncolumns, etc.
Zeolite sandbags, etc.

*New fuel not included(b) Number of fuel assemblies of spent fuel(Units 1 to 4)(c) Radioactivity of Cs-137 released at the accident(Units 1 to 3)

Fig. 6 Risk reduction process for major risk sources and the progress (as of March 2023) (1/2)

27

4

5

6

7

1

8

Suppression of criticality

Retrieval

①

②

③

2

3

(Logarithmic scale)3

Requiring Level for Safety Management

2(Logarithmic scale)Requiring Level for Safety Management

1

4

5

①

7

8

Transfer to Dry casks

Retrieval

④

6

②

③

④

* The difference in the components related to thecontainment performance in ① to ③ is due to thedifference in the multiplicity of the components withdiffusion suppression function.
* Requiring Level for Safety Management of ④ is acurrent assumption and may change depending on
the progress of future studies.

(d-1) Fuel debris
Sludge (To solid waste storage)
4

5

①

②

③

④

⑤

⑥

② Residual water in flanged tanks③ Sorption vessels⑦ ALPS slurry (HIC to be transferred)①④ Stored water in welded tanks(Sr-treated water)*Disposal of secondary waste generated by contaminated water treatment of ③ and ⑥ is shownin (d-4).

③

5

6

7

8

②

③

④

⑤

①

Zeolite sandbags⑤②

Sorption vessels⑥③

Concentrated liquid waste etc.

④

ALPS slurry⑥

Sludge generated at thedecontamination device
Solid waste storage facility* Requiring Level for Safety Management of ④ is acurrent assumption and may change depending on the
progress of future studies.

④

Legend＜Likelihood of Occurring＞(Logarithmic scale)Requiring Level for Safety Management②4(d-4) Secondary waste generated by water
treatment(d-3) Contaminated water①

3

Transferred to solid
waste storage⑦⑤ Stored water in welded tanks(ALPS-treated water)⑥ ALPS slurry

2

Stabilization

HIC replacement(Slurry to betransferred)

Multinuclide
removal① Stagnant water in buildings

1

6
7
Exceeded
the standard
for integrated absorbed
dose of HIC(Logarithmic scale)3

Cs・Sr treatment(Logarithmic scale)Requiring Level for Safety Management

2

Requiring Level for Safety Management

Filtered water1(d-2) Spent fuelComponents related to containment in Likelihood of Occurring
Demolition/removal

Components of long-term stability in Likelihood of Occurring
Region of sufficiently stable management

Transferred to solid waste
storage facility

Lower limit of Likelihood of occurring (calculated from thelower limit of components related to containment and thelong-term stability)

Purging Residual Hydrogen
①

②

③

①

Soil covered②

Outdoor storage③

Contaminated structures in the buildings④

Solid waste storage facility

Lower limit of components related to containment④＜Processing process＞
Processing in progressFuture processing required (improved containment)(d-5) Rubbles, Contaminated structures inFuture processing required (securing long-term stability)
buildings etc.
(d) Changes in Requiring Level for Safety Management for major risk sources

Fig. 6 Risk reduction process for major risk sources and the progress (as of March 2023) (2/2)

28

2.2.2.2 Basic approach to risk reduction
The decommissioning of the Fukushima Daiichi NPS is a project that involves considerable
uncertainties. To date, the internal status of PCVs of Units 1 to 3 has been estimated to some extent
through simulation of the accident development process, estimation of the places with fuel debris
by muon-based fuel debris detection technology, placement of investigation equipment into thePCVs, radiation dose measurement and video photographing in the buildings, and other means.
However, there are still significant uncertainties. Eliminating these uncertainties requires many
resources and, in particular, a considerable amount of time. In order to realize prompt reduction ofrisk, it is necessary to promote the decommissioning work through a flexible and prompt approach,based on the directions determined with previously obtained experience and knowledge, and withexperiment and analysis-based simulation, making safety the top priority, even though uncertainties
remain to a certain extent.
Regarding the perspective from which these comprehensive decisions will be made, NDF
summarizes the following five guiding principles:(Five guiding principles) SafeReduce the risks posed by radioactive materials and ensure work safety(Issues such as containment of radioactive materials [environmental impact],
exposure of workers to radiation, assessment of the effect of risk reduction)
 Proven

Highly reliable and flexible technologies(Issues such as conformity to requirements, effectiveness and flexibility
against uncertainty)

 Efficient

Use resources effectively (e.g., people, things, money and space)(Issues such as reduction of waste generation, cost, efficiency, securing
necessary work area and site) Timely

Be conscious of time
(Issues such as the early start of fuel debris retrieval and estimation of timerequired for fuel debris retrieval) Field-oriented Comprehensive three-reality policy by checking actual site, actual things,
and actual situation(Issues such as workability including environment-friendliness, accessibility,
and operability, and maintainability including ease of maintenance andtroubleshooting)

In applying the five guiding principles to the actual site, it is important to proceed with thedecommissioning operation after greatly emphasizing safety assurance for the purpose ofprotecting human beings and the environment from the radioactive materials associated with theoperations, thoroughly conducting radiological impact evaluations, and taking appropriate
radioprotective measures (Safe).
In the decommissioning of the Fukushima Daiichi NPS, because the public risk level is risingwith time as the degradation of facilities damaged by the accident progresses, controlling this risk29to be as low as reasonably achievable (Proven, Efficient) as promptly as possible (Timely) in lightof the situation at the site, and proceeding with the decommissioning in a reliable manner by
feasible ways in the harshest on-site state (Field-oriented) will lead to ensuring safety in themedium-to-long-term.
As for the result judged based on these guiding principles, it is also important to work todisseminate information carefully so that the results will be widely accepted by society.

2.3 Approach to ensuring safety during decommissioning
2.3.1 Basic policy for ensuring safety based on the characteristics of Fukushima Daiichi
NPS
Decommissioning of the Fukushima Daiichi NPS containing the reactors involved in the accident
is an unprecedented activity that takes place in a peculiar environment different from that of anormal reactor, and therefore, to ensure safety, the following characteristics (peculiarities)
regarding safety should be fully recognized:
 A large amount of radioactive material (including α-nuclides that have a significant impact

in internal exposure) is in an unsealed state, as well as in unusual (atypical) and various
forms Barriers for containing radioactive materials, such as reactor buildings and PCVs, areincomplete Significant uncertainties exist regarding the state of these radioactive materials andcontainment barriers, etc.
 Difficulty in accessing the site and installing instrumentation devices to obtain on-site

information due to constraints such as high radiation levels on site
 Since the current level of radiation is high and further degradation of containment barriers

is a concern, it is necessary to take measures in consideration of the time axis
Therefore, in proceeding with decommissioning work, TEPCO, as the decommissioning project
executor, needs to consider the following points with particular attention, based on the five guiding
principles.
First, with regard to “safe”, a large amount of atypical, unsealed radioactive material will behandled in an incomplete containment state in a situation where there are large uncertainties in theradioactive material and containment barrier conditions, and where on-site access andinstrumentation to reduce these uncertainties are also restricted. Therefore, it is necessary toassume a wide range of possibilities (cases) and to check that it is possible to ensure safety forthem as the starting point for all considerations. At the same time, with regard to “safe”, it isimportant not to prolong the work period considering the risks over the entire work period, and it isnecessary to avoid excessive safety measures out of proportion to the risks and to take sensible

30

safety measures (ALARP10). It is important that this perspective on “safety” (the safety perspective)
is reflected in the consideration of decommissioning work.
Second, with regard to “field-oriented”,
 The on-site environment is unique, with high radiation levels, etc., and attention must be paid
to the on-site feasibility when constructing/taking safety measures, and Response by design alone is limited due to large uncertainties.
It is essential to reflect the information obtained from the actual site in engineering appropriately.
In order to reliably implement unprecedented engineering such as fuel debris retrieval, it isimportant to value the viewpoints and senses of people and organizations (operators) who are
directly involved in the actual site work (operation, maintenance, radiation control, instrumentation,
analysis, etc.) and familiar with the site, and to respect the viewpoints and judgments that are
directly addressed at the site (the operator’s perspective). Moreover, in promoting long-term
decommissioning, it is necessary to maintain and strengthen the operator's viewpoint andsensibility, TEPCO itself should take over the operator's perspective. To this end, TEPCO needs tomake efforts that are constantly aware of the site throughout the decommissioning work, such as
inviting outside experts, people with experience in difficult tasks, and engineers with an 'operator's
perspective' such as those who have left the frontline, and asking for guidance and education.

In the actual study of the decommissioning work, TEPCO, as the decommissioning project
executor, should define the “requirements” to satisfy regulatory demands for the work, and should
consider specific safety measures to achieve them. In doing so, it is essential to apply the safety
perspective and the operator’s perspective to handling the characteristics (peculiarities) of
decommissioning the Fukushima Daiichi NPS.
In this decommissioning work with significant uncertainties, it is frequently difficult to uniquely
define requirements and the equipment/operational specifications that will satisfy thoserequirements. Even in such cases, the decommissioning work should be carried out flexibly andpromptly by verifying and improving the selected, specifical safety measures with the “preliminary
implementation and utilization of the obtained information in the latter stages” and “iteration-based11
engineering” as described later.
This section first calls for promulgation of the “Safety First” by operators. Next, in terms of thecharacteristics of Fukushima Daiichi NPS, the section describes the importance of the safetyassurance measures based on safety assessment which includes the operator’s perspective, andthe operator’s perspective that should be incorporated at multiple levels in the safety assurance

10

Abbreviation of As Low As Reasonably Practicable. This is the principle that the radiological impact must be as
low as reasonably achievable.
11
A method of gradually increasing the level of completion of engineering by finding the next result based on acertain result and repeating this cycle.

31

process. Lastly, the section refers to the importance of ALARP judgment. Moreover, the relationshipbetween these points and aforementioned Five guiding principles of risk reduction will be discussed.
2.3.1.1 Promulgating the “Safety First” principle that safety perspective comes first
The use of any method or device is basically unacceptable unless the safety perspective issufficiently reflected in them. Therefore, it is important that all who work in the processes (projects)
leading up to the use of methods and devices on the site, keep the safety perspective first in mind
as they engage in their work (hereinafter referred to as “safety first”). The specific application of thegeneral “safety first” principle in the projects means, “Conducting extensive assessments on safety
matters associated with methods and devices when reviewing any project and, upon verifying thatnecessary and sufficient levels of safety have been ensured, taking into account factors such astechnical reliability, reasonableness, speed, and actual site applicability in a comprehensive
manner to decide which methods or devices to use, and which safety measures to apply
consequently”.
Since the accident at Fukushima Daiichi NPS, leaders of nuclear operations at TEPCO have
stepped up to the plate and continue to work hard to raise awareness on the issue of nuclear safety,
such as through dialogue amongst themselves, as well as through messages that they
communicate to other TEPCO employees. In order to thoroughly disseminate the safety-firstprinciple to all persons involved in the projects including on-site workers, the attitude of top
management (the approach to reiterating the special nature of nuclear safety and that special
attention is needed accordingly) is important.
The above concepts can be organized on the basis of the Five Guiding Principles, and it can besaid that “safety” is the most important principle in proceeding with a project, and the other four
principles should be considered next to “Safe” as a safety-first principle. However, as described in
2.3.1.3, in the decommissioning operation of the Fukushima Daiichi NPS, “Field-oriented” is aprinciple that should function in a complementary manner to “Safe”.
2.3.1.2 Optimization of judgement with a safety assessment as its basis and ensuring
timeliness in decommissioning
In decommissioning work that is technically difficult, has significant uncertainties, and handles alarge amount of radioactive materials, such as fuel debris retrieval, it must be conducted with a“safety-first” mindset, in which it is most important to ensure the safety by taking appropriate
measures. On that mindset, by using a well-reviewed safety assessment as the basis for making
decisions on safety measures, resources can be allocated neither sparingly nor excessively, andnecessary, sufficient, and feasible safety measures can be realized (Proven and Efficient).
In addition, the importance of making progress in the decommissioning work without delay canbe mentioned as the safety perspective unique to the decommissioning of Fukushima Daiichi NPS.
Considering the high radiological impact that has already been observed, and danger ofprogressive degradation of containment barriers, etc., making progress in the decommissioning

32

work without delay will have great significance for ensuring the safety of the entire decommissioning
process (Timely).
The above concepts can be organized on the basis of the Five Guiding Principles, which are that
“Proven” and “Efficient” safety measures can be realized by making judgments through sufficient
safety assessment based on the premise of safety first, and that this will lead to “Timely” progressin decommissioning work.
2.3.1.3 Ensuring safety by incorporating “the operator’s perspective”
It is essential to reflect the information obtained from the actual site in the engineering work
appropriately, because it is necessary to pay attention to the on-site feasibility whenconstructing/implementing safety measures, and there is a limit to be addressed by design alone
due to significant uncertainties. In other words, to make safety measures truly effective, it isnecessary to respect the viewpoints and judgments of people and organizations that are familiar
with the actual site and are responsible for practical operations, maintenance, radiation control,
instrumentation, analysis, or other tasks at the site (operator's perspective). The operator's
perspective is also important from the following points, which differ from those of normal reactors.
・Complementation of design by operations, including operating controls:：
Since there is a limit to addressing all situations by design alone due to significant
uncertainties, it is effective to supplement the design with operator response and on-site
operation, and improve safety collectively with operation. For example, information which
contributes to criticality safety, (the composition of fuel debris and subcriticality, etc.) has a highmeasurement uncertainty due to difficulties in the measurement on site. Even in such anenvironment, it is necessary to proceed with fuel debris retrieval with a certain operational scale,
while ensuring safety in criticality. To this end, fuel debris retrieval operators should be aware of
the signs of criticality that change with each work step as significant fluctuations of measured
value. Even if cutting and other work of sufficient magnitude to cause noise, identifiable andsignificant fluctuations in measured values are performed with relatively small subcriticality, it ispossible to take action by maintaining subcriticality or identifying signs of criticality throughoperations based on design and actual measurement values. In other words, as describedabove, in environments with significant uncertainties, the development of detection technologies
to enable operational responses will become even more important.

・Utilization of information in design obtained through monitoring, analysis, etc.:
To cope with significant uncertainties, information obtained from monitoring and analysis
through on-site operations will be utilized in designing in the next phase to make it more
appropriate.

・Consideration of time available for response to abnormality:
Although it is essential to take all possible measures to prevent progress of an abnormality,
on-site response as a precaution to prevent the occurrence of an abnormality is effective

33

considering the characteristics that the progress of abnormalities is moderate and there issufficient time to respond12。
2.3.1.4 ALARP judgment based on safety
For safety, there is a minimum level of safety standards that must be met before the relevant
retrieval method/equipment can be used. After satisfying this minimum level, what level of safety
achieved should be optimized between the safety level to be achieved and resource required(project cost, duration workers’ radiation dose, etc.) to determine the retrieval method/equipment
to be adopted. In the process of determination, it is important to decide retrieval methods/equipment to be adopted eventually through the cycle of “defining the safety standards (safety
perspective)”, “indicating the feasibility on-site (operators’ perspective)”, and “examining anddiscussing at projects (project management)” as shown in Fig.7. As shown in this figure, the safety
perspective and the operator’s perspective are not independent from each other. The ALARP
judgement made by the project based on the safety perspective will be linked to the decision of theretrieval method/equipment after going through the feasibility check based on the operator’s
perspective. The operator's perspective is essential to actually incorporate the safety perspective
into the site, and the judgment based on the safety perspective is needed to utilize the operator's
perspective.
The above concepts can be organized on the basis of the Five Guiding Principles, which are thesame as 2.3.1.3 in that “Safe” and “Field-oriented” should be complementary principles. The
concept is to ensure a minimum level of safety and to consider project perspectives such as“Proven”, “Efficient”, and “timely” as factors in ALARP decisions.

① Define the safety standards
to be achieved(Legal/regulatory requirements)

Set management
standards from theoperatorʼs perspective,
with a margin to safety
standards.
(Operatorʼs perspective)

Inform retrieval methods andequipment proposals② Examine and discuss
methods and equipment
to be adopted in the
project (ALARP)③ Examine feasibility onsite (by experts).
(Operatorʼs perspective)

Provide retrieval method andequipment options to meetproject operatorʼs targets.

④ Determine retrieval methods
and equipment at the project.

Inform availability(if possible)(Safety perspective)

Inform availability(if not possible)
Review management targets in some cases.

Fig. 7 ALARP centered on safety (conceptual diagram)

12

Since a long time has passed since the accident at the Fukushima Daiichi NPS, the intrinsic energy (decayheat) that drives dispersion of radioactive materials is small. Therefore, in general, abnormalities have thecharacteristic of progressing slowly so there is a large time available for response.

34

2.3.2 Preliminary implementation and utilization of the obtained information in the latterstagesThe on-site conditions at the Fukushima Daiichi NPS containing the reactors involved in theaccident includes considerable uncertainties. If a large-scale project such as fuel debris retrieval is
implemented based only with existing knowledge, assumptions of an extremely large safety margin
and wide range of technical options will be needed. Thus, extension of the work period or the riskof rework will be unavoidable. As a result, the feasibility or predictability of the entire project may
be reduced, leading to a delay in the entire decommissioning, a rise in the decommissioning cost,or increased radiation exposure of workers.
However, considering the environment with an already high radiation level, further deteriorationof containment barriers, and the possibility of future major natural events (such as earthquakes ortsunamis), it is necessary to immediately improve the state of such risks and reduce uncertainties.
Therefore, a “sequential type approach” is important where the whole operation is divided into
several stages, “operation at first stage” is implemented for which practical safety can be ensured,and then the information obtained there is utilized in the next stage. With this approach13, operation
proceeds with safety ensured through monitoring the condition inside reactor, restricting operational
actions and flexible on-site responses at each stage of the process14. The information obtained ateach stage of operation and testing is utilized in the design of subsequent stages. This approach
reduces uncertainties in the operations in subsequent stage as well as improve the reliability ofsafety assurance and rationalize design.
TEPCO should actively introduce an approach like this into actual engineering and project
management15.
As a related activity, though not a sequential type approach itself, TEPCO has been conducting
reactor water injection shutdown tests since FY 2019. One of the purposes of these tests is tocontribute to determining whether or not to terminate water injection in the future, which also takes
into account maintaining flexibility in selecting fuel debris retrieval methods. Knowledge on whether
or not to terminate water injection has been accumulated by identifying different risks (risingtemperature of fuel debris and the RPV bottom, increased dust scattering outside the PCV, and recriticality when resuming water injection), and by gradually extending the testing time while taking
certain risks. Based on these knowledge, TEPCO has decided to reduce the water injection amountfor Unit 2 while maintaining continuous water injection.
Hereafter, it is recommended to make it clear as a policy that the information to be gained throughon-site operation should be fully incorporated and accumulated as knowledge in consecutive
activities for ensuring safety. The examples are shown below.
13This is also used in the UK, for example, for the decommissioned facilities in Sellafield, and it is called Lead &Learn.
14
Some example measures include installing nuclear instrumentation to the extent feasible; limiting the amount ofdebris fabrication; and setting the value for managing radioactive dust concentration and regulating operations.
15
This is stated in the Decommissioning Implementation Plan (February 17, 2021, Tokyo Electric Power Company
Holdings Inc.), which summarizes the policies on implementing decommissioning at the Fukushima Daiichi
Nuclear Power Station. https://www.tepco.co.jp/press/release/2022/1693977_8712.html

35



Risk identification associated with hydrogen at the time of fuel debris retrieval: Testing to
reduce nitrogen supply and exhaust flow rate for an experimental purpose may help identify
the risk of leading to hydrogen accumulation and combustion, which contributes todetermining functions to ensure safety, such as the necessary amount of nitrogen supply,
and air volume and number of exhaust systems.

Basis for contributing to the design of water injection facilities during fuel debris retrieval:
Information, such as number of water injection pumps required during fuel debris retrieval,appropriate amount of water to be injected, changes in the cooling status of fuel debris due
to differences in water injection points, etc., will be obtained.

By accumulating successful/unsuccessful experience gained in the process of these sequential
approach as a track record, allowing gradual reduction in major uncertainties associated withdecommissioning work. It is important to combine this with uncertainty reduction measures, forexample, by sampling, and to reduce uncertainty. These efforts to reduce uncertainties will lead tosteady progress in decommissioning and help contribute to ensuring safety in decommissioning
the Fukushima Daiichi NPS from the perspective of risk reduction in the medium-and-long term.

2.3.3 Approach to address a temporary increase in risk level associated withdecommissioning operations
While the decommissioning work is striving for prompt risk reduction from a medium-and-longterm perspective, careful deliberation of the possibility that the performance of decommissioning
work may temporarily change the risk levels and may increase the radiation exposure of workers
is required. Executing the decommissioning work involves taking some action on the current
situation of the NPS, which is maintained in a state with a certain level of stability despite somerisks. Such risks may materialize, depending on the way action is taken. For example, accessing
the inside of the reactor to retrieve fuel debris will affect the current containment status, and thespecial operations and maintenance performed in the retrieval work will increase the exposure ofworkers involved in these activities.
The possibility of a temporary increase in the risk level and a rise in workers’ exposure arisingfrom such decommissioning work must be addressed by taking measures to prevent and restrict
them. In particular, as for the radiation safety of workers, it is imperative to limit the increase in therisk level during decommissioning as much as practicably possible by thorough preparations as
achieved through application of the concept of ALARP.
Note that the basic stance for promptly implementing the decommissioning must stand firm
because if the decommissioning work is delayed excessively, it means that existing major risks willremain over the long term and their risk levels may gradually rise as the buildings and facilities
deteriorate over time. Therefore, cautious and comprehensive decision making is required for early
implementation of decommissioning in consideration of many constraints such as time, cost, and36

worker’s exposure needed for relevant preparations and work, while giving priority to limiting therisks involved in the decommissioning work (Attachment 7).

The decommissioning of the Fukushima Daiichi NPS needs to be promoted with the broad
understanding of not only the government, NDF, TEPCO, and others, but also of a wide range of
people, including local residents. To this end, it is essential for them to fully understand the overallrisk reduction efforts described in this chapter and to gain their understanding of thedecommissioning project. In particular, it is important to establish a system for continuous risk
monitoring that is easy to understand for a wide range of people and to communicate to the public
how the decommissioning work will be conducted based on the risk reduction strategy, how thesafety of the decommissioning work will be ensured, and how the overall risk reduction of the site
is continuously progressing through the decommissioning work, and to disseminate theseinformation to society.
In addition to sharing the status of risks regard to the decommissioning of the Fukushima Daiichi
NPS through the Technical Strategic Plan on a constant basis, NDF is considering providing therisk reduction process along with the progress of the decommissioning work described in 2.2.2.1.
TEPCO also needs to develop a mechanism to identify risks for the entire site and become awareof the need to take action to communicate the status of risk reduction to society in a proactive
manner.

37

3. Technological strategies toward the decommissioning of the
Fukushima Daiichi NPS
3.1 Fuel debris retrieval
3.1.1 Target(1) Retrieve fuel debris safely after thorough and careful preparations, and bring it to a state ofstable storage that is fully managed.
(2) The trial retrieval process in Unit 2 is under review to improve work safety and reliability during
retrieval, and trial retrieval will begin in late FY 2023. Continue the series of operations,
including the gradual expansion of fuel debris retrieval, to acquire the knowledge andexperience necessary for further expansion of fuel debris retrieval in scale (for the fuel debris
targeted for retrieval, see Attachment 8).
(3) With regard to the further expansion of fuel debris retrieval in scale, consideration will be given
to the methods including those for containing, transferring, and storing of fuel debris, throughthe assessment of fuel debris retrieval in Unit 2, internal investigations, research anddevelopment, and the on-site environmental improvement, etc.
3.1.2 Progress
The progress on fuel debris retrieval in each unit is also shown below. Fig. 8 shows the estimated
fuel debris distribution, access route and surrounding structures of Units 1 to 3.
a. Unit 1
PCV internal investigations were performed from February 2022 to March 2023 using asubmersible boat-type access investigation vehicle (hereinafter referred to as “submersible ROV”),
which can be equipped with various measurement sensors. The submersible ROV is inserted into
the PCV through the PCV penetrating part X-2 (hereinafter referred to as “penetration X-2”) to
access the basement floor outside the pedestal (Fig. 9). Detailed visual observation, measurementof deposit thickness, detection and evaluation of deposit debris (neutron flux level, etc.), and 3D
mapping measurements of deposits were conducted outside the pedestal from February 2022.
Deposit sampling was also successful, and the plan is to analyze it in the future. In March 2023,
the investigation by inserting a submersible ROV into the pedestal succeeded for the first time. As
a result, much information was obtained, including the fact that there is missing concrete at thelower part of the pedestal, the condition of the deposits and fallen objects at the inner bottom of thepedestal, and the condition of the upper structures, such as the control rod drive (hereinafterreferred to as “CRD”) housings (Fig.10). The main findings are as follows.
(a)

Outside the pedestal, deposits are distributed over a wide area from the vicinity of thepedestal opening (worker access opening). They are relatively high near the pedestal
opening and become gradually lower as it approaches penetration X-2 through which thesubmersible ROV is inserted.

38

(b)

As for the deposits outside the pedestal, powdery and sludgy deposits are thin in general,
shelf-like deposits exist near the pedestal opening, and the inside is hollow.

(c)

Thermal neutron flux and Eu-154 were detected at all survey points outside the pedestal,and no correlation was observed between the distance from the pedestal opening and theheight of the deposit for these values. Therefore, it is presumed that materials released
from fuel debris (derived from fuel debris) exist extensively in the survey areas.

(d)There are deposits of nearly uniform height and some upper structures, such as CRD
housings, at the inner bottom of the pedestal.

(e)

A lump that appears to be solidified molten materials adheres to the upper CRD housings.

(f)

The vicinity of the worker access opening and almost the entire inner wall of the pedestal
have lost their lower concrete.

Following the discovery of the partial loss of concrete in the pedestal, based on the discussion
during the 12th NRA meeting on May 24, 2023, the NRA directed TEPCO, (1) with the assumptionthat the pedestal cannot be expected to provide support, to evaluate the impact of dust scatteredat the site boundary, including the case where the RPV sinks and the PCV has an opening
equivalent to the main steam pipe; (2) to consider possible countermeasures regardless of theevaluation results; and (3) to evaluate the structural impact on the RPV and the PCV in the eventof subsidence of the RPV due to loss of support functions16. In response to this directives in (1)and (2), TEPCO assumes that it is unlikely to cause large-scale damage based on the results ofthe strength evaluation of the pedestal, at the same time, TEPCO is evaluating the impact ofexternal exposure, supposing the pedestal’s RPV support function deteriorates to form a large
opening in the PCV. As a result of evaluating conditions inside the PCV by setting conservative
conditions, TEPCO considers that there is no significant risk of radiation exposure17. In addition,although it is not considered to pose a significant risk of radiation exposure, further safety measures
such as mobile response and enhancement of PCV containment function are being considered17.
These evaluations by TEPCO were reported by the NRA at the NRA Committee and approved on
the spot18. In response to directive (3), TEPCO conducted a strength evaluation assuming Ss900of the earthquake ground motion, and evaluated that the inner skirt of the RPV pedestal foundationand the stabilizer/the bulkhead of the pedestal superstructure could not be damaged on a large
scale because they could support seismic loads 19 . In response to this evaluation, the NRA

16

May 24, 2023, meeting minutes, interview on future actions based on the status of the Fukushima Daiichi
Nuclear Power Station Unit 1 pedestal
17
The 108th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, Material 21, “Status of response to the directives on future responses based on the situation of the Unit 1 pedestal”(TEPCO)18
The 24th Nuclear Regulation Authority Committee in FY 2023 “Material 2: Response to the situation of Unit 1
pedestal at the TEPCO’s Fukushima Daiichi Nuclear Power Station, (NRA).
19
The 109th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, Material 21, “Status of response to the directives on future responses based on the situation of the Unit 1 pedestal”(TEPCO)39

recognized that there are limitations to conducting evaluations that reflect the actual situation after
the accident because the premises and input values for the evaluation must be set based onassumptions, and concluded that it is difficult to confirm the validity of the evaluation. However, the
NRA expressed the views that the structural integrity of the reactor building as a whole can be
sufficiently maintained even if extreme events are assumed20. With regard to the environmental
impact, the NRA also offered the view that it has confirmed that the aforementioned TEPCO’s
evaluation remains conservative and maximized, and this NRA's view was also accepted at the
NRA Committee20.
The retention of hydrogen which flowed into the inside at the accident was observed during thedrainage of high-radiation-dose equipment (Reactor Building Cooling Water System (hereinafterreferred to as “RCW”)) to improve the on-site environment (reduce radiation dose) in the reactor
building. Therefore, operations are carried out while carefully reducing and monitoring the hydrogenconcentration.
b. Unit 2
After completing the manufacture and confirmation tests of the arm-type access equipment in
the UK in June 2021 (hereinafter referred to as “robot arm”) for use in trial retrieval, the equipment
was brought to Japan and has been undergoing performance confirmation tests, verification tests
in simulated environment of actual machine (hereinafter referred to as “mock-up tests”), andtraining in the following facilities.


Domestic factory from July 2021 (Kobe)

Naraha Center for Remote Control Technology Development (NARREC), the JAEA fromFebruary 2022

Modification and verification of the control software for the robot arm and improvement of somedevices, which are newly required as a result of these tests, are implemented, and verification of
the required functions of the robot arm alone is in progress. In addition, as on-site preparatory work,
installation of the isolation chamber for the hatch opening of the existing PCV penetrating part X-6(hereinafter referred to as “penetration X -6”) began in November 2021. During the installation,
countermeasures were implemented against damage to the rubber box of the isolation chamber(damage due to contact during installation work of isolation chamber), bending of the guide roller(impact of the earthquake occurred on March 16, 2023), misalignment of the shielding door (impactof the earthquake occurred on March 16, 2023), and damage to the pressing mechanism parts(insufficient margin of design intensity), then, the installation of isolation chamber was completed
in April 2023. Currently, removing the flange bolt and opening the hatch of the penetration X-6, andremoving the deposits inside the penetration are in progress, these works should be implemented
safely and carefully.

20

The 37th Nuclear Regulation Authority Committee in FY 2023 “Material 2: Response to the situation of Unit 1
pedestal at the TEPCO’s Fukushima Daiichi Nuclear Power Station (second meeting)”, (NRA).

40

A plan for the gradual expansion of fuel debris retrieval is also underway, and the retrieval device
will be improved by increasing the weight capacity and enhancing accessibility based on the
improvements identified during the verification of the devices for trial retrieval. In this plan, therequirements related to performance of the robot-arm and enclosures and the requirements at thedesign and installation have been clarified and examined. The retrieved fuel debris will be stored
in container for fuel debris retrieval and transport container in the enclosure, and then transferred
to and stored in the first storage facility21 on site (receiving/delivery cells and storage containers,etc.). In addition, some of the fuel debris will be collected in the receiving/delivery cells for analysis
and transported to the Radioactive Material Analysis and Research Facility Laboratory-2 or thefacilities for analysis located in Ibaraki Prefecture. Designing of the retrieval device, the first storage
facility is in progress (Fig. 12).
c. Unit 3
For the further expansion of fuel debris retrieval in scale, TEPCO has performed the conceptual
study on retrieval methods, many challenging issues have been identified with respect to methods
proposed for discussion. The actual site applicability and technical feasibility associated withmeasures for mitigating these issues are being verified. In FY 2023, evaluation including business
continuity2 is underway, with continued issue studies of each method. In addition, since February
2023, the Sub-Committee for the Evaluation of Fuel Debris Retrieval Methods has been establishedunder the Decommissioning Strategy Committee, a committee of NDF, technical feasibility andbusiness continuity in each of fuel debris retrieval method are being studied and evaluatedtechnically and intensively. (For details, refer to 3.1.3.4)
Moreover, due to the high-water level in the PCV, the plan is to lower the PCV water level, taking
into account the conducting of the PCV internal investigation and the improved seismic resistanceof the S/C. In the reactor water injection shutdown tests in June 2022, the PCV water level becamealmost stable when water injection was resumed and adjusted after it was determined that the PCV
water level fell below the lower end of the new PCV thermometer/water level gauge. Therefore, itis estimated that the leakage point was located below the lower end of the thermometer/water level
gauge22. Installing a water gauge at a lower position than the current one is under discussion tofurther reduce the PCV water level in the future. In parallel to this, the operation of the PCV water
intake facility began in October 2022, which takes water from the S/C bottom for replacement withthe reactor injection water, and efforts are being made to improve the S/C water quality to reduce
the PCV water level.

21

As the study progressed, the name was changed because TEPCO decided to store retrieved fuel debris atstorage facilities instead of temporarily storing it in temporary storage facilities.
22
Tokyo Electric Power Company Holdings Inc., Fukushima Daiichi Decontamination and Decommissioning
Engineering Company, July 19, 2022, “Completion of Fukushima Daiichi NPS Unit 3 reactor water injection
shutdown tests”

41(Prepared in reference to “Material 4-1: Progress of treatment of stagnant water in buildings”, the 81st meeting of the Study group on
monitoring and assessment of specified nuclear facilities)

Fig. 8 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 3

42

Fig. 9 Scope of internal investigation for Unit 1 PCV (Outside the pedestal on the basement
floor of the PCV from 0 to 215 degrees, pedestal opening and inside the pedestal)23“Progress of internal investigation for Unit 1 PCV (second half)”, Meeting of the Secretariat of the Team for Countermeasures for
Decommissioning and Contaminated Water/Treated Water, April 27, 2023, IRID/Tokyo Electric Power Company Holdings Inc.

Fig. 10 Results of the internal investigation for Unit 1 PCV24
23“Progress of internal investigation for Unit 1 PCV”, Meeting of the Secretariat of the Team for Countermeasuresfor Decommissioning and Contaminated Water/Treated Water, February 24, 2022, IRID/Tokyo Electric Power
Company Holdings Inc.
24
“Progress of internal investigation for Unit 1 PCV (second half)”, Meeting of the Secretariat of the Team forCountermeasures for Decommissioning and Contaminated Water/Treated Water, April 27, 2023, IRID/Tokyo
Electric Power Company Holdings Inc.

43

(Prepared by NDF based on TEPCO and IRID materials)

Fig. 11 Image of fuel debris retrieval system25(Trial retrieval and gradual expansion of fuel debris retrieval)(TEPCO material edited by NDF)

Fig. 12 Conceptual drawing from retrieval to storage of fuel debris(Gradual expansion of fuel debris retrieval)

3.1.3 Key issues and technical strategies to realize themWith regard to the design and planning of fuel debris retrieval, the challenge is to adequately
incorporate the findings to be gained (through internal investigations, R&D results, etc.) andinformation and experience acquired from trial retrieval in Unit 2 into the subsequent gradualexpansion and further expansion of fuel debris retrieval in scale.
25“Preparation of PCV Internal Investigation and trial retrieval operation for Unit 2”, Meeting of the Secretariat of
the Team for Countermeasures for Decommissioning and Contaminated Water/Treated Water, June 29, 2023,
IRID/Tokyo Electric Power Company Holdings Inc.

44

TEPCO established Toso Mirai Technology Company (Decom. Tech) in October 2022 to engage
in the basic design and R&D of systems and installations for the further expansion of fuel debris
retrieval in scale, and it has moved forward with activities for debris retrieval under an appropriate
division of roles among relevant organizations including this Decom. Tech. The technologies
cultivated through these initiatives should be effectively leveraged to improve engineering basedon TEPCO’s own safety and operator’s perspectives, as will be mentioned later.

This section describes the following.


3.1.3.1: Fuel debris retrieval strategies in each unit



3.1.3.2: Trial retrieval (Internal investigation and fuel debris sampling)

3.1.3.3: Gradual expansion of fuel debris retrieval



3.1.3.4: Further expansion of fuel debris retrieval in scale

3.1.3.5: Status of accident analysis activities

3.1.3.6: R&D status

3.1.3.1 Fuel debris retrieval strategies in each Unit
(1) A common strategy for each unit

Since each unit has many areas where direct visual information is unavailable, the issue isconducting further internal investigations to gain diverse information. Assuming further
expansion of fuel debris retrieval in scale, the investigation will proceed while developing andupdating the internal investigation plan in the future to clarify which areas should be prioritized.
Technology development for this purpose is underway, so the direction of the fuel debris
retrieval strategy should be verified based on the acquired information to avoid regressing inengineering and to increase the certainty of the method to be selected.



The issues are to analyze and determine the causes of the problems experienced on-site andmake improvements, including to the organization and structure, then prevention of recurrence
will be incorporated into the following work. Based on these experiences, the retrieval methods
that eliminate anticipated risks should be developed, and measures should be prepared inadvance for risks that cannot be eliminated in case such risks occur.



Fuel debris retrieval will be executed in a high-dose, severe environment. Although remotecontrol devices are used under various circumstances, workers will have many on-site
operations. The maintenance of remote-control devices and restoration in case of failure alsoneed to be considered. The issue is examining the retrieval methods in consideration for eachprocess including the entire construction sequence from preparation to completion of retrieval
and required resources to be allocated/volume (waste).

45With a view to business continuity, methods that enable retrieval even if all on-site conditions
cannot be identified, and other methods (robust methods) not easily affected by external
events such as earthquakes should be examined while taking into account on-site conditions
such as damage to facilities and equipment.



Since work under high radiation doses is required, the following measures should be taken. In

advancing these initiatives, it is important to develop a database that can streamline work
plans and exposure management.

Prevention of concentration of worker radiation exposure on specific individuals

Reduction of radiation exposure for all workers

Securing of human resources from a long-term perspective in operations

Further consideration should be given to the events during the accident, and more knowledge
should be gained through internal investigation in each Unit. In Unit 1, it has been confirmedthat deposits flowed out of the pedestal. Therefore, methods of removing deposits inside andoutside the pedestal and the possibility of deposits flowing into the S/C should be examined
and incorporated into fuel debris retrieval methods, including for other Units.

(2) Unit 1
The following should be considered to proceed with planning for the further expansion of fueldebris retrieval in scale.


R&D and engineering to apply the R&D results on-site will be promoted. The findings gained
through trial retrieval and the gradual expansion of fuel debris retrieval in Unit 2 will beincorporated into device design, retrieval procedures, and safety assessments. The initialstudy results of the retrieval method for Unit 3 will also be incorporated.

In previous investigations and analyses using muon, it has been assessed that there is almost
no fuel debris in the core. There have been PCV internal investigations, but not RPV internal
investigations. In light of all this, the issue is to obtain more information about the inside of the
RPV/PCV and take into account the information obtained.



As a result of the PCV internal investigation, the following findings have been obtained andwill be considered.
Outside the pedestal, deposits are distributed over a wide area.



There are deposits of nearly uniform height and part of the upper structures, such as CRD
housings, at the inner bottom of the pedestal.



The concrete near the pedestal opening (worker access opening) and the inside wall of
the pedestal is missing at the entire circumference.



Appropriate consideration is also given to the following differences from other Units.

46The sizes of the RPV and PCV are smaller than those of Units 2 and 3, and the systemlayout is different as well.



As a result of the previous investigations, it was revealed that the distribution of deposits
inside/outside the pedestal is different from that of Units 2 and 3.

(3) Unit 2Preparations for trial retrieval are underway, and the plan is to gradually expand fuel debris
retrieval.



The issue is leveraging the knowledge gained through trial retrieval for the further gradualexpansion of fuel debris retrieval. The design, production, and installation of the following
facilities needed for fuel debris retrieval should proceed based on this knowledge.
Facilities for retrieving fuel debris/safety systems (containment, fuel debris cooling,
criticality control, etc.)

Fuel debris storage facilities (The first storage facility)

Maintenance installations for retrieval system

The previous PCV internal investigations (inside the pedestal) and investigations/analyses
using muon indicated that a large amount of fuel debris is at the RPV bottom, and there is apossibility of there being some fuel in the core. Furthermore, it is unlikely that the fuel debris
that fell to the PCV bottom has spread outside of the pedestal. Investigations inside the RPV
and outside the pedestal have not been conducted. In light of all this, more information about
the inside of the RPV/PCV should be obtained.



The issue is leveraging the knowledge gained through trial retrieval in Unit 2 for further
expansion of fuel debris retrieval in scale. However, since it is not the plan to retrieve all thefuel debris with this side-access method, retrieval methods should be examined based on theknowledge gained and the initial study results of the method for Unit 3.

(4) Unit 3
Considering that the removal of fuel in pool has been completed and there is little interferencewith other operations, and working environment of the reactor building will be improved fasterthan Unit 1, retrieval methods are being examined for further expansion of fuel debris retrieval
in scale ahead of other Units. The actual site applicability and technical feasibility should bestudied for the issues and risks associated with the methods.

Previous PCV internal investigations (inside the pedestal) revealed that the CRD housing
support has partially fallen and deformed, that several structures have fallen on the lower partof the pedestal, including structures presumed to be structures inside the reactor, and that
there are deposits assumed to be fuel debris. According to muon surveys and analyses, it isestimated that a larger amount of fuel debris than in Unit 2 may have fallen into the pedestal

47

and spread out of the pedestal through the worker access opening. Investigations inside the
RPV and outside the pedestal have not been conducted. In light of all this, more information
about the inside of the RPV/PCV should be obtained.
3.1.3.2 Trial retrieval (Internal investigation and fuel debris sampling)
The trial retrieval, which is under preparation at Unit 2, is intended to access the inside of thepedestal from outside the PCV for further internal investigations and collect small amount of fueldebris.
In this operation, an expansion will be made to provide an isolation chamber (composed of arobot carrying-in room, etc.) to be built during the opening of the hatch of penetration X-6, and an
enclosure to be newly provided (which encloses a robot-arm, etc.), since the conventional
containment barrier was located in the hatch of the penetration X-6. Although it is small in scale,this is a fundamental form of site construction for future retrieval work, in which containment barrieroutside the PCV is extended by opening the existing hatch of penetration X-6 of the PCV. It is highly
significant to be an approach that enters a new stage.
The information obtained will be used for subsequent gradual expansion of fuel debris retrieval
and further expansion of retrieval in scale. In addition, since this will be the first fuel debris retrieval
at the Fukushima Daiichi NPS, the experience gained during the process from the examination to
the retrieval operation and the information obtained through the analysis of the retrieved samples
will be used in future decommissioning efforts.
The issue is to gradually proceed with the series of trial retrieval operations described below (Fig.
13). Moreover, due to the uncertainty of the conditions inside the PCV, assuming the possibility that
additional work or rework may be required depending on the actual on-site situation and that thework may not go as planned. Bearing this in mind, the work should proceed safely and carefully.
Furthermore, each of these operations has no precedent, and the valuable information, experience,
etc., gained through them should be leveraged appropriately in subsequent retrieval operations. In
addition, it is important to consider in advance troubleshooting and a system for a prompt responseto go with it.

48

(TEPCO material edited by NDF)

 The analysis results will be used for subsequent gradual expansion of fuel debris retrieval and further
expansion of retrieval in scale.

Fig. 13 Work steps of trial retrieval (internal investigations and fuel debris sampling)
Since February 2022, mock-up testing of the newly developed robot arm have been conductedat the JAEA Naraha Center for Remote Control Technology Development. Modification andverification of the control software and improvement of some devices, which are newly required asa result of these tests, are almost completed, and verification of whether the requirements of therobot arm alone are satisfied is in progress. In the future, there are plans for mock-up tests andtraining on the entire system combining the robot arm and the enclosure.
The issues for on-site applications with uncertainty are functional verification checks undervarious conditions and ensuring that equipment can be saved in an emergency. Therefore, it isnecessary to make the necessary preparations, to reliably ensure that the required functions are
satisfied by conducting mock-up tests that simulate the actual site, even if it takes time, and toensure that newly identified risks are eliminated. Furthermore, thorough preparation of themeasures should be performed for the practical application, not only by simulating severe
environments on site in mock-up testing, but also by clarifying any areas that are not simulated,such as the current situation after the accident in particular.

49

On the other hand, in constructing an on-site access route, the installation of the isolationchamber, which had been delayed while operational and design defects were addressed, andseismic countermeasures, were completed in April 2023, and the works of removing the flange bolt
and opening the hatch of the penetration X-6, and removing deposits inside the penetration are
underway. After that, the plan is to continue the installation of the penetration X-6 connection
structures and enclosure (with the built-in robot arm, etc.) in order to establish an access route.
During the installation of the isolation chamber, it took time to take countermeasures against
damage to the rubber box of the isolation chamber (damage due to contact during installation workof isolation chamber), bending of the guide roller (impact of the earthquake occurred on March 16,2023), misalignment of the shielding door (impact of the earthquake occurred on March 16, 2023),
and damage to the pressing mechanism parts (insufficient margin of design intensity). In particular,
it is regrettable that the design did not adequately consider the workability in a high radiation dose
environment or the repair workability in the unlikely event of parts damage.
In addition, in the work to open the hatch of the penetration X-6, because several bolts weremore severely adhered than previously expected and could not be removed, the removal method
was revised to cope with it. It is important to be prepared in advance in order to flexibly respond tosuch events that differ from the prior assumptions.
Furthermore, given the adhering condition of the bolts, difficulty in deposits removal may be alsoa concern inside the penetration X-6, so it is necessary to study in advance a method that enables
fuel debris retrieval even if the deposits inside the penetration cannot be completely removed.
TEPCO is also considering the use of a telescopic device that has been used in past investigations
and confirmed to be accessible to the bottom of the pedestal as a method to complement theinternal investigation and trial retrieval by the robot arm (Fig. 14).
In the future, when installing apparatus such as the robot arm system that interface with theexisting structures outside the PCV to extend the containment barrier, it will also be a challenging
task in a high-dose environment. Thus, careful preparation based on this event will be a challenge.
Paying full attention to the unique characteristics of the Fukushima Daiichi NPS, such as thatearthquakes of equivalent or greater magnitude are expected to occur in the future, the work
descriptions should be reviewed again, and operation training should be provided to enhance future
work safety and reliability. The above characteristics and the knowledge and experience gained
this time should be incorporated into examining fuel debris retrieval methods for the further
expansion of fuel debris retrieval in scale.

The key technical issues, countermeasures, and points to consider are described below.


Dust dispersion prevention associated with removal of deposits in the penetration X-6.
In light of a dust dispersion event caused by an abrasive water jet (hereinafter referred to as“AWJ”) to construct access routes for PCV internal investigation in Unit 1, measures such as
removal of deposits by low-pressure water cleaning, and dispersion control by spray curtains

50

have been prepared to prevent dust dispersion due to removal of deposits inside the penetration
X-6. It is confirmed that due consideration has been given to safety measures in the operation
procedures, such as monitoring dust concentration and gradually expanding operations. Whileplacing the highest priority on ensuring safety, the issue is to set an appropriate operational
value for dust concentration control that will not significantly extend the process due to operation
constraints.
Considerations in project management
The project should proceed while paying attention to the process progress management of
the contractors including overseas enterprises and subcontractors. As part of their project
management activities, TEPCO should perform prior-evaluation of risk of delays, and develop
alternative plans and measures to prevent the occurrence of risks. NDF also participates inmeetings with contractors and their subcontractors to closely check the status and support risk
assessment.



Limitations in the scope of trial retrieval and incorporation into gradual expansion of fuel debris
retrieval
In the PCV internal investigation using a robot arm, following will be ascertained; the state ofexisting structures, and the distribution of deposits inside the pedestal (3D data), the distributionof gamma rays and neutron counts at the bottom and on the platform. However, since morestructures and platforms in the pedestal remained than the initial design plan, the range in which
the robot-arm can access the bottom of the pedestal is limited. Thus, the possible range ofneutron measurement and trial retrieval from the bottom of the pedestal is limited.
Incorporating the results of the arm/tool combinational test in the JAEA Naraha Center for
Remote Control Technology Development, the scope and type of data that can be acquired,
and the evaluation method of the conditions inside reactor (e.g., fuel debris distribution) basedon such data are planned.
Assuming that fuel debris at the bottom of the pedestal cannot be retrieved, it is also planned
to retrieve the deposits on the platform which are highly likely to be fuel debris, as same as
those at the bottom of the pedestal. Given the limited scope of investigation and trial retrieval,greater consideration is required in advance to determine what information is needed for gradualexpansion of fuel debris retrieval as a next step for promoting the retrieval work in a reliable
manner.



Human resource development and technology transfer for the next step (gradual expansion offuel debris retrieval)With regard to the trial retrieval, there are uncertainties and difficulties in the development of
the robot arm and the removal of deposits and obstacles due to a limited understanding of theconditions inside the PCV. Therefore, when performing such work, it is necessary for TEPCO
and parties concerned to utilize human resources with a wealth of field experience, including51

those invited from outside as needed, to develop human resources to foster field-oriented
perspectives/feelings, and to transfer techniques cultivated through these activities.

(Source: TEPCO)

Fig. 14 Conceptual drawing of telescopic device to complement robot arm
3.1.3.3 Gradual expansion of fuel debris retrieval
Preparations of gradual expansion of the fuel debris retrieval are underway in Unit 2 with themain objectives of verifying the retrieval equipment, obtaining data on the environmental impact
during the retrieval operation, increasing the retrieved volume, obtaining data on the compositionand properties, etc. of fuel debris from a larger number of samples, and accumulating experienceof workers in retrieval during the period before the start of further expansion of fuel debris retrieval
in scale.
(1) Retrieval equipment
The retrieval equipment to be used for gradual expansion of fuel debris retrieval will be improvedby increasing the payload and enhancing accessibility while complying based on the
improvements identified during the verification phase of the equipment for trial retrieval. It isplanned to expand the range of retrieval step by step while making achievements, starting withretrieval of fuel debris that can be gripped and sucked, and expanding it to fuel debris retrieval
with cutting. Consideration will also be given to the possibility of cutting platform beams and therange of cutting. Since the enclosure containing the robot-arm, etc. brings fuel debris from inside
the PCV into the enclosure, shielding, measures against hydrogen and prevention of, methods fortransferring fuel debris from the enclosure, and methods for confirming the maintenance ofcontainment barrier and dynamic equipment functions and for remote maintenance are being
studied.
The key technical issues and countermeasures are described below.


Ensuring containment performance of enclosure for fuel debris52

In the retrieval operation, the process is repeated from carrying fuel debris retrieved from thePCV into the enclosure, storing in unit cans26 and carrying out to the outside of the enclosurefor on-site transportation. As a result, the enclosure gradually becomes contaminated, and theissue is to secure the containment performance of the enclosure.
This work is performed by controlling the pressure in the enclosure as the robot arm is moved
in/out. Therefore, in order to confirm airtightness performance and operation reliability, throughthe duration, the issue is to perform prior mockup test, post-installation test of the equipment,
and subsequent abnormality monitoring.
Ensuring the reliability of the manipulator
The manipulator to be installed in the enclosure plays an important role in performing various
operations and maintenance in the enclosure. Therefore, ensuring the reproducibility of the work
is a challenge. Sufficient training for a wide range of operation/maintenance should be provided
in advance to train operators.

Ensuring maintenance of devices and countermeasures during the in-service period
Since the work period is on the order of several years, in addition to periodic maintenance,
preparation in case of failure is a challenge. Since the Unit 2 reactor building, where theenclosure will be installed, has a high radiation dose and is a difficult place to perform
maintenance, it is planned to construct a maintenance building outside the building, transfer theequipment or enclosure itself, and decontaminate, dismantle, repair, or replace it inside themaintenance building. Another issue is to leverage the experience gained through the in-service
maintenance of equipment/devices for the further expansion of fuel debris retrieval in scale. A
system that can reliably preserve maintenance records, including failure histories andcorresponding measures, should be established.

From the perspectives of research/development and engineering by TEPCO, and in terms of
ensuring safety and the actual site applicability, NDF continues to observe and check the statusof technology development and preparations for application to the site for retrieval equipment ina timely manner.
(2) The first storage facility
When designing the storage facility, there are many connections with related facilities forreceiving retrieved fuel debris and sending samples for analysis. Moreover, during installation,
they have a lot of interfacing and connections with various types of work and operation, including
peripheral work. Although the first storage facility is small in scale, project management by TEPCO
is essential for process management and to resolve pending issues during design and installation.
The experience and knowledge gained from this design and installation work are expected to be

26

One proposal is to retrieve fuel debris from the PCV by putting it in a unit cans, and store the unit canscontaining the fuel debris in containers.

53leveraged in project and construction management for the further expansion of fuel debris retrieval
in scale in the future.
As various remote-control devices will be used for handling fuel debris in the first storage facility,
critical issue is if they can be operated as we previously envisioned. The work details using thesedevices should be thoroughly checked and countermeasures against potential risks should beestablished at the design stage, and they should be incorporated into the design. Furthermore,
the design verification and mock-up tests/operator should be conducted by referring to theknowledge and experience gained from design and operation of remote-control devices in thepreceding PCV internal investigation and trial retrieval.
3.1.3.4 Further expansion of fuel debris retrieval in scale
Toward the further expansion of fuel debris retrieval in scale, TEPCO should take responsibility
for examining the methods based on the viewpoint that “fuel debris retrieval is an important
process in decommissioning, and its retrieval in a reliable manner affects the success/failure of
the decommissioning project”, and from a comprehensive standpoint in anticipation of technicalfeasibility as well as business continuity. Therefore, this section describes in detail the procedure
for examining the methods. (As a reference, changes in considerations on retrieval methods inthe previous Technical Strategic Plans are shown in Attachment 9.)
The Fukushima Daiichi NPS containing the reactors involved in the accident has a uniqueenvironment that is substantially different from a conventional reactor, requiring understanding of
the following factors that make fuel debris retrieval difficult.
①

Extremely high radiation dose in PCVs and RPVs
The dose equivalent rates in the PCVs/RPVs are on the order of several Sv/h to several
hundred Sv/h, and they are inaccessible to humans.

②

High-radiation dose in reactor buildings
The dose equivalent rates in reactor buildings are on the order of a few mSv/h to tens of
mSv/h, with human access limited to a short time.

③

Lack of on-site information
Due to the restrictions in [1] and [2] above, it is difficult to obtain on-site information (andprospects are uncertain), and discussions must be based on the presumed conditions.

④

Building containment barriers
If reactor buildings or PCVs are used as containment barriers, consideration must be given
to the fact that they are damaged by the accident and to the risk of aging deterioration. On
the other hand, if new containment barriers are constructed, it requires containment
performance, including seismic resistance according to the site conditions.

⑤

Criticality control

54

An external force, such as a process during retrieval, will cause a movement or change theform of fuel debris currently in a subcriticality condition. In order to properly assess theimpact caused by such a change in state, it is necessary to incorporate on-site information(fuel debris composition, distribution, neutron flux, etc.).
⑥

Waste management
Solid waste newly generated as a result of decommissioning work must be considered inaccordance with the Basic Concept of Solid Waste presented in the Mid-and-Long-term
Roadmap. In particular, it is necessary to reduce the amount of solid waste generated asmuch as possible to reduce the overall burden of solid waste management.

Therefore, the following should be considered when examining and evaluating methods.
(1) Considerations when examining retrieval methodsAppropriate establishment of requirements for ensuring safety
Given an unusual environment different from normal reactors, to ensure safety, the optimal
approach to safety (ALARP) should be implemented throughout the entire project, not toprolong the work period. For this reason, it is important to perform an impact assessment if
an event that threatens safety occurs, such as an earthquake or criticality, and then to set therequirements appropriately and consider countermeasures.

Estimation of information needed to study retrieval methods
Information on the location, quantity, and properties of fuel debris, fission productdistribution, and PCV internal conditions are important to examine retrieval methods.
Therefore, comprehensive analysis and evaluation have been carried out on the basis of thepresumption through internal investigations, analysis, knowledge of the previous accidents
and studies, experiments, etc., to presume the information necessary to examine retrieval
methods. These efforts should be continued hereafter to improve accuracy of retrieval method
examination by incorporating the results newly obtained through the internal investigations
into the information for the retrieval methods examination.



Development of retrieval scenarios
Given the limited understanding of the situation in the PCV, it is important to examine
several scenarios of fuel debris retrieval by each unit and to clarify several paths from start tocompletion in this retrieval method examination. The intention of this study on fuel debris
retrieval scenarios is to estimate in advance the different results that will be obtained from theprogress of PCV/RPV internal investigations, on-site information and technical studies in the
future and then conduct an examination based on the preconditions of using such results.
After reviewing these several paths, it is important to combine ad narrow down the paths totake according to the information obtained afterward.

55

In considering several paths, it is necessary to control potential risks in each process frompreparatory work to the completion of fuel debris retrieval, and it is also necessary to develop
the scenario while constantly checking the risk level and risk measures.


Clarification of requirements
As for the further expansion of fuel debris retrieval in scale, compared to the case of
retrieving fuel debris from Unit 2 (trial retrieval and the gradual expansion of fuel debris
retrieval), the operations, devices and equipment, and facilities will be larger, and the scopeof construction will be wider. Therefore, the challenge is to perform the examination by
overviewing the entire Fukushima Daiichi NPS, including other construction work. For thisreason, in addition to the requirements for operations and equipment related to retrieval
methods (containment, criticality control, operability, maintainability, throughput, etc.), therequirements for the entire power plant (site use area, interfacing with existing systems,
groundwater management, waste management, etc.) should be clarified further. Theinteraction among the requirements should also be considered.

Issue identification and verification of actual site applicability and technical feasibility
If the developed retrieval method has even one potential technical issue or if an issue thatwas overlooked in construction work, retrieval work, or maintenance becomes apparent, thework may be derailed and it may not be possible to proceed. To prevent this, issues should
be identified through systematic and exhaustive methods at the design stage. For thispurpose, an effective means is to examine the construction sequence from preparatory workthrough fuel debris retrieval, maintenance and completion of fuel debris to exhaustively
identify issues that may significantly affect the technical feasibility of each process work. The
issues identified should be verified as to whether they can be addressed from the perspectiveof actual site applicability and technological feasibility while considering countermeasures.

(2) Considerations when evaluating retrieval methods


Setting indicators/criteria for determination
When evaluating retrieval methods, in addition to evaluation to check the actual site
applicability and technology feasibility based on the Five guiding principles (safe, proven,efficient, prompt, and field-oriented), the methods related to business continuity, should also
be used as decision indexes. In addition, decision indexes should be defined from the initialstage of studying retrieval methods to clarify the criteria used in the evaluation. Information(e.g., exposure assessment reports, structure evaluations) to objectively determine whether
the criteria are met should also be clarified in advance.

