Technical Strategic Plan 2019 for the Decommissioningof the Fukushima Daiichi Nuclear Power Station ofTokyo Electric Power Company Holdings, Inc.

September 9, 2019
Nuclear Damage Compensation
and Decommissioning 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 appropriate and steady implementation of decommissioning . 2
1.2 Strategic Plan ........................................................................................................................ 3
1.2.1 Positioning of the Strategic Plan ..................................................................................... 3
1.2.2 Overall Structure of Strategic Plan 2019 ........................................................................ 4
2. Decommissioning of the Fukushima Daiichi NPS as risk reduction strategies ........................... 7
2.1 Basic concept of the decommissioning of the Fukushima Daiichi NPS ................................. 7
2.2 Progress status of the decommissioning of the Fukushima Daiichi NPS .............................. 7
2.3 Basic concept of reducing risk of radioactive materials ....................................................... 10
2.3.1 Quantitative grasping of risk ......................................................................................... 10
2.3.2 Identification of Risk Source and Risk assessment ...................................................... 10
2.3.3 Risk Reduction Strategy ............................................................................................... 13
3. Technological strategies toward decommissioning of the Fukushima Daiichi NPS................... 19
3.1 Fuel debris retrieval ............................................................................................................ 19
3.1.1 Sectoral target .............................................................................................................. 19
3.1.2 Sectoral Strategies ....................................................................................................... 20
3.1.3 Technical issues for developing sectoral strategies and future plans ........................... 28
3.2 Waste management ............................................................................................................ 57
3.2.1 Sectoral target .............................................................................................................. 57
3.2.2 Sectoral strategies ........................................................................................................ 57
3.2.3 Technical issues and plans for promoting sectoral strategies ....................................... 62
3.3 Contaminated water management ...................................................................................... 67
3.3.1 Sectoral target .............................................................................................................. 67
3.3.2 Sectoral strategies ........................................................................................................ 67
3.3.3 Technical issues for promoting sectoral strategies and future plans ............................. 71
3.4 Fuel removal from spent fuel pools ..................................................................................... 75
3.4.1 Sectoral target .............................................................................................................. 75
3.4.2 Sectoral strategies ........................................................................................................ 75
3.4.3 Technical issues for promoting sectoral strategies and future plans ............................. 78
3.5 Other specific measures ..................................................................................................... 82
3.5.1 Sustaining of reactor cold shutdown status .................................................................. 82
3.5.2 Radiation dose reduction and contamination expansion prevention all over the power
station .......................................................................................................................... 82
3.5.3 Plan for decommissioning measures for nuclear reactor facilities ................................ 88
3.5.4 Concrete efforts toward securing safety ....................................................................... 89
3.6 Comprehensive efforts for the decommissioning project of the Fukushima Daiichi NPS .... 92
4. Handling critical enablers for smooth operation of the project .................................................. 94
4.1 Actions toward improvement of working environment and conditions ................................. 94
4.2 Enforced management structure for steady mid-and-long-term decommissioning ............. 97
4.3 Developing and securing human resources ...................................................................... 103
4.3.1 Developing and securing operators and engineers .................................................... 103
4.3.2 Fostering the next generation to handle the decommissioning of the Fukushima Daiichi
NPS ......................................................................................................................... 104
5. R&D initiatives ........................................................................................................................ 106
5.1 Basic policy for R&D ......................................................................................................... 106
5.1.1 Basic policy ................................................................................................................ 106
5.1.2 Entire perspective of R&D .......................................................................................... 107
5.2 R&D of decommissioning required for on-site work/engineering ....................................... 109
5.2.1 Promotion of effective R&D ........................................................................................ 109

5.2.2 Future approach to R&D ............................................................................................. 110
5.3 Enhancement of basic study and R&D infrastructure for the success of thedecommissioning project .................................................................................................. 110
5.3.1 Essential R&D Themes and its strategic promotion derived from the needs .............. 111
5.3.2 Construction of basic research center and R&D infrastructure for mid-and-long-term
prospects ................................................................................................................. 111
6. Enhancement of international cooperation ............................................................................. 114
6.1 Significance of international cooperation........................................................................... 114
6.2 Facilitation of international cooperation activities .............................................................. 115
6.2.1 Enhancement of partnership with overseas decommissioning agencies .................... 115
6.2.2 Integrating and utilizing wisdom in the world .............................................................. 115
6.2.3 Dissemination of information to the global society ...................................................... 118
6.2.4 Participation in international cooperative activities ..................................................... 119
6.3 Close cooperation with relevant domestic organizations................................................... 119
7. Local community engagement ................................................................................................ 121
7.1 Approaches for local community engagement .................................................................. 121
7.2 Actual effort for better Communication .............................................................................. 121
7.3 Measures against reputational damages .......................................................................... 122
7.4 Decommissioning moves forward together with the recovery of the community ............... 123
List of Acronyms/Glossaries ....................................................................................................... 125
List of Attachment ....................................................................................................................... 128

Table of Figures

Fig. 1 Division of roles of related organizations in the decommissioning of the Fukushima
Daiichi NPS
3Fig. 2 Positioning of the Strategic Plan based on the system of the Reserve Fund4
Fig. 3 Three principles and measures
8
Fig. 4 Reduction of risks contained in the Fukushima Daiichi NPS
12Fig. 5 Examples of Risk Levels of Major Risk Sources at the Fukushima Daiichi NPS
13
Fig. 6 Flow of Examinations on “Strategic Recommendation for Determinig the Fuel Debris
Retrieval Method for the First implementing unit”
25
Fig. 7 Conceptual drawing of fuel debris retrieval, containment, transfer, and storage
26
Fig. 8 Estimation of fuel debris distribution in Units 1 to 3, access route and the condition ofsurrounding structures
33
Fig. 9 Example of containment function (gas phase) by pressure control system
36
Fig. 10 Example of containment function (liquid phase)
40
Fig. 11 Fundamental technologies for fuel debris retrieval and internal structures
52
Fig. 12 Technical issues and further plan on fuel debris retrieval (Process chart)
56
Fig. 13 Summary of Waste Hierarchy at the NDA, UK and Countermeasures at the
Fukushima Daiichi NPS
59
Fig. 14 Key technical issues and further plans on waste management (Process chart)
66
Fig. 15 Status of the stagnant water in the buildings
69
Fig. 16 Transitions in the generated amount of contaminated water and the inflow amount ofgroundwater/rainwater, etc., into the buildings
72
Fig. 17 Technical issues and further plans on contaminated water management (Process
Chart)
74
Fig. 18 Storage situation of spent fuel, etc. (as of August 29, 2019)77
Fig. 19 Technical issues and further plan on removing fuel from the spent fuel pool (Process
chart)
81
Fig. 20 Radioactive material concentration in seawater in the port
84
Fig. 21 Evaluation of annual radiation exposure dose at site boundaries due to radioactive
materials (Cesium) emitted from Units 1 to 4 reactor buildings
85
Fig. 22 Effective radiation dose evaluation at site boundaries
87
Fig. 23 Decision points and review of the long-term plan
93
Fig. 24 Changes in worker’s monthly radiation exposure dose (monthly average radiationdose) (Radiation exposure dose by month after March 2011)95
Fig. 25 NDF and TEPCO organizational system for Project Control
98
Fig. 26 Whole picture of R&D structure of the decommissioning of the Fukushima Daiichi
NPS (As of FY 2019)108
Fig. 27. A conceptual picture of the division of roles among main R&D institutions for thedecommissioning of the Fukushima Daiichi NPS
109
Fig. 28 Overview of Fukushima Innovation Coast Framework
124
Fig. 29 Structural drawing inside reactor building
127
Fig. 30 Structural drawing inside Reactor Pressure Vessel(RPV)127

Table 1 Major risk sources of the Fukushima Daiichi NPS
Table 2 Solid Waste Storage Management Status
Table 3 Description of the Projects included in the Withdrawal Plan
Table 4 Cooperative relationship among the institutions for the decommissioning of the
Fukushima Daiichi
Table 5 Approach for dissemination of information to the world

11
60
99
117
120

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 fuel pools,
have been given top priority in this effort. However, to complete the decommissioning, mid-andlong-term measures are required such as fuel debris 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 the “NDF”), a neworganization responsible for technical studies needed to proceed with the decommissioning
properly and steadily from the mid-to-long-term 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.
Eight years have passed since the accident at the Fukushima Daiichi Nuclear Power Station.
There has been a certain outlook for the short-term response, as progress has been made at theaccident site in managing contaminated water including the construction of the land-side
impermeable wall and in removing fuel from the spent fuel pools as well as improving work
environment at the site. Going forward, mid-and-long-term approach like fuel debris retrieval isneeded and mid-and-long-term responses are required. When addressing the issues of long andhighly difficult with a large uncertainty, approaches to solve issues should be proceed from more
systematic and mid-and-long-term perspective, rather than performing project tasks by resolving
imminent issues one by one. Under the circumstances, as engineering toward fuel debris retrieval
is well under way, the phase of decommissioning moves to response for mid-and-long-term vision.
With that in mind, in the Technical Strategic Plan 2019 for Decommissioning of the Fukushima
Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc., the direction froma mid-and-long-term perspective in overlooking total approach for decommissioning of the
Fukushima Daiichi NPS is presented including waste management, as well as the strategicalrecommendation to determine methods of fuel debris retrieval for the first implementing unit inaccordance with the milestone presented in the Government-developed “Mid-and-Long-Term
Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station”(hereinafter referred to as the “Mid-and-Long-term Roadmap”) that was revised in September 2017.

1

1.1 Structure and system toward appropriate and steady implementation of
decommissioning
As the decommissioning project is shifting focus to mid-and-long-term challenges, the structuresand systems for the decommissioning are being reinforced to ensure that the decommissioning
project continues and that mid-and-long-term issues are properly addressed.
Tokyo Electric Power Company Holdings, Inc. (hereinafter referred to as the “TEPCO”), as theoperator of the project, is reinforcing its project management structure with the goal of steadydecommissioning by implementing the ongoing activities for sure while responding to mid-and-longterm issues in a strategic manner. To ensure the implementation of the decommissioning financially,a law to partially revise the Nuclear Damage Compensation Facilitation Corporation Act (hereinafterreferred to as the “NDF Act”) was established in May 2017 and came into effect in October of thesame year. Under the Revised NDF Act, NDF has been assigned the new duty of managing theReserve Fund for Decommissioning. TEPCO is required to reserve an amount of funds at NDF
every year that NDF determines to be necessary for the appropriate and steady implementation of
the decommissioning and is authorized by the competent minister (the Minister of Economy, Tradeand Industry). TEPCO will proceed with the decommissioning while withdrawing the reserved funds
in accordance with “Withdrawal plan for Reserve Fund” (hereinafter referred to as the “Withdrawal
Plan”), which will be prepared jointly by NDF and TEPCO and approved by the competent minister.
This ensures that the necessary amount of funds for the appropriate and steady implementation of
the decommissioning will be reserved, building a consistent decommissioning structure that works
irrespective of TEPCO’s earnings or other factors. In this Reserve Fund system, NDF will play evengreater roles and responsibilities than before as the major supervisor and administrator of thedecommissioning project conducted by TEPCO. These include (1) appropriate management of thefunds for decommissioning, (2) maintenance of an appropriate system for executing thedecommissioning, and (3) steady work management based on Reserve Fund system.
Specifically, prior to the preparation of the Withdrawal Plan, NDF will present to TEPCO the worktargets and major tasks to be included in the Withdrawal Plan by dividing them into major projects
in accordance with “The Policy for Preparation of Withdrawal Plan for Reserve Fund for
Decommissioning” (hereinafter referred to as the “The Policy for Preparation of Withdrawal Plan”).
NDF will also support the appropriate and steady implementation of the decommissioning throughactivities such as evaluating the adequacy of TEPCO’s efforts in the course of jointly preparing theWithdrawal Plan in terms of project execution including the aspect of collaboration andcommunication with local communities.
The division of roles among the organizations directly involved in the decommissioning of the
Fukushima Daiichi NPS, the Japanese government, NDF and TEPCO, as well as organizations
specializing in R&D (the International Research Institute for Nuclear Decommissioning (hereinafterreferred to as the “IRID”) and the Japan Atomic Energy Agency (hereinafter referred to as the“JAEA”), is shown in Fig.1, which also indicates how the abovementioned systems are implemented.
2

Among these roles, R&D are discussed in Chapter 5, and dialogue with local residents andcommunities is described in Chapter 7.

Nuclear Emergency Response Headquarters (Director: Prime Minister)Council for the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station

Nuclear Regulation Authority(Chairperson: Chief Cabinet Secretary) Approval of implementation
plan, pre‐service inspection,
welding inspection, etc.

Mid‐and‐Long‐Term Roadmap

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

Progressmanagement

Granting of
project budget

R&D organization

Apply forapproval

Approve

Nuclear Damage Compensation and Decommissioning Facilitation Corporation

 Development of a mid‐to‐long‐term strategy
Withdrawal plan Tech. support for progress mgmt 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

ReportReport on theoutcome

Minister of Economy, Trade and Industry
Presentation ofimportant issues

Apply for report Progress management of each countermeasure according to
Mid‐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 spent fuel pools, fuel debris retrieval, waste disposal,
improvement of power plant premises and working environment, management of Units 5 and 6, etc.
 Through TEPCO's management reform, the funds required for decommissioning should be reserved
responsibly (Implementation of new comprehensive special project plan)

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

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

1.2 Strategic Plan
1.2.1 Positioning of the Strategic Plan
NDF has issued a Technical Strategic Plan for Decommissioning of the Fukushima Daiichi NPSof Tokyo Electric Power Company (hereinafter referred to as the “Strategic Plan”) every year since2015 with the goal of providing reliable technological grounds for the government’s Mid-and-Longterm Roadmap and contributing to its smooth and steady implementation (Attachment 1).
Since the Strategic Plan 2018, it should include not only the issues focused on fuel debris
retrieval and waste management but also measures against contaminated water and fuel removalfrom the spent fuel pools and should propose future directions from mid-and-long-term perspectives
that oversee the overall efforts toward the decommissioning of the Fukushima Daiichi NPS. Any
issues that are identified through these studies as requiring current attention will be reflected in the
Policy for Preparation of Withdrawal Plan for Reserve Fund for Decommissioning that NDF will
present to TEPCO (Fig.2).

3

Fig. 2 Positioning of the Strategic Plan based on the system of the Reserve Fund1.2.2 Overall Structure of Strategic Plan 2019
Strategic Plan 2019 consists of seven chapters.
Chapter 1 (Introduction) states that for the decommissioning of the Fukushima Daiichi NPS, a
more proactive, systematic approach will be needed to solve the challenges from mid-and-longterm perspective rather than fulfilling tasks in a reactive manner, in addressing more complex and
uncertain challenges over the long term, such as fuel debris retrieval, and it also states the
structures and systems including Reserve Fund system.
Chapter 2 (Decommissioning of the Fukushima Daiichi NPS as risk reduction strategies)
presents a basic policy for the decommissioning of the Fukushima Daiichi NPS as a strategy to
reduce risks, along with risk reduction tools that should be used in carrying out this policy, such as
near-term targets, the basic concept of risk reduction, the approach to priority, the concept of
securing safety and promotion of cooperation and the stance on responding to a temporary
increase in the risk level.
Chapter 3 (Technological strategies toward decommissioning of the Fukushima Daiichi NPS)
sets targets in each of the four areas: fuel debris retrieval, waste management, contaminated water
management, and fuel removal from the spent fuel pools. Area-specific strategies to achieve thetargets are described, along with technological challenges in implementing these strategies, and aplan for future actions to address them.
Section 3.1 (Fuel debris retrieval) of Chapter 3 states the overview of the strategic
recommendations to determine the fuel debris retrieval method for the first implementing unit and4describes continual implementation of internal investigation as well as accelerated and prioritized
technological development, etc. The section also proposes technological issues to be examined on
fuel debris retrieval for the first implementing unit.
Section 3.2 (Waste management) presents, in accordance with the basic policies on processing
and disposing of solid waste, specific targets to gain a technological vision for waste
processing/disposal for around FY 2021, along with a plan for R&D needed to reach these targets.
Section 3.3 (Contaminated water management) proposes, in introducing the approaches being
made to complete the treatment of the stagnant water in the buildings by the end of 2020, thedirection of efforts toward treatment of contaminated water in the reactor buildings after the start offuel debris retrieval work.
Section 3.4 (Fuel removal from spent fuel pools) refers to the appropriate and specific operation
plan depending on the conditions of each unit, and proposes the directions of the efforts to secure
capacity required for proper storage of removed fuel within the site and of the efforts to determine
the future treatment and storing methods for fuel in Spent Fuel Pools (SFPs) including evaluationof the long-term integrity of such fuelSection 3.5 (Other specific measures) states the other approaches including sustaining reactor
cold shutdown status, reducing radiation dose/preventing further spread of contamination all overthe power station, decommissioning plan for reactor facilities, and specific efforts toward ensuringsafety.
Section 3.6 (Comprehensive efforts for the decommissioning project of the Fukushima Daiichi
NPS) states the directions of the approaches from the viewpoints of necessities of systematic
operation by thinking ahead and necessities to proceed with complex and inter-related operations
by ensuring consistency across the operations.
Chapter 4 (Handling Critical enablers for smooth operation of the project) states actions toward
improvement of working environment and conditions, enforced management structure for steady
mid-and-long-term decommissioning and developing and securing human resources fromperspective of the smooth operation of the project, as well as technological study as stated in
Chapter 3.
Chapter 5 (R&D initiatives) summarizes the efforts that are expected in government, enterprises
and the relevant researching institutions and proposes the directions of further efforts to achieve
project-based R&D management that the R&D tasks of which the necessity became clear byengineering considerations should be carried out by the right institutions at the right time andaccurately. The chapter also discusses, from the mid-and-long-term point of view, the establishmentof a center for basic research and the construction of R&D infrastructure, as well as the importanceof fundamental R&D.
Chapter 6 (Enhancement of international cooperation ) describes the need to strengtheninternational cooperation, such as partnerships with institutions involved in decommissioning
projects in countries with legacy nuclear sites, in order to gather wisdom and knowledge fromaround the world, and proposes efforts that should be made in this regard.
5

Chapter 7 (Local community engagement) notes how these institutions should work together
toward that end, to implement continuous decommissioning of the Fukushima Daiichi NPS thatspans long period of time, in consideration that we will have seek for decommissioning developedwith the restoration in local communities.

62. Decommissioning of the Fukushima Daiichi NPS as risk reduction
strategies
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 the usual 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 considered to be at great risk because fuel debris andspent fuels still remain in reactor buildings damaged by the accident, some of the status of the NPS
are not sufficiently grasped, and the site has radioactive contaminated water and enormous
amounts of extraordinary radioactive wastes. If left unaddressed, these risks may increase due tothe 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: (i) improving the containment function of the damaged
facilities, (ii) changing the properties and form of the confined radioactive material to more stableones, and (iii) strengthening monitoring and control over the equipment to better prevent or mitigate
the occurrence or propagation of abnormalities. To enable these actions comprehensively, (iv)removing radioactive materials from the damaged facilities or insufficient confinement status andplacing them in sound storage is also effective.
These diverse risk reduction measures have been continued based on careful preparations
aimed at preventing accidents and radiation exposure of workers (refer to Attachment 2).

2.2 Progress status of the decommissioning of the Fukushima Daiichi NPS(1) Contaminated water management
Contaminated water has been addressed in accordance with the three principles (“Removing”
contamination sources, “Redirecting” fresh water from contamination sources, and “Retaining”
contaminated water from leakage) (Fig.3).

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Fig.3 Three principles and measures
As a measure of “Removing” contamination source, radioactive materials are removed fromcontaminated water with multi-nuclide removal equipment. As a measure of “Redirecting” fresh
water from contaminated sources, freezing operation of the land-side impermeable walls wascompleted in all area by September 2018. With this, reinforcement of the sub-drain system led tothe suppression of the groundwater inflow into the buildings, in addition, the sharp decrease in theamount of water transferred from the groundwater-drains to the buildings, resulting in the reduction
in contaminated water generated. Because of this kind of preventive and multi-layered measures,
total generation amount of contaminated water has been decreased to approximately 170 m3 per
day in FY 2018 from approximately 400 m3 per day in FY 2016. As a measure of “Retaining” thecontaminated water from leakage, the strontium-treated water stored in flange tanks has been
purified with multi-nuclide removal equipment and transferred to more reliable welded tanks in
November 2018. In addition, transferring of treated water stored in flange tanks to welded tanks
has been completed in March 2019, resulting in a drastic reduction of the risk of leakage fromflange tanks.
In treating stagnant water in the buildings, the amount of stored water has been decreasing
steadily by lowering the water level in turbine buildings, etc., with the goal 1 of completing thetreatment in 2020. At present, the lowest floor of the turbine building at Unit 1 and the middle floorof the lowest floor of the turbine buildings at Units 2 to 4 are exposed. Furthermore, thedisconnection of the connecting section between Units 1 and 2 was accomplished by the end of
2018 (the disconnection for Units 3 and 4 was completed in 2017). On the other hand, with regard
to the goal of reducing the amount of radioactive materials in the stagnant water in buildings down
to 1/10 of the level at the end of FY 2014 by the end of FY 2018, the evaluation became difficult.

1 Exposing the floor line for buildings other than the reactor buildings and lowering the water level of the reactor
building to T.P.-1740mm (O.P. - 300 mm) or less. (Cyclic water injection cooling is carried out in the reactor building,and stagnant water continues to exist).

