Technical Strategic Plan 2022 for Decommissioning of
the Fukushima Daiichi Nuclear Power Station of Tokyo
Electric Power Company Holdings, Inc.

October 11, 2022

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.

2

Table of Contents
1. Introduction ................................................................................................................................... 6
2. Concept for reducing risks and ensuring safety in the decommissioning of the Fukushima
Daiichi NPS................................................................................................................................ 11
3. Technological strategies toward decommissioning of the Fukushima Daiichi NPS .................. 31
3.1 Fuel debris retrieval .............................................................................................................. 31
3.2 Waste management.............................................................................................................. 86
3.3 Contaminated and treated water management .................................................................... 97
3.4 Fuel removal from spent fuel pools .................................................................................... 113
4. Analysis strategy for promoting decommissioning................................................................... 120
5. Efforts to facilitate research and development ......................................................................... 131
6. Activities to support our technical strategy............................................................................... 140
6.1 Further strengthening of project management and improvement of capability required as adecommissioning executor ................................................................................................ 140
6.2 Strengthening international cooperation ............................................................................ 159
6.3 Local community engagement............................................................................................ 165
List of Acronyms/Glossaries ......................................................................................................... 171
List of Attachment ......................................................................................................................... 175

3

Table of figures
Fig. 1 Division of roles of related organizations responsible for decommissioning of the Fukushima
Daiichi NPS .......................................................................................................................... 7
Fig. 2 Positioning of the Technical Strategic Plan based on the Reserve Fund .............................. 8
Fig. 3 Reduction of risks present in the Fukushima Daiichi NPS .................................................. 17
Fig. 4 Risk levels posed by major risk sources at the Fukushima Daiichi NPS............................. 18
Fig. 5 Risk reduction process for major risk sources and its progress (as of March 2022) .......... 21
Fig. 6 ALARP centered on safety (conceptual diagram) ................................................................ 28
Fig. 7 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 3............................................................................................................................................. 35
Fig. 8 Image of fuel debris retrieval system ................................................................................... 36
Fig. 9 Image from retrieval to temporary storage of fuel debris ..................................................... 36
Fig. 10 Schematic drawing of containment barrier during opening operation of the Penetration X-6............................................................................................................................................. 43
Fig. 11 Schematic drawing of containment barrier during trial retrieval (internal investigations andfuel debris sampling) ........................................................................................................... 43
Fig. 12 Work steps of trial retrieval (internal investigations and fuel debris sampling) .................. 44
Fig. 13 Enclosure and manipulator ................................................................................................ 47
Fig. 14 Conceptual diagram of each work phase (a division of process) ...................................... 50
Fig. 15 Examination flow for retrieval methods in FY 2021 (outline) ............................................. 50
Fig. 16 An example of partial submersion method ......................................................................... 52
Fig. 17 Reference : Conventional submersion method.................................................................. 52
Fig. 18 An example of submersion method.................................................................................... 52
Fig. 19 Conceptual diagram of how to proceed with examining methods after FY 2022 .............. 53
Fig. 20 An example of building containment function (gas-phases) by negative pressure control 60
Fig. 21 An example of building containment function (liquid phase) ............................................. 64
Fig. 22 An example of examining the liquid-phase particle (particle collection/removal) in the Projectof Decommissioning, Contaminated Water and Treated Water Management ................... 80
Fig. 23 Key technical issues and future plans on fuel debris retrieval (progress schedule) ......... 85
Fig. 24 Summary of waste hierarchy at the NDA, and countermeasures at the Fukushima Daiichi
NPS ..................................................................................................................................... 90
Fig. 25 Procedure to reasonably select safe processing/disposal methods of solid waste .......... 95
Fig. 26 Key technical issues and future plans on waste management (progress schedule) ........ 96
Fig. 27 Outline of contaminated water management ..................................................................... 98
Fig. 28 Progress of contaminated water management and changes in the amount of contaminatedwater generated................................................................................................................... 99
Fig. 29 Lowering of sub-drain and building water levels .............................................................. 100

4

Fig. 30 Water treatment systems for stagnant water in buildings and measurement results of total
α-nuclides .......................................................................................................................... 106
Fig. 31 Zeolite sandbag recovery procedure ............................................................................... 108
Fig. 32 Key technical issues and future plans on contaminated water/treated water management
and natural disaster preparedness (progress schedule) ...................................................112
Fig. 33 State of the collapsed rubble on the Unit 1 operating floor...............................................114
Fig. 34 Fuel removal method from Unit 1 SFP..............................................................................114
Fig. 35 Fuel removal method from Unit 2 SFP..............................................................................115
Fig. 36 Storage status of spent fuel (As of May 2022)..................................................................116
Fig. 37 Key technical issues and future plans for fuel removal from SFPs (Progress schedule).119
Fig. 38 Incorporation of analyses and investigation results, and their relationships ................... 122
Fig. 39 Three elements of the fuel debris analysis strategy ........................................................ 122
Fig. 40 Construction and operation schedule for fuel debris retrieval and new analytical buildings........................................................................................................................................... 124
Fig. 41 Characteristics and roles of each facility for analysis ...................................................... 125
Fig. 42 An example flow of non-destructive assay in the handling process for retrieved fuel debris........................................................................................................................................... 130
Fig. 43 Scope of studying decommissioning R&D and implementation entities ......................... 132
Fig. 44 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPS ...... 133
Fig. 45 Standard workflow of risk management ........................................................................... 143
Fig. 46 Design flow of fuel debris retrieval (conceptual) .............................................................. 149
Fig. 47 Exchanging opinions with experts overseas through face-to-face meeting and online .. 161
Fig. 48 Structural drawing inside Reactor building ...................................................................... 174
Fig. 49 Structural drawing inside Reactor Pressure Vessel (RPV) .............................................. 174
Table 1 Major risk sources at the Fukushima Daiichi NPS ............................................................ 16
Table 2 Status of solid waste storage............................................................................................. 88
Table 3 Major initiatives for discharging ALPS-treated water into the ocean............................... 102
Table 4 Personnel exchanges between TEPCO and JAEA and accepting personnel from NFD to
TEPCO .............................................................................................................................. 126
Table 5 Relative comparison of principal specifications between the sample analysis to be
performed in the analysis facility and non-destructive assay to be performed outside theanalysis facility................................................................................................................... 128
Table 6 Difference between “Making” and “Buying” ..................................................................... 150
Table 7 Future project management (To Be)................................................................................ 151

5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.
In March 2022, the earthquake occurred with its seismic center off the coast of Fukushima
Prefecture, measured a lower 6 on the Japanese seismic intensity scale of 7. However, there wasno leakage of radioactive materials into the environment and no significant impact on the plant
operations. The Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company
Holdings, Inc. (hereinafter referred to as “TEPCO”) is avoiding any effect on safety assurance
caused by personnel shortages by taking thorough infection prevention measures against newcoronavirus infections, which have been ongoing since FY2020. Nonetheless, the effects of global
action restrictions and semiconductor shortages are unavoidable, and efforts are being made tominimize these effects. Under these circumstances, the decommissioning of the Fukushima Daiichi
NPS is being prepared for the trial retrieval of fuel debris (internal investigation and fuel debris
sampling) in Unit 2. Theis trial retrieval (internal investigation and fuel debris sampling) is the final
stage of Phase 2 as indicated in the Mid-and-Long-term Roadmap and will be the basic form of onsite configuration for the future fuel debris retrieval work. Therefore, this phase requires more
careful and cautious preparation. After transited to Phase 3-[1], preparations for full-scale debris
retrieval and efforts to complete fuel removal from the spent fuel pools in all units will be promoted.
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 (Attachment 1), with the objectives of providing a solid technical basis for the Mid-and-Longterm Roadmap and contributing to its smooth and steady implementation, consideration of revisions,and achievement of the goals of the Nuclear Regulation Authority (NRA)'s "Measures for Mid-term
Risk Reduction at TEPCO’s Fukushima Daiichi NPS (hereinafter referred to as “Target Map for
Reducing Medium-term Risks”)", as well as providing a basis for “The Policy for Preparation ofWithdrawal Plan for Reserve Fund for Decommissioning” (hereinafter referred to as “the Policy for
Preparation of Withdrawal Plan”.

61.1 Structures and systems toward the decommissioning of the Fukushima
Daiichi Nuclear Power Station
The division of roles among the organizations directly involved in the decommissioning of the
Fukushima Daiichi NPS, including the Japanese government, NDF and TEPCO, as well asorganizations specializing in R&D, such as the International Research Institute for Nuclear
Decommissioning [IRID] and the Japan Atomic Energy Agency [JAEA], is shown in Fig 1, which
also indicates how the abovementioned systems are implemented.
Based on this division of roles, TEPCO has been working to build and strengthen the project
management structure, and is in the process of making it more effective by enhancing andupgrading the management methods, in order to make systematic and steady progress inaddressing each issue with a view to the mid-to-long-term decommissioning work. From thefinancial perspective, NDF has been carrying out the management of a reserve fund fordecommissioning to ensure immediate decommissioning work. Under this management task, NDF
is to (1) manage the fund for decommissioning appropriately, (2) manage the implementation
structure for proper decommissioning, and (3) steadily manage the decommissioning work basedon the Reserve Fund for Decommissioning, and NDF is assigned roles and responsibilities as anorganization to manage and oversee TEPCO's decommissioning activities. NDF prepared "ThePolicy for Preparation of Withdrawal Plan ", which was drawn up based on the "Technical StrategicPlan", and presented to TEPCO the work goals and main activities to be incorporated in theWithdrawal Plan for reserve fund for decommissioning, and evaluated the appropriateness of
TEPCO's efforts in the process of jointly preparing the Withdrawal Plan for reserve fund fordecommissioning from the perspective of symbiosis and communication with the community, etc.
(Fig. 2).
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

Apply forapproval

Nuclear Damage Compensation and Decommissioning Facilitation Corporation➢ 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

International Research Institute for
Nuclear Decommissioning (IRID)*2
Share progress
Japan Atomic Energy Agency (JAEA), and challengesetc.
➢ R&D implementation
ReportReserve Fund for
Decommissioning

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

Disburse-ment

Apply for report

R&D organization

Approve

Monitoring, examination

Progressmanagement

Granting of
project budget

Target map for Reducing
Medium-term Risk

Minister of Economy, Trade and Industry
Presentation ofimportant issues

ReportReport on theoutcomeReportBidirectional dialogue

Local residents and communities

Organizations related to decommissioning

Council for the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station*1

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)*1 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.
*2 TEPCO, a decommissioning project operator, participates as a member of IRID and shares the needs, challenges, and results of research and development.

Fig. 1 Division of roles of related organizations responsible for decommissioning of the
Fukushima Daiichi NPS

7

Government* Continually revised based on the progress of programs,
in the past revised once a couple of years

Mid-and-Long-Term Roadmap*
Proposals for Revise

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. 2 Positioning of the Technical Strategic Plan based on the Reserve Fund

1.2 The Technical Strategic Plan 2022
The Technical Strategic Plan 2022 consists of six chapters and features the status of efforts
toward trial retrieval from Unit 2 (internal investigation and fuel debris sampling), the status of theexamination of methods toward further expansion of fuel debris retrieval in scale, the status ofefforts toward the discharge of ALPS-treated water into the ocean, and analytical strategies forpromoting decommissioning. Followings are the contents after Chapter 2.
 Chapter 2 presents the approach to risk reduction and ensuring safety as well as the basic
policies of them. For the approach to risk reduction, it describes the immediate targets in
implementing strategies and risk reduction process and its progress of major risk sources. For
the approach to ensuring safety, it describes the basic policy of ensuring safety based on thecharacteristics of the Fukushima Daiichi NPS, incorporating the safety perspective and theoperator’s perspective.
 In Chapter 3, sector-specific goals are set for each of the major four areas (fuel debris retrieval,waste management, Contaminated Water/Treated Water management, and fuel removal fromSFP), and describes current progress, major issues to achieve them and the technicalstrategies to realize them respectively
Section 3.1 (Fuel debris retrieval) describes the status of the primary containment vessel(hereinafter referred to as "PCV”) internal investigation of Unit 1 as well as the preparations
for trial retrieval (internal investigation and fuel debris sampling) of Unit 2. This section also

8

describes the status of studies on subsequent gradual expansion of fuel debris retrieval andthe process to develop retrieval method for further expansion of fuel debris retrieval in scale.
Section 3.2 (Waste management) describes examination status for establishing waste streamin accordance with the characteristics of solid waste, which is being studied based on “theProspects of processing/disposal method and technology related to its safety” presented in
FY2021.

Section 3.3 (Contaminated water and treated-water management) describes the progress andthe issues for discharge of ALPS-treated water into the sea, which was indicated to be
implemented in two years’ time under the government’s basic policy in 2021, in addition to theexamination status for the issues focused on further decommissioning processes including
treatment of stagnant water in the buildings and fuel debris retrieval.

Section 3.4 (Fuel removal from spent fuel pools) describes the progress and the issues of theefforts being made in Units 1 and 2 to complete fuel removal from Units 1 to 6. This section
also describes the direction of efforts to determine the future processing and storage methods,
such as evaluating the long-term integrity of the fuel in SFP.



Chapter 4 (Analysis strategy for promoting decommissioning) describes, for the significanceand system of analysis, the importance of building and maintaining analytical facilities andfunctions required for handling waste and fuel debris, and establishing a system including
human resource development, as well as the application of a method to evaluate the amountof nuclear fuel without destructing samples to retrieve fuel debris.
 Chapter 5 (Efforts to facilitate research and development) describes the individual researchand development described in Chapters 3 and 4 with a view to the medium and long term as
a whole, and summarizes the approaches expected of the government, project operators, andrelated research organizations.
 Chapter 6 (Activities to support our technology strategy) describes the significance, current
status, and major issues and strategies in the following areas: further enhancement of project
management, improvement of capabilities as a decommissioning operator, enhancement ofinternational collaboration, and regional symbiosis.
➢ Section 6.1 (Project management) describes the efforts to enhance owner’s engineering
capabilities (project management capability and engineering capability based on safety andoperator’s perspectives) with the increasing difficulty of the project.
➢ Section 6.2 (Strengthening international cooperation) describes the efforts to promote
decommissioning in a mutually beneficial manner that is open to the international community,
including returning to the international community the knowledge and lessons learned fromthe decommissioning of the Fukushima Daiichi NPS.

9➢ Section 6.2 (Local community engagement) describes the efforts to realize “Commitment to
the people of Fukushima to achieve both reconstruction and decommissioning” including
the organization of a new company for the concentration of decommissioning-relatedindustries in Hamadori region, that TEPCO is promoting.

10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 2)
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 - 6.
• Undertake trial retrieval of fuel debris and promote gradual expansion of fuel debris retrieval inscale.
• Minimize and stably maintain the amount of contaminated water generated.
• Eliminate the temporary storage of rubble etc., as a waste management measure.

11

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 thoughmore than about eleven 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, it is undeniable that risks that were previously perceived as small may
become relatively large or that unknown risks may become apparent. To effectively respond to risks
toward further expansion of fuel debris retrieval in scale, it is necessary to improve the ability toobserve 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 type andnumber 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 water12

retained 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.
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, and determine
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, it is assumed that effects due to contact with the molten core materials andtheir heat occurred. 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,and degradation 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. 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 andincorporate the latest in-core information for reducing uncertainty. Details of initiatives are shownin 3.1.2.6.1.5.
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.



It is necessary to establish a system for securing, training and managing operators andcomplete 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.

13

In preparation for hardware, it is necessary to complete environmental improvements in thesurrounding area, such as dismantling and removing exhaust stacks and radioactive waste
disposal buildings.

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
2.2.1 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 likelihoodof occurrence 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” × “Safety Management”“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. “Safety
Management” is an index of the likelihood that an event will occur. It is determined by factors that
depend on the integrity and other aspects of the facility and on the packaging/monitoring status of
the risk source (Attachment 3).
The major risk sources of the Fukushima Daiichi NPS are summarized in Table 1, and Fig. 3
shows the risks of the Fukushima Daiichi NPS as the sum of these risk sources. The current risk
levels assigned to the respective risk sources are expressed in Fig. 4 with “Hazard Potential” and“Safety Management” as the axes.
In the Mid-and-Long-term Roadmap, management of these risk sources is broadly classified
into three major categories: (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 (fuel14debris), and (3) Increased risk unlikely in the future, but appropriate decommissioning efforts are
required (solid waste such as sludge generated by the decontamination device). Their priorities areset, and appropriate measures are being taken. In Fig.4, above (1) is represented in pink, (2) inyellow, and (3) in green, with the risk sources in the “sufficiently stable management” region (inpale blue area) are shown in light blue.
Major risk sources identified at the Fukushima Daiichi NPS are shown in Table 1. In addition, theoverall decommissioning work over the 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 stablemanner. Since the Technical Strategic Plan 2019, these issues have also been presented. 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 that have been determined to be prioritized and addressedin the same manner as major risk sources will be evaluated for risk levels in the future. (Attachment
4).
As events that were not anticipated have occurred during the long period of thedecommissioning work, it is important to identify unexpected risks. Although it is not easy to identify
such risks, when an unexpected event occurs, analyzing the event to clarify causes that had notbeen anticipated before provides a clue for risk identification.
At the event of total-β contamination leakage in the rubble temporary storage area1 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 leakage2. 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, 20213, 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 temporary

1 Tokyo Electric Power Company Holdings Inc., “Report on the accident event of the drainage at the shallow draft

wharf and storage of rubble,” study group on monitoring and assessment of specified nuclear facilities meeting(90th), Material 4, April 19, 2021
2 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 Decommissioning and Contaminated Water/Treated Water Management (90th), Material 3-6, May 27,
2021
3 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, April 19, 2021

15

storage area was confirmed4. 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 inadvance 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. (ALPS-treatedtanks

water and water under treatment) stored in welded 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
by the end of FY2023.

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
liquid waste
4 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

16

Solid waste storage
facility
Soil-covered temporarystorage, etc.

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), felled 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), felled trees stored in
outdoor storage
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

Outdoor storage, etc.

(Logarithmic scale)

Risk level (Linear scale)

Risk level

Contaminated structures, etc., in thebuildings

Fuel removal from Unit
4 SPF started

Risk level (Linear scale)

Rubble, etc.

0 1 2 3 4 5 6 7 8 9 10 11
Year 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

2.5

3

4

Year after the accident
Fuel debris
燃料デブリ

*1
*2

Fuel in SFPs
プール内燃料

5

6

7

8

9

10

11

Year after the accident

Contaminated
汚染水等
water, etc.

Fuel debris
燃料デブリ

Fuel in SFPs
プール内燃料

Contaminated

汚染水等
water, etc.

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. 3 Reduction of risks present in the Fukushima Daiichi NPS

17

(Reference)The Technical Strategic Plan 2021

The Technical Strategic Plan 2022

Fuels incommonpool

Fuels indry casks

Rubble instoragefacility

Region of sufficiently
stable management(March 2022)

Hazard Potential (logarithmic scale)Hazard Potential (logarithmic scale)

Region of sufficiently
stable management

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)
Stagnant waterin bldgs
Zeolitesandbags
Stored water
Color-coding of risk
in welded tanks Residual water
sources within flanged tanks
reference to the MidSoil covered
and-Long-term
temporarystorage, etc.
Roadmap *Fuels indry casks(March, 2021)

Fuels incommonFuel debris
pool
Contaminatedstructures in bldgs.
Unit 1
Unit 3
ALPS
Waste slurry
Uint 2absorption
Unit 2
Fuels incolumns
Waste
SFPs
Unit 1
Concentrated sludge
liquid waste, etc.

Rubble instorage
Stored water
facility
in welded tanks

Stagnant waterin bldgs.
Zeolitesandbags

Soil covered
temporarystorage, etc.
Outdoorstorage, etc.

Outdoorstorage, etc.

Residual waterin flanged tanks

Safety Management (logarithmic scale)

Safety Management (logarithmic scale)* 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 those thatare 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 2021 (as of March 2021).
The origin of the arrow indicates the location for the residual water in flanged tanks reported in the TechnicalStrategic Plan 2021, which has been moved upward to reflect the results of the analysis of the radioactivity
concentration prior to the treatment. ALPS slurry (to be transferred to other HICs) was separated from ALPS slurry
this time and shown in pink, as is the fuel in the pool.

Fig. 4 Risk levels posed by major risk sources at the Fukushima Daiichi NPS
2.2.2 Risk reduction strategy
2.2.2.1 Interim targets and progress of the risk reduction strategy
Measures for risk reduction include the reduction of the “Hazard Potential” and the reduction of
the “Safety Management” level. Examples of reduction of the “Hazard Potential” include thedecrease in inventory and decay heat associated with radioactive decay, and changing the form ofliquid and gas into a less moveable form. Processing contaminated water to change it into
secondary waste is an example of form change.
Examples of reduction of the “Safety Management” level include transferring fuel in SFPs to the
Common Spent Fuel Storage Pool, and placing rubble stored outdoors into storage. Of the various
risk reduction measures, reduction of the “Safety Management” level is generally considered to beeasily realized. Consequently, the decommissioning of the Fukushima Daiichi NPS, which is
implemented under the basic policy of “to continuously and quickly reduce the risks arising fromthe radioactive materials caused by the accident and that do not exist in normal nuclear power
plants” (refer to Section 2.1), should first focus on steadily managing risk sources by keeping themin higher-integrity facilities to lower their Safety Management levels. The interim target of the risk
reduction strategy is to bring the risk levels into the “Sufficiently stable management” region (thepale blue area) as shown in Fig. 4.

18

Regarding the progress of work from Technical Strategic Plan 2021 toward this goal, Fig. 4 shows
the status of treatment of the residual water (concentrated salt water) at the bottom of the flanged
tanks, and the need to replace some high integrity containers (hereinafter referred to as “HIC”s)storing ALPS slurry in consideration of the effect of β-ray irradiation.
Of the residual water in flanged tanks, sludge sedimentation containing α-nuclides has been
confirmed in the tanks5 that received the residual bottom water when dismantling tanks in eachtank area, recovery of the remaining water is currently underway6. Supernatant water has beentransferred to the process main building, and the water level is lower than assessed in the TechnicalStrategic Plan 2021. Only one tank contains residual water, including the sludge, and the collectionof the sludge through a filter is being carried out. In evaluation incorporating total α-nuclides
concentrations and the high strontium concentrations identified by the analysis of radioactive
concentrations prior to the treatment (analysis of the residual water sampled from two tanks on July
21 and August 5, 2021), high strontium concentrations have a significant impact, thereby increasing
the hazard potential compared to the Technical Strategic Plan 2021. However, it is a reflection of
the findings from the analysis and does not indicate the risk itself has increased. Not only in thiscase, but in other cases, there is uncertainty in risk source information. If an assessment isconducted based on estimates with limited information or fragmentary sampled data, there is apossibility of the risk being underestimated or overestimated.
Regarding the ALPS slurry, among the HICs affected by β irradiation, those accumulated
absorbed doses have exceeded the criterion value of 5,000kGy (accumulated absorbed dose withconfirmed HIC’s structural integrity against drop7)8 or are evaluated to be close to exceeding thecriterion value, and those ALPS slurry are planned to be transferred to other HICs by the end of
FY20239 is shown in pink in Fig. 4. Since the number of HICs whose accumulated absorbed doseis close the criterion value will gradually increase with time, it is important to carry out transfer
operation steadily and manage not exceeding the criterion value. To this end, the slurry stored in
HICs that exceeds the criterion value should be eliminated by systematically transferring them by
the end of FY2023. After that, the transfer operation should be made before the criterion value is
exceeded in a systematic manner. In addition, an early transition to storage in containers with longterm integrity leads to an intrinsic reduction in the risk of deterioration over time. TEPCO is

5 Tokyo Electric Power Company Holdings Inc., “Policy to respond to α-nuclide detected in remaining water in the

E area (flanged) tank,” Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water and Treated Water Treatment (94th), Material 3-1, September 30, 2021
6 Tokyo Electric Power Company Holdings Inc., “Future policy toward dismantling E area tanks,” Meeting of theSecretariat of the Team for Countermeasures for Decommissioning and Contaminated Water Treatment (100th),Material 3-1, March 31, 2022
7 Tokyo Electric Power Company Holdings Inc., “Design for slurry stabilization process,” study group on
monitoring and assessment of specified nuclear facilities meeting (88th), Material 1-2-1, February 22, 2021
8 The allowable strain was established from the material test results of HIC polyethylene specimens irradiatedwith 5,000 kGy of β-rays. It was confirmed that the maximum strain obtained from the drop analysis was lessthan the allowable strain.
9 Tokyo Electric Power Company Holdings Inc., “Status of HIC slurry transfer work,” study group on monitoring
and assessment of specified nuclear facilities meeting (98th), Material 3-6, March 14, 2022

19

reviewing the design of containers with long-term integrity in the design for stabilizing slurry10, andthis should be promoted without delay. As the decommissioning work becomes more prolonged,
important actions are monitoring and managing risk sources in consideration of the deterioration offacilities and systems and promptly bringing risk sources to a stable and controlled state.
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 response to the “Risk in external events”, TEPCO is proceeding with studies related to natural
disasters, including measures against tsunami and large-scale rainfall, and building integrity
evaluations, as stated in the Mid-and-Long-term Decommissioning Action Plan 202111 and 202212.
TEPCO should continue verification on the system and facility integrity against external events
including natural disasters, and develop their actions commensurate with the degree of risk.
2.2.2.2 Risk reduction process for major risk sources and its progressFig. 5 shows the process to bring major risk sources into the “Sufficiently stable management”
region as the interim goal, and representing the decommissioning work progress along this process.
Fig. 5(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. 5(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.
As changes from Technical Strategic Plan 2021, the treatment process of the residual water in theflanged tanks (sludge recovery by water filtering) are shown, and the ALPS slurry is indicated ingreen and pink, some ALPS slurry is planned to be transferred in light of the impact of β irradiation.
The number of spent fuel assemblies as an indicator to make the work progress easier to see in
Fig. 5(b), and for Cs-137, the estimated radioactivity (Bq) common to various risk sources as anindicator in Fig. 5(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. 5(b)has made no progress since Technical Strategic Plan 2021. Fig. 5(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 2021. In this Figure, the significant increase in the percentage ofattenuation is shown in light gray. In light of the impact of β irradiation, the ALPS slurry stored in
HICs to be transferred is transferred to the pink area.

10 Tokyo Electric Power Company Holdings Inc., “Design for slurry stabilization process,” study group on

monitoring and assessment of specified nuclear facilities meeting (92nd), Material 2-2, July 12, 2021
11 Tokyo Electric Power Company Holdings Inc., “Mid-and-Long-term Decommissioning Action Plan 2021”, March

25, 2021
12 Tokyo Electric Power Company Holdings Inc., “Mid-and-Long-term Decommissioning Action Plan 2022”, March

31, 202220

Color-coding is the same as in Fig. 4
Arrows show the diffusion/processing flow of risk sources.
Dotted lines indicate the scope of future studies and being studied.

Category

Sufficiently stable
management condition

Processing

Risk source

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※3※2
Cs-137
released during
the accident

Stagnant water inbuildings

Purify Cs/Sr

Welded tanks(Sr-treated water)

Removemultinuclide

Water
filtering*１

Residual water inflanged tanks

Filtered water* 2, *３
Concentrateby evaporation(Operation stopped)*１

Concentrated liquid
waste, etc.

Welded tanks(ALPS-treated water)

Sludge *４

Solid waste
storage facility

Dehydrate/stabilize

ALPS slurry(Incl. to be transferred to（高線量HIC含む）
other HICs)

Temporary storageof used 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”*３ Connect the arrow from
“Water filtering”(For detail in progress)*４ Place to be stored is being
arranged.

Soil-covered, etc.

Discharge into theenvironment(a) Risk reduction process
Additional

Residual water in the buildings(FY2021)(to be transferred to other HICs)

事故時に放出されたCs-137
and ALPS slurryattenuation

Spent fuelstored in SFP

AttenuatedEnvironmental
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. 5 Risk reduction process for major risk sources and its progress (as of March 2022)(Attenuation in Fig. 5 (c) takes into account radioactive decay of Cs-137 from the time of the accident to the end of March 2022)

2.2.2.3 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 the primary containment vessels (hereinafter referred
to as “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 the PCVs, radiation dose measurement and21

video photographing in the buildings, and other means. However, there are still significant
uncertainties. Eliminating these uncertainties requires many resources and, in particular, aconsiderable amount of time. In order to realize prompt reduction of risk, 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 with experiment and analysisbased 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 five guiding principles)
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 risk
to be as low as reasonably achievable (“Efficient”) as promptly as possible (“Timely”) in light of thesituation at the site, and proceeding with the decommissioning in a reliable manner (“Proven”) 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.

22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 without
prolonging the decommissioning activities
Consequently, TEPCO, as the operator of the decommissioning project, needs to pay special
attention to the following points in proceeding with the decommissioning based on the five guiding
principles.
Firstly, with regard to “safety”: There is great uncertainty about the state of radioactive materials
and containment barriers, and on-site access and installation of instrumentation devices to reduce
the uncertainty are also restricted. Under these circumstances, a large amount of atypical andunsealed radioactive material will be handled in an incomplete state of containment. Therefore, thestarting point for all reviews should be confirmation of the feasibility of ensuring safety with a wide
range of possibilities (cases) assumed. At the same time, with regard to “safety”, it is important not
to prolong the work period in light of risk reduction over the entire work period. Therefore, it isnecessary to avoid excessive safety measures and to take optimum safety measures (ALARP13).
Such perspective on “safety” (the safety perspective) should be reflected in the decommissioning
work review.
Secondly, with regard to “field-oriented”:
・ The on-site environment is in a peculiar state that includes a high level of radiation, andtherefore attention should be paid to the feasibility of construction/implementation ofsafety measures on site.
13Abbreviation of As Low As Reasonably Practicable. This is the principle that the radiological impact must be as

low as reasonably achievable.

23

・ An approach through design alone has limitations due to significant uncertainties.
From the above-mentioned reasons, it is essential to accurately apply the information gained onsite into engineering. In order to ensure the implementation of unprecedented engineering such asfuel debris retrieval, the views and feelings of the individuals and organizations (operators) that are
responsible for the on-site work (including operation, maintenance, radiation control,
instrumentation, analysis, etc.) and very familiar with actual site should be highly respected.
Moreover, it is important to respect their perspectives and judgements directly based on the site(the operator’s perspective). In promoting the prolonged decommissioning work, it is necessary tomaintain and strengthen the operator's perspectives/feelings, and TEPCO themselves should
inherit their perspectives. Therefore, TEPCO needs to take action that always accounts for theworksite in the overall decommissioning work process, such as by inviting outside experts andtechnicians with operator’s perspectives for coaching/educational training, including experienced
workers in difficult operations and those who experienced on-site operations.
In the actual study of the decommissioning work, TEPCO, as the decommissioning project
executor, should clearly define the “requirements” for the work in advance, 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. Specifically, requirements should be established in consideration of“the safety perspective” and “the operator’s perspective”, and specific safety measures selected
for the work that should satisfy the requirements, considering the two perspectives. In each stageof reviewing the decommissioning work, in this manner, sufficient attention should be paid to “thesafety perspective” and “the operator’s perspective”.
In this decommissioning work with significant uncertainties, it is frequently difficult to clearly
define requirements in advance. Even in such cases, the decommissioning work should be carriedout flexibly and promptly with by verifying and improving the selected, specifical safety measures
as the “preliminary implementation and utilization of the obtained information in the latter stages”
and “iteration-based14 engineering” as described later.
This section first calls for promulgation of the “Safety First” by operators. Next, the section
describes the importance of the safety assurance measures in terms of the characteristics ofFukushima Daiichi NPS based on safety assessment which includes the operator’s perspective.
Then, it describes the operator’s perspective-specific importance that should be incorporated at
multiple levels in the safety assurance process while requesting spread of “Safety first” performedby project operator. Lastly, the section refers to the importance of ALARP judgment.
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)
14 A method that gradually increases the level of completion of engineering by obtaining the next result from one

result and repeating this process.

24

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 (safety first). The specific application of the general “safety first”
principle in the projects means, “Conducting extensive assessments on safety matters associatedwith methods and devices when reviewing any project and, upon verifying that necessary andsufficient levels of safety have been ensured, taking into account factors such as technical reliability,
reasonableness, speed, actual site applicability and project risks in a comprehensive manner todecide 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 first”
principle 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.
2.3.1.2 Optimization of judgement with a safety assessment as its basis and ensuring
timeliness in decommissioning
With an aim of reducing risk through decommissioning, it is most important to take appropriate
measures and ensure the safety of work in which a large amount of radioactive material is handledthat is technically difficult and has significant uncertainties, such as fuel debris retrieval. Thus,
decommissioning work should be carried out with such “safety perspective”.
Specifically, when designing safety measures for each decommissioning activity, it is essential
to make decisions based on the five guiding principles after conducting a thorough safety evaluationand confirming that the required safety is ensured. As mentioned above, the decommissioning workof the Fukushima Daiichi NPS is unprecedented and has significant uncertainties. Using
deliberated safety evaluation as the basis for making decisions regarding safety measures, thedecisions will not be significantly unstable (that is, without devoting too little or excessive resources),and thus necessary, sufficient, and reasonably feasible safety measures can be realized(optimization of judgment based on safety assessment). In regard to reasonably feasible safetymeasures, it is particularly important in the safety assessment of the Fukushima Daiichi NPS to
conduct safety assessment with incorporating operator’s perspective stated in the section 2.3.1.3.
In addition, the importance of making progress in the decommissioning work without delay (theimportance of time-axis-conscious action) can be mentioned as “the safety perspective” unique tothe decommissioning of Fukushima Daiichi NPS. Considering the high radiological impact that has
already materialized, and the possibility of further degradation of containment barriers, etc., making
progress in the decommissioning work without delay will have great significance for ensuring thesafety of the entire decommissioning process from a medium-and-long term perspective. Therefore,
it should be noted, for ensuring safety, that different perspectives from normal reactors are required,
which have a certain margin in terms of human, physical, and financial resources and have low

25radiological impacts and high stability. On the condition that safety is secured, rational judgement
should be made on resource allocation and the time-axis-conscious progress in thedecommissioning work without delay based on the relationship with the overall balance (ensuring
timeliness in decommissioning activities).
2.3.1.3 Ensuring safety by incorporating “the operator’s perspective”
To ensure that safety measures are truly effective, it is necessary to satisfy the needs from thestandpoint of those who actually perform the operations and tasks on site, "the operator's
perspective" (perspectives and judgements from the standpoint of those who are familiar with thesite and perform operations and tasks on site) is important. In addition to this standpoint, when
determining the feasibility of safety measures in decommissioning the Fukushima Daiichi NPS, it
is necessary to take into account the fact that the facility has suffered from the accident, and its
decommissioning requires an unprecedented approach in a peculiar environment, such as one withhigh radiation levels, unlike normal reactors.
“The operator’s perspective” is also important for ensuring safety from the following perspectives,
which are different from those of normal reactors.
Complementation of design by operations, including operating controls:
Due to significant uncertainties, there is a limit to addressing all situations by design alone.
Therefore, 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 tocriticality safety, (the composition of fuel debris and subcriticality, etc.) at the current Fukushima
Daiichi NPS has high uncertainty due to difficulties in the measurement environment on site,even if it can be acquired. Even in such an environment, it is necessary to proceed with fueldebris 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 eachwork step as significant fluctuations of measured value. Even if cutting and other work ofsufficient magnitude to cause noise, identifiable and significant fluctuations in measured values
are performed with relatively small subcriticality, it is possible to take action by maintaining
subcriticality or identifying signs of criticality through operations based on design and actual
measurement values. In other words, as described above, 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, it is important to utilize information obtained throughon-site operations such as monitoring and analysis, etc., in designing safety measures. Whenutilizing such information, it should be linked with calculational evaluation, etc., to “make acomprehensive use of it”.

26

・ Handling an 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
considering the characteristics that the progress of abnormalities is moderate and there issufficient time to respond15.
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 or equipment can be used. At levels above the level that meets this minimum level,
there is a range of choices and, within this range, retrieval methods and equipment to be adopted
will be determined based on trade-off between the safety level to be achieved and project cost andduration (note that retrieval method and equipment involving long-term large safety measures are
not necessarily beneficial to safety, especially at Fukushima Daiichi NPS), a kind of ALARP. Thereis also an issue as to whether such retrieval methods and equipment are feasible in the field.
Based on the above, in the process of determination, it is important to decide retrieval methods
and equipment to be employed eventually through the cycle of “defining the safety standards(safety perspective)”, “indicating the feasibility on-site (operators’ perspective)”, and “examining
and discussing at projects (project management)” as shown in Fig.6. As shown in this figure, thesafety 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 and 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.

Fig.6 ALARP centered on safety (conceptual diagram)

15Since 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 margin to respond.

27

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 the whole operation of a large-scale project suchas fuel debris retrieval is to be designed 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 risk of rework will be unavoidable. As a result, the feasibility or predictability of theentire project may be reduced, leading to a delay in the entire decommissioning, a rise in thedecommissioning 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 approach16, operation
proceeds with safety ensured through monitoring the condition inside reactor, restricting operational
actions and flexible on-site responses at each stage of the process17. 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
management18.
In a case that uses a similar approach, TEPCO has been conducting reactor water injection
shutdown tests since FY 2019. One of the purposes of these tests is to contribute 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 (rising temperature of fuel debris andthe RPV bottom, increased dust scattering outside the PCV, and re-criticality when resuming water
injection), and by gradually extending the testing time while taking certain risks. In the future, efforts
should not be limited to identifying risks and accumulating knowledge during the shutdown of water
injection, but should be expanded to account for acquiring a basis that contributes to the design ofwater injection systems for fuel debris retrieval, i.e., obtaining information on the number of pumps

16This is also used in the UK, for example, for the decommissioned facilities in Sellafield and is called Lead & Learn.
17 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.
18 This is stated in the Decommissioning Implementation Plan (March 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/2021/1585525_8711.html

28required for water injection, the appropriate amount of water injection and changes in the coolingconditions of fuel debris due to differences in the points of water injection.
These reactor water injection shutdown tests have resulted in the clarification of the relationshipbetween the lowering of the PCV water level and pressure in Unit 1. According to the informationon the damaged piping that was obtained from the on-site investigation conducted before the tests,
it was assumed that the PCV pressure might decrease when the water level reached the pertinent
damaged area. In fact, the occurrence of the event, which developed as predicted, further
enhanced the degree of confidence of the presumed cause that “the PCV pressure dropped as aresult of exposing the damage area due to the lowering of the PCV water level”.
This example yielded results that led to reducing the uncertainty through examination in
combination with the information gained from on-site investigations, although this information is notdirectly related to the purpose of the test.
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. For example, the same applies to risk identification associated withhydrogen at the time of fuel debris retrieval. Testing to reduce nitrogen supply for an experimental
purpose may help identify hydrogen risk, and determine requirements on the necessary amount of
nitrogen supply and reliability of the exhaust systems to ensure safety.
It is important to accumulate successful/unsuccessful experience gained in the process of thesesequential approach as a track record, allowing gradual reduction in major uncertainties in theoverall decommissioning work in the future. This will lead to steady progress in decommissioning
and contribute to ensuring safety in decommissioning the Fukushima Daiichi NPS from theperspective 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 as29

achieved through application of the concept of ALARA (to suppress radiation exposure to As Low
As Reasonably Achievable).
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, with regard to the selection of work methods, the design andmanufacture of equipment and safety systems, and the development of work plans for thedecommissioning work, cautious and comprehensive decision making is required for early
implementation of decommissioning in consideration of many constraints such as time, cost, andworker’s exposure needed for relevant preparations and work, while giving priority to limiting therisks involved in the decommissioning work (Attachment 5).
The approach to risk reduction and ensuring safety in the decommissioning of the Fukushima
Daiichi NPS, as described in this chapter, needs to be promoted with the broad understanding of
not only the people directly involved but also the local people. Therefore, it is necessary for the
local community, the government (METI, NRA), NDF, TEPCO, and others to cooperate with eachother to reduce risks based on the approach to ensuring safety taking their respective positions
into account. In doing so, it is important to establish a system for on-going risk monitoring whichenables a wide range of people to easily understand how the overall risks at the site have been
continuously reduced through the decommissioning work, and to communicate such progress tothe public. In addition to sharing the status of risks through the Technical Strategic Plan on aconstant basis, NDF is considering providing the status of risk reduction along with the progress ofthe decommissioning work described in 2.2.2.2. TEPCO also needs to develop a mechanism toidentify risks for the entire site and become aware of the need to take action to communicate thestatus of risk reduction to society in a proactive manner.

30

3. Technological strategies
Fukushima Daiichi NPS

towarddecommissioning

of

the

3.1 Fuel debris retrieval
3.1.1 Targets and progress(Targets)(1) Retrieve fuel debris safely after thorough and careful preparations, and bring it to a state ofstable storage that is fully managed.
(2) Trial retrieval in Unit 2 was scheduled to begin within 2021, but the process will be reviewed
to improve work safety and reliability during retrieval in light of the impact of the COVID-19
pandemic, ongoing mock-up tests at the Naraha Center for Remote Control Technology
Development since February 2022, and the status of the on-site preparatory work in Unit 2,
and trial retrieval is expected to begin in late FY 2023. Continue a series of work, including
gradual expansion of fuel debris retrieval, to acquire the knowledge and experience necessary
for further expansion of fuel debris retrieval in scale (for the fuel debris targeted for retrieval,see Attachment 6).
(3) With regard to 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, byassessing fuel debris retrieval in Unit 2, internal investigations, research and development,
and the on-site environmental improvement, etc.
(Progress)
Fig. 7 shows the estimated fuel debris distribution, access route and surrounding structures ofUnits 1 to 3. The progress in each unit is also shown below.
① Unit 1
PCV internal investigations have been conducted using a boat-type access investigation device
with a diving function (hereinafter referred to as “underwater ROV”), which can be equipped withvarious measurement sensors. The underwater ROV is inserted into the PCV through thepenetration X-2 to access the basement floor outside the pedestal. To construct this access route,installation of isolation valves on the penetration X-2, drilling of holes in the outer and inner doors,
removal of obstacles in the PCV, and installation of a guide pipe, etc., were completed in October
2021. Afterward, before investigation started problems occurred due to underwater ROV dosimeter
noise and a camera monitor display malfunction, but after taking measures to prevent a recurrence
based on the results of an investigation of the cause, the investigation began in February 2022.

So far, visual investigations and deposit thickness measurements have been in progress. In
the visual investigations, lump deposits have been observed outside and inside the peripheryof the worker access opening in the pedestal. However, whether they are existing structures
or fuel debris has not been determined. In addition, reinforcing bars were observed in the vicinity31

of the worker access opening, and it was confirmed that concrete in the pedestal area was partially
missing. Regarding this matter, IRID conducted a seismic assessment of the partially damaged
pedestal in FY 2016 under the Project of Decommissioning and Contaminated Water Management
and confirmed that its supporting function was not significantly impaired. TEPCO is also considering
the impact of the pedestal damage on the plant based on the currently available information,
assuming that TEPCO will continue to expand and evaluate its findings through internal
investigations19. According to the consideration, based on the observations of the external surfaceof the pedestal, TEPCO assumes that the movement, collision, or fall of structures to be supported,which is considered to be caused by damage to the pedestal, is unlikely to lead to large-scale
damage or other problems. In addition, as a result of examining the impact on the cooling of fueldebris, dust dispersion, and criticality as the impact on safety in the case where the pedestal
support function declines and the RPV and other structures incline or sink, TEPCO has concluded
that there is no significant risk of radiation exposure to the surrounding public. NDF believes that itis necessary to expand and evaluate knowledge through internal investigations in the future andwill validate the results of internal investigations conducted by TEPCO and the impact assessmenton the plant based on these results.
Further investigations are planned to observe the distribution of deposits widely scattered at thebottom of the outside of the pedestal, the presence or absence of fuel debris in deposits,
sampling/analysis of deposits, and the condition of structures inside the pedestal.
As a future action, lowering the water level is planned to improve the seismic resistance of the
S/C. As preparations to lower the water level, such as by water intake using existing piping andwater quality surveying of the S/C water, an investigation of the northern side of the first floor of thereactor building is underway to improve the on-site environment.
② Unit 2
The 2019 Mid-and-Long-term Roadmap specified Unit 2 as the first implementing unit where fueldebris retrieval would be implemented, and trial retrieval was supposed to launch within 2021. The
process has been delayed due to the impact of the COVID-19 pandemic, work proceeded to limit
the delay to about one year.
Then, after completing the manufacture and verification tests of the arm-type access equipment(hereinafter referred to as “robot arm”) in the UK in June 2021, the equipment was brought to Japanand has been undergoing performance confirmation tests, mock-up tests, and training at thedomestic factory (Kobe) since July 2021, and at the Naraha Center for Remote Control Technology
Development, JAEA since February 2022. Modification and verification of the control software andimprovements to some equipment, which are new requirements based on these tests, are being
progressed. Furthermore, the plan is to expand one-through testing for higher reliability.