TEPCO is currently conducting a conceptual study on the further expansion of fuel debris
retrieval in scale, starting with Unit 3, and examining scenarios and methods for fuel debris retrieval.
Many challenging issues have been identified with respect to methods proposed by the end of FY
2021. In FY 2022, the actual site applicability and technical feasibility associated with measures for56

mitigating these issues were verified. In FY 2023, issue studies of each method are continued andevaluated including business continuity. In addition, preparation work such as yard maintenance,
which becomes necessary regardless of the retrieval method, has been identified and summarized
to have it take shape as soon as possible. Selecting a specific method is an extremely important
decision to determine the success or failure of decommissioning over the medium to long term.
Thus, not only TEPCO but also the national government and NDF must cooperate tocomprehensively examine and evaluate technological feasibility, with safety as a major prerequisite.
To this end, since February 2023, the Sub-Committee for the Evaluation of Fuel Debris Retrieval
Methods has been established under the Decommissioning Strategy Committee, a committee of
the NDF, to conduct technical and intensive study and evaluation on the technical feasibility andbusiness continuity for each method of fuel debris retrieval.
The followings are the overview and the issues of the partial submersion method ((Water injection
into RPV), its option (RPV solidification)) and submersion method (shell structure). The outline ofeach method is only an example and is not definitive.
3.1.3.4.1 Overview of and issues with the partial submersion method
3.1.3.4.1.1 Overview of and issues with the partial submersion method (water injection into
RPV)(1) Overview of the proposed partial submersion method (water injection into RPV)
The partial submersion method (water injection into RPV) is a method for retrieving debris
exposed in the air or immersed at a low water level while pouring water into the RPV. (Fig. 15)
Previous examinations have been conducted on the top and side access methods alone, but
this retrieval method does not use either method alone but rather combines them. This makes it
possible to share the safety and pre-transfer treatment systems installed in the additional building
to streamline the entire facility. The roles of the top and side access are as follows: the top accesswill be the main route to retrieve debris inside the RPV and the pedestal, based on the fact that alarge working opening can be taken and that access is possible in a linear direction. In contrast,
the side access route will be used to retrieve from outside the pedestal, which is not easily
accessible from the top. Regarding side access, safety measures, are implemented inside/outside
the pedestal ahead of the top access, such as criticality control due to the accumulation of cutting
particles during fuel debris fabrication and preventing heavy objects from falling from the RPV.
Duplexed containment barriers will be constructed to prevent radioactive dust dispersion and the
spread of contamination during retrieval. The primary containment barrier comprises PCVs andother structures while the secondary containment barrier comprises reactor buildings and otherstructures. In addition, a gas phase containment system is installed at the primary and secondary
containment barriers to achieve active containment through difference pressure control inside andoutside the containment barriers.

57

The retrieved fuel debris is transported to the additional building connected to the reactor
building, where pre-transfer treatment is performed. Storage in transfer containers and inspection
including hydrogen concentration measurements are carried out in pre-transfer treatment. The
transfer containers are transferred from the additional building to a pre-storage treatment facility
to analyze, sort, and dry fuel debris as pre-storage treatment. They are then stored in storage
containers and stored in storage facilities.

Access direction of thedevices
Transfer direction of fueldebris and radioactive waste

Fig. 15 Example of the proposed partial submersion method (water injection to RPV)(Conceptual drawing of combination of top access and side access)(2) Issues with the proposed partial submersion method (water injection to RPV)
For the proposed partial submersion method (water injection to RPV) described in (1) above, theissues and the possible measures were summarized according to the abovementioned factors ①
to ⑥ that make fuel debris retrieval difficult.
For factor ① (extremely high radiation dose in PCVs and RPVs), the issue is that all
operations will be conducted using remote control devices because it is inaccessible tohumans. After identifying the required operations including what is expected to be done,such as fuel debris retrieval and removal of obstacles in PCVs, the function, structure, andgeneral safety requirements (radiation resistance, water resistance, temperature range,
remote inspection/maintenance, remote operability, ensuring field of views, protective
mechanisms such as collision avoidance and automatic shutdown in case of abnormalities,
high reliability and appropriate redundancy, etc.) of equipment should be established.

For factor ② (high radiation dose in reactor buildings), although some works in buildings canbe implemented manually, in such cases, the issues are careful exposure control as well as
environmental improvement (decontamination and shielding). Operations using remotecontrol devices are another issue in high radiation dose areas where dose reduction isdifficult. Because establishing an access route for retrieval will be conducted by remotely,
the same measures will be required as with factor ①.



For factor ③ (insufficient on-site information), the issue is that the retrieval method must be
considered based on the uncertainty of on-site information due to the limited results of the58

on-site survey. Therefore, in addition to obtaining on-site information through internal
investigations, remote control devices and work procedures should be considered to allow
for flexible response in cases where the on-site situation still cannot be identified.


For factor ④ (building containment barriers), it is necessary to support a heavy cell with ashielding function or retrieval devices on a platform for top access, and the issues are theirseismic feasibility and airtightness of the interface with existing structure. As acountermeasure, it is necessary to assess the validity of seismic conditions as well as study
measures for reducing the upper load and examination of structure to ensure airtightness.
In addition, because existing structures such as reactor buildings and PCVs are used as
containment barriers facilities, the issue is to examine airtightness and seismic resistance inconsideration of the fact that they are damaged by the accident and the aging deterioration.
In view of long-term use in the future, it is necessary to monitor, investigate, and assess
damage, deterioration, and corrosion conditions, and by taking these into account, it is also
necessary to continuously check the earthquake resistance and structural integrity.

For factor ⑤ (criticality control), the issue is to have criticality control (monitoring, criticality
prevention, impact mitigation measures) take shape appropriately for the on-site conditions.
Measures should be considered from both a design and operational perspectives. Design
measures to be considered include the use of multiple monitoring means (rare gas
concentration monitors, neutron detectors, etc.), setting limits on cutting operations(criticality prevention), and installing systems capable of injecting neutron absorbers (impact
mitigation). Meanwhile, as operational measures, the amount of state change is assessed(monitored), and when a condition approaching criticality is detected, criticality is prevented
by stopping operations, adding neutron absorbers, and determining whether operations canbe resumed. In the future, accumulating and evaluating the information obtained during onsite operations (fuel debris composition, distribution, neutron flux, etc.) will make it possible
to validate the initial design.

For factor ⑥ (waste management), the issue is handling a large amount of waste, such as
dismantled buildings and excavated soil in areas that interfere with new structure
construction (such as platforms to support cells for top access, additional buildings, etc.). A
plant-wide waste storage plan should be developed to verify that the waste to be generated
can all be stored.

Countermeasures against these issues are under discussion, and the actual site applicability,
technical feasibility, and business continuity will be evaluated.
3.1.3.4.1.2 Overview of and issues with the partial submersion method option (RPV fillingand solidification)
Among factors related to the proposed partial submersion method (water injection into RPV), to
reduce the difficulty of issues associated with factors ① and ②, it is effective to minimize and59

simplify operations using remote control devices and attended operations in the reactor building.
Moreover, based on factor ④, a method that can mitigate the impact of damage to the existing
structures and the deterioration of airtightness and strength due to aging degradation is desirable.
For factor ⑤, reducing the possibility of criticality by suppressing the movement and form changeof the fuel debris associated with operations is possible. As a possible measure to achieve this,partial submersion method option (RPV filling and solidification) is considered. An overview of thisoption and related issues are described below.
(1) Overview of the partial submersion method option (RPV filling and solidification)
The partial submersion method option (RPV filling and solidification) is a retrieval method where
the pedestal bottom, RPV, reactor well, etc. are physically stabilized by solidifying with fillers, andthen excavates, and retrieves fuel debris with fillers. (Fig. 16)
The method for retrieving fuel debris and removing other objects inside the RPV and pedestal is
as follows; first, filler materials are injected into the bottom of the pedestal by side-access, then thefiller materials are injected from the reactor well into the RPV and pedestal by top-access to solidify,
and then excavate to the bottom of the pedestal by top-access for retrieval of fuel debris. For fueldebris outside the pedestal, filler materials are injected, a casing is installed, and then fuel debris
is retrieved by excavation. In order to reduce the amount of waste generated due to filling, there isalso an option of not filling the core and pedestal, but only the upper part of the RPV head and thelower part of the pedestal from the reactor well, and then installing a casing for recovering fueldebris from the upper part of the RPV to the bottom of the pedestal to recover fuel debris by drilling.
There is also an option of not filling the core and pedestal, filling only the upper part of the RPV
head and the lower part of the pedestal from the reactor well, installing a casing for recovering fueldebris from the upper part of the RPV to the bottom of the pedestal, and recovering fuel debris bydrilling.
The drilling section would be supplied with water to fluidize the crushed fuel debris, which would
be transferred together with filling material to a filter-type recovery container for circulation recovery.
Duplexed containment barriers will be constructed to prevent radioactive dust from dispersing
and stop contamination from spreading during retrieval. Similar to the partial submersion method(water injection into RPV), the primary containment barrier comprises PCVs and other structures
while the secondary containment barrier comprises reactor buildings and other structures. However,compared with the partial submersion method (water injection into RPV), since the filler covers fueldebris and other materials, the containment performance is expected to become stronger. In
addition, a gas phase containment system is installed at the primary and secondary containment
barriers to achieve active containment through difference pressure control inside and outside thecontainment barriers.
Transport and storage of the fuel debris stored in containers should be examined with reference
to the proposed partial submersion (water injection into RPV) and submersion (shell structure)methods.

60

Access direction of thedevices
Transfer direction of fueldebris and radioactive waste
FillerFig. 16 Overview of the partial submersion method option (RPV filling and solidification)(2) Issues with the partial submersion method option (RPV filling and solidification)
For the proposed partial submersion method option (RPV filling and solidification) described in(1) above, the issues and possible measures were summarized according to the abovementioned
factors ① to ⑥ that make fuel debris retrieval difficult.
For factor ① (extremely high radiation dose in PCVs and RPVs), the issue is to prevent
leakage of contaminated water inside the cell or to the outside because the excavated debris
is recovered in a state mixed with water. It is necessary to examine detection methods incase of leakage, measures to prevent the spread of contamination, and restoration methods
after contamination.

For factor ② (high radiation dose in reactor buildings), the issue is how to lay the filling hosebecause the filler materials are injected into the bottom of the pedestal via side-access. The
study is expected to be based on past examples of internal investigations of the Unit 2 PCV,
which has been accessed to the inside of the pedestal.

For factor ③ (insufficient on-site information), an issue is that the uncertainty of site
information must be considered in discussing the method. An issue unique to this option is
the flow and solidification properties of the filler. Fillers need to be injected in the areas to be
excavated and to the extent to improve excavation-ability, but better fluidity makes it easierfor fillers to leak through openings. On the other hand, there are limitations in investigating
the conditions inside the PCV and RPV, and it is difficult to identify the location and size ofcracks in the PCV/RPV. Therefore, it is necessary to assess the flow and solidification
characteristics of filler materials through tests and to consider the selection of filler materials
and procedures that allow them to be filled appropriately under various conditions, as wellas methods or alternatives to confirm that the filler has been completed. The development
should be promoted after clarifying the functions required for fillers. Moreover, since fueldebris is covered with fillers, decay heat removal is also a challenge, including whether it isnecessary. Although it is unclear how much decay heat is generated and from where, thepossibility that the heat decay removal is inhibited should also be considered.

61

As for factor ④ (building containment barriers), the issues are the seismic feasibility of thecell to be installed in the reactor building and on the operating floor and securing airtightnessof the interface necessary for the cell, cover over the cell, and existing structures. As acountermeasure, seismic assessment should be carried out after specifying the equipment
installed on the operating floor, and the structures to ensure airtightness should be examined.
In the case of top-access in the partial submersion method (water injection into RPV), thecell requires a shielding function because the structures with high radiation doses are
exposed to the air. In this option, however, they are not exposed. Thus, the shielding function
required for the cell and other structures is expected to be reduced compared to the partial
submersion method (water injection into RPV), and there is a possibility that the platform
supporting the cell, retrieval equipment, etc., will become unnecessary. In addition, because
existing structures such as reactor buildings and PCVs are used as containment barriers,
another issue is to examine the airtightness and seismic resistance in consideration of thefact that they have been damaged by the accident and of the aging degradation. Given longterm use in the future, similarly to the partial submersion method (water injection into RPV),
it is necessary to monitor, investigate, and assess damage, deterioration, and corrosion
conditions and continuously verify seismic resistance and structural integrity. If fillers can beused as expected, the impact due to aging degradation is expected to be mitigated.

For factor ⑤ (criticality control) has the same issue as with the proposed partial submersion
method (water injection to RPV). Measures specific to this option include, for example,
limiting the size of the fuel debris recovery line to a size that will not cause criticality andadding neutron absorbers to the filler materials in advance. However, after clarifying thepossibility of criticality, it is necessary to evaluate the impact of exposure should a criticality
occur and consider necessary countermeasures in detail.



As for factor ⑥ (waste management), the issue is that a large amount of fillers are used for
excavation and recovery, and all of them must be treated as radioactive waste. For thisreason, reducing the filling range should be considered, a plant-wide waste storage planshould be developed to verify that the waste to be generated can all be stored. In addition,although the origin of the recovered excavation powder is clear if the excavation site is
identified, the method of sorting fuel debris and waste should also be considered, especiallysince the excavation powder recovered from the vicinity of fuel debris is a mixture of fueldebris, structures, and fillers.

623.1.3.4.2 Overview of and issues with the submersion method (shell structure)(1) Overview of the proposed submersion method (shell structure)
The submersion method (shell structure) involves enclosing the entire reactor building with a new
structure, called a shell structure, as containment barriers, flooding the reactor building, andretrieving fuel debris. (Fig. 17)
Fuel debris inside the RPV and inside/outside the pedestal will be retrieved via top-access.
Operations outside the pedestal will be performed from inside the pedestal via worker access
opening in the basement.
The shell structure is established to enclose the entire reactor building, and it is filled with enoughwater to flood the reactor building inside. It has a three-layer structure, with the inner wall in contact
with water and a cell installed on the operating floor as a primary containment barrier, the shellstructure interior as a secondary containment barrier, and the outer wall as a water shielding
containment barrier. In addition, a gas phase containment system is installed at the primary andsecondary containment barriers to achieve active containment through difference pressure control
inside and outside the containment barriers.
The pre-transfer treatment of the retrieved fuel debris is carried out underwater until it is stored
in a shielded container, and then the container is cleaned, drained, capped, and inspected in the
air. To ensure a hydrogen concentration below the flammable limit for the radioactive decompositionof water contained in the transfer container, the amount of hydrogen generated should be measured
beforehand, and the amount stored should be limited. The transfer containers are transferred fromthe shell structure to a pre-storage treatment facility to analyze, sort, and dry fuel debris as a prestorage treatment. They are then stored in storage containers and stored in storage facilities.
Access direction of thedevices
Transfer direction of fueldebris and radioactive waste

Fig. 17 Example of the submersion method (Shell structure)(Conceptual drawing of the shell structure)(2) Issues with the proposed submersion method (shell structure)
For the proposed submersion method (shell structure) described in (1) above, the issues andpossible measures were summarized according to the abovementioned factors ① to ⑥ that makefuel debris retrieval difficult.

63For factor ① (extremely high radiation dose in PCVs and RPVs), effect of the water shielding
by submersion allows a person to approach the middle working framework on which theretrieval work is carried out in the Shell structure. However, since all work inside the
PCV/RPV will be performed remotely, it is necessary to take similar measures to the onesin the proposed partial submersion method (RPV water injection).



For factor ② (high radiation dose in reactor buildings), in some of the preparatory work prior
to the installation of the Shell structure, such as rerouting of reactor water injection facilities,
work inside the reactor building is required. Since the operations are mainly manual, careful
exposure control as well as environmental improvement are the issues, as in the case of the
proposed partial submersion method (RPV water injection). In the event that remote work is
required, it is necessary to take a response similar to that of the proposed partial submersion
method (RPV water injection).



As for factor ③ (insufficient on-site information), it is necessary to verify the conditions ofsoil contamination by doing sea-side sub-drain water and geological (boring) surveys aroundthe reactor building to install temporary structures (pit, shield tunnel) for constructing theshell structure. However, the issue is that the possibility of soil contamination around thereactor building cannot be completely excluded. It is also necessary to examine construction
feasibility, in advance, assuming that the excavated soil (including groundwater) is
contaminated.

For factor ④ (establishing containment barriers), in addition to studying the methods basedon the uncertainty of on-site information, the issue is to assemble the bottom of the Shellstructure into the space inside the shield tunnel with only the side access. The feasibility of
welding work and inspection methods should be verified. Another issue is to prevent
contaminated water from leaking outside the shell structure, which has three layers ofcontainment barriers. It is necessary to study measures to detect leakage between thecontainment barriers and to recover from leakage. For the integrity of the temporary
structures, surrounding ground, and shell structure during construction and earthquake, theprospects for feasibility have been confirmed through analysis and evaluation using the finite
element method considering water pressure (internal water, ground water), earth pressure,seismic load, etc.

For factor ⑤ (criticality control), the issues are the same as for the partial submersion
method (water injection to RPV). In addition, as a countermeasure in case of criticality, theissues are the maintenance/management of boron concentration and the control of the
supply of boric acid for a constant boric acid solution environment.

For factor ⑥ (limiting waste amount generated), due to the construction of the Shell structure,
the amount of waste such as demolished buildings and excavated soil, which interfere with64

yard maintenance, will be enormous, and the same measures as those proposed for thepartial submersion method (RPV water injection) will be necessary.
As with the partial submersion method, countermeasures against these issues are underdiscussion, and the actual site applicability, technical feasibility, and business continuity have been
evaluated.

The above describes issues and measures for each method. While technical issues remain witheach method, there are also complementary technologies (for example, the shielding effect fromusing fillers is a common element technology applicable to both the partial submersion andsubmersion methods).
In the future, it is desirable to extract elements with high technical feasibility, project continuity,and high effectiveness in solving issues out of technologies examined for each retrieval method,and combine them to proceed with examination to establish a more rational and feasible retrieval
method.
3.1.3.5 Continuation of accident analysis activities (clarification of events that occurred at
the time of the accident)
Referring to the findings obtained through the PCV internal investigations and the analysis dataof the collected deposit samples, TEPCO has been examining the estimation of RPV and PCV
conditions to incorporate the results into planned on-site investigations and studies of fuel debris
retrieval methods and storage management. On the other hand, there are still many places whereinternal investigation is not possible due to high radiation doses. Therefore, it is important to refine
the information, such as the location and distribution of fuel debris and radiation dose distribution,
through activities to improve understanding of the events during the accident, including analysis of
the accident sequence in light of the on-site finding and solving pending issues in accident
progression, and then incorporate them into the estimation of RPV and PCV conditions. Activities
to improve understanding of the events during the accident and incorporate knowledge gained into
decommissioning work will continue. Furthermore, the NRA, in cooperation with TEPCO, isreviewing findings from accident analyses to help investigate the causes of the accident andimprove nuclear safety in the future. With regard to international cooperation, projects on accident
analysis are in progress at the OECD/NEA based on the knowledge of various countries andorganizations.
A list of the progresses related to this section is provided in Attachment 10, and the details of
OECD/NEA activities are provided in Chapter 4.
3.1.3.6 Progress of research and development for further expansion of fuel debris
retrieval in scale

For issues that are difficult to address in engineering or far-sighted issues, the Project ofDecommissioning, Contaminated Water and Treated Water Management has been promoting65research and development. This R&D is being carried out in accordance with the R&D mediumand-long-term plan and the next-term R&D plan that are described in Chapter 5.2, and it isimportant to proceed exhaustively, systematically and efficiently while confirming that it is inline with the needs of TEPCO as the entity responsible for decommissioning. The followings
are a list of research and development items being performed. The sections describe researchand development that is common to all methods, regardless of the method to be selected,
except for Section 3.1.3.6.8. Although Research and development described in Section
3.1.3.6.8 is only for partial submersion method at present, those for other methods will be
initiated by identifying research issues as necessary in the future.
3.1.3.6.1 Technology for investigation inside the RPV
To avoid regressing in engineering in the fuel debris retrieval method inside the RPV, verifying
the distribution of fuel debris and environmental conditions such as situations and radiation dosesin the RPV is useful.
So far, the Project of Decommissioning, Contaminated water and Treated water Management
has examined a method to access the core via top access (investigation by drilling the upper part)and a method to access the core via side access (investigation by drilling the side). By FY 2019,
the project verified the equipment function toward practical application. In the investigation methodby drilling the upper part, the plan is to use AWJ (abrasive water jets) for the drilling holes (openings)of the in-core structures (dryer, steam-water separator, and shroud head). However, issues suchas the impact on internal investigations and the increase in waste have been pointed out becausea large amount of abrasive enters the PCV and RPV due to the AWJ cutting.
For this reason, from FY 2020, cutting techniques that reduce secondary waste (abrasive, etc.)
were examined. As a result, AWJ with small nozzles and laser cutting were selected as candidate
techniques. A verification test of remote workability from the operating floor using this fabricationequipment is scheduled for FY 2023.
Regarding the investigation by drilling the upper part, it is necessary to specify the details of theengineering work plan, including interference with fuel removal work from spent fuel pool,investigation of the site condition where an ROV for the RPV internal investigation is installed, andimprovement of the site environment.
Considering that it is important to promote the development of a method capable of conducting
RPV internal investigations at an earlier stage, an internal investigation method via lower accesshas been studied since FY 2020. In this method, an investigation device is inserted into the PCV
by using an established access route for PCV internal investigation, and then to the RPV throughthe opening that is assumed to exist at the bottom of the RPV. As a result of the study, the following
methods were developed: for Unit 1, a small drone is inserted into the pedestal through a CRD
opening for investigation, and for Units 2 and 3, a telescopic device mounted on a robot arm isinserted into the pedestal for investigation. By FY 2023, the plan is to perform tests to verify thepractical applicability of these investigation devices via lower access.

66

TEPCO is studying a simple investigation method in which a fiberscope with a small diameterand high radiation resistance is inserted into existing instrumentation piping (small-diameter piping)to access and investigate the inside of the RPV.
As an extension of this study, concerning the technical issues with internal investigation using
the existing piping accessible inside the shroud (passing of clogged sections such as check valves
and T-shaped pipe fittings in the middle of piping, etc.), the Project of Decommissioning,
Contaminated water and Treated water Management is developing elemental technologies to solve
the issues from FY 2022.
Since each unit has many areas where direct visual information of RPV internals is unavailable,
the challenge is gaining the information inside the RPV as early as possible by promoting
engineering leveraging technical development in the Project of Decommissioning, Contaminatedwater and Treated water Management and the developed technologies. The direction of the fueldebris retrieval strategy will be verified based on the acquired information to avoid regressing inengineering and to increase the certainty of the method to be selected.
3.1.3.6.2 Technology for work environmental improvement in reactor building
In accordance with the Mid-and-Long-term Roadmap and TEPCO's Mid-and-Long-term
Decommissioning Action Plan, the removal of obstacles and radiation dose reduction in the reactor
buildings are in progress as improvements of the work environment in work areas/access routes.
In future work related to fuel debris retrieval, the issue in environmental improvement is reducing
exposure during work by establishing safe and reasonable methods to remove obstacles such as
the high radiation dose and highly contaminated installations and through radiation dose reduction
in work areas. The Project of Decommissioning, Contaminated Water and Treated Water
Management Research and Development has promoted R&D on technologies to improve theenvironment in the reactor buildings to support TEPCO’s engineering.
The main work areas related to fuel debris retrieval are high radiation dose areas, such as inside
the reactor buildings. Moreover, the need will arise to handle nuclear fuel materials containingalpha-ray emitting nuclides with a large dose contribution in the case of internal exposure.
Therefore, when considering measures to improve the environment, it is essential to prevent
excessive exposure on the part of workers and to reduce exposure by implementing radiation
protection measures appropriately based on the work environment, such as structures, systemequipment, radiation sources, and doses, as well as operation modes, such as decontamination,
shielding, and removal. Regarding protection from external radiation exposure, the radiation
exposure dose is evaluated considering the radiation sources, the radiation dose rate, and work
hours in the work area. Then, based on the three principles, namely “time, distance, and shielding,”
it will be necessary to implement radiation exposure reduction measures as low as reasonably
achievable. For protection from internal exposure, in addition to system measures such as
suppressing the dispersion of radioactive dust and prevention of the spread of contamination, it isessential to select protective measures according to the contamination state in the work area and67

to strive to prevent inhalation ingestion and body contamination. With these ideas in mind, anappropriate combination of measures such as decontamination, shielding, and remote technology
should be pursued.
In particular, the following are important perspectives to consider in fuel debris retrieval.


The PCV should be accessed from the penetration X-6, etc. after the work environment in
the reactor building is sufficiently secured.

As the reactor building still has areas where the extent of damage due to the accident
remains unknown in the high radiation dose environment, sufficient investigations on theradiation dose distribution and state of contamination, including the contribution from thesurroundings of the target areas, will be conducted to identify the source locations andintensity as much as possible and to build work plans.



Upon adequate verification on the operation feasibility, the target dose rate in the work areas
and access routes shall be set in consideration of the margin for the radiation exposure dose
limit (50 mSv/year and 100 mSv/5 years) for workers specified by laws and regulations.



In the radiation dose reduction plan for high radiation dose areas, operational needs will beclarified and measures will be discussed to reduce the total radiation exposure dose to as
low as reasonably achievable and to accomplish operations with respect to work hours inaccordance with dose limits and the work hours required to accomplish operations.



The development of remote technology will be promoted to remove obstacles that are
relatively difficult to remove, such as equipment in high places and heavy objects.

Based on the above, and as R&D tasks by the Project of Decommissioning, Contaminated Water
and Treated Water Management, the development of technologies to identify radiation sources
using environmental survey data and to digitize the environment and radiation source distribution
visualized by digital technology, for the formulation of safe and efficient work plan has been inprogress since FY 2021. A prototype was built in FY 2022, and development has been underway
since FY 2023 to improve functions for practical applications. Long-term operation is expected tohelp build a system that can accumulate proven knowledge. In order to remove heavy objects,
system equipment in high places, and other obstacles that are relatively difficult to remove, thedevelopment of remote technologies for environmental improvement and removing obstacles underhigh radiation doses began in FY 2020. As a result, the obstacles to be removed were selected,
and the specifications of a remote-control device in accordance with the required functions were
proposed and ended in FY 2022. Going forward, TEPCO’s engineering will promote development
in order to actualize the proposal.

683.1.3.6.3 Development of analytical technology for radiation exposure dose assessment
In the event of intake of alpha-ray emitting nuclide or other nuclides into worker’s body, theeffective radiation dose should be properly assessed using external counting (lung monitor) andbioassays. For this reason, the following is important:

Select alpha-ray emitting nuclides that are important for exposure assessment in advance,
and incorporate them into the control of airborne concentrations, standards for wearing
protective equipment, and equipment calibration management.

Control the surface contamination density in the work environment and the bodies of workers
entering/leaving contaminated areas for the early detection of the spread of contamination
beyond the area division and to prevent the intake of re-suspended dust from loose
contamination.

Relatively high α-contamination has been observed in some parts of the reactor building, and thefrequency of operations in the reactor building has increased as decommissioning work, hasprogressed. As restoration work by human workers in response to problems has also occurred, it
is necessary to proceed with more attention to the intake than before. In preparation for full-scaledebris retrieval in the future, the challenge is to promptly assess the amount of radioactivity of theradioactive materials taken in and evaluate the radiation dose in order to consider more accurately
improving protection functions against the intake as well as responses and measures in the eventof such intake.
The intake of alpha-ray emitting nuclides must be evaluated as early as possible throughbioassay and other methods because of the difficulty of measuring α-rays and the large contribution
to internal radiation exposure dose. In recent years, medical interventions such as medication
administration have been implemented for internal exposure to plutonium, and more complex
actions to intake events have become a challenge. Furthermore, the particularity in the work
environment for decommissioning the Fukushima Daiichi NPS should be taken into consideration
as there are significant differences from existing facilities in Japan and overseas in terms of thenuclide composition and concentration of the radioactive materials handled, the operational
conditions to be controlled, and the number of personnel involved.
In light of the above, in FY 2021, the Project of Decommissioning, Contaminated Water andTreated Water Management began R&D activities to protect against intake and assess the radiationdose in the event of intake, and technical development is moving forward that includes studying
the concept of an internal radiation exposure dose assessment program, investigating andexamining the acceleration of bioassay methods, and optimizing protective equipment. Since
FY2023, developing an internal radiation exposure dose assessment program has been underway
through establishing a comprehensive internal radiation exposure dose assessment system using
bioassays and external measurements, developing standards, and the continued technology
development related to measuring and assessing internal radiation exposure doses.

693.1.3.6.4 Liquid treatment system (α-emitting nuclide removal technology)
Fuel debris retrieval may cause mixing and leaching of granular particulate or soluble alpha-ray
emitting nuclides in higher concentrations than in the current contaminated water because fueldebris is cut or fabricated in a wet or underwater environment. In decommissioning the Fukushima
Daiichi NPS, removing alpha-ray emitting nuclides is a particularly important issue. While water
treatment facilities (SARRY, ALPS, etc.) to remove radioactive materials from contaminated water
are currently in operation, it is necessary to establish a technology that can remove alpha-ray
emitting nuclides from contaminated water and reduce the concentration to a predetermined leveleven when the concentration of alpha-ray emitting nuclides increases. Therefore, the Project ofDecommissioning, Contaminated Water and Treated Water Management technologies have been
engaged in technical research and development to remove particles containing radionuclides,
remove soluble alpha-ray emitting nuclides in an environment simulating practical application, andtreat secondary waste. However, the quality of contaminated water during fuel debris retrieval isunclear until the retrieval begins. Thus, the design of the retrieval facilities will need to set facility
specifications conservatively to compensate for such uncertainties, including the presence of
colloidal alpha-ray emitting nuclides that are difficult to remove. Therefore, it is considered useful
to expand knowledge of the retrieval methods proposed in previous research and development
activities and continue to develop technologies by conducting further tests using contaminatedstagnant water in existing buildings to realize more rational designs. In addition, further researchon secondary waste treatment technology needs to be conducted in coordination with subsequentsorting, transfer, and storage operations. The ongoing efforts in FY2023 include developing
removal technologies that can accommodate colloidal α-emitting nuclides in addition to solublealpha-ray emitting nuclides, preparing tests using contaminated stagnant water in buildings, anddeveloping more rational secondary waste treatment technologies.
Although the basic design and detailed design of the retrieval facilities will be carried out in
preparation for the further expansion of fuel debris retrieval in scale, it would be more rational if theresearch and development results could be incorporated sequentially at each design stage.
Engineering should be promoted considering this point.
3.1.3.6.5 Analytical and estimation techniques for the characterization of fuel debris
The technical development necessary for analysis and estimation techniques for fuel debris
characterization is in progress in the aim of contributing to developing methods for fuel debris
retrieval and removal of in-core structures, and technology for the collection, transfer, and storageof fuel debris. Since FY 2023, as shown in Fig. 18, two primary focuses in these efforts are the“technology development necessary for fuel debris characterization” and the “development of thenondestructive measurement technology necessary for sorting”.
In the technology development necessary for fuel debris characterization, the plan is to analyze
in hot lab facilities fuel debris samples, planned to be collected during trial retrieval in Unit 2, andthe deposit samples collected during PCV internal investigation using the submersible ROV in Unit70

1. Structural analysis and X-ray CT imaging of fuel debris from the Unit 2 of Three Mile Island
Nuclear Power Plant (hereinafter referred to as “TMI-2”) accident are also planned to compare itwith fuel debris at the Fukushima Daiichi NPS. In addition, severe accident progression analysis,material melting tests, and evaluation of relocation behavior of molten materials are underway, witha focus on damage to the reactor pressure vessel. A simple analysis technique is also being
developed to promptly check whether fuel components are contained to reduce the burden oftransporting samples to hot lab facilities when the amount of fuel debris retrieved increases in the
future.
In fuel debris sample analysis, only a portion of the fuel debris to be retrieved is able to be
characterized. Therefore, non-destructive measurement techniques necessary for sorting is underdevelopment, with a focus on the amount of nuclear fuel in the fuel debris. As the analysis involves
the risk of spreading contamination and internal exposure, the aim is to measure the radiation
emitted or transmitted from a sealed object in a container to determine the amount of nuclear fuelpromptly without destroying it. Since fuel debris is a heterogeneous mixture of many nuclides andelements, such as neutron absorbers, which can interfere with measurements, a wide range ofchemical compositions is reproduced through simulation analysis, and the effects of the inhibiting
factors are verified by tests using existing test equipment. The conceptual design of the equipment
and sorting scenarios are under discussion based on these results.

Development of Analysis and Estimation Technologies for Characterization of Fuel Debris
Contents of Project

Development for Characterization of
Fuel Debris

 Characterization of obtained fuel debris
samples, etc. and technology development
to enhance analytic accuracy
 development of estimation technologies of
RPV damaged condition and fuel debris
migration behavior in PCV, etc.
 Technology development for abbreviated(in-situ) analysis of fuel debris

Development of Non-Destructive
Measurement Technologies for Sorting
and Segregation of Fuel Debris andOthers Evaluation of non-destructive measurement
technologies through simulation analysis
 Tests for verification of elemental
technologies
 Conceptual design of non-destructive
measurement devices considering on-site
application
 Investigations of the evaluation methods
and sorting and segregation scenarios※ It does not strictly match the expression in the guidelines, since concise expression and comprehensibility were prioritized.

Fig. 18 Research topics and key activities in analysis and estimation technologies for fueldebris characterization

713.1.3.6.6 Technologies for containment, transfer and storage of fuel debris
Before initiating the gradual expansion of fuel debris retrieval work, a comprehensive systemshould be established that consists of a series of steps from containing and transferring to storageof retrieved fuel debris (pebble or powder) furnished with safety functions such as maintaining
subcriticality, containment functions, countermeasures against hydrogen generation, and cooling.
Accordingly, the examination of the following is underway until the end of FY 2022.27 28
Development of basic specifications for the container (storage cans)26, such as height inconsideration of handling of it, internal diameter, quality of materials and lid structure in lightof work efficiency and maintaining subcriticality, etc., and demonstration of the structural
integrity of the container by testing.

Examination of a practical and rational prediction method of hydrogen generation from fueldebris stored in containers; determination of a vent mechanism for hydrogen gas releaseon the container lid by using the said prediction method and establishment of safe transfer
conditions with consideration for the accumulation of hydrogen gas in transferring casks.



Development of efficient drying technology applicable to fuel debris in unit cans26, andestablishment of a drying system and drying process conditions using this drying
technology



Table-top study of the behavior of powdery fuel debris in containers

Moreover, in reference to the results of these studies, TEPCO continues their activities tomaterialize canisters used for storage and the first storage facilities (receiving/delivery cell, storagecasks, etc.) needed for the gradual expansion of fuel debris retrieval in coordination with otherassociated projects. In addition, study on transfer/storage process, research on storage
technologies/types, narrowing down of candidates, and the investigations of treatment required
before storage fuel debris and survey of method and route of transfer of fuel debris to the storagesite are ongoing toward the further expansion of fuel debris retrieval in scale. These studies havefocused on pebble or grain state of fuel debris. Retrieving the powder fuel debris generated by fueldebris working (cutting and machining) are considered to be retrieved in a powder state in the gas
management systems, or slurry, or sludge state in cooling water circulation ones. Therefore,technical issues for the safe, reliable, and rational storage of powder or sludge/slurry fuel debris
have been identified in the Project of Decommissioning, Contaminated Water and Treated Water
Management in FY2020. Based on these results, since FY2021, desktop studies on the method ofdrying slurry/sludge fuel debris, the characteristics of hydrogen gas generation and its release
behavior from them, and their behavior during handling from transfer to storage operation havebeen in progress. From FY2023 onward, based on the study results in the Project of27

Publication of the 2022 Performance Report on the Development of Fuel Debris Drying Technology)(https://irid.or.jp/wp-content/uploads/2023/06/2022013syuunoukankansouF202306.pdf）
28
Publication of the 2022 Performance Report on the Development of Handling Pulverized, Slurry and Sludge
Fuel Debris (https://irid.or.jp/wp-content/uploads/2023/06/2022014syuunoukankonajyouF202306.pdf)

72Decommissioning, Contaminated Water and Treated Water Management and new findings on fueldebris properties and conditions in PCVs, the consideration on the previous study and evaluation
results will be deepen and will be verified component tests. It is necessary to steadily advancethese activities in order to accumulate and share information that will contribute to theestablishment of processes for the safe, reliable, and rational storage of slurry/sludge fuel debris
and the design of equipment and systems necessary for composing such process.
At present, since the information and knowledge on the properties of fuel debris are limited,
equipment and installations are designed based on conservative assumptions of the properties offuel debris in the studies by the Project of Decommissioning, Contaminated Water and Treated
Water Management and by TEPCO. In the design of equipment and installations for the containing,transferring, and storage of fuel debris for the further expansion of fuel debris retrieval in scale, it
is important to proceed in a streamlined manner by utilizing a variety of measurement data thathave been collected and accumulated during the trial retrieval and gradual expansion of fuel debris
retrieval, such as the amount of hydrogen generation and debris properties as well as knowledge
and experience of the handling of fuel debris during the operations from transfer of fuel debris tostorage. In developing the specific equipment and installations for handling and storing retrieved
fuel debris, it is also necessary to consider satisfying the safeguard requirements.
Unit cans and containers in which fuel debris is stored should be handled by remote control
devices in a safe and reliable manner. Therefore, it is useful to perform mock-up testing of possible
tasks using an actual or similar remote-control devices in the initial stage of detailed design.
Moreover, to prevent design change/modification, it is also considered to be a useful approach todetermine the specifications of equipment and installations required for containing, transferring,and storing fuel debris, as well as their size, their layout, and the flow of fuel debris handling basedon the knowledge gained through mock-up tests.
The Mid-and-Long-term Roadmap stipulates that the processing/disposal method of the retrieved
fuel debris shall be investigated and fixed during the third phase after starting the fuel debris
retrieval work.
3.1.3.6.7 Data acquisition of dust dispersion rate
For the further expansion of fuel debris retrieval in scale, it is necessary to develop fuel debris
retrieval methods and safety assessment techniques for accident events. In safety assessment, in
addition to understanding the relocation from the point of retrieval to the air and the amount, it isnecessary to assess the relocation behavior of the dust generated by fuel debris fabrication, cutting,etc., during fuel debris retrieval, including dispersion, deposition, and resuspension as a basis. In
the acquisition of dust dispersion rate data, with a focus on the above points, knowledge about dust
dispersion, such as dust generation and relocation, has been acquired through tests simulating fueldebris retrieval environments to gain knowledge on dust dispersion rates.
To develop this safety assessment technique, data on the dust dispersion rate in dry conditions
were acquired to understand the basic effects of dust dispersion during fuel debris retrieval. The73

assumed environment during fuel debris retrieval is a wet environment in PCVs, and the acquisitionof data on dust dispersion rates in such an environment for multiple retrieval methods has been inprogress since FY 2023 based on the results obtained up to FY 2022. The acquired data are beingorganized systematically to serve as a technical basis for safety assessment during fuel debris
retrieval in the future decommissioning work of the Fukushima Daiichi NPS.
3.1.3.6.8 Fuel debris retrieval method
For the fuel debris retrieval method for the further expansion of fuel debris retrieval in scale, on
the assumption that the fuel debris retrieval work will be a remote operation under an environment
with high radiation dose, high contamination, and high uncertainty, the issue is developing thetechnology for the devices, equipment, and systems required for establishing access routes to the
PCV and fuel debris retrieval. In response to these issues, the Mid-and-Long-term Roadmap(September 26, 2017) indicated a fuel debris retrieval policy focused on the partial submersion
method. Accordingly, as subsequent R&D activities, the Project of Decommissioning,
Contaminated Water and Treated Water Management is developing retrieval methods via side andtop access for the partial submersion method and elemental technologies common to the side andtop access methods. Elemental technologies for the side access retrieval method have beendeveloped, such as a fuel debris retrieval system (suction, gripping, etc.), a fuel debris cutting/dustcollection system, technologies to prevent the spread of contamination to the S/C, cell structures
for access route construction, carry-in and installation technologies, technologies to connect with
the PCV, technologies to remove obstacles, and remote-control support systems. As for the
retrieval method via top access, initially, there were discussions on retrieving fuel debris byshredding it in the reactor and carrying it out. However, a method of cutting the in-core structuresand fuel debris into large units and carrying them out has been under study since FY 2019 toincrease throughput. The following have been developed as elemental technologies: methods anddevices for cutting into large units, large transport devices, isolation mechanisms between theoperating floor and the additional building to prevent the spread of contamination, and largetransport containers. The development of remote decontamination and maintenance technologies
for contaminated equipment and the development of dust dispersion control materials during fueldebris fabrication have been promoted as elemental technologies common to the side and top
access methods.
From FY 2023, as a response to the issues identified in the results obtained in the developmentof the retrieval method via the top access so far, the system development for the upper part of theoperating floor, such as large transport equipment considering the containment performance, andtechnology development such as for filling, stabilizing, and cutting damaged in-core structures will
be promoted. In addition, to address new issues, since heavy objects may fall to the bottom of thepedestal during retrieval via top access due to cut pieces and vibration during fabrication,technology development for fall prevention will be promoted to prevent re-criticality due to falls,
dust dispersion, or equipment damage. TEPCO is in process of conducting a conceptual study to74

develop methods for the further expansion of fuel debris retrieval in scale to verify actual site
applicability and technical feasibility of measures against the issues related to partial submersion
and submersion methods (shell structure), as shown in Section 3.1.3.4. For issues that are
determined to have a high need for new development and high technical difficulty, the Project ofDecommissioning, Contaminated Water and Treated Water Management will proceed with thenecessary technological development.
3.1.3.7 Issues in examining safeguards strategies
Since material accountancy and safeguards for the retrieved fuel debris are unprecedented,
TEPCO may face technical issues in examining and applying them to the site. For this reason, NDF
will conduct wide-ranging surveys on existing technologies related to material accountancy andsafeguards to prepare in case that TEPCO needs technical assistance. NDF will also check the
progress of the project from an engineering perspective to confirm that the application ofsafeguards to systems does not affect the decommissioning process.

3.1.4 Summary of key technical issues
The key technical issues and future plans described in this section are summarized as shown in
Fig.19.

75

Fig. 19 Key technical issues and future plans on fuel debris retrieval (progress schedule)763.2 Waste management
3.2.1 Target(1) The Solid Waste Storage Management Plan (hereinafter referred to as the “Storage
Management Plan”) is developed and revised with updating the estimated amount of solid
waste29 to be generated in the next 10 years, as well as appropriate storage/management
should be implemented including waste prevention, volume reduction, and monitoring ofstorage/management conditions based on it.
(2) Based on the prospects of processing/disposal methods of solid waste and technology
related to their safety (hereinafter referred to as “Technical Prospects”) presented in FY 2021,
the creation of options for processing/disposal measures and their comparison andevaluation should be conducted with promoting characterization to establish waste streams
that are suitable for the features of solid waste. Proceed study on specific management of
the solid waste to present appropriate measures as a whole.
(3) Develop and update the analysis plan necessary to advance the consideration ofstorage/management and processing/disposal, and proceed steadily with analysis based onit.
3.2.2 Progress
Waste management is a long-term effort that needs to attain the prospect of implementing final
disposal, while reducing risks in every stage from generation through storage/management,
processing, and disposal. Definitions of terms related to radioactive waste management in the IAEA
Safety Glossary Terminology are shown in Attachment 11, and classification and disposal ofradioactive waste in Japan and abroad are shown in Attachment 12.
Since a large amount of solid waste with various characteristics is generated in association withdecommissioning of the Fukushima Daiichi NPS, the efforts based on the following “Basic Policies
on Solid Waste” summarized in the Mid-and-Long-term Roadmap are underway.

<Key points of “Basic Policies on Solid Waste”>① Thorough containment and isolation
・Thoroughly containment and isolation radioactive materials to prevent human access tothem, in order not to cause harmful radiation exposure.
② Reduction of solid waste volume
・To reduce the amount of solid waste generated by decommissioning as much as possible.
③ Promotion of characterization

29

In the Mid-and-Long-term Roadmap, “solid waste” is defined as “some of the rubbles and other materials
generated after the accident may not be treated as waste or radioactive waste due to reuse at the site, etc., as
described below, but these, including secondary waste generated by water treatment and radioactive solid
waste stored at the Fukushima Daiichi NPS before the accident, are hereinafter referred to as “solid waste”.

77・Proper characterization addressing an increase in the number of analysis samples toproceed with studies on processing/disposal methods of solid waste.
④ Thorough storage/management
・Generated solid waste should be stored/managed safely and reasonably according to its
characteristics.
・Storage capacity should be secured to ensure that the waste can be stored/managed within
the site of the Fukushima Daiichi NPS.
⑤ Establishment of selection system of preceding processing methods in consideration of disposal
・To establish selecting methods of processing for stabilization and immobilization (preceding
processing) and then select preceding processing methods before technical requirementsof disposal are established.
⑥ Promotion of effective R&D with an overview of overall solid waste management
・To establish the continuous operational framework including development of relevant
facilities and human resources in order to continue safe and steady solid waste
management.
⑦ Development of continuous operational framework
・To establish the continuous operational framework including development of relevant
facilities and human resources in order to continue safe and steady solid waste
management.
⑧ Measures to reduce radiation exposure of workers
・Thorough implementation of radiation exposure control, health and safety management
based on the relevant laws/regulations.

TEPCO is required to ensure safe and reasonable storage/management of the solid waste
generated. Led by NDF, the organizations concerned are promoting efforts based on each role toadvancetechnical

examinationof

integrated

measuresfromcharacterization

toprocessing/disposal of solid waste. The Technical Prospects were provided in FY 2021 in light ofthe development results for improving analysis abilities for characterization and establishing aflexible and reasonable waste stream (the flow of the integrated measures from characterization toprocessing/disposal). The Mid-and-Long-term Roadmap stated that the properties of solid waste
would be analyzed, and the specifications of waste form and their production methods will be
determined in Phase 3. Therefore, the study was initiated for specific management of solid waste
to present appropriate measures as a whole.
Until FY 2021, IRID took the lead in the Project of Decommissioning, Contaminated Water andTreated Water Management related to solid waste, with the JAEA as a key player. However, the
JAEA is taking the main role in the projects by itself which are started from FY 2022.

a. Current status of storage/management in Fukushima Daiichi NPS
Table 2 shows the current storage/management status for solid waste. To store/manage thesesolid wastes properly, TEPCO releases its Storage Management Plan, and estimates the volume78

of solid waste that will be generated in the next ten years and shows their policy such as onbuilding waste management facilities to be required based on the volume.
According to this Plan, all the temporary outdoor storage of the solid waste will be eliminatedcompletely by FY 2028, except for secondary waste generated by water treatment and targetsof reuse/recycling. Facilities needed to achieve this goal are under development (Attachment 13)
and the processing plan30 and transfer plan31 related to this were examined.
To date, waste has been stored/managed by classification based on the surface radiation dose
rate as an index because a large amount of rubble is contaminated by fallout. From now on, formore appropriate storage/management, the radioactivity concentration will be assessed throughanalysis of each waste product with a view to promoting reuse on-site.
The Technical Prospects have provided the examples of foreign countries that have
implemented the waste hierarchy concept (the priorities for measures to be taken as waste
management are in the following order: (1) prevention of waste generation, (2) minimization ofwaste volume, (3) reuse, (4) recycling, and (5) disposal. In waste management, it is important toprioritize (1) as much as possible and consider (5) disposal as the last option (Fig. 20)), andTEPCO has also been implementing initiatives corresponding to this concept.
Among the targets of reuse/recycling, concrete rubble is crushed and recycled as roadbed
material on the premises of Fukushima Daiichi NPS after confirming that the surface dose rateis equivalent to the background radiation dose. In addition, such as by melting is underconsideration as a decontamination method for recycling metal. The Project of Decommissioning,
Contaminated Water and Treated Water Management is in progress to clarify the nuclide
distribution behavior during melting and decontamination and examine validation methods after
melting processing as required research and development to achieve the above.
Secondary waste generated by water treatment is planned to be transferred to store in abuilding, with priority given to sorption apparatus that contain large amount of radioactivity, anda large waste storage building is being constructed as a storage facility for sorption vessels.
Moreover, ALPS slurry generated by the multi-nuclide removal equipment, etc., and the waste
sludge generated at the decontamination equipment have high water content and flowability. For
safer storage/management, ALPS slurry will be examined for performing stabilization(dehydration) treatment based on the issues related to storage risk reduction and volume
reduction at the Study group on Monitoring and Assessment of Specified Nuclear Facilities andthe Technical Meeting on the Examination of the Implementation Plan of the Measures for theSpecified Reactor Facilities (scheduled installation of processing facility in FY 2026). Waste
sludge will be collected from the underground storage tanks in the building, where it is currently

30

Verification of whether the necessary volume reduction will be completed by estimating the operation andprocessing periods based on the completion time of the construction of each facility for volume reduction.
31
Assessment of the impact on receiving operations in terms of the impact of the completion time of the solid
waste storage.

79

stored, dehydrated and then stored into containers, before being transferred to higher ground(starting in FY 2025).
In the Measures for Mid-term Risk Reduction at TEPCO's Fukushima Daiichi NPS, a policy forsolidifying dehydrated and recovered materials and sorption associated with water treatment
waste (unstable) will be developed by FY 2025. As further goals from FY 2026 to FY 2034, it also
shows the transition to a more stable condition (dehydration or solidification processing andstorage in facilities with the required seismic resistance) is the conditions to be realized.
Such solid waste requiring proper storage/management in the Fukushima Daiichi NPS willcontinue to be generated with some exceptions. The Storage Management Plan published in
February 2023 describes a considerable amount of waste is expected to be generated in futurepreparatory work for fuel debris retrieval, etc. The amount of waste generated is estimated to beat least 300,000 m3, including specifically that from dismantling the buildings around Unit 1 to 4
and resin and other wastes generated before the earthquake, on the assumption that there is
uncertainty due to the fact that the fuel debris retrieval method has not been determined. In the
future, the amount of waste generated will be scrutinized in anticipation of the volume reduction
effects of incineration/crushing, etc. Solid waste will be also generated from fuel debris retrieval.
It is also necessary to consider how to deal with this solid waste in the future.

80

Table 2 Status of solid waste storage/management(a) Management status of rubble, fallen trees, used protective clothing, etc. (As of July 31, 2023)
Stored volume (m3) / Storage capacity (m3)(Percentage)
302,200 / 397,900(76%)
43,700 / 55,300(79%)

Classification
Outdoor storage(surface radiation dose rate ≤ 0.1 mSv/h)
Outdoor sheet covered storage(surface radiation dose rate 0.1 - 1 mSv/h)Soil-covered temporary storage facilities,
outdoor container storage(surface radiation dose rate 1 - 30 mSv/h)

16,400 / 17,200(95%)
29,700/ 39,600(75%)
392,000 / 509,900(77%)

Containers* (in solid waste storage building)
Total

Fallen trees
Stored volume (m3) / Storage capacity (m3)(Percentage)
70,000 / 134,000(52%)
37,300 / 41,600(90%)
107,300 / 175,600(61%)

Classification
Outdoor storage(trunks, roots, branches, leaves)Temporary storage pool(branches, leaves)
Total

Used protective clothing, etc.
Stored volume (m3) / Storage capacity (m3)(Percentage)
20,000/ 25,300
Temporary storage(79%)* Including secondary waste generated by water treatment (e.g. small filter)
Note that the storage volume is rounded to the nearest 100m3, so the total and the breakdown may not be
consistent.
Classification(b) Management status of secondary waste generated by water treatment (As of August 3, 2023)
Sorption vessels, etc.

Outdoor temporary storage area ofused sorption vessels

Place stored

Storage volume

Cesium sorption apparatus

779

2nd Cesium sorption apparatus

263

3rd Cesium sorption apparatus

18

HICs from multi-nuclide removal
systemUsed vessels from highHighperformance multiperformance
nuclide removal system
Used columns frommulti-nuclide removal
Existing
systemUsed vessels and filters from mobile
treatment systems

4,212

81

Number of vessels
and filters
Number of vessels
and filters
Number of vessels
and filters
Number ofcontainers

90

Number of vessels

17

Number of Columns

229

Number of vessels

Storedvolume/capacity(Percentage)

5,608 / 6,500(86%)

Waste sludge
Stored volume (m3) / storage capacity (m3)(Percentage)
434 / 700
(62%)

Storage place
Sludge storage facility (indoor)

Concentrated liquid waste
Storage method
Concentrated liquid waste storage tanks (outdoor)

Stored volume (m3) / storage capacity (m3)(Percentage)
9,468 / 10,300(92%)

Fig. 20 Summary of waste hierarchy at the NDA, and countermeasures at the Fukushima
Daiichi NPS
b. Examination of processing/disposal methods
For characterization, examinations are in progress to establish a methodology for developing
a medium-to-long-term analysis strategy that defines the solid waste to be analyzed, its priority,and quantitative targets for analysis, etc. The outcome of the analysis methods for simplified andspeed-up data acquisition, which have been studied, are being evaluated for feasibility andvalidity for use as standard analysis methods at the Radioactive Material Analysis and Research
Facility Laboratory-1. Moreover, sampling of sorption from cesium sorption apparatus (KURION
and SARRY) is in progress at the Fukushima Daiichi NPS site to obtain analytical data on highactivity waste.
For storage/management, nuclide distribution behavior when melting and decontaminating
contaminated metals for volume reduction and reuse technology of metal waste and theconfirmation method after melting processing is being studied.
As for the processing technology, while the prospects of the application as actual equipmentof normal-temperature processing technology were confirmed through full-scale tests, further
discussions are underway on the inspection methods for verifying the possibility of solidification82

and evaluation methods of the stability of solidified waste (leaching characteristics, long-term
alteration phenomenon, radiological impact, etc.) produced by various processing technologies.
To contribute to the expansion of technological options, such as expanding the scope of
application of normal-temperature processing technologies, verification of the applicability ofpyrolysis processing and other interim processing technologies to detoxifying organic substances
and inactivating reactive/corrosive substances is underway. Studies are also being underway on
the following possibilities as a preliminary study to address anticipated issues flexibly andrationally in the immediate decommissioning work.
The bulk solidification technologies without segregating a large amount of miscellaneous
rubble which is difficult to segregate and may contain hazardous materials etc.



The technology to process slurry dehydrates and their containers together whichsimplifies the preceding process when processing slurry dehydrates after stabilization toeliminate the need for development related to removal from container.

Concerning disposal technology, the necessary information and knowledge are being
investigated to develop measures that meet the needs of the disposal concept for waste, forwhich review of the waste stream is underway. A storyboard on the progression of important
events in disposal facilities is under development to identify critical scenarios for solid waste
disposal.
3.2.3 Key issues and technical strategies
The Mid-and-Long-term Roadmap stated that the characterization of solid waste would bepromoted and the specifications of waste form and their production methods will be determined inPhase 3. Therefore, in coordination among the areas of characterization and processing/disposal,
the following study will be conducted to present appropriate overall measures for specificmanagement approaches for solid waste while reviewing the necessary R&D tasks.
The first step is to create processing/disposal options by examining pending issues related
to processing technology, interim processing, and disposal options.

Then, the options will be compared and evaluated using the property data that are becoming
clear, and examinations will be conducted to establish a waste stream that is suitable forthe characteristics of solid waste.

Institutions concerned, led by NDF, are conducting technical studies on integrated measuresfrom characterization to processing/disposal of solid waste based on their respective roles.
To facilitate these efforts toward continued actions through an R&D organization with a high levelof technology and human resources, it is essential for institutions concerned to make constantefforts to develop human resources and improve technological capabilities in the area of waste andmake efficient use of resources by strengthening collaboration within this area and making mutual
use of the results of such efforts. An environmental arrangement that enables the maintenance and83

strengthening of the supply chain, including the elemental technologies necessary for each stageof waste management and peripheral technologies supporting them, should also be considered.
3.2.3.1 Characterization(1) Acquisition and management of analysis data
While accumulating analytical data, inventory for solid waste will be continuously improved, whichis the basic information for solid waste management, including processing/disposal. In this case,efforts will be made for low-activity waste, such as rubble, and high-activity waste, such as
secondary waste generated by water treatment and waste generated from fuel debris retrieval,according to the characteristics of each type of waste.
Although the analysis work itself is not difficult, low-activity waste has the feature of enormousvolume. And the limited number of analysis data obtained for high-activity waste due to the difficultyof sampling. Considering their features, analysis of such waste makes it important to take anapproach that ensures the required accuracy efficiently. For these issues, efforts to establish an
efficient analysis project approach that combines the DQO process32 with statistical methods areunderway and will continue.
In addition, the development of technologies necessary for the analysis of samples to becollected from cesium sorption apparatus, waste generated from fuel debris retrieval, and difficultto-measure nuclides will be promoted.
(2) Developing a framework for improving analysis capabilities and steady implementation ofanalyses
Efforts are being made to improve facilities, develop human resources for analysis, and pass onand strengthen analysis techniques capabilities to promote characterization steadily. Capacity ofanalysis has been enhanced with the completion of Radioactive Material Analysis and Research
Facility Laboratory-1 in June 2022. With that capacity in mind, analyses contributing to solving
issues in the decommissioning process will be performed systematically, considering the priority ofsamples.
The Project of Decommissioning, Contaminated Water and Treated Water Management is
promoting the development of mid-to-long-term analysis strategies; annual analysis planning; dataacquisition and analysis; the incorporation of the acquired data into an examination ofprocessing/disposal methods and an evaluation of the outcome; the development of the next midto-long-term analysis plans based on the evaluation results; and the establishment of a flow. As
acquired data should be used for overall waste management, TEPCO should provide
comprehensive management of solid waste characterization, including adjustment of the analysis
supply chain33.

32

Method for planning the sampling of analytical samples for decision making developed by the U.S.
Environmental Protection Agency.
33
The entire process of securing facilities for sampling and analysis, transporting samples, etc.

84

In March 2023, TEPCO developed an analysis plan for the characterization and optimization ofstorage/management to discuss solid waste processing/disposal methods. Based on the plan, thefollowing will be addressed in cooperation with the JAEA:


Incorporate into specific analysis work,

Review the analysis plan,

Identify the details of necessary technical development tasks,Establish the operational structure of the analysis supply chain early,

Radioactive Material Analysis and Research Facility Laboratory-1 started analysis work using
radioactive materials in October 2022. By the end of FY 2023, the simplified and speed-up analysis
techniques that have been developed will be demonstrated as standard analysis methods.
Moreover, TEPCO’s new facility for analysis is scheduled to be operational in the second half ofthe 2020s. The facility should be developed systematically with due consideration for the above
analysis plan, emerging analysis needs in the decommissioning process, and the appropriate role
allocation with the existing facilities.
3.2.3.2 Storage/management
Storage/management of solid waste should be appropriately implemented for the risk dependingon the radioactivity concentration and properties, etc. Moreover, it is important to reconsider
measurement items and timing, etc., in terms of diverse information for characterization, while
acquiring necessary information through continuous monitoring and surveillance of thestorage/management status commensurate with the risks involved.
(1) Transition to management by classification of radioactivity concentration
Currently, waste is stored/managed by classification based on the surface radiation dose rate
because a large amount of rubble is contaminated by fallout. In preparation for the expected
increase in the amount of solid waste generated with the progress of decommissioning, it will transit
to the management of radioactive waste based on the concentration of radioactivity and examine
the rational classification of waste and reuse on-site.
(2) Efforts to eliminate temporary outdoor storage
The Mid-and-Long-term Roadmap calls for eliminating temporary outdoor storage of all solid
waste, excluding secondary waste generated by water treatment and waste subject to reuse andrecycling, by the end of FY 2028. To achieve this goal, it is necessary to develop necessary facilities
and installations systematically including incineration/volume reduction facilities and solid waste
storage, and promote steadily consolidate storage of solid waste inside buildings.