8

Because high radioactive concentrations were detected in some areas with the progress in thetreatment of the stagnant water, though treating of radioactive materials has been conducted morethan scheduled. Thus, ongoing efforts will be made to complete the treatment of stagnant water inthe buildings in FY2020.
Decreasing both the amount of the stagnant water and the concentration of the radioactive
materials accelerate the reduction of inventory of the radioactive materials in the stagnant water.
Moreover, the water treated by the multi-nuclide removal equipment is stably stored and managed
in the welded type tanks in order. Comprehensive discussion including social standpoints such as
mitigation of the reputational damages have been made in the Government-led subcommittee on
the Water Treated by the Multi-nuclide Removal Equipment2.
(2) Progress of removing fuel from the spent fuel pool
In Unit 1, to remove fuel from SFP at the operating floor, rubble removal on the operating floor
has been underway since 2018.
In Unit 2, the contamination status of the operating floor was investigated from November 2018
to February 2019. Based on the outcome, the process toward removing fuel in SFP is being
examined. In addition, as the supporting structure of the exhaust stack for Units 1 and 2 waspartially broken due to the impact of the earthquake, it was decided to dismantle the upper part ofthe stack in order to secure seismic safety margin and not to affect the removal operation of fuel in
SFP.
Fuel removal from Unit 3 began in April 2019, although it was delayed from the first implementing
schedule due to a defect in the fuel handling machine that occurred during the trial operation tostart fuel removal.
(3) Fuel debris retrieval
In Unit 1, since it was confirmed that the deposits identified during the surveillance of the PrimaryContainment Vessel (hereinafter referred to as the “PCV”) in 2017 are present underwater, the PCVinternal investigation using a newly developed boat-type access surveillance device with a diving
function is scheduled to be performed in FY2019. This surveillance also plans to sample deposits,
which are found at the bottom of the PCV, in small amounts.
In Unit 2, remote equipment was used to conduct contact survey on deposits in the PCV in
February 2019. As a result, the same surveillance was performed at the bottom of the PCV pedestal
and the platform, and it was confirmed that deposits (pebbles, etc.) were movable. In addition,
videos, radiation doses, and temperature data were obtained under the condition, which was closer
to the deposit than in the surveillance in January 2018.
In Unit 3, as the water level at the bottom of the PCV is as high as approximately 6 m, the study
on lowering the water level has been made and the water quality will be checked as the first step.
2

Subcommittee on the Water Treated by the Multi-nuclide Removal Equipment
https://www.meti.go.jp/earthquake/nuclear/osensuitaisaku.html#task_force49(4) Waste management
The operation of the No. 9 solid waste storage building, which stores high radiation dose rubble
generated from Units 1 and 2, started in February 2018. Secondary waste generated fromcontaminated water purification treatment is currently in temporary storage, and large waste
storage to store the waste is scheduled to commence operation after this. TEPCO has revised
Storage Management Plan to store and manage these solid waste properly in June 2019 based on
the review of the predicted generation of solid waste (Attachment 12).

2.3 Basic concept of reducing risk of radioactive materials
2.3.1 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 of
occurrence of the event.
In the Strategic Plan, the method based on the Safety and Environmental Detriment score (SED),
which accounts for the public impact developed by Nuclear Decommissioning Authority (NDA) is
used to study the reduction of the risk level of 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).
2.3.2 Identification of Risk Source and Risk assessment
For the development of risk reduction measures, the major risk sources of the Fukushima Daiichi
NPS are indicated in Table 1. The sum of these risk sources represents the overall risks for the
Fukushima Daiichi NPS, and the overall risk levels are shown in Fig. 4. Continuous efforts havebeen made to reduce these risks through various measures, including those described in Section
2.2. Moreover, the risk levels of each risk source expressed using Hazard Potential and Safety
Management are shown in Fig. 5.
In the Mid-and-Long-term Roadmap, management of these risk sources is classified into the10three broad categories: [1] Highly contaminated water and fuel in SFPs, etc., relatively high risks
given a high priority, [2] Fuel debris, etc., risks unlikely to appear immediately though, it may growin case of dealing with haste, [3] Solid waste, etc. risks unlikely to increase in the future though,appropriate decommissioning efforts necessary. The appropriate measures are taken by giving
these priorities. Risk reduction strategies for each of these sources will be described in Section 3.
As for fuel in SFPs, the testing on SFP cooling shutdown was performed, and it was found thatthe rise in water temperature after cooling shutdown was slower than expected. By incorporating
this finding, the risk of fuel in SFPs is lower than previously evaluated, because the time margin
before this risk becomes apparent increases.
Table 1 Major risk sources of the Fukushima Daiichi NPS
Fuel debris
Spent fuelContaminate
d water etc.

Secondarywaste fromwater
treatment
systems

Rubble etc.

Fuel debris in the RPVs/PCVs in Units 1 to 3
Fuel in SFPs

Fuel assemblies stored in the spent fuel pools (SFPs) in
Units 1 to 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 in thebuildings

Contaminated water accumulated in the reactor buildings
and turbine buildings in Units 1 to 4, main process building,and high temperature incinerator building.

Stored water in weldedtanks

Strontium-treated water and ALPS-treated water stored inwelded tanks

Residual water in flange
tanks

Concentrated salt water, strontium-treated water and ALPStreated water remaining in the bottom of flange tanks

Waste adsorption
columns

Spent adsorbent used in the cesium adsorption apparatus,
the second cesium adsorption apparatus, high-performance
ALPS, mobile-type strontium removal equipment, second
mobile-type strontium removal equipment and mobile-type
treatment equipment, etc.

HIC slurry

Slurry produced during the treatment by ALPS and stored inhigh integrity containers (HIC)

Waste sludge

Precipitation from the decontamination instruments

Concentrated liquid
waste, etc.

Concentrated liquid waste generated by evaporative
concentration of concentrated salt water and carbonate
slurry collected from concentrated liquid waste

Solid waste storage
facility

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

Soil covered temporarystorage, etc.

Rubbles stored in Soil covered temporary storage facility,
Temporary storage tent and Outdoor container storage(1~30mSv/h), and felled trees stored in Temporary storage
pool

Outdoor storage, etc.

Rubbles stored in Outdoor seat covered storage(0.1~1mSv/h), Rubbles stored in Outdoor storage (Under
0.1mSv/h), and Felled trees stored in Outdoor storage

Contaminated structures, etc. in thebuildings

Structures, pipes, components, and other items inside thereactor buildings, PCVs or RPVs that are contaminated withradioactive materials dispersed due to the accident; andactivated materials from operation before the accident

11

1

2

3

4

5

6

7

Risk level (linear scale)

Risk level(Logarithmic scale)

Risk level (linear scale)0

Fuel removal from
Unit 4 SFP started

8

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

Year after accident
Fuel debris

Fuel in SFPs

5

6

7

8

Year after accident

Contaminated water

Fuel debris

Fuel in SFPs

Contaminated water1.

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 inwater temperature after cooling shutdown was slower than expected, the risk of fuel in SFPs is lower thanpreviously estimated, because the time margin before this risk becomes apparent increases.

Fig. 4 Reduction of risks contained in the Fukushima Daiichi NPS
To date, the Strategic Plan has focused on the risk sources containing a large amount ofradioactive materials. On the other hand, when looking at the overall decommissioning processfrom a long-term perspective, certain measures should be taken for the potential risk sources
regardless of the amount of radioactive materials and the waste that have generated before theaccident. Thus, survey has been initiated, which expands its scope to identify items requiringconsideration in long-term strategies.
Specifically, consideration of issues from a wider vision of entire work will proceed in adding
targets including accumulated water on site, underground water tanks, contaminated soil, α sludge,
spent control rods; and pool water. (Attachment 4)

12

Hazard Potential (logarithmic scale)

Region of sufficiently
stable management(March, 2019)

Fuels incommonFuel debris
pool
ContaminatedUnit 1structures in bldgs. Unit 3
HIC
Waste
slurryabsorption
columns

Fuels in
Uint 2
Unit 3 Unit 2 SFPs
Unit 1
Waste
Concentrated sludge Stagnant waterin bldgs.
liquid waste, etc.

Fuels indry casks

Rubble inStored water
storage
in welded tanks
facility
Soil covered
temporarystorage, etc.

Residual waterin franged tanks

Outdoorstorage, etc.

Safety Management (logarithmic scale)Fig.5 Examples of Risk Levels of Major Risk Sources at the Fukushima Daiichi NPS
2.3.3 Risk Reduction Strategy
2.3.3.1 Interim Targets of the Risk Reduction Strategy
The risk levels of the risk sources shown in Fig. 5 are higher toward the upper right corner. There
are two risk reduction strategies which are reduction in Hazard Potential or reduction in Safety
Management.
The examples of the former strategy include decrease in inventory and decay heat associatedwith radioactive decay, and changing the form of liquid and gas into the form that is hard to move.
To process contaminated water to change into the secondary waste is an example of form change.
The examples of the latter one include transfer of fuel in SFPs to the common spent fuel storage
pool, and placement of rubbles stored outside to the storage. Of the various risk reduction
measures, the reduction in Safety Management is considered generally to be easily achieved.
Therefore, the decommissioning of the Fukushima Daiichi NPS, which is implemented under thebasic policy of “reducing continually and quickly the risks associated with the radioactive materials
that resulted from the accident and do not exist in normal nuclear power plants” (Section 2.1),
should first focus on steadily managing risk sources by keeping them in higher-integrity facilities tolower their Safety Management levels. The interim goal of risk reduction strategies is to bring therisk levels into the “Region of sufficiently stable management” (pale blue area) indicated in Fig. 5.
13

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.
2.3.3.2 Basic approach to risk reduction
The decommissioning of the Fukushima Daiichi NPS is a project with inherent considerable
uncertainty. To date, internal status of PCV in the Units 1 to 3 is presumed to some extent by
simulation of the accident progression using various measurements, estimation of location of fueldebris by measurement of muon-base, projection of investigation equipment into PCV, radiationdose measurement in the buildings and others. However, since the radioactive environment inside
the reactors is still too severe for workers to easily access, the properties of some radioactive
materials and the degree of damage to the field equipment and structures left there remain
unknown, creating uncertainty.
While it is desirable to eliminate uncertainty by grasping all the above unknowns that are difficult
to know, many resources, especially a considerably long time are required. To realize prompt risk
reduction, it is necessary to make integrated decisions taking flexible and prompt approach, basedon the directions determined with previously obtained experience and knowledge and withexperiment- and analysis-based simulation, placing safety at the top priority, even though a certain
extent of uncertainty remains. At this time, it is not necessary to take the same steps among thedifferent units, and it is important to flexibly address the issues with experiences, reflecting theinternal information, technical feasibility and other information obtained in advance in a certain unit
on the subsequent works and the works in other units. As the viewpoint to make integrated
decisions like this, which are not easy to do, NDF summarizes the following five guiding principles.
(Five guiding principles)

Safe

Reduction of the risks posed by radioactive materials and ensuring worksafety(Examples of considerations: confinement of radioactive materials[environmental impact], workers’ radiation exposure, risk reduction effects)ProvenHighly reliable and flexible technologies(Examples of considerations: conformity with the requirements, flexible
stance to uncertainty)

Efficient

Effective utilization of resources (e.g. human, physical, financial andspace)(Examples of considerations: restricting the generation of waste, cost,
securing the work area and space)TimelyAwareness of time axis

14

(Examples of considerations: early start of fuel debris retrieval, durationneeded for fuel debris retrieval)

Field-oriented

Thorough application of the “Three Actuals” (actual field, actual things andactual situation)(Examples of considerations: workability [environment, accessibility,
operability], serviceability [maintenance, troubleshooting])

These guiding principles are the viewpoint necessary to discuss priority of approaches and total
optimization.
2.3.3.3 Order of priority
It is necessary to proceed with the project based on this five guiding principles in managing
progress of overall project. In particular, the situation at the site is gradually becoming clearer as
the decommissioning work progresses. If this basic concept is applied to the actual site, the overallbalance should be considered during the decommissioning work at present, while placing emphasis
on “safety” and “reliability”, such as controlling radiation exposure and ensuring the safety andreliability of devices and equipment. Moreover, It is important to be aware of position of each project
and their mutual relationship in their respective fields In other words, although addressing thehighest risks first may seem effective from a near-term perspective, such an approach may notalways be optimal when viewed from a long-term perspective that considers various factors, suchas the feasibility of the relevant technologies and the time required for preparation.
For instance, although the exhaust stack for Units 1 and 2 located near Unit 2 is contaminatedwith radioactive materials, mainly cesium that were released by the accident and adhered to its
inner surface, its risk associated with radioactive materials is rated as lower than that of fuels in
SFP. However, considering fractures and deformation were found at the junctions of the diagonalbracing of the steel tower that supports the exhaust stack, the upper part of the stack is going to
be dismantled with remotely controlled equipment as an environmental improvement ahead of fuelremoval from SFP.
Thus, in the decommissioning of the Fukushima Daiichi NPS, which aspires to continuous andprompt risk reduction, the traditional approach of proceeding with project tasks by resolving
imminent issues one by one would not be effective. Instead, it is important to aim at choosing thebest option among the various possible options, with the integrated viewpoint of looking at the entire
site on a long-term basis and considering milestones. This idea of pursuing risk reduction optimized
for the entire project is discussed in Section 3.6. Taking into account such point of view, TEPCO
and NDF have introduced and promoted strengthening of the project management structures. Thisis discussed in Section 4.2.

15

2.3.3.4 Concept of securing safety and promotion of cooperation
This is the first attempt in Japan at decommissioning damaged reactors. There are no
established or standardized regulations associated with the risk reduction of accident-hit nuclear
power facilities. As represented by fuel debris retrieval, the decommissioning of damaged reactors
involves reducing existing potential risks, leading to stabilizing the Fukushima Daiichi NPS. The
concept of safety is essentially different from the operation at normal nuclear facilities. Considering
time variation in the risk level described in Sub-section 2.3.3.1, in other words, it is required toachieve transition to the storage condition under a higher-level of management as early as possible.
On the other hand, safety assurance in and outside the premises may be influenced if retrieval
starts with insufficient preparations and measures. Furthermore, if excessive protective measures
are implemented for associated risks, retrieval may be difficult. Therefore, it is a challenge to realizebalanced risk reduction.
Referring to safety efforts from overseas damaged reactors and legacy sites (refer to Chapter6), when conducting tasks for which no preceding experience exists in the world, principle ofsecuring safety should be established according to the conditions and circumstances of the
Fukushima Daiichi NPS. Therefore, appropriate approaches to safety at the Fukushima Daiichi
NPS need to be determined in consideration of unprecedented circumstances, such as significant
uncertainties in the situation and the difficulty in implementing measures due to high radiation doses
at the site.
In light of this situation, with NDF as the main player, TEPCO and system design manufacturers,
etc., are collaborating and studying the concept of determining appropriate approaches to safety
for the decommissioning work (an approach to ensuring safety). Specifically,

examination toward establishment of determination criteria and the safety assessment
method applicable to the decommissioning work at the Fukushima Daiichi NPS,

safety assessment by selecting representative accident scenarios for fuel debris retrieval,and consideration of a perspective to determine appropriate approaches to safety basedon the results, and others.

NDF should continue to cooperate with other stakeholders, such as TEPCO and the Agency for
Natural Resources and Energy, to promote discussions, hold active conversation with the Nuclear
Regulation Authority, and reach an agreement on how to determine reasonable approaches tosafety for the decommissioning work at the Fukushima Daiichi NPS. For the organizations involved,
including regulation authorities, sharing the goal of safe and smooth decommissioning andperforming their own roles regarding the reduction of on-site hazards and risks, it is important tomake positive efforts while sharing purposes and challenges, and for this safety assurance concept
to be effective, it is desirable to promote cooperation among the organizations involved.
As an example, one year after the accident at the United States Three Mile Island Nuclear Power
Plant Unit 2 (“TMI-2”), four parties; namely, General Public Utilities (GPU), the Electric Power
Research Institute (EPRI), the Nuclear Regulatory Commission (NRC) and the United States

16Department of Energy (DOE), signed a cooperation agreement for fuel debris retrieval. Named
after the initials of the parties, GEND was a unified team that shared technological challenges
beyond the boundaries of the organizations, as various reports3,4 indicate. At the Sellafield site,
U.K., the G6 group was established to carry out decommissioning, with the stakeholders having
the common purpose of accelerating the reduction of hazards and risks at the site. G6 included
Sellafield Ltd., NDA, the Office for Nuclear Regulation (ONR), the Environment Agency (EA), UK
Government Investments (UKGI) and the Department for Business, Energy and Industrial Strategy(BEIS). The group has discussed the order of priority for risk reduction, effective resource use, andhow to realize the balance when risks may temporarily grow to reduce the risk in the long run. As
an achievement of this commitment, acceleration of the hazard and risk reduction has been
observed at the legacy sites in the Sellafield.
2.3.3.5 Addressing temporary increase of risk levels associated with the decommissioning
operations
As mentioned in Sub-sections 2.3.3.1 to 2.3.3.3, implementation of the decommissioning work
aims at prompt risk reduction from the mid-and-long-term viewpoint. However, the possibility that
conducting the work may temporarily change the risk levels and increase the radiation exposure ofworkers must be carefully considered. 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 ofstability despite some risks. 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
confinement status, and special operations and maintenance performed for the retrieval will
increase the radiation exposure of workers involved in these activities.
This possibility of a temporary increase in the risk level and a rise in workers’ radiation exposure
arising from the decommissioning work must be addressed by ensuring measures to prevent andrestrict them. It is imperative to limit the increase in the risk level during the decommissioning workwithin the permissible range by thorough preparations for the work. In particular, the radiation safety(i.e. restricting radiation exposure) of workers should be ensured in accordance with the conceptof ALARA5.
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, the selection of the method of work, the design and production of equipment and safety
3

EPRI, The Cleanup of Three Mile Island Unit 2, a Technical History: 1979 to 1990, EPRI NP-6931 (1990).
NRC, Three Mile Island Accident of 1979 Knowledge Management Digest, Recovery and Cleanup, NUREG/KM0001, Supplement 1 (2016).
5 ALALA is the principle of optimization for radiological protection recommended by International Commission on
Radiological Protection (ICRP), and is the abbreviation of “as low as reasonably achievable”. It is advocated that
individual dose, number of the exposed people and likelihood of radiation exposure must be kept as low asreasonable achievable in consideration of economic and social factors. (The 1990 Recommendation by ICRP,
Japan Radioisotope Association (issued in 1991),
417systems, and the development of work plans for the decommissioning work should many
constraints such as consider time, cost and workers’ radiation exposure needed for associatedpreparations and work, while giving priority to limiting the risks involved in the decommissioning
work. Based on these considerations, cautious and comprehensive decision-making are required
for the early implementation of the decommissioning (See Attachment 5).
It must also be strongly emphasized that the decommissioning of the Fukushima Daiichi NPS
as a risk reduction project should be promoted, not by the understanding among the limited working
parties, but by gaining the broad understanding and support by wide range of public including local
residents. It is crucial to foster public understanding of the overall risk reduction efforts, including
measures to prevent a temporary increase in the risk associated with various decommissioning
work; and thus gain understanding of the decommissioning project. It is particularly important to
inform local residents, in an easily understandable manner, of issues such as what kind of risk
reduction strategy has been established for the decommissioning work, how the safety of thedecommissioning work is ensured, and how the overall risks at the NPS have been continuously
reduced through the decommissioning work. For this purpose, it is important to implement an easyto-understand mechanism of monitoring of risks for local residents NDF is considering such amechanism, and it is important for TEPCO to consider the introduction of a similar structure in the
future.

18

3. Technological strategies toward decommissioning of the
Fukushima Daiichi NPS
3.1 Fuel debris retrieval
3.1.1 Sectoral target
For the time being, the objectives of fuel debris retrieval are as follows (For the objects of fueldebris retrieval refer to Attachment 6).
(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) Toward determination of fuel debris retrieval method for the first implementing unit in FY 2019,and start of fuel debris retrieval work for the first implementing unit within 2021, necessary
approaches will be taken, according to the “Policy on Fuel Debris Retrieval”.
Policy on Fuel Debris Retrieval①

Step-by-step approach
In order to reduce associated risk as early enough, adopt a step by step approach to flexibly
coordinate the direction based on information that comes out as retrieval proceeds, after setting methodof fuel debris retrieval to be started first,
Fuel debris retrieval operation and internal investigations of PCV/RPV should be performed in acoordinated, integrated manner. Fuel debris retrieval starts from a small-scale and the scale of retrieval
should be expanded by step up, while reviewing operations flexibly based on new findings obtained
from the property of fuel debris and working experiences.

②

Optimization of entire decommissioning work
Examine fuel debris retrieval work as a comprehensive project aimed at total optimization, frompreparation to cleanup through retrieval work, transportation, processing and storage, including
coordination with other construction works at the site.

③

Combination of multiple methods
Combine the optimum retrieval methods for each unit, depending on the locations where fuel debris
is considered to be present, instead of making an assumption that all the fuel debris is to be taken out
using a single method.
At present, from an accessibility standpoint, examine assuming sideward access to the bottom of
the primary containment vessel and downward access into the reactor pressure vessel from the upper
part of the vessel.

④

Approach focused on partial submersion method
Given the technical difficulty of stopping leaks at the upper part of the primary containment vessel
and expected radiation doses during such works, the full submersion method is technically difficult at
present, so make efforts to focus on the partial submersion method that is more feasible.
However, given the advantages of the total submersion method, such as being effective in providing
shielding against radiation, consider adopting the full submersion method in the future depending on
the progress of R&D.

