Technical Strategic Plan 2020 for Decommissioning of
the Fukushima Daiichi Nuclear Power Station of Tokyo
Electric Power Company Holdings, Inc.

October 6, 2020

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.

Table of Contents
1. Introduction ................................................................................................................................... 1
1.1 Structure and system toward the decommissioning of the Fukushima Daiichi Nuclear
Power Station ......................................................................................................................... 2
1.2 The Strategic Plan .................................................................................................................. 4
1.2.1 Positioning of the Strategic Plan ...................................................................................... 4
1.2.2 Overall Structure of Strategic Plan 2020 ......................................................................... 4
2. Concept on risk reduction and safety assurance for decommissioning of the Fukushima
Daiichi NPS .................................................................................................................................. 7
2.1 Basic concept of the decommissioning of the Fukushima Daiichi NPS ................................. 7
2.2 Concept of reducing risk caused by radioactive materials ..................................................... 7
2.2.1 Quantitative grasping of risk ............................................................................................ 7
2.2.2 Risk Reduction Strategy ................................................................................................ 10
2.3 Approach to ensuring safety during decommissioning......................................................... 13
2.3.1 Basic policy for ensuring safety based on the characteristics of Fukushima Daiichi
NPS ................................................................................................................................ 13
2.3.2 Preliminary implementation and utilization of the obtained information in the latterstages ............................................................................................................................ 16
2.3.3 Approach to address a temporary increase in risk level associated withdecommissioning operations ......................................................................................... 16
3. Technological strategies toward decommissioning of the Fukushima Daiichi NPS .................. 18
3.1 Fuel debris retrieval .............................................................................................................. 18
3.1.1 Targets and progress ..................................................................................................... 18
3.1.2 Key issues and technical strategies to realize them...................................................... 20
3.2 Waste management .............................................................................................................. 51
3.2.1 Targets and progress ..................................................................................................... 51
3.2.2 Key issues and technical strategies to realize them...................................................... 53
3.3 Contaminated water management ....................................................................................... 58
3.3.1 Targets and progress ..................................................................................................... 58
3.3.2 Key issues and technical strategies to realize them...................................................... 59
3.4 Fuel removal from spent fuel pools ...................................................................................... 63
3.4.1 Targets and progress ..................................................................................................... 63
3.4.2 Key issues and technical strategies to realize them...................................................... 65
3.5 Utilization of Analysis Results for Smooth Promotion of Decommissioning ........................ 70
3.5.1 Significance and the current status of analysis ............................................................. 70
3.5.2 Key issues and strategies .............................................................................................. 70
4. Efforts to facilitate research and development ........................................................................... 72
4.1 Significance and the current status of research and development ...................................... 72
4.2 Key issues and strategies..................................................................................................... 74
4.2.1 Strengthening the research and development management organization in the
Government-led R&D program on Decommissioning and Contaminated Water
Management .................................................................................................................. 74
4.2.2 Formulating the R&D medium-to-long-term plan foreseeing about ten years for thetime being ...................................................................................................................... 75
4.2.3 Matching of needs and seeds of decommissioning work site and universities/research institutions ...................................................................................................... 76
5. Activities to support our technical strategy ................................................................................. 78

5.1 Further strengthening of project management and improvement of capability required asa decommissioning executor ................................................................................................ 78
5.1.1 Significance and the current status of project management ......................................... 78
5.1.2 Key issues and strategies .............................................................................................. 79
5.2 Strengthening international cooperation .............................................................................. 84
5.2.1 Significance and the current status of international cooperation................................... 84
5.2.2 Key issues and strategies .............................................................................................. 86
5.3 Local community engagement.............................................................................................. 87
5.3.1 Significance and the current status of local community engagement ........................... 87
5.3.2 Key issues and strategies .............................................................................................. 89
List of Acronyms/Glossaries ........................................................................................................... 92
List of Attachment ........................................................................................................................... 95

Table of Figures
Fig.1 Division of roles of related organizations responsible for decommissioning of the Fukushima
Daiichi NPS ............................................................................................................................................ 3
Fig.2 Positioning of the Strategic Plan based on the Reserve Fund ................................................................ 4
Fig.3 Reduction of risks contained in the Fukushima Daiichi NPS .................................................................. 9
Fig.4 Example of risk levels assigned to the major risk sources at the Fukushima Daiichi NPS ................... 10
Fig.5 Image of fuel debris retrieval system (Trial retrieval and subsequent gradual expansion of fueldebris retrieval) ..................................................................................................................................... 19
Fig.6 Image from retrieval to temporary storage of fuel debris (Gradual expansion of retrieval scale) .......... 19
Fig.7 Schematic drawing of Isolation Chamber to be installed at Penetration X-6 ......................................... 22
Fig.8 Schematic drawing of Enclosure to Penetration X-6 ............................................................................. 22
Fig.9 Study flow of the retrieval method (Conceptual diagram) ..................................................................... 26
Fig.10 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 3 ............... 29
Fig.11 Example of containment function (gas-phase) by negative pressure control ...................................... 32
Fig.12 Build example of containment function (liquid phase) ......................................................................... 36
Fig.13 Technical issues and future plans on fuel debris retrieval (progress schedule) .................................. 50
Fig. 14 Summary of waste hierarchy at the NDA, UK, and countermeasures at the Fukushima Daiichi
NPS ...................................................................................................................................................... 56
Fig.15 Main technical issues and future plans on waste management (progress schedule) ......................... 57
Fig.16 Tree principles and measures for the issue of contaminated water .................................................... 58
Fig.17 Measurement result of total α in the stagnant water in buildings [Bq/L] .............................................. 60
Fig.18 Study on stabilization of zeolite, etc. ................................................................................................... 60
Fig.19 Key technical issues and future plans on contaminated water management (progress schedule) ................... 62
Fig.20 Condition of the collapsed rubble on the Unit 1 operating floor........................................................... 63
Fig.21 Removal method of fuel from Unit 1 SFP............................................................................................ 64
Fig.22 Removal method of fuel from Unit 2 SFP............................................................................................ 64
Fig.23 Storage status of spent fuel (as of August 2020) ................................................................................ 65
Fig.24 Status of 16 fuel assemblies with deformed handle ............................................................................ 68
Fig.25 Key technical issues and future plans for fuel removal from SFPs (Progress schedule) .................... 69
Fig.26 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPS (As of FY 2020)(Red: Areas with strengthened systems) .............................................................................................. 73
Fig.27 Design flow of fuel debris retrieval (Image) ......................................................................................... 82
Fig.28 ALARP centered on safety (Image) .................................................................................................... 83
Fig.29 Presenting at a side event of the IAEA General Conference (September 2019)................................. 86
Fig.30 Example of commitment to Fukushima residents for the coexistence of reconstruction anddecommissioning .................................................................................................................................. 91
Fig. 31 Structural drawing inside Reactor building ......................................................................................... 94
Fig. 32 Structural drawing inside Reactor Pressure Vessel (RPV) ................................................................ 94

Table1 Major risk sources at the Fukushima Daiichi NPS................................................................................ 8
Table2 Solid waste storage status ................................................................................................................. 55
Table3 Measures based on the concept of the waste hierarchy in the UK..................................................... 56

1. Introduction
The overall 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”) started under the Mid-and-Long-term Roadmap towards the Decommissioning of
TEPCO’s Fukushima Daiichi NPS Units 1 to 4, released by the Japanese Government in
December 2011.
Urgent issues, such as treating contaminated water and removing fuel from the spent fuelpools (hereinafter referred to as “fuel removal from SFP”), have been given top priority in thiseffort. However, to complete the decommissioning, long-term measures are required such as fueldebris retrieval work, and so it is essential to prepare a mid- and long-term decommissioning
strategy. On August 18, 2014, the former Nuclear Damage Compensation Facilitation Corporation
was reorganized into the Nuclear Damage Compensation and Decommissioning Facilitation
Corporation (hereinafter referred to as “NDF”), a new organization responsible for technicalstudies needed to proceed with the decommissioning properly and steadily from the mid- to longterm perspective. NDF’s duties include, in addition to those assigned to its forerunner, conducting
R&D of decommissioning technologies, and providing advice, guidance and recommendations
for ensuring the appropriate and steady implementation of the decommissioning.
Almost 10 years has passed since the accident at the Fukushima Daiichi NPS, and the phaseof decommissioning work is shifting from the short-term response to the mid-and-long term
response. During this period, concrete progress has been made, such as stabilization of
measures at a certain level for contaminated water management that required emergency
responses immediately after the accident, completion of fuel removal from Unit 4 SFP, and startof fuel removal from Unit 3 SFP. At the same time, a significant reduction in the radiation dose
within the power station has been achieved.
In the future, definite measures to retrieve fuel debris, which is the core of decommissioning
work, must be promoted. The government's “Mid-and-Long-Term Roadmap towards theDecommissioning of TEPCO.’s Fukushima Daiichi Nuclear Power Station” (hereinafter referred
to as “Mid-and-Long-term Roadmap”), revised in December 2019, clearly states that the retrievalof fuel debris will start from Unit 2 by the end of 2021. To achieve this, Tokyo Electric Power
Company Holdings, Inc. (hereinafter referred to as “TEPCO”) announced in March 2020, the“Mid-and-Long-term Decommissioning Action Plan 2020” (hereinafter referred to as the “Mid-andLong-term Decommissioning Action Plan”) as the main work process for the overall
decommissioning project. Through this announcement, TEPCO, as a nuclear power operator,
has made clear its stance of taking the initiative in decommissioning in order to materialize
complicated and long-term work prospects and to make the decommissioning project transparent
to the local community and society.
At present, TEPCO is working on a daily basis to achieve milestones in the Mid-and-Long-term
Roadmap, including full-scale engineering to retrieve fuel debris. Based on the new milestones

1presented in the Mid-and-Long-term Roadmap, “Technical Strategic Plan 2020 for
Decommissioning of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power
Company Holdings, Inc.” (hereinafter referred to as “Strategic Plan 2020”) presents a technicalstrategy from a mid-and-long-term perspective that overviews the overall approach taken by the
Fukushima Daiichi NPS, aiming for steady implementation of the decommissioning project.
Strategic Plan 2020 is characterized by the formulation of a Mid-and-Long-term Decommissioning
Action Plan 2020, the identification of requirements necessary for considering fuel debris retrieval
methods towards the further expansion of fuel debris retrieval, the clarification of the concept ofensuring safety in decommissioning work, and the strengthening of management systems in
response to the growing importance of research and development.
On the impact of coronavirus, TEPCO is taking measures1 to prevent infection to its staff andworkers. As a result of this, as of September 2020, no person has infected with the disease in
Fukushima Daiichi NPS. Going forward, based on the circumstances inside and outside of thecountry, it is necessary to examine strategies for promoting the project in due consideration of
measures against coronavirus. In particular, if infected, any effort to secure continuity of thedecommissioning project will be needed.

1.1 Structure and system toward the decommissioning of the Fukushima Daiichi
Nuclear Power Station
Since April 2020, TEPCO has strengthened its control system over the decommissioning workand converted itself to a project-type organization in order to steadily proceed withdecommissioning work by systematically implementing measures to address various issues overthe mid-and-long term. From the financial perspective, the Nuclear Damage Compensation andDecommissioning Facilitation Corporation has been carrying out the management of a reserve
fund for decommissioning since October 2017 to ensure immediate decommissioning work. The
management task aims are, in every fiscal year, (1) TEPCO will deposit the amount at NDF thatis specified by NDF to implement decommissioning appropriately and steadily, as well as thatapproved by the Minister of Economy, Trade and Industry, and (2) based on the “Withdrawal Plan
for Reserve Fund for Decommissioning” (hereinafter referred to as “Withdrawal Plan”), that was
jointly prepared by NDF and TEPCO and approved by the Minister of METI, TEPCO will withdraw
the reserve fund and implement decommissioning (Fig.1).
Under this management task, NDF will (1) appropriately manage the fund for decommissioning,(2) manage the implementation structure for proper decommissioning and (3) manage thedecommissioning work based on the Reserve Fund for Decommissioning appropriately, and NDF
assumes responsibility as an organization to manage and oversee TEPCO’s decommissioning

1

TEPCO, ”Measures against coronavirus infection at Fukushima Daiichi NPS”
・https://www.tepco.co.jp/decommission/common/images/20200702.pdf
・https://www.tepco.co.jp/decommission/common/images/20200730.pdf
・https://www.tepco.co.jp/decommission/information/newsrelease/reference/pdf/2020/2h/rf_20200807_2.pdf

2activities. NDF prepared “the Policy for Preparation of Withdrawal Plan for Reserve Fund for
Decommissioning" (hereinafter referred to as “The Policy for Preparation of Withdrawal Plan”),
which was drawn up based on the “Technical Strategic Plan for the Decommissioning of the
Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc.”(hereinafter referred to as “Strategic Plan”), and presented to TEPCO the work goals and main
activities to be incorporated in the Withdrawal Plan, and evaluated the appropriateness of
TEPCO's efforts in the process of jointly preparing the Withdrawal Plan from the perspective of
symbiosis and communication with the community, etc. (Fig.2).
In addition to the operation of these systems, 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 as organizations specializing in R&D, such as theInternational 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. Among these roles, R&D are discussed in Chapter 4, and dialogue with local
residents and communities is described in Chapter 5.
Nuclear Emergency Response Headquarters (Director: Prime Minister)Council for the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station(Chairperson: Chief Cabinet Secretary)

Mid-and-Long-Term Roadmap

Nuclear Regulation Authority
 Approval of implementation
plan, pre-service inspection,
welding inspection, etc.

The Team for Countermeasures for Decommissioning and Contaminated Water Treatment(Head of Team: Minister of Economy, Trade and Industry)

Progressmanagement

ReportGranting of
project budget

R&D organization

Approve

Apply forapproval

Nuclear Damage Compensation and Decommissioning Facilitation Corporation

 Development of a mid-to-long-term strategy
Withdrawal plan Tech. support for progress management of important
issues (in collaboration)
 R&D planning and progress management
Strategic  Strengthen international partnershipReserve Fund forplan  Management of Reserve Fund for
Decommissioning
Decommissioning

International Research Institute for
Nuclear Decommissioning (IRID)*
Share progress
Japan Atomic Energy Agency (JAEA), and challengesetc.
 R&D implementation
ReportAdvice, guidance, recommendations,supervision and support
Reserverelated to project management, etc.

Monitoring, examination

Report on theoutcome

Minister of Economy, Trade and Industry
Presentation ofimportant issues

Apply for report Progress management of each countermeasure according toMid-and-Long-Term Roadmap

ReportBidirectional dialogue

Local residents and communities

Organizations related to decommissioning Decide the direction of decommissioning and contaminated water
treatment

Disburse-mentTokyo Electric Power Company Holdings, Inc. (Fukushima Daiichi Decontamination and Decommissioning Engineering Company)
 Contaminated water management, fuel removal from SFP, fuel debris retrieval, waste management, entire site management, etc.
 Through TEPCO's management reform, the funds required for decommissioning should be reserved
Mid-and-Long-term
responsibly (Implementation of new comprehensive special project plan)
Decommissioning Action Plan Detailed measures for facility safety and protection of nuclear fuel material (Development of
implementation plan for specified nuclear facility* TEPCO, a decommissioning project operator, parti cipates 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 decommissioningof the Fukushima Daiichi NPS

3

Government

Mid-and-Long-Term Roadmap*
Proposals for Revise* Continually revi sed based on the progress of programs,
i n the past revised once a couple of years
Next R&D Plan
(The Government-led R&D program on
Decommissioning and Contaminated Water Management)

NDF

Strategic Plan (a nnual)
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

Joi ntly created with NDF a nd a pproved by METI
• Conta minated water management PG• Spent Fuel removal PG• Fuel debris retrieval PG• Wa ste management PG• General management of the site PG• Fa ci lity ma intenance/Operational Management

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

Engineering

Feedback

R&D

Promotion of Decommissioning projectFig.2 Positioning of the Strategic Plan based on the Reserve Fund

1.2 The Strategic Plan
1.2.1 Positioning of the Strategic Plan
NDF has been compiling a Technical Strategic Plan every year since 2015, with the aim ofproviding a solid technical basis for the Mid-and-Long-term Roadmap, contributing to a smoothand steady implementation as well as the review of revisions, and accomplishment of the target
shown in “Measures for Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS at TEPCO(Risk Map)” provided by the NRA, moreover, providing a reliable basis for The Policy for
Preparation of Withdrawal Plan (Attachment 1). The Strategic Plan will also have a technicalimpact on the annual revision of the Mid-and-Long-term Decommissioning Action Plan.
In response to the revision of the Mid-and-Long-term Roadmap made at the end of last year,
the Strategic Plan 2020 presents a technical strategy from the mid-and-long-term perspectivethat overviews the overall efforts made by the Fukushima Daiichi NPS in order for the operator
to steadily carry out decommissioning work in accordance with the new target processes. In
particular, the retrieval of fuel debris, which is a highly difficult task, is coming very close, and theroles of the government, NDF, TEPCO, research institutes, etc., have become even greater forthe realization of this task. This document also takes these viewpoints into consideration.
1.2.2 Overall Structure of Strategic Plan 2020
Strategic Plan 2020 consists of five chapters.
Chapter 1 (Introduction) stated that in the decommissioning of the Fukushima Daiichi NPS, anattempt has been made to shift from the conventional short-term response to thedecommissioning work phase with an eye towards a medium to long-term response, and thatTEPCO is now working on engineering towards fuel debris retrieval on a full scale, such as theformulation and publication of a Mid-and-Long-term Decommissioning Action Plan.

4

Chapter 2 (Concept on Risk Reduction and Safety Assurance for Decommissioning of the
Fukushima Daiichi NPS) presents the basic policy for decommissioning the Fukushima Daiichi
NPS as an approach to risk reduction and ensuring safety. It also describes the immediate targets,basic approach to risk reduction, and the approach on the order of priority, as well as preliminary
implementation and utilization of the obtained information in the latter stages, and the approachon how to deal with temporary increases in risk levels as the policy of ensuring safety.
Chapter 3 (Technical strategies toward decommissioning of the Fukushima Daiichi NPS) setstargets for each of the four areas of fuel debris retrieval, waste management, contaminated water
management, and fuel removal from SFPs, and describes the current progress toward thesetargets, the major challenges in accomplishing them, and the technical strategies to achieve them.
In promoting these four areas, significance of analyses and current situation as well as its issues
and strategies are specially referred to, since utilization of analyzed result is commonly important.
Chapter 3, Section3.1 (Fuel debris retrieval3.1) describes the points to be noted based on theexperience and research and development obtained so far in conducting the trial retrieval of fueldebris and the expansion of the scale of the gradual retrieval at the first implementing unit, Unit
2. Additionally, in further expanding the scale of the retrieval, the flow of examining the retrieval
method is shown as a conceptual diagram, as well as its concept of important requirements(Boundary conditions).
Chapter 3, Section3.2 (Waste management) presents, in accordance with the basic policies
on processing/disposal of solid waste, specific targets along with a plan for R&D needed to reachthese targets to gain a technological vision for waste processing/disposal to be presented in order
starting from the Strategic Plan 2021.
Chapter 3, Section3.3 (Contaminated water management) stipulates new targets forcontaminated water management and issues such as zeolite sandbags in accordance with
progress in the stagnant water in buildings. In addition, it also describes the direction ofcontaminated water management in the reactor buildings after starting the fuel debris retrieval
work.
Chapter 3, Section 3.4 (Fuel removal from spent fuel pools) refers to the new target forremoving fuel from SFPs and the appropriate and specific operation plan depending on theconditions of each unit, and proposes the directions of the efforts to secure capacity required forproper storage of removed fuel within the site and of the efforts to determine the future treatment
and storing methods for fuel in SFPs including evaluation of the long-term integrity of such fuel.
Chapter 3, Section 3.5 (Utilization of Analysis Results for Smooth Promotion of
Decommissioning) describes the implications of analysis results in proceeding with thedecommissioning including positioning of importance and analysis of establishment andimprovement of analysis system or analysis facilities as a superordinate concept of each project,
as well as the need for early initiation of whole strategy for analysis.
Chapter 4 (Efforts for research and development) describes the individual R&D activities
described in Chapter 3 in a medium to long-term as a whole, and summarizes the efforts expected5

of the government, business operators, and related research institutions. It also presents the
direction of future efforts toward the acceleration of R&D, including the strengthening of the R&D
management system for the Government-led R&D program on Decommissioning andContaminated Water Management, and the preparation of medium to long-term R&D plans. In
addition, from a medium to long-term perspective, the role of each player centered on the JAEA
and the importance of fundamental R&D, in matching needs and seeds between
decommissioning sites and universities and research institutions, and establishing centers ofbasic research/research infrastructure are described.
Chapter 5 (Efforts supporting technical strategies) describes the significance, the current
situation, the main issues and strategies in each area of further strengthening of project
management, improvement of skills required in the decommissioning project operator,
enhancement of international cooperation, and local community engagement.
Chapter 5, Section 5.1 (Further strengthening of project management and improvement ofskills required in the decommissioning project operator) describes not only the technologicalinvestigations described in Chapter 3, but also the implications of the formulation of the Mid-andLong-term Decommissioning Action Plan, further strengthening of project management, inparticular, enhancement of the “safety and operator's perspective” for ensuring safety,
improvement of owner's engineering capability, and development and securing of humanresources.
Chapter 5, Section 5.2 (Enhancement of international cooperation) describes the need tostrengthen international cooperation, such as partnerships with institutions involved indecommissioning projects in countries with legacy nuclear sites, in order to gather wisdom andknowledge from around the world, and proposes efforts that should be made in this regard.
Chapter 5, Section 5.3 (Local community engagement) notes how these institutions, mainly
TEPCO should work together toward that end under the fundamental principle of “the coexistenceof reconstruction and decommissioning”, to implement continuous decommissioning of the
Fukushima Daiichi NPS that spans a long period of time, in consideration that we will seek
decommissioning developed with the reconstruction in local communities.

62. Concept on risk reduction and safety assurance
decommissioning of the Fukushima Daiichi NPS

for

2.1 Basic concept of the decommissioning of the Fukushima Daiichi NPS<Basic concept of the Decommissioning of the Fukushima Daiichi NPS>
To continuously and quickly reduce the radioactive risks caused by the accident that do notexist in a normal NPS
The Fukushima Daiichi NPS has the necessary safety measures in place that are required by
the NRA in “the matters for which measures should be taken” and is maintained in a state with acertain level of stability.
However, the Fukushima Daiichi NPS is at great risk because fuel debris and spent fuels still
remain in reactor buildings damaged by the accident, some of the status of the NPS are notsufficiently grasped, and the site has radioactive contaminated water and enormous amounts ofextraordinary radioactive wastes. If left unaddressed, these risks may increase due to the 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 “toreduce continually and quickly the risks associated with the radioactive materials that resulted fromthe accident and do not exist in normal nuclear power plants” by taking measures specificallydesigned for risk reduction. In general, actions that are effective for reducing the risks at nuclear
facilities that have suffered an accident are as follows;

Improving the containment function of the damaged facilities



Changing the properties and form of the contained radioactive material to more stable onesStrengthening monitoring and control over the equipment to better prevent or mitigate theoccurrence or propagation of abnormalities.

To enable these actions comprehensively,
Removing radioactive materials from the damaged facilities or insufficient containment
status and placing them in sound storage is also effective.

These diverse risk reduction measures have been continued based on careful preparations
aimed at preventing accidents and exposure of workers to radioactivity (refer to Attachment 2).

2.2 Concept of reducing risk caused by radioactive materials
2.2.1 Quantitative grasping of risk
The term “risk” may have various meanings depending on the field or scene of use. In general,in the context of appropriate risk management, “risk” can be understood as an expectation valueof the negative impact of an event. In other words, the magnitude of a risk (risk level) posed by asubject (risk source) can be expressed as the product of the level of impact and the likelihood of7

occurrence of the event.
In the Strategic Plan, the method based on the Safety and Environmental Detriment score(hereinafter referred to as “SED”) developed by the Nuclear Decommissioning Authority(hereinafter referred to as “NDA”) is used to express the magnitude of risk (risk level) for radioactive
materials. 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 impact of the event, namely, the impact of internal exposurein the event of human intake of the radioactive material contained in the risk source. It can be
expressed as the product of Inventory, which is the radioactivity of the risk source (toxicity of theradioactive 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 and monitoring status of the risk source (Attachment 3).
The major risk sources of the Fukushima Daiichi NPS are summarized in Table1, 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 the spent fuel pools), (2) Immediate risk unlikely, but risk may grow when handling withhaste (fuel debris), and (3) Increased risk unlikely in the future, but appropriate decommissioning
efforts required (solid waste such as sludge generated from the decontamination device). Theirpriorities are set, and appropriate measures are taken.
Table1 Major risk sources at the Fukushima Daiichi NPS
Fuel debris
Spent fuelContaminatedwater, etc.

Fuel debris in RPVs/PCVs in Units 1 - 3
Fuel in SFPs

Fuel assemblies stored in the spent fuel pools (SFPs) in Units 1-3

Fuel in the Common
Spent Fuel Storage
Pool

Fuel assemblies stored in the Common Spent Fuel Storage Pool

Fuel in dry casks

Fuel assemblies stored in dry casks

Stagnant water inbuildings

Contaminated water accumulated in the reactor buildings/theturbine buildings in Units 1 to 4, process main building and hightemperature incinerator building, and sludge containing α-nuclides
at the bottom of buildings in Units 1-3

Zeolite sandbags

Sandbags containing zeolite placed on the basement floors ofprocess main building and high-temperature incinerator building

Stored water in weldedtanks

Strontium-treated water and ALPS-treated water stored in weldedtanks

Residual water inflanged tanks

Concentrated salt water and residual ALPS-treated water left at thebottom of flanged tanks

8

Rubble, etc.

Waste adsorption
vessels, etc.

Spent adsorbents used in the cesium adsorption apparatus, asecond cesium adsorption apparatus, a third cesium adsorption
apparatus, advanced multi-nuclide removal equipment, mobile-type
strontium removal equipment, a second mobile-type strontium
removal equipment and mobile-type treatment equipment, etc.

HIC slurry

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

Sludge generated fromdecontamination
deviceFlocculated sludge generated during the operation of thedecontamination system

Concentrated liquid
waste, etc.

Concentrated liquid waste generated by evaporative concentrationof concentrated salt water with further volume reduction by
concentration, and carbonate slurry collected from the concentrated
liquid waste

Solid waste storage
facility

Rubble with high-dose (30 mSv/h and above) stored in the solid
waste storage facility

Soil-covered
temporary storage,etc.

Rubble stored in the soil-covered temporary storage facility andcontainers (1-30 mSv/h), fallen trees stored in the temporarystorage pool

Outdoor storage, etc.

Rubble stored in outdoor sheet-covered storage (0.1-1 mSv/h),
rubble stored in outdoor storage (below 0.1 mSv/h), fallen trees
stored in outdoor storage

Contaminated structures, etc., in thebuildings

Fuel removal from Unit 4 SFP started

Risk level(logarithmic scale)

Risk level (linear scale)

Structures, pipes, components, and other items inside the reactor
buildings and PCVs/RPVs that are contaminated with radioactive
materials dispersed due to the accident; and activated materials
generated from operation before the accident

0

1

2

3

4

5

6

7

8

Risk level (linear scale)

Secondarywaste
generated bywater
treatment

9

Year after 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

5

Year after accident
Fuel debris

Fuel in SFPs

6

7

8

9

Year after accident

Contaminated water

Fuel debris

Fuel in SFPs

Contaminated water*1: The risk level was high due to fuel debris right after the accident, however, it became largely lower because
Hazard Potential has been largely decreased by attenuation of radioactive materials inside fuel debris over one
year after the accident.
*2: In the evaluation of eight years after the accident, as a result of incorporating the insight that the rise in watertemperature after cooling shutdown was slower than expected, the risk of fuel in SFPs is lower than previously
estimated, because the time margin before this risk becomes apparent increases.

Fig.1 Reduction of risks contained in the Fukushima Daiichi NPS
9

Major risk sources identified at the Fukushima Daiichi NPS are shown in Table1. 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 introduction of the Strategic Plan 2019, these issues have also been presented.
In particular, regarding the facilities containing risk sources that had not been expressly consideredin the past, investigations and examinations are being conducted in consideration of external
events such as earthquakes, tsunamis, and rainwater (Attachment 4).

Fig.4 Example of risk levels assigned to the major risk sources at the Fukushima Daiichi NPS
2.2.2 Risk Reduction Strategy
2.2.2.1 Interim targets of the risk reduction strategy
Measures for risk reduction include the reduction in “Hazard Potential” and the reduction in“Safety Management.” The examples of reduction in “Hazard Potential” include the decrease ininventory and decay heat associated with radioactive decay, and changing the form of liquid andgas into a form that is hard to move. To process contaminated water to change into secondary
waste is an example of form change.
The examples of reduction in “Safety Management” include transfer of fuel in SFPs to the
Common Spent Fuel Storage Pool, and placement of rubble stored outdoors into storage. Of thevarious risk reduction measures, the reduction in “Safety Management” is generally considered tobe easily realized. Consequently, the decommissioning of the Fukushima Daiichi NPS, which is
implemented under the basic concept of “to continuously and quickly reduce the radioactive risks
caused by the accident that do not exist in a normal NPS” (refer to Section 2.1), should first focus
on steadily managing risk sources by keeping them in higher-integrity facilities to lower their Safety

10Management levels. The immediate target of the risk reduction strategy is to bring the risk levels
into the “Sufficiently stable management” region (the pale blue area) as shown in Fig. 4.
SED quantitatively shows a current condition of a risk attributable to radioactive materials, andthis is an effective method to determine the order of priority for measures against risk sources.
When conducting the actual risk reduction, it is required to take measures from engineering aspect
in order to inhibit development of risks from radioactive materials associated with its operation.
Regarding the Table1, what was changed from last year is that zeolite sandbags were added2 aspart of contaminated water management after the accident. It was revealed in December 2019 thatthey would be present in a state of high radiation dose in the process of treatment of stagnant waterin buildings (For details, see Section 3.2, Contaminated water management). Compared with thestagnant water in buildings shown in the table, “Safety Management” is deemed close to the regionin pale blue because its form is difficult to leak through the building walls. Moreover, “Hazard
Potential” of residual water in the flanged tanks becomes relatively low because its treatment has
progressed.
2.2.2.2 Direction of risk consideration for external events
In the preceding paragraph, based on the concept of SED, Fig.4 is shown as the major risk
sources for the Fukushima Daiichi NPS using the indicators of “Hazard Potential” and “Safety
Management”. However, how to estimate and evaluate the risks associated with external events
such as earthquakes and tsunamis3 remains to be solved. The definitions of “Hazard Potential”
and "Safety Management" (Attachment 3) do not necessarily adequately address the frequency of
external events or the consequences. Therefore, it is important to consider the risk managementof the whole site promoted by TEPCO, taking into account the seismic resistance and installation
height of the facilities against earthquakes and tsunamis to complement the SED concept while
adopting a probabilistic approach. In doing so, it is necessary to (1) implement risk reduction byfocusing on the high priority external events such as earthquakes, tsunamis, and rainfall that
become the source of contaminated water; (2) develop a comprehensive database of seismic
resistance, failure rates, and location information for facilities where direct containment is carriedout; and (3) enhance scenario analysis and assessment of exposure estimates that may be causedby external events.
2.2.2.3 Basic approach to risk reduction
Decommissioning of the Fukushima Daiichi NPS is a project with considerable uncertainties
involved. To date, the internal status of Units 1 to 3 has been estimated to some extent through thesimulation of the accident development process, estimation of the places with fuel debris by muon-

2

In the Strategic Plan 2019, zeolite sandbags were extracted as one of the risk sources that include radioactive
materials other than major risk sources. Strategic Plan 2020 added it to the major risk sources.
3 Earthquakes, tsunamis, rainwater, etc., are listed as external events that need responses in the Measures for
Mid-term Risk Reduction at TEPCO’s Fukushima Daiichi NPS at TEPCO (Risk Map), (Nuclear Regulation
Authority March 2020).