19The 100th meeting of the Study group on monitoring and assessment of specified nuclear facilities, “Material 3:

Status of primary containment vessel internal investigation in Unit 1 (International Research Institute for Nuclear
Decommissioning, Tokyo Electric Power Company Holdings Inc.)”32

In addition, as on-site preparatory work, installation of the isolation chamber for opening hatchof the penetration X-6 started in November 2021. As countermeasures for the damage to the box
rubber and the bent guide rollers (in response to the earthquake) in the isolation chamber that
occurred during installation, replacement of the rubber box with metal plates, cutting off hatch
handle of the penetration X-6, and structural changes to the guide roller are planned. In the future,
work feasibility will be verified through factory mock-up testing. Remanufacturing of the isolationchamber is also under consideration in case any issues are identified in the verification results andinstallation condition of the isolation chamber after implementing countermeasures. As operations
such as opening of the penetration X-6 hatch and removal of deposits in the penetration X-6 areplanned, work should be carried out safely and carefully. (See Section 3.1.2.2 for details).
As described above, given the response status based on the mock-up test of the robot arm andthe arrangement of countermeasures in on-site preparatory work, it has been decided to add
another 1 to 1.5-years to the preparation period along with the preceding delay of about one year
due to the impact of the COVID-19 infection to improve work safety and reliability and to change
the process to start trial retrieval in late FY 2023.
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 while complying
with specifications for the devices for trial retrieval (internal investigations and fuel debris sampling).
In this plan, the requirements related to performance of the robot-arm and enclosures and therequirements at the design and installation have been clarified and examined. The retrieved fueldebris will be stored in container for fuel debris retrieval and transport container in the enclosure,and then transferred to the receiving/delivery cells on site and stored in temporary storage cells. In
addition, some of the fuel debris will be collected in the receiving/delivery cells for analysis andtransported to the facility for analysis. Designing of the retrieval device, receiving/delivery cells, andtemporary storage cells is in progress (Fig. 8, Fig. 9).
In response to the unprecedented approach to retrieving fuel debris from the first implementing
unit, NDF continues working while verifying the actual site applicability of the device and the resultsof the review on modifications to the safety system from the perspectives of safety, reliability,
reasonability, timeliness, and a field-oriented stance, in accordance with the progress ofengineering at TEPCO.
③ Unit 3
Regarding Unit 3, due to the high water level in the PCV, the plan is to lower the PCV water levelin two steps, taking into account the conducting of the PCV internal investigation and the improved
seismic resistance of the S/C. The plan for lowering the water level in Step 1 was to drain the PCV
water by self-suction pumps using the existing pipe connected to the S/C to reduce the current
water level below the first floor surface of the reactor building. However, after the earthquake on
March 16, 2022, it was confirmed that the PCV water level was gradually declining. After the startof the planned reactor water injection shutdown tests in June, water injection was resumed tocontinue water level measurement because it was determined that the PCV water level had fallen

33

below the lower end of the new PCV thermometer/water level gauge. After that, the amount of water
injection was adjusted in July, confirming that the PCV water level was generally stable.20 Basedon the above circumstances, for the plan to lower the water level in Step 1, monitoring of plantparameters will be continued, and a reduction of the amount of water injection or the shutting downof water injection will be discussed to install instruments at lower locations than current levels andlower the PCV water level21. In Step 2 in the future, the plan is to connect the guide pipe to the S/C
and lower the water level to the bottom of the S/C by underwater pumps installed inside the S/C.
Although retrieval methods for further expansion of fuel debris retrieval in scale were examinedin the conceptual study, many challenging issues and risks associated with each discussed method
were identified. Since FY 2022, studies have been conducted on countermeasures for these issues
and risks from the perspective of feasibility. (Refer to 3.1.2.1.4 for detail)20. 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”
21 The 103rd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated/Treated Water, “Reference 3-5: Unit 3 reactor water injection shutdown tests”

34 Little fuel debris remains.
Core region

 Little fuel debris remains.

At RPV lowerhead A small amount of fuel debris is present.
 Large amount of fuel debris is present.
 Part of fuel debris is present.
 A small amount of fuel debris is present A small amount of fuel debris is present A small amount of fuel debris is present
inside and on the outer surface of the CRD inside and on the outer surface of the CRD inside and on the outer surface of the CRD
housing.
housing.
housing.

At the PCV
bottom(Inside thepedestal) Most of the fuel debris is present.

 A certain amount of fuel debris is present.

 Amount of fuel debris in Unit 3 is morethan that in Unit 2.

At the PCV
bottom(Outside thepedestal) Fuel debris may have spread outside thepedestal through the personalentrance(Deposits have been observed).

 The possibility of fuel debris spreading
outside the pedestal through thepersonal entrance is low.

 Fuel debris may have spread outside thepedestal through the personal entrance.

(Partially intact fuel might exist in the peripheral
region) Little fuel debris remains.

 Radiation dose on the first floor of R/B
Radiation dose  Radiation dose around the penetration X-6
 Radiation dose on the first floor of R/B had
in operationon the first floor of R/B is high (145reaches several to tens of mSv/h or higher
reducedtoapprox.
5
mSv/h
as
a
whole.
*1
site
mSv/h).
than those, indicating a high dose level.

 Exposed rebars were observed aroundthe personal entrance.
 The D/W bottom outside the pedestal isaccessible from the upper side of the steel  No large obstacles have been observed
Information on
on the CRD rail and around the pedestal
grating.
the access The bottom inside the pedestal isentrance.
accessible through the pedestal entrance.
route to fuel  Condition around the CRD rail connecting The bottom inside the pedestal is*2debrisinto the pedestal from the penetration X-6
accessible through the pedestal entrance.
has not been observed.
 At personal entrance, the inner rebar andinner-skirt are exposed, and the PCW
 While a part of fuel assemblies havesystem piping is missing.
 Some damaged structures and fallen
fallen, no damage has been observed on
Information on  A deposit approx. 1.0 m thick has been
objects (which may include internal
the CRD housing support in the examinedthe condition of observed around the personal entrance ofstructures), and the fall and deformation ofrange .
outside the pedestal (condition, e.g.
a part of the CRD housing support havestructures
cavities, of the deposit inside could not be  No damage has been observed on the
been observed inside the pedestal.
around theconfirmed)
 No damage has been observed on theaccess routewall surface and the structures (CRD No significant damage has been observed
wall surface inside the pedestal.
exchanger, etc.) inside the pedestal.
on the wall surface outside the pedestal on
the steel grating upper side.
*1 Data provided by TEPCO*2 Results obtained through PCV internal investigation performed up to date were presented for judging whether any obstacles such as fallen objects
may exist on the route to the inside of the pedestal from X-6 penetration, which is considered as a dominant access route for fuel debris retrieval by
the side access method.
Other access routes through the equipment hatch and others have been investigated under the Governmental-led R&D program on Decommissioning
and Contaminated Water Management.
Due to high dose rate around X-6 penetration of Unit 1, an access route through the equipment hatch may be used in case that it is difficult to improvethe environmental condition around X-6 penetration.
PCV internal investigation of Unit 1 will be performed through X-2 penetration (equipment hatch) considering accessibility of devices for PCV internal
investigation.

(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. 7 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 335

エンクロージャ

PedestalPedestal
opening
ペデスタル開口

Connection
pipe
接続管

エンクロージャEnclosure

PenetrationX-6
X-6ペネ

Penetration X-6
Robot arm

ロボットアーム
Robot arm

エンクロージャEnclosure

Enclosure
Operation area

ロボットアーム
Robot arm

Photo : Testing facility in Naraha Center for
Remote Technology Development (JAEA)

Photo : Robot arm and Enclosure

Enclosure side

Pedestal side

Robot arm

Photo : Robot arm at maximum extension(Prepared by NDF based on TEPCO and IRID materials)

Fig. 8 Image of fuel debris retrieval system(Trial retrieval and gradual expansion of fuel debris retrieval)(TEPCO material edited by NDF)

Fig. 9 Image from retrieval to temporary storage of fuel debris(Gradual expansion of retrieval scale)
3.1.2 Key issues and technical strategies to realize them
Since the understanding the situation inside the PCVs is still limited, the current design and theplan for on-site operations related to fuel debris retrieval should be continuously reviewed basedon knowledge that will be obtained in the future, and it is also important to accurately incorporate
the results of studies, research and development toward fuel debris retrieval.
The trial retrieval (internal investigation and fuel debris sampling) in Unit 2 will be the first retrievalof fuel debris, and it is necessary to make steady preparations to utilize the valuable informationand experience obtained through these works in subsequent retrieval operations. Thereafter, the36

gradual expansion of fuel debris retrieval will be implemented based on the findings obtained fromthe retrieval in Unit 2. In addition, a conceptual study on the further expansion of fuel debris retrieval
in scale for Unit 3 is planned. TEPCO has established Toso Mirai Technology Company (Decom.
Tech) (hereinafter referred to as the “New Engineering Company”) to be engaged in the basic
design and R&D of systems and installations for further expansion of fuel debris retrieval in scale
22. From now on, under the strong leadership of TEPCO, it is necessary to proceed withdecommissioning with cooperation between TEPCO as a parent company, the New Engineering
Company, manufacturers, researching institutions, and other related organizations based on properrole assignment. It is also important to effectively leverage the technologies cultivated mainly in the
New Engineering Company through these initiatives to improve TEPCO’s technical capabilities built
on safety and operator's perspective, as mentioned later.
Since each unit is in a different situation, this section first describes each unit's fuel debris
retrieval strategy in 3.1.2.1, followed by the strategies for trial retrieval (internal investigation andfuel debris sampling) in 3.1.2.2, and gradual expansion of fuel debris retrieval in 3.1.2.3, and further
expansion of fuel debris retrieval in scale in 3.1.2.4. This chapter then describes the continuous
accident analysis activities in 3.1.2.5, technical issues for technical requirements, and future plansin 3.1.2.6.
3.1.2.1 Fuel debris retrieval strategies in each Unit
(1) Unit 1• Toward the further expansion of fuel debris retrieval in scale, it is necessary to promote R&D andengineering to apply the results on-site and then incorporate into equipment design, retrieval
procedures, and safety assessments for the use of the knowledge gained through trial retrieval
in Unit 2, e.g., conditions of existing structures and sediment distribution, gamma-ray and neutron
count distribution, the degree of impact on containment functions caused by loading/unloading
equipment, and information on fuel debris to be collected during retrieval. In addition, the retrieval
methods should be examined based on the initial study results of the method for Unit 3.
• In the ongoing PCV internal investigation, the condition of the existing structures and distribution
status of deposits outside the pedestal are being confirmed, an investigation inside the pedestal
through the worker access opening is also scheduled. However, although the previous
investigations and analyses using muon have evaluated that there is almost no fuel debris in thecore, they were not direct investigations. Thus, a direct video investigation is required in a future
study. As technological development for this purpose is in progress, the information obtained
from these investigations should be incorporated as necessary when examining retrieval
methods hereafter.

22 Tokyo Electric Power Company Holdings Inc., “Establishment of ‘Toso Mirai Technology Company’ toward fueldebris retrieval at Fukushima Daiichi NPS”, October 3, 2022

37

• The size of the RPV and PCV is smaller than Units 2 and 3 due to a lower plant output, and thelayout of plant systems also differs. In addition, although it is expected to be clarified in a future
investigation, the distribution of deposits inside the RPV and inside/outside the pedestal isconsidered to be different from Units 2 and 3. Therefore, it is necessary to examine retrieval
methods considering these differences.
(2) Unit 2• Preparations for trial retrieval are underway, and the plan is to gradually expand fuel debris
retrieval. However, since there is no plan to retrieve all the fuel debris using the side-accessmethod, it is necessary to examine methods for the further expansion of fuel debris retrieval inscale.
• Toward the gradual expansion of fuel debris retrieval, it is necessary to advance R&D andengineering for applying the results on-site, and then to promote design, manufacturing, andinstallation of fuel debris retrieval systems, safety systems (e.g., containment, fuel debris cooling,
criticality control), temporary fuel debris storage, and maintenance systems for retrieval systems,
based on the knowledge gained through trial retrieval.
• Toward the further expansion of fuel debris retrieval in scale, it is necessary to examine theretrieval methods based on the knowledge gained through retrieval in Unit 2 and the initial study
results of the method for Units 3.
• 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 a possibilityof some fuel in the core, and this needs to be considered when examining retrieval methods.
Furthermore, although it is unlikely that the fuel debris that fell to the PCV bottom has spreadoutside of the pedestal, no investigation has been conducted inside the RPV and outside thepedestal. Thus, a direct video investigation is required in a future study.
(3) Unit 3• As described in 3.1.2.4 below, retrieval methods are being examined to further expand fuel debris
retrieval ahead of other units. From FY 2022 onward, the actual site applicability and technicalfeasibility should be studied for the issues and risks to be examined in greater depth.
• Previous PCV internal investigations (inside the pedestal) revealed that the control rod drive
housing support has partially fallen and deformed, several structures have fallen on the lower
part of the pedestal, including structures presumed to be structures inside reactor, and that there
are deposits assumed to be fuel debris. According to muon surveys and analyses, it is estimatedthat a larger amount of fuel debris than in Unit 2 may have fallen into the pedestal and spreadout of the pedestal through the worker access opening. In order to improve the reliability of themethods to be selected, it is necessary to consider survey planning to observe the distribution of38

deposits outside the pedestal, consider additional investigations in the pedestal and the RPV andincorporate these investigation results into the examination and design of the methods.
• When examining retrieval methods, it is necessary to examine containment facilities considering
the damage to the reactor building.
(4) A common strategy for each unit
• The PCV internal investigation of Unit 1 confirmed that the pedestal was partially damaged.
However, in past research and development, it was confirmed that its supporting function was
not significantly impaired in the seismic evaluation assuming the extent of the damage. Alongwith expanding knowledge through internal investigations, it is also necessary to discuss theevents during the accident, assumed from the fact that hot deposits (fuel debris) flowed out ofthe pedestal. Based on these discussions and knowledge, removal methods of deposits insideand outside the pedestal and the possibility of deposits flowing into the S/C should be examined,
while incorporating the findings gained from internal investigation into fuel debris retrieval
methods, including for other units.
• Information about the inside the PCV of each unit obtained so far is limited, and there are many
areas where direct video information is not available. Therefore, additional internal investigationof the PCV and RPV of each unit should be considered to promptly collect more information,
including the condition of the damage at the RPV bottom and the presence or absence anddistribution of deposits outside the pedestal. Gaining such information at an early stage enables
verification of the direction of the fuel debris retrieval strategy to be pursued in the future, leading
to engineering with less regressing.
• After analyzing and clarifying the causes of a number of on-site problems experienced in the onsite decommissioning work to date, improvements should be made, including in the organizationand structure, and consideration should be given to incorporating measures to prevent
recurrence into the next phase of the work. Planned fuel debris retrieval requires developmentof a method that can eliminate the potential risks based on these experiences, and for risks thatcannot be eliminated, preparing a response plan if these occur in advance.
• Fuel debris retrieval, including preparatory work, will be executed in a high-dose, severe site
environment. Although remote devices are used under various circumstances, workers will have
many on-site operations to reduce radiation dose on-site, prepare for the removal of the existing
structures, and prepare and arrange equipment for use. The maintenance of remote devices andrestoration in case of failure also need to be considered. It is necessary to examine methods
considering the entire field work sequence from preparation to retrieval and select methods thatenable retrieval even if all on-site conditions cannot be identified and methods (robust method)
not easily affected by external events such as earthquakes.

39• Although the amount of remaining fuel debris differs, it is assumed that fuel debris exists in the
RPV of each unit. Therefore, in the partial submersion method, using side-access only, which isconsidered to have limited access to the inside of the RPV, is not sufficient to cope with thesituation, and top-access is also required. Therefore, it is considered essential to accelerate thedevelopment and engineering of the top-access method again and then examine the fuel debris
retrieval method using a combination of top and side access methods. From this perspective,
examinations will be made on the methods, operation procedures, shielding systems and cellstructures to be installed on the operating floor, fuel debris and waste transfer flow, andclassification of contamination control.
3.1.2.2 Development status and prospects of trial retrieval (internal investigation and fueldebris sampling)
For the trial retrieval (internal investigation and fuel debris sampling) in Unit 2, the operation will
be performed by opening the flange of the penetration X-6 to make a larger opening than before,
through which the robot-arm is moved in/out to retrieve fuel debris inside the PCV. In this operation,
an expansion will be made to provide an isolation chamber (composed of a robot carrying-in room,etc.) to be built during opening the penetration X-6 (Fig. 10), and an enclosure to be newly provided(which encloses a robot-arm, etc.) (Fig. 11), since the conventional containment barrier was locatedin the close flange part of the penetration X-6. Although small in scale, this is a fundamental formof site construction for future retrieval work, in which an opening will be newly provided in the PCV
to extend the containment barrier outside the PCV. This presents an approach that enters a newstage.
As described above, trial retrieval (internal investigation and fuel debris sampling) is entering a
new phase, and the series of work described below should be carried out in a phased manner (SeeFig. 12). Moreover, due to the uncertainty of the conditions inside the PCV, it is necessary toproceed with the work safely and carefully, bearing in mind that additional work or rework may berequired depending on the actual on-site situation and that the work may not go as planned.
Furthermore, each of these operations has no precedent, and it is very important to utilize thevaluable information, experience, etc. gained through them in subsequent retrieval operations. In
addition, it is important to consider in advance troubleshooting and a system for a prompt responseto go with it.
(1)

Preparatory work (completed)[1] Environmental improvement around the penetration X-6 in the reactor building[2] Hole diameter enlargement of the penetration X-53
(2)

Installation of an isolation chamber (isolation room inside stage, hatch isolation room,
robot carry-in room) (in progress)(3)

Opening of the penetration X-6 hatch by hatch releasing apparatus(4)

Removal of deposits in the penetration X-6 by deposit remover

40

(5)

Robot arm installation (removal of the robot carry-in room, installation of the penetration
X-6 connection structure, extension pipe, and enclosure)(6)

Robot arm entry (penetration X-6 - CRD opening - inside the pedestal), surrounding check,and removal of obstacles (Abrasive water jet)

(7)

Internal investigation and fuel debris sampling by robot arm[1] Internal investigation from the PCV inlet to outside the pedestal[2] Internal investigation inside the pedestal (above the grating, PCV bottom, etc.)[3] Sampling from the inside the pedestal (sampling from above the grating and PCV bottom,
etc., is under consideration)(8)

Storage to shipping containers from fuel debris retrieval equipment, and dose
measurement(9)

Acceptance into gloveboxes and measurement(10)

Removal of containers, storage in shipping containers, and carry-out(11)

Off-site transport and off-site analysis (analysis of fuel debris properties)

Regarding preparation status of trial retrieval (internal investigations and fuel debris sampling),
it is expected that the production and installation of the required devices, site preparation, andinstallation of glovebox for transporting retrieved fuel debris will be completed, workers including
operators of various equipment/devices required for retrieval and on-site leaders will be secured,and the framework for verification tests, mock-up tests, training, and retrieval will be established by
the end of Phase 2 of the Mid-and-Long-term Roadmap.
Verification tests of the newly developed robot arm were conducted in Kobe (Kobe Shipyard &Machinery Works, Mitsubishi Heavy Industries) from July 2021 until January 2022, following
verification tests at a factory in the UK. Since February, verification tests (mock-up tests) have been
conducted in an actual simulated environment using the mock-up facility at the Naraha Center for
Remote Control Technology Development (JAEA), which covers the entire PCV from thepenetration X-6 and beyond.
It is important for on-site applications with uncertainty to ensure functional verification checks
under various conditions and equipment can be rescued in case of emergency. Therefore, it isnecessary to make the preparations needed, ensure that the required functions are satisfied byconducting mock-up tests that simulate the actual site even if it takes time, and ensure that newly
identified risks are eliminated. This process needs to be reiterated when necessary. For example,
mock-up testing at the Naraha Center for Remote Control Technology Development, progress isunderway to modify and verify control software and improve some equipment, both of whichbecame additionally required based on the results of verification tests in Kobe and in the UK.
Moreover, the plan is to expand one-through testing for higher reliability. Furthermore, it isnecessary to thoroughly prepare the measures required for the practical application, not only bysimulating severe environments on site in mock-up testing, but also by making clear any areas thatare not simulated.

41

In constructing the access route on-site, the installation of the isolation chamber has been
delayed due to the unevenness of the floor at the location of the isolation room inside stage andairtight leakage-proofing in the hatch isolation room, etc. After installation of the robot carry-in room
is completed, the plan is to open the hatch of the penetration X-6, remove deposits inside thepenetration X-6, and establish the penetration X-6 connection structures and the enclosure (with abuilt-in robot arm, etc.).
During the installation of the isolation chamber, leakage from the newly installed isolation room
inside stage was observed in an airtight leak test (leakage from rubber containment barrier). This
event reaffirmed that expanding the containment barrier outside the PCV, which interfaces with theexisting structures in a high-dose environment, would be a challenging task. It was also reaffirmedthat since heavily equipped workers need to be replaced in a short time for operations in a highdose environment, it is always necessary to ensure quality and safety in performing work. Moreover,in the future, when the installations of apparatus such as the robot arm system that are interfacingwith the existing structures outside the PCV to extend the containment barrier, it will also be achallenging task in a high-dose environment. Thus, careful preparation based on this event will benecessary. In addition to the above, paying full attention to the unique characteristics of Fukushima
Daiichi NPS, such as the fact that containment barriers are imperfect and uncertain, and thatearthquakes are expected to occur in the future, work descriptions should be reviewed again andoperation training should be provided to enhance future work safety and reliability. It is also
necessary to incorporate above features, knowledge and experience gained this time into
examining fuel debris retrieval methods after the gradual expansion of the retrieval scale.
Given the above events, equipment should be deployed on-site after sufficient performance andoperational verifications.

42

(TEPCO material edited by NDF)

Fig. 10 Schematic drawing of containment barrier during opening operation of the Penetration X-6

From Enclosure, Connecting pipe to Penetration X-6 connecting structure(approx.W3.6xL11.8xH2.1m(max))

Robot-armShielding
Isolation room inside Stage
Retractable Shielding
Airtight Door
Measuring
Hatch Isolation room
Instrument Gate Valve
Isolation Valve

InsidePCV

X-6
Connecting
Penetration X-6
PipeConnecting Structure

Enclosure：Previous Containment barrier：Containment barrier after expansion(TEPCO material edited by NDF)

Fig. 11 Schematic drawing of containment barrier during trial retrieval(Internal investigation and fuel debris sampling)43

(1) Preparatory work (completed)
Cutting machine (hole saw)

●Prework for spray jig installation(Hole diameter enlargement of thepenetration X-53)(6) Robot arm entry(7) Internal investigation and fuel debris sampling① Internal investigation by robot arm(2) Installation of an isolation chamber (in progress)●Isolation chamber
installed prior to opening
hatch⚫ Remove obstacles (CRD rail,
conduit) with【AWJ】at theend of the arm②Fuel debris sampling by robot arm
Tip of fuel debris retrieval device(3) Opening of the penetration X-6<Wire brush type>

Hatch releasing apparatus●Opening of the hatchof penetration X-6 byhatch opener<Vacuum vessel type>(Note) - Isolation valve : Valve installed to separate inside/outside of PCV- AWJ (Abrasive Water Jet) : Processing machine that mixes abrasives with high-pressure
water to improve cutting performance(8) Storage to shipping containers from fuel debris retrieval equipment,
and dose measurement(4) Removal of deposits in the penetration X-6(9) Acceptance into glovebox and measurement

Remove deposits and cables in the penetration X-6⚫ 【Low/High pressure
water】to push deposits●Accept into a glovebox
with negative pressure
inside●Weighing and storing incontainers in a glovebox

Law/high pressure water
Penetration X-6
Entrance side

Deposits⚫ 【AWJ】to remove cable
Glovebox
Push-in device<Appearance of a glovebox>

Cable removal with AWJ⚫ 【Push-in device】
to push-in cables(10) Removal of containers, storage in shipping containers, and carry-out●Remove the container with a plastic bag to prevent
contamination from spreading●Stored in off-site transport cask and loaded ontotransport vehicles(5) Robot arm installation
Isolationvalve

Off-site transport cask ＊Plastic bag

Robot arm

Transport to transport vehicles*: Measure the surface dose and contamination density of the transported materials prior totransport and confirm that they are below the legal standard value(11) Off-site transport/off-site analysis (analysis of fuel debris properties)(TEPCO material edited by NDF)

Fig. 12 Work steps of trial retrieval (internal investigations and fuel debris sampling)
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 havebeen 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(e.g., prior understanding of dust behavior by test injection, segmentation of cutting work), whichtake measures to control dust dispersion into account, such as monitoring dust concentration andgradually expanding operations. While placing the highest priority on ensuring safety, discussions
will be held with TEPCO on setting an appropriate operational value for dust concentration control
that will not significantly extend the process due to operation constraints.

44

・ Considerations for the risk of re-spreading impact of the COVID-19 infection
For the performance confirmation test in Naraha Center for Remote Control Technology
Development, it is essential to support by the UK engineers, and it is necessary to maintain the
backup system on the UK side in the event of a defect, while sharing information andcommunicating smoothly with the UK engineers.
It is also important to make all possible preparations for the risk of the COVID-19 pandemic reexpanding in Japan. NDF will confirm these responses.
・ Considerations in project management
It is important to proceed with the project while paying attention to the process progress
management of the contractors including overseas enterprises and subcontractors. As part of theirproject management activities, TEPCO needs to make further efforts to perform prior-evaluation ofrisk of delays, and develop alternative plans and measures to prevent the occurrence of risks. NDF
also participates in meetings with contractors and their subcontractors to closely check the status
and support risk assessment.
・ Limitations in the scope of trial retrieval (internal investigation and fuel debris sampling) andincorporation into gradual expansion of the retrieval scale
In the PCV internal investigation using a robot arm, it is planned to ascertain the state of existing
structures, and the distribution of deposits inside the pedestal (3D data), the distribution of gamma
rays and neutron counts at the bottom and on the platform, in as wide a range as possible.
However, since more structures 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, thepossible range of neutron measurement and trial retrieval from the bottom of the pedestal is limited.
Incorporating the results of the arm/tool combinational test in Naraha Center for Remote Control
Technology Development, the scope and type of data to be acquired by neutron sensors, 3D
scanners, gamma sensors, etc., and the evaluation method of the conditions inside reactor (e.g.,fuel debris distribution) based on such data are planned and prepared in advance.
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 thoseat 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 to gradually expand
the retrieval scale 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 of
the retrieval scale)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 andparties concerned to utilize human resources with a wealth of field experience, including those45

invited from outside as needed, to develop human resources to foster field-oriented
perspectives/feelings, and to transfer techniques cultivated through these activities.
3.1.2.3 Development status of gradual expansion of fuel debris retrieval and further
prospects
The retrieval equipment to be used for gradual expansion of the retrieval scale will be improvedby increasing the payload and enhancing accessibility while complying with specifications of thedevices for trial retrieval (internal investigations and fuel debris sampling).
It is planned to expand the range of retrieval step by step while making achievements, startingwith retrieval 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. The enclosure containing the robot-arm, etc. is connected to the PCV via
penetration X-6 connection structures to secure containment functions. In order to bring fuel debris
into the enclosure, it is necessary to consider shielding, measures against hydrogen and preventionof the spread of contamination, methods for transferring fuel debris from the enclosure, andmethods for confirming the maintenance of boundary and dynamic equipment functions and forremote maintenance.
From the perspectives of research/development and engineering by TEPCO, and in terms of
ensuring actual site applicability and safety, NDF continues to observe and check the status oftechnology development and preparations for application to the site in a timely manner.
The key technical issues and countermeasures are described below.
・ Ensuring containment performance of enclosure for fuel debris
In the retrieval operation, the process is repeated from carrying fuel debris retrieved from thePCV into the enclosure, storing in unit cans and carrying out to the outside of the enclosure for onsite transportation. As a result, the enclosure gradually becomes contaminated, and it is importantto 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, through theduration, it is important to perform prior mockup test, post-installation test of the equipment, andsubsequent abnormality monitoring.
・ Ensuring reliability of a manipulator (Fig.13)
The manipulator to be installed in the enclosure plays an important role in performing various
operations and maintenance in the enclosure, and thus it is important to ensure its reliability.
Therefore, it is necessary to improve the reproducibility of work through a wide range of
operation/maintenance training in advance, and to train operators.

46

(IRID material edited by NDF)

Fig. 13 Enclosure and manipulator
・ Ensuring maintenance of devices and countermeasures during the in-service period
To expand the retrieval scale in a gradual manner, in addition to periodic maintenance, repair or
replacement is required in case of failure. Since the radiation dose in the Unit 2 reactor building,where the enclosure will be installed, is high and it is difficult to perform maintenance in that place.
Therefore, 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.
In addition, since the manipulator that performs various operations may require repair or
replacement during the in-service period, a device for carrying out the manipulator to themaintenance building is under development.
Thus, the device to carry out the manipulator to the maintenance building is under development.
Since it is extremely important to ensure the maintenance of equipment/devices and their measures,
including repairs, NDF will check the examination and preparation status for them in TEPCO. It isalso important to leverage the experience gained through the in-service maintenance ofequipment/devices for further expansion of fuel debris retrieval in scale. Therefore, a system thatcan reliably preserve maintenance records, including failure histories and their measures, shouldbe established.
・ Points of attention in detailed design, manufacturing, and installation of temporary storage
facilities
The basic and detailed design of the temporary storage facilities is being undertaken by several
companies. Furthermore, installation requires process adjustments, including eliminatinginterference with the existing systems in advance and avoiding congestion with other operations.
In installation work, construction work and equipment installation, including cells, may be conductedalmost simultaneously. Thus, design and installation involve a great deal of interfacing, and TEPCO
is expected to perform project management by managing processes and resolving pending issues.
Even though construction management for designing, manufacturing, and installing these47

temporary storage facilities is small in scale, many companies are involved, and it is necessary toproceed with construction according to the schedule while adjusting the specifications andinterfacing. We believe the experience and knowledge gained from this construction work will be
helpful in project and construction management for further expansion of fuel debris retrieval in scalein the future. Even though a wide range of problems might occur, it is important to keep records ofthem, including their solutions, and leverage the experience in subsequent work.
The plan is to use manipulators and remote devices for operations in receiving/delivery cells
and temporary storage cells. It is important to thoroughly check the work details using these devices
at the design stage, identify potential risks, and examine and implement countermeasures against
them. It is also essential to verify the design and perform mock-up test/training by referring to theknowledge and experience of remote devices in the preceding PCV internal investigation and trial
retrieval.
3.1.2.4 Further expansion of fuel debris retrieval in scale
Toward further expansion of fuel debris retrieval in scale, methods should be examined basedon 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 froma comprehensive standpoint (in anticipation of technical feasibility as well as business continuity).
In addition, TEPCO should take responsibility for examining the methods to be used. Therefore,
this section describes in detail the procedure for developing methods.
At the Fukushima Daiichi NPS, where uncertainty still exists, the uncertainty of the condition
inside the PCV hinders examination, which forces preconditions to be set to perform examination.
In judging technical feasibility in the future, it is important to clarify and examine the requirements(boundary conditions) and constraints (site use area, existing system interface, etc.) for methods
and systems, including criticality control, dust containment, shielding, and heat removal. (Forreference, Attachment 7 shows the transition of retrieval method considerations in the TechnicalStrategic Plans in the past.)
TEPCO is currently conducting a conceptual study on further expansion of fuel debris retrieval
in scale, starting with Unit 3, and examining scenarios and methods for fuel debris retrieval. In thisprocess, retrieval methods were examined by the end of FY 2021. However, many challenging
issues and risks have been identified for each discussed method. Therefore, from FY 2022 onward,
the actual site applicability and technical feasibility associated with these issues and risks will beverified. Since there may be cases resulting from the above verification where the predetermined
criteria cannot be satisfied, other methods should also be considered.
The following are the points to be considered for examining retrieval scenarios and methods.
・ Development of retrieval scenarios
In examining methods, based on the five guiding principles (safe, proven, efficient, timely, andfield-oriented), a determination should be made not only to satisfy the target safety level but also48

to use attributes (evaluation items) such as cost and schedule as decision indexes. At the initialstage of the study, it is necessary to quantify these evaluation items as much as possible using
multi-attribute decision analysis23 (hereinafter referred to as “MADA evaluation”) and other methods,
and it is most important to clarify decision indexes and criteria. Setting these evaluation items
requires clarifying in advance information (e.g., exposure assessment report, strength calculation
report) for objectively determining whether the criteria are met. As for the results of examining themethods, it is also important to make efforts to disseminate information in a careful manner so thatthe evaluation results will be widely accepted by society.
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 to completion.
The intention of this study on fuel debris retrieval scenarios is to estimate in advance different
results obtained from PCV/RPV internal investigations or technical studies in the future and thenconduct an examination based on the preconditions of using such results.
After reviewing these numerous paths, it is important to narrow down promising candidates for
retrieval methods at a certain point of the path, and then further narrow down the path to takeaccording to the information obtained afterward.
・ Clarification of requirements
With regard to further expansion of fuel debris retrieval in scale, the methods will be considered,including those for containment, transfer, and storage of fuel debris, based on the findings from fueldebris retrieval in Unit 2 (trial retrieval, gradual expansion of fuel debris retrieval), PCV/RPV internal
investigation, research and development and the on-site environment improvement, etc. In doingso, operations, devices and equipment, and facilities will be larger than, and the scope of
construction will be wider than in the case of retrieving fuel debris from Unit 2. Therefore, much
more attention should be paid in overviewing the entire Fukushima Daiichi NPS, including otherwork. In addition, in light of the high radiation dose on-site, the limited understanding of the situation
inside the PCVs, and the extensive scope of work, it is important to specify the requirements(containment, criticality, operability, maintainability, throughput, etc.) required for operations anddevices even more clearly and proceed with the work. Attention should also be paid to theinteraction between the requirements.
The following describes the status of TEPCO's examination on the methods and NDF's view on
the matter.
・ Specific procedure and approach for examining retrieval methods

23. 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)) x (weight of each attribute (evaluation item) = importance)” will remain. This was used to
examine retrieval methods, it is considered that evaluation by this methodology will be effective in narrowing
down multiple method options (e.g. access device, etc.) hereafter.

49

Followings are the works implemented in FY2021. In examining methods, the work process wasroughly divided into two processes, the retrieval process, and the transfer/storage process. 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. Thismeans there were four major work phases, Phase 1 to Phase 4 (See Fig. 14). To examine methods
by work phase, the potential methods for each work phase was identified exhaustively, not rulingout any possibilities (setting a longlist), and then methods with low rationality was screened out(organizing a shortlist). Next, each of the shortlisted methods was scored by MADA evaluation. The
basic specifications and conditions of these discussed methods were tentatively established to
examine methods by incorporating the development results of the Project of Decommissioning,
Contaminated Water and Treated Water Management, TEPCO's engineering output, and technicalknowledge in Japan and overseas, and then issues and risks were identified and summarized (SeeFig. 15). In parallel with TEPCO's examination of methods, NDF is also independently examining
them, and TEPCO and NDF are mutually confirming their approach to the examination results andexchanging opinions.
【Retrieval process】【Transfer and storage process】

Phase Ⅰ
Preparatory work

Phase Ⅱ
Work inside the PCV

Phase ⅢWork outside the PCV

Phase Ⅳ
Transfer and storage• Reuse, decontamination anddismantling of existing facilities• Establish PCV access route• Introduce safety system andfacility• Install debris collection andprocessing equipment• Install monitoring and control
device• Handling and collecting of fueldebris• Cutting and downsizing• Transport collected debris out of
PCV, Separation of solid andliquid• Maintenance of collection
equipment• Construct fuel debris and related
facilities• Handle, sort and separate
collected fuel debris• Characteristic evaluation of fueldebris• Processing of fuel debris (drying)• Load and seal container fortransferring to interim storage
facility• Construct interim storage facility(in 1F site)• Transport packed debris tointerim storage facility• Receive and load container atinterim storage facility• Operation, monitor andmaintenance of interim storage
facility

Ⅰ Preparatory work

Ⅲ Work outside the PCV
Ⅳ Transfer andstorage

Ⅱ Work inside
the PCV(TEPCO material edited by NDF)

Fig. 14 Conceptual diagram of each work phase (a division of process)• Development results of the Project of Decommissioning
and Contaminated/Treated Water Management• TEPCO’s engineering output• Technical knowledge in Japan and overseas

Longlist

Shortlist

Examinationof methods

Identify potential
methodexhaustively

Screen out
methods with low
rationality

ExamineMADA
evaluation

Partial submersion
method (example)
Submersion
method (example)

Issues andrisks in eachmethodTentatively establish
basic specifications andconditions, examine
methods

Identify/organize
issues and risks(TEPCO material edited by NDF)

Fig. 15 Examination flow for retrieval methods in FY 2021 (outline)

50

・ Status of examining retrieval methods[Retrieval process (preparatory work, work inside the PCV)]In the retrieval process, methods are classified according to the work environment, accessdirection, and primary boundary. The partial submersion and submersion methods were on thediscussion table. This partial submersion method does not use the top or side access method
alone but combines them, which has been examined previously. (See Fig. 16 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 (fill the PCV withwater: 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. 17 for the conceptual drawingof the conventional submersion method (PCV submersion method)). For this reason, the previous
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 structure24 as a boundary. (See Fig. 18 for aconceptual drawing of the current submersion method (shell method))

24 Shell structure: A shell structure is a structure in which stiffener (a framework that holds deflection) supports theforce applied by the plate (surface) and it is used in ships and airplanes.

51◆Common to Figures 14 to 16
Access direction of
the devices
Transfer direction of fuel debris
and radioactive waste

Fig. 16 An example of partial submersion method(Conceptual drawing of combination of top and side access)Fig. 17 Reference : Conventional
submersion method(Conceptual drawing of the PCV
submersion method)

Fig. 18 An example of submersion methods(Conceptual drawing of shell method)

Since then, the partial submersion and submersion (shell method) methods have been
examined. However, both methods have no proven track record in the nuclear industry, and many
challenging issues and risks have been identified. As an example of a common issue for all
methods, preparatory work in the reactor building involves work in an extremely harsh, high-dose
environment. Therefore, the feasibility of the construction work needs to be verified inconsideration of exposure to workers. Moreover, construction of containment barriers and safetysystems involves the removal of surrounding buildings/facilities and the installation of new large
structures, resulting in enormous work and the associated waste. Furthermore, during fuel debris
retrieval, a function is required to reliably contain without fail the radioactive materials resulting
from fuel debris fabrication, such as cutting. In addition, systems and operations should becapable of early detection and transition to a subcritical state so that workers and the environment
are not affected in the event of a criticality. To solve these issues, it is important to summarize
common conditions for study, such as preconditions and requirements, rather than examining
each method alone, share and utilize the results obtained through internal investigations and R&D
activities.

52

Since 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 should be established to evaluate on-site applicability, technological feasibility, andbusiness continuity such as cost and construction schedule. If the criteria are not satisfied, it isnecessary to consider ① or ② below. As described above, other methods should also be
considered (See Fig. 19).
① Reconsider measures to address issues and risks without changing the method.
② Start over from the identification of issues and risks of other methods.

【Perspectives at HP】
・Evaluate on-site applicability and technical feasibility
・Evaluate including business continuity

Hold points (HP)・・・

Since FY2022

Feasibility verification phase⇒Verify feasibility to address
issues and risks (multiple)

Narrow downoptions stepby step while proceedingwith the design

Design Phase
Manufacture/
installation Phase

HP: Criteria not satisfied
HP: Criteria not satisfied (consider ① or ②)① Reconsider measures to address issues and risks without changing the method② Start over from the identification of issues and risks of other methods

Fuel debris retrieval in Unit 2 (trial retrieval and gradual expansion of fuel debris retrieval), PCV/RPV internal investigation,
research and development and the on-site environment improvement, etc.

Fig. 19 Conceptual diagram of how to proceed with examining methods after FY 2022

[Transfer and storage process (work outside the PCV, transfer and storage)]
For the transfer and storage process, the methods are classified according to fuel debris
processing, fuel debris/waste separation, container, hydrogen management, storage shielding,etc. Each option was evaluated as having no significant difference in terms of feasibility.
Since FY 2022, giving priority to the study of the retrieval process, examinations have been
made in terms of connectivity with the transfer process.
・ Toward initiatives for FY 2022 and beyond
As described above, from FY 2022 onward, it is necessary to systematically verify the on-site
applicability and technical feasibility to address the issues and risks. Therefore, it is necessary topromptly establish engineering planning for this study and reliably promote management,
including checking and reviewing output. To promote this, it is necessary to secure sufficient
TEPCO personnel and proceed with the study under a robust TEPCO project framework. In

53

addition, since there are many items to be considered, it is essential to prioritize the issues with ahigh impact on the feasibility of the method, perform checks and share information at hold points
with responsible personnel in each area (e.g., safety/radiation exposure dose, structure (seismic),
retrieval method, system, criticality, waste). For this purpose, TEPCO/NDF review structure needs
to be clarified and further strengthened. Moreover, in examining methods, not only technicalfeasibility but also business continuity, such as cost and construction schedule, should be taken
into account from a comprehensive perspective.
Issues in each technical field for further expansion of fuel debris retrieval in scale are described in
3.1.2.6.
3.1.2.5 Continuation of accident analysis activities (clarification of events that occurred at
the accident and the process of accident progression)
Analysis of deposit samples collected by the previous internal investigation for fuel debris
retrieval is in progress25.The information obtained by such investigation and analysis is directly
incorporated into fuel debris retrieval methods and storage management. Moreover, examinationand study in light of the accident history will promote understanding of phenomena, contribute to
studying the cause of the accident and decommissioning, and indirectly to the improvement of
nuclear safety.
TEPCO and the JAEA are cooperating in implementing activities for estimating and verifying
individual events that occurred at the accident, including overheating, melting, chemical reactions
and hydrogen explosions, the process of their progression over time, the operation status of
emergency cooling, depressurization equipment, and the amount of combustible gases generated
from cables, etc., by comparing the results of sample analyses with mock-up testing on accident
progression and past scientific knowledge26,27,28. Moreover, TEPCO is carrying out independent

25 The 84th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated

Water Treatment, “Material 3-3: Analytical results of samples related to the Unit 1-3 PCV internal investigations
and others”
26 IRID, supplementary budget in FY 2018, “Subsidies for the Project of Decommissioning and Contaminated
Water Management” (Development of analysis and estimation technologies for characterization of fuel debris),
results for FY 2020, (2021)
27 The 29th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 1-1:
Analysis results of gases generated by pyrolysis of organic materials in BWR primary containment vessel”
28 The 29th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 1-2:
Evaluation test results of the amount of combustible gases generated from cables, paints, and insulators”

54

investigations of the operating floor 29 ,30 ,31 and standby gas treatment system 32 ,33 (hereinafterreferred to as "SGTS") and so forth in each unit.
The Secretariat of the Nuclear Regulation Authority (NRA), which is responsible for 34continuing
accident investigations/analyses, established the “The Study Committee on Accident Analysis of
the Fukushima Daiichi Nuclear Power Station” to discuss accident analyses and investigate theoperating floor in Unit 2, the inside of the reactor building in Unit 3, and SGTS filter trains, etc., withcooperation from TEPCO according to the situation, and compiled these results in an interim
report35. Based on these investigations, the NRA has assessed that a large amount of Cs exists
between the first and second layers of the shield plug installed on the operating floor in Units 2 and3. Additional dose measurements36 in the holes bored in the shield plug of Unit 2 and geometry
measurements37 to check for deformation of the shield plug were also made.
In addition, the information necessary for accident analyses is affected by decommissioning
work, such as facility dismantlement. At the same time, there may be cases where efforts for
accident analyses interfere with decommissioning work and other operations. As such, the NRA
established the Liaison Council on accident investigation of Fukushima Daiichi Nuclear Power
Station 38 , 39 for communication and coordination of accident analyses and decommissioning
between the NRA, Agency for Natural Resources and Energy, TEPCO, and NDF. An example ofmanaging both decommissioning work and accident investigation, in the partial removal of SGTS
piping in Unit 1 and Unit 240, TEPCO is planning to take measurements of the radiation dose rates
and with a gamma cameras, and to collect piping samples for analysis after cutting. As acountermeasure against releasing radioactive dust during cutting, injection of urethane foam

29 The 69th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated

Water Treatment, “Material 3-2: Investigation on obstacles in the SFP and well-plugs of the Unit 1 reactor building”
30 The 88th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated

Water Treatment, “Material 3-2: Preliminary report on investigations of the operating floor of the Unit 2 reactor
building”
31 The 24th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water Treatment, “Material 3-2: γ-ray spectrum measurement results of the operating floor of the Unit 3 reactor
building”
32 The 84th meeting of the study group on monitoring and assessment of specified nuclear facilities, “Material 4-3:
Surveillance results for removal of SGTS piping at Units 1 and 2”
33 The 30th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station “Material 2:
Partial removal of SGTS piping of Units 1 and 2 of Fukushima Daiichi Nuclear Power Station”
34Article 4, Paragraph 1, Item 11 of the Act for Establishment of the Nuclear Regulation Authority stipulates thescope of authority as “Affairs concerning investigations of causes of accidents that have resulted from theoperation, etc., of reactors and causes of damage that has arisen from nuclear accidents.”
35 The 19th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 4:
Interim report on investigation/analysis of the accident at the TEPCO Fukushima Daiichi NPS”
36 The 27th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 2-1,
Attachment 1: Measurement inside new holes of the Unit 2 shield plug”
37 The 28th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 2-13: Deformation of the Unit 2 shield plug”
38 NRA, "Material 2: Continuous survey and analysis on the accident of the Fukushima Daiichi Nuclear Power
Station” (27th meeting)
39 The 7th Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station, “Material 2:
Continuous survey and analysis on the accident of the Fukushima Daiichi Nuclear Power Station”
40 The 21st Study Committee on Accident Analysis of the Fukushima Daiichi Nuclear Power Station “Material 5-1:
Partial removal of SGTS piping of Units 1 and 2 of the Fukushima Daiichi Nuclear Power Station”

55

started in September 2021 41 to improve the cutting process by checking the injection point ofurethane foam with a camera and a laser pointer 42 . Care is being taken to ensure that
decommissioning work and accident investigations do not affect neighborhood residents or theenvironment.
In addition to accident investigation activities in Japan, as an international forum on accident
progress and fuel debris analysis, projects of the Organization for Economic Cooperation andDevelopment/Atomic Energy Agency (hereinafter referred to as "OECD/NEA.”) have been
implemented since 2012. Following BSAF and BSAF-2, the FACE project, which integrates
PreADES and ARC-F, was launched in July 2022. 23 organizations from 12 countries are
participating in this project, and details are described in Chapter 4.
TEPCO is also planning to systematically conduct on-site investigation while estimating the stateof the reactor cores and PCVs, and discussing43 unsolved issues. After a lapse of about 11 years
since the accident, the radiation dose has decreased due to the decay of fission products(hereinafter referred to as "FP") and environmental improvements on site, and accessibility to thereactor buildings has improved. However, there are still many places with high radiation doses. In
order to locate FP released at the accident with a low radiation exposure dose, it is important tocollaborate with each organization, and continue these activities to a reasonable extent to clarify
the events that occurred at the accident, the process of their progression and the equipment
operation status. When new facts about the accident are revealed through further investigations
and other activities, it is also important to deepen and incorporate knowledge by performing severe
accident progression analysis evaluations, etc.
Since the shield plugs are installed on the operating floor, trial retrieval (internal investigation andfuel debris sampling) and gradual expansion of fuel debris retrieval, which is accessed from thefirst floor of the reactor building, are not directly affected by this. In order to further expand theretrieval scale, however, it is important to examine retrieval methods with decontamination shielding,and containment in mind, taking into account the possibility that access from the operating floor(top-access) is required, with full understanding of high radiation doses on the shielding plugs.
3.1.2.6 Technical issues for technical requirements and future plans
The current status and issues of the following items are described below.
(The following is a description of the partial submersion method. Although the submersion
method (shell method) was identified as one of the retrieval methods taken up for discussion insection 3.1.2.4, the remaining issues shall be summarized, and a plan for future technological

41The 95th Meeting of the Secretariat of the Team for Decommissioning and Contaminated Water/Treated Water

Management, “Material 3-3: Progress status of partial removal of SGTS piping in Units 1 and 2”
Electric Power Company Holdings Inc., Fukushima Daiichi Decontamination and Decommissioning
Engineering Company, June 9, 2022, “Resuming partial removal of SGTS piping in Units 1 and 2 of the Fukushima
Daiichi Nuclear Power Station”
43 Tokyo Electric Power Company Holdings Inc., “The 5th progress report on the Investigation and Exasmination of
Unconfirmed and Unresolved issues on the Fukushima Daiichi Nuclear Accident”
42 Tokyo56

development shall be developed in the process of the feasibility verification of the method against
the issues and risks after FY 2022.)
3.1.2.6.1 Technical issues for ensuring safety of fuel debris retrieval work
In general, when considering ensuring safety at a nuclear facility, a series of evaluations are
conducted by assuming accident scenarios in which the potential hazards of the facility becomematerialized, evaluating that these scenarios fall within the safety standards, and confirming thatthe safety measures are appropriate. In an ordinary nuclear power plant, such a series of safetyassessment procedures are established and standardized by national regulations and guides.
However, since there are no established and standardized regulations and guides for thedecommissioning work at the Fukushima Daiichi NPS, it is necessary to organize an approach toensuring safety based on the safety-related features of the Fukushima Daiichi NPS and to share itwith the parties concerned.
Decommissioning work of the Fukushima Daiichi NPS containing the reactors involved in theaccident is an unprecedented activity that takes place in a peculiar environment different from thatof a normal 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 without
prolonging the decommissioning activities
Based on these characteristics, NDF is organizing an approach to ensuring safety with thefollowing as the basis:• Optimization of judgement with safety assessment as its basis:
When making decisions by comprehensively considering technical reliability, reasonableness,
promptness, etc., safety assessments should be fully used to avoid a great variance in decisions
for safety measures to avoid (too excessive or too insufficient resource input).
• Ensuring timeliness in decommissioning activities:
While paying attention to the prevention of accidents and the mitigation of their impacts,
measures should be taken with concentration on the time axis so as not to prolong the57decommissioning period, in consideration of high radiological impacts that have already become
apparent, as well as further deterioration of containment barriers, etc.
• Complementing design by operating controls, monitoring, analysis, and on-site operation in theevent of an abnormality:
Due to significant uncertainties, there is a limit to addressing all situations by design alone. For
this reason, the information obtained at the operation stage, including that obtained throughmonitoring and analysis, should be utilized in design, and design should be complemented byoperators’ efforts and on-site operation to enhance safety in total with operations. In preparations
for abnormalities, consideration should be given to on-site response considering thecharacteristics that the progress of abnormalities is moderate and there is sufficient time torespond.
In addition, along with organizing the concept for ensuring safety, technical requirements havebeen established for ensuring safety of fuel debris retrieval and intensive studies are being
conducted as shown in the following Sub-sections 3.1.2.6.1.1 to 3.1.2.6.1.6.