⑤

Prioritizing fuel debris retrieval by side access to the bottom of the PCV
According to an analysis, fuel debris is expected to be present in both the bottom of PCV and theinside of RPV of each unit, although their distribution varies among the units. In view of mitigating risks
from fuel debris as early enough, while minimizing any increase in risks that might be caused by19

retrieval, prioritize retrieval of fuel debris in the bottom of PCV by sideward access by taking thefollowing into account:○○○

The bottom of PCV is most accessible and a certain amount of knowledge about it has already been
accumulated through the investigation inside PCV;
There is a possibility that fuel debris retrieval could be started earlier;
Fuel debris retrieval could be performed at the same time as spent fuel removal

3.1.2 Sectoral Strategies
3.1.2.1 Approach to risk reduction in fuel debris retrieval work
It is hard to consider that the fuel debris immediately appears as a risk, but it is a risk source6
that risk may grow in case of dealing with rush and haste. (refer to Section 2.3). On the other hand,the fuel debris is currently maintained in a state with a certain level of stability. However, on a longterm, the possibility of changes in the form and physical property due to aging degradation isconsidered. Namely, two types of risk exist in fuel debris. One is a risk from medium-term
perspective that adverse effects on the environment can occur due to the development of criticality
and cooling problems though its possibility is low as far as it is properly managed in a state with acertain level of stability. The other is a risk from a long-term perspective that environmental pollution
can occur resulting from any leaks of included nuclear fuel material due to deterioration of thebuildings in future. Therefore, as indicated in (1) of Sectoral target, fuel debris should be retrieved
safely after thorough and careful preparations such as safety measures and brought to a state ofstable storage that is fully managed as early as possible. To realize this, it is important to wellorganize and examine the matters to be considered, such as securing of safety during fuel debris
retrieval and technical requirements, including the feasibility of the fuel debris retrieval method andstable storage of fuel debris.
According to the concept of the fuel debris retrieval policy, the retrieval starts from accessing to
the bottom of PCV from its side by partial submersion method using remote operation equipment.
Retrieving of fuel debris by partial submersion method is unprecedented project in the world. It isnecessary to proceed with operation carefully upon enough and well making preparations in orderto properly inhibit increase of risks associated with its operation, due to the limited information on
the internal condition of PCVs in Units 1 to 3 at the beginning, it should be appropriate to start from
retrieval based on use of existing safety system, with no significant changes in the state of the site,
including condition of PCV. Specifically, retrieval should start from small-scale from the scope thatcan be conducted by utilizing existing penetration without making major changes in the state such
6

Based on the current risk assessment for each unit, there would be a difference in terms of safety management
across the units. Unit 1 has no upper reactor building and Unit 3 has a cover for fuel removal instead of an upper
reactor building. On the other hand, the reactor building of Unit 2 is in a sound state, and the damage level of the
RPV is considered small because most of fuel debris is presumed to remain inside the RPV. Regarding the shapeof fuel debris influencing Hazard Potential, there is a possibility of various states such as a state close to fineparticles to a solid state, but the specification of the shape has not been done currently. The calculation in Fig. 5
has been estimated from the findings obtained so far. Particularly with respect to Unit 2, much of the fuel debris ispresumed to remain in the RPV, and hazard potential becomes relatively low because it is considered to be a stableform due to the low ratio of molten core concrete interaction products compared to Units 1 and 3.

20

like processing PCV wall. This allows continuations a series of operations from containing andtransferring through storing steadily after retrieving fuel debris without giving non-reversible statechanges to PCV, and to reduce the risk from fuel debris and to conduct confirmations ofeffectiveness of systems and internal conditions required for further operations to be developed.
Through small-scale retrieval in the first implementing unit, the following effects can be
expected:(1) Enables verification of equipment, facilities and safety systems, including remote operationsin the phase of small-scale retrieval by obtaining information (including the release ratio ofradionuclides into the air and water) on the effectiveness and work efficiency reviews ofequipment, facilities, and safety systems from fuel debris retrieval to containment, transfer,and storage.
(2) Enables use of work experience gained from fuel debris retrieval to containment, transfer, andstorage including remote operations as the process to master fuel debris retrieval operations
for TEPCO.
(3) Enables acquisition of information that contributes to understanding situation inside the PCV(fuel debris distribution [including characteristics], information on access routes, information
on structural conditions, etc.).
Since then, amount of retrieved fuel debris shall be increased or further retrieval shall be started
from units other than the first implementing unit after taking necessary measures such as expansion
and modification of PCV openings, installation of new openings, expansion of scale of remote
operation equipment, and addition of new equipment for securing safety, based on the new findings
including information and experiences acquired through this small-scale retrieval operation of thefirst implementing unit. Fuel debris retrieval at expanded-scale mentioned above or at units otherthan the first implementing unit will require following items of development.
a) Consideration of actual site applicability based on such as conceptual study on safety systemb) Information organization such as radio nuclide airborne release fractions for examining
necessary and sufficient safety systems (safety assessment)c) Site environment preparation such as radiation reduction, water level lowering in PCV and areaplanningd) Further understanding of inside condition of PCV and RPVe) Technologies to make efficient fuel debris retrieval including removing obstaclesf)Technologies to reduce dispersion of radionuclide airborne particles during fuel debris retrievalg) Consideration on sorting and distinction of fuel debris and radioactive wasteh) Technologies to analyze and estimate fuel debris properties and distributions for understanding
In such manner, fuel debris retrieval of the first implementing unit will be contentiously examined.
Also engineering regarding new safety systems on its actual site applicability, site environmental
preparation, investigation inside condition of PCV and necessary R&D shall be conducted
continuously.

21

3.1.2.2 Fuel debris retrieval method for the first implementing unit (Outline of the strategic
recommendation for determining the fuel debris retrieval method for the first
implementing unit)
The Mid-and-Long-term Roadmap revised in September 2017 stipulates that “Regarding themethod of fuel debris retrieval for the first implementing unit to begin the operation, the fuel debris
retrieval for the first implementing unit will start within 2021 by determining the method of containing,transfer and storage (by FY2019) after due consideration of the results of the preliminary
engineering work and R&D”
In response to this, the first implementing unit and its fuel debris retrieval method have been
investigated, and the results are summarized as the “Strategic Recommendation for Determining
the Fuel Debris Retrieval Method for the First Implementing Unit”. (Attachment 7) The
recommendation for determining the fuel debris retrieval method for the first implementing unit has
been concluded through the examination of overall optimization of the combination of the whole
site planning and fuel debris retrieval scenarios of each unit which were established based on theevaluation of the conceptual design of the fuel debris retrieval system and its actual site applicability
to each unit created as a result of preliminary engineering by TEPCO using the past research anddevelopment results and the PCV internal investigation results. The flow of the above mentioned
process is as shown in Fig.6.
As a result of the above mentioned examination, selected “fuel debris retrieval work”, which canbe defined as a series of operations from containing, transferring and then storing in steadycondition, is to start “promptly” from small scale retrieval operation keeping in minimum of riskincrease caused by fuel debris retrieval work and to accumulate experience and knowledge“promptly” for expanded-scale of fuel debris retrieval work (expanded-scale retrieval) as well asother units than first implementing unit. This approach of fuel debris retrieval operation enables toreduce risk existing in Units 1, 2 and 3. In particular, operation starting from gripping and sucking
by using the arm-type access equipment that actual site applicability is getting in sight and the air
tightened enclosure that contains the arm-type access equipment combined with existing safetysystem without significant modification is evaluated possible to retrieve fuel debris “safely”, “reliably”
and “promptly”. In addition, fuel debris retrieval by crushing or cutting other than gripping andsucking will be performed without significant modification of existing safety system.
As well, proposed method of containing, transfer and storage of retrieved fuel debris, that
retrieved fuel debris firstly contained in the small container is transferred and contained in thecanister and stored in dry condition at the temporary storage facility built within Fukushima Daiichi
NPS site, is also judged to be able to contain, transfer and storing the retrieved fuel debris “safely”,“reliably” and “promptly”. The schematic drawing about fuel debris retrieval and handling(containing, transfer and storage) is shown in Fig.7.
From the view point of optimization of entire decommissioning work of Fukushima Daiichi NPS,
Unit 2 is currently judged to be appropriate for the first implementing unit. Its reasons are that22

sufficient information on PCV internal condition and the site condition (radiation dose, degree of air
tightness of the existing safety system) has been obtained as well as that information andexperience on fuel debris retrieval work can be promptly obtained by starting its fuel debris retrieval
work “safely”, “surely” and “promptly” based on the site condition such that fuel debris retrieval workand fuel removal work from SFP can be done in parallel. Small scale of fuel debris retrieval
operation starting at Unit 2 enables to reduce risks existing in Units 1, 2 and 3.
In Unit 2, in this way, fuel debris will be retrieved by using the arm-type access equipment, anda series of operations from retrieving, containing, transferring, and storing of fuel debris should becontinued safely and reliably, and then information/experience required for further implementation
should be gained promptly.
The points of recommendations for determining the fuel debris retrieval method of the first
implementing unit, which were obtained from the results of these examinations and evaluations,are as follows:①

Fuel debris retrieval work is to start from small-scale operation such as gripping and sucking byusing the arm-type access equipment that actual site applicability is getting in sight and the air
tightened enclosure that contains the arm-type access equipment combined with existing
safety system without significant modification.

②

Using information and experiences accumulated through fuel debris retrieval operations bygripping and sucking, crushing method for fuel debris retrieval and removing of obstacles areto be studied. Fuel debris retrieval by crushing or cutting during the small-scale fuel debris
retrieval work phase is also to be performed under without significant modification of existing
safety system.

③

Retrieved fuel debris firstly contained in the small container is transferred, contained in thecanister and stored in dry condition at the temporary storage facility built within Fukushima
Daiichi NPS site.

④

From the view point of optimization of entire decommissioning work of Fukushima Daiichi NPS,
Unit 2 is currently judged to be appropriate for the first implementing unit. Thus, series ofoperations from fuel debris retrieval to containing, transfer and storage of the retrieved fueldebris will be continued at Unit 2, and information and experience will be accumulatednecessary for expanded scale of fuel debris retrieval work in the future. However, certain holdpoints should be appropriately defined on the process of necessary study or planning to start
fuel debris retrieval work for verifying the appropriateness of current study/planning.

⑤

Retrieval methods including containing, transferring and storing of the retrieved fuel debris
applicable for the expanded-scale of retrieval work phase or other than the first implementing
unit need to be established by proceeding with PCV internal investigation, necessary R&D and
improvement of working environment such as lowering of PCV water level, radiation dose
reduction and securing working space, as well as engineering of new safety system, fuel debris
retrieval and storage facility using accumulated information and experience through fuel debris

23retrieval work of the first implementing unit including study on safety evaluation and actual site
applicability of above mentioned engineering results.
“The Strategic Recommendation for Determining Fuel Debris Retrieval for the First
implementing Unit” also discusses the efforts to be made toward the fuel debris retrieval in the first
implementing unit and expanding retrieval scale and retrieval in units other than the first
implementing unit, which is described later in Sub-section 3.1.3.1.

24

Progress of ancillary R&D and
PCV internal investigation

Progress of work environment
improvement

Progress of site-wideplanning•••

It was observed that there are some
movable pebble size deposits in
Unit 2.
Get development of arm-typeaccess equipment and the canisterfor retrieved fuel debris into shape.

•

In contrast with relatively low radiationdose in Unit 2, radiation dose
reduction is needed in Units 1&3 aswell as lowering of water level in PCV
in Unit 3.

Study on concept of fuel debris retrieval••••

Use of existing safety system.
Use of arm-type access equipment that actual site
applicability is getting in sight and use of air-tightend
enclosure which contains it.
Start from small-scale retrieval by such gripping or
sucking, and progress to plan fuel debris retrieval bycrushing.
Contain retrieved fuel debris in a small canister,transfer it, contain it in a canister and stored it in dry
condition at the temporary storage facility within site

Fuel removal operation from
SFP completes in Unit 3 first.
Fuel debris retrieval work andspent fuel removal work can bedone in parallel at every unit.

Study result of actual site applicability of fueldebris retrieval work by Unit•••

Unit 1: Maintaining relatively high airtightness with current
safety system, but the radiation dose is high in working
environment and deposits potential of fuel debris andaccess route to reach them are unidentified.
Unit 2: Maintaining high airtightness with current safetysystem and the radiation dose is relatively low in working
environment, deposits potential of fuel debris is movable
and access route to reach them has been identified.
Unit 3: Deposits potential of fuel debris and access routeto reach them has been identified, but airtight level withcurrent safety system is lower than Units 1&2, theradiation dose is relatively high in working environment.

Comprehensive assessment【 Fuel debris retrieval method】 →The arm-type access equipment & the canister enables to retrievefuel debris safely, reliably and promptly.
- Actual site applicability of the arm-type access equipment/canister for retrieved fuel debris are getting in sigh.

【 The first implementing unit】 → Unit 2 is judged to be appropriate because fuel debris retrieval can bestarted “safely”, “reliably” and “promptly” and overall
decommissioning work can be optimized.
- Safe: The radiation dose in working environment is relatively lower than other units and the airtightness with existing
safety system is higher than other units.
- Reliable : Some deposits with potential for fuel debris are movable, and access route to reach them has been identified.
- Prompt : It has a possibility to start fuel debris retrieval work promptly, as well as to accumulate information andexperiences on fuel debris retrieval work.

Unit 2 has potential to reduce risks resulted from entire fuel debris at unit 1, 2 and 3 promptly because theessential information and experiences will be accumulated necessary for expanded scale of fuel debris
retrieval work in the future through a series of operations from fuel debris retrieval by using the arm-typeaccess equipment to containing, transfer and storage of the retrieved fuel debris safely, reliably and promptly.

The points to be recommended for determining fuel debris retrieval method of the first implementing unit
① Fuel debris retrieval work is to start from small-scale operation such as gripping and sucking by using the arm-typeaccess equipment that actual site applicability is getting in sight and the air tightened enclosure that contains the armtype access equipment combined with existing safety system without significant modification.
② Using information and experiences accumulated through fuel debris retrieval operations by gripping and sucking,crushing method for fuel debris retrieval and removing of obstacles are to be studied. Fuel debris retrieval by crushingor cutting during the small-scale fuel debris retrieval work phase is also to be performed under without significant
modification of existing safety system.
③ Retrieved fuel debris firstly contained in the small container is transferred, contained into the canister and stored in dry
condition at the temporary storage facility built within Fukushima Daiichi NPS site.
④ From the view point of optimization of entire decommissioning work of Fukushima Daiichi NPS, unit 2 is currently
judged to be appropriate for the first implementing unit. Thus, a series of operations from fuel debris retrieval tocontaining, transferring and storing of the retrieved fuel debris will be continued at unit 2, and information andexperience will be accumulated necessary for expanded-scale of fuel debris retrieval work in the future. However,certain hold points should be appropriately defined on the process of necessary study or planning to start fuel debris
retrieval work for verifying the appropriateness of current study/planning.
⑤ Retrieval methods including containing, transferring and storing the retrieved fuel debris applicable for the expandedscale of fuel debris retrieval work phase or other than the first implementing unit need to be established by proceedingwith PCV internal investigation, necessary R&D and improvement of working environment such as lowering of PCV
water level, radiation dose reduction and securing working space, as well as engineering of new safety system, fueldebris retrieval and storage facility using accumulated information and experience through fuel debris retrieval work of
the first implementing unit including study on safety evaluation and actual site applicability of engineering results.

Fig.6 Flow of Examinations on “Strategic Recommendation for Determining the Fuel Debris
Retrieval Method for the First implementing unit”
25

(TEPCO material edited by NDF)

Fig. 7 Conceptual drawing of fuel debris retrieval, containment, transfer, and storage
3.1.2.3 Continued internal investigation and accelerated/prioritized R&D
Fuel debris retrieval will proceed according to the step-by-step approach that allows to flexibly
coordinate the direction based on the information gradually obtained. Then, it is important toimplement internal investigations steadily to understand the initial condition of PCV.
As for understanding about internal investigation of PCV, various information has been gained
as a result of internal investigation of PCV that have been conducted so far. However, internal
investigation of RPV has not been made and grasping of the internal condition of PCV and RPV islimited as a matter of fact. Thus, research and development (R&D) to implement internal
investigation of PCV for collecting more detailed data such as distribution of deposits and fueldebris are underway as well as R&D to implement internal investigation of RPV for obtaining
information about the internal condition of RPV.
As internal investigation of PCV, it should be implemented after thoroughly identified what kindof data is necessary. The required data which are distribution (and feature) of deposits and fueldebris inside PCV, information for access route and one for structural condition, are identified fromthe continuous project in preparing for fuel debris retrieval, which is progressing with step-by-step
approach.
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 and26steadily 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”7. (Attachment 8)
Basic principles toward the planned analysis and investigation on the decommissioning andcontaminated water management of Fukushima Daiichi Nuclear Power Station
(1)

(2)

(3)

(4)

(5)

To proceed with the decommissioning of Fukushima Daiichi NPS safely and steadily is ofprimary importance. With these efforts, it is necessary to achieve “decommissioning as soon
as possible”. For that sense, the analysis and the investigation on the decommissioning andcontaminated water management of Fukushima Daiichi NPS (hereinafter referred to as“Fukushima Daiichi NPS Analysis and Investigation”) should be conducted, to the extent thatcan proceed with the decommissioning in safe and steady.
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 be given to the necessity of the Fukushima Daiichi NPS
Analysis and Investigation from the viewpoint of Forensic, on the premise of the safe andsteady decommissioning of Fukushima Daiichi NPS.
The Fukushima Daiichi NPS Analysis and Investigation is to be planned on the premises ofrealistic working situations and difficulties of the site, giving the highest priority on the safety
for local residents, surrounding environment and workers. In addition, it must be proposed
after clarifying the concreteness of technology commensurate with it.
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.
Taking into account of Japan’s responsibility to the international society, as a country 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.

Acceleration and prioritization for R&D, including the establishment of a containment function
on the assumption of the presence of α-nuclides and technology to control the water level in PCV,7

TEPCO, The basic principles toward the planned analysis and investigation on the decommissioning andcontaminated water management of Fukushima Daiichi NPS, Handout 4-1 from The secretariat Meeting of 67th
Team meeting on decommissioning and contaminated water treatment, issued on June 27, 2019http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/06/4-1-1.pdf

27

are encountered based on the decision of advancing the side access to the bottom of PCV that has
been made according to the fuel debris retrieval policy, as well as focusing on the partial
submersion method. Preparing for expanding the scale of retrieval, it is important to obtain more
information about internal condition of PCV and RPV; to proceed with technological developments
to optimize efficiency of retrieval work; to reduce diffusion of radioactive fine particles during
retrieval operation; to classify fuel debris and waste; and to analyze and examine the characteristicof fuel debris. In addition, it is also important to proceed with technological development whichassume how to respond to top access method for fuel debris retrieval. In the future, it will benecessary to strengthen R&D management on a project basis by identifying R&D tasks required
through engineering studies and implementing them in a timely and appropriate manner.
3.1.3 Technical issues for developing sectoral strategies and future plans
3.1.3.1 Technical issues and plans related to the fuel debris retrieval from the first
implementing unit
3.1.3.1.1 Initiatives toward start of retrieving fuel debris from the first implementing unit
Considerations should be given to the fuel debris retrieval for the first implementing unit inaccordance with the recommendations for determining fuel debris retrieval methods for the first
implementing unit as described in Sub-section 3.1.2.2.
To safely and reliably retrieve fuel debris for the first implementing unit, it is necessary toappropriately provide hold points in the course of engineering activities by TEPCO considering theelements such as validation of safety and actual site applicability at the occasion of mock-up testing
regarding small-scale retrieval equipment and verification on accessibility at the PCV internal
investigation, then proceed with the retrieval operation while confirming validity.
To make decision on the method of fuel debris retrieval of the first implementing unit, it is also
required to pay attentions to the work schedule examination based on the issues through PCVinternal investigations and work interference examination based on the considerations on the fuelremoval method from SFP as mentioned followings.


It becomes apparent through PCV internal investigation that there are obstacles in theaccess route to the fuel debris and improvement of measures to prevent dust diffusion isnecessary when removing such obstacles. Accordingly detail planning and examination on
work schedule aiming at start of fuel debris retrieval shall be promoted, considering removal
method of the obstacles including enhancement of prevention of radioactive airborne
material diffusion during obstacles removal work.

It becomes apparent through PCV internal investigation, research & development andpreliminary engineering by TEPCO that the works such as installation of the enclosure
require many human works at the site. Accordingly detail planning and examination on work
schedule aiming at start of fuel debris retrieval shall be promoted, considering further

28

reduction method of the radiation dose rate at the first floor of R/B(about 5mSv/h) wheremost human works take place.


It is observed through the investigation of operating floor of Unit 2 that the radiation dose isreduced so that human works would be available to some limited extent. Several plans are
considered on fuel removal from SFP with method to reduce risk of dust diffusion.
Accordingly coordination of work interferences when making parallel works both for fuelremoval from SFP and fuel debris retrieval including preparation works shall be well
examined based on the progress of engineering on method of fuel removal from SFP.
Toward start of retrieving the fuel debris for the first implement unit, TEPCO announced a planof the future internal investigations in July, 2018. For Unit 2, it is scheduled to conduct ① deposit
contact investigation, ② investigation to grasp the distribution of deposits as well as samplingin small amount of deposits, and ③ sampling in larger amount of deposits. The status andpurpose of each investigation and sampling are as follows.
① The deposit contact investigation was implemented in February, 2019. The purpose is tocontact the deposits and to check the change of the state before and after contacting. As results,
it is confirmed that deposits which are considered as the fuel debris are able to be moved bygripping.
② The investigation to grasp the distribution of deposits as well as sampling in small amount ofdeposits is scheduled to be implemented in future, and it is appropriate to be conducted before
start of retrieving the fuel debris for the first implement unit. The purposes are a) to confirm thatthe arm type access equipment can go into PCV, and b) to characterize the fuel debris byanalysis.
③ The plan of sampling in larger amount of deposits is under consideration now. The purposes
are a) to confirm that the fuel debris retrieval can be carried out, and b) to characterize the fueldebris by analysis using larger amount of deposits.
The start of retrieving the fuel debris was scheduled to be conducted after confirmation of a) of③. This confirmation is evaluated so for to be obtained by the confirmation of ① and ②. In
addition, the fuel debris retrieval in small amount is scheduled to start by gripping and sucking, andthe data required for assessment of cutting the fuel debris, etc. is evaluated so for to be obtainedby sampling in larger amount of fuel debris by using the same equipment as that for the fuel debris
retrieval in small amount. Thus, the fuel debris retrieval for the first implement unit is possible to be
integrally conducted with ③, and by this procedure it is possible to reduce the total amount ofworkers’ radiation exposure and waste. Therefore, it is appropriate to revise a plan that the fueldebris retrieval for the first implement unit and ③ is scheduled to be integrally carried out.