11

based fuel debris detection technology, placement of investigation equipment into the PrimaryContainment Vessel (hereinafter referred to as “PCV”), dose measurement and video
photographing in the buildings, and others. There was still significant uncertainty, however, toeliminate uncertainties, many resources and, in particular, a considerably long time are required.
In order to realize prompt risk reduction it is necessary to make integrated decisions through aflexible and prompt approach, based on the directions determined with previously obtained
experience and knowledge, and with experiment and analysis based simulation, placing safety as
the top priority, even though a certain extent of uncertainties remain.
As the viewpoint to make these comprehensive decisions, NDF summarizes the following fiveguiding principles:(Five guiding principles) SafeReduction of the risks posed by radioactive materials and ensuring of worksafety(Issues such as containment of radioactive materials [environmental impact],
workers’ radiation exposure, assessment of risk reduction effects)ProvenHighly reliable and flexible technologies(Issues such as conformity to requirements, effectiveness, flexibility against
uncertainty)

Efficient

Effective use of resources (e.g. people, things, money and space)(Issues such as reduction of waste generation, cost, efficiency, securing
necessary work area and site)TimelyTime consciousness(Issues such as early start of fuel debris retrieval, estimation of time required
for fuel debris retrieval)

Field-oriented Comprehensive three-reality policy by checking actual site, actual goods,
and actual situation(Issues such as workability including environment-friendliness, accessibility,
and operability, and maintainability including ease in maintenance andtroubleshooting)If the five guiding principles are applied to the actual site, it is important to proceed with thedecommissioning operation after greatly emphasizing on safety assurance for the purpose ofprotecting human beings and environment from radioactive materials associated with theoperations, thoroughly conducting radiological consequence evaluation, and taking appropriate
radioprotective measures. (“Safe” of five guiding principles)
For 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, while controlling thisrisk 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 condition on-site (“Field-oriented”) will lead to ensuring safety inmedium-to-long-term.
As for the result judged based on these five guiding principles, it is also important to work to12

disseminate information carefully so that the results of this judgment will be widely accepted bysociety.

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 reactor involved in the accident
is an unprecedented activity that takes place in a special environment different from that of a normal
reactor, and therefore, to ensure safety, the following characteristics (peculiarity) in safety should
be fully recognized:
・ A large amount of radioactive materials (including α-nuclides that have a significant impact oninternal exposure) are in an unsealed state, as well as in unusual and various (atypical) forms
・ The barriers to contain radioactive materials, such as reactor buildings and PCVs, areincomplete
・ Significant uncertainties exist in the conditions of these radioactive materials and containment
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 there is a concern about further degradation ofconfinement barriers, etc., it is necessary to take measures considering 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 work when considering
the work based on five guiding principles.
Firstly, with regard to “safety”: There is great uncertainty about the status of radioactive materials
and confinement 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 materials will be handled in an incompletely confined state. 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, while paying attention to risk reduction over the entire work period.
Therefore, it is necessary to avoid excessive safety measures and to take optimum safetymeasures (ALARP4). Such perspective on “safety” (the safety perspective) should be reflected in
the decommissioning work review.
Secondly, with regard to “field-oriented”:

4

An abbreviation for As Low As Reasonably Practicable. It means that radiological impacts must be as low asreasonably practicable.

13

・ The on-site environment is under special conditions such as a high level of radiation, andtherefore, attention should be paid to the feasibility of construction and implementation ofsafety measures on site.
・ An approach through design alone has limitation due to significant uncertainties.
From the above-mentioned reasons, it is essential to accurately reflect the actual on-site
information into engineering. For this purpose, the views and senses of the individuals and theorganizations (operators) that are responsible for the on-site work (including operation,
maintenance, radiation control, instrumentation, analysis, etc.) and very familiar with actual siteshould be highly respected. And their perspectives and judgements directly based on the site (theoperator’s perspective) are important.
In the actual design of the decommissioning work in the project, TEPCO, as the project executor,
should clearly define the “requirements” for the work in advance, and should design specific safetymeasures to achieve them. In doing so, it is essential to reflect “the safety perspective” and “theoperator’s perspective” to respond to the characteristics (peculiarity) of decommissioning of the
Fukushima Daiichi NPS. Specifically, requirements shall be stipulated in consideration of “the safety
perspective” and “the operator’s perspective”, and specific safety measures shall be selected forwork which satisfies the requirements, considering the two perspectives. When designing thedecommissioning work, sufficient attention should be paid to “the safety perspective” and “theoperator’s perspective” at each stage of the design.
In this decommissioning work with very significant uncertainties, it is often difficult to clearly
define the requirements in advance. Even in such a case, the decommissioning work should beproceeded with flexibly and promptly by fully utilizing the "preliminary implementation and utilizationof the obtained information in the latter stages" as described later and “iteration-based 5
engineering”.
2.3.1.1 Optimization of judgment with safety evaluation as its basis and ensuring thetimeliness in decommissioning
In proceeding with the decommissioning work with an aim for risk reduction, it is most importantto take appropriate safety measures and ensure safety of the work handling a large amount ofradioactive materials that is technically difficult and has significant uncertainties, such as fuel debris
retrieval. Thus, decommissioning work should be carried out by concentrating on “the safety
perspective”.
Specifically, when designing safety measures for each decommissioning activity, it is essential
to make decisions based on Five guiding principles after conducting a thorough safety evaluationand confirming that the required safety is ensured. In the decommissioning work of the Fukushima
Daiichi NPS, which is unprecedented and has significant uncertainties, by using deliberated safety
evaluation as the basis for making decisions regarding safety measures, the decisions will not be
5

Approach to obtain a subsequent result based on one result and gradually improve completion rate ofengineering by repeating this.

14

significantly unstable (that is, without devoting too little or excessive resources).Necessary,
sufficient and reasonably feasible safety measures can be realized (optimization of judgment basedon safety evaluation).
In addition, as "the safety perspective" unique to the decommissioning of the Fukushima Daiichi
NPS, the importance of making progress in decommissioning work without delay (importance oftime-axis-conscious action) can be mentioned. Considering high radiation effects that have alreadybecome materialized, and the possibility of further degradation of containment barriers, etc., making
progress in the decommissioning work without delay will significantly contribute to ensuring thesafety of the entire decommissioning process from a mid-and-long term perspective. Therefore,
unlike ensuring safety for normal reactors, which have a certain margin in terms of human, physical,
and financial resources and have low radiological impacts and high stability, it is particularly
required to make rational and time-axis-conscious judgement on making progress in thedecommissioning work without delay and the resource input. This judgement should be made on
the condition that safety is secured, and based on the relationship with the overall balance.
(Ensuring timeliness in decommissioning activities)
2.3.1.2 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 operations and tasks on site. For this purpose, “theoperator’s perspective” (perspectives and judgements from the standpoint of those who are familiar
with the site and perform operations and tasks on site) is important. In addition to this standpoint,
the Fukushima Daiichi NPS is a facility that has suffered from an accident, and its decommissioning
requires an unprecedented approach that could be carried out in the special environments such as
high radiation levels, unlike normal reactors. Therefore, when determining the feasibility of safetymeasures on site, special on-site conditions such as high radiation levels and the environment shallbe considered.
“The operator’s perspective” is also important for ensuring safety from the following viewpoints,
which are different from those of normal reactors.
Complementation of design by operations, including operating controls: Due to significant
uncertainties, there is a limit in addressing all situations by design alone. For this reason, an
effective way is to use the information obtained at the operation stage for the design ofsubsequent stages, and complement the design with the operators’ actions and on-site
operations to improve safety in total with the operation.

Utilization of information in design obtained through monitoring, analysis, etc.: To cope withsignificant uncertainties, it is important to utilize the information obtained through on-site
operations such as monitoring and analysis, etc., in designing safety measures. When utilizing
the information, it should be linked with calculational evaluation, etc., to “make a comprehensive
use of it”.

15

Responses in case of an abnormality: Although it is essential to take all possible measures toprevent an abnormality from occurring, on-site response as a precaution against the occurrenceof an abnormality 6 is effective considering the characteristics that the progresses ofabnormalities is moderate and there is sufficient time for response.

2.3.2 Preliminary implementation and utilization of the obtained information in the latterstagesOn-site conditions of the Fukushima Daiichi NPS containing the reactors involved in the accident
includes considerable uncertainties. If whole operation of large-scale project such as fuel debris
retrieval is to be designed under such circumstances, assumptions of extremely large safety margin
and wide range of technical options will be needed. Thus, extension of work period or risk of rework
will be unavoidable. As a result, feasibility or predictability of the entire project may reduce and that
leads to delay in entire decommissioning, rise in decommissioning cost, or increased radiation
exposure of workers.
On the other hand, considering current environment with already high radiation level, further
deterioration of containment barrier, and the possibility of future major natural events (such as
earthquake or tsunami), it is necessary to improve such risk state and reduce uncertainties as
quickly as possible. 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 to the next stage. In thisapproach7, the operation proceeds with its safety ensured through monitoring the condition inside
reactor, restricting operational actions and flexible on-site responses8 at each stage of the process.
The information obtained at each stage of operation is utilized in the design of subsequent stages.
This approach allows to reduce uncertainties in the operation of subsequent stage as well as toimprove the reliability of safety assurance and rationalize design.
TEPCO is required to quickly introduce approach like this into actual engineering and project
management. It is important to accumulate experiences that went well or failed acquired in thisapproach. It will lead to steady progress in decommissioning and contribute to ensuring safety indecommissioning the Fukushima Daiichi NPS from the perspective of risk reduction in the mid-andlong 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 the mid-and-long-term
viewpoint, careful deliberation is required over the possibilities that the performance of
6

As a long time passed since the accident of Fukushima Daiichi NPS occurred, its immanent energy (decayheat) that becomes the driving force of diffusion of radioactive materials is small. Therefore, it is characterized
by abnormity that progresses moderately and sufficient time for response.
7 The same approach is applied in the UK including the decommissioning site in Sellafield and it is called “Lead &Learn”.
8 For example, taking measures including installing nuclear instrumentation system, limiting processing volume ofdebris and restricting operations with the control value of radioactive dust concentration stipulated.

16

decommissioning work may temporarily change the risk levels and may increase the radiation
exposure of workers. This is because carrying out the decommissioning work involves acting on
the current situation of the NPS, which is kept in a state with a certain level of stability despite somerisks. Such risks may materialize, depending on the way actions are taken. For example, accessing
the inside of the reactor to retrieve fuel debris will affect the current containment status, and special
operations and maintenance performed for the retrieval will increase the exposure of workers
involved in these activities.
The possibility of a temporary increase in the risk level and a rise in workers’ exposure arisingfrom such decommissioning work must be addressed by taking measures to prevent and restrict
them. In particular, as for the radiation safety of workers, it is imperative to limit the increase in therisk level during decommissioning as much as practicably possible by thorough preparations as
achieved through application of the concept of ALARA (to suppress radiation exposure to As Low
As Reasonably Achievable).
Note that the basic stance of promptly implementing the decommissioning must be firmly
maintained because if the work is delayed excessively, existing large risks will remain over the longterm and their risk levels may gradually rise as the buildings and facilities deteriorate over time. For
this reason, with regard to the selection of work methods, the design and manufacture of equipment
and safety systems, and the development of work plans for the decommissioning work, cautious
and comprehensive decision making are required for early implementation of decommissioning inconsideration of many constraints such as time, cost, and worker’s exposure needed for relevant
preparations and work, while giving priority to limiting the risks 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. Consequently, it is necessary for
local communities, the government (Ministry of Economy, Trade and Industry, Nuclear Regulation
Authority), NDF, TEPCO, and others to cooperate with each other to reduce risks based on theapproach to ensuring safety based on their respective positions. In doing so, it is important toestablish a system for on-going risk monitoring which enables a wide range of people to easily
understand how the overall risks at the site have been continuously reduced through thedecommissioning work. NDF and TEPCO are considering such a system, and TEPCO needs tointroduce such a system in the future.

17

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 including safety measures,and bring it to the state of stable storage that is fully managed.
(2) Beginning trial retrieval of fuel debris from Unit 2, the first implementing unit within 2021, thenstart the gradual expansion of fuel debris retrieval and a series of operations timely. Through thisprocess, acquire knowledge and experience necessary for the further expansion of fuel debris
retrieval in the future. (For the target of fuel debris retrieval, see Attachment 6)(3) To further expand fuel debris retrieval, thoroughly examine the result and progress of the fueldebris retrieval from the first implementing unit, through internal investigation, R&D (thegovernment-led program on decommissioning and contaminated water management andTEPCO’s voluntary project), on-site environmental conditions. Through this process, study thebest methods of contain, transfer, and store.
(Progress)
According to the Mid-and-Long-term Roadmap, Unit 2 is designated as the first implementing
unit for fuel debris retrieval, and trial retrieval will be started by the end of 2021. After that, theoperation to gradual expansion of fuel debris retrieval will be promoted. For a trial retrieval, theretrieval device is inserted through an existing opening part that leads to the inside of the PCV.
TEPCO has presented the work schedule up to 2031 in the Mid-and-Long-term Decommissioning
Action Plan, and is working according to this schedule.
(1) Unit 1
Since the second half of FY 2020, further detailed information inside PCV is planned to be gainedby inserting a boat-type access investigation device with diving capabilities (an underwater ROV)
into PCV and investigating the internal status such as distribution of deposits widely scattered at
the bottom of outside the pedestal, presence or absence of fuel debris involved in deposits, andstructures inside the pedestal. In preparation for the start of this investigations, removal of obstacles
within the PCV is being promoted while taking measures to control dust dispersion and monitoring
dust concentration by considering the change in dust concentration when opening the inner door at
the penetration X-2.
(2) Unit 2
An arm-type access investigation device (a robot arm) is being manufactured (Fig.5), andmeasures to control dust dispersion are under consideration in preparation for the trial retrieval and18

the start of internal investigations of PCV by the end of 2021.
A plan to 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 withspecifications for the devices for trial retrieval and internal investigations of PCV. The retrieved fueldebris is transferred to the receiving/delivery cells on site and stored in temporary storage
installations. In addition, some of the fuel debris will be collected in the receiving/delivery cells foranalysis and transported to the facility for analysis. At present, the retrieval device,receiving/delivery cells, and temporary storage installations are being designed. (Fig.6)
In response to the unprecedented approach to retrieving fuel debris from the first implementing
unit, NDF is considering confirming the actual site applicability of the device and the results of thereview on modifications to the safety system from the viewpoints of safety, reliability, reasonability,
timely, and the field-oriented stance, in accordance with the progress of engineering at TEPCO.

(TEPCO material edited by NDF)

Fig.5 Image of fuel debris retrieval system (Trial retrieval and subsequent gradual expansion of fueldebris retrieval)(TEPCO material edited by NDF)

Fig.6 Image from retrieval to temporary storage of fuel debris (Gradual expansion of retrieval scale)(3) Unit 3
As for Unit 3, due to high water levels in the PCVs, it is planned to gradually lower the PCV water

19

levels, taking into account the improvement of earthquake resistance of the suppression chamber(hereinafter referred to as “S/C”) and conducting internal investigations of PCV. The concentrationof radioactivity may be high in the S/C-encapsulated water, and measures depending on the water
quality in S/C should be taken. Therefore, in the design and construction of a PCV water intake
installation and in the planning of water treatment, activities are under way to determine water
quality by sampling the S/C-encapsulated water.
3.1.2 Key issues and technical strategies to realize them
Since the research and development necessary for understanding the situation inside the PCVs
and for fuel debris retrieval is still limited, the current design and the plan for on-site operations
related to fuel debris retrieval should be continuously reviewed based on the knowledge that will beobtained in the future. In addition, considerations are given and the research and development forfuel debris retrieval is being promoted, which should lead to an accurate reflection of the outcome
thereof.
3.1.2.1 Trial retrieval, internal investigation of PCV, and gradual expansion of fuel debris
retrievalWith regard to the trial retrieval, there are uncertainties and difficulties in the development ofrobot arms and the removal of deposits and obstacles due to a limited understanding of theconditions inside the PCV. Therefore, it is important to conduct a mock-up test simulating the sitefrom the operator's perspective, while adequately confirming safety and the actual site applicability
to steadily proceed. Especially for a mock-up test, it is important to simulate its severe environment
at the site. Moreover, it is needed to make a sufficient preparation for countermeasures at the actualsite application, while clarifying operations that cannot be simulated.
In addition, it is also important for TEPCO to take the initiative in promoting engineering basedon the considerations in (1) to (3) that have been gained from past experience under thestrengthened project management system.
Based on the engineering schedule led by TEPCO, NDF will set in advance the points to be
confirmed, such as the actual site applicability of access devices, results of examinations on
modifications to the safety system, and the safety assessment of dry storage, and will confirm theoutcome of research and development, engineering results, and the progress in on-site operations
from the viewpoints of safety, reliability, reasonability, timely, and the field-oriented stance.
At Unit 2, while reviews have proceeded toward the start of a trial retrieval and internal
investigations of PCV using the same robotic arm by the end of 2021, the review process should
be proceeded with after ensuring safety by reaffirming that safety is most important. Furthermore,
due to the restricted attendance of engineers and technicians because of the recent worldwide
spread of the coronavirus, it is assumed that the planned work would be more difficult than before,
and therefore, more deliberate and careful attention should be paid to ensuring safety.
In the conventional internal investigations of PCV, an opening of 115 mm in diameter was made20

in the blank flange part of the penetration X-6 to maintain airtightness using an isolation valve or
the like. In the future trial retrievals and internal investigations of PCV, pressure will be reduced toa level close to the atmospheric pressure in order to suppress dust dispersion. The work will be
performed by opening the flange of the penetration X-6 to make a larger opening than before(approx. 550 mm in the inner diameter of the penetration X-6) through which the arm-type accessinvestigation equipment is moved in and out to retrieve fuel debris inside the PCV. In this work, an
expansion will be made to provide an isolation chamber (composed of a robot carrying-in room,etc.) to be built during the penetration X-6 opening work (Fig. 7) and an enclosure to be newly
provided (which will enclose an arm-type access investigation equipment, etc.) (Fig. 8), since theconventional containment barrier was located in the blank flange part of the penetration X-6.
Although small in scale, this is a fundamental form of site construction for future retrieval work, inwhich an opening will be newly provided in the PCV to extend the containment barrier outside thePCV. This presents an approach that enters a new stage. The information obtained through thisapproach will be reflected in future work.
When extending the containment barrier of the penetration X-6, the penetration X-6 shall be
opened while maintaining the function by installing an alternative device, etc., in order to maintainthe containment barrier function that is currently retained. In doing so, there will be very difficult
considerations, including building an isolation mechanism to continuously maintain the opening
device and the containment barrier function that is currently retained, installing these devices
through remote operation, etc. In the opening work of the penetration X-6, it is planned to cover thecircumference of the penetration X-6 with an isolation chamber when devices and equipment are
installed. As described above, since the opening work of the penetration X-6 is associated withmaintaining the containment barrier function, a review shall be carried out with considerable
attention to safety in particular, and preparations, verifications and training shall be performed in amore deliberate and careful manner.
The removal of obstacles, a trial retrieval, and internal investigations of PCV that are performed
after opening the penetration X-6 shall be conducted based on the information on the inside of thepenetration X-6 obtained on site and the varying site conditions, etc. According to the state ofobstacles in the PCV and the internal conditions actually obtained, the sequence and method of
removing obstacles, a trial retrieval, and internal investigations of PCV may vary depending on theobservation results obtained at that time. Therefore, these activities shall be deemed as integratedwork.
In the future, based on the knowledge to be obtained through trial retrieval, we will proceed withthe design and review of the retrieval installations and safety systems toward gradual expansion offuel debris retrieval.

21

(TEPCO material edited by NDF)

Fig.7 Schematic drawing of Isolation Chamber to be installed at Penetration X-6(during the opening work of the penetration X-6)

(TEPCO material edited by NDF)

Fig.8 Schematic drawing of Enclosure to Penetration X-6(during a trial retrieval and internal investigations of PCV)
(1) Promoting the project with a strong awareness of safety from the initial stage
When opening the inner door of the penetration X-2 to conduct Internal investigations of PCV of

22

Unit 1, the dust monitor for monitoring the work reached the control value, and the measures tocontrol dust dispersion and dust concentration monitoring were carried out by taking sufficient time.
Specifically, the work was carried out with the cutting amount limited, and a number of measures
were taken, such as cutting with a reduced peak density based on the data obtained on dust
dispersion characteristics and the addition of a new dust monitor for monitoring the work. Despite
the unknown conditions inside the PCV, these measures were taken by carefully working while
newly obtaining knowledge on dust diffusivity. Giving more consideration to dust dispersion control
from the viewpoint of safety at the initial stage of the project will enable the work to be implemented
systematically. To smoothly proceed with the project by utilizing this experience, safetyassessments should be conducted more often than ever from the initial stage of the examinationand the requirements should be defined clearly by considering the actual site applicability.
(2) Clarification of quality requirements considering actual site applicability
Based on the experience obtained in the research and development and the TEPCO-led
engineering, development of devices will be carried out for gradual expansion of fuel debris retrieval
and further expansion of fuel debris retrieval. Depending on the amount of fuel debris to be retrieved,
the scale of the device becomes large and stable reliability should be ensured over the long term.
Consequently, it is important to proceed with the development of the devices after clarifying thespecifications such as the functional requirements, in consideration of the actual site applicability inadvance. Quality control of the fuel debris retrieval device is especially important. TEPCO isrequired to proceed with the development of the devices on the premise that TEPCO will ensure
the quality by sorting out the quality level and the basic requirements concerning quality in advanceaccording to the situation at the Fukushima Daiichi NPS.
In addition, it is expected that more and more efforts will be made in the future in considering thefuel debris retrieval and in the construction work by combining with knowledge and experiencesfrom overseas. In the research and development carried out with overseas companies, etc., wehave experienced several challenges in the process control other than quality control, as well as inunderstanding the design and production capabilities of the suppliers. To exploit overseas
knowledge and experience, more detailed process control must be carried out also by contractors
and their subcontractors.
(3) Acquisition and utilization of information during fuel debris retrieval
TEPCO has begun to consider the selection of data to be acquired and the installations foracquiring such data, aiming for gradual expansion of fuel debris retrieval and further subsequent
expansion. This study involves difficulties in overcoming various limitations such as the weightcapacity of the handling equipment, the cumulative dose of the equipment, remote operability, etc.
Although the on-site situation is uncertain, it is important to acquire data through condition
monitoring, such as instrumentation monitoring and visual observation during the fuel debris
retrieval operation to make simulation-based assessments, and to acquire the parameters to be23

used as design conditions for safety systems and various devices. Thus, an approach is required
to link the data to the results of analyses that will be separately conducted, and to utilize them inconsidering the retrieval method and the safety assessment.
In addition, it is necessary to study the methods for storage and control of solid waste generated
during fuel debris retrieval. It is important to collect various samples, improve data, and repeat
analyses and assessments from the viewpoint of contributing to the examination of processing anddisposal methods, in addition to the acquisition of data indispensable for immediate storage andmanagement during the stage of trial retrieval and gradual expansion of fuel debris retrieval,examinations, and work. For this purpose, the analysis and assessment should be proceeded within a systematic and flexible manner as required.
The most important thing in the debris retrieval work and in the handling of the waste generated
during retrieval is to proceed with the work under strict work safety management.
3.1.2.2 Further expansion of fuel debris retrieval
To further expand fuel debris retrieval, more consideration should be given to study the retrieval
method from the perspective of the entire Fukushima Daiichi NPS, in association with the scale-upof operations, devices, and facilities. Since TEPCO is at the stage of making a very important
decision for decommissioning as the project executor, TEPCO is required to set up a basic policy
with the perspectives on cost, duration, and total exposure dose, while giving top priority to ensuringsafety, and taking responsibility for carrying out the project. The outcome and information newly
obtained from R&D and internal investigations should be reflected in the study of the retrieval
method, and an approach has to be taken in a flexible manner considering the retrieval method. In
addition, it is important to ensure safety through design and on-site operations, such as reflecting
the information obtained from on-site operations in the design of subsequent stages, based on theconcept of preliminary implementation and utilization of the obtained information in the latter stages,
while paying attention to social aspects such as the impact attributable to the long-term
decommissioning project.
With regard to further expansion of fuel debris retrieval, we will continue to improve theenvironment inside and outside the buildings of Units 1 and 3, and continue to study the concept offuel debris retrieval installations and safety systems, as well as promote the installation design,
based on the research and development results and knowledge obtained through the retrieval at
Unit 2. In particular, it is important to ascertain the feasibility of safety systems designed to secure
the safety functions necessary for proper operation of equipment and devices for the safe retrieval
and storage of fuel debris, and to steadily proceed with studies on the fuel debris retrieval method
through a reliable approach.
(1) Study flow of the retrieval method
With regard to further expansion of fuel debris retrieval, consideration will be given to themethods including those for collection, transfer, and storage of fuel debris, by ascertaining the24

progress in the fuel debris retrieval at the first implementing unit, Internal investigations of PCV,
research and development, and the on-site environmental improvement, etc. In doing so,
operations, devices and equipment, and facilities will be larger in scale and the scope of
construction will be wider than in the case of retrieving fuel debris from the first implementing unit
(Unit 2). Therefore, much more attention should be paid in overviewing the entire Fukushima Daiichi
NPS, including other work. In addition, due to a wider range of operations to be done and studies
in technical fields to be conducted, consideration should be given to the retrieval method bycontinuously gathering international insights. In addition, because of the high dose on site and thelimited understanding of the situation inside the PCVs, the scope of operations will be enlarged.
Therefore, it is important to specify the requirements required for operations and devices moreclearly and to proceed with the study of the systematic retrieval method. NDF will evaluate theactual site applicability and feasibility of the retrieval method based on the results of TEPCO'sconceptual study. The study flow (conceptual diagram) is shown in Fig 9.
TEPCO's Mid-and-Long-term Action Plan for Decommissioning assumes that the study for Unit 3
will be conducted in advance to apply to Unit 1. While a trial retrieval and gradual expanded scaleof the retrieval will be implemented at Unit 2, it is Unit 1 or Unit 3 that enables easy access to alarge amount of fuel debris, because fuel debris remains in bulk at the bottom of the pedestal ofthese Units.
As for Unit 1, the outside of the pedestal will be investigated through the penetration X-2 first forinternal investigations of the PCV, and. Based on the result of these investigations, the retrieval
method should be examined. As for Unit 3, the structures inside the PCV and the bottom of the PCV
were investigated from the penetration X-53 using cameras and dosimeters in October 2015, andthe inside of the pedestal was investigated to obtain information by inserting an underwater ROVfrom the penetration X-53 in July 2017.
In addition, from the viewpoint of securing the work area for accessing to the penetration X-6 andothers, it is estimated to take time in reducing the radiation dose in high dose areas at Unit 1. As for
Unit 3, although the PCV water level must be lowered below the first floor of the reactor building toinsert the survey equipment and the retrieval device, the work can be considered to proceed fasterthan that of Unit 1.
In view of the sufficiency of information mentioned above and the site conditions, Unit 3 will beable to commence debris retrieval and obtain information earlier.
By setting a certain unit as a representative one, it will enable advancement of engineering
including study of retrieval method, and earlier obtainment of technical points and items to be further
studied. Utilizing the results in other units will lead to reducing the overall risk of fuel debris in Units
1 to 3. From the above, it is deemed appropriate to consider Unit 3 as a pioneer unit.
In this way, while taking a pioneering approach at Unit 3, the status of other units and the review
results should be reconfirmed, and the unit under review as a pioneer unit may need to bereconsidered, depending on the outcome. Even if the first implementing unit (Unit 2) is in the processof retrieving fuel debris, the method of proceeding with the fuel debris retrieval shall be flexibly25considered in light of optimizing the overall decommissioning work, for example, by starting theretrieval from another unit that is in preparation for retrieval based on the operation experience from
Unit 2.
On-site work such as
retrieval of fuel debris fromthe initial unit and internal
investigations
 New insight obtained from fueldebris retrieval from the initial
unit and internal investigations

Research and development

 Progress in R&D (theGovernment-led R&D programon Decommissioning andContaminated Water
Management, TEPCO’s
independent project)

Status in the improvement of
workplace environment
 Status in the on-site environment(radiation dose, water level in PCV) Various new installations (including
buildings)
Prospects of site securing (planning forremoval of obstacles including rubble),etc.

Evaluation on the review results of the retrieval concept(including the review on the overall concept)

Status of site-wide planning Contaminated water
management
 Plan for solid waste Interference with other works,
etc.

Evaluation on the actual site applicability
 Safety
 Reliable Reasonable Prompt Field-oriented

 Requirements
 The methods of retrieval, accessing, and debris recovery
 Safety system
 Storage, transport and storage facilities, etc.

Comprehensive evaluation
 Comprehensive evaluation from the above perspectives

Fig.9 Study flow of the retrieval method (Conceptual diagram)(2) Concept of important requirements for the retrieval method (Boundary conditions)
At present, TEPCO is studying the retrieval method by tentatively setting preconditions forrequirements based on the research and development. Although the gradual expansion of fueldebris retrieval has entered the stage of engineering, the phases of design improvement,
performance verification, operation training, and preparatory work have not yet been started. The
further expansion of fuel debris retrieval is still in the research and development stage, and theextraction and examination of the technologies and installations that are supposed to supplement
R&D have just started toward commercialization, but narrowing down a method based on realistic
feasibility has yet to be performed. In narrowing down the method, the uncertainty of the conditions
inside the reactor are an obstruction to full-scale engineering.
To proceed with the examination of a systematic retrieval method in the future, it is required toreexamine the important requirements related to the determination of a retrieval method (theboundary conditions) among the preconditions established at the initial stage of research anddevelopment based on the information and the results of the analyses that have been obtained tothat point to clearly define the requirements, and to revise them as required. In addition, theappropriateness of the concept of the construction method devised at the research anddevelopment stage should be considered and, with regard to a realistic methods, it is also required
to carry out engineering processes such as a trial manufacture in design, performance verification
by mock-up, design improvement, addition of functions in view of the approach to safety, ancillary
preparatory work, and design of the surrounding installations on a considerable scale.
Based on the basic policy, including the perspective described at the beginning of this section,

26

when stipulating the requirements and proceeding with the study on retrieval methods, TEPCO isrequired to clearly define the important requirements (the boundary conditions) as the project
executor. The important requirements (the boundary conditions) shall be stipulated based on thesafety perspective and the operator’s perspective, regarding which requirements to be defined asimportant and which level of performance is required. For example, the important requirements (theboundary conditions) may include the total exposure dose of workers, criticality, dust (containment),
reduction of waste generation, and the recovery rate of fuel debris. Requirements shall be definedin specifics to evaluate the actuality: For example, for the total exposure dose, requirements fromthe viewpoint of how to control the total exposure dose of workers and the exposure dose ofindividual workers; for criticality, requirements for subcriticality monitoring and prevention ofcriticality with the retrieval method; for dust (containment), requirements for suppression ofdispersion of radioactive dust and gas-phase containment; for suppression of waste generation,requirements from the viewpoint of characteristics of generated waste and suppression ofgenerated amount by the retrieval method; for the recovery rate of fuel debris, arrangement ofrealistic targets in terms of achievable recovery speed and recovery rate from the operation side.
In addition to these, TEPCO is required to take the initiative in making decisions on various
important requirements (the boundary conditions) to steadily proceed with the examination of
retrieval methods.
(3) A flexible approach in studying the retrieval method
TEPCO is examining retrieval methods according to research and development. Going forward,
after the aforementioned important requirements (the boundary conditions) are stipulated, it isrequired to take a flexible approach depending on the situation, including partial improvement of
the retrieval method, according to the assessment of the actual site applicability to be implemented
based on the cases of dust dispersion during the opening work of the inner door of the penetration
X-2 for the Internal investigation of PCV at Unit 1, the results to be obtained from future researchand development, and the information to be acquired from a trial retrieval, Internal investigations of
PCV, and gradual expansion of fuel debris retrieval at Unit 2.
When studying the dust dispersion control in “containment” as an example, although the limits
for the amount of release during normal operations and the limits for public exposure during an
accident must be satisfied, we are studying the retrieval method by establishing preconditions
including assumptions, because the amount and properties of particles generated vary dependingon the processing method and the object. In addition to the outcome obtained through these studies,a repetitive and iteration-based approach will be required by incorporating newly obtained
information to verify the appropriateness of the preconditions to be established based on the safety
perspective and the operator’s perspective, and to review the retrieval method based on the results.
(4) Ensuring safety through design and on-site operation
Since the decommissioning of the Fukushima Daiichi NPS is an unprecedented approach, the27

perspective and awareness of those responsible for on-site operations (operation, maintenance,
radiation control, instrumentation, analysis, construction, etc.) are more important than those forconventional reactors. Chapter 2 describes the concept of safety assurance in the decommissioning
work. For example, the operability of the retrieval device for safe handling of fuel debris, condition
monitoring to understand the state of dust dispersion during the retrieval work, and exposure
assessment during the retrieval work are important information for on-site operations. In addition tothis information, it is necessary to acquire information through on-site operations such as analysis
while conducting trial retrieval, gradual expansion of fuel debris retrieval, as well as investigations
and work, and reflect the information in the next design to ensure safety.
In addition, the perspective and awareness of those responsible for on-site operations should beconsidered in establishing the requirements stated in [2], and should be treated as the requirements
in studying the retrieval method in order to determine specific conditions thereof.
3.1.2.3 Continuation of internal investigations, etc., and steady implementation of the Midand-Long-term Decommissioning Action Plan
Fig.10 shows the comprehensive analysis and the evaluation results of the distribution of fueldebris, access routes to fuel debris and condition of the structures around fuel debris of Unit 1 to 3.
These results were derived from actual measured values of plant parameters obtained during theaccident, results of the severe accident progression analysis, information obtained by internal
investigations of PCV, and the knowledge obtained through various examinations. Although thestate of distribution may vary, the analysis indicates that fuel debris exists both inside the Reactor
Pressure Vessel (hereinafter referred to as “RPV”) and at the bottom of the PCV. In order to retrievefuel debris from each unit, better understanding of the conditions inside the RPV and PCV throughcontinuous implementation of internal investigations as well as research and development. In
addition to these efforts, since it is important to understand the current condition of each unit andwhat happened in the accident in order to proceed with decommissioning safely and reliably,
activities should be taken to clarify the causes of the accident at the Fukushima Daiichi NPS to thereasonable extent, in cooperation with domestic and international organizations. (Attachment 7)
The Mid-and-Long-term Decommissioning Action Plan presents the work schedule for trial
retrieval, gradual expanded scale of the retrieval, and further expanded scale of the retrieval, andwill be reviewed and revised on an ongoing basis, based on the knowledge to be obtained throughfuture Internal investigations of PCV, etc. The work schedule should be broken down into more
specific items to realize steady implementation of preparatory work toward fuel debris.