85

In addition, taking into account the views34 of the Study group on Monitoring and Assessment ofSpecified Nuclear Facilities and the Technical Meeting on the Examination of the Implementation
Plan of the Measures for the Specified Reactor Facilities, regarding the practicality and rationalityof storage of low-level concrete and other waste, an examination will be carried out on
storage/management methods which are safe, reasonable and feasible, such as classificationaccording to the characteristics of the main nuclides with a view to long-term processing/disposal.
(3) Storage/management of ALPS slurry
Although there is a delay in installing the ALPS slurry stabilization/treatment system, theimmediate storage capacity has been secured. The upper limit of the integrated absorbed dose
(5,000 kGy) will be evaluated to exceed before the commencement of the stabilization process,and the HICs that needed to be transferred continuously increased. To ensure storage capacity for
HIC and transfer for the time being and to transit to a more stable state, stabilization/treatment
system installation and processing will proceed in a planned manner.
(4) Storage/management of solid waste generated from fuel debris retrieval
With regard to high-activity waste such as waste generated from fuel debris retrieval, the issues
and countermeasures assuming the further expansion of fuel debris retrieval in scale have beenclarified according to the results of Project of Decommissioning, Contaminated Water and Treated
Water Management up to FY 2021. Going forward, reviews will be performed along with examining
the fuel debris retrieval methods. Measures will be taken to ensure the storage/management ofsolid waste expected to be generated during fuel debris retrieval (trial retrieval, gradual expansionof fuel debris retrieval) before full-scale retrieval.
According to the preparatory works for fuel debris retrieval, it was estimated that at least
300,000 m3 of waste would be generated, including that from dismantling the buildings around Units
1 to 4, and resin and other waste generated before the earthquake, regardless of the fuel debris
retrieval method. It is not expected that this amount of waste can be reduced in volume byincineration and volume reduction facilities. Although further examination is required, solid waste
will continue to be generated during decommissioning work in the future, so only increasing storage
capacity for solid waste will eventually reach the limit. First, it is essential to steadily continue
measures for volume reduction implemented so far (Fig. 20) and examine further possibilities forvolume reduction by referring to advanced cases overseas.
3.2.3.3 Processing/Disposal
To specify a suitable overall picture covering the entire waste stream, the trial examples of setting
appropriate waste streams will be accumulated to acquire findings by waste stream widely.
Therefore, the R&D of processing and disposal technologies required for the series of studies, as
shown in Fig. 21, will be continued.
34

The 107th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, Material
3-1, “Approach to Solid Radioactive Material Target in Medium-term Risk Reduction Target Map,” NRA

86

(1) Processing technology
Regarding the normal-temperature and thermal processing technology for which research anddevelopment have been promoted:

Assessment of waste streams not yet considered for applicability,

Evaluation of the stability, etc., of the solidified waste to be produced,

Activities to address the above pending issues will continue.
As for normal-temperature processing technology, consideration is given to the transformation ofsolidified waste as well as test methods to verify the possibility of solidification. In the case ofthermal processing technology, the feasibility of the whole processing system, including supply andexhaust systems, is an issue in addition to the solidification process, and therefore it is necessary
to carry out examination in a timely manner according to the start time of processing.
Securing storage capacity is an issue for ALPS slurry constantly generated from water treatment.
Thus, in light of the point at issue regarding the dehydrate technologies for ALPS slurry in the Studygroup on Monitoring and Assessment of Specified Nuclear Facilities and the Technical Meeting on
the Examination of the Implementation Plan of the Measures for the Specified Reactor Facilities,
the issues related to dehydration should be considered sufficiently to discuss requirements inselecting treatment technologies to be applied, with priority.
In addition to measures for the issue of establishing a medium-to-long-term waste stream, astudy will be conducted as follows to address anticipated issues in the immediate decommissioning
work flexibly and reasonably.


As measures for a large amount of miscellaneous rubble, which is difficult to segregate andmay contain hazardous materials etc., the potential of bulk solidification technologies forwithout the segregation will be examined. Collecting information on the segregation-based
approach will also continue for consideration.



The potential of technologies to process dehydrated ALPS slurry together with the container
will be considered, simplifying the preprocess when processing dehydrated ALPS slurry
produced in the slurry stabilization processing system where early installation is required,and eliminating the need for development associated with removal from containers.

(2) Disposal technology
Concerning disposal technology, to enhance the reliability of the disposal concept, feasibility ofdisposal concept will be evaluated based on a study of the long-term evolution behavior of thedisposal facilities and incorporated the results into its discussion in light of the characteristics ofsolid waste. To appropriately allocate waste to a disposal concept that is shown to be feasible,
knowledge on the sensitivity structure of scenarios and parameters to radiation should be expandedby adequately incorporating the characteristics of waste, changes in environmental conditions inand around disposal facilities into those scenarios and parameters of radiation dose assessment,
and repeating tests. By using this knowledge, safe and reasonable disposal options are proposed.

87

Furthermore, after expanding the target of waste streams incorporating this disposal option, a groupof disposal options will be examined with a bird-eye-view of all solid waste at the Fukushima Daiichi
NPS. Then, contributions will be made to considering specific management approaches for solid
waste in coordination with areas other than disposal, such as presenting targets for waste form
performance and the accuracy required for characterization.

Generation ofwaste

Pretreatment andtreatment

Near-term storageand management

・ Improve accuracy of data on
properties, for disposal safetyassessment
・ Acquire additional data,
review transfer models
・ Quantify factors interferingwith waste conditioning

・ Based on treatment
schedules, update plans forrequired timing, capacity,
etc. of storage facilities
・ Update waste classifications
・ Change combinations ofwaste to be treated

Waste conditioning

・ Review waste specification
proposals to meet disposal
requirement proposals
・ Identify technologies that canbe applied
・ Improve quality control
processes

・ Review disposal methods(design of disposal facilities)
and assessment methods(scenarios, models,assessment parameters)

DisposalRequirement
proposals

・ Specify processing
technology suitable for
waste
・ Designate waste
specifications

Policy fornarrowing
down

Disposal・ Specify reasonable andfeasible disposal
methods
・ Conduct disposal safetyassessments

Proposals forprocessing/disposal options

・ Manage risk throughmonitoring and surveillance・ Consider risk reduction
measures as necessary

Processing

Waste
specification
proposals

Storage/management

Stablestorage・ Set inventories

Property
data

Characterization

DisposalReflect in TEPCO and solid
waste storage management plans

Fig. 21 Procedure to reasonably select safe processing/disposal methods of solid waste
3.2.4 Summary of key technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
22.
The Mid-and-Long-term Roadmap stated that the properties of solid waste would be analyzed,
and the specifications of waste form and their production methods will be determined in Phase 3.
Therefore, in Phase 3-[1], the study will be initiated to present appropriate overall measures for
specific management approaches for solid waste. Specifically, based on the realistic inventory
setting that incorporates property data evaluated by accumulating analysis data and applying
statistical methods,Widely acquire findings by waste stream by accumulating trial examples of appropriate waste
stream settings under the assumption of ensuring safety,Then, consideration will be given to specify appropriate overall picture covering the entire
waste stream, allowing clarification of approaches toward such purposes.

In examining these, it is important to flexibly consider appropriate measures, taking into accountthe actual use and economic feasibility by reflecting the newest findings and applying the conceptof the Best Available Techniques. As the examination progresses, in finalizing the88

processing/disposal methods for the overall picture of waste, it will be important to share theexamination process for overall optimization, such as by sharing the awareness of problems withlocal communities and society.
Fiscal year

2021

2022

2023

2026

2031 (Year)

On-site work
Technical studies for on-site construction

Related Milestones

Research and development

Processing/disposal methods
and technical prospects
regarding their safety

Outdoor storage will be eliminated completely

1. Waste characterization(1) Acquisition/managementof analysis data

Sampling
Development of samplingtechnology for high activity samples
Analyzing

Development/establishment of waste confirmation method

Analyses and measurements
for waste confirmation(2) Enhancement of efficiency
on waste characterization

Investigating the applicability of statistical inventory estimation methods and improving their accuracy
Study on analysis plan (Developing mid-to-long-term/yearly analysis plan, study on nuclides to be analyzed,
lower limit of quantification and number of samples to be collected, etc.)(3) Improvement of analysis
capacity

Development of Radioactive Material
Analysis and Research Facilities
Human resources development for analysis

Storage/management

2.Storage/management(1) Storage Management Plan

(2) Study and evaluation ofstorage methods(3) Reduction in volume

Development and review of the Storage Management Plan

Review according to fuel debris retrieval (Evaluation of type, volume, etc.)

Reduction of carry-in, re-use, recycling, volume reduction treatment, etc.

Development of technology for volume
reduction/recycling

3. Processing/disposal(1) Processing technology

Development of processing technology, Evaluation of long-term stability of solidification

Development of interim treatment technology(2) Disposal technology

Creating disposal concept suitable for solid waste

Improving reliability of safety assessment technology(3) Study on waste stream

Identifying waste stream
suitable for solid waste

Building a methodology
for safety assurance

Study on appropriate measures for entire waste management

Fig. 22 Key technical issues and future plans on waste management (progress schedule)
893.3 Contaminated water and treated water management
3.3.1 Target(1) Under the three principles concerning the contaminated water issues (“removing”
contamination sources, “redirecting” fresh water from contamination sources, and “retaining”
contaminated water from leakage), the target is to control the amount of contaminated water
generated to less than 100 m3/day or less with the average rainfall by the end of 2025, andabout 50 to 70 m3/day by the end of FY 2028, while continuing the operation of the constructedwater-level management system. Moreover, to ensure the stable implementation ofcontaminated water management, measures for mitigating large-scale natural disaster risks,such as tsunamis and storm rainfall, will be implemented in a planned manner.
(2) To arrange the relationship with a decommissioning process including full-scale fuel debris
retrieval beginning in the near future, and to promote examination of the measures of thecontaminated water management for medium-and-long term prospects.
(3) To discharge ALPS-treated water35 safely and reliably to secure the site and other resources
and steadily advance the entire decommissioning process.
3.3.2 ProgressFig. 23 shows the outline of contaminated water management. Stagnant water in buildings, thatis, contaminated water with a mixture of cooling water that has come into contact with the fueldebris and groundwater/rainwater that leaked into the buildings is liquid containing a considerable
amount of the dissolved radioactive materials (inventory) from the perspective of measures toreduce the risk from radioactive materials. Therefore, its Hazard Potential is high and so is theRequiring Level for Safety Management, as the storage condition of such stagnant water deviatesfrom what is originally intended. For this stagnant water in buildings, excluding the reactor buildingsof Units 1 to 3, where circulating water injection is ongoing, and the process main building and hightemperature incinerator building storing contaminated water temporarily for purification treatment,
the treatment of stagnant water in buildings was completed in 2020, and the inventory wassignificantly reduced. However, the Hazard Potential is still high.

35

Water that has been purified by multinuclide removal equipment systems (ALPS：Advanced Liquid Processing
System), etc., to a level that is definitely below the regulatory standard for safety of radioactive materials otherthan tritium

90

Red
Purification
Welded tanks

Remove Cs
Desalination

Pump out

Pavement

Groundwater bypass

Groundwater level

Repair damaged
part of the roof
Tide
embankments
Ground improvementwith waterglass
Bottoming
TrenchPump out megafloat

T/B

Pump out

Pump out

Harbor

Sea-side
Impermeable wall

Open channel

Pump out

Groundwater
drain

Further lowering of
the water level

Land-side impermeable wall

Stagnantwater

Sub-drain

Sub-drain

Land-side impermeable wall

Pumping well

R/B

: (1) Contaminated water management in accordance withthe three principles
Blue : (2) Completed stagnant water treatment
Green : (3) Stable operation of contaminated water management(Source: TEPCO)

Fig. 23 Outline of contaminated water management

36

Currently, the following four measures are being implemented as contaminated water
management:(1) Efforts to promote contaminated water management in accordance with the three principles(“removing” contaminant sources, “redirecting” fresh water from containment sources, and“retaining” contaminated water from leakage)
To reduce the amount of contaminated water generated to less than 100 m3/day by the end of2025, the groundwater level in the vicinity of the reactor buildings was stably controlled at low
levels through multilayered contaminated water management such as land-side impermeable
walls and sub-drains, along with the prevention of rainwater infiltration by repairing damaged
roofs and facings on site. As a result, the increase in the amount of contaminated water
generated during rainfall also tended to be controlled. The amount of contaminated water
generated decreased from about 490 m3/day (FY 2015) before management was in place toabout 90 m3/day (FY 2022). However, because the amount of rainfall in FY 2022 was lower than
the average year, whether the goal of the Mid-and-Long-term Roadmap is achieved will be
evaluated based on data from FY 2023 onward. With the aim to limit the amount of contaminatedwater generated to about 50 to 70 m3/day by the end of 2028, local water sealing in the buildings37
has been implemented as a countermeasure to control the inflow to the buildings. Fig. 24 shows
the progress of contaminated water management and changes in the amount of contaminatedwater generated.38

36

Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water (112nd), Material 2-1, “Outline of decommissioning, contaminated water and treated water
management,” March 30, 2023
37
Water seal at the end of the gap between buildings (the gap between the exterior walls formed whenconstructing buildings next to each other around the reactor building, in which penetration sites of piping ispresent).
38
Material 3-4, The 108th the Study group on Monitoring and Assessment of Specified Nuclear Facilities

91

(Source: TEPCO)

Fig. 24 Progress of contaminated water management and changes in the amount ofcontaminated water generated.38(2) Efforts to complete stagnant water treatment in buildings
With the objective of reducing the risk of off-system leakage of stagnant water in the reactor
building, efforts have been made to reduce the stagnant water inventory in the buildings (lowering
the level of stagnant water in the buildings), the concentration of radioactive materials containedin stagnant water, and the amount of contaminated water generated. As a result, in addition tocompleting the exposing of the building floors in FY 2020 except for the reactor buildings in Units
1 to 3, the process main building, and the high-temperature incinerator building, FY 2022 saw
the achievement of a milestone in the Mid-and-Long-term Roadmap: to reduce the amount of
stagnant water in the reactor buildings in FY 2022 to 2024 to about half of the level at the end of
2020. Currently, the following measures continue to be implemented:
Study on a method to recover the sludge located on the floor in the turbine buildings inUnits 1 to 4 where the exposing of the floor was completed.

Preparation for recovering the zeolite sandbags located on the lowest floor to complete thestagnant water treatment in the process main building and the high-temperature incinerator
building.

(3) Efforts for stable operation of contaminated water management
As for tsunami countermeasures, the construction of the Kuril Trench tsunami tide walls wascompleted in September 2020, and the measures for closing building openings were taken in
January 2022, followed by the installation of the Japan Trench tsunami tide walls, the92

reinforcement of the land-side impermeable walls, the relocation of the sub-drain and other watercollection systems from the revetment side to higher ground, and the transfer of sludge generated
by decontamination devices to higher ground. As a countermeasure for heavy rain, the new
Drainage Channel D was installed to eliminate the risk of inundation in the vicinity of Units 1 to4, which has been in service in low radiation-dose areas since August 2022. After a constantmonitoring system for Drainage Channel D was completed in November 2022, and the widening
and bypassing of the existing drainage was completed in February 2023, the full operation ofDrainage Channel D began to enhance the drainage function of the existing drainage channels.
Although the importance of multilayered measures such as land-side impermeable walls has
not changed, in light of the damaged systems and other factors, the management structure is
being established, combining preventive maintenance and condition-based maintenance.
(4) Efforts toward discharging ALPS-treated water into the sea
With regard to the disposal method of ALPS-treated water, a report published in February 2020
after more than six years of comprehensive discussions at expert meetings39,40, concluded that“discharge into the sea is more realistic.” In response, the IAEA also assessed that it “has ascientific basis”. After that, based on hundreds of exchanges of opinions with local governments,
agricultural, forestry, and fishery companies, listening to opinions by deputy ministers of eachministry, and requests for written public opinions (more than 4,000 comments), the government
finalized the basic policy41 at the Inter-Ministerial Council for Countermeasures on Contaminated
Water, Treated Water and Decommissioning Issues in April 2021. In the basic policy, the basic
concept for “coexistence of reconstruction and decommissioning”, specific methods for discharging
ALPS-treated water into the sea, and responses to the influence of reputational damage weresummarized. The government also established a Cabinet Meeting for the Steady Implementationof the Basic Policy on Disposal of ALPS-treated water to follow up on the implementation status ofmatters specified in the basic policy and implement additional measures flexibly. Table 3 showsmajor initiatives toward the discharge of ALPS-treated water into the sea after the basic policy wasannounced. To date, the government has held six meetings with the Cabinet Meeting to compile
immediate measures and a specific action plan and manage the progress. The government has
held six meetings of related ministers to date to compile immediate measures and concrete actionplans and manage progress. Since 2021, meetings of the task force on monitoring and measuring
the marine environment and the Expert Meeting for Marine Monitoring have been held continuously
to enhance marine monitoring. In October 2022, the ALPS-Treated Water Monitoring Symposium
was launched for fishery product distributors and retailers to provide detailed explanations anddialogue on monitoring and other initiatives to protect food safety and security.
39

Tritiated Water Taskforce Report, June 3, 2016
Report by the subcommittee dealing with water treated with multi-nuclide removal equipment, February 10,
2020
41Inter-Ministerial Council for Contaminated Water, Treated Water and Decommissioning Issues (5th meeting),
Material 1, “Basic policy for disposing of treated water by multi-nuclide removal equipment at the TEPCO
Fukushima Daiichi Nuclear Power Station (draft),” April 13, 2021
40

93

In light of the government’s basic policy, TEPCO proceeded with detailed studies on the designand operation of ALPS-treated water dilution/discharge facilities and related facilities and submitted
Application Documents for Approval to Amend the Implementation Plan for Fukushima Daiichi
Nuclear Power Station Specified Nuclear Facility (installation of facilities related to the discharge of
ALPS-treated water into the sea) to the NRA in December 2021 and obtained approval in July 2022.

Table 3 Major initiatives for discharging ALPS-treated water into the sea
FiscalYear

FY 2021

FY 2023

FY 2022▼Released ”The Basic Policy on Disposal of ALPS-treated Water”

Government▼Started marine monitoring
The Cabinet Meeting for the Steady Implementation of the Basic Policy on Disposal of ALPS-treated Water
▼2nd
▼5th
▼1st
▼3rd
▼4th
▼Established the task force on monitoring and measuring the marine environment▼Established the Expert Meeting for Marine Monitoring▼6th

ALPS-treated water Monitoring Symposium▼1st▼2nd ▼3rd▼Signed the Terms of Reference with IAEA (TOR)▼Conducted third-party analyses for ALPS-treated water before the discharge by IAEA
▽Discharge started(on August 24)▼Released ” TEPCO Holdings’ Action in Response to the Government’s Policy”▼Announced ”The status of the facilities study for ensuring safety”▼Published ”The Radiological Impact Assessment Report regarding the Discharge of ALPS-Treated Water into the sea (Design stage)▼Published ”The Radiological Impact Assessment Report (Construction stage)▼Submitted ”Written Application for Approval to Amend the
Implementation Plan for a Specified Nuclear Facility (Operation during
ALPS-Treated Water Discharge into the sea”

TEPCO

Submitted ”Written Application for Approval to Amend the Implementation Plan
for a Specified Nuclear Facility (Installation of ALPS Treated Water Dischargerelated Facilities”▼
Construction for facility installation▼1st Review Meeting▼2nd Review Meeting▼▼Submitted ”Partial amendment to Application for
approval of changes in Implementation Plan”

Inspection before use
Review Meetings(3rd to 15th)

NRA

Review Public comments

Publiccomments▼ Approved▼Issue certificate of completion▼Approved▼2nd Safety review→▼Report④▼Signed the TOR with the Japanese government▼1st Safety review→▼Report①▼Report③(Sampling/data supporting/analysis)

IAEA▼1st Regulatory review→▼Report②▼Integrated review▼Published Integrated report▼ILC Report(comparison among analytical facilities)▼2nd Regulatory review→▼Report ⑤

Subsequently, TEPCO specified the organizational structure for the operation, maintenance,
management of ALPS-treated water dilution/discharge facilities, selected nuclides to be measured
and assessed to verify whether the discharge standards are satisfied. It also revised theradiological impact assessment on humans and the environment based on the selected nuclides
to be measured and assessed. Then, TEPCO submitted the Application Documents for Approval
to Amend the Implementation Plan for Fukushima Daiichi Nuclear Power Station Specified
Nuclear Facility (operation at the time of discharging ALPS-treated water into the sea) in
November 2022. Reflecting the discussions at the subsequent technical meetings to review the
implementation plan for the specified nuclear facility by the NRA, the Application Documents for
Approval to Amend the Implementation Plan were partially revised from February to April 2023
and approved in May of the same year.
With regard to discharging ALPS-treated water dilution/discharge facilities, full-scaleconstruction, including an undersea tunnel, began in August 2022, and was completed in June
2023, after that, pre-service inspection by the NRA was completed.

94

A conceptual diagram and general view of the discharge facility published by TEPCO are shownin Fig. 25 and Fig. 26, respectively 42 ,43 . These discharge facilities consist of processes from
Purification, Analysis/Confirmation, and Dilution to Discharge. The key facilities and procedures
are shown below.
①

Measurement/confirmation facility
Afterhomogenizingbycirculating

andagitatingthe

ALPS-treated

water

in

measurement/verification facility, the water is sampled and analyzed to confirm that (1) theconcentrations of radionuclides other than tritium are purified to ensure that they are reliably
below the regulatory limits for discharge (the sum of the ratios to regulatory concentrations limitsof radionuclides other than tritium must be less than 1), that (2) the tritium concentration is below
1 million Bq/L, that (3) the nuclides to be removed44 are not significantly present, and that (4)there are no water quality problems.
②

Diluting facility
ALPS-treated water confirmed to meet regulatory standards is mixed and diluted using

seawater so that the tritium concentration is less than 1,500 Bq/L.45 The tritium concentration
after dilution by seawater will be monitored in real time by the flow rate of the ALPS-treated waterand the seawater to dilute and confirmed in both rates.
③

Intake/discharge facility
In order to avoid the impact of radioactive material in the harbor, for the water intake facility,
the seawall was constructed at the opening ditch of the intake channel of Units 5 and 6, as well
as a part of the permeation prevention works of the North Breakwater was removed in order totake water for dilution from outside the port. The discharge facility discharges ALPS-treated water
via the undersea tunnel (approx. 1 km) to prevent discharged water from recirculating into theseawater that is taken in.

④

Measures in the event of abnormality
If the seawater pump to dilute the water to be discharged shuts down, the emergency
isolation valves shall be closed promptly to stop the discharge. The discharge shall also be
stopped if the values that exceed the criterion level to suspend discharge are confirmed in themarine monitoring.

42

98th meeting of the study group on monitoring and assessment of specified nuclear facilities, Material 2-2,
Installation of New ALPS Treated Water Dilution/ Discharge Facilities and the Related Facility, March 14, 2022
43
TEPCO webpage, https://www.tepco.co.jp/press/release/2023/pdf3/230822j0101.pdf
44
Nuclides to be removed by ALPS (39 nuclides) other than those to be measured and assessed (29 nuclides)
45This is 1/40 of the regulatory concentration limit (60,000 Bq/L) and approximately 1/7 of the World HealthOrganization's (WHO) drinking water quality guidelines (10,000 Bq/L).

95

(Source: TEPCO)
Fig. 25 Conceptual drawing of discharge facilities(TEPCO material edited by NDF)
Fig. 26 General view of discharge facilities 43

Based on the Terms of Reference with the government, the IAEA has conducted reviews on
safety, regulations, sampling, and analyses associated with handling ALPS-treated water and96

published the reports for each review, and the comprehensive report46 that summarizes thosereviews in July 2023. The IAEA concluded that:

The approach to the discharge of ALPS-treated water into the sea, and the related activities
by TEPCO, the NRA, and the Japanese government are consistent with the relevantinternational safety standards.

The discharge of ALPS-treated water into the sea that TEPCO is currently planning would
have a negligible radiological impact on humans and the environment.
At the sixth meeting of the Inter-Ministerial Council concerning Decommissioning,

Contaminated Water, and Treated Water Management and the sixth meeting of the InterMinisterial Council concerning the Continuous Implementation of the Basic Policy on Handling of
ALPS Treated Water held on 22 August 2023, the entire government confirmed the status ofefforts to date on safety assurance and reputational measures related to the disposal of ALPStreated water47, the ALPS treated water was discharged to the sea on 24 August, based on the
proposed exact timing of the discharge of ALPS-treated water into the sea .
In order to ensure that the efforts related to the discharge of the ALPS-treated water proceed,
TEPCO strengthened the systems, such as establishing of the “ALPS-treated water Integrated
Countermeasure Project Team” under the direct control of the President, which oversees all
relevant internal departments, and the “Response Team on the Impact of ALPS-treated water”
which is responsible for centrally handling information dissemination, reputational measures andcompensation, not only in Fukushima but also in various regions across the country. The system
was strengthened by establishing the “ALPS-treated water Impact Response Team”48.
Moreover, efforts are being made to disclose the on-site situation in a timely and easy-tounderstand manner through communication on various occasions, such as visiting explanations
and briefing sessions, and through information dissemination via various media, such as thewebsite (Treated water portal site). As an example, a single page has been newly published on
the Treated water portal site to summarize the status of each facility for discharging ALPS-treatedwater into the sea. On the “Status of dilution and water discharge facilities” page 49, real-time dataon seawater and ALPS treated water flow rates, tritium concentration in diluted ALPS treatedwater, etc. can be checked at a glance. These data are also available on the IAEA website.
3.3.3 Key issues and technical strategies to realize them3.3.3.1 Control of contaminated water generation amountAs for the control of the amount of contaminated water generated, efforts are being made toachieve the roadmap target of 100 m3/day or less for average rainfall by 2025 through measuresin progress to reduce inflow to buildings, such as lowering the sub-drain water level and facing. In
46

https://www.iaea.org/sites/default/files/iaea_comprehensive_alps_report.pdf, on IAEA website
https://www.kantei.go.jp/jp/singi/hairo_osensui/dai6/siryou2.pdf, on Prime Minister’s Office of Japan website
48
https://www.tepco.co.jp/press/release/2023/1666016_8713.html, on TEPCO website
49
https://www.tepco.co.jp/decommission/progress/watertreatment/dischargefacility/, on TEPCO website
47

97

addition, efforts to further reduce inflow to buildings are planned with local water sealing even after
2025 (Fig. 27).
The penetration in exterior walls and gaps between buildings, which are the main factors ofgroundwater inflow into buildings, has a depth distribution as shown in Fig. 2850. Especially in thegaps between buildings, there are nearly 200 sites of penetration at T.P. -0.65 m (Fig. 27), thecurrent sub-drain water level (L value). If the water level is lowered to the assumed groundwaterlevel in FY2025 (about T.P. -1 m), the number of penetration sites will be reduced by almost half,
which is expected to reduce the inflow to buildings. However, there will still be nearly 100
penetration sites below T.P. -1 m.
To suppress groundwater inflow from the penetration sites of these gaps, the plan is to establish
a water seal part by boring holes at the ends of the gaps between buildings and filling them withmortar, etc. (Fig. 30). As for the water seal at the ends of the gaps, the construction method andmaterials were tested using test specimens off-site, and the results will be deployed in Unit 3. In
addition, water sealing at penetration sites of the exterior walls of the buildings and facing of theareas around the buildings will be carried out in parallel while coordinating with otherdecommissioning work, targeting at the end of FY2028 (about 50–70 m3/day).

(Source: TEPCO)
Fig. 27 Conceptual drawing of water sealing at the edge of the gaps between buildings

50

Committee on Countermeasures for Contaminated Water Treatment (26th meeting), Material 1, “Status ofcontaminated water management at the Fukushima Daiichi NPS”, December 21, 2022

98

(TEPCO material edited by NDF)
Fig. 28 Depth distribution of the building penetrations50(TEPCO material edited by NDF)
Fig. 29 Lowering of sub-drain and building water levels50

Fig. 30 Conceptual drawing of water sealing at the edge of the gap between buildings50

99

3.3.3.2 Treatment of stagnant water in buildings(1) Further reduction of stagnant water
Due to the presence of high-radiation dose sludge containing Cs and α-nuclides near the floorof the reactor building, there will be the following concerns when lowering the water level of thebuilding excessively to reduce the stagnant water inventory in the building.


Reduced shielding effect causes increased radiation dose and dust dispersion in thereactor buildings, deteriorating the work environment.



If contaminated water with a radioactivity concentration several orders of magnitude higher
than usual flows into a Cs sorption apparatus such as KURION and SARRY, the purification
performance is significantly degraded.

Although reducing the amount of stagnant water in the reactor building to about half the level atthe end of 2020 has been achieved, setting a new goal to reduce the stagnant water should beconsidered in integration with the fuel debris retrieval method, and shifted to the steps of stablestagnant water control through decommissioning work.
(2) Stagnant water treatment in the process main building and high-temperature incinerator
building
Stagnant water is also stored in the basement floors of the process main building and hightemperature incinerator building. A plan is to lower the water level to expose the floor surface of
these buildings from FY 2024. The following actions are essential to achieving this.


Recover zeolite sandbags with high-radiation doses placed on the basement floors of theprocess main building and high-temperature incinerator building51.

Install temporary storage facilities for stagnant water instead of storage on the basement
floor52.

The basement floors of both the process main building and the high-temperature incinerator
building contain high-radiation dose zeolite sandbags, which were placed shortly after the accident
to improve the stagnant water quality (the maximum surface dose: approximately 4,400 mSv/h).
Activated charcoal sandbags were also observed in the stair hall. Although the stagnant water isalso a source of high radiation doses, exposing these basement floors will eliminate water
shielding for zeolite sandbags with higher radiation doses, resulting in an expected significant risein the radiation dose in the opening of the ground floors.
The work plan to recover zeolite sandbags under consideration is shown below. Fig. 30 shows
the outline.
(1) Collect zeolite sandbags in a submerged state as much as possible to improve work
efficiency.

51
52

The 5th Engineering Meeting, Material 2-2 “Status of zeolite sandbags disposal study”, February 1, 2023
NRA website; https://www.nra.go.jp/disclosure/law_new/FAM/140000310.html

100

(2) Transfer the collected zeolite and other materials to the ground floor by a robot forrecovery (ROV (Remotely Operated Vehicle) + pump).
(3) Desalinate, dehydrate them in the building, seal them in metal storage containers, andtransfer them to temporary storage facilities.
In this task, zeolite will be collected and recovered by suction as granular particles. This
procedure may apply to the recovery of high-radiation dose sludge deposited on the floor surfaceof the reactor building to be planned, providing critical knowledge for the future progress of
decommissioning work.

(Source: TEPCO)

Fig. 31 Overview of the zeolite sandbag recovery task51

Because lowering the water level in the process main building and the high-temperatureincinerator building to expose the floors will prevent the storage of stagnant water in thesebuildings, designing temporary storage facilities for stagnant water is in progress. This will takeover the following functions that these buildings have performed.
Receiving stagnant water in buildings

Stagnant water buffer for the stable operation of cesium sorption apparatus (KURION,SARRY, and SARRY II)Concentration the averaging of stagnant water in each buildingSettling separation of sludge

These temporary storage facilities for stagnant water will be installed on the fourth floor of theprocess main building. The basement floor of the process main building after installation will be
used only when the in-leak volume increases during heavy rain. The temporary storage facilities
for stagnant water will combine the following two types of tanks to take over the above functions.

101



Temporary receiving tank (capacity: approximately 15 m3): Receive stored water andseparate sludge by settling.

Temporary storage tank (capacity: approximately 24 m3): Store the supernatant water thatwas settled and separated in temporary receiving tanks and homogenize water
concentration.

As the capacity of temporary storage tanks will become much smaller than that of the basement
floor of the process main building (maximum capacity: approximately 16,000 m3) and the basement
floor of the high-temperature incinerator building (maximum capacity: approximately 5,000 m3),
design studies are underway to maintain their function even with a smaller capacity, and installation
work followed by operational checks is scheduled from FY 2023 to FY 2024.
3.3.3.3 Issues of contaminated water management considering the decommissioning
process such as fuel debris retrieval(1) Examination of water treatment systems to prevent the dispersion of α-nuclides and for fueldebris retrieval
The relatively high total alpha concentrations have been detected in the stagnant watercollected from the bottom of the torus room of the reactor building, and they have been confirmed
to exist mainly in the form of granular particles (alpha sludge).53 Since the effective dose factorsof α-nuclides are remarkably high when inhaled or ingested, special management andcountermeasures are required if α-nuclides spread to stagnant water in buildings or water
treatment systems. The challenge is limiting the spread of α-nuclides as much as possible to avoid
such a situation.
Currently, a total alpha concentration in the order of 10 Bq/L is maintained at the cesium sorption
apparatus (SARRY/SARRY II) inlet, and the spread of contamination to the downstream side issuppressed. However, with the increase in the accumulated sludge at the bottom of the buildingin the future, more sludge may be mixed into the contaminated water, and the total alphaconcentration at the water treatment system inlet may rise. To address such concerns, installing
filter systems in the subsequent stage of the cesium sorption apparatus is under consideration54.
With regard to water treatment systems for fuel debris retrieval, it is important to examine thetiming and method of retrieval and the performance of the treatment facilities required at that timein a consistent manner.
When retrieving fuel debris, contaminated water containing a large amount of fine particles isgenerated by fabrication, including cutting and other processes, and α-nuclides in fuel debris may
exist in various forms, such as fine particles, ions, and colloids. Because the water quality of such

53

Committee on Countermeasures for Contaminated Water Treatment (24th meeting), Material 1, “Status ofcontaminated water management at the Fukushima Daiichi NPS, References,” June 15, 2022
54
From the viewpoint of removing the α-nuclides, the filter system should be installed in the front stage of thecesium sorption apparatus. However, in this case, the filter will capture granular particulate radioactive cesium,
resulting in a high radiation dose to the filter system and making replacement work difficult. Therefore, the filter
system will be installed in the subsequent stage of the cesium sorption apparatus.

102contaminated water depends on the fabrication method, including cutting and other processes, it
is difficult to assume the water quality when the fuel debris retrieval method has not been
determined. Thus, the challenge is designing the water treatment system for fuel debris retrieval
to cope with various water quality conditions and forms of α-nuclides.
However, analysis of the stagnant water in buildings has shown that the total alpha can be
reduced by two to three orders of magnitude by filtration, indicating that most α-nuclides can beremoved by filtration. Since mechanical fabrication without using chemicals leads to only smallchanges in chemical water quality, most α-nuclides are generated as fine particles, as in theseanalysis results, and the concentration of soluble α-nuclides may be maintained at a low level.
Therefore, the form and particle size of α-nuclides at the sampling points should be verified toincorporate them into the system design for further expansion of fuel debris retrieval in scale.
Specifically, to establish fabrication methods, including cutting and other processes, laboratory
tests should be conducted to determine their impact on the chemical changes in water quality,
which will enable the establishment of realistic water quality conditions for contaminated water andlead to rationalization and improved reliability of the water treatment systems.
(2) Medium-and-long term measures for contaminated water management systems
The challenge is to ensure that periodic inspection and updating of equipment, including landside impermeable walls, sub-drain systems, and existing water treatment systems (e.g., SARRY,
ALPS), are implemented in order to maintain the effectiveness of contaminated water
management over the medium-to-long term. For this purpose, it is necessary to anticipate various
risks, such as the deterioration of system functions caused by aging and the damage to piping
caused by material degradation and natural disasters, to procure/arrange backup and alternative
items for the enhanced structure for monitoring, early recovery, and stable operation, and topromote maintenance/management and system updates in a planned manner.
In addition, since it will take a long time to complete fuel debris retrieval, the challenge is to takea bird's-eye view of contaminated water management in the medium to long term and to establish
an approach to more stable contaminated water management and more appropriate
maintenance/management for each system, in conjunction with the selection of methods forfurther expansion of fuel debris retrieval in scale that is currently underway. With this, studies onthese issues should be carried out, and the interference with the fuel debris retrieval work should
be considered. Specifically, if fuel debris retrieval is to be conducted under submersed conditions(the submersion method), the method will naturally have water seals, and therefore the current
contaminated water management for the target units will no longer be necessary. On the other
hand, if the method is not based on the submersion method (i.e., partial submersion method), it isdesirable to employ the method that allows contaminated water management combined with inleak control on the assumption of preventing out-leak of contaminated water. Thus, consideration
should be given not to interfere with installing structures to retrieve fuel debris or demolishingsurrounding facilities. In all methods, medium and long-term contaminated water management103

should be considered in anticipation of fuel debris retrieval methods, together with the verificationof actual site applicability and technical feasibility.
3.3.3.4 Future efforts for the discharge of ALPS-treated water into the sea
The discharge of liquid waste generated in nuclear facilities into the sea, pursuant to the law,with a sufficiently small radiological impact on the human population and the natural environmentis a globally method recognized and is adopted widely in Japan and abroad. The IAEA has
published a review finding that activities related to the discharge of ALPS-treated water into the sea
are consistent with relevant international safety standards and have a negligible radiological impact
on humans and the environment. It is necessary to disseminate highly transparent information
based on scientific evidence, including the above, to prevent the impact of reputational damage.
Based on the Action Plan for Steady Implementation of the Basic Policy on the Disposal of ALPS
Treated Water formulated by the government, it is essential for TEPCO to reliably operate thefacilities in accordance with its own plan for the discharge of ALPS-treated water into the sea andcommunicate the status with high transparency.
(1) ALPS-treated water analysis and evaluation structure
Fig. 32 shows the analysis and evaluation structure of ALPS-treated water collected at themeasurement and confirmation facilities.
In addition to its own analysis before the discharge to the sea, TEPCO outsources to independent
external organizations with ISO/IEC 17025 55 certifications and performs analysis to determine
whether or not to discharge according to regulatory standards. The JAEA Okuma Analysis andResearch Center (Radioactive Material Analysis and Research Facility Laboratory-1) also conducts
analysis every time before the discharge in accordance with the government’s basic policy.
The NRA conducts safety inspections to verify whether TEPCO is developing structures foranalyzing nuclides to be measured and assessed in accordance with the Implementation Plan andis properly implementing quality assurance activities related to analysis. In addition, the NRA has
commissioned the JAEA’s Nuclear Safety Research Center to analyze ALPS-treated water andindependently verify the analytical quality provided by TEPCO.
Led by the IAEA, the IAEA and other analytical institutions in third countries are also engaged in
ALPS-treated water analyses to support data submitted by TEPCO and verify analysis quality. The
first inter-laboratory comparison (ILC) result report56 published in May 2023 concluded that TEPCO
has the ability to analyze ALPS-treated water accurately and precisely, and sampling procedures
and nuclide analysis methods are appropriate.

55

International standards developed by the International Organization for Standardization for general
requirements on the competence of testing and calibration laboratories.
56
IAEA Website，
https://www.iaea.org/sites/default/files/first_interlaboratory_comparison_on_the_determination_of_radionuclides_in_alps_treated_water.pdf

104

(Source: NRA)
Fig. 32 ALPS-treated water analysis and evaluation structure 57
In this manner, several institutions are conducting various third-party analyses of pre-discharge
ALPS-treated water for comparison with the analysis data disclosed by TEPCO. It is importantthat those data are made publicly available in a prompt and transparent manner. It is important tomaintain such a system from the viewpoint of maintaining the quality of analysis and evaluationin light of the long-term nature of ocean discharges.
(2) Periodic verification of nuclides to be measured and evaluated
The target nuclides to be measured and evaluated before the discharge of the ALPS-treatedwater into the sea were selected after re-examining the nuclides that could be contained in thecontaminated water before treated by cesium sorption equipment, ALPS and other systems insignificant amounts, based on knowledge of decommissioning and buried facilities at nuclear
power plants in Japan. A flow for selecting target nuclides (Fig. 33) was established, based on
experts’ opinions, by combining inventory assessment, measured data of nuclide concentrations
in stagnant water in buildings, and study of the physical and chemical properties of nuclides.
Consequently, 29 nuclides were selected as nuclides to be measured and evaluated based on
this procedure 58 (Table 4). The approach to the selection of nuclides to be measured andevaluated is summarized in the Attachment 14.
When discharging ALPS-treated water into the sea, it is necessary to confirm that the sum of
the ratios to the regulatory concentrations limits of the selected nuclides to be measured andevaluated is less than 1. On the other hand, although the target nuclides are selected after
checking the results of the past analysis, it may change depending on the progress of
decommissioning work in the future, for example due to factors such as changes in the transfer
57
58

The 101st Study group on monitoring and assessment of specified nuclear facilities, Material 1-1, Attachment 2
Partial Revision of the “Application Documents for Approval to Amend the Implementation Plan for Fukushima
Daiichi Nuclear Power Station Specified Nuclear Facility,” February 20, 2023

105

coefficient from fuel debris to contaminated water. Therefore, it is necessary to confirm that the
ALPS-treated water does not contain significant amounts of nuclides other than the selected ones
to be measured and evaluated (hereafter referred to as “other nuclides”). If it is confirmed thatsignificant amounts of other nuclides are contained (at 1/100 or more of the regulatory
concentration limit), the target nuclides should be reevaluated based on the flow in Fig. 33. The
decay of the radionuclides will also be reflected in the selection flow. If other nuclides are identified
as a result of this reevaluation, an additional environmental impact assessment must be
conducted. Of the 62 nuclides to be removed by ALPS, 39 nuclides 59 not to be subject tomeasurement and evaluation this time will be independently measured before the release toconfirm that they are not contained in significant amounts to prevent reputational damage.

*1: The decay period of the inventory evaluation is appropriately set according to the time when the selection result is to be
used. (First time set to 2023 (12 years after the accident))*2: Nuclides that have been detected in the past are confirmed by the maximum value of the detection value, and nuclides thathave never been detected are confirmed by the minimum value of the detection limit value*3: Nuclides that shall be continuously confirmed if significantly exists in contaminated water.

(Source: TEPCO)
Fig. 33 Flow to select nuclides to be measured and evaluated58

59

The 29 nuclides selected this time include six nuclides (C-14, Fe-55, Se-79, U-234, U-238, and Np-237) thatare not included in the 62 nuclides to be removed by ALPS. Therefore, out of 62, the nuclides excluded frommeasurement are 62 − (29 − 6) = 39.

106

Table 4 Nuclides to be measured and evaluated and their quantification methods58
No. Nuclides

No. Nuclides

Quantification method
Beta-ray measurement after chemical separation

16

Quantification method

1

C-14

Ce-144 Gamma-ray nuclide analysis

2

Mn-54

Gamma-ray nuclide analysis

17

Pm-147 Evaluated from the radioactivity concentration

3

Fe-55

Beta-ray measurement after chemical separation

18

Sm-151 of representative nuclides (Eu-154)

4

Co-60

Gamma-ray nuclide analysis

19

Eu-154 Gamma-ray nuclide analysis

5

Ni-63

Beta-ray measurement after chemical separation20

Eu-155 Gamma-ray nuclide analysis

6

Se-79

Beta-ray measurement after chemical separation

21

U-234

7

Sr-90

Beta-ray measurement after chemical separation

22

U-238

8

Y-90

Radiative equilibrium with Sr-90

23

Np-237 Evaluated as included in total alpha

ICP-MS measurements

9

Tc-99

24

Pu-238 radioactivity10

Ru-106 Gamma-ray nuclide analysis

25

Pu-23911

Sb-125 Gamma-ray nuclide analysis

26

Pu-24027

Pu-241

12 Te-125m Radiative equilibrium with Sb-125
ICP-MS measurements

Evaluated from the radioactivity concentration

13

I-129

14

Cs-134 Gamma-ray nuclide analysis

28

Am-241 Evaluated as included in total alphaof representative nuclides (Pu-238)

15

Cs-137 Gamma-ray nuclide analysis29

Cm-244 radioactivity(Source: TEPCO)(3) Strengthening and enhancing marine monitoring
In order to ensure and systematically conduct detailed radiation monitoring related to theaccident at the Fukushima Daiichi NPS, the government established the Monitoring Coordination
Council under the Nuclear Emergency Response Headquarters, chaired by the Minister of theEnvironment, and formulated a comprehensive monitoring plan60. Based on this plan, relevant
ministries, municipalities, and business operators will cooperate to conduct monitoring.
Given the “Basic Policy on the Disposal of ALPS-treated water”, which was decided by thegovernment in April 2021, incorporated the strengthening and expansion of marine monitoring,“the Monitoring and Measurement Task Force on Marine Environment” led by the Ministry of theEnvironment and the “Marine Monitoring Expert Meeting on ALPS-treated water” were establishedunder the Monitoring and Coordination Council in the same year, and efforts have been made tostrengthen marine monitoring (Fig. 34). In March 2022, the comprehensive monitoring plan wasrevised based on expert advice, and in April, marine monitoring began before discharge into thesea. According to this, in addition to TEPCO, the Ministry of the Environment, the NRA, andFukushima Prefecture are also supposed to monitor the same marine areas independently inmarine areas near the Fukushima Daiichi NPS. A framework has been established for each ofthem, including TEPCO, to conduct monitoring to increase objectivity and transparency. Moreover,
immediately after the start of the ocean discharge, swift analysis is performed, and the results are
published in a preliminary report.
In addition, to maintain and improve the reliability and transparency of marine monitoring data,
analysis of supporting data and inter-analytical laboratory comparison (ILC) were conducted by
the IAEA. In the ILC result report on radionuclide analysis of seawater, seabed soil and fish,

60

https://radioactivity.nra.go.jp/ja/contents/16000/15822/24/1001_0802r.pdf, on NRA website

107

published in June 2022 61 , the sampling methods of the participating Japanese analyticalinstitutions (10 institutions, including TEPCO and the JAEA) were evaluated as adequate, highly
accurate, and competent. The IAEA's comprehensive report also assessed that “Enhanced
environmental monitoring by TEPCO and the Japanese government to deal with the discharge of
ALPS-treated water has a clearly defined plan”.

Fig. 34 Framework for discussion and implementation system for marine monitoring(Monitoring Coordination Council material 62 , compiled by NDF with reference to TEPCO
website63 and other material etc.)
To prevent reputational damage, it is important to expedite analysis and disseminate
information on monitoring results that is easy to understand in a timely manner. Marine
monitoring requires sophisticated analytical techniques and long-time measurements to detectextremely low concentrations of radionuclides. To expedite the analysis, in addition to thedevelopment of pretreatment technologies for concentrating radionuclides, operational efforts
are being made, such as the disclosure of preliminary data from short-time analysis and final
data from long-time analysis at different times.
To disseminate easy-to-understand information on analysis results, TEPCO publishes web
pages on its Treated Water Portal Site that display monitoring results simply using visualelements and provides the latest information to domestic and international audiences in multiple
languages (English, Chinese, and Korean). TEPCO also launched the Overarching Radiationmonitoring data Browsing System in the coastal ocean of Japan (ORBS) website in March 2023
to provide a quick view of the analysis results of each party64.
61

IAEA Website，https://www.iaea.org/sites/default/files/22/06/2022-06-21_japan_ilc_2021_report_v4.2.pdf
The Ministry of the Environment Website, https://www.env.go.jp/content/000120258.pdf
63
TEPCO Website, https://www.tepco.co.jp/decommission/progress/watertreatment/monitoring/64
Launch of the Overarching Radiation-monitoring data Browsing System in the coastal ocean of Japan (ORBS),
March 13, 2023
62108

Since multiple organizations, including TEPCO, the Ministry of the Environment, the NRA, andFukushima Prefecture, conduct sampling and analysis as marine monitoring, it is important tooperate the system continuously so that these pieces of data are disclosed promptly andtransparently.
(4) Future operational plans, etc.
TEPCO should continue to conduct checks and reviews on the operational performance of the
facilities for the discharge of ALPS-treated water into the sea and the results of marine
environmental monitoring, and review and expand the plan flexibly as necessary. Then, theprompt and reliable implementation of site usage after the release of treated water is a challenge.
With this, it is necessary to develop a discharge plan in accordance with the site use plan andrevise it appropriately according to the situation while considering the concentration/decay oftritium contained in treated water in tanks and attenuation. Moreover, providing of education andtraining will be needed in a planned manner, including for contractors engaged in system
operation and analysis, in order to proceed with prolonged decommissioning work safely andsteadily.
The IAEA is committed to continuously reviewing the safety assurance measures taken by thegovernment and TEPCO before, during and after the discharge, and a system has been
established in which IAEA personnel are stationed at the Fukushima Daiichi NPS before andafter the discharge to continue the confirmation. It is important for the government and TEPCO
to continue sharing the necessary information with the IAEA, and provide explanations to Japanand the international community based on scientific evidence with a high degree of transparency.
NDF will provide technical and professional support for TEPCO’s planning and operation ofcountermeasures on contaminated and treated water, while promoting the distribution of accurate
information and increasing understanding in line with the interests of those who will receive theinformation, through meetings and conferences with relevant domestic and overseasorganizations. NDF will also ensure that measures to minimize reputational damage are
implemented and that action is taken with adequate and sufficient compensation in the event of
reputational damage.

109

3.3.4 Key technical issues and future plans
The key technical issues and future plans described in this section are summarized as shown in
Fig. 35.
Fiscal year

2023

2024

2025

To reduce stagnant water in the reactor building toapproximately half that of the end of 2020 (FY 2022 to FY 2024)

Relatedmilestones

2028

2034

▽To control the contaminated water generation amount to 100 m3/day or less(in 2025)

Maintenance management operation of a groundwater bypass, a sub-drain, and a land-side impermeable wall

▽ Reduce the amount of contaminated water generation
to about 50 to 70m3/day (End of FY2028)

Units 5/6 (Unit 4)
Unit 3

Stagnant water in buildings

Contaminated water management

Site pavement inside the land-side impermeable wall (mountain-side)

Contaminated Repair broken parts of roofs (incl. theinstallation of a large cover on Unit 1 R/B)）
water generation
amountLocalized water sealing of the building
Units 1/2

Implementing required measures in accordance with the stage of fuel debris retrieval

Units 1 to 3 ▽ Completed in March 2023(Lowering water level toward halving)
Reactor
α-nuclides removal equipment
Buildings
DesignManufacture and installation
Units 1 to 4
TurbineBuildings etc.

Examination of methods forcollecting sludge on the floor

Operation

Manufacturing/installatin/ of equipment for collecting sludge on the floor

Process
Alternative tankmain
DesignManufacture and installationbuilding,
HighMeasures for zeolite sandbags
Manufacture
temperature Designand
Collection
installation
incinerator
building
Removing stagnant water on premises＜Legend＞

Water level lowering for exposing
the floor surface

︓Dulation of work

︓Processes added

period in which
︓ Thechange is expected︓Processes changed

︓Relationships between processes

Investigation and Removal of Trench Reservoir at Uninvestigated Sites

Dismantling underground water storage tankConceptual study
Design/removal

Measuresagainst stagnant
water

Examination of methods for treating untreated water (supernatant water) in tanks
Experimental prior treatment

Treating untreated water (supernatant water) in tanks

Discharge into the sea

Treated-water
management

Operation

Installation

Marine monitoring

Measures against
natural disaster

Installation of tsunami tide walls in the Japan Trench
Maintenance of drainage

Fig. 35 Key technical issues and future plans on contaminated water/treated water
management and natural disaster preparedness (progress schedule)

1103.4 Fuel removal from spent fuel pools
3.4.1 Target(1)

To complete fuel removal from the spent fuel pools of all Units from 1 to 6 by the end of 2031.

(2)

As the return of residents and reconstruction in the surrounding area gradually advances, tocarry out a risk assessment and ensure safety, including preventing the dispersion ofradioactive materials, and to start removal of fuel in SFPs in FY 2027 to FY 2028 for Unit 1
and FY 2024 to FY 2026 for Unit 2.

(3)

The fuel in Units 1 to 4, which were affected by seawater and rubble, is retrieved from the
SFPs and transferred to the Common Spent Fuel Storage Pool, etc., where it is appropriately
stored to be in a stable management state. In order to secure the Common Spent Fuel
Storage Pool capacity, the fuel stored there is transferred to and stored in the dry cask at theTemporary Cask Custody Area.

(4)

To perform the evaluation of long-term integrity and the examination for treatment for the
retrieved fuel and to decide the future treatment and storage method.

3.4.2 Progress
Based on the work plan outlined in the Mid-and-Long-term Roadmap and the Mid-and-Long-term
Decommissioning Action Plan, efforts are underway to complete the removal of fuel from the spent
fuel pools in all units, Units 1 to 6, by the end of 2031. Fig. 36 shows a layout drawing of theCommon Spent Fuel Storage Pool, the Dry Cask at the Temporary Cask Custody Area, and theoverall workflow. Fig. 37 shows the available capacity. Securing the available capacity of theCommon Spent Fuel Storage Pool is required to remove all the fuel in SFPs, including Units 5 and6, and store them in the Common Spent Fuel Storage Pool. To this end, expanding the storage
capacity of the dry cask at the Temporary Cask Custody Area and systematic off-site transportationof new fuel are underway to transfer some fuel from the Common Spent Fuel Storage Pool. Suchefforts will be made to complete fuel removal in all units in 2031. Regarding the transfer of new fueloff-site, the plan is to start transferring new fuel from Unit 6 after FY 2023, and radiation dose
measurement/cleaning of new fuel removed from Unit 4 was completed in March 2022.

111

Number of spent fuel, etc.

10000

8000

For fuel removal from Units 1, 2, 5 and 6(4389), efforts are underway to expand
storage capacity for Dry Cask Temporary
Custody Facility and to export new fuel offpremises (360 planned).

Spare:502

6000
In all Units 1, 2, 5
and 6：4389

4000

Stored6156
Spare:1449
Unit 6: 1840

2000
Unit 2: 615

0Fig. 36 Layout drawing of the Common Spent
Fuel Storage Pool and dry cask at theTemporary Cask Custody Area and theworkflowa.

Number of available capacities asof now in entire common spent fuelstorage pool and Dry Cask
Temporary Custody Facility ：1951

Stored2516

Unit 5: 1542

Unit 1: 392

Units 1/2 SFP

Units 5/6 SFP

Common Spent Fuel Storage
Pool

Dry Cask Temporary
Custody Facility

Fig. 37 Storage status of spent fuel(As of June 2023)

Unit 1
Due to the hydrogen explosion, roof sheets and building materials, such as steel frames, whichconstituted the upper part of the building, an overhead crane, and other elements collapsed andproduced rubble on the operating floor (Fig. 38). While the residents were returning, from theperspective of the further reduction of the radioactive dust dispersion risk, the whole operating floor
was covered with a large cover, and the removal method was changed to one in which rubble
removal and fuel removal from SFP would be carried out inside the cover in December 2019. Fig.
39 shows a conceptual drawing of this method.
In preparation for the installation of the large cover and the subsequent rubble removal, thefollowing measures have been completed.
Curing of spent fuel pool (completed in June 2020)

Installation of supports for the overhead crane and fuel handling machine (completed in
November 2020)



Removal of interfering existing building covers (remaining parts) (completed in June 2021)

Subsequently, the area around the reactor building has been improved. Still, delays in removing
Standby Gas Treatment System (hereinafter referred to as “SGTS”) piping (removal of high-dose
pipes by remote control) caused delays in the preparatory work. The Mid-and-Long-term
Decommissioning Action Plan 2023 states that, (as in the 2022 edition) due to delays in preparatory
works, the installation of the large cover in Unit 1 is expected to be completed by the middle of FY
2024. Fuel removal in Unit 1, a milestone in the Mid-and-Long-term Roadmap, is expected to begin112

in FY 2027 to FY 2028 as planned. Work is underway to assemble a large cover frame in the offsite yard in parallel to installing a lower frame in the reactor building of Unit 1.
South

West

East

North
Condition of the existing installations under
the collapsed roof (conceptual drawing)

Condition of the collapsed southside roof

Fig. 38 State of the collapsed rubble on the Unit 1 operating floor

During rubble removal (Conceptual drawing)

During fuel removal (Conceptual drawing)

Fig. 39 Fuel removal method from Unit 1 SFP
b.

Unit 2
From the perspective of the further reduction of the radioactive dust dispersion risk, a method

was adopted in which the upper part of the operating floor will not be dismantled and in which
there is access from the working platform for fuel removal to be installed on the south side of thereactor building. Fig. 40 shows a conceptual drawing of this method.
Ground improvement and the installation of the working platform base mat for fuel removal werecompleted in April 2022 and November 2022, respectively, and steel structure erection began in
January 2023. Production of fuel handling equipment is also ongoing. Based on the results ofdose surveillance in the operating floor conducted in 2021, the decontamination and installationof shielding on the upper part of the well-plug were carried out. The effectiveness of radiation dose
reduction was rechecked in May 2022. In addition, the existing fuel handling equipment was
relocated in June 2022, removing of obstacles from the spent fuel handling equipment operation
room located on the south side of the spent fuel pool was completed of in March 2023, anddecontamination is underway.

113

Fuel removal method (conceptual drawing)

Fuel handling facility (conceptual drawing)

Fig. 40 Fuel removal method from Unit 2 SFP
c.

Units 5 and 6
For Units 5 and 6, the policy is to conduct fuel removal operation so as not to interfere with

operations in Units 1 and 2, fuel transfer from the SFP to the Common Spent Fuel Storage Poolcommenced in August 2022. The transfer of fuel from the Common Spent Fuel Storage Pool to
dry casks at the Temporary Cask Custody Area was underway to secure the available capacity of
the Common Spent Fuel Storage Pool. However, in May 2022, it became necessary to re-verify
airtightness after loading fuel into dry casks. This led to a reconsideration of the fuel transfer
process for Unit 6 from the Common Spent Fuel Storage Pool to the dry cask at the Temporary
Cask Custody Area, causing a delay in the entire process of transferring spent fuel from Unit 6 to
the Common Spent Fuel Storage Pool. Therefore, improvements have been made to ensure
airtightness, including the cleaning of spent fuel with a newly introduced fuel cleaning system in
the Common Spent Fuel Storage Pool and the addition of a process for water displacement in thedry cask. The presumed reason for the rework is that iron oxide (cladding) or calcium components(granular particles or ions) entered the flange surface when placing the primary lid of the dry cask
in the Common Spent Fuel Storage Pool and formed foreign materials due to the effect of thetransfer of fuel from the SFPs of Units 3 and 4 to the Common Spent Fuel Storage Pool.
d.