29

3.1.3.1.2 Initiatives for expanding retrieval scale and retrieval in units other than the first
implementing unit
Retrieval will start from small-scale with no significant changes in the state of the site in using
existing safety system as a base, and expand the scale or retrieve fuel debris from units otherthan the first implementing unit based on new findings including information and experiences
acquired from the small scale retrieval operation. To allow for this, following activities arenecessary.
a) Consideration of actual site applicability based on such as conceptual study on safety systemb) Information organization such as radionuclide airborne release fractions for examining
necessary and sufficient safety systems (safety assessment)c) Site environment preparation such as radiation reduction, water level lowering in PCV and areaplanningd) Further understanding of inside condition of PCV and RPVe) Technologies to make efficient fuel debris retrieval including removing obstaclesf)Technologies to reduce dispersion of radionuclide airborne particles during fuel debris retrievalg) Consideration on sorting and distinction of fuel debris and radioactive wasteh) Technologies to analyze and estimate fuel debris properties and distributions for understanding
In this regard, improving site work environment, PCV internal investigation and R&D arecontinued, regarding to the retrieval method in case of expanding the scale or applied to the unit
other than the first implementing unit. The retrieval method in conjunction with containing,transferring and storage should be determined after proceeding with engineering to examine newsafety system, retrieval facilities and the prospect of their actual site applicability, which is basedon the information and experiences obtained through fuel debris retrieval for the first implementing
unit.
Since the fuel debris retrieval is carried out in parallel with other works, it is necessary to revise
the work plan in accordance with the overall situation of decommissioning activities. Especially inorder to realize the regular full scale fuel debris retrieval safely and smoothly, efficient site spaceplan with appropriate margin is an important issue by keeping stably available area in the site.
Furthermore, the way of fuel debris retrieval shall be flexibly considered in view of optimizationof total decommissioning activities, as example the retrieval at the units other than the first
implementing unit can start if prepared well, even though the retrieval of the first implementing unit
is still continuing.
3.1.3.2 Comprehensive understanding of conditions of PCVs by continued internal
investigation, etc.
3.1.3.2.1 Previous internal investigations and inside reactor conditions
The comprehensive analysis and evaluation results about the distribution of fuel debris, theradiation dose at the working area, the access route to fuel debris and the situation of thesurrounding structure in Units 1 to 3 are as follows, that have been derived from actual values of30

plant parameters, etc., which were obtained at the time of accident, severe accident progression
analysis, the knowledge obtained by internal investigations of PCV and muon-based detection
technology, etc.
(1) Internal condition of Unit 1
It is presumed that most of the fuel debris is at the bottom of the PCV. It is presumed that thefuel debris at the bottom of the PCV has spread to the pedestal inside floor line and has reactedwith the concrete to form products of molten core and concrete interaction. There is a possibility
that a part of the fuel debris has spread to the outside of the pedestal through the worker access
opening.
As the radiation level in working area, it was confirmed that the radiation dose rate around X6
penetration was high i.e. 630mSv/h.
Regarding access routes, it is confirmed that access from the top of the steel grating to thebottom of the PCV outside of the pedestal is possible as per the PCV Internal investigation of 2015.
Regarding the situation of the surrounding structure, no large damage was detected on the outerwall surface of the pedestal on the top of the steel grating by the PCV Internal investigation of 2015.
Large damage was not detected to the structure in the PCV Internal investigation of March 2017,neither.
(2) Internal condition of Unit 2
Fuel debris is presumed to be mostly present at the bottom of RPV and from muon measurement,
it is evaluated that the fuel is present in RPV. Based on evaluation of core energy it is estimatedthat an equivalent quantity of non-melting fuel pellet is also present. In the PCV internal
investigation of 2018, deposits that appeared to be pebble/rock-like in shape were observed inmost of the bottom area of the pedestal. Since a part of the fuel assembly had fallen to the bottomof the pedestal, the deposit observed around it is presumed to be fuel debris. However, large-scale
damage and deformation to the concrete wall in the pedestal, melting of cable trays and steel pillarsof the CRD handling machine, etc., were not observed, so the fuel debris is considered to becontaining a lot of metal components such as internal structural materials. There may have several
drop paths of fuel debris because there are other deposits that are accumulated higher than thesurroundings. Also, although the worker entrance of the basement floor of the pedestal has been
confirmed, it has not been able to observe outflow of fuel debris outside the pedestal. The PCVinternal investigation in February 2019 revealed that pebble-like deposits could be moved bygripping, but there was a possibility that deposits like hard rocks existed, which could not be
gripped8.
As the radiation level in working area, it was confirmed that the radiation dose rate on the firstfloor of reactor building reduced by about 5mSv/h approximately in general.
8

TEPCO, Unit 2 Primary Containment Vessel Internal Investigation Results, Handout 3-3, 64th Meeting of
Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water Treatment, March 28,
2019.
http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/03/3-3-3.pdf

31

Regarding the access route, in the PCV internal investigation of 2018, it was observed fromPCV X-6 penetration that access was possible from the worker entrance to the bottom of thepedestal via the CRD rail.
Regarding the condition of the surrounding structure, in the PCV internal investigation of 2017and 2018, it was observed that part of the steel grating of the pedestal inside the platform had fallen,
but no significant damage was found on the pedestal inner wall surface and the existing structuresin the pedestal. It was also confirmed that a part of the fuel assembly had fallen to the bottom of
the pedestal, but no large damage was observed in CRD housing support within a range of theinvestigation.
(3) Internal condition of Unit 3
It is presumed that there is more fuel debris at the bottom of the PCV of Unit 3 than that of Unit2, although some fuel debris may be left at the bottom of the RPV. In the muon measurement, it isalso shown that a range of the original core in the RPV does not have any large lump of fuel debris.
The evaluation of core energy shows the possibility of a large massive fuel solidifying after melting
once existing at the bottom of the RPV. In the PCV internal investigation of July 2017, it wasobserved that the molten material had solidified in the pedestal. In addition, since the sandy or
massive deposits were observed at the bottom of the RPV as well as structures presumed to be
the internal structures have been observed, it is presumed that the surrounding deposits may
include fuel debris. The worker entrance of the basement floor of the pedestal could not be
observed. Since the deposit was observed in the vicinity, the possibility that fuel debris has spreadoutside the pedestal cannot be ruled out. On the other hand, cooling water was injected into thedrywell (“D/W”) at the time of the accident, which may have restricted the spread of the fuel debris.
As the radiation dose in working area, it was confirmed that the radiation dose rate was higher
than tens of mSv/h on the first floor of reactor building.
Regarding the access route, it was observed that it is possible to access the bottom of thepedestal via the worker entrance of the pedestal in the PCV internal investigation by the underwater
ROV in July 2017.
Regarding the condition of the surrounding structure, in the PCV internal investigation in July
2017, damage to the structures and fallen substances in the pedestal, missing portions anddeformation of CRD housing supports were observed. Also, in a range of the investigation, the steel
grating was not observed on the platform and it was observed that the steel grating had fallen in
the lower part of the pedestal. No large damage was detected on the pedestal inner wall surface.
This information is summarized as in Fig. 8.

32

(Prepared by Achievement Report 2017 Subsidy for “the Government-led R&D program on Decommissioning and Contaminated Water Management by
the supplementary budget (Advancement of comprehensive internal PCV condition analysis)” (June 2018) provided by IRID, The Institute of Applied Energy),etc.

Fig. 8 Estimation of fuel debris distribution in Units 1 to 3, access route and the condition ofsurrounding structures33

3.1.3.2.2 Future plan on internal investigations
In Unit 2, for which an internal investigation is relatively advanced, it is scheduled hereafter to
conduct the internal investigation to grasp the distribution of structures and deposits in the pedestal
and to conduct samplings in small amounts of deposits. In such an internal investigation andsampling, it is necessary to make preparations for the investigation in advance by carefully allowing
a certain time for adequate tests of the investigation equipment and training of its remote control,
because the equipment which would be bigger than before and would be used for handling of
obstacles, etc., will be different from that conducted in the previous investigations. During theinternal investigation and sampling, it is not always necessary to obtain information only on thebottom of the PCV, but it is also important to obtain information necessary for the future work,
including the characteristic (hardness, adherence situation, and elemental composition, etc.) of
deposits adhering on the platform of PCV and the location of internal components.
For Unit 1, grasping of the distribution of structures and deposits outside the pedestal andsampling in small amounts are scheduled for FY 2019. In addition to this, investigations to confirm
the condition inside the pedestal should also be considered.
For Unit 3, it is necessary to examine the applicability of techniques for internal investigations
which

were

developed

andverifiedthroughtheGovernment-led

R&D

programon

Decommissioning and Contaminated Water Management, and the necessity of further
investigations by use of the underwater ROV which was used in the previous investigation, inparallel with the examination on the lowering of PCV water level.
For Units 1 and 3, considerations should be given to the method of fuel debris retrieval, in
addition to these internal investigations.
In the future, prior to implementing further detailed internal investigations, and in association
with the use of large-scale equipment, giving due considerations will be required for continuously
ensuring safety, including prompt recovery of containment functions during abnormal events as wellas measures against radiation exposure, dust control and containment functions, in considerationof maximum use of existing penetrations into the internal PCV that have been used in the previous
investigations.
In addition, fuel debris and deposits at the Fukushima Daiichi NPS are unique due to differencesin the reactor structures and countermeasures to settle the accident, and the data are limited witha high level of uncertainty. Therefore, it is necessary to develop analytical and estimation
technologies for characterization. In particular, in order to establish analytical techniques, it needs
to demonstrate analytical methods for fuel debris using actual fuel debris samples. For
development of radioactive material analysis and research facilities, it is important to take into
consideration the demonstrated outcome to proceed with characterizing fuel debris according to alocation of PCV.

34

3.1.3.3 Technical issues and future plans for technical requirements
3.1.3.3.1 Technical issues and future actions for ensuring the safety of fuel debris retrieval
work
Generally, when it comes to deal with securing safety at nuclear facilities, it is required toestablish the concept of securing safety of nuclear facilities, which clarifies the necessary safetyfunctions and corresponding protective measures based on the scope of typical accident events,
in order to avoid unnecessary exposure to radiation or excessive meaningless protective measures.
However, in the decommissioning operation of the Fukushima Daiichi NPS, it may be difficult toapply the idea of a stereotyped and standardized concept of securing safety like a normal nuclear
power plant. Therefore, it may be necessary to establish the concept of securing safety according
to the severe actual circumstances at the site. For this reason, NDF has been working on organizing
the idea of securing safety at the site (see Sub-section 2.3.3.4) in order to foster a sharedunderstanding among related organizations including regulatory authorities that share the purposeof promoting safe and smooth decommissioning.
In operations involving unprecedented uncertainty such as the fuel debris retrieval, it may benecessary to incorporate reasonable protective measures at each conceptual design phase for thefuel debris retrieval steps while taking continuous actions to reduce the uncertainties about theinternal conditions of PCVs.
As the concept of ensuring safety during the fuel debris retrieval work is being constructed, NDF
is focusing on the studies on specifying the technical requirements to ensure safety during fueldebris retrieval work, as shown in Sub-sections 3.1.3.3.2 to 3.1.3.3.7. Specific measures forsecuring safety not limited to fuel debris retrieval work are described in Sub-section 3.5.4.
3.1.3.3.2 Establishing the containment functions (gas-phase)
Normally, dispersion of radioactive material in operating nuclear power plant is prevented bykeeping negative pressure inside of reactor building against the ambient air (active containment
function due to by maintaining under negative pressure) and pressure inside PCV is maintained
equal to inside of a reactor building (passive containment function). On the other hand, inFukushima Daiichi NPS, the reactor buildings and PCVs have been partially damaged by thehydrogen explosion and their containment function has been deteriorated. Because of this,establishment of an active containment function due to negative pressure inside PCV during fueldebris retrieval work is being investigated. Moreover, in order to prevent hydrogen explosion due
to continuous hydrogen generation by radiolysis of water and in order for the structural members
to prevent corrosion caused by the oxygen (inactivation), nitrogen is injected into the PCVs tomaintain it inert atmosphere. The dispersion of radioactive material has been preventing by the
PCV exhaust gas control system which involves filters to remove radioactive material and involves

35

radioactivity measurement system9.
As for retrieving of the fuel debris, applicability for the small scale retrieval starting from grippingor sucking together with existing safety systems has been studied and confirmed. However, thedispersion of radioactive fine particles containing α-nuclides (α-dust) may occur due to the crushingworks such as cutting and drilling fuel debris, and there may be a concern for increasing theconcentration of radioactivity in PCVs gas phase. Therefore, a function for containing the gas phaseshould be established to suppress the radiation dose impact on workers and the public within theallowable value, by minimizing the spread of α-dust from PCVs.
In this regard, the approach for the expansion of the scale of fuel debris retrieval work, while
accumulating the tendency of dust dispersion depending on scale expansion and verifying thevalidity of the containment function built in the subsequent stage is evaluated to be reasonable. For
example, during PCV internal investigations or the small scale retrieval near future, α-dust
dispersion can be managed by reducing amount to be retrieved or by careful handling of the fueldebris. At this moment, the dust monitoring system inside and outside PCV should be investigated.
And the appropriate measures together with the existing systems that secure the pressure inside
PCVs equal or less than outside should be investigated as well.
If it is evaluated that the expansion of retrieval work may induce effects on the surrounding
environment, further investigation is required for the means to strengthen the containment function
by equalization or negative pressurization inside PCVs as well as constructing a secondary
containment function outside PCVs.
R/B and Container

Primary Containment Boundary(PCV Repair + Work Cell)*Top of PCV closed in the case of side access

Cell (Top Access)Secondary Containment
Boundary(R/B + Cover or Container)* Necessity of secondary boundary
will be studied

Negative
Pressure
Control System

Air Phase
Region isabove PCV
water level(Air Phase Section)

Cell
Land
Surface

PCV Repair (formaintaining Negative
Pressure)
Inner PCV waterlevel should be kept
at/below this level

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

Ground Water level

Fig. 9 Example of containment function (gas phase) by pressure control system
9 While the estimated radiation exposure dose at the site boundary due to the release of airborne waste is 3.0 ×
10-2 mSv/year, the estimated additional release from Units 1 to 4 reactor buildings is approximately 2.2 × 10-4
mSv/year (Estimated value as of March 2019) (See Sub-section 3.5.2.2).

36

For building this containment function (gas phase), technical issues to be addressed
immediately are as follows.
(1) Understanding of dispersion rate of α-dust, etc.
As described above, for the purpose of fuel debris retrieval work, it is necessary to collectconcerned data such as α-dust dispersion rate and to establish measures to suppress the transitionof α-dust gas phase as much as possible.
In order to collect concerned data such as dispersion rate of α-dust, it is required to establish
the plan for dispersion rate measurement during sampling work and small-scale retrieval work.
Moreover, in order to proceed with the technology investigation and R&D activities for establishing
the fuel debris retrieval method/system under the condition where such actual data cannot be
obtained, approximately understanding on the general behavior of α-dust dispersion is required.
R&D for verification of general behavior of α-dust dispersion using mock-up debris is currently
underway10.
In order to suppress the transition of α-dust to the gas phase, it is preferable to submerge thefuel debris and to retrieve it in submerged condition as much as possible. However, the water levelin the PCV is to be adjusted with other technical requirements such as the containment function of
the liquid phase described in the next Sub-section. Therefore, mitigating transition of α-dust to gas
phase by supplying water on the fuel debris is under way, because all of the fuel debris cannot be
retrieved in submerged condition.
(2) Feasibility of negative pressure control in the PCVA.

Technical feasibility of maintaining negative pressure based on site conditions
In order to maintain negative pressure in the PCV, enough capacity in the gas exhaust system

is required according to the 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 tomaintain sufficient pressure difference to respond to the internal pressure rise of the PCV due toabnormal events such as an internal temperature rise or stoppage of the gas exhaust system. In
order to achieve these, repair of the damaged parts of at the upper part of the PCV will be studied
as necessary, but there are some difficulties such as remote work or radiation exposure for workers
due to work under high radiation dose circumstances.
In this way, it is necessary to ascertain the technical feasibility of maintaining the negative
pressure in the PCV according to the site conditions as well as the information through the fueldebris retrieval work.

10

Refer to (4) Clarify behavior of radioactive airborne particles generated during decommissioning (incl. α-dust
treatment) in Attachment 15.

37

B.

Influence of air flow into PCV on negative pressure control
Air flow comes into the PCV when maintaining inside of PCV pressure in negative. Therefore, it

is required to collect the data of hydrogen generation by radiolysis of water inside of PCV and to
study possibility of hydrogen explosion caused by air (oxygen) into the PCV. It is required toelaborate the countermeasure for maintaining inert atmosphere by increasing nitrogen gas supply,
if necessary. Evaluation results on influence of air (oxygen) inflow on corrosion of structural material
and its preventive measure are discussed in Sub-section 3.1.3.3.6 for details.
C.

Necessity of secondary containment function
As shown in Fig. 9, fuel debris is planned to retrieved and collected into the container which is

to be packed into the transport container equipped in the working cell which is connected with PCV.
The PCV and this working cell have a primary containment function to prevent of α-dust to theexterior.
In addition to this, in order to respond to the event that radioactive material is dispersed fromthe containment boundary caused by loss of primary containment function by fail of maintaining
negative pressure in the PCV and connected working cell, necessity of the secondary containment
function has been investigated. The secondary containment function is established by maintaining
negative pressure inside of the Reactor Building and a connected cover or cell which is installed
close to the Reactor Building. However, large capacity of gas exhaust system might be required tomaintain negative pressure in the secondary containment boundary since the reactor building has
a large volume and the its leak tightness may have been deteriorated due to the accident. Therefore,
based on the accumulated results of the tendency of dust dispersion obtained hereafter, it isnecessary to identify the required functions to establish the secondary containment boundary andto perform the necessary technology development.
D. Control of deterioration of PCV containment function
In order to maintain inside of PCV negative pressure during the fuel debris retrieval work,
preparation for maintaining containment function against earthquakes and aging is required. Thisis discussed in detail in Sub-section 3.1.3.3.6.
(3) Study on exhaust gas management
During PCV inside pressure maintained negative pressure by gas exhaust system, radioactive
material derived from fuel debris in exhaust gas shall be managed under the level of radiation dose
limit for public by monitoring and controlling released radioactive material condition (concentration
and amount). In addition, concentration or amount of the nuclides derived from the fuel debris which
releases α or β (ɤ) rays in the exhaust gas needed to be regularly measured so as to evaluate theirnormal fluctuation range in advance during fuel debris retrieval work. By using such data, it isnecessary to develop a system to detect abnormal events such as nuclides leakage in advanceand to mitigate the impact of the released nuclides on environment and workers.
38

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.
3.1.3.3.3 Establishing the containment functions (Liquid-phase)
As discussed in the previous Sub-section, to mitigate the dispersion rate of generated α-dust
and to minimize the transition to the gas phase, the fuel debris retrieval work would be performed,
submerging the fuel debris or by pouring water over the fuel debris. Dedicated investigation of
applicability for the small scale retrieval starting from gripping or sucking with existing safetysystems has been performed and confirmed. A large amount of α-particles (radioactive particulates
containing α-nuclides) will flow into cooling water (liquid phase) during crushing of fuel debris orremoving of the obstacle. To prevent the cooling water containing α-particles from affecting theenvironment, it may be important to establish a cooling water circulation/purification system, and aliquid phase containment function.
For this reason, the investigations, that establish technologies of removing soluble nuclides tobe leached from fuel debris as well as treatment of solid matter trapped by the filter equipped in thecirculating cooling water system, shall be conducted. Also, it is requested to investigate the PCV
circulation cooling system which takes the water of the bottom of PCV and injected cooling water
into RPV and has an advantage of preventing dispersion of α-particles.
The Mid-and-Long-term Roadmap requests to investigate feasibility of the PCV cooling water
circulation line for cooling water taken from PCV and injected to the RPV which is necessary at thetime of fuel debris retrieval work. As describes in Sub-section 3.3.2.3, this PCV cooling water
circulation and purification line is effective to prevent α-dust dispersion during the fuel debris
retrieval work because it has an effect of preventing contamination of stagnant water in the building.
At this time, to ensure a more reliable containment function, water sealing methods by repairing
the bottom of the PCV pouring the grout materials have been studied. However, based on the
results of previous experimental studies, it is becoming clearer that water sealing by repairing thebottom of the PCV is very difficult. Thus, in consideration of the PCV repair technology and theresults of the actual scale test11, it may be important to explore a retrieval method to minimize
leakage with the realization of suitable circulation and purification systems of cooling water(Attachment 9).
To establish a reasonable containment function in accordance with scale expansion, it is rational
to monitor the radioactive concentration of the cooling water and validate the validity of thecontainment function built in the subsequent stage. For example, if the PCV internal investigations
11

IRID, FY 2015 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Development of Repair Technology for Leakage Sections in PCV, FY
2016/2017 achievement report, July 2018, http://irid.or.jp/wp-content/uploads/2018/06/20170000_08.pdf
IRID, FY 2015 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Full-scale Testing of Technology for Repairing PCV Leakage Points, FY 2017
achievement report (final report), March 2018,
http://irid.or.jp/wp-content/uploads/2018/06/20170000_07.pdf

39

and small scale retrieval work would be performed using the current water circulation system, it
may be possible to suppress the increase in the radioactive concentration of cooling water byreducing the retrieved volume and carefully performing the crushing work, together with thecontainment function (gas phase). At this time, it is requested to monitor the circulating water
system from the viewpoint of investigating the methods to detect the effects induced by the retrieval
work on liquid phase, and also requested to investigate necessity of additional facilities andinstallations for the purpose of reducing the concentration of radioactive materials at the inlet in theexisting water treatment systems. Based on the monitoring and the evaluation for thecharacteristics changes of the liquid waste including α-nuclides, the scale of the fuel debris retrieval
will likely be expanded gradually. If an abnormal event such as a large volume of cooling water
outflow from a PCV to the torus rooms of a nuclear reactor building occurs, measures should betaken such that the water level in the torus room be maintained lower than the groundwater levelto prevent the outflow of cooling water to the surrounding ground. For this reason, it is necessary
to establish an appropriate PCV water level and a PCV water level control system.
In establishing this containment function (liquid phase), technical issues to be addressed
immediately are as follows.
R/B and Container

Primary Containment Boundary(PCV Repair + Work Cell)*Top of PCV closed in the case of side
accessCell (Top Access)Secondary Containment
Boundary(R/B + Cover or Container)* Necessity of secondary boundary
will be studied

Circulating water
Cooling system

Water Level
Management

PCV Repair (Liquidphase)(Liquid Phase Region)