28

(Created based on “Reference 1 : Water sampling included inside the suppression chamber (S/C)” in Unit 3, The 81st Study on Specified Nuclear Facility
Monitoring and Assessment, etc.)

Fig.10 Estimated fuel debris distribution, access route and surrounding structures of Units 1 to 329

3.1.2.4 Technical issues for technical requirements and future plans
3.1.2.4.1 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 that thesafety measures are appropriate. In an ordinary nuclear power plant, such a series of safetyassessment procedures are established and standardized by national regulations and guides. On theother hand, 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 of the Fukushima Daiichi NPS containing the reactor involved in the accident is
an unprecedented activity that takes place in a special environment different from that of a normal
reactor, and therefore, to ensure safety, it should be fully recognized that following characteristics(peculiarity) in safety.
・ A large amount of radioactive materials (including α-nuclides that have a significant impact oninternal exposure) are in an unsealed state, as well as in unusual (atypical) and various forms
・ The barriers to contain radioactive materials, such as reactor buildings and PCV, are incomplete
・ Significant uncertainties exist in the condition of these radioactive materials and containment
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, etc.,
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 the following
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 thedecommissioning period, in consideration of high radiation effects 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:30

Due to significant uncertainties, there is a limit in 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 the design should be complemented
by operators’ efforts and on-site operation to enhance safety in total with the operation. In the
preparation for abnormalities, consideration should be given to on-site response considering thecharacteristics that the progresses of abnormalities is moderate and there is sufficient time forresponse.
In addition, along with organizing the concept for ensuring safety, technical requirements have been
established for ensuring safety of fuel debris retrieval and intensive studies are being conducted asshown in the following Sub-sections 3.1.2.4.2 to 3.1.2.4.7.
3.1.2.4.1.1 Establishing the containment functions (gas-phase)
Dispersion of radioactive material in ordinary operating nuclear power plant is prevented bykeeping interior of a reactor building under negative pressure against the ambient air (active
containment function by maintaining under negative pressure) and pressure in a PCV is maintained
to be equal to that inside of a reactor building (passive containment function). On the other hand,
the reactor buildings, PCVs, etc. of the Fukushima Daiichi NPS are partially damaged by thehydrogen explosion and their containment function has been deteriorated. Due to this,establishment of an active containment function by controlling pressure in negative is being
considered during fuel debris retrieval work. Moreover, from the viewpoint 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, therelease of radioactive materials has been prevented by the PCV gas control system, which isfurnished with filters to remove radioactive materials and measure radioactivity9.
We expect that existing safety systems will be able to cope with the retrieval of fuel debris, suchas gripping and suction, in the case of a trial retrieval or gradual expansion of fuel debris retrieval.
In the subsequent work such as fuel debris cutting, it is necessary to construct the containment
function of the gas phase system in consideration of re-scattering of Cs, etc., that adhere to theequipment and structures in the PCV, aerosolization of water containing radioactive materials, andgeneration of short-lived iodine and noble gases if criticality should occur.
In addition to re-scattering of Cs, etc., it is concerned that dispersed fine particles (α-dust)
containing α-nuclides may be generated and the radioactivity concentration in the PCV gas-phasepart may increase. Therefore, dispersion of α-dust from inside the PCV must be suppressed as

9

TEPCO, The assessment result of the additional volume of release from Units 1 to 4 reactor buildings (June2020). presented as Handout 3-6 at the 80th Meeting of the Secretariat of the Team for Countermeasures for
Decommissioning and Contaminated Water Treatment, May 28, 2020
https://www.tepco.co.jp/decommission/information/committee/roadmap_progress/pdf/2020/d200528_11-j.pdf

31much as possible, and a function for containing the gas-phases should be provided to make thedose 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
conducted by TEPCO, the improvement of dust monitoring installations inside and outside thereactor buildings and the study of equalizing or reducing pressure in the PCV using existing
equipment are being carried out based on the outcome of the Government-led R&D program on
Decommissioning and Contaminated Water Management. In the future, the effect on thesurroundings will be assessed based on the monitoring results of the changes in condition such as
the dispersion of α-dust associated with the work, and the retrieval scale of fuel debris will be
gradually expanded.
In doing so, we are considering establishment of a secondary containment function and study its
necessity, while assuming the possibility of an increasing impact on the surroundings.
R/B and Container

Primary Containment Boundary(PCV Repair + Work Cell)

Cell (Top Access)*PCV closed w/top head in the case of side accessSecondary Containment Boundary(R/B + Cover or Container)*The necessity will be examined.

Negative Pressure
Control System

Air Phase
Section above
PCV water level(Air Phase Section)

PCV Repair (Negative
Pressure Maintained)
Cell
Inner PCV water levelshould be kept
at/below this level

Land Surface

PCV Repair Water Shielding (Liquid–phase)
Stagnant Water Level

Ground Water levelFig.11 Example of 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 are as follows:(1) Understanding of the dispersion rate of α-dust
As described above, for the purpose of fuel debris retrieval work, it is necessary to collect datasuch as α dust dispersion rate and to establish measures to suppress the transition of α-dust gas
phase as much as possible based on the collected data.
To collect data such as the dispersion rate of α-dust, it is necessary to plan demonstration and32

confirmation of the dispersion rate measurement during a trial retrieval and the gradual expansionof fuel debris retrieval that are expected in the future. Moreover, in order to proceed with the reviewof technologies and R&D activities for the fuel debris retrieval method/system under conditions
where such demonstration data have not been obtained, the general behavior related to α-dust
dispersion should be roughly understood. For this purpose, verifications are currently underway byusing the mock-up debris for developing analysis and estimation techniques to characterize the fueldebris.
In order to suppress the transition of α-dust to the gas phase, it is desirable to submerge the fueldebris and to perform retrieving of it as much as possible under water. However, the water level in
the PCV is to be adjusted with other technical requirements such as the building of the containment
function of the liquid phase described in the next section. Therefore, not all fuel debris can be
retrieved under water, and transition of α-dust to gas phase is considered to be mitigated bysplashing water on the fuel debris that is not submerged.
(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 pressure in the PCV in negative, enough capacity of gas exhaust system isrequired considering PCV damage condition. Although damaged part have not been identified yet,and the exhaust capacity is currently evaluated based on the relationship between actual nitrogen
supply volume and actual PCV internal pressure. At this time, it is necessary to maintain sufficientpressure difference to respond to the internal pressure rise of the PCV due to abnormal events
such as an internal temperature rise or stoppage of the gas exhaust system. In order to achievethese, repair of the damaged parts of at the upper part of the PCV will be considered as necessary,
but there are some difficulties such as remote work or exposure of workers due to work under highdose 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
Air flows into the PCV when maintaining pressure in the PCV in negative. Therefore, it isnecessary to examine measures of maintaining inactivated condition in the PCV by increasing
nitrogen gas supply into the PCV as necessary based on evaluation on occurrence of accidents
such as fire and Hydrogen explosion using accumulated information regarding to volume ofhydrogen 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.11, for fuel debris retrieval, it is assumed that a working cell is newly installed33

as connected to the PCV under negative pressure control, and the work from retrieving the fueldebris to collecting the container into a transfer cask is performed in this cell. The PCV and thisworking cell have a primary containment function to prevent α-dust to the exterior.
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,large capacity of 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 the its leaktightness may have been deteriorated due to the accident. Therefore, based on the accumulated
results of the tendency of dust dispersion obtained hereafter, it will be necessary to ascertain therequired functions to establish a secondary containment function and to proceed with research anddevelopment accordingly.
D.

Deterioration control of the containment function of the PCV
In order to maintain pressure in the PCV in negative during the fuel debris retrieval work, it isnecessary to consider how to respond deterioration of the primary containment function consistedof the PCV and the attached cell due to earthquakes and aging. This is outlined in Section
3.1.2.4.1.5.
(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 by measuring
and controlling the release concentration and the release amount. In addition, α-nuclides 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 in advance. By using such data,a system for early detection of abnormal events such as leakage and implementing appropriate
impact mitigation measures should be established for preventing an impact on environment andworkers.
Reliability or accuracy of mechanical property and chemical composition of the fuel debris needs
to be improved because these are essential information for designing the decontaminationequipment for efficient collection of radioactive dust.
3.1.2.4.1.2 Establishing the 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 by34

gripping 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 affecting the environment, it may be of great importanceto establish a cooling water circulation/purification system, and a liquid phase containment function.
(Fig.12)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, theGovernment-led R&D Program on Decommissioning and Contaminated Water Management has
been promoting research and development. 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 is beneficial in terms of preventing the spread of cooling water containing α particles, wasconsidered in research and development by the Government-led R&D Program on
Decommissioning and Contaminated Water Management.10
To establish a reasonable containment function in each phase of the scale expansion of fueldebris retrieval, it is rational to monitor the radioactive concentration of cooling water per phase andverify the validity of the containment function to be built in the subsequent phase. As with thecontainment function (gas phase), from the viewpoint of verifying/investigating the impact of theretrieval work on the liquid phase, TEPCO, through the engineering work, has been discussing
monitoring of the circulating water system as well as system addition/installation, etc., for the
purpose of reducing the concentration of radioactive materials at the inlet in the existing water
treatment systems according to the results of the Government-led R&D Program on
Decommissioning and Contaminated Water Management.11 With regard to the effects on the liquid
phase during debris retrieval operations, the scale of fuel debris retrieval will be expanded gradually,
based on the results of monitoring changes in the condition of waste fluid containing α-nuclides.
The water level in the reactor building is required to be maintained lower than the groundwater levelto prevent the outflow of cooling water to groundwater and to appropriately control the water levelin the PCV. Safety systems are to be established taking this into consideration.
In establishing this containment function (liquid phase), technical issues to be addressed
immediately for further expansion of fuel debris retrieval are as follows.

10 IRID,FY 2017 Supplemental subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management, “Technical Development for Water Circulation System Establishment in thePrimary Containment Vessel (Full-scale Test)”, Final Implementation Report for FY 2019, August 2020.
http://irid.or.jp/wp-content/uploads/2020/09/2019006mizujyunkan.pdf
IRID, FY 2017 Supplemental subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management, Technical Development for Water Circulation System Establishment in thePrimary Containment Vessel (Full-scale Test), Final Implementation Report for FY 2019, August 2020
http://irid.or.jp/wp-content/uploads/2020/09/2019007mizujyunkanjitukibo.pdf
11 IRID, FY 2016 Supplementary Budget, Subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management, Advancement of Retrieval Method and System of Fuel Debris and Internal
Structures, FY 2018 Final Report, July 2020.
http://irid.or.jp/_pdf/20180000_13.pdf

35

R/B and Container

Primary Containment Boundary(PCV Repair + Work Cell)*PCV closed w/top head in the case of side access

Cell (Top Access)Secondary Containment Boundary(R/B + Cover or Container)*The necessity will be examined.

Circulating
Water Cooling
SystemWater Level
Management

PCV Repair (Gas-phase)(Liquid Phase Section)
Cell

Inner PCV water levelshould be kept
at/below this level

Land Surface

PCV Repair Water Shielding (Liquid–phase)

Liquid Phase
Section below
PCV water level

Stagnant Water Level

Ground Water levelFig.12 Build example of 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 waste liquid when gradually expanding the scale of retrieval.
To suppress an increase of radioactive concentration in cooling water in the PCV, dust generated
by fuel debris cutting is planned to be collected through the PCV circulating cooling system tomitigate dispersion of dust. It is recommended to incorporate the results of monitoring by theexisting water circulation system into examinations on the PCV circulating cooling system asnecessary in the phase of gradually expanding the scale of retrieval.
(2) Setting of water level in the PCV
Due to a low seismic margin of SC support columns, it is recommended to lower the water levelin the S/C. In this instance, it is required to appropriately set and manage the water level in the PCV
with consideration for the damage situation of the PCV in each Unit and prevention of the outflow
of cooling water to groundwater (maintaining the water level in the reactor building below thegroundwater level), etc., and to confirm that safety is ensured in terms of fuel debris cooling andcontrol of dust dispersion.
3.1.2.4.1.3 Maintaining the cooling functions
Fuel debris generates heat due to the decay of radioactive materials. At Unit 2 after a lapse of
10 years since the accident, for example, the amount of heat generation has reduced to 1/1000 of36

the level at the time of the accident. However, the maximum heat generation is still estimated to be
69 kW12. Therefore, unless cooling is continued, the surrounding materials gradually absorb heatgenerated and there is concern that the following events may occur.


The oxidation proceeds caused by increasing the temperature of uranium oxide in fuel debris(increased O/U ratio) resulting in volume expansion, crack generation, and thereby
progression of pulverization.



Moisture in concrete structures is also dissipated and dried by heat, and then cracks occur todecreased 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 above four events and excessive temperature rise of fuel debris, thetemperature is being maintained below 100°C (cold shutdown condition) currently by conducting
circulating cooling with water injection into the reactor.
Until FY 2019, water injection into the reactor has been temporarily suspended with the aim of
optimizing operation/maintenance management of cooling systems and emergency response
procedures, etc. In addition, during the fuel debris retrieval work, it is necessary to keep thetemperature below the level at which the fuel debris retrieval device can continue to work without
any problems for a long period of time.
However, it should be considered that the injection of cooling water may become redundant in
the future due to further decrease in the amount of decay heat along with reduction in the remaining
amount of fuel debris, as the fuel debris retrieval progresses.
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 flexible countermeasures, etc., it is necessary toevaluate changes 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.
In addition, during the fuel debris retrieval operation, the processing of cutting fuel debris while
12

Nishihara Kenji, et al., JAEA, “Evaluation of fuel composition in Fukushima Daiichi NPS”, JAEA-DATA/Code2012-018(2012).

37

spraying water is conceivable from the viewpoint 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 order to carefully promote fuel debris retrieval work while observing
how this work will affect the existing circulating water cooling and purification system, as well as its
cooling function.
3.1.2.4.1.4 Criticality Control
At present, monitoring of the concentration of Xe-135, which are short-half-life fission products,
has shown no sign of criticality as the concentration remains lower than the criticality criterion of 1
Bq/cm3. In addition, the possibility of re-criticality of the fuel debris at the Fukushima Daiichi NPS
is presumed to be low based on the expected condition of the existing fuel debris from theengineering viewpoint, because the alternation of molten fuel assemblies is not likely to reachcriticality due to the abundance ratio with water, and the mixture of impurities, such as internal
structures, can be expected in the course of core meltdown. Furthermore, the fuel debris ispresumed to scatter in a wide area beyond the core as a result of the accident progression. Even
assuming the possibility that control rods may have melted down before the fuel elements in thecourse of core meltdown and that the optimum mixing of incidentally crushed fuel debris with water
occurs, the scale of criticality is considered to be small.
Though the possibility of criticality is low, fuel debris retrieval alters the shape, etc., of fuel debris.
Therefore, it is essential to prevent reaching criticality during retrieval without fail by investigating
what conditions would lead to criticality if shapes, etc., of fuel debris change, and to establish an
appropriate control method for ensuring prompt detection and shutdown in case of an unexpected
criticality.
In the initial phase of fuel debris retrieval work, fuel debris should be retrieved by limiting thetreatment amount based on methods that will not significantly change the fuel debris shape, suchas by gripping and sucking, as well as the estimated fluctuation of reactivity. Also in the process of
expanding the retrieval scale and cutting, the retrieved volume of fuel debris will likely be increased,
while taking measures such as measurement of pre-work subcriticality and preparation for insertionof neutron absorbers. In addition, through the overall retrieval operations, unless the criticality is
unlikely to occur in consideration of the retrieval conditions, it is necessary reliable criticality
prevention measures that combine design and evaluation with operator monitoring and judgment,
specifically fuel debris retrieval while evaluating it’s criticality by checking the amount of neutron
signal fluctuation in the vicinity of the fuel debris.
To maintain the subcritical condition more reliably for fuel debris storage after retrieval, it isimportant to store it stably while controlling the shape and size, for instance, by storing the debris
in canisters.
For this criticality control, technical issues to be addressed for the time being are as follows.

38

(1) Establishment of criticality evaluation method
It is necessary to refine the information on the conditions for reaching re-criticality in fuel debris
based on information to be obtained from each phase of fuel debris retrieval, including internal
investigations. In this regard, an evaluation method has been developed to estimate the conditions
for subcriticality and the degree of influence of criticality if it should happen. In conducting theseevaluations, a plan should be made so that the information on the critical parameters with highimpact on the criticality evaluation can be obtained in the course of internal investigation andretrieval, and to revise the plan through information updates as needed.
(2) Local neutron measurement around retrieval point
There are various kinds of existing neutron detectors according to application such as fission
chamber, B-10 proportional counter tube, semiconductor detector, etc. Taking advantage of eachfeature, selection of neutron detectors to each phase is under consideration. The key specifications
for the neutron detectors required for criticality monitoring are; (1) ability to survive accumulated
radiation dose (Gy) according to the operation period and (2) installability in assumed equipment(size/weight, cable diameter) or installability at a work site (size/weight, cable routing); and (3)required detection efficiency (time, accuracy). Accordingly, it is important to select an optimal
detector based on the information on PCV dose rate obtained by internal investigation and theprogress of equipment development for each unit. In addition to subcriticality measurement, a small
detector is highly likely to be used for continuous monitoring of local neutron measurement as asingle detector, and therefore it is necessary to continue discussions toward practical applicationsof local and continuous monitoring. More specifically, the feasibility of continuous monitoring needs
to be examined, including not only the specifications of neutron detectors and their location andquantity, but also what kind of evaluation can be performed based on the obtained data. As specificoperation methods, moreover, it is required to set up determination criteria on operationsuspension/resuming due to fluctuation of the neutron flux and on boron injection as a neutron
absorber.
The possibility of criticality needs to be examined in places other than retrieval locations. For
example, criticality may occur in places where fuel debris cutting particles are accumulated, whichcannot be collected in the circulating water cooling system (i.e. outside the PCV bottom pedestal,in piping, water filters, waste water receiving tanks, etc.). Though criticality can be detected by the
PCV gas monitor system, countermeasures will be considered in accordance with criticality risk
scenarios and evaluations, including the feasibility of approach-to-criticality monitoring.
In the engineering work, the concept design is in progress for circulating water system
configurations and system specifications for further expansion of fuel debris retrieval. In order toavoid redoing work in a later phase, criticality assessment for each device needs to be performed
early, and activities are in progress to extract criticality prevention measures that greatly affect thedevice specifications in advance.

39

(3) Feasibility study of measuring the degree of sub-criticality
When measuring the degree of sub-criticality, in addition to the required specification of (2), it isnecessary to select a detecting device with high fidelity and response speed in order to measure aweak neutron signal, capturing a neutron fluctuation in a very short time under a gamma rayenvironment. From the examination to date, considering the equipment mountability(size/weight/electromagnetic noise) and operation methods (measurement time and duration,
installation location, etc.) by sensitivity are key issues due to the necessity of lead shielding in ahigh ɤ-ray environment (assuming 1000 Gy/h). In the future, it will be necessary to consider
selection and optimization of the neutron detector, reflecting the constraints (weight, size, cablehandling, interference with arms, balance between measurement and processing time, etc.)
introduced by the fuel debris retrieval methods and systems. Meanwhile, practical applicability ofthe detectors on site is under review in light of an approach to assess the ɤ-ray radiation dose rate
and neutron count rate in the vicinity of the fuel debris as well as constant monitoring, and bydownsizing with the combined use of several detectors, etc.
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 required to assess the technical feasibility andlimit the applicability by planning and demonstration for technical verification.
(4) Feasibility study of neutron absorber
Based on the information obtained in each phase of scale expansion, in preparation for cases
where the level of fuel debris criticality is high or technical feasibility of measuring the degree ofsubcriticality has limitations, assessments on the required boron concentration and feasibility
studies on installations are in progress for the cases of filling with sodium pentaborate during normal
fuel debris retrieval. As a result, environmental impact in the event of leakage and compatibility withconcrete as structural materials has been evaluated 13 . While examining operation details tomaintain the boron concentration in consideration of the impact on the PCV circulation coolingsystem as well as the impact on systems and waste during segregation, collection, re-use andtreatment of boric acid, their needs to be consideration of the necessity and adverse effect ofconstant injection of sodium pentaborate, and verification of the applicability on site together withcritical approach monitoring methods described in (2) Local neutron measurement around retrieval
point.
In addition, if criticality should occur, emergency sodium pentaborate injection would be used toachieve a subcritical state, however, the methods for maintaining subcriticality after transition(lowering the water level, maintaining the boric acid concentration, etc.) as well as recovery
methods need to be determined.
13 IRID, FY 2017 Supplementary Budget, Subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management, Advancement of Retrieval Method and System of Fuel Debris and Internal
Structures (Development of Technology for Criticality Control in Fuel Debris Retrieval), Final Report, July 2019,http://irid.or.jp/_pdf/20180000_04.pdf

40

Moreover, to ensure subcriticality maintenance when the margin for criticality of fuel debris issmall, development is also underway for a non-soluble neutron absorber that can locally limit the
impact on the PCV circulating cooling system. Until now, fundamental property testing and radiation
resistance testing have been conducted to list B4C metal sintered materials, glass containing B/Gdand Gd2O3 particles, sodium silicate and Gd2O3 granulated powder as candidates for non-soluble
neutron absorbers. For these candidates, the impact of long-term irradiation on the integrity ofcanisters during storage of fuel debris, the method of spraying on fuel debris for debris crushing,
and the effect after spraying have been verified.
To introduce non-soluble neutron absorbers, it is required to study the impact on PCV corrosionand environmental impact in the event of an environmental release.
(5) Detection of criticality by PCV gas management installations
Immediate criticality monitoring and sophistication of detectors in the PCV gas monitor is required
to detect when approaching criticality and criticality in the vicinity of fuel debris retrieval, and to
detect criticality due to the fall of fuel debris and/or accumulation of powder debris in locations otherthan fuel debris retrieval.
By measuring Kr-87/88 with high trackability for reactivity changes, in addition to Xe-135 that has
already been measured, it has been found that criticality detection can be accelerated and that thelevel of subcriticality of the entire PCV can be presumed. However, the method of application to theactual plants is to be examined in the future.13
3.1.2.4.1.5 Ensuring the structural integrity of PCVs and buildings
As for the main devices in the PCV/PRV pedestal, etc., and reactor buildings, their structural
integrity has been evaluated in post-accident studies by TEPCO and the Government-led R&D
Program on Decommissioning and Contaminated Water Management. As a result, it has been
confirmed that the main devices and reactor buildings have a certain level of seismic margin.
Hereafter, the existing main devices and reactor buildings, as well as devices/systems(hereinafter referred to as “systems”) and buildings (including modified areas of the existing
systems and building) 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 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 Internal investigations of PCV and debris analysis results,
etc., to the design of fuel debris retrieval systems and the study of retrieval methods. The followingshows the key functional requirements as examples.


Existing systems 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,

41

etc., and control/prevent large release of radioactive materials (maintaining
containment functions).
 Reactor buildings, etc., safely support systems to be newly installed in the reactor
buildings for fuel debris retrieval in addition to the existing main devices (maintaining
support functions).


Systems and buildings to be newly installed for fuel debris retrieval (including
connections to the existing systems)
 Have functions according to design requirements and control/prevent large releaseof radioactive materials (ensuring containment functions).
 Safely support 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.).

With further progress in designing, the loading conditions (layout, size, weight of the new systems,
new openings on PCV/biological shielding walls, etc.) during fuel debris retrieval will be specified.
In order to ensure the structural integrity of systems and buildings, while reflecting the site
conditions, examinations will be promoted steadily based on the latest design information.
In the specific design of new systems and buildings, it is important to define seismic classes andperform seismic evaluation accordingly. On the other hand, it is still challenging to repair andreinforce buildings and major devices damaged by the accident in a high radiation dose
environment. Because of that, earthquake motions and criteria used in the design will beappropriately defined, taking into account the viewpoint of risk assessments.
3.1.2.4.1.6 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 and access routes.
As a related operation to fuel debris retrieval, removal of equipment with high radiation doses isplanned, in which reduction of exposure during operation is an issue.
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 occupational workers throughappropriate radiation protection schemes depending on the working environment and working style.
Regarding protection from external radiation exposure, the radiation exposure dose is evaluatedconsidering the radiation sources and the radiation dose rate in the work area. Then, based on the42three principles, namely “time, distance, and shielding”, taking measurements to reduce radiation
exposure to as low as reasonably achievable will be needed.
Therefore,anappropriate

combinationofexposure

reductionmeasuressuchasdecontamination, shielding, remote technology etc. is to be selected, with the following ideas inmind.
Consider first of all the reduction of exposure to radiation by 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 contaminated areas such as inside the PCV and torus rooms, work shouldbe 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 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 and personnel
employment must be made based on factors such as the dose rate in the target areas, typeof contamination, space for work, frequency of use, applicability and development situationsof remote technologies, schedule and cost, etc.