3.1.2.6.1.1 Establishing the containment functions (gas-phase)
Leakage of radioactive materials in an ordinary operating nuclear power plant is prevented by
implementing static containment for a PCV and keeping the interior of a reactor building undernegative pressure against the ambient air (active containment function by negative pressure
control). However, the reactor buildings, PCVs, etc. of the Fukushima Daiichi NPS were partiallydamaged by the hydrogen explosion and their containment function is deteriorated. Due to this,establishment of an active containment function by negative pressure control is being consideredduring fuel debris retrieval work. Moreover, from the perspective of prevention of hydrogen
explosions due to steadily generated hydrogen by the process of radiolysis of water and of
corrosion (inactivation) of structural materials due to the presence of oxygen, nitrogen is injected
into the PCV to maintain it in a nitrogen atmosphere. As for the exhaust from inside the reactor
buildings, the release of radioactive materials has been prevented by the PCV gas control system,
which is furnished with filters to remove radioactive materials and measure radioactivity44.
We expect that existing safety systems will be able to cope with the retrieval of fuel debris, suchas gripping and sucking, in the case of a trial retrieval or gradual expansion of fuel debris retrieval.
The AWJ used to remove obstacles during the PCV internal investigation in Unit 1 caused anincrease in dust concentration. Going forward, it is necessary to roll out this experience to similar
operations so that they can proceed carefully on a step-by-step basis while the dust concentration

44 TEPCO, evaluation results of the additional release amount from the Units 1 - 4 reactor buildings (June 2020),

the Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat (80th)material 3-6, May 28, 2020
https://www.tepco.co.jp/decommission/information/committee/roadmap_progress/pdf/2020/d200528_11-j.pdf

58

is checked. In the subsequent work such as fuel debris cutting, it is necessary to construct thecontainment function of the gas phase system in consideration of re-scattering of Cs, etc., thatadhere to the equipment and structures in the PCV, aerosolization of water containing radioactive
materials, and generation of short-lived iodine and noble gases if criticality should occur.
In addition to re-scattering of Cs, etc., the fact that dispersed fine particles (α-dust) containing
α-nuclides may be generated and the radioactivity concentration in the PCV gas-phase may
increase is a concern. Therefore, dispersion of α-dust from inside the PCV must be suppressed asmuch as possible, and a function for containing the gas-phases should be provided to make theradiation dose impact on workers and the public fall within the allowable value.
Accordingly, it is reasonable to expand the retrieval scale while understanding the tendency of
dust dispersion at each stage of expanding the fuel debris retrieval scale, and verifying theappropriateness of the containment function built in the subsequent stage. In the engineering work
conducted by TEPCO, the improvement of dust monitoring installations inside the reactor buildings
and the study of decreased or negative pressure in the PCVs using existing equipment are in
progress based on the outcome of the Project of Decommissioning, Contaminated Water andTreated Water Management. In the future, the effect on the surroundings will be assessed basedon the monitoring results of the changes in condition such as the dispersion of α-dust associatedwith the work, and the retrieval scale of fuel debris will be gradually expanded.
In the process, TEPCO is considering establishing a secondary containment function andstudying its necessity through their engineering work, while assuming the possibility of anincreasing impact on the surroundings.
The issues involved in constructing system installations to maintain containment functions are
outlined in section 3.1.2.6.2.3.

59

Fig. 20 An example of building containment function (gas-phase) by negative pressure control
In establishing the containment function (gas-phases), technical issues to be addressed
immediately for further expansion of fuel debris retrieval in scale are as follows:(1) Understanding of the dispersion rate of α-dust
As described above, for fuel debris retrieval work, it is necessary to understand the impact of αdust dispersion and establish measures to suppress the transition of α-dust to the gas phase as
much as possible.
To understand the impact of α-dust dispersion, a plan is required to measure data on dispersion
in trial retrieval and gradual expansion of fuel debris retrieval and then demonstrate and verify
safety assessment methods. It is necessary to understand the general and approximate behaviorof α-dust dispersion for proceeding with technical studies and R&D related to fuel debris retrieval
methods and systems in situations where these demonstration data have not been obtained. In
addition, tests are planned to obtain dispersion data for several fabrication methods to determine
the α-dust dispersion rate. Currently, tests to analyze differences among several methods are
ongoing, and tests to improve applicability to on-site environmental conditions are also planned.
In order to suppress the transition of α-dust to the gas phase, it is desirable to submerge thefuel debris and to fabricate it underwater as much as possible. However, the water level in the PCV
is to be adjusted with other technical requirements such as the building of the containment functionof the liquid phase described in the next section. Therefore, not all fuel debris can be fabricatedunderwater, and transition of α-dust to the gas phase is considered to be mitigated by splashingwater on the fuel debris that is not submerged.

60

(2) Ascertaining the feasibility of negative pressure control in the PCVA.

Technical feasibility of negative pressure control based on the site conditions
In order to maintain negative pressure in the PCV, sufficient gas exhaust system capacity thatconsiders the condition of PCV damage is required. Although damaged parts have not been
identified yet, the exhaust capacity is currently established based on the relationship between
actual nitrogen supply volume and actual PCV internal pressure. At this time, it is necessary tomaintain sufficient differential pressure to respond to the internal pressure rise of the PCV due toabnormal events such as an internal temperature rise or shutdown of the gas exhaust system. In
order to achieve this, repair of the damaged parts of the PCVs will be considered as necessary,
but some difficulties such as remote work or exposure of workers are assumed due to work underhigh radiation dose conditions.
In this way, it is necessary to ascertain the technical feasibility of maintaining the negative
pressure in the PCV based on the site conditions and the information obtained during trial retrievalor the gradual expansion of fuel debris retrieval.
B.

Effect of air flow into the PCV during negative pressure control
Since air flows into the PCV in case of negative pressure control, measures of maintaining

inactivated condition in the PCV by increasing nitrogen gas supply into the PCV will be examined
as necessary based on evaluation on occurrence of accidents such as fire and hydrogen
explosion using accumulated information regarding volume of hydrogen generated by radiolysis
of water in the PCV and inflow volume of air (oxygen) into the PCV.
C. Study on the necessity of a secondary containment function
As illustrated in Fig. 20, for fuel debris retrieval, it is assumed that a working cell is newly installed,which will be connected to the PCV under negative pressure control, and the operation from
retrieving the fuel debris to storing the container for fuel debris in a transfer cask is performed inthis cell. The PCV and this working cell have a primary containment function to prevent α-dust to
the exterior (out-leakage).
In addition to this, in order to respond to an event in which radioactive materials are dispersed
from the containment boundary caused by loss of primary containment function through negative
pressure control, the necessity of the secondary containment function has been investigated byinstalling building covers and containers in the existing reactor buildings and maintaining slightly
negative pressure inside of the reactor buildings to recover and treat radioactive materials. However,a large capacity gas exhaust system is considered to be required to maintain negative pressure in
the secondary containment boundary since the reactor building has a large volume and its leaktightness may have deteriorated due to the accident. Therefore, based on the accumulated resultsof the tendency of dust dispersion obtained hereafter, it will be necessary to ascertain the required
functions to establish a secondary containment function and to proceed with research anddevelopment accordingly.

61

D. Deterioration control of the containment function of the PCV
In order to maintain negative pressure in the PCV during the fuel debris retrieval work, it isnecessary to manage risks of earthquakes and aging after considering how to handle
deterioration of the primary containment function consisting of the PCV and the attached cell. Thisis outlined in Section 3.1.2.3.1.5.
(3) Study on exhaust gas management
In control of exhaust gas associated with negative pressure control, it should be confirmed thatradioactive materials in gases that may contain nuclear fuel materials derived from fuel debris aremaintained below the radiation dose standard for the public in the vicinity of the facility bymeasuring and controlling the release concentration and the release amount. In addition, αnuclides derived from fuel debris should be included in the assessment and constantly
monitored/measured during fuel debris handling so as to evaluate their normal fluctuation range inadvance. By using such data, a system for early detection of abnormal events such as leakage andimplementing appropriate impact mitigation measures should be established for preventing any
impact on environment and workers.
The reliability and accuracy of the mechanical properties and chemical composition of the fueldebris needs to be improved because these are essential information for designing thedecontamination equipment for efficient collection of radioactive dust.
As described above, regarding establishing a containment function (gas-phase), TEPCO has
been ascertaining the feasibility of negative pressure control in the PCV through their engineering
work, and in parallel, it has been examining the necessity of a secondary containment function andits establishment. In the future, TEPCO will incorporate the results gained from the Project ofDecommissioning, Contaminated Water and Treated Water Management, trial retrieval and gradualexpansion of the retrieval scale, and give shape to the system specification necessary forestablishing a containment function through their engineering work. (See Chapter 3.1.2.6.2.3 forthe progress status of installing covers on the side and top of the Unit 3 reactor building to improveits containment performance.)
3.1.2.6.1.2 Issues in containment functions (liquid-phase)
To mitigate the dispersion rate of generated α-dust and to minimize the transition to the gas
phase, fuel debris cutting, etc., would be performed by pouring water over the fuel debris for fueldebris retrieval. Existing safety systems are expected to be capable of fuel debris retrieval bygripping and suction. For the subsequent work such as fuel debris fabrication and removal of
obstacles, a large amount of α-particles will flow into cooling water (liquid phase). To prevent thecooling water containing α-particles from leaking into the environment, it is necessary to establish
a cooling water circulation/purification system and a liquid-phase containment function inconsideration of prevention of the spread of contamination (Fig. 21).

62

For this reason, it is necessary to examine technologies for removing soluble nuclides that may
be leached from fuel debris to the circulating cooling water as well as treatment technologies forsolid matter trapped by the filter equipped in the circulating cooling water system. Accordingly, theProject of Decommissioning, Contaminated Water and Treated Water Management has beenpromoting research and development45. In parallel with this, the establishment of a PCV circulating
cooling system that takes water from the PCV and injects it into the reactor for cooling, which isbeneficial in terms of preventing the spread of cooling water containing α particles, was considered
in research and development by the same Project46.
To establish a reasonable containment function of liquid-phase in each stage of the scale
expansion of fuel debris retrieval, it is rational to monitor the radioactive concentration of coolingwater by stage and verify the validity of the containment function to be built in the subsequent stage
based on the results (information on fuel debris properties, etc.) obtained from research anddevelopment by the Project of Decommissioning and Contaminated Water Management. As withthe containment function (gas phase), from the viewpoint of verifying/investigating the impact of theretrieval work on the liquid phase, TEPCO, through engineering work, has been discussing system
addition/installation, etc., for the purpose of monitoring the circulating water system according to
the results of the Project47. With regard to the effects on the liquid phase during fuel debris retrieval
operations, the scale of fuel debris retrieval will be expanded gradually, based on the results ofmonitoring changes in the state of liquid waste containing α-nuclides. The water level in the reactor
building is required to be maintained lower than the groundwater level to prevent the outleak ofcooling water to groundwater and to appropriately control the water level in the PCV. Safetysystems are to be established taking this into consideration.
The issues involved in constructing system installations to maintain containment functions are
outlined in section 3.1.2.6.2.3.
In establishing the containment function (liquid-phases), the technical issues to be addressed
immediately for further expansion of fuel debris retrieval in scale are as follows:

45 IRID, additional subsidies in FY 2018 for the Project of Decommissioning and Contaminated Water

Management, “Technology development for further expansion of technologies to retrieve fuel debris/in-core
structures”, actual results in FY 2019, August 2020.
https://irid.or.jp/wp-content/uploads/2020/09/2019008kibonosaranarukakudai.pdf
46 IRID, additional subsidies in FY 2017 for the Project of Decommissioning and Contaminated Water
Management, “Development of technology to establish primary containment vessel water circulation system(full-scale test), final report for FY 2019, August 2020.
https://irid.or.jp/wp-content/uploads/2020/09/2019006mizujyunkan.pdf
https://irid.or.jp/wp-content/uploads/2020/09/2019007mizujyunkanjitukibo.pdfhttps://irid.or.jp/wpcontent/uploads/2020/09/2019007mizujyunkanjitukibo.pdf
47 IRID, supplementary budget in FY 2016, “subsidies for the Project of Decommissioning and Contaminated
Water Management”, sophistication of retrieval method and system of fuel debris and internal structures, final
report in FY 2018, July 2019.
http://irid.or.jp/_pdf/20180000_13.pdf

63

Fig. 21 An example of building containment function (liquid phase)(1) Suppression of radioactive concentration increase in cooling water due to fuel debris retrieval
work
As an approach to assess the radioactive concentration in the cooling water, it is necessary toplan to investigate the impact on liquid waste when gradually expanding the scale of retrieval.
To suppress an increase of radioactive concentration in cooling water in the PCV, cutting
particles generated by fabrications such as cutting is planned to be collected through the PCV
circulating cooling system to mitigate dispersion of dust. It is recommended that the results ofmonitoring by the water circulation system are taken into account and incorporate them into
modifications of the PCV circulating cooling system as necessary in the stage of gradually
expanding the scale of retrieval.
(2) Setting of water level in the PCV
Due to a low seismic margin of S/C support columns, it is recommended that the water level in
the S/C is lowered, and thus, considerations are being given to lower the water level. In this instance,
it is necessary to appropriately set and manage the water level in the PCV with consideration forthe damaged condition of the PCV in each unit and prevention of the outleak of cooling water togroundwater (maintaining the water level in the reactor building below the groundwater level), etc.,
and to confirm that safety is ensured in terms of fuel debris cooling and control of dust dispersion.
As described above, regarding establishing a containment function (liquid-phase), based on the
results of the Project of Decommissioning, Contaminated Water and Treated Water Management(technology for removing soluble nuclides that are considered to have leached from fuel debris
into circulating cooling water, technology for treating solids collected by filters of the circulating
cooling water system, etc.), construction of a PCV circulating cooling system has been under64

investigation through TEPCO’s engineering. Going forward, based on the monitoring results
obtained from trial retrieval and gradual expansion of the retrieval scale, consideration will begiven to modifications required for the PCV circulating system while verifying the validity of thecontainment function to be established in the next phase.
3.1.2.6.1.3 Issues in cooling functions
Fuel debris generates heat due to the decay of radioactive materials. In Unit 2 after a lapse of
11 years or more since the accident, for example, the amount of heat generation has reduced to
1/1000 of the level at the accident. However, the maximum heat generation is still estimated to be
several tens kW48 . Therefore, unless cooling is continued, the surrounding materials graduallyabsorb the generated heat and there is concern that the following events may occur:・ Oxidation caused by increasing the temperature of the uranium oxide in fuel debris(increased O/U ratio) proceeds resulting in volume expansion, crack generation, andthereby progression of pulverization.
・ Moisture in concrete structures is also dissipated and dried by heat, and then cracks occur
to decrease the concrete strength.
・ The inside of the PCV becomes dry, causing radioactive dust to be easily scattered and sent
airborne.
・ When water is injected after the PCV becomes dry, the water that contacts fuel debris turns
into steam and raises the PCV internal pressure, which leaks from damaged areas withradioactive dust.
In order to prevent the above four events and excessive temperature rise of the fuel debris, thetemperature is being maintained below 100°C (cold shutdown state) currently by conducting
circulating cooling with water injection into the reactor. In FY 2019, water injection into the reactor
was temporarily suspended with the aim of optimizing operation/maintenance management ofcooling systems and emergency response procedures, etc. In light of these water injection
shutdown tests, from FY 2020 onward, testing will be planned and performed depending on the
purpose, taking into account the situation of each unit, for decommissioning in the future. Basedon this policy, the amount of water injection in Units 2 and 3 was decreased from 3.0 m3/h to 1.7
m3/h in tests performed in FY 2021 (Unit 2: January to March 2022, Unit 3: November 2021 toJanuary 2022) to gradually lower the amount of water injection. In Unit 3, the amount of water
injection was increased to 2.1 to 2.2 m3/h since late June 2022 because the water level continued
to drop after the earthquake that occurred on March 16, 2022. Thus, the amount of water injected
into the plant may change depending on future conditions. Based on the condition of lowering thePCV water level, the study is underway to determine water injection methods for the future,including further reduction of water injection.

48 Kenji Nishihara et al., "Evaluation of fuel properties at the Fukushima Daiichi Nuclear Power Station”, Japan

Atomic Energy Agency (JAEA), JAEA-DATA/Code 2012-018(2012).

65

In the future, when accessing the vicinity of fuel debris during the fuel debris retrieval work, it isnecessary to keep the temperature below the level at which the fuel debris retrieval device cancontinue to work without any problems for a long period of time.
However, the need for cooling water injection should also be considered now, assuming that theamount of decay heat decreases with a reduction in the remaining amount of fuel debris as fueldebris retrieval progresses in the future. The water injection shutdown test described above should
be further promoted with the additional objective of identifying the scale (i.e., flow rate, diversity) ofsuch a cooling system.
In maintaining this cooling function, the technical issues to be addressed for the time being
include setting of the target temperature inside the PCV to make each task feasible, as well as thecountermeasures to be taken under the assumption of cooling function abnormalities when eachtask is performed. While essential countermeasures would be to continue cooling by early recoveryof the cooling water circulation system or by mobile equipment, etc., it is necessary to evaluatechanges in the PCV internal condition based on the time margin in an emergency and to consider
emergency response measures and procedures, etc., including collection of devices.
As temperature monitoring in the PCV is also evaluated by the temperature of devices and wateraround the fuel debris, the fuel debris temperature is not directly measured. In preparation for
reducing the amount of cooling water, a temperature measurement of fuel debris must be made or,if direct measurement is difficult, examining techniques to estimate it from the temperature of thedevices and water used for the current assessment. Therefore, examinations are being madethrough research and development by the Project of Decommissioning, Contaminated Water andTreated Water Management.
In addition, during fuel debris retrieval operation, the processing of cutting fuel debris while
spraying water is conceivable from the perspective of dust dispersion control, and attention should
also be paid to water level control inside the PCV, as well as controlling of the contaminated water
generated.
From the above, monitoring parameters and their criterion need to be studied and preparedthrough engineering work in TEPCO in order to carefully promote fuel debris retrieval work whileobserving how this work will affect the existing circulating water cooling and purification system, as
well as its cooling function.
3.1.2.6.1.4 Issues in criticality control
Currently, subcriticality state monitoring based on the implementation plan confirms that no signsof criticality have been observed. In addition, it is assumed that impurities such as in-core structures
were introduced during core meltdown caused by melted fuel assemblies. It is estimated that fueldebris were dispersed over a wide area outside the core due to the progress of the accident.
Therefore, the criticality of the fuel debris at the Fukushima Daiichi NPS is not likely from anengineering perspective. Even assuming that control rods may melt down before the fuel elements

66

in the course of core meltdown and that the optimum mixing of incidentally crushed fuel debris withwater occurs, the possibility of criticality is considered small.
Although the possibility of criticality is considered low, fuel debris retrieval involves an operationthat changes the shape of the fuel debris. It is important to plan criticality control based on the
shape of the fuel debris, working conditions, and other factors and to establish a reliable control
method through prompt detection and shutdown in the case of an unexpected criticality.
In the initial stage of fuel debris retrieval, criticality control is implemented by retrieving fuel debris
while limiting the amount of fabrication based on methods that will not significantly change the fueldebris shape, such as gripping and sucking. Also, in the process of expanding the retrieval scaleand cutting, measures such as neutron measurement, pre-work subcriticality measurement, andpreparation for inserting neutron absorbers will be taken. Reliable criticality control (criticality
monitoring) is required that combines design and monitoring by operators with the decision-making
process to suspend and resume work.
The retrieved fuel debris will be placed in containers that can maintain a subcritical state and be
appropriately stored. In TEPCO’s engineering work, the concept design is in progress for circulatingwater system configurations and system specifications for further expansion of fuel debris retrieval
in scale. Criticality assessment of equipment has been performed early, and criticality prevention
measures that greatly affect the equipment specifications have been extracted in advance in order
to avoid rework at a later stage.
For this criticality control, technical issues to be addressed for the time being are as follows.
(1) Establishment of criticality evaluation methods
Based on the information obtained from each stage of fuel debris retrieval, including internal
investigations, evaluation methods have been developed to assess the likelihood of criticality andthe degree of influence associated with the criticality of fuel debris. For evaluating these methods,
a plan will be made so that information on the parameters with a high impact on the criticality
evaluation can be obtained in the course of internal investigation and retrieval work. The
information should also be updated as needed and appropriately reviewed by incorporating onsite information from prior operations into the safety assessment at a later stage.
(2) Local neutron measurement around retrieval points
There are various kinds of existing neutron detectors according to the application (fission
chamber, B-10 proportional counter tube, semiconductor detector, etc.). Taking advantage of eachfeature, the selection of neutron detectors for each stage has been considered. The required
specifications for the neutron detectors for criticality monitoring are; (1) the ability to survive theaccumulated radiation dose (Gy) for the operation period and (2) installability of the assumed
equipment, and (3) the guaranteed detection efficiency at the required level (time, accuracy). In
the future, the optimal detector will be selected according to the information on PCV radiation dose67

rates obtained by internal investigations and the progress of the equipment development of eachunit.
In addition to subcriticality measurement, a small neutron detector is used as a standalone
detector for constant monitoring of local neutron measurement. Toward practical application of
constant monitoring during fuel debris retrieval, development of specifications of neutron detectors
and approach-to-criticality monitoring technologies has been discussed in the Project ofDecommissioning, Contaminated Water and Treated Water Management. In FY 2021, theapplicability of neutron detectors to the on-site environment was confirmed through tests49. Goingforward, it will be necessary to consider detailed operations, including determination criteria on
operation suspension/resuming if the fluctuation of the neutron flux is detected and on boron
injection as a neutron absorber.
For the possibility of criticality at locations other than the retrieval worksite (i.e., outside the PCV
bottom pedestal, in piping, water filters, wastewater receiving tanks, areas where cutting particles
of fuel debris has accumulated, etc.), criticality detection by the PCV gas management system isrequired.
(3) Feasibility study of measuring the degree of subcriticality
When measuring the degree of subcriticality, in addition to the required specifications of (2), a
neutron detector with high time resolution and high sensitivity is needed to capture neutron
fluctuations in a short time. Considering the equipment mountability (size, weight, electromagnetic
noise, etc.) and operation methods (measurement time and duration, installation location, etc.)
are key issues due to the necessity of lead shielding in a high ɤ-ray environment (assuming 1000Gy/h). In the future, optimization based on the fuel debris retrieval method and system constraints(balance of size, weight, measurement and fabrication time, etc.) and a combination of multiple
detectors will be examined.
In addition, in order to verify the applicability to fuel debris, where various mixes of compositions
and properties of the fuel debris are expected, it is necessary to assess the technical feasibility,
including applicability, by planning and demonstration.
(4) Feasibility study of neutron absorber
For cases where the high possibility of criticality of the fuel debris cannot be denied by the
information obtained at each phase of expanding the retrieval scale, the application of a neutron
absorber (sodium pentaborate) during normal fuel debris retrieval work is also being considered

49 IRID，Subsidies for the Project of Decommissioning and Contaminated Water Management, (2) Developmentof criticality control technologies of fuel debris, “Development of safety system (Liquid-phase system/gas-phasesystem, criticality control technique)”, Results for FY2021 implementation August 2022.
https://irid.or.jp/wp-content/uploads/2022/09/2021011anzensystem.pdf

68in TEPCO’s engineering. As a result, environmental impact in the event of leakage andcompatibility with concrete as structural materials have been evaluated50.
Impacts on the PCV circulation cooling system and operations to maintain boron concentrations(e.g., impacts on systems and waste during segregation, collection, re-use, and processing) arealso under consideration. It is necessary to verify the applicability on-site for the case of sodium
pentaborate injection, together with the approach-to-criticality monitoring technologies describedin (2) Local neutron measurement around retrieval points.
How to maintain and restore subcriticality in the event of criticality and emergency injection of
sodium pentaborate should also be considered.
Non-soluble neutron absorbers are also under development to ensure maintenance ofsubcriticality when the margin for criticality is small. Non-soluble neutron absorbers haveadvantages such as a local impact on the PCV circulation cooling system. Methods and effects ofspraying according to the fabrication operations have been verified for the candidate materials
that underwent fundamental property testing and radiation resistance testing (B4C metal sinteredmaterials, glass containing B/Gd, Gd2O3 particles, and sodium silicate/Gd2O3 granulated powder).
From FY 2021 onward, technology development is underway to materialize on-site operation
methods suitable for fuel debris retrieval work conditions.
To introduce non-soluble neutron absorbers, it is necessary to study the impact on PCV
corrosion and environmental impact in the event of an environmental release.
(5) Detection of criticality by PCV gas management system
The sophistication of detectors in the PCV gas management system is required to detect whenapproaching criticality and criticality in the vicinity of fuel debris retrieval points and to detect
criticality due to the fall of fuel debris and/or accumulation of pulverized debris in other locations
than retrieval points. In addition to subcriticality measurement, a small neutron detector is used
as a standalone detector for constant monitoring of local neutron measurement.
3.1.2.6.1.5 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 and Contaminated Water Management. As a result, it has been confirmed thatthe 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 level

50IRID, supplementary budget in FY 2017, subsidies for the Project of Decommissioning and Contaminated Water

Management, Sophistication of retrieval method and system of fuel debris and internal structures (Technology
development for establishing criticality control methods), final report, July
2019.http://irid.or.jp/_pdf/20180000_04.pdf

69

of safety against external events such as earthquakes and tsunamis. Assuming (3) long-term
maintenance management, in addition, it is important to (4) feedback new knowledge to be gained
from planned PCV internal investigations and fuel debris analysis results, etc., to the design of fueldebris retrieval systems and the study of retrieval methods. The following shows the key functional
requirements as examples.
 Existing equipment and buildings (including modified areas. The impact of aging is also
considered as necessary)・ Control deterioration of containment functions of PCV, RPV and reactor buildings, etc., andcontrol/prevent large release of radioactive materials (maintaining containment functions).
・ Reactor buildings, etc., safely support equipment/systems to be newly installed in the reactor
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 release 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 has formulated a long-term maintenance management plan for existing onsite systems/equipment and buildings in consideration of the progress of time-related deterioration,and started implementation of the plan. When new facts about the accident are revealed throughfurther investigations and other activities, it is also necessary to clarify the impact of theaccident, especially damage, by performing severe accident progression analysis evaluations,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, lowering of the water level in the PCVs of Units 1 and 3 was confirmed in theearthquakes 51 , 52 with their epicenter off the coast of Fukushima Prefecture that occurred on
February 13, 2021, and March 16, 2022. Although cooling functions were maintained in both cases,
in light of both earthquakes, in order to maintain and manage the equipment/systems and buildings
51 The earthquake off the coast of Fukushima Prefecture, measured maximum upper 6 on the Japanese seismic

intensity scale of 7 in Miyagi and Fukushima Prefectures. In Fukushima Daiichi NPS, 2nd basement floor (onthe foundation plate) of the Unit 6 reactor building recorded the quake with its maximum acceleration of 235 gal.
This is equivalent to the response level of about half of the seismic response analysis results of the buildings
against the design basis earthquake ground motion (Ss) (600 gal) before the new seismic design policy
determined by the NRA was applied.
52 The earthquake off the coast of Fukushima Prefecture, measured maximum upper 6 on the Japanese seismic
intensity scale of 7 in Miyagi and Fukushima Prefectures. In Fukushima Daiichi NPS, 2nd basement floor (onthe foundation plate) of the Unit 6 reactor building recorded the quake with its maximum acceleration of 221gal.

70with the 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 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 toactively introduce the latest knowledge and achievements not only in the nuclear field but also inother fields.
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.
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-dose environment, the information available is limited, and establishingconservative conditions for examination may increase the difficulty of implementing measures.
Therefore, considering that high uncertainties result in moderately conservative conditions, it isalso 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 are limited, it 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 Unit 3, drainage of the main bodyof the PCV is underway, which is required before drainage of the S/C.
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, verification of the seismic safety over a long
period during fuel debris retrieval is required.

71

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,deterioration, and condition of the 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
・ Detailed surveillance by core sampling using 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 to large
earthquakes, it is important to update the information on the condition of buildings and incorporate
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 can be for the
structures themselves and the environment in which they are installed. Generally, measures for theformer includes coatings. However, it is extremely difficult considering humans cannot easily
approach the structures. Therefore, priority will be given to examining the latter environmental
approach. For reactor water injection as ongoing action, measures are being taken to reduce thedissolved oxygen concentration by nitrogen bubbling and hydrazine injection in the tanks. For thegas 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 thestructural 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 to repair
and reinforce buildings and main equipment damaged by the accident in a high radiation dose
environment. Because of that, earthquake ground motion and design criteria used in the design will72

be appropriately defined in accordance with the new seismic design policy53.54 determined by the
NRA while considering the perspective of risk assessments. In doing so, although ensuring safety
is with no doubt the top priority in the design policy of systems required for individual
decommissioning operations, including planned fuel debris retrieval, we believe it is important toestablish 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 the application while
securing the independence of the review.
In addition, in the evaluation of existing systems, even for components that do not directly affectseismic resistance or are ignored in the seismic assessment, if parts or other components damagedby 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 to monitor the
progress of deterioration daily and to implement comprehensive management from the viewpointof personnel and system safety.
〇New seismic design policy determined by the NRA (Reference)
The NRA stated, “Given the fact that the earthquake ground motion of the Great East Japan
Earthquake in 2011 exceeded Ss 600, and that 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”53, and “...For the time being, it is appropriate toreorganize ‘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)”53. The NRA approved theapplication of the system based on the existing earthquake ground motion for review55 (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 B53.
Based on the above, the following seismic policy53 applies to newly installed systems.
 The earthquake ground motion for review (Ss 900) shall be established as the new designbasis 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 beappropriately combined.

53 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.
54 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.
55TEPCO, “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

73

 For Class B+, safety functions shall be maintained against Sd 450 in addition to the earthquake
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 the seismic resistancecommensurate with the applicable seismic class, measures for early reduction of risk causedby the insufficient seismic resistance shall be separately examined for those that cannot be
reinforced within a reasonable range in consideration of the impact on the decommissioning
work and the risk of exposure due to the implementation of measures.
Regarding the concept of classification of seismic classes and the application of earthquake

ground motion in the seismic design of the Fukushima Daiichi NPS, “In the seismic evaluation offacilities and systems at 1F, earthquake ground motion to be applied shall be established taking
into consideration (1) Seismic class (S, B+, B, C), and (2) Impacts on decommissioning activities,
consequent impacts on upper classes, service life, design progress, amount of radioactivity ofcontained liquid, etc., and measures shall be determined as needed.”54 The procedures forestablishing earthquake ground motion and determining the necessary measures according to theseismic classes and characteristics of facilities are provided in Attachment54.
3.1.2.6.1.6 Issues in reduction of radiation exposure during work
In accordance with the Mid-and-Long-term Roadmap and TEPCO's Mid-and-Long-term
Decommissioning Action Plan, removal of obstacles and radiation dose reduction in the reactor
buildings are in progress as improvement of the work environment in work areas/access routes.
In preparation for trial retrieval, ongoing on-site radiation dose reduction has resulted in reducing
the radiation dose around the aisle on the west side of the first floor of the Unit 2 reactor building
and the penetration X-6 in the northwest area to approximately 5 mSv/h or less (average 2 to 3
mSv/h). In the future, as work related to fuel debris retrieval, reduction of exposure during work
such as removal of high-radiation dose equipment, etc. is an issue, and research and development
has been promoted by the Project of Decommissioning, Contaminated Water and Treated Water
Management 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. Also, there comes the need to handle nuclear fuel materials containing αnuclides from fuel debris with a large dose contribution in the case of internal exposure. Accordingly,
enhanced control of not only for external exposure but also for internal exposure is essential for
reduction of exposure.
Specifically, it is important to prevent excessive exposure to workers through appropriate
radiation protection schemes depending on the working environment and working style. Regarding
protection from external radiation exposure, the radiation exposure dose is evaluated considering
the radiation sources and the radiation dose rate in the work area. Then, based on the three74

principles, namely “time, distance, and shielding”, taking measures to reduce radiation exposure to
as low as reasonably achievable will be needed.
Therefore, anappropriate

combinationof exposure reduction

measures suchasdecontamination, shielding, remote technology etc. is to be selected, with the following ideas inmind.
・ Priority should be given to reducing radiation exposure through a combination of remotetechnologies and decontamination. Then, plan on-site radiation exposure management forsite workers by the “time, distance and shielding” approach.
・ In the extremely high-radiation dose areas such as inside the PCV and torus rooms, work
should be pursued by remotely controlled machines, etc. to avoid engaging personnel
inside.
・ With regard to the inside of the reactor buildings, except for the areas mentioned above,
consideration should be given to the optimal combination of decontamination, shielding,removal of unnecessary objects, remote technology, and reduction of working time in orderto keep the accumulative radiation dose for the entire project at a low level.
・ Where remote technologies are employed, additional work will be required, such as theinstallation of systems, maintenance and technical troubleshooting, which must be taken
into consideration in the above evaluation and planning.
・ As for the decontamination tasks, the judgment between remote technologies andpersonnel employment must be made based on factors such as the radiation dose rate in
the target areas, type of contamination, space for work, frequency of use, applicability anddevelopment situations of remote technologies, schedule and cost, etc.
・ Priority must be placed upon areas where work requirements are clearly identified.
Considerations must not be pursued if task requirements are unclear, or in a non-specific“betterment-oriented” manner such as to aim for an overall reduction of radiation dose.
Regarding protection from internal exposure, measures such as suppressing dispersion ofradioactive dust and prevention of the spread of contamination are being taken and appropriate
protective measures are to be selected depending on the target nuclides, airborne concentrationand surface contamination density in the work area, to prevent inhalation ingestion and bodycontamination leading to internal exposure. In the event of intake, the effective radiation doseshould be properly assessed using external counting (lung monitor) and bioassays. For this reason,
it is important to select α-nuclides that are important for exposure assessment in advance, and toincorporate them into the control of airborne concentrations, standards for wearing protective
equipment, and equipment calibration management. Controlling the surface contamination density
in the work environment and the body of workers entering/leaving contaminated areas is also
important to early detect the spread of contamination beyond the area division and to prevent anintake of re-suspended dust from loose contamination.

75

Based on the above, research and development for the protection of intake and radiation dose
assessment for inhalation ingestion under the Project of Decommissioning, Contaminated Water
and Treated Water Management have been in progress since FY 2021.
With the objective of dose reduction in long-term decommissioning, it is important to accumulateknowledge such as on-site operation experiences and lessons learned and hand down know-how.
For further expansion of fuel debris retrieval in scale, it is necessary to share information such as
the technique of handling α-nuclides during trial retrieval and allow prompt feedback for the next
work plan. Since May 2021, JAEA, which has the knowhow, has been providing guidance inpreparation for trial retrieval due to concerns about body contamination and internal exposure risks
in handling α-nuclides.
In particular, in fuel debris retrieval operation, access to the PCV should be made from thepenetration X-6, etc., after the work environment in the reactor building is sufficiently secured. To
reduce the radiation exposure of workers in the reactor building, it is important to conduct sufficientinvestigations on the radiation dose distribution and state of contamination, including thecontribution from the surroundings of the subject areas, to identify the source locations and intensity
as much as possible and to build the radiation dose reduction plan. Upon adequate verification on
the operation feasibility, the target dose rate in the work areas and access routes shall be set inconsideration 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 highradiation dose areas, it is important to take management measures to reduce the total radiation
exposure dose to as low as reasonably achievable and accomplish operations with respect to work
hours in accordance with dose limits and required work hours to accomplish operations. 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. This has led to the development in accordance with the required functions.
Moreover, in developing remote technologies for environmental improvement and removal of
obstacles under high radiation dose, the obstacles to be removed have been selected and theelemental technologies have been extracted in accordance with the required functions, andspecifications of remote control device have been studied for engineering implemented by TEPCO
based on the results of technical investigation and element test since FY 2020.
It is necessary to formulate a long-term work plan to help reduce the total radiation exposure ofworkers without concentrating worker exposure on specific individuals, implement holistic andadequate radiation exposure control, and secure workers as human resources from a long-term
perspective. Support should be provided to develop a database that can improve the efficiency ofwork planning and radiation exposure control and establish a system that manages and operates
various information on the entire Fukushima Daiichi NPS in an integrated, step-by-step manner.

763.1.2.6.2 Technical issues related to fuel debris retrieval methods
3.1.2.6.2.1 Issues in securing access routes
For carrying in, installing, and carrying out devices and equipment used for fuel debris retrieval
work, and transporting fuel debris and waste, access routes should be established by removing
obstacles on the access routes and reducing the radiation dose in the R/B to the level at whichsuch tasks can be performed. When establishing new openings in the PCV or other areas toconstruct access routes to fuel debris, suppression of the release of radioactive materials from the
PCV and RPV and maintaining the integrity of existing structures should be kept in mind taking into
account the gas phase containment function described in 3.1.2.6.1.1.The Mid-and-Long-term
Roadmap indicates that the first implementing unit would be Unit 2 and trial retrieval begins toward
gradual expansion of fuel debris retrieval. Accordingly, TEPCO is currently proceeding with specificengineering studies to conduct an access route from penetration X-6 in Unit 2.
On the other hand, toward further expansion of fuel debris retrieval in scale, studies areunderway on the construction of access routes from the side opening of the PCV to fuel debris (theside access method), based on the results of research and development conducted to date by the
Project of Decommissioning, Contaminated Water and Treated Water Management. In the sideaccess method, the issue is to address containment, shielding for connecting structures between
newly installed heavy structures and the side-opening of the PCV, and seismic displacement, andtechnical development of the method is underway using lightweight cells and fixed rails as well as
access tunnel systems.
As for the construction of access routes including top access (top-access method), in addition toside access, the technology for removing obstacles and transportation methods that can shorten
the preparation processes for retrieval are under study in order to enhance throughput. Since FY
2020, the Project of Decommissioning, Contaminated Water and Treated Water Management has
been examining the feasibility of a method to cut, retrieve and transport interfering structures as asingle or large unit while ensuring containment and shielding. TEPCO’s engineering has been
studying the overall process of the methods for Unit 3, assuming that it will be necessary to combine
side-access retrieval, which provides easy access to the inside and outside of the pedestal, andtop-access retrieval, which provides easy access to the inside of the RPV. The NRA pointed out
the possibility that a large amount of Cs might exist on the undersurface of the shield plugs of Units
2 and 3 from their evaluation of TEPCO's radiation dose measurements on the operating floor. In
this respect, consideration needs to be given to establishing access routes for the top-accessretrieval method based on the results of additional investigations in the second half of 2021,
including surveys on the situation and radiation doses in the reactor well below the shield plug andradiation dose surveys in the borehole.
In the future, based on the above-mentioned issues, it is necessary to clearly define the accessroute to be built at the next stage from the data obtained at each phase of scale expansion of
retrieval. In particular, when cutting the inner door of the penetration X-2 in unit 1, the dust77

concentration in the PCV increased more than expected before the start of the work, and thepressure in the PCV dropped while installing a camera chamber for investigating obstacles.
Therefore, not only countermeasures to prevent dust dispersion, but also the extra time required
for responding to when faced with such an unexpected situation need to be considered and planned.
Since the fuel debris retrieval policy stipulates that the optimum combination of retrieval methods
should be selected depending on the location where fuel debris exists for each reactor Unit, it isimportant to proceed with research and development toward a planned scale expansion.
3.1.2.6.2.2 Issues in development of devices and equipment
In each phase of trial retrieval, gradual and further expansion of fuel debris retrieval in scale,devices and equipment for fuel debris retrieval need to be developed with emphasis on safety,
reliability, and efficiency. To flexibly respond to the situation inside the RPV and the PCV bottom
where the fuel debris is predominantly present, the specifications of devices/equipment to be
developed in these phases should be established in consideration of radiation resistance, dust
resistance, waterproofness, range of temperature, remote inspection/maintainability, remote
operability, securing visual field, seismic resistance, protection mechanism for collision avoidanceor automatic shutdown in case of abnormality, high reliability, appropriate redundancy, a rescue
mechanism that does not disturb the subsequent work when a problem occurs, and efficiency offuel debris retrieval.
Equipment development for trial retrieval and gradual expansion of fuel debris retrieval has
progressed as part of research and development of the Project of Decommissioning, Contaminated
Water and Treated Water Management. Testing and training of the robot arm and other equipment
to be applied to the trial retrieval of Unit 2, which had been underway since 2021, has been
completed at the manufacturer's plant. Testing and training are now in progress at the Naraha
Center for Remote Control Technology Development from 2022. After the gradualexpansion of fuel debris retrieval, TEPCO needs to take over and substantiate the development
results. While preparing education/training scheduled to be started from 2021 for the fuel debris
retrieval operations using these remote devices. Prior to installing remote equipment such as robot
arms on site, adequate performance verification and operation training are essential by using
mockups simulating the expected PCV internal environment. For this purpose, examination ofmockup systems has been made.
Regarding devices and equipment for further expansion of fuel debris retrieval in scale, thefollowings are underway: development of the installation methods of access systems and sideaccess retrieval methods associated with dismantling/removal techniques for interfering equipmentin the PCV, and development of top-side retrieval methods for cutting and transporting large
equipment and for preventing the spread of contamination. Since the stage of further expansion offuel debris retrieval in scale is prolonged, and in order to ensure safe, efficient and continuous
retrieval work, it is also important to develop integrated support technologies for decommissioningof the Fukushima Daiichi NPS, such as development of rational maintenance technologies for a78

wide variety of remote devices and equipment, and system development to continuously monitor
environmental changes in the PCV along with work progress. These development activities havebeen promoted since FY 2021. TEPCO is currently conducting a conceptual study to examine
methods for further expanding the scale of retrieval. In FY 2021, TEPCO examined retrieval
methods to identify issues and risks for each method. Since FY 2022, studies have been conductedon these issues and risks in terms of feasibility. Further development of devices and equipment
should be planned and promoted in light of the status of examination of the methods.
As for how to proceed with development, it is necessary to flexibly promote operations in thesubsequent phase based on the information gradually obtained from preceding investigations andretrieval work, and to continue development for emerging important issues. The developed devices
and equipment need to be combined as a system and undergo a series of mockup tests todemonstrate that they can realize their performance safely and reliably at the actual site. These
mockup tests need to be implemented in a facility simulating the on-site environment in order toverify the applicability of remote equipment and operability/maintainability of the entire remotesystem under severe environmental conditions containing significant uncertainties. Therefore, in
cooperation with the organizations concerned, NDF and TEPCO have been engaged in examining
how to proceed with the remote mockup test plan, the test plan review, the scope of the mockup
facility to be maintained, the time required, and operation management, etc. From FY2021, TEPCO
has taken the initiative in promoting examination and materialization.
3.1.2.6.2.3 Issues in system installations and working areas
Assuming that safety functions are ensured, and considering avoidance of excessive system
specifications, it is necessary to examine the establishment of system installations, etc., takenecessary measures such as system additions based on the results of such examination, and thento operate them properly. In carrying out examination, sufficient areas should be secured to satisfy
the required environmental conditions while considering installing shields for reducing radiation
exposure for workers in addition to system installation, operation/maintenance management.
The system installations include a negative pressure control system required for establishingcontainment functions (gas phase), a circulating water cooling and purification system required formaintaining the containment functions (liquid phase) and cooling functions, and a criticality control
system required for controlling criticality. Moreover, realization of measurement systems (forpressure, temperature, water level, radiation, etc.) to monitor the PCV internal state is a significant
issue, which is essential for fuel debris retrieval. For building of safety systems incorporating theabove, prerequisites (system design criteria) are provided tentatively based on the research anddevelopment performed by the Project of Decommissioning, Contaminated Water and Treated
Water Management, and TEPCO has been examining the system design and layout through theirengineering work.
Regarding the gas-phase system, in FY 2021, the preconditions for negative pressure control
and the concept of ancillary systems were summarized with a view to the lowered airtightness of79

the PCV. Fig. 22 shows an example study in research and development for the liquid-phase systemby the Project 56. In this project, technologies to remove soluble alpha-nuclides and treatment of
secondary waste generated by water treatment are under development.
In engineering work by TEPCO, a basic plan for system configuration has been developed inreference to the results of the Project. A case study is also conducted on the feasibility of the systemlayout (installing devices in the reactor building or installing only some devices in the reactor
building if there are restrictions on arrangement) under the reactor building environment (ease of
securing equipment installation space, radiation dose in the subject area, etc.). Based on the resultof this examination, further investigation will be given on feasibility as a safety system. As describedabove, in establishing safety systems, steady efforts are required to improve the quality of design
by repeatedly adjusting system layout design, and reconsidering device specifications as thesituation demands.