Removing high radiation dose equipment
In addition to fuel, other high radiation dose equipment is also stored in the spent fuel pool ofeach unit, such as control rods, channel boxes, and filters. Although cooling is not necessary,shielding is required, and there is still the risk that the source in the pool will be exposed if the poolwater leaks. Therefore, in terms of risk reduction, the removal of such a high radiation dose
equipment is needed following the fuel in SFP. With the removal equipment on the spent fuel poolside and the site bunker on the receiving side ready, the removal of high radiation dose equipmentfrom the spent fuel pool of Unit 3 began in March 2023.
3.4.3 Key issues and technical strategies to realize them
3.4.3.1 Fuel removal from SFPs
For Units 1 and 2, it is necessary to advance the work steadily to realize the new retrieval methodthat has been determined.

114

In promoting the project, it is essential to evaluate safety in association with work, to confirm thatnecessary and sufficient safety is ensured, and then to comprehensively consider the technicalreliability, rationality, the promptness of the work schedule, the actual site applicability, the projectrisk, etc., in order to address issues.
(1) Unit 1
Although overhead crane support is installed on the upper part of the operating floor for fall
prevention, it is still in an unstable state. Therefore, removing the overhead crane in a safe andreliable way is one of the main issues to prevent it from collapsing onto the fuel handling machineand falling into the SFP. Therefore, in the ongoing examination of how to remove the overheadcrane, it is assumed that safety assessments will be performed, and it is important to carry out acomprehensive examination in light of rationality and impact on other operations by:65

Formulating specific work procedures and work plans enabling identification of risk items

Considering anticipated risk scenarios and countermeasures

Identifying points to consider, such as exposure of workers, from the operator's
perspective

As for how to remove the overhead crane, because the information on the condition of the lower
part of the roof slab is currently limited, a detailed investigation will be conducted after the removalof the slab. There is a risk that the process of dismantling the crane may be delayed dependingon the investigation results. Therefore, work procedures should be developed after identifying therequired tasks, such as surveys and verification. Then, the overhead crane should be investigatedpromptly as soon as the investigation becomes possible in order to incorporate them into safetyassessments and rubble retrieval plans, including risk cases.
Regarding the contamination state of the well-plugs of Units 1 to 3, the Study Committee on
Accident Analysis of the Fukushima Daiichi NPS pointed out that, due to their high level ofcontamination, the well-plugs have important implications for safety and decommissioning work.66
Although the well-plugs of Unit 1 have been evaluated by the above-mentioned Study Committee
to be about two orders of magnitude less contaminated than several dozen PBq of Units 2 and 3,
as those in Unit 1 become deformed and unstable due to the impact of the explosion at theaccident, measures to deal with this are being considered. A comprehensive decision should bemade on how to handle these well-plugs based on the study results and by taking into
consideration the impact on fuel removal from SFPs and fuel debris retrieval in the subsequent
stage and performing thorough safety assessments.

65

NDF, “Evaluation on the selection of fuel removal methods (plan) at the Fukushima Daiichi Nuclear Power
Station Unit 1,” Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water (73rd), Material 3-2, December 19, 2019.
66
Nuclear Regulation Authority, “Draft revision of the interim report (draft) based on the results of publiccomments,” The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station (19thmeeting), Material 3 (pages 81 to 83), March 5, 2021

115

A detailed handling plan for 67 fuel assemblies with damaged cladding tubes, which have been
stored in the Unit 1 SFP since before the accident, is under development toward the completionof fuel removal in 2031. In particular, efforts should be made to ensure the verification of the postaccident condition, examination/development of handling methods, and risk study associated withhandling.
(2) Unit 2
The key challenge is to remove fuel in the SFP from the opening on the south side of theoperating floor using a fuel handling machine composed of a boom-type crane system, which has
not yet been used for nuclear facilities in Japan. Since this fuel handling machine lacks precedent,
the following measures should be implemented without fail.67
Development of appropriate design and production schedules with a marginConducting of mock-up tests that sufficiently simulate field conditions and operating
methods, and feedback of these test results into design and production

Sufficient mastery of system operation and functionality in advance due to the remotecontrolled nature of the retrieval work

To install a fuel handling system, the issue is to steadily carry out preparatory work, including
installing an anterior chamber on the working platform and an opening on the south side of theoperating floor of the reactor building. The basic assumption in fuel removal from SFP is
unattended operation by remote control. However, the challenge is to reduce the radiation doseon the operating floor as much as possible and improve the environment in light of the fact that
attended operation is also assumed partially for system installation or troubleshooting, and thestudy group meeting mentioned above has pointed out that the well-plugs are highly
contaminated66.While decontamination and shield installation are underway for radiation dose
reduction after relocating the existing fuel handling machine, installing an opening on the south
side of the operating floor is scheduled after decontamination. Since the work area may becontaminated again, thorough measures to prevent dust dispersion should be taken whenestablishing the opening.
(3) Removing high-radiation dose equipment
As removing high-radiation dose equipment is an issue in light of risk reduction in the event ofpool water leakage, efforts are being made toward removal. Once removing high-radiation dose
equipment is completed, it is possible to exclude pool water from management by draining it,
leading to smooth fuel debris retrieval in the later stages because of the increased flexibility of useof the operating floor.

67

NDF, “Evaluation on the selection of fuel removal methods (plan) at the Fukushima Daiichi Nuclear Power
Station Unit 2,” Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water (71st), Material 3-2, October 31, 2019116

It is effective for removing high-radiation dose equipment to utilize the devices used for fuel andrubble removal. From the viewpoint of maintenance and management of existing equipment,
removal should be started as soon as preparations are made, such as securing a storage place.
The fuel removal system for Unit 1, which will be installed in the future, should also be designed
and maintained in anticipation of the removal of high-radiation dose equipment. Moreover,because the capacity of existing site bankers for storing high-radiation dose equipment of Unit 3,
where removal has started, is limited, additional bunkers should be installed for other units where
removal is also scheduled.
When draining the pool water, the radiation dose and dust dispersion from the pool afterdrainage should be evaluated to confirm safety in advance.
3.4.3.2 Decision on future treatment and storage methods
The future treatment and storage methods for fuel in SFPs needs to be decided after considering
the impact of seawater and rubble exerted during the accident and the damaged fuel stored since
before the accident. The impact of seawater and rubble has been evaluated for the fuel removed
from Unit 4, and it is expected that the impact is small. On the other hand, future treatment andstorage methods should be determined in light of the condition of the fuel to be removed while
examining the long-term integrity assessment and treatment.
It is planned to transfer fuel in SFPs of all Units to the Common Spent Fuel Storage Pool by theend of 2031. Subsequently, taking into account the tsunami risk, the possibility of dry storage onhigher ground has been studied, including existing fuel in the Common Spent Fuel Storage Pool.
In addition to the existing metal casks, TEPCO has announced that it will study the application of
concrete casks using canisters with proven track records overseas, as dry storage facilities. 68
Regardless of which dry storage facility is applied, the issue is the storage of damaged fuel existed
in the pool.
Advantages of concrete casks include the following:

Many overseas track records of storing intact or damaged fuel.



Use of local companies for concrete production.



Reduction in the amount of waste after use with fewer metal parts.

Reduction of procurement risk by expanding options for dry storage facilities.

On the other hand, there is concern about the risk of deterioration of the sealing function ofcanisters caused by stress corrosion cracks (SCCs) due to salt adhesion. Thus, countermeasures
should be established. If concrete casks are used, it is essential to set an engineering schedulethat clarifies the necessary items to be verified, such as demonstration tests, for smooth operationcommencement and to proceed systematically.

68

Tokyo Electric Power Company Holdings Inc., Mid-and-Long-term Decommissioning Action Plan 2023 (March
30, 2023)

117

The advantage of metal casks is their proven track records in storing intact fuel in Japan andoverseas. However, there are limited cases of storing damaged fuel overseas and no cases inJapan.
The dry storage facilities to be applied should be determined based on the advantages anddisadvantages of both casks and the characteristics of Fukushima Daiichi NPS, including fuelaffected by seawater and rubble.
3.4.4 Summary of key technical issues
The key technical issues and future plans described in this section are summarized as shown in
Fig. 41.
Fiscal year
Related milestones

2021

2022

2023

2024

Complete installation of Unit 1 large cover(around FY 2023)▽

Unit 12025

2027

2034(Yr)

Complete fuel removal (in 2031)▽
Start Unit 2 fuel retmoval(FY 2024 to FY 2026)

Start Unit 1 fuel removal(FY 2027 to FY 2028)

Installation of large cover
Removal of rubble, the overhead crane, etc.
/well-plug disposal /decontamination and shielding ofan operating floor/installation of fuel handling machine, etc.

Removal of building cover(remaining parts)

Removing high-dose equipment/ Draining the pool

Fuel removal

Unit 2<Legend>: Fuel retmoval work

Yard clean-up/
Ground improvement, etc.

: The period in whichchanges are expected

Decontamination and shieldingof operating floor: Works other than fuelretmoval

Installation of a working platform on thesouth side and an opening/fuelhandling machine installation, etc.

: The period in whichchanges are expected

Fuel removal

Units 3 and 4

Removing high-dose equipment/ Draining the pool

Removing high-dose equipment in
Unit 3 / Draining the pool

Removing high-dose equipment in Unit 4/ Preparing large equipment for removal/ Draining the pool

Units 5 and 6

Unit 6 fuel removal

Unit 5 fuel removal

Dry cask manufacturing
Transfer from the Common Spent Fuel Storage Pool to the
Dry Cask at the Temporary Cask Custody Area

Common Spent Fuel
Storage Pool
Cask

Expanding of storage capacity in Dry
Cask Temporary Custody Facility

Examination, design and installation of dry storage facility (metal or concrete cask made)Carrying out fuel from Common Spent Fuel
Storage Pool/Dry storage on higher groundExamination, design and installation of a new site bunker (storage facility for high-dose equipment, etc.)

Fig. 41 Key technical issues and future plans for fuel removal from SFPs (Progress schedule)

118

4. Analysis strategy for promoting decommissioning
4.1 Significance of analysis on decommissioning
The accident at the Fukushima Daiichi NPS was the first core meltdown accident at BWRs in theworld, and many records, including temperature records, are unavailable due to the loss of powerat the time of the accident. In addition, many uncertainties remain regarding the state inside thereactors, the state of the fuel debris, fission product release paths, etc., due to the unclear
operational status of the safety equipment and seawater injection to bring the accident undercontrol.
In decommissioning the Fukushima Daiichi NPS, analysis with various analysis targets, purposeof analysis, and radiation dose rates must be performed, as shown in Fig. 42.

Purpose of analysis（Needs）

Equipment required for characterazartion

 Storage management
 Processing and disposal
 Assessing contaminationlevels Environmental monitoring

Hot cellFuel debris

Generalliving environment

 Storage management ✓Processing and disposal
 Investigation of accident history

 Confirmation for discharge

Glove box

Hood

 Retrieval method✓ Safeguards
 Storage management ✓Processing and disposal
 Investigation of accident history

Waste generated fromfuel debris retrieval
Secondary waste generated by water treatment
Zeolite sandbags
Rubble, etc.

Environmental samples
ALPS-treatedwater

10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1
Radiation dose rate (Sv/h)

1

10

Fig. 42 Relationship between the purpose of the analysis, equipment required forcharacterization, and radiation dose rates of the analysis targets
It is considered that fuel debris would be heterogeneous in various physical properties, such as
chemical composition, microstructure, and density, because there is uncertainty in its formation
process, and it is not under human control. Concerning the design of safety measures fordecommissioning the Fukushima Daiichi NPS, it is assumed to use the 4 to 5 mass% U-235 content
of the fuel before the accident to conservatively study safety assessment and safety measures forcriticality control and transport. In addition to the U-235 content decreasing as a result of nuclear
fission in the reactor, the severe accident analysis and the videos of PCV internal investigations
suggest that the U-235 content is likely to have been decreased by melting and mixing with thesurrounding structural materials. However, the fact that the data used for the assessment is
unknown leads to the inclusion of excessive margins in safety measures. If the range of such
uncertainty is reduced by analyzing collected samples, there will be no need to include excessive
margins in handling fuel debris, safety assessments, and safety measures, which will improve thepromptness and rationality of decommissioning.

119

Conducting proper storage management and examining processing and disposal methods forsolid waste, it is essential to assess the physical and chemical properties of solid waste to improve
its safety during storage, and steadily advance analysis to acquire property data, such as nuclide
composition and radioactivity concentration, which will contribute to examining a processing anddisposal strategy. Therefore, based on the characteristics of solid wastes, which have diverse
properties and are large in quantity, it is necessary to establish facilities for analysis, develop
analytical personnel, and conduct analysis using analytical and evaluation methods for efficientcharacterization. As Phase 3 is approaching, where the properties of solid waste will be analyzed,
and the specifications of waste form and their production methods will be determined, as stated in
the Mid-and-Long-term Roadmap, reliable analysis of solid waste becomes an important issue to
steadily proceed with the overall waste countermeasures, including such determinations. Therefore,
it is imperative to develop a structure for systematic analysis based on the results of previous efforts.
A plan is to collect and contain fuel debris and waste in containers for storage/management, sothey are not released into the environment. On the other hand, to safely discharge ALPS-treatedwater into the sea, an analysis must confirm that the sum of the ratios to regulatory concentrations
limits of nuclides other than tritium contained in ALPS-treated water before dilution is less than 1,
etc. It is also important to continue monitoring activities for environmental samples in the sea area
to observe the diffusion status of tritium and other nuclides. As a measure to strengthen marine
monitoring by TEPCO, the monitoring of seawater, seaweed, and fish within a 20 km radius outside
the port and along the coast of the Fukushima Daiichi NPS started in April 2022.
It is essential to obtain appropriate analytical results in the light of the above-mentioned
objectives for proceeding with decommissioning the Fukushima Daiichi NPS safely and steadily. To
obtain good analysis results, it is effective to improve the analysis methods and systems, the qualityof the analysis results, and the size and quantity of samples, as shown in Fig. 43, and efforts arebeing made to achieve this.
・Establishing facilities, systems and coordination
・Assigning roles according to permission and facility
・Selecting the right analysis method for each purpose, etc.

Methods andsystems for analysis

・Increase the amount ofcollectable samples
・Examine the minimum
amount for analysis
・Consider number ofrepetitions, etc.

Appropriate
analysis
results
QualitySize and(accuracy)
quantity ofof analysis
sampleresults

・Reduction of insoluble
residues
・Countermeasures forinhibitory nuclides
・Reducing uncertainty, etc.

Fig. 43 Three elements of the fuel debris analysis strategy forthe decommissioning of the Fukushima Daiichi NPS

120

4.2 Current status and strategies for analysis
4.2.1 Measures to strengthen analytical method and analysis structure
4.2.1.1 Measures to strengthen analysis structure
While the government has taken the lead in developing a Mid-and-Long-term Roadmap 69 ,TEPCO, the JAEA, NDF, and other related organizations have been working together to establish
an analysis system, such as developing facilities for analysis, collaborating with domestic hotlaboratory organizations, developing analysis and evaluation methods, and exchanging humanresources. As Phase 3 is around the corner after the fuel debris retrieval in the initial unit, an urgent
task is to accelerate further the development of the analysis structure, which has been promoted
so far.
The NRA has acknowledged that the amount of solid waste generated and the work of analyzing
radioactive materials will certainly increase further in line with the progress of the decommissioning
work70, and revised the Measures for Risk Reduction Map and added Analysis Planning (including
facilities and human resources) as one of its key targets.71 Additionally, with a view to strengthening
the analysis system necessary for the decommissioning of the Fukushima Daiichi NPS, the NRA
has proposed to discuss measures to immediately resolve the issues (such as an all-Japan
approach).72
The increased analytical work was a concern for TEPCO, the JAEA, NDF, and other relatedorganizations. Therefore, to enhance the analysis structure, efforts have been steadily promoted
by examining analytical plans, developing analytical and evaluation methods, securing facilities foranalysis and analytical personnel, as well as strengthening cooperation among relatedorganizations. The Agency for Natural Resources and Energy has compiled measures for thedevelopment of such an analysis structure and published and reported them at the Meeting of theSecretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water and the NRA meetings (refer to Attachment 15 for the action plan for eachrelevant organization) 73,74. The immediate efforts will continue to be steadily implemented andnecessary measures will be taken in the light of the situation.
69

The 4th Ministerial Conference on Measures for Decommissioning, Contaminated Water, and Treated Water,
December 27, 2019, “Material 2 : the Mid-and-Long-term Roadmap towards the Decommissioning ofFukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc.”70
The 97th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
1-1: Revision of Measures for Mid-and-long-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Risk
Map) (1st)”71
The 98th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material 11: Measures for Mid-and-long-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Risk Map) (as ofMarch 2022)”
72
The 102nd meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
1-2: Enhancement of the Analysis Structure Necessary for Decommissioning of TEPCO’s Fukushima Daiichi
NPS”
73
The 112nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-4：The immediate measures to the development of analyticalsystems for Decommissioning of TEPCO’s Fukushima Daiichi NPS”
74
The 1st NRA committee FY2023” Material 1 : Policy initiatives to strengthen the analytical systems for
Decommissioning of TEPCO’s Fukushima Daiichi NPS”

121

4.2.1.2 Discussion on analysis plans
TEPCO assumes that as the decommissioning work progresses, the type and quantity of theanalysis targets will increase, and the demand for analysis will expand accordingly. 75 As thedemand expands for the analysis of lower concentration areas such as ALPS-treated water andenvironmental samples, it will become necessary to improve detection accuracy. With the growing
demand for analysis of high-radiation dose areas such as fuel debris and high-activity waste, it isnecessary to expand radiation protection functions such as shielding and containment and todiversify analysis such as element distribution and structural analysis. Systematic preparations
must be made to respond to such changes in demand flexibly and not to stagnate decommissioning
work due to analyses. In particular, objects with high-radiation dose rates, such as fuel debris andsecondary waste generated by water treatment, require hot cells with shielding and containment
capabilities as an analytical system, but the numbers are limited. To make effective use of theavailable hot cells, it is important to balance the desired information to be acquired for the analysis
targets and their quantity, detection accuracy, frequency of analysis, etc., and develop an analysis
plan that considers periodic maintenance, etc.
TEPCO extracted wastes with high priority for analysis based on the progress of analysis andrisks associated with storage management, and reviewed the characterization policy and analysis
plan according to the characteristics of each waste76. Table 5 provides the objective for analysis
planning. In addition, after integrating and coordinating analysis plans for each type of waste,
TEPCO designs the annual development of the necessary analysis capabilities and incorporates
them into analysis personnel plans. This analysis plan is continuously updated to reflect changes
in needs as decommissioning progresses. Moreover, TEPCO will implement the initiatives in theplan and, based on the progress made, will constantly review the necessary measures. Fig. 44
shows the analysis implementation flow for solid waste.

75

The 104th meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
1-3-2: Activity Status to Establish Analysis Structure”
76
The 112nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-4：The analysis plan of solid waste for Decommissioning of
TEPCO’s Fukushima Daiichi NPS”

122

Table 5 Objective for analysis planning
Response to
decommissioning
progress

Details
・Transition to management of radioactivity concentration for all waste

Transition to waste
management byradioactivity
concentrationconsidering the following :Obtaining data that contributes to the study of rational safetymeasures, etc. according to the characteristics of each waste.
Accumulation and management of data for disposal and re-use(radioactivity concentration control for a wider range ofradionuclides)
・By assessing the behavior of waste during storage and examining the

Safe and stable storage
management

appropriate safety measures, the physical and chemical
characteristics of waste is identified to study storage methods that canmaintain containment over a long period of time.

Response to the・Developing technology and human resources to handle samplingincreasing difficulty of

associated with debris retrieval and samples with high analyticalsampling and analysis

difficulty, etc. .

Systematic sampling
and analysis

・Systematic sampling and analysis with due consideration for the
representativeness・Rational characterization based on the characteristics of each waste(Source: TEPCO)
Scope of current study(Green shaded area)
Outcome (preliminary safety assessment)

Taking shape and progress of
1F decommissioning process

Assessment of analysis needs

Waste for which an improved estimation system is desirable

Targets, status,
conditions and changes thereof

Analysis plan (per waste)

Analysis plan (per waste)

Technical
issuesOutcome(Sampling,
analysis methods)

Technical developments• Analytical methods/technicaldevelopment• Sampling technology
development• Analytical method development• Preliminary safety assessment

Analysis plan (Overall)

Ensuring analytical capacity(facility, organization)
Proper storage management ofsolid waste/Study on waste
processing/disposal method

Outcome(Analysis methods,
technologies, etc.)

Analysis results

Conducting analysis

Analytical results(Source: TEPCO)
Fig. 44 Analysis implementation flow for solid waste at the Fukushima Daiichi NPS

The JAEA, in cooperation with Nippon Nuclear Fuel Development Co., Ltd. (hereinafter referred
to as “NFD”) and MHI Nuclear Development Corporation (hereinafter referred to as “NDC”), havebeen analyzing deposits, adhered materials, solid waste and other samples from PCV internal123

investigations77,78,79. As a result, some properties of fuel debris and waste have been clarified.
Based on past experience and the results to date, the JAEA is reviewing the analysis target items
and analysis flow of fuel debris necessary to solve issues from the viewpoint of the need to promote
decommissioning work safely and steadily80. In addition to the JAEA review, it will be extended tofuel debris analysis plans with the assistance of the analysis support team described below.
4.2.1.3 Development of analysis and evaluation methods
Solid waste is characterized by a variety of nuclide compositions and radioactivity concentrations
and a large amount of material. Therefore, unlike the development of waste identification methods
in conventional power reactors, it is necessary to develop waste identification methods specific to
the waste at the Fukushima Daiichi NPS, such as data acquisition, storage, organization, andapplication of statistical methods to establish the Scaling Factor method and other evaluation
methods. In particular, inventories necessary for discussing a processing and disposal strategy
must be characterized promptly and efficiently. For this reason, efforts will be made to develop
analytical methods for the purpose of obtaining data easily and quickly, to standardize analyticalmethods accelerated by streamlining and automating pretreatment of samples81, and to develop
analytical methods for handling various sample forms and the difficult-to-measure nuclides. In
addition, together with this effort, the Project of Decommissioning, Contaminated Water andTreated Water Management, and other projects are engaged in establishing methods forcharacterization with less analytical data, such as data acquisition planning using the DQO process
and Bayesian statistics and statistical inventory estimation methods. In the future, in developing
analytical methods, verification will be conducted at the JAEA’s Radioactive Material Analysis andResearch Facility Laboratory-1 to establish analytical methods and perform characterization basedon the analysis plan incorporating TEPCO’s needs.82 In addition, since molten fuel and structural
materials will be mixed in the waste during fuel debris retrieval, it is expected that the workability
will be improved if it is possible to promptly confirm whether uranium is contained in the materials
adhered to damaged supports, pipes, and other structures. Therefore, technology development
utilizing laser-induced breakdown spectroscopy is in progress as a technology development ofsimple (in-situ) analysis.

77

Subsidy for the Project of Decommissioning and Contaminated Water Management (Development of analysis
and estimation technologies for characterization of fuel debris), Outcome for research in FY 2021 (IRID) (2022)
78
The 108th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-4：Recent results on waste characterization –Characterization of major risk sources -”79“Subsidy for the Project of Decommissioning and Contaminated Water Management (Research andDevelopment for processing/disposal of solid waste)” starting in FY2021, 2021 Final report, September 2022,(IRID), (2022)
80
Working group on fuel debris and other research strategies, Japan Atomic Energy Agency, “Fuel debris analysis
of TEPCO’s Fukushima Daiichi NPS”, JAEA-Review 2020-004, (2020)
81“Subsidy for the Project of Decommissioning and Contaminated Water Management (Research andDevelopment for processing/disposal of solid waste)” starting in FY2021, 2021 Final report, September 2022,(IRID), (2022)
82
The 104th Meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
1-3-3: Development flow of analysis and evaluation methods”

124

4.2.1.4 Securing facilities for analysis
As an essential facility for the decommissioning of the Fukushima Daiichi NPS, the JAEA
develops and operates the Radioactive Material Analysis and Research Facilities adjacent to the
Fukushima Daiichi NPS under the supplementary budget of the government (FY2012).83, 84 Upon
commencing its operation, they will be designated as facilities in the peripheral monitoring area of
the Fukushima Daiichi NPS, which has the advantage that off-site transportation is not required.
Leveraging this, it is effective to promptly identify the basic physical properties and incorporate
them into safety assessment and work procedures. The objectives of Laboratory-1 are solid waste
analysis and third-party analysis of ALPS-treated water,85 and Laboratory-2 is intended to conduct
fuel debris analysis. Laboratory-1 was completed in June 2022,86,87 where the controlled area andother areas were set as a part of the specified nuclear facility, and analytical operation using
radioactive materials started in October.88 It also began third-party analyses of ALPS-treated waterin March 2023. 89 Laboratory-2 is in the process of screening applications for approval of
implementation plan changes and selecting the operator, and the construction is expected to becompleted in FY2026. TEPCO is also considering the construction of facilities for analysis(comprehensive facilities for analysis) in response to the future needs of analysis, including analysis
of fuel debris and solid waste, in addition to current routine analyses. The construction is expected
to be completed in the second half of the 2020s.
As shown in Fig. 45, since Laboratory-2 and the comprehensive facilities for analysis arescheduled to commence operation after the trial retrieval of fuel debris, the analysis will be
conducted at the facilities for analysis in the Ibaraki area until Laboratory-2 becomes operational.
Since there are more analysis items for fuel debris than for waste analysis, such as metallographic
observation, microstructural observation, and elemental mapping, there is a concern that theanalytical capacity of Laboratory-2 will be exceeded after it commences operation. To reduce theworkload in Laboratory-2, if special techniques are required for pretreating samples with a highradiation dose or if analysis and testing require an extended period, these analyses should be
performed in the Ibaraki area, even after Laboratory-2 commences operation. This is because (i)83

The 24th Meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
3-1: Development of R&D Hub Facilities for Decommissioning”
84
The 52nd Meeting of the Study Group on Monitoring and Assessment of Specified Nuclear Facilities, “Material
3-4: Opening of the Okuma Analysis and Research Center Facility Management Building”
85
The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 4: Development Status of Radioactive Material Analysis andResearch Facility Laboratory-1”
86
Japan Atomic Energy Agency (JAEA), June 24, 2022 “Completion of Laboratory-1 of the Radioactive Materials
Analysis and Research Facility (Okuma Analysis and Research Center) and Future Plans”
87
The 103rd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 4-1: Completion of Laboratory-1 of the Radioactive Materials
Analysis and Research Facility (Okuma Analysis and Research Center) and Future Plans”
88
The 106th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material, Others: Commencement of Analysis Work at Laboratory-1 of theRadioactive Materials Analysis and Research Facility”
89
Sector of Fukushima Research and Department, Japan Atomic Energy Agency (JAEA), March 30, 2023, “Startof Third-party Analysis of ALPS-treated Water in Radioactive Material Analysis and Research Facility,
Laboratory 1”125there are many researchers and engineers, (ii) many types of special analysis devices are available,and (iii) there are a large number of hot cells with containment and shielding functions andapplication options. Currently, Laboratory-1 does not have a license for using nuclear fuel materials.
However, in the long term, one of the measures to expand the analysis capacity of fuel debris is to
examine the possibility of analysis using diluted solutions in Laboratory-1 after dissolving anddiluting fuel debris in Laboratory-2 and prioritize analyses requiring promptness on-site and inadjacent areas of the Fukushima Daiichi NPS.
As for solid waste analysis, as the trial retrieval of the fuel debris progresses, it is anticipated that
it will generate solid waste with which TEPCO does not have previous experience, such as fine fueldebris and filters that have captured fission products. Regarding high-radiation dose solid wastewith which TEPCO has limited experience, it is desirable to analyze solid waste in the Ibaraki area
for the same reasons described above, and it is necessary to continue it in the Ibaraki area forsome time after Laboratory-1 is put into operation. Based on the above, since the target nuclides
for permission for use and the situation with or without off-site transportation differ between facilities
for analysis in the Fukushima Daiichi NPS site/adjacent areas and those in the Ibaraki area, it iseffective to assign roles according to the characteristics and expand the analysis data of fuel debris
and solid waste. However, since all the facilities for analysis in the Ibaraki area have been in
operation for more than 30 years and the JAEA plans to consolidate and increase its focus on thefacilities,90 consideration should be given to facilities that will continue to be used going forward.

90

Japan Atomic Energy Agency (JAEA), April 1, 2022, Medium-/Long-Term Management Plan for the JAEA
Facilities

126

Fiscal Year
2023

2024

Manufacturing /installationof retrieval device

Fuel debris
retrieval(Unit 2)2025

2026 onwards

Characterization of fuel debris

Trial retrieval/ internal investigation

Gradual expansion of fuel debris retrieval

RPV internal investigation

Transport to off-site

Solid waste

Rubble etc.(rubbles, felled trees, used protective clothing)

Elimination of temporary
outdoor storage (in FY2028)

Secondary waste generated by water treatment (Sorption vessels, waste sludge, concentrated waste liquid slurry)
Analysis facilities in
Ibaraki (JAEA, NFD, Analysis of deposit/
NDC)
adhesion

Analysis of fuel debris

Analysis of waste
Lab.
1

Transport to on-site

Start of operation with radioactive materials
Lab.

Okuma
Analysis/Res
earch Center(JAEA)

Design/Approval, etc.

2Construction
TEPCO’s analysis
facility

ALPS-treatedwater

Start of operation (incl. cold run)
Design/Approval/Construction

Start of operation (incl. cold run)
Installation of discharge facilities
Operation of discharge facility
Marine monitoring※※

indicate the destination of the sample, and do not correspond to the number of transfer.
(dashed arrow) may change depending on the operation status of other facilities.

Fig. 45 Construction and operation schedule for fuel debris retrieval and new analyticallaboratories
4.2.1.5 Securing human resources for analysis
Not only the facilities for analysis in the Ibaraki area but also the facilities for analysis on-site andin the area adjacent to the Fukushima Daiichi NPS are short of the human resources required tocontinue stable facility operation, so the securing and maintaining of analytical personnel needs tobe considered. In this respect, it is important to consider in advance the qualities expected of eachanalytical personnel in various types of analytical work and develop analytical personnel
systematically to achieve the required roles appropriately. TEPCO estimates that in addition to thecurrent structure with 117 persons, about 30 additional persons will be required for waste analysis
by the 2030s. In FY2023, TEPCO began training employees so that they can gain practicalexperience by participating in analysis projects related to the Project of Countermeasures on
Decommissioning, Contaminated Water and Treated Water91. As the JAEA’s Medium-/Long-Term
Management Plan for JAEA Facilities describes the implementation of back-end measures,
including decommissioning, the development of human resources necessary for decommissioningrelated analysis is an important issue also for the JAEA. It is necessary for TEPCO and the JAEA
91

The 112nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-4：The analysis plan of solid waste for Decommissioning of
TEPCO’s Fukushima Daiichi NPS”

127

to mutually identify changes in analytical needs and issues over time and cooperate in humanresource development, while relevant organizations such as the Agency for Natural Resources andEnergy and NDF also need to provide support for securing analytical personnel.
In normal nuclear power plants, fuel is sealed in fuel cladding, and before the accident, theunsealed alpha-ray emitters were not directly handled in the Fukushima Daiichi NPS. The fuel debris
generated by the accident contains unsealed fuel and fission products, and analyses entails the riskof internal/external exposure or spreading contamination. For this reason, TEPCO must develop
human resources for fields with little experience in as short a time as possible. It is necessary for
TEPCO to effectively work on developing analytical technicians with the cooperation of the JAEA
and private-sector enterprises that have accumulated sufficient knowledge and experience inhandling alpha-ray emitters and fuel analysis techniques. 92 , 93 Table 6 shows the records of
personnel exchange between TEPCO and the JAEA and personnel acceptance from NFD to
TEPCO.
Table 6 Personnel exchange between TEPCO and JAEA and accepting personnel from
NFD to TEPCO
Fiscal Year
2018
2019
2020
2021
2022
From TEPCO to JAEA
From JAEA to TEPCO
From NFD to TEPCOAssigned, temporary,external researcher
Transfer, reemployment
Assigned, temporary
Transfer, reemployment
Assigned, temporary
Transfer, reemployment

1

1

3

3

4

0
0
0
0
1

0
3
0
0
1

0
11
1
1
0

1
4
0
0
1

0
1
0
0
0

Analytical workers of the Fukushima Daiichi NPS on site have been mainly experienced in theanalysis of liquid samples only. Therefore, in preparation for the launch of the comprehensive facility
for analysis, training for analyzing samples with a high radiation dose using hot cells and glove
boxes will be provided in Laboratory-1. Moreover, from FY2023, potential candidates will be sent
to the JAEA and private sectors to join R&D for development of analytical technicians94.
In efforts to develop and secure analytical workers, the Fukushima Institute for Research,
Education and Innovation (hereinafter referred to as “F-REI”) and the Agency for Natural Resources
and Energy are collaborating to prepare a “human resource development training program” forradioactivity analysis, to expand the human resource base who will be analytical workers.

92

Tokyo Electric Power Company Holdings Inc., Japan Nuclear Fuel Limited., Conclusion of “Agreement on
Technical Cooperation for the decommissioning of the Fukushima Daiichi Nuclear Power Station,” January 27,
2022
93Tokyo Electric Power Company Holdings Inc., Nippon Nuclear Fuel Development, “Memorandum ofUnderstanding for cooperation in debris analysis for the Fukushima Daiichi Nuclear Power Station,” August 1,
2022”
94
The 112nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-4：The immediate measures to the development ofanalytical systems for Decommissioning of TEPCO’s Fukushima Daiichi NPS”

128

As the demand for analysis is expected to increase in the future, there will be a need for highly
skilled personnel capable of analysis planning in anticipation of how the analysis results will be
used. Analytical evaluators in charge of this task are required to have the ability to (i) appropriately
incorporate the evaluation results into the areas required for the decommissioning process(retrieval method, safeguards, storage/management, and processing/disposal), (ii) provide
appropriate instructions for the subsequent sampling, and (iii) logically and accurately understandaccident events from analytical results. However, it is difficult for individuals to have all theseabilities. Therefore, the Analysis Coordination Meeting and an Analysis Support Team wereorganized within NDF, as shown in Fig. 46. The Analysis Coordination Meeting is responsible for
confirming analysis plans and providing advice on problem-solving in response to the increased
types and numbers of objects to be analyzed. The Analysis Support Team, consisting ofresearchers and engineers with extensive experience and knowledge in analytical practice, is to
examine and discuss solutions to the issues raised, propose how to solve the issues, and report
the progress. The first meeting of the Analysis Coordination Meeting and the Analysis Support Teamwas held in August 2023 to discuss analysis planning and problem solving95.

Fig. 46 Role of the Analysis Coordination Meeting and Analysis Support Team4.2.2 Improvement of the quality of analysis results
Fuel debris contains difficult-to-measure nuclides, interfering elements, immiscible substances,
etc., and there are problems in pretreatment and measurement, such as uniform dissolution ofsamples and selection of isobar. Therefore, it is difficult to identify and quantify all elements and95

The 1st Analysis Coordination Meeting, https://www.dd.ndf.go.jp/tech-committee/

129isotopes down to trace components by analysis. As such, it is important to have a multifaceted pointof view on the analytical results of samples in consideration of the impact of the error factor. As partof the verification of sample analysis results, through studies in light of existing findings, such as
results of analysis, investigation, and testing, deriving consistent property evaluations will improve
the reliability of analysis results, leading to higher quality in the analysis results.
To improve the quality of analysis results, the JAEA, the NFD, NDC, and Tohoku University havebeen cooperating to conduct chemical analysis and structural analysis using the same samples
since FY 2020.96 97Currently, the Ibaraki area offices are preparing to analyze the Three Mile Island
Unit 2 reactor (TMI-2) debris using the latest technologies to expand the fuel debris data. TEPCO
and the JAEA are cooperating in implementing activities that estimate accident behavior.98
Furthermore, the BSAF, BSAF-2, PreADES, and ARC-F, which have been implemented as
projects of the OECD/NEA as opportunities to have international discussions and acquire accident
progression and fuel debris analysis and evaluation techniques, have come to an end, and the
FACE project was launched in July 2022. The scope of the FACE project is (i) in-depth discussions
for accident progression and associated fission product behavior and H2 combustion; (ii)characterization of uranium-bearing particles and establishment of techniques for future fuel debris
analysis for D&D; and (iii) collection and sharing of data and information. There are 24
organizations from 13 countries participating in the project, with 6 organizations from Japan: NRA,
Agency for Natural Resources and Energy, the JAEA, Central Research Institute of Electric Power
Industry, the Institute of Applied Energy, and NDF.
As for waste, to perform characterization of all solid waste which exists in large amounts using
the limited analytical data, an efficient approach to ensure the required accuracy will be essential,and efficient analytical planning methods utilizing the DQO process and statistical inventory
estimation methods with Bayesian statistics are being developed. Accuracy is one of the indicators
for the quality of analytical data, but accuracy and measurement time are interrelated, and it isexpected that increasing the measurement time can improve the accuracy. However, if
measurements take weeks or months, it is difficult to keep up with the increasing volume of analysis.
Therefore, according to the analytical purpose, objects to be analyzed, and analytical method, it isalso important to properly select the accuracy, measurement time, and measurement frequency
based on the concerned analysis method.

96

Subsidized project related to “the Project of Decommissioning and Contaminated Water Management(Development of technologies for improving analytical accuracy and estimation of thermal behavior of fueldebris),” Final report of FY 2020, August 2021, Japan Atomic Energy Agency (JAEA) (2021)
97
Ikeuchi, Koyama, Osaka et al., Japan Atomic Energy Agency ”Development of technology for improving
analytical accuracy of fuel debris, FY2020 Outcome report, (Supplementary budget for the Project ofDecommissioning and Contaminated Water Management)”, JAEA-Technology 2022-021, (2022)
98
Supplementary budget, “The Project of Decommissioning and Contaminated Water Management(Development of analytical and estimation techniques for characterization of fuel debris),” implementation
results for FY 2021, International Research Institute for Nuclear Decommissioning (IRID), (2022)

1304.2.3 Diversification of analytical techniques to increase sample size and volume
4.2.3.1 Comprehensive evaluation by diversified analysis and measurement methods
The current sample analysis is mainly performed using electron microscopes after transporting
smear samples to facilities for analysis in the Ibaraki area. Since density, hardness, and other items
cannot be measured for micro or very small quantity of samples, it is necessary to increase thesize and quantity of samples in accordance with the progress of the fuel debris retrieval process. A
manipulator is used in an analysis process in a hot cell. Since it requires time for each process andthe amount to be used in each hot cell is restricted for each nuclide that can be handled, it is difficult
to analyze many samples. Consequently, there is a large gap between the volume to be
retrieved/stored and the amount of sample for analysis.
Particularly, since fuel debris is heterogeneous, the analytical values vary depending on thesampled parts, and the situation is such that a sufficient amount of fuel debris cannot be analyzed,
resulting in a range of uncertainty in evaluation. Given the limitations on improving the quality ofanalysis and sample volume, it is necessary not only to focus on increasing the number of analysis
samples in conventional hot labs but also to diversify analysis and measurement methods. It iseffective to assess the advantages and disadvantages of the analysis items obtained by othermethods, consider complementing each other according to the use of the analysis results, andmake a comprehensive evaluation. Depending on the application, it may also be worth considering
methods that can only measure single items.
4.2.3.2 Use of sample analysis and non-destructive assays
Although sample analysis in a hot lab can measure many analysis items, the time required foranalysis is long and the amount analyzed at one time is small. Since the samples themselvescontain nuclear fuel and are likely to be adhered to with fine particles of radioactive materials, they
carry the risk of exposure accidents and the spread of contamination. It is difficult to analyze large
quantities of samples promptly because a certain amount of resources is to be allocated to curing
equipment, decontaminating, and treating the radioactive liquid waste generated during analysis.
One of the analysis and measurement methods that complement the results of sample analysis
is to evaluate the amount of radioactivity in solid waste and the amount of nuclear fuel in fuel debris
without destroying the sample using radiation, quantum, etc., emitted, scattered, or transmitted
from the sample (hereinafter referred to as “non-destructive assay”). Table 7 shows the relative
comparison of the items for sample analyses to be performed inside the facility for analysis and fornon-destructive assays to be performed outside the facility for analysis and the sample amounts.
Although sample analysis can measure many analysis items, the time required for analysis is long,and the amount analyzed at one time is small. Among the solid wastes, those with a high radiationdose generated during retrieval of fuel debris stored in containers are measured with gamma raysfrom Cs-137, Co-60, etc., which can be measured non-destructively. With these nuclides as
indicators, technology development is underway to evaluate the radioactivity of other difficult-tomeasure nuclides. Although non-destructive assay can measure fewer items than that of sample

131

analysis, the measurement time is shorter, and a larger quantity can be measured per
measurement. Moreover, measurement can be performed with the object stored in a sealedcontainer to prevent the spread of contamination, generating no radioactive waste liquid.
Table 7 Relative comparison of principal specifications between the sample analysis in thefacility for analysis and the non-destructive assay outside the facility for analysis

On the other hand, since fuel debris has entrained the surrounding control rods (neutron
absorbers) when the nuclear fuel melted, there are concerns about the accuracy of nondestructive
measurement techniques using neutrons. Moreover, if the fuel assembly was intact, a method toevaluate burnup could be used by measuring gamma rays from Cs-137, a gamma-ray source witha strong penetration force. However, due to the volatilization of Cs-137 during the melting of nuclear
fuel, the gamma-ray doses and burnup have become incomparable. Thus, since fuel debris has
impediments to non-destructive assays, it is necessary to verify the extent to which these
impediments affect measurements. Therefore, the Project of Decommissioning, Contaminated
Water and Treated Water Management promotes technology development aiming at on-site
application through simulation analysis and actual measurement tests using existing testing
devices.99
As an example of the application of non-destructive assay, Fig. 47 shows its use in the handlingprocess from fuel debris retrieval to storage/management. In the figure, the non-destructive assay① aims to classify the level of the waste, the non-destructive assay ② to maintain subcriticality,
and the non-destructive assay ③ to price waste for transportation and storage. Fig. 47shows one
example, and the flow may change depending on future R&D and study results. If non-destructive
assay can be performed on fuel debris containers or waste storage containers, it will be possible
to support the number of sample analyses, promptly verify the mass less than the minimum criticalmass, transition to the following process in a subcritical condition, and reduce the burden during
99

Subsidy program for ”the Project of Decommissioning and Contaminated Water Management (Development ofTechnologies for Scaling up Retrieval of Fuel Debris and Internal Structures (Development of Technologies for
Sorting and Distinction between Fuel Debris and Radioactive Waste)” starting FY 2020, Final report, August
2022, International Research Institute for Nuclear Decommissioning (IRID), 2022

132

storage/management. In so doing, it is desirable to keep the range of uncertainty in the propertiesof fuel debris as small as possible while increasing information about the sample, including thenumber of sample analyses and the coordinate information at sample collection, to improve thereliability of the data.

Fig. 47 An example flow of non-destructive assay in the handling process for retrieved fuel debris

Among non-destructive assay techniques, methods that detect neutrons from nuclear fission andthose that use the scattering of elementary particle muons are effective for measuring fuel debris
containing nuclear fuel and waste contaminated with alpha-ray emitters, but unsuitable for waste
not containing alpha-ray emitters. On the other hand, methods for measuring gamma-rays fromfission and activation products and external measurement methods using X-ray CT can obtain
information on the contents of containers even for waste that does not contain alpha-ray emitters,
and are in practical use in industrial and medical applications.
4.2.3.3 Improvement in number of analyses
Although it is important to increase the number of analyses for each sample to obtain a complete
picture, the number of analyses is insufficient for cases with a high radiation dose, such as fueldebris and cesium adsorption vessel samples, for which sampling is difficult. It is also important toimprove the number of samples collected through the development of a sampling device.

133

5. Efforts to facilitate research and development fordecommissioning of the Fukushima Daiichi NPS
5.1 Significance and the current status of research and development
There are many difficult technical issues requiring research and development in promoting thedecommissioning of the Fukushima Daiichi NPS from the safety, reliability, efficiency, timeliness,and field-oriented perspectives. At present, when trial retrieval of fuel debris is about to begin, it isnecessary to accelerate research and development in consideration of the practical application for
the gradual expansion of fuel debris retrieval and the further expansion of fuel debris retrieval inscale.
To solve these technical issues, various industrial-academic-governmental institutions, including
overseas enterprises, are engaged in basic/fundamental research and application research by
universities inside and outside Japan and by researching institutions such as the JAEA, and inpractical application research and field demonstrations by manufacturers, and TEPCO (Fig. 48).

TEPCO
1F
decommissioning
Manufactures(incl. overseas enterprises)

Practical
application
research

JAEA

Applied research
Universities/
Research institutions, etc.

Basic research

Fig. 48 Scope of studying decommissioning R&D and implementation entities

For application research and practical application research for decommissioning, the government
provides support for the R&D carried out by each organization to solve highly difficult issues throughthe Project of Decommissioning, Contaminated Water and Treated Water Management and topromote basic/fundamental research and human resource development by universities andresearching institutions in Japan and overseas through the Nuclear Energy Science & Technology
and Human Resource Development Project (hereinafter referred to as the “World Intelligence
Project”).
TEPCO has been working on technology development that is directly linked to site application. It
identiﬁes research and technology development issues and examines solutions related to the Mid-134

and-Long-term Decommissioning Action Plan, manages the progress of technology development,
and incorporates them into the development plan.
NDF is considering the planning of the R&D medium-and-long-term plan and the next-term R&D
plans, and it supports the World Intelligence Project. NDF has also established theDecommissioning R&D Partnership Council with representatives of institutes involved andintellectuals from universities as its members, which discusses information sharing on needs andseeds for R&D, adjustment of R&D based on the needs of decommissioning work, and issues inpromoting cooperation related to R&D and human resource development. Moreover, coordination
between the Project of Decommissioning, Contaminated Water and Treated Water Management
and the World Intelligence Project has been promoted through the Decommissioning R&D
Partnership Council.
The JAEA, as the executing entity of the World Intelligence Project, promotes basic/fundamental
research and human resource development. It also plays a significant role in R&D related toanalysis and estimation for the characterization of fuel debris and waste management by leveraging
its knowledge and experience in the Project of Decommissioning, Contaminated Water and Treated
Water Management.
The R&D implementation structure is outlined in Fig. 49.

Fig. 49 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPSGiven that the progress of investigation inside the reactors has clarified on-site needs indecommissioning and TEPCO has begun full-scale engineering work for fuel debris retrieval, the135leading players in the Project of Decommissioning, Contaminated Water and Treated Water
Management have shifted from the current IRID-centered structure to researching institutions andmanufacturers as key implementers based on TEPCO’s needs, requiring smooth coordination
between the R&D implementers and TEPCO. IRID deleted Articles 52 of its articles of incorporation(the term ending) in April 2023 and is engaged in research and development that should be
addressed continuously, including a detailed investigation inside the Unit 2 PCV and trial retrievalof fuel debris.
In addition, F-REI was established by the government in April 2023 to contribute to thereconstruction and revitalization of Fukushima. F-REI plans R&D in five fields ([1] robots, [2]agriculture, forestry and fisheries, [3] energy, [4] radiation science, drug discovery, and medicalcare, and [5] collection and dissemination of data and knowledge on nuclear disasters). Among the
R&D that will contribute to decommissioning, the plan in the field of [1] robots includes thedevelopment of remote-operated elemental technologies (e.g., tactile feedback) assuming
decommissioning, the development of analytical methods and human resources, and thedevelopment of international researchers in cooperation with the IAEA100.
F-REI integrates technologies and methods multidisciplinary and academically to advanceinitiatives in new areas. As these efforts will lead to participation in decommissioning R&D from awide range of fields other than nuclear power. NDF will continue to collect information on the statusof F-REI’s R&D and human resource development, and will also collaborate with the F-REI basedon its implementation.

5.2 Key issues and strategies
5.2.1 R&D medium-and-long-term plan
NDF and TEPCO have been preparing the R&D Medium-to-Long-term Plan for thedecommissioning of the Fukushima Daiichi NPS every fiscal year since fiscal 2020. The plan
overlooks the overall research and development for about next 10 years for decommissioning, sothat R&D activities for decommissioning of Fukushima Daiichi NPS can be promoted
comprehensively, systematically, and efficiently. Based on the engineering schedule of TEPCO, theR&D Medium-to-Long-term Plan is developed to identify the required R&D and appropriately
incorporate R&D results when needed. The plan has also included basic/fundamental research
since FY 2022. In FY 2023, the R&D Medium-to-Long-term Plan was revised based on the revisionof TEPCO’s Mid-and-Long-term Decommissioning Action Plan, study on retrieval method for further
expansion of fuel debris retrieval in scale, progress of ongoing R&D activities, and making requests
for information (RFI), as well as the medium-to long-term issues that are being discussed by four
parties,

including

TEPCO,

Decom.Tech,

Collaborative

100

Laboratories

for

Advanced

The 11th Decommissioning R&D Partnership Council, Material 1-1-3, “F-REI research and development
contributing to decommissioning”

136Decommissioning Science of the JAEA, Sector of Fukushima Research and Development,
Fukushima Research Institute (hereafter referred to as “JAEA/CLADS”), and NDF (Attachment 16).
5.2.2 Initiatives for the Project of Decommissioning, Contaminated Water and Treated
Water Management(1) The Project of Decommissioning, Contaminated Water and Treated Water Management
The Ministry of Economy, Trade and Industry has been providing support of research anddevelopment through the Project of Decommissioning, Contaminated Water and Treated Water
Management to solve technically challenging issues for decommissioning since FY2013. In the
Project of Decommissioning, Contaminated water and Treated water Management to date, anumber of decommissioning R&Ds have been performed the main achievements and challengesof which are listed below.


The investigation equipment was inserted into the PCV, where the situation had been
unknown due to the high radiation doses and high contamination, and revealed the situation
inside and outside the Unit 1 pedestal, the deposits of possible fuel debris in Unit 2, and thefailure situation of in-core structures in Unit 3. However, there are still issues, such as
observing the damage on the RPV bottom.

Muon surveys inside the RPVs have estimated the remaining fuel state, but the challenge isan internal investigation by actually entering inside.

Concerning the unprecedented analysis of fuel debris in BWRs, analytical methods forprompt and accurate analysis have been established and standardized, and thecharacterization of fuel debris based on the analysis of deposits and adhered materials
sampled inside the buildings and in investigation inside the reactors has also been advanced.
However, the challenges are to continue these efforts and address the increase in the sizeand quantity of fuel debris, and establish data evaluation methods due to the heterogeneouscomposition.



Fuel debris retrieval will be extremely difficult because the operation needs to be carried out
remotely to avoid working in an environment with high-radiation doses and highcontamination. Several solutions for safety measures, such as retrieval methods, criticality
control, and containment of radioactive materials, have been proposed. Moreover, it isnecessary to solve emerging issues that will arise from examining the fuel debris retrieval
method in the future.

Efforts were made to establish a flexible and reasonable waste stream for a large amountof solid waste with diverse properties (the flow of the integrated measures fromcharacterization to processing/disposal). As a result, the Technical Prospects were provided
in FY 2021. From now on, to present appropriate overall measures for specificstorage/management approaches for solid waste storage, the challenge is examining137

options for processing/disposal management, comparing and evaluating them, while
promoting characterization.


Futurechallenges,

such

as
101

decommissioning management

developing

supporting

technologies

forintegrated, which need to be solved after further expansion of fueldebris retrieval in scale
Given the above, the Project of Decommissioning, Contaminated Water and Treated Water
Management should be promoted continuously as part of important research and developmenttasks to complete decommissioning. Attachment 17 shows the R & D efforts to date.
(2) The next fiscal year’s decommissioning R&D plan
In order to support the Project of Decommissioning, Contaminated Water and Treated Water
Management, NDF is formulating the next fiscal year’s decommissioning R&D plan for the next two
years. After adjustment and discussion with parties concerned at R&D planning meetings attended
by TEPCO, the Ministry of Education, Sports, Culture, Science and Technology (MEXT), theMinistry of Economy, Trade and Industry (METI), and NDF, the next fiscal year’s decommissioning
R&D plan is first deliberated on by the Fuel Debris Retrieval Expert Committee and Waste
Management Expert Committee, which are the committees at NDF, and then by theDecommissioning Strategy Committee. After this, it is summarized as an NDF proposal. This next
fiscal year’s decommissioning R&D plan was reported by METI to the Meeting of the Secretariat of
the Team for Countermeasures for Decommissioning and Contaminated Water/Treated Water, and
the Project of Decommissioning, Contaminated Water and Treated Water Management has been
implemented accordingly. The list of FY2023 decommissioning R&D plans as the next fiscal year’s
decommissioning R&D plan reported at the 111st Meeting of the Secretariat of the Team forCountermeasures for Decommissioning and Contaminated Water/Treated Water 102 held in
February 2023 is shown in Fig. 50.

101

Development of an information management system to integrate and share monitoring and operational dataacquired during the long decommissioning period using digital technology, and to maintain safe operations byimplementing accurate on-site operations.
102
The 111st Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water. “FY2023 decommissioning R&D plans”

138

Engineering次期研究開発計画（一件一葉）のグループ案
by operators, Study on future measures[A] Trial retrieval
Gradual expansionof fuel debris
retrieval[A1] Trial retrieval
in Unit 2[B1]
Environmental
improvement of
the in thebuildings<N/A>[A2] Gradualexpansion of fueldebris retrieval in
Unit 2[A2] Technology
for gradualexpansion of fueldebris retrieval(by FY2024)(New)[C] Wastemanagement[B]Further expansion of fuel debris retrieval[B1] Technology
for improving
the environment
in the reactor
building(by FY2024)(New)[B2] Investigationof PCV/RPV insideand graspingproperties of fueldebris[B2①]
Technologies for indepth investigationof PCV inside(by FY2022) (notcontinued after
FY2023)[B2②]
Investigation
technologies inside
RPV (by FY2023)(Partly new)
[B2③] Analyticaland estimation
techniques forcharacterization offuel debris(by FY2024)(New)[B3] Retrieval facility/
safety system/
Maintenance facility/
storage[B3①] Retrieval method offuel debris(by FY2024) (New)[C] R&D ofprocessing/dispos
al of solid waste(by FY2023)(Partly new)

[B3②] Safety system(by FY2024) (New)[B3③] Technologies formaintaining remoteequipment(by FY2022) (notcontinued after FY2023)[B3④] Technologies forcontaining, transferring,and storing fuel debris(by FY2024) (New)

LegendResearch &Development
supported by
METI[B3⑤] Support technology
for integrated
management of Fukushima
Daiichi NPS(by FY2024) (continued)

Fig. 50 List of FY 2023 decommissioning R&D plans

In considering the next fiscal year’s decommissioning R&D plan, the R&D results have been
evaluated to identify issues whose level of achievement should be improved and emerging issues,
as well as to identify new challenges and organize technical issues with a view of the R&D mediumand-long-term plan. When identifying issues, it is also important to identify them exhaustively,
confirm whether each issue is in line with the needs of TEPCO as the entity responsible fordecommissioning, and aim for R&D results to be utilized for TEPCO’s engineering.
Since FY 2022, to contribute to discussions on the next fiscal year’s decommissioning R&D plan,
requests for information (RFI) have been made as R&D proposals and planning to widely solicit
information on the R&D details to be addressed toward the decommissioning of the Fukushima
Daiichi NPS.
(3) Further research and development implementation structure for the Project ofDecommissioning, Contaminated Water and Treated Water Management
Given that the progress of investigation inside the reactors has clarified on-site needs indecommissioning and TEPCO has begun full-scale engineering for fuel debris retrieval,decommissioning research and development is changing from a joint effort by IRID to a stage
where TEPCO’s engineering-based development is being advanced. In light of theseenvironmental changes, the implementation structure of the Project of Decommissioning,
Contaminated Water and Treated Water Management shifted from an IRID-led subsidized project
structure to a new R&D structure led by researching institutions and manufacturers based on
TEPCO’s needs. In addition, as a structure, TEPCO applies for issuance jointly with research

139

leadership to facilitate cooperation with them and is responsible for the project management inthis Project.
As a result of the transition to such a new implementation structure, the issues below remain.
Therefore, NDF is undertaking requests for information (RFI) and project reviews to ensure
cooperation between research leadership and TEPCO and further strengthen functions related
to planning proposals for R&D and securing the actual site applicability of research results (Fig.
51).
Discuss R&D details from broad perspectives in the Project of Decommissioning,
Contaminated Water and Treated Water Management.



Perform project assessment in terms of practical engineering and actual site applicability
and incorporate the results into R&D tasks.

a.

Request for Information (RFI)
As R&D planning and proposal, a request for information (RFI) is an initiative to widely solicit

information on R&D details to be addressed toward decommissioning the Fukushima Daiichi NPS.
Specifically, this is a request for the public to provide information on R&D themes, details of R&D(technical issues to be resolved and details of implementation), the scale of R&D, potential joint
R&D partners, and R&D fields. For RFIs made in FY 2022, dozens of proposals were made, someof which were incorporated into the FY 2023 decommissioning R&D plan. In FY 2023, based on
the experience of FY2022, public participation through RFI has been solicited after improving theapplication process, including extending the application period and changing the entry procedure.
The system will be improved continuously, including how to scrutinize proposals. The previous
IRID-led system for subsidized projects had faced challenges, such as the lack of new participation
by business operators and the unearthing of development seeds for new research. Therefore, theaim is for the RFI to broad base of operators who join the Project of Decommissioning,
Contaminated Water and Treated Water Management, and to widely collect R&D seeds throughpublic solicitation, which will lead to accelerating the resolution of issues in decommissioning.
b.

Project review
The project review is an initiative for subsidized projects in which experts and relevantorganizations evaluate subsidized operators’ activities of planning, testing, design, and production
at an appropriate time from the following perspectives after setting appropriate milestones andprovide necessary guidance and advice.
Whether a plan aligns with the set target

Check practical engineering and applicability to actual site

The project review started in FY 2023. Since this is the first trial, results will be reviewed to
improve the system continuously.