A 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 the protection from internal exposure, measures such as suppressing dispersion ofradioactive dust and prevention of contamination expansion 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. In the abnormal event of intake, in order to assess the committed effective radiationdose by external counting (lung monitor) or bioassay, it is important to select α-nuclide importantfor exposure assessment in advance and incorporate it into the control of airborne concentration,
standards of wearing protective equipment, and device calibration management. Controlling thesurface 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 an intake of re-suspended dust from loose contamination.
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 to hand down knowhow.
For further expanding fuel debris retrieval, it is necessary to develop a database that enables

43

sharing of information and prompt feedback for the next work plan.
In particular, concerning the reduction of radiation exposure of workers in the reactor building, it
is important to conduct sufficient investigations on the dose distribution and contamination
conditions, including the contribution of surroundings of the subject areas, to identify the source
locations and intensity as much as possible and to develop a plan for radiation dose reduction for
securing the essential work environment for work areas and access routes. Upon adequate
verification on the operation feasibility, the target dose rate in the work areas and access routes
shall be set in consideration of the margin for the radiation exposure dose limit (50 mSv/year and
100 mSv/5 years) for workers specified by laws and regulations. In the radiation dose reduction
plan for high radiation dose areas, it is important to take management measures to reduce the total
radiation exposure dose to as low as reasonably achievable and accomplish operations withrespect to work hours in accordance with dose limits and required work hours to accomplish
operations.
Once fuel debris retrieval is started in the future, the generation of α-nuclide increases in theseries of operation processes. In addition to normal operations, management methods and systems
are required, which are capable of containment and leakage detection in preparation for diffusionin the air and to the water treatment system due to problems, etc. Since α-nuclides have been
detected in the stagnant water and on contaminated floors, it is necessary to take measures toprevent body contamination of workers and the spread of contamination outside the R zone, and it
is important to have changing places and improve contamination detectors for α-rays.
In addition, adequate radiation exposure control should be conducted after formulated a longterm work plan that includes not to concentrate workers’ radiation exposure on individual workers
and to help reduce whole workers’ radiation exposure.
3.1.2.4.2 Technical issues related to fuel debris retrieval methods
3.1.2.4.2.1 Securing access route
For transporting, installing, and unloading the devices and equipment used for fuel debris
retrieval work, and transporting fuel debris and waste, access routes should be established byremoving obstacles on the access routes and reducing the radiation dose in the R/B to the level atwhich such tasks can be performed. When establishing new openings in the PCV or the like toconstruct the access routes to fuel debris, it should be kept in mind suppressing of the release ofradioactive materials from the PCV and RPV and integrity maintaining the existing structures interms of the gas phase containment function described in Sub-section 3.1.2.4.1.1.
The Mid-and-Long-term Roadmap indicates that the first implementing unit would be Unit 2 andtrial retrieval begins within 2021 toward gradual expansion of fuel debris retrieval. Accordingly,
TEPCO is currently proceeding with specific engineering studies to conduct an access route from
penetration X-6 at Unit 2.
On the other hand, toward a further expansion of fuel debris retrieval, studies are underway on

44

the construction of access routes from the side opening of the PCV to fuel debris (the side accessmethod), based on the results of research and development conducted to date by the Governmentled R&D Program on Decommissioning and Contaminated Water Management. In the side-accessmethod, suspension bridge and access tunnel systems is being examined. However, the issue isto address containment, shielding for connecting structures between newly installed heavy
structures and side-opening of the PCV, and seismic displacement.
As for the construction of access routes including top access, in addition to the side access, thetechnology to remove obstacles as well as transportation methods that shorten the preparation
processes for retrieval are under review for enhancing throughput. The Government-led R&D
Program on Decommissioning and Contaminated Water Management is currently examining thefeasibility of the method to retrieve and transport interfering structures as a single or a large unit
while ensuring containment and shielding.
In the future, based on the above-mentioned tasks, it is necessary to define the access route
clearly to be built at the next stage from the data obtained at each phase of scale expansion. In
particular, at the time of cutting the inner door of the penetration X-2 at Unit 1, the dust concentrationin the PCV increased more than expected before the start of the work. Therefore, not only
countermeasures against dust dispersion, but also the time required for responding to such asituation shall be considered and planned.
Since the fuel debris retrieval policy stipulates that an 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 future scale expansion.
3.1.2.4.2.2 Development of devices and equipment
In each phase of trial retrieval, gradual and further expansion of fuel debris retrieval, devices andequipment for fuel debris retrieval need to be developed with emphasis on safety, reliability, andefficiency. To flexibly respond to the situations inside the RPV and the bottom of the PCV wherefuel debris is predominantly present, the specifications of devices/equipment to be developed inthese 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 avoidance or automatic
shutdown in case of abnormality, high reliability, appropriate redundancy, a rescue mechanism that
does not disturb the subsequent work when trouble occurs, and efficiency of fuel debris retrieval.
Equipment development for trial retrieval and gradual expansion of fuel debris retrieval has beenin progress as part of research and development of the Government-led R&D Program on
Decommissioning and Contaminated Water Management. After the gradual expansion of fueldebris retrieval, TEPCO needs to take over and substantiate the development results. TEPCO isproceeding with the engineering of robot arms, etc., to be applied to Unit 2, while preparing
education/training for the operation of fuel debris retrieval using these remote devices. Prior to
installing remote equipment such as robot arms on site, adequate performance verification and45

operation training are essential by using mockups simulating the expected PCV internal
environment. For this purpose, development of mockup systems is required.
As for devices and equipment for further expansion of fuel debris retrieval, development isunderway for construction methods for improving efficiency, retrieval/handling systems according
to diverse conditions of fuel debris, and dust collection systems for dust generated during fuel debris
crushing. Specific examples of ongoing development activities include: Research and development
for removal of large-scale structures by the top access and removal of obstacles by top and side
access methods; development of fuel debris cutting/crushing systems (mechanical, thermal) anddust collection/dispersion control systems; development of retrieval/collection systems according
to diverse conditions of fuel debris (fragments, sludge, fine powders, etc.); remote operation support
for robot arms, etc.; on-site transportation of unit cans including fuel debris; removal of soluble
nuclides in circulating cooling water; treatment of deposits collected from the PCV; and predictionof dust behavior in the PCV. Furthermore, techniques to install devices and equipment used for fueldebris retrieval are required. With the assumption of remote operation, research and development
is under way for installing work cells to establish radiation shielding and gas phase containment
functions and for connection methods with the existing structures.
As for how to proceed with development, it is required 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 demonstrate their performance safely and reliably at the actual site. This
mockup test needs 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 organizations concerned, NDF and TEPCO are engaged in examining how toproceed with the remote mockup test plan, the test plan review, the scope of the mockup facility to
be maintained, the necessary time, operation management, etc.
3.1.2.4.2.3 Establishment of system equipment and working areas
Assuming to ensure safety functions, and considering avoiding excessive system specifications,
it is required to examine the establishment of system installations, etc., take necessary measures
such as system additions based on the results of such examinations, and then to operate themproperly. In examinations, 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 equipment include a negative pressure control system required for establishing acontainment function (the air phase), a circulating water cooling/purification system required formaintaining the containment function (the liquid phase) and cooling function, and a criticality control
system required for controlling criticality. Moreover, realization of measurement systems (for46

pressure, temperature, water level, radiation, etc.) to monitor the PCV internal conditions is asignificant issue, which is essential for fuel debris retrieval. In order to build safety systems
incorporating the above, TEPCO, through engineering work, has tentatively set assumptions(design conditions for installations) based on research and development by the Government-led
R&D Program on Decommissioning and Contaminated Water Management, and has been
examining system design and layout. In particular, it is important to ascertain the feasibility of safetysystems designed to secure the safety functions necessary for proper operation of equipment anddevices for the safe retrieval and storage of fuel debris, and to steadily proceed with studies on thefuel debris retrieval method through a reliable approach.
The working area required for installing fuel debris retrieval equipment/related devices andsystem installations is now being calculated. Considering the handling of high radiation dose areasin the reactor buildings and interference with other tasks, study of setting up the systems, including
outside of the existing buildings, is underway.
3.1.2.4.3 Technical issues related to safe and stable storage of fuel debris
3.1.2.4.3.1 Handling of fuel debris (collecting, transferring and storing)
Before initiating fuel debris retrieval work, a comprehensive system should be established thatconsists of a series of steps from containing and transferring to storing of retrieved fuel debris
furnished with safety functions such as maintaining subcritical condition, containment function,
countermeasures against hydrogen generation, and cooling. The following examinations are in
progress accordingly14.
Drawing up of basic specifications of the container, that is, overall length considering its
handling, internal diameter in light of work efficiency and maintaining subcriticality, etc.,
and demonstration of the structural integrity of the container by performing structuralverification test.

Examination of a practical and rational prediction method of hydrogen generation from fueldebris stored in container; determination of vent mechanism for hydrogen gas exhaust 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 the container or theunit can, and consideration on a drying system using this technology

In the future, based on the results of these studies, specific systems and devices/facilities fromcontaining to storing fuel debris should be developed in coordination with other associated projects.
In addition, further studies should be made on the specific transfer method, the specific type andsize of the storage facility, and others by taking into account the amount of fuel debris to be retrieved
14 IRID, FY 2018 Supplementary Budget, Subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management “Development of Technology for Collection, Transfer and Storage of Fuel
Debris), FY 2019 Implementation Report, August 2020,
https://irid.or.jp/wp-content/uploads/2020/09/2019010syuunouisouhokan.pdf

47per day and the fill rate of containers. In developing the specific facilities and systems for handlingand storing retrieved fuel debris, it is also necessary to give consideration to the system/devices
responding to safeguards requirements.
It is important to reflect various measurement data such as the amount of hydrogen generated
from fuel debris, as well as knowledge and experiences on handling fuel debris during theoperations from receiving the fuel debris by containers for on-site transportation to temporarystorage collected and accumulated during gradually expanded scale of fuel debris retrieval work,
into the design of systems and facilities for containing, transporting, and storing fuel debris safely,
reliably, and reasonably at further expanded scale of fuel debris retrieval work as much as possible.
In addition, it is necessary to specify transfer routes and storage facility locations for further
expanded scale of fuel debris retrieval work in light of the usage plan for the entire site.
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.
3.1.2.4.3.2 Classifying of fuel debris and radioactive waste during fuel debris retrieval
In each operation phase of fuel debris retrieval, preparations and cleanup work for that, etc., avariety of radioactive waste such as removed or disassembled structures or parts, with nuclear fuelmaterials attached or fused will be retrieved from the PCV in addition to fuel debris. Of these, if
substances containing (or are adhered to) a small amount of nuclear fuel materials are all deemed
as fuel debris, the amount would be enormous. It is not rational because scales of equipment andfacilities become larger and securing of site will be needed. For this reason, it is important to develop
classification criteria between fuel debris and radioactive waste and their necessary measuring
technologies.
At present, progress has been made to collect and analyze the information on the distribution
and properties of fuel debris and structures in the PCV necessary to examine methods forclassifying retrieved material from PCV into fuel debris or radioactive waste including various
obstacles and structures, and storing properly. However, it is practically difficult to accumulate,organize, and analyze sufficient information necessary for research and development ofclassification prior to actual fuel debris retrieval work. Under these circumstances, it isrecommended to aim for classifying retrieved material into fuel debris or waste based on themeasurement results of the amount and concentration of nuclear fuel materials. The following
studies were conducted as a first step in response to this.15
Considering in which steps in a series of operation processes, from retrieval in the PCV to
storage, classifying is feasible to sort retrieved materials from the PCV (fuel debris,

15 IRID, FY 2018 Supplementary Budget, Subsidies for the Government-led R&D Program on Decommissioning andContaminated Water Management (Development of Technology for the Further expansion of Fuel Debris andInternal Structure Retrievals), FY 2019 Implementation Result, April 2020
https://irid.or.jp/wp-content/uploads/2020/09/2019008kibonosaranarukakudai.pdf

48

structures, etc.) into fuel debris and radioactive waste (consideration of categorizing
scenarios)

Investigation of techniques/equipment that may be capable of measuring the content of
nuclear fuel materials contained in the materials retrieved from the PCV for classifying(investigation of possible measurement techniques)

From these studies, it is currently considered as highly difficult challenge to measure or estimate
the amount and concentration of nuclear fuel materials in the retrieved material from the PCV.
However, it is determined that development of classifying criteria and necessary measuring
techniques/equipment to appropriately judge whether the materials retrieved from the PCV shouldbe treated as fuel debris or radioactive waste at the time of further expanded scale of fuel debris
retrieval work will contribute to achieving efficient and safe decommissioning, such as by reducing
the physical amount of materials to be stored as fuel debris. For this reason, it is recommended tocontinue development of criteria for classifying into fuel debris and radioactive waste, andmeasurement techniques/equipment. It is also important to continue activities to enhance theeffectiveness and practical applicability of classification methods (classifying criteria, scenarios) andtechniques (measuring techniques/equipment) by leveraging knowledge and information obtainedby survey of internal PCV and analysis results of samples batched off from fuel debris retrieved
during trial scale, gradually expanded scale or further expanded scale of fuel debris retrieval work.
3.1.2.4.3.3 Examining safeguards methods
At the Fukushima Daiichi NPS, the safeguards implemented before the accident are notapplicable due to the damage on fuel assemblies and destruction of reactors/buildings. However,
the appropriate safeguards have been applied along with the progress of the decommissioning
process through cooperation and information sharing between Japan Safeguards Office(hereinafter referred to as “JSGO”) of the NRA, International Atomic Energy Agency (hereinafterreferred to as “IAEA”) and TEPCO. As a result, the IAEA and JSGO confirmed that there had beenno diversion of nuclear materials and undeclared nuclear materials or nuclear activities. (For theconcept of the safeguards, refer to Attachment 8)
New material accountancy and safeguards are expected to be applied to the retrieved fuel debris
depending on its properties and conditions. As it is unprecedented, TEPCO may face technicalissues in examining and applying them to the site.
In response to that, NDF will support the examinations aimed at solving such technical issues
from an engineering viewpoint, and will share information on the progress of the project with TEPCO
in order to ensure that system arrangements related to the application of safeguards do not affectthe decommissioning process.
3.1.2.5 Summary of key Technical issues
The main technical subjects and plans described in this section are summarized as shown in
Fig.13.

49

Short term (approx. 3 years)
Period 3 - (1) (Starting from fuel debris retrieval up to the end of 2031)
Fiscal Year

2020

2021

Gradual expansion of fuel debris
retrieval(Unit 2)

2025

▽Start of the fuel debris retrieval in theinitial unit (by the end of 2021)

RM milestones

Trial retrieval(Unit 2)2022

Improve the environment
inside the building

On-site operation: Work period: The period during whichchange is expected
Technical studies on individual items relating to on-site construction

Experimental retrieval and internal
investigations

Manufacture and install the
retrieval device

2031 (Year): To be conducted as required

R&D

Technical issues in the Government-led R&D program on
Decommissioning and Contaminated Water Management

Characterize the fueldebris
Improv e the env ironment
inside the building

Fuel debris retrieval facility/safety system/fuel debris temporarystorage facility/maintenance f acility
Design and production

Gradual expansion of retrieval scale

Installation

Characterize the f uel debris

Review of the program on
Decommissioning and Contaminated
Water Management andTEPCO'voluntary project- Development of Technology for
Detailed Investigation inside PCV- Development of technologies forgrasping and analyzing propertiesof fuel debris- Development of technology forgradually expanded-scale retrievalof fuel debris
Technical study by TEPCO- Fuel debris characterization/Development of analysis
technology(1) Advancement of fine particle (dust) behavior
estimation technology(2) Estimation of aging properties- Development of technology for gradually expanded-scale retrieval of fuel debris(1) Addressing payload growth and upgrading end tools(Trial manufacturing of arms/enclosures --> Use them as a mock-up during training)

Improvement of the environment inside and outside the Unit 1 building (Inside of the building: Dose reduction/removalof obstacles; Outside of the building: Removal of exhaust tow ers of Units 1 and 2/removal of transf ormers, etc.)

Further expansion of fuel debris Improvement of the environment inside and outside the Unit 3 building(Inside the building: PCV w ater lowering/dose reduction; Outside the building: removal of the exhaust tow ers of Units 3 and 4, removal of transformers, etc.)
retrieval(Units 1 and 3)
Fuel debris retrieval facility/safety system/fuel debris storage f acility/maintenance facility *Review on the concept

Actual site applicability verification,
development(Remote installation, dust diffusion control, etc.)

DesignProduction, installation, and retrieval

Review of the program on
Decommissioning and Contaminated
Water Management and TEPCO's
voluntary project- Development of technologies toretrieve fuel debris and internal
structures toword further expansionof retrieval- Development of Technology forCollection, transfer and Storage ofFuel Debris- Development of technology forinvestigation inside the RPVTechnical study by TEPCO- Development of technologies to retrieve fuel debris and internal structures, addressing
a further scale expansion- Development of technology for investigation inside the RPVConstruction method by top/side/bottom-access(1) Development of fuel debris retrieval method (ensuring safety --> higher efficiency)
a. Improvement of installations and devices for access/technology for removing
obstacles/internal audit methodb. Preventing the spread of radioactive materials(1) Technology for removing obstacles, etc, Access device(2) Development of safety systems (liquid and gaseous systems, criticality control)a. Enhancement of the containment of radioactive materials; b. Enhancement of
the removal of radioactive materialsc. Enhancement of criticality prevention/criticality monitoring functions(2) Surveillance devices (camera, radiation detector,
experimental retrieval device, etc.)(3) Preventing the spread of radioactive materials* It is assumed that Unit 3 w ill be examined in advance and expanded to Unit 1.

Fig.13 Technical issues and future plans on fuel debris retrieval (progress schedule)503.2 Waste management
3.2.1 Targets and progress(Targets)(1) The Solid Waste Storage Management Plan (“Storage Management Plan”) is appropriately
developed, revised and implemented including waste prevention, volume reduction andmonitoring, with updating the estimated amount of solid waste to be generated in the next ten
years periodically.
(2) Countermeasures integrated from characterization to processing/disposal of solid waste arestudied from the expert point of view, and the prospects of a processing/disposal method andtechnology related to their safety should be made clear by around FY2021.
<Key Points of "Basic Policies on Solid Waste">(1) Thorough containment and isolation
Thorough containment and isolation of radioactive materials to prevent theirdispersion/leakage and human access to them, in order not cause harmful radiation
exposure.
(2) Reduction of solid waste volume
The amount of solid waste generated by decommissioning is reduced as much as possible.
(3) Promotion of characterization
Proper characterization addressing an increase in the number of analysis samples toproceed with study on processing/disposal method of solid waste.
(4) Thorough storage
Generated solid waste should be stored safely and reasonably according to characteristics
of solid waste. Storage capacity should be secured to ensure that the waste can be stored
within the site of the Fukushima Daiichi NPS.
(5) Establishment of selection system of preceding processing methods in consideration of
disposal
To establish selecting methods of processing for stabilization and immobilization (preceding
processing) and select a method of the preceding processing before technical requirementsof disposal are established.
(6) Promotion of effective R&D with a bird’s-eye-view of overall solid waste management
To confirm required R&D tasks after cooperating with each field of R&D for characterizationand processing/disposal and overviewing the overall management of solid waste.
(7) Development of continuous operational framework
In order to continue safe and steady solid waste management, the continuous operationalframework including development of relevant facilities and human resources must be
undertaken.
(8) Measures to reduce radiation exposure of workers
Radiation exposure control, safety management and healthcare programs should be
implemented thoroughly 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 stages. The definitions of the terms regard to radioactive
waste management, provided by the IAEA is shown in Attachment 9, and the classification anddisposal of radioactive waste inside and outside the country are shown in Attachment 10.
51

Since a large amount of solid waste with various characteristics is generated in association withdecommissioning of the Fukushima Daiichi NPS, a flexible and reasonable waste stream (the flowof the measures united from characterization to processing/disposal) is being developed in addition
to improvements in characterization analysis ability. Specifically, the related organizations arepromoting efforts based on each role in accordance with the fundamental view for solid waste
arranged in the Mid-and-Long-term Roadmap, and NDF is taking the initiative to advance thetechnical examination for measures united from characterization to processing/disposal of solid
waste.
3.2.1.1 Storage
To store solid waste 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 suchas on building waste management facilities to be required based on the volume (refer to Table2 forthe status of solid waste storage).
Based on this plan, TEPCO decided that any outdoor storage of solid waste, excluding
secondary waste generated by water treatment and re-use/recycle objects, would be eliminated by
the end of FY 2028, and TEPCO is promoting the arrangement of the required system (Attachment11). The concrete rubble which dose level is corresponding to it of the background of the site is
being recycled as roadbed material from the standpoint of reducing the waste generation amount.
The recycle and re-use of the metal, concrete, and dismantled pieces of flange tanks with a very
low surface dose is being studied while they are temporarily stored outside solid waste storage
facilities for the time being.
Secondary waste generated by water treatment is planned to be transferred to store in a building,and large waste storage building is being constructed as a storage facility for adsorption vessels.
Also, the slurry generated in the Multi-nuclide Retrieval Equipment, etc., and the waste sludge havea comparatively high risk in storage and management due to high mobility. Stabilization(dehydration) treatment will be carried out for the slurry (operation will start in FY 2022), and transfer
will be carried out from the underground storage tank in a building, the present storage area to highground for the waste sludge (to be completed in FY 2023).
For waste generated in association with fuel debris retrieval, the type and amount of materials
are evaluated, and, studies are being carried out for the storage method, the storing method, andthe specifications for containers including measures against hydrogen gas generation, are being
carried out in the Government-led R&D program on Decommissioning and Contaminated Water
Management.
3.2.1.2 Study on the processing/disposal measures
With regard to the processing/disposal approach to solid waste, the Mid-and-Long-term
Roadmap specifies that the prospects of a processing/disposal method and technology related toits safety should be made clear by around FY2021. The overall picture of solid waste becomes
clear step by step according to the progress of the effort. Keeping it in mind that it will still remain52

in a stage of accumulating necessary information on its characteristics around FY2021, theconcrete targets for technical perspective are listed as follows:Establish safe and rational disposal concept based on characteristics and volume of the solid
waste generated in the Fukushima Daiichi NPS with its applicable processing technology, anddevelop safety assessment method reflecting features of the disposal concept, withconsidering examples of foreign countries.



Clarify radiological analysis and evaluation method for characterization.

Clarify processing technology that could be expected to introduce the actual equipment forstabilization and immobilization considering disposal for several important waste streams suchas secondary waste generated by water treatment.



Establish method of rationally selecting processing technology to stabilize and immobilize
waste based on the above methodology although the technical requirements for disposal are
not determined (i.e. preceding processing).



Have prospect of setting processing/disposal measure for solid waste of which the processing
technology considering disposal is not clarified, using a series of methods to be developed byaround FY2021.

Clarify issues and measures concerning storage of solid waste until it is conditioned
To achieve these matters, the applicability of various processing methods (thermal/non-thermal

processing) using engineering-scale testing equipment, etc., is being confirmed, the disposal
concept based on the characteristics of the waste and applicable processing technologies is being
established, and a safety assessment method is being developed, through the Government-led
Project of Decommissioning and Contaminated Water Management.
Also, to effectively understand the characteristics of solid waste required for the study, simplified
and speed-up analysis methods, analysis ability improvement focusing on the arrangement ofRadioactive Material Analysis and Research Facility Building 1 in which waste samples with a low
dose will be analyzed, and accuracy improvement of the analytical inventory estimation method
are being advanced. Sampling and analysis are being carried out for rubble, contaminated water,
secondary waste generated by water treatment, and so on, and the correlation of the nuclide
composition for each analyzed waste is becoming clear gradually.
3.2.2 Key issues and technical strategies to realize them
3.2.2.1 Promotion of characterization and enhancement of analysis systems and technicalcapabilities
Human resources development for radiological analysis, and transfer/strengthening, technicalcapabilities on analysis, are important issues in addition to the arrangement of facilities to promotecharacterization steadily. For the time being, it is important to proceed with human resource
development for analysis in the organized manner as well as to arrange the Radioactive Material
Analysis and Research Facility and to reflect achievement of simplified and speed-up analysis
methods.

53

3.2.2.2 Storage
Since the measures against hydrogen generation become an issue in the safe storage of highdose waste, the concepts for a container with a vent and drying technologies are being studied.
Also, since integrity evaluations of storage containers becomes an issue when storage is prolonged,
the study, including the evaluation method and the measures against the generation of corrosion,
is being advanced.
3.2.2.3 Development of processing/disposal concept and safety assessment method
In order to select candidate technologies for preceding processing methods, it is necessary to
identify reasonable and feasible processing technology and develop safety assessment techniquefor disposal corresponding to such technology.
For the selection of processing technology, it is necessary to confirm the technical feasibility as
the whole processing system, including a supply system and an exhaust system, in addition to theconfirmation of the feasibility of solidification. Also, the required items and information are collected
and arranged to develop safety assessment method for disposal.
Furthermore, concerning the disposal approach, various possibilities will be studied using
overseas examples as reference, due to the fact that the waste from the Fukushima Daiichi NPS
is large in quantity, having various properties, and showing characteristics of having large
uncertainties.
3.2.2.4 Examining further approaches based on the view of the waste hierarchy
Many measures are being implemented based on the concept of the waste hierarchy (desirable
approaches in the order of (i) waste prevention, (ii) waste minimization, (iii) re-use, (iv) recycling,and (v) disposal) in the UK and the USA (Fig. 14). In UK, the NDA developed low-level solidradioactive waste management strategy in 2010 based on the application of this concept, and soon, and the initiatives shown in Table 3 has been implemented. As a result, 95% of the low-level
radioactive waste generated in the UK in 2009 was transferred by waste producers to the existing
low-level radioactive waste disposal facilities as they were, but now, the amount of low-level
radioactive waste to be disposed of directly to the facility was reduced to 5% in 2019. It is achievedby establishing routes such as disposal of very low-level radioactive waste in the specific landfills
based on appropriate segregation with characterization, treatment through volume reduction by
metal recycling via melting, incineration, and compression. The measures based on this concept
are being practiced at the Fukushima Daiichi NPS as well. Further possibilities will be studied basedon preceding examples in other countries in advancing reasonable waste management.
With regard to the prospects of a processing/disposal method and technology related to its
safety based on the results of these efforts, should be made clear by around FY 2021 as the target
based on the results of R&D and TEPCO’s engineering achievements, etc.

54

Table 2 Solid waste storage status(a) Storage of rubble, felled trees, used protective clothing, etc. (as of June 30, 2020)
Stored volume (m3) / Storage capacity (m3)(Percentage)
212,900 / 266,500(80%)
42,800 / 71,000(60%)

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

17,900 / 24,600(73%)
22,500/ 48,000(47%)
296,000 / 410,100(72%)

Containers* (in solid waste storage building)
Total
----

Cut down trees
Classification

Storage method

Trunks, roots, branches,leavesOutdoor storage

Branches, leaves

Temporary storage pool

Total

----

Stored volume (m3) / Storage capacity (m3)(Percentage)
97,000 / 134,000(72%)
37,300 / 41,600(90%)
134,300 / 175,600(77%)

Used protective clothing
Stored volume (m3) / Storage capacity (m3)(Percentage)
37,800 / 68,300
Container(55%)*Including secondary waste generated by water treatment (small filters, etc.)
Storage method(b) Management status of secondary waste generated by water treatment (as of July 2, 2020)
Adsorption vessels, etc.

Outdoor Temporary Storage area of used
Vessels

Storage Place

Storage Number

Cesium adsorption apparatus
2nd Cesium adsorption apparatus
HICs from multiple nuclides
removal system

Number of vessels
and filters
Number of vessels
232
and filters
Number of
1,788
containers
Number of
1,741
containers
779

Existing
Expansion

Used vessel from highHighperformance multi-nuclides
performanceremoval equipment
Used column from multiple
Existing
nuclides removal system
Used vessels and filters from mobile-type
strontium system

74

Storedvolume/Capacity(Percentage)
4,332 / 6,372(68%)

Number ofvessels

Number ofcolumns
Number of vessels
213
and filters
17

Waste sludge
Stored volume (m3) / Storage capacity (m3)(Percentage)
419 / 700
(60%)

Storage Place
Sludge storage facility (Indoor)

55

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

Examples of countermeasures at the
Fukushima Daiichi NPS

Summary of the Waste Hierarchy(Concept of waste hierarchy)
Waste Prevention(Control of amount generated)
Waste Minimisation(Minimization of waste amount)Preferred
Approach(Preferred approach)Stored volume (m3) / Storage capacity (m3)(Percentage)
9,380 / 10,300(91%)

Re-use of Materials(Re-use)Installation of a vehicle service station, prevention ofcarrying in packing material, and common use of
construction equipment

Classification, separation, etc., of waste

Examination of re-use of metals, concrete, anddismantled pieces of flange tanks with a very low
surface dose

Recycling(Recycling)

Application of volume reduction equipment (anincineration system, a crusher, and a metal cutting
machine)Disposal(Disposal)

Fig. 14 Summary of waste hierarchy16 at the NDA, UK, and countermeasures at the Fukushima
Daiichi NPS
Table 3 Measures based on the concept of the waste hierarchy in the UK
Countermeasures
Minimization ofDiversification of classification/segregation by extensive
waste amountcharacterization
Volume reduction (cutting, compression, incineration)
Decontamination
Re-useTransfer of assets that have accomplished their original
purpose of use
Use as backfilling materials of soil and rubble
Recycling
Metal recycling by melting
Disposal

Setting of new classification for very low-level radioactive
waste and its disposal at landfills

16 The figure is based on NDA, Nuclear Decommissioning Authority Strategy Effective from April 2016 (2016),

p.60, Figure 7. Summary of the Waste Hierarchy.

56

3.2.2.5 Summary of the main technical issues
The main technical issues and plans described in this section are summarized as shown in Fig.
15.

Fig.2 Main technical issues and future plans on waste management (progress schedule)573.3 Contaminated 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.
(2) To arrange the relationship with a decommissioning process including full-scale fuel debris
retrieval beginning in the near future, and to promote examinations of the measures of thecontaminated water management for mid-and-long-term prospects.
(Progress)
Fig. shows three principles and measures for the issue of contaminated water. From theviewpoint of measures to reduce the risk from radioactive materials, 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). Therefore, its hazard potential is relatively high and sois the Safety Management level, as the storage condition of such stagnant water deviates fromwhat is originally intended and has high uncertainties (refer to Section 2.2).
Out of such stagnant water in buildings, efforts are being promoted for more stable operation
based on three principles in order to complete the treatment of stagnant water in buildings in 2020,
excluding the Units 1 to 3 reactor buildings, where circulating water injection is ongoing, and theprocess building/high-temperature incinerator storing contaminated water temporarily for
purification treatment.

Fig.16 Tree principles and measures for the issue of contaminated water58

With regard to “removing” contamination sources, the third cesium adsorption apparatus(SARRY2) purifying high-concentration contaminated water has started full-scale operation since
July 2019, and a system using three units together with two established units (KURION andSARRY) has made possible stable purification treatment.
With regard to “redirecting” fresh water from contamination sources, the groundwater levelaround the reactor building is stably managed at a low level by multistory contaminated water
management, such as land-side impermeable walls and sub-drains, and the increase of thegeneration amount of contaminated water during rainfall also tends to be controlled by the site’ssurrounding pavement and the repair of broken parts of roofs. Through these measures, thegeneration amount of contaminated water has been reduced to about 180 m3/day (FY 2019) fromabout 540 m3/day (May 2014) before taking measures. The aim is to control the generation amountof contaminated water at about 150 m3/day in 2020 and below 100 m3/day in 2025.
With regard to “retaining” contaminated water from leakage, since all water purified by the multinuclide removal equipment and the like, has been stored in welded type tanks since FY 2019,leakage risk from tanks is reduced. Treatment of the remaining water in the multi-nuclide removal
equipment in the bottom of a flange type tank has been completed (July 2020), and only approx.
500 m3 of the concentrated salt water remains in storage (as of the end of August, 2020). Also,
efforts and monitoring for the prevention of the spread of contamination are being carried out by
the maintenance of a sea-side impermeable wall, and monitoring of groundwater and the harbor.
As a result of the above efforts, treatment of the stagnant water in buildings excluding the Units
1 to 3 reactor buildings, the process building, and the high-temperature incinerator, is planned tobe completed in 2020. It is considered that contaminated water management has shifted to acertain level of stability compared with the situation requiring emergency measures immediately
after the accident.
In addition, for handling the water treated with the multi-nuclide removal equipment, so-called
ALPS, etc., a comprehensive examination, including technical aspects and the social impact suchas rumors was conducted by the governmental subcommittee, and a report was published in
February 2020. Based on the report, the government has been arranging opportunities since April
2020 to hear the opinions of citizens at large and a wide range of relevant parties, including local
governments and agricultural, forestry, and fishery businesses, in order to determine the policy forhandling ALPS-treated water as the government.
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
According to the investigation since March 2019, a relatively high total α is detected at thebottom of the torus chamber of the reactor buildings of Units 2 and 3. In reducing the stagnant
water in the reactor buildings to about half of the level at the end of 2020 in FY 2022 to FY 2024, it
will be an important issue to prevent the spread of α-nuclides (Fig.17). As measures, it is required
to strengthen the monitoring of α-nuclides concentration in each building and the water treatment

59

system as well as property analysis. Research and development are also required to establish ameasure to remove sludge-like sedimentation containing α-nuclides.

Fig.17 Measurement result of total α in the stagnant water in buildings [Bq/L]
Also, in the process building and the high-temperature incinerator, it became clear in December
2019 that there were zeolite sandbags (approx. 20 tons) with a high dose installed at theunderground floor after the earthquake disaster. The maximum radiation dose rate on the surface
of sandbags is as high as approximately 3000 mSv/h in the process building and approximately
4000 mSv/h in the high-temperature incinerator. Therefore, in order to complete the treatment of
the stagnant water in these buildings in the future, dose mitigation measures will be an important
issue. A method to remotely collect zeolite and store it in containers and the like, and a method toremotely accumulate zeolite on the underground floor and temporarily store it in containers and thelike, are being examined. It is required to select an appropriate method by comprehensively
evaluating radiation exposure dose received during work, long-term safety, and the construction
period, etc. (Fig. 18).
Dehydrated
zeolite↓Shielding container

Recovery equipment↓Draining
Temporary storage container

Fig.18 Study on stabilization of zeolite, etc.
60

3.3.2.2 Issues of contaminated water management considering the decommissioning
process such as fuel debris retrieval
In the fuel debris retrieval, it will be an important issue to examine the whole system ofcontaminated-water management based on various information, experience, and results obtainedin trial retrieval, gradual expansion of retrieval scale, and further expansion of retrieval scale. The
possibility that the material derived from fuel debris containing α-particles is mixed into the water
treatment system in association with cutting, fabrication, etc., of fuel debris cannot be denied. It is
required to take measures, such as the strengthening of monitoring of water treatment systems,
installation of α-particle collection systems, and criticality monitoring.
The expansion of the treatment capacity of the water treatment system and the systemconstruction to realize continuous stable operation will be the issues in the further expansion of fueldebris retrieval. Here, it is required to examine downsizing of equipment in consideration of an
installation space, operation and maintenance under higher radiation dose, utilization of existing
purification equipment, etc., in addition to the removal system of α-particles and other radioactive
materials.
Also, it is required to ensure that a periodical inspection and update of equipment is carried out
in order to maintain the effect of contaminated water management over a long period. Furthermore,
as for the risk of large-scale natural disasters such as tsunamis and heavy rain, according to the“Review on Large Earthquake Model along the Japan Trench and Krill Trench (Summary Report)”
published by the Cabinet Office in April 2020, the impact was re-assessed for tsunamis and thetide embankment of Japan trench is scheduled to be newly installed by 2023. Going forward, themeasures should be taken in light of resilience (robustness) based on the re-assessment results.
While the current contaminated water management is shifting to a certain stable state, a long
period is required to complete fuel debris retrieval. It is important to see a medium-to-long period,
overlook the current contaminated water management anew, and examine the principles of morestable contaminated water management and more appropriate maintenance and management.
3.3.2.3 Summary of key Technical issues
The summary of the key technical issues and future plans mentioned in this section is shownin Fig.13 and Fig 19.