2. Outline of the subsidized project
The diagram shows the liquid-phase system and gas-phase system under consideration in the subsidy project.
Development of a dissolved radionuclide removal system and sludge dehydration/stabilization system will be
conducted in this term.
① Development of dissolved α-nuclide removal technology
a. Study on removal tests for dissolved α-nuclides assuming use of actual fluidb. Element tests assuming fuel debris retrieval operations

Pretreatment
facility② Development of RO concentrated
water treatment technology③ Development of secondary
waste treatment technology

a. Selection of sorbent and condensing agent
b. Study on practical applicability

a. Research of pre-treatmentb. Study on practical applicability

To exhaustGas-phasefilterDevelopment items
in each facility

Boric acid (Silo)

vent
Exhaust fan

Recovered boric
acid tank

CoolerFacilities subject tothis project
Particle
removal filter
Water generated by debris
retrieval operation

Drain water/
Backwash water

Sorption vessel toremove soluble
nuclidesTanks (incl. boric
acid control)

Supernatant water/
Permeate water

Nitrogen

Groundwater

Drain water/
Backwash water

Sorption vessel toremove soluble
nuclidesTo existingwater treatment
facility

Supernatant water

SludgeDehydration/
Sedimentation
Stabilization/Separation Systemtreatment system
for Sludge Recovery
Permeate water

All filtration
apparatus for
sludge recovery

Boric acidrecoverysystem*RO membrane :Reverse osmosis
membrane

RO membrane
to removesoluble nuclides

Atmosphere

Particle
removal filter*Use only when boric acid isregularly used

Recoveredboric acid water

Concentrated Supernatant
water
water
Sedimentation/Separation System
for sludge recovery
SludgeDehydration/
Stabilization
treatment system

Supernatant water/
Sludge (filter)

To existingwater treatment
facility

Sludge Dehydration/
Sedimentation
Stabilization/Separation Systemtreatment system
for Sludge Recovery*Particle removal: Used for drain water recovery after large-particle removal treatment

To Wastestorage

To Storage
container

Fig. Liquid/gas-phase system for fuel debris retrieval (Subsidized project basis)
Note: This conceptual diagram is an example of the system configuration (in case of no leakage from PCV).

(Source : IRID)
Fig. 22 An example of examining the liquid-phase particle (particle collection/removal) in the
Project of Decommissioning, Contaminated Water and Treated Water Management

56 IRID, Subsidies for the Project of Decommissioning and Contaminated Water Management, “Development ofsafety systems (Liquid-phase system and gas-phase system, Development of criticality control technologies offuel debris), FY2021 implementation result, August 2022.
https://irid.or.jp/wp-content/uploads/2022/09/2021011anzensystem.pdf

80

In order to improve the airtightness of the Unit 3 reactor building, constructing covers on the sideand upper part of the building is under investigation. In this process, consideration is given to thesurrounding environment in addition to securing the space necessary for cover construction. As theradiation dose on the upper floor of the reactor building is currently high, construction of the coverby the remote operation is under discussion. Sufficient verification that simulates the actual
condition is required to achieve accurate construction of the cover. However, it is expected that
there will be a limit to improvement of airtightness. Therefore, in parallel with the investigation of
the structure and workability, the environment around the reactor building should be improved froma comprehensive viewpoint so that workers can be engaged in key operations and airtightness canbe enhanced.
3.1.2.6.3 Technical issues related to safe and stable storage of fuel debris
3.1.2.6.3.1 Issues in handling fuel debris (containing, transferring, and storing)
Before initiating gradual expansion of fuel debris retrieval work, a comprehensive system shouldbe established that consists of a series of steps from containing and transferring to storing of
retrieved fuel debris furnished with safety functions such as maintaining subcriticality, containment
functions, countermeasures against hydrogen generation, and cooling. Accordingly, examination of
the following is being progressed until the end of FY 202157,58.
・ Development of basic specifications for the container, such as overall length in considerationof handling, internal diameter, quality of materials and lid structure in light of work efficiency
and maintaining subcriticality, etc., and demonstration of the structural integrity of thecontainer 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 release on
the container lid by using the said prediction method; and establishment of safe transferring
conditions with consideration for accumulation of hydrogen gas in transferring casks.
・ Development of efficient drying technology applicable to fuel debris in unit cans, andconsideration on a drying system using this technology.
Moreover, in reference to the results of these studies, TEPCO continues their activities tomaterialize the equipment and installations (including canister for temporary storage,
receiving/delivery cell, and storage cell) needed for containment, transfer, and storage of fuel debris,which will be retrieved during the gradual expansion of fuel debris retrieval, in coordination withother associated projects. Toward further expansion of fuel debris retrieval in scale, storage

IRID, supplementary budget start from FY 2018, “Subsidies for the Project of Decommissioning andContaminated Water Management (Development of technology for collection, transfer, and storage of fuel debris(Dry technology of fuel debris)),” FY 2021 Interim report, August 2022
https://irid.or.jp/wp-content/uploads/2022/08/20220825syunoukansou.pdf
58 IRID, supplementary budget start from FY 2018, “Subsidies for the Project of Decommissioning andContaminated Water Management (Development of technology for collection, transfer, and storage of fuel debris(Handling of pulverized fuel debris slurry/sludge))” FY2021 Final report, August 2022
https://irid.or.jp/wp-content/uploads/2022/08/20220825syunousurajji.pdf
5781

locations have been examined based on the usage plan for the entire site, and specific transferring
routes and storing technologies/types are also under consideration. This study has focused on
granular and mass fuel debris. The pulverized fuel debris generated by fuel debris cutting in a slurryor sludge state in the cooling water circulation system as well as in powder state in the gas
management system. Therefore, in line with the progress of this study, examination is underway of
methods for safe, reliable, and rational storage of powdered and sludge/slurry fuel debris, as wellas the necessary equipment and installations, and it is necessary to progress this steadily.
At present, since the information and knowledge on the properties of fuel debris is limited, thesystems and devices/installations will be designed based on conservative assumptions of theproperties of fuel debris. In the design of equipment and facilities for containing, transferring andstoring of fuel debris for further expansion of fuel debris retrieval in scale, it is important to proceed
in a streamlined manner by utilizing various measurement data such as the amount of hydrogengeneration and debris properties as well as knowledge and experience of the handling of fuel debris
during the operations from receiving of the onsite transport container to the storage facility whichhave been collected and accumulated during the trial retrieval and gradual expansion of retrieval
scale.
Unit cans and containers in which fuel debris is stored should be handled and maneuvered bya remote device in a safe and reliable manner. Therefore, the assumed mockup operations need
to be executed (e.g., handling of unit cans and containers as well as fuel debris sampling foranalysis by using actual or similar remote device including a remote device) in the initial stage ofdetailed design. Moreover, in terms of preventing design change/modification, the approachthrough the mockup operations, which determines the specifications/sizes of these remote devices
and the devices/equipment required for containing, transferring, and storing fuel debris, their layout,
and the flow of fuel debris handling, is considered to be useful. In developing the specificinstallations and systems for handling and storing retrieved fuel debris, it is also necessary to giveconsideration to the installations to satisfy safeguards requirements (such as monitoring device).
The Mid-and-Long-term Roadmap stipulates that the processing/disposal method of theretrieved fuel debris shall be investigated and fixed during the third phase after starting the fueldebris retrieval work.
3.1.2.6.3.2 Issues in sorting out fuel debris and radioactive waste during fuel debris retrieval
In the fuel debris retrieval work, obstacles and structures to which molten fuel are partiallyadhered will also be retrieved from the PCV in addition to fuel debris in which molten core fuel are
mixed with metals and solidified, and compounds (MCCI product) produced by mixing molten corefuel with concrete at the PCV bottom. Furthermore, pulverized fuel debris generated during fueldebris cutting is also recovered. Of these, if substances on which a small amount of molten fueladheres or is mixed are all stored as fuel debris, it may become an obstructive factor in advancing
decommissioning because the scale of facilities and sites for fuel debris storage become larger.

82

Since it has been determined from the fuel debris properties that special attention andinstallations/systems for handling and storing are required to maintain subcriticality, it isrecommended that fuel debris and radioactive waste be separated based on the measurement
results of the amount and concentration of nuclear materials and stored separately (sorting). The
following studies were conducted in response to this59.
・ Consideration of which steps in the operation processes, from retrieval to storage, sorting isfeasible to separate retrieved materials from the PCV (fuel debris, structures, etc.) into fueldebris and radioactive waste (consideration of sorting scenarios).
・ Investigation of techniques/devices that may be capable of measuring or estimating theamount and concentration of nuclear materials contained in the materials retrieved from thePCV in non-destructive methods (investigation of possible measurement techniques).
Based on these studies, it is currently considered an incredibly difficult challenge of requiring
innovative technology development to measure or estimate the amount and concentration of
nuclear materials in the materials retrieved from the PCV using non-destructive methods because
various materials, including rod components (neutron absorber), are mixed inhomogeneously.
In developing measurement techniques and devices, it is important to understand themeasurement errors. Other than major factors affecting measurement errors such as the fuel debris
properties, location of nuclear fuel material in fuel debris and the storage condition of them in unitcans or containers, there are many factors affecting errors depending on techniques/devices itself.
The extent of such impact is highly uncertain at present due to a lack of knowledge on the propertiesof fuel debris. Therefore, in parallel with the accumulation of measurement data and thedevelopment of actual measurement devices by iterating actual measurement using mockup fueldebris, etc., it is considered beneficial in terms of R&D cost and time saving to identify factors
influencing measurement errors and their strength by a number of numerical experiments bycomputer and to incorporate the findings such as the extent of influence into the development of
the actual measurement technologies/devices. Thus, the impact of various condition of fuel debris
with different properties and storage conditions on the measurement errors as well as
modifications/improvements (e.g., specifications of shielding materials and their installation
location) of measurement techniques/devices to reduce measurement errors can also be examinedthrough numerical experiments by computer. Some positive results were obtained in theexamination mainly on the numerical experiments in the Project of Decommissioning,
Contaminated Water and Treated Water Management in FY 2021. From FY 2022 onward, in
addition to the development of measurement devices based on the analytical approach mainly
through numerical experiments described above, it is important to continue and accelerate thedevelopment of measurement devices by actual measurement of mockup fuel debris and fuel59 IRID, supplementary budget in FY 2018, subsidies for the Project of Decommissioning and Contaminated

Water Management, “Technology development for further expansion of fuel debris /in-core structure retrieval,”
results for FY 2019, August 2020.
https://irid.or.jp/wp-content/uploads/2020/09/2019008kibonosaranarukakudai.pdf

83debris of the Three Mile Island Nuclear Power Plant Unit 2 (hereinafter referred to as "TMI-2".) inparallel, using currently available measurement devices.
Trial retrieval and gradual expansion of fuel debris retrieval may provide knowledge on actual
fuel debris properties through limited sample analysis. Once this knowledge is obtained, it also
becomes possible to check whether the measurement results of the non-destructive measuring
devices contain significant errors.
It is important to enhance practical applicability and effectiveness of the measurement
technologies/devices by continuing the development of them in order to separate (sort) the storage
conditions of fuel debris and radioactive waste by such a method.
3.1.2.6.3.3 Issues in examining safeguards strategies
Material accountancy and safeguards to the retrieved fuel debris is 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 and safeguards toprepare 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 of safeguards to systems
has not affected the decommissioning process.
3.1.2.7 Summary of key technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
23.

84

Short term (recent 3 years)
Fiscal Year2022

Mid-to-Long-term (FY2025 to End of FY2033)
27
28
29
30
31
2027
2033(yr)26▽ Start of fuel debris retrieval in Unit 2* According to the Roadmap, the retrieval was supposed to start by the end of 2021, but the process waschanged to improve the work safety and certainty based on the impact of coronavirus infection,subsequent testing and site condition.

RM milestones
Trial retrieval(Internal investigation and fuel debris sampling)(Unit 2)

24
25
2024

2023

Improveenvironment
inside the building
Manufacture/ install the retrieval
deviceOn-siteoperation

Trial retrieval(internal investigations andfuel debris sampling)
Characterize the fuel debris：The period during whichchange is expected
Technical studies on individual items relating to onsite construction
R&D：To be conducted as required
Technical issues in the program on Decommissioning
and Contaminated Water Management
Basic/fundamental research

Improve environment
inside the building

Gradual expansionof fuel debris retrieval(Unit 2)

Fuel debris retrieval facility/safety system/fuel debris
temporary storage facility/maintenance facility
Design and production：Work period

Gradual expansion of fuel debris
retrievalInstallation

Characterization of fuel debris

RPVinternal investigation

Review of the program on Decommissioning and Contaminated
Water Management and TEPCO's voluntary project--PCV内部詳細調査技術の開発
Development of technology for detailed investigation inside PCV--燃料デブリの段階的に規模を拡大した
Development of technology for the gradual expansion of fueldebrisretrieval
取り出し技術の開発

Technical study by TEPCOTechnological issues for gradual expansion of fuel debris retrieval(1) Preparing retrieval system (improving durability of equipment, transfer test by transport truck)(2) Manufacturing equipment for gradual expansion of fuel debris retrieval (3) Providing storage facility of fuel debris / waste

Further expansionof fuel debris retrieval(Units 1/3)

Improvement of the environment inside and outside the Unit 1 building(Inside of the building: Dose reduction/removal of obstacles;
Outside of the building: Removal of lower part of exhaust stack of Units 1 and 2/removal of transformers, etc.)
Improvement of the environment inside and outside the Unit 3 building(Inside the building: PCV water lowering/dose reduction/removal of obstacles;
Outside the building: removal of the exhaust stack of Units 3/4, removal of transformers, etc.)
PCV internal investigation

Fuel debris retrieval facility/safety system/fuel debris storage facility/maintenance facility/training facility and others *Review on the concept, Actual siteapplicability verification,
developmentv and design

Production, installation, and retrieval

Reviews of the Program on Decommissioning and Contaminated/-原子炉建屋内・外の環境改善のための技術開発
TreatedWater Management and Basic/fundamental research
躯体・機器設備の劣化状況等の評価方法の開発- Developmentof technologies for environmental improvement of
inside and outside reactor building-放射性物質の分布を可視化し、被ばく量の低減に寄与する研究
Development of evaluation method for deterioration of building
放射線と腐食・材料劣化の関係に関する研究
frame and equipment--１号機PCV内部詳細調査技術の開発
Research to visualize the distribution of radioactive materials andcontribute to the reduaction of radiation exposure
Research on the relationship between radiation and corrosion/-RPV内部調査技術の開発／RPV内部調査の高度化
material degradation- Development of technology for detailed investigation inside Unit 1-RPV内部簡易調査技術の開発
PCV- Development of technology for investigation inside
RPV/Advancement of investigation inside RPV-燃料デブリ性状把握のための分析技術の開発- Development of technology for simplified investigation inside RPV-分析技術の実証（放射性物質分析・研究施設活用）- Development of analytical techniques for characterization of fueldebris-非破壊測定を含む取り出された燃料デブリの分析評価手法に関する研究- Demonstration of analytical techniques (analysis of radioactive
放射性物質・核燃料物質の分析技術の高度化に関する研究
material/utilizationof research facilities)--PCV内状況推定の高度化
Research on analytical evaluation methods for retrieved fueldebris, including non-destructive measurement
Research on advancement of analytical techniques for-燃料デブリの分析と解析・評価により炉内状況の推定及び事故事象に関す
radioactive/ nuclear fuel materialる研究- Advanced estimation of the state in the PCVs
-燃料デブリ・炉内構造物の取り出し規模の更なる拡大に向けた技術の開発- Research on estimation of the state inside reactor and accident
event through analysis and evaluation of fuel debris--燃料デブリ取り出し及び保管時の安全を確保に関する研究
Development of technologies toward further expansion of fueldebris/ internal structure retrieval--遠隔装置保守技術の開発
Research on ensuring safety for retrieving and storing fuel debris- Research on visualizing distribution of radioactive materials andcontributing to reduction of radiation exposure-燃料デブリ収納・移送・保管技術の開発- Development of technologies for containing, transferring andstoring fuel debris-１Ｆ廃止措置統合管理のための支援技術の開発- Research on ensuring safety for retrieving and storing fuel debris- Development of support technology for integrated management of
1F decommissioning

Technical study by TEPCOTechnical issues toward further expansion of fuel debris retrieval(1) Development of fuel debris retrieval method (Side access/top access/of common)
Development of access facility installation, dismantlement technology, technology development for realization of large piece
removal cocept, crashing and containing technology(2) Development of safety system (Liquid system/ gas system and critiality control system)
Strengthening function to remove radioactive material, development of boric acid management technology such as boric acidrecovery, evaluation of dust behavior and recovery(3) Strengthening and sofistication of containment technology
Development of containment technology for radioactive material by passive control(4) Development of safety assessment technology
Data aquisition of debris dispersion rate and analytical method for evaluating radiation exposure(5) Development of technologies for maintaining remote equipment
Development of decontamination and maintenance technology for contaminated remote equipment* It is assumed that Unit 3 will be examined in advance and expanded to Unit 1.

Fig. 23 Key technical issues and future plans on fuel debris retrieval (progress schedule)853.2 Waste management
3.2.1 Targets and progress(Targets)(1) The Solid Waste Management Plan (hereinafter referred to as the "Storage Management
Plan") is appropriately developed, revised and implemented including waste prevention,
volume reduction and monitoring, with updating the estimated amount of solid waste to begenerated in the next ten years periodically.
(2) Based on the prospects of processing/disposal method of solid waste and technology related
to its safety (hereinafter referred to as Technical Prospects) presented in FY 2021, creation of
options for processing/disposal measures and their comparison and evaluation should be
conducted with promoting characterization to establish a waste stream that are suitable forfeatures of solid waste. Proceed study on specific management of the solid waste to present
appropriate measures as a whole.

<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
・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 within the siteof 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.

86

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.

(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, storage, processing to disposal.
Definitions of terms related to radioactive waste management in the IAEA Safety Glossary
Terminology are shown in Attachment 8, and classification and disposal of radioactive waste inJapan and abroad are shown in Attachment 9.
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 "Basic Policies on Solid
Waste” summarized in the Mid-and-Long-term Roadmap are underway. TEPCO is required toensure safe and reasonable storage/management of the solid waste generated. Led by NDF, theorganizations concerned are promoting efforts based on each role to advance technicalexamination of integrated measures from characterization to processing/disposal of solid waste.
The Technical Prospects were provided in FY 2021 in light of the development results for improving
analysis abilities for characterization and establishing a flexible and reasonable waste stream (theflow of the integrated measures from characterization to processing/disposal). The Mid-and-Longterm Roadmap stated that the properties of solid waste would be analyzed, and the specificationsof 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.
The Project of Decommissioning, Contaminated Water and Treated Water Management related
to solid waste has been mainly conducted by the IRID. However, in preparation for the deadline forthe termination of IRID around the summer of 2023, JAEA is taking the main role in the projects
which are started from FY 2022.
3.2.1.1 Current status of storage/management in Fukushima Daiichi NPS
Table 2 shows the current storage/management status for solid waste. To store these solid
wastes properly, TEPCO releases its Storage Management Plan, and estimates the volume of solid
waste that will be generated in the next ten years, and shows their policy such as on building waste
management facilities to be required based on the volume.
According to this Plan, temporary outdoor storage of the solid waste will be eliminated completely
by FY 2028, except for secondary waste generated by water treatment and targets ofreuse/recycling. Facilities needed to achieve this goal are under development (Attachment 10).

87

The Technical Prospects have provided the examples of overseas 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. 24), and TEPCO
has also been implementing initiatives corresponding to this concept.
Among the targets of reuse/recycling, concrete rubble is crushed and recycled as roadbed
material after confirming that the surface dose rate is equivalent to the background radiation dose.
In addition, such as by melting is under consideration as a decontamination method for recycling
metal. The Project of Decommissioning, Contaminated Water and Treated Water Management has
also begun to clarify the nuclide distribution behavior during melting and decontamination andexamine validation methods after melting treatment as required research and development toachieve the above.
Secondary waste generated by water treatment is planned to be transferred to store in a building,with priority given to sorption apparatus that contain large amount of radioactivity, and a large waste
storage building is being constructed as a storage facility for sorption vessels. Moreover, the slurry
generated at ALPS (hereinafter referred to as “ALPS slurry”) generated by the multi-nuclide removal
equipment, etc., and the waste sludge generated at the water purification system (hereinafterreferred to as “waste sludge”) have high water content and flowability. For safer
storage/management, ALPS slurry will undergo stabilization (dehydration) treatment (Scheduledinstallation of treatment facility in FY 2024), while waste sludge will be collected from theunderground storage tanks in the building, where it is currently stored, dehydrated and then stored
into containers, before being transferred to higher ground (starting in FY 2023).
Such solid waste will continue to be generated with some exceptions, and additional solid waste
will be generated from fuel debris retrieval.
Table 2 Status of solid waste storage/management(a) Management status of rubble, felled trees, used protective clothing, etc.
(As of July 31, 2022)
Classification
Outdoor storage (surface radiation dose rate ≤ 0.1 mSv/h)
Outdoor sheet covered storage (surface radiation dose rate 0.1 1 mSv/h)Stored volume (m3) / Storage
capacity (m3)(Percentage)
237,500 / 266,300(89%)
47,700 / 50,700(94%)

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

16,800 / 17,900(94%)

Containers* (in solid waste storage building)

28,000/ 39,600(71%)
330,000 / 374,500
(88%)

Total

88

Felled trees
Stored volume (m3) / Storage capacity (m3)(Percentage)
92,000 / 134,000(69%)
37,300 / 41,600(90%)
129,300 / 175,600(74%)

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

Used protective clothing, etc.
Stored volume (m3) / Storage
capacity (m3)(Percentage)
30,400/ 52,500(58%)

Classification
Temporary storage* 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.

(b) Management status of temporary storage (As of July 31, 2022)
Classification

Stored volume (m3) / Storage
capacity (m3)(Percentage)

Outdoor storage47,900/ 62,600(77%)(c) Management status of secondary waste generated by water treatment (As of August 4, 2022)
Sorption vessels, etc.

Outdoor temporary storage area ofused sorption vessels

Storage place

Storage volume

Cesium sorption apparatus

779

2nd Cesium sorption apparatus

254

3rd Cesium sorption apparatus

13

HICs from multi-nuclide
removal system

Existing

1,986

Expansion

2,041

Used vessels from highHighperformance multi-nuclide
performanceremoval system
Used columns from multiExisting
nuclide removal system
Used vessels and filters from mobile typestrontium system

91
17
221

Number ofvessels and filters
Number ofvessels and filters
Number ofvessels and filters
Number ofcontainers
Number ofcontainers

Storedvolume/capacity(Percentage)

5,402 / 6,372(85%)

Number ofvessels
Number ofColumns
Number ofvessels

Waste sludge
Stored volume (m3) / storage
capacity (m3)(Percentage)442 / 700
(63%)

Storage place
Sludge storage facility (indoor)

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

89

Stored volume (m3) / storage
capacity (m3)(Percentage)
9,380 / 10,300(91%)

Fig. 24 Summary of waste hierarchy at the NDA, and countermeasures at the Fukushima
Daiichi NPS

3.2.1.2 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, andquantitative targets for analysis, etc. Initiatives have begun to use the results of the establishedsimplified and speed-up data acquisition for radiological analysis as standard analytical methods
at the Radioactive Material Analysis and Research Facility Building-1 (construction to be completed
in June 2022). A field demonstration of techniques to collect sorption from cesium sorption
apparatus is in progress to obtain analytical data on high activity waste.
For storage/management, factors affecting filter degradation (blockage/damage) such ashydrogen embrittlement, radiation degradation, etc. and their verification methods were examinedand summarized to maintain vent filter functions, which are important as hydrogen generation
measures during storage of high radiation-dose waste. Issues during storage and theircountermeasures were also examined based on domestic and overseas cases associated with
events of concern other than hydrogen generation.
As for the processing technology, the prospect of the application as actual equipment of thermal
processing technology to ALPS slurry has been confirmed through the Technical Prospects. Further,a detailed examination was carried out to control Cs volatilization during processing. While theprospect of the application as actual equipment of normal-temperature processing technology wasconfirmed through full-scale tests, issues related to the transformation of solidified waste andinspection methods for verifying the possibility of solidification are being examined. To contributeto the expansion of technological options, such as expanding the scope of application of normaltemperature processing technologies, verification of the applicability of pyrolysis treatment and90other interim treatment technologies to detoxifying organic substances, and inactivating
reactive/corrosive substances is underway.
Concerning disposal technology, necessary information and knowledge are being investigatedto develop measures that meet the needs of the disposal concept for waste, which review of thewaste stream is progressed. Development of a storyboard60 on the progression of important eventsin disposal facilities has started for the purpose of identifying critical scenarios for solid waste
disposal.
3.2.2 Key issues and technical strategies to realize them
In Phase 3, the plan is to determine the specifications of waste forms and their production
methods with proceeding characterization of solid waste. Therefore, in coordination among areasof characterization and processing/disposal, a study will be conducted to present appropriate
overall measures for specific management approaches for solid waste, while reviewing necessary
R&D tasks. Specifically, the first step is to create processing/disposal options for solid waste byexamining pending issues related to processing technology, interim treatment, 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 for thecharacteristics of solid waste.
To facilitate these efforts toward continued actions through an R&D organization with a high levelof technology and human resources, it is essential for stakeholders to make constant efforts todevelop human resources and improve technological capabilities in the area of waste and makeefficient use of resources by strengthening collaboration within this area and making mutual use of
the results of such efforts. It is also necessary to consider environmental arrangement that enables
the maintenance and strengthening of the supply chain, including the elemental technologies
necessary for each stage of waste management and peripheral technologies that are supportingthem.
3.2.2.1 Characterization
It is necessary to improve evaluation of inventory for solid waste and continuously incorporate
them into solid waste management, including processing/disposal, while accumulating analytical
data. In this case, efforts should 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 fueldebris retrieval, according to the characteristics of each type of waste.
For low activity waste, it is not so challenging to perform the analysis work itself. However, ittakes an immense amount of time to measure the entire quantity because of the enormous volume
of waste. Therefore, efficient analyses and analysis planning methods are needed along with thevolume reduction mentioned above. For that purpose, it is important to take an approach that

60 Storyboards provide a plain view of the behavior on the entire disposal system and allow for confirming

consistency in temporal and spatial scale.

91

efficiently ensures the required accuracy. To achieve this, it is needed to aim for promoting efficient
analyses by simplified and speed-up, and for establishing an efficient analysis planning methods
that combines the DQO process61 with statistical methods.
For high radiation dose waste, sampling and analysis themselves are difficult, and the amount ofanalysis data to be obtained is limited. Thus, statistical inventory estimation based on theradionuclide transfer model becomes important. It is necessary to efficiently obtain actual sample
data with an analysis planning method that combine the DQO process with statistical methods,
such as ongoing efforts for sampling from cesium sorption apparatus and its analysis, which iscurrently in progress. The priority of the data to be collected should also be considered to enhance
the accuracy of the radionuclide transfer model.
Following the phase of analyzing samples that are easy to collect, characterization is now in thephase of collecting/analyzing samples that are important for waste management. Going forward, it
is important to develop a medium-to-long-term analysis strategy that defines the solid waste to beanalyzed, its priority, the objective of the analysis, quantitative targets, etc., and to proceed withanalysis/evaluation accordingly. It is useful to accumulate trial results and verify their validity inorder to establish a flow from the development of an analysis planning method that combines the
DQO process and statistical methods; data acquisition and analysis; the incorporation of theacquired data into an examination of processing/disposal methods and evaluation of the outcome;to the development of the fiscal analysis plan based on the evaluation results.
As for facilities for analysis, in addition to the existing facilities in the JAEA’s Ibaraki area, etc.,
the Radioactive Material Analysis and Research Facility Building-1 was completed in June, andTEPCO also plans to install new facility for analysis, enabling characterization of a variety of solid
waste in parallel. Since the target nuclides, analysis items, accuracy, and the number of samples
for analysis differ depending on the target solid waste, a structure should be established based on
the appropriate division of roles according to the characteristics of facilities and the objective ofanalysis.
3.2.2.2 Storage/management
For storage/management of solid waste should be appropriately made to the risk depending onradioactivity 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 the storage/management
status commensurate with the risks involved.
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 andrecycle, by the end of FY 2028. To achieve this goal, it is necessary to promote volume reduction

61 A method to plan analytical samples for decision makings developed by U.S. Environmental Protection Agency

92

through incineration of felled trees, used protective clothing, etc., and cutting/crushing of metals
and concrete, and steadily consolidate storage inside buildings.
Due to the delay in installing the ALPS slurry stabilization/treatment system, the upper limit of the
cumulative absorbed dose (5,000 kGy) has been exceeded before the commencement ofstabilization process, and the number of HICs that need to be transferred has increased. Although
there is no immediate impact on their integrity in a stationary state, it is necessary to manage HICs
appropriately until they are transferred and safely complete the early installation of thestabilization/treatment system and immediate transfer.
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 research/development as of FY 2021. Going forward, reviews
should be performed along with the examination of the fuel debris retrieval methods. Measures
should be taken to ensure storage/management of solid waste that is expected to be generated
during fuel debris retrieval (trial retrieval, gradual expansion of the retrieval scale) before full-scale
retrieval.
The site also has solid waste stored before the accident, and a large volume of dismantled waste
is expected to be generated after the completion of fuel debris retrieval. Only increasing storage
capacity for solid waste will eventually reach the limit, so efforts should be made to reduce thevolume of solid waste to be generated as much as possible.
As volume reduction is extremely important for the safe and reasonable management of solid
waste according to the progress of decommissioning work in the future, the measures in progressshould be continued steadily. Since solid waste continues to be generated, it is important tocontinuously examine further possibilities by referring to advanced cases of overseas for morevolume reduction. It is recommended that volume reduction is realized in consideration of the
expected outcome and feasibility.
With an aim to reuse/recycle metals with extremely low surface dose rate, decontamination bymelting (decontamination by melting slag), are under consideration as metal decontamination
methods for recycling. As metal recycling with decontamination by melting slag has already beenused in many Western countries, it is considered a promising candidate technology. Thus, it isimportant to focus on the areas where the conditions are different between Western countries andthe Fukushima Daiichi NPS (target nuclides, etc.), and to evaluate the applicability of the method.
The portion of concrete debris for which the surface dose rate has been confirmed to beequivalent to the background radiation dose has already been recycled as roadbed materials.
However, given that it will be continuously generated as the decommissioning work progresses tobe generated, it is necessary to appropriately evaluate the balance between the amount generated
and the amount recycled in the future and consider the lead time if additional measures are required.

93

3.2.2.3 Processing/disposal
To specify measures for the optimization and rationalization of the overall picture covering theentire waste stream, the trial examples of optimization/rationalization of processing/disposal
methods will be accumulated by waste stream to acquire findings on optimization by waste stream
widely. Therefore, it is necessary to continue R&D of processing and disposal technologies required
for the series of studies as shown in Fig. 25.
Regarding the processing technologies, pending issues in low and thermal processing
technology, for which research/development is promoted, should be addressed. Waste streams,
for which the application of normal-temperature and thermal processing technologies has not been
investigated, will be evaluated as necessary, and performance of solidified waste to be produced
to leach to groundwater after disposal will be evaluated. As for normal-temperature processing
technology, consideration is given to transformation of solidified waste as well as inspection
methods to verify the possibility of solidification. In the case of thermal processing technology, thefeasibility of the whole processing system, including supply and exhaust systems, is an issue in
addition to the solidification process, and therefore it is necessary to carry out examination in atimely manner according to the start time of processing.
Concerning disposal technology, to enhance the reliability of the disposal concept, it isnecessary to evaluate its feasibility based on a study of the long-term evolution behavior of thedisposal facilities in light of the characteristics of waste form and to incorporate the results into thediscussion of the disposal concept. To appropriately allocate waste to a disposal concept that isshown to be feasible, knowledge on the sensitivity structure of the scenarios and parameters toradiation should be expanded by adequately incorporating the characteristics of waste, changes inenvironmental conditions in and around disposal facilities into those scenarios and parameters ofradiation dose assessment, and repeating tests. Using this knowledge to propose safe andreasonable disposal options is important. Furthermore, after expanding the target of waste streams
incorporating this disposal option, a group of disposal options will be examined with a bird-eye-viewof 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 forcharacterization.

94

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 treatment
technology suitable for
waste
・ Designate waste
specifications

Policy fornarrowing
down

Disposal・ Specify reasonable andfeasible disposal
methods
・ Conduct disposal safetyassessments

Proposals fortreatment/disposal options

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

Treatment

Waste
specification
proposals

Storage

Stablestorage・ Set inventories

Property
data

Characterization

DisposalReflect in TEPCO and solid
waste storage management plans

Fig. 25 Procedure to reasonably select safe processing/disposal methods of solid waste
3.2.2.4 Summary of key technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
26.
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, the trial examples of optimization/rationalization of processing/disposal
methods will be accumulated by waste stream under the assumption of ensuring safety to widelyacquire findings on optimization by waste stream. Moreover, consideration will be given to specify
strategies for optimization/rationalization of the overall picture covering the entire waste stream,
allowing clarification of approaches toward such purposes.
In examining these, it is important to flexibly consider the most appropriate measures, taking into
account the actual use and economic feasibility by reflecting the newest findings and applying theconcept of the Best Available Techniques. As the examination progresses, and theprocessing/disposal methods for the overall picture of waste are finalized, it will be important toshare the examination process for optimization, such as by sharing the awareness of problems
with local communities and society.

95

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 sampling technology forhigh 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

2.Storage(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 methodlogy for safetyassurance

Study on appropriate measures for entire waste management

Fig. 26 Key technical issues and future plans on waste management (progress schedule)963.3 Contaminated and treated water management
3.3.1 Targets and progress(Targets)(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), to reduce the stagnant water in the reactor buildings in FY
2022 to FY 2024 to about the half of the amount of the end of 2020 while continuing theoperation of the constructed water-level management system and controlling the generation
amount of the contaminated water to 100 m3/day or less in 2025. Moreover, to ensure stable
implementation of contaminated water management, measures against 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) For ALPS treated water currently stored in tanks, measures will be taken for discharging
approximately two years after the “Basic Policy on Disposal of ALPS-Treated Water” (releasedin April 2021).
(Progress)
Fig. 27 shows the outline of the contaminated water management. Stagnant water in buildings,
that is, the contaminated water with a mixture of cooling water contacted with the fuel debris andgroundwater/rainwater flowed into the buildings is liquid containing a considerable amount of the
dissolved radioactive materials (inventory) from the perspective of measures to reduce the risk fromradioactive materials. Therefore, its hazard potential is high and so is the Safety Management level(refer to Section 2.2), as the storage condition of such stagnant water deviates from what isoriginally intended. For this stagnant water in buildings, excluding the reactor buildings of Units 1
to 3, where circulating water injection is ongoing, the process main building and high-temperatureincinerator building storing contaminated water temporarily for purification treatment, the treatmentof stagnant water in buildings was completed in 2020, and the inventory was significantly reduced.
However, the hazard potential is still high.
Currently, the following four measures are being implemented as contaminated water
management:

97

Red

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

Remove Cs
Desalination

T/B

Pump
Tide
out embankments

Groundimprovementwith waterglass Bottoming
TrenchPump out megafloat
Pump
out
Open channel

Sea-side
Impermeable
wall

Further lowering of
the water level

Groundwaterdrain

Stagnantwater

Sub-drain

Sub-drain

Pumping wellRepair damaged
part of the roof

Pump out
Land-side impermeable wall

Groundwater
level

R/B

（出典：東京電力）

Land-side
impermeable
wall

Groundwater bypass

Pavement

HarborPurification
Replace to welded tanks
and expansion of tanks
Pump out(Source : TEPCO)
Fig. 27 Outline of contaminated water management 62(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")
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 andsub-drains. The increase in the amount of contaminated water generated during rainfall also tended
to be controlled by repair of damaged roofs and facings on site. As a result, the amount ofcontaminated water generated decreased from approx. 490 m3/day (FY 2015) before the measures
were taken to approx. 130 m3/day (2021). In order to reduce the amount of contaminated water to
100m3/day or less by the end of 2025, roof repair and expansion of facing range are being
addressed while adjusting interference with other decommissioning work. Fig. 28 shows the
progress of contaminated water management and changes in the amount of contaminated water
generated.63

62 Secretariat Meeting of the Team for Countermeasures for Decommissioning and Contaminated Water/Treated

Water Treatment (100th), Material 2, “Outline of decommissioning, contaminated water and treated water”,
March 31, 2022
63 Committee on Countermeasures for Contaminated Water Treatment (24th meeting), Material 1, “Status ofcontaminated water management at the Fukushima Daiichi NPS”, June 15, 2022

98

Water level before
SD operation

Approx.220m3/day(1,375mm)

Setting water level
for SD operation

Approx.170m3/day Approx.180m3/day(1,633mm)(999mm)Approx.140m3/day Approx.130m3/day(1,349mm)(1,572mm)

FY 2014

FY 2015

FY 2016

FY 2017

FY 2018

FY 2019

FY 2020

Amount of inleak into building (b)Amount of contaminated water
generated

Amount of inleak into building (a)Transfer amount generated bydecommissioning work

FY 2021

Approx.100m3/day
or less

FY 2022

FY 2023

Amount transferred at El. T.P.+2.5m

Sub-drain water level (T.P. m)

Amount of inleak into building (a) : Of the building inleak amount of rainwater/groundwater, etc, theestimated amount of inleak into building when rainfall is zero,
based on the relationship between monthly rainfall and building
inleak in each fiscal year.
Amount of inleak into building (b) : Building inleak amount of rainwater/groundwater, etc. minus
amount of inleak into building (a)Approx.410m3/day(1,337mm)

Progress rate (%)

Generated amount of contaminated water (m 3/day)Approx.490m3/day(1,429mm)

Approx.470m3/day(1,638mm)

FY 2024
FY 2025
Amount of chemical solution during
ALPS purification

Setting water level for SD operation

Progress is noted as of the end of the fiscal year.
It is assumed that the effects of rainfall infiltration control
measures will appear in the following year or later.
FY 2013

FY 2014

Facing (Wide area)

FY 2015

FY 2016

FY 2017

FY 2018

FY 2019

FY 2020
Land-side
Impermeable walls

Facing (River dike area)

FY 2021

FY 2022

Roof measures

FY 2023

FY 2024

FY 2025

Facing/paving (area around buildings)

In FY2014, the amount of contaminated water generated was not calculated by each breakdown, it was not accumulated by breakdown.
(See Slide 18 for breakdown of contaminated water)

Major multilayered contaminated water management

March 2020
August 2017
September 2015
May 2014
FY 2023◆ Groundwater ◆ Sub-drain operation started ◆ Land-side Impermeable walls ◆ Roof measures for Rw in Unit 3 ◇ Target of 50% completion By the end of FY 2025
completed(Closed)◇ Amount of contaminated waterby-pass
October 2015
for facing in frozen soil
FY 2017
to 100 m3/day or lessoperation started ◆ Sea-side impermeable
FY 2020◆ Joint control of El. 2.5m facing
wall closed◆ Roof measures for T/B
FY 2023in Unit 3 completed
November 2015
◇ R/B cover of Unit 1 installed
February 2018
◆ Northeast roof for R/B◆ Groundwater drain(Incl. rainwater measures◆ R/B cover for Unit 3 installed
FY 2015
in Unit 3
operation started
for Rw/B of Unit 1)◆ Wide area facing◆ Measures taken
March 2018
FY 2016
March 2016
established◇ Measures being planned◆ Freezing of land-side ◆ Freezing of seaward ◆ Enhancing processing capacity of SD
system completed (1,000⇒2,000m3/day)side of land-side
impermeable wall
impermeable wall
(Phase 1)(Source : TEPCO)

Fig. 28 Progress of contaminated water management and changes in the amount ofcontaminated water generated(2) Efforts to complete stagnant water treatment
In 2020, the treatment of stagnant water in buildings, excluding the reactor buildings of Units 1
to 3, the process building and high-temperature incinerator building, was completed. With the aimof reducing the amount of stagnant water in reactor buildings to approximately half of that at theend of 2020 between FY 2022 and FY 2024, moreover, the water level in Unit 2 reactor building
was carefully lowered while parameters such as PCV pressure and dust concentration weremonitored, and the target level of T.P.-2,800 was first reached in March 2022 64(Fig. 29).

64 Meeting of the Secretariat of the Team for Decommissioning and Contaminated Water/Treated Water

Management (100th), Material 3, “Progress status of treatment of stagnant water in buildings,” March 31, 2022

99

FY2020

FY2021
Water level in sub-drain

FY2022

FY2023

FY2024Present

Water level of stagnant water in buildings
and groundwater level

Floor surface of T/B / Rw/B
Water level of stagnant water in Unit 1 R/B
Water level of stagnant water in Unit 3 R/B

Water level of stagnant water in Unit 2 R/B

Fig. 29 Lowering of sub-drain and building water levels64

Around T.P.-2,200

Around T.P.-2,800(Source : TEPCO)

The plan is to lower the water level in the reactor building while continuously lowering the subdrain water level in order to reduce the amount of stagnant water in the reactor building by half. In
association with this, the importance of issues in handling sludge containing α-nuclides at thebottom of the reactor building (hereinafter referred to as “α-sludge”) is increasing. As the particle
size distribution and chemical composition of the α-sludge have been analyzed, it is expected thatmost of the sludge can be removed by a filter with an appropriate pore diameter. In order tocomplete the treatment of stagnant water in the process building and the high-temperatureincinerator building, moreover, methods for radiation dose rate surveillance or recovery are underconsideration for high-dose zeolite sandbags located on the lowest floor. In the case of a building
where the treatment of stagnant water has been completed and the floor surface has been exposed,a method for recovering sludge located on the floor is being studied.
(3) Efforts for stable operation of contaminated water management
As for tsunami countermeasures, construction of the Kuril Trench tsunami tide walls werecompleted 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, , reinforcementof the land-side impermeable walls, relocation of sub-drain and other water collection systems fromthe revetment side to higher ground, and transfer of sludge generated by decontamination devices
to higher ground. As a countermeasure for heavy rain, installation of drainage channel D toeliminate the risk of inundation in the vicinity of Units 1 to 4 and reinforcement of discharge functionsof the existing drainage channel, etc., are underway.
Although the importance of multilayered measures such as land-side impermeable walls has notchanged, damages to systems such as brine leakage have occurred. Considering that, in the future,
it is important to strengthen monitoring, procures, and arrange spare parts and substitutes, andestablish a framework for taking restoration measures as soon as possible. Furthermore, theearthquakes that occurred on February 13, 2021, and March 16, 2022, did not cause leakage intanks for storing the treated water, but caused sliding of the tanks (53 units and 160 units,
respectively). Displacement exceeding the manufacturer’s recommended value65 was observed in
65 It is a reference value that allows the pipe to be used safely even if displacement occurs. The design value has

a margin of about 2 to 4 times to this value.