Cell

Land
SurfaceLiquid Phase
Region is
below PCV
water level

Inner PCV water levelshould be kept
at/below this level

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

Ground Water level

Fig. 10 Example of containment function (liquid phase)(1) Suppression of radioactive concentration increase in the cooling water due to fuel debris
retrieval work
It is necessary to plan to investigate the impact of small scale of the fuel debris retrieval workon radioactive concentration in the circulating cooling water.
For suppressing an increase of radioactive concentration in cooling water in the PCV, dust
generated by fuel debris cutting is planned to be collected through PCV circulating cooling water40

system for mitigate dispersion of dust. It is required to validate the performance of the PCV
circulating water system according to monitoring and evaluation results even in the small-scale fueldebris retrieval Thereby, it is also required to take necessary actions properly.
(2) Feasibility of PCV water sealing
With the aim of improving the containment function of liquid phase at the bottom of the PCV by
suppressing leakage of cooling water into the torus room, various PCV water sealing methods
including blockage of the vent tubes, burying of the tip of the down-comers and burying the pipe
strainers on the S/C wall by concrete have been studied.
Based on the investigation results through Government-led R&D program on Decommissioning
and Contaminated Water Management, it was found not to be able to achieve complete watersealing. Even in the case of practical water sealing work of blockage of the vent tubes, it isnecessary to install the PCV circulation cooling system for controlling the water level in the PCV. In
addition, due to the low seismic margin of the S/C supports and water leakage paths from the PCV
other than from S/C, control of water level in the PCV and torus room has been studied low bycooling water circulation system. In the future, additional study will be carried out, as necessary, toresolve the technical issues identified through the examination on the applicability of current watersealing technologies to each unit which is being performed as a part of the engineering work.
(3) Setting of water level in PCV
Because the seismic margin of the S/C supports is low, water level in the PCV is heavily depends
on the applicability/usability of water sealing technologies to each unit.
In the case that flow of cooling water from the Dry Well (D/W) into the S/C can be suppressedby the blockage of the vent tubes, the water in the PCV (D/W) can be maintained at relatively highlevel. If not, it shall be kept at low level. In such case, evaluation will be needed from the perspectiveof cooling of fuel debris and radioactive dust dispersion. In addition, the water levels in the PCV,
S/C, torus room and groundwater are required to be monitored and controlled as well as locationof taking water from the D/W need to be examined.
Attachment 10 shows the water level in the PCV of each unit for the three cases of water sealing
work application. First is the cases of blockage of the vent tubes, second is burying of the tip of thedown-comers and the pipe strainers on the S/C wall by high-flow concrete and last is no watersealing work.
3.1.3.3.4 Maintaining the cooling functions
The decay heat of the fuel debris has been decreased dramatically since the core melt accidents.
However, it may be necessary to keep the cooling function to prevent nuclides from shifting fromthe liquid phase to the gas phase due to thermal energy during the fuel debris retrieval work. At
present, the cold shutdown state is maintained with keeping the temperature well below 100°C
using cooling water. In addition, during the fuel debris retrieval work, it may be necessary to keep41

the temperature below the level at which the fuel debris retrieval device can continue to workwithout any problems for a long period of time. Further, it may be required to consider alternative
water injection functions including mobile equipment, in preparation for an event the permanentequipment cannot maintain cooling due to a large earthquake, tsunami or other events.
At this time, to maintain the cooling function at each phase of scale expansion, the consistency
with other systems should be checked, such as the water level control system within the PCVs forconfining the liquid phase and the circulating water cooling and purification systems. Based on thedata obtained for each phase of scale expansion, it is necessary to examine and establish thecirculation cooling system in the next stage, including consideration of the adequate circulating flowrate required for cooling. However, it should be considered that the injection of cooling water may
become redundant in the future due to further decrease in the decay heat, as the fuel debris
retrieval progresses.
In maintaining this cooling function, the technical issues to be addressed for the time being areto establish the target temperature inside the PCV to secure fuel debris retrieval work and toinvestigate countermeasures against the unanticipated abnormal condition as well. An essential
countermeasure would be to continue cooling water circulation by early recovery of the coolingwater circulation system or by the recovery action by mobile equipment, as well as it is necessary
to establish countermeasures and their implementation process/step such as salvage of equipment
taking change of condition in the PCV including time margin until reaching the abnormal condition.
Also, monitoring items and their criterion need to be studied and prepared through theengineering work, in order to carefully proceed with fuel debris retrieval work with observing how
this work will affect the existing cooling water circulation and purification system as well as its
cooling function.
3.1.3.3.5 Criticality Control
At present, the monitoring of the concentration of rare gas (Xe-135), which is a fission product(hereinafter referred to as “FP”), has shown no sign of criticality as the concentration remains at a
sufficiently low level with respect to 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 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, that can be expected in the course of core meltdown. Furthermore, the fuel debris ispresumed to scatter in a wide area outside the core as a result of the accident progression. Evenif criticality should occur, its impact would be small because it is estimated that the fuel debris isdispersed over a wide area.
Though the possibility of criticality is low, the shape of fuel debris alters during retrieval.
Therefore, it is essential to prevent fuel debris from reaching criticality during retrieval byinvestigating what conditions would lead to criticality when the shape of fuel debris changes.
Establishing an appropriate management method is also required to ensure prompt detection and42termination, given 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. In the process of
expanding the retrieval scale and cutting, the retrieved volume of fuel debris will likely be increased,based on the results of measurement of subcriticality before work, or taking measures such as
placing 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, such as storing the debris incanisters.
For this criticality control, technical issues to be addressed for the time being are as follows.
(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 obtained information in each step of expanded-scale fuel debris retrieval. In this regard,an evaluation method has been developed to estimate the conditions for subcriticality and thedegree of influence of criticality if it should happen. In conducting these evaluations, a plan should
be made so that the information on the critical parameters with high impact on the criticality
evaluation can be obtained in the course of internal investigation and retrieval, and to revise theplan through information updates as needed.
(2) Local neutron measurement around retrieval point
As existing neutron detectors, there are various kinds according to the application such as
fission chamber, B-10 proportional counter tube, semiconductor detector, etc. It is important toselect a neutron detector taking advantage of each feature. 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 theinformation on PCV radiation dose rate obtained by internal investigation and the progress ofequipment development for each unit.
For the preparation of the actual operations, it is necessary to examine the installation locationof neutron detectors and also to set up criteria for stopping retrieval operations and for determining
the injection rate of boric acid, which is a neutron absorber, if fluctuations in neutron flux shouldarise.
43

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.
(3) Feasibility study on the measuring method for the degree of subcriticality
When measuring the degree of subcriticality, 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 ɤ-ray environment.
From the examination to date, considering the equipment mountability (size/weight/electromagnetic
noise) and operation methods (measurement time and duration) by sensitivity are key issues dueto the necessity of lead shielding in a high ɤ-ray environment (assuming 1000 Gy/h) 12. In the future,
it is necessary to consider selection and optimization of the neutron detector, reflecting theconstraints introduced by the study results of the project for the fuel debris retrieval method andsystem. Meanwhile, practical applicability is under review with consideration of the initiatives toascertain the ɤ- ray radiation dose rate and neutron count rate in the vicinity of the fuel debris anddownsizing the detector for continuous monitoring.
In addition, in order to verify the applicability to fuel debris, where various mixes of compositions
and characteristics of the fuel debris are expected, a plan for technical verification has beendeveloped and demonstrated, and then applicability evaluation is needed based on the results.
(4) Feasibility study of neutron absorber
Based on the information obtained in each phase of scale expansion, in preparations for cases
where the level of fuel debris criticality is high, the evaluation on the required boron concentrationand system feasibility study 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 andcompatibility with concrete as structural materials has been evaluated 13 . While examining theinfluence on the PCV circulation cooling system and concrete operation to maintain boron
concentration, based on the fuel debris composition obtained by the retrieval operation, it isnecessary to judge whether the injection of sodium pentaborate would be required during normal
retrieval operations.
12

IRID, FY 2015 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management (Development of Technology for Criticality Control in Fuel debris Retrieval), Finalreport, March 2018, http://irid.or.jp/wp-content/uploads/2018/06/20170000_05.pdf
13 IRID, FY 2017 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Advancement of methods and systems to retrieve fuel debris and to remove
structures inside reactor (Development of Technology for Criticality Control in Fuel debris Retrieval), Final report,
July 2019, http://irid.or.jp/_pdf/20180000_04.pdf

44

In addition, if criticality should occur, urgent sodium pentaborate injection would be used toachieve subcritical state, but after the suspension, it is necessary to select a method of maintaining
subcriticality, which may be the decrease in water level or the maintenance of boron concentration.
Moreover, the development of a non-soluble neutron absorbent that can locally restrain theinfluence on the PCV circulation cooling system has been performed as well. Until now,
fundamental property testing and radiation resistance testing have been conducted to list B4C metal
sintered materials, glass containing B/Gd, Gd2O3 particles, water glass, and Gd2O3 granulated
powder as candidates for non-soluble neutron absorbent. For those candidates, no impact of longterm irradiation on the integrity of canisters during storage of fuel debris, the method of spraying
fuel debris for debris fabrication, and the effect after spraying have been verified.13
Use of non-soluble absorbents is also under consideration in order to ensure subcriticality canbe maintained in the case of low subcriticality during normal condition.
(5) Detection of criticality by PCV gas monitor system installations
Immediate criticality monitoring and sophistication of detectors in the PCV gas monitor isrequired 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 inlocations other than fuel debris retrieval.
By measuring Kr-87/88 in addition to Xe-135 that has already been measured, it has been foundthat criticality detection can be accelerated and that the level of subcriticality of the entire PCV canbe presumed. However, the applicability to the actual plants is to be examined in the future.12

3.1.3.3.6 Securing structural integrity (earthquake resistance) of the PCVs and reactor
buildings
The reactor buildings, PCVs, and RPVs experienced the hydrogen explosions when theaccident occurred. Further, the exposure to the high-temperature environment and the corrosion
due to seawater injection may have affected the integrity of the structures. During the period of thefuel debris retrieval work, it is necessary to secure the integrity for the important structures like
PCVs and RPVs and to suppress the deterioration of containment functions of PCVs and reactor
buildings, considering the influence mentioned above and the possible occurrence of a severe
earthquake. Furthermore, it may be required to prepare for the mitigation measures in advance,
evaluating the impact on human beings and the environment induced by the postulated damage toimportant functions due to a large earthquake
In maintaining the structural integrity and safety functions of the PCVs and the buildings, thetechnical issues to be addressed for the time being are as follows.

45

(1) Evaluation of earthquake resistanceA.

Evaluation of earthquake resistance based on the impact of accidents and secular changes
In the previous studies, the reactor buildings and major components of PCV, RPV and RPV

pedestal of each unit, have been evaluated such that they have relatively large seismic safetymargin against a design basis seismic ground motion Ss (600 Gal), taking into account the damage
caused by the accident, the degradation over 40 years and increased weight of new facilities
required for the fuel debris retrieval work.
In these evaluations14, while taking into account major damage caused by hydrogen explosions
in the reactor buildings of Units 1, 3 and 4, on-site damage investigations such as observation of
cracks, have been performed by engineers and/or robots. Particularly, in the reactor building of Unit
4 that was heavily damaged by the hydrogen explosion but with low radiation dose, the investigationof cracks and concrete strength of major structural parts have been done periodically. According to
the results of the investigations, it was identified that there has been no development of harmful
crack and the concrete strength of major structural parts exceed the design strength as well.15
However, the periodic investigations of the buildings have to be implemented continuously over theperiod of the fuel debris retrieval work and a maintenance plan for the buildings shall be preparedto suppress the deterioration, in which remote repairing methods are to be included in case ofharmful cracks are found. No openings where size affects the building strength are assumed to beestablished in small-scale retrieval, which may have no significant impact on seismic resistance ofthe buildings. However, examinations on local allowable load on the floor and verification of
supporting performance are required against the weight of the new systems. During expandedscale retrieval, a case is assumed where there are openings where the size affects the building
strength. Therefore, reassessment of seismic resistance with consideration for impact byincreasing seismic force is required in addition to examinations on local allowable load on the floor
and verification of supporting performance against the weight of the new systems.
For the evaluation of pedestals, conservative conditions have been set taking into account the
influences of exposure to the high-temperature environment, based on the results of accident
progress analyses and the information obtained by PCV internal investigation. Since there might
be a possibility of erosion by the fuel debris, case studies of seismic margin of pedestals have been
performed by analyses with the variation of hypothesized eroded zones of the pedestals, taking
into account the material test results of both concrete and rebars on the effects exposed to hightemperature environment.
The S/C supports have relatively small seismic margins and may be greatly affected by the wayof lower PCV repair. Therefore, the evaluation has been performed by detailed analytical models.

14 TEPCO, The seismic safety assessment against a design-basis seismic ground motion Ss of main buildings ofUnits 1 to 4 of Fukushima Daiichi NPS, February 21, 2013, http://www.nsr.go.jp/data/000050857.pdf
15 E.g. Periodic Inspection Results for Integrity Verification of the Reactor Building in Unit 4, Fukushima Daiichi
Nuclear Power Station, TEPCO (9th), Nuclear Regulation Authority website, measures against the Fukushima
Daiichi Accident, July 2014, Interview Appointment/Interview with Regulators, July 24, 2014,
http://www.nsr.go.jp/data/000054381.pdf

46

The results shows that the S/C supports may have a certain level of safety margin against thedesign basis earthquake ground motion in the case of the water seals at the bent tubes and thestrainers or down-comers inside S/C with relatively small berried depth of grout.16
It is necessary to evaluate the seismic safety margin of R/Bs, PCVs and RPVs in more detailand to implement the countermeasures, according to the progress of the further PCV internal
investigation and the studies of the fuel debris retrieval methods.
B.

Evaluation of the impact induced by postulated damage due to a large earthquake and the
preparation of the countermeasures
Preparatory studies of the countermeasures have been done for the postulated damage to major

structural components such as a pedestal during a large earthquake. In the studies,countermeasures using mobile equipment are also included such as a countermeasure using
mobile pumps for the drainage of the torus room in case major leakage from a PCV occurs due tolarge cracks induced by the damage to the pedestal. As future investigations improve theunderstanding of the PCV internal situations, it may be necessary to reevaluate thecountermeasures and to reflect the results into the concept of the fuel debris retrieval. In addition,
it is considered necessary to determine the seismic design class of new systems and to evaluate
their seismic performance based on the current situation (high radiation dose work environment,
partial damage to PCV, etc., drastic reduction of decay heat, etc.) after examining appropriate
countermeasures.
(2) Countermeasures to suppress the deterioration during the fuel debris retrieval work
As described in Sub-section 3.1.3.3.2, when maintaining negative pressure in the PCV, there
may be a concern that the concentration of oxygen rises and corrosion of PCV/RPV structures andrequired pipes progresses due to inflow of atmospheric air during fuel debris retrieval work. The
evaluations of earthquake resistance described in (1) have been performed considering the impact
of corrosion progress. It has been evaluated such that they have relatively large seismic margin
against the design basis earthquake ground motion Ss (600 Gal) taking into account of thinning bymaterial corrosion for 40 years as described above. On the other hand, in order to maintain thecurrent conditions of PCVs, RPVs and major piping, it may be necessary to suppress the progressof the corrosion during the long period of the fuel debris retrieval work. In the subsidies for
Government-led R&D program on the Decommissioning and Contaminated Water Management,
countermeasures against further suppression of corrosion, have been studied to select suitablecorrosion inhibitors and to investigate the practical application of corrosion control measures, which
would be able to get into alignment with the current liquid process system.
The effectiveness of steel corrosion inhibitors for the PCVs, RPVs, piping, etc. have been tested,
16

IRID, FY 2013 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Development of Technology for Integrity Assessment for RPV/PCV and
Progress, November 2015, http://irid.or.jp/_pdf/201509to10_09.pdf

47

taking into account the influence of radiation environment and seawater injection, and corrosion
inhibitor options effective for not only overall corrosion but also localized corrosion are extracted17.
On the other hand, in order to mitigate the influence of the corrosion inhibitors on the existing watercooling circulation and purification system, it has been shown that it is necessary to reduce thecorrosion inhibitors concentration considerably before the preliminary stage of the water purification
system17. Henceforth, to realize a PCV circulation cooling system for the fuel debris retrieval, it may
be required to come up with the countermeasures that satisfy both the corrosion control and otherrequired functions such as the water purification, in an integrated manner.
3.1.3.3.7 Reduction of radiation exposure during work
The main work areas of the fuel debris retrieval to be scheduled are high radiation dose areas
such as inside the reactor buildings. Also, there comes a need of handling nuclear fuel materials
containing α-nuclides with a large internal radiation dose impact. Accordingly, continued strict
control of not only for external exposure but also for internal exposure is essential.
Specifically, it is important to prevent excessive radiation exposure to workers throughappropriate radiation protection schemes depending on the working environment (target nuclide,radiation dose equivalent rate, airborne concentration, surface density) and working style (direct
operation or remote). Regarding protection from external radiation exposure, the radiation
exposure dose is evaluated considering the radiation sources and the radiation dose rate in thework area. Then, based on the three principles, namely “time, distance, and shielding” (to shorten
the exposure time, distance from the radiation source, shield if possible), it is needed to takemeasures to keep the radiation exposure dose as low as reasonably achievable.
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.

In the areas inside the R/B buildings other than the above, the best combination of
decontamination, shielding, removal of unnecessary objects, remote technologies andreduction of on-site time, with considerations for the balance between the exposure during
the decontamination tasks and the exposure during the PCV repair tasks, to minimize thecumulative radiation dose for overall work.

17

IRID, supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Development of Technology for Controlling RPV/PCV Corrosion, Report, July
2017,
http://irid.or.jp/wp-content/uploads/2017/06/20160000_10.pdf

48

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 radiation dose rate in the target
areas, type of contamination, space for work, frequency of use, applicability anddevelopment situations of remote technologies, schedule and cost, etc.



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 radiation dose reduction.

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, e.g. installing air filter, are to be selected depending on the target nuclides,
airborne concentration and surface contamination density in the work area, to prevent inhalation
ingestion and body pollution. In addition, it is essential to prepare for countermeasures againstinternal exposure cases in advance and establish an emergency exposure medical care system
including exposure evaluation by bioassay etc.
Meanwhile, for the reduction of radiation exposure in the long-term decommissioning, it isnecessary to have an overall perspective and comprehensive, shared measures of exposure
reduction. It is important that actual on-site performance and lessons learned from them provide
feedback to the planning of subsequent steps to improve the accuracy of the plans, and to prevent
recurrence of problems such as delays in work procedures. The above approach must be adopted
to develop systems of cross-sectional exposure reduction management and knowhow/technology
transfer.
In particular, concerning the reduction of radiation exposure of workers in the reactor building, it
is important to set up a dosage reduction plan in consideration of the work and its contamination
condition in order to secure the necessary work environment for the operation area. In
consideration of the radiation exposure dose limit (50 mSv/year and 100 mSv/5 years) specified bylaws and regulations, it is necessary for the target radiation dose rate of the operation area toconsider and set the operation methods, working hours and the number of workers by considering
them in a single group. Further, it is important to appropriately update the information on dosage
reduction technologies in line with the three principles and utilize it on-site.
Since various nuclides are mixed at the Fukushima Daiichi NPS, for radiation exposure
management, it is necessary to select nuclide (attention nuclide) for which an appropriately
estimation of the radiation exposure dose (internal exposure and external exposure) for each curve
font can be rationally conducted. In other words, in the external exposure management, it shallreflect on the radiation dose rate management and the basis for wearing the protection equipment.
In the internal exposure management, it shall reflect on the management standard of airborne

49

concentration in the operation environment and the basis for wearing the operator's respiratory protection equipment etc. In particular, it is necessary to study the measurement management
considering the mixture of α-nuclides from both hardware and software sides and to prepare for theapplication to the fuel debris retrieval work.
In addition, it is required to create a long-term work plan that enables radiation exposure dose
reduction for the entire workforce without excessive radiation exposure to individual workers forappropriate exposure control.
3.1.3.4 Technical issues related to fuel debris retrieval methods
3.1.3.4.1 Securing access route
For transporting, installing and unloading the devices and equipment used for fuel debris
retrieval work, and transporting fuel debris and waste, an access route should be established byremoving obstacles and reducing the radiation dose to the level at which such tasks can be done.
When establishing a new opening in the PCV or the like to construct an access route to fuel debris,it should be kept in mind to suppressing the release of radioactive materials from the PCV and RPV
and maintaining the integrity of existing structures in terms of the containment function in the gas
phase described in Sub-section 3.1.3.3.2.
According to the fuel debris retrieval policy based on the partial submersion method that extends
the side access to the bottom of the PCV, TEPCO is now conducting the engineering work. Basedon the results of R&D of Government-led R&D program on Decommissioning and Contaminated
Water Management, an access route from the PCV side opening to the fuel debris is to beconstructed. Then, a plan will be drawn up in which a side wall opening is made on the reactor
building and the side wall opening on the PCV is enlarged as required. In this case, in the side
access method, it is a problem that there is a risk of exceeding the load bearing capacity of thereactor building floor at the time of installation of the cells and the like. For this reason, acomparative study of a method of releasing the load to the outside of the building is being conducted,
such as suspension bridge system and access tunnel system. In addition to the side access, thetechnical feasibility of removing obstacles to shorten the work processes is under review as
research necessary for constructing access routes including upper access.
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.
According to the fuel debris retrieval policy, the optimum retrieval method should be selected
depending on where the fuel debris exists for each reactor unit. It is important to proceed withtechnical development toward the scale expansion.
3.1.3.4.2 Development of devices and equipment
In order to retrieve fuel debris safely, reliably and efficiently, it is necessary to develop fuel debris
retrieval devices and equipment that meet the site requirements and have the necessary functions.