140

Request for information (RFI)The Project of Decommissioning,
Contaminated water and Treated water

Used as materials forformulating futuredecommissioning R&D plans

Project review meeting Is the plan geared towards the set goals?
 Confirmation of actual equipment engineering, andapplicability to the site

Technical issues ofdecommissioning
and R&D content

Operators

Relevantorganizations

Experts

The Secretariat of the Project ofDecommissioning, Contaminatedwater and Treated water management

Guidance/Advice

ReportResearching
Institutions

Subsidiaries

Universities

Fig. 51 RFI and project review

Regarding the outcome of the development that has been conducted through the Project ofDecommissioning,

Contaminated

Water

and

Treated

Water

Management,

since

the

decommissioning of the Fukushima Daiichi NPS is a national/social issue, the challenge isestablishing an easily accessible structure where organizations involved in the research anddevelopment for decommissioning can make effective use of the R&D results, including theknowledge obtained. Therefore, the outcome should be archived in terms of disclosure of results
and sharing knowledge, and TEPCO currently leads this initiative. The results that can be madepublic are disclosed on the Secretariat's website103 immediately after the completion of the project.
5.2.3 Promotion of cooperation between decommissioning sites and universities/
researching institutions(1) The Nuclear Energy Science & Technology and Human Resource Development Project
Universities/researching institutions tasked with basic/fundamental research are expected tomaintain and develop human resources, knowledge and infrastructure to make a quick responsewhen technical issues requiring scientific knowledge occur. It is important that universities/
researching institutions share awareness of issues faced by the field of decommissioning. In orderto facilitate the long-term decommissioning project of the Fukushima Daiichi NPS, it is important to
conduct scientific and technological investigations based on understanding of the principles andtheories from the medium-and-long term perspectives.
In this background, MEXT has been promoting fundamental/basic research and human resource
development activities, which contribute to problem-solving for the decommissioning of the
Fukushima Daiichi NPS, by bringing together domestic and overseas intelligence fromuniversities/researching institutions as the World Intelligence Project, crossing over the boundaries
103

Management Office for the Project of Decommissioning, Contaminated Water and Treated Water Management
Website（https://dccc-program.jp/category/result）

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of the nuclear field, and through close coordination and alignment including international joint
research. JAEA/CLADS is responsible for the implementation of this World Intelligence Project tostrengthen cooperation between universities and researching institutions, and establish a system
to implement medium-and-long term R&D and human resource development, contributing todecommissioning more stably and continuously. In the World Intelligence Project public call, the“overall map of the basic/fundamental research” is used in soliciting applications, which provides
an overview of the entire decommissioning process from contaminated water management towaste processing/disposal and identifies the R&D needs and seeds required104.
The following three programs are in progress in the World Intelligence Project FY 2023. Moreover,although the project will start in FY 2024, public applications for joint research between Japan andthe United States have been launched this autumn in addition to Japan and the United Kingdom.
Attachment 18 shows the selected issues of the World Intelligence Project adopted in the past.


The Issue-solving Decommissioning Research Program: To solve issues by promoting
needs-based research and development for steady progress in decommissioning the
Fukushima Daiichi NPS.

The International Collaborative Decommissioning Research Program (Japan-UK Joint
Research): To promote R&D by integrating and collaborating research in various fields inJapan and the UK to gather broad knowledge and contribute to accelerating thedecommissioning of the Fukushima Daiichi NPS.



Decommissioning research program based on development of research humanresources: Toward the decommissioning of the Fukushima Daiichi NPS, the JAEA anduniversities have established a collaboration laboratory to promote human resource
development that supports decommissioning research over the mid to long term105.

Further, since FY 2021, efforts have been made to match decommissioning needs with researchseeds, such as holding workshops with the participation of TEPCO and companies involved indecommissioning. In FY 2022, Research Supporters (RS)106 were introduced to maximize the use
and outcomes of the results at the decommissioning sites.
The challenge is adequately applying basic/fundamental research results contributing to issuesolving to decommissioning sites. It is important to promote better matching needs fromdecommissioning sites with seeds at universities/researching institutions by using the opportunityof Decommissioning R&D Partnership Council and serve as a bridge to share outstanding research
results obtained mainly in the World Intelligence Project.
104

The overall map of basic/fundamental research compiles the necessary research elements based on the six
Essential R&D Themes. The Six Essential R&D Themes were identified by a task force on researchcollaboration established in NDF in 2016 and summarized in an interim report of this task force (November 30,2016).
105“Industry-academia collaboration laboratory,” where the JAEA, as leadership, works closely with universities
and private companies.
106
Research Supporters are JAEA personnel who support research as the JAEA/CLADS to individual WorldIntelligence Project-adopting institutions.

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(2) Collaboration between the Project of Decommissioning, Contaminated Water andTreated Water Management and the World Intelligence Project, and initiatives forbusiness-academia collaboration by TEPCO
To deepen the matching between needs and seeds and implement R&D for decommissioning
consistently from basic/fundamental research to applied practical application research, to date,there has been a collaboration between the Project of Decommissioning, Contaminated Water andTreated Water management and the World Intelligence Project, with some of the World Intelligence
Project being deployed in the Project of Decommissioning, Contaminated water and Treated water
Management. In order to develop future research and development further than before, NDF andorganizations concerned should actively exchange and share information on the results of eachproject and work together on the use of the Decommissioning R&D Partnership Council andinitiatives to share future directions and issues shared at such Meeting. Further collaboration withTEPCO is required for the field application of the research results.
TEPCO is also engaged in industry-academia collaboration efforts with universities (The
University of Tokyo, Tokyo Institute of Technology, Tohoku University, and Fukushima University) tounearth technological seeds that meet needs useful for decommissioning from a wide range of
research resources at universities, not only in the nuclear field but also in the basic/fundamental
research field.
The Government, JAEA/CLADS, NDF, TEPCO, and other organizations involved should further
strengthen their cooperation for better matching needs with seeds and serve as a bridge to shareoutcomes.
(3) Establishment of the centers of basic research/research infrastructure
In order to make the long-term decommissioning of the Fukushima Daiichi NPS proceed steadierin technical aspects, it is essential to work on developing R&D infrastructure and accumulatetechnological knowledge, develop fundamental technologies and collect basic data, building up
research centers, facilities and equipment, and human resource development. In R&D for thedecommissioning of the Fukushima Daiichi NPS, the accumulation of such activities is expected to
become a source of innovation.
The Collaborative Laboratories for Advanced Decommissioning Science (Tomioka-machi,
Fukushima Prefecture) of the JAEA, with JAEA/CLADS as its core, is working on research anddevelopment based further on decommissioning needs, to enhance the base functions by
establishing a network of universities, researching institutions, and industry in Japan and overseas
to promote the R&D and human resource development in an integrated manner, establishing the“Decommissioning research program based on development of research human resources” in theWorld Intelligence Project, and the research, development, and human resource development

143

projects that connect organizations through a cross-appointment system107 after the establishmentof a research/human resource development base (collaborative lab).
It is also important to build research and development infrastructures as hardware. The Naraha
Center for Remote Control Technology Development of JAEA, which began full-scale operation in
Naraha Town, Fukushima Prefecture, in April 2016, is a facility where mock-up testing can be
performed for the development and demonstration of remote-control devices and equipment. In
particular, prior to the introduction of equipment into a severe environment that cannot be accessedby humans, it is essential to conduct full-scale mock-up tests for verifying the performance and forremote operation training and establishment of operating procedures, etc. In 2023, a mock-up testof the robot-arm was conducted for the trial retrieval of fuel debris since February 2022.
In Okuma Town, Fukushima Prefecture, to conduct research and development throughcharacterization of solid waste and fuel debris for the decommissioning of Fukushima Daiichi NPS,
the JAEA Okuma Analysis and Research Center (Radioactive Material Analysis and Research
Facility) is under construction. The Laboratory-1 of Radioactive Material Analysis and Research
Facility, where low-dose and medium-dose solid waste analysis as well as third-party analysis of
ALPS-treated water are to be conducted, was completed in June 2022, and its controlled area wasset in October of the same year, and its operation was started after hot testing with radioactive
materials. The preparatory construction work for Laboratory-2, which analyzes high-activity
samples such as fuel debris, started in the autumn of 2022, and the preparation is being advancedwith the aim of completion in FY 2026. The data from the analysis and research will be utilized toestablish a technical basis and clarify fuel debris properties for the reliable processing/disposal
management of radioactive waste and its safety for decommissioning the Fukushima Daiichi NPS.
In this way, research facilities related to decommissioning projects by the JAEA are located in
Fukushima Prefecture, where a global center for R&D for decommissioning has been established,
and R&D infrastructures for medium-and-long-term prospects have been built. (Fig. 52)

107

Cross-appointment system is a system that allows researchers to engage in research, development, andeducation according to their roles in universities and public research institutions, while being employed by two
or more institutions, under certain engagement rate (effort) control.

144

Fig. 52 Research centers for Decommissioning in Fukushima108

108

Source: The 11th Decommissioning R&D Partnership Council, Material 2-1, “Status and direction of researchand development”

145

6. Activities to support our technical strategy
6.1 Capabilities, organization, and personnel to proceed with decommissioning
6.1.1 Ensuring the capability, organization and personnel that TEPCO should possess as
the owner of the Fukushima Daiichi Nuclear Power Station
As the site owner responsible for decommissioning the Fukushima Daiichi NPS, TEPCO
manages decommissioning projects and is also responsible as a utility. While there are some roles
common to both positions, how to implement the technical strategy required as a site owner of the
Fukushima Daiichi NPS is extremely important for TEPCO to decommission the Fukushima Daiichi
NPS. This section describes the current status of TEPCO’s management of decommissioning
projects, and the future efforts related to the capabilities, organization, and human resources thatTEPCO should have to support implementing the decommissioning technical strategy.
6.1.1.1 Significance and current status of decommissioning project management
In project-type work, such as decommissioning work at the Fukushima Daiichi Nuclear Power
Station, the series of tasks consists of clarifying the objectives (i.e., what to do by when for what),
determining the specific work content as a means to achieve the objectives, checking the safety
and efficiency of the work, designing/manufacturing/building necessary equipment, ensuring thenecessary personnel, and using them to achieve the objectives. Thus, the significance of the project
management is to clarify the objectives, means, required resources and timelines, and then, tosystematically manage project execution in order to accomplish the objectives.
TEPCO has been working to build and strengthen its project management system, which was
reorganized in April 2020. Project-based organization management has been almost establishedthrough three years of operation. Now that it is in phase 3-[1], the decommissioning work becomes
more difficult and uncertain, and in order to smoothly coordinate and align the entire project with aview to the medium- to long-term, it will be more important than ever that the relevant organizations
will further strengthen a management framework in cooperation with each other towards the goal
to be achieved, and increase the collective strength.
Examples of main initiatives undertaken by TEPCO up to fiscal 2022 include enhancing theauthority of project managers through reorganization, building and operating a risk monitoring
system, improving safety and quality levels, and preparing a forward-looking plan (Mid-and-Longterm Decommissioning Action Plan). The major initiatives are listed below.
①

Strengthening the authority of project managers through reorganization, and improving safety
and quality levels
In April 2020, the Fukushima Daiichi Decontamination and Decommissioning Engineering
Company was reorganized to establish a program109/project structure and the Decommissioning
Safety & Quality Office was set up directly under the Chief Decommissioning Officer (CDO). As

109

Program is the upper level of project, and it is a project in which multiple projects are organically combined torealize the overall mission.

146

a result, the authority of project managers has been strengthened by assigning full-time project
managers and granting budget implementation authority. In terms of operation, while process
management is being promoted using process management software, efforts were made to
improve the operational propelling force of the decommissioning project by establishing a system
in which management and other related parties share information on the progress, issues andrisks of each program and project every month. Moreover, the Decommissioning Safety andQuality Office was set up to ensure the safety of decommissioning work and to maintain andimprove the level of work quality in the face of the extremely uncertain and technically challenging
tasks such as fuel debris retrieval.
TEPCO established Decom.Tech in 2022 to undertake engineering and other activities related
to large-scale debris retrieval. In addition, TEPCO’s employees are seconded here to address
themselves on the management of costs and processes required for completion of work, risk
management for uncertain factors, and acquisition of design expertise, which have been
dependent on manufacturers. By improving the capabilities through OJT, TEPCO has been trying
to enhance its independence in engineering and EPC110 management activities associated with
the increasingly difficult decommissioning work, it is important to strengthen project management
capabilities.
②

Strengthening of risk management
Risk management is an activity to identify uncertain events before they materialize and to “takepreventative measures” so as not to let events that negatively affect the project happen, or to“minimize the effects” even if they occur.
TEPCO is aware of the importance of risk management through actual decommissioning workand promoting efforts to strengthen systematic risk management in line with the workflow in
Fig.53. In fact, there have been cases caused by a lack of risk awareness that should have beenaddressed in advance, such as delays in SGTS pipe removal operations.111 There are a wide
range of risks, such as those related to safety and project feasibility. In the future, the importanceof risk management will increase to prevent or minimize the impact of such risks in thedecommissioning work, which will become full-scale from Phase 3-[1].
Many facilities have been installed and operated at the Fukushima Daiichi NPS to proceedwith decommissioning, and risk assessments need to be made for these facilities to ensure thatthey are properly maintained and operated. Therefore, as part of its risk management, TEPCO
carries out risk assessments of facilities considered in the course of operating the facilities andevaluates the risks based on the probability of occurrence and the degree of impact. For facilities
assessed as having a high risk, necessary responses are preferentially taken, and effective risk

110

E：Engineering, P：Procurement, C：Construction,
The pipe removal process was significantly delayed due to a lack of risk awareness, including the gap between
the mock-up and actual on-site conditions (pipe-cutting equipment being stuck, oil leakage from the cranehydraulic hose, and cutting of parts where urethane was unfilled). This is considered a case where the risk
became apparent due to insufficient risk management.

111

147

reduction measures are conducted. Furthermore, as a response to the aged deterioration risk of
the above facilities, TEPCO is promoting the centralized management of facility information byincorporation of facilities subject to maintenance in a database format and is developing a system
to assess aged deterioration risk based on this information and to reflect the results in long-term
maintenance management plans.

Fig. 53 Standard workflow of risk management③

Preparation of a plan focusing on long term perspective (Mid-to-Long-term Decommissioning
Action Plan)
Since the accident at the Fukushima Daiichi NPS, TEPCO has been implementing thedecommissioning project, referring to the requirement based on the Act on Special Measures

148

Concerning Nuclear Emergency Preparedness and the Nuclear Reactor Regulation Law112, theMid-and-Long-term Roadmap decided by the Ministerial Conference on Measures for
Decommissioning, Contaminated Water, and Treated Water, and the target process (milestone)of the Target Map for Reducing Medium-term Risk prepared by the Nuclear Regulation Authority.
In March 2020, TEPCO prepared and announced the Mid-and-Long-term Decommissioning
Action Plan with the aim of presenting a concrete work plan to achieve the milestones of the Midand-Long-term Roadmap and the Target Map for Reducing Medium-term Risk. After this, in March
2023, TEPCO published the Mid-to-Long-Term Decommissioning Action Plan 2023, which was
updated every year based on the progress of the work.
The plan provides work plans for about the next ten years for each key measure, and basedon the plan for the next three years, a withdrawal plan for reserve funds for decommissioning
has been prepared.
Mid-and-Long-term Decommissioning Action Plan gives a certain level of transparency to thecomplex and long-term decommissioning project, and it can serve as effective communication
tools with the local community and society.
④

Formulation of R&D medium-to-long-term plan113
As project difficulty and uncertainty are expected to increase in the future, coordination with
R&D is becoming more important in ensuring project feasibility. TEPCO established theDecommissioning Technology Development Center in August 2021 with the aim of strengthening
R&D planning and management functions to examine technical development issues and promote
implementation plans. The Center identifies technology and development issues related to theMid-and-Long-term Decommissioning Action Plan, and incorporates important issues into the
R&D medium-and-long-term plan.
Such a move is necessary to facilitate the decommissioning work. Considering that the degreeof difficulty and uncertainty of the project will increase in the future, it is increasingly important tostrategically advance technology development, which will determine the feasibility of the project,
starting from the upstream stage of the project in the medium to long term, while establishing a
structure.

⑤

Enhanced budget planning
Each fiscal year, budget plans for program/project work, non-program work (maintenance andutility facilities), and operating costs necessary for decommissioning are formulated, and efforts
were made to improve budget accuracy through the appropriation of subjects based on the Midand-Long-term Decommissioning Action Plan, determination of designs at an early stage,
preparation and analysis of monthly report budget difference reasons. As a result of these efforts,
there has been a downward trend in the budgetary variance caused by problems with work
procedures (insufficient consideration, poor coordination, lack of confirmation, etc.).

112
113

Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors
For detail, refer to Chapter 5.

149

On the other hand, there are still cases where the contract period of work to be carried out toadvance the project is set with the fiscal year in mind, and the acceptance inspection isconcentrated at the end of the fiscal year. As a result, there have been cases of recording outside
the period when it should have been. We believe it is important to set the contract period in amore project-oriented manner to level workloads and proceed with operations efficiently.
⑥

Addressing issues across projects
Addressing cross-project issues, such as preventing α-nuclide diffusion, developing a unified
approach to seismic design, and eliminating work conflicts around accident reactors, becomes
more important as the number of interrelated projects increases and becomes more complex.
TEPCO has established a cross-divisional structure to deal with cross-sectional issues that do
not fit into individual programs/projects. As such a structure is now functioning, theconsciousness of these cross-sectional issues has been shared with the CDO, and othermanagement and awareness of moving toward solutions is becoming established.

⑦

Nuclear security management
In September 2021, TEPCO submitted to the NRA the Improvement Action Report on the
nuclear material protection incident involving unauthorized ID card use and partial loss of functionof nuclear material protection equipment at the Kashiwazaki-Kariwa Nuclear Power Station ofTokyo Electric Power Company Holdings, Inc. (hereinafter referred to as “Kashiwazaki-Kariwa”).
The Improvement Action Plan for this nuclear material protection incident covers 36 items.
TEPCO has moved to the implementation phase for all the items and has begun effectivenessevaluations for most items. Through additional inspections, TEPCO has been improving
measures as needed with advice from the NRA. Based on the policy for confirmation announced
by the NRA in September 2022, TEPCO is promoting “continuous improvement of system
reliability,” “proactive involvement of the management in establishing operations for
improvement,” and “establishment of a mechanism that does not make improvement actions
temporary.” In addition, TEPCO will not hesitate to invest resources to strengthen on-site
capabilities, particularly for nuclear security.
In the future, TEPCO plans to compile measures to strengthen the nuclear material protection
function and evaluation of each measure in the Improvement Action Results Report.
In accordance with the above policy, at the Fukushima Daiichi NPS engaged indecommissioning, the Security Management Department was established in May 2022 directly
under the site superintendent to manage and operate the general nuclear security of the plant.
In addition to security (monitoring and patrols), access control, and facility management related
to nuclear security, the Security Management Department is also tasked with overallcybersecurity management. Since the Fukushima Daiichi NPS plans fuel removal from SFP andtrial retrieval of fuel debris, it is imperative that not only TEPCO employees but also employeesof contractors are more aware of the fact that there are always threats related to nuclear security
in all operations, and they must exercise extreme caution. TEPCO headquarters and plants are150

working together to foster an organization and a corporate culture that can gain the trust of local
communities and society. In addition, they are discussing the structure with the aim of the
improved site-oriented project management from the perspective of ensuring nuclear security
functions, work safety, and coexistence with the local community through decommissioning.
6.1.1.2 Capability an owner should possess
The importance of owner’s engineering is stated in the 4th Special Business Plan. The owner's
engineering capability here refers to the capability required of TEPCO as a site owner and a license
holder, specifically, it is a capability that consists of both project management capability andtechnical capabilities based on safety and operator’s perspectives. These capabilities are all very
important. Additionally, in view of the peculiarities of the Fukushima Daiichi NPS, there are required
abilities for upgrading the overall decommissioning strategy to advance a coexistence ofreconstruction and decommissioning. In 2022, TEPCO signed a partnership agreement with
Jacobs, which has extensive experience in decommissioning nuclear facilities overseas. With theirsupport, TEPCO is working to strengthen the capabilities that an owner should have bybenchmarking international good practices.
In the following paragraphs, the capabilities that should be strategically enhanced by TEPCO in
the future, as NDF believes, are described. As for TEPCO, instead of addressing only the issues
pointed out, regarding the capabilities required for all activities from the development of thedecommissioning project strategy and plan to its implementation, the company should consider
what should be acquired in priority among such capabilities and continue taking a proactive
approach for the acquisition.

6.1.1.2.1 Establishment of safety first 114 and engineering based on safety and operator’s
perspectives114
As described in the previous chapters, the on-site situation at the Fukushima Daiichi NPS haschanged significantly from before the accident. A large amount of radioactive materials exist in
unconventional and unsealed conditions without complete barriers to contain the radioactive
materials, such as reactor buildings and PCVs. Furthermore, the environment is subject to constantchanges due to natural events such as weather and earthquakes, as well as aging degradation ofequipment and buildings, and has uncertainties in the conditions of radioactive materials andcontainment barriers. In addition, the accessibility of personnel and systems is limited due to highradiation doses and damage to equipment and buildings, making it difficult to obtain complete onsite information. Moreover, unlike other plants, it is not always clear what safety requirements
should be met to achieve the objectives of individual operations.

114

Refer to Chapter 2 for details.

151

On the other hand, each plant contains significantly less energy with less active equipment to be
managed and fewer constraints on plant configuration management than that of a conventional
reactor.115
Although radioactive materials such as fuel debris and contaminated water are now controlled ina stable state, the decommissioning of the Fukushima Daiichi NPS involves a series of tasks thathave never been experienced in the past in terms of construction, operation, and maintenance.
Therefore, while always keeping in mind that unpredictable situations may occur, TEPCO
continuously needs to observe the site, detect changes on site as soon as possible, and look fromthe perspective of the site.
At this point, TEPCO should keep in mind that even if the Fukushima Daiichi NPS is in an unusual
state, neglecting the safety related to decommissioning at the station is not appropriate. For
example, it may be difficult to apply maintenance operation and aging management required tomaintain the safety functions of conventional reactors to the Fukushima Daiichi NPS due to worksafety restrictions and other reasons. However, it is not appropriate to simply relax the requirements
on long-term maintenance and deterioration management due to such circumstances alone. It
should also be kept in mind that the reaction of the local community will be more severe if defects
resulting from deterioration occur due to such a simple management116. In view of the peculiaritiesof the Fukushima Daiichi NPS, TEPCO needs to continue instilling the safety-first approach.
To achieve this, consideration must be given not only to the on-site perspectives of those familiar
with the site of the Fukushima Daiichi NPS but also to the on-site perspectives in areas where
TEPCO has no experience, such as handling unsealed radioactive materials. Therefore, as suchconsiderations need the breadth and depth of knowledge and experience beyond the scope of asingle organization, TEPCO is required to establish an interdisciplinary structure.117
In other words, TEPCO should appropriately establish its general safety requirements at the
Fukushima Daiichi NPS, which has no precedent and high uncertainties, establish agreements withvarious stakeholders on the matters it has established, and proceed with the decommissioning
work in cooperation with other parties based on the agreements.

115

Configuration management refers to a mechanism for constantly verifying and guaranteeing that eachsystem/equipment of a nuclear power plant is manufactured and installed, operated, and maintained as
required by design.
116
In February 2021, for example, the information on the failure of the seismometer installed on a trial basis in the
Unit 3 reactor building of the Fukushima Daiichi NPS was not shared within the organization, and it was not
fixed/restored for a long period of time. This incident was severely criticized externally. Reflecting on thisincident, TEPCO is working to improve the long-term maintenance process and other initiatives.
117
In particular, fuel debris retrieval is extremely complicated and technically challenging. Thus, it is not easy toaccomplish with only one organization’s technology. Therefore, TEPCO must have engineering capabilities
that enable judging the advantages and disadvantages of individual technologies and other capabilities tointegrate elemental technologies to be incorporated as a system to achieve the desired performance. For thispurpose, TEPCO is required to establish an interdisciplinary structure by cooperating with multiple domestic
and overseas organizations with experience in technology development and application or by incorporatingexternal personnel with extensive experience.

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Then, it is necessary to establish a process in which operators who are familiar with the siteshould be based on the actual situation of the site118, check the safety comprehensively, determine
the appropriate general safety requirements for the site, and work on it. The overall capability
required for this purpose, including field capabilities 119 , is engineering based on safety andoperator’s perspectives, and it goes without saying that TEPCO is required to further enhance thiscapability. The TEPCO’s ongoing Insourcing 120 is an important measure to strengthen thesecapabilities and should continue to be pursued vigorously.
6.1.1.2.2 Investigation capability at the upstream side of the project
As mentioned above, TEPCO needs to figure out for itself what to do in the face of extremely
difficult and uncertain tasks without precedent, established standards, and methods to follow indecommissioning the Fukushima Daiichi NPS, which does not have the upstream design concepts
and standards, unlike conventional nuclear power plants. In decommissioning work at the
Fukushima Daiichi NPS, the cases 121have been accepted, where the project is allowed to returnto the process that reexamines what functions should be achieved and what general safety
requirements need to be satisfied for that after the project is launched and proceeded with.
In addition, as described in Chapter 3, it is necessary to consider in advance how to deal withand manage the waste generated with the progress of the decommissioning work, including waste
generated during the preparation work for fuel debris retrieval. In the future, TEPCO should clarify
the significance and objectives of the project (what to do by when and for what), specify generalsafety requirements, develop a comprehensive waste strategy covering its generation control,
reuse, etc., and ensure the feasibility of the project. To this end, in the decommissioning processfrom its planning to implementation, enhancing the investigation capability is needed, especially at
the upstream side.
However, due to the extremely high uncertainty particular to decommissioning at the Fukushima
Daiichi NPS, it should also be noted that even if the investigation at the upstream side is enhanced,
it does not necessarily mean that everything will proceed according to the result of the investigation.
TEPCO, based on the assumption that iteration-based engineering is inevitable to some degree in

118

When any work is to be carried out at 1F, in addition to the “actual situation” of the normal power plant, it isnecessary to consider the feasibility and improvement of the work, including the sequential type approach and
ALARP approach, given uncertainties in on-site information peculiar to 1F, the lack of work experience, highradiation doses, differences in regulations, low contained energy, the lack of dynamic equipment, and the
difficulty in judging the over/underestimation of the safety margin to prepare for such conditions. “Actual onsite situations” refers to such situations.
119
On-site capability here refers to the ability to keep in mind that unpredictable situations may occur, observe onsite situations, detect changes on-site immediately, and think appropriately from the on-site perspective.
120
Insourcing” means acquiring an ability to implement planning, design, maintenance, and operation
independently, aiming at improving employees’ technical capability, productivity, and operation quality. Thisinitiative will ultimately contribute to the improvement of safety. In addition, appropriate management ofknowledge acquired by insourcing can have various effects, such as improvement of engineering judgment for
inexperienced work, improvement of operation and maintenance quality, and enhancement of on-site
capability.
121
One of those cases is the delay in installing the ALPS slurry stabilization/treatment system, as described in
Chapter 3. The lack of awareness of the general safety requirements for containing radioactive materials has
led to rework in facility design.

153the future, should aim to optimize its research capability in the upstream of the project by adding
the latest knowledge from research and development.
6.1.1.2.3 Capability to upgrade project management
In implementing larger, more complex, and highly uncertain high-difficulty projects are expectedin the future, project management based on a new concept is advocated, in which both thecontractor and the recipient cooperate, share the contractual risks, and aim for the agreed-upongoals. Instead of one-way “Buying” from an ordering party to an order-receiving party, they work
together as partners and aim to acquire the final result “Acquisition” by “Making”, with considerationof all steps from development, manufacturing, to even operation/maintenance (Table 8).
To deal with such Making-based projects, in addition to improving the engineering capability,
such as the ability to materialize specifications, it is required to have project management capability
with a focus on “Acquisition of the final result”.
NDF and TEPCO are benchmarking the acquisition management122,123, one of the precedent
cases leveraging such a project management structure, as adopted by the U.S. federal government,
and are actively learning the methodology with the cooperation of external experts starting from FY
2017. Taking examples from actual projects, they are implementing a part of the work required
when employing this management structure on a trial basis and verifying procedures.
Since 2022, with the assistance of Jacobs, which is well-versed in managing such projects,
TEPCO has been discussing the project management required for future decommissioning workand the capabilities required for its implementation. Jacobs has extensive decommissioning
experience at Sellafield site of the UK NDA and the US DOE's nuclear sites. TEPCO is currently
analyzing the gap between international good practice and TEPCO's present situation, based on a
wealth of prior experience held by Jacobs. In addition, TEPCO made a cooperation agreement with
Sellafield in the UK and continues to gain knowledge and develop human resources by sending
employees on loan to the company. An easy path to imitating other example cases should be
avoided because the best project management depends on project characteristics, the state of thecountry, and the situation of owners and contractors. However, TEPCO should upgrade its project

122

Acquisition management is a project management method adopted (and legislated) in the U.S. federal
government budgeting process in the 1990s and has been continuously improved. It aims at acquiring
outcomes (products, structures, and deliverables) using scientific and systematic management techniques
based on reliable data. This method differs significantly from conventional in that it breaks down work in theWork Breakdown Structure (WBS) into the elements of outcomes (products, structures, and deliverables) to beobtained rather than tasks. In addition, by accumulating the costs of each decomposed element based on theplanning process and visualizing the progress of the project, it becomes possible to appropriately identify thegap between the plan and the actual situation, to grasp the risk at an early stage, and to takecountermeasures.
123
In acquisition management, acquisition and procurement are defined as follows and adequately used
depending on the case. Acquisition refers to acquiring the value and capability related to specific equipment
and other deliverables throughout their lifecycle, from development, manufacturing, and operation tomaintenance, to achieve a specific goal or objective. However, a part of this acquisition flow is sometimes
contracted to an external organization at each phase, such as development and manufacturing, and thegaining of specific elements in such a contract basis is called procurement. In other words, acquisition consistsof several procurements (deliverables based on contracts).

154management, including the relationship and contracting with contractors, to adapt to the situation
where buying-oriented operation is no longer easy.
In particular, the effectiveness of collaborating with a contractor as a “partner to achieve results”
should be assessed for projects where risks are high and it is difficult to have prospects, andconsideration should be given to introducing such a structure.

Table 8 Difference between “Making” and “Buying”
MakingObjectives

What to call the order
receiving parties andtheir roles
How to decide who will
receive the order
Contract method
Cost estimation methods

BuyingAcquisition of the outcome of the
project (Acquisition)
Contractor, a partner who is
responsible for obtaining theoutcome of the project
Select based on proposal content
and feasibility
Contracts in line with risk allocation
Data-based cost estimation (analogy:
analogy, integration, parametric:
sensitivity, analysis, etc.)

Purchase products (things) thatmeet the specifications
Vender, who supplies equipmentthat conforms to specifications
Select by priceFixed price contract
Quotation/price list, etc.

6.1.1.2.4 Nuclear security management capability
With regard to improvement actions in response to the physical protection incidents that occurredat the Kashiwazaki-Kariwa, although the situation is different from that of the Fukushima Daiichi
NPS in many ways, it is necessary to ensure that the same measures are taken to the aspects incommon to make improvements.
As trial retrieval of fuel debris is planned to start at the Fukushima Daiichi NPS, sustained efforts
to enhance nuclear security and safety awareness are needed. Through these efforts, it isnecessary to communicate to local communities and society that safe conditions are maintained.
6.1.1.3 Initiatives related to organization
The Fukushima Daiichi NPS has been taking various actions, including establishing andstrengthening a project management structure, from the perspective of “completing thedecommissioning project”. To achieve “The commitment to the people of Fukushima for achieving
both reconstruction and decommissioning (hereinafter referred to as “Commitment”)” announced
by TEPCO in 2020, in cooperation with other offices in the Fukushima area, including the
Fukushima Division and Fukushima Daini NPS, they are working to increase orders fordecommissioning work at the plant to local companies, which has attained some positive results.
In order for TEPCO to further promote coexistence of reconstruction and decommissioning, allemployees, both inside and outside the Fukushima Daiichi NPS, must share the same aspirations

155

and sense of responsibility regarding how TEPCO can contribute to this region, and must do theirbest to transcend organizational barriers.
In order to achieve this, TEPCO decided to consider integrating and reorganizing the Fukushima
Daini NPS and its head office, which currently belong to the Nuclear Power and Site Headquarters,
into Fukushima Daiichi Decontamination and Decommissioning Engineering Company, and in July
2023, the Office of Organizational Restructuring Preparation was established as the umbrellaorganization for this.
Until now, as an organizational structure, Fukushima Daiichi Decontamination andDecommissioning Engineering Company is in charge of the Fukushima Daiichi NPS with accident
reactors, and the Nuclear Power & Plant Siting Division is in charge of the Fukushima Daini NPS
with normal reactors. However, a decision was made that Fukushima Daiichi Decontamination andDecommissioning Engineering Company should decommission both plants in an integrated
manner because it is effective to share the knowhow at the Fukushima Daiichi NPS engaged indecommissioning over ten years for decommissioning the Fukushima Daini NPS, and it is desirable
that both plants work together to promote coexistence with the local community by increasing orderplacement to local companies. Through this reorganization, TEPCO plans to accelerate further
efforts for coexistence of reconstruction and decommissioning. NDF also regards these TEPCO
efforts positively, and intends to confirm the activities so that TEPCO will step up progress toachieve coexistence of reconstruction and decommissioning as the integration and reorganization
advance.
6.1.1.4 Initiatives to recruit and develop personnel
In Fukushima Daiichi NPS, it is necessary to systematically secure and develop humanresources in anticipation of the expansion of operations in line with the progress of the fuel debris
retrieval plan. Specifically, they are to develop a staffing plan that includes the required skills andqualities and headcount, to prepare an organizational personnel development plan that outlines
tactics to achieve them, and to implement measures to increase personnel motivation, while
addressing short-term needs.
Furthermore, to further deepen and advance the Commitment, which has been promoted since2020, it is necessary as a stance to consider human resource allocation with a view of coexistenceof reconstruction & decommissioning beyond decommissioning of the Fukushima Daiichi NPS.
6.1.1.4.1 Short-term efforts
The decommissioning work at the Fukushima Daiichi NPS is at the phase of starting the mostcritical milestone in recent years, the trial retrieval of fuel debris. To be in line with the gradualexpansion of fuel debris retrieval, the entire workload of the plant is also increasing. In such asituation, the sense of busyness at the power station is also getting stronger year by year and thenumber of personnel required on-site is increasing.

156

Although TEPCO is actively recruiting to meet such strong demand for personnel on-site, it is nota one-way process and does not always ensure that the desired personnel are available.
Active recruitment should therefore continue, though, in addition to that, it is essential that its
leaders124 clarify work priorities and promote resources allocation according to the priorities, anddevelopment of human resources should be promoted to enhance versatility and productivity ofexisting personnel. TEPCO has been conducting kaizen activities for a long time, and it is an
initiative that incorporates the methods of Toyota’s kaizen/continuous improvement method withthe aim of improving quality and safety. As this is also useful for solving secondary resource issues,
the activities should be continued vigorously. Other than that, it is also indispensable to provide
education and training125, conduct digital transformation (DX) 126, and obtain the necessary outputs
with limited resources through efforts.
6.1.1.4.2 Medium- and long-term initiatives
Because TEPCO's goal of the coexistence of reconstruction & decommissioning cannot be
achieved only through decommissioning work at the Fukushima Daiichi NPS, it is desirable toreview the necessary operational management and governance of all organizations involved in thereconstruction of Fukushima and decommissioning and give shape how to secure and train
required human resources in the future. The integration of the Fukushima Daiichi Decontamination
and Decommissioning Engineering Company and the Fukushima Daini NPS, which TEPCO has
been working on, is also crucial in the sense that it aims to optimize the use of personnel beyond
the boundaries of business sites through organizational restructuring. The consolidation should beaccompanied by the diversification of personnel, standardization and streamlining of business
operations, and efforts to ensure the necessary personnel.
In addition, in promoting the securing of human resources over the mid-to-long term, it isnecessary to pay full attention to the fact that Fukushima Daiichi Decontamination andDecommissioning Engineering Company is shifting from a routine work implementation
organization as a utility to a project-based one as a decommissioning site owner. While determining
the scope of the measures to secure human resources, which TEPCO has continued to apply
based on the operation and maintenance of normal power stations, workloads in decommissioning
work are expected to increase from now on, and it will require personnel for ever-changing projectbased work as well as personnel for operation and maintenance of the new facilities that will be
installed as a result of the execution of projects. To ensure such personnel, TEPCO itself should
determine what type of and when personnel will be needed in the medium- to long-term, and clearly124

A leader is a person who leads a team toward solving issues or meeting goals and is required to achieve
results. In terms of TEPCO positions, this includes CDOs to team leaders.
125
In addition to personnel development and multi-skilling through education and training, including on-the-job
training (OJT) that meets direct operational needs, education and training aimed at avoiding the increase insocial anxiety caused by external communication errors, preventing errors by ensuring psychological safety
through internal communication, and improving management skills to facilitate projects are effective for
efficient utilization of human resources.
126
The sophistication of long-term maintenance and management of systems and equipment promoted by
TEPCO is an example of saving human resources through DX promotion.

157

present the necessity at an early stage so that the company can carry out the activities to recruit
personnel from inside and outside the company widely through various channels. This is necessary
for hiring 127 , reskilling employees with a view to the medium- to long-term 128 , personnel
management including attractive career path design for young employees, enhancing theunderstanding of the community129, and making up for personnel shortages through collaboration
with external organizations130.
In view of the fact that decommissioning is a long-term activity, TEPCO needs to work to cultivate
leaders who will be responsible for decommissioning in a planned and systematic manner from a
medium- to long-term standpoint. In the face of many difficult and diverse short-, medium- and longterm challenges, in order to establish a system that allows them to make choices and tackles whatneeds to be done according to the priorities of their work on a daily basis, it is undeniable thatleaders in charge of unprecedented and difficult decommissioning projects require a higher level ofcourage and people skills compared to other projects, in particular. In addition, they need topossess a keen sense of perception that anticipates the changing business environment as well as
the ability to adapt to change, and the ability to learn. Furthermore, if other people in theorganization are influenced by the leaders who are working on decommissioning as a national
challenge as well as by the leadership group following those leaders, and become aware of theirown potential and motivated to grow, this will also lead to the recruitment and development of
decommissioning personnel over the medium to long-term. TEPCO should systematically promote
the development of leaders, as it takes a long time to develop them, and a suitable career pathshould be set up for their development.
6.1.2 Fostering the next generation responsible for the decommissioning of Fukushima
Daiichi NPS and promoting public understanding
6.1.2.1 Fostering the next generation who will
decommissioning of Fukushima Daiichi NPS

beresponsible

for

the

futureIn order to continue decommissioning of the Fukushima Daiichi NPS over a long period and tocontinue the R&D activities necessary to that end, it is essential to train and secure future
researchers and engineers and to ensure the inheritance of technological skills. It is necessary for127

For example, in initiatives to acquire experts, it is necessary to organize the elements that can becommunicated effectively, such as the fact that this is an unprecedented project that requires many cuttingedge technologies and interaction with a wide variety of highly skilled human resources, including thoseoverseas, can be expected.
128
For example, it is necessary to identify and strategically acquire practical knowledge that is advanced andlikely to have higher demand in the future, such as actinide chemistry, analytical assessment, and seismic andenvironmental impact assessment.
129
For example, toward coexistence of reconstruction and decommission for a long period, the initiatives toacquire local talent by employing those from local high schools, technical colleges, and universities or
employing local talents who have entered higher education in different areas are expected to deepen regional
understanding as a side benefit.
130
For example, training and securing analytical personnel is urgent, and TEPCO has started human resource
development through OJT training at the JAEA and other organizations with expertise in analysis. Throughsuch cooperation, it is necessary to promote the development of personnel engaged in analysis, including not
only those performing analysis but also highly skilled analytical technicians involved in analysis planning andevaluation.

158

industrial-academic-governmental institutions overall to move steadily ahead with efforts according
to each level of the secondary and higher education stages.
As described in the section 6.1.1, it goes without saying that securing human resources by
TEPCO is critical. At the same time, in decommissioning the Fukushima Daiichi NPS, it isnecessary to recruit and develop personnel specialized in nuclear energy as well as those withdifferent backgrounds who have expertise in science and technology in other fields.
Therefore, in addition to securing decommissioning personnel by TEPCO, the challenge is how
to open up opportunities so that excellent human resources who have graduated from universities,
graduate schools, technical colleges, high schools, etc., and are specialized in science andtechnology are continuously sourced to various organization involved in decommissioning. In orderto achieve this stably, it is necessary for higher and secondary educational institutions to create
opportunities for learning and acquiring peripheral knowledge in addition to expertise, and tomaintain associated systems and structures so that they can function as a whole, including
teachers.
Under these circumstances, the World Intelligence Project by MEXT and JAEA/CLADS has
introduced a system in which students and young researchers are engaged in decommissioning
research. From the perspective of human resource development, it provides support for young
researchers and teachers in preparing and implementing lecture curriculums related todecommissioning. In the Creative Robot Contest for Decommissioning for technical college
students as part of the World Intelligence Project, on an ongoing basis, students present theirresearch results, exchange views with researchers and engineers involved in the decommissioningof the Fukushima Daiichi NPS, and are given awards for excellent performance.
As eight years have passed since the launch of the World Intelligence Project, these mechanisms
and their implementation have produced significant results in terms of both research and humanresource development in higher education institutions, and they have led to activating humanresources, including graduates who are actually engaged in decommissioning-related projects. The
Conference for R&D Initiative on Nuclear Decommissioning Technology by the Next Generation(NDEC), a conference for students to present their research findings, which has been held seventimes, gives students an opportunity to interact directly with researchers and engineers involved indecommissioning. The conference was held in person for the first time in 4 years in 2023, when theimpact of coronavirus infection had eased. Under this system, the project should be implemented
continuously so that the perspectives of decommissioning sites in TEPCO and those of the activities
in higher education institutions can be more aligned.
For junior and high school students in the earlier stage of secondary education, it is important tointroduce the appealing points of engaging in the nuclear energy field, including decommissioning,
and to make efforts to attract their technical interest with a focus on decommissioning, as well as
to improve their understanding of the decommissioning and reconstruction of the Fukushima Daiichi
NPS, and in a broad sense, of the career path in science and technology fields. The secondary
education stage is an important preparatory stage before participating in and contributing to society

159while developing one's individuality and exploring one's interests. It is of great significance forstudents in this stage to be inspired by researchers, engineers, and science teachers who are
active in society and to leverage such inspiration to make independent choices and decide theircareer paths. From this perspective, NDF has been organizing the International Mentoring
Workshop Joshikai in Fukushima since 2019 in cooperation with the OECD/NEA. This event aims
to attract female science and engineering professionals to address challenges in Fukushima,including decommissioning. It is designed for female high school students, mainly in Fukushima
Prefecture, to increase their interest in science and engineering through interaction with female
researchers and engineers in Japan and abroad. In addition, Student Sessions for high school
students, etc., have been held to give thought to the reconstruction of Fukushima, along with theInternational Forum on the Decommissioning of the Fukushima Daiichi NPS (hereinafter referred
to as the “International Forum”). In the Student Session 2022, a tour to observe the situation in the
Futaba area was conducted for the first time, and the knowledge gained from the tour was utilized
in the next day’s Future Workshop. The Future Workshop is designed to discuss what to do now todevelop a desirable future for the Futaba area based on future prospects, decommissioning status,and other information derived from statistical data in the Futaba area. These opportunities havebeen provided to approximately 60 high school students and others who are in the period of
considering the specifics of their career options in order to broaden their understanding ofdecommissioning and reconstruction and to foster interest and willingness to contribute, and there
has been some level of success.
It is also necessary, through these initiatives, to expand the scope of human resource
development related to the decommissioning of the Fukushima Daiichi NPS to include fundamental
and related research. It is expected that initiatives to deal with the nuclear legacy and nuclear safety
will take deeper root in the course of raising the level of the entire fundamental technological basein Japan.
The institutions concerned should continuously promote and strengthen their efforts to secureand develop human resources for the next generation according to their respective roles and levels.
6.1.2.2 Dissemination of basic knowledge and promoting people's understanding ofdecommissioning and the radiation safety involved in decommissioning
If many citizens acquire basic knowledge of the accident and decommissioning, disaster
response, radiation safety, and food safety related to the Fukushima Daiichi NPS, it will serve as abasis for discussions on decommissioning and related radiation safety, etc. based on accurate
information and for promoting public understanding. In particular, from the perspective of enhancing
resilience to various disasters in the future, the challenge is to acquire knowledge and experienceof nuclear energy and decommissioning and to ensure that children have opportunities to learn
depending on their developmental stage. Since children take an interest through the knowledge
and experiences of teachers, parents, and other adults around them, it is effective to further spread
scientific-evidence-based knowledge of nuclear energy and decommissioning to a wide range of160

people, including those involved in primary education institutions. In this regard, based on the
Action Plan for Steady Implementation of the Basic Policy on the Disposal of ALPS Treated Water(formulated on December 28, 2021, and revised on August 30, 2022), the government is promoting
the continuation and expansion of on-site classes and the use of radiological supplementary
readers. NDF also holds workshops for local students to discuss decommissioning andreconstruction, as described above.

6.2 Strengthening international cooperation
6.2.1 Significance and the current status of international cooperation
6.2.1.1 Significance of international cooperation
In recent years, nuclear reactors and nuclear fuel cycle-related facilities built at the dawn of theuse of nuclear energy have reached the end of their operational life, and decommissioning of thesefacilities is in full swing in many countries. Among the reactors that have experienced severe
accidents are the Windscale Pile-1 reactor in the UK, the Three Mile Island Unit 2 reactor (TMI-2)
in the US, and the Chernobyl Unit 4 reactor (ChNPP-4) in Ukraine. These facilities have been
undergoing stabilization work and safety measures for many years. In addition, there are large
uncertainties in the management of a wide variety of radioactive materials at legacy sites overseas,
and decommissioning and environmental remediation efforts are expected to take a long time.
These facilities and respective conditions of the facilities in legacy sites are diverse, but in eachcase, each country continues to face challenges such as technical difficulties what is called“unknown unknowns (don't know what we don't know)”, long-term project management, andsecuring large amounts of funding.
Decommissioning the Fukushima Daiichi NPS is expected to take a long time. While Japan does
not have sufficient experience in investigations and analyses to estimate conditions inside reactor
buildings, PCVs, and RPVs, research and development to execute such activities, and mockup
tests, including training of workers, there are challenging engineering issues. Although there has
not been sufficient experience or research accumulated in Japan to address these issues in the
period of accumulating efforts after the accident, it is believed that learning and incorporating
experience and lessons learned from decommissioning activities at sites in other countries, in which
the knowledge described above is already accumulated, will make the difference in the success or
failure of the decommissioning of the Fukushima Daiichi NPS, and is important as a risk reduction
strategy. To this end, as specific efforts, it has been recognized that it is necessary to promotebilateral cooperation in line with the circumstances of partner countries and utilize the frameworkof multilateral cooperation through international organizations such as the IAEA and theOECD/NEA to incorporate and implement useful global experience in decommissioning.
These international organizations also play a number of important and useful roles, including
establishing international standards for decommissioning, consolidating and introducing technicalinformation, collaborating and organizing researchers and engineers, peer reviews based on161international standards and good practice experience, and international public relations. The
involvement of engineers and researchers in formulating international standards, consolidating
technical issues, and peer reviews based on Japan’s experience in decommissioning is meaningfulin promoting to the international community the decommissioning of the Fukushima Daiichi NPS in
an open manner. It is also expected to fulfill part of Japan’s responsibility to the international
community by sharing its knowledge and information accumulated in Japan through many initiatives
since the accident with other countries.
It is important to gain international understanding as our country moves forward with thedecomissioning of Fukushima Diichi NPS. To this end, in addition to gathering of wisdom andsharing of experience, it is necessary to disseminate transparent information to the international
community and to engage in continuous dialogue.
6.2.1.2 Current status of international cooperation
From this perspective of international cooperation, Japan has been holding annual dialogue andestablishing a conference to share information with governmental bodies and researching
institutions in other countries as an intergovernmental framework for bilateral cooperation indecommissioning. In coordination with such an intergovernmental framework, NDF and TEPCO
have formed and maintained cooperative relationships with professional organizations with aproven track record in decommissioning activities in the US, the UK, and France. In this way,
institutions concerned in Japan are strengthening international cooperation by concluding
cooperation agreements with overseas institutions concerned and other initiatives.
With regard to multilateral cooperation, meanwhile, the government and institutions concernedin Japan have participated in various conferences and expert committees of internationalorganizations. While TEPCO has participated in various conferences and projects organized by the
IAEA and the OECD/NEA, NDF has served as a deputy chairman of the Committee on
Decommissioning of Nuclear Installations and Legacy Management, a standing committee at the
OECD/NEA, to contribute to maintaining the foundation for multilateral cooperation on
decommissioning and disseminating information (Attachment 19).
The Japanese government, TEPCO, and NDF are each working with their counterparts to sharetechnical cooperation, information, experience, lessons learned, etc., with the aim of building astrong cooperative relationship for long-term decommissioning in the future.
As the engineering of Fukushima Daiichi NPS is in full swing, it is important to grasp the latest
status of excellent technologies and human resources in the world and to utilize them effectively.
Currently, decommissioning is being carried out under contracts between many companies anddecommissioning executors both in Japan and abroad, and the global market for decommissioning
is expanding greatly. In this context, TEPCO has been actively engaged in technological exchangewith private companies overseas.

162

As international travel was restricted from 2020 amid the global COVID-19 pandemic,
conferences were mostly held online, but they are now held in person again, with more
opportunities to speak on-site. NDF is considering and holding in-person, online, and hybrid
meetings, taking into account the movements of overseas organizations and what is convenient forparticipants (Fig. 54) The widespreaduseof

onlinesystemstoholdmeetings has made it easier to secure
opportunities for communication withoverseas institutions than before thepandemic,

therebyimproving

operational efficiency and contributing
to the maintenance and developmentof relationships.

Fig. 54 The 7th International Forum on the Decommissioningof the Fukushima Daiichi Nuclear Power Station

6.2.2 Key issues and strategies
6.2.2.1 Integrating and giving back wisdom and knowledge from around the world
To move steadily ahead with the decommissioning of the Fukushima Daiichi NPS, which involvesdifficult engineering issues, it is necessary to learn lessons from achievements in overseas nuclear
facilities executing difficult decommissioning work and decommissioning of legacy sites, and apply
them to the decommissioning and utilize the world’s highest level of technology and humanresources for technologies in Japan. In other words, it is necessary to gather and utilize the world’s
wisdom and knowledge and, at the same time, promote research and development in Japan tosolve issues while accumulating experience and achievements. Japan has received various kindsof support from foreign governmental organizations, regulatory authorities and R&D institutions
staff, and independent experts by disseminating information on issues related to decommissioning
to the international community and participation in international joint activities.
Public decommissioning implementation entities are leading in promoting decommissioning of
legacy sites in each country, offering many points of reference regarding technology andmanagement as a leading model. The issues they are confronting on the technology side include
the necessity of expertise, approaches, and new technologies that are different from the operationand maintenance of nuclear reactors. On the management side, such issues include developing
systems, policies, and strategies, project planning and management, safety assurance, and local
communication. TEPCO has stationed staff at legacy sites to gain practical experience andconducts visits and periodic information exchanges with decommissioning-related organizations
and companies. NDF needs to collect wisdom and knowledge, including lessons learned fromdecommissioning of overseas legacy sites and facilities engaged in highly difficult decommissioning
work around the world through long-term partnerships with the public decommissioning
implementation entities with a central role in each country, including NDA in the UK, CEA (French163

Alternative Energies and Atomic Energy Commission) in France, and Department of Energy, Officeof Environmental Management (DOE) in the US.
Therefore, it is expected that the decommissioning will be undertaken with the following threestrategies into consideration.
As a first strategy, it is important for TEPCO, as an entity that implements decommissioning
steadily, and NDF, as an organization that provides advice and guidance to ensure proper andsteady implementation of decommissioning from a mid-to-long-term perspective, to strengthen
cooperation with its counterparts. To realize the decommissioning of the Fukushima Daiichi NPS,
it is expected to integrate global technical and operational wisdom and knowledge and fully
incorporate them into solving the issues by maintaining a high level of cooperation with relevantorganizations in Japan and existing personal contacts with overseas experts at the engineer andexecutive levels, and by continuing regular information exchange.
As a second strategy, in addition to the countries mentioned above, it is desirable to explore thepossibility of applying general-purpose technologies from more countries to decommissioning andcollect technical information to obtain cooperation from more experts, including countries that do
not use nuclear technology. Decommissioning of the Fukushima Daiichi NPS is a process of solving
unexplored engineering problems by combining knowledge from various fields, including remotetechnology, and not limited to the nuclear field, and it can be expected that the decommissioningof the Fukushima Daiichi NPS could become a powerful opportunity for the creation of innovation.
Thirdly, twelve years have passed since the accident, and it is important to continue thesemutually beneficial relationships as a strategy while being conscious of returning the expertise andresults accumulated so far to the international community. In participating in international joint
activities, with the premise of the steady implementation of decommissioning, which is Japan’s toppriority, securing the interests of the international community should also be taken into
consideration. From the aspect of returning the results, there is a growing interest in not only theaccident and decommissioning itself but also in application to issues other than nuclear field. It isalso useful to respond to these changes in the international community to maintain this interest.
Consolidating diverse knowledge and experience from around the world in Fukushima is, in thefirst instance, an important effort to steadily advance the decommissioning of the Fukushima Daiichi
NPS itself. This is also an important initiative from the perspective of leading innovation throughthe decommissioning process to the restoration of local industry and building a symbiotic
relationship with the local community which is essential for the long-term progress of
decommissioning.
6.2.2.2 Maintaining and developing the international community’s understanding, interest
and cooperation in decommissioning
The challenge is to maintain and develop the international community’s understanding, interest
and cooperation in order to bring together the world’s wisdom in the decommissioning of Fukushima
Daiichi NPS and to limit the risk of confrontational structures to the implementation of164decommissioning as far as possible. International opinion can considerably impact the progressand success of decommissioning. Therefore, the spread of misperceptions regarding thedecommissioning of the Fukushima Daiichi NPS overseas affects the decommissioning progress.
Recognizing this, it is important to strategically discuss and implement international cooperation.
Efforts should be made to ensure that the view, “decommissioning of the Fukushima Daiichi NPS
can be carried out safely,” is fully disseminated not only in Japan but also overseas. If such a view
does not prevail, it should be kept in mind that conflicting structures may arise, and there is a riskthat public opinion and understanding in Japan will be formed to affect decommissioning results.
Therefore, for example, if there is a situation involving a lack of understanding in overseas
societies at the launch of a new technological initiative or policy discussion that is considerednecessary, realistic, and feasible, it could have the impact of expressing concern about suchinitiative, and further, calls for the suspension of the initiative for the sake of international security.
This risk can be reduced by assessing these possibilities in advance by NDF and relevantorganizations concerned in Japan and disseminating information proactively. On the other hand, adelayed response may risk the decommissioning project being hindered and ultimately delaying
the local reconstruction. The global energy landscape is also changing, affected by recent initiatives
to address climate change, changes in energy safety and security policies resulting frominternational conflicts, and the growing need for a more robust energy supply infrastructure. In
response to this, many countries have been reviewing their energy policies. Even under suchcircumstances, the challenge is maintaining smooth cooperative relationships with other countries
toward decommissioning of the Fukushima Daiichi NPS while gaining an accurate understandingof the updated status in the countries concerned.
The strategy for gaining international understanding needs to be divided into ① an approach forexperts and ② an approach for the general public.
① Approach to experts
It is fundamental for the international community to understand that the efforts toward thedecommissioning of the Fukushima Daiichi Nuclear Power Station are scientifically andtechnically valid and accurately understood by experts abroad. Approximately 12 years havepassed since the accident, and there are signs of a decline in international interest in
decommissioning technology and progress, as seen in the decreasing number of papers on
decommissioning of the Fukushima Daiichi NPS presented at recent international conferences.
In order to maintain interest outside Japan, dialogue and exchange should be activated outside
Japan among technology implementers, technology developers, and researchers involved in thepractical implementation of the technology, beyond the public and private sectors.
Until now, based on the framework for cooperation in decommissioning technology,
information has been disseminated and exchanged mainly with advanced nuclear power
countries that own legacy sites. For instance, NDF and TEPCO have provided technical briefing
and disseminated information on the current status and challenges of decommissioning to the165international community through various opportunities such as International Forums, periodic
bilateral meetings, and participating in multilateral frameworks. In addition, TEPCO has actively
provided opportunities for overseas experts to visit the Fukushima Daiichi NPS. These activities
are significant in complementing the international publicity and are important in gaining
international understanding in that they can directly communicate the latest technical information
to foreign experts. Furthermore, with regard to unprecedented efforts being made in a peculiar
environment of the Fukushima Daiichi NPS, such as fuel debris retrieval and waste management,
it is also important to incorporate opinions from new perspectives as well as gain an accurate
understanding of the efforts being made through dialogue with many experts from neighboring
countries and countries that do not use nuclear technology. It is also expected that theunderstanding of these experts can be used as a springboard for the spread of correctunderstanding in their countries. Japan should also support socially influential experts to speakout based on correct knowledge in their own countries and ultimately have a positive impact oninternational public opinion. In the future, Japan's government agencies, TEPCO, and, inparticular, the IAEA's Department of Nuclear Safety and Security, will cooperate in wide-ranging
discussions to build new, strategically resilient international partnerships.
In order to contribute to the formation of international public opinion based on scientific andaccurate information, the world's experts must first be correctly understood. Recognizing this,Japan should work with national government agencies and international organizations todisseminate information on the achievements of its efforts towards decommissioning, as well as
to engage in more careful dialogue and continue to do so.
② Approaches to the general public
The interests of the recipients of the information have changed since the time of the accident,
and there are some gaps between countries in the amount of knowledge and information thatare the basis of understanding. Moreover, it is desirable for Japan to actively provide informationon the accident at the Fukushima Daiichi NPS, and activities and achievements toward
decommissioning to countries other than advanced nuclear nations in cooperation withinternational organizations.
To this end, the following considerations should be made;

Disseminating information that is easy to understand not only to experts but also tolaypeople.

Prepare well-crafted explanations by using videos and illustrations effectively whileconsidering the interest and understanding of the recipient.

Disseminate information in multiple languages other than Japanese and English.

It is also important to deepen the understanding of information recipients by disseminating andaccurately visualizing information on the current status and issues related to decommissioning,paying attention to their level of interest and understanding, as this will eventually lead to building166

a trusting relationship. As Japan’s responsibility as the country that caused the accident, theissue for the government and other domestic organizations is to continuously and transparently
disseminate accurate information on decommissioning in order to maintain and increase theunderstanding of the international community, and build trusting relationships.
Regarding the discharge of ALPS-treated water into the sea, the Ministry of Foreign Affairs ofJapan (MOFA) and the Ministry of Economy, Trade and Industry (METI) are taking the lead inproviding briefings at numerous ministerial meetings, international conferences, bilateraldialogues and diplomatic missions abroad, based on scientific perspectives. In addition, theJapanese government has implemented concerted measures, such as responding to IAEA
reviews by the Ministry of Economy, Trade and Industry and the NRA. In this way, the Japanese
government is leveraging diplomatic channels to strengthen and continue to provide explanations
to international organizations, national governments, and overseas media outlets, and actively
conduct public relations by disseminating information in multiple languages, and provide
information to foreign media organizations via websites and media outlets. When news reports
are not based on facts, they provide appropriate media responses, including briefing to media
and publishing counter statements.
It is difficult to proceed with the decommissioning of the Fukushima Daiichi NPS without global
understanding. We will endeavor to build trust by actively and strategically returning to theinternational community the knowledge, etc. obtained in the course of conducting research on
the accident at the Fukushima Daiichi NPS and the decommissioning of the plant. Furthermore,as a responsibility of Japan, which caused the accident, the government and other domesticorganizations concerned must continue to provide highly transparent and accurate information
on decommissioning of nuclear power stations, which should be strategically addressed in the
future.