61

Fiscal year

2020

2021

2025

2022

 To control the contam inated water generation amount to approximately 150 m 3/day (in 2020)
 To complete the proces sing of stagnant water in the building (in 2020) *Related milestones

2031
 To control the contaminated water generation
amount to 100 m 3/day or less (in 2025)

To reduce s tagnant water in the reactor building to approximately half that of the end of 2020 (FY 2022 to FY 2024)

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

Contaminated water
generation amount

Site pavement ins ide the land-side impermeable wall (sea-side)

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

Stagnant water in buildings

Repair broken parts of roofs (incl. the installation of a large cover on Unit 1 R/B)

Units 1 to 4 T/B, etc. Water level lowering
Confirmation of stagnant
w ater characteristics

To implement required measures in accordance with the stage of fueldebris retrieval

Water level lowering for a 50% reduction

Simple measuresagainst α-nuclides

Units 1 to 3 R/B

α-nuclides retrieval equipment: Des ign, m anufacture, and installation

α-nuclides removal equipment: Operation

Alternative tank: Des ign, manufacture, and installation

Process building
High-temperatureincinerator

Zeolite dose mitigation measures/equipment: Conceptual examination, des ign,
m anufacture, installation, and measures
Zeolite stabilization measures: Examination, des ign, manufacture, installation, and measures
Tide embankment
installation< Legend>

Building opening closure

Measures against natural
disasters: The period of work

Sludge transfer equipment of decontamination equipment: Examination, design,
manufacture, ins tallation, and transfer:The period during whichchange is expected

Measures for VLFS

Examination, desig and construction for Tsunami disaster prevention ofJapan Trench

Measures against
stagnant water

Reversing valve pit
blockade

Underground water storage tank: Dismantling/retrieval and conceptual examination/design/retrieval*Except Units 1 to 3 reactor buildings, process buildings and high-temperature incinerator building.
Fig.19 Key technical issues and future plans on contaminated water management (progress schedule)

623.4 Fuel removal from spent fuel pools
3.4.1 Targets and progress(Targets)(1) While the return of residents and reconstruction in the surrounding area is gradually advanced,
to carry out a risk assessment and ensuring safety certainly including preventing dispersion ofradioactive materials and to start the removal of fuel in SFPs (Spent Fuel Pools) in FY 2027 to
FY 2028 for Unit 1 and FY 2024 to FY 2026 for Unit 2. To complete the removal of fuel in SFPs
in FY 2020 for Unit 3.
(2) The fuel in Units 1 to 4 that were affected by the accident are taken out of 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 in the Common Spent Fuel Storage Pool is transferredand stored in the Dry Cask Temporary Custody Facility.
(3) To carry out the evaluation of long-term integrity and the examination for treatment for theremoved fuel and to decide the future treatment and storage method.
(Progress)
TEPCO is working on the new work plan indicated in the Mid-and-Long-term Roadmap and the
Mid-and-Long-term Decommissioning Action Plan.
In Unit 1, due to the hydrogen explosion, a roof stab, building materials, such as a steel frame,
which constituted the upper part of the building, an overhead crane, etc., have collapsed as rubble
on the operating floor as shown in Fig.20. While the residents were returning, from the viewpointof further reduction of radioactive dust dispersion risk, the whole operating floor was covered witha large cover for the removal of fuel in Unit 1 SFP. The removal method was changed to one inwhich rubble removal and the removal of fuel in SFP are carried out inside the cover. Fig.21 showsa conceptual drawing of this method. At present, the preparation to install the large cover isadvanced, and the operating floor work such as rubble removal is continuing.
South

West

East

North
State of the existing installations under thecollapsed roof (conceptual drawing)

State of the collapsed
south-side roof
(TEPCO material edited by NDF)

Fig.20 Condition of the collapsed rubble on the Unit 1 operating floor

63

Overhead craneLarge cover

Crane

Demolition
heavymachineryOpening for rubble unloading

During removal of rubble (conceptual drawing)

During fuel removal (conceptual drawing)(TEPCO material edited by NDF)

Fig.21 Removal method of fuel from Unit 1 SFPFor Unit 2, new method that the upper part of the operating floor will not be dismantled andaccess from the south side of the reactor building was adopted from the viewpoint of further
reduction of radioactive dust dispersion risk similar to Unit 1. Preparations are being advanced atpresent. Fig.22 shows a conceptual drawing of this method.

Reactor Building
Fuel handling Crane
facility
Fuel handling

Front
Chamber

Fuel handlingfacility

Assemblybase

machineWell plug

Assembly basefor fuel removal

Spent fuel pool
Front
Chamber

Base

Opening for load in/out

Fuel removal method (conceptual drawing)

Reactor Building

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

Fig.22 Removal method of fuel from Unit 2 SFP
Also, for dismantling the Units 1 and 2 common exhaust gas stack, which was being carried out
as part of the environmental improvement around Units 1 and 2, a local company worked as aprincipal contractor, and the work was completed in May 2020.
For Unit 3, fuel removal work is being advanced, considering safety the highest priority tocomplete the removal in FY 2020. As of August 2020, 315 fuel assemblies17 are removed, andtransfer to the Common Spent Fuel Storage Pool is being continued.
For Units 5 and 6, fuel will be appropriately stored in the SFPs of the units for the time being.
Then, the fuel will be removed in a range so as not to affect the work in Units 1 to 3.
The securing the available capacity of the Common Spent Fuel Storage Pool and the transfer
of some fuel in the Common Spent Fuel Storage Pool to the Dry Cask Temporary Custody Facility
are required to remove all the fuel in SFPs, including Units 5 and 6, and store them in the Common
17

TEPCO, “Storage status of spent fuel”, presented as Handout 3-2 at the 81st Meeting of the Secretariat of theTeam for Countermeasures for Decommissioning and Contaminated Water Treatment, August 27, 202064

Spent Fuel Storage Pool. To achieve this, TEPCO is working on plans for expanding of storage
capacity in Dry Cask Temporary Custody Facility and for off-site transportation of new fuel. The
available storage capacity in the Common Spent Fuel Storage Pool and Dry Cask Temporary
Custody Facility is shown in Fig.23.
Efforts will be made to complete the removal of fuel in all units in 2031.

Number of spent fuel, etc.

10000

8000

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

Number of available capacities asof now in entire common spent fuelstorage pool and Dry Cask
Temporary Custody Facility ： 1211

Unit 3 (under transportation):
251 remained

Spare: 412

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

4000
Stored6322

Unit 6:1884

Spare: 897

2000
Unit 3:251
Unit 2:615

0Stored2033

Unit 5:542

Unit 1:392

Units 1-3 SFP

Units 5/6 SFP

Common Spent Fuel Storage
Pool

Dry Cask Temporary
Custody Facility

Fig.23 Storage status of spent fuel (as of August 2020)
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 required to advance the work steadily to realize the determined new
removal method.
In promoting the project, it is essential to comprehensively consider concerning technicalcertainty, reasonability, rapidity, actual site applicability, project risk, etc., and a work schedule toresponse to issues after making all evaluations of safety in association with work and confirmingthat required sufficient safety is ensured.
For Unit 1, the design and installation of the large cover, and the removal of leftover objects
such as rubble on the operating floor will be promoted. There is an overhead crane in an unstablestate on the operating floor. Therefore, removing the overhead crane safely and certainly is one of
the main issues to prevent it from collapsing onto the fuel handling machine and falling into thespent fuel pool. Therefore, in the ongoing examination of how to remove the overhead crane, it isrequired to perform all safety assessments as an assumption, and it is important to carry out acomprehensive examination based on the viewpoints of (i) formulating concrete work procedures
and work plans enabling the extraction of risk items, (ii) the risk scenario assumed from (i) and themeasures, (iii) extraction of points to consider such as the exposure of workers, from an operator's

65perspective, and (iv) reasonability and impact on other work18.
Regarding the 67 fuel assemblies in the cladding tube was damaged and stored in Unit 1 SFP
before the accident, specific handling plan needs to be considered such as checking status of theseafter the accident, study and its development of handling method and risk study for handling.
In Unit 2, fuel in SFP will be removed from the opening on the south side of the outer wall of theoperating floor using a fuel handling machine composed by a boom-type crane-system, which has
not been used for nuclear facilities in Japan. Since it is a new system, the following is important: (i)to set up a design schedule with appropriate margins, (ii) to carry out a mockup test simulating thesituation in the field and an operation method fully reflecting the results on the design/manufacturingcertainly, and (iii) to be sufficiently familiar with the operation and functionality of systems
beforehand since removal is carried out by remote operation19.
For Unit 3, 16 fuel assemblies with deformed handle were confirmed, the status is shown in Fig.
24. Removing these fuel is scheduled in the second half of FY 2020. As for removal of fuelassemblies with deformed handle, it is important to load them reliably into transport cask by liftingsafely from fuel rack. Fully based on the condition on site, TEPCO proceeds the following
preparations while conducting analytical evaluation of impact of rubbles and strength test byconsidering deformation of handles.


A tool for removing small rubbles on the top of fuel rack is manufactured to avoid interference
between fuel and rubbles or fuel rack.



For 4 fuel assemblies with significantly deformed handle that could not be lifted with existinggrapple of fuel handling machine, new grapple is being designed and lifting test will be
conducted when it is ready.



For 11 fuel assemblies that can be lifted with existing gripper of fuel handling machine, lifting
tests were conducted in May 2020, in which the lifting loads were limited to 700 kg in the test(the specified load is 1 ton in general). As a result, it was found that 7 fuel assemblies could
be lifted (including of 3 fuel assemblies which their seating positions became higher than
before testing), three could not be lifted, and there was 1 fuel assembly that the mast of fuelhandling machine couldn’t be approached. To reliably lift 3 fuel assemblies that have been
confirmed to be unliftable, multiple measures are being prepared as below.


Removing rubbles on the top of fuel rack using a tool that can remove small rubbles



Additional lifting tests in lifting load by the reassessed load based on the strength test ofhandlesMeasures with a view to cutting fuel racks

Moreover, regarding 1 fuel assembly that the mast of fuel handling machine couldn’t beapproached, it was verified to be able to lift in the lifting test in August 2020, by pushing the
18 NDF, Evaluation on Selecting the Fuel Removal Method (Plan) for Unit 1 at the Fukushima Daiichi NPS,

presented as Handout 3-2 at the 73rd Meeting of the Secretariat of the Team for Countermeasures for
Decommissioning and Contaminated Water Treatment, December 19, 2019
19 NDF, Evaluation on Selecting the Fuel Removal Method (Plan) for Unit 2 at the Fukushima Daiichi NPS,
presented as Handout 3-2 at the 71st Meeting of the Secretariat of the Team for Countermeasures for
Decommissioning and Contaminated Water Treatment, October 31, 201966

mast using a manipulator and approaching the fuel.


Regarding 1 fuel assembly with deformed handle that was found after the lifting test conductedin May 2020, it was also verified to be able to lift in the lifting test in August 2020.
As mentioned so far, it is important to reliably execute the preparations for removal including,verifying in advance, giving these feedback and examining multiple responses.
Besides, it is also required to accumulate knowledge obtained, including these responses at Unit 3
and experiences at Unit 4, and to leverage it for the subsequent fuel removal from Units 1 and 2,
as well as to improve quality assurance organization and reliably secure the backup supply basedon the experience.

67Fig.24 Status of 16 fuel assemblies with deformed handle20

20

Extracted from Spent fuel pool management presented as Handout 3-2 at the 81st Meeting of the Secretariatof the Team for Countermeasures for Decommissioning and Contaminated Water Treatment, August 27, 202068

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 removed, it is required to advance theevaluation of long-term integrity and the examination for treatment and to decide the future
treatment and storage methods.
3.4.2.3 Summary of key Technical issues
The main technical subjects and plans described in this section are summarized as shown in
Fig.25.
Fiscal year

2020 2021 2022

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

Milestones▽

Rubbleremoval, etc.

Unit 1

2025
Start Unit 2 fuel retmoval(FY 2024 to FY 2026)

2031
Complete fuel removal(in 2031)
Start Unit 1 fuel removal(FY 2027 to FY 2028)

Installation ofa 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.

FuelremovalUnit 2

Installation of a working platform on
Yardmaintenance/foundationthe south side and an opening/fuelhandling machine installation, etc.
improvement, etc.

<Legend>: Fuel retmoval w ork: The period during w hichchange is expected: Works other than fuelretmoval: The period during w hichchange is expected

Fuel removal

Unit 3
Units 5 and 6
Peripheral
environment

Common Spent
Fuel Storage Pool
cask

Fuel
removalUnit 6 fuelremovalDismantling of the upper partof Units 1/2 exhaust stack(completed in May 2020)

Suspended while
work is performed

Suspended while
work is performed
at Units 1 and 2

Unit 5 fuel removal

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

Fig.25 Key technical issues and future plans for fuel removal from SFPs (Progress schedule)

693.5 Utilization of Analysis Results for Smooth Promotion of Decommissioning
3.5.1 Significance and the current status of analysis
To safely and steadily proceed with decommissioning of the Fukushima Daiichi NPS, it isnecessary to establish and develop analysis facilities and functions required for handling of waste
or fuel debris. In addition, it is important to build a system to effectively utilize analyzed results foreach decommissioning operation.
TEPCO currently utilizes three facilities including the laboratory for Units 5 and 6, the chemical
analysis building, and the environmental management building, and performs analyses required forfacility administration and decommissioning progress, while planning to establish an analyticalfacility necessary for smooth performance of routine analyses related to processing/disposal ofwaste and fuel debris retrieval in the future. Moreover, as fuel debris retrieval proceeds, risk of α
contamination intake is supposed to be gradually increased, a bioassay function contributes toassessment of internal exposure is planned to be established.
The Radioactive Materials Analysis and Research Facility (Facilities Management Building,
Building 1, and Building 2) is being developed by JAEA under an official supplementary budget as
an essential analytical facility for decommissioning of the Fukushima Daiichi NPS. The analysis
results obtained are required to contribute to facilitation of smooth decommissioning, reliable
processing/disposal measures of radioactive material in decommissioning operation, andestablishment of technical foundation, etc. Solid waste analysis under current conditions has been
carried out at JAEA Ibaraki, Japan, and at private analytical facilities (Nippon Nuclear Fuel
Development Co., Ltd. (NFD), Nuclear Development Co., Ltd. (NDC)), and is expected to be usedeffectively in the future.
3.5.2 Key issues and strategies
The analysis results of solid waste are important basic information for the study on
processing/disposal measures for various kinds of waste generated by the accident. In addition,
the analysis results of fuel debris are reflected in a number of areas, including retrieval methods,
storage management, processing/disposal, investigation to determine the cause of the accident,
and enhancement of nuclear safety. Their relationship changes with the progress made in
decommissioning of the Fukushima Daiichi NPS (Attachment 7). It is necessary to correctly
recognize that the analysis results are “an important piece” to reduce the range of uncertainties
identified as above for the smooth decommissioning, and to establish and improve the analysis
system, as well as facilities and functions for analysis for enabling efficient collection andassessment of analysis results. In particular, analytical data, as well as monitoring data, play animportant role in the study on the retrieval method to mitigate excessive safety design while
ensuring safety. Therefore, analysis shall be positioned at a higher level in the decommissioning
project.
Role sharing among the facilities that are currently planning to conduct analysis shall beappropriately optimized based on the characteristics of each facility, taking into account that the70content, quality, quantities, etc., of the analysis required will change with the progress of
decommissioning. In doing so, the scalability of facilities and the flexibility of operations should beconsidered, taking into account a risk that the demand for analysis may increase.
In addition, due to the shortage of human resources required for stable operation of the abovementioned facilities, consideration should be given to securing and retaining of the analyticalengineers. In this respect, it is necessary to consider in advance the qualities expected for analyticalengineers in various analytical works that are required for optimization as mentioned above, andto develop a plan so that the required roles are appropriately achieved. Regarding the fostering offield analysts and supervisors of commissioned analysis, although it is conceivable that TEPCO
educates non-chemical personnel through OJT21, etc., by referring to the approach taken by private
facilities for analysis. However, since there are few talented personnel (analysis evaluators) who
can design the analytical range and items in anticipation of how to use the analysis results inadvance, it is important to make efforts in increasing them.
From the viewpoint of speeding up decommissioning, “immediacy” and “readiness” are requiredfor operating the facilities that do not need off-site transportation, such as radioactive material
analysis and research facilities. Although the analysis work for fuel debris retrieval is assumed tobe very difficult, especially when unknown samples are handled, an important stance is that thedecommissioning work shall be carried out on schedule by conducting analyses without delay. It isalso important to pursue a reasonable analysis plan by comprehensively utilizing analysis results
and on-site information, such as by taking note of the fact that analysis results have functions tobenchmark the estimation results of internal conditions given by instrumentation monitoring, visualobservation, in-situ measurement, and evaluation of calculations (simulation).
Considering that the content, quality, quantities, etc., of the analysis required will change in theprocess of the decommissioning project (engineering of construction methods and equipment,
safety assessment and safety design, and decommissioning operations), TEPCO should establish
a system where TEPCO itself will actively commit control and leadership of the whole of activities
related to the analysis, by appropriately developing a role sharing of the organizations and facilities
in line with this consideration and make decisions based on comprehensive evaluation. From thisviewpoint, TEPCO is required, with the cooperation of outside experts, to start examining the overall
strategy and a plan for the analysis of decommissioning work as early as possible.

21

OJT (On the Job Training）means a occupational training by practicing in the workplace.

714. Efforts to facilitate research and development
4.1 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 viewpoints of safety, certainty,
reasonability, rapidity, and field orientation. At present, when trial retrieval of fuel debris in 2021 isimminent, it is required to accelerate research and development under the consideration of theapplication to the site for a gradual expansion of retrieval scale and further expansion of retrieval
scale.
In order to solve these technical issues, basic fundamental research and application researchby universities in and outside of Japan and research institutions such as the JAEA and practicalapplication research and field demonstrations by IRID, overseas enterprises and TEPCO, etc., arebeing performed by various entities of industry/academia/government. In order to promote theresearch and development, the government is supporting highly-difficult ones among appliedresearch, practical application research and field verification by the Government-led R&D programon Decommissioning and Contaminated Water Management, and ones regarding basic andfundamental research by the World Intelligence Project for Nuclear Science & Technology and
Human Resources Development (hereinafter referred to as "World Intelligence Project"). TEPCO
is also working on the research and development directly linked with actual site applicability. The
outline of the research and development organization is shown in Fig.26.
NDF established a “Decommissioning R&D Partnership Council”, which examines the issues,
such as the information sharing of R&D needs and seeds, the arrangement of research anddevelopment based on the needs of decommissioning work, and the promotion of cooperation forresearch and development and human resources development, with the related organizations as
members.
Also, in promoting research and development, it is important to make use of the Naraha Remote
Technology Development Center, the Okuma Analysis and Research Center, and Collaborative
Laboratories for Advanced Decommissioning Science (hereinafter referred to as “JAEA/CLADS”)
and arrange the decommissioning R&D base, including international viewpoints.

72

73

Participation

Project
implementation

Secretariat

NDF

Support*9

Consignment

TEPCO
Holdings

Sharing and planning oftechnical development
information

Cooperation

Examination request
and support*1(Constitution)
NDF, JAEA, the Tokyo Electric Pow er Company, IRID,
plant makers, related experts, the Ministry of Economy,
Trade, and Industry, the Ministry of Education, Culture,
Sports, Science, and Technology

Decommissioning R&D
Partnership Council

Technical committees for decommissioning, etc.

Support*8

Cooperative relation*7
Assistance

Basic research for decommissioning
Platform

Universities,
research
institutions,etc., inJapan

A company
making a contract

Joint
research

Overseas
universities
and research
institutions

Foreigngovernmentorganization

Cooperative relation

Project
implementation

Secretariat
Consignment
and joint
research

Participation*6

Administrative
instructions

Project Management
Operation

Exchange of research needs
and seeds
Bridge-building for results

CLADS

Okuma Analysis andResearch Center

Naraha Remote Technology
Dev elopment Center

Fukushima research anddevelopment department

JAEA

Operating costsubsidyWorld Intelligence Project for Nuclear
S&T and Human Resource
Development

Ministry of Education, Culture, Sports,
Science, and Technology

Fig.3 Overview of the R&D structure of the decommissioning of Fukushima Daiichi NPS (As of FY 2020) (Red: Areas with strengthened systems)*1 The Decommissioning R&D Partnership Council is established in the NDF based on the determination by Team for Countermeasures for Decommissioning and Contaminated Water Treatment.
*2 The arrow draw n in a thick solid line indicates expenditures such as research expenses and operating expenses (excluding facilities expenses), the arrow draw n in a thin solid line indicates a cooperative relation, etc., and the arrow draw n in adotted line indicates the participation in the Decommissioning R&D Partnership Council.
*3 Some organizations such as JAEA are located at tw o or more places.
*4 Each organization has cooperative relations w ith foreign organizations based on MOU, etc., respectively.
*5 Research and development uniquely conducted by the Central Research Institute of Electric Pow er Industry, etc., are omitted in this figure.
*6 Although among the World Intelligence Project for Nuclear S&T and Human Resource Development the part adopted up to FY 2017 is the consignment from the Ministry of Education, Culture, Sports, Science, and Technology to a company
making a contract, it is omitted in this figure.
*7 Although the subsidy for the World Intelligence Project for Nuclear S&T and Human Resource Development is delivered to JAEA, it is expressed as w hat is delivered to CLADS, to make it easier to understand.
*8 With regard to the Government-led Project of Decommissioning and Contaminated Water Management, based on the policy in the Mid-and-Long-ter m Roadmap or Strategic Plan and the progress situation of research and development, the NDF
formulates a draft plan of the next research and development, and the Ministry of Economy, Trade, and Industry determines it.
*9 The NDF participates as a member in a steering committee of the World Intelligence Project for Nuclear S&T and Human Resource Development.

Companies in Japan andoverseas companies

National Research and
Dev elopment Agency
Plants, manuf acturers, etc.
Electric power companies,
etc.

International ResearchInstitute for Nuclear
Decommissioning

Subsidized company

Othermakers, etc.
(including
overseascompanies)

Assistance

Assignment

Fund for Countermeasures for Decommissioning
and Contaminated Water Treatment

Fund establishment corporation

Assistance

Government-led Project ofDecommissioning andContaminated Water
Management

Ministry of Economy, Trade,and Industry

Joint application, etc.

4.2 Key issues and strategies
4.2.1 Strengthening the research and development management organization in the
Government-led R&D Program on Decommissioning and Contaminated Water
Management
4.2.1.1 Decommissioning and contaminated water management project
The Ministry of Economy, Trade and Industry is providing support through the Government-led
R&D program on Decommissioning and Contaminated Water Management for research anddevelopment to solve technical issues that are difficult to solve in decommissioning. As shown in
Fig.26, in the Government-led R&D program on Decommissioning and Contaminated Water
Management, necessary assistance is provided through corporations with funds and the secretariat,
including for the selection of project operators, such as IRID, and other companies conducting R&D.
Through the Government-led R&D program on Decommissioning and Contaminated Water
Management, significant results have been obtained in the progress of decommissioning work andprogress is being made in the investigation of the inside of the PCV and understanding the internal
conditions. Attachment 12 outlines the implementation of the Government-led R&D program on
Decommissioning and Contaminated Water Management up to now.
4.2.1.2 Strengthening the R&D Management System
Although TEPCO focused on the research and development for immediate decommissioning
work, it has been transferring to strategic efforts based on the mid-and-long-term plan in researchand development, such as publishing the Mid-and-Long-term Decommissioning Action Plan. Basedon this situation, for the Government-led R&D program on Decommissioning and Contaminated
Water Management, it is required to strengthen the research and development under theconsideration of needs and actual site applicability by TEPCO. Therefore, it was decided that NDF
and TEPCO should be further involved in the Government-led R&D program on Decommissioning
and Contaminated Water Management in the future.
Specifically, in the Government-led R&D program on Decommissioning and Contaminated
Water Management, the organization resulted in one in which NDF participated in the secretariatof the Government-led R&D program on Decommissioning and Contaminated Water Management
and clarified the involvement of TEPCO as an actual site applying party, with the recognition ofissues that the functions of both planning and status control of a project should be strengthened.
TEPCO reflects requirements from the viewpoint of actual site applicability by jointly applying for
subsidy with R&D implementation entities, and carries out status control cooperating with project
management.
As a result, the Government-led R&D program on Decommissioning and Contaminated Water
Management has become more needs-driven research and development, and the site applicabilityof the research and development has become high. In addition, the role of NDF in planningresearch and development in the Government-led R&D program on Decommissioning andContaminated Water Management has become clearer.
TEPCO is required to construct such a scheme and strive to focus on research and development74

it performs. While strengthening communication by means of information exchange and dialogues
with TEPCO, NDF will plan matters considering needs in the field and actual site applicability andmanage status control of research and development to achieve research and development
conforming to the purpose of research and development and the target period for achieving results.
4.2.2 Formulating the R&D medium-to-long-term plan foreseeing about ten years for thetime being
4.2.2.1 Formulating the R&D medium-to-long-term plan
The Mid-and-Long-term Roadmap indicated the course of action for about ten years for the time
being and the promotion of research and development to support it. With regard to this matter,based on the Mid-and-Long-term Decommissioning Action Plan, NDF and TEPCO decided toformulate the R&D medium-to-long-term plan overlooking the overall research and development
for about ten years for the time being in order to appropriately manage the extraction and executionof the required research and development for achieving the further expansion of fuel debris retrieval(Attachment 13). In the R&D medium-to-long-term plan, the items and content of research anddevelopment assumed at present in each stage of fuel debris retrieval are identified in a manner
linked with the TEPCO’s Mid-and-Long-term Decommissioning Action Plan. Also, formulated basedon this R&D medium-to-long-term plan, the Next-term R&D plan formulated every fiscal year will
clarify how and where each research and development project corresponds to thedecommissioning process. The R&D medium-to-long-term plan will be updated and expanded
continuously based on the information made clear by the progress of Internal investigations of PCV,
etc., and fuel debris analysis, the progress of research and development, the revision of the
TEPCO’s Mid-and-Long-term Decommissioning Action Plan, etc.
4.2.2.2 Preparation of the Next-term R&D Plan
In order to support the Government-led R&D program on Decommissioning and Contaminated
Water Management, every fiscal year NDF drafts the Next-term R&D Plan for the decommissioning
research to be carried out in the upcoming two years from the next fiscal year. The plan is firstdeliberated on by Fuel Debris Retrieval Expert Committee and Waste Management Expert
Committee, and then by Decommissioning Strategy Committee. After this, it is summarized as NDF
proposal. The Ministry of Economy, Trade and Industry reports this Next-term R&D Plan to the
Meeting of the Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water Treatment, and the decommissioning research will be conducted inaccordance with this plan from the next fiscal year. In the Government-led R&D program on
Decommissioning and Contaminated Water Management, decommissioning research anddevelopment is carried out by selected operators who have been invited to participate in public
solicitations based on this Next-term R&D Plan.

75

4.2.3 Matching of needs and seeds of decommissioning work site and universities /research
institutions
4.2.3.1 Important R&D tasks derived from the needs and the overall map of the basic
foundation research
Universities/research institutions bearing basic infrastructure research are expected to maintainand develop human resources and knowledge/infrastructure to make a quick response whentechnical issues requiring scientific knowledge occur. It is important that universities/research
institutions deeply share recognition of issues of decommissioning work site.
In addition, to facilitate the long-term decommissioning project of the Fukushima Daiichi NPS, it
is important to conduct scientific and technological investigations based on understanding of theprinciples and theories from the mid-and-long term perspectives. Based on the discussions at theDecommissioning R&D Partnership Council, NDF set up a “task force on research collaboration”
for discussion, and identified six important R&D tasks to be addressed with priority strategically,
including investigation of issues, problem awareness on the side of the needs, and the assumed
research image (Attachment 14). At present, these important R&D tasks are being further examinedin the Platform of Basic Research for Decommissioning22. These important R&D tasks have beenused to solicit applications for the World Intelligence Project launched by JAEA/CLAD in May 2018.
In soliciting applications for the current World Intelligence Project, JAEA/CLAD is using the “overall
map of the basic foundation research”, which provides an overview of the entire decommissioning
process from contaminated water management to the processing/disposal of waste, includingthese important R&D tasks, and identifies the R&D needs and seeds required.
4.2.3.2 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 generic technologies and collect basic data, including theimportant R&D tasks, building up research centers, facilities and equipment, and human resource
development. Decommissioning of the Fukushima Daiichi NPS is an opportunity for trial of stateof-art science and technology and such the accumulation of such activity is expected to become asource of innovation.
The building for International Research Collaboration of JAEA/CLADS (Tomioka-machi,
Fukushima Prefecture) is a place where universities, research institutions, industries, etc., in andoutside Japan form a network and promote research and development and human resource
development in an integrated manner. TEPCO and universities are also moving into the building toconduct research. In the future, it is expected that a network will be formed for the exchange ofdiverse human resources from Japan and abroad, such as universities, research institutions, andindustries, and that JAEA/CLADS will become a central organization serving as a hub for such

22

Promotion council of basic and generic research jointly managed by JAEA/CLADS and MEXT the Center of theWorld Intelligence Project: Decommissioning Research and Human Resource Development Promotion Program
selection agency. See https://fukushima.jaea.go.jp/initiatives/cat05/haishi05.html.

76

activities. Following this idea, the World Intelligence Project has shifted from the projectcommissioned by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) to a
subsidy project intended for JAEA/CLADS (a subsidy project for Nuclear S&T and Human
Resource Development). The project is implemented by a system centered on JAEA/CLAD fromthe newly adopted tasks in FY 2018. The “Program for Decommissioning Research by Human
Resource Development” was newly established in the Center of World Intelligence Project in FY
2019. It created a basis of research and human resource development (Collaboration laboratory)
in both educational research institutions and JAEA/CLADS23, and has started R&D and a humanresource development project that connects these organizations by cross-appoint system. It
contributes to functional enhancement of JAEA/CLADS. From FY 2020, while focusing on“problem-solving decommissioning research program” to provide R&D that directly relates to theneeds at the decommissioning site, quota for young person under the age of 39 was establishedin the program to promote the participation of younger researchers.
4.2.3.3 For strengthening the matching of needs and seeds
Some

basic

fundamental

research

contributing

toproblem-solving

in

the

on-sitedecommissioning have obtained outstanding research results mainly in the World Intelligence
Project. It is an important issue to reflect the results in the on-site of decommissioning directly. In
order to achieve this, it is essential to match the needs of the decommissioning site with the seedsof universities and research institutions, build bridges for excellent results obtained, while making
use of the overall map of the basic foundation research by JAEA/CLAD. Based on this recognition,in the World Intelligence Project, JAEA/CLAD has been tackling assessment of actual site
applicability for its adopted subjects to date and acceleration of on-site application as the result ofsuch assessment with the help of knowledge of TEPCO. The “steering committee24” that presents
the basic policy for the operation of the World Intelligence Project has been strengthening to further
reflect the viewpoint of needs in the Project with the participation of members, such as the Ministryof Economy, Trade and Industry in charge of the Government-led R&D program on
Decommissioning and Contaminated Water Management, and domestic decommissioning
operators, along with TEPCO as Program Officer (PO) that is newly responsible for research
management. In addition, joint research with universities was newly started in TEPCO from FY
2019 to find the technical seeds for decommissioning owned by universities25 based on the resultof the World Intelligence Project. The related organizations, such as the government (the Ministryof Education, Culture, Sports, Science, and Technology, the Ministry of Economy, Trade, andIndustry), JAEA/CLADS, NDF, and TEPCO, need to strengthen cooperation towards further
matching of the needs and seeds and bridging for the results.