100some connecting pipes. However, since the coupling valve is fully closed, there would be noleakage of water stored in tanks, even in the case of pipe rupture.
(4) Efforts toward discharging ALPS-treated water into the sea
On April 13, 2021, under the overriding principle of Balancing between Reconstruction andDecommissioning, and on the premise of ensuring safety and implementing comprehensive
measures to prevent reputational damage, the Government announced the basic policy fordischarging ALPS-treated water into the sea from the Fukushima Daiichi NPS after comprehensive
discussions at expert meetings for more than six years.66,67 In addition, the Government requested
TEPCO to proceed with preparations, including the installation of a specific discharge system,
aiming to start the discharge of ALPS-treated water into the sea in about two years68.
In response to this policy, on April 16, 2021, TEPCO indicated their approach to ensuring safety
through further efforts and in compliance with regulatory standards pursuant to laws andregulations; minimizing reputational damage; providing compensation in the event of reputational
damage69, and addressing issues for the future. TEPCO has also started working to provide abriefing for stakeholders, and to obtain permission for the implementation plan.
Table 3 shows major initiatives toward discharge of ALPS-treated water into the sea after thebasic policy was announced. The government compiled and disclosed immediate measures at thesecond meeting of the Cabinet Meeting for the Steady Implementation of the Basic Policy on
Disposal of ALPS-treated Water and a specific action plan at the third meeting. The task force on
monitoring and measuring the marine environment and the Expert Meeting for Marine Monitoring
related to ALPS-treated water were established in 2021 to enhance marine monitoring. In July 2021,
the government signed the Terms of Reference with the International Atomic Energy Agency(hereinafter referred to as “IAEA”) and requested support for the discharge of ALPS-treated water.

66Tritiated Water Taskforce Report, June 3, 2016
67 Report by the subcommittee dealing with water treated with multi-nuclide removal equipment, February 10,

2020
68 Inter-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
69 TEPCO: Attachment 1, “TEPCO Holdings’ Action in Response to the Government’s Policy on the Handling of
ALPS Treated Water from the Fukushima Daiichi Nuclear Power Station,” press release, April 16, 2021

101

Table 3.
Schedule

Major initiatives for discharging ALPS-treated water into the sea
FY 2021

FY 2022First half of FY 2023

▼Released ”The Basic Policy on Disposal of ALPS-treated Water”
The Cabinet Meeting for the Steady Implementation of the Basic Policy on Disposal of ALPS-treated Water
▼2nd
▼1st
▼3rd

Government▼Established the task force on monitoring and measuring the marine environment▼Established the Expert Meeting for Marine Monitoring▼Signed the Terms of Reference with IAEA (TOR)▼Conducted third-party analyses for ALPS-treated water before the discharge▼Started marine monitoring▼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 Regarding the Discharge of ALPS-Treated Water into theocean (Design stage)”▼Submitted ”Application Documents for Approval to Amend the▽Will begin to discharge
Implementation Plan for a Specified Nuclear Facility for ALPS Treatedinto the ocean
Water Dilution/Discharge Facilities and Related Facilities”
Installs facility, etc.
Pre-operation inspection

TEPCO

NRA

▼1st Review Meeting▼2nd Review Meeting
Review Meetings (3rd to 15th)

IAEA

Publiccomments▼ Approved▼Signed the TOR with the Japanese government▼Conducted a safety review on the handling of ALPS-treated water▼Published review results reports▼Conducted a review of the regulations of ALPS-treated water▼Published review results reports

Meanwhile, TEPCO announced in August 2021 the status of the facilities study for ensuringsafety and published the results of its assessment that the impact of the discharge of ALPS
treated-water into the sea on human and the environment would be extremely small in theRadiological Impact Assessment Regarding the Discharge of ALPS Treated Water into the Sea(Design stage) in November 2021 to solicit comments. In December 2021, TEPCO submitted
Application Documents for Approval to Amend the Implementation Plan for a Specified Nuclear
Facility for ALPS Treated Water Dilution/Discharge Facilities and Related Facilities to the Nuclear
Regulation Authority for review on facilities for offshore discharge of ALPS-treated water, theiroperation methods, and safety during discharge into the sea, and gained approval in July 2022.
In addition, the IAEA conducted a safety review on the handling of ALPS-treated water in
February 2022 and a review of the regulations of ALPS-treated water in March 2022 based on theTerms of Reference with the government. The IAEA published review results reports in April 2022
and June 2022, respectively.
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 method recognized globally and widely adopted in Japan and abroad. On the other hand, it isalso a fact that there have been concerns about reputational damage due to the discharge of
ALPS-treated water into the sea. Therefore, efforts should be continued to deepen understanding
to eliminate such concerns. Therefore, greater transparency is required, for example, by
repeatedly providing explanations in an easy-to-understand and careful manner, mainly by
TEPCO, in order to increase understanding of (1) an operation plan for offshore discharge; (2) the
effects of radioactive material such as tritium contained in the water to be discharged to the sea
on the human body; and (3) the method for verifying the operation status as the basics for102

implementing safe discharge, and by verifying these through reliable third parties such as IAEA incooperation with organizations concerned, and by delivering accurate information.
TEPCO's planned discharging system, if operated reliably, will have no adverse effects onhumans and the environment, and therefore it is an important issue to operate the system"reliably" “as planned”. The following is a summary of the progress made by TEPCO on each of
the items listed in Technical Strategic Plan 2021.
In the operational phase, develop a series of operation plans including system operation,
analysis of ALPS-treated water, flow control of the treated/diluted water, marine monitoring,
maintenance, and troubleshooting, and then develop a system plan that minimizes risks andeliminates social concerns=> TEPCO's system and operation plans will be approved by the Nuclear Regulation Authority
in July. However, the nuclides to be measured/assessed before discharge into the sea will
be selected after verifying the nuclides that can be significantly present in ALPS-treatedwater. NDF provides technical advice and support on the selection method of nuclides tobe analyzed and the evaluation method of nuclide concentration.



Perform a radiological impact assessment on the human population and the naturalenvironment, and disclose evaluation results based on the specific discharge plan=> In April 2022, TEPCO submitted to the NRA the statement of the radiological impact
assessment revised based on the review by IAEA and the international experts as well as
discussion with NRA. Based on the selection results of the nuclides to be assessed, theradiation environmental impact will be verified.

Verify safety by experts from IAEA and other agencies=> In February 2022, the IAEA conducted a safety review on the handling of ALPS-treatedwater, confirmed and announced in a report70 that preventive measures were adequately
taken in the design of the discharge facilities in light of international safety standards, andthat the radiological impact on humans is significantly smaller than the level specified byregulatory authorities. The next review mission is scheduled in November 2022, and acomprehensive report with final conclusions and findings will be published before thedischarge of ALPS-treated water begins.
The IAEA also reviewed the NRA in March 2022 and announced that the NRA isfunctioning as an independent regulatory agency and is fulfilling its responsibility todevelop an appropriate regulatory framework and evaluate safety71.
The IAEA also plans to conduct analyses of ALPS-treated water at a laboratory of IAEA
and research institutions in a third country as third-party analyses. In addition to its

70 IAEA review of safety related aspects of handling ALPS-treated water at TEPCO’s Fukushima Daiichi Nuclear

Power Station, Report 1: Review mission to TEPCO and METI (February 2022), April 29, 2022
71 IAEA review of safety related aspects of handling ALPS-treated water at TEPCO’s Fukushima Daiichi Nuclear

Power Station, Report 2: Review mission to NRA (March 2022), June 16, 2022

103

independent analysis, TEPCO plans to outsource analysis to external organizations with
ISO/IEC 17025 certifications72. The Japanese government also intends to have the Japan
Atomic Energy Agency (JAEA) conduct third-party analyses before the discharge. The
results of these analyses will be disseminated domestically and internationally with hightransparency.


Develop a plan to strengthen marine monitoring, and perform marine monitoring before thedischarge=> The Government’s Monitoring Coordination Council, held on March 30, 2022, provided aplan for strengthening and expanding marine monitoring by the government (MOE, NRA,etc.), TEPCO, and Fukushima Prefecture. The monitoring started in April 2022. TEPCO isproactively conducting monitoring in cooperation with the government and local
governments, etc.



Education and training on analysis for parties concerned including contractors=> TEPCO explained education and training plans on analysis to the NRA in the open
screening panel. A review was performed on competence management methods related
to analysis, and education and training.



Development of strategies to provide accurate and understandable information domesticallyand internationally without causing anxiety from a social perspective, and timely disseminationof the status of preparations=> TEPCO has continuously held 1F tours and round-table talks for residents living in 13
municipalities along Hamadori and other areas in Fukushima Prefecture, anddisseminated information on decommissioning and ALPS-treated water through the local
newspaper advertisement. In addition, TEPCO has accepted site visits by foreign
government officials, etc., as well as provided the latest information on the discharge of
ALPS-treated water into the sea not only in Japanese, but available in English, Chinese,and Korean on TEPCO’s “Treated Water Portal Site”.

Ensuring implementation of measures against reputational damage as set forth in the
Government's basic policy announced in April 2021=> The Government announced an action plan at “the third meeting of the Cabinet Meetingfor the Steady Implementation of the Basic Policy on Disposal of ALPS-treated Water”(revised in August 2022) held in December 2021. Based on the action plan, TEPCO ismaking efforts to minimize reputational damage through reviews by the NRA and the IAEA,
and safety checks by local governments based on agreements to ensure the safety ofdecommissioning. NDF promotes understanding and disseminating accurate information

72International standards developed by the International Organization for Standardization for general requirementson the competence of testing and calibration laboratories.

104according to the interests of the recipients through meetings with relevant organizations
in foreign countries and international conferences.

3.3.2 Key issues and technical strategies to realize them
3.3.2.1 Issues in the future treatment of stagnant water in buildings
The following three points are the key issues for the future treatment of stagnant water inbuildings.
(1) Prevention of spreading α-nuclides
At the bottom of the torus room of the reactor building, stagnant water in which α-nuclides fromfuel debris exist in the form of fine particles (α-sludge) and ions, and a relatively high concentrationof total α-nuclides has been detected 73 . Since the effective dose factors of α-nuclides isremarkably high when inhaled or ingested, special management and countermeasures are
required if α-nuclides spread to stagnant water in buildings or water treatment systems. The
spread of α-nuclides should be as limited as possible to avoid such a situation.
The investigation in FY 2021 revealed the following two points on the spread of α-nuclides73.
The highest total α concentration to date was detected in accumulated water collected in theMain Steam Isolation Valve room of Unit 3.

A relatively high total α concentration was detected in the bottom sludge of the D1 and D2
tanks in the Area E.

The total α concentration of the accumulated water collected in the Main Steam Isolation Valve
chamber of Unit 3 was about three times (1.7 × 106 Bq/L) that of the stagnant water collected fromthe bottom of the reactor building of Unit 3, which had the highest concentration. It is presumed
that this accumulated water is part of the water inside the PCV flowing directly into the Main Steam
Isolation Valve chamber from the damaged expansion joint of the main steam pipe connected to
the PCV74. Moreover, It was found that the total α concentration of the collected accumulated water
would decrease to about 1/1000 by filtration, indicating that most of the α-nuclides exist as fineparticles 73.
Tanks D1 and D2 in Area E store water collected from residual water at the bottom of the tanks
generated by dismantling flanged tanks that stored RO-enriched saltwater. As a result of measuring
the total α concentration of the water mixed with sludge at the bottom of the tanks, the total αconcentration (5.3 x 103 Bq/L) of the same level as the stagnant water in buildings was detected75.
73 Committee on Countermeasures for Contaminated Water Treatment (24th meeting), Material 1, “Status ofcontaminated water management at the Fukushima Daiichi NPS, References,” June 15, 2022
74Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water

Treatment (91st), contaminated water management, Material 3-1-8, “Drilling holes on the first floor of the Unit 3
reactor building”, June 24, 2021
75 Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water
Treatment (94th), contaminated water management, Material 3-1-9, “Policy to respond to α-nuclide detected inremaining water in the Area E (flanged) tank,” September 30, 2021

105

This bottom sludge is to be recovered from the top manway of the tank by feeding an underwaterpump.
As described above, the situation of α contamination in the Unit 3 reactor building and thepresence of α sludge due to the treatment of residual water at the tank bottom are becoming
apparent. In particular, attention should be paid to the fact that α contamination spreads mainly
through fine particles (sludge components). At present, a total α concentration in the order of 10
Bq/L is maintained at the cesium sorption apparatus (SARRY/SARRYII) inlet, and the spread ofcontamination to the downstream side is suppressed. However, as the stagnant water level of thereactor building is lowered further in the future, more sludge at the bottom of the building may bemixed, and the total α concentration at the water treatment system inlet may rise. TEPCO isconsidering installing filter systems in the subsequent stage of the cesium sorption apparatus in
response to such concerns76.
Sampling Point Analysis Date Concentration

Sampling PointSARRY Entrance

SARRY Entrance

SARRY II Entrance

SARRY II Entrance

Sampling Point

Analysis Date

Analysis Date

Concentration

Sampling Point

Concentration

G1S,G3,G6,G7,H1-H5, H4N,
H6(I) ,H6(II), J1-J7,
K1-K4, B, B South area

Sampling Point

Analysis Date Concentration

ALPS Exit
Add. ALPS EXIT

Concentration
El.8.5m

El.33.5m

３MSIV
Room

Water injection
Sampling
Point

Analysis Date

ALPS-treated water tanks
Sampling Point

Concentration

Analysis Date Concentration

SARRY, etc.

T/B, etc.

Sr-treated water tanks
Centralized Rw

Sampling Point

Analysis Date

Concentration

Analysis Date

Concentration

ALPS Exit
Add. ALPS EXIT
Sampling Point*1 : Sampling at the bottom using sampling apparatus*2 : Sampling at 1m from the bottom using pump
*3 : Sampling during treatment of residual water in tanks

Supernatant of Sr-treatedwater tank
Bottom of Sr-treatedwater tank

*1 The evaluation is based on the latest analysis data, but may be subject
to change depending on the results of future analysis of total alpha nuclides(Source : TEPCO)

Fig 30 Water treatment systems for stagnant water in buildings and measurement results of total
α-nuclides73(2) Further lowering of groundwater levels to reduce the amount of contaminated water generated
Since there is highly concentrated stagnant water at the bottom of the torus room of the reactor
building, a sudden change in concentration during treatment of the stagnant water will interferewith the treatment system in the subsequent stage. Therefore, the water level of stagnant waterin buildings will be carefully lowered to approximately 10 cm in 2 weeks for each building.
Although the water level is controlled in the floor sump in the buildings with exposed floor
surfaces, there is a possibility that the sump may overflow temporarily during heavy rains such as
76 From the viewpoint of removing α-nuclides, the filter system should be installed in the front stage of the cesium

sorption apparatus. However, in this case, the filter will capture particulate radioactive cesium, resulting in ahigh radiation dose to the filter system and making replacement work difficult. Therefore, the filter system will be
installed in the rear stage of the cesium sorption apparatus.

106

typhoons. The overflowing water must be treated as stagnant water in the building, which is highly
contaminated by fuel debris, and the water level difference with the sub-drain must be secured(800 mm or more). Therefore, in preparation for the risk of deviation from the limiting conditions
for operation (LCO) during heavy rain, the sub-drain water level is maintained higher in advance,
causing an increase in the inleak into buildings. Since the floor of these buildings is higher thanthe level of stagnant water in the reactor building, water that inleaks into the floor sumps during
heavy rainfall is derived from rainwater and groundwater. As the risk of leakage of stagnant waterin the reactor building does not increase even if the water level rises, it is necessary to review thewater level management method for the buildings where exposed floor surface has been achievedin the future.
(3) Stagnant water treatment in process main building and high-temperature incinerator building
As the basement floors of the process main building and the high-temperature incinerator
building are storing stagnant water, TEPCO aims to lower the water level to expose the floor surfaceof the buildings from FY 2024. To realize this, it is essential to take measures against high-dose
zeolite sandbags placed on the basement floors of the process main building and the hightemperature incinerator building and install temporary storage tanks for stagnant water in place ofstorage in the basement floors77.
In the basement floors of both the process main building and the high-temperature incinerator
building, zeolite sandbags placed shortly after the accident are found to exist in a high-dose state,
and the maximum surface dose from the sandbags is extremely high at approximately 4,400 mSv/h,and activated carbon sandbags also exist. When these basement floors are exposed, it is expectedthat the radiation dose will increase significantly at the openings of the above-ground floors due tothe loss of water shielding.
The recovery procedure of zeolite sandbags under consideration is shown in Fig. 31. The
procedure is to first collect as many zeolite sandbags as possible in a submerged environment toincrease work efficiency, then transfer the collected zeolite and other materials to the ground level
using a recovery robot (ROV + pump), desalinate and dehydrate them in the building, seal them inmetal storage containers, and transfer them to temporary storage facilities77. The first step ofcollecting will be carried out in FY 2023, and the second step of containing will be from FY 2023 to
FY 2024. In this task, zeolite will be collected and recovered by suction in the form of particles,
which may apply to the recovery of high-dose sludge deposited on the floor surface of the reactor
building to be planned, providing critical knowledge for the future progress of decommissioning
work.
However, the basement floors of the process main building and the high-temperature incinerator
building have been used as storage tanks for tens of thousands of cubic meters worth of stagnant
water in buildings, where water with different chemical properties and radioactivity transferred from77 Committee on Countermeasures for Contaminated Water Treatment (24th meeting), Material 2, “Issues andcountermeasures concerning contaminated water management at the Fukushima Daiichi NPS,” June 15, 2022

107the Unit 1 to 4 buildings has been mixed, averaged, and treated by the cesium sorption apparatus.
For this reason, studies are underway on temporary storage tanks for stagnant water that will takeover the following functions that the process main building and the high-temperature incinerator
building have performed78.


Receiving stagnant water in buildings

Stagnant water buffer for stable operation of cesium sorption apparatus (KURION, SARRY,
and SARRYII)

Concentration averaging of stagnant water in each buildingSettlement of sludge

These temporary storage tanks for stagnant water will be installed on the fourth floor of theprocess main building. The basement floor of the process main building after tank installation will
be used only when the inleak volume increases during heavy rain. To take over the functions
described above, temporary storage tanks for stagnant water will consist of two types of tanks: atemporary receiving tank for receiving water and settling sludge and a temporary storage tank forhomogenizing the water concentration. The capacity of the temporary receiving tank is assumed tobe approximately 10 - 20 m3, and that of the temporary storage tank is approximately 20 m3. The
capacity is considerably smaller than that of the basement floors of the process main building(maximum capacity: approximately 16,000 m3) and the high-temperature incinerator building(maximum capacity: approximately 5,000 m3). In the future, an examination from operational
aspects is needed to maintain the functions even with a small capacity. The installation work of thetemporary storage tanks for stagnant water is scheduled from FY 2023 to FY 2024, and these tanks
will be operated from FY 2024.

Collecting operation

Containing operation Dehydrate/sealing unit
Container

Hoses are laid on thefirst floor in PMB

Groundfloor

Hoses are laid on the first
basement floor in HTIFirst basement
floor

Second basement
floor

Collecting robot(Source : TEPCO)

Fig. 31 Zeolite sandbag recovery procedure 77

78 Committee on Countermeasures for Contaminated Water Treatment (24th meeting), Material 2, “Issues andcountermeasures concerning contaminated water management at the Fukushima Daiichi NPS, References,”
June 15, 2022

108

3.3.2.2 Issues of contaminated water management considering the decommissioning
process such as fuel debris retrieval
The following two points are the key issues of contaminated water management considering thedecommissioning process such as fuel debris retrieval.
(1) Examination of water treatment systems for fuel debris retrieval
In examining water treatment systems for fuel debris retrieval, it is essential to review the overall
picture of how to share the functions with the existing treatment systems for stagnant water inbuildings (SARRY, ALPS, etc.) and establish an appropriate configuration. At the same time,planned replacement of the existing water treatment systems is also required. To carry out such an
examination, determination of the required specifications and basic design for the water treatment
systems for fuel debris retrieval must be implemented promptly.
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 suchcontaminated water depends on fabrication method including cutting and other processes, it isdifficult to assume the water quality in a situation where the fuel debris retrieval method has notbeen determined. An issue arises that the water treatment systems for fuel debris retrieval shouldhave a complicated system configuration to cope with a wide range of water quality and different
forms of α-nuclides.
However, analysis of the stagnant water in buildings has shown that the concentration of total
α can be reduced to 1/100 to 1/1,000 by filtration, indicating that most α-nuclides can be removed
by simple filtration. Since simple fabrication including cutting and other processes without the useof chemicals lead to only small changes in chemical water quality, most α-nuclides are generated
as fine particles, as in these analyses, and the concentration of soluble α-nuclides may be
maintained at a low level. Therefore, it is important to verify the form and particle size of α-nuclides
at the sampling points and incorporate them into the system design for further expansion of fueldebris retrieval in scale.
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 and lead torationalization and improved reliability of the water treatment systems.
(2) Medium-and-long term measures for contaminated water management systems
It is necessary to ensure that periodical inspection and updating of equipment, including landside impermeable walls, sub-drain systems and existing water treatment systems (e.g. SARRY,
ALPS), is implemented in order to maintain the effectiveness of contaminated water management
over the medium-to-long term. For this purpose, it is important to anticipate various risks, such asdeterioration of system functions caused by aging, metallic fatigue due to traffic loads, damage ofpiping caused by natural disasters; to procure/arrange backup and alternative items for the109

enhanced structure for monitoring and early recovery, and for stable operation; and to promote
maintenance/management and system updates in a planned manner.
In addition, although the current contaminated water management is shifting to a certain level ofa stable state, it is difficult to immediately implement drastic water sealing against groundwater
inleak in the entire building. As a medium-to-long-term issue, it is necessary to conduct a broadand comprehensive study on the most appropriate measures to further reduce the amount of inleak
into the building, in coordination with the future decommissioning work and by comparing thecurrent measures with those to be taken. In addition to measures to prevent rainwater inleak using
facing around Units 1 to 4, TEPCO is considering water sealing (e.g., filling and ground
improvement) at building penetrations (e.g., pipe) and gap ends between buildings in Unit 3 as
local water sealing. It is important to accumulate knowledge obtained through a series of on-site
applications of water sealing measures in order to consider drastic water sealing in the future whileclarifying issues and studying countermeasures through construction tests and field tests.
However, it takes a long time to complete fuel debris retrieval. Along with the selection of methods
for further expanding the scale of fuel debris retrieval currently in progress, it is important to see a
medium-and-long term, overlook the current contaminated water management anew, and examine
the principles of more stable contaminated water management and more appropriate
maintenance/management of each system. Furthermore, the interference with fuel debris retrieval
work needs to be considered as contaminated water management in anticipation of thedecommissioning process. Partial submersion and submersion methods exemplified in 3.1 arecurrently under examination for fuel debris retrieval. In addition to verification of actual site
applicability and technical feasibility, both methods need consideration of measures to prevent
contaminated water from leaking out from inside the building and control groundwater inleak into
the building from the outside. In the future, it will be necessary to consider medium and long-term
contaminated water management and fuel debris retrieval methods.
3.3.2.3 Issues for discharging ALPS-treated water into the sea
In July 2022, TEPCO gained approval from the NRA on facilities for offshore discharge of ALPStreated water, their operation methods, and safety during discharge into the sea. TEPCO also
underwent a review on safety in handling ALPS-treated water by the IAEA, indicating thatpreventive measures were adequately taken in the design of the discharge facilities in light ofinternational safety standards and that the radiological impact on humans is significantly smaller
than the level specified by regulatory authorities.
Going forward, it is an important issue for TEPCO to operate the established plan "reliably", and
it is necessary to ensure the implementation of each plan (system, operation, information
distribution, etc.), to perform check and review, and to review and expand the plan as needed, as
well as to ensure its transparency. It is necessary to build systems based on the approved
implementation plan and ensure that education, training, and other preparations for its operation
are provided.

110



Ensuring establishment of planned facilities and their reliable operation (including system
operation, analysis of ALPS-treated water, flow control of the treated/diluted water, marine
monitoring, maintenance, and troubleshooting)

Reassessment of radiation impacts on human and environment based on the selection
results of nuclides to be analyzed and publication of the assessment results

Perform marine monitoring before, during and after the discharge in accordance with thedeveloped marine monitoring planContinued implementation of the following➢ Verify safety by experts from IAEA and other agencies Education and training on system
operation and analysis, etc., for parties concerned including contractors➢ Development of strategies to provide accurate and understandable information
domestically and internationally without causing anxiety from a social perspective, andtimely dissemination of the status of preparations➢ Ensuring implementation of measures to prevent reputational damage as set forth in the
Government's basic policy announced in April 2021

In order to prepare for ensuring prompt and reliable site usage after the discharge of treatedwater, TEPCO also needs to develop a plan to discharge in accordance with the site use plan andappropriately revise the plan according to the situation, in considering concentration of tritiumcontained in treated water in tanks and attenuation.
NDF will provide technical and professional support for TEPCO's construction of facilities andpreparations for the start of operations, while promoting distribution of accurate information andincreasing understanding through meetings with relevant organizations in other countries andinternational conferences in line with the interests of those who will receive the information. NDF
will also ensure that TEPCO implements measures to minimize reputational damage, and thatTEPCO takes action with adequate and sufficient compensation in the event of reputational
damage.
3.3.2.4 Summary of major technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
32, and the future plans for the water treatment system for fuel debris retrieval are shown in
Fig.23.

111

Fig. 32 Key technical issues and future plans on contaminated water/treated water management
and natural disaster preparedness (progress schedule)

1123.4 Fuel removal from spent fuel pools
3.4.1 Targets and progress(Target)(1) The aim is to complete fuel removal from all spent fuel pools of Units 1 to 6 in Phase 3-[1] of
the Mid-and-Long-term Roadmap.
(2) While the return of residents and reconstruction in the surrounding area is gradually advanced,
to carry out a risk assessment and ensure safety including preventing dispersion of radioactive
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 that were affected by the accident are retrieved from the SFPs andtransferred to the Common Spent Fuel Storage Pool, etc., where they are appropriately stored
so that they are 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 Dry Cask Temporary
Custody Facility.
(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.
(Progress)
TEPCO is working on the work plan indicated in the Mid-and-Long-term Roadmap and the Midand-Long-term Decommissioning Action Plan.
In Unit 1, due to the hydrogen explosion, roof stabs, building materials, such as steel frames,
which constituted the upper part of the building, an overhead crane, etc., have collapsed as rubble
on the operating floor as shown in Fig. 33. While the residents were returning, from the perspectiveof further reduction of radioactive dust dispersion risk, the whole operating floor was covered witha large cover for fuel removal in Unit 1 SFP. In December 2019, the removal method was changed
to one in which rubble removal and fuel removal from SFP are carried out inside the cover. Fig. 34
shows a conceptual drawing of this method.
In preparation for the installation of large covers and subsequent rubble removal operations,
measures to prevent and mitigate the dropping of rubble, such as installing supports for overheadcranes and fuel handling machines, and curing the SFP in order not to affect fuel in SFP, werecompleted in November 2020. The removal of the existing interfering building cover (remaining
portion) was completed in June 2021. Subsequently, the area around the reactor building has been
improved. Still, delays in removing SGTS piping (removal of high-dose pipes by remote control)caused delays in the preparatory work. In light of the review status of the application of the newseismic design policy presented by the NRA, TEPCO states in its Mid-and-Long-term
Decommissioning Action Plan 2022 that it will reconsider the installation process of the large coverfor Unit 1 due to the construction work interference (caused by the delay in preparatory work). The
installation period in the progress schedule is set until around the end of FY2024, with the goal of113completing the installation by FY2023. Fuel removal in Unit 1, a milestone in the Mid-and-Longterm Roadmap is expected to begin in FY 2027 - FY 2028 as planned. TEPCO plans to obtainapproval of the implementation plan for installing the large cover and to commence the installation
work of the main unit.

(TEPCO material edited by NDF)

Fig. 33 State of the collapsed rubble on the Unit 1 operating floor(TEPCO material edited by NDF)

Fig. 34 Fuel removal method from Unit 1 SFPFor Unit 2, a method in which the upper part of the operating floor will not be dismantled and withaccess from the working platform for fuel removal to be installed on the south side of the reactor
building was adopted from the perspective of further reduction of radioactive dust dispersion risk
similar to Unit 1. Fig. 35 shows a conceptual drawing of this method.
In associated with the changes in the implementation plan for the fuel handling system, etc.,
applied in December 2020, TEPCO submitted the amended application in March 2022, dividing theapplication into two parts: a working platform for fuel removal and a fuel handling system, based114

on the status of the review for the application of the new seismic design policy, etc., and theprogress of the preparation work. Among those, the working platform for fuel removal was approvedin April 2022. Ground improvement was completed in April 2022, and installation of the base mat
for the working platform for fuel removal started in May.
Based on the results of dose surveillance on well-plug of the operating floor and conducted in
2021, decontamination and installation of shielding on the upper part of the well were carried out.
The effectiveness of radiation dose reduction was rechecked in May 2022. Preparations areunderway for fuel removal, including the transfer of the existing fuel handling machine and further
decontamination/shielding.

Existing overhead crane(remained)

Reactor Building
Front
Chamber
Working
platform

Fuel handling facility

Crane

Fuel handlingfacility

Working platform
for fuel removal

Transportation
cask

Fuel handlingmachineWell plug

Runway girder

Spent fuel pool

Runway girder

Existing fuel exchanger(Move to north side)

Base mat
Front Chamber
Reactor Building
Opening for load in/out

Fuel removal method (conceptual drawing)

Fuel handling facility (conceptual drawing)(TEPCO material edited by NDF)

Fig. 35 Fuel removal method from Unit 2 SFP
The policy is that fuel removal from Units 5 and 6 is planned so as not to interfere with operationsin Units 1 and 2. In Unit 6, fuel transfer from the SFP to the common spent fuel storage pool hascommenced in August 2022.
Fig. 36 shows the available capacity of the Common Spent Fuel Storage Pool and Dry Cask
Temporary Custody Facility. Securing the available capacity of the Common Spent Fuel Storage
Pool and transfer of some fuel in the Common Spent Fuel Storage Pool to Dry Cask Temporary
Custody Facility are required to remove all the fuel in SFPs, including Units 5 and 6, and store themin the Common Spent Fuel Storage Pool. For this purpose, TEPCO is working on expanding
storage capacity of Dry Cask Temporary Custody Facility and systematic off-site transportation of
new fuel. Regarding the transfer of new fuel off-site, the plan is to start transferring new fuel from
Unit 6 after FY 2022, and cleaning of new fuel in Unit 4 was completed in March 2022. Such efforts
will be made to complete fuel removal in all units in 2031. Further, the earthquake off the coast of
Fukushima Prefecture on March 16, 2022, disturbed the overhead crane operation in the cask
carry-in area on the first floor of the Common Spent Fuel Storage Pool. Therefore, the transfer fromthe Common Spent Fuel Storage Pool to the Dry Cask Temporary Custody Facility scheduled forMarch 2022 was started in August 2022 after the crane was restored.

115

Fuel removal from Unit 3 was all completed in February 2021, but other high-radiation dose
equipment such as control rods, channel boxes, and filters are also stored in the SFP. Althoughcooling is not necessary for them, shielding is required, and risk remains that the source in the pool
will be exposed if the pool water leaks. Therefore, in terms of risk reduction, removal of such highradiation dose equipment is needed following the fuel in SFP. In this case, it is efficient to utilize thedevice used for fuel removal and rubble removal. Therefore, as soon as preparations for removal
are completed, including securing storage facility (Existing site banker is planned for Unit 3),
removal work should be implemented immediately. Thereafter, pool water can be excluded frommanagement by draining the pool. Prior to draining the pool, however, the radiation dose and dust
dispersion from the pool after drainage should be evaluated to confirm safety. This leads to smooth
fuel debris retrieval in the later stages because of the increased flexibility of use of the operating
floor, etc.
As with Unit 3, for Units 1, 2 and 4, high radiation dose equipment is stored in each SFP. Giving
priority to fuel removal from SFP (removal is completed in Unit 4), fuel removal and drainage of thepool should be performed in a planned manner. In designing fuel handling facility, it is necessary toconsider not only the fuel in SFP but also the plan and process for removing the high-radiation dose
equipment.

Number of spent fuel, etc.

10000

8000

Number of available capacities as of
now in entire common spent fuelstorage pool and Dry Cask Temporary
Custody Facility ：2064

For fuel removal from Units 1, 2, 5 and 6(4433), efforts are underway to expand
storage capacity for Dry Cask Temporary
Custody Facility and to export new fueloff-premises (360 planned).

Spare: 132

6000
In all Units 1, 2, 5 and 6: 4433

4000

Stored6602
Unit 6 :1884

Spare
1932

2000
Unit 2 : 615

0Stored2033

Unit 5 :542

Unit 1 : 392

Units 1/2 SFP

Units 5/6 SFP

Common Spent Fuel Storage
Pool

Dry Cask Temporary
Custody Facility

Fig. 36 Storage status of spent fuel (As of May 2022)
3.4.2 Key issues and technical strategies to realize them
3.4.2.1 Fuel removal from SFPs
For Units 1 and 2, it is necessary to advance the work steadily to realize the determined new
removal method.

116

In promoting the project, it is important to make assessment of safety in association with workand confirming that necessary and sufficient safety is ensured. Moreover, it is essential tocomprehensively consider technical reliability, rationality, promptness in the work schedule, actualsite applicability and project risk, etc.
(1) Unit 1
For Unit 1, the installation of the large cover, and the removal of leftover objects such as rubble
on the operating floor will be promoted. 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 theoverhead crane in a safe and reliable way is one of the main issues to prevent it from collapsing
onto the fuel handling machine and falling into SFP. Therefore, in ongoing examination of how to
remove the overhead crane, it is necessary to perform all safety assessments as an assumption,and it is important to carry out a comprehensive examination based on the perspectives of (i)formulating specific work procedures and work plans enabling identification of risk items, (ii) therisk scenario assumed from (i) and the measures, (iii) identification of points to consider such as
exposure of workers, from an operator's perspective, and (iv) rationality and impact on otherwork.79 Although TEPCO has drafted the removal method of the overhead crane, the informationon the condition of the lower part of the roof slab is limited at present, requiring reverification by adetailed investigation after the removal of the slab. There is a risk of delay in the crane dismantlingprocess depending on the reverification result. Therefore, it is important to plan work procedures
after identifying required tasks such as surveys and verification, promptly investigate overheadcranes, etc., as soon as investigation becomes possible, and incorporate them into safetyassessments and rubble retrieval plans, including risk cases.
Regarding the contamination state of the well-plugs of Unit 1 to 3, the Study Committee on
Accident Analysis of the Fukushima Daiichi NPS pointed out that the well- plugs have important
implications in safety and decommissioning work due to the high level of their contamination80.
Although the well-plugs of Unit 1 has been evaluated by the above mentioned Study Committee
to be about two orders of magnitude less contaminated than several tens of PBq of Units 2 and 3,
those in Unit 1 become deformed and unstable due to the impact of the explosion at the accident.
For this reason, TEPCO is studying the impact of a fall on the PCV during an earthquake. It isnecessary to make a comprehensive decision 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 fueldebris retrieval in the later stage and performing thorough safety assessments.
While applying overseas findings, a detailed handling plan for 67 fuel assemblies with damaged
cladding tubes, which have been stored in Unit 1 SFP since before the accident, is under
79 NDF, "Evaluation on the selection of fuel removal methods (plan) at the Fukushima Daiichi Nuclear Power

Station Unit 1”, Secretariat Meeting of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water (73rd), Material 3-2, December 19, 2019.
80NRA, "Draft revision of the interim report (draft) based on the results of public comments”, The Study Committeeon Accident Analysis of the Fukushima Daiichi Nuclear Power Station (19th meeting), Material 3 (pages 81 to83), March 5, 2021

117

development toward the completion of fuel removal in 2031. In particular, efforts should be madeto ensure verification of the post-accident condition, examination/development of handling
methods, and risk study associated with handling.
(2) Unit 2
In Unit 2, fuel in SFP will be removed from the opening on the south side of the operating floorusing a fuel handling machine composed of a boom-type crane-system, which has not yet beenused for nuclear facilities in Japan. Since it is a new system, it is important to do the following: ①
to set up an appropriate design/manufacturing schedule with margins, ② to perform mockup tests
fully simulating on-site situations and operation methods and ensure feedback on the results todesign and production, and ③ to be sufficiently familiar with the operation and functionality ofsystems beforehand in preparation for removal by remote operation.81
To install a fuel handling system, it is necessary 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. Fuel removal from the SFP basically assumes unattended
operation by remote control. However, it is important to reduce the dose on the operating floor asmuch as possible and improve the environment in light of the fact that attended operation is also
assumed partially for system installation or troubleshooting, and the study group meeting
mentioned above pointed out80 highly contaminated well-plugs. Therefore, TEPCO plans to carryout decontamination and install shields in FY 2023 after completing the transfer of the existing fuelhandling machine, etc. Under the current plan, there is a risk that the work area after
decontamination will be contaminated again, and the process will be delayed due to establishing
the opening on the south side of the operating floor after decontamination. Therefore, it isimportant to take thorough measures to prevent dust dispersion when establishing an opening.
3.4.2.2 Decision of future treatment and storage methods
The future treatment and storage methods for the fuel in SFPs need to be decided after
considering the impact of seawater and rubble exerted during the accident. The impact of seawaterand rubble has been evaluated for the fuel removed from Unit 4, and it is expected that the impact
is small. However, based on the situation of the fuel to be retrieved, it is necessary to advance theevaluation of long-term integrity and the examination for treatment and to decide the future
treatment and storage methods.
It is planned to transfer fuel in SFPs of all Units to the Common Spent Fuel Storage Pool by theend of 2031. Considering tsunami risk, however, it is recommended to transfer to higher ground,
TEPCO is considering fuel storage on higher ground. In the case of storage on higher ground, it isrecommended that dry storage is used, in which natural convection (ventilation) of the air is used
for cooling, and system and maintenance/ management can be simplified. However, consideration
81 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 Treatment (71st), Material 3-2, October 31, 2019118

should be given in reference to overseas findings, including handling of fuel with damaged cladding
tubes. It is necessary to prepare this storage facility from the perspective of safety and operator.
3.4.2.3 Summary of key technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
37.
Fiscal year

2020

Related milestones

Unit 1

2021

2022

2023

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

Removal of building
cover(remaining parts)

2024

2026

2032(yr)

To 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 of an
operating floor/installation of fuel handling machine, etc.

Fuel removal
Removing high-dose equipment/ Draining the pool

<Legend>

Unit 2

Yard cleanup/
Soil improvement, etc.

: Fuel retmoval work
: The period in whichchanges are expected: Works other than fuelretmoval: The period in whichchanges are expected

Decontamination and shieldingof operating floor
Installation of a working platform on
the south side and an opening/fuelhandling machine installation, etc.

Fuel removal

Removing high-dose equipment/ Draining the pool
Unit 3 fuel removal

Units 3 and 4
Removing high-dose
equipment in Unit 3/ Draining the pool
Removing high-dose
equipment in Unit 4/ Draining the pool

Units 5 and 6

Unit 6
fuel removal

Suspended while work
is performed at Unit 2

Suspended while
work is performed
at Units 1 and 2

Unit 5 fuel removal

Dry cask manufacturing

Common Spent Fuel
Storage Pool
Cask

Transfer from the Common Spent Fuel Storage Pool to the
Dry Cask at the Temporary Cask Custody Area
Expanding of storage capacity in Dry
Cask Temporary Custody Facility

Examination, design and installation of dry storage facility (for Common Spent Fuel Storage Pool)

Carrying out fuel from Common Spent Fuel
Storage Pool/Dry storage on higher groundFig. 37 Key technical issues and future plans for fuel removal from SFPs (Progress schedule)

1194. Analysis strategy for promoting decommissioning
4.1 Uncertainty of fuel debris, etc. and importance of analytical results
The accident at the Fukushima Daiichi NPS was the first core meltdown accident at BWRs in theworld, and there are no records of temperature and other plant parameters due to loss of power at
the accident. In addition, many uncertainties remain regarding the state inside the reactors, thestate of the fuel debris, and FP release paths, etc., due to the unclear operational status of thesafety equipment and the injection of seawater to bring the accident under control. Since there is
uncertainty in the formation process of fuel debris and it is not under human control, it is consideredthat fuel debris would have heterogeneity in various physical properties such as chemicalcomposition, microstructure, and density.
In cases where the uranium content is unknown, it is assumed to use the 97 to 98% uranium
content of the fuel assembly before the accident to conservatively study safety assessment andsafety measures for criticality control and off-site transport. According to the calculation results ofthe severe accident codes and the videos and photos of PCV internal investigations, it is highly
likely that the uranium content decreases by melting and mixing with the surrounding structural
materials. However, since there is no value to be used for the evaluation, an excessive margin is
included in the safety measures. If the range of such uncertainty is reduced, there will be no needto include excessive margins in handling fuel debris, safety assessments, and safety measures.
Thus, the promptness and rationality of decommissioning will be improved.
The analysis results of solid waste are important basic information for the study on
processing/disposal methods for various kinds of waste generated by the accident. The analysis
results of fuel debris are applied in a number of areas, including retrieval methods, storage,
necessity of treatment, investigation to clarify the accident cause, and improvement of nuclear
safety. As shown in Fig. 38, their relationship changes with the progress made in decommissioningof the Fukushima Daiichi NPS. It is important to correctly recognize that the analytical results are"one of the important criterion for decisions" for reducing the range of uncertainty in the above
examination for facilitating decommissioning. TEPCO, incorporating analysis results in eachdecommissioning process, should take the lead in establishing and developing analysis systems,
facilities, and functions that can efficiently collect and evaluate analysis results.
It has been reported that fuel debris at the Chernobyl NPP in Ukraine became powdered due tochanges over time, making it a source of radioactive dust82,83. In contrast, fuel debris at the TMI-2
has not undergone significant changes over time, even 40 years after the accident. What causes
aging in fuel debris over time is not clearly known. It is also unknown whether or not aging will also
happen to fuel debris at the Fukushima Daiichi NPS. Therefore, the Project of Decommissioning,

82 National Report of Ukraine, Ministry of Ukraine of Emergencies, "Twenty-five Years after Chernobyl Accident:

Safety for the Future" (2011)
83 B. Burakov, V. G. Khlopin Radium Institute, the 2nd International Forum on the Decommissioning of the

Fukushima Daiichi NPS (2017)120

Contaminated Water and Treated Water Management and the Nuclear Energy Science &Technology and Human Resource Development Project are studying aging in fuel debris and its
stability evaluation84,85,86,87, respectively. The occurrence of aging is considered to depend on thechemical stability of the fuel debris. If the chemical stability is low, it is assumed that the chemical
form of the fuel debris gradually changes over time, resulting in volume changes, cracking, andleaching into the water. Therefore, in the process after retrieval, it is assumed that measures against
the spread of contamination due to power generation and leaching into the water and the increasein the risk of internal and external exposure will become more important. The results of the sample
analysis need to be compared with the findings obtained from the above studies, and it is necessary
to confirm whether or not aging has occurred and to know the extent of aging which would beoccurred. While accumulating them to reduce uncertainty in the properties of fuel debris, it isimportant to provide feedback to examination on the future retrieval methods and appropriate
measures for storage. In addition to conventional sample analyses, studies on reducing uncertainty
of fuel debris properties by other measurement methods have already started since FY 2020 in the
Project of Decommissioning, Contaminated Water and Treated Water Management.

84 TENEX and ROSATOM, "Development of Analysis and Estimation Technology for Characterization of Fuel Debris(Development of Estimation Technology of Aging Properties of Fuel Debris)", Final report for FY 2019 and 2020(2021)
85 Toshiba Energy Systems Corporation, Subsidy for the Government-led R&D program on Decommissioning andContaminated Water Management “Development of analysis and estimation technology for characterization offuel debris (developing estimation technology for aging characteristics of fuel debris)”, FY 2020 Final Report(2021)
86 Akira Kirishima, “Fundamental research for stability evaluation of fuel debris, including alloy phase”, FY 2021
results report, meeting materials for the project to promote development of nuclear science, technology andhuman resources gathering wisdom and intelligence (2022).
87 IMRAM of Tohoku University, JAEA and Kyoto University, ”Solid-solution phase determines “afterwards” of fueldebris – New chemical insights into the safe storage and processing/disposal of nuclear fuel debris”, June 13,
2022

121

Past
Accident
occurrence

Present
Estimation of fuelInternal
debris distribution investigation

Accident history
investigation


Amount of fuel andstructural materials
Amount of adhesion to FP
Thermal history
Operation condition ofequipment

FutureSampling

Fuel debris analysis
RPV internal investigation
PCV internal and external
investigations

Dismantlingof facilities

Containmentand storage

Fuel debris
retrieval

Accomplishment of
decommissioning

Retrieval method

 Countermeasures against criticalityCountermeasures against dust
Cooling measures
Countermeasures against hydrogen
Decision of termination during pedestal
excavation
 Accessibility study Examination of the difficulty indismantling and removal

Safeguards
 Nuclear materials

management

StorageCountermeasures against
criticality

 Nuclides and the amount ofradioactivity
 Chemical stability
 Rationalization of storage
facilities

Processing anddisposal

Understandingof phenomena

Improvement of severe accident progression
analysis code, emergency response and the facilities

Countermeasures against
criticality
Nuclides and the amountof radioactivity
Chemical stability

Clarification of accident
cause

Improvement of nuclear safety

Fig. 38 Incorporation of analyses and investigation results, and their relationships

4.2 Three elements of analysis strategy
To safely and steadily proceed with decommissioning of the Fukushima Daiichi NPS, it isnecessary for TEPCO to establish and develop facilities for analysis and the functions required forhandling of solid waste or fuel debris. In addition, it is important to build a system that effectively
utilizes analyzed results for each decommissioning operation. In order to obtain good analysis
results, it is effective to properly maintain ① the methods and systems for analysis, ② the qualityof the analysis results, and ③ the size and quantity of sample, as shown in Fig. 39.