6.3 Local community engagement
6.3.1 Significance and the current status of local community engagement
6.3.1.1 Basic concept
The fundamental principle for decommissioning the Fukushima Daiichi NPS is “coexistence ofreconstruction and decommission.” In the areas where the evacuation order has been lifted,
progress toward reconstruction is gradually being made, not only by the return of residents and theresumption of business activities, but also by the promotion of migration and settlement fromoutside the area and new investment. While giving top priority to further reducing risks to thesurrounding environment and ensuring safety, it is necessary to strengthen communication with thelocal people and promote coexistence with local communities to gain the trust of the community.
Decommissioning should never hinder reconstruction efforts due to anxiety and distrust ofdecommissioning.

167

Therefore, it is important to deepen the understanding of local residents and reassure them about
the decommissioning through interactive communication, not one-way dissemination of information,
but sincere listening to the concerns and questions of local residents to eliminate them.
In addition, to accomplish the decommissioning over a very long period of time, the continuous
cooperation of companies, especially local companies, is essential. At the same time, theparticipation of local companies in the decommissioning project is an important pillar of contribution
to the reconstruction of Fukushima, as it will not only revitalize decommissioning-related industries
in the region and create employment and technology but also lead to the spread of the results toother regions and industries. In light of this, while collaborating with initiatives in the Fukushima
Innovation Coast Framework Promotion Organization, the goal is to contribute to job creation,
human resource development, and the creation of industrial and economic infrastructure in theregion through decommissioning and to achieve coexistence of reconstruction and decommission.
6.3.1.2 Specific measures under the current situation(1) Communication initiatives
The government has been exchanging opinions with local related organizations at the“Fukushima Advisory Board on Decommissioning, Contaminated Water and Treated Water” andother meetings held by the government, disseminating information on the current status ofdecommissioning through videos, websites, brochures, etc., and holding briefings androundtable discussions for local residents and related local governments.
NDF holds International Forums to share the latest knowledge, technical achievements, andissues on decommissioning with experts in Japan and overseas, as well as a frank exchange of
opinions on decommissioning with participants, including local communities and organizations
concerned. In order to promote the exchange of opinions, an “interviewing activity” is held every
year to hold conversations with local communities, including high school and technical college
students, before the International Forum is held. Then, their real voices are collected,
summarized, and edited as a booklet and distributed as the “Voice from Fukushima” at theInternational Forums. Through these activities, NDF is working to explain the progress of
decommissioning at meetings organized by the government or local communities.
TEPCO has been working to provide briefings and dialogue to regional representatives atconferences hosted by the government and Fukushima Prefecture, as well as to hold regularpress conferences and lectures for the media and to disseminate information through its website
and brochures. In addition, accepting site visitors is very effective because observing the current
decommissioning status and frank opinion exchanges contribute to forming a common
understanding. With this in mind, TEPCO is actively accepting visitors to the Fukushima Daiichi
NPS (number of visitors: 18,238 in FY 2019, 4,322 in FY 2020, 6,138 in FY 2021, and 14,728 in
FY 2022). On the other hand, in the current situation where the COVID-19 pandemic
necessitated or, in the future, may necessitate limiting site visits or some people are not able tovisit directly, a virtual tour of the decommissioning site of the Fukushima Daiichi NPS has been168available on TEPCO’s website since 2018 to proactively disseminate information utilizing such
simulated experience programs.
In addition, the TEPCO Decommissioning Archive Center, established in Tomioka Town as aplace where people can learn about the process of the nuclear power plant accident and theprogress of decommissioning, has about 100,000 visitors as of the end of March 2023. Since FY
2020, the Center has been collaborating with The Great East Japan Earthquake and Nuclear
Disaster Memorial Museum opened by Fukushima Prefecture in Futaba Town.
(2) Approach to create regional industrial and economic infrastructure through decommissioning
Based on their “Commitment” established at the end of March 2020 (hereinafter referred to as“Commitment”),

TEPCO

has

summarized

theirinitiatives

for

the

accumulationofdecommissioning work into the following three categories: (1) Increased participation of local
enterprises, (2) Support for local enterprises to step up and (3) Creation of new local industries,
and has started to implement them in a phased manner. TEPCO reorganizes, as needed, steadily
promotion of these efforts for coexistence with the local community. Specifically, TEPCO
established the local partnership promotion group in the Fukushima Daiichi Decontamination andDecommissioning Engineering Company in April 2020, a specialized department working toengage in promoting coexistence with the local community at the Fukushima Daiichi NPS in
October 2020, and the Hamadori decommissioning industry project office that directly reports tothe president. Under their assigned roles, they are engaged in internal and external coordination,
on-site support in the region, and discussing medium-to-long-term direction.
With regard to initiatives (1) and (2), the following are being implemented in collaboration with
the Fukushima Innovation Coast Framework Promotion Organization and the Fukushima Soso
Recovery Promotion Organization.
Establishment and operation of a joint consultation service to support matching local
companies interested in participating in decommissioning projects with prime contractors
considering placing orders with local companies

Matching of decommissioning-related industries between prime contractors and local
companiesHolding decommissioning-related industrial exchange meetings to build relationships
between prime contractors and local companiesIndividual visits to local companiesTours to the Fukushima Daiichi NPS for local companies

In addition, a survey of the needs of both prime contractors and local companies for humanresource development and joint research with several universities have started. The contents of
the “Medium-to-Long-Term Outlook” prepared in September 2020 are being updated asnecessary to reflect the progress of decommissioning work, and briefing sessions are also being169

held for local commercial and industrial organizations, as well as prime contractors. In particular,
since FY2022, the “Medium-to-Long-Term Outlook” has been provided to indicate specific tasks
in which local companies may be able to participate and share information contributing to theconsideration of participation by local companies.
These initiatives have led to steady results, with a total of 706 decommissioning-related
matches as of the end of March 2023 since the establishment of the Matching Support Office(organized by TEPCO, Fukushima Innovation Coast Framework Promotion Organization, andFukushima Soso Recovery Promotion Organization) in July 2020.
With regard to initiative (3), in order to build an integrated decommissioning project
implementation system locally, from “development and design” to “manufacturing”, “operation,”“storage,” and “recycling,” TEPCO plans to establish and operate several new facilities in the
2020s, so that design and technology development of relatively great difficulty, and manufacturingof high-performance products, which have been ordered outside Fukushima Prefecture, including
overseas, can be completed in the Hamadori region. In particular, for “development and design”
and “manufacturing,” TEPCO aims to create local employment, develop human resources, andbuild industrial and economic infrastructure by establishing a joint venture with partner companies
and working closely with local companies (announced on April 27, 2022). As specific initiatives, in
October 2022, TOUSOU MIRAI MANUFACTURING was established to establish a plant tomanufacture various core products required for decommissioning, such as spent fuel casks, andTousou Mirai Technology Co. Ltd. (Decom.Tech) was also established to conduct basic design
and research and development of systems and installations necessary for large-scale fuel debris
retrieval.
6.3.2 Key issues and strategies
6.3.2.1 Communication issues and strategies
Misunderstandings, concerns, and rumors caused by the inappropriate dissemination of
information on the decommissioning will lead to a loss of reputation and trust in thedecommissioning not only in the local community but also in society as a whole, which will not only
delay the decommissioning but also hinder the reconstruction of Fukushima. Therefore, TEPCO’s
challenge is to promptly disseminate information on the current decommissioning status in an easyto-understand manner by taking every possible measure. Therefore, in addition to continuously
providing opportunities for direct participation, including face-to-face meetings and site visits,
TEPCO should strengthen communication that is possible even in non-face-to-face and noncontact situations by active use of tools, such as virtual tour programs and online conference
systems, and further enhancing photo and video content.
Another issue for the government, NDF, and TEPCO is to make appropriate coordination andbuild trust with local communities by providing information more carefully. Therefore, by capturing
opportunities to hold round-table talks and join local meetings/events, direct interaction with local
communities and collaboration with organizations concerned will be promoted proactively. Efforts

170

will also be made for two-way communication by conversation, including listening to concerns andquestions carefully through events such as International Forums and delivering accurate
information in an easy-to-understand and careful manner. The community, TEPCO, the government,
NDF, and organizations concerned should take these opportunities to deepen their knowledge
together in changing circumstances.
In particular, based on the “Action Plan for Steady Implementation of the Basic Policy on the
Disposal of ALPS-Treated Water” (formulated on December 28, 2021, and revised on August 30,2022), the government is implementing measures to overcome rumors by communicating safety
based on scientific evidence, providing support for capital investment and expansion of sales
channels for fishermen, and enhancing safety nets such as funds and compensation.
TEPCO has been working to suppress reputational damage through information dissemination
via its “Treated-water portal site” and safety confirmation by related organizations, etc., based on
the TEPCO Holdings’ Action in Response to the Government’s Policy on the Handling of ALPS
Treated Water from the Fukushima Daiichi Nuclear Power Station (released on April 16, 2021).
TEPCO should continue the utmost efforts to foster understanding of local communities and build
a relationship of trust.
6.3.2.2 Issues and strategies related to the creation of a regional industrial and economic
base through decommissioning
As shown in 6.3.1.2 (2), TEPCO is making various efforts to realize the Commitment, but these
efforts will not produce visible results immediately and will require a certain period. Initiative (3),“Creation of new local industries” (construction and operation of several new facilities in the 2020sand the establishment of joint ventures with partner companies), involves relatively large-scale
investment and is expected to have a great economic impact on the Hamadori area. Therefore, itis necessary to steadily promote and strengthen these efforts.
However, as advanced techniques are required to produce high-performance products, the issue
is how to connect them to promoting active participation in local companies.
Therefore, for the time being, the current activities should be continued and strengthened in a
credible manner, including “(1) Increased participation of local enterprises” and “(2) Support for
local enterprises to step up.” It is also necessary to carefully explain to local governments,
commercial and industrial organizations, and other organizations concerned with the siting locationand scale of new decommissioning-related facilities, the schedule from construction to operation,and the status of considering engagement with local communities in terms of employment,cooperation and order placement, and to proceed with the activities while gaining understanding
and cooperation.
With the understanding of prime contractors, it is also necessary to consider specific methods ofordering and contracting that will make it easier for local companies to receive orders and to
implement these methods on a trial basis. As a result of interviews conducted with local companies
in FY 2020, it became clear that local companies do not necessarily want to be the main contractors,

171but tend to want to enter the market as a subcontractor to gain technology and experience. Afterproperly understanding the intentions and needs of these local companies, a scheme can beestablished to benefit both parties by not only approaching local companies but also encouraging
existing prime contractors to place orders with local companies, including technical guidance. In
addition, this scheme will grant contract incentives, such as multi-year contracts and priority orderplacement, if certain results are achieved in placing orders to local companies or personnel
development. Adopting such beneficial methods for both parties can promote awarding contracts
to local companies. In particular, since the last fiscal year, the “Medium-to-Long-Term Outlook” hasbeen provided to indicate specific tasks in which local companies may be able to participate. It is
important to continuously implement initiatives to expand the participation of local companies. Whilecontinuously considering initiatives that facilitate the participation of local companies and that will
enable them to receive constant and a certain scale of orders, a stance that proceeds with longterm decommissioning with the local community, Fukushima Prefecture, should be expressed.
At the same time, with regard to human resource development, the challenge is to leverage the
Fukushima Decommissioning Engineer Training Center of the Fukushima Nuclear Energy
Suppliers Council, which was established in 2018 and has been providing education on radiation
protection and special education on specific matters such as low-voltage electricity handling, andto expand training exclusively for local companies. These various efforts should be steadily
promoted while responding to changes in the situation as appropriate to build a foundation for local
industry and economy through the decommissioning project and to develop local companies andhuman resources.
In addition to research and development related to decommissioning, as companies from outside
the region move into the region and provide technical guidance to local companies, the number ofengineers and researchers visiting and staying in the region is expected to increase. Therefore, itis necessary to establish the necessary environment and support system so that such external
personnel can integrate into the local community and play an active role as a member. In particular,
it is necessary to take into consideration a wide range of functions such as daily life and education
so that not only single people but also families can live together with peace of mind. To addressthese issues, in addition to promoting the return of residents, Fukushima prefecture opened the“Fukushima 12-municipality Migration Support Center,” which helps people move and settle in the
12 municipalities, mainly from outside the prefecture, to accelerate the reconstruction of theevacuated areas by promoting wide-area migration and settlement. The prefecture has been
disseminating information to people throughout the country who are interested in migration andproviding various types of support to those who wish to move to the 12 cities, towns, and villages.
TEPCO should consider the possibility of collaboration and cooperation with these local initiatives.
To steadily promote these efforts for coexistence with the local community, it is essential to haveclose cooperation between each department within TEPCO. As mentioned in 6.3.1.2 (2), TEPCO
has been reorganizing itself to set up specialized departments for regional symbiosis, and initiatives
to promote local industries through decommissioning are gradually moving forward and gaining a172certain level of recognition from the local community. While keeping this trend advancing steadily,
TEPCO should further strengthen internal efforts as necessary for promoting local industries.
Moreover, it is necessary to further strengthen cooperation and collaboration with local
governments, including Fukushima Prefecture, and local related organizations, including the
Fukushima Innovation Coast Framework Promotion Organization and the Fukushima Soso
Recovery Promotion Organization, which are operating a joint consultation service and co-hosting
matching meetings. NDF will provide appropriate support to TEPCO’s efforts for regional symbiosis,
and will strive to strengthen cooperation and collaboration with local governments and relatedorganizations.

173

List of Acronyms/Glossaries
Acronym

Official NameALARPAs Low As Reasonably Practicable：Risk should be reduced as far
as reasonably practicable including risk/benefit criteria or cost while
taking feasibility of risk reduction measures into account.

ALARA

As Low As Reasonably Achievable：The principle of radiologicalprotection in which it advocates that all radiation exposure must be
maintained as low as reasonably achievable in consideration of socialand economic factors.

ALPS-treated water

Radioactive materials other than tritium have been removed from“contaminated water” to the level below regulatory standards using
multinuclide removal equipment systems (ALPS：Advanced Liquid
Processing System)

AWJ

Abrasive Water Jet

CRD

Control Rod Drive

DOE

United States Department of Energy

DQO process

Data Quality Objectives process: A method developed by the UnitedStates Environmental Protection Agency for planning sampling ofanalytical samples for decision making

FP

Fission Products

F-REI

Fukushima Institute for Research, Education and Innovation

HIC

High Integrity Container

IAEA

International Atomic Energy Agency

ILC

Interlaboratory Comparison

IRID

International Research Institute for Nuclear Decommissioning

JAEA

Japan Atomic Energy Agency

JAEA/CLADS

JAEA Collaborative Laboratories for Advanced Decommissioning
Science:

MADA evaluation

Multi-attribute decision analysis

NDA

Nuclear Decommissioning Authority

NDC

Nuclear Development Corporation

NDF

Nuclear Damage Compensation and Decommissioning Facilitation
Corporation

NFD

Nippon Nuclear Fuel Development Co., Ltd, MHI

OECD/NEAOECD Nuclear Energy Agency

ORBS

Overarching Radiation-monitoring data Browsing System in the
coastal ocean of Japan

PCV

Primary Containment Vessel

ROV

Remotely Operated Vehicle

RPV

Reactor Pressure Vessel

S/C

Suppression Chamber

174

SED

Safety and Environmental Detriment

SGTS

Standby Gas Treatment System

TMI-2

Three Mile Island Nuclear Power Plant Unit 2

Penetration X-2

PCV penetrating part X-2

Penetration X-6

PCV penetrating part X-6

Center of the WorldIntelligence project

The project that promotes nuclear science and technology andhuman resource development gathering wisdom and knowledge

Operating Floor

Operating Floor of the buildings

Commitment

The commitment to the people of Fukushima for achieving bothreconstruction and decommissioning

Kashiwazaki-Kariwa

TEPCO’s Kashiwazaki-Kariwa Nuclear Power Station

Technical Strategic Plan for Decommissioning of the Fukushima
Technical Strategic Plan Daiichi Nuclear Power Station of Tokyo Electric Power Company
Holdings, Inc.
Technical Prospects

Prospects of processing/disposal method and technology related toits safety

International Forum

International Forum on the Decommissioning of the Fukushima
Daiichi Nuclear Power Station

Submersible ROV

A submersible boat-type access investigation vehicle (ROV: Remotely
Operated Vehicle)

Mid-and-Long-term
Roadmap

Government-developed “Mid-and-long-term Roadmap” toward thedecommissioning of TEPCO’s Fukushima Daiichi Nuclear Power
Station Units 1 to 4

TEPCO

Tokyo Electric Company Holdings, Inc.

Non-destructive assay

A method to evaluate the amount of nuclear fuel and radioactivity
without destroying the sample by using radiation, quantum, etc.
emitted, scattered, or transmitted from the sample

Fukushima Daiichi NPS

Fukushima Daiichi Nuclear Power Station of Tokyo Electric Company
Holdings, Inc.

Measurement by muon(fuel debris detection
technology with muon)

A technology to grasp location or shape of fuel in using thecharacteristics by change of number or track of particle depending on
the difference of density, when muons atoms (muon) arrive from thecosmos and atmospheric air and pass through a substanceTarget Map for
Reducing Medium-term
Risk

Measures for Mid-term Risk Reduction at TEPCO’s Fukushima
Daiichi NPS (Risk Map)

175

Glossary

Description

Inventory

Amount of radioactive material contained in the risk source (radioactivity,
concentration of radioactive material, or toxicity possessed by theradioactive material)

Well plug(Shield plug)

A top cover to screen upper part of Primary Containment Vessel made ofconcrete (It is the floor face of the top floor of reactor building in operation)

Engineering

Design and other work to apply technical elements to the site

Cask

Special container used for transporting and storing spent fuelSubdrain

Wells near the building

Sludge generated at
decontamination
device (waste
sludge)Sludge containing high level of radioactive material generated at thedecontamination device (AREVA), which was operated for contaminatedwater treatment from June to September 2011

Spray curtain

Watering to contain dust and allow it to settle

SludgeMuddy substance, dirty mud

SlurryA mix of dirty mud and mineral, etc. in water

ZeoliteSorbent used to recover radioactive materials such as cesium

Shell structure

A structure in which stiffener (a framework that holds deflection) supports
the force applied by the plate (surface) and it is used in ships and airplanes

Torus room

A room that houses a large donut-shaped suppression chamber that holds
water for emergency core cooling system.

Fuel debris

Nuclear fuel material molten and mixed with a part of structure inside
reactor and re-solidified due to loss of reactor coolant accident condition

Bioassay

A method for evaluating the types and amounts of radionuclides ingested
into body by analyzing samples from the human body, such as excrement

Facing (paving)

Covering the ground surface in the power station with asphalt, etc.

Platform

Footing for work installed under RPV inside pedestal

Flanged tankBolted assembly tanks

Pedestal

A cylindrical basement that supports a body of reactor

Manipulator

Robot arm to support fuel debris retrieval

Mock-up

A model which is designed and created as close to real thing to possible

176

Well shieldplug

Operating floor
Spent
Fuel
Pool
(SFP)

Component
Pit

Primary
Containment
Vessel (PCV)

4th floor

ReactorPressure
Vessel (RPV)

3rd floor

2nd floor

Pedestal
Vent Tube

1st floor

1st basement Fl.

Suppression
Chamber (S/C)

Torus room

(Courtesy of IRID)

Fig. 55 Structural drawing inside Reactor building

Top cover of RPV
Steam dryer
RPV body
Steam separator
Water-feed sparger
Core spray piping
Upper grid plate
Fuel assemblyCore shroud

Core support plate
Fuel assemblyControl rod

Neutron flux measuring guideJet pump

Differential pressure detector/
Piping of Boric acid solution
injection system

Control Rod Drive Mechanism

Pedestal for RPV(Courtesy of IRID)

Fig. 56 Structural drawing inside Reactor Pressure Vessel (RPV)177

List of Attachment
Contents
Attachment 1 Revision of the Mid-and-Long-term Roadmap and the earlier published TechnicalStrategic Plan ..................................................................................................... 179
Attachment 2 Major accomplishments to date relating to the decommissioning of the Fukushima
Daiichi NPS ......................................................................................................... 181
Attachment 3 Major risk reduction measures performed to date and future course of action .. 187
Attachment 4 Issues in the structural integrity of PCVs and buildings...................................... 193
Attachment 5 Overview of SED indicator ................................................................................. 198
Attachment 6 Risk sources that are not explicitly addressed in the major risk sources ........... 205
Attachment 7 Change in risk over time ..................................................................................... 208
Attachment 8 Coverage of fuel debris retrieval ......................................................................... 209
Attachment 9 Changes in considerations on retrieval methods in the previous TechnicalStrategic Plans.....................................................................................................211
Attachment 10 Continuation of accident analysis activities (clarification of events that occurredat the time of the accident) (progress of recent activities) ................................ 219
Attachment 11 Terms related to radioactive waste management ............................................. 223
Attachment 12 Disposal of radioactive waste,, .......................................................................... 224
Attachment 13 Overall image of Storage Management Plan for the Fukushima Daiichi NPS 227
Attachment 14 Approach to the selection of nuclides to be measured and assessed when
discharging ALPS-treated water into the sea.................................................... 229
Attachment 15 Individual Action plans of relevant organizations pertaining to analysis ........... 243
Attachment 16 R&D medium-to-long-term plan ........................................................................ 246
Attachment 17 Past Research and Development initiatives in the Project of Decommissioning,
Contaminated Water and Treated water Management ..................................... 248
Attachment 18 Selected subjects in the Nuclear Energy Science & Technology and Human
Resource Development Project (the World Intelligence Project)...................... 249
Attachment 19 Major activities related to enhancing international collaboration ...................... 255

178

Attachment 1

Revision of the Mid-and-Long-term Roadmap and the earlier publishedTechnical Strategic Plan

[1st Edition of the Mid-and-Long-term Roadmap (December 21, 2011)]
 In response to completion of Step 2 described in “the Roadmap towards Restoration from the Accident at
the Fukushima Daiichi NPS” compiled by the government and Tokyo Electric Power Company (TEPCO)
after the accident, the necessary measures to be progressed over the mid-and-long-term, including efforts
to maintain securely stable conditions, fuel removal from spent fuel pools (SFPs), fuel debris retrieval, etc.
were compiled by three parties of TEPCO, Agency for Natural Resources and Energy, and Nuclear andIndustrial Safety Agency and conclude at The Government and TEPCO’s Mid-to-Long-Term
Countermeasure Meeting.

 Basic principles towards implementation of mid-to-long efforts were proposed and targets with timeschedules were established by dividing the period up to completion of decommissioning into three parts;
the period up to spent fuel removal start (1st period), the period up to fuel debris retrieval start fromcompletion of the 1st period (2nd period) and the period up to completion of decommissioning fromcompletion of the 2nd period (3rd period).
[Mid-and-Long-term Roadmap Revised 1st Edition (July 30, 2012)]
 “Specific plan on the matters to be addressed with priority to enhance mid-and-long-term reliability”
developed by TEPCO after completion of Step 2 was reflected and revised targets based on the state ofwork progress were clearly defined.
[Mid-and-Long-term Roadmap Revised 2nd Edition (June 27, 2013)]
 Revised schedule was studied (multiple plans were proposed) based on the situation of each Unit
concerning fuel removal from SFP and fuel debris retrieval, and R&D Plan was reviewed based on theabove.
[Technical Strategic Plan 2015 (April 30, 2015)]
 The first edition of the Technical Strategic Plan was published to provide a verified technological basis to theMid-and-Long-term Roadmap from the viewpoint of proper and steady implementation of decommissioningof the Fukushima Daiichi Nuclear Power Station.
(NDF was inaugurated on August 18, 2014 in response to reorganization of existing Nuclear Damage
Compensation Facilitation Corporation)
 Decommissioning of the Fukushima Daiichi Nuclear Power Station was regarded as “Continuous risk
reduction activities to protect human beings and environment from risks caused by radioactive materials
generated by the severe accident”, and Five Guiding Principles (Safe, Reliable, Efficient, Prompt, Fieldoriented) for risk reduction were proposed.
 Concerning the field of fuel debris retrieval, feasible scenarios were studied by regarding the following
methods as the ones to be studied selectively; the submersion-top entry method, the partial submersion-top
entry method, and the partial submersion-side entry method.

 Concerning the field of waste management, policies for storage/management, control, etc. were studied
from a mid-and-long-term viewpoint based on the basic concept for ensure safety during disposal or for aproper processing method.
[Mid-and-Long-term Roadmap Revised 3rd Edition (June 12, 2015)]
 While much importance was placed on risk reduction, priority-setting for actions was performed so that risks
could definitely be reduced in the long term.

 Targets for several years from now were concretely established including policy decision on fuel debris
retrieval (two years later from now was targeted), volume reduction of radioactive materials contained in
the stagnant water in the buildings by half (FY2018), etc.
[Technical Strategic Plan 2016 (July 13, 2016)]
 In response to the progress state of decommissioning after publication of the Technical Strategic Plan

179

2015, concrete concepts and methods were developed based on the concept and direction of the effortsof the Technical Strategic Plan 2015 to achieve the target schedule specified in “Policy decision on fueldebris retrieval for each unit” which is expected to be completed by about summer 2017 defined in the
Mid-and-Long-term Roadmap, “Compiling of the basic concept concerning processing/disposal ofradioactive waste” which is expected to be complete in FY2017, etc.
[Technical Strategic Plan 2017 (August 31, 2017)]
 Feasibility study was conducted on the three priority methods for fuel debris retrieval. Recommendations fordetermining fuel debris retrieval policy were made and efforts after policy decision including preliminary
engineering were recommended as strategic recommendations.

 Recommendations were made for compiling the basic concept concerning solid waste
processing/disposal.
[Mid-and-Long-term Roadmap Revised 4th Edition (September 26, 2017)]
 Policy on fuel debris retrieval and immediate efforts were decided based on NDF technicalrecommendations.
 Basic concepts concerning solid waste processing/disposal were compiled.

 Individual work was defined based on the viewpoint of “Optimization of total decommissioning work”.
[Technical Strategic Plan 2018 (October 2, 2018)]
 The Plan added contaminated water management and fuel removal from SFP, and presented the direction
from mid-to-long-term perspective that overlooks entire efforts of decommissioning of Fukushima Daiichi
NPS.
[Technical Strategic Plan 2019 (September 9, 2019)]
 The plan presented the strategic recommendation for determining fuel debris retrieval methods for the first
implementing unit as well as the direction from mid-to long-term perspective that overlooks entire efforts ofdecommissioning of Fukushima Daiichi NPS including waste management, etc.
[Mid-and-Long-term Roadmap Revised 5th Edition (December 27, 2019)]
 The first implementing unit and the method of fuel debris retrieval were determined.
 The methods of fuel removal from SFP in Units 1 and 2 were changed.

 TEPCO maintains the current target to suppress the amount of contaminated water generation to about
150m3/day within 2020, in addition, set the new target to less than 100m3/day within 2025.
[Technical Strategic Plan 2020 (October 6, 2020)]
 The plan characteristically included providing of the Mid-and-Long-Term Decommissioning Action Plan,
identifying of requirements for the study of fuel debris retrieval methods toward further expansion of thescale, clarifying of the concept for ensuring safety in decommissioning operations, and strengthening ofmanagement system in response to the growing importance of R&D.
[Technical Strategic Plan 2021 (October 29, 2021)】

 The plan presented the issues to be addressed for the trial retrieval of fuel debris to minimize the impactof the new coronavirus infection, the issues to be discussed for the selection of methods for further
expansion of fuel debris retrieval in scale, and the efforts for the ALPS-treated water, while offering theprospects of processing/disposal method and technology related to its safety,[Technical Strategic Plan 2022 (October 11, 2022)】

 The plan presented the status of preparations for the trial retrieval in Unit 2, the overview and issues of the
proposed retrieval methods that have been discussed (partial submersion method and submersion
method) toward further expansion of fuel debris retrieval in scale, the status of efforts to discharge ALPStreated water into the sea and the analytical strategy for promoting decommissioning.

180

Attachment 2

Major accomplishments to date relating to the decommissioning of the
Fukushima Daiichi NPS131

131

The 117th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water. “Material 2: Progress towards decommissioning, etc.”

181

182

183

184

185

186

Attachment 3

Major risk reduction measures performed to date and future course ofactionChange in the risk level over time assessed and expressed by SED for the entire Fukushima
Daiichi NPS is shown in Fig. A3-1. The vertical axis in the top graph in the figure shows the risk
level in common logarithmic scale and the horizontal axis shows number of years after the accident.
Although the risk level at the time of zero year after the accident was at high level caused by thefuel in SFP which lost its cooling function and the molten nuclear fuel, over the time of 0.5 years
after the accident the risk level has been reduced with a significant decrease in both Hazard
Potential and Requiring Level for Safety Management, because of implementation of safetymeasures including cooling function restoration of SFPs, cooling of fuel debris with water injection
by core spray system, nitrogen injection, etc. (in 2011) as well as the contribution of inventory anddecay heat decrease due to decay of radioactive materials.
The risk level in 0.5 to 2.5 years after the accident is shown in the enlarged graph (the verticalaxis is in linear scale) with the breakdown of major risk source (fuel debris, fuel in SFP andcontaminated water, and the others) at the bottom left in the figure and the similar graph since 3
years after the accident is given in the bottom right with the risk level multiplied by 10. These graphs

Fuel removal from
Unit 4 SPF started

0

1

2

3

4

5

6

7

8

Risk level (Linear scale)

Risk level
Risk level (Linear scale)(Logarithmic scale)demonstrate that a continuous risk reduction has been achieved.

9 10 11 12

Years after the accident

Mid-and-Long-term
Roadmap Phase 2

Mid-and-Long-term
Roadmap Phase 1

Risk level in the rightgraph is multiplied by 10

0.5

1
1.5
2
Year after the accident

Fuel debris
燃料デブリ

プール内燃料
Fuel in SFPs

2.5

3

4

5

6
7
8
9
10
Year after the accident

燃料デブリ
Fuel debris

Contaminated
汚染水等
water, etc.

プール内燃料
Fuel in SFPs

11

12

Contaminated water, etc.
汚染水等

* Evaluation of fuel in SFP 8 years after the accident occurred reflects the results of water temperaturerise in the testing on SFP cooling shutdown. (For detail, see Fig. 4 in Chapter 2 of main part.)

Fig. A3-1

Reduction of risks contained in the Fukushima Daiichi NPS

Change in the risk level with further breakdown of major risk sources over time since 0.5 years
after the accident is shown in Fig. A3-1. With a logarithmic scale, risk sources can be indicated that187

are too small to be displayed in the linear scale of Fig. A3-1. Fuel in the Common Spent Fuel
Storage Pool and the Dry Cask Temporary Custody Facility are not shown which stay in the regionof sufficiently stable management. The “stagnant water in buildings + zeolite sandbags” shown in
Fig. A3- 2 was assessed based on the information on the stagnant water in buildings for the periodof 0-8 years after the accident. However, since 9 years after the accident, the condition of zeolitecontaining sandbags placed in the basement of the process main building and the high-temperatureincinerator building has become clear, and this information was incorporated into the assessment.
Among the major risk sources, fuel debris, fuel in SFPs, stagnant water in buildings, zeolitecontaining sandbags, and secondly waste generated by water treatment have relatively high-risk
levels. Although, in recent years, the treatment of the stagnant water in buildings has progressed
and the risk level of the “stagnant water in buildings + zeolite sandbags” has been on a declining
trend, attention should be paid to zeolite sandbags laid with a high dose because they may hinder
future decommissioning work. In regard to secondly waste generated by water treatment, the risk
level became higher presented in the Technical Strategic Plan 2022 (11 years after the accident),
because some ALPS slurry stored in HICs affected by beta irradiation need to be transferred.
However, it is tending down in the Technical Strategic Plan 2023 (12 years after the accident) as aresult of the transfer operations that have been carried out. In addition, the risk level of the water
stored in tanks (flanged tank and welded tank) is decreasing as the treatment of stored water inflanged tanks progresses, and is expected to decrease further once the treatment of the remaining
concentrated saltwater is completed. The risk level of contaminated structures in the building has
increased based on the accumulated hydrogen that flowed into the system connected to the PCV
during the accident and the results of the integrity assessment that assumed hydrogen explosions

Risk level (Logarithmic scale)in the relevant piping in case.

サイト全体
Site total
Fuel in SFPs
プール内燃料
Fuel debris

燃料デブリ
Stagnant water in buildings+ Zeolite sandbags
建屋内滞留水＋ゼオライト土嚢
Contaminated water in trenches

トレンチ内汚染水

Stored water in tanks

タンク内貯留水Stored water in tanks (Estimated)

水処理二次廃棄物
Secondary waste generated bywater treatment

建屋内汚染構造物等
Contaminated structures, etc. inbuildings

ガレキ等
Rubbles, etc.
0

1

2

3

4

5

6

7

8

9

10

11

12

Year after the accident

Fig. A3-2

Change in the risk level for each major risk source(1) Fuel in SFPs
From one year after the accident, rubble was removed and a cover for fuel removal was installed188

at Unit 4 in preparation for fuel removal, thereby enhancing the functions of reducing the risk offuel damage by rubble in SFP and controlling the dispersion of damaged fuel. Further, 2.5 years
after the accident, fuel removal was started and the fuel was transferred into the Common Spent
Fuel Storage Pool with low Requiring Level for Safety Management, and the risk level was lowered(completed in 2014)132.
Although the effect of risk level reduction was observed due to the decrease in Requiring Level
for Safety Management through the diffusion control function of the building cover at Unit 1(installed in 2011), this effect has been currently lost because the building cover was removed (in2015) in preparation for removal of fuel in SFP133. In order to prevent dust scattering during rubble
removal, a large cover will be installed, and fuel removal from SFP is planned to start in FY2027
to FY2028134.
For Unit 2, a gantry for fuel removal will be installed on the south side of the reactor building,and the removal of the fuel in SFP is scheduled to start in FY2024 to FY2026120121.
In Unit 3, a cover for fuel removal was installed in 2018 after rubble removal was performed in
preparation for fuel removal from SFP, then fuel removal from SFP was started from April 2019.
After that, transfer to the Common Spent Fuel Storage Pool was completed in February 2021135.
In case cooling fuel in SFPs is stopped, the pool water temperature may rise and the pool waterlevel may lower due to decay heat. In and after the eighth year after the accident, as a result ofincorporating the observation that the rise in water temperature after cooling shutdown of SFPs
was slower than expected, the risk level of fuel in SFPs is lower than previously estimated,because the time margin before the risk of water level lowering becomes apparent increases.
(2) Fuel debris
Although fuel debris was at a high-risk level just after the accident because it was at molten
state, and in addition, radioactive materials were released, the risk level was reduced, not only bydecay of the radioactive materials, but also by reduction of Hazard Potential and Requiring Level
for Safety Management because of restoration and strengthening of cooling function.
As described in (1), the diffusion control function of the building cover of Unit 1 reduced the risk
associated with the dispersion of fuel debris, and lowered the risk level due to the decrease in
Requiring Level for Safety Management; however, this effect is currently lost.
(3) Stagnant water in buildings + Zeolite sandbags
Although stagnant water in buildings is generated by cooling of fuel debris and immersion ofgroundwater into the buildings, etc., the risk level has been lowered due to the start of operationof cesium sorption apparatus (KURION) and Second cesium sorption apparatus (SARRY), the132

Decommissioning project, Status of the decommissioning work, Fuel removal work of Unit 4, (Website), Tokyo
Electric Power Company Holdings, Inc.
133
The 57th Study Group on Monitoring and Assessment of Specified Nuclear Facilities, Reference 7 “State ofprogress of Unit 1 of Fukushima Daiichi NPS and rubble removal on the north side of the operating floor”, Tokyo
Electric Power Company Holdings, Inc.
134
Mid-and-Long-term Decommissioning Action Plan (March 31, 2022), Tokyo Electric Power Company Holdings,
Inc.
135
Decommissioning project, Status of the decommissioning work, Fuel removal from spent fuel pool in Unit 3,(Website), Tokyo Electric Power Company Holdings, Inc.

189

effect of subdrains and land-side impermeable walls, water drainage in condensers, and the startof the operation of Third cesium sorption apparatus (SARRY-II). This stagnant water treatment in
the buildings so far significantly contributes to risk level reduction of the total site following
contribution by fuel removal in SFP.
(4) Contaminated water in trenches
Although the contaminated water of high concentration has been stagnated in the seawater
pipe trenches in Units 2 to 4 since immediately after the accident, the trenches were blocked andthe treatment of the stagnant water has been completed (in 2015)136. With regard to the seawater
pipe trench of Unit 1, the concentration of which is lower than that of Units 2 to 4, purification of
the stagnant water is under consideration 137.
(5) Stored water in tanks
There are several types of stored water in the tank with different radioactive material
concentrations depending on the stage of purification treatment. First of all, the strontium treatedwater generated from the purification process of the water in the buildings by KURION, SARRY
and SARRY Ⅱ is stored as welded tank water. After that, the risk level is further reduced by multiradionuclide removal equipment (ALPS), etc., and the water is stored in welded tanks as ALPStreated water, etc. (ALPS-treated water and water under treatment). For the concentrated liquid
waste generated from the evaporation-enrichment system, which operated only for a short period
immediately after the accident, the precipitated slurry with a high concentration of radioactive
materials (concentrated liquid waste slurry) was separated, and the remaining liquid (concentrated
liquid waste) is transferred to welded tanks, to reduce the leakage risk and lower the risk level.
The treatment of the concentrated salt water generated from the treatment with KURION before
ALPS came into operation was completed in 2015 through the operation of ALPS and theadvanced multi-nuclide removal equipment (Advanced ALPS)138.
Risk level of these stored water in the tanks are also lowered by raising and duplexing the weir(for the existing tanks completed in 2014), transferring from flanged tanks to welded tanks, andtreating the Sr-treated water remaining at the bottom of the flanged tanks (in 2019), and treating
ALPS-treated water (in 2020). The remaining concentrated saltwater at the bottom of flanged
tanks is being collected for dismantling the tanks as at the end of March 2023, then the remaining
water, after sludge removal by filtering, is planned to be transferred to the process main building.
(6) Secondary waste generated by water treatment
Many radioactive materials have moved from contaminated water to secondary waste throughwater treatment. What has been generated includes the sludge from decontamination device, thewaste sorption vessels by operation of KURION and SARRY (in 2011) and by the SARRY-II (in136

Decommissioning project, Status of the decommissioning work, Removal of contaminated water in seawater
pipe trenches, (Website), Tokyo Electric Power Company Holdings, Inc.
137
Inspection of stagnant water contains radioactive materials observed in trenches of Fukushima Daiichi NPS,
(FY2021)”, Tokyo Electric Power Company Holdings, Inc.
138
Decommissioning project, Status of the decommissioning work, Purification of contaminated water, (Website),Tokyo Electric Power Company Holdings, Inc.

190

2019), ALPS slurry by operation of ALPS (in 2013), the waste sorption vessels by the advanced
ALPS (in 2014), waste sorption vessels by the mobile-type treatment system that treated seawater
pipe trenches, etc. The risk level is the dominant factor among the secondary waste generated bywater treatment due to the ALPS slurry stored in the HIC to be transferred since eleven years after
the accident. HICs that are evaluated to have exceeded or are close to exceeding the standard
value for cumulative absorbed dose are planned to be transferred during FY2023, the risk level ison a downward trend based on the progress of the transfer work during FY2022. Although thenumber of HICs whose cumulative absorbed dose approached the standard value will gradually
increase over time, ensuring that the cumulative absorbed dose can be managed so as not toexceed the standard value will reduce the risk level by systematically implementing the transfer
operation. For other risk sources, the sludge from decontamination device greatly contributes tothe risk level though, sludge is not newly generated at present, and thus, the risk level of the total
secondary waste generated by water treatment is not on an increasing trend. As a tsunami
countermeasure, the sludge from decontamination equipment stored in the main process building(T.P. 8.5m) will be extracted (planned for FY2025), placed in a storage container, and transferredto the elevated area (T.P. 33.5m) 139.
Although the concentrated liquid waste slurry separated from the concentrated liquid waste wasstored in horizontal welded tanks without the weir and placed on the ground without the base, its
risk level has been lowered due to the approach to safety taken by installing the reinforcedconcrete base and the weir.
(7) Contaminated structures, etc., in the buildings
The risk level of contaminated structures, etc. in the buildings comprised of structures, piping,components, etc. (shield plug, piping of emergency gas processing system and the like) in thereactor buildings, PCVs or RPVs that are contaminated by dispersed radioactive materials causedby the accident, has been increased from that indicated in the Technical Strategic Plan 2022,
based on the accumulated hydrogen that flowed into the system connected to the PCV during theaccident and the results of the integrity assessment that assumed hydrogen explosions in therelevant piping in case. As a result of the integrity assessment assuming hydrogen explosions,plans for purging operations, etc. are being considered for Unit 3 S/C and HPCI turbine exhaustlines that exceed the elastic deformation range140.
(8) Rubble, etc.
Rubbles, etc. as solid waste are stored under a variety of conditions such as in solid waste
storage, in temporary waste storage and by outdoor accumulation. Each has different Requiring
Level for Safety Management, and the rubbles stored in outdoor sheet covered storage and139

Reference 1-1-7, “Changes to the process for extracting sludge from decontamination equipment(Supplementary explanation material)”, The 104th Study group on monitoring and assessment of specified nuclear
facilities, Tokyo Electric Power Company Holdings, Inc.
140
Reference 2-1, “Response to Unit 1 RCW in light of hydrogen accumulation event (Impact assessment ofhydrogen accumulation event)”, The 10th Technical meeting on the examination of the action plan for specificnuclear facilities, Tokyo Electric Power Company Holdings, Inc.

191

outdoor accumulation are of the highest risk level. In the past, the facilities with better
management condition have been enhanced by soil covered temporary storage facilities (in 2012),
fallen tree temporary storage pool (in 2013), expansion of solid waste storage facilities (in 2018),
etc. In addition, the rubble from temporary storage facilities was transferred to the better-controlled
solid waste storage facility (in 2020). With the start of operation of the additional solid waste
incineration facility (May 2022), combustible rubbles and other materials stored outdoors can betransferred to the solid waste storage facility after incineration to reduce their volume. Furthermore,
outdoor temporary storage is planned to be discontinued by the end of FY 2028 by further
increasing volume reduction installations and solid waste storages, etc., in accordance with the
Solid Waste Storage Management Plan141.

141

The Solid Waste Storage Management Plan at the Fukushima Daiichi NPS (February 2023 Edition), Tokyo
Electric Power Company Holdings, Inc.

192

Attachment 4 Issues in the structural integrity of PCVs and buildings
As for the main equipment in the PCV/RPV pedestal, etc., and reactor buildings, their structural
integrity has been evaluated in post-accident studies by TEPCO and the Project ofDecommissioning, Contaminated Water and Treated Water Management. As a result, it has been
confirmed that the main equipment and reactor buildings have a certain level of seismic margin.

Hereafter, the existing main equipment and reactor buildings, as well as equipment/systems andbuildings (including modified areas of the existing equipment/systems and buildings) to be newly
installed for fuel debris retrieval over a relatively long period, should satisfy the functional
requirements and (1) be capable of performing operations safely and (2) ensure the required levelof safety against external events such as earthquakes and tsunamis. Assuming (3) long-term
maintenance management, in addition, it is important to (4) feed back new knowledge to be gained
from planned PCV internal investigations and fuel debris analysis results, etc., into the design offuel debris retrieval systems and the study of retrieval methods. The following shows the key
functional requirements as examples.
○

Existing equipment/systems and buildings (including modified areas; the impact of aging is
also considered necessary)・Control the deterioration of containment functions of PCV, RPV, and reactor buildings, etc.,
and control/prevent large releases of radioactive materials (maintaining containment
functions).

・

Reactor buildings, etc., safely support equipment/systems to be newly installed in thereactor buildings for fuel debris retrieval in addition to the existing main equipment(maintaining support functions).

○

Equipment/systems and buildings to be newly installed for fuel debris retrieval (including
connections to the existing equipment/systems)

・Have functions according to design requirements and control/prevent large releases ofradioactive materials (ensuring containment functions).

・

Safely support equipment/systems to be installed for fuel debris retrieval (ensuring support
functions).

・

New buildings, etc., provide a safe work environment as required (ensuring shielding
performance, etc.).

In FY 2020, TEPCO formulated a long-term maintenance management plan for existing on-site
systems/equipment and buildings in consideration of the progress of time-related deterioration,and started the implementation of the plan. When new facts about the accident are revealed
through further investigations and other activities, it is also necessary to clarify the impact of theaccident, especially damage, by performing severe accident progression analysis evaluations,193

etc., and to secure functions throughout the decommissioning period in consideration of the
progress of time-related deterioration. Moreover, regarding the existing equipment/systems andbuildings, the lowering of the water level in the PCVs of Units 1 and 3 was confirmed in theearthquakes that occurred on February 13, 2021, and March 16, 2022 with epicenters off the coastof Fukushima Prefecture.142, 143 Although cooling functions were maintained in both cases, in lightof both earthquakes, in order to maintain and manage the equipment/systems and buildings withthe above functions over the medium-and-long term, it is necessary to conduct impact
assessments on the accident impact, aging degradation, and external events (earthquakes andtsunamis, etc.) anticipated during the decommissioning period. In view of the fact that the pastassessment of these effects was limited, it is necessary to make maximum use of existing
techniques and evaluation results for planning and implementing an investigation plan, in whichremote control under a high-radiation dose environment is a challenging issue, and to develop
underlying technologies to understand the situation. In so doing, while giving priority to safety, it
is useful to actively introduce the latest knowledge and achievements not only in the nuclear field
but also in other fields. Specifically, for RPV pedestal in Unit 1, PCV internal investigations
revealed the loss of concrete in the lower part of the pedestal near the worker access entrance
and almost the entire inner wall of the pedestal, so TEPCO is conducting assessments based onthese findings. However, the information obtained is still limited, and many of the conditions for
examination will be based on assumptions. Therefore, regardless of the evaluation results, it isimportant to assess the impact of anticipated events such as loss of support function, and to
consider the necessary measures. In addition, the information obtained will provide useful leads
to clarify the accident progression, which should be used with other information for futureevaluation.
Based on the above impact assessment, it is crucial to prepare for these risks caused byearthquakes or aging degradation expected hereafter. The following discusses preparedness forseismic and aging degradation risks.
(1) Seismic risk preparedness
To prepare for possible seismic risks in the future, it is important to specify and implement
measures after determining the margin through seismic assessment. In this process, theuncertainty in the on-site environment, the work difficulty, and the workers’ exposure should befully considered.

142

An earthquake with its epicenter off the coast of Fukushima Prefecture. A maximum intensity of upper 6 wasobserved in Miyagi and Fukushima Prefectures. In the Fukushima Daiichi NPS, the second basement floor of
the Unit 6 reactor building (on the foundation plate) recorded the quake with a maximum acceleration of 235
gal. This is equivalent to the response level of about half of the seismic response analysis results of thebuildings against the design basis earthquake ground motion (Ss) (600 gal) before the application of the newseismic design policy determined by the NRA.
143
An earthquake with its epicenter off the coast of Fukushima Prefecture. A maximum intensity of upper 6 wasobserved in Miyagi and Fukushima Prefectures. In the Fukushima Daiichi NPS, the second basement floor of
the Unit 6 reactor building (on the foundation plate) recorded the quake with a maximum acceleration of 221
gal.

194

Seismic assessment needs to consider the impact of the accident and thinning caused by aging
degradation in line with the actual situation and set the conditions for examination. However,
because of the high-radiation dose environment, the information available is limited, andestablishing conservative conditions for examination may increase the difficulty of implementing
measures. Therefore, considering that high levels of uncertainty result in excessively conservative
conditions, it is also important to work to understand the impact of the accident and the actual
state of aging degradation with high accuracy. For example, although the measurable areas arelimited, a method should be devised to reduce uncertainties in the scope and method of feedback,etc., such as utilizing the measurement results of the corrosion growth rate in piping for estimating
locations where measurement is not possible based on model analysis.
In addition, one method for seismic risk preparedness is reducing the stress generated during
an earthquake. For example, drainage is planned for the S/C in Units 1 and 3 with a water level
higher than during normal operation caused by the accident. In all cases, measures are being
taken to first install new water level gauges with a wide measurement range to ensure that all
possible measures are implemented to reduce water levels.
Regarding the reactor buildings of Units 1 to 3, a certain level of safety has been confirmed
through seismic assessments that take into account the state of damage after the accident.
However, as with the main facilities described above, the verification of seismic safety over a long
period during fuel debris retrieval is required.
For this purpose, although it is challenging to perform investigations due to the high radiationdose, continuous investigations should be carried out to observe the condition of the damage, thedeterioration, and the condition of corrosion.
As TEPCO undertakes the following activities, it is important to accumulate knowledge throughongoing investigations and consolidate information on the condition of the buildings.
・Application of unattended and labor-saving technologies that utilize robots and drones.

・

Investigation of concrete in Unit 4, where detailed assessment is practical.

・

Installation of seismometers and utilization of observation records.

When the above investigation reveals new facts or findings for components considered in theseismic assessment, such as a decline in structural performance or additional damage due tolarge earthquakes, it is important to update the information on the condition of buildings andincorporate it into the seismic assessment as appropriate.
(2) Aging degradation risk preparedness
Since thinning due to corrosion is assumed to cause degradation of RPVs and PCVs due toaging, the structural strength tends to decrease over time. Possible preparedness measures canbe for the structures themselves and the environment in which they are installed. Generally,measures for the former include coatings, but this is extremely difficult considering that humans
cannot easily approach the structures. Therefore, priority will be given to examining the latterenvironmental approach. For reactor water injection as ongoing action, measures are being taken195

to reduce the dissolved oxygen concentration through nitrogen bubbling and hydrazine injectionin the tanks. For the gas phase, nitrogen is sealed inside the PCVs.
However, since the PCVs are damaged, and degradation due to aging progresses over time, it
is important to implement measures to maintain the low oxygen concentration in the PCVs
appropriately and continuously.

As for existing and new equipment/systems and buildings, the loading conditions (layout, size,
weight of the new equipment/systems, new openings on PCV/biological shielding walls, etc.)
during fuel debris retrieval will be specified with further progress in designing. In order to ensure
the structural integrity of equipment/systems and buildings, while considering the state of the site,examination will be promoted steadily based on the latest design information.
In the specific designing of new equipment/systems and buildings, it is important to define
seismic classes and perform seismic evaluation accordingly. However, it is still challenging torepair and reinforce buildings and main equipment damaged by the accident in a high radiationdose environment. Because of this, the earthquake ground motion and the design criteria used in
the design will be defined appropriately in accordance with the new seismic design policy
determined by the NRA144, 145 while considering the perspective of risk assessments. In doing so,
although ensuring safety is without doubt the top priority in the design policy of systems requiredfor individual decommissioning operations, including planned fuel debris retrieval, we believe it isimportant to establish and implement a framework that allows TEPCO to exchange opinions on
the earthquake ground motion to be applied and its interpretations with the NRA before application
while ensuring the independence of the review.
In addition, in the evaluation of existing systems, even for components that do not directly affectseismic resistance or that are ignored in the seismic assessment, if parts or other components
are damaged by the accident collapse, they may have a significant social impact even if it does
not cause structural and radiation safety hazards. To avoid such a situation, it is necessary tomonitor the progress of deterioration daily and to implement comprehensive management fromthe viewpoint of personnel and system safety.

144

NRA, “The concept of earthquake ground motion and its application in the seismic design of TEPCO Fukushima
Daiichi Nuclear Power Station in light of the earthquake on February 13, 2021,” Nuclear Regulation Authority(19th meeting), Material 3, July 7, 2021.
145
NRA, “The concept of earthquake ground motion and its application in the seismic design of TEPCO Fukushima
Daiichi Nuclear Power Station in light of the earthquake on February 13, 2021 (2nd),” Nuclear Regulation
Authority (30th meeting), Material 2, September 8, 2021.

196

①

New seismic design policy determined by the NRA (Reference)

The NRA stated, “Given that the earthquake ground motion of the Great East Japan
Earthquake in 2011 exceeded Ss 600, and that the ground motion of the earthquake on
February 13, 2021, exceeded Sd 300, the earthquake ground motion to be used in the
future seismic design of 1F should take into account these seismic motions observed,”3and”. For the time being, it is appropriate to reorganize ‘the concept of earthquake
ground motion and its application to the seismic design of 1F’ based on the earthquake
ground motion for review (Ss 900).”3 The NRA approved the application of the system
based on the existing earthquake ground motion146 for review (the Ss 900 system). In
addition to the conventional seismic classes (Classes S, B, and C), B+ was newly
adopted as a seismic class higher than Class B.3
Based on the above, the following seismic policy3 applies to newly installed systems.
• The earthquake ground motion for review (Ss 900) shall be established as the new
design basis earthquake ground motion at the Fukushima Daiichi NPS (Ss 900).
• 1/2 Ss (maximum acceleration 450 gal [1/2 of Ss 900]; hereinafter referred to as“Sd 450”) shall be applied as the new earthquake ground motion (Sd) for elastic
design.
Then, the following shall be met, considering the situation at the Fukushima Daiichi
NPS:• When calculating seismic forces, two horizontal directions and a vertical direction
shall be appropriately combined.
• For Class B+, safety functions shall be maintained against Sd 450 in addition to theearthquake ground motion applicable to Class B.
• In principle, the same concept as above shall apply to already installed systems.
However, among the facilities that require additional measures after evaluating theseismic resistance commensurate with the applicable seismic class, measures forearly reduction of risk caused by insufficient seismic resistance shall be separately
examined for those that cannot be reinforced within a reasonable range inconsideration of the impact on the decommissioning work and the risk of exposuredue to the implementation of measures.
Regarding the concept of classification of seismic classes and the application ofearthquake ground motion in the seismic design of the Fukushima Daiichi NPS, “In theseismic evaluation of facilities and systems at 1F, the earthquake ground motion to be
applied shall be established taking into consideration (1) seismic classes (S, B+, B, C),and (2) impacts on decommissioning activities, consequent impacts on upper classes,
service life, design progress, amount of radioactivity of contained liquid, etc., andmeasures shall be determined as needed.”4 The procedures for establishing earthquake
ground motion and determining the necessary measures according to the seismicclasses and characteristics of facilities are provided in Attachment.4 However, theprocedures have been changed to make a decision after examining the exposure
assessment period and realistic mitigation measures, including radiation protection
measures and building seismic design.147 In addition, for facilities and systems in the B+
class whose functions shall be maintained against 1/2 Ss, there must be an evaluationof the impact on them from the earthquake off the coast of Fukushima Prefecture on
March 16, 2022.

146

Tokyo Electric Power Company Holdings Inc., “Examination of protection against external events at the
Fukushima Daiichi Nuclear Power Station,” Study group on monitoring and assessment of specified nuclear
facilities meeting (27th), Material 2, October 3, 2014.
147
NRA, “The concept of classification of seismic classes and the application of earthquake ground motion in Tokyo
Electric Power Company Holdings Inc. Fukushima Daiichi Nuclear Power Station,” Nuclear Regulation Authority(51st meeting), Material 3, November 16, 2022

197

Attachment 5

Overview of SED indicator

Risk analysis targeting various risk sources, which have diverse characteristics and exist all overthe site, was conducted in reference to the SED indicator148 developed by the NDA. The SED
indicator is an important factor to decide priority to implement risk reduction measures. It waspartially modified (refer to the following pages) so that unique characteristics of the Fukushima
Daiichi NPS could be easily reflected when it was applied to the Fukushima Daiichi NPS. Overview
of the SED indicator and the modified part to be applied to the Fukushima Daiichi NPS aredescribed below.

The SED indicator is expressed by the following formula. The first formula is the one widely used
for waste assessment and the second is for contaminated soil assessment. In each formula, thefirst term is referred as to “Hazard Potential” and the second as “Requiring Level for Safety
Management” of risk sources.

or

𝑆𝐸𝐷 = (𝑅𝐻𝑃 + 𝐶𝐻𝑃) × (𝐹𝐷 × 𝑊𝑈𝐷)ସ

𝑆𝐸𝐷 = (𝑅𝐻𝑃 + 𝐶𝐻𝑃) × (𝑆𝑆𝑅 × 𝐵𝐸𝑅 × 𝐶𝑈)ସHazard Potential is an indicator that shows the impact on the public based on the radioactivity
and other material of the risk source, while the Requiring Level for Safety Management in the first
formula is an indicator of the long-term stability and handleability of the risk source due to thesufficiency of the containment function of the facility containing the risk source and thecharacteristics (degradation, activity level), etc. of the risk source. The Requiring Level for Safety
Management in the second formula is an indicator that shows the time delay until the risk ofcontaminated soil becomes apparent to the public due to the distance to the site boundary,groundwater flow conditions, etc., the benefits of early implementation of risk reduction measures,and the current assessment and the uncertainty of future predictions. The SED indicators for the
major risk sources at the Fukushima Daiichi NPS are assessed according to the first formula. Both
Hazard Potential and Requiring Level for Safety Management are factors to be considered indetermining the priority of risk reduction measures, and the SED indicator developed by the NDA
is expressed in the form of a multiplication so that the contribution of both Hazard Potential andRequiring Level for Safety Management to the priority can be roughly expressed. Risk sources withweak containment and large amounts of radioactivity have a high priority for action, whereas risk
sources with adequate containment and small amounts of radioactivity have a low priority for action.
When comparing the intermediate state of these risk sources, i.e. risk sources with sufficient
containment function and large amounts of radioactivity with those with weak containment function

148

NDA Prioritization – Calculation of Safety and Environmental Detriment score, EPGR02 Rev.6, April 2011.

198

and small amounts of radioactivity, the latter have a higher priority for action, and therefore, as acontribution to priority, Requiring Level for Safety Management should be set to dominate over
Hazard Potential. However, as discussed below, while the Hazard Potential is directly influenced
by numerical values such as radioactivity, the FD and WUD, which constitute Requiring Level for
Safety Management in the first formula, are each assigned a score in the range of 2 to 100, if theRequiring Level for Safety Management is defined only by the product of FD and WUD andmultiplied by the Hazard Potential, the Hazard Potential can be more dominant as a contribution to
the priority of measures. Taking these considerations into account, to increase the contribution of
Requiring Level for Safety Management to the priority of countermeasures, the SED indicator is set
to multiply the Hazard Potential by the Requiring Level for Safety Management, defined as the
product of FD and WUD to the fourth power149.
Each indicator is explained below. Although CHP stands for “Hazard Potential” of the chemical
substance, details are not given here as it is not used in this section.