23

JAEA can use bases in Tokai and Oarai as well as a base in Fukushima
Consisting of program directors, experts from universities and research institutions, NDF, and TEPCO, it wasestablished in the Ministry of Education, Culture, Sports, Science and Technology.
25 Tohoku University, Fukushima University, the University of Tokyo, and the Tokyo Institute of Technology (It wasstarted from FY 2020 other than Tokyo University.)
24

77

5. Activities to support our technical strategies
5.1 Further strengthening of project management and improvement of capability
required as a decommissioning executor
5.1.1 Significance and the current status of project management
Individual work in each field of decommissioning work is generally carried out through processes
such as research and development → conceptual design → detailed design → production → site
installation work → inspection → operations. In addition, inspections by the Nuclear Regulation
Authority and other examinations will be conducted as necessary. In order to carry out this seriesof processes without omission or delay, it is effective to set up the large work flow defined in thelong-term plan as an individual project as a management unit of appropriate scale. In addition, it isimportant to promote a comprehensive approach under a sophisticated project management
system so that correlation and time-series relationships between the projects can be optimized andrisks inherent in the project can be appropriately managed.
5.1.1.1 Formulating the Mid-and-Long-term Decommissioning Action Plan
Since the accident at the Fukushima Daiichi NPS, TEPCO has conducted decommissioning
project in accordance with the requests based on the Act on Special Measures Concerning Nuclear
Emergency Preparedness and the Nuclear Reactor Regulation Law26 and the target process of
the Mid-and-Long-term Roadmap determined in the Inter-Ministerial Council for Contaminated
Water and Decommissioning Issues. By formulating and publishing the Mid-and-Long-term
Decommissioning Action Plan showing the processes for how to achieve such targets, in light of
the ten years that have passed since the accident, TEPCO made transparent the decommissioning
project to local areas and society, made clear its attitude toward tackling decommissioning
independently, and materialized the complicated work prospect over a long period.
The decommissioning work for the Fukushima Daiichi NPS is a project with significant
uncertainty. However, since the plan under the consideration of the medium and long term can beformulated for research and development, human resources, and procurement by thinking of the
Mid-and-Long-term Decommissioning Action Plan, the meaning of formulating the Mid-and-Longterm Decommissioning Action Plan is significant. It is also important to carry out constant review
based on new knowledge, the on-site situation, etc., for utilizing the Mid-and-Long-term
Decommissioning Action Plan effectively in the future.
5.1.1.2 Further strengthening of project management
As “a condition that must be urgently addressed” such as contaminated water management andthe removal of fuel from SFP has been settling down, TEPCO is currently faced with “a phase of
tackling uncharted territory systematically” in the “stage of addressing situations proactively andstrategically.”26

The Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material, and Reactors

78During this, in April 2020, TEPCO converted the decommissioning project into a project
management type by changing the organization of Fukushima Daiichi D&D Engineering Company.
TEPCO, however, has just started as a project management type organization, and is accelerating
efforts with extremely high levels of uncertainty and technical difficulty, such as retrieval of fueldebris. Even under such circumstances, in order to proceed with complex and multi-layered largescale projects such as simultaneous execution of multiple tasks under an environment with highradiation level in a safe, reliable, and prompt manner, the following efforts will be thoroughly
implemented to further strengthen project management.


Clarify the authority and responsibility of project implementation divisions with regard tobudget management, etc., as well as instill in project managers a sense of responsibility tocarry out the project and improve their project management capabilities.



The project manager carries out the integrated management of the project budget, process,work, risk, quality, personnel, etc., to accomplish the project. The project manager will
integrate engineering and R&D into the project to ensure the execution of projects with ahigh level of uncertainty and technical difficulty.



The project management division appropriately updates the Mid-and-Long-term
Decommissioning Action Plan based on the actual situation and progress of the site. It also
issues monitors the progress of each project, gives instructions on necessary corrections
according to the progress, and controls resources based on the progress in the project. The
project manager coordinates the relevant projects to accurately implement the instructionsof the project management division. During this, when the project manager acknowledges
that it would be adequate to change the region of each project from the viewpoint of
optimizing the overall decommissioning work, the project manager will make a proposal tothe project management division accordingly to review the project mission.

Effective project management will be carried out by aggressively introducing the necessary
project management methods and tools from inside and outside Japan.

5.1.2 Key issues and strategies
5.1.2.1 Reinforcement of “safety and operator's perspectives” in project activities
When promoting efforts such as design examination (engineering) for construction method andequipment, there is a tendency to focus on realizing a construction method, equipment, etc.,
physically, especially for issues with severe technical difficulty. However, in order to realize theresults of efforts in the field, it is indispensable to fully reflect the following in the construction
method and equipment in addition to a physical realization:
“The safety perspective” as a project executor handling dangerous substances27 of nuclear
fuel material, etc.

27

Although the fuel debris is in a certain safe state now, the fuel debris retrieval work will cause disturbances tothis stable state. Namely, since α-radioactive material is handled in an unsealed state in fuel debris retrieval
work and a criticality risk may be increased temporarily, more elaborate work management than before(criticality control, radiation protection, operation management, monitoring strengthening, etc.) is required.

79

“The operator’s perspective” 28 familiar with the field of the Fukushima Daiichi nuclear
power plant decommissioning

Therefore, these perspectives need to be fully reflected in the project activities until aconstruction method and equipment are realized in the field. Without sufficient feedback, the resultsof the construction method and equipment that are unsuitable to the site will be brought about, andsafe and stable decommissioning will be disturbed.
To avoid such a situation, a business process to incorporate a “safety perspective” and an“operator's perspective” in the upstream of project activities needs to be established at an earlystage.
5.1.2.2 Promulgating the “Safety First” principle that safety perspective comes first
The handling of nuclear fuel materials that still remain in large amounts at Fukushima Daiichi
NPS is permitted only if the operator sufficiently suppresses the potential hazards of thesepotentially hazardous materials, and ensures conditions that pose no problems with regard to
accident prevention. This must be clearly understood for the decommissioning project as well, nowthat operations at Fukushima Daiichi NPS have transitioned from the emergency evacuation andemergency response phase in the immediate aftermath of the accident to the phase where longterm issues are being addressed in a planned manner.
The use of any method or device is basically unacceptable unless the safety perspective issufficiently reflected in them. Therefore, it is important that all who work in the processes (projects)
leading up to the realization of methods and devices on the site, keep the safety perspective firstin mind as they engage in their work (safety first). The specific application of the general “safety
first” principle in projects is about, “Conducting extensive assessments on safety mattersassociated with methods and devices when reviewing any project and, upon verifying thatnecessary and sufficient levels of safety have been ensured, comprehensively taking into accountfactors such as technical reliability, reasonableness, speed, actual site applicability and project risks
to decide which methods or devices to use, and which attendant safety approach to apply”.
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 promulgate the “safety first”
principle to all persons who work on projects including on-site, the attitude of top management (theapproach to reiterates the special nature of nuclear safety and how it must be approached with anaccordingly special kind of awareness) is important.
5.1.2.3 Improving the owner's engineering capability(1) Role of TEPCO as project executor (Requestor)
To ensure that the complex and extensive engineering, such as retrieval of fuel debris, proceeds
28

An operator is a collective term for the people and organizations handling the site (operation, maintenance,
radiation control, instrumentation, analysis, etc.)80without any rework, it is effective for the project executor (Requestor), TEPCO, to clearlycommunicate the requirements to the supply chain supplier candidate (manufacturers, generalcontractors, etc.) at the upstream of the project in order to prevent rework in the project. In therequirement specifications, the performance requirements for the entire system are first described,
followed by the functional requirements for individual equipment and facilities necessary to meetthe performance requirements. TEPCO, the requestor, needs to describe at least the performancerequirements of the entire system, and if the company entrusts the function requirements to the
supply chain supplier candidates or prepares it with them, there should not be significant problems.
(2) Importance of “safety and operator's perspectives” in Owner's Engineering
Engineering for the retrieval of fuel debris on the expanded scale is complex and extensive.
Besides, the conventional engineering approach29 does not necessarily apply to unprecedented
work of high uncertainty and difficulty due to the limited information obtained, and it is highly likelythat it does not.
Since fuel debris retrieval has never been conducted before, the target setting and required
specifications by TEPCO, the executor of the decommissioning project, are not necessarily clarified
at the time of the commencement of engineering. With this, it is inevitable that the defining
performance requirements, and the degree of physical feasibility and performance assurance forthe construction method and equipment will be based on trial-and-error. Therefore, the project
executor's performance requirements and supply chain's function setting and engineering need tobe carried out by iteration30 to some extent (Fig.27 routes 1 through 3).
For iteration-type engineering, the contract between a project executor and a supply chain is notconventional 31 . Therefore, it is strongly required that TEPCO, as a project executor, “make a
judgment on engineering and is responsible for the results.” Therefore, it is required to improve theengineering capability (owner's engineering capability) carried out independently by TEPCO, aproject executor as an owner 32 , such as the project management capability, the capability to
optimize the whole supply chain that should be owned as a project executor, specifically, thecapability to make an engineering judgment, the capability to evaluate business risk, the capability
to materialize order specifications.
The retrieval of fuel debris is not work to be delivered by guaranteeing the performance ofcompleted products like the design and construction of nuclear power plants. Therefore, the cost
will reach astronomical figures unless TEPCO, the project executor, eventually bears the technicaland business risks. When the project executor is responsible for the technical risks, they need to

29
30
31
32

A supply chain advances engineering based on requirement specifications provided by TEPCO, a project
executor.
A method of gradually increasing the completeness of engineering by finding the next result based on acertain result and repeating this cycle.
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).
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)81

have the insight to assess reliability related to the establishment of the function and engineering
design, which means that TEPCO is required to improve existing technical skills. The mostimportant thing in Owner's Engineering is to incorporate “safety and operator's perspectives” as
upstream as possible in engineering.
Setting boundary condition
from "Safety perspective
and operators' perspective"

Elaborated boundary condition based on "Safety
perspective and Operators' perspectives"◎ Operator Requirement Specifications〇 Performance requirements(Functional requirements if unable toindicate here)a) Safery : Criticality, exposure ・・・b) Operability : ・・・c) Easy of maintenance : ・・d) ・・・〇 Verifying perfomancea) Safery : Criticality, exposure ・・・b) Operability : ・・・c) Easy of maintenance : ・・d) ・・・〇 Quality assurancea) QA planb) Sub-vendor list (below secondary
contractorsc) Procurement control for subvendor (specially foroverseas vendors)

Input：Design process of actual equipment：R&D Process

Conceptual review
Confirmation on how the "Safety

Output 1 perspective and operators'

perspectives“ are being reflectedusing deliverables (document)

Actual machine

R&D◎ Conceptual review drawingsand docments• Performance requirements
confirmation document• Safety assessment document(Criticality, exposure, dust
dispersion, heat removal ...）

◎Specifying development
specifications• Identify technical issues andtechnical trend(Technical matuarity)①〇〇 Developed②△△ In the practival application
stage
・・・
• Method developed②・・TEPCO's voluntary PJ by 〇〇③・・Government-led PJ by 〇〇 ・Specification developed
Budget, schedule…

Route 1

• Conceptual
review
redoneNo
Route 2・ Performancerequirements revised
・ On-site investigation
added to reduce
uncertainty

Output 2

All the performancerequirements
satisfied?

Conceptual
review
redoneYes
Elaborated boundary
condition further

Incorporating R&D results

Next step (basic design, etc.)
Route 3• The status of satisfaction can be left as
pending and verification on whether
they satisfy persormance requirements
may be performed at a later date in the

Output◎ Basic design drawing• System design
specifications• Machine design
specifications• Shielding calculation
sheet• P&ID•…

Confirmation of how the"Safety perspective andoperators' perspectives"
are being reflected using
Basic design drawing

Fig.27 Design flow of fuel debris retrieval (Image)(3) ALARP judgment based on safety
For safety, there is a minimum level of safety standards that must be met before the relevant
construction 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, construction methods and equipment to be
adopted will be determined based on trade-off between the safety level to be achieved and project
cost and duration (note that construction method and equipment involving long-term large safetymeasures are not necessarily beneficial to safety, especially at Fukushima Daiichi NPS), a kind of
ALARP33. There is also an issue as to whether such construction methods and equipment arefeasible in the field.
Based on this, in determining construction methods and equipment, it is important that
construction methods and equipment to be adopted in the end will be decided through the cycle of“define the safety standards (safety perspective)”, “indicate the feasibility on-site (operators’
perspective)”, and “examine and discuss at project (project management)” as shown in Fig.28. As
shown in this figure, the safety perspective and the operator’s perspective are not independent
33 It is that radiation impact must be as low as reasonably practicable.

82

from each other. The ALARP judgement made by the project based on the safety perspective will
be linked to the decision of the construction method and equipment after going through thefeasibility check based on the operator’s perspective. The operator's perspective is necessary toactually incorporate the safety perspective into the site, and the judgment based on the safety
perspective is needed to utilize the operator's perspective.

(1) Define the safety
standards

Options for retrieval
methods andequipment that meet
safety standards

Communicate retrieval methods
and equipment proposals(2) Examine and discus s(3) Examine feasibility
methods and equipment
on-site (by experts).
to be adopted in the(Operator’s
perspective)
project (ALARP)[4] Determine retrieval methods
and equipment at the project.

Inform advisability(if possible)(Safety perspective)

Inform advisability(if not possible)

Fig.28 ALARP centered on safety (Image)
5.1.2.4 Developing and securing human resources(1) Human resources development based on the Mid-and-Long-term Decommissioning
Action Plan
Human resources development is indispensable as infrastructure to implement
decommissioning project over a long period smoothly. Therefore, it is important to assume
occupational categories, the number of engineers and the time to be required in the future (design,operation, maintenance, chemical analysis, safety assessment, radiation control, etc.) in light of
the Mid-and-Long-term Decommissioning Action Plan, to summarize them as the medium-to-longterm human resources development plan, and to promote human resources development and staff
securing systematically. Fuel debris retrieval is the work of remotely handling unsealed radioactive
materials, and we have never done this in the operation of power plants before. In particular tosuch work, we need to consider securing and developing human resources in individual cases
through operations at mock-up facilities in Japan and overseas, and actual work of trial retrieval to
the retrieval on gradually expanded scale.
In addition, the development of human resources such as engineers and researchers frommanufacturers who support the decommissioning project is also a critical issue. It is important todevelop human resources with training, such as the decommissioning human resource
development course that was planned and executed by NDF in FY 2019 based on the On-the-Job
Training (OJT) through the implementation of the decommissioning research, engineering anddecommissioning work. (Attachment 15)(2) Fostering the next generation to handle the decommissioning of the Fukushima
Daiichi NPS
In order to continue decommissioning the Fukushima Daiichi NPS for a long period of time and83

to continue R&D activities for a long period of time, it is essential to train and secure future
researchers and engineers. For this purpose, it is important for industrial-academic-governmental
institutions relating to nuclear power, as a whole, to steadily promote making efforts.
It is necessary for the industry and educational institutions such as universities to continuously
carry out activities to promote understanding of the nuclear industry for students at the higher
education level. It is also necessary to convey 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 and demonstrate various career paths for researchers and engineers to thrive.
To be more specific, stable production of researchers and engineers is of paramount importancefor the development of human resources that will lead the next generation. From this perspective,
a program for a research group consisting of research representatives under the age of 39 has
been implemented in the World Intelligence Project. In addition, at the “Conference for R&D
Initiative on Nuclear Decommissioning Technology by the Next Generation (NDEC)” a conference
for students, and the Creative Robot Contest for Decommissioning for Technical College Students,
students present their research results, awards are given to recognize excellent performance, andthere is an exchange of views with researchers and engineers involved in the decommissioning ofFukushima Daiichi NPS. Furthermore, NDF holds the “International Mentoring Workshop Joshikai
in Fukushima” in cooperation with the Organization for Economic Cooperation and Development
and the Nuclear Energy Agency (hereinafter referred to as “OECD/NEA”) as an effort to raiseawareness of decommissioning, etc., through exchanges with female researchers and engineers
for middle and high school girls including Fukushima Prefecture in order to enhance understanding
among women and help increasing the motivation to participate in development studies.
It is necessary to further promote and strengthen measures for securing human resources whowill lead the next generation, such as children in elementary and secondary education stage,
students in the higher education stage including universities or colleges of technology, young
researchers and engineers, etc.

5.2 Strengthening international cooperation
5.2.1 Significance and the current status of international cooperation
In recent years, nuclear reactors and nuclear fuel cycle facilities, constructed in the dawn ofnuclear power, are coming to the end of operating life and these decommissioning have alreadybeen progressing in the world. And, there are three nuclear reactors experienced severe accidents:
Windscale Unit 1 in UK (Windscale Pile-1), Three Mile Island Unit 2 in the US (TMI-2), Chernobyl
Unit 4 in Ukraine (ChNPP-4). Stabilization and safety measures have been taken in these facilities
for a long time. In addition, for past overseas nuclear-related sites (legacy sites), it is expected that
there was significant uncertainty in the management of a variety of radioactive substances and it
would take a long period for decommissioning and environmental remediation. Despite facing
technical difficulty called “unknown unknowns” (things we don’t know we don’t know), and issues
such as longtime project management and securing a large amount of money, each country
84continues the challenge for overcoming them.
In order to steadily advance decommissioning of the Fukushima Daiichi NPS handlingengineering issues with a high level of difficulty, it is important as a risk reduction strategy to learn
lessons from examples such as precedent decommissioning activities and utilize them indecommissioning. Also, to maintain and develop continuous understanding/concern andcooperative relations with international society over decommissioning, it is important to return theknowledge, etc., which was obtained through the accident and decommissioning of the Fukushima
Daiichi NPS to international society positively and strategically and to promote reciprocal
decommissioning open to international society through information dissemination to internationalsociety and participation in the international joint activities.
Moreover, the decommissioning of the Fukushima Daiichi NPS is a process to solve unexplored
engineering issues combining various fields of knowledge not limited to nuclear field. It can beinterpreted as which the decommissioning of Fukushima Daiichi NPS may be an influential groundto create innovation. Assembling diverse wisdom and experiences to Fukushima from all over theworld is primary an important effort to steadily proceed with decommissioning itself of Fukushima
Daiichi NPS. It is also an important effort from the perspective of that innovation to be createdthrough the decommissioning process leads to the reconstruction of the local industries and toestablish the local community engagement that is essential to continue decommissioning over along period of time.
In international cooperation, it is important to advance bilateral cooperation based on eachcountry's situation and utilize the framework of multilateral cooperation through the IAEA,
OECD/NEA, etc. These international organizations have an important role, such as formulating theinternational standard for decommissioning. It is important to take part in formulating theinternational standard, etc., based on the experience of decommissioning in Japan for advancing
the decommissioning of the Fukushima Daiichi NPS in form open internationally. It is also expectedthat part of Japan's responsibility to international society is fulfilled since each country shares
Japan's experience. From such a viewpoint, based on these matters, NDF is making efforts toprovide information on decommissioning through opportunities, such as participation in a side eventof the IAEA general meeting and the rostrum in main international conferences, including theOECD/NEA steering committee. (Fig.29) (Attachment 16)85

Fig.29 Presenting at a side event of the IAEA General Conference (September 2019)
5.2.2 Key issues and strategies
5.2.2.1 Disseminating information to the international community and participating ininternational joint activities
We will soon mark ten years since the accident. From the viewpoint of concentrating the wisdomin the world for the decommissioning of the Fukushima Daiichi NPS, since a recipient's concerns,
etc., may change a little from the time of the accident, it is important to provide informationconsidering this point even if it is the same information. Specifically, in addition to providing detailed
exact information for experts, it is also necessary to provide intelligible information for non-experts
or devise appropriately considering recipients' intelligibility concerning the circumstances of theaccident.
In addition, in order to gather the wisdom of the world toward decommissioning and to give backthe knowledge gained through decommissioning to the international community, it is also importantto take part in international joint activities in addition to disseminating information to the international
community. In joining in international joint activities, it is necessary to work in such a way as tosecure the interests of the international community on the major premise that steady
implementation of decommissioning, which is the top priority issue for our country, is ensured. In
particular, in terms of the return of results, it is important to strive to maintain the level of interest
while responding to changes in the international community, such as growing interest not only inthe aspects of accidents and decommissioning itself but also in the aspects of application to otherissues.
5.2.2.2 Integrating and utilizing wisdom and knowledge from around the world
Decommissioning of the Fukushima Daiichi NPS is expected to last for a long time, anddecommissioning of legacy sites has many technical and operational implications as a leading
model. In countries with legacy sites, these activities are mainly promoted by public
decommissioning organizations in order to deal with issues, such as the need for expertise, ideas
and new technologies that are different from the operation and maintenance of nuclear reactors
and nuclear fuel cycle facilities. Therefore, NDF will continuously establish and reinforce long-term
86partnerships with public institutions related to decommissioning that play a central role in eachnation, such as the UK’s Nuclear Decommissioning Authority (NDA), Commissariat a l’energie
atomique et aux energies alternatives (CEA), United States Department of Energy, Office ofEnvironmental Management (DOE), etc., based on the government-level framework.
Additionally, in regard to decommissioning of the Fukushima Daiichi NPS, wisdom andknowledge from around the world that our country should obtain are implemented with a variety of
approaches such as system/policy, providing strategy, project plan/operation, ensuring security,
regional communications, and so forth, not only in technical aspects but operational aspects. For
that reason, with the assistance of the international community, Japan received a variety of support
from overseas governmental organizations and experts, such as the DAROD project by the IAEA
and the joint project by the OECD/NEA. It is therefore necessary to continue reciprocal relationships
while working to return the results through information dissemination to the international communityand participation in international joint activities.
Moreover, regardless of whether it is inside or outside the country, decommissioning is
implemented under a contract between many companies and the decommissioning operator forwhich the global market is widely expanding. While the engineering of the Fukushima Daiichi NPS
is put into practice, it is important to always keep up the latest situation of world's superior
technologies and human resources and effectively exploit them. Therefore, it is necessary tounderstand the latest global information, including even the private sector situation, make efforts
for continuous communication with these private enterprises, and form an environment in which
required technology is accessible when required while sharing information on the progress of
decommissioning work.

5.3 Local community engagement
5.3.1 Significance and the current status of local community engagement
5.3.1.1 Basic approach
While the residents are returning and reconstruction is progressing gradually in the surroundingarea of the Fukushima Daiichi NPS, the confidence from the communities is indispensable toadvance decommissioning safely and steadily. Therefore, it is important to listen to uneasiness andquestions of the local residents sincerely and make efforts to have them understand and feel easeabout the decommissioning work through bidirectional communication of delivering exact
information intelligibly and quickly. In addition, to accomplish the long-term decommissioning, it isessential to have continuous cooperation from local businesses and other companies. At the sametime, participation of local businesses in the decommissioning project is a crucial pillar for TEPCO
to contribute to the reconstruction of Fukushima, because it will revitalize the decommissioning
related industry, create jobs and technologies in this area, and spread the results to other regions
and industries.
Under the fundamental principle of “coexistence of reconstruction and decommissioning”,
TEPCO will also cooperate with efforts to realize the “Fukushima Innovation Coast Framework”
87holding up decommissioning related industry accumulation to the Hamadori region as priority areas
and accomplish decommissioning while coexisting with the region.
5.3.1.2 Specific measures under the current situation
The government has been working on careful communication by providing information to andstrengthening communication with various people including local residents by holding “The
Fukushima Advisory Board” as an occasion to discuss public relations, by dissemination of
information through videos, a website, and brochure that summarize the decommissioning status,
as well as by active explanations to and conversations with local residents and officials of related
municipalities.
NDF holds the “International Forum on the Decommissioning of the Fukushima Daiichi NPS”,
that focuses on interactive communication with local residents, provides clear information on thedecommissioning, and exchanges honest opinions with the participants, while sharing the latest
progress and the technical results of the decommissioning efforts among both Japanese andforeign experts. In addition, NDF makes efforts to gain attention and interest in decommissioningby holding workshops targeted at future generations who are to face decommissioning.
TEPCO is continuously working on explanations and conversations through management andthe risk communicators with the local representatives at the “The Fukushima Advisory Board”
hosted by government and “Prefectural Safety Assurance Conference for the Decommissioning of
the Fukushima Nuclear Power Station” sponsored by Fukushima Prefecture, and so on. The
company is also working to provide timely and accurate information on the status ofdecommissioning through nuclear power regular press conferences, regular lectures at the
Fukushima Prefectural Government Press Club, and meetings they attend, while trying to provide
easy-to-understand information through public relations tools, such as websites and information
magazines.
In formulating a common understanding of decommissioning, it is also very effective to havepeople observe the real state of progress of the decommissioning tasks on the site. TEPCO has
been proactively accepting visitors to the Fukushima Daiichi NPS, including evacuees, and 18,238
visitors were accepted in FY 2019, although there were impacts of typhoons and covid-19. In
addition, the “TEPCO Decommissioning Archive Center” was built in Tomioka-machi as a place tolearn about the nuclear power plant accident and the progress of decommissioning work and, asof the end of August in 2020, about 60,000 people have visited.
Last fiscal year, while obtaining the Fukushima Innovation Coast Framework Promotion
Organization's cooperation, TEPCO held a decommissioning project matching event for local
businesses. Also, at the end of March 2020, it formulated the “commitment to Fukushima residents
for the coexistence of reconstruction and decommissioning” (hereinafter referred to as"Commitment") summarizing the efforts, such as the participation of local businesses indecommissioning project, the attraction of companies outside the area, support for local companies
toward human resources development and cooperation with universities, etc. It re-expressed thedetermination to fully address decommissioning project as a member of the community.
88Moreover, for the purpose of strengthening a structure for local engagement, TEPCO
established Promotion of Partnership with local communities Group under the Fukushima Daiichi
Decontamination and Decommissioning Engineering Company in April 2020, as well as Hama-doriDecommissioning Industry Project Office under the direct control of the president in October 2020.
To undertake the efforts of the “Commitment,” TEPCO has set up a joint consultation counter
for local companies who are interested in participating in the decommissioning project incooperation with the Fukushima Innovation Coast Framework Promotion Organization and the
Fukushima So-So (Soma and Futaba regions) Reconstruction Promotion Agency, and is preparing
to hold business fairs between the prime contractor and local companies. To provide support tohelp local companies participate in the projects, TEPCO subdivided the medium-to-long-term
outlook in the decommissioning project as well as the detail, timing and scale of the project orders
to be placed as much as possible, and formulated “Medium-to-long-term outlook in thedecommissioning” that specifically states equipment or technology required for each project in
September 2020. Now, TEPCO is explaining the outlook to the prime contractor and the local
governments and association of commerce and industry.
5.3.2 Key issues and strategies
Misunderstanding, concern, and rumors are caused by inappropriate information transmission
about decommissioning, which ruins appreciation and confidence in the decommissioning projectof the regions and the whole society and leads to the delay of decommissioning. Therefore, TEPCO
needs to utilize various tools, such as informational magazines, WEB sites, and motion videos, inaddition to the visit of the Fukushima Daiichi NPS and the decommissioning museum (Tomiokacho), and inform as to the present situation and progress status of decommissioning intelligibly andquickly.
Also, the government, NDF, and the TEPCO, under suitable cooperation, need to provide
information more carefully and make efforts to build confidence with regions. Therefore, we needto positively arrange an opportunity to communicate directly with the people in regions. We alsoneed to make efforts for bidirectional communication by dialog, such as listening to uneasiness andquestions of the participants sincerely through the events of the International Forum on theDecommissioning of the Fukushima Daiichi NPS, etc., held by NDF, and deliver exact information
intelligibly and quickly.
TEPCO must not end this “Commitment” just as a shape, but secure effectiveness. Therefore,
the specialized department working on community symbiosis plays a key role to update and add
the detail of “Medium-to-long-term outlook in the decommissioning project” as required with theprogress of the decommissioning project. In addition, they will positively provide coordination withthe local communities by carefully explaining it continuously via the local governments or the
association of commerce and industry through dedicated joint consultation centers and business
fairs targeting local companies. (Fig.30). TEPCO itself is providing support to local companies toenhance their technical capabilities, while inviting companies from outside the region to do businesswith them. In addition, TEPCO establishes a system where the local companies are encouraged to89

offer technical guidance to the primary contractors and, if certain results are achieved, incentives
are to be given. Efforts are being made to build a foundation for the local economy and foster local
businesses and human resources through the decommissioning project. Furthermore, not only the
research and development on decommissioning, but as companies outside the region expand theirbusinesses in the area and technical support to local companies progresses, it is expected that the
number of engineers and researchers visiting and staying from outside the region will increase. It
is required to develop the necessary environment and support so that such external humanresources can fit into the regional society and play an active role as a member of the local
community. As for the environmental improvement, in particular, it is necessary to consider a wide
range of living functions and educational functions so that their whole family can stay with peace inmind.
For carrying out the work of community symbioses, it is also required to strengthen organizations
if needed since close cooperation is required between each department. In addition, NDF needs tocontinue and strengthen cooperation and collaboration with local governments, including
Fukushima prefecture, the Fukushima Innovation Coast Framework Promotion Organization, andthe Fukushima So-So (Soma and Futaba regions) Reconstruction Promotion Agency, etc. NDF will
support TEPCO's community symbiosis efforts and work on cooperation strengthening with local
governments and related organizations.

Commitment toFukushima
residents for thecoexistence ofreconstruction &decommissioning

Tokyo Electric: Power Company Holdings, Inc.

90

3-year procurement
plan

TEPCO
Mid-to-long-term
perspective
Recent •initiatives

•

Local
Enterprises

3-year procurement plan was announced (Made in every April)
Briefing for enterprises through mid-to-long-term overlook (Held in April 2020)

TEPCO
Fukushima ICP *2
Promotion Organization

Cooperation

Government-private
Sector *1

Businessnegotiations

Consultation
service

Local
Enterprises*1 Fukushima So-So (Soma and Futaba regions)Reconstruction Promotion Agency*2 Fukushima Innovation Coast Framework Promotion Organization

Recentinitiatives• Holding business negotiations for local enterprises(1st:Dec 2019, 2nd :Feb 2020)• Arranging consultation service/tool for local enterprises
seeking to enter the business (Established the counter in May 2020)(TEPCO material edited by NDF)

Fig.30 Example of commitment to Fukushima residents for the coexistence of reconstruction
and decommissioning91

List of Acronyms/Glossaries
Acronym

Official Name

CEA

Commissariat à l'énergie atomique et aux énergies alternatives

D/W

Dry Well

DOE

United States Department of Energy

FP

Fission Products

IAEA

International Atomic Energy Agency

ICRP

International Commission on Radiological Protection

IRID

International Research Institute for Nuclear Decommissioning

JAEA

Japan Atomic Energy Agency

JAEA/CLADS

JAEA Collaborative Laboratories for Advanced Decommissioning
Science

MCCI

Molten Core Concrete Interaction

NDA

Nuclear Decommissioning Authority

NDF

Nuclear Damage Compensation and Decommissioning Facilitation
Corporation

OECD/NEAOECD Nuclear Energy Agency

PCV

Primary Containment Vessel

RPV

Reactor Pressure Vessel

S/C

Suppression Chamber

SED

Safety and Environmental Detriment

TMI-2

Three Mile Island Nuclear Power Plant Unit 2

Penetration X-6

Penetration PCV X-6

Center of the WorldIntelligence project

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

Operating Floor

Operating Floor of the buildings

Submersible ROV

A remotely operated submersible survey vehicle (Remotely Operated
Vehicle)Strategic Plan

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

Matters to beaddressed

As a specific nuclear facility, “the matters for which measures should
be taken” that The Fukushima Daiichi NPS must have the necessary
safety measures in place that are required by the NRA.

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.

Withdrawal Plan

Withdrawal plan for reserve fund

The Policy of
Preparation ofWithdrawal Plan

The Policy of preparation of withdrawal plan for reserve fund fordecommissioning
92

Fukushima Daiichi NPS

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

ALARPAs 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.

Glossary

Description

CRD housing

Housing that contains Control Rod Drive mechanism

MCCI ProductA product generated by high temperature molten core and concreteinteraction (MCCI)T.P.