50

To flexibly respond to the situations inside the RPV and the bottom of the PCV where fuel debris ispredominantly present, this devices/equipment should necessarily meet specifications of radiation
resistance, dust resistance, waterproofness, target temperature described in Sub-section 3.1.3.3.4,
remote inspection/maintainability, remote operability, securing visual field, earthquake-resistance,
protection mechanism for collision avoidance or automatic stop in case of abnormality, highreliability, appropriate redundancy, a rescue mechanism that does not disturb the subsequent workwhen trouble occurs, such as efficiency of retrieving fuel debris (payload).
Based on above, devices and equipment for fuel debris retrieval need to be examined. As thefunctions to be specifically implemented, the development of retrieval system that can handle
various fuel debris conditions (fragments, sludge, or fine powder), fuel debris cutting system (laser,
boring, or crushing, etc.) and dust collecting system are underway. Though the cutting system has
good prospects, development of recovery and dust collecting systems are still in progress.
Furthermore, techniques for installing fuel debris retrieval equipment are required. The
technologies used for remote operation, including installing the work cell for establishing radiation
shielding and containment functions (gas phase), boundary connection with existing structures,
securing an access route for the top access and removing obstacles required for each of the top
access method and side access method, are now under development (Refer to Fig. 11).
These technological developments are currently underway in the Government-led R&D programon Decommissioning and Contaminated Water Management, in the future the developed devices
and equipment will be combined and undergo remote mock-up tests to verify that performance isdemonstrated safely and reliably for the actual site application.
This remote mock-up test needs to be implemented by a facility simulating the site in order toverify applicability of technically developed remote equipment to the actual environment andoperability/maintenance ability of entire remote system under the harsh environmental conditions
including uncertainties. It is therefore important to rationally implement according to the purposes,
such as utilization of Naraha Remote Technology Development Center of JAEA and Units 5 and/or
6 of Fukushima Daiichi NPS. Therefore, in cooperation with related organizations, NDF is working
on organizing and examining how to proceed with the remote mock-up test plan, the way of thetest plan review, the scope of the mock-up facility to be maintained, the necessary time, operation
management, etc. From the viewpoint of the necessity of full-scale mock-up facilities and systems,
which are considered to be particularly important, these are classified into the following categories:“Development mock-up” to verify the basic performance of remote equipment; “Environment mockup” to confirm the applicability of remote equipment to the on-site environment; and a “Training
mock-up” to provide work training for practical application to specify relevant requirements.

51

Example of removing obstacle
technology (side access)
Example of removing obstacle technology(top access)

Example of working cell installation
technology(Inflate seal)

Example of working cell installation
technology (biological shielding wall drilling)

Example of fuel debris collection system

Examples of contamination spread prevention
technology

Example of cutting system element technology(chisel, ultrasonic wave)(Data provided by IRID)

Fig. 11 Fundamental technologies for fuel debris retrieval and internal structures (examples)
3.1.3.4.3 Establishment of system equipment and working areas
When retrieving fuel debris, it is necessary to evaluate the necessity/sufficiency of systemequipment (including containers/ working cells/ devices and equipment) to establish safetyfunctions and newly install and operate them appropriately. Also, it should be prepared thatsufficient spaces for installation, operation, and maintenance, and for installing shields for reducing
radiation exposure to operators, so that the required environmental conditions are satisfied.
The system equipment includes a negative pressure control system required for establishing acontainment function of the gas-phase described in Sub-section 3.1.3.3.2, a circulating watercooling/purification system required for maintaining the containment function of the liquid phase
described in Sub-section 3.1.3.3.3 and cooling function described in Sub-section 3.1.3.3.4, and acriticality control system required for controlling criticality described in Sub-section3.1.3.3.5. The
installation plan for the respective system is being examined. 18 In addition, development of
measurement systems (pressure, temperature, water level, radiation, criticality (rare gas
concentration, etc.) hydrogen concentration, etc.) to monitor the internal situation, which is essential
for retrieving fuel debris, is an important future issue to be addressed. How to implement systeminstallations as the integrated entire system should be specified, which satisfy these system
functional requirements.
The working area required for installing the fuel debris retrieval equipment/related devices andsystem equipment is now being calculated. Considering the handling of the high radiation dosearea in the reactor buildings and interference with other tasks, study of setting up the systems,
18

IRID, FY 2016 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management, Advancement of Retrieval Method and System of Fuel Debris and Internal
Structures, FY 2017 report, April 2018, http://irid.or.jp/wp-content/uploads/2018/06/20170000_10.pdf

52

including outside of the existing buildings, is underway. From now on, in order to carry out fueldebris retrieval work and to implement detailed examination of the layout of the area for installationand operation of the facilities constituting each system, proceed with consideration of the place fortemporary placement/treatment of the removed equipment, on-site plot plan for storing the retrieved
fuel debris, etc.
3.1.3.5 Technical issues related to safe and stable storage of fuel debris
3.1.3.5.1 Handling of fuel debris (containing, transferring and storing)
Before initiating fuel debris retrieval work, a comprehensive system should be established,which consists of a series of steps from containing, 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 accordingly.19
Drawing up of basic specifications of the canister for retrieved debris storage, that is, overall
length considering its handling, internal diameter in light of work efficiency and maintaining
subcriticality, etc., and planning and implementation of tests to verify the structural integrityof the canisterExamination of a practical prediction method for hydrogen generation from fuel debris stored
in the canister, and consideration on safe transfer conditions using the examination resultsStudy on drying technology applicable to fuel debris in the canister, and consideration on adrying system using this technology

In the future, specific facilities and systems should be developed from containing to storing
retrieved fuel debris based on the results of these studies. In addition, further studies should bemade on the specific transfer method, the specific type and size of the storage facility, and others,
taking into account the amount of fuel debris to be retrieved per day and the filling rate of thecanister. In developing the specific facilities and systems for handling and storing retrieved fueldebris, it is also necessary to include responses to safeguards requirements.
It is important to reflect various measurement data collected and accumulated during the smallscale retrieval such as the amount of generated hydrogen , as well as knowledge and experienceson handling fuel debris during the operations from receiving the fuel debris by containers for onsite transfer to storing them at the temporary storage facility, into the design of equipment andfacilities for storing fuel debris safely, reliably, and reasonably at expanding scale of retrieval. In
addition, it is necessary to specify transfer routes and storage facility locations for expanded-scale
retrieval in light of the usage plan of the entire site.
The Mid-and-Long-term Roadmap states that the processing/disposal method of the retrieved

19 RID, FY 2015 supplementary budget, Subsidies for Government-led R&D program on Decommissioning andContaminated Water Management (Development of Technology for Collection, Transfer and Storage of Fuel
Debris), FY 2017 implementation report, June 2018, http://irid.or.jp/wp-content/uploads/2018/06/20170000_03.pdf

53

fuel debris are investigated and fixed during the third phase after starting fuel debris retrieval work.
3.1.3.5.2 Treatment of radioactive waste during fuel debris retrieval
During fuel debris retrieval work, a variety of radioactive waste such as replaced ordisassembled structures or parts other than retrieved fuel debris are to be generated frominside/outside of the PCV at each phase of its preparation, retrieval and cleaning work. They should
be properly classified and stored under safe conditions.
It is practically difficult to accumulate and organize necessary and sufficient information such as
distribution and characteristics of the fuel debris and the radioactive waste in the PCV prior to its
actual retrieval work which are essential for investigating classification standard and storing method,even though it is continued in operation with collecting and organizing such information. Also, since
the essence of the fuel debris is considered to be the existence of nuclear fuel material in it, it isdesirable that the retrieved material is classified into fuel debris or radioactive waste based on theconcentration of nuclear fuel material in it. However, it is currently considered as highly-difficult
technical challenges to accurately measure or estimate the concentration of nuclear fuel material
in the retrieved material itself or in it collected into the canister.
As a practical issue during retrieval, therefore, it is important to develop classification criteria
toward expanded-scale retrieval in order to appropriately classify such materials as fuel debris orradioactive waste, even if only limited information on the retrieved material is available in advance.
For this reason, it is necessary to consider possible methods to classify fuel debris and waste basedon knowledge and information that will be obtained in future PCV internal investigations, etc., andto promote survey of component technology and address of technical issues, which are necessary
for realizing such classification.
3.1.3.5.3 Study on Safeguards Measures
Nuclear facilities in Japan need to fulfill obligations concluded with the International Atomic
Energy Agency (hereinafter referred to as the “IAEA”) of comprehensive safeguards agreement
and its additional protocol, and are expected to show that nuclear materials are utilized for peacefulpurpose only as declared by implementing material accountancy as a part of the domestic
safeguards system, and by accepting containment/surveillance of nuclear materials, and inspection
and complementary access by IAEA. In the Fukushima Daiichi NPS, as above, it had been
confirmed via the IAEA safeguards activities that the nuclear material had been used as declared.
After the nuclear accident, however, the basic information of the facilities and the situation for
utilization and storage of the nuclear materials, provided in advance for the implementation of thesafeguards, greatly changed. In a sound nuclear power plant, the nuclear material is clearlyaccounted for in each material balance area (MBA) as an item one by one with a fuel assembly ofa certain defined shape as one unit for material accountancy. However, large amount of fuelassemblies would no longer maintain their shape due to melting in Units 1 to 3 of the Fukushima
Daiichi NPS. Implementation of pre-accident material accountancy and safeguards is deemed54difficult since the damaged facilities would not allow the same containment/surveillance systems at
strategic points as the level of pre-accident, or high radiation would restrict access into the areas
for inspection and prevent verification activities. Additional safeguards activities are currently
applied under this situation to the Units 1 to 3 as an alternative measure to ensure no undeclared
movements of the nuclear materials.
Given that further fuel debris sampling and retrieval operations intrinsically move nuclear
materials from the inside of the PCVs to the outside of the PCVs in Units 1 to 3 of the Fukushima
Daiichi NPS, corresponding new material accountancy and safeguards will be required. However,fuel debris is highly likely to contain structural materials other than nuclear materials, and theconfirmation of the composition and quantitative evaluation of contained nuclear materials are
believed quite hard to technically achieve. Accordingly, material accountancy and safeguards to be
applied to the Units 1 to 3 of the Fukushima Daiichi NPS would pose an essential question on how
realistic solution could be found to replace the pre-accident scheme.
In response to those issues, discussion in regard to the safeguards in Fukushima Daiichi NPS
continues and discussion in regard to material accountancy newly applied to small-scale samplingof fuel debris have commenced in Fukushima Task Force Meeting organized between IAEA and
NRA. Japan has been providing necessary updated information to stakeholders, including the IAEA
from the early stage, aiming at the smooth application of safeguards and proper material
accountancy. These efforts are consistent with the idea of the IAEA’s “Safeguards by Design(considerations to be paid to the safeguards from the design phase)”. Moving ahead, realistic andtransparent material accountancy and safeguards that do not impose excessive burden on the onsite operations must be proposed proactively by Japan to reach an agreement among thestakeholders, including the IAEA.
3.1.3.6 Summary of key Technical issues
The main technical subjects and plans described in this section are summarized as shown in
Fig. 12.

55

Fiscal Year
Milestones

2019

2020

Determination of fuel debris retrieval methods
for the first implementing unit

2021

2022

2023

Start of fuel debris retrieval
at the first implementing unit

On-site work
Technical reviews for on-site construction
Research and development

Internal investigation etc.
Study for the Government-led R&D program on
Decommissioning and Contaminated Water
Management

Preparation for investigation/ Internal investigation / Characterization of fuel debris (from retrieved sampling, etc.)

Technologies to establish access route
Technologies toestablish access route

Technologies to analyze and estimate fuel debris properties- Development of technologies for in-depth
investigation inside PCV- Development of sampling technologies for retrieving
fuel debris and internal structures- Development of technologies for grasping andanalyzing properties of fuel debris- Development of investigation technologies
inside RPVTransfer method to outside the site
Adaption plan for Safeguards
Additional plan for internal
investigation

Engineering for internal investigation
Fuel debris retrieval

Preparation for small-scale retrieval

Retrieval method (layout, etc.)
Containing/transfer plan
Temporary storage facility plan
Ideas for secure safety

Retrieval equipment
Facilities for containing, transfer
and temporary storage
Measures for securing safety(including modification of existing
facilities)
Safeguards policy→- Small-scale retrieval- Preparation of expanded-scale offuel debris retrieval work

Optimization of retrieval method (layout plan, etc.)
Containing/transfer plan
Storage facility plan
Actual site applicability of measures for securingsafety (Containment, water level control andcriticality control)
Gathering and organizing information for safetyassessment
Improvement of working environment such asradiation dose reduction, PCV water level
lowering and securing working space

Engineering involved with fuel debris retrieval
Study for the Government-led R&D program on
Decommissioning and Contaminated Water
Management

Circulating water
system design

For the investigation of measures toensure safety and safer fuel debris
handling according to expanded-scaleof fuel debris retrieval*Continue as necessary- Development of closed circulation systems forwater inside PCVContinue asnecessary- Development of technologies for retrieving
fuel debris and internal components- Development of technologies for containing,transferring and storing fuel debris* Other R&Ds listed below are to be
performed accordingly.
• Technologies to make efficient fuel debris
retrieval including removing obstacles• Technologies for redueing dispersion ofradio nuclide airborne particles during fueldebris retrieval• Consideration on sorting and distinction offuel debris and radioactive waste• Technologies for analyzing and estimating
characterization of fuel debris

Fig. 12 Technical issues and further plan on fuel debris retrieval (Process chart)56

3.2 Waste management
3.2.1 Sectoral target
Near-future targets in waste management are as follows:(1) As the approaches of solid waste storage, the Solid Waste Storage Management Plan(“Storage Management Plan”) is appropriately developed, revised and implemented including
waste prevention, volume reduction and monitoring, with updating the estimated amount ofsolid waste to be generated in the next ten years periodically.
(2) As the approaches for processing/disposal, countermeasures integrated from characterization
to processing/disposal of solid waste are studied from the expert point of view, and theprospects of a processing/disposal method and technology related to its safety should be madeclear by around FY2021.
3.2.2 Sectoral strategies
3.2.2.1 The concept of risk reduction in waste management
Waste management is a long-term effort that needs to attain the prospect of implementing final
disposal, while reducing risks in every stages. For the terms regard to radioactive waste
management, the definitions of terms provided by the IAEA is shown in Attachment 11.
The solid waste, such as concentrated waste water, waste sludge, slurry in the high integrity
container (HIC), rubbles, etc., and contaminated building structures, is unlikely to increase in riskin the future; however, it is still a source of risks which should make its countermeasures properlyin the decommissioning process. (refer to Section 2.3) Compared with other major risk sources,
they are in a state where the risk level is generally lower than other major risk sources, and it isconsidered that a constant risk level can be continuously maintained by appropriate maintenanceand management in the future. Solid waste is, however, highly diverse of characteristics, including
waste contaminated by radioactive materials adhering to the surface, waste in the form of sludge,
and waste with high radiation dose that generates hydrogen. For this, risk reduction measures areto be implemented systematically by continuously conducting research on risk reduction for safer
management, by seeing throughout disposal and by ensuring safety as a precondition.
3.2.2.2 The basic policies on solid waste
The Strategic Plan 2017 explains the properties of solid waste estimates based on the accident
conditions, post-accident decommissioning efforts, and the results of the characterization of waste
so far. Based on these findings, the plan proposes a policy of solid waste management, along withstrategic recommendations that include specific tasks to be performed at present (i.e. statement
for the preparation of the basic concept for the processing/disposal of solid waste).
The Mid-and-Long-term Roadmap revised in September 2017 summarizes the basic policies on57

solid waste, based on the content of the strategic recommendations.
The basic policies on solid waste[1] Thorough containment and isolation
Solid waste management should be implemented thoroughly, with containment and isolation ofradioactive materials to prevent their dispersion/leakage and human access to them, in order notcause harmful radiation exposure.
[2] Reduction of solid waste volume
The amount of solid waste generated by decommissioning is reduced as much as possible in order toease the burden of solid waste management.
[3] Promotion of characterization
To proceed with study on processing/disposal method of solid waste, characterization of solid waste
such as nuclide composition and radioactive concentration is needed. In addition to the fact that solid
waste of the Fukushima Daiichi NPS is large in volume, and have varied nuclide compositions, it isnecessary to address an increase in the number of analysis samples and proceed with theircharacterization properly.
[4] Thorough storage
To dispose of solid waste, it is essential to understand the volumes and characteristics of the solid
waste, and to establish specifications of disposal facilities and technical requirements for waste
packages (technical requirements for disposal). However, the volumes and characteristics of solid
waste will become clear step by step, with the future clarification of progress and plan ofdecommissioning. Therefore, the solid waste generated should be stored safely and reasonably
according to characteristics of solid waste. Storage capacity should be secured to ensure that thewaste can be stored within the site of the Fukushima Daiichi NPS.
[5] Establishment of selection system of preceding processing methods in consideration of disposal
In order to safely store solid waste, the system for selecting the method of processing for stabilizationand immobilization (preceding processing) will be established, and selecting the method of thepreceding processing, before the technical requirements of disposal are established.
[6] Promotion of effective R&D with a bird’s-eye-view of overall solid waste management
To efficiently proceed with R&D concerning solid waste management, close cooperation should be
realized between R&D fields such as waste characterization, processing/disposal. Issues anddiscussions on R&D should be shared between parties, and necessary planning made with a bird’seye-view of overall solid waste management, should be progressed collectively.
[7] Efficient implementation of R&D projects from the perspective of overall solid waste management
In order to continue safe and steady solid waste management, the continuous operational frameworksystem including development of adequate facilities and human resources, which are concerned withsolid waste management, must be undertaken.
[8] Measures to reduce radiation exposure of workers
To steadily proceed with solid waste management, it is important to ensure the safety and health ofworkers. Therefore, radiation exposure control, safety management and healthcare programs shouldbe implemented thoroughly based on the relevant laws/regulations.

The challenge on solid waste generated by decommissioning of the Fukushima Daiichi NPS isthe existence of a large volume of waste with various characteristics compared to the waste
generated from the decommissioning of normal nuclear power plants. While the characteristics ofthe solid waste are known to some extent so far, it is necessary to improve capabilities ofradiological analysis (i.e. efficiency and capacity) to further clarify such characteristics, to foresee
the final disposal and to develop a flexible and reasonable waste stream (integrated measures fromcharacterization to processing/disposal of the waste).
Specifically, the relevant organizations should proceed with their efforts based on each role in58

line with the basic policies, and NDF takes the initiative on proceeding with the technical study on
the integrated countermeasures, from the characterization to processing/disposal of solid waste,according to the following policies.
3.2.2.3 Storage
3.2.2.3.1 Storage at present
The fundamentals of managing solid waste are to confine not to scatter or leak, by placing it into
container or immobilizing, and so on, as need. Also, it should be kept isolated in a properly storage
place, and managed appropriately by monitoring and so on.
From the view point of minimizing the volume of solid waste to be generated and to be disposedof in order to lower environmental impact, “Waste hierarchy” (1.Waste Prevention, 2.Waste
Minimization, 3.Re-use of Materials, 4. Recycling, 5.Disposal, in the order of preferred approach)is shared as a priority of measures to be taken in the U.S. and the UK. It has succeeded insuppressing the final volume of disposal by implementing waste management according to thisconcept. For practically developing Waste Hierarchy, it has been pointed out that the department
in charge of waste management should be involved in it from the stage of developing construction
work plan for decommissioning.
In the Fukushima Daiichi NPS, such efforts are being made in line with the “Waste Hierarchy”
shown in Fig. 13. It is important to instill the concept of the waste hierarchy, and raise awarenesson reducing the volume of solid waste to be generated.

Summary of the Waste Hierarchy

Examples of countermeasures
for the Fukushima Daiichi NPS

Waste Prevention

Installation of vehicle maintenance area; prevention ofcarrying-in the packaging materials; sharing
construction equipment

Waste Minimization

Waste classification, segregation, etc.

Re-use of Materials

Study on the recycle and reuse of metal andconcrete with extremely low surface dose
rate and dismantled pieces of flange tanks

Preferred
Approach

Recycling

Application of the volume reduction facilities (e.g.
incineration system, crusher and metal cutting
machine)DisposalFig. 13 Summary of Waste Hierarchy at the NDA, UK20 and Countermeasures at the Fukushima
Daiichi NPS

20

Edited Figure 7. Summary of the Waste Hierarchy p. 60, NDA, Nuclear Decommissioning Authority Strategy
Effective from April 2016 (2016)59

Among the solid waste that has been generated by March, 2019, rubble, etc. have beenclassified into rubble, felled trees, used protective clothing and so on, and about 460,000 m3 ofwaste is stored in temporary storage areas according to the surface radiation dose rates. Amongthe secondary waste generated by water treatment, about 4,300 used vessels, which haveundergone additional measures such as adding shields and increasing water tightness, are stored
in used adsorption column storage facilities. Table2 shows the status of storage of the solid waste.
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.
The Storage Management Plan states that the volume of rubbles, etc. should be reduced as far
as possible, and will be carried to store in the solid waste storage building around FY 2028,
excluding reusable rubble. Regarding secondary waste generated by water treatment, large, heavy
waste such as used vessel is planned to be stored in a building that will be built to accommodate
large waste. These measures will consolidate waste storage areas and supersede many of thecurrently scattered temporary storage areas (Attachment 12).
In the Storage Management Plan, however, the future generation of some items is left
uncalculated. It will be reflected to the estimated amount of generation when the decommissioning
plan is taking shape and the possibility of activity such as dismantlement become known in the next
10 years. Since the estimated amount of generation fluctuates depending on the progress of thedecommissioning work and plans in the future, it is necessary to revise the estimated amount oncea year and update the Storage Management Plan as appropriate, as TEPCO expresses to do.
Table 2 Solid Waste Storage Management Status(a) Management status of rubble, felled trees, used protective clothing, etc.
(as of Mar 29, 2019)RubbleSurface radiationdose rate(mSv/h)Storage method≤0.1

Outdoor storage

0.1~1

Outdoor sheet covered storage

1~30
>30
Total

Soil-covered temporary storage facility,
Temporary storage tent, Outdoor container
storage
Containers (in Solid waste storage
building)----

Stored volume (m3) / Storage
capacity (m3)(Percentage)
195,300 / 252,700(77%)
37,900 / 71,000(53%)
18,500 / 31,700(58%)
15,100 / 45,600(33%)
266,800 / 401,000(67%)

Felled trees
Classification

Storage method

Root

Outdoor storage

Branch/leaves

Temporary storage pool

Total

----

60

Stored volume (m3) / Storage
capacity (m3)(Percentage)
96,800 / 134,000(72%)
37,300 / 41,600(90%)
134,100 / 175,600(76%)

Used protective clothing, etc.
Stored volume (m3) / Storage
capacity (m3)(Percentage)
56,000 / 68,300(82%)

Storage method
Container

Storageplace

Type of Used Vessels

Outdoor Temporary
Storage areaof used Vessels(b) Management status of secondary waste generated by water treatment(as of Apr 4, 2019)
Used vessels

Cesium adsorption apparatus
2nd Cesium adsorption apparatus
HICs from Multi-nuclide Removal Equipment
HICs from improved Multi -nuclide Removal Equipment
Used vessel from high-performance Multi-nuclide
Removal Equipment
Used column from multi-nuclide Removal Equipment
Used vessels and filters from mobile-type strontium
systemStoredNumber
775
216
1,590
1,460
74

StoredNumber/Capacity(Percentage)

4,332 / 6,372
(68%)

11
206

Waste sludge
Storage place

Store volume (m3)

Sludge storage facility (Indoor)

597

Stored volume (m3) / Storage
capacity (m3)(Percentage)
597 / 700(85%)

Concentrated waste liquid
Storage Method

Store volume (m3)Concentrated waste liquid storage
tanks (Outdoor)

9,364Stored volume (m3) / Storage
capacity (m3)(Percentage)
9,330 / 10,300(91%)

3.2.2.3.2 Further safety improvement in storage
The secondary waste generated by water treatment, which has high fluidity (such as slurry
generated from multi-nuclide removal equipment and waste sludge generated from thedecontamination system) poses a relatively large risk in the storage because of the fluidity, and it
should be stored in a more stable and reasonable way after risk reduced by performing a certain
processing. In general, it is ideal to conduct waste processing based on the technical requirementsof disposal once it is established, if the processing is conducted prior to disposal. However, there
may be cases where processing for stabilization and immobilization are required although thetechnical requirements for disposal are not determined (i.e. preceding processing). Therefore,
study will be continued on how to select the preceding processing method with disposal in mind.
The possibility that the specifications of solid waste conducted preceding processing areincompatible with the technical requirements for disposal should be minimized. Therefore, safetyassessment should be conducted for each specification of processed solid waste, using scenarios,
models, data and so on, for multiple disposal methods which are rational and feasible to implement,
and also suitable for features of the waste without specifying disposal facility’s place, scale and soon. The selection of preceding processing method should be studied based on the result.