(1) Hazard Potential
Radiological Hazard Potential (RHP) is an indicator representing the potential impact ofradioactive materials and represents the impact to the public by the following formula when the
total amount of radioactive materials is released.
𝑅𝐻𝑃 = 𝐼𝑛𝑣𝑒𝑛𝑡𝑜𝑟𝑦 ×

𝐹𝑜𝑟𝑚 𝐹𝑎𝑐𝑡𝑜𝑟
𝐶𝑜𝑛𝑡𝑟𝑜𝑙 𝐹𝑎𝑐𝑡𝑜𝑟

Inventory is defined as shown below by Radioactivity of risk sources and the Specific Toxic
Potential (STP) and corresponds to the effective radiation dose150 . The STP is defined as thevolume of water required to dilute 1TBq of radioactive materials and corresponds to the radiationdose coefficient. Ingestion of a certain amount of such diluted water throughout the year will resultin a radiation exposure dose of 1mSv. The SED indicator conservatively uses the larger radiationdose coefficient between ingestion and inhalation.
𝐼𝑛𝑣𝑒𝑛𝑡𝑜𝑟𝑦(𝑚ଷ ) = 𝑅𝑎𝑑𝑖𝑜𝑎𝑐𝑡𝑖𝑣𝑖𝑡𝑦(𝑇𝐵𝑞) × 𝑆𝑇𝑃(𝑚ଷ ⁄𝑇𝐵𝑞 )Form Factor (FF), as shown in Table A5-1, is an indicator representing how much radioactive
material is actually released depending on material form, such as gas, liquid, solid, etc. The
indicator is set assuming that 100% of radioactive material is released in the case of gas and liquid
when containment function is totally lost and that 10% of radioactive material is released in thecase of powder based on the measurement data. Because of no clear basis, the indicator in caseof solid is set to a sufficiently small value assuming that the solid materials are less easily released.

149
150

The NDA Prioritization Process - Development Process Route Map Report, EGR014 Rev.0, July 2006.
Instruction for the calculation of the Radiological Hazard Potential, EGPR02-WI01 Rev.3, March 2010.

199

In Table A5-1, several expected forms, especially for fuel debris, are added to the definition usedby the NDA. The scores for the form of No.4 and No.5 are newly established.
Control Factor (CF), as shown in Table A5-2, is an indicator representing time allowance available
before restoration when safety functions maintaining current stable state are lost. CF is taking into
account exothermicity, corrosivity, flammability, hydrogen generation, reactivity with air or water,
criticality, etc. which are typical characteristics of risk sources. CF is the same as the one definedby the NDA(2) Requiring Level for Safety Management – FD and WUD
Facility Descriptor (FD) is an indicator representing whether containment function of the facility
is sufficient or not. Risk sources are ranked by score based on a combination of the factors including
integrity of the facility, redundancy of containment function, safety measure condition, etc.
Waste Uncertainty Descriptor (WUD) is an indicator representing whether any impact isgenerated or not when the risk source removal is delayed. Risk sources are ranked by score basedon a combination of the factors including degradation or activity of the risk source, packaging state,monitoring condition, etc.
As these indicators are difficult to be applied to the Fukushima Daiichi NPS if they are used as
defined by the NDA, they are re-defined as shown in Table A5-3 and Table A5-4 respectively.
(3) Requiring Level for Safety Management - SSR, BER and CU
The definition of SSR, BER and CU used for Requiring Level for Safety Management assessment
for contaminated soil is the same as the one defined by the NDA and each score is shown in Table
A5-5.
Speed to Significant Risk (SSR) is an indicator concerning the time until the public is affected
through such as distance to the site boundary, groundwater flow conditions, etc. and to assess
urgency of taking measures.
Benefit of Early Remediation (BER) is an indicator to assess benefits obtained from early
implementation of measures against risks.
Characterization Uncertainty (CU) is an indicator to assess reliability or uncertainty in the risk
assessment model.
Table A5-1 Definition and score of FF
No.

Form

FF

1

Gas, liquid, watery sludge* and aggregated particles*

1

2

Other sludge

1/10 = 0.1

3

Powder and removable contaminants (surface
contamination, etc.)*

1/10 = 0.1

200

4

Adhesive* or penetrating contaminants (surface
penetrating contamination)*

1/100 = 0.01

5Fragile and easily decomposable solid (porous MCCI
(Molten Core Concrete Interaction), etc.)*

1/10,000 = 1E-4

6Discrete solid (transportable size and weight byhuman power such as pellets, etc.)

1/100,000 = 1E-5

7Large monolithic solid, activated component

1/1,000,000 = 1E-6

* : Form which is added to the NDA definition to enhance applicability to the case of the Fukushima
Daiichi NPS
Table A5-2 Definition and score of CF

Category

No.

Time allowance available before any risk is realized

CF

1

Hours

1

2

Days

10

3

Weeks

100

4

Months

1,000

5

Years

10,0006

Decades

100,000

Table A5-3 Criteria and score of FD
Criteria(NDA definition is modified to enhance applicability to the caseof the Fukushima Daiichi NPS)

NDF
Score

1

No component for diffusion control function exists. Therefore, noassessment for containment function is available.

100

2“Safety assessment criteria*2” are not satisfied at “the time ofassessment*1” caused by the accident effects, etc. The component for
diffusion control function is single.

91

3“Safety assessment criteria” are not satisfied at “the time of assessment”
caused by the accident effects, etc.
The component for diffusion control function is multiple.

74

4“Safety assessment criteria” are not satisfied until “the time of work
(such as transfer, treatment, recovery, etc.) *3” for the risk source
contained in the component for diffusion control function.
The component or diffusion control function satisfying “safetyassessment criteria” exists at “the time of assessment”.

52

5

Integrity of diffusion control function has been assessed and “safetyassessment criteria” are satisfied until “the time of work (such astransfer, treatment, recovery, etc.)” for the risk source.
Frequency of occurrence of “contingency*4” is high, and whencontingency occurs countermeasures preventing diffusion of the risk
source contained in the component are not sufficient.
The component for diffusion control function is single.

29

6“Safety assessment criteria” is satisfied until “the time of work (such astransfer, treatment, recovery, etc.)” for the risk source.

15

201

Frequency of occurrence of “contingency” is high, and countermeasures
preventing diffusion of the risk source contained in the component are
not sufficient.
The component for diffusion control function is multiple.
7“Safety assessment criteria” are satisfied until “the time of work (such astransfer, treatment, recovery, etc.)” for the risk source.
Facilities dissatisfying “safety assessment criteria” exist in thesurrounding area, and the potentiality is high to make (receive) the
diffusion impact*5 of the risk source to (from) these adjacent facilities.
The component for diffusion control function is single.

88“Safety assessment criteria” are satisfied until “the time of work (such astransfer, treatment, recovery, etc.)” for the risk source.
The potentiality is high to make (receive) the diffusion impact of the risk
source to (from) these adjacent facilities.
The component for diffusion control function is multiple.

5

9“Safety assessment criteria” are satisfied until “the time of work (such astransfer, treatment, recovery, etc.)” for the risk source.
The potentiality is low to make (receive) the diffusion impact of the risk
source to (from) these adjacent facilities.
The component for diffusion control function is single.

3

10“Safety assessment criteria” are satisfied until “the time of work (such astransfer, treatment, collection, etc.)” for the risk source.
The potentiality is low to make (receive) the diffusion impact of the risk
source to (from) these adjacent facilities.
The component for diffusion control function is multiple.

2*1. This refers to “at the time” of study on SED score, i.e., “at the present time” of assessment.
*2. “Safety assessment criteria” described in this sentence refer to “the matters for whichmeasures should be taken” or “securing of diffusion control function within the scope of designbasis event”.
*3. This refers to the time of “recovery” of the risk source for disposition and carrying out for which
SED score shall be studied.
*4. External events (natural disasters, etc.) are postulated as contingencies.
*5. The potentiality of diffusion of the risk source exists to (from) adjacent facilities when facilities
receive external impact caused by contingencies or impact caused by any events (fire, etc.),
etc.

202

Category

Table A5-4 Criteria and score of WUD
Criteria(NDA definition is modified to enhance applicability to the caseof the Fukushima Daiichi NPS)

NDF
Score

1

The material is fuel (which contains fissile material) and active*1.
Necessary information (existent amount, existent location, radioactivity,etc.) for work including treatment, recovery, etc. is insufficient (cannot
be confirmed or estimated), and control and surveillance with
monitoring, etc. are unavailable.
Handling is impracticable for the current form or condition because ofreasons where the form is not proper for handling, or that it is not stored
in a special container.

100

2

The material is fuel and active (which has fissile properties).
Necessary information for work including treatment, recovery, etc. isinsufficient, and control and surveillance are unavailable.
Handling is practicable for the current form or condition because ofreasons where the form is proper for handling or that it is stored in a
special container.

90

3

Although the material is active, it is not fuel (but waste).
Necessary information for work including treatment, recovery, etc. isinsufficient.

74

4

The material is fuel and active (which has fissile properties).
Necessary information for work including treatment, recovery, etc. is
obtained (can be confirmed or estimated), and control and surveillancewith monitoring, etc. are available.
Handling is impracticable for the current form or condition.

50

5

The material is fuel and active (which has fissile properties).
Necessary information for work including treatment, recovery, etc. is
obtained, and control and surveillance are available.
Handling is practicable for the current form or condition.

30

6Although the material is active, it is not fuel (but waste).
Necessary information for work including treatment, recovery, etc.

177Although the material is inactive*2, it has physical or geometricalinstability.
Handling is impracticable for the current form or condition.

98

Although the material is inactive, it has physical or geometricalinstability.
Handling is practicable for the current form or condition.

5

9

The material is inactive and has no physical or geometrical instability or
has sufficiently low level of instability.
Handling is impracticable for the current form or condition.

3

10

The material is inactive and has no physical or geometrical instability or
has sufficiently low level of instability.
Handling is practicable for the current form or condition.

2*1 “Active” refers to possession of activity defined by CF at such a significant level as that activity
affects control and work.
*2 “Inactive” refers to non-possession of activity or possession of sufficiently low level of activity.

203

Table A5-5 Definition and score of SSR, BER and CU
Indicator

SSR

BER

Score

Criteria

25

Risks may be realized within 5 years.

5

Risks may be realized within 40 years.

1

40 years or over (There is very little possibility that risks are realized.)

20

Implementation of measures can reduce risks by 2 or more orders ofmagnitude or can facilitate control stepwise.

4

Implementation of measures can reduce risks by 1 or more order ofmagnitude, but cannot facilitate control.

1

Implementation of measures can only bring negligible risk reduction effects,
and cannot facilitate control, either.

20(1)+(2)=
5 to 6points4(1)+(2)=3 to 4points1(1)+(2)=
2 points

CU(1) Assessment for the present state
1 point: Major nuclear types and diffusion pathways aremonitored.
2 points: Monitored, but insufficient data for construction ofassessment model
3 points: Not monitored(2) Assessment on future prediction
1 point: Sufficient site characteristics are obtained forconstruction of assessment model.
2 points: Major characteristics representing the site are
obtained.
3 points: There is no model usable for future prediction

204

Attachment 6

Risk sources that are not explicitly addressed in the major risk sources

Major risk sources are listed in the Table 1 in Chapter 2 of the body part. Looking ahead to thedecommissioning of the entire Fukushima Daiichi NPS, it is necessary to focus on risk sources thatare not explicitly addressed in the major risk sources. Table A6-1 focuses on waste existed before
the accident and radioactive materials with low concentration diffused by the accident, and issummarized with reference to Measures for Mid-term Risk Reduction at TEPCO’s Fukushima
Daiichi NPS (Risk Map)” provided by the NRA.151.

Table A6- 1
Issue

Liquidradioactive
materials

Spent fuelRisk sources that are not explicitly addressed in the major risk sources (1/3)
Risk source

Descriptions

Sludge on the floor in
the buildings

The floor surface of turbine buildings and radioactive waste
disposal buildings of Units 1 to 4, waste process building and Unit
4 reactor building remain exposed, and radioactivity of sludge after
the exposure was 1.9×1013Bq152. For reactor buildings of Units 1
to 3, process main building and high temperature incinerator
building, stagnant water processing is underway.

Underground watertank

The residual water in all the underground water tanks werecompletely recovered 153 . Dismantling and removal policies areunder consideration.

Accumulated water onsite

Extracted by the comprehensive risk inspection performed in
2015154. Since then, the concentration of radioactive materials andvolume of water are being checked accordingly 155.

Fuel in Units 5/6 SFP

Unit 5 : 1,374, Unit 6 : 1,456156

Spent control rods,
etc.

Spent control rods, etc.: 23,547. Shroud fragments, etc.:
193 m3 157. The major nuclide is Co-60.

In-pool water

Salt removal in Units 2 to 4 was completed in 2013.

151

NRA, “Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Risk Map)”, (March 2023
Edition)152
The 87th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 3-5: Progressof the treatment of stagnant water in buildings, etc.”
153
The 44th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water “Reference 3-6: On-site Monitoring Status (Conditions of Water Discharge Channels inUnits 1 to 3 and Underground Water Storage Tanks)”
154
Comprehensive Risk Inspection of Fukushima Daiichi NPS that impacts outside the Site Boundary - Review
Results - (April 28, 2015) Tokyo Electric Power Co., Inc.
155
The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water “Reference 1: Status of contaminated water and other accumulated wateron the premises (as of March 24, 2022)”
156
The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water “Reference 3-2 : Storage status of spent fuel, etc.”
157
NRA, Material of interview with the licensee “Solid Waste at Fukushima Daiichi NPS” June 18, 2021, Tokyo
Electric Power Company Holdings, Inc.

205

Table A6- 1
Issue

Risk sources that are not explicitly addressed in the major risk sources (2/3)
Risk source
Rubbles aroundbuildings

Solidradioactive
materials
Waste before theearthquake

Countermeasures toexternal
events, etc.

Importantissues toprogress
decommissioning

Descriptions
Dismantling of rubbles scattered on the roof floor of thebuildings due to hydrogen explosions is now in operation andplanned. The amount of rubbles has not been confirmed.

185,816 drums are stored158. The major nuclide is Co-60.

Rainwater inleak into
buildings

Rubble on the roof was removed and waterproofing was newly
provided. Purification materials were installed in the gutters.
Check valves were installed in the drainpipes. The roof drain
was repaired and closed 159 . Facing of the Elevation T.P.2m,
T.P.6m and T.P.8.5m was completed160.

Megafloat

The work of bottoming and internal filling was completed161.
Revetment maintenance and embankment work are underway.

Dust in operating floor

Below the target value of release control (1×107 Bq/h).
Gradually declining162.

Radiation source on
the 3rd and 4th floorsof Unit 3 R/B

On the 3rd floor, beams at several locations were damaged. A
maximum of 45 mSv/h was measured. On the 4th floor, 104
mSv/h was observed163.

Drainage

In drainage A, Cs-137: lowered to ND ~ 23 Bq/L 164. In
drainage K, the contamination source on the roof of the Unit 2
Reactor building was removed, and the contamination level fell
to 67 Bq/L. In addition, purification materials were installed165,
and measures such as operation of discriminating-type PSF
monitors were taken166.

158

NRA, Material of Interview with Licensee “Restoration Status of Exhaust Radiation Monitor at Auxiliary
Common Facilities for Common Spent Fuel Storage Pool and Ventilation & Air Conditioning System at Fuel
Storage Area of Fukushima Daiichi NPS” September 21, 2018, Tokyo Electric Power Company Holdings, Inc.
159
The 78th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Reference 3-1: Progress Status in Rooftop Rainwater Measures”
160
The 84th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 1-3: Progressand status of studies on measures to control the generation of contaminated water, amount of groundwaterand rainwater inleak per building”
161
The 81st Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Reference 3-1: Progress Status of Megafloat Project at Fukushima Daiichi NPS to
Reduce Tsunami Risks”
162
Daily Analysis Results of Radioactive Materials at Fukushima Daiichi NPS, (Website), Tokyo Electric Power
Company Holdings, Inc.
163
The 14th Study Committee on Accident Analysis of the Fukushima Daiichi NPS “Reference 3: Progress of onsite Investigation”
164
The 32nd Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 2: Status of
measures for reducing the concentration of waste water in drainage K”
165
The 63rd Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 2: Measures
for rainwater inleak control (Progress status of installing purification materials for rainwater drainage in turbine
buildings)”
166
The 74th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water “Reference 3-6: Starting of operation of PSF monitor in the drainage K”

206

Table A4- 1
Issue

Risk sources that are not explicitly addressed in the major risk sources (3/3)

Exhaust stack
Importantissues toprogress
decommissioning

Descriptions

Risk source

Contaminated soil

Exhaust stack of Units 1/2 : dismantlement work was carried out
since August 2019, and the upper part of 61 m out of the totalheight of 120 m was divided into 23 blocks in total for
dismantling. On May 1, 2020, a lid was installed on a barrel 59
meters above the ground to prevent rainwater inleak, anddismantling was completed167.
Exhaust stack of Units 3/4 : Measured 3mSv/h at the base168.
As a result of the topsoil analysis, more than half of thesamples are in excess of the designated standards (8,000
Bq/kg) based on the Act on Special Measures Concerning theHandling of Environmental Pollution by Radioactive
Materials169

167“Completion of Dismantling of Exhaust Stack of Units 1/2 at Fukushima Daiichi NPS” (May 1, 2020), Tokyo
Electric Power Company Holdings, Inc.
168
The 19th Committee on Accident Analysis of the Fukushima Daiichi NPS “Reference 4 : Interim report on theinvestigation and analysis of the accident at TEPCO’s Fukushima Daiichi NPS (proposal)”」169
Results of daily analysis of Radioactive substances at Fukushima Daiichi Nuclear Power Station (Website ,Tokyo Electric Power Company Holdings, Inc.

207

Attachment 7

Change in risk over time

Overview of the concept of risk management in the UK is shown in Fig. A5-1. Even if the current
risk level is plotted in the white region of the graph, it does not mean such risk level can always be
accepted over time, but the time will come when such risk level cannot be accepted in the future(yellow region). In addition, as time passes, the risk level may increase caused by degradation offacilities and risk sources (represented by the dotted line). On the other hand, when risk reduction
measures are taken, the risk level can be reduced so that it may not reach the unacceptable region(red region) with careful preparation and thorough management, although it may be temporarily
increased. In this way the risk level shall be targeted to be sufficiently reduced (represented by thesolid line) so that it may not reach into the unacceptable or intolerable region.

Fig. A7-1 Change in risk over time170

170

V. Roberts, G. Jonsson and P. Hallington, “Collaborative Working Is Driving Progress in Hazard and Risk
Reduction Delivery at Sellafield” 16387, WM2016 Conference, March 6-10, 2016. M. Weightman, “TheRegulation of Decommissioning and Associated Waste Management” 1st International Forum on theDecommissioning of the Fukushima Daiichi Nuclear Power Station (April 2016).

208

Attachment 8

Coverage of fuel debris retrieval

In the Mid-and-Long-term Roadmap issued on December 21, 2011, fuel debris is described as“material in which fuel and its cladding tubes, etc. have melted and re-solidified”, namely, fuel debris
is “fuel assembly, control rod and structures inside reactor have melted and solidified together”
according to the report by IAEA171,172.
The condition inside PCV is as shown in Fig. A8-1, as the comprehensive estimations from theinside investigation of reactor, the past accidents including TMI-2 or ChNPP-4, and the result of thesimulation test. It does not show any of specific unit. For more detail, as shown in the Fig A8-1, fueldebris can be classified by form such as damaged pellets, debris, crust, etc.

Fig. A6-1 Estimated inside of the PCV of the Fukushima Daiichi NPS
171

International Atomic Energy Agency Experiences and Lessons Learned Worldwide in the Cleanup andDecommissioning of Nuclear Facilities in the Aftermath of Accidents, IAEA Nuclear Energy Series No. NW-T2.7, Vienna (2014)
172
Managing the Unexpected in Decommissioning, IAEA Nuclear Energy Series No. NW-T-2.8, Vienna (2016)209

Since nuclear fuel material requires considerations to prevent criticality, it is rational that objects
which exist inside PCV should be broadly sorted into two from the viewpoint of retrieval,containment, transfer and storage. The one includes nuclear fuel material and the others. The onethat does not include nuclear fuel material is to be treated as a radioactive waste in case radioactive
cesium or cobalt are contained or adhered.
Based on this, an example of fuel debris concept as a retrieval target of fuel debris is as shownin Fig. A8-2. Objects generated by core damage have been classified depending on necessity ofcriticality measures and the content of fuel, in spite that a lot of names are used according to thecontent of fuel component or form in appearance.

Fig. A6-2 An example of organized concept of fuel debris as fuel debris retrieval target at the
Fukushima Daiichi NPS【Glossaries and Terms】
FCM: Fuel Containing Materials. It refers broadly that molten fuel component comes tosolidify in conjunction with structural materials. It is also called lava-like FCM due toits appearance.
Corium: A substance that mainly fuel assembly and component of control rod as corecomponent have molten and solidified.
Crust: A hard outer layer or shell on the surface. When molten fuel is solidified, it may
become a hard solid state of shell because of higher cooling speed on the surface
layer.
MCCI product: A product generated by Molten Core Concrete Interaction, which includes calcium,silicone, etc. which are concrete component.
Fuel deposits: Molten fuel that has adhered to and solidified on components that do not originallycontain fuel components, like CRD housing and grating, where fuel adhesions can beobserved by sight.
Fuel contaminant : A substance that adhering molten fuel cannot be confirmed by sight, but fuelcomponent can be detected with α ray detector. It is impossible to locate fuelcomponent other than using by electron microscope because particle of adhered fuelcomponent is extremely small and whit.

210

Attachment 9

Changes in considerations on retrieval methods in the previous
Technical Strategic Plans

In the Technical Strategic Plans 2015 and 2016, options for fuel debris retrieval methods
were explored based on a combination of the PCV water level (full submersion, submersion,
partial submersion, and dry methods) and access directions (top, side, and bottom-access) tofuel debris. As a result, three priority methods ([1] Submersion-Top access method, [2] Partial
submersion-Top access method, and [3] Partial submersion-Side access method) have been
selected and examined. (See Fig. A9-1 to A9-3）
Combination of PCV water level and access direction
Access direction (see Fig. 3)
Top
Full
submersion
PCV water Submersion
level
Partial(See Fig. 2)
submersion

Side

Bottom- Possibility of water flowing
out of the access openinga.

- Difficulty in establishing a
new access routeb.

- Difficulty in evaluatingc.

cooling performance

Dry

Examine the methods based on these factors:

a.
b.
c.

Method of focus and its name
Full submersion and submersion
methods with access from the top
Partial submersion method withaccess from the top
Partial submersion method withaccess from the side

Fig. A9-1→→→

Submersion-Top accessmethodPartial submersion-Top
access method
Partial submersion-Sideaccess method

Examination of the methods by a combination of the PCV water level andaccess directions to fuel debris

211

Full submersion method Submersion method Partial submersion method

Dry method

Full submersion method: Fill the reactor well to the top with water.



Submersion method: Fill water to the top from the point where fuel debris is
distributed.

(Supplement) It is currently assumed that fuel debris is not distributed
above the core region, and the water level above the upper
end of the core region is referred to as the submersion
method.
Partial submersion method : Fill water to a level below the highest point of the
distributed fuel debris, and retrieve fuel debris while pouring
water into the fuel debris that is exposed to the air.
(Supplement) It is currently assumed that there is fuel debris exposed tothe air at the water level below the upper end of the coreregion. This is referred to as the partial submersion method.

Dry method: Expose the entire area of the distributed fuel debris to theair, with no water-cooling or spraying at all.

Fig. A9-2 Classification of methods according to the PCV water level

Top-access

Side-access

Bottom-accessFig. A9-3

Access direction to fuel debris212

In the Technical Strategic Plan 2017, the feasibility of the above three fuel debris retrieval
methods was evaluated on three technical requirements (① containing, transferring, and storing;② handling of waste generated during retrieval operations; and ③ safeguards for the safe andstable storage of fuel debris in addition to nine technical requirements (① containment functions;② cooling functions; ③ criticality control; ④ structural integrity; ⑤ reduction of radiation exposure;⑥ work safety; ⑦ access route; ⑧ device and equipment development; and ⑨ system installations
and area construction}), all of which should be satisfied for the safe retrieval of fuel debris. Then,based on the comprehensive evaluation based on the five guiding principles (safe, proven, efficient,
timely, and field-oriented), strategic recommendations for determining a fuel debris retrieval policy
were made (recommendations for determining a fuel debris retrieval policy and post-determination
actions. In the Mid-and-Long-term roadmap revised in September 2017, the fuel debris retrieval
policy was determined as follows based on the details of the strategic recommendations.

Policy on Fuel Debris Retrieval①

Step-by-step approach
In order to reduce associated risk as early enough, adopt a step-by-step approach to flexibly
coordinate the direction based on information that comes out as retrieval proceeds, after setting methodof fuel debris retrieval to be started first,
Fuel debris retrieval operation and internal investigations of PCV/RPV should be performed in acoordinated, integrated manner. Fuel debris retrieval starts from a small-scale and the scale of retrieval
should be expanded by step up, while reviewing operations flexibly based on new findings obtained
from the property of fuel debris and working experiences.

②

Optimization of entire decommissioning work
Examine fuel debris retrieval work as a comprehensive project aimed at total optimization, frompreparation to cleanup through retrieval work, transportation, processing and storage, including
coordination with other construction works at the site.

③

Combination of multiple methods
Combine the optimum retrieval methods for each unit, depending on the locations where fuel debris
is considered to be present, instead of making an assumption that all the fuel debris is to be taken out
using a single method.
At present, from an accessibility standpoint, examine assuming sideward access to the bottom of
the primary containment vessel and downward access into the reactor pressure vessel from the upper
part of the vessel.

④

Approach focused on partial submersion method
Given the technical difficulty of stopping leaks at the upper part of the primary containment vessel
and expected radiation doses during such works, the full submersion method is technically difficult at
present, so make efforts to focus on the partial submersion method that is more feasible.
However, given the advantages of the total submersion method, such as being effective in providing
shielding against radiation, consider adopting the full submersion method in the future depending on
the progress of R&D.

⑤

Prioritizing fuel debris retrieval by side access to the bottom of the PCV
According to an analysis, fuel debris is expected to be present in both the bottom of PCV and theinside of RPV of each unit, although their distribution varies among the units. In view of mitigating risks
from fuel debris as early enough, while minimizing any increase in risks that might be caused byretrieval, prioritize retrieval of fuel debris in the bottom of PCV by sideward access by taking thefollowing into account:○

The bottom of PCV is most accessible and a certain amount of knowledge about it has already been
accumulated through the investigation inside PCV.

213

○
○

There is a possibility that fuel debris retrieval could be started earlier.
Fuel debris retrieval could be performed at the same time as spent fuel removal

The Technical Strategic Plans 2018 and 2019 examined the first implementing unit and its fueldebris retrieval method. In the process of examining the first implementing unit and its retrieval
method, based on the results of research and development and PCV internal investigations, andaccording to the scenario (draft work schedule) in light of the conceptual study of the fuel debris
retrieval system in TEPCO’s preliminary engineering and actual site applicability by unit, the overall
optimization combining scenarios for each unit and the site-wide plan were considered in order toprovide recommendations for determining fuel debris retrieval methods for the first implementing
unit. The examination flow is shown in Fig. A9-4.
As a result of the above discussion, as “a fuel debris retrieval method” involving a series ofcontinuous operations from fuel debris retrieval, containing/transferring to safe storage, the plan is
to initiate “timely” small-scale retrieval while minimizing the increase in risk associated with theretrieval, leading to reducing the overall risk of fuel debris in Units 1 - 3 by obtaining “timely”
information/experience toward expanded-scale retrieval and retrieval other than in the first
implementing unit. Specifically, using the existing safety systems without significantly changing thesite condition, in principle, evaluation has indicated that fuel debris retrieval may be carried out“safely, reliably, and promptly,” starting with methods such as gripping and sucking with arm-typeaccess equipment and an airtight enclosure for containing the equipment, which have goodprospects for actual site applicability. In addition to gripping and sucking, cutting fuel debris during
the small-scale retrieval should also be performed to the extent that significant modification of theexisting safety systems is not required.

214

Fig. A9-4 Flow of examinations for determining the fuel debris retrieval method for the
first implementing unit”
215

The Technical Strategic Plans 2020 and 2021 proposed approaches and policies for fuel debris
retrieval methods. Since no new progress has been made in examining the methods themselves,
however, this Attachment omits the details of the Strategic Plans
Lastly, the status of examining retrieval methods in the Technical Strategic Plan 2022 is shown
below.
TEPCO is currently conducting a conceptual study on the further expansion of fuel debris
retrieval in scale, starting with Unit 3, and examining scenarios and methods for fuel debris retrieval.
The following are the works implemented in FY 2021. In examining methods, the work process
was roughly divided into two processes: retrieval and transfer/storage. The retrieval process was
further divided into preparation work and work inside the PCV. The transfer/storage process was
divided into work outside the PCV and transfer/storage work. This means that there were four major
work phases, from Phase 1 to Phase 4 (see Fig. Fig. A9-5). To examine methods by work phase,the potential methods for each work phase were identified exhaustively, not ruling out any
possibilities (setting a longlist), and then methods with low rationality were screened out (organizing
a shortlist). Next, each of the shortlisted methods was scored by multi-attribute decision analysis(MADA) evaluation.173 The basic specifications and conditions of these discussed methods weretentatively established to examine methods by incorporating the development results of the Projectof Decommissioning, Contaminated Water and Treated Water Management, TEPCO's engineering
output, and technical knowledge in Japan and overseas, and then issues and risks were identified
and summarized (see Fig. Fig. A9-6).

(TEPCO material edited by NDF)

Fig. A9-5

Conceptual diagram of each work phase (a division of process)173

A method for determining the relative merits and demerits for decision-making based not only on one attribute(evaluation item) but also on multiple attributes (evaluation items). This methodology is applied to the process
of examining the methods, and those with a high score calculated from “Σ (Evaluation of each attribute(evaluation item)) × (Weight of each attribute (evaluation item) = Importance)” will remain. As this was used to
examine retrieval methods, it is thought that evaluation by this methodology will be effective in narrowing down
multiple method options (e.g., access devices) hereafter.

216

(TEPCO material edited by NDF)

Fig. A9-6

Examination flow for retrieval methods in FY 2021 (outline)

As a result of the above examination, the partial submersion methods and submersion methods
are in discussion. This partial submersion method does not use the top or side access method
alone, which has been examined previously, but combines them (see Fig.A9-7) for a conceptual
drawing of the current partial submersion method).
On the other hand, the current submersion method differs from the conventional concept ofsubmersion, as shown below. Although the conventional submersion method (filling the PCV withwater: the PCV submersion method) had advantages in the radiation shielding effect, it wasdetermined to have low feasibility given the technical difficulty of sealing the water in the upper
part of the PCV and the radiation exposure during work (see Fig. A9-8) for the conceptual
drawing of the conventional submersion method [PCV submersion method]). For this reason, theprevious retrieval policy in Mid-and-Long-term Roadmaps 2017 and 2019 focused on the partial
submersion method and it was planned to examine the submersion method again sometime in
the future based on R&D progress. Unlike the PCV submersion method mentioned above, thissubmersion method uses a new idea to submerge the reactor building by enclosing the entire
reactor building with a new structure called a shell structure as containment barriers (see Fig. A99) for a conceptual drawing of the current submersion method [shell method])◆Common to Figures 14 to 16
Access direction of
the devices
Transfer direction of fuel debris
and radioactive waste

Fig. A9-7 An example of partial submersion method(Conceptual drawing of combination of top and side access)217

Fig. A9-8 Reference : Conventional
submersion method(Conceptual drawing of the PCV
submersion method)

Fig. A9-9 An example of submersion methods(Conceptual drawing of shell method)

After FY 2022, the feasibility of each method will be examined. Since there are several possible
countermeasures against issues and risks, the options will be narrowed down step by step while
proceeding with the design once the feasibility has been confirmed to some extent. In addition,
hold points will be established to evaluate the actual site applicability, technological feasibility, andproject continuity. If the criteria are not satisfied, the following items ① and ② will be considered.
①

Reconsider measures to address issues and risks without changing the method②Start over from the identification of issues and risks of other methods.

218

Attachment 10

Continuation of accident analysis activities (clarification of events that
occurred at the time of the accident) (progress of recent activities)TEPCO is incorporating the findings obtained through the PCV internal investigations and theanalysis data of the collected deposit samples into studies of fuel debris retrieval methods andstorage management.
In FY 2022, PCV internal investigations in Unit 1 were conducted jointly by TEPCO andIRID/Hitachi-GE Nuclear Energy, Ltd. using an submersible ROV, and they succeeded in observing
the conditions inside the pedestal for the first time since the accident.174, 175, 176, 177, 178, 179, 180, 181, 182,
183, 184, 185, 186, 187

Neutron and gamma-ray measurements revealed that fuel-containing substanceswere deposited extensively in the drywell area, and image analysis revealed that only the lower
concrete was lost and that only the rebar remained in the vicinity of the pedestal opening and almost

174

The 101st Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Status of PCV internal investigation in Unit 1,” April 27,
2022
175
The 102nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Status of PCV internal investigation in Unit 1,” May 26,
2022
176
The 103rd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Status of PCV internal investigation in Unit 1,” June 30,
2022
177
The 104th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Status of PCV internal investigation in Unit 1,” July 28, 2022
178
The 106th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: PCV internal investigation in Unit 1 (latter part),” September
29, 2022
179
The 107th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: PCV internal investigation in Unit 1 (latter part),” October27, 2022
180
The 108th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Policy of PCV internal investigation in Unit 1 (latter part),”November 25, 2022
181
The 109th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water/Treated Water, “Material 3-3: Policy of PCV internal investigation in Unit 1 (latter part),”December 22, 2022
182
The 30th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-1: Status of PCV internal investigation in Unit 1 [International Research Institute for
Nuclear Decommissioning, Tokyo Electric Power Company Holdings Inc.],” June 30, 2022
183
The 31st Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-1: Status of PCV internal investigation in Unit 1 [International Research Institute for
Nuclear Decommissioning, Tokyo Electric Power Company Holdings Inc.],” September 6, 2022
184
The 32nd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-1: PCV internal investigation in Unit 1(latter part) [International Research Institute for
Nuclear Decommissioning, Tokyo Electric Power Company Holdings Inc.],” October 31, 2022
185
The 33rd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-1: Information gained from PCV internal investigation in Fukushima Daiichi Nuclear Power
Station Unit 1 (Summary of the investigation of the first part) [Tokyo Electric Power Company Holdings Inc.],”December 5, 2022
186
The 34th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-1: PCV internal investigation in Unit 1 (latter part) [Tokyo Electric Power Company
Holdings Inc.],” December 20, 2022
187
The 36th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 3: PCV internal investigation in Unit 1 (latter part) [Tokyo Electric Power Company HoldingsInc.],” March 7, 2023

219

the entire circumference of the inner wall surface. Based on these observations, the refinement of
the internal PCV condition analysis of Unit 1 is underway.188, 189, 190, 191
In addition, TEPCO is independently investigating the reactor building of each unit. In FY 2021
and FY 2022, investigations were conducted including the following: the contamination condition of
the fifth floor of the reactor building of Unit 2; the damage condition of the reactor building of Unit
3; the exterior of the reactor building of Unit 1; 3D laser scanner investigations of the reactor buildingof Unit 4; the interior of the SGTS, the fuel rod handling control room of Unit 2; the RCW heatexchanger of Unit 1; and the sludge on the underground floor of the turbine building of Unit 1.192,
193 , 194 , 195 , 196 , 197 , 198

The analysis of the samples collected in the residual water survey of theresidual heat removal system (hereinafter referred to as “RHR”) heat exchanger of Unit 3 was also
performed.199, 200 In addition, TEPCO and the JAEA jointly incorporated the results of the latest
internal investigation of Units 2 and 3 to conduct an evaluation of the accident progression of Units
2 and 3 and a detailed analysis of the RPV failure and the fuel debris transfer process by using the188

The 30th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Reference 1: Fuel debris distribution estimation by analysis and evaluation [International ResearchInstitute for Nuclear Decommissioning, The Institute of Applied Energy],” June 30, 2022
189
The 32nd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-2: Examination of events related to concrete observed in PCV internal investigation in
Fukushima Daiichi Nuclear Power Station Unit 1 [Graduate School of Osaka University],” October 31, 2022
190
The 33rd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 3: Report on investigation/examination results of unconfirmed and unexplained mattersrelated to the detailed progression mechanism after the Fukushima Daiichi Nuclear Power Station accident 6th progress report - [Tokyo Electric Power Company Holdings Inc.],” December 5, 2022
191
The 34th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 1-2: Examination of events related to concrete observed in PCV internal investigation in
Fukushima Daiichi Nuclear Power Station Unit 1 [Osaka University],” December 20, 2022
192
The 30th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 3-1: Implementation status of on-site investigation (investigation of the fifth floor of thereactor building of Unit 2; investigation of damage to the reactor building of Unit 3; investigation of the exteriorof the reactor building of Unit 1; 3D laser scanner investigation of the reactor building of Unit 4; andinvestigation of samples of cut SGTS piping of Units 1 and 2)," June 30, 2022
193
The 31st Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 6-1: Investigation of Unit 2 fuel handling machine control room [Tokyo Electric Power
Company Holdings Inc.],” September 6, 2022
194
The 32nd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 4-3: Contamination of Unit 2 shield plug [Tokyo Electric Power Company Holdings Inc.],”October 31, 2022
195
The 32nd Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 6-1: Investigation of Unit 2 fuel handling machine control room [Tokyo Electric Power
Company Holdings Inc.],” October 31, 2022
196
The 36th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 2-1: Sampling of residual gas in the RCW heat exchanger inlet header piping and water inthe heat exchanger in Unit 1 [Tokyo Electric Power Company Holdings Inc.],” March 7, 2023
197
The 36th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 2-2: Condition of damage on RCW piping [Tokyo Electric Power Company Holdings Inc.],”March 7, 2023
198
The 36th Meeting of The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power
Station, “Material 4-2: Investigation of sludge in the basement floor of the turbine building of Unit 1 [Tokyo
Electric Power Company Holdings Inc.],” March 7, 2023
199
Supplementary budget in FY 2018, the Project of Decommissioning and Contaminated Water Management(Development of analytical and estimation techniques for characterization of fuel debris), implementation
results for FY 2021, International Research Institute for Nuclear Decommissioning (IRID), November 2022
200
Supplementary budget started in FY 2021, the Project of Decommissioning and Contaminated Water
Management (Development of analytical and estimation techniques for characterization of fuel debris),
implementation results for FY 2022, International Research Institute for Nuclear Decommissioning (IRID),
2023

220

analysis code.201 The findings obtained from these investigations and analysis, are incorporated
into the diagram that estimates the condition inside the reactor vessel, which is used to determine
the cause of the accident.202, 203, 204, 205 The analysis data and diagram are available to the public
on debrisWiki.206 Concerning the analysis of the hydrogen explosion in Units 1 and 3, combustion
tests using materials equivalent to actual equipment are being conducted to estimate the amountof combustible gas from cables for evaluating hydrogen explosion conditions. The generation
conditions of combustible gas and its composition are also under investigation.207, 208, 209, 210, 211
The NRA,212 which is in charge of the ongoing accident investigation and analysis, has established
The Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station incooperation with TEPCO and has been engaged in studies on accident analysis.213, 214, 215 The
interim report for FY 2020 showed the study results of contamination of the SGTS piping systemsof Units 1 to 4 and the high-radiation dose on the lower face of the shield plugs of Units 2 and 3
concerning the release/leakage paths and points of fission products from PCVs. Regarding thehydrogen explosion and the operating status of the reactor cooling equipment, the analysis of the201

Supplementary budget started in FY 2022, the Project of Decommissioning and Contaminated Water
Management (Development of analytical and estimation techniques for characterization of fuel debris[technical development for estimation of RPV damage condition]), implementation results for FY 2022, Japan
Atomic Energy Agency (JAEA), 2023
202
The 90th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 3-3: Status of countermeasures against highly contaminated shield plugs ofUnit 2,” May 27, 2021
203
The 91st Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 3-3: Status of countermeasures against highly contaminated shield plugs ofUnit 2,” June 24, 2021
204
The 94th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 3-3: Investigation of drilling hole on the shield plug of the Unit 2 operating
floor,” September 30, 2021
205
The 95th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 3-3: Investigation of drilling hole on the shield plug of the Unit 2 operating
floor,” October 28, 2021
206
debrisWiki main page: https://fdada-plus.info/wiki/index.php?title=メインページ
207
The 29th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 11: Analysis results of gases generated by pyrolysis of organic materials in BWR primary containment vessel[Japan Atomic Energy Agency (JAEA)],” April 26, 2022
208
The 29th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 12: Evaluation test results of the amount of combustible gases generated from cables, paints, and insulators[Tokyo Electric Power Company Holdings Inc.],” April 26, 2022
209
The 31st Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 41: Plan for analysis of pyrolysis product gas generated from organic materials in BWR primary containment
vessel [Japan Atomic Energy Agency (JAEA)],” September 6, 2022
210
The 31st Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 42: Evaluation plan for combustible organic gas [Tokyo Electric Power Company Holdings Inc.],” September 6,
2022
211
The 33rd Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 12: Evaluation test results of the amount of combustible gases generated from cables, paints, and insulators[Tokyo Electric Power Company Holdings Inc.],” December 5, 2022
212
Article 4, Paragraph 1, Item 11 of the Act for Establishment of the Nuclear Regulation Authority, “Affairs
concerning investigations of causes of accidents that have resulted from the operation, etc., of reactors andcauses of damage that has arisen from nuclear accidents”
213
Interim report on the investigation and analysis of the accident at TEPCO’s Fukushima Daiichi Nuclear Power
Station - Review from September 2019 to March 2021 - March 5, 2021
214
Nuclear Regulation Authority, "Interim report on the investigation and analysis of the accident at TEPCO’s
Fukushima Daiichi Nuclear Power Station,” June 19, 2021
215
Interim report on the investigation and analysis of the accident at TEPCO’s Fukushima Daiichi Nuclear Power
Station (2023 version)

221hydrogen explosion situation in Units 1 and 3 and the examination of the pressure fluctuation in the
RPV and PCV in Unit 3 were carried out.212, 213 In addition, the interim report for FY 2022 discussed
the movement mechanism of Cs -137 based on the contamination of vent pipes and shield plugs
and examined the impact of core materials collapsed in Units 1, 2, and 3 on PCVs.214 Based onthese investigations, the NRA and TEPCO jointly conducted dose measurements inside the drilling
holes in the shield plug of Unit 2 and geometry measurements to check for deformation of the shieldplug.
The NRA established the Liaison Council on the accident investigation of Fukushima Daiichi
Nuclear Power Station for communication and coordination of accident analyses anddecommissioning between the NRA, the Agency for Natural Resources and Energy, TEPCO, andNDF so that they can address cases where decommissioning work, such as facility dismantling,affects on-site information necessary for accident analysis, and, conversely, other cases where
efforts toward accident analyses interfere with decommissioning work. In FY 2021, the mediumterm risk reduction target map in decommissioning was revised and the goal for about ten years in
the future was presented at the Liaison Council.216 In addition, the aforementioned PCV internal
investigation of Unit 1, the stagnant gas217 in the RCW heat exchanger inlet header piping, and theremoval of SGTS piping in Units 1 and 2218 were shared.

216

The 9th Liaison Council on the accident investigation of Fukushima Daiichi Nuclear Power Station, “Material 11: Revision of Measures for Mid-and-long-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Risk
Map),” May 13, 2022
217
The 10th Liaison Council on the accident investigation of Fukushima Daiichi Nuclear Power Station, “Material
3-1: Residual gas in the RCW heat exchanger inlet header piping in Unit 1 [Tokyo Electric Power Company
Holdings Inc.],” December 13, 2022
218
The 10th Liaison Council on the accident investigation of Fukushima Daiichi Nuclear Power Station, “Material
3-2: Progress of removing the standby gas treatment system piping in Fukushima Daiichi Nuclear Power Station
Units 1 and 2 [Tokyo Electric Power Company Holdings Inc.],” December 13, 2022

222

Attachment 11

Terms related to radioactive waste management

IAEA Safety Requirements GSR-Part 5 219 explains that predisposal of radioactive waste
encompass all stages of radioactive waste management from generation to disposal, including
processing, storage and transportation. Terms related to the management of radioactive waste as
defined in the IAEA glossary are shown in Fig A11-1. Within the pre-disposal management,
processing of radioactive waste is classified into pretreatment, treatment and conditioning.
Processing is carried out to be in the form of waste suitable for selected or anticipated disposal
options. Radioactive waste may also be stored in for its management, therefore it is thought to benecessary that the form is suitable for transportation and storage.
Processing: a generic term used to refer to thefollowing steps that change waste
characteristics
Pretreatment: a process before treatment(Treatment)
Treatment: a process intended to benefit safety
and economics efficiency by changing waste
characteristics
Conditioning: a process of manufacturing awaste package suitable for handling,transportation, storage and / or disposal

Fig. A11-1 Terms related to radioactive waste management (IAEA)220 and their translation
examples (For the Japanese translation example, refer to the materials of the Japan
Atomic Energy221,222)
219

IAEA, Predisposal Management of Radioactive Waste, IAEA Safety Standards Series No. GSR Part 5, (2009).
(NSRA, IAEA Safety Standard/Predisposal of Radioactive Waste/General Safety Requirement 5, No. GSR-Part5,
July, 2012)
220
IAEA, IAEA Safety Glossary Terminology Used in Nuclear Safety and Radiation Protection 2007 Edition, p.216,(2007).
221.
AESJ, The Report of 2013, - Organizing information of radioactive waste and matters to be considered for solving
the issues (p.7), March 2014, the Expert Committee, “Processing /disposal of radioactive waste generated by
the accident of Fukushima Daiichi NPS”
222
AESJ, Seiya Nagao and Masafumi Yamamoto, “Introduction to radioactive waste - Management of radioactive
waste from operation and decommissioning of nuclear and other facilities” Perspective of radioactive waste
management, the 56 of (9) of Journal of the Atomic Energy Society of Japan, p.593, (2014).

223

Attachment 12

Disposal of radioactive waste223,224,225

１．International classification of radioactive waste
Radioactive waste contaminated with radioactive materials is generated through operation anddismantling of nuclear power plants and the use of radioisotopes in medical and industrial
applications. Radioactive waste shall be classified appropriately according to the radioactivity leveland properties of waste, types of radioactive materials, etc., and strictly controlled, and then shallbe reasonably processed and disposed of so as not to affect the human living environment.
The IAEA's Specific Safety Requirements SSR-5 “Disposal of Radioactive Waste” (2011) 226
specifies that a preferred strategy for the management of radioactive waste that is internationallyagreed is to contain the waste and isolate it from the living environment, while minimizing thegeneration of radioactive waste. The required isolation and containment depend on the magnitudeof the hazards of the waste and the time, thereby a disposal option (design and depth of facilities)
being selected accordingly.
The IAEA’s General Safety Guide GSG-1 “Classification of Radioactive Waste”227 indicates therelationship between the classification of radioactive waste and disposal options depending on themagnitude of the hazards (amount of radioactivity) and the duration (the half-life) of the radioactive
waste, as shown in Fig. A12-1. Each classification is also shown in Table A12-1.

Fig. A12-1 Conceptual diagram of waste classification

223

Osamu Tochiyama, Principles and Basics of Radioactive Waste Disposal, Radioactive Waste Management
Funding and Research Center (a Public Interest Incorporated Foundation) (2016)
224
https://www.enecho.meti.go.jp/category/electricity_and_gas/nuclear/rw/
225
https://www.fepc.or.jp/nuclear/haikibutsu/index.html
226
IAEA SSR-5 "Disposal of Radioactive Waste" (2011)
227
IAEA GSG-1 "Classification of Radioactive Waste" (2009)224

Table A12-1

Classification of radioactive waste in GSG-1

Classification

Description of Classification

Exempted waste (EW)

Waste satisfying the criteria for clearance, exclusion and exemption
from regulatory control for radiation protection purposes

Very short-lived waste(VSLW)

Waste that is decay-stored for a limited period of time up to several
years and then exempted from regulatory control, as approved by
the regulatory body.

Very low-level waste(VLLW)

Waste that does not necessarily satisfy EW standards but does not
require high-level containment and isolation. Suitable for disposal inshallow landfills where regulatory control is limited.

Low level waste (LLW)

Waste that exceeds clearance levels but has a limited amount oflong-lived nuclides. Rigid isolation and containment are required for
periods of up to several 100 years and are suitable for disposal inengineering facilities in shallow soils.

Intermediate level waste(ILW)

Waste that requires higher-level containment and isolation than thenear surface disposal because of the nuclides it contains, especiallylong-lived nuclides. However, considerations on heat removal are
hardly required. Because ILW may contain concentrations of longlived nuclides (especially α-nuclide) that are not manageable innear surface disposal, a depth of tens to hundreds of meters are
required for disposal.

High Level waste (HLW)

Waste with a large amount of heat generation at high activity
concentration levels or waste containing large amounts of long-lived
nuclides for which a design equivalent to a disposal facility for such
waste needs to be considered. Generally, waste is disposed of in astable stratum at the depth of several hundred meters or more fromthe ground surface. In some countries, spent fuel is classified as
HLW.

2. Classification and disposal in Japan
In Japan, radioactive waste is broadly divided into “low-level radioactive waste” (equivalent to
VLLW to ILW in GSG-1), which is generated through the operation of nuclear power plants, and“high-level radioactive waste” (equivalent to HLW of GSG-1), which is generated through thereprocessing of spent fuel that is generated through the operation of nuclear power plants and isvitrified with a high level of radioactivity. When disposed of, waste shall be classified appropriately
according to its radioactivity level and properties, types of radioactive materials, etc., and shall bestrictly controlled, and reasonably processed and disposed of under the principle that
responsibilities lie with those who have generated the waste.
“High-level radioactive waste” is a vitrified liquid waste with a high radioactivity level that is
produced in the process of reprocessing spent fuel generated through the operation of nuclear
power plants. In Japan, the act (the Designated Radioactive Waste Final Disposal Act (the Final
Disposal Act)) stipulates that radioactive waste shall be disposed of in strata more than 300 meters
deep underground.

225

The term “low-level radioactive waste” refers to all types of radioactive waste other than “highlevel radioactive waste”, and is further divided into several categories depending on where it isgenerated and the level of radioactivity.
The types of radioactive waste generated by the operation of nuclear power plants and thedisposal methods assumed are shown in Table A12-2.
Of these, only waste with relatively low-level radioactivity generated through the operation of
nuclear power plants has been subject to disposal in pits since 1992 at the Rokkasho Low-level
Radioactive Waste Disposal Center of Japan Nuclear Fuel Limited in Rokkasho Village, Aomori
Prefecture. Including the existing facilities, approximately 1 million drums of waste contained in
200-liter drums are planned to be buried, and eventually the scale will be enlarged to approximately
3 million drums using 200-liter drums.

Table A12-2

Fig. A12-2

Types of Radioactive Waste Generated by the Operation of Nuclear Power Plants

Japan Nuclear Fuel Ltd. Low-level Radioactive Waste Disposal Center
226

Attachment 13

Overall image of Storage Management Plan for the Fukushima Daiichi NPS 228

228

TEPCO, Solid Waste Storage Management Plan for Fukushima Daichi Nuclear Power Station of Tokyo ElectricPower Company Holdings, Inc., February 2023 edition (issued on February 20, 2023)

227

(a) Present storage condition of “rubble, etc.” and “secondary waste generated by water
treatment”(b) Future storage condition of “rubbles, etc.” and “secondary waste generated by water
Fig. A13-1 Present and future storage conditions of “rubble, etc.” and “secondary waste
generated by water treatment” on site of the Fukushima Daiichi NPS

228

Attachment 14

Approach to the selection of nuclides to be measured and assessed
when discharging ALPS-treated water into the sea

In November 2022, TEPCO described and submitted the concept of selecting nuclides to bemeasured and assessed for discharging ALPS-treated water into the sea in the Application
Documents for Approval to Amend the Implementation Plan for Fukushima Daiichi Nuclear Power
Station as Specified Nuclear Facility (Operations related to the discharge of ALPS-treated water
into the sea). 229 Subsequently, after a total of five technical meetings were held by the NRA todiscuss the action plans for specific nuclear facilities, and a partial revision of the application was
submitted incorporating the results of these meetings and was approved in May 2023.
Based on the “Application for Approval of Change”, the “Supplemental Explanatory Material onCompliance with the Matters to be Addressed Required of the Fukushima Daiichi NPS (Concerning
Changes to the Operation System for Discharging ALPS-treated Water into the Sea and Selectionof Nuclides to be Measured and Evaluated) 230” and other documents, this attachment summarizes
an approach to selecting nuclides to be measured and assessed, the specific selecting procedures
and types of nuclides selected according to these procedures.

1. How to proceed with examination
To ensure that radionuclides other than tritium in ALPS-treated water satisfy the sum of the ratios
to regulatory concentrations limits of less than 1, the policy is to select the target nuclides to bemeasured and assessed (hereafter referred to as the “nuclides to be measured/assessed”) after
thorough verification of whether the nuclides could be significantly contained in contaminated water
before treated with cesium adsorption equipment, ALPS, or other treatments based on knowledgeof decommissioning and disposal facilities in Japan.

To verify the nuclides that could be contained in contaminated water in significant amounts at the
Fukushima Daiichi NPS, an analysis of the nuclides contained in the contaminated water and an
inventory evaluation considering the fuel and structural materials of Units 1 to 3 are conducted.


Nuclide analysis

Whether the nuclides to be assessed in the research on decommissioning and disposal facilities
are also significantly present in contaminated water is verified by actual water analysis. The resultsof past nuclide analyses are also verified (details are provided in 2.1.4.5 (1)).
Inventory evaluation

An inventory of fission products (FP) is assessed in the same way as in the study of nuclides
subject to removal by ALPS. The inventory quantity generated by the activation of structures inreactor pressure vessels is assessed based on the studies on decommissioning and disposal

229

NRA website，https://www.nra.go.jp/activity/earthquake/kisei/plan/140000233.html

230

NRA website，https://www2.nra.go.jp/data/000428079.pdf

229

facilities. In the assessment, the period that elapses since the accident should be set appropriately,
and the reduction in inventory quantity due to attenuation should be considered. The code used forthe evaluation is ORIGEN (ORNL Isotope Generation and Depletion Code), as in the previous
safety assessment, available findings, and previous evaluations.
According to the results of nuclide analysis and inventory evaluation, the presence of nuclides
that may be contained in the contaminated water in significant amounts should be verified,considering the ease of transfer to the water and other factors.

2. Method for selecting nuclides to be measured/assessed
Based on the results of nuclide analysis and the inventory evaluation described in Section 1, thenuclides to be measured/assessed are selected according to the flow shown in Fig. A14-1.

*1: The decay period of the inventory evaluation is appropriately set according to the time when the selection
result is to be used. (First time set to 2023 (12 years after the accident))*2: Nuclides that have been detected in the past are confirmed by the maximum value of the detection value, andnuclides that have never been detected are confirmed by the minimum value of the detection limit value*3: Nuclides that shall be continuously confirmed if significantly exists in contaminated water.

Fig. A14-1 Flow for selecting nuclides to be measured/assessed at the discharge of ALPStreated water to the sea
2.1 Selection procedures and results
2.1.1 Step 1
In Step 1, “Are nuclides present in the assessment in the results of the inventory assessment?”
nuclides will be evaluated by the criteria of whether they are found to exist through the inventory
assessment (if 1 Bq or more of the nuclide exists in each core of Units 1 to 3), and nuclides thatare not found to exist through the assessment will be excluded.

230

In this assessment, the decay period was set at 12 years after the accident (March 2023), andas a result, 210 nuclides were found to exist, as shown in Table A14-1.

Table A14-1 Nuclides that were found to exist through Step 1 (210 nuclides)
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

Nuclide
H-3
Be-10
C-14
Na-22
Si-32
P-32
Cl-36
Ar-39
Ar-42
K-40
K-42
Ca-41
Ca-45
Sc-46
V-49
Mn-54
Fe-55
Co-60
Ni-59
Ni-63

No.
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

Nuclide
Zn-65
Se-75
Se-79
Kr-81
Kr-85
Rb-87
Sr-90
Y-88
Y-90
Zr-93
Nb-91
Nb-92
Nb-93m
Nb-94
Mo-93
Tc-97
Tc-98
Tc-99
Ru-106
Rh-101

No.
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

NuclideRh-102
Rh-102m
Rh-106
Pd-107
Ag-108
Ag-108m
Ag-109m
Ag-110Ag-110m
Cd-109
Cd-113m
In-113m
In-115
Sn-113
Sn-119m
Sn-121
Sn-121m
Sn-123
Sn-126
Sb-125

No.
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80

NuclideSb-126
Sb-126m
Te-121
Te-121m
Te-123Te-123m
Te-125m
Te-127
Te-127m
I-129
Cs-134
Cs-135
Cs-137
Ba-133Ba-137m
La-137
La-138Ce-139Ce-142Ce-144

No.
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100

NuclidePr-144Pr-144m
Nd-144
Pm-144
Pm-145
Pm-146
Pm-147
Sm-145
Sm-146
Sm-147
Sm-148
Sm-149Sm-151
Eu-150Eu-152
Eu-154Eu-155
Gd-152
Gd-153
Tb-157

No.
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122

NuclideTb-158Dy-159Ho-163
Ho-166m
Tm-170
Tm-171
Lu-176
Lu-177
Lu-177m
Hf-182
Ta-182
W-181
Re-187
Os-194Ir-192
Ir-192m
Ir-194Ir-194m
Pt-190Pt-193
Tl-204Tl-206

No.
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

NuclideTl-207
Tl-208Tl-209
Pb-205
Pb-209
Pb-210
Pb-211
Pb-212
Pb-214
Bi-208Bi-210Bi-210m
Bi-211
Bi-212
Bi-213
Bi-214Po-210Po-211
Po-212
Po-213Po-214Po-215

No.
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166

NuclidePo-216
Po-218
At-217
Rn-219
Rn-220
Rn-222
Fr-221
Fr-223
Ra-223
Ra-224Ra-225
Ra-226
Ra-228
Ac-225
Ac-227
Ac-228
Th-227
Th-228
Th-229Th-230Th-231
Th-232

No.
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188

NuclideTh-234Pa-231
Pa-233
Pa-234Pa-234m
U-232
U-233
U-234
U-235
U-236
U-237
U-238
U-240
Np-235
Np-236
Np-237
Np-238
Np-239
Np-240m
Pu-236
Pu-238
Pu-239

No.
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210

NuclidePu-240Pu-241
Pu-242
Pu-243
Pu-244Am-241
Am-242
Am-242m
Am-243Am-245
Cm-242
Cm-243
Cm-244
Cm-245
Cm-246
Cm-247
Cm-248
Bk-249
Cf-249
Cf-250
Cf-251
Cf-2522.1.2 Step 2
In Step 2, “Is noble gas (excluding Rn) present?,” given that noble gas nuclides generated while
the reactor is in operation are not considered to exist in the core due to the release at the time ofoperation and the accident and that, even if they exist, noble gases are stable elements and231therefore insoluble in contaminated water, they are judged not to fall within the scope of nuclides
to be measured/assessed at the discharge of ALPS-treated water into the sea and are excluded.
On the other hand, radon (Rn) is considered to still exist in the core due to the decay chains ofuranium, neptunium, etc. Therefore, even though it is a rare gas, it is not excluded in this step.
In Step 2, four nuclides were excluded: Ar-39, Ar-42, Kr-81, and Kr-85.