A height from the average surface of the bay of Tokyo (Tokyo Peil) as astandard of elevation.
(cf. O.P: Onahama Port construction level (the lowest position of thewater surface)

Well 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 inoperation)

Basis seismic
ground motion

A magnitude of shake associated with earthquake that may affect greatly
to nuclear facilities. Based on the latest scientific and engineeringknowledge, it is provided in accordance with the geological structure or
ground structure, etc.

Submersion method

A method to retrieve fuel debris by submerging all fuel debris in watering
up to upper part of Primary Containment Vessel

Partial submersion
methodA method to retrieve fuel debris in a state that a part of fuel debris is
exposed in the air without watering

Grating

A lattice-type scaffolding used for side ditch lid or work scaffold

SludgeMuddy substance, dirty mud

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

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

Platform

Footing for work installed under RPV inside pedestal

Pedestal

A cylindrical basement that supports a body of reactor

Measurement bymuon (fuel debris
detection technology
with muon)

A technology to grasp location or shape of fuel in using characteristics bychange of number or track of particle depending on the difference ofdensity, when muons (muonic atoms) arrive from the cosmos andatmospheric air and pass through a substance

Mock-up debris

An artificial fuel debris, its chemical composition and chemical form were
estimated based on the case of Unit 2 of Three mile Island Nuclear
Power Plant accident

Mock-up

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

93Well shieldplug

Operating floor
Spent
Fuel
Pool
(SFP)

Component
Pit

Primary
Containment
Vessel (PCV)

4th floor

ReactorPressure
Vessel (RPV)

3rd floor

2nd floor

Pedestal
Vent Tube

1st floor

1st basement Fl.

Suppression
Chamber (S/C)

Torus room

（Courtesy of IRID）

Fig. 31 Structural drawing inside Reactor building

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

Core support plate

Control rod

Neutron flux measuring guideJet pump

Differential pressure detector/
Piping of Boric acid solution
injection system

Control Rod Drive Mechanism

Pedestal for RPV（Courtesy of IRID）

Fig. 32 Structural drawing inside Reactor Pressure Vessel (RPV)94

List of Attachment
Attachment 1

Revision of the Mid-and-Long-term Roadmap and the earlier published Strategic Plan ...... 96

Attachment 2

Major risk reduction measures performed to date and future course of action .................... 98

Attachment 3

Overview of SED indicator ................................................................................................. 103

Attachment 4

Risk sources containing radioactive materials except major risk sources on the site of
Fukushima Daiichi NPS ..................................................................................................... 109

Attachment 5

Change in risk over time ..................................................................................................... 111

Attachment 6

Coverage of fuel debris retrieval ......................................................................................... 112

Attachment 7

Analysis and investigation plan ........................................................................................... 114

Attachment 8

Concept of Safeguards ....................................................................................................... 117

Attachment.9

Terms related to radioactive waste management ................................................................ 119

Attachment 10

Disposal of radioactive waste,, .......................................................................................... 120

Attachment 11 Overall image of Storage Management Plan for the Fukushima Daiichi NPS ................... 124
Attachment 12 Current Progress of the Government-led R&D program on Decommissioning andContaminated Water Management .................................................................................... 126
Attachment 13

R&D medium-to-long-term plan ........................................................................................ 129

Attachment 14

Basic Direction of 6 Essential R&D Themes ..................................................................... 130

Attachment 15 Recruitment brochure for manpower development training on the decommissioning of
TEPCO Fukushima Daiichi NPS ........................................................................................ 136
Attachment 16

Major activities related to enhancing international collaboration ....................................... 138

95

Attachment 1 Revision of the Mid-and-Long-term Roadmap and the earlier published 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, fuel debris retrieval, etc. werecompiled by three parties of TEPCO, Agency for Natural Resources and Energy, and Nuclear and Industrial
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 the spent fuel pool and fuel debris retrieval, and R&D Plan was reviewed
based on the above.
[Strategic Plan 2015 (April 30, 2015)]
 The 1st edition of the Strategic Plan was published to provide a verified technological basis to the Mid-andLong-term Roadmap from the viewpoint of proper and steady implementation of decommissioning of 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 treatment
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), reduction of amount of radioactive materials contained in
the stagnant water in the buildings by half (FY2018), etc.
[Strategic Plan 2016 (July 13, 2016)]

 In response to the progress state of decommissioning after publication of the Strategic Plan 2015, concrete
concepts and methods were developed based on the concept and direction of the efforts of the Strategic

96Plan 2015 to achieve the target schedule specified in “Policy decision on fuel debris 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 of radioactive waste” which is expected tobe complete in FY2017, etc.
[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”.
[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.
[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.

97

Attachment 2 Major risk reduction measures performed to date and future course of action
Change 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 the spent fuel pools, cooling of fuel debris with water injection bycore spray system, nitrogen injection, etc. (in 2011) as well as the contribution of inventory anddecay heat decrease due to decay of radioactive materials.
The risk level in 0.5 to 2.5 years after the accident is shown in the enlarged graph (the verticalaxis is in linear scale) with the breakdown of major risk source (fuel debris, fuel in SFP andcontaminated water) at the bottom left in the figure and the similar graph since 3 years after theaccident is given in the bottom right with the risk level multiplied by 10. These graphs demonstratethat a continuous risk reduction has been achieved.

Evaluation of fuel in SFP 8 years after the accident occurred reflects the results of water temperaturerise in the testing on SFP cooling shutdown. (For detail, see Fig. 3 in Chapter 2 of main part.)

Fig. A 2-1 Reduction of risks contained in the Fukushima Daiichi NPS
Change in the risk level with further breakdown of major risk sources over time since 0.5 years
after the accident is shown in Fig. A 2-2. With a logarithmic scale, risk sources can be indicatedthat are too small to be displayed in the linear scale of Fig. A 2-1. Fuel in the Common Spent Fuel98

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. A 2-2 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, and the stagnant water in buildings andzeolite-containing sandbags have relatively high risk levels. Although, in recent years, the treatmentof the stagnant water in buildings has progressed and the risk level of the “stagnant water inbuildings + 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 addition,
as for the water stored in tanks (flange-type tank and welded tank), the risk of leakage andconsequently the risk level has been greatly reduced as a whole because the treatment of the water
stored in the flange-type tanks, which have a higher risk of leakage than welded tanks, hasproceeded well.

Total

Risk level (logarithmic scale)

Fuel in SFPs

0

Fuel debris
Stagnant water in buildings + Zeolite
sandbags
Contaminated water in trenches
Stored water in tanks
Secondary waste generated by water
treatment
Contaminated structures, etc., in thebuildings
Rubble, etc.

1

2

3

4

5

6

7

8

9

Year after accident

Fig. A 2-2 Change in the risk level for each major risk source(1) Fuel in SFPs
From one year after the accident, rubble was removed and a cover for fuel removal was installed
at Unit 4 in preparation for fuel removal, thereby enhancing the functions of reducing the risk of fueldamage 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 in 2014)34.

34

Decommissioning project, Status of the decommissioning work, Fuel removal work of Unit 4, (Website), Tokyo
Electric Power Company Holdings, Inc.

99

Although the effect of risk level reduction was observed due to the downgrading of 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 SFPs35.
In Unit 3, rubble removal was also performed in preparation for fuel removal from SFP, and thecover for fuel removal was installed in 2018. Moreover, fuel removal from SFP was started from
April 2019, resulting in lowering of risk level36.
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 above, 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 downgrading of
Safety Management; however, this effect is currently lost.
(3) Stagnant water in buildings + Zeolite sandbags
Although stagnant water in buildings is generated by cooling of fuel debris and immersion ofgroundwater into the buildings, etc., the risk level has been lowered due to the start of operation ofcesium adsorption apparatus (KURION and SARRY), the effect of subdrains and land-side
impermeable walls, water drainage in condensers, and the start of the operation of cesium
adsorption apparatus (SARRY-II). This stagnant water treatment in the buildings so far significantly
contributes to risk level reduction of the total site following contribution by fuel removal in SFP.
(4) Contaminated water in trenches
Although the contaminated water of high concentration has been stagnated in the seawater pipe
trenches in Units 2 to 4 since immediately after the accident, the trenches were blocked and thetreatment of the stagnant water has been completed (in 2015)37. With regard to the seawater pipe

35

Decommissioning project, Status of the decommissioning work, Fuel removal from spent fuel pool in Unit 1,(Website), Tokyo Electric Power Company Holdings, Inc.
36 Decommissioning project, Status of the decommissioning work, Fuel removal from spent fuel pool in Unit 3,(Website), Tokyo Electric Power Company Holdings, Inc.
37 Decommissioning project, Status of the decommissioning work, Removal of contaminated water in seawater
pipe trenches, (Website), Tokyo Electric Power Company Holdings, Inc.

100

trench of Unit 1, the concentration of which is lower than that of Units 2 to 4, purification of thestagnant water is under consideration38.
(5) Stored water in tanks
In each tank, there are several types of stored water with different radioactive material
concentration. Although the concentrated liquid waste generated by the operation of theevaporation-enrichment system immediately after the accident had a high concentration ofradioactive materials, the evaporation-enrichment system stopped after a short period of operationand concentrated liquid waste is not generated at present. In addition, the concentrated liquid waste
slurry is separated from the concentrated liquid waste and transferred to the secondary waste
generated by water treatment, and the remaining concentrated waste fluid is transferred to a safer
welded tank and its inventory is decreased, thereby reducing the risk of water leakage and lowering
the risk level.
The treatment of the concentrated salt water generated from the treatment with the cesium
adsorption apparatus was completed in 2015 through the operation of multi-nuclide removal
equipment and the advanced multi-nuclide removal equipment39.
Risk levels are also lowered by raising and duplexing the weir (for the existing tanks completed
in 2014), transferring from flange-type tanks to welded tanks, and treating the remaining water atthe bottom of the flange-type tanks where the Sr-treated water is stored (in 2019). The remaining
water at the bottom of other flange-type tanks is being treated for dismantling the tanks.
(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 adsorption vessel by operation of the cesium adsorption apparatus (KURION and SARRY)(in 2011) and by the cesium adsorption apparatus (SARRY-II) (in 2019), HIC slurry by operation of
the multi-nuclide removal equipment (in 2013), the waste adsorption vessel by the advanced multinuclide removal equipment (in 2014), waste adsorption vessel by the mobile-type treatment systemthat treated seawater pipe trenches, etc. Although the sludge from decontamination device greatly
contributes to the risk level, sludge is not newly generated at present, and thus, the risk level of thetotal secondary waste generated by water treatment is not on an increasing trend.
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 reinforced-concretebase and the weir.
(7) Contaminated structures, etc., in the buildings
38 The 82nd Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 3: Roadmap

for Instruction Items to be Considered Based on the Measures for Mid-term Risk Reduction at TEPCO’s
Fukushima Daiichi NPS at TEPCO (Risk Map), (March 2020 Edition)”
39 Decommissioning project, Status of the decommissioning work, Purification of contaminated water, (Website),Tokyo Electric Power Company Holdings, Inc.

101

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. in the reactor buildings, PCVs
or RPVs that are contaminated by dispersed radioactive materials caused by the accident sincefuel debris retrieval is not started yet.
(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), fallen tree temporary storage pool(in 2013), expansion of solid waste storage facilities (in 2018), etc. In addition, the rubble from
temporary storage facilities is being transferred to the better-controlled solid waste storage facility
for risk reduction. Furthermore, outdoor temporary storage is planned to be discontinued by theend of FY 2028 by increasing incinerators, volume reduction installations and solid waste storages,
etc., in accordance with the Solid Waste Storage Management Plan40.

40 The Solid Waste Storage Management Plan at the Fukushima Daiichi NPS (July 2020 Edition), Tokyo ElectricPower Company Holdings, Inc.

102

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 indicator41 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.
=

+

×

×

or
=

+

×

×

×

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.
=×

Inventory is defined as shown below by Radioactivity of risk sources and the Specific Toxic
Potential (STP) and corresponds to the effective radiation dose42. The STP is defined as the volume
of water required to dilute 1TBq of radioactive materials and corresponds to the radiation dosecoefficient. Ingestion of a certain amount of such diluted water throughout the year will result in aradiation exposure dose of 1mSv. The SED indicator conservatively uses the larger radiation dosecoefficient between ingestion and inhalation.
=

×⁄

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
41
42

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

103

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.

104

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 isrealized

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

105

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.

106

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.

107

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

108

Attachment 4 Risk sources containing radioactive materials except major risk sources on the siteof Fukushima Daiichi NPS
Table 4-1 Risk sources containing radioactive materials except major risk sources (1/2)
Item
Underground watertank
Liquidradioactive
materials

Accumulated wateron siteDrainage

Spent control rods
In-pool water
Spent fuelpool

Rubbles on
operating floor
Waste before theearthquakeSolidradioactive
materials

Contaminated soil

Rubbles aroundbuildings

Descriptions
The residual water in all the underground water tanks were completely
recovered43. Dismantling and removal policies are under consideration.
Extracted by the comprehensive risk inspection performed in 2015. Since
then, the concentration of radioactive materials and volume of water arechecked accordingly44.
In drainage A, Cs-137: lowered to ND ~ 23 Bq/L.45 In drainage K, thecontamination source on the roof of the Unit 2 R/B was removed, and thecontamination level fell to 67 Bq/L. In addition, purification materials were
installed46 and measures such as operation of PSF monitors were taken47.
Spent control rods, etc.: 24,030. Shroud fragments, etc.: 193 m348. The
major nuclide is Co-60.
Salt removal in Units 2 to 4 was completed in 2013.
Investigation was conducted in Unit 1 and Unit 3. In Unit 1, a high radiationdose was measured near the lower plug49. In Unit 3, scattered radiationfrom Cs-134 and Cs-137 were measured50. In Unit 2, leftover objects were
removed51 and a measurement of 683 mSv/h was taken in the clearance of
the upper plug52.
185,816 drums are stored53. The major nuclide is Co-60.
As a result of the topsoil analysis, more than half of the samples are inexcess of the designated standards (8,000 Bq/kg) based on the Act on
Special Measures Concerning the Handling of Environmental Pollution byRadioactive Materials54.
Dismantling of rubbles scattered on the roof floor of the buildings due tohydrogen explosions is now in operation and planned. The physical quantity
has not been confirmed.

43

The 44th Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat
Meeting “Reference 3-6: On-site Monitoring Status (Conditions of Water Discharge Channels in Units 1 to 3
and Underground Water Storage Tanks)”
44 Comprehensive Risk Inspection of Fukushima Daiichi NPS that impacts outside the Site Boundary - Review
Results - (April 28, 2015) Tokyo Electric Power Co., Inc.
45 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”
46 The 63rd Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 2: Measures
for rainwater inflow control (Progress status of installing purification materials for rainwater drainage in turbine
buildings)”
47 The 74th Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat
Meeting “Reference 3-6: Starting of operation of PSF monitor in the drainage K”
48 Nuclear Regulation Authority, Material of interview with the licensee “Solid Waste at Fukushima Daiichi NPS”
September 21, 2018, Tokyo Electric Power Company Holdings, Inc.
49 The 69th Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat
Meeting “Reference 3-2: Investigation of Obstacles in SFPs in Reactor Building of Unit 1 and Well Plug
Investigation”
50 The 38th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 5: Radiation
Source Investigation on the Operating Floor of Unit 3 Reactor Building (Flash Report)”
51 Completion of Work to Move and Clear Leftovers on the Operating Floor of Unit 2 Reactor Building at
Fukushima Daiichi NPS (November 7, 2018), Tokyo Electric Power Company Holdings, Inc.
52 The 10th Review Meeting on the Accident Analysis at TEPCO's Fukushima Daiichi NPS “Reference 3: Field
Investigation Results”
53 Nuclear Regulation Authority, 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.
54 Daily Analysis Results of Radioactive Materials at Fukushima Daiichi NPS, (Website), Tokyo Electric Power
Company Holdings, Inc.

109

Table A4-0 Risk sources containing radioactive materials except major risk sources (2/2)
Item

Descriptions

Dismantlement work was carried out since August 2019, and theupper part of 61 m out of the total height of 120 m was divided into
Exhaust stack of Units
23 blocks in total for dismantling. On May 1, 2020, a lid was installed
1/2
on a barrel 59 meters above the ground to prevent rainwater inflow,
and dismantling was completed55.
Response toexternal events,
etc.

Megafloat

The work of bottoming and internal filling is in progress56.
Measurement on the entire surface inside the megafloat is less than
4 Bq/cm257. Measurement of one location at No. 1 VOID is approx.
1.4 Bq/cm2.

Dust in operating floor

Below the target value of release control (1×107 Bq/h). Gradually
declining58.

Rainwater inflow into
buildings

Rubble on the roof was removed and waterproofing was newly
provided. Purification materials were installed in the gutters. Checkvalves were installed in the drain pipes. The roof drain was repairedand closed59. Facing of the T.P.8.5m board is to be completed60.
High air dose rate was measured in each filter and exhaust stack ofUnits 1 to 4. A value of 4.35 Sv/h was measured in the vent line
leading to the exhaust stack of Units 1/261. Investigation andmeasurement are ongoing for removal.

Vent line
Importantmatters inpromotingOn the 3rd floor, beams at several locations were damaged. A
decommissioning
The 3rd and 4th floors maximum of 50 mSv/h was measured62. On the 4th floor, a strong
workof Unit 3 R/B
radiation source was observed by a gamma camera. Other details
are unknown.

55“Completion of Dismantling of Exhaust Stack of Units 1/2 at Fukushima Daiichi NPS” (May 1, 2020), Tokyo
Electric Power Company Holdings, Inc.
56 Progress Status of Megafloat Project at Fukushima Daiichi NPS to Reduce Tsunami Risks (Starting of Step 2)(March 5, 2020), Tokyo Electric Power Company Holdings, Inc.
57 The 75th Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat
Meeting “Reference 3-1: Progress Status of Megafloat Project to Reduce Tsunami Risks”
58 Daily Analysis Results of Radioactive Materials at Fukushima Daiichi NPS, (Website), Tokyo Electric Power
Company Holdings, Inc.
59 The 78th Team for Countermeasures for Decommissioning and Contaminated Water Treatment/Secretariat
Meeting “Reference 3-1: Progress Status in Rooftop Rainwater Measures”
60 The 74th Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 1: Progress
Status in Rainwater Inflow Measures”
61 The 81st Study Group on Monitoring and Assessment of Specified Nuclear Facilities “Reference 4-2:
Implementation Status of On-site Investigation for Removal of SGTS Piping of Units 1/2”
62 The 9th Review Meeting on Analysis of the Accident at TEPCO's Fukushima Daiichi NPS “Reference 2:
Investigation Results on the 3rd Floor of Reactor Building of Unit 3 - Results of On-site Investigation on
December 12, 2019, etc. -”110

Attachment 5 Change in risk over time
Overview of the concept of risk management in the UK is shown in the conceptual diagram
below. Even if the current risk level is plotted in the white region of the graph, it does not meansuch 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 increasecaused by degradation of facilities 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 notreach 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 the solid line) so that it may not reach into the unacceptable or intolerable
region.

Risk Level

Unacceptable area

Area where risk level
cannot be allowed
when taking a longview of the future.

Area where judgment is madewhether the risk level is
acceptable or not with close
examination of difficulty of risk
reduction

Broadly acceptable area

Time
Fig. A5-1 Change in risk over time63

63

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, “The Regulationof Decommissioning and Associated Waste Management” 1st International Forum on the Decommissioning of the
Fukushima Daiichi Nuclear Power Plant (April 2016)..

111

Attachment 6

Coverage of fuel debris retrieval

In the Mid-and-Long-term Roadmap issued in 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 IAEA64,65.
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

64

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-T-2.7,
Vienna (2014)
65 Managing the Unexpected in Decommissioning, IAEA Nuclear Energy Series No. NW-T-2.8, Vienna (2016)112

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 bysight, 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.

113

Attachment 7

Analysis and investigation plan

1 Purposes of the analysis and the investigation
Safe and steady decommissioning of the Fukushima Daiichi NPS is a top priority and toaccomplish the decommissioning work is needed as early as possible. To proceed withdecommissioning safely and reliably, it is important to understand the current situation and what
has happened by analyzing fuel debris and conducting investigations on the on-site condition.
The results obtained from the analyses and investigations can be reflected in the following threeareas, including decommissioning.
① Analyses and investigations of fuel debris should be carried out in the process of
decommissioning so that they can directly contribute to “the accomplishment of
decommissioning” through the retrieval process, safeguards, storage, treatment anddisposition.
② To contribute to “the accomplishment of decommissioning”, an accident history investigation
represented by analyses and investigations of fuel debris, etc., shall be conducted, and thecause of the accident at Fukushima Daiichi NPS shall be clarified to disseminate theknowledge obtained overseas and to future generations.
③ As a by-product of the analyses and investigations on fuel debris, etc., improvement of thesevere accident progression analysis code, emergency response and the facilities has been
made, which can indirectly contribute to the improvement of the safety of nuclear powerreactors.
Fig. A7-1 shows the relationship between analyses/investigations and decommissioning,
clarification of the cause of the accident, and studies on safety. Needless to say, the information
obtained through the analyses and investigations will not only directly contribute to the future“decommissioning at Fukushima Daiichi NPS” but also play a part in the investigation of theaccident’s history. Adequate understanding, examination, and consideration of the information
obtained from historical investigations on past accidents will ensure the advancement in “theunderstanding of phenomena”. Knowledge gained through the understanding of phenomena will,in turn, contribute to “clarification of the cause of the accident” and “decommissioning”, and, in theend, indirectly contribute to “Improving Nuclear Safety” through improvements in the severe
accident progression analysis code, emergency response and the facilities.

114

Fig. A7-1 Where analyses and investigation results are reflected and their relationships
2 Basic principles toward the planned analysis and investigation
Analyses and investigations on the decommissioning and contaminated water management ofFukushima Daiichi NPS should be implemented within the range of efforts to proceed withdecommissioning safely and steadily, since the top priority is to realize decommissioning safely andsteadily as early as possible. The necessity to implement these analyses and investigations should
be sufficiently considered from the viewpoint of investigating the cause of the accident andimproving the safety of nuclear power in the future. After clarifying how the information obtained
will contribute to decommissioning, these analyses and investigations should be conducted to theextent that it is reasonably acceptable as a decommissioning project based on the considerationof their significance and the associated burden. As described above, it is important to conduct
analyses and investigations on decommissioning and contaminated water management at the
Fukushima Daiichi NPS in a planned manner. A plan for the analyses and investigations needs tobe developed in engineering in accordance with the following “Basic principles toward the planned
analysis and investigation on the decommissioning and contaminated water management ofFukushima Daiichi Nuclear Power Station.

115

Basic principles toward the planned analysis and investigation on the decommissioning
and contaminated water management of Fukushima Daiichi Nuclear Power Station(1) To proceed with the decommissioning of Fukushima Daiichi NPS safely andsteadily is of primary importance. With these efforts, it is necessary to achieve“decommissioning as soon as possible”. For that sense, the analysis and theinvestigation on the decommissioning and contaminated water management ofFukushima Daiichi NPS (hereinafter referred to as “Fukushima Daiichi NPS
Analysis and Investigation”) should be conducted, to the extent that can proceedwith the decommissioning in safe and steady.
(2) At the same time, it is also necessary to proceed with the Fukushima Daiichi
NPS Analysis and Investigation from the viewpoint of ascertaining the causes of
the Fukushima Daiichi NPS accident and improving the nuclear safety for future(hereinafter referred to as “Forensic”). Therefore, due consideration is to begiven to the necessity of the Fukushima Daiichi NPS Analysis and Investigationfrom the viewpoint of Forensic, on the premise of the safe and steadydecommissioning of Fukushima Daiichi NPS.
(3) The Fukushima Daiichi NPS Analysis and Investigation is to be planned on thepremises of realistic working situations and difficulties of the site, giving thehighest priority on the safety for local residents, surrounding environment andworkers. In addition, it must be proposed after clarifying the concreteness oftechnology commensurate with it.
(4) While clarifying what is the information obtained from the Fukushima Daiichi NPS
Analysis and Investigation used for and what will it contributes to, it must be
conducted in reasonably acceptable range as Fukushima Daiichi NPS
decommissioning project, considering its significance and the responsibility
associated with it.
(5) Taking into account of Japan’s responsibility to the international society, as acountry where the Fukushima Daiichi NPS accident occurred, information
obtained in the Fukushima Daiichi NPS Analysis and Investigation should be
provided in a proactive way. There is a possibility for institutions requesting
additional information to bear a reasonable burden.

116

Attachment 8 Concept of Safeguards
Safeguards are verification activities undertaken to ensure that nuclear materials are used only
for peaceful purposes and not diverted to nuclear weapons, etc.
Japan has concluded the Safeguards Agreement between Japan and the International Atomic
Energy Agency (IAEA) pursuant to the “Treaty on the Non-Proliferation of Nuclear Weapons” (NPT).
In accordance with this Agreement, relevant domestic laws (the Law for the Regulations of Nuclear
Source Materials, Nuclear Fuel Materials and Reactors (the Nuclear Reactor Regulation Law) andothers) have been developed to establish a domestic safeguards system and accept the IAEA’s
safeguards.
Specifically, the Safeguards Office of the Nuclear Regulatory Agency (JSGO) has confirmed that
all nuclear materials in Japan have not been diverted to nuclear weapons, etc., by conducting thefollowing activities, and the IAEA has acknowledged this authorization through inspections, etc.
(1) Material accountancy by nuclear operators
A nuclear operator shall determine the places where nuclear materials are handled at its
facilities, shall perform a strict and accurate material accountancy including the amount of
nuclear materials to be entered or transferred from its premises and the periodic inventory of
nuclear materials, and shall report to the Nuclear Regulation Authority. The JSGO will compile
these reports received from operators and submit them to the IAEA.
(2) Containment/Monitoring
To ensure that nuclear materials have not been secretly transferred, the JSGO and IAEA haveattached a “seal” on the lids of containers in which nuclear materials are stored and on thegateway for fuel at nuclear power plants. At nuclear power plants, etc., “surveillance cameras”
are installed to constantly monitor the movement of nuclear materials.
(3) Inspection
Inspectors from the JSGO and the IAEA will visit the nuclear facilities in person and conduct
inspection activities such as verifying the consistency of reports and records, checking thequantity and volume of nuclear materials on site, collecting samples for analysis, andassessing the containment/monitoring data.

117

NMCC
(TechnicalSupport)Additional Protocol (AP)･R&D activities without nuclear material･Buildings on sites, etc.

Nuclear Material
Accounting
Reports

Nuclear Regulation Authority(Planning/Implementation)

Design Information Verification/ Inspection

Ministry of Foreign Affairs

AP Declarations

Complementary AccessInternational Atomic Energy Agency(IAEA)Countries with
Bilateral
Agreements

・Report on Inventory& Transfer
・Notification &Confirmation ofTransfer etc.

CSA Activities
AP Activities

Comprehensive Safeguards Agreement (CSA)

NUCLEAR FACILITIES0*1 : Except for complementary access occurred during regular domestic inspection*2 : Based on Nuclear Power Plant Regulation, specify Nuclear Material Control Center (authorized foundation)
as “Specified safeguards inspection Agency” and “Specified information processing Agency”

Fig. A8-1 Safeguards implementation system in JapanThe safeguards shall be applied to the Fukushima Daiichi NPS without exception. TEPCO, asa nuclear operator, will consult with the JSGO and IAEA to determine the method of implementing
the safeguards (material accountancy, containment/monitoring, inspection) to be applied to
Fukushima Daiichi NPS, and practically apply them on site.

118

Attachment 9

Terms related to radioactive waste management

IAEA Safety Requirements GSR-Part 5 66 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 A9-1. 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 terms used to refer to thefollowing steps that change waste characteristics
Pretreatment: a process before treatment (Treatment)
Treatment: a process intended to benefit safety andeconomics efficiency by changing waste
characteristics
Conditioning: a process of manufacturing a waste
package suitable for handling, transportation,
storage and / or disposal

Fig. A9-1Terms related to radioactive waste management (IAEA)67 and their translation examples(For the Japanese translation example, refer to the materials of the Japan Atomic Energy68,69)

66 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)
67 IAEA, IAEA Safety Glossary Terminology Used in Nuclear Safety and Radiation Protection 2007 Edition, p.216,(2007).
68.AESJ, The Report of 2013, - Organizing information of radioactive waste and matters to be considered forsolving the issues (p.7), March 2014, the Expert Committee, “Processing /disposal of radioactive waste generated
by the accident of Fukushima Daiichi NPS”
69 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).

119

Attachment 10

Disposal of radioactive waste70,71,72

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) 73
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”74 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 Figure A10-1. Each classification is also shown in Table A10-1.