61

3.2.2.4 Study on the processing/disposal measures
The Mid-and-Long-term Roadmap specifies that the prospects of a processing/disposal method
and technology related to its safety should be made clear by around FY2021, including waste which
does not need preceding processing. 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 remain in a stage ofaccumulating necessary information on its characteristics around FY2021, the concrete targets fortechnical 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
It is described in the Mid-and-Long-term Roadmap that, in accord with these efforts,
specifications and production methods of the waste packages associated with decommissioning
work should be determined in the third phase after the start of fuel debris retrieval. Then, a
processing system should be installed in the Fukushima Daiichi NPS. After establishing theprospects of disposal, production of waste packages should be started; and then carried out.
3.2.3 Technical issues and plans for promoting sectoral strategies
3.2.3.1 Promotion of characterization and enhancement of analysis systems and technicalcapabilities
It is essential to analyze and understand a wide variety of radioactive waste generated in thedecommissioning process in order to consider reasonable storage and study processing/disposal
methods. In order to carry out such analysis work, there are important issues, such as arranging
facilities as hardware, developing human resources for analysis, and inheriting and enhancing
technical capability on analysis. Therefore, for the time being, it is important to systematicallypromote the establishment of the Radioactive Material Analysis and Research Facility and thedevelopment of human resources for analysis. Through these efforts, it is desirable that technology,
facilities, and systems be established, and that the necessary analytical work for decommissioning
be carried out continuously and in a timely and appropriate manner.
Under the circumstance that the Laboratory-1 of the Radioactive Material Analysis andResearch Facility is scheduled to commence operation at the end of FY 2020, it is important to62

improve the accuracy of models to obtain evaluation data based on the limited number ofradiological analysis data. The study will be advanced on the method of reflecting dispersion ofradiological analysis data to inventory evaluation using analytical method, and concept of setting
and revising radioactive inventory based on comprehensive evaluation of radiological analysis data
and analytical value.
Analysis for characterization has been studied but, in the future, clarification of analyticalaccuracy and review of the nuclides to be analyzed in accordance with the objectives of storage,
as well as processing/disposal, will be carried out, and simplification and acceleration of radiologicalanalysis methods will be studied to develop an efficient analytical technique. While reducing
radiation exposure by introducing remote sampling methods, high radiation dose sampling will be
conducted.
In addition, R&D for characterization is being conducted by the Government-led R&D programon Decommissioning and Contaminated Water Management, and the sampling and analysis of
rubble, contaminated water, secondary waste generated by water treatment, etc., are being carriedout, and the correlation of nuclide composition of each analysis object is being gradually clarified.
Through these efforts, it will be a challenge to build an environment where system,
facilities/equipment, and technologies for highly accurate characterization of solid waste will beestablished by the end of FY 2020, and necessary radiological analysis data will be acquired forsome solid waste.
3.2.3.2 Further safety improvement in storage
As temporary risk reduction measures concerning secondary waste generated by water
treatment, processes to be dehydrated for stabilization and extracted/removed the waste will be
implemented to transfer from temporary storage facilities to storage facilities on a hill. Specifically,
adsorption vessels and the like are temporarily stored in the used adsorption vessel storage facility
after taking measures according to the type and, in the future, the plan is to store them in a large
waste storage. The waste sludge is temporarily stored in the waste sludge storage facility, and theplan is to remove it from the storage tank to be transferred to a hill for storage in FY 2020.
On the technologies for stabilization, immobilization and conditioning of the secondary waste
generated by water treatment, challenges for introducing the actual equipment should be dealt with,and gathering and evaluation of data on technical requirements should proceed by means ofengineering scale test equipment, etc., processing technology expected to be applicable for theactual processing should be identified, and specification of waste packages should be determinedfrom the point of view of whether it may contribute to establishing a selection method for preceding
processing methods.
Regarding the methods of storing high radiation dose solid waste generated as a result of fueldebris retrieval, study should proceed on the items such as the way of sorting fuel debris/waste,
the type of waste, the evaluation of waste volume, and the flow of handling waste, and narrow down
candidate methods for storage. For Storage, it is necessary to study measures against hydrogen63

generation, and reasonable storage, such as application of vented containers, needs to proceedfor study.
For other solid waste, study should proceed on generation of hydrogen during storage, together
with the timing and content for the case of further measures those are required in order to securesafety, and reflects to the Storage Management Plan as needed.
3.2.3.3 Development of processing/disposal concept and safety assessment method
In order to select candidate technologies for preceding processing methods, it is necessary to
conduct safety assessment with the specifications of the waste package associated withdecommissioning work that is developed by the respective candidate technologies, as a target. The
selection of reasonable and feasible candidate technologies and the development of suitable safetyassessment methods corresponding to it will proceed until the end of FY 2021.
Solid waste from the Fukushima Daiichi NPS is characterized by a large amount of waste witha wide variety of properties. Therefore, it is necessary to consider solidification performance,
detoxification performance, control of hydrogen generation, processing speed, volume reduction
performance, etc., when selecting processing technologies, based on the R&D status of eachtechnology. From this viewpoint, the R&D of low-temperature processing technology (cement
solidification, and AAM solidification) and high-temperature processing technology (vitrification, andmolten solidification) are being carried out as concrete processing technologies in the governmentled R&D program on decommissioning and contaminated water management.21
In addition, study on domestic and international waste acceptance criteria, disposal concepts
and safety assessment methods, etc., are conducted. Then, the study of disposal concepts basedon the characteristics of solid waste of the Fukushima Daiichi NPS is promoted. Subsequently,
multiple disposal methods are to be presented, and suitable safety assessment methods will be
developed. Furthermore, it is necessary to proceed with studies considering issues such asincreasing the capacity of disposal facilities, the acceptability of various types of waste, anduncertain risks, 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. From this pointof view, the approach will be studied for the case using the preceding overseas examples asreference.
3.2.3.4 OtherAs solid waste to be generated with the retrieval of fuel debris in future, structures such as coreinternals and the outside of reactors to be dismantled and removed and secondary waste such asfilters generated during fuel debris retrieval related works are expected. It should be noted that thiskind of waste may contain α-nuclides derived from fuel debris, it is necessary to proceed with study
21 IRID, FY 2016 supplementary budget “Subsidies for the Government-led R&D program on Decommissioning
and Contaminated Water Management” R&D for Treatment and Disposal of Solid Waste, FY 2017 report, February
2019 http://irid.or.jp/wp-content/uploads/2018/06/2017000₋ 14.pdf

64

on the storage methods for this type of solid waste, along with study on the method of fuel debris
retrieval.
As a long-term challenge, TEPCO is scheduled to develop the decommissioning plan in the third
term after the start of fuel debris retrieval, as later described in Sub-section 3.5.3. At that time,measures against the waste generated from such as dismantling buildings should be establishedbased on the progress and prospect of decommissioning work, the conditions of reactor and otherbuildings, and the latest status of R&D, etc.
Further, as measures for promoting efficient decommissioning, the characterization using quick
measurement (in situ analysis and on-site analysis) by means of spectroscopic methods should be
examined in addition to radiochemical analysis, and necessary R&D in this regard is expected to
be promoted.
3.2.3.5 Summary of key Technical issues
In regard to the technical issues described in this Section, studies will be carried out on theefforts to respective issues with close cooperation between them as shown in Fig. 14, with having
bird’s-eye view of overall management of solid waste

65Fig. 14 Key technical issues and further plans on waste management (Process chart)66

3.3 Contaminated water management
3.3.1 Sectoral target
The near term objectives of measures against contaminated water are as follows.
(1) Under the three basic principles concerning contaminated water issues (“Removing”
contamination sources, “Redirecting” fresh water from contamination sources, and “Retaining”
contaminated water from leakage),22 the reinforcement and optimum operation of the waterlevel control system should be continued. The multilayered measures should be implemented
to complete the processing the stagnant water in the buildings by 2020.1(2) Considering the total decommissioning process including the full-scale fuel debris retrieval
beginning in near future, the long term strategy should be examined for the measures of thecontaminated water.
3.3.2 Sectoral strategies
3.3.2.1 Concept of risk reduction in contaminated water management
Measures have been taken based on the three principles on the issue of contaminated water at
Fukushima Daiichi NPS (“Removing” contamination sources, “Redirecting” fresh water fromcontamination sources, and “Retaining” contaminated water from leakage).
From the viewpoint of measures to reduce the risk due to the radioactive material, safetymeasures for the stagnant water in the building are required as soon as possible. Since thestagnant water is generated from groundwater/rainwater mixed with the cooling water contactedwith the fuel debris, it contains a considerable amount of the dissolved radioactive materials. The
storage conditions of the stagnant water are not inherently and include uncertainties. Thus the
Safety Management of the stagnant water in the buildings is relatively high (refer to Section 2.3).
The stagnant water is recovered and treated with cesium adsorption apparatus (KURION andSARRY), etc., and the radioactive materials are transferred to the water treatment secondary waste
such as adsorption vessels with lower Safety Management.
As measures against risk reduction so far, disconnection of the penetrations between Units 1
and 2 was carried out due to lowering of the water level of residual water in the buildings, and thestrontium-treated water inside the flange tank was treated for purification by multi-nuclide removal
equipment and was transferred to more reliable welded tanks (this was completed in November2018). The risk will be reduced on a continuous basis in the future.

22 Nuclear Emergency Response Headquarters “Tokyo Electric Power Company, Incorporated Basic Policy on
Contaminated Water Problems at the Fukushima Daiichi Nuclear Power Station,” September 3, 2013, Nuclear
Emergency Response Headquarters “Tokyo Electric Power Company, Incorporated Additional measures for the
problem decommissioning and of decommissioning and contaminated water at the Fukushima Daiichi NPS”
December 20, 201367

3.3.2.2 Steady execution of contaminated water management indicated in the Mid-andLong-term Roadmap
Since the Fukushima Daiichi NPS is located in an area with abundant groundwater, thegroundwater flows into the reactor buildings and mixes with the cooling water injected to the fueldebris. This is the main cause of generation of the contaminated water in the site. Treating thecontaminated water and the ground water was urgent issue. Currently, as a result of the preventive
and multilayered measures based on the three principles on contaminated water, the site situation
has shifted from that requiring urgent measures immediately after the accident to certain stablesituation that can examine a mid-and-long-term plan. Those measures are; pumping up highconcentration contaminated water in the underground tunnel (trench), blockage of the trench,
purification by multi-nuclide removal equipment (ALPS), paving (facing) of the site to prevent the
rainwater infiltration to reduce the amount of groundwater, pumping up of the groundwater bypass
system and the groundwater in wells (sub drains) near the reactor buildings, installation of a landside impermeable wall to reduce the groundwater inflow into the area of the reactor buildings,
installation of the sea-side impermeable wall for suppressing the outflow of groundwater into theocean, and soil improvement with the water glass in the seawall area of the ocean-side of thebuildings.
The milestones (major goals schedule) mentioned in the Mid-and-Long-term Roadmap are as
follows: (1) reduction of the contaminated water generation to about 150 m3/day (by 2020), (2)storing all the water treated for purification by multi-nuclide removal equipment in the welded typetanks (FY 2018), (3) by lowering the level of stagnant water in the buildings, separation of thecommunication sections between Units 1 and 2 and between Units 3 and 4, respectively (by 2018),(4) reduction of the radioactive materials in the stagnant water in the buildings up to approximately
one tenth of the amount at the end of FY 2014 (FY 2018), and (5) completion of the treatment of
stagnant water in the buildings (by 2020). As of September 2019, (2) and (3) have been completed.
On the other hand, as to (4), although the quantity of radioactive nuclide that has been processedis higher than planned, with the progress in the processing of stagnant water, a high radioactivity
concentration was detected in the Unit 3 reactor building, etc., making it difficult to perform
assessment. However, efforts will be made to complete the treatment of stagnant water in thebuildings by the end of 2020. It is expected that the specific measures outlined in the Mid-andLong-term Roadmap will continue to be steadily implemented to achieve the milestones.

68

Item/YearFY2015FY2016FY2017FY2018FY2020Stagnant water treatment in the
Current
building is completed except for
Units 1 to 3 reactor buildings
T.P.-400where circulating water injection
is being carried out.

Water level of
Groundwater/building
Groundwater levelNo. 1 T/B only Low
water level1- 4 Building waterlevel

Approx.
T.P.460※3

T.P.-100
Plan for advanceprocessing of Unit 4

Water levels in the building
for main processes /hightemperature incinerationbuilding *2

Building stagnant
water storage

FY2019

T.P.3000

Approx. T.P.-1700

Less than T.P.-1740
Less than T.P.-2240

T.P.-1360▽End of 2014 Almost 86,000 m3▽Approx.33,000m 3

1-4 Buildings andintegrated water
processing buildings▽Approx.12,000m 3
Less than about 6,000m3 △*1 Selection of vacuum pump and so on will be considered depending on the situation at the site.
*2 Water level in the building for main processes is displayed as the representative. In addition, there is a temporary fluctuation due to rainfall because it is used for temporarystorage during heavy rain.
*3 As for subdrains, while maintaining the specified water level difference from the south-east triangle corner of the Unit 3 R/B, which has the highest water level, reducing thewater level in the building is scheduled while assessing the groundwater inflow.
In case the inflow increases with the expansion of water level difference, the reducing of the water level in the building will be suspended.
（Source : TEPCO）

Fig.15 Status of the stagnant water in the buildings23
3.3.2.3 Study on contaminated water management based on the relationship with fueldebris retrieval
As mentioned above, the contaminated water management at the Fukushima Daiichi NPS,
although out of a state where urgent countermeasures are required and it still needs further efforts,
it seems that it has shifted to a certain stable condition where the mid-and-long-term plan can be
examined. Because the full-scale decommissioning work including the fuel debris retrieval will start
after a while, it is necessary to discuss the optimal control of the contaminated water and thegroundwater together at each stage of the decommissioning process. Furthermore, it should
examine a future images of the contaminated water management considering the inherent
measures and the issues to be addressed with a long-term perspective until the completion of thefuel debris retrieval.
At present, as for the stagnant water in the reactor building, a circulating water cooling andpurification system is adopted in which the cooling water injected into the RPV flows into the PCV,the leaked water from the PCV stays in the torus room on basement floor of the reactor building,and this stagnant water is recovered and purified by cesium adsorption apparatus, etc., before
being reused as cooling water. At this time, by controlling the water level of the stagnant water inthe reactor buildings lower than that of the groundwater around the buildings to let the groundwaterflow into the building (in-leak), containment function in the buildings can be secured by preventing
outflow of the radioactive materials to the outside of the building. (Attachment 9).
As described in the preceding Sub-section, according to the target process of the Mid-and-Longterm Roadmap, it is considered that the processing of the stagnant water in the buildings other than
the reactor buildings of Unit 1 to 3 will be completed by 2020. By that time, the circulation watercooling and purifying system needs to be modified to the system that the stagnant water isrecovered in the reactor buildings (instead of turbine buildings) and purified to use as the cooling
TEPCO, “Progress on the stagnant water in the buildings” Handout 4 of 73rd Meeting of the Study group on
monitoring and assessment of specified nuclear facilities, July 22nd , 2019 http://www.nsr.go.jp/data/000277899.pdf

2369

water. It is shifting to such circulation cooling system at the present. It is necessary to consider the
possibility of using a circulating cooling system even for small scale debris retrieval. In addition, it
is important to proceed with the lowering of the stagnant water level in the reactor building and theexamination of the lowering of the water level in the suppression chamber.
In addition, studies are under way on the feasibility of a PCV circulation cooling system by taking
water from the PCV when the scale of fuel debris retrieval is expanded, and also on the water seal
by repairing the lower part of the PCV, etc., from the viewpoint of ensuring the multiple boundaries.
However, it became clear that a complete water seal through repairing the bottom of PCVs is very
difficult. Based on this, in preparation for the inflow of α-particles from inside of PCVs to the stagnant
water in the reactor buildings, the response on the PCV circulation cooling system is needed. Even
if the water shielding is applicable, it is necessary to consider the setting of a sufficient differencein water levels between stagnant water in the reactor building and the groundwater, in case ofcooling water leaks from the PCV into the reactor building.
The details of the containment function of this liquid phase have been described in Sub-section
3.1.3.3.3. In addition to this, requirements from both sides of the fuel debris retrieval work and thecontaminated water management should be clarified and coordinate them in case of items to bereconciled such as the increase of the radioactive materials concentration arose as the fuel debris
retrieval work proceeds.
Also, as the fuel debris retrieval proceeds, when the water injection for cooling the fuel debris
will be no longer necessary, it can be expected that there is no water inflow into the reactor buildings.
In such a case, it is important to plan to develop a system that can stably control the groundwaterlevel for a long period by studying the combination of the dynamic equipment such as pumps, andthe passive equipment with lower potential for machine trouble.

70

3.3.3 Technical issues for promoting sectoral strategies and future plans
3.3.3.1 Steady execution of contaminated water management in the Mid-and-Long-term
Roadmap
Since there are penetrations between the buildings of each unit, the water levels of the stagnant
water in the buildings are almost the same in all buildings. In order to prevent the stagnant waterin the building from leaking to the outside, it is necessary to make the water level lower than the
groundwater level (keep the water level difference). Stable management of groundwater aroundthe buildings has been made by strengthening the function of sub-drains and completing the landside impermeable wall, etc.
By proceeding with these preventive and multilayered measures, the amount of contaminatedwater has been reduced to approx. 170 m3 per day in FY 2018 from approx. 470 m3 per day in FY
2014 24 (Fig. 16). Also, the amount of the groundwater pumped-up from sub-drains and thegroundwater drains in the seawall area have been reduced as well.25
In this way, the condition of contaminated water is being controlled. From now on, further
measures based on the three basic policies should be taken to complete the treatment of thestagnant water while addressing the measures for contaminated water directed by the Governmentled Committee on Contaminated Water Management, and focusing on the problems that have notbeen clarified yet.
(1) Reduction of occurrence of stagnant water in buildings, including countermeasures against
rainwater inflow
Reduction of the generation of the contaminated water to 150 m3/day or less in 2020, which isindicated as a milestone in the Mid-and-Long-term Roadmap, and 170 m3 per day of thecontaminated water is generated based on the result of FY 2018.
In the future, further effort to reduce the generation of the contaminated water should becontinued by implementing the multilayered countermeasures such as stagnant water treatment in
the buildings, lowering the sub-drain water level, measures against inflow of rainwater into thebuildings. Further measures continuously need to be taken in the future, such as the suppressionof the inflow of groundwater and rainwater through the repair of the building roof and the water sealof the connecting trench, and the suppression of rainwater infiltration into the soil through facingson the T.P. 6 m and T.P. 8.5 m panels. Further, as to the facing on the inside the land-side
impermeable wall, while coordinating with other works, the measure needs to be carried out fromthe area where it is possible to work on. As for the inflow26 of groundwater into the site banker

24

Average from May 2014 to March 2015.
“Evaluation of Frozen Soil Wall and further Contaminated Water Management”, Government-led Committee on
Contaminated Water Treatment, issued on March 7, 2018
http://www.meti.go.jp/earthquake/nuclear/osensuitaisaku/committtee/osensuisyori/2018/pdf/020_s04_00.pdf
26 This is because the amount increased from approx. 5 m3/day to approx. 40 m3/day since mid-November 2018.
https://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/08/3-1-2.pdf
2571

building outside the land-side impermeable wall, water blockage has completed at the inflow points
confirmed in 2018, it should be suppressed continuously.
1000

Start operation of
地下水バイパス稼働開始
groundwater
bypassAverage
Daily Inflow
日平均量Completefreezing land-side
陸側遮水壁(海側)凍結完了
impermeable wall (sea side)

Inflow amount of groundwater/storm※
2
建屋への地下水・雨水等流入量※2sewage into the buildings

Completion of 深部の一部を除き
land-side impermeable wall,
except for a portion of the deep part, and
陸側遮水壁完成と評価
assessment

40(Freezing of three deep unfrozen areas will be completed by（深部未凍結箇所3箇所については、2018年9月までに凍結完了）
September 2018.)30

600
Approx.490
約490

Approx.470
約470

※1

Approx.400
約400

400

20

Approx.350
約350

Approx.220
約220

Approx.
170
約170

Approx.270
約270

200

10

Approx.200
約200
Approx.140
約140

日平均降雨量（福島第一）Completeclosing sea海側遮水壁閉合完了
side impermeable wall

50

Generatedamount of contaminated water*2
汚染水発生量Start closing land-side impermeable wall
陸側遮水壁凍結開始

800

mm/daymm/日Amount of rainfall of Fukushima Daiichi
福島第一降雨量

Start
operation of sub-drain
サブドレン稼働開始

Average Daily Rainfall （Fukushima Daiichi）

3/日
m3m/day

Approx.100
約100

0FY20142014年度

2015年度FY2015FY20172017年度

2018年度FY2018

Jul
7月

May
5月

Jan
1月

Mar
3月

Nov
11月

Jul
7月

Sep
9月

May
5月

Jan
1月

Mar
3月

Nov
11月

Jul
7月

Sep
9月

May
5月

Jan
1月

2016年度FY2016

Mar
3月

Nov
11月

Jul
7月

Sep
9月

May
5月

Jan
1月

Mar
3月

Nov
11月

Jul
7月

Sep
9月

May
5月

Jan
1月

Mar
3月

Nov
11月

Jul
7月

Sep
9月

May
5月

0

ov

2019年度FY2019*1：The values are different from the announced one in the 20th Government-led Committee on Contaminated Water Treatment held on August 25th, 2017
due to the review of the calculating method of the generated amount of contaminated water on March 1, 2018. The detail of the review is indicated in thehandouts of the 50th and 51st meetings of Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water Treatment*2：The daily average amount per month is calculated from the amount per day from previous Thursday through Wednesday added up based on the datameasured at 7:00 every Thursday.