Fig. 39 Three elements of the fuel debris analysis strategy

122

4.3 Current status of establishing an analysis system and strategy
As an essential facility for decommissioning of the Fukushima Daiichi NPS, the JAEA is
proceeding with the construction of Radioactive Material Analysis and Research Facilities adjacentto the Fukushima Daiichi NPS88 under the supplementary budget of the Government (FY2012)89.
At commencing their operations, they will be designated as controlled areas of the Fukushima
Daiichi NPS, which has the advantage that off-site transportation is not required. Leveraging this,
it is effective to promptly identify basic physical properties, and incorporate them into safetyassessment and work procedures. The objectives of laboratory-1 are solid waste analysis and thirdparty analysis of ALPS-treated water 90, and laboratory-2 is intended to conduct fuel debris analysis.
The facility management building has been operating since 2018. The construction of laboratory-1
was completed in June 202291,92, and the controlled area and other areas were set as a part of thespecified nuclear facility in October, then, analytical operation using radioactive materials has
started93. The laboratory-2 is in the process of screening application for approval of implementation
plan changes and selecting the operator. TEPCO is also considering the construction of analysis
facilities (comprehensive analytical facility) in response to the future needs of analysis including
analysis of fuel debris and solid waste in addition to current routine.
As shown in Fig.40, since the laboratory-2 and the comprehensive facilities for analysis arescheduled to commence operation after the trial retrieval of fuel debris. Analysis will be conductedat the facilities for analysis in the Ibaraki area until the laboratory-2 is operational. Even after theoperation commencement of the laboratory-2, if special techniques are required for sample
pretreatment or if analysis and testing requires an extended period, it is more efficient to perform
analysis in the Ibaraki area, because (i) there are many researchers and engineers, (ii) many typesof special analysis devices are available, and (iii) there are a large number of hot cells withcontainment and shielding functions and application options, and to prioritize promptness on-siteand adjacent areas of the Fukushima Daiichi NPS. As for solid waste analysis, as trial retrieval offuel debris progresses, it is anticipated that solid waste that TEPCO has not had experience withpreviously, such as fine fuel debris and filters that have captured FPs, will be generated. Regarding
high dose solid waste for which there is limited experience, it is desirable to analyze solid waste in

88 The 52nd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated

Water Treatment, “Material 3-4: Opening of the Okuma Analysis and Research Center facility managementbuilding”
89 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”
90 The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 4: Development status of Radioactive Material Analysis and Research Facility
Laboratory-1”
91 Japan Atomic Energy Agency (JAEA), June 24, 2022 “Completion of the laboratory-1 of the Radioactive Materials
Analysis and Research Facility (Okuma Analysis and Research Center) and future plans”
92 The 103rd Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water/Treated Water, “Material 4-1: Completion of the laboratory-1 of the Radioactive Materials Analysis andResearch Facility (Okuma Analysis and Research Center) and future plans”
93 The 106th Meeting of the Secretariat of the Team for Decommissioning and Contaminated Water/Treated Water,“Material: Commencement of analysis work at the laboratory-1 of the Radioactive Materials Analysis andResearch Facility”

123the Ibaraki area for the same reasons as for the fuel debris described above, and it is necessary tocontinue it in the Ibaraki area for some time after the Laboratory-1 is put into operation. Based on
the above, since target nuclides for permission for use and the situation with or without off-sitetransportation differ between facilities for analysis in the Fukushima Daiichi NPS site/adjacent areas
and those in the Ibaraki area, it is effective to assign roles according to the characteristics shownin Fig.41 and expand the analysis data of fuel debris and solid waste. However, since all thefacilities for analysis in the Ibaraki area have been in operation for more than 30 years,
considerations on measures are required for aging facilities that will be used continuously.

Fiscal Year

2022

2023

Environmental
improvement in buildings

Fuel debris
retrieval(Unit 2)2024

2025 and after

Trial retrieval(internal investigation/fuel debris sampling)

Characterization of fuel debris

Manufacturing /installationof retrieval device

Internal investigation of RPV

Gradual expansion offuel debris retrieval

Transportation outside the site
Rubble etc.(rubbles, felled trees, used protective clothing)

Solid waste

Elimination of temporary outdoor storage

Secondary waste generated by water treatment (Sorption vessels, waste sludge, concentrated waste liquid slurry)

Analysisfacilities in
Ibaraki (JAEA,
NFD, NDC)

Lab.
1

Lab.

Okuma
Analysis/
ResearchCenter(JAEA)

Analysis of deposit/ adhesion

Analysis of fuel debris

Analysis of waste
Transportation inside the site▼Completion

Cold run and controlled area setting
Start of operation with radioactive materials

Design/Approval, etc.
Construction

2
TEPCO’sanalysisfacility

Start of operation (incl. cold run)
Design/Approval/Construction
Start of operation (incl. cold run)**indicates the place to be transferred to, but not corresponds to number of transfer.
(dashed arrow) may change depending on the operation status of other facilities.

Fig. 40 Construction and operation schedule for fuel debris retrieval and new analytical buildings124

Fig. 41 Characteristics and roles of each facility for analysis
Not only the facilities for analysis in the Ibaraki area, but also the Radioactive Material Analysis
and Research Facilities to be operated in the area adjacent to the Fukushima Daiichi NPS are shortof the human resources required to continue stable facility operation, and the securing andmaintaining of analytical engineers needs to be considered. In this respect, it is necessary toconsider in advance the qualities expected of analytical engineers in various analytical works, andto develop a plan so that the required roles are appropriately achieved. In normal nuclear power
plants, fuel is sealed in fuel cladding, and before the accident, the unsealed alpha-nuclides were
not directly handled in the Fukushima Daiichi NPS. The fuel debris generated by the accident
contains unsealed fuel and FP, and there is a risk of internal/external exposure or spread ofcontamination in performing analyses. Therefore, in addition to knowledge on general chemical
analysis and electronic equipment analysis, a wide range of knowledge is required, including
radiation protection, laws and regulations related to nuclear power and radiation, chemical reactivityof fuel and materials, physical, chemical and biological properties of radioisotopes, properties ofvarious types of radiation and measurement methods.
While such knowledge is acquired over time, TEPCO must develop human resources for fields
where there is little experience in as short a time as possible. It is important to effectively work on
developing analytical technicians with the cooperation of the JAEA and private-sector enterprisethat have accumulated sufficient knowledge and experience on the handling of alpha-nuclides andfuel analysis techniques94,95. Personnel exchanges between TEPCO and the JAEA and personnel

94 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
95 Tokyo 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”

125

acceptance from Nippon Nuclear Fuel Development Co., Ltd. (hereinafter referred to as “NFD”) to
TEPCO have been ongoing. Table 4 shows the state of personnel exchange. An agreement ontechnical cooperation between TEPCO and Japan Nuclear Fuel Limited. on the handling andanalysis of alpha-nuclides was also signed in January 2022.94
Table 4 Personnel exchanges between TEPCO and JAEA and accepting personnel from NFD to
TEPCO
Fiscal year
2018
2019
2020
2021
1
1
3
3
From TEPCO Assigned, temporary, external researcher
to JAEA
Transfer, reemployment
0
0
0
1
0
3
11
4
From JAEA to Assigned, temporary, cross-appointment
TEPCO
Transfer, reemployment
0
0
1
0
0
0
1
0
From NFD to Assigned, temporary
TEPCO
Transfer, reemployment
110
1

4.4 Improvement of the quality of sample analysis results and use of nondestructive assay
4.4.1 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 considered difficult to identify and quantify all
elements and isotopes down to trace components by analysis. It is also an important to have askeptical point of view to the analytical result of the samples in consideration of the impact of theerror factor. Monitoring data, sampling analyses, PCV internal/on-site investigation, analyses using
SA codes, and past knowledge and experimental results have been accumulated. As part ofverification of sample analysis results, through discussion and studies in light of existing findings,
such as results of analysis, investigation and testing, deriving consistent property evaluations will
improve reliability of analysis results, leading to higher quality of the analysis results.
To improve the analytical accuracy, the JAEA, the NFD, MHI Nuclear Development Corporation(hereinafter referred to as “NDC”), and Tohoku University have been cooperating to conduct
chemical analysis and structural analysis using the same samples since FY 202096. Consideration
is being given to analysis of TMI-2 debris in Ibaraki area offices using the latest technologies so as
to expand the fuel debris data in future.
TEPCO and the JAEA are already cooperating in implementing forensic activities that estimate
accident behavior and causes by comparing the results of sample analyses with simulation on
progression of meltdown and past scientific knowledge97. Furthermore, as an international forum,the BSAF, BSAF-2, PreADES, and ARC-F, which have been implemented as projects of the
96 IRID (2021), “Subsidized Project relate to grants for “Development of technologies for improving analyticalaccuracy and estimation of thermal behavior of fuel debris)”, Final report of FY2020, August 2021
97 IRID (2021), Supplementary budget in FY 2018, “Subsidies for the Project of Decommissioning andContaminated Water Management” (Development of analytical and estimation techniques for characterization offuel debris), implementation results for FY 2020126OECD/NEA, 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 FP behavior
and H2 combustion (ii) characterization of U--bearing particles and establishment of techniques for
future fuel debris analysis for D&D; and (iii) collection and sharing of data and information. 23
organizations from 12 countries are participating in the project, with 6 organizations from Japantaking part in it: Nuclear Regulation Authority, Agency for Natural Resources and Energy, JAEA,
Central Research Institute of Electric Power Industry, the Institute of Applied Energy, and NDF.
Since there are few personnel (analytical evaluators) who can design the analytical range anditems in anticipation of how to use the analysis results in advance, it is also important to makeefforts in increasing such personnel. Analytical evaluators are required to have the ability to (i)logically and accurately understand accident events from analytical results, (ii) appropriately
incorporate the evaluation results into the areas required for the decommissioning process(retrieval method, safeguards, storage/management, and processing/disposal), and (iii) provide
appropriate instructions for the following sampling. However, since it is difficult for individuals to
address these all abilities, TEPCO should take the lead in organizing an analysis and evaluationteam (One Team) by selecting researchers and engineers from domestic organizations withknowledge of fuel debris and decommissioning.
4.4.2 Sample analysis of fuel debris
The current sample analysis is mainly performed using electron microscopes after transporting
smear samples to facilities for analysis in Ibaraki area. Since the density, hardness, and other items
cannot be measured for micro or very small quantity of the samples, it is necessary to increase thesize and quantity of the samples in accordance with the progress of the fuel debris retrieval process.
Analysis is performed by using a manipulator in analysis process in a hot cell, and in one facility,
analysis of about 0.5 to 1 samples per month will be conducted. Further, the amount to be used ineach hot cell is restricted for each nuclide that can be handled, and therefore, it is difficult to analyze
a large number of samples. Consequently, there is a large gap between the volume to be
retrieved/stored and the amount of sample for analysis.
Since fuel debris has heterogeneity, the analytical values vary depending on the sampled parts,and the situation is such that a sufficient amount of fuel debris cannot be analyzed, resulting in arange of uncertainty in evaluation. To increase the volume of good analytical results, regardless of
the restrictions on improving analysis quality and sample quantity, it is effective to not only focus
on increasing the volume in conventional sample analyses in hot laboratories but also to diversify
and expand other analytical and measurement methods, understand the disadvantages andadvantages of each item, and consider complementing them according to the intended use of theanalytical results, for a comprehensive evaluation. Depending on the application, it may be
worthwhile to consider methods that can only measure single items.

127

4.4.3 Use of sample analysis and non-destructive assay
One of the analysis and measurement methods that complement the results of sample analysis
is to evaluate the amount of nuclear fuel without destroying the sample using radiation, quantum,
etc. emitted, scattered, or transmitted from the sample (hereinafter referred to as "non-destructive
assay”). Table 5 shows the relative comparison of the items for sample analyses to be performed
inside analysis facility and for non-destructive assays to be performed outside the analysis facility
and the sample amounts. Sample analysis can perform many analysis items, but the time required
for analysis is long, and the amount analyzed at one time is small. Although non-destructive assay
can handle fewer items, the measurement time is shorter than that of sample analysis, and a larger
quantity can be measured per measurement. Moreover, measurement can be performed with theobject stored in a sealed container to prevent the spread of contamination.
Table 5 Relative comparison of principal specifications between the sample analysis to be
performed in the analysis facility and non-destructive assay to be performed outside
the analysis facility

Analysis of samples
performed in analysis
facility*

Non-destructive assay
performed out ofanalysis facility**

Time for analysis/ measurement

Long (△)

Short (〇)

Items for analysis/ measurement

Many (◎)

Few (△)

Amount per analysis/ measurement

Small (△)

Large (◎)

Generated (△)

None (〇)

Confinement during analysis andmeasurement

Unsealed

Unsealed or sealed

Dust prevention

Necessary

Necessary

Radiation shielding facility

Necessary

Necessary

Generation of liquid waste◎ : Excellent〇 : Good△ : Acceptable* ： The analysis will be conducted in a facility dedicated to analysis, such as a hotlaboratory suitable for dealing with fuel debris samples.
**：The facility will be used in the process from retrieving to storing fuel debris.
The analysis will be conducted in a facility not dedicated to analysis.

If, in addition to the sample analysis in the facility for analysis, non-destructive assay focusing on
specific items, for example, the quantification of nuclear fuel, is measured in the container of fueldebris, the small number of analyses can be supplemented, and the amount of nuclear fuel in thefuel debris can be promptly grasped (i.e., confirming that it is less than the minimum critical mass),
making it possible to move to the next process while maintaining the subcriticality state. At this time,
it is desirable to keep the range of uncertainty in the properties of fuel debris as small as possible
while increasing information about the sample, including the number of sample analyses and thecoordinate information at the time of sample collection, to improve the reliability of the data. In orderto improve the accuracy of fuel debris characterization and the safety in storing retrieved fuel debris,128

specific application methods of non-destructive assay should be studied at the facilities used in theprocess from retrieval to storage of fuel debris.
As an example of the application of non-destructive assay, Fig. 42 shows its use in the handlingprocess from fuel debris retrieval to storage. Consideration is being given to performing the nondestructive assays ①, ②, and ③ shown in the figure. The amount of nuclear fuel in the retrieved
fuel debris is quantified by non-destructive assay ②. The retrieved fuel debris is classified
according to the amount of gained nuclear fuel, e.g. uranium quantity. Fuel debris with a large
uranium quantity is stored in small-diameter containers, and fuel debris with a small uranium
quantity is stored in large-diameter containers. In this case, the state of subcriticality can be
maintained by applying dimension control for the small-diameter containers and mass control (total
amount of nuclear fuel obtained by non-destructive assay ②) for the large-diameter containers. If
the amount of nuclear fuel obtained by non-destructive assay ② is integrated, the amount of
nuclear fuel for each container can be calculated. However, in non-destructive assay ②, it isexpected that the amount of fuel debris used for one measurement will be small, and detectedsignal will be small as well. Therefore, it is desirable to perform non-destructive assay ③ after
sealing to finally measure the value of nuclear fuel for transportation and storage. In non-destructive
assays ② and ③, since the neutron absorber (B4C), which is a control rod component, is containedin the fuel debris, the active neutron method may not be able to measure correctly. Other methods
need to be examined to compensate for the inadequacies of the method using neutron.
However, it is expected that particles containing uranium and Cs -137 released at the accident
have adhered to the surface of the upper internal structures. If the upper internal structures are cut
and non-destructive assay ① can confirm no adhesion of particles containing uranium or Cs -137
after decontamination of the surface in consideration of necessity and feasibility, then the burdenof solid waste storage and management levels can be lowered. Therefore, non-destructive assay① requires a technique capable of measuring with high sensitivity and accuracy.
Technical development on non-destructive assay for fuel debris is in progress in the Project ofDecommissioning, Contaminated Water and Treated Water Management. Since there is noprecedent for non-destructive assay of fuel debris, and fuel debris has obstructive factors, it isnecessary to verify the capability, applicability, and possibility of a combination of several nondestructive assay methods. Fig. 42 is an example and is subject to change depending on the statusof future R&D and studies. However, considering the trial retrieval of fuel debris, characterizationof fuel debris and gradual expansion of fuel debris retrieval, development of non-destructive assay
methods ② and ③ is of high priority.

129Unit 3・Steam separator, Steamdryer, etc.
Adhesion of U : Very small
quantity
Adhesion of B : None
Adhesion of 137Cs : Existence➢ Quantification of alphanuclides and 137Cs, etc.
for waste levelclassification.

※Confirmationof no melting/deformation

・Solid waste (LLW)

Particles with
137Cs+U

・Fuel debris inside RPVContent of U(%) : HighContent of Pu(%) : Low
Content of B(%) : High✓ L1 and L2(in the case of
surface decontamination)✓ Without critical control✓ Out of inspection for safeguard

Φ＜220mm
Draining

U＜ND U＞ND
In-situ analysis➢ Existence of U

Non-destructive assay ②➢ Quantification of nuclear fuel forcontinuance of subcritical condition

・CRD exchanger, Steel grating,etc.
Adhesion of U : Low
Adhesion of B : Extremely low
to low
Adhesion of 137Cs : Existence
・Fuel debris inside pedestal
Content of U(%) : Low
Content of Pu(%) : Extremely low
Content of B(%) : Low: Location of fuel debris

Non-destructive
assay ①Visualinspection

Cutting/Surface
decontamination✓ High U
content

・Canister withsmall diameter✓ Low U
content

・Canister withlarge diameter

Non-destructive
assay ③➢ Quantification of Nuclear
fuel and FP for final
value of transportationand storage: Fuel debris mainly: Waste mainly ※Which facility to be used for non-destructive
assay ① to ③ will be determined based on
the results of future examination, etc.

・Fuel debris/ waste✓ Criticality measure : dimension
control✓ Target for safeguard

・Fuel debris/ waste✓ Criticality measure : masscontrol (sum of non-destructive
assay ②)✓ Target for safeguard

Fig. 42 Example flow of non-destructive assay in the handling process for retrieved fuel debris

1305. Efforts to facilitate research and development
5.1 Significance and the current status of research and development
There are many difficult technical issues requiring research and development to promote thedecommissioning of the Fukushima Daiichi NPS from the perspectives of safe, proven, efficient,
timely, and field-oriented. 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 fora gradual expansion of retrieval scale and further expansion of fuel debris retrieval in scale.
In order to solve these technical issues, basic/fundamental research and application research by
universities in and outside of Japan and researching institutions such as JAEA, practical application
research and field demonstrations by IRID, manufacturers, and TEPCO are being performed byvarious industrial-academic-governmental institutions, including overseas enterprises (Fig. 43).
For application research and practical application research for decommissioning, theGovernment provides supports the R&D carried out by each organization to solve issues of highlydifficult ones through "the Project of Decommissioning, Contaminated and Treated Water
Management", and to promote basic and fundamental research and human resource development
by universities and research institutes in Japan and overseas through "The Nuclear Energy Science& Technology and Human Resource Development Project (hereinafter referred to as "WorldIntelligence Project")".
TEPCO has been working on the technology development directly linked to site application, andestablished the Decommissioning Technology Development Center in August 2021 to strengthen
the system for planning and management of technology development. The Center identifies
research and technology development issues and examines solutions related to the Mid-and-Longterm Decommissioning Action Plan and manages the progress of technology development andreflects them in the development plan.
The NDF considers planning of the R&D medium -and-long-term plan and next-term R&D plans
and supports the World Intelligence Project. NDF also has established the Decommissioning R&D
Partnership Council with representatives of institutes involved and intellectuals from universities as
its members, which considers information sharing on needs and seeds for R&D, adjustment of R&D
based on the needs of decommissioning work, and issues on promoting cooperation related to the
R&D and human resource development. Moreover, coordination between the Project ofDecommissioning, Contaminated Water and Treated Water Management and the WorldIntelligence Project has been promoted through the Decommissioning R&D Partnership Council.
From FY 2022, JAEA plans to implement actions in accordance with the Phase 4 medium-tolong-term goals and plans. It is expected that JAEA will leverage its knowledge and experience in
R&D related to decommissioning of the Fukushima Daiichi NPS and play a significant role ininitiatives for characterization of fuel debris and R&D for waste management and analysis. The
R&D implementation system is shown in Fig. 44.

131

The R&D fields to be conducted at “the Fukushima International Research and Education Center”,
that will be established by the government in April 2023, are ① robots, ② agriculture, forestry andfisheries, ③ energy, ④ radiation science, drug discovery and medical care, and industrial use ofradiation, and ⑤ collection and dissemination of data and knowledge on nuclear disasters, andcollaboration in R&D related to decommissioning is also expected. Therefore, NDF will consider
collaboration in the future with a view to outreach activities related to this Center’s R&D, while also
taking into account the basic plan98 for the promotion of R&D99.

TEPCO
1F
IRID/Manufactures
decommissioning(incl. overseas enterprises)
Universities/
Research institutions, etc.

Practical
application
research

JAEA

Applied research

Basic research

Fig. 43 Scope of studying decommissioning R&D and implementation entities

98 Basic Plan for Research and Development for new industry creation (Provided by Cabinet Office, Governmentof Japan, August 26, 2022)
99 Basic Concept for the Fukushima International Research and Education Center (Provided by Reconstruction

Promotion Council, March 29, 2022)

132Fig. 44 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPS

5.2 Key issues and strategies
5.2.1 R&D medium-and-long term plan
In FY 2020, NDF and TEPCO developed the R&D medium-to-long-term plan overlooking theoverall research and development for about ten years for decommissioning and have updated it
every fiscal year since then. The R&D medium-to-long-term plan will be updated based on therevised Mid-and-Long-term Decommissioning Action Plan of TEPCO, the concept study for further
expansion of fuel debris retrieval in scale, and the progress in ongoing R&D. Major revisions include
updating the main decommissioning process and incorporating basic/fundamental research. The
updated mid-and-long-term R&D plan is shown in Attachment 11. In reviewing the R&D mid-andlong-term plan, TEPCO, Ministry of Education, Culture, Sports, Science and Technology, Ministryof Economy, Trade and Industry, and NDF have participated in the R&D planning meeting and to
discuss the required results, timing, implementation structure, etc. through the meetings. The plan
will be updated and expanded continuously based on the information made clear by the progressof PCV internal investigation and fuel debris analyses as well as progress of R&D.
Moreover, in accordance with the discussion at the 10th Decommissioning R&D PartnershipCouncil held in February 2022, TEPCO, Collaborative Laboratories for Advanced Decommissioning
Science of JAEA (hereinafter referred to as “JAEA/CLADS”) and NDF jointly shared analysis oftechnical issues, including long-term issues exceeding ten years, to promote collaboration between
the World Intelligence Project and the Project of Decommissioning, Contaminated Water and133

Treated Water Management, and have reviewed issues in a comprehensive and exhaustive
manner. The results will be incorporated into the R&D medium-and-long-term plan and the overall
map of basic/fundamental research for reference.
5.2.2 Initiatives for the Project of Decommissioning, Contaminated Water and Treated Water
Management
5.2.2.1 the Project of Decommissioning, Contaminated Water and Treated Water
Management
The Ministry of Economy, Trade and Industry is providing support through the Project ofDecommissioning, Contaminated Water and Treated Water Management to solve technicallychallenging issues for decommissioning.
As shown in Fig. 44, the Project of Decommissioning, Contaminated Water and Treated Water
Management selects project operators conducting R&D and provides necessary assistancethrough corporations with funds and the secretariat. Through the Project to date, significant results,
such as internal PCV condition analysis by PCV investigations, have been obtained for promoting
decommissioning work. Attachment 12 outlines the implementation of the Project up to now.
In the Project of Decommissioning, Contaminated Water and Treated Water Management, since2020, NDF has been participating in the Secretariat of the Project to strengthen the functions ofproject planning and progress management. Also, in order to incorporate requirements in terms ofactual site applicability into the R&D, TEPCO has been responsible for project management of the
Project, jointly applying for issuance in cooperation with research leadership.
This enhanced functionality has enabled the Secretariat to follow the progress of R&D, leading
to the smooth execution of projects and achieving intended results. In addition, TEPCO’s needs interms of actual site applicability have been incorporated into the Project, and the positioning of the
Project in TEPCO’s engineering schedule has been clarified.
5.2.2.2 Next-term R&D Plan
In order to support the Project of Decommissioning, Contaminated Water and Treated Water
Management, and based on the R&D medium-and-long-term plan, every fiscal year, NDF is
formulating the next-term R&D plan as the R&D to be carried out over the next two years. The nextterm R&D plan aims to solve issues related to fuel debris retrieval and processing/disposal of solid
waste.
After adjustment and discussion with parties concerned at R&D planning meetings, the next-term
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 plan
was reported by the Ministry of Economy, Trade and Industry (METI) to the Team Meeting for
Decommissioning and Contaminated Water/Treated Water Management/Secretariat Meeting, and
the Project of Decommissioning, Contaminated Water and Treated Water Management has been
implemented accordingly.

134In considering the next-term 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 newchallenges and organize technical issues with a view of the R&D medium-and-long-term plan.
When identifying issues, it is also important to identify them exhaustively, confirm whether eachissue is in line with the needs of TEPCO as the entity responsible for decommissioning, and aim
for R&D results to be utilized for TEPCO’s engineering.
In FY 2022, as a new initiative to develop the next-term R&D plan, a request for information (RFI)
was made to widely solicit information on technical issues to be resolved toward thedecommissioning of the Fukushima Daiichi NPS.100 In order to contribute to the consideration of
the next R&D plan, 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), scale of R&D, potential joint
R&D destinations, and R&D fields.
5.2.2.3 Further research and development implementation system for the Project ofDecommissioning, Contaminated Water and Treated Water Management
The IRID has played a major role in research and development for decommissioning for about
eleven years since the time that the post-accident situation inside the reactors was unknown. In
particular, the IRID has established a good track record in internal PCV condition analysis throughits internal investigations, as well as development of analytical and estimation techniques forcharacterization of fuel debris, development of fuel debris retrieval equipment and storage
containers, and development of processing/disposal technologies for solid waste.
Meanwhile, as the engineering work by TEPCO progresses, the situation in the reactors and theneeds are gradually becoming clear. In addition, development is currently being promoted basedon the engineering work by TEPCO, which is a shift from joint activities through the Collaborative
Innovation Partnership. In light of changing environment, consideration is being given to a R&D
structure in preparation for IRID’s current continuity deadline after summer 2023.
Since it is still important to review R&D tasks from a broad perspective in the Project ofDecommissioning, Contaminated Water and Treated Water Management, evaluate the Project interms of actual site applicability and incorporate them into R&D. Accordingly, NDF plans to further
strengthen and restructure the functions related to R&D planning and proposals and efforts toensure operation quality in cooperation with TEPCO and other organizations concerned.
Starting this fiscal year, as a proposal for R&D planning, a request for information (RFI) was
made to widely solicit information on technical issues to be resolved toward the decommissioningof the Fukushima Daiichi NPS. In the future, the system is planned to be improved based on theimplementation results.
As an effort to ensure the quality of the Project, a Review System will be established for all
Projects of Decommissioning and Contaminated Water/Treated Water Management. The objective
100 The 102nd Team Meeting/Secretariat Meeting of the Decommissioning, Contaminated Water/Treated Water

Management “Commencement of Request for Information (RFI) on Project of Decommissioning andContaminated Water/Treated Water Management”

135

is to ensure the actual site applicability of the Project and to improve the quality of research anddevelopment. The details of the System will be discussed in the future.
On the other hand, for the projects that need to be succeeded to in the Project ofDecommissioning, Contaminated Water and Treated Water Management, the following issues
must be addressed if projects are to be implemented smoothly so as not to cause any problems,and discussions are being carried out by relevant organizations.
・The project executor when taking over the Project・Appropriate succession of hardware (tangible assets e.g. facilities and equipment) and software(intangible assets e.g. result products and technical information) necessary to continue R&D
・How to maintain and utilize the know-how accumulated by the subsidized projects
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, it is important toestablish an easily accessible structure where organizations involved in the research anddevelopment for decommissioning can make effective use of the R&D results, including knowledge
obtained. Therefore, it is recommended that archiving in terms of information disclosure andknowledge sharing is promoted. In this case, the issues are to establish rules for the compilationand sharing of archival materials, establish a framework for the establishment/management ofarchival materials, and develop the management tools to be used.
TEPCO should be fully aware of the significance and role of each R&D project in all R&D activities,
from basic/fundamental research to practical application research. Then, while being involved in
R&D appropriately, under the management of the technology development by the D&D Research& Development Center, TEPCO needs to be committed to decommissioning research moreproactively including independent technology development by TEPCO. In doing so, it is necessary
to collaborate with a new engineering company established in October 2022.
5.2.3 Promotion of cooperation between decommissioning sites and universities/
researching institutions
5.2.3.1 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 in the field of decommissioning. In order tofacilitate 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.

136

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 barriers of thenuclear field, and through close coordination and alignment including international joint research.
JAEA/CLADS implements this World Intelligence Project to strengthen cooperation between
JAEA/CLADS and universities, and establish a system to implement medium-and-long term R&D
and human resource development, contributing to decommissioning more stably and continuously.
Based on the discussions at this Decommissioning R&D Partnership Council, NDF set up “a task
force on research collaboration”,101 and identified six Essential R&D Themes mainly in the area ofbasic/fundamental research to be addressed with priority, in light of investigational issues andproblem awareness on the side of the needs. Research and development on these Essential R&D
Themes has been carried out in the World Intelligence Project and the Project of Decommissioning,
Contaminated Water and Treated Water Management, and results have been obtained. In order tocontinue to position it as one of the Essential R&D Themes in basic fundamental research, it iscompiled in the “overall map of basic/fundamental research” prepared by JAEA/CLADS.
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 processfrom contaminated water management to waste processing/disposal and identifies the R&D needs
and seeds required.
For the World Intelligence Projects in FY2022, public participation was called for in two cases:
the “Problem-Solving Decommissioning Research Program,” which aims to solve issues bypromoting needs-based R&D to steadily advance the decommissioning of the Fukushima Daiichi
NPS, and the “International Collaborative Decommissioning Research Program (Japan-UK Joint
Research),” which promotes R&D by integrating and collaborating research in various fields inJapan and the UK to gather broad knowledge and contribute to accelerating the decommissioningof the Fukushima Daiichi NPS. In Attachment 13, the selected issues of the World Intelligence
Project adopted in the past are shown.
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. From FY 2022, the plan is to introduce Research Supporters (RS) to maximize
the use and outcomes of the results at the decommissioning sites.
It is an important issue to directly apply the results of some basic/fundamental researchcontributing to problem-solving in on-site decommissioning, and it is important to promote better
matching needs from decommissioning site with seeds at universities/researching institutions and

101It was established in NDF in 2016 and held 6 times in total. It consists of NDF, intellectuals fromuniversities/researching institutions, and TEPCO. Six Essential R&D Themes were identified, which should
strategically and preferentially ascertain the principle in promoting decommissioning at the Fukushima Daiichi
NPS, and the interim report on the task force on research collaboration was developed (November 30, 2016).

137

serve as a bridge to share outstanding research results obtained mainly in the World Intelligence
Project.
5.2.3.2 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, it isessential to promote collaboration between the Project of Decommissioning, Contaminated Water
and Treated Water management and the World Intelligence Project. For that purpose, 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 the Meeting.
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 need to further
strengthen their cooperation for better matching needs with seeds and serve as a bridge to shareoutcomes.
5.2.3.3 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. R&D for thedecommissioning of the Fukushima Daiichi NPS is an opportunity to practice state-of-art scienceand technology and the accumulation of such activities is expected to become a source ofinnovation.
The Collaborative Laboratories for Advanced Decommissioning Science of JAEA/CLADS(Tomioka-machi, Fukushima Prefecture) is working to enhance the base functions of JAEA/CLADS
by establishing a network of universities, researching institutions, and industry in Japan andoverseas to promote the R&D and human resource development in an integrated manner,
establishing the “Decommissioning research program based on development of research humanresources” in the World Intelligence Project, and starting the research, development, and humanresource development projects that connect organizations through a cross-appointment systemafter the establishment of 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 in138

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 fortraining and establishment of operating procedures, etc. In 2022, a mock-up test of the robot-arm
was conducted for the trial retrieval of fuel debris (internal investigation and fuel debris sampling).
In Okuma Town, as described in 4.3, Fukushima Prefecture, the JAEA Okuma Analysis andResearch Center (Radioactive Material Analysis and Research Facility) is under construction. The
Laboratory-1 of Radioactive Material Analysis and Research Facility, where low-dose and mediumdose 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 was set in October, and its operation wasstarted. The Laboratory-2, which analyzes high-dose samples such as fuel debris, is being
designed in detail.
In this way, research facilities related to decommissioning projects 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.

139

6. Activities to support our technical strategy
6.1 Further strengthening of project management and improvement of capability
required as a decommissioning executor
6.1.1 Significance and current status of project management
In order to smoothly proceed with the entire project with a view to the medium and long term
decommissioning work while coordinating and harmonizing, it is necessary for TEPCO to establish
a management system in which the organizations involved in the project work together to achieve
the goals and enhance their overall capabilities.
The individual work in each work area of a decommissioning project generally proceeds throughthe following processes: conceptual design, research and development, basic design, detailed
design, manufacturing, on-site installation, inspection, and operation. In addition, the Nuclear
Regulation Authority (NRA) will conduct reviews and inspections, as necessary. In order to carryout such a series of processes without omission or delay, it is effective to set up the major workflow
defined in the long-term plan as individual projects, which are management units of an appropriate
scale. It is then important to optimize the interrelationships and chronological relationships among
the projects, and to proceed with overall consistency under a sophisticated project management
system so that the risks inherent in the projects can be appropriately managed. From thisperspective, TEPCO has been working to build and strengthen its project management system,
which was reorganized in April 2020. Project-based organization management has been gradually
established through two years of operation.
As difficult projects such as fuel debris retrieval will be implemented at full-scale in the future,
and TEPCO intends to take the lead in EPC 102 management, further enhancement of project
management capabilities is required.
As the decommissioning work is well underway, entering Phase 3 of the Mid-and-Long-term
Roadmap, it is anticipated that the projects to be handled will become more diverse, and interface
management between projects will become more complex, further increasing the level of project
difficulty. As a result, TEPCO's workload for project management is also expected to increase. The
leadership of TEPCO management will become even more critical in securing personnel over thelong term, for example, by prioritizing work and peak work shifting to equalize the workload andincreasing the number of personnel if the workload still cannot be supported.
Examples of key initiatives up to FY2022 include: strengthening the authority of project managers
through organizational restructuring, process management using dedicated software (P6),establishing and operating a risk monitoring system (risks are quantified using risk management
sheet - risks are mapped on two axes, frequency of occurrence and impact, and risk trends aremonitored regularly at meetings with the management's attendance.), strengthening project
management based on partnership agreements with overseas companies with knowledge and102 E: Engineering, P:Procurement, C:Construction

140

experience in decommissioning projects, improving the level of safety and quality, and developmentof a forward-looking plan (Mid-and-Long-term Decommissioning Action Plan). Major initiatives arelisted 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 program103/project structure and the Decommissioning
Safety & Quality Office was set up directly under the Chief Decommissioning Officer (CDO). As aresult, the authority of project managers has been strengthened by assigning full-time project
managers and granting budget implementation authority. In terms of operation, efforts were madeto 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 and risksof each program and project every month. Moreover, the Decommissioning Safety and Quality
Office was set up to ensure the safety of decommissioning work and to maintain and improve thelevel of work quality in the face of the extremely uncertain and technically challenging tasks suchas fuel debris retrieval.
However, there are many issues for project-based operations to reach a mature level. For
example, workforce and work content should be properly controlled so as not to ruin motivation ofmembers due to fluctuations in workload between projects. Operations in the decommissioning
safety/quality assurance office, a wide range of activities are needed, including establishing asystem involved in engineering work by each lead group and developing members specializing insafety.
②Strengthening of risk management

A “risk” refers to “uncertain events” that may occur in the future, not an event that has alreadyoccurred. In “uncertain events”, some have negative effects (Threats) and the others have positiveeffects (Opportunities). Many of the “Uncertainty” 104 in the decommissioning of the Fukushima
Daiichi NPS are “causes” that have a negative impact (threats) on the project. On the other hand,an event that has already occurred or an event that is surely to occur (probability of 100%) becomesan “issue (issues and problems)”.
Risk management involves using resources to address potential root causes and mitigate serious
consequences. Issue management, on the other hand, uses the appropriate resources to deal withand solve issues and problems that have occurred. A risk becomes an issue if it is mishandled.
Therefore, handling risks appropriately will reduce issues.

103 Program is the upper level of project, and it is a project in which multiple projects are organically combined torealize the overall mission.
104 As uncertainty that has a negative impact on the project include, for example: Uncertainty of design input

conditions due to the inability to obtain 100% of site information, uncertainty due to the development of highly
challenging technologies, and uncertainty in estimating cost schedules due to many tasks that have not been
experienced in the past.

141

If risk management works out fine, “things that may be a problem will not occur”. However, if
something happens as a result of a failure, “it will be seen as a problem, and accountability will be
required “. With this, much of the project manager’s work is focused on eliminating, improving, andmitigating costs, schedules, and causes that affect performance. In other words, risk management
is a core activity for project 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 (the standard workflow of risk management is shown in
Fig. 45).
TEPCO is fully aware of the importance of risk management, and has begun systematic efforts
in line with the workflow in Fig. 45 from FY 2021 to further strengthen risk management.

142

START(1)

Identify risk events(2)(Scoring for level of impact,
probability of occurrence)(3)(Cause, Risk, Impact)

Current analyze risks

Current assess risks(Level of impact x Probability of occurrence)

Determine risk
acceptability(4)

Acceptable

Not acceptable(5)

Examine specific risk measures(avoidance, mitigation, transfer)Analyze risks after measured

(6)

(7)

(8)

Risk
management
sheet(Scoring for level of impact,
probability of occurrence)

Assess risks after measured(Level of impact x Probability of occurrence)No

Has it become acceptable?
Yes(9)
Incorporate into project planning

END

Fig. 45 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
Concerning Nuclear Emergency Preparedness and the Nuclear Reactor Regulation Law105, theMid-and-Long-term Roadmap decided by the Ministerial Conference on Measures for
105Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors

143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
2022, TEPCO published the Mid-to-Long-Term Decommissioning Action Plan 2022, which was
updated every year based on the progress of the work.
Mid-and-Long-term Decommissioning Action Plan is proof of the attitude of TEPCO toindependently tackle the decommissioning as its responsible business. A certain level oftransparency is given to the complex and long-term decommissioning project, and it is essential
to maintain and improve transparency and the appropriateness of the content so that it can serve
as effective communication tools with the local community and society.
Mid-and-Long-term Decommissioning Action Plan provides work plans for about the next 10
years for each major measure, and based on the plan for the next 3 years, a Withdrawal Plan forreserve fund for decommissioning has been prepared.
④ Formulation of R&D medium-to-long-term plan
The decommissioning of the Fukushima Daiichi NPS has entered a "strategic stage of foresight"
and is entering a "phase of systematically tackling unexplored areas" such as the retrieval of fueldebris whose location and properties are unknown. For this reason, collaboration with R&D is
becoming increasingly important, and TEPCO is preparing the R&D medium- to long-term planjointly with NDF starting in FY2020. After that, with the aim of strengthening the planning andmanagement functions of research and development to examine technology development issues
and promote implementation plans, TEPCO established the D&D Research & Development Centerin August 2021.
In order to work on the development in cooperation with each PG, the Center has launched amissiontoidentify

technical

development

issuesrelatedtothe

Mid-and-Long-term

Decommissioning Action Plan and to reflect important issues in the R&D mid-and-long-term plan.
This mission is an important one for realizing the target process of the Mid-and-Long-term
Roadmap, and it is necessary to plan mid-and-long-term R&D through early enhancement of
resources.
In particular, regarding the research and development of fuel debris retrieval, it will be
indispensable to carry out integrated promotion in close cooperation with a new engineering
company that is to be established in October this year, and therefore, the Center's structure needs
to be further improved. It will also be an important role for the Center to monitor the R&D progressof each PG at all times, evaluate the effectiveness of R&D on a regular basis, and appropriately
feed the evaluation results back to each PG.

144

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.). On the other
hand, the following issues need to be addressed continuously.
Fukushima Daiichi Decontamination and Decommissioning Engineering Company concludes
hundreds of construction contracts every year. At the planning stage, the completion date of theconstruction contract (hereinafter referred to as “acceptance inspection period”.) is set not to beat the end of the fiscal year (March), but the subsequent engineering does not proceed as planned,
and at the contracting stage the acceptance inspection period has to be set to March. As a result,
there is no buffer to absorb the process changes caused by the actual construction within thefiscal year, and there are many cases in which the acceptance inspection is carried over to thenext fiscal year.
In the future, it is important to examine appropriate processes at the planning stage, set theacceptance inspection period with a certain level of margin relative to the end of the fiscal year,
and establish an acceptance inspection plan that is as uniform as possible throughout the year todiversify resources.
⑥ Addressing issues across projects
TEPCO constantly identifies and shares risks and issues, and each project deals with them, but
for issues that do not fit into individual programs/projects, a cross-divisional system is establishedto deal with them. Examples are shown below.
In the decommissioning of the Fukushima Daiichi NPS, the prevention of the spread of alphanuclides to the environment and the prevention of internal exposure of workers have been
identified as future issues, and a cross-program/project working group has been establishedto deal with these issues.

Work on multiple projects is congested around the west side of the reactor buildings ofUnits 1 and 2. In response to this, a cross-program/cross-project working team has been
set up to study the issues.

In October 2021, a person in charge of seismic design and evaluation was established, andcross-organizational adjustments are being carried out to prevent delays due to variations inseismic design and rework.

145

6.1.2 Key issues and strategies to be strengthened in the future
As shown in 6.1.1, various measures are being implemented to ensure the safe and reliable
implementation of the decommissioning project, and it is necessary to continuously upgrade andimprove the operation of each of these measures. The following is the important items to bestrengthened in the future.
6.1.2.1 Safety and Operator's Perspectives and promulgating the "Safety First"
In April 2021, TEPCO received an order from the Nuclear Regulation Authority (NRA) to prohibit
the transfer of specified nuclear fuel materials due to non-conformities in the protection of nuclear
materials at the Kashiwazaki-Kariwa Nuclear Power Station (hereinafter referred to as"Kashiwazaki-Kariwa"). As a result, TEPCO's nuclear regulatory inspection response category
became Category 4 ("the objectives of the activities in each monitoring area are satisfied, but there
is a prolonged or significant deterioration in the safety activities conducted by the operator"), andmany inspections will now be conducted under the supervision of the NRA.
The operation of Fukushima Daiichi NPS differs from that of the Kashiwazaki Kariwa in terms of
the form of business, and as for the management system, the full-scale project management has
been implemented in the Fukushima Daiichi, which is also different compared to KashiwazakiKariwa. In February 2021, on the other hand, a non-conformance event occurred, where
information on the failure of the seismometer installed on a trial basis in the Unit 3 reactor buildingof the Fukushima Daiichi NPS was not shared within the organization, and it was not fixed/restored
for a long period of time. Although there were no issues with work safety or exposure, etc., a seriesof events are receiving severe external criticism. At the Fukushima Daiichi NPS, the management
themselves are engaged in conversation with all site personnel to understand the organizational
issues behind the events.
In order to establish safety as part of the organizational culture, so that is not just a slogan, it isinsufficient to just ask employees to prepare themselves, and instead each and every employee
needs educational materials and opportunities to learn about safety in a systematic way.
Moreover, to regain the trust of the public, it is important for TEPCO to continuously promotemeasures for preventing nonconformities, especially those that could lead to environmental
impacts, personal injury, and radiation dispersion, as well as to disseminate information and build
systems that incorporate the perspective of the local community. Because 11 years have passed
since the accident and the systems are aging, as measures against aging degradation, the attempts
are being made to improve the process of long-term maintenance planning, to prevent humanerrors (HEs), and to analyze factors and take actions from the on-site perspectives according toeach department's structure and tasks in the prevention of occupational accidents.
Frequent occupational accidents, human errors, and system failures will cause the communityand society to lose trust. Especially with respect to occupational accidents, since many workers at
Fukushima Daiichi are local resident, continued occupational accidents can cause anxiety not only
for on-site workers but also for their families. Ensuring “a safe workplace” is the responsibility of146

the owner. TEPCO will further refine its on-site capabilities as an owner and aim for a "three zeros"
workplace with zero occupational accidents, zero HEs, and zero system failures.
Ultimately, it is the people and organizations (operators) who handle all aspects of the"Fukushima Daiichi NPS site" (operation, maintenance, radiation control, instrumentation, analysis,etc.) that will realize safety. At Fukushima Daiichi NPS, the effectiveness and sufficiency of radiation
exposure reduction and personal safety measures are confirmed at "ALARA Meeting 106 " and"Safety pre-evaluation Meeting 107 ". However, it is important that operators (including not only
TEPCO employees but also employees of subcontractors) who are familiar with the work site
participate in these meetings, and that the work process is designed so that safety can becomprehensively checked from the "on-site perspective" (experience) of the various operators. In
other words, it is important to establish the business process as a mechanism, such asincorporating into the gate process the business process of "systematizing and manualizing
experience and related information from the field about procedures, rules, and precautions toensure safety at work, and having the personnel and operators in charge of managing andoperating the field work familiarize themselves with them. It is important to establish such a system.
6.1.2.2 Owner's engineering capability
In the case of large scale projects, where the technology is mature and the performancerequirements are clear, such as the construction of nuclear power plants, waterfall-type 108
engineering is generally used. In this type of waterfall engineering, it is effective to clearlycommunicate the requirements of the client (TEPCO) to the potential contractors (manufacturers,
general contractors, etc.) in the supply chain as far as possible upstream of the project to proceedwith the project smoothly.
However, since the fuel debris retrieval is an inexperienced approach, the target setting andrequired specifications from TEPCO, the executor of the decommissioning project, are not always
clear at the time of engineering, and the degree of performance requirement setting, physicalfeasibility of the method and equipment, and performance assurance must be trial and error.
Therefore, in addition to “the sequential approach” that addresses “work in the initial stage” andthen rolls out the information gained to the next stage, the operation executor’s performancerequirements, the establishment of the supply chain functions, and its engineering process should

106 The purpose of this meeting is to reduce the radiation exposure of workers and to discuss the effectivenessand sufficiency of engineering measures (physical measures) such as removal of radiation sources andinstallation of shielding.
107 The purpose of this meeting is to prevent the occupational accidents and to deliberate on the effectiveness andsufficiency of personal safety measures using risk management methods (risk identification, risk analysis andrisk assessment).
108 It is a method of increasing the accuracy of the design in stages, from conceptual study to basic design andthen to detailed design. Since the process proceeds in a single direction from upstream to downstream, it has
the advantage of easy control of budget, process and resources (personnel), but it also has the disadvantage of
not being able to go back once the next phase is underway. It is called the waterfall type, because it resembles
a waterfall where water falls from the top to the bottom.