Fig. A10-1 Conceptual diagram of waste classification

70

Osamu Tochiyama, Principles and Basics of Radioactive Waste Disposal, Radioactive Waste Management
Funding and Research Center (a Public Interest Incorporated Foundation) (2016)
71 https://www.enecho.meti.go.jp/category/electricity_and_gas/nuclear/rw/
72 https://www.fepc.or.jp/nuclear/haikibutsu/index.html
73 IAEA SSR-5 "Disposal of Radioactive Waste"(2011)74 IAEA GSG-1" Classification of Radioactive Waste" (2009)120

Table A10-1 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 Waste that requires higher-level containment and isolation than the(ILW)near 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 waste liquid 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.
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. In Japan, radioactive waste is broadly divided into “low121

level radioactive waste” (equivalent to VLLW to ILW in GSG-1), which is generated through theoperation of nuclear power plants, and “high-level radioactive waste” (equivalent to HLW of GSG1), which is generated through the reprocessing of spent fuel that is generated through theoperation of nuclear power plants and is vitrified with a high level of radioactivity. When disposedof, waste shall be classified appropriately according to its radioactivity level and properties, typesof radioactive materials, etc., and shall be strictly controlled, and reasonably treated and disposedof under the principle that responsibilities lie with those who have generated the waste.
“High-level radioactive waste” is a vitrified waste liquid 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.
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 A10-2.
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 A10-2 Types of Radioactive Waste Generated by the Operation of Nuclear Power Plants

122

Fig. A10-2 Japan Nuclear Fuel Ltd. Low-level Radioactive Waste Disposal Center

123

Attachment 11

Overall image of Storage Management Plan for the Fukushima Daiichi NPS75

75

Solid Waste Storage Management Plan for Fukushima Daichi Nuclear Power Station of Tokyo Electric Power
Company Holdings, Inc., July 2020 edition (issued on July 30, 2020)124

(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
treatment”
Fig. A11-1 Present and future storage conditions of “rubble, etc.” and “secondary waste
generated by water treatment” on site of the Fukushima Daiichi NPS

125

Attachment 12 Current Progress of the Government-led R&D program on Decommissioning andContaminated Water Management76
1. Grasping state inside reactor, characterizing of fuel debris, and internal investigation
1-(1) 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)
1-(2) Development of analytical and estimation techniques for characterization of fuel debris,
Development of analytical and estimation techniques for characterization of fuel debris(Development of estimation technologies for variation character across the ages) (FY 2019 2020), Development of analytical and estimation techniques for characterization of fuel debris(Development of technologies for improving analytical accuracy and estimation of thermal
behavior of fuel debris) (since FY2020)(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)
1-(3) Development of technologies for in-depth investigation of PCV inside (On-site verification)(FY 2018 - 2020)(Related projects) Development of investigation technologies of inside of PCV (FY 2011 - 2013)
Development of investigation technologies of inside of PCV (FY 2014 - 2015)
Development of investigation technologies of inside of PCV (FY 2016 - 2017)
Development of technologies for in-depth investigation of PCV inside (FY 2017
- 2018)
1-(4) Development of investigation technology inside RPV (FY 2016 - 2020)(Related projects) Development of investigation technologies inside RPV (FY 2013 - 2015)
1-(5) Development of technologies for the detection of fuel debris inside reactors (using muon) (FY
2014 - 2015)76

Information Portal for the Research and Development for the Fukushima Daiichi Decommissioning(http://www.drd-portal.jp/)126

2. Retrieval of fuel debris
2-(1) Development of technologies for retrieving fuel debris to be gradually expanded in scale(FY2020)77(Related projects) Development of technologies for retrieval of fuel debris and internal structures(FY 2014)
2-(2) Technologies toward further expansion in scale for retrieval of fuel debris and internal
structures (FY 2020)76(Related projects) Development of fundamental technologies for retrieval of fuel debris andinternal structures (FY 2015 - 2016)
Advancement of retrieval method and system of fuel debris and internal
structures (FY 2015 - 2018)
Development of technologies for retrieving fuel debris and internal structures,
Development of technologies for retrieving fuel debris and internal structures(development of technologies for dust collecting system) (FY2019 - 2020)
2-(3) Development of sampling technologies for retrieving fuel debris and internal structures (FY2017 - 2018)
2-(4) Development of PCV closed water circulation systems (FY 2018 - 2019)
2-(5)-1 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)
2-(5)-2 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)
2-(6) 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 and PCV(FY 2011 - 2013)
Development of evaluation methods for the structural integrity of RPV and PCV(FY 2014 - 2015)
2-(7) Development of corrosion inhibition technology for RPV and PCV (FY 2016)(Related projects) Full-scale test of repair methods for leak spots in PCV (FY 2014 - 2015)
2-(8) Development of criticality control technologies of fuel debris (FY 2012 - 2016)
2-(9) Development of technologies for non-destructive detection of radioactive material depositedin S/C, etc. (FY 2014)
2-(10) Development of remote decontamination technology in the reactor building (FY 2014 - 2015)

77

Renamed (In accordance with the revision of “Mid-and-Long-term Roadmap towards the Decommissioning of
TEPCO’s Fukushima Daiichi Nuclear Power Station” on December 27, 2019)

127

(Related projects) Development of remote decontamination technology in the reactor building (FY2011 - 2013)
2-(11) Formulation of comprehensive radiation dose reduction plan (FY 2012 - 2013)
2-(12) Development of technologies for containing, transferring and storing fuel debris (FY 2016 2020)(Related projects) Development of containing, transferring and storing technologies of fuel debris(FY 2014 - 2015)
3. Waste management
3. Research and development of processing and disposal of solid waste (FY 2019 - 2020)(Related projects) Development of technologies for processing/disposal of secondary waste bytreatment of contaminated water (FY 2012)
Development of technologies for processing/disposal of radioactive waste (FY2012)
Research and development of processing/disposal of solid waste (FY 2013 2014)
Research and development of processing/disposal of solid waste (FY 2015 2016)
Research and development of processing and disposal of solid waste
Research and development of preceding processing methods and analyticaltechniques
4. Spent fuel management
4-(1) Evaluation of long-term integrity of fuel assembly removed from spent fuel pools (FY 20152016)(Related projects) Evaluation of long-term structural integrity of fuel assemblies removed fromspent fuel pools (FY 2012 - 2014)
4-(2) Investigation of method for processing damaged fuel, etc. removed from spent fuel pools (FY2013 - 2014)
5. Contaminated water management
5-(1) Verification tests of tritium separation technologies (FY 2014 - 2015)
5-(2) Verification of technologies for contaminated water treatment (FY 2014)
5-(3) Large-scale verification of impermeable walls (frozen wall) (FY 2014)
5-(4) Development and verification of high-performance multi-nuclide removal equipment (highperformance ALPS) (FY 2014)

128

Attachment 13

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
Key Milestones

2019

2020

2021

Phase 2

2022

2025

2031

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

Legend:[1. Experimental retrieval at Unit 2]

Trial retrieval
Gradual expansion of fuel debris retrieval A

Further expansion offuel debris retrieval
scale

Gradual expansion of retrieval scale

Improve the environment
inside the building
Manufacturing and testing of a retrieval
device, etc. *1, Change of operation of
the installed s afety s ystems, Removalof obs tacles in openings, etc.

Main Process es1)
Experimental retrieval andinternal inves tigations

Major R&D activities
Key technical iss ues*1: The Naraha Remote Technology Development Center is useds

Development of technology for detailed PCV internal investigations[]

1) Described bas ed on TEPCO DAP2020

To fuel debris characterization: Linkage between process es[2. Gradual expansion of retrieval scale at Unit 2]: Where R&D results are applied
Improve the environment
ins ide the building

Fuel debris retrieval facility/safety s ys tem/fuel debris temporary s torage facility/maintenance facility
Des ign, manufacturing and testing (Utilization of the Naraha Remote Technology
Development Center)

Installation
Gradual expansion of retrieval 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 retrieval

To fuel debris characterization(1) Addressing payload growth and upgrading end tools(2) Manufacturing equipment for gradual expansion of fuel debris retrieval(3) Preparing the safety systems (gas system, water treatment system, criticality
control system)(4) Preparing fuel debris and waste storage facilities[1. Environmental improvement of inside and outside the buildings]
Environmental improvement
inside and outs ide the Unit 1 buildingsIns ide the buildings: Radiation dose reduction/Removal of obstacles, etc.
Outside the buildings: Removal of exhaust s tacks at Units 1/2, removal of trans formers, etc. => Secure the s ite *2
Ins ide the buildings : PCV water level lowering/Radiation dose reduction, etc.
Outs ide the buildings: Removal of exhaust stacks and removal of transformers at Units 3/4, Improvement of thebas ement floor, etc. => Secure the site *2

Environmental improvement
inside and outs ide the Unit 3 buildings

Lowering of PCV
water level wasachieved

Development of as sessment methods for deterioration s tatus, etc.,
of building frames and equipment*2: Added buildings, maintenance buildings, storage buildings[2. PCV/RPV internal investigations, Characterization of fuel debris]
PCV internal investigations at Unit 3

Development of technology for PCV internal inves tigations at Unit 1*3: At this point, the bottom access method is as sumed.

Enhancement of the access method *3

Development of RPV internal investigation technology

Characterization of fuel debris
Demonstration of analytical technology (Utilization of radioactive material
analysis and res earch facilities)

Development of Analytical and Estimation Technologies for Fuel Debris Characterization

Further expansion of fuel debris retrieval B[3. Retrieval equipment, safety systems & maintenance equipment, and storage facility *4] *4: Main proces ses for proceeding with the s tudy on Unit 3 as a preceding case are shown below:
Findings obtained after the startof a gradual scale expansion
are reflectedExperimental retrieval at Unit 2• Internal investigation results
are reflected

Verificationof the actual site applicability

Conceptual study

Study of safety systems

Des ign of retrieval ins tallations

Manufacturing, ins tallation, testing, and trainingof retrieval equipment

Design of s afety s ys tem installations

Production, installation and testingof s afety s ystem ins tallations

Promotion of development for verification of
actual site applicability
Development of technologies toward further expansion of fuel debris retrieval scale
Side-access retrieval method: Examination and enhancement of elemental technologies, verification of the actual site applicability
Top access method: Conceptual study, examination and enhancement of elemental technologies

Technical issues toward further expansion of fuel debris retrieval(1) Development of fuel debris retrieval method
Obstacle removal technology, Cutting and recovery technology, Sorting
technology, Preventing the diffusion of radioactive materials(2) Development of safety systems
Liquid systems / gas systems, Criticality control technology(3) Development of full assessment technology
Data acquisition on debris scattering rate, Analysis method for exposure
assessment
Development of maintenance policy, Study of maintenancemethods

Design of facilities , manufacturing of equipment, and construction of facilities

Start ofoperation

Development of remote and support technologies for optimizing 1F decommissioning
Basic des ign of fuel debris s torage facilities

Equipment design, Equipment manufacturingStart ofoperation

Development of Technology for Collection, Transfer and Storage of Fuel Debris

Waste Management C

Characterization of solid waste
Study on the policy according to "Prospects of rocessing/disposal methods abd safety in technology"
Enhancement of efficiency on waste characterization

Development of sampling technology, Characterization with use of measured data and analyzed data

①Characterization efficiency②Development of sampling technology
Development of procesing/disposal concept and safety assessment

Establishment of selection systrem of processing/disposal concept in accordance with the progress of characterization①Establishment of a selection system of preceding procesing②Development of procesing/disposal concept and safetyassessment methods
Storage①Study and evaluation of storage methods②Development of technology for contamination evaluation

129

RetrievalAttachment 14

Basic Direction of 6 Essential R&D Themes
December 12, 2017
Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF)
The Basic Direction of 6 Essential R&D Themes

The Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi Nuclear
Power Station (September 26, 2017) specifies enhancement of the activities for matching the R&D required fordecommissioning (Needs) with the basic and fundamental R&D (Seeds) and for human resource development. It
also specifies enhancement of the functions of Japan Atomic Energy Agency’s Collaborative Laboratories for
Advanced Decommissioning Science (JAEA/CLADS) and promotion of joint researches with domestic andinternational universities and researching institutions to establish the international decommissioning research centerwith concentrated wisdom.
Following the above, the Ministry of Education, Culture, Sports, Science and Technology (MEXT) states in its
budget request for FY2018 that they will reform the Center of World Intelligence Project for Nuclear Science andTechnology and Human Resource Development (“World Intelligence Project”) into a subsidy program intended for
JAEA/CLADS and the program will be implemented under the system centered by JAEA/CLADS from the newly
adopted proposals from FY2018.
On the occasion of this reform, MEXT showed NDF their intention to discuss how to proceed with the future
R&D of the World Intelligence Project. This includes selection of the theme for the call for proposal considering the
Essential R&D selected by the task force from the viewpoint of promoting basic and fundamental researches withsatisfactory understanding of the Needs.
Therefore, concerning the 6 Essential R&D Themes which are described in the interim report of the Task Forceon Research Collaboration (November 30, 2016), the Basic Direction of the 6 Essential R&D Themes was compiled
including the background of the issues, the problem consciousness, and the expected research image, with
consulting the discussions in the working group for each theme.
Theme(1) To identity process of characteristic change in fuel debris over time

“Descriptions /Background issues”
on the interim report

The fuel debris retrieval is scheduled for 2021 onward, 10 years after the fuel debris
production. And since it is anticipated that the retrieval will require a long period of time,
the fuel debris will remain inside the reactors over 10 years. In addition, the retrieveddebris must be stored safely. Choosing the best possible methods ofretrieve/transmission/storage of fuel debris requires predictions of characteristic changes
of fuel debris over time.
In relation to the accident of Chernobyl nuclear power plant, detection of particulatesof the micron order which contain fuel components from around the fuel debris has beenreported and the national report of the Ukrainian government showed concerns about theincrease risk of radioactive dust emergence over time through self-decay. One of thepossible reasons is that the fuel debris with high radioactivity exposed to rich humidity
caused rapid progress of aging which quite slowly proceeds with normal uranium mineralin the geological environment. It results in oxidation activated by radioactive dissolution
and generate hexavalent uranium compound. On the other hand, because the PCV of
the Fukushima Daiichi NPS (hereinafter referred to as “1F”) is currently in the nitrogen
atmosphere under subtle positive pressure, oxidation is unlikely to proceed immediately.
In the future, such an event similar to the above may occur because the air that contains
oxygen may flow into the PCV when a negative pressure control is applied to retrieve thefuel debris. Since the radiation level is about one order higher in 1F than that of the fueldebris in the case of the Three Mile Island Unit 2 (TMI-2) accident (occurred in a shorttime after the operation started), it is under unexperienced condition. In addition, it should
be noted that it will take a longer period to complete the retrieval of the fuel debris fromthe time of accident than in the case of TMI-2.
Various factors are involved in the aging of such fuel debris in addition to the oxidation
described above. Roughly classifying, those factors may include the chemical mechanism(oxidation-reduction, leaching of included components, changes in the chemical form or
the phase state, etc.), physical mechanism (structural or characteristic changes by heat
cycle etc., irradiation damage by α-ray), and coupled actions of these factors.
Since decay or leaching of fuel debris due to aging lead to emission of FP particles
or gas, or effluent of particles that contain α-nuclides that are confined in the fuel debris,they have significant impact on the system design and procedures. It includes the retrieval
mechanism, the cooling and circulating system, the containment function, the criticality
monitoring system, the PCV gas control system, exposure evaluation, containing,transferring and storing, and processing and disposal. In particular, as for the Mid-andLong-term Roadmap, while the processing and disposal method of the fuel debris will be

Basic direction130

decided in the third period (from 2022) after the retrieval of the fuel debris is started,
obtaining the aging information of the fuel debris is an urgent issue. While taking into
consideration the permission and authorization about the safety regulation, to provide
sufficient prediction and explanation of the risk changes resulted from the aging of thefuel debris, it is required to clarify the real situation of what are expected to have critical
impacts on the decommissioning works preferentially.
Therefore, it is necessary to build a fundamental theory of the aging model byclarifying the aging process while using the current knowledge of the actinoid chemistry.
To do so, demonstration test should be performed using real uranium according to thematrix pattern of parameters (temperature, pH, etc.) to collect basic data, and it needs toestablish the prediction method of aging. In this case, it is important to maintain thefoundations for advancement of the actinoid chemistry, which provides the basis for
examination of the physical property of fuel debris. In addition, heat analysis for 1F should
be included in the basis of investigation since the temperature distribution of the fueldebris has to be understood by calculating the heat distribution and the impact of regionaltemperature rise due to the decay heat should also be required to be examined.
Theme(2) To elucidate corrosion mechanisms under unusual/extreme circumstances“Descriptions /Background issues”
on the interim report

It is required to collect data on corrosion under a variety of circumstances withconsideration of the circumstances specific to 1F decommissioning such as high radiationlevels and unsteady routes of cooling water in order to prepare for potential corrosion
during decommissioning.
A boiling water reactor (BWR) consists of various metallic material. While stainlesssteel, which is corrosion resistant, is used inside reactor where it is high temperature andhigh oxidizing environment, carbon steel, which is not corrosion resistant, is used for the
PCV that is the confinement boundary and is assumed to be used in the normal
atmosphere. On the other hand, substantial knowledge has been collected so far about
corrosion of structure and piping for commercial electric generation reactors, andespecially, data has been collected being focused on the corrosion data in theenvironment of high radiation, high temperature, and deionized water for the operation of
BWR.
However, after the accident, 1F has been in a special environment with highradiation, room temperature, suspended solids and deposited materials. The knowledge
about such environment is not sufficient. Since water has been injected into PCV to cool
the fuel debris, carbon steel is dipped in the water. In addition, it is known that chemical
species of oxidation nature such as hydrogen peroxide and various radical species havebeen generated through radiolysis of water. Currently, since nitrogen has been injected
into PCV to prevent hydrogen explosion and the oxygen density has been decreased, thedensities of the oxygen and the hydrogen peroxide are considered to be decreased in thewater and corrosion of PCV is also considered to be suppressed in some degree. In the
future, since the air containing oxygen flows into PCV when a negative pressure control
is applied to retrieve the fuel debris, it is important to maintain soundness of the structure
and pipes that form the boundary for confinement of radioactive materials and it is also
important to prepare countermeasures based on the knowledge on corrosion in suchenvironment.
Since the corrosion is essentially a kind of battery reaction, it is likely to happen if theelectric conductivity of water raises, pH falls, and the electric potential raises under thecondition of declining of surrounding water quality. Although corrosion has been
suppressed by nitrogen injection in general, it is still under the condition of potential
corrosion. Regional changes of the environmental condition may lead to an increase of
corrosion speed at the part. It is quite a special environment surrounded by various factorsthat promotes corrosion such as a formation of liquid film of dew, a humid environmentthat repeats wet and dry conditions near the water surface, an irregular flow of coolingwater, convection flow, or backwater due to irregular paths created by gaps between
various shapes of fallen objects or deposited materials, a progress of corrosion on theanode side between different kinds of metals touching each other, a progress of acidbase reaction by microbes, or any other potential factors. In the future, further changes
may occur in the internal environment when the air that contains oxygen flows into the
PCV when a negative pressure control is applied to retrieve the fuel debris. Since thecorrosion progresses over time during the decommissioning works under the special
environmental conditions, estimation of corrosion phenomenon and investigation ofcountermeasures are required based on the consideration on the environmental changes
resulted from the progress of the decommissioning process.
Therefore, it is necessary to collect basic data related to the progress of corrosion
phenomena and systematically clarify and understand the phenomena in order to provide
satisfactory prediction and explanation of the risk changes that follow corrosion of

Basic direction

131structures taking the permission and authorization of the safety regulation into accountwith giving priority to the factors of higher needs that may have critical impacts on thedecommissioning works from the viewpoint of the probability of occurrence such as thefactors above and the impacts on the functionality (parts and severity), the scale and thetiming. In this case, in order to examine various approaches including not only the use ofexisting anti-corrosive agents but also electric protection, it is important to accumulate
and maintain the knowledge related to the corrosion phenomena in addition to theelectronic state of materials in a special environment through principle analysis andclarification of the corrosion progression mechanism.
Theme(3) Radiation measurement technologies adopting innovative approaches“Descriptions /Background issues”
on the interim report

The radiation levels are still extremely high inside the 1F reactors/buildings due to theaccident and the existing measurement devices do not meet the capability/functional
requirements to provide accurate figures. It is vital to develop an innovational device
adopting brand-new ideas/principles based on 1F needs.
Currently, radiation measurement can be performed following a predefined operation
procedure without detail knowledge of measurement since a number of radiation
measurement products using various principles or materials including ionizationchambers, counting tubes, semiconductor detectors, and scintillation detectors are
already offered. However, it is very important to develop the human resources formeasurement since it is necessary to understand the principles of the equipment in order
to interpret the measurement data and address possible troubles such as the case of thedisorder (inversion of data value) between the all β-radioactivity value and the value of
Sr-90 because miss-counting has not been taken into account for the resolution time in
the analysis of the sampled water at the under-ground water observation hole on 1F.
In addition, general radiation measurement products are not able to offer satisfactory
performance and functionality to inspect the conditions inside reactors and buildings at
the decommissioning site of 1F. The decommissioning works on 1F must be performedby remote operation since the radiation level is extremely higher than the one in the work
environment of existing nuclear facilities. It is necessary to develop highly radiation
resistant and small sized measurement sensor, electronic circuits, and systems in order
to be remotely operated. In addition, it is necessary to research on the basic mechanism
related to radiation damages of materials in order to develop highly radiation resistantsensors and circuits. As for the specific examples of sensor development, it is necessary
to develop measurement devices of neutron from the viewpoint of criticality prevention,
real time measurement of α-ray from the viewpoint of identification of the fuel debris, andɤ-ray measurement with high energy resolution for nuclide estimation under the
background of high gamma radiation, those what satisfy various needs: radiation
resistance, noise resistance, size (small size), counting rate and responsiveness, highradiation resistance, energy discrimination, space resolution (identification of radiation
source position), ease of operation, and maintainability. As for the composition of themeasurement targets, development of the technology so-called “on-site analysis” isrequired since there are needs of functions that can be used to analyze the target withouttransferring a sample to other facility or equipment and obtain rough results used topromptly judge if the target is debris or not, and if the target is debris, the function to judge
co-existence of reactor internals and neutron poison is required.
In addition, effective support tools for the decommissioning can be provided bydeveloping the technology to visualize the radiation field and the contamination situationand clarify the profile of the fuel debris based on the information of the strength and the
direction of the radioactive sources.
It is necessary to develop the generic technologies for innovative measurement ofradiation using new ideas and principles by considering on-site measurement
requirements.

Basic direction

Theme“Descriptions /Background issues”
on the interim report

Basic direction(4) To clarify behavior of radioactive airborne particle generated duringdecommissioning (incl. α-dust treatment)
As thermal cutting of the fuel debris via machine or Laser may produce a large amount of
α-dust, it requires safety measures and dust confinement solutions. It is necessary tounderstand physical/chemical properties of α-dust, to predict the amount of dust to be
produced for each method, and to consider how to seal the dust according to the resultsin order to make sure the retrieval will be conducted in a safe and effective manner.
As the fuel debris retrieval work will start, cutting the fuel debris will create a lot ofradioactive airborne particles (α-dust) that contain α-nuclide and they will be dispersed132within the boundary. When retrieving the fuel debris, since the work will be performed in
the confinement boundaries which are the broken buildings, it is important to understandthe property of the α-dust for studying how to secure the confinement capability,
designing the filtering system, and performing the exposure evaluation of the surrounding
environment and workers including the time of accident.
With regard to the data about the scattering rate when α-dusts are generated, thereis the data obtained at the decommissioning of JAEA’s JPDR and the dismantling of glove
box of JAEA’s Nuclear Fuel Cycle Engineering Laboratories. However, the data has notbeen collected just for the nuclear fuels but collected for the objects polluted by the
nuclear fuels, and the data has been collected for the amount of the radioactive materials
and their densities from the viewpoint of radiation exposure control and it is not
systematically organized.
On the other hand, the radioactive airborne particles in 1F will be generated directlyfrom the fuel debris when retrieving the fuel debris and from the polluted objects in thedecommissioning process. The types of radioactive materials are α-nuclides and β (ɤ)nuclides. While the α-nuclide of which typical element is plutonium is important from theviewpoint of internal exposure, the β(ɤ)-nuclide such as cesium should be wellconsidered as well from the viewpoint of the total exposure evaluation.
In order to study on collection of radioactive airborne particles, efficient filtering andpurification, criticality prevention, etc., it is necessary to grasp the amount of generated
particles, distribution of particle diameters, radioactive diameters, and the physical andchemical property of particles according to the differences of the target objects and themethod of cutting. It is also important to understand the behavior of the generated
particles in the gas phase, at the air-liquid interface, and in the liquid phase duringtransportation or transition. For example, it is important to understand the growth ofparticles through coagulation in the gas phase, evaluation of mist generation from the airliquid interface, leaching behavior of the components into the water of the liquid phase,transportation behavior such as settling of particles in the water or filtering, etc.
With regard to the exposure evaluation of radioactive airborne particles, it isimportant to evaluate the impact of exposure to radioactive materials derived from thefuel debris, especially the one of α-nuclides. In this case, it is important to decide whether
the conventional exposure evaluation methods can be applied by judging if the chemical
form and the particle diameter of the radioactive airborne particles represented byplutonium is consistent with the ones that have been used as the criteria of internal
exposure evaluation for plutonium.

Theme(5) To understand fundamentally mechanisms of radioactive contamination“Descriptions /Background issues”
on the interim report

To figure out the mechanism of radioactive contamination towards effective
decontamination; it is critical to implement effective approaches of decontamination
based on the mechanism of the contamination to radiation sources, and to decrease thevolume of radioactive wastes as well.
With regard to reduction of the radiation in the buildings, the target object of
decontamination are pipes and ducts, metals in the equipment, resins in cables and soon, paints, and concretes of the walls or floors. The contamination source includes molten
high temperature fuels at the time of accident, steams that contain radioactive materials
such as Cs leaked in consequence of hydrogen explosion and so on, dusts andcontaminated water that contain radioactive materials. Currently, as for radiation
reduction in the buildings on 1F, decontamination of floors and walls has only limited
effects since there are other contamination sources such as objects remained in pipes,
and hidden side behind the pipes located at high inaccessible positions. In the future,when considering each step in the long decommissioning process, it is expected thatmany situations that require decontamination will arise, therefore, effective and efficientdecontamination is considered highly necessary. With regard to decontamination, notonly reduction of radiation but also reduction of wastes should be taken into consideration.
For decontamination, while engineering approaches are required, including physicalmethods such as dry ice blast, chemical methods such as chemical decontamination
using chemicals such as acid or alkali, and decontamination methods using parting
agents, it is indispensable to understand the contamination mechanism of target objects
in order to perform such decontamination activities effectively.
In the field of researches for clarifying the contamination mechanism, there are a
sufficient number of existing researches on the metal materials, which are used in pipes,
tanks and so on to confine radioactive materials. However, there is almost no researchon the concrete of structures or radiation shields that does not directly touch radioactive
materials.

Basic direction

133

The inside the buildings of 1F is widely contaminated by the radioactive materials
emitted by the accident. Since most parts of the buildings consist of concrete, it isimportant to clarify the contamination mechanism of both concrete and radioactive
materials in principle in order to reasonably and effectively manage concrete wastes
resulting from the decontamination and the process of decommissioning. Therefore, thecontamination mechanism must be clarified in principle on the concrete exposed to theaccident and the subsequent environment and the process of decommissioning by
obtaining the basic data about sorption, penetration, and leaching of the typical nuclide(Cs, Sr, U, Pu, etc.) that should be well considered. In addition, from the mid-and-longterm viewpoint, it is necessary to establish the evaluation method based on theunderstanding of the contamination mechanism including the changes over time in thecontamination state and the penetration behavior in the concrete.
Even though a number of researches have been conducted on removal ofcontamination source in pipes during nuclear fuel reprocessing regarding thecontamination mechanism of the metal of the piping and equipment by radioactive
materials, few number of researches are found on the contamination mechanism of themetal of the piping and equipment in the environment of the 1F. While it is considerednecessary to clarify the contamination mechanism inside PCV or RPV exposed to thehigh temperature environment at the time of accident, it is not necessary to take into
consideration a special contamination mechanism such as penetrate into metals outside
PCV. As for the decontamination mechanism of resins and paints of cables, it isconsidered that it not necessary to conduct a special research on decontamination since
they can be replaced or removed.

Theme“Descriptions /Background issues”
on the interim report
Basic direction(6) Environmental fate studies of radioactive materials generated duringdecommissioning
It is essential to clarify the behavior of radioactive materials such as adsorption,
dispersion, moving along with groundwater flow in shallow underground in order to
conduct environmental fate studies to ensure they will not affect the environment.
In order to properly evaluate and reduce the risk of future environmental impact
caused by radioactive materials in the Fukushima Daiichi NPS site, it is necessary toprovide proper evaluation and estimation of the environmental fate of radioactive
materials around the site via the shallow underground water and the surface water, or the
ports, the marine, and the air, and to provide appropriate environmental
countermeasures.
Targeted radioactive materials are (1) the radioactive materials that exist in the
ground or on the surface of the ground through the contaminated water leaked just after
the accident (137Cs, 90Sr, 3H, etc.), (2) the radioactive materials that poured into the ports
in past and accumulated on the bottom of the sea (137Cs, 90Sr, etc.), and (3) theradioactive materials that are contained in the contaminated water that will be generated
as the result of retrieval of the fuel debris or decommissioning and dismantling of thebuildings (including ion such as actinide and suspended solids) that can be the futuresource term impacting environment.
In order to estimate the impact of radioactive materials on the surrounding
environment, it is indispensable to understand the existence form and the transport
behavior of the radioactive materials as the required basic knowledge. Specifically, thetargets include the existence form of the radioactive materials in the underground water,
the distribution in the soil, the advection and diffusion behavior in the underground water,
the existence form and the advection and diffusion in the surface layer, the existence form
and the molten and diffusion behavior of the radioactive materials in the seawater in theport and on the bottom of the sea, and the transportation behavior to the surrounding
environment through marine or air.
Although all of those depend on the characteristic of the intermedium such as theproperty of soil and the geological condition, since the measurement work on 1F is limited,
it is necessary to aim at establishing the evaluation method in a similar environment.
In addition, in order to provide the accurate future estimation of the environmental
fate, it is also necessary to develop the monitoring technology to identify the accuratecontamination condition and the analysis technology to simulate the transportation
behavior of the radioactive materials. As for the monitoring technology, the technology forlong term and continuous remote measurement and the mapping and behavior
identification technology using the big data are expected. As for the simulation
technology, the creation model that can be used to analyze the behavior (influence of
unsaturated layer, kinetic evidence, etc.) specific to shallow underground and theestimation technology using the code are expected.
It is also important to aim at reducing the risk of the radioactive materials as
environmental countermeasure. While a number of technologies can be developed

134including control of the amount of underwater, soil improvement, stabilizing agent,adsorbent for purification of contaminated materials, and the permeable reaction wall, it
is necessary to examine the factors that have priority since they may have criticalinfluence on the decommissioning works.
In order to provide reasonable environmental fate studies for the radioactive
materials, it is important to proceed with considerations on the risk of environmental
influence so the development of the evaluation method related to the risk of environmental
influence has to be taken into account from this viewpoint.

135

Attachment 15 Recruitment brochure for manpower development
decommissioning of TEPCO Fukushima Daiichi NPS

136

training

on

the

137

Attachment 16 Major activities related to enhancing international collaboration
Table A16-1 Intergovernmental Framework between Japan and other countries
Framework

Descriptions

Annual Japan-UK Nuclear
Dialogue

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).

Japan-France Nuclear Energy
Committee

It was established under the joint statement of Japan–
France top-level meeting in October 2012 (Since February2012).

Japan-US Decommissioning
and Environmental
Management Working Group

After the Fukushima Daiichi NPS accident in March 2011,
the establishment 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)”
was established (Since December 2012).

Japan-Russia Nuclear
Working GroupThe Nuclear Working Group was established after
confirming that Energy is one of the eight areas ofcooperation plan approved at the Japan-Russia top-levelmeeting in September 2016, (Since September 2016).

Table A16-2 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
as needed. (Concluded in September 2013)

TEPCO

Sellafield, Ltd.

Information Exchange Agreement for site’s operation, etc.
was concluded. (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 onmolten core-concrete interaction, etc.

JAEA

Belgium Nuclear
Research Center

Agreement of Cooperation for Nuclear R&D and Researchon 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

138

Table A16-3 Dissemination of information to the world (Holding or attending International
Conference (from April 2019 to August 2020))

Conference Name

PeriodOrganization

ATOMEXPO2019

April, 2019

NDF
METI
TEPCO

INSIDER Project Meeting

May, 2019

NDF

International Meeting on Fukushima Decommissioning
Research 2019 (FDR2019)

May, 2019

METI

The 27th International Conference on Nuclear
Engineering (ICONE27)

May, 2019

IRID

WTO/SPS Committee, Briefing for EU countries

July, 2019METI

The 60th Annual INMM Meeting (US)July, 2019

NDF

The 4th International Forum on the Decommissioningof the Fukushima Daiichi NPS

August, 2019

NDF

The 63rd IAEA Conference Side event

September,
2019

NDF
METI
JAEA

10th International Conference on Isotopes

February, 2020

NDF

The 4th UK-Japan Nuclear Industrial Forum

February, 2020

NDF
METI

ICONE International Conference, Fukushima Session

August, 2020

TEPCO

The 64th IAEA Conference Side event

September,
2020

NDF
METI
TEPCO

Fukushima Research ConferenceYear round

JAEA

139

Table A16-4 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
（http://www.meti.go.jp/english/earthquake/nuclear/decommissioning/）

METI

Monthly 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（http://www.dd.ndf.go.jp/eindex.html）

NDF

Information Portal for the Research and Development for the Fukushima
Daiichi Decommissioning (http://www.drd-portal.jp/en/)

NDF

Activities for Decommissioning（https://fukushima.jaea.go.jp/english/）

JAEA

IRID website (http://irid.or.jp/en/)

IRID

Fukushima Daiichi Decommissioning Project（http://www7.tepco.co.jp/responsibility/decommissioning/index-e.html）

TEPCO

Providing English version of Press release to foreign media

TEPCO

Management Office for the Government-led R&D program on
Decommissioning and Contaminated Water Management(https://en.dcccprogram.jp/)

MRI(Businessconsignee)

Table A16-5 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
to the modeling of phenomenological issues obtained bymember 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

NRA
IR

140

to investigate the situation of the accident in more detail andutilize it for further researches to improve safety of lightwater reactor
・Project period : 2019 to 2021 (scheduled)

JAEA

PreADES・Sharing characteristics information that helps tounderstand properties of fuel debris such as its phase stateand composition.
・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 2020 (scheduled)

METI
NRA
IR
JAEA
IRID
NDF
TEPCO

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
and its producing mechanism. Then, providing materialscientific knowhow and result of detail evaluations tointernational cooperation project including PreADES, ARC-F,
TAF-ID, and domestic decommissioning project like IRID.
・Project budget was contributed from MEXT.
・Project period : 2017 to 2019

MEXT
JAEA
IR
Tokyo
Institute ofTechnology

EGCUL

・Discussing on characterization method for waste fromunknown derivation

141

METI
NDF
JAEA
TEPCO