2.1.3 Step 3
In Step 3, “Does the ratio of the concentration of each radionuclide to the regulatory concentration
limit exceed 1/100 in the assessment results on the transition of nuclides to the water in the ALPStreated water, etc. storage tank?,” nuclides are evaluated to see whether their impacts on the dose
assessment are sufficiently small (1/100 or less of the ratio to the regulatory concentration limit),
and nuclides with sufficiently small impact on the dose assessment are excluded by this criteria.
This evaluation assumes that all of the inventory existing in the PCV will have been dissolved in
ALPS-treated water, etc., tanks (evaluated as of March 2023). Therefore, given the current statusconfirmed through the PCV internal investigation, it is thought that an adequate level ofconservativeness is ensured under this assumption.

<< Conditions for determination >>As a result, 93 nuclides proceeded to Step 4 (Table A14-2), and 113 nuclides were excluded. It
has also been confirmed that the sum of the ratios to regulatory concentration limits (assessedvalues) of the nuclides excluded in Step 3 is sufficiently small at 6.7E-02, compared to 2.4E+07,
the sum of the ratios to the regulatory concentration limits (assessed values) of the nuclides thatproceed to Step 4. Thus, it was deemed appropriate to use 1/100 of the ratio to the regulatory
concentration limit as the selection criterion.

232

Table A14-2 Nuclides that proceed to Step 4 (93 nuclides)
No.
1
3
7
16
17
18
19
20
21
23
27
29
30
33
34
35
38
39
43
44

Nuclide
H-3
C-14
Cl-36
Mn-54
Fe-55
Co-60
Ni-59
Ni-63
Zn-65
Se-79
Sr-90
Y-90
Zr-93
Nb-93m
Nb-94
Mo-93
Tc-99
Ru-106
Rh-106
Pd-107

No.
46
49
50
51
55
56
57
59
60
61
62
67
70
71
72
73
74
75
79
80

NuclideAg-108m
Ag-110m
Cd-109
Cd-113m
Sn-119m
Sn-121
Sn-121m
Sn-126
Sb-125
Sb-126
Sb-126m
Te-125m
I-129
Cs-134
Cs-135
Cs-137
Ba-133Ba-137m
Ce-142Ce-144

No.
81
82
86
87
93
95
96
97
104
106
120
121
130
136
141
145
149
153
154
157

NuclidePr-144Pr-144m
Pm-146
Pm-147
Sm-151
Eu-152
Eu-154Eu-155
Ho-166m
Tm-171
Pt-193
Tl-204
Pb-212
Bi-212
Po-212
Po-216
Rn-220Ra-223
Ra-224Ra-228

No.
159
162
164
165
167
168
169
172
173
174
175
176
177
178
182
183
184
186
187
188

NuclideAc-227
Th-228
Th-230Th-231
Th-234Pa-231
Pa-233
U-232
U-233
U-234
U-235
U-236
U-237
U-238
Np-237
Np-238
Np-239Pu-236
Pu-238
Pu-239

No.
189
190
191
194
195
196
197
199
200
201
202
203
208

NuclidePu-240Pu-241
Pu-242
Am-241
Am-242
Am-242m
Am-243
Cm-242
Cm-243
Cm-244
Cm-245
Cm-246
Cf-2502.1.4 Step 4
In Step 4, “Does the ratio of the concentration of each radionuclide to the regulatory concentration
limit exceed 1/100 in the transition assessment of nuclides to contaminated water?,” the nuclides
that were advanced to Step 4 are grouped according to their radioactive equilibrium, isotopes, thesimilarityofnuclideproperties,

etc.,

and

the

relative

relationship

of

dose

effects(inventory/regulatory concentration limit) is confirmed within the group, and nuclides with sufficiently
small dose effects (relative ratio 1/100 or less) on representative nuclides are excluded.
Then, based on the actual analysis results of individual groups or nuclides that could not begrouped, the ease of transfer into water is calculated by radionuclide (hereinafter referred to as the“transfer coefficient”). Then, the concentrations in contaminated water of individual radionuclides
are evaluated using the coefficient.

2.1.4.1 Progeny nuclides in radioactive equilibrium
Among the nuclides that have proceeded to Step 4, those that exist in radioactive equilibrium areshown in Tables A14-3 and A14-4. The progeny nuclides shown in Table A14-3 have short halflives, and 12 years after the accident, when ALPS-treated water is set to be discharged into thesea, they exist only as nuclides produced by the decay of parent nuclides. Therefore, in evaluating
the transfer to contaminated water, they are assumed to behave the same as the parent nuclides.
In the meantime, the progeny nuclides shown in Table A14-4 have relatively long half-lives, and it
takes time for the parent and progeny nuclides to reach radioactive equilibrium. Based on this, theparent and progeny nuclides are assessed separately in this evaluation.

233

Table A14-3 Progeny nuclides that are in radioactive equilibrium and assumed to behave thesame as the parent
No.
1

Parent nuclide

Progeny nuclide

NuclideHalf-life

NuclideHalf-life

Sr-90

2.9E+01 [y]Y-90

2.67 [d]2Ru-106

1.0E+00 [y]Rh-10630.07 [s]3Sn-121m

4.4E+01 [y]Sn-121

1.13 [d]4Sn-126

2.3E+05 [y]Sb-126
Sb-126m

12.35 [d]19.15 [m]5

Sb-1252.8E+00 [y]Te-125m

57.40 [d]6Cs-1373.0E+01 [y]Ba-137m

2.552 [m]7

Ce-144

7.8E-01 [y]Pr-144Pr-144m

17.28 [m]7.2 [m]8

Pu-241

1.4E+01 [y]U-237

6.752 [d]9Am-242m

1.4E+02 [y]Np-2382.117 [d]10Am-242m

1.4E+02 [y]Am-242
Cm-24216.02 [h]162.9 [d]11

Am-243

7.4E+03 [y]Np-2392.356 [d]Table A14-4 Progeny nuclides that are in radioactive equilibrium but assumed to behave
differently from the parent
No.
1

Parent nuclide

Progeny nuclide

NuclideHalf-life

NuclideHalf-life

Zr-93
Mo-93

1.6E+06 [y]4.0E+03[y]Nb-93m

1.6E+01 [y]2.1.4.2 Nuclides produced from decay chains of uranium, neptunium, etc.
Among the nuclides that have proceeded to Step 4, those produced from decay chains ofuranium and neptunium, etc., are outlined in red in Fig. A14-2. In evaluating the transfer tocontaminated water, those nuclides are evaluated assuming they behave the same as the parent
nuclides (neptunium and uranium). That is, nuclides produced from the uranium, actinium, andthorium chains are evaluated as a subgroup of uranium isotopes because they are considered tobehave the same as the original uranium.

234

Fig. A14-2 Nuclides produced from the decay series of uranium, neptunium, etc.

2.1.4.3 Isotopes
Of the nuclides that have advanced to Step 4, the nuclides that exist as isotopes are shown in
Table A14-5. Since the outermost electrons determine the chemical properties of materials, thechemical properties of isotopes with the same number of electrons are almost identical. Therefore,
each isotope is considered to behave together in evaluating the transfer to contaminated water.

Table A14-5 Nuclides that are assessed to behave together because of their isotopes
No.

Element

Nuclide1

Ni isotope

Ni-59,Ni-63

2

Nb isotope

Nb-93m,Nb-94

3

Ag isotope

Ag-108m,Ag-110m

4

Cd isotope

Cd-109,Cd-113m

5

Sn isotope

Sn-119m,Sn-121m,Sn-126

6

Cs isotope

Cs-134,Cs-135,Cs-137

7

Ce isotope

Ce-142,Ce-1448

Pm isotope

Pm-146,Pm-147

9

Eu isotope

Eu-152,Eu-154,Eu-155

10

U isotope

U-232,U-233,U-234,U-235,U-236,U-238

11

Pu isotope

Pu-236,Pu-238,Pu-239,Pu-240,Pu-241,Pu-242

12

Am isotope

Am-241,Am-242m,Am-243

13

Cm isotope

Cm-243,Cm-244,Cm-245,Cm-246

2.1.4.4 Chemical similarity underwater
There are some nuclides for which no analytical data is available because the analyticaltechniques have not been established as of 2022, making individual analysis difficult. These235

nuclides are evaluated as having characteristics similar to those of the nuclides with which thesimilarity has been confirmed after the similarity of chemical forms of nuclides in water (Eh-pH
diagram, etc.), ionic radii, adsorption characteristics in water treatment, etc. is verified.

(1) Lanthanoids (Pm, Sm, Ho, Tm)
Lanthanoids have not previously been detected, except for Ce-144 and Eu-154, which weredetected in the analysis of stagnant water in the PCVs of Units 2 and 3. The results of these two
nuclides are used in evaluating the transfer to contaminated water for other lanthanoids. Therefore,
the validity was checked with Eh-pH diagrams. 231 As a result, verification has revealed thatlanthanoids are similar in that they are stable trivalent cations at hydrogen-ion exponents (pH) of 6
to 8 in reactor injection water and building stagnant water.
Rare earth ions, including lanthanoids, generally have similar chemical properties and behaviors,
and they are produced together in minerals, and it is difficult to separate them from each otherduring the refining process. Therefore, assessing all lanthanoids as the same group is deemed
appropriate.232
The transfer coefficients of Ce-144 and Eu-154, which belong to this group and have been
analyzed, were evaluated in Section 2.1.4.5 to be described later, and it was confirmed that they
were almost the same value and that they actually behaved similarly on the 1F site.

(2) Platinum group (Ru, Pd, Pt)
As for the platinum group, Ru-106 (Rh-106) has been detected (Rh is produced from the decayof Ru), and Pd-107 has been detected at a very low concentration in stagnant water in buildings
and Sr-treated water. Although Pt-193 has proceeded to Step 4, it has yet to be analyzed due tothe lack of a measurement method that can measure the nuclide independently.
Therefore, when evaluating the transfer of Pt to contaminated water based on the analysis resultsof Ru-106 and Pd-107, the validity was examined with Eh-pH diagrams and solubility. As a result,the verification has revealed that the platinum group exists in a solid state at hydrogen-ion
exponents (pH) of 6 to 8 in reactor injection water and stagnant water in buildings. Ru was found
to exist as a single metal or solid of oxides, and Pd and Pt as solids of single metals. Their solubility
in water was found to be very small.233 Given that the physical and chemical properties of theplatinum group elements are generally similar to one another and that they do not react with waterand are not easily affected by acids and bases, it is deemed appropriate to treat Pt-193 together
with Ru-106 and Pd-107 as one group in evaluating the transfer to contaminated water.

231

Naoto Takeno, Eh-pH Atlas - Intercomparison of the thermodynamics database, Geological Survey of Japan,
Research Material No. 419, Geological Survey of Japan, National Institute of Advanced Industrial Science andTechnology (2005)
232
Jiro Shiokawa, "Characteristics of Rare Earth Elements and Their Applications"233
Excerpt from “The technical reliability of geological disposal of high-level radioactive waste in Japan - Second
summary of research and development on geological disposal” (2000 Report)

236

The transfer coefficients of Ru-106 and Pd-107, which belong to this group and have been
analyzed, were evaluated in Section 2.1.4.5 as will be described later, and it was confirmed thatthey were almost the same value and that they actually behaved similarly on the 1F site.

(3) Thallium (Tl)As for thallium, although Tl-204 has proceeded to Step 4, it has yet to be analyzed due to thelack of a measurement method that can measure the nuclide independently.
According to the Eh-pH diagrams, it has been revealed that Tl, which is element 13,234 is a stablemonovalent cation at hydrogen-ion exponents (pH) of 6 to 8 in reactor injection water and stagnant
water in buildings. In addition:• The ionic radius is between the alkali metal Cs and K ions.
• The adsorption selectivity by zeolites has been evaluated as equal to that of K ions.235• It has the same level of adsorption property as Cs to soil.236
Given the above, it is reasonable to evaluate thallium together with alkali metals as the same groupwhile assuming that it will behave similarly throughout the process, from the transfer tocontaminated water to water treatment.

(4) Californium (Cf)Although Cf-250 has proceeded to Step 4 for californium, no analysis has been performed.
For californium, although it was not possible to check the validity with Eh-pH diagrams, it isconsidered a stable trivalent cation in a solution whose chemical behavior is very similar to that oftrivalent trans-plutonium elements (Am, Cm).237 It has also been confirmed that the trivalent cations,
Am, Cm, and Cf, have almost the same radii.238 Given the above, it is reasonable to evaluate thetransfer of californium to contaminated water together with Am and Cm as one group. The transfer
coefficients of Am-241, Cm-242, and Cm-244 were evaluated in Section 2.1.4.5 and found to bealmost the same values. It has been confirmed that this group actually behaves similarly even on
the 1F site.

2.1.4.5 Evaluation of transfer coefficients
Among the nuclides that have proceeded to Step 4, the ease of transfer into water is calculatedby radionuclide (hereinafter referred to as the “transfer coefficient”) based on the actual analysis
results of individual nuclides. Then, the concentrations in contaminated water of individual

234

It is also referred to as the boron group element, and it includes boron, aluminum, gallium, indium, and thallium.
Nitta and Aomura, "Study on the Site Selectivity of Exchangeable Cations in Synthetic Zeolite A”
236
John E. Till, Helen A. Grogan, "Radiobiological Risk Assessment and Environmental Analysis," Oxford
University Press (2008).
237
Lester R. Morss, Norman M. Edelstein, Jean Fuger, "The Chemistry of The Actinide And Transactinide
Elements - 4th Ed."238
R.D. Shannon, “Revised Eﬀective Ionic Radii and Systematic Studies of Interatomic Distances in Halides andChalcogenides”
235

237

radionuclides are evaluated using the coefficient. The transfer coefficient is evaluated using thefollowing formula:(1) Analysis results to be used for the evaluation of transfer to contaminated water
The analysis results to be used in the calculation of the transfer coefficient were classified andsummarized into four types as shown in Table A14-6 and Fig. A14-3.
Since all the contaminated water is collected in the Centralized Rw (the process main building(PMB) and the high-temperature incinerator building [HTI]) and then treated with a cesium sorption
apparatus (SARRY/SARRY2), and this water finally becomes ALPS-treated water, the analysis
results of Centralized Rw will be used in principle. However, it is impossible to obtain data on allradionuclides with only the analysis results of Centralized Rw, and because detection limits arehigh for stagnant water in buildings due to high Cs concentration, there are some nuclides for which
there is not enough data available. Therefore, for those nuclides, the analysis results of stagnant
water, etc. from Units 1 to 4 buildings, and water before ALPS treatment will be used to complement
the data.
Table A14-6 Classification of analysis results
No.

Classification of analyses

Details(1)

Stagnant water in Unit 1
to 4 buildings

Analysis results of stagnant water in Unit 1 to 4
PCVs and buildings(2)

Stagnant water inCentralized Rw building

Analysis results of water in Centralized Rw(PMB/HTI), at the inlet of SARRY, etc.

(3)

Cesium adsorption
system - inlet of ALPS

Analysis results of water from the outlet of cesium
adsorption system to the inlet of ALPS

(4)

Outlet of ALPS

Analysis results of water after ALPS treatment

Fig. A14-3 Classification of analysis results to be used for the evaluation of transfer

The results of the analysis of the radionuclides that have proceeded to Step 4 are summarized
in Fig. A14-4 for each sampling point. The figure shows the concentration ranges of individual
radionuclides throughout the process from the stagnant water in buildings to ALPS-treated water.
238

It also shows regulatory concentration limits to allow comparison of the analysis results withregulatory limits.
Fig. A14-4 was developed using the following data: FRAnDLi data published by the JAEA thatis available as of September 2022 (including data published by TEPCO), analyses of 62 nuclides
at the time of ALPS performance verification, etc. (FY 2013 to 2021), data of water before and after
ALPS treatment which is available on the Treated Water Portal Site, data on tanks, etc. containing
ALPS-treated water, etc.

Fig. A14-4 Summary of analysis results to be used for the evaluation of transfer coefficients(2) Evaluation results of the transfer coefficients to contaminated water
The analysis results shown in Fig. A14-4 and the results of the inventory evaluation as of March
11, 2011, are used to calculate the transition coefficients. As described previously, the maximum
value among the results of the centralized Rw is generally used to evaluate transfer coefficients,
and transfer coefficients rounded up to a higher order of magnitude are used to account for thevariation in the analytical values.
As an example of the evaluation results, Fig. A14-5 shows the results for Ni, Sr, Ba, Nb, andplatinum group elements. It was confirmed that these tended to be similar in each group. In addition,
though the results of barium, which is also an alkaline earth metal, were shown next to Sr, it was
confirmed that Ba-140 of the FP nuclide (excluded in Step 1 due to short half-life) showed theequivalent transfer coefficient as Sr-89 and Sr-90 of the same FP nuclide.

239

Fig. A14-5 Example of transfer coefficient evaluation results

2.1.4.6 Evaluation results of Step 4
In Step 4, the nuclides were narrowed down by grouping based on their radiative equilibrium,
isotopes, and similarity in nuclide properties, and the transfer coefficients evaluated in Section
2.1.4.5 were used to evaluate the transfer to contaminated water. As a result, 36 nuclides
proceeded to Step 5 (Table A14-7), and 57 were excluded.
Compared to the sum of the regulatory concentration limit ratios (evaluated value) of 7.7E+07 fornuclides proceeding to Step 5, the sum of the regulatory concentration limit ratios (evaluated value)
for nuclides excluded in Step 4 is 3.6E-02, which is sufficiently small, and it was judged appropriate
to use 1/100 of the regulatory concentration limit ratio as the selection criterion.

Table A14-7 Nuclides to proceed to Step 5 (36 nuclides)
No.

NuclideNo.

NuclideNo.

NuclideNo.

NuclideNo.

Nuclide

1

H-3

27

Sr-90

60

Sb-12593

Sm-151

189

Pu-240

3

C-14

29

Y-90

67

Te-125m96

Eu-154190

Pu-241

7

Cl-36

33

Nb-93m

70

I-129

97

Eu-155

194

Am-241

16

Mn-54

34

Nb-94

71

Cs-134

174

U-234

201

Cm-244

17

Fe-55

35

Mo-93

73

Cs-137

178

U-238

18

Co-60

38

Tc-99

74

Ba-133182

Np-237

20

Ni-63

39

Ru-10680

Ce-144187

Pu-238

23

Se-79

51

Cd-113m87

Pm-147

188

Pu-239240

2.1.5 Step 5
In Step 5, “Is the ratio of the concentration of each radionuclide to the regulatory concentration
limit less than 1/100 on the analysis results as contaminated water in the past?,” the nuclides thathave proceeded to this step are checked if they have been detected in significant amounts (1/100
or more of the regulatory concentration limit). Then, the nuclides confirmed to be less than 1/100of the regulatory concentration limit are defined as nuclides to be monitored. Therefore, those
nuclides are not to be measured upon each discharge into the sea but monitored constantly tocheck for a significant presence in contaminated water. The nuclides to be monitored will beanalyzed continuously and re-evaluated based on the selection flow according to such analysis
results.
This time, six nuclides to be monitored were selected: Cl-36, Nb-93m, Nb-94, Mo-93, Cd-113m,
and Ba-133.

2.2 Results of selecting nuclides to be measured/assessed
After selected in accordance with the approved flow shown in Fig. A14-1, the nuclides excepting
tritium to be measured/assessed are 29 as shown in Table A14-8. The table also shows thequantification methods that are currently planned for these nuclides. When checking the discharge
standard (the sum of the ratio to the regulatory concentration limits of radionuclides other thantritium is less than 1) in the measurement and confirmation facility, the ratio to the regulatory
concentration limit of α-nuclides is calculated by dividing the gross α value by the lowest regulatory
concentration limit (4 Bq/L) among the selected α nuclides.
In addition to the 29 nuclides shown in the table below, the H-3 concentration is measured before
discharge into the sea to set the dilution ratio.

Table A14-8 Nuclides to be measured/assessed and quantification methodsNo.
1

Nuclide
C-14

2
3

Mn-54
Fe-55

4
5

Co-60
Ni-63

6

Se-79

7

Sr-90

8

Y-90

Quantification method
After chemical
separation, measure βrays
γ-ray nuclide analysis
After chemical
separation, X-ray
measurement
γ-ray nuclide analysis
After chemical
separation, measure βrays
After chemical
separation, measure βrays
After chemical
separation, measure βrays
Radioactive equilibriumwith Sr-90

No.
16

NuclideCe-144

Quantification method
γ-ray nuclide analysis

17
18

Pm-147
Sm-151

Assessed from theactivity concentrationof representative
nuclide (Eu-154)

19
20

Eu-154Eu-155γ-ray nuclide analysis
γ-ray nuclide analysis

21

U-234

22

U-238

23

Np-237

241

Assessed as includedin the gross α
radioactivity

3.

9
10
11

Tc-99
Ru-106
Sb-125

24
25
26

I-129

ICP-MS
γ-ray nuclide analysis
γ-ray nuclide analysis
Radioactive equilibriumwith Sb-125
ICP-MS12

Te-125m

13

Pu-238
Pu-239Pu-24027

Pu-24114

Cs-134

γ-ray nuclide analysis

28

Am-24115

Cs-137

γ-ray nuclide analysis29

Cm-244

Assessed from theactivity concentrationof representative
nuclide (Pu-238)
Assessed as includedin the gross α
radioactivity

Regular confirmation of nuclides to be measured and evaluated

In view of the possibility that the nuclides to be measured and evaluated may change with theprogress of future decommissioning work, the nuclides to be measured and evaluated are analyzed
continuously, the validity of the nuclides to be measured and evaluated is regularly confirmed and,if necessary, re-evaluated.

242

Attachment 15

Individual Action plans of relevant organizations pertaining to analysis
Agency for Natural Resources and Energy, TEPCO, the JAEA and NDF

Core measures①︓Eﬀorts for Securing Human Resource
Measure 1: Securing Human Resources
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【TEPCO】【TEPCO】

・Organized the requirements for analytical・Secure the personnel necessary to review the ・Secure the personnel necessary to review the【TEPCO】

personnel (Analytical Technician, Analyticalanalysis plan.

analysis plan. [Continued]

Manager, and Analytical Worker)

・Secure the necessary personnel to・Secure personnel necessary for conducting

・Organized analysis system focusing on fuelimplement the analysis plan.

analysis at a comprehensive analysis facility

debris, waste and bioassays.

(new graduates/mid-careers).

【JAEA】【JAEA】

・Hire new employees (new graduates and・Hire new employees (new graduates and【JAEA】

mid-careers), including people with skills andmid-careers), including people with skills and・Utilize and develop experienced personnel

experiences.

experience. [Continued]

throughout JAEA
・Hire new employees (new graduates andmid-careers), including people with skills andexperiences. [Continued]

Measure 2: Human Resource Development
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【TEPCO】【TEPCO】【TEPCO】

・Organize the requirements necessary for

・OJT for potential analytical technicians will・Develop analytical technicians. [Continued]

analytical personnel and to build analyticalbegin at JAEA.

・Continue training to maintain analyticaltechnology focusing on fuel debris, waste and・Development of analysis managers/analysis

technology by gaining on-site experience atbioassays.

workers will begin by utilizing training support

JAEA, and through OJT in 1F by analytical・Develop analytical technicians through OJT at provided by external organizations.

technicians already trained.

external analytical organizations including JAEA

・Maintain analytical capability in 1F to ensure

to develop analytical personnel.

analytical managers/analytical workers required

・Train analysis workers by utilizing training

for achieving the analytical plan by continuing

support by external organizations, etc. 【P】

education.

【JAEA】【JAEA】【JAEA】

・Provided training at TEPCO 1F and private

・Provide OJT in the JAEA Ibaraki area and・Provide OJT in the JAEA Ibaraki area andanalytical laboratories.

Okuma Building 1. [Continued]

Okuma Building 1. [Continued]

・Provided OJT in the JAEA Ibaraki area and・Engaged in research and development in the ・Engaged in research and development in the

Okuma Building 1.

Project of Decommissioning, ContaminatedProject of Decommissioning, Contaminated・Engaged in research and development in the water, and Treated water Management, andwater, and Treated water Management, andProject of Decommissioning, Contaminatedthe World Intellegence Project. [Continued]

the World Intellegence Project. [Continued]

water, and Treated water Management, and・Examine a training system for analytical・Build a training system for analyticalthe World Intellegence Project.

personnel for the entire JAEA.

personnel for the entire JAEA to develop moreadvanced human resources.

Measure 3: Support for Human Resource Development
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【JAEA】【JAEA】

・The acceptance of the analytical engineer

・At the JAEA Ibaraki area and Okuma Building ・At the JAEA Ibaraki area and Okuma Building【JAEA】

candidate of Tokyo Electric Power Co. was1, candidates for analytical technicians from1, candidates for analytical technicians fromexamined and adjusted in JAEA Ibaraki district

TEPCO will be accepted to participate in

TEPCO will be accepted to participate inand Okuma Building 1.

research and development.

research and development. [Continued]

【NDF】

【NDF】

【NDF】

・An analysis coordination meeting was・Advise on TEPCO's analysis plan at the・Advise on TEPCO's analysis plan at theorganized to provide advice on problems

analysis coordination meeting.

analysis coordination meeting. [Continued]

related to the analysis plan and analysis related ・The analysis support team will establish

・The analysis support team will establish

to the decommissioning of the Fukushima Dai- working groups as necessary to address newworking groups as necessary to address new

ichi NPS, and an analysis support team wasanalysis issues, and review and advise on how

analysis issues, and review and advise on howorganized to discuss and review solutions toto resolve these issues.

to resolve these issues. [Continued]

problems.

・Strengthen cooperation between TEPCO and【Others】

the analysis community and, in cooperation[Others]

・Conduct training for human resourcewith them, support TEPCO to develop the・In order to broaden the base of humandevelopment for analysis workers [Continued] capacity to take the initiative in coordinating

resources to become analysis workers, the・Examine human resource development

Fukushima International Research andtraining programs to become analysis

Education Organization will launch a humanmanagers and analysis technicians, and【Others】

resources training program for radioactivity

conduct training sequentially.

・Continue to conduct human resource

analysis and start a training program.

and executing analysis plans.

development training for analysis workers,
managers and engineers, and review training
programs as necessary.

243

Core measures②︓Eﬀorts to Develop Analytical Facilities
Measure 4: Development and Operation of Analysis Facilities
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【TEPCO】【TEPCO】

・Conceptual study was completed and design

・Design studies (basic design/detailed design) ・For the comprehensive analysis facility,【TEPCO】

study (basic design) was started on thewill be conducted on the improvement of theapproval will be obtained and construction will

improvement of the comprehensive analysis

comprehensive analysis facility, and approval

be completed with a view to its steady

facility.

will be obtained.

completion in the latter half of the 2020s.

【JAEA】【JAEA】【JAEA】

・Waste samples and internal investigation

・Analytical R&D will be conducted at the・Analytical R&D will be conducted at the

samples were analyzed, licenses for fuel debris Ibaraki area and Okuma Building 1

Ibaraki area and Okuma Building 1

analysis were aquired, and analyticalcomplementarily, which is utilized for human

complementarily, which is utilized for humanequipment in the Ibaraki area was introduced.

resource development.

resource development. [Continued]

・Okuma Building 1 started operation.

・The analysis will be performed in Okuma

・Analysis will be continued in Okuma Building

・Construction of Okuma Building 2 has

Building 1, and the necessity of enhancing the1, and the capability for analysis will bestarted.

analysis capability (equipment and personnel)

enhanced as necessary.

will be examined.

・The target for completion of construction in

・Okuma building 2 will be constructed.

FY2026, operation of Okuma Building 2 will be[Continued]

started.

Measure 5: Development of tequniques to expand analytical capabilities
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【Agency for Natural Resources and Energy】【Agency for Natural Resources and Energy】

・Necessary measures are being taken for the・Necessary measures are taken for the stable ・Necessary measures are taken for the stable【Agency for Natural Resources and Energy】

stable operation of the Okuma Analysis andoperation of the Okuma Analysis and Research operation of the Okuma Analysis and Research

Research Center.

Center. [Continued]

Center. [Continued]

【NDF】

【NDF】

【NDF】

・In the Project of Decommissioning,・In the Project of Decommissioning,・Development and upgrading of analyticalContaminated water and Treated waterContaminated water and Treated watertechnology (speed-up, automation, labor-

Management, development of analysis andManagement, the necessary technologies willsaving) will be conducted for both fuel debris

estimation technology to grasp the properties

be developed for speeding up, automation, and and solid waste, and the acquired analyticalof fuel debris and R&D on processing andlabor saving of analysis. Non-destructive

disposal of solid waste have been conducted.

measurement technology for fuel debris, which fuel debris retrieval, waste

data will be incorporated into examininaiton foris different from the conventional technology,

storage/management, and【JAEA・NDF】

will be examined and developed as necessary.

processing/disposal.

・In the OECD/NEA project, the accident

・Based on the proposals of the Analysis

progress, estimation of condition inside theCoordination Meeting and the Analysis Support

reactors, and preliminary study of fuel debris

Team, technical development for solving

analysis were made.

analysis issues will be conducted as necessary.

【JAEA】【JAEA・NDF】【JAEA・NDF】

・The development of analytical tequniques for ・Through the OECD/NEA project, discussions

・Regarding fuel debris properties, global

samples and nuclides that are difficult towill be made on fuel debris properties andknowledge will be absorbed through OECD/NEA

measure.

damage conditions inside the reactors toprojects, etc. to use for decommissioning and・The development of the analysis planningabsorb global knowledge and disseminate

disseminate information internationally.

method (DQO process) which sets the analysis international information.
point statistically is being performed.

【JAEA】

・R&D on new analytical tequniques (ICP-【JAEA】

MS/MS, SIMS, etc.) are conducted to improve

・The development of analytical tequniques for samples and nuclides that are difficult to・The development of analytical tequniques forthe accuracy, simplify and accelerate analysis

samples and nuclides that are difficult tomeasure. [Continued]of fuel debris.

measure. [Continued]

・Develop and verify necessary analytical・The development of the analysis planningtequniques based on the analysis plan.

method which sets the analysis point[Continued]

statistically is continued.
・R&D on new analytical tequniques (ICPMS/MS, SIMS, etc.) are continued to improve
the accuracy, simplify and accelerate analysis
of fuel debris.

Core measures②︓Development of a framework for steady implementation of analysis
Measure 6: Review of Analysis Plan and System
Efforts to date

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【TEPCO】【TEPCO】【TEPCO】

・The analysis plan was formulated based on・Based on the analsis results and analysis

・Based on the analsis results and analysis

the analysis priority and the progress of theneeds of each fiscal year, annual analysis planneeds of each fiscal year, annual analysis plan

decommissioning event in the future, and theand necessary systems will be reviewed as aand necessary systems will be reviewed as aanalysis system was examined accordingly.

rule.

rule. [Continued]

244

Core measures②︓Development of a framework for steady implementation of analysis
Measure 7: Coordination of Overall Processes related to collection of analytical samples, transportation, securing of facilities, etc.
Efforts to date
【TEPCO・JAEA・IRID】

Short-term Efforts (in the next two years) Mid-to long-term Efforts (around 10 years)【TEPCO】【TEPCO】

・ Debris samples from 1F were transported to ・The content and schedule of sampling are

・The content and schedule of sampling are

JAEA Okuma Building 1.

reviewed and, in coordination with relevant

reviewed and, in coordination with relevant・Samples were transported to facilities inorganizations, necessary measures to secureorganizations, necessary measures to secure

Ibaraki area.

sampling, transport and analysis facilities are

sampling, transport and analysis facilities aretaken.

taken. [Continued]

・Based on the analysis plan, samples are・Samples are analyzed at the comprehensive

transported to JAEA Okuma Building 1 andanalysis facility.

facilities in Ibaraki. [Continued]

・Samples for which analytical tequniques need
to be developed will continue to be transferred
to JAEA facilities. [Continued]

Measure 8: Development, Review and Follow-up of Action Plans
【NDF】

【NDF】

【NDF】

・In the Technical Strategic Plan, the analysis

・While following up with the Government on

・While following up with the Government on

strategy was expanded from the one centered

the progress made on the efforts described in

the progress made on the efforts described in

on fuel debris to the overall analysis required

the Action Plan, and the details will be

the Action Plan, and the details will be

for the overall decommissioning work at thereviewed and materialized in line with thereviewed and materialized in line with the

Fukushima Dai-ichi NPS, and the action plan

revisions of the Technical Strategic Plan.

revisions of the Technical Strategic Plan.

was prepared.

[Continued]

245

Attachment 16

R&D medium-to-long-term plan246

R&D Mid-and-Long-term Plan
- Major Processes and Approach to Major R&D Activities for Decommissioning [Fuel Debris Retrieval] of the Fukushima Daiichi NPS of TEPCO FY

2022

Key
Milestones

Phase 2

2023

2024

2025

2028

Start of debris
retrieval at the first
implementing unit

[B]
Further expansion offuel debris retrieval

2033〜

Phase 3-(1)(Next phase)
Gradual expansion of retrieval scale

Design of fuel debris storage facilities

Further expansion of fuel debris retrieval scale

Trial operation, Start of operation

Construction/installation of facility

Development of technology for collection, transfer and storage of fuel debris
Target : - Establish safety and risk assessment for fuel debris storage

Resarch onsafety assurance during fuel debris retrievaland storage
Development of support technology for 1F decommissioning integrated management［１］Characterization
Characterization
Acquisition and maagement of analysis data, etc.

[C] Waste Management

Improvement of efficiency in characterization
Technical issues for characterization① Development of non-destructive measurement technology ② Development of analytical techniques for importantnuclides for disposal ③ Refinement and operation of analytical and material database④ Study of applicability of statistical inbentory estimation methods ⑤ Examination of rational waste confirmation
methods
The rerated issues and needs are taken up in the processing/disposal fields of tghe over all map of basic andfundamental research, and implemented as basic fundamental research.

［２］Storage
Storage
Development of alpha surface
contamination measurement technology
Research on waste reduction through reuse［３］Processing/disposal
Development of processing technology
Development of disposal technology
Study on waste stream
Technical issues for processing/disposal① Development of low-temperature processing technology ② Evaluation of stability of solidified products③ Study of slab processing, disposal, reuse, etc. ④ Development of intermediate processing technology⑤ Trial to improve reliability of safety assessment technology for solid waste disposal
The rerated issues and needs are taken up in the processing/disposal fields of tghe over all map of basic and fundamental
research, and implemented as basic fundamental research.

In reviewing the R&D Mid-and-Long-term plan, TEPCO, MEXT, METI and NDF have discussed the required results, timing needed and implementing structures through the R&D planning meetings. The plan is being
prepared by incorporating basic/fundamental research into practical application development and applied research, such as the Project of Decommissioning and Contaminated water/Treated water, as an integral part.

247

Attachment 17

Past Research and Development initiatives in the Project ofDecommissioning, Contaminated Water and Treated water
Management

Japnese Calender

H23

Fiscal Year2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

H24

H25

H26

H27

H28

H29

H30

R1

R2

R3

R4

R5

R6

1. Waste management
Legend

1.1 Tritium separation technologies
1.2 Development and verification of high-Terminated orTransited to TEPCOʼs
voluntary projects
Ongoing

performance multi-nuclide removal equipment(highperformance ALPS)
1.3 Large-scale verification of impermeable
walls (frozen wall)
2. Spent fuel management
2.1 Evaluation of long-term integrity of fuelassembly removed from SFPs
2.2 Investigation of method for processing
damaged fuel, etc. removed from SFPs
3. Grasping of state inside reactor/Graspingproperties of fuel debris/internal
3.1 Grasping conditions inside reactor
3.2 Characterization of fuel debris
3.3 Investigation of PCV inside
3.4 Investigation of RPV inside
3.5 Technologies for the detection of fueldebris (using muon)
4. Environmental improvement
4.1 Remote decontamination technology in thebuilding
4.2 Development of evaluation technology forthe structural integrity of RPV and PCV
4.3 Repair methods for leak spots in PCV(including water circulation systems)
4.4 Envitonmental improvement inside thebuildings (Removal of interference objects,
dose source deginalization, cathodic
protection of S/C)
5. Fuel debris retrieval
5.1 Technologies for retrieving fuel debris tobe gradually expanded in scale (Developmentof sampling technologies)
5.2 Technologies for further expansion of fueldebris retrieval and in-core structure remova
in scale (Study on retrieval methods,
development of safety system, developmentof element technologies)
5.3 Technologies for collecting, transportationand storage of fuel debris
5.4 Technologies for maintaining remoteequipment
5.5 Support technologies for integrated
management
6. Waste management
6.1 Research and development of processing
and disposal of solid waste* See below for links to the results of the Project.

< List of the projects of The Secretariat for the Project of Decommissioning, Contaminated Water and Treated Water Management >https://dccc-program.jp/project< Decommissioning R & D Information Portal Site >http://www.drd-portal.jp/

248

R7

Attachment 18 Selected subjects in the Nuclear Energy Science & Technology and Human
Resource Development Project (the World Intelligence Project)
Selected subjects in the FY2023 Issue-solving Decommissioning Research Program (7 subjects)
Subject of proposal
Development of a prototype radiation-resistantdiamond neutron measurement system that
requires no shielding

Development of an innovative n-γ scintillation
detection system for simple non-destructive
measurement
Study on physical and chemical alteration of
constituent materials for understanding thedamage behavior of reinforced concrete inpedestal sections
High-speed 3D in-core environment modelingbased on the amount of characteristic
extraction from dynamic images
Study on rational processing and disposal
considering volume reduction of radioactive
concrete waste
Development of technology for exploration
inside the piping in high background radiation
environments
Research and development of remote opticalmeasurement technology for estimation of
PCV gas-phase leakage position and leakage
amountStudy representative[Organization]
Junichi Kaneko[Hokkaido University]

Kei Kamada[The University ofTokyo]
Go Igarashi[Nagoya University]

Participating institution
High Energy Accelerator
Research Organization (KEK),
National Institute of Advanced
Industrial Science and Technology(AIST), Nagoya University,
Kyushu University, Japan Atomic
Energy Agency (JAEA)The University of Tokyo, AIST,JAEAThe University of Tokyo, Tohoku
University, JAEA

Keita Nakamura[Sapporo University]

Iwate Prefectural University, JAEA

Kozaki Tamotsu

University of Fukui, Central
Research Institute of ElectricPower Industry (CRIEPI), JAEA
Osaka University, Kobe University,
Tohoku University, Saitama
University, JAEA
Institute for Laser Technology(ILT)[Hokkaido University]
Tatsuo Torii[University of Fukui]
Tatsuo Shiina[Chiba University]

Selected subjects in the FY2023 international cooperative decommissioning research program (2 subjects)
Subject of proposal

Study representative[Organization]

Japan-UK Joint Research on Nuclear Energy: 2 subjects
Challenges in visualization of fuel debris byHiroaki Muta
innovative spectroscopic image analysis and[Osaka University]
verification by LIBS
Design and characterization of metakaolinYogarajahbased geopolymers with various properties for
Elakneswaran
fuel debris removal[Hokkaido University]

249

Participating institution

Nippon Nuclear Fuel Development
Co., Ltd. (NFD), JAEA
JAEA

Selected subjects in the FY2022 issue-solving decommissioning research program (6 subjects)
Subject of proposal
Practical Application of Innovative Alpha Dust
Imaging Device and High Dose Rate Field
MonitorEstablishment of Three-Dimensional Dose
Diffusion Prediction Method and Developmentof In-Structure Investigation Method Using
Gamma-Ray Transmittance Difference
Development of elemental technology for α
contamination visualization hand foot crossmonitorDevelopment of Radiation Field Mapping
Observation System Using Solar Cells for Low
Illumination with High Radiation Resistance

Development of a Passive WirelessCommunication System that Can
Communicate under Poor Conditions Caused
by Obstacles
Development and Evaluation of Real-Time 3D
Position Positioning and Integration System
Combining Wireless UWB and Camera Image
Analysis

Study representative[Organization]
Shunsuke Kurosawa[Tohoku University]

Participating institution
Mitsubishi Electric Corporation,
Kyoto University, JAEA

Tatsu Tanimori[Kyoto University]

Fukushima SiC Application
Technology Laboratory Co., Ltd.,JAEA

Mikio Higuchi
Hokkaido University

AIST, JAEA

Yasuki Okuno[Kyoto University]

National Institute of Technology
Kisarazu College, AIST, RIKEN,
Japan Aerospace Exploration
Agency, Tohoku University, andNational Institute for Quantum
Science and Technology (QST)
Niigata University, Nagoya Instituteof Technology

Hiroyuki Arai
[Yokohama National
University]
Kojiro Matsushita[Gifu University]

The University of Tokyo,
LocationMind Corporation, National
Institute of Technology Fukushima
College, Nagoya University, JAEA

Selected subjects in the 2022 international cooperative decommissioning research program (2 subjects)
Subject of proposal

Study representative[Organization]
Japan-UK Joint Research on Nuclear Energy: 2 subjects
Development of Embedded Systems Using
Minoru Watanabe
Radiation-Resistant Processors[Okayama University]
Exploration of Nano-Interface Phenomena on
Takehiko Tsukahara
Dissolution and Agglomerative Dispersion of[Tokyo Institute ofAlpha Microparticles Using MicroTechnology]
Nanotechnology

Participating institution

Kobe City College of Technology,
Lancaster University
Waseda University, JAEA,
University College London

Selected subjects in the 2021 issue-solving decommissioning research program (8 subjects)
Subject of proposal
Research and development of a hybrid-typeevaluation method of the long-term integrity ofreactor buildings using building responsemonitoring and damage imaging technology

Study representative[Organization]
Masaki Maeda[Tohoku University]

Clarification of the actual debris formation
Masayoshi Uno
mechanism by synthesizing mock-up debris[University of Fukui]based on the analysis results of materials
around fuel debris and the sophistication of thedebris property database by verifying the severe
accident progression analysis results
Study on water sealing, repair, and stabilization Shunichi Suzukiof the lower part of the PCV by geopolymer and [The University of Tokyo]
other substances
Establishment of a characterization analysis
Tetsuo Sakamoto
method for small amounts of fuel debris using[Kogakuin University]
the world's first isotope analyzer

250

Participating institution
Shibaura Institute ofTechnology, Tokyo Institute ofTechnology, Nippon Institute ofTechnology, National Institute ofTechnology Kisarazu College,
JAEA
Osaka University, Tokyo
Institute of Technology, Tohoku
University, JAEA

Tokyo City University, AIST,ATOX Co., Ltd., JAEA
Nagoya University, TEPCO,
JAEA

Sophistication of mass spectrometry of single
particles for actual measurement of alphaparticles
Research and development of a robotic system
for source exploration through cooperative
measurement
Development of a continuous tritium water
monitoring method through mid-infrared laser
spectroscopy

Atsushi Toyoshima[Osaka University]

Kyoto University

Keitaro Hitomi[Tohoku University]

National Institute of Technology,
Toyama College, Fukushima
University, JAEA
Hirosaki University

Ryo Yasuhara[National Institutes of
Natural Sciences, National
Institute for Fusion Science]
Challenges to the novel hybrid solidification ofMasahiko Nakase
difficult-to-stabilize nuclides from the Fukushima [Tokyo Institute ofTechnology]
NPS accident and development/safetyassessment of a rational disposal concept

Radioactive Waste
Management Funding andResearch Center (RWMC),
Okayama University of Science,
Tohoku University, JAEA

Selected subjects in the 2021 international cooperative decommissioning research program (4 subjects)
Subject of proposal

Study representative[Organization]

Participating institution

Japan-UK joint research on nuclear energy: 2 subjects
Study on radioactive aerosol control andShuichiro Miwa
ATOX Co., Ltd., JAEA,
decontamination in decommissioning the Fukushima[The University of Tokyo]
University of Bristol
Daiichi NPS
Navigation and control of a mechanical manipulator for
Hajime Asama
RITECS Inc, JAEA,
fuel debris retrieval[The University of Tokyo]
University of Sussex
Japan-Russia joint research on nuclear energy: 2 subjects (* Transferred to issue-solving decommissioning
research program from FY2023)
Reducing the uncertainties of FPs and debris behavior
Yoshinao Kobayashi
Kyushu University,and determining in-core contamination and debris[Tokyo Institute of
JAEA, Saint Petersburg
Technology]
properties based on the accident progression scenario
State University
for Fukushima Daiichi NPS Units 2 and 3
Sophistication of fuel debris criticality analysis technology Toru Obara
AIST, National Researchusing the non-contact measurement method[Tokyo Institute of
Nuclear University
Technology](MEPhI)251

Selected subjects in the FY2020 issue-solving decommissioning research program (8 subjects)
Subject of proposal
Grant-in-aid for young scientists: 2 subjects
Investigation of environment-induced property changes
and cracking behavior in fuel debris
Development of genetic and electrochemical diagnosis
and inhibition technologies for invisible corrosion causedby microorganisms
General research: 6 subjects
Technology development of diamond-base neutron
sensors and radiation-resistive integrated-circuits for ashielding-free criticality approach monitoring system
Development of a new corrosion mitigation technology
using nanobubbles toward corrosion mitigation in a PCV
system under the influence of α/β/γ-ray radiolysis
Development of rapid and sensitive radionuclide analysis
method through the simultaneous analysis of beta,
gamma, and X-rays
Quantitative evaluation of long-term state changes ofcontaminated reinforced concrete considering the actual
environments for rational disposal

Study on the rational treatment/disposal of contaminatedconcrete waste considering leaching alteration
Challenge to the advancement of debris composition anddirect isotope measurement by microwave-enhanced
LIBS

Study representative[Organization]

Participating institution

Yang Huilong[The University of Tokyo]
Akihiro Okamoto[National Institute forMaterials Science (NIMS)]

Nagaoka University ofTechnology
Japan Agency for
Marine-Earth Scienceand Technology, CRIEPI,JAEAManobu Tanaka[KEK]

Hokkaido University,
AIST, Nagoya University,
JAEA
QST, National Institutefor Materials Science(NIMS), JAEA
Niigata University,
Kyushu University, Taisei
Corporation, QST, JAEA
National Institute forEnvironmental Studies,
Taiheiyo Consultant Co.,
LTD., Taiheiyo Cement
Corporation, Nagoya
University, Hokkaido
University, JAEA
University of Fukui,
CRIEPI, JAEA
JAEA

Yutaka Watanabe[Tohoku University]
Hirofumi Shinohara[Japan Chemical Analysis
Center]Ippei Maruyama[The University of Tokyo]

Tamotsu Kozaki[Hokkaido University]
Yuji Ikeda[iLabo Co., Ltd]

Selected subjects in the FY2020 international cooperative decommissioning research program (2 subjects)
Subject of proposal

Study representative[Organization]

Japan-UK joint research on nuclear energy: 2 subjects
Development of environmental mitigation technology with Naoki Asao
novel water purification agents[Shinshu University]

Research and development of the sample-return
So Kamadatechnique for fuel debris using an unattended underwater [National Institute of
Maritime, Port and Aviation
vehicleTechnology, National
Maritime ResearchInstitute]

252

Participating institution

National Institutes of
Natural Sciences,
Institute for Molecular
Science, Tohoku
University, DiamondLight Source
KEK, JAEA, Lancaster
University

Selected subjects in the FY2019 common-based nuclear research program (7 subjects)
Subject of proposal
Grant-in-aid for young scientists: 2 subjects
Development of tailor-made adsorbents for uranium
recovery from seawater on the basis of uranyl
coordination chemistrySemi-autonomous remote-control technology of anarticulated mobile robot to recover from stuck states

Study representative[Organization]

Participating institution

Koichiro Takao[Tokyo Institute ofTechnology]
Motoyasu Tanaka[The University of ElectroCommunications]

JAEA

General research: 5 subjects
Measurement methods for radioactive source distribution Akira Uritani
inside reactor buildings using a one-dimensional optical [Nagoya University]
fiber radiation sensor
Study on oxidative stress status in organs exposed to
Masatoshi Suzuki
low dose/low dose-rate radiation[Tohoku University]
Basic study for online monitoring of tiny particles
Atsushi Toyoshimaincluding alpha emitters by aerosol time-of-flight mass
[Osaka University]
spectroscopy
Establishing a new evaluation system to characterize
Daisuke Iizuka
radiation carcinogenesis by stem cell dynamics[QST]
Development of radiation-hardened diamond imageShinya Omagari
sensing devices[AIST]-

JAEA

Hiroshima University,
Osaka University(Cooperation within theinstitution)
The University of Tokyo
Hokkaido University

Selected subjects in the FY2019 issue-solving decommissioning research program (4 subjects)
Subject of proposal
Estimation of the in-depth debris status of Fukushima
Unit-2 and Unit-3 with multi-physics modeling
Fluorination method for classification of the waste
generated by fuel debris removal
Development of a stable solidification technique for
ALPS sediment wastes with apatite ceramics
Challenge to the investigation of fuel debris in RPV withan advanced super dragon articulated robot arm

Study representative[Organization]
Akifumi Yamaji[Waseda University]
Daisuke Watanabe[Hitachi-GE Nuclear
Energy, Ltd.]
Takehiko Tsukahara[Tokyo Institute ofTechnology]
Shuji Takahashi[Tokyo Institute ofTechnology]

Participating institution
Osaka University, JAEA
Saitama University,
JAEA
CRIEPI, JAEA

JAEA

Selected subjects in the FY2019 decommissioning research program for research personnel
development (4 subjects)
Subject of proposal
Human resource development related to remotecontrol technology for monitoring inside the RPV
pedestal during the retrieval of fuel debris
Development of methodology combining chemical
analysis technology with informatics technology tounderstand the perspectives property of debris andtie-up style human resource development
Study on the degradation of fuel debris through the
combined effects of radiological, chemical andbiological functions
Development of extremely small amount analysis
technology for fuel debris analysis

253

Study representative[Organization]
Hajime Asama[The University of Tokyo]

Participating institution

Yoshitaka Takagai[Fukushima University]

PerkinElmer Co., Ltd.,KAKEN Co., Ltd., JAEA

Takehiko Tsukahara[Tokyo Institute ofTechnology]
Yasuyoshi Nagai[Tohoku University]

Visible Information
Center, Inc., JAEA

Fukushima University,
Kobe University, JAEA

Nagaoka University ofTechnology, NFD,
Kyushu University, JAEA

Selected subjects in the FY2019 international cooperative decommissioning research program (4 subjects)
Subject of proposal

Study representative[Organization]

Participating institution

Japan-Russia joint research on nuclear energy: 2 subjects
Improvement of critical safety technology in fueldebris retrieval

Toru Obara[Tokyo Institute ofTechnology]

Tokyo City University,
Russia National
Research Nuclear
University (MEPhI)

Study of corrosion and degradation of objects in a
nuclear reactor by microorganisms

Akio Kanai[Keio University]

RIKEN, JAEA, Kazan
State University

Safe, efficient cementation of challenging radioactive
wastes using alkali-activated materials with highflowability and high-anion retention capacity

Tsutomu Sato
[Hokkaido University]

ADVAN ENG. Co., Ltd.,JAEA, The University of
Sheffield

Radiation tolerant rapid criticality monitoring withradiation-hardened FPGAs

Minoru Watanabe[Shizuoka University]

Kobe City College ofTechnology, Lancaster
University

Japan-UK joint research on nuclear energy: 2 subjects

Note: The details of the project implementation (project plan, contract amount, etc.) may be changed, or the
adoption of the project may be canceled due to changes in circumstances that arise after the adoption.

254

Attachment 19 Major activities related to enhancing international collaboration
Table A19-1 Intergovernmental Framework between Japan and other countries
Framework
Annual Japan-UK Nuclear
Dialogue

Japan-France Nuclear Energy
Committee
Japan-US Decommissioning
and Environmental
Management Working Group

Japan-Russia Nuclear
Working Group

Descriptions
This dialogue is held based on the appendix to the jointstatement of the Japan-UK top level meeting in April 2012,“Japan-UK Framework on Civil Nuclear Energy Cooperation”(Since February 2012).
It was established under the joint statement of Japan–France
top-level meeting in October 2012 (Since February 2012).
After the Fukushima Daiichi NPS accident in March 2011, theestablishment of the US-Japan Bilateral Commission on Civil
Nuclear Cooperation (the Bilateral Commission) wasannounced in April 2012 based on the relationship between
Japan and the US to further reinforce bilateral cooperation.
Under this commission, “the Decommissioning andEnvironmental Management Working Group (DEMWG)” wasestablished (Since December 2012).
The Nuclear Working Group was established after confirmingthat Energy is one of the eight areas of cooperation plan
approved at the Japan-Russia top-level meeting in September
2016, (Since September 2016).

Table A19-2 Inter-organizational Cooperation Agreement
Domestic

International

Descriptions

NDF

NDA

Exchange of information for various technical knowledge on
decommissioning, etc. and personal exchange are provided.
(Concluded in February 2015)

NDF

CEA

Exchange of information for various technical knowledge on
decommissioning, etc. and personal exchange is provided.
(Concluded in February 2015)

TEPCO

DOE

Umbrella Contract was made and information is exchanged asneeded. (Concluded in September 2013)

TEPCO

Sellafield, Ltd.

Information Exchange Agreement for site’s operation, etc. wasconcluded. (September 2014)

TEPCO

CEA

Information Exchange Agreement on for decommissioning
was concluded. (September 2015)

JAEA

NNL

Comprehensive Agreement for advanced technology on
nuclear R&D, advanced fuel cycles, fast reactor, radioactive
waste

JAEA

CEA

Cooperation Agreement for specific technical issues on molten
core-concrete interaction, etc.

255

JAEA

Belgium Nuclear
Research Center

Agreement of Cooperation for Nuclear R&D and Research on
the accident of the Fukushima Daiichi

JAEA

Nuclear Safety
Research Center(Ukraine)

Memorandum for decommissioning research, etc. of the
Fukushima Daiichi NPS and Chernobyl was concluded.

JAEA

IAEA

Research Agreement on characterization of fuel debris

Table A19-3 Dissemination of information to the world (Holding or attending International
Conference (from September 2021 to August 2022))
Conference Name

PeriodOrganization

September, 2021

NDF
METI
TEPCO

IAEA International Conference on a Decade of Progress
after Fukushima-Daiichi

November, 2021

NDF
METI
TEPCO
JAEA

Japan-UK Nuclear Dialogue

December, 2021

METI

International briefing

February, 2022

METI

US Waste Management 2022

March, 2022

TEPCO
IRID

Regulatory Information Conference (US NRC)

March, 2022

NDF

Fukushima Research ConferenceYear round

JAEA

The 64th IAEA Conference Side event

Table A19-4 Dissemination of information to the world (on web (in English)
Site

Organization

Mid-and-long-term Roadmap towards the Decommissioning of TEPCO’s
Fukushima Daiichi Nuclear Power Station Units 1 to 4
(https://www.meti.go.jp/english/earthquake/nuclear/decommissioning/)

METI

Annual report to the embassies concerning discharging and seawater
monitoring from the Fukushima Daiichi NPS

METI, MOFA

Nuclear Damage Compensation and Decommissioning Facilitation
Corporation’s website (https://www.dd.ndf.go.jp/english/)

NDF

Information Portal for the Research and Development for the Fukushima
Daiichi Decommissioning (https://www.drd-portal.jp/en/)

NDF

Activities for Decommissioning (https://fukushima.jaea.go.jp/english/)

JAEA

IRID website (https://irid.or.jp/en/)

IRID

256

Responsibility for the Revitalization of Fukushima(https://www.tepco.co.jp/en/hd/responsibility/revitalization/index-e.html)

TEPCO

Providing English version of Press release to foreign media

TEPCO

Management Office for the Project of Decommissioning, Contaminated
Water and Treated Water Management (https://en.dccc-program.jp/)

MRI (Businessconsignee)

Table A19-5 Major collaborative projects with foreign organizations
Contents/Period of project

Participating
Organization

・Knowledge and experience obtained from the efforts onchallenges of decommissioning and recovery of damaged
nuclear power facilities (regulations, technologies, systems,
and strategies) are shared among the relevant countries.
・Project period : 2015 to 2017

NDF

Project
IAEA Project

DAROD

OECD/NEA Project

BSAF

・Researching institutions and governmental organizations
from eleven countries joined to conduct benchmark study
using severe accident analysis codes developed by theseorganizations to find out how the accident in the Fukushima
Daiichi NPS progressed and how the fuel debris and FPs
spread inside the reactors. Knowledge and findings related tothe modeling of phenomenological issues obtained by member
countries’ organizations are being utilized.
・Data measured during the accident and information
database regarding the post-accident radiation levels areshared.
・Project period : 2015 to 2018

IRID
JAEA
TEPCO

ARC-F

・In succession to the BSAF project, researching institutions
and governmental organizations from twelve countries joined
to investigate the situation of the accident in more detail andutilize it for further research to improve safety of light-water
reactor・Project period : 2019 to 2021

NRA
IR
JAEA

PreADES・Sharing characteristics information that helps to understandproperties of fuel debris such as its phase state andcomposition.
・Enhancing “Fuel debris Analytical Chart” that summarizes
needs and priority of fuel debris analysis.
・Maintenance of tasks after analysis and analysis facility
information
・Project period : 2018 to 2021

METI
NRA
IR
JAEA
IRID
NDF
TEPCO

257

FACE

・A project launched by integrating ARC-F and PreADES
・Analyzing fuel debris samples and accident scenarios
・Sharing the results of the analysis among participating
countries
・Project period : 2022 to 2026

TCOFF

・In reference to the accident progression of the Fukushima
Daiichi NPS, (1F) advancing molten core and molten fuelmodels, FP migration behavior model and thermodynamic
database as their basis. Based on the material scientificknowhow, evaluating details of molten core and fuel on
condition of 1F accident, and characteristics of fuel debris andits producing mechanism. Then, providing material scientificknowhow and result of detail evaluations to international
cooperation project including PreADES, ARC-F, TAF-ID, anddomestic decommissioning project like IRID.
・Project budget was contributed from MEXT.
・Project period : 2017 to 2019

EGCUL・Discussing on characterization method for waste fromunknown derivation

258

METI
NRA
JAEA
NDF
TEPCO

MEXT
JAEA
IR
Tokyo Institute ofTechnology

METI
NDF
JAEA
TEPCO