147

be iteration approach-based, to some extent109. In this regard, it would be effective to proceed byreferring to case examples in other industries that are also implementing the same iteration-type
engineering. For iteration-type engineering, the contract between a project executor and a supply
chain is not conventional110. Therefore, TEPCO, as a project executor, is strongly required to “makea judgment on engineering and is responsible for the results.” To do so, TEPCO needs to improve,
specifically the engineering ability that TEPCO, the project executor, proactively performs as theowner111 (owner's engineering capability).
The owner's engineering capability here refers to the capability required of TEPCO itself as a site
owner and a license holder, specifically, it is a capability that consists of both project management
capability and technical capabilities based on safety and operator’s perspectives.
Fuel debris retrieval, in which the applicable technology, environment, and target objects are all
unknown, is not work like designing and constructing a nuclear power plant, where the finishedproduct is delivered with a performance guarantee. Therefore, unless TEPCO, the executor of the
project, bears the business and technical risks ultimately, there is a risk that the performancerequirements will be unlimited. The fact that the project executor bears the business and technicalrisk also means that the project executor itself must have the technical ability to assess the reliabilityof the functional settings and engineering design, as well as project management capability. Here,the most important point is to incorporate “safety and operator's perspectives” as upstream as
possible in engineering. (Fig.46)
For example, in the evaluation of fuel debris retrieval method selection, it is necessary to evaluate
from the viewpoints of quality (fuel debris retrieval status, safety, etc.), project (cost, time and othervisions), and technical feasibility. Alternatively, a project that would previously have been ordered
by a single company can be divided among multiple companies, and TEPCO can oversee andmanage the entire construction. It is also important for the enhancement of owner's engineering
abilities to accumulate and feedback various field experiences, such as by these activities and thepromotion of insourcing to be described later.

109 A method of gradually increasing the percentage of completion of engineering by finding the next result basedon a certain result and repeating this cycle.
110 In the conventional construction of nuclear power stations, a supply chain has delivered completed products to

a project executor after guaranteeing the performance (Full turnkey contract).
111 An owner here has three positions of a party responsible for disaster occurrence, a specified nuclear facility

licensee, and a facility owner. TEPCO is executing the decommissioning project from these three positions. (Aproject executor of decommissioning)148

Fig. 46 Design flow of fuel debris retrieval (conceptual)
6.1.2.2.1 Project management capability
The decommissioning of the Fukushima Daiichi NPS must be carried out reliably over a long
period of time under changing site conditions, and it will be difficult to cope with conventional
contracts, especially for high-risk project work such as fuel debris retrieval. Therefore, it isnecessary to prepare a contract method based on a new concept, in which both the contractor andthe recipient cooperate, share the contractual risks, and aim for the agreed-upon goals. In terms ofprocurement, instead of one-way “Buying” from an ordering party to an order-receiving party, bothparties should bear in mind the concept of “Acquisition” of the final result by “Making”, withconsideration of all steps from development, manufacturing, to even operation/maintenance (Table
6).
To deal with such Making-based projects, in addition to improving the engineering capability,
such as the ability to materialize specifications, it is necessary to have project management
capability with a focus on “Acquisition of the final result”.
Based on the shared awareness that conventional Buying-oriented project management alone
is not enough to properly control projects with large uncertainties such as fuel debris retrieval,

149

TEPCO and NDF are benchmarking the acquisition management112,113 as adopted by the U.S.
federal government as a precedent to further develop current project, and are actively learning themethodology with the cooperation of external experts starting from FY2017, and currently
customizing it to fit the decommissioning project of the Fukushima Daiichi NPS.
This approach will be tested in a pilot project. After determining its effectiveness and scope, itwill be gradually rolled out to other projects. (Table 7)
Table 6 Difference between “Making” and “Buying”
MakingBuyingAcquisition of the outcome of the project

Purchase products (things) that meet the(Acquisition)

specifications

What to call theContractor, a partner who is responsible

Vender, who supplies equipment thatorder receiving

for obtaining the outcome of the project

conforms to specifications

How to decide

Select based on proposal content andSelect by price

who will receive

feasibility

parties and theirroles

the order
Contract method

Contracts in line with risk allocation

Fixed price contract

Data-based cost estimation (analogy:

Quotation/price list, etc.

analogy, integration, parametric :sensitivity, analysis, etc.)“Do the Right Things”※ * When doing things, always think
about what the right purpose, the right“Do Things Right”※ * Do things right, by the rules, by theprocedures.

goal, and the right means.

112 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 the Work Breakdown
Structure (WBS) into the elements of outcomes (products, structures, and deliverables) to be obtained rather thantasks. In addition, by accumulating the costs of each decomposed element based on the planning process andvisualizing the progress of the project, it becomes possible to appropriately identify the gap between the plan andthe actual situation, to grasp the risk at an early stage, and to take countermeasures.
113 In acquisition management, acquisition and procurement are defined as follows and adequately used dependingon the case. Acquisition refers to acquiring the value and capability related to specific equipment and otherdeliverables throughout their lifecycle, from development, manufacturing, and operation to maintenance, toachieve a specific goal or objective. However, a part of this acquisition flow is sometimes contracted to an externalorganization at each phase, such as development and manufacturing, and the gaining of specific elements on
this contract basis is called procurement. In other words, acquisition consists of several procurements(deliverables based on contracts).

150

Table. 7 Future project management (To Be)

Control Parameter

Present project management

Future project management (To Be)

Definition of
Purpose and“Success”

 Purposes are set but “Success”(achievement evaluation criteria) is notclarified in advance.

 Define the evaluation criteria to beachieved as well as purposes at the time theproject is launched

Feature(Structure of
WBS*1)

 Break down “Works” into the work-elements
to be performed

 Decompose “Works” into outcome elements(product, structure, deliverable) to beacquired Budget phase : In the phase cost cannot be
estimated, cost estimated based on

Cost Budget phase : In the phase cost cannot be
estimated, infer from similar works, get aquote from vendors
 Execution phase : Actual costs are notcollected at the breakdown level Planning phase : Best Effort process Execution phase :Subjectively assess
progress against milestone Planning phase : Process with risk factored in Execution phase : Quantitatively assess thestatus of results acquisition using objective
and scientific methods (EVM*2, etc.)

Technical
Performance Assumed that it will be achieved(performance is guaranteed as an obligation of
the ordering party and is not subject to control) Set a baseline of technical performance tocontrol technical performance at the WBS level
as well

Contract Fixed-price contracts

 Risk-based contract (type, scale, etc.)

Schedule

reliable data Execution phase : Collect actual costs by
WBS unit※1：Work Breakdown Structure※2：Earned Value Management

6.1.2.2.2 Engineering capability based on safety and operator’s perspectives
In the past, the construction of nuclear power plants was achieved on-time, on-budget, and onperformance by placing bulk orders with companies with extensive construction experience.
However, no company has experienced the decommissioning of a plant that has experienced ameltdown like the Fukushima Daiichi NPS. Especially, fuel debris retrieval is extremely technicallychallenging, and it is not easy to accomplish with only one company’s technology. It is necessary
to call upon each company's unique and top technologies and establish a single system. To achievethis, TEPCO must have more technological capabilities than before, i.e., the engineering
capabilities being able to judge the merits and demerits of individual technologies ("insight”) andthen integrate them into a system to achieve the desired performance. Through the insourcing thatthey are promoting, TEPCO aims to improve its ability to make engineering judgments on individual
technologies, enhance capabilities for integration as a system, and reduce technical risks.
“Insourcing” means to develop an ability that enables TEPCO to implement planning, design,
maintenance, and operation on its own. It aims at reducing unreasonableness and waste, further
deepening the level of productivity improvement, and improving the operation quality of TEPCO
employees including the quality of design and procurement. The improvement of these qualities
will ultimately contribute to the improvement of safety. While insourcing is effective for a wide range
of issues, it is advisable to proceed with an awareness of the issues that are expected in the future
to gain more benefits. Examples of future issues are listed below.

151・Improvement of operation and facility quality through internal integration of operation andmaintenance know-how
In terms of operation and maintenance of facilities, it is expected that the number of operation
tasks will increase due to the installation of new facilities and that maintenance costs will increase
due to the aging and deterioration of facilities. It is necessary to devise more "Smart Maintenance"
methods to keep maintenance costs low while not degrading reliability. For example, in the caseof a new system to be used for a long period of time, sensors (vibration, heat, sound, etc.) for
online monitoring of the operating status can be mounted in advance, a large amount ofaccumulated maintenance data be processed by computer to be used for prediction maintenance,and maintenance data obtained from existing systems be utilized. In this way, systematization andsophistication of maintenance knowledge management facilitate accumulation of maintenanceknowhow internally. Accordingly, a databased system for the equipment to be maintained will go
live. It is important to expand the information on maintenance in the future and to establish it while
improving its operation.
Furthermore, for long-term operations such as fuel debris retrieval, where highly radioactive
materials (and nuclear fuel materials) are handled, TEPCO employees, who are the license
holders, should perform the operations themselves, and the operator should ensure radiation
safety and strive to internally accumulate operational know-how.
・Enhanced capability to make an engineering judgment
For a task like fuel debris retrieval, which is inherently subject to great uncertainty and for which
TEPCO has no previous experience, TEPCO needs to make engineering judgments on its own,
and to do so, it must have a firm grasp of the details of design, construction, maintenance, andoperation. Therefore, to take design as an example, TEPCO should improve its competence byworking on system design and determining the required specifications of equipment from thecurrent stage.
・Strengthening site capabilities
The on-site situation at the Fukushima Daiichi NPS has changed significantly from before theaccident. As described in 2.3.1 Basic policy for ensuring safety based on the characteristics ofFukushima Daiichi NPS, a large amount of radioactive materials exist in unconventional andunsealed conditions without complete barriers to contain the radioactive materials, such as reactor
buildings and PCVs. Furthermore, the environment is subject to constant changes in situations
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.
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 that152

have never been experienced in the past in terms of construction, operation, and maintenance.
Therefore, TEPCO must always keep in mind that unpredictable situations may occur and observe
the site, and it will be particularly important to have the ability to think about things from theperspective of the site by detecting changes on site as soon as possible ("on-site capability").
Specifically, the following capabilities should be developed based on a thorough knowledge ofthe functions and performance of the equipment to be acquired.
 in the design phase, ability to develop specifications to ensure that a given function can be
performed over its life cycle (from installation, verification, operation to maintenance) under onsite operating conditions (operating environment, with/without interfering objects, etc.),
 in the on-site operation phase, ability to assess the latest on-site conditions, identify potential
risks (e.g., accidents involving personnel, procedural errors, etc.) in conjunction with thecontractor, and take appropriate risk measures to ensure safety and quality on the operation
site, and
 in the event of an emergency, ability to troubleshoot problems by TEPCO employees themselves,
even without support from partner companies.
6.1.2.3 Securing and developing human resources
6.1.2.3.1 Securing and developing human resources for smooth implementation of
decommissioning projects
In addition to the fact that the decommissioning project of the Fukushima Daiichi NPS is an
unprecedented task for which nobody has experience, it is necessary to systematically secure anddevelop human resources in anticipation of the expansion of operations in line with the progress ofthe fuel debris retrieval plan. Specifically, based on the Mid-and-Long-term Decommissioning
Action Plan and mid-to-long-term business outlook with a view to subsequent businessdevelopment, it is desirable to develop a staffing plan that includes the required skills and qualities
and headcount as well as an organizational development plan that outlines tactics to achieve them,and implement measures to increase personnel motivation. Of these, human resource
development is particularly time-consuming. Thus, it is also necessary to reduce inefficient
operations and use limited human resources effectively. With such awareness, TEPCO is expected
to take the following actions.
(1) Error prevention and improvement of two-way communication with society
TEPCO has established a system to prevent mistakes and errors and improve two-way
communication with the public in order to eliminate mistakes and errors on-site, which cause a lossof trust in the eyes of society, including nonconformance in nuclear material protection in
Kashiwazaki-Kariwa NPS and failure to share information on the failure of seismometers installed
on a trial basis at the Fukushima Daiichi NPS, and other incidents such as delays in reporting or
confusing reporting. In addition to continuing efforts, it is necessary to further promote creation ofan open workplace, including with contractors. In creating an open workplace, for example,
management constantly disseminating information is effective and, although it takes time, so is

153

providing education and training for the middle management, including group managers, to ensure
psychological safety114.
(2) Efforts to improve operational efficiency and effective use of resources
Now that operations are becoming more project-based, this is an excellent opportunity tocontinue to explore how to improve the way of working and optimize and enhance the allocation of
resources. It is important to constantly review operations, improve operational efficiency, and use
resources effectively, so as not to be hindered by prior ways of working. While efforts have alreadybeen made through Kaizen activities, it is desirable to promote these efforts further. In addition, as
mentioned above, TEPCO is aiming for project management that focuses primarily on obtaining
results, which will further improve the quality of operations in terms of costs, schedules, etc.
Furthermore, this initiative is expected to contribute to efficient operation management by improving
the time planning of work and enabling members to check the performance of members.
(3) Securing and developing human resources
In decommissioning projects, it cannot be denied that the installation of new systems andfacilities will continue, and the workload will increase to ensure the safe and reliable operation of
the installed systems, etc. To cope with increasing workloads with limited human resources, it isnecessary to develop staffing and development plans with a mid-to-long-term perspective, increaseheadcount and reallocate personnel accordingly, promote human resource development
systematically and steadily even if it takes time, and establish a system to implement these plans
flexibly and smoothly. In the future, a higher level of engineering and expertise will be required toachieve more technically challenging goals than in the past, such as selecting methods for fueldebris retrieval and designing new systems and facilities. Therefore, in the mid-to-long-term staffing
plan, it is desirable to anticipate the required headcount in each technical field and when they areneeded, including personnel with more advanced expertise (e.g., actinide chemistry, analyticalevaluation, seismic resistance, environmental impact, etc.) in addition to those in each job category(project management, design, operation, maintenance, chemistry, analysis, safety assessment,
radiation control, etc.) that will be needed in the future.
For securing human resources, in addition to extracting available human resources by improving
operational efficiency as mentioned above, it would also be effective to introduce a system that is
conscious of the local community, such as employing from local high schools, technical colleges,
and universities, or employing local people who have entered higher education in different areas,in anticipation of the decommissioning project to be carried out in cooperation with the local
community over the long term. In addition, more efficient use of human resources becomes
possible by reviewing personnel allocation and job assignment flexibly and smoothly in responseto changes in workload and required skills as the work progresses.

114 Psychological safety: The belief that your opinion won’t be rejected, or other members won’t punish you. Sucha state of mind allows you to speak without fear.

154

Moreover, training and securing analyzers are urgent for human resource development. TEPCO
has started human resource development through OJT training115 at JAEA and other organizations
with expertise in analysis. At present, the training of analysis managers is a priority, but from now
on, it is also necessary to concentrate on training analytical engineers (management) who candetermine applicable analytical techniques according to the situation and formulate analysis plans.
It is also desirable to train analytical evaluators who understand the process of eachdecommissioning work, what analysis is necessary for it, and who can plan the scope and items ofanalysis in anticipation of how to utilize the analysis results.
<<Example idea of human resource development: Development of technical leaders fordecommissioning under the unique environment of 1F>>
Under the unique conditions of Fukushima Daiichi NPS described in 2.3.1 Basic policy forensuring safety based on the characteristics of Fukushima Daiichi NPS, the technical leadershipat the program manager level must possess a wide range of capabilities to safely and steadily
promote decommissioning. This requires basic knowledge and technical experience to gain acomprehensive understanding of handling nuclear fuel materials and associated requirements
and develop it. In developing such knowledgeable and experienced leaders, the issues are how
to help them acquire these skills (training), how to check that each person has these skills (check),and how to raise each person's awareness (motivation) to acquiring these skills. To solve theseissues, as mentioned above, it is necessary to prepare a human resource development plan andimplement it systematically and steadily. An example of the implementation structure is described
below.
a) Personnel development planning
For each skill item required of technical leaders, an organizational human resource
development plan should be prepared, which defines [1] the target, required knowledge andtechnical level, etc., [2] OJT and training items, etc. as a means and needed for the acquisition,and [3] standards to determine whether the skills have been acquired. Based on the plan, groupmanagers as superiors prepare individual development plans for the personnel to be trained,with a vision of their future as a career path.
b) Development and skill check
The basis of human resource development lies in OJT training. By assigning tasks thatexceed or are outside the scope of the target’s abilities and having them perform, they canacquire new skills. Under the coaching of an instructor appointed as necessary, the target
personnel develop and fulfill the procedures and implementation schedule for the assigned
115 It stands for “On the Job Training”, a method of training employees to acquire knowledge, skills, etc., byproviding instruction through actual work.

155

tasks. The schedule should include acquiring basic technologies as needed, utilizing the Core
Decommissioning Technology Course, etc. that have already been provided. It is difficult to set
skill standards to judge whether or not a person has acquired the skill and to judge it. Therefore,
assigning one person, who is most proficient in the skill, is effective, leaving it to that person to
make a judgment. If the skill level required matches the official qualification (e.g., Nuclear Fuel
Protection Supervisor), acquisition of the qualification could be used as a skill check.
c) Motivation improvement
Since decommissioning itself is a national challenge that requires the collective wisdom of
humankind, and the skills to be acquired and personalities to be demonstrated for the challenge
are diverse, activities to increase motivation leading employees in various directions will bediverse in themselves. Common and important to all of these activities is to visualize outstanding
employee performance that embodies the future beyond the efforts of individual employees. It
is important for TEPCO as an organization to develop a more robust culture that nurtures andvalues employees who can serve as role models.

6.1.2.3.2 Fostering the next generation who will be responsible for the futuredecommissioning of Fukushima Daiichi NPS
In order to continue decommissioning of the Fukushima Daiichi NPS for a long period of time
and to continue R&D activities necessary for that, it is essential to train and secure future
researchers and engineers, and ensure inheritance of technological skills. As the entire industrialacademic-governmental institutions, it is important to make steady advancement of efforts
according to each level of secondary and higher education stages.
Primarily, the assumption is that TEPCO will establish the decommissioning of the Fukushima
Daiichi NPS as a planned and sustainable project, under which activities of human resource
development and acquisition, including their employees and contractors, will be promoted
independently and continuously. Human resources involved in decommissioning of the Fukushima
Daiichi NPS are required not only to specialize in nuclear energy but also to possess science andtechnical knowledge in fields other than nuclear energy, and ensuring and nurturing humanresources with such diverse technical backgrounds are being required.
For this reason, in addition to the importance of strongly encouraging human resource
development and recruitment directly within TEPCO and contractors, it is most important thatexcellent human resources who have graduated from universities, graduate schools, technicalcolleges, high schools, etc., and have specialized in science and technology are continuously
sourced to these companies. In order to achieve this in a stable manner, it is necessary for higher
and secondary educational institutions to create an opportunity for learning and acquiring
peripheral knowledge in addition to professional knowledge, and to maintain associated systems
and structures so that they can function as a whole, including teachers.

156

For students in higher education such as universities, graduate schools, and technical colleges,
it is important for the industry and higher education institutions to cooperate and continuously
implement activities to promote understanding of the nuclear industry. In recent years, due to thereorganization of faculties and departments related to nuclear energy, it has been pointed out thatthe human resource development function in higher education institutions in the nuclear field is
weakening. Therefore, attention must be paid to maintaining and enhancing the human resource
development function in the nuclear field nationwide. In particular, it is necessary to communicate
the idea that the decommissioning of the Fukushima Daiichi NPS is an extremely advanced
technical challenge, which is unprecedented in the world, and to establish various career paths foryoung researchers and engineers to thrive in the nuclear industry including decommissioning, andto specifically demonstrate and make them feel a career view. For the development of nextgeneration human resources, it is fundamentally important that young researchers/engineers areconstantly produced from these higher education institutions.
In particular, the World Intelligence Project by MEXT and JAEA/CLADS has introduced a system
in which students and young researchers are made to be aware of decommissioning as animportant research area, and is engaged in decommissioning research. From the perspective ofhuman resource development, support has been provided for young researchers and teachers in
preparing and implementing lecture curriculums related to decommissioning. After more than five
years since the launch of the World Intelligence Project, it has produced great results in terms ofboth research and human resource development. At “the Conference for R&D Initiative on Nuclear
Decommissioning Technology by the Next Generation (NDEC)”, a conference for students topresent their research findings as part of the World Intelligence Project, and the Creative Robot
Contest for Decommissioning for technical college students, students present their research results,
exchange views with researchers and engineers involved in the decommissioning of the Fukushima
Daiichi NPS, and are given awards for excellent performance on a constant basis. As for an
initiative for young researchers in the World Intelligence Project, in addition to the existing program
represented by young researchers under the age of 39, a new program was launched in FY 2021
that requires young researchers to assume commensurate research responsibilities within R&D
projects as a requirement for application. In order to encourage autonomous research activities, an
initiative has been taken since April 2021 where young researchers engaged in the WorldIntelligence Project are allowed to be involved in independent research activities up to 20% of theefforts devoted to the project with the consent of the research representatives (relaxation of theobligation of full-time commitment).
The World Intelligence Project’s mechanism and implementation have produced some results
for researchers and students belonging to the higher education organizations, and humanresources have been activated, with graduates being engaged in decommissioning-related projects.
Hereafter, it is important to implement this project so that the perspectives of decommissioning
sites in TEPCO and those of the activities in higher education institutions can be more aligned.

157

For junior and high school students in the stage of secondary education, it is important tointroduce appealing points of engaging in the nuclear energy field including decommissioning, andto make efforts to attract their technical interests with a focus on decommissioning, as well as toincrease their understanding of 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 a stage in which, as a preparatory stage for participating in and contributing to society,students can develop their individuality and competence while being influenced by researchers,
engineers, and science teachers who are active in society, and can make independent choices anddecide their career paths. From this perspective, NDF holds the “International Mentoring Workshop
Joshikai in Fukushima” for middle and high school female students mainly in Fukushima Prefecture
in cooperation with the OECD/NEA as an effort to increase interest in science and engineering,
especially in decommissioning, etc., through exchanges with female researchers and engineers inorder to enhance understanding among women and help increase their motivation to participate indevelopment studies. In 2020, the "International Mentoring Workshop Virtual Joshikai in Fukushima
2020" was held using the online system, even in the midst of the global outbreak of the newcoronavirus infection, and it was held using the online system in 2021 in succession. In addition,“student sessions” for high school students, etc., were held to give thought to the reconstruction of
Fukushima along with the International Forum on the Decommissioning of the Fukushima Daiichi
NPS (hereinafter referred to as “International Forum”). In 2022, as in 2021, workshops are being
held to discuss a vision of the future in the Futaba area in 2050, based on prospects derived fromstatistical data on the Futaba area, the status and plans for decommissioning, and information onhuman and natural resources in the entire Hamadori area. Through these efforts, high school
students, etc., are given an opportunity to think about activities to achieve both decommissioningof the Fukushima Daiichi NPS and reconstruction, enabling them to increase their awareness that
decommissioning is an important issue in reconstruction of local communities, and foster interest
in and willingness to contribute to decommissioning and reconstruction efforts. Such activities haveachieved some positive results. These sessions and forums will continue to be held in 2021 byutilizing an online system.
For the development of such technical personnel associated with decommissioning of the
Fukushima Daiichi NPS, it is also necessary to expand into wider fields including fundamental
research and related research. In the course of raising the level of the entire fundamental
technological base in Japan, it is expected that initiatives to deal with the nuclear legacy andnuclear safety will take deeper root.
Institutions concerned are continuously required to promote and strengthen their efforts to secureand develop human resources for the next generation according to their respective roles and levels.

158

6.1.2.3.3 Dissemination of basic knowledge and promoting the people's understanding fordecommissioning and radiation safety involved in decommissioning
It is important for many citizens and local residents to acquire basic knowledge of the accident
and decommissioning, disaster response, radiation safety, and food safety related to the
Fukushima Daiichi NPS from the perspective of future resilience of the whole country. This isbecause it will serve as basis for discussions on decommissioning, and related radiation safety,
etc., based on accurate information and for promoting public understanding. In addition, although
it is not directly aimed at fostering human resources who will play a leading role in the nuclear fieldin the next generation, it is also an aspect of indirectly broadening the range of human resources
who are interested in not only in the nuclear field but in science in general. Particularly in the fieldof nuclear energy, it is necessary to learn about the relationships in local communities and society
through various opportunities according to the development stage of children, as well as to acquire
knowledge and experience on nuclear energy and decommissioning. To do so, since it is importantthat children take an interest through the knowledge and experiences of adults around them, suchas teachers and parents. Therefore, it is important to further spread knowledge on nuclear energy
and decommissioning based on scientific evidence, which to a wide range of 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 thecontinuation and expansion of on-site classes and the promotion of the use of radiologicalsupplementary readers. The NDF also holds workshops for local students to consider
decommissioning and reconstruction, as described above.

6.2 Strengthening international cooperation
6.2.1 Significance and the current status 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. Eachcountry 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, and securing large
amounts of funding.
In order to steadily proceed with the decommissioning of the Fukushima Daiichi NPS, which
deals with difficult engineering issues, it is important to learn lessons from precedent159

decommissioning activities, etc. and apply them to the decommissioning of the plant as a risk
reduction strategy, and to utilize the world's highest level of technology and human resources, i.e.,
to gather and utilize the wisdom of the world.
In addition, the decommissioning of the Fukushima Daiichi NPS is a process to solve unexplored
engineering problems by combining knowledge from various fields, not limited to the nuclear field,
and it can be interpreted that the decommissioning of the Fukushima Daiichi NPS can be an
important place to create innovation. Consolidating diverse knowledge and experience from aroundthe world in Fukushima is, in the first instance, an important effort to steadily advance thedecommissioning of the Fukushima Daiichi NPS itself. This is also an important initiative from theperspective of leading innovation through the 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.
To bring together the wisdom of the world, it is important to maintain and develop theinternational community's continuous understanding, interest, and cooperation in decommissioning.
Therefore, it is important to promote decommissioning in a mutually beneficial manner that is open
to the international community by gaining the trust of the international community and disseminating
accurate information on the progress of decommissioning, etc., and by actively and strategically
returning to the international community the knowledge and other findings gained through theaccident at the Fukushima Daiichi NPS and decommissioning.
Specifically, it is important to promote bilateral cooperation in line with the circumstances of eachcountry and to utilize the framework of multilateral cooperation through the IAEA and theOECD/NEA. These international organizations have an important role in establishing international
standards for decommissioning. It is important to participate in formulating international standards
based on Japan’s experience in decommissioning to promote the decommissioning of the
Fukushima Daiichi NPS in an open manner to the international community. It is also expected tofulfill part of Japan’s responsibility to the international community by sharing Japan’s experience
with other countries. From this perspective, Japan has been holding an annual dialogue andestablishing a conference body to share information with other countries as an intergovernmental
framework. Moreover, each of the relevant domestic organizations has concluded cooperative
agreements and arrangements with relevant overseas organizations, and has disseminatedinformation at international conferences. NDF has been working on disseminating information on
decommissioning through participation in their side events of the IAEA General Conference andspeaking at major international conferences such as the OECD/NEA Steering Committee. By
securing the confidence of the international community and promoting mutually beneficial
decommissioning, we are trying to maintain and develop the international community's continuous
understanding and interest as well as cooperative relationships. (Attachment 14)
In addition, in the course of the above-mentioned international cooperation, due to the global
outbreak of the COVID-19, many meetings and events related to IAEA, OECD/NEA, etc. are held
online. NDF has also been actively utilizing the online systems and other means and ensuring160

continuous opportunities for information exchange to gather the world's wisdom, maintain andenhance the international society's continuous understanding and interest, and maintain anddevelop cooperative relationships with international community, such as the exchange of views withinvited overseas experts in previous years and the holding of annual meetings withdecommissioning-related organizations in other countries online. Meanwhile, IAEA, OECD/NEA
and other overseas organizations concerned are holding face-to-face meetings as in the past, andthere are increasing opportunities to participate in, and speaking at conference venues. As thenumber of cases of COVID-19 infection has been increasing and decreasing repeatedly, NDF is
considering and holding face-to-face meetings, online meetings, and meetings combining face-toface and online meetings, taking into account the movements of overseas organizations and theprevalence of the COVID-19 at home and abroad. (Fig. 47)
In the future, it is important to further expand the opportunities for communication with othercountries by taking advantage of the experience gained so far.

Fig. 47 Exchanging opinions with experts overseas through face-to-face meeting and online(Held in June 2022)

6.2.2 Key issues and strategies
6.2.2.1 Integrating and giving back the wisdom and knowledge from around the world
The decommissioning of the Fukushima Daiichi NPS is expected to be a long-term project withchallenging engineering issues. To solve these issues, it is important to utilize the world's highest
level of technology and human resources and incorporate the experience and knowledge gained
from decommissioning the legacy sites that have preceded this project.
The decommissioning of legacy sites has many points of reference in terms of technology andmanagement as a leading model. From a technical aspect, in each country with a legacy site, publicorganizations related to decommissioning are playing a central role in promoting decommissioning
to cope with issues such as the necessity of new technologies and expertise that differ from theoperation and maintenance of nuclear reactors. From an managemental aspect, public
decommissioning-related organizations also play a central role in developing systems, policies, andstrategies, project planning and management, safety assurance, and local communication.

161

Therefore, it is important for Japan to conclude cooperative agreements and arrangements among
domestic and overseas organizations under the intergovernmental framework, continue to
implement regular information exchange, and accumulate and learn the world’s intelligence ontechnical and managemental aspects.
NDF needs to continue to maintain and develop long-term partnerships with public
decommissioning organizations that play a central role in each country, such as NDA in the UK,
CEA (French Alternative Energies and Atomic Energy Commission) in France, and DOE(Department of Energy) in the US, and integrate wisdom and knowledge including learning obtained
from decommissioning of overseas legacy sites through information exchanges and leverage themfor decommissioning in Japan.
In moving forward with decommissioning Japan has received support from the international
community and has received various kinds of assistance from foreign governmental organizations
and experts, through the dissemination of information on issues related to decommissioning to theinternational community and participation in international joint activities such as the DAROD projectby the IAEA and the joint project by the OECD/NEA.
About eleven years have passed since the accident, and it is important to deepen the mutually
beneficial relationship while also working to return the know-how and results accumulated so far to
the international community. The situation of the Fukushima Daiichi NPS and the knowledge
obtained have been disseminated through the international joint activities and conferences
mentioned above, and it is necessary to promote these activities continuously. In addition, it isdesirable for Japan to actively provide information on the accident at the Fukushima Daiichi NPS,
activities, and achievements toward decommissioning to countries other than advanced nuclear
nations in cooperation with international organizations.
The difficulty in traveling to and from other countries due to the pandemic outbreak of the COVID19 are an obstacle to the continuation and enhancement of such mutually beneficial relationships.
However, it is important to secure opportunities for communication and work to maintain anddevelop relationships by utilizing online systems and other means so that the unprecedented
situation, not limited to the COVID-19, does not dilute relationships with relevant organizations,experts, and international organizations in other countries.
In addition to disseminating information on the current status and challenges of thedecommissioning to the world through a series of the International Forums, NDF has collected thewisdom including lessons learned and technologies derived from decommissioning around theworld. It is important to continue to make the International Forum an effective opportunity to gather
and return wisdom from all over the world by using the online system, even in the situation where
direct participation from other countries is difficult. On the other hand, in light of the epidemic
situation of the COVID-19and possible changes in the way measures are taken to prevent the
spread of infection, NDF will gather and return wisdom and knowledge by using effective methods
with a view to proactively secure opportunities for face-to-face communication.

162

Currently, the decommissioning of the Fukushima Daiichi NPS, is being carried out undercontracts between many companies and decommissioning executors both in Japan and abroad tosteadily proceed with decommissioning, and the global market for decommissioning is expanding
greatly. As the engineering of Fukushima Daiichi NPS is in full swing, it is important to grasp thelatest status of excellent technologies and human resources in the world and to utilize themeffectively. In this context, TEPCO has been actively engaged in technological exchanges withoverseas private companies. For instance, the robot arm for the trial retrieval of fuel debris from
Unit 2 was developed by a British company and is currently undergoing training in Japan. It isnecessary for TEPCO to continue to keep abreast of the latest information from around the world,
including the situation in the private sector, and to engage in continuous communication with these
private companies, sharing information on the progress of decommissioning work and forming anenvironment in which the necessary technologies can be accessed when needed.
6.2.2.2 Maintaining and developing the international community's understanding of andinterest in decommissioning and cooperative relationships
In order to mobilize the wisdom of the world for the decommissioning of the Fukushima Daiichi
NPS, it is important to maintain and develop the understanding, interest, and cooperative
relationship of the international community. Until now, an online system has been used to maintainexchange opportunities. However, considering that the face-to-face activities of the international
community is returning, it is essential to maintain and develop cooperative relationships with
relevant organizations and international organizations, with a view to restoring face-to-faceinteractions as well as online exchanges.
It is important for the government and other domestic organizations to ensure transparency of
information on decommissioning and continuously disseminate accurate information in order tomaintain, increase understanding of the international community, and build a trusting relationship.
Regarding information dissemination, about eleven years have passed since the accident, theinterests 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 that are the baseof understanding116. For this reason, consideration should be given to providing easy-to-understandinformation not only for experts but also for non-experts, devising ways of providing explanations
that consider the level of understanding of the recipients by effectively using videos and illustrations
and disseminating information in languages other than Japanese and English. It is also important
to deepen the understanding of information recipients by disseminating and accurately visualizing
information on the current status and issues related to decommissioning, paying attention to theirlevel of interest and understanding, as this will eventually lead to building a trusting relationship.
In this way, in participating in international joint activities, with the steady implementation of
decommissioning, which is Japan’s top priority, as a premise, it is necessary to work in such a way

116 Brought up in the Decommissioning Strategy Committee in June 2021

https://www.dd.ndf.go.jp/files/user/pdf/committee/pdf/summary/20210618dscsum.pdf

163

that the interests of the international community can also be secured. Disseminating accurate
information continuously is also important as a means to return knowledge obtained indecommissioning to the international community. From the aspect of returning the results, it is also
becoming more important to maintain the level of interest by responding to the changes in theinternational community, such as the growing interest in not only the accident and decommissioning
itself but also the application to other issues.
Furthermore, in response to changes in the global energy situation in the wake of the recent
Ukraine crisis, many countries have been reviewing their energy policies. Even under suchcircumstances, it is necessary to maintain smooth cooperative relationships with other countries
toward the decommissioning of the Fukushima Daiichi NPS while gaining an accurate
understanding of the updated status in the countries concerned.
It is important for NDF to disseminate and collect information accurately and in accordance with
the interests of recipients through various opportunities, and to return to the international
community the knowledge gained in the course of decommissioning.
≪An example and issue that revealed the importance of ensuring transparency of informationand disseminating information≫～Discharging of ALPS-treated water into the sea～
As one example that revealed the importance of ensuring transparency and information
dissemination, the reaction from countries can be given, following the announcement of thepolicy on the discharge of ALPS-treated water into the sea.
In April 2021, the Japanese government announced the discharge of ALPS-treated water into
the sea on the premise that safety would be ensured and that measures against reputational
damage would be thoroughly taken.
In response to this announcement by the Japanese government, foreign governments, relatedorganizations, and international organizations that understand the status of Japan’s
decommissioning and appreciate the transparency of the national efforts, based on theinformation that has been disseminated so far, provided comments in support of Japan’s
decision, with the expectation of ensuring transparency continuously. In addition, the IAEA
announced that it would actively cooperate with the discharge of ALPS-treated water into thesea from a third-party standpoint by dispatching a review mission and supporting environmental
monitoring. These actions are pushing to gain international understanding of offshore release,
the importance of ensuring transparency, accurate information dissemination, and building
cooperative relationships with the international community were recognized again.
On the other hand, some countries issued comments expressing concern about the impact
on the environment and questioning the transparency in discharge. The follow-up review

164mission 117 by IAEA made in April 2020 held the view that to support the implementation of thechosen disposition path, supported by a local, national and international communication plan
ensuring a proactive and timely dissemination of information to all stakeholders and generalpublic are necessary. In order to gain the understanding of the international community on thesafety of ALPS-treated water, it is necessary to fully cooperate with IAEA and continue todisseminate information carefully by ensuring the transparency of information.
It is important to continue to obtain the understanding and cooperation of these countries forthe steady implementation of decommissioning, including the future discharge of ALPS-treatedwater into the sea. On the premise of ensuring transparency of information, TEPCO needs toensure that the government and other relevant domestic organizations disseminate accurate
and easy-to-understand information based on the interests and in the amount of knowledge andinformation of the recipient at international conferences, international joint activities, and on
websites.

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 the decommissioning of the Fukushima Daiichi NPS is "Balancing
between reconstruction and decommissioning". 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 the resumption of business activities, but also by the promotion of migration and settlementfrom outside 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 andpromote coexistence with local communities to gain the trust of the community. Decommissioning
should not be allowed to have a negative impact on the reconstruction process due to anxiety anddistrust of decommissioning, in other words, decommissioning should never be a hindrance toreconstruction efforts.
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 and promptly providing themwith accurate information in an easy-to-understand manner to eliminate them. In addition, toaccomplish the decommissioning over a very long period of time, the continuous cooperation ofcompanies, especially local companies, is essential. At the same time, the participation of local
companies in the decommissioning project is an important pillar of TEPCO's contribution to thereconstruction of Fukushima, as it will not only revitalize decommissioning-related industries in theregion and create employment and technology, but also lead to the spread of the results to other
117 The follow-up review mission (April 2, 2020)

https://www.meti.go.jp/english/earthquake/nuclear/decommissioning/iaea_review.html

165

regions and industries. In light of this, TEPCO will contribute to job creation, human resource
development, and the creation of industrial and economic infrastructure in the region throughdecommissioning, while collaborating with efforts to realize the "Fukushima Innovation Coast
Framework Promotion Organization", which sets the accumulation of decommissioning-relatedindustries in the Hamadori region as a priority field, and aims to achieve "Balancing between
reconstruction and decommissioning”.
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 and roundtablediscussions for local residents and related local governments.
NDF is holding the International Forums for the purpose of frank exchange of opinions on
decommissioning with participants including local communities and organizations concerned, andfor sharing of the latest knowledge, technical achievements, and issues on decommissioning withexperts in Japan and overseas. They also hold briefings on the progress of decommissioning at
meetings hosted by the national and local governments. In order to promote the exchange of
opinions at the International Forums, a “hearing activity” is held every year to hold a conversation
with local communities including high school and technical college students before theInternational Forum is held. Then, their real voice is collected, summarized and edited as a booklet,
and distributed as the “Voice from Fukushima” at the International Forums.
TEPCO has been making efforts to provide explanations and dialogue to regional
representatives at conferences hosted by the government and Fukushima Prefecture, as well as
to hold regular press conferences and lectures for the media, and to disseminate information
through its website and brochures. In addition, the company is actively accepting visitors to the
Fukushima Daiichi NPS and holding roundtable discussions, as it is very effective in forming acommon understanding to have people see the current status of decommissioning as it is (numberof visitors: 18,238 in FY2019, 4,322 in FY2020, and 6,138 in FY2021). On the other hand, in thecurrent situation where direct observation of Fukushima Daiichi NPS is limited and because of thefact that some people are not able to make direct inspections due to the new coronavirus infection,a virtual tour of the decommissioning site of the Fukushima Daiichi NPS has been available on
TEPCO's website since 2018. It is also important to proactively disseminate information utilizing
such simulated experience programs are more useful than ever.
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 80,000 visitors as of the end of April 2022, and since

166fiscal year 2020, the center has been collaborating with the "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 to the people of Fukushima to achieve both reconstruction anddecommissioning” established in March end, 2020 (hereinafter referred to as “Commitment”),
TEPCO has summarized their efforts for the accumulation of decommissioning work into thefollowing 3 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 themin a phased manner. At the same time, in order to steadily promote initiatives for local community
engagement, TEPCO has reformed their organization as needed. The local partnership promotion
group was established in the Fukushima Daiichi Decontamination & Decommissioning Engineering
Company in April 2020, TEPCO set up the specialized department working to engage with local
community at the Fukushima Daiichi NPS in October 2020, and the Hama-dori decommissioning
industry project office that directly reports to the president was also established. Based on thedivision of roles, they are engaged in internal/external coordination, field response to local
communities and consideration of medium-and-long-term direction.
With regard to the efforts ① and ②, in cooperation with the Fukushima Innovation Coast
Framework Promotion Organization and the Fukushima Soso Reconstruction Promotion
Organization, TEPCO has set up and is operating a joint consultation service to support matching
between local companies interested in participating in decommissioning projects and prime
contractors who are considering placing orders with local companies, as well as holding a matchingbusiness meetings between prime contractors and local companies, making individual visits to local
companies, and organizing inspection tours of Fukushima Daiichi NPS for local companies. In
addition, it is also conducting a survey of the needs of both prime contractors and local companies
regarding human resource development, and has started joint research with several universities,
Moreover, the contents of the "Medium- to-Long-Term Outlook in the Decommissioning" preparedin September 2020 are being updated as necessary to reflect the progress of decommissioning
work, and briefing sessions are being held for local commercial and industrial organizations, andlocal contractors as well as the prime contractors, paying close attention to the spread of the newcoronavirus infection.
In addition, with regard to the effort 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 technologies and products of relatively high difficulty and importance, which havebeen ordered outside Fukushima Prefecture, including overseas, can be completed in the
Hamadori region. In particular, for "development and design" to "manufacturing", TEPCO aims tocreate local employment, develop human resources, and build industrial and economic
infrastructure by establishing a joint venture with partner companies and working closely with local

167businesses (announced on April 27, 2022). In October 2022, as a joint venture for fuel debris
retrieval, a new engineering company was established (announced on October 3, 2022).
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 of the nuclear power station will lead to a loss of reputationand trust in the decommissioning of the nuclear power station not only in the local community but
also in society as a whole, which will not only delay the decommissioning of the nuclear power
station but also hinder the reconstruction of Fukushima. For this reason, TEPCO needs to continue
to take various measures to promptly communicate the current status of decommissioning in aneasy-to-understand manner. In this regard, while the impact of the new coronavirus infection are
expected to continue for the foreseeable future, TEPCO will make active use of rapidly developing
tools such as virtual tour programs and online conference systems, and it is also important tostrengthen communication that is possible even in non-face-to-face and non-contact situations,such as by further enhancing photo and video content.
Furthermore, the government, NDF, and TEPCO must work to build trust with local communities
by providing information more carefully under appropriate coordination. Therefore, capturing
opportunities to hold round-table talks and join local meetings/events, it is necessary to have directinteraction with local communities. Efforts should also be made for two-way communication by
conversation, including listening to their concerns and questions carefully through events such as
International Forums, and to deliver accurate information in an easy-to-understand and carefulmanner. In addition, it is important that the community, TEPCO, the government, NDF, and relatedorganizations take these opportunities to deepen their knowledge together in the various changing
circumstances.
In particular, some remain opposed to the disposal policy of the ALPS-treated water, and local
governments and related organizations are strongly urged to provide accurate information, foster
understanding, and take all possible measures to prevent rumors. For that reason, 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 the measures to overcome rumors by communicating safety based on scientificevidence, providing support for capital investment and expansion of sales channels for fishermen,
and enhancing safety nets such as funds and compensation. TEPCO has been making efforts tosuppress 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). It is important to continue to do its
utmost to foster understanding of local communities, and to build a relationship of trust.

168

6.3.2.2 Issues and strategies related to the creation of a regional industrial and economic
base through decommissioning
As described in 6.3.1.2 (2), TEPCO is making various efforts to realize the "Commitment", butthese efforts will not produce visible results immediately and will require a certain period of time.
For the effort of "③ Creation of new local industries ", construction and operation of several new
facilities in the 2020s and establishment of joint ventures with partner companies were announced
on April 27, 2022. It is necessary to steadily promote and strengthen these effort, because they are
relatively large-scale investment and are expected to have a great economic impact on the
Hamadori area. 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, it is important to continue and strengthen the current activities in a
credible manner, including "① Increased participation of local enterprises" and "② Support for local
enterprises to step up". It is also important to carefully explain to local governments, commercial
and industrial organizations, and other organizations concerned the location and scale of new
decommissioning-related facilities, the schedule from construction to operation, and the status ofconsidering engagement with local communities in terms of employment, cooperation and orderplacement, and to proceed with the activities while gaining understanding and cooperation.
With the understanding of prime contractors, it is 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 2020, it became clear that local companies do not necessarily want to be the main contractor,
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. This
will contribute to the promotion of orders from local companies by adopting methods that are
beneficial to both parties. It is important to indicate that TEPCO will work together with the local
community and Fukushima prefecture for the long term decommissioning work in the future. For
example, by considering initiatives that will enable local companies to receive constant and acertain scale of orders, after analyzing the details of procurement and the characteristics of local
companies with relevant organizations while keeping in mind the decommissioning work.
At the same time, with regard to human resource development, the Fukushima Decommissioning
Engineer Training Center of the Fukushima Nuclear Energy Suppliers Council, which wasestablished in 2018, and has been providing education of radiation protection and special education
on specific matters such as low-voltage electricity handling, should be used to provide the training.
In parallel, specific studies and preparations for training specifically for local companies should beaccelerated. It is important to steadily promote these various efforts while responding to changes
in the situation as appropriate, and to build a foundation for local industry and economy throughthe decommissioning project and to develop local companies and human resources.

169

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 of it. In
particular, it is necessary to take into consideration a wide range of functions such as daily life andeducation so that not only single people but also families can live together with peace of mind. In
this regard, as well as promoting the return of residents, Fukushima prefecture opened "Fukushima
12-municipality Migration Support Center" that helps people move and settle in the 12
municipalities, mainly from outside the prefecture for accelerating 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.
It is also important to consider the possibility of collaboration and cooperation with these local
initiatives.
To steadily promote these efforts for coexistence with local community, it is essential tostrengthen the organizational structure within TEPCO and to have close cooperation between eachdepartment. As mentioned in 6.3.1.2 (2), TEPCO has been reorganizing itself to set up specialized
departments for regional symbiosis, and efforts to promote local industries throughdecommissioning are gradually moving forward, and gaining a certain level of recognition from thelocal community. While keeping this trend advancing steadily, it is important to further strengtheninternal 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 business meetings. NDF will provide appropriate support to TEPCO's efforts for regional
symbiosis, and will strive to strengthen cooperation and collaboration with local governments andrelated organizations.

170

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.

AWJ

Abrasive Water Jet

DOE

United States Department of Energy

FP

Fission Products

HIC

High Integrity Container

IAEA

International Atomic Energy Agency

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

PCV

Primary Containment Vessel

RPV

Reactor Pressure Vessel

S/C

Suppression Chamber

SED

Safety and Environmental Detriment

SGTS

Standby Gas Treatment System

TMI-2

Three Mile Island Nuclear Power Plant Unit 2

Penetration X-2

Penetration X-2 of PCV

Penetration X-6

Penetration X-6 of PCVCenter 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

Kashiwazaki-Kariwa Nuclear Power Station

171

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 remotely operated submersible survey vehicle (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 without destroying
the sample by using radiation, quantum, etc. emitted, scattered, ortransmitted 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)

172

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

Boric acid, sodium
chloride

Soluble neutron absorber (boric-acid solution)

173

ウェルシールド
Well shield
プラグplug

Operating floor

オペレーティングフロア
Spent階
4th4floor

使用済燃
Fuel
Pool
料プール
(SFP)
（SFP）

Component

機器ピット
Pit

Primary
原子炉格納容器Containment（PCV）
Vessel (PCV)
Reactor
原子炉圧力容器Pressure（RPV）
Vessel (RPV)階
3rd3floor階
2nd2floor

ペデスタル
Pedestal

Vent Tube
ベント管

11st階floor
1st 地下basement
Fl.
1階

Suppression
サプレッション
Chamber(S/C)
チェンバ（S/C）

Torus room
トーラス室

(Courtesy of IRID)

Fig. 48 Structural drawing inside Reactor building

Top cover of RPV
原子炉圧力容器上蓋
Steam dryer
蒸気乾燥器
RPV body
原子炉圧力容器本体
Steam separator
気水分離器
Water-feed
sparger
給水スパージャCore spray piping
炉心スプレイ配管

Upper
grid plate
上部格子板
Fuel
assembly
燃料集合体

Core shroud
炉心シュラウドControl rod
制御棒

Core炉心支持板
support plate
Fuel assembly

Neutronflux measuring guide
中性子束計測案内

Jet pump
ジェットポンプ

Differential pressure detector/
Piping of Boric差圧検出/
acid solution
管
injection system
ホウ酸水注入系配管

制御棒駆動機構
Control Rod Drive Mechanism
原子炉圧力容器用
Pedestal for RPV
ペデスタル(Courtesy of IRID)

Fig. 49 Structural drawing inside Reactor Pressure Vessel (RPV)174

List of Attachment
Contents
Attachment 1 Revision of the Mid-and-Long-term Roadmap and the earlier published TechnicalStrategic Plan....................................................................................................... 176
Attachment 2 Major risk reduction measures performed to date and future course of action .. 178
Attachment 3 Overview of SED indicator .................................................................................. 184
Attachment 4 Risk sources that are not explicitly addressed in the major risk sources ........... 190
Attachment 5 Change in risk over time ..................................................................................... 193
Attachment 6 Coverage of fuel debris retrieval ......................................................................... 194
Attachment 7 Changes in considerations on retrieval methods in the previous TechnicalStrategic Plans ..................................................................................................... 196
Attachment 8 Terms related to radioactive waste management ............................................... 201
Attachment 9 Disposal of radioactive waste,, ............................................................................ 202
Attachment 10 Overall image of Storage Management Plan for the Fukushima Daiichi NPS 205
Attachment 11 R&D medium-to-long-term plan......................................................................... 207
Attachment 12 Current progress of the Project of Decommissioning and Contaminated Water
Management ...................................................................................................... 209
Attachment 13 Selected subjects in the Nuclear Energy Science & Technology and Human
Resource Development Project (the World Intelligence Project) ...................... 213
Attachment 14 Major activities related to enhancing international collaboration ...................... 218

175

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 1st 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, control, etc. were studied from a mid-andlong-term viewpoint based on the basic concept for ensure safety during disposal or for a proper
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 thestagnant 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

176

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 retrieval scale, and the efforts for the ALPS-treated water, while offering the prospects ofprocessing/disposal method and technology related to its safety,

177

Attachment 2

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. A 2-1. 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 Safety Management, because of implementation of safety measures 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 and decay 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

Risk level (Linear scale)(Logarithmic scale)

Risk level (Linear scale)

Risk level

demonstrate that a continuous risk reduction has been achieved.

0 1 2 3 4 5 6 7 8 9 10 11
Year 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

2.5

3

Year after the accident
Fuel debris
燃料デブリ

Fuel in SFPs
プール内燃料

4

5

6

7

8

9

10

11

Year after the accident

Contaminated
汚染水等
water, etc.

Fuel debris
燃料デブリ

Fuel in SFPs
プール内燃料

Contaminated

汚染水等
water, etc.

Evaluation of fuel in SFP 8 years after the accident occurred reflects the results of water temperature rise in thetesting on SFP cooling shutdown. (For detail, see Fig. 3 in Chapter 2 of main part.)
Fig. A2- 1 Reduction of risks contained in the Fukushima Daiichi NPS

178

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. A2-2. With a logarithmic scale, risk sources can be indicated thatare too small to be displayed in the linear scale of Fig. A2- 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. A2- 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 is higher than the assessment of the Technical Strategic Plan 2021 (10 years after theaccident), because some ALPS slurry stored in HICs affected by beta irradiation need to betransferred. In addition, as for the water stored in tanks (flanged tank and welded tank), the risk
level is higher than 10 years after the accident by reflecting the high radioactivity levels of strontium
detected in the remaining concentrated saltwater in the flanged tanks during 2021. However, since
the treatment of stored water in flanged tanks itself was in progress, the actual risk level was
considered to be higher (broken line: Stored water in tanks (estimated)) than the level shown in the

Risk level (Logarithmic scale)Fig. A2-2 (solid line : stored water in tanks).

サイト全体
Site
total
プール内燃料Fuelin SFPs
燃料デブリ
FueldebrisStagnant
water in buildings
建屋内滞留水＋ゼオライト土嚢+ Zeolite sandbags
トレンチ内汚染水
Contaminatedwater in trenches

Storedwater in tanks
タンク内貯留水

タンク内貯留水（推定）Storedwater in tanks (Estimated)
Secondarywaste generated by
水処理二次廃棄物
water treatment
Contaminatedstructures, etc. in
建屋内汚染構造物等
buildings

ガレキ等etc.
Rubbles,

0

1

2

3

4

5

6

7

8

9

10

11

Year after the accident

Fig. A2- 2 Change in the risk level for each major risk source

179

(1)

Fuel in SFPs
From one year after the accident, rubble was removed and a cover for fuel removal was installed

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 Safety Management, and the risk level was lowered (completed in2014)118.
Although the effect of risk level reduction was observed due to the decrease in 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 (in 2015) in preparation
for removal of fuel in SFP119. In order to prevent dust scattering during rubble removal, a large
cover will be installed by FY2023, and fuel removal from SFP is planned to start in FY2027 to
FY2028.120.
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 FY2026120.
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 2021121.
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 8th 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 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
Safety Management; however, this effect is currently lost.

118 Decommissioning project, Status of the decommissioning work, Fuel removal work of Unit 4, (Website), Tokyo

Electric Power Company Holdings, Inc.
119 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.
120 Mid-and-Long-term Decommissioning Action Plan (March 31, 2022), Tokyo Electric Power Company Holdings,
Inc.
121 Decommissioning project, Status of the decommissioning work, Fuel removal from spent fuel pool in Unit 3,(Website), Tokyo Electric Power Company Holdings, Inc.

180

Stagnant water in buildings + Zeolite sandbags(3)

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), theeffect 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.
Contaminated water in trenches(4)

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)122. 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 123.
Stored water in tanks(5)

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)124.
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

122 Decommissioning project, Status of the decommissioning work, Removal of contaminated water in seawater

pipe trenches, (Website), Tokyo Electric Power Company Holdings, Inc.
98th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 1 ”Work
Schedule for Instruction Items to be Considered Based on the Measures for Mid-and-long-term Risk Reduction
at TEPCO’s Fukushima Daiichi NPS (Risk Map), (March 2021 Edition)”, Tokyo Electric Power Company Holdings,
Inc.
124 Decommissioning project, Status of the decommissioning work, Purification of contaminated water, (Website),Tokyo Electric Power Company Holdings, Inc.
123 The181

tanks is being collected for dismantling the tanks, 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 (in2019), 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 higher than the assessment of Technical Strategic Plan 2021
due to the ALPS slurry stored in the HIC to be transferred and is the dominant factor among thesecondary waste generated by water treatment. HICs that are evaluated to have exceeded or areclose to exceeding the standard value for cumulative absorbed dose are planned to be transferredduring FY2023. Although the number of HICs whose cumulative absorbed dose approached thestandard value will gradually increase over time, ensuring that the cumulative absorbed dose canbe managed so as not to exceed 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 to the risk level though, sludge is not newly generated at present, andthus, the risk level of the total secondary waste generated by water treatment is not on an
increasing trend. As a tsunami countermeasure, the decontamination sludge stored in the mainprocess building (T.P. 8.5m) will be extracted (planned for FY2023), placed in a storage container,
and transferred to the elevated area (T.P. 33.5m) 125.
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
There is no significant change at the present moment in 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 the reactor buildings, PCVs or RPVs that arecontaminated by dispersed radioactive materials caused by the accident.
(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 Safety
Management, and the rubbles stored in outdoor sheet covered storage and outdoor accumulation
are of the highest risk level. In the past, the facilities with better management condition have beenenhanced by soil covered temporary storage facilities (in 2012), felled tree temporary storage pool(in 2013), expansion of solid waste storage facilities (in 2018), etc. In addition, the rubble from125 Safety Monitoring Council for the decommissioning of Fukushima Daiichi NPS (March 8, 2021), Reference 5-1

182temporary storage facilities was transferred to the better-controlled solid waste storage facility (in2020). With the start of operation of the additional solid waste incineration facility (May 2022),
combustible rubbles and other materials stored outdoors can be transferred to the solid waste
storage facility after incineration to reduce their volume. Furthermore, outdoor temporary storageis 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 Plan126.

126 The Solid Waste Storage Management Plan at the Fukushima Daiichi NPS (July 2022 Edition), Tokyo ElectricPower Company Holdings, Inc.

183

Attachment 3 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 indicator127 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 “Safety Management” of risk
sources.
𝑆𝐸𝐷 = (𝑅𝐻𝑃 + 𝐶𝐻𝑃) × (𝐹𝐷 × 𝑊𝑈𝐷)4or
𝑆𝐸𝐷 = (𝑅𝐻𝑃 + 𝐶𝐻𝑃) × (𝑆𝑆𝑅 × 𝐵𝐸𝑅 × 𝐶𝑈)4
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 dose128 . 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(𝑚3 ) = 𝑅𝑎𝑑𝑖𝑜𝑎𝑐𝑡𝑖𝑣𝑖𝑡𝑦(𝑇𝐵𝑞) × 𝑆𝑇𝑃(𝑚3 ⁄𝑇𝐵𝑞)

127 NDA Prioritization – Calculation of Safety and Environmental Detriment score, EPGR02 Rev.6, April 2011.
128 Instruction for the calculation of the Radiological Hazard Potential, EGPR02-WI01 Rev.3, March 2010.

184Form Factor (FF), as shown in Table A3-1, 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.
In Table A3-1, 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 A3-2, 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) 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 A3-3 and Table A3-4 respectively.
(3) Safety Management - SSR, BER and CU
The definition of SSR, BER and CU used for Safety Management assessment for contaminatedsoil is the same as the one defined by the NDA and each score is shown in Table A3-5.
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.

185

Table A3-1 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

4Adhesive* 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 A3-2 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 A3-3 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

186

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.
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.

15

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.

187

Category

Table A3-4 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.

188

Table A3-5 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

189

Attachment 4

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 A4-1 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.129.
Table A4- 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 1.9×1013Bq130. 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 131 . Dismantling and removal policies areunder consideration.

Accumulated water onsite

Extracted by the comprehensive risk inspection performed in
2015132. Since then, the concentration of radioactive materials andvolume of water are being checked accordingly 133.

Fuel in Units 5/6 SFP

Unit 5 : 1,374, Unit 6 : 1,456134

Spent control rods,
etc.

Spent control rods, etc.: 23,547. Shroud fragments, etc.: 193
m3135. The major nuclide is Co-60.

In-pool water

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

129 NRA, Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS (Risk Map)”, (March 2021

Edition)130 The 87th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 3-5: Progressof the treatment of stagnant water in buildings, etc.”
131 The 44th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated

Water Treatment “Reference 3-6: On-site Monitoring Status (Conditions of Water Discharge Channels in Units
1 to 3 and Underground Water Storage Tanks)”
132 Comprehensive Risk Inspection of Fukushima Daiichi NPS that impacts outside the Site Boundary - Review
Results - (April 28, 2015) Tokyo Electric Power Co., Inc.
133 The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water Treatment “Reference 1: Status of contaminated water and other accumulated water on
the premises (as of March 24, 2022)”
134 The 100th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water Treatment “Reference 3-2 : Storage status of spent fuel , etc.”
135 NRA, Material of interview with the licensee “Solid Waste at Fukushima Daiichi NPS” June 18, 2021, Tokyo
Electric Power Company Holdings, Inc.

190

Table A4- 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 stored136. 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 drain pipes. The roof drain
was repaired and closed 137 . Facing of the Elevation T.P.2m,
T.P.6m and T.P.8.5m was completed138.

Megafloat

The work of bottoming and internal filling was completed139.
Revetment maintenance and embankment work are underway.

Dust in operating floor

Below the target value of release control (1×107 Bq/h).
Gradually declining140.

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 observed141.

Drainage

In drainage A, Cs-137: lowered to ND ~ 23 Bq/L 142. 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 installed143,
and measures such as operation of discriminating-type PSF
monitors were taken144.

136 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.
137 The 78th Secretariat Meeting of the Team for Countermeasures for Decommissioning and Contaminated Water
Treatment, “Reference 3-1: Progress Status in Rooftop Rainwater Measures”
138 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”
139 The 81st Secretariat Meeting of the Team for Countermeasures for Decommissioning and Contaminated Water
Treatment, “Reference 3-1:Progress Status of Megafloat Project at Fukushima Daiichi NPS to Reduce Tsunami
Risks
140 Daily Analysis Results of Radioactive Materials at Fukushima Daiichi NPS, (Website), Tokyo Electric Power
Company Holdings, Inc.
141 The 14th Study Committee on Accident Analysis of the Fukushima Daiichi NPS “Reference 3: Progress of onsite Investigation”
142 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”
143 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)”
144 The 74th Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated
Water Treatment “Reference 3-6: Starting of operation of PSF monitor in the drainage K”

191

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 completed145.
Exhaust stack of Units 3/4 : Measured 3mSv/h at the base146.
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
Materials147

145 “Completion of Dismantling of Exhaust Stack of Units 1/2 at Fukushima Daiichi NPS” (May 1, 2020), Tokyo

Electric Power Company Holdings, Inc.
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)”」
147 Results of daily analysis of Radioactive substances at Fukushima Daiichi Nuclear Power Station (Website ,Tokyo Electric Power Company Holdings, Inc.
146

192

Attachment 5

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. A5-1 Change in risk over time148

148 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)..

193

Attachment 6

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 IAEA149,150.
The condition inside PCV is as shown in Fig. A6-1, 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 A6-1, 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
149 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)
150 Managing the Unexpected in Decommissioning, IAEA Nuclear Energy Series No. NW-T-2.8, Vienna (2016)194

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. A6-2. 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 to solidify inconjunction with structural materials. It is also called lava-like FCM due to its appearance.
Corium : A substance that mainly fuel assembly and component of control rod as core component
have molten and solidified.
Crust : A hard outer layer or shell on the surface. When molten fuel is solidified, it may become ahard solid state of shell because of higher cooling speed on the surface layer.
MCCI product : A product generated by Molten Core Concrete Interaction, that includes calcium,silicone, etc. which are concrete component.
Material with fuel : A substance that molten fuel has adhered to material that does not include fuelcomponent originally, like CRD housing, grating and s, then solidified. It is
possible to confirm fuel adhesion state by sight.
Material contaminated by fuel : A substance that adhering molten fuel cannot be confirmed by sight,
but fuel component can be detected with α ray detector. It is
impossible to locate fuel component other than using by electron
microscope because particle of adhered fuel component isextremely small and whit.

195

Attachment 7

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) to fuel 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 andexamined. (See Figures 1 to 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→→→

Submersion-Top accessmethodPartial submersion-Top
access method
Partial submersion-Sideaccess method

Fig. A7-1. Examination of the methods by a combination of the PCV water level andaccess directions to fuel debris

196

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 theupper end of the core region is referred to as thesubmersion 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 theair.
(Supplement) It is currently assumed that there is fuel debris exposedto the air at the water level below the upper end of thecore region. This is referred to as the partial submersion
method.

⚫

Dry method: Expose the entire area of the distributed fuel debris tothe air, with no water-cooling or spraying at all.

Fig. A7-2. Classification of methods according to the PCV water level
Top-access

Side-access

Bottom-accessFig. A7-3. Access direction to fuel debris197

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] systeminstallations and area construction}), all of which should be satisfied for the safe retrieval of fueldebris. Then, based on the comprehensive evaluation based on the five guiding principles (safe,
proven, efficient, timely, and field-oriented), strategic recommendations for determining a fueldebris 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:

198

○
○
○

The bottom of PCV is most accessible and a certain amount of knowledge about it has already been
accumulated through the investigation inside PCV;
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. A7-4.
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.
Lastly, the Technical Strategic Plans 2020 and 2021 proposed approaches and policies for fueldebris retrieval methods. Since no new progress has been made in examining the methods
themselves, however, this Attachment omits the details of the Strategic Plans.

199

Fig. A7-4 Flow of examinations for determining the fuel debris retrieval method for the
first implementing unit”
200Attachment 8

Terms related to radioactive waste management

IAEA Safety Requirements GSR-Part 5 151 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 A8-1. 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. A8-1 Terms related to radioactive waste management (IAEA)152 and their translation
examples (For the Japanese translation example, refer to the materials of the Japan
Atomic Energy153,154)
151 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)
152 IAEA, IAEA Safety Glossary Terminology Used in Nuclear Safety and Radiation Protection 2007 Edition, p.216,(2007).
153.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”
154 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).

201

Attachment 9

Disposal of radioactive waste155,156,157

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) 158
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”159 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. A9-1. Each classification is also shown in Table A9-1.

Fig. A9-1 Conceptual diagram of waste classification
155 Osamu Tochiyama,

Principles and Basics of Radioactive Waste Disposal, Radioactive Waste Management
Funding and Research Center (a Public Interest Incorporated Foundation) (2016)156 https://www.enecho.meti.go.jp/category/electricity_and_gas/nuclear/rw/
157 https://www.fepc.or.jp/nuclear/haikibutsu/index.html
158 IAEA SSR-5 "Disposal of Radioactive Waste" (2011)
159 IAEA GSG-1 "Classification of Radioactive Waste" (2009)202

Table A9-1

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.

203

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 A9-2.
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 A9-2

Fig. A9-2

Types of Radioactive Waste Generated by the Operation of Nuclear Power Plants

Japan Nuclear Fuel Ltd. Low-level Radioactive Waste Disposal Center
204

Attachment 10

Overall image of Storage Management Plan for the Fukushima Daiichi NPS 160

160 TEPCO, Solid Waste Storage Management Plan for Fukushima Daichi Nuclear Power Station of Tokyo ElectricPower Company Holdings, Inc., July 2021 edition (issued on July 29, 2021)

205

(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. A10-1 Present and future storage conditions of “rubble, etc.” and “secondary waste
generated by water treatment” on site of the Fukushima Daiichi NPS

206

Attachment 11 R&D medium-to-long-term plan
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

KeyMilestones

2021

2022

2023

2024

2027

Phase 22033～

Phase 3-(1)Start of debris
retrieval at the first
implementing unit

(Next phase)［１］Trial retrieval at Unit 2[A] Trial retrieval/
Gradual expansion of fuel debris retrieval

Further expansion of fueldebris retrieval scale

Gradual expansion of retrieval scale

Legends :Improvement of the environment inside the buildings

Trial retrieval (internal investigations and fueldebris sampling), Characterization of fueldebrisMain Processes*1: Reveraging Naraha Center for Remote Control Technology Development

Basic/fundamental research

Manufacturing, testing and installation of retrieval devices, etc. *1,
Operational change of the safety systems, Removal of obstacles
in openings, etc.

Described based on
TEPCO DAP 2022
Practical application development
and Applied research

Development of technology for detailed PCV internal
investigations

Major studies on
debris retrieval

Key Technical issues: Where R&D results are applied: Linkage between main processes［２］Gradual expansion of retrieval scale at Unit 2
Improvement of the environment
inside the buildings
Fuel debris retrieval facility/Safety system/Fuel debris temporary storage facility/Maintenance facility
Design, manufacturing and testing(Reveraging of the Naraha Remote Technology Development Center)

Installation
Fuel debris retrieval (Gradual expansion of scale)Operation of temporary storage facility for fuel debris
Operation of maintenance equipment

Technological development for gradual expansion of retrieval scaleTechnical issues for gradual expansion of fuel debris retrieval① Providing retrieval system (improving device durability, verifying passing with transport truck)② Manufacturing equipment for gradual expansion of fuel debris retrieval③ Preparing storage facilities for fuel debris/waste

To fuel debris characterization［１］Environmental improvement
Environmental improvement
inside and outside the Unit 1 buildings

Inside the buildings: Radiation dose reduction/Removal of obstacles, etc.
Outside the buildings: Removal of SGTS piping/lower part of exhaust stacks at Units 1/2, and transformers, etc. => Securing space *2

Environmental improvement
inside and outside the Unit 3 buildings

Inside the buildings: PCV water level lowering/Radiation dose reduction, etc.
Outside the buildings: Removal of exhaust stacks and transformers at Units 3/4,
Improvement of the basement floor, etc. => Securing space *2*2: Added buildings, maintenance buildings, storage buildings

Development of technology for environmental improvement inside/outside reactor buildings
Development of assessment methods for deterioration status, etc., of building frames
To achieve lowering thePCV water leveland equipment
Target : - Improvement of a system for work planning to reduceradiation exposure- Establishment of measures and evaluation methods
considering the effects of corrosion on long-term
integrity

Research to visualize the distribution of radioactive materials and contribute to the reduction of radiation exposure
Research on the relationship between radiation and corrosion and material degradation［２］PCV/RPV internal investigations, Characterization of fuel debris
Development of technology for detailed PCVinternal investigations at Unit 1

PCV internal investigations
at Unit 3
To RPV internal investigation design

Development of RPV internal investigation technology/Advancement of RPV internal investigation
RPV internal investigations
at Unit 2
Development of technology for RPV quick internal investigation[B] Further expansion of fuel debris retrieval

Characterization of fuel debris

Demonstration of analytical technology(Radioactive material analysis/Utilization of r esearch facilities)

Development of analytical technology for fuel debris characterization

Target : - Establishment of analytical evaluation method
including non-destructive measurement, and methods
for radioactive waste sorting and inventory evaluation- Establishment of remote/in-situ/rapid analysis techniqueResearch on analytical evaluation methods for retrieved fuel debris, including non-destructive measurement
Research on the advancement of analytical techniques for radioactive material and nuclear fuel material

Advanced estimation of the situation in the PCV
Target : - Grasping of in-core situation and refinement ofunderstanding of FP behavior in the PCV based on
on-site knowledge and actual debris data

Estimation of in-core conditions and research on accident events by analyzing and evaluating fuel debris［３］Retrieval equipment, safety systems, maintenance equipment, and storage facility *3

Conceptual study

Verification of theactual site applicability

Study of safety systems/maintenance methods*3: Main processes for proceeding with the study on Unit 3 as a preceding case

Reflecting findings obtained
after the start of a gradualscale expansion

Reflecting the results of Trial
retrieval (Internal investigation /fuel debris sampling)

Design of safety system / maintenance installations
Forecast

Development of technologies toward further expansion of fuel debris and in-core structure retrieval
Side-access retrieval method: Examination and enhancement of elemental technologies, Verification of the actual site applicability*4: Process for side-access retrieval installation
Manufacturing, installation and testing of retrieval equipment *4/
training facility and fuel debris retrieval

Design of retrieval installations *4

Manufacturing, installation and testingof safety systems/ maintenance installations＊5
Sharing issues to strengthen cooperation among TEPCO, JAEA and NDF- An examples of issue Issues for conceptual study/scenario development of fuel debris retrieval

Top-accessretrieval installation/
retrieval
Retrievalin otherunits

Backcast＊5：Being considered to build a basis for analyzing and sharing,
including long-term issues beyond 10 years

Top access method: Conceptual study, examination and enhancement of elemental technologies
Research on safety assurance during fuel debris retrieval and storage
Research to visualize the distribution of radioactive materials and contribute to the reduction of radiation exposure

Target : - Eestablishment of effective evaluation methods for
ensuring safety during long-term in-core residency
and after retrieval- Improvement of a system for work planning to reduceradiation exposure

Technical issues toward further expansion of fuel debris retrieval① Development of fuel debris retrieval method (side-access/top-access/of common)
Development of access facility installation method, dismantling technology, technology for realizing a removal concept for large structure, and crashing and collection technology② Development of safety systems (liquid-phase system/gas-phase system and criticality control)
Strengthening of function to remove radioactive material, development of boric acid management technology such as boric acid recovery, evaluation/collection of dust behavior,and establishment of containment function of radioactive material③ Development of safety assessment technology Data acquisition of debris dispersion rate and analytical method for evaluating radiation exposure④ Development of technologies for maintaining remote equipment

Development of decontamination and maintenance technology for contaminated remote equipment

Basic design of fuel debris storage facilities

Equipment design, Equipment manufacturing

Trial operation, Start of operation

Development of technology for collection, transfer and storage of fuel debris
Resarch onsafety assurance during fuel debris retrievaland storage

Development of support technology for 1F decommissioning integrated management

207

Target : - Establish safety and risk assessment for fueldebris storage

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

2021

2022

2023

2024

2027

Phase 2

Key
Milestones

Phase 3-(1)Start of debris
retrieval at the first
implementing unit

Gradual expansion of retrieval scale

2033～(Next phase)
Further expansion of fueldebris retrieval scale［１］Characterization
Characterization
Acquisition and maagement of analysis data, etc.
Improvement of efficiency in characterization[C] Waste Management

Technical issues for characterization① Development of non-destructive measurement technology ② Development of analytical techniques forimportant nuclides 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
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.

［２］Storage
Storage
Development of alpha surface
contamination measurement technology

Research on waste reduction through reuse［３］Processing/disposal
Development of processing/disposal concept
and safety asessment methods

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. From this time
onward, the plan is being prepared by incorporating basic/fundamental research into practical application development and app lied research, such as the Decommissioning and Contaminated water/Treated water
Project, as an integral part.

208

Attachment 12 Current progress of the Project of Decommissioning and Contaminated
Water Management161【Ａ】Trial retrieval/Gradual expansion of fuel debris retrieval［Ａ１］Trial retrieval in Unit 2・Development of technologies for in-depth investigation of PCV inside (Field demonstration oftechnologies for in-depth investigation using penetration X-6) (FY2018 – 2019)(Related projects) Development of technologies for the detection of fuel debris inside reactors(using muon) (FY 2014 - 2015)
Development of investigation technologies of inside of PCV (FY 2016 - 2017)
Development of technologies for in-depth investigation of PCV inside (FY2017 - 2018)［Ａ２］Gradual expansion of fuel debris retrieval in Unit 2・Development of technologies for retrieving fuel debris to be gradually expanded in scale(FY2017 – 2022)*Change in the project name in 2020 : (Former title : Development of sampling technologies
for retrieving fuel debris and internal structures)【Ｂ】Further expansion of fuel debris retrieval in scale［Ｂ１］Environmental improvement of inside and outside the buildings
・Development of technology for environmental improvement of inside the buildings (FY 2021 2022)
・Development of evaluation methods of seismic performances of RPV and PCV and theimpacts of the damages (FY 2016 - 2017)(Related projects) Development of evaluation methods for the structural integrity of RPV andPCV (FY 2011 - 2013)
Development of evaluation methods for the structural integrity of RPV andPCV (FY 2014 - 2015)
・Development of remote decontamination technology in the reactor building (FY 2014 - 2015)(Related projects) Development of remote decontamination technology in the reactor building(FY 2011 - 2013)［Ｂ２］Investigation of PCV/RPV inside and grasping properties of fuel debris① Development of technologies for in-depth investigation of PCV inside (FY2021 – 2022)(Related projects) Development of technologies for in-depth investigation of PCV inside (Field
161 Information Portal for the Research and Development for the Fukushima Daiichi Decommissioning(http://www.drd-portal.jp/)209demonstration of technologies for in-depth internal investigation assuming
deposit control measures) (FY2018 – 2020)② Development of investigation technologies inside RPV (FY 2013 - 2023)③ Development of analytical and estimation techniques for characterization of fuel debris(FY2017 – 2022)(Related projects) Characterization of fuel debris using mock-up debris and development of fueldebris processing technologies (FY 2011 - 2014)
Construction of material accountancy method related to fuel debris (FY 2011
- 2013)
Property analysis of actual debris (FY 2014)
Grasping properties of fuel debris (FY 2015 - 2016)
Development of techniques for characterizing and analyzing fuel debris (FY2017 - 2018)(Other R&D)
・Formulation of comprehensive radiation dose reduction plan (FY 2012 - 2013)
・Development of technologies for non-destructive detection of radioactive material deposited in
S/C, etc. (FY 2014)
・Advancement of comprehensive grasping of state inside reactor (FY 2016 - 2017)(Related projects) Advancement of accident progression analysis technology for assessing
conditions inside reactor (FY 2011)
Assessing conditions inside reactor by advancement of accident
progression analysis technology (FY 2012 - 2013)
Assessing conditions inside reactor through application of severe accident
analysis code (FY 2014)
Advancement of grasping conditions inside reactor by accident progression
analysis and actual data, etc. (FY 2015)［Ｂ３］Retrieval facility/safety system/maintenance facility/storage①

Development of retrieval method of fuel debris (FY2021 – 2022)(Related projects) Development of technologies for retrieving fuel debris and internal structures(FY 2014)
Advancement of retrieval method and system of fuel debris and internal
structures (FY 2015 - 2018)210

Development of basic technologies for retrieving fuel debris and internal
structure (FY 2015 – 2018)
Development of technologies toward further expansion in scale for retrieving
fuel debris and internal structures (FY2019 - 2021)②

Safety system (FY2021 – 2022)(Related projects) Development of criticality control technologies of fuel debris (FY 2012 2016)③

Development of technologies for maintaining remote equipment (FY2021 – 2022)④

Development of technologies for containing, transferring, and storing fuel debris (FY 2014 2022)⑤

Development of support technologies for integrated management of Fukushima Daiichi NPS
decommissioning (FY2021 – 2022)(Other R&D)
・Development of PCV closed water circulation systems (FY 2018 - 2019)
・Advancement of fundamental technologies for retrieving fuel debris and internal structures (FY2017 - 2018)(Related projects) Development of fundamental technologies for retrieving fuel debris andinternal structure (FY 2015 - 2016)
・Development of repair methods for leak spots in PCV (FY 2016 - 2017)(Related projects) Development of identification technology of leaks in PCVs (FY 2011 - 2013)
Development of repair method for PCVs (FY 2011 - 2013)
Development of repair (water stoppage) technology toward water filling in
PCV (FY 2014 - 2015)
・Full-scale test of repair methods for leak spots in PCV (FY 2016 - 2017)(Related projects) Full-scale test of repair methods for leak spots in PCV (FY 2014 - 2015)
・Development of corrosion inhibition technology for RPV and PCV (FY 2016)【Ｃ】Waste management
・Research and development of processing and disposal of solid waste (FY 2013 - 2023)(Related projects) Development of technologies for processing/disposal of secondary waste by211

treatment of contaminated water (FY 2012)
Development of technologies for processing/disposal of radioactive waste(FY 2012)
Development of technologies for processing/disposal of waste generated
from the accident (FY2014)(Other R&D)
【Ⅰ】Spent fuel management
・Evaluation of long-term integrity of fuel assembly removed from SFPs (FY 2015- 2016)(Related projects) Evaluation of long-term structural integrity of fuel assemblies removed from
SFPs (FY 2012 - 2014)
・Investigation of method for processing damaged fuel, etc. removed from SFPs (FY 2013 2014)【Ⅱ】Contaminated water management

Verification tests of tritium separation technologies (FY 2014 - 2015)



Verification of technologies for contaminated water treatment (FY 2014)

Large-scale verification of impermeable walls (frozen wall) (FY 2014)

Development and verification of high-performance multi-nuclide removal equipment (highperformance ALPS) (FY 2014)212

Attachment 13

Selected subjects in the Nuclear Energy Science & Technology and
Human Resource Development Project (the World Intelligence Project)

Selected subjects in the 2021 issue-solving decommissioning research program (8 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Shibaura Institute of
Research and development of a hybrid-type
Masaki Maeda
Technology, Tokyo
evaluation method of the long-term integrity of reactor [Tohoku University]
Institute of Technology,
buildings using building response monitoring andNippon Institute ofdamage imaging technology

Technology, National
Institute of Technology,
Kisarazu College, Japan
Atomic Energy Agency(JAEA)

Clarification of the actual debris formation mechanism
by synthesizing mock-up debris based on the analysis
results of materials around fuel debris and thesophistication of the debris property database byverifying the severe accident progression analysis
results
Study on water sealing, repair, and stabilization of thelower part of the PCV by geopolymer and othersubstances

Masayoshi Uno[University of Fukui]

Establishment of a characterization analysis method
for small amounts of fuel debris using the world's firstisotope analyzer

Tetsuo Sakamoto[Kogakuin University]

Shunichi Suzuki[The University of Tokyo]

Sophistication of mass spectrometry of single particles Atsushi Toyoshima
for actual measurement of alpha particles[Osaka University]
Research and development of a robotic system for
Keitaro Hitomi
source exploration through cooperative measurement [Tohoku University]

Development of a continuous tritium water monitoring
method through mid-infrared laser spectroscopy

Ryo Yasuhara[National Institutes of
Natural Sciences,
National Institute for
Fusion Science]
Challenges to the novel hybrid solidification of difficult- Masahiko Nakase
to-stabilize nuclides from the Fukushima NPS[Tokyo Institute ofaccident and development/safety assessment of aTechnology]
rational disposal concept

Osaka University,
Tokyo Institute ofTechnology, Tohoku
University, Japan
Atomic Energy Agency(JAEA)
Tokyo City University,
National Institute ofAdvanced Industrial
Science andTechnology, ATOX Co.,
Ltd., Japan Atomic
Energy Agency (JAEA)
Nagoya University,
Tokyo Electric Power
Company Holdings Inc.,
Japan Atomic Energy
Agency (JAEA)

Kyoto University
National Institute ofTechnology, Toyama
College, Fukushima
University, Japan
Atomic Energy Agency(JAEA)
Hirosaki University

Radioactive Waste
Management Funding
and Research Center(RWMC), Okayama
University of Science,
Tohoku University,
Japan Atomic Energy
Agency (JAEA)

Selected subjects in the 2021 international cooperative decommissioning research program (4 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Japan-UK joint research on nuclear energy: 2 subjects

213

Study on radioactive aerosol control anddecontamination in decommissioning the Fukushima
Daiichi NPS

Shuichiro Miwa
[The University of Tokyo]

Navigation and control of a mechanical manipulator
for fuel debris retrieval

Hajime Asama[The University of Tokyo]

Japan-Russia joint research on nuclear energy: 2 subjects
Reducing the uncertainties of FPs and debris
Yoshinao Kobayashi
behavior and determining in-core contamination and[Tokyo Institute ofdebris properties based on the accident progression
Technology]
scenario for Fukushima Daiichi NPS Units 2 and 3
Sophistication of fuel debris criticality analysis
technology using the non-contact measurement
methodToru Obara[Tokyo Institute ofTechnology]

ATOX Co., Ltd., Japan
Atomic Energy Agency(JAEA), University ofBristol
RITECS Inc, Japan
Atomic Energy Agency(JAEA), University of
SussexKyushu University,
Japan Atomic Energy
Agency (JAEA), SaintPetersburg State
University
National Institute ofAdvanced Industrial
Science and Technology,
National Research
Nuclear University(MEPhI)

Selected subjects in the 2020 issue-solving decommissioning research program (8 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Grant-in-aid for young scientists: 2 subjects
Investigation of environment-induced property
Yang Huilong
Nagaoka University ofchanges and cracking behavior in fuel debris[The University of Tokyo] Technology
Development of genetic and electrochemical
Akihiro Okamoto
Japan Agency for
diagnosis and inhibition technologies for invisible[National Institute forMarine-Earth Sciencecorrosion caused by microorganisms
Materials Scienceand Technology,(NIMS)]
Central ResearchInstitute of ElectricPower Industry, Japan
Atomic Energy Agency(JAEA)
General research: 6 subjects
Hokkaido University,
Technology development of diamond-base neutron
Manobu Tanaka
sensors and radiation-resistive integrated-circuits for [High Energy Accelerator National Institute ofa shielding-free criticality approach monitoring system Research Organization] Advanced Industrial

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

Yutaka Watanabe[Tohoku University]

Development of rapid and sensitive radionuclide
Hirofumi Shinohara
analysis method through the simultaneous analysis of [Japan Chemicalbeta, gamma, and X-rays
Analysis Center]

Quantitative evaluation of long-term state changes ofcontaminated reinforced concrete considering theactual environments for rational disposal

214

Ippei Maruyama[The University of Tokyo]

Science and Technology,
Nagoya University,
Japan Atomic Energy
Agency (JAEA)
National Institutes for
Quantum Science andTechnology, National
Institute for Materials
Science (NIMS), Japan
Atomic Energy Agency(JAEA)
Niigata University,
Kyushu University, Taisei
Corporation, National
Institutes for Quantum
Science and Technology,
Japan Atomic Energy
Agency (JAEA)
National Institute forEnvironmental Studies,
Taiheiyo Consultant Co.,
LTD., Taiheiyo Cement
Corporation, Nagoya

Study on the rational treatment/disposal ofcontaminated concrete waste considering leachingalteration

Tamotsu Kozaki[Hokkaido University]

Challenge to the advancement of debris compositionand direct isotope measurement by microwaveenhanced LIBS

Yuji Ikeda[iLabo Co., Ltd]

University, Hokkaido
University, Japan Atomic
Energy Agency (JAEA)
University of Fukui,Central ResearchInstitute of ElectricPower Industry, Japan
Atomic Energy Agency(JAEA)
Japan Atomic Energy
Agency (JAEA)

Selected subjects in the 2020 international cooperative decommissioning research program (2 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Japan-UK joint research on nuclear energy: 2 subjects
National Institutes ofDevelopment of environmental mitigation technology Naoki Asao
Natural Sciences,with novel water purification agents[Shinshu University]

Research and development of the sample-return
technique for fuel debris using an unattended
underwater vehicle

So Kamada[National Institute of
Maritime, Port andAviation Technology,
National Maritime
Research Institute]

Institute for Molecular
Science, Tohoku
University, DiamondLight Source
High Energy Accelerator
Research Organization,
Japan Atomic Energy
Agency (JAEA),
Lancaster University

Selected subjects in the 2019 common-based nuclear research program (7 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Grant-in-aid for young scientists: 2 subjects
Japan Atomic Energy
Development of tailor-made adsorbents for uranium
Koichiro Takao
Agency (JAEA)
recovery from seawater on the basis of uranyl[Tokyo Institute ofcoordination chemistry
Technology]
Semi-autonomous remote-control technology of anMotoyasu Tanaka
articulated mobile robot to recover from stuck states[The University of ElectroCommunications]
General research: 5 subjects

Measurement methods for radioactive source
Akira Uritani
distribution inside reactor buildings using a one[Nagoya University]
dimensional optical 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[National Institutes for
Quantum Science andTechnology]
Development of radiation-hardened diamond image- Shinya Omagari
sensing devices[National Institute ofAdvanced Industrial
Science and Technology]

215

Japan Atomic Energy
Agency (JAEA)
Hiroshima University,
Osaka University(Cooperation within theinstitution)
The University of Tokyo

Hokkaido University

Selected subjects in the 2019 issue-solving decommissioning research program (4 subjects)
Subject of proposal
Study representative
Participating institution[Organization]
Osaka University, Japan
Estimation of the in-depth debris status of Fukushima Akifumi Yamaji
Atomic Energy Agency
Unit-2 and Unit-3 with multi-physics modeling[Waseda University]
Fluorination method for classification of the waste
generated by fuel debris removal

Daisuke Watanabe[Hitachi-GE Nuclear
Energy, Ltd.]
Takehiko Tsukahara[Tokyo Institute ofTechnology]

Development of a stable solidification technique for
ALPS sediment wastes with apatite ceramics

Challenge to the investigation of fuel debris in RPVwith an advanced super dragon articulated robot arm

Shuji Takahashi[Tokyo Institute ofTechnology](JAEA)
Saitama University,
Japan Atomic Energy
Agency (JAEA)

Central ResearchInstitute of ElectricPower Industry, Japan
Atomic Energy Agency(JAEA)
Japan Atomic Energy
Agency (JAEA)

Selected subjects in the 2019 decommissioning research program for research personnel development(4 subjects)
Subject of proposal

Study representative[Organization]
Hajime Asama[The University of Tokyo]

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

Yoshitaka Takagai[Fukushima University]

Development of extremely small amount analysis
technology for fuel debris analysis

Yasuyoshi Nagai[Tohoku University]

Takehiko Tsukahara[Tokyo Institute ofTechnology]

Participating institution
Fukushima University,
Kobe University, Japan
Atomic Energy Agency(JAEA)PerkinElmer Co., Ltd.,KAKEN Co.,Ltd., Japan
Atomic Energy Agency(JAEA)
Visible Information
Center, Inc., Japan
Atomic Energy Agency(JAEA)
Nagaoka University ofTechnology, Nippon
Nuclear Fuel
Development Co., Ltd.,
Kyushu University,
Japan Atomic Energy
Agency (JAEA)

Selected subjects in the 2019 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,
National Research
Nuclear University(MEPhI)

Study of corrosion and degradation of objects in a
nuclear reactor by microorganisms

Akio Kanai[Keio University]

RIKEN, Japan, Japan
Atomic Energy Agency(JAEA), Kazan State
University

Japan-UK joint research on nuclear energy: 2 subjects

216

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.,
Japan Atomic Energy
Agency (JAEA), The
University of Sheffield

Radiation tolerant rapid criticality monitoring withradiation-hardened FPGAs

Minoru Watanabe[Shizuoka University]

Kobe City College ofTechnology, Lancaster
University

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.

217

Attachment 14 Major activities related to enhancing international collaboration
Table A14-1 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 A14-2 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.

218

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 A14-3 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 A14-4 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

219

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 A14-5 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

220

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

221

METI
NRA
JAEA
NDF
TEPCO

MEXT
JAEA
IR
Tokyo Institute ofTechnology

METI
NDF
JAEA
TEPCO