(Courtesy of TEPCO27)

Fig. 16 Transitions in the generated amount of contaminated water and the inflow amount ofgroundwater/rainwater, etc., into the buildings(2) Work associated with the lowering of the water level in the building due to the progress oftreatment of stagnant water in the building
As progress is made in the treatment of stagnant water in buildings, high concentrations ofradiation are being found. When continuing to work on the treatment of stagnant water in thebuilding, the inventory water level needs to be reduced. On the other hand, when there is a largechange in the concentration of radiation, the stable operation of the cesium adsorption apparatus
may be hindered, it needs to be treated on a continuous basis while observing the concentrationof radiation in stagnant water in buildings. Further, in the area where oil content is observed on thesurface of the stagnant water, it is necessary to collect the oil content before exposing the floor
surface so that declines in performance of the contaminated water treatment equipment can beprevented, and this will be carried out adequately.
After radiation exposure of the floor surface, there is also a concern that dust may be generated
because of drying of sludge on the floor, and it is necessary to monitor the work of closing openings,
the status of generation and scattering of dust, and the total α concentration in sludge. In particular,
there will be work such as installing pumps to the floor drain sump to expose the lowest floor surface
and transferring and processing the remaining water in the isolated area. Accordingly, after
exposing the floor surface of the intermediate part on the lowest floor, in order to suppress theradiation exposure dose of workers, the radiation dose needs to be reduced.
27

Handout 2 of “Overview of Decommissioning and Contaminated Water Treatment”, the 69th meeting of
Secretariat of the Team for countermeasures for Decommissioning and Contaminated Water Treatment,
August 29, 2019http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/08/2-1.pdf

72

(3) Enhanced contaminated water management installations
It is essential to appropriately maintain and reinforce the established water level management
system and the purification equipment, including the land-side impermeable wall and sub-drain.
As for subdrains, there was a case in which the issue of influence to the operation due to rising
tritium concentration in some of the subdrains. Considering these issues, measures need to betaken, such as groundwater quality surveys and soil improvement as required, while continuing
appropriate management and operation.
The land-side impermeable wall is sequentially shifting to maintenance operation that allows tostop circulation of coolant according to the soil temperature, it has completed in all the area inFebruary 2019. From the planning stage, the material is designed to maintain its functions throughmaintenance and replacement in consideration of the long-term operation of the frozen soil wall.
However, to continue the operation for a long time, in addition to daily and regular inspections, it isimportant to renew the system appropriately and to consider a systematic replacement andconstruction plan.
3.3.3.2 Study on contaminated water management based on the relationship with fuel debris
retrieval
As described in Sub-section 3.3.2.3, there are matters to be adjusted between retrieval of fueldebris and contaminated water management. As problems to be solved, there are concerns that
deposit at the bottom of the PCV reduces the visibility of the water when retrieving fuel debris andincreases the processing load of the purification equipment (especially, removing solid particles).
In the case of small-scale retrieval, it is assumed that the existing purification system such as
cesium adsorption apparatus will be used, however, fuel debris-derived materials containing αparticles may be mixed. Therefore, it is necessary to examine the entire system, such as checking
status of α-nuclides concentration in the existing purification system, and the impact of α particulate
on the system, enhancing monitoring to check the concentration of radioactive materials at the inletof the water treatment system, and the installation of systems to reduce the concentration ofradioactive materials.
When expanding the scale of fuel debris retrieval, establishment of a PCV circulation coolingsystem will be examined but, at this time, the material derived from fuel debris that contains αparticles will be mixed. Therefore, it is necessary to properly remove α-particles in the PCV
circulation cooling system. Since the groundwater flows into the buildings continuously, a part of
the water treated by the PCV circulation system will be sent to the existing circulating water coolingand purification system in order to maintain the water balance. There is a possibility that the water
will be treated with equipment such as multi-nuclide removal equipment. Therefore, it is necessary
to monitor the α-nuclides concentration of the stagnant water in the reactor buildings and to set theconditions for receiving a part of water treated by the PCV circulation cooling system in the existing
circulation water cooling and purification system in parallel with considering the system.

73

In addition, to maintain the effectiveness of contaminated water management in the future, it isnecessary to conduct regular inspections and renewals of facilities, and to further expand themonitoring system for groundwater level and radioactive materials (observation points, observation
frequency, data management, etc.) to control the groundwater around the buildings in a stablemanner. It is also necessary to consider necessary contaminated water management while taking
into account the risk of large-scale natural disasters such as tsunamis and torrential rains, and therelationship with future decommissioning work.
3.3.3.3 Summary of key Technical issues
The main technical subjects and plans described in this section are summarized as shown in
Fig.17.
Fiscal Year

Milestone

2019

2020
2021
Reduction of the contaminated water
generation to about 150 m3/day

REDIRECTING fresh water fromcontamination sources2023

On‐site work
Technical studies for on‐site construction ineach item

Completion of the treatment of
stagnant water in the buildings

REMOVING contamination sources
Maintain additional effective
radiation dose at the site boundaries
at a level below 1 mSv/year2022

Treatment with purification Systems
Reducing the total amount of contaminated water to about 150 m3 per day

Controle by groundwater by-pass, subdrainage and land-side impermeable walls

Reduce the contaminated water
generation to about 150 m3/day by
average rainfall

Paving the site, Removal of rubble fromthe roof, Waterproofing

RETAINING contaminated water fromleakage

Securing Tank capacity

To be responded properly according to generation of contaminated water, etc.

Ground stabilization, Maintenance of land-side impernmeable wall , Monitoring of groundwater/inside harbor
Completion of stagnant
water in the buildings

Treatment for the stagnant water inthe buildings

Contaminated water management
based on the relationship with fueldebris retrieval

Lowering the level of groundwater/ stagnant water in the building
Determination of fuel debris retrieval
methods for the first implementing unit

Maintaining exposed condition of thefloor line for turbine buildings

Start of fuel debris retrieval at
the first implementing unit
Taking required actions in accordancewith the phase of fuel debris retrival

Study for consistency between existing circulation cooling system
and PCV circulation cooling systems and monitoring method

Fig.17 Technical issues and further plans on contaminated water management (Process Chart)74

3.4 Fuel removal from spent fuel pools
3.4.1 Sectoral target
The immediate objectives of fuel removal from the spent fuel pool are as follows.
(1) Risk assessment and management for the progress of the work will be carried out properly,
and measures for safety and security including the prevention of scattering of radioactive
materials will be taken thoroughly. For Units 1 and 2, the removal of fuel from the SFPs will
start by 2023. For Unit 3, the removal is scheduled to be completed within FY 2020.
(2) By transferring the fuel stored in the common spent fuel storage pool to the dry cask temporary
custody facility, the fuel in the spent fuel pools of Units 1 to 4 is to be stored in the common
spent fuel storage pool appropriately.
(3) Based on the assessment of the long-term integrity and investigation for future treatment of
the removed fuel, the storage and future treatment methods of them will be fixed around 2020.
3.4.2 Sectoral strategies
3.4.2.1 Risk reduction concept and concrete plan for removing fuel from SFP
The fuel assemblies (fuel in SFP) stored in the spent fuel pool of the reactor buildings of Units
1 to 3, some of which were damaged by hydrogen explosions, etc. are relatively high risk sources(see Section 2.3). From the viewpoint of reducing risks due to radioactive materials, the fuel is kept
in a solid state so as not to diffuse when confined in the cladding tube. Furthermore, even though
the decay heat of spent fuel is decreasing and coolant supply stops, the time until the pool water
evaporates and the fuel assemblies start to be exposed becomes relatively longer. Moreover, since
it is a nuclear fuel material with a substantial amount of inventory, there is a certain level of hazard
potential impact. In addition, due to damage to the cooling facility due to the accident, and damage
to the reactor buildings at Units 1 and 3, the same functions as the conventional containment
function and management function are not completely secure and Safety Management is also
high28. For this reason, it is planned to transfer them immediately to the common spent fuel storage
pool that is sound and of low Safety Management as shown in Fig. 5.
On the basis of this, it is necessary to draw up an appropriate and concrete work plan based ona sufficient understanding of the situation at each reactor unit and to respond carefully. Especially,
return of the local residence and reconstruction approaches began after the first evacuation
instruction has released in the locating municipalities of Fukushima Daiichi NPS in April 2019.
28 Since the number of spent fuel assets held by each unit is different, there are slight differences in the degree of
hazard potential impact. Due to the rubble status in SFPs and on the operation floor, as well as the damage to thereactor building, in terms of the diffusion suppression function, Unit 1 is inferior to Unit 2 where the upper part ofthe building has not collapsed. Unit 3 is superior to Unit 2, considering the installation of the fuel removal cover in
SFP and the status of maintenance of the operation floor. In addition, there are failed fuels in Unit 1, and it is judgedthat it can affect the removal. There are differences in safety management among these.

75Considering these circumstances, careful approaches focusing on safety more are necessary
against dust dispersion, and the like. For example, in Unit 1, there is rubble on the operating floor.
Considering that there are operational risks such as rubble falling into the spent fuel pool during
the rubble removal work, as well as the impact of dust scattering on the surrounding area andworkers, it is necessary to carefully prepare for the removal of fuel from SFPs.
As for the fuel in SFPs, the testing on SFP cooling shutdown was performed, and it was
confirmed that the rise in water temperature after cooling shutdown was slower than expected. As
a result of incorporating this insight, the risk of fuel in SFPs is lower than previously estimated,because the time margin before this risk becomes apparent increases.
3.4.2.2 Specific plan for fuel removal from SFPs
Work schedule for fuel removal in Unit 1 to 3 SFPs was already specified in the Mid-and-Longterm Roadmap, and TEPCO has been proceeding with their tasks to meet this schedule.
In Unit 1, the roof slabs, steel frame building materials for the upper part of the buildings andfuel handling machine were scattered around the operating floor. The removal work for this rubble
started in 2018 and has been continuing, and the removal of fuel from the SFP is scheduled to startin FY 2023.
In Unit 2, in order to install the fuel removal facility, based on the surveillance on radiation doseon the operating floor conducted in FY 2018, a method to access the operating floor is being
considered, and fuel removal from the SFP is scheduled to start around FY 2023.
For Unit 3, there were some delays due to dealing with malfunctions of the fuel handling machinein the test runs. However, the fuel removal work from the SFP was started since April 2019 basedon the safety first policy towards the completion of removal within FY 2020.
Unit 4 was under periodic inspection at the time of the accident, so all fuels were kept in the
SFP without suffering significant damage. Although the rubbles had fallen into the SFP due to the
influence of hydrogen explosion, after carefully installing a cover for fuel removal from the SFP,
installation of a frame for supporting the crane was performed and the fuel removal work from the
SFP started prior to other units and was completed in December 2014.
The fuel in Units 5 and 6 SFP are being stored under stable conditions same as a normal nuclear
power plant. The Mid-and-Long-term Roadmap states that the fuel of Units 5 and 6 SFP should beproperly stored in each SFP for the time being and should be removed from each SFP so as not toaffect operations of Units 1 to 3. Part of new fuel is planned to be transported to a fuel processing
manufacturers, but the spent fuel should be removed at an appropriate time in view of the capacityof the common spent fuel storage pool and the dry cask temporary custody facility.
While conducting the above-mentioned safety measures properly, fuel removal operations from
SFPs should be carefully and steadily pursued by fully considering the status of each unit. Althoughthese efforts are first examined according to the condition of each unit, as a whole, operation space(yard) adjustment and resource management, etc. between interfering operations are necessary.
Also, when removing fuel handling equipment, it is necessary to reuse or treat waste. Based on the76

above and on the technical considerations described in Sub-section 3.4.3, detailed build plans
should be considered from the viewpoint of global optimization described in Section 3.6.
3.4.2.3 Storage plan for removed fuelFor removal of fuel from SFPs, appropriate storage capacity should be reserved both in thecommon spent fuel storage pool and the dry cask temporary custody facility. As of now, despite
there is sufficient free capacity to transfer fuel of Unit3 SFP in the common spent fuel storage pool,additional capacity to transfer fuel of Units 1,2, 5 and 6 SFPs is insufficient (Fig. 18). Accordingly,
it is necessary to advance the expansion of the dry cask temporary custody facility etc. and tosecure the spare capacity by transferring the fuel out of the site. Incidentally, in terms of design,
dry casks store fuels that satisfy conditions such as fuel type and cooling duration. Among the fuels
currently stored in the common spent fuel storage pool, those that satisfy the conditions and havea relatively long cooling period are to be stored.

Number of spent fuel, etc.

10000
Number in the capacity
available as of now in entire
common spent fuel storage pooland dry cask temporary
custody facility : 1563

8000

Unit 3 (under transportation):
538 remained

For fuel removal from
Units 1, 2, 5 and 6 (4433),
it is necessary to ensure
storage capacity of dry
cask temporary custodyfacility and to consider
exporting fuel to off-site.

Vacancy: 666

6000
In all Units 1, 2, 5 and 6: 44334000
Storage6133
Vacancy: 897

Unit6:
1884

2000
Unit3:538
Unit2:615

0

Unit1:392

Units 1-3 SFP

Unit5:
1542

Units 5/6 SFP

Common Spent Fuel
Storage Pool

Storage2033

New Fuel to be exported：360(Plan)

Dry Cask Temporary
Custody Facility

Export to off-site(nuclear fuelmanufacturer)

Fig. 18 Storage situation of spent fuel, etc. (as of August 29, 2019)
3.4.2.4 Decision on future treatment and storage methods
The fuel in SFPs includes many kinds of spent fuel such as damaged spent fuel before theaccident by embrittlement of the cladding tube and falling of the fuel body, and that may bedamaged by the fallen rubbles into the spent fuel pool, as well as flawless one. There was also ahistory of seawater injection into the spent fuel pools of Units 2, 3 and 4 when the accident occurred.
Although the effects on long-term integrity and treatment of spent fuel due to this are expected tobe small, it is necessary to identify and confirm whether there are technical factors that impedes
the same treatment as ordinary spent fuel.
In the future, considering the status of fuel removed from Unit 3 SFP, future treatment and77

storage methods for such fuel will be decided around FY 2020 based on the investigation results
on long-term integrity assessment and treatment method for them.
3.4.3 Technical issues for promoting sectoral strategies and future plans
3.4.3.1 Removal of fuel from SFPs
(1) Items common to each unit
Operating floor dosage reduction measures are necessary in order to limit operation exposure
during the installation work of fuel removal installations (fuel removal cover, fuel handling equipment,etc.), manned work during removal work, maintenance check of installations and so forth.
Meanwhile, depending on the dosage reduction condition, it is necessary to reflect shielding to
instrument design related to removal and introduction of remote devices, etc., based on experiencesuch as decontamination in other units, it is necessary to determine the final operational dosage at
an appropriate time.
Also as stated in Sub-section 3.4.2.2, there are a number of things to be prepared in parallel,such as fuel removals from SFPs of both Units 1 and 2 that start for FY 2023, preparation work on
fuel debris retrieval at the time of removal of fuel from Unit 3 SFP. Therefore, it is necessary toadjust yards (securing flow line) with interfering works and resources management and to preparea detailed construction plan. As described before, fuel of Units 5 and 6 SFPs should be removed
in appropriate time. In case such operations use common spent fuel storage pool, adjustment isrequired as such removal work becomes not to affect fuel removal work, etc. of Units 1 to 3.
(2) Unit 1 fuel removal from the SFPFor Unit 1, the roof collapsed due to the hydrogen explosion and has accumulated as rubble on
the operation floor, and the fuel handling machine (FHM) and the overhead crane that are deformed
and damaged are covering the spent fuel pool. When removing rubble, it is important to takemeasures against rubble, the FHM, and the overhead crane falling onto the spent fuel pool. The
necessary work, such as protection for the spent fuel pool and support for the overhead crane,
needs to be carefully performed over a certain time. In addition, with the progress of the rubble
removal work, it is considered that the status of the site, such as the distribution of rubble, will be
revealed. Therefore, it is necessary to make steady progress in the work step by step based on theonsite information.
In addition, from the viewpoint of the impact on the surrounding environment, it is necessary totake measures against dust dispersion at the time of removal of the rubble and for the removal of
rubble on the well plug. It is confirmed that the well plug is shifted from the original position and, on
the plug, and the radiation dose rate of approx. 200 mSv/h is confirmed, making it difficult to getclose to the area easily. Further, there is a concern of skyshine (the effect that the radiation going
upward from the radiation source falling to the ground surface due to diffusion in the air causing
the dosage near the surface to rise). Hence, rubble removal should be promoted while coordinating
safety measures such as preventing dust dispersion and radiation dose monitoring and following
78

that, action should be taken for the well plug based on the investigation results of the condition of
the well plug and its contamination status, which has been conducted from July 2019.
Regarding the 67 fuel bodies damaged by the cladding stored before the earthquake, although
the radioactive material concentration in pool water before the earthquake was also sufficiently low,
its influence is considered small, but appropriate response is required for handling when removal.
(3) Unit 2 fuel removal from the SFP
In the case of Unit 2, based on the plan to dismantle the entire upper part of the operating floorof the reactor building, examination was carried out for the plan to share the container for removing
fuel from SFP with the container for fuel debris retrieval, as well as the plan to install a cover for
removing fuel from the SFP individually. In addition, from the viewpoint of safe and stable
construction, a plan has been examined, that includes the construction method of accessing fromthe south side of the reactor building to reduce risk of dust dispersion during the dismantling ofbuilding, without dismantling the upper part of operating floor as much as possible.
When selecting a plan for removing fuel from the SFP, it is needed to comprehensively consider
the feasibility with dust dispersion countermeasures, securing safety in the surrounding
environment, ensuring the safety of workers, measures against rainwater, and the other work to be
conducted concurrently.
As mentioned in Sub-section 2.3.3.3, there is an exhaust stack of Units 1/2 in the vicinity of Unit
2. There is a possibility that radioactive materials, mainly cesium released from the accident, areattached to the inside of the stack and that the joints of diagonal bracing of the steel towers
supporting the exhaust stack are broken or deformed. Therefore, the collapse of the exhaust stack
may affect the fuel removal process from the SFP. Based on this, prior to the removal of the fuelfrom the SFP, the dismantling of the upper part of the exhaust stack using a remote device has
started from August 2019 and is to be completed within FY 2019.
(4) Unit 3 fuel removal from the SFP
As for Unit 3, malfunctions in the fuel removal device caused a significant delay in starting theremoval work as described in the initial plan. However, of the fuel in the SFP, removal of 28 newpieces fuel from the SFP was started in April 2019, which has been transferred to the common
spent fuel storage pool. For the remaining fuel in the SFP, steady progress should be made tocomplete the removal within FY 2020.
3.4.3.2 Proper storage of removed fuelFor systematic transfer of the fuel in SFPs retained at the entire site to the common spent fuelstorage pool, a fuel transport plan needs to be developed, taking the fuel stored in Units 5 and 6
into account, and the installation of an additional dry cask temporary custody facility according to
the plan is needed as well.
In particular, when retrieval of fuel in Units 5 and 6 SFPs precedes other units, it is necessary
to take measures such as additional installation of dry cask temporary custody facilities by the79appropriate time so as not to put pressure on the capacity for transferring fuel in Units 1 and 2
SFPs to the common spent fuel storage pool. As mentioned earlier, some of the new fuel is planned
to be moved to the fuel processing company and it is important to secure the capacity of thecommon spent fuel storage pool by these efforts.
3.4.3.3 Decision of future treatment and storage methods
As described in Sub-section 3.4.2.4, if there are technical matters necessary for treating theremoval fuel as equivalent to ordinary spent fuel for long-term soundness assessment andprocessing of the extracted fuel, it is necessary to organize and identify the same.
So far, in the Government-led R&D program on Decommissioning and Contaminated Water
Management, R&D on the long-term integrity of the fuel in SFPs which has contacted with seawateror fallen rubble has indicated that removed fuel can be stored safely under the environment of thecommon spent fuel storage pool for a long period. Also, it was confirmed that the effect of seawaterand scratches by fallen rubble on the fuel is limited for integrity of stored fuel in the dry cask. In
addition, proposals have also been made regarding a fuel inspection method for dry storage.
Furthermore, another R&D on potential for processing retrieved fuel in SFP showed a technicalperspective that the impact to fuel by earthquake disaster including contamination of chloride ionsand concrete is very limited.
In the future, necessity of further study on possibility of its long term storage and processing
need to be evaluated based on the investigation results of the fuel taken out from Unit 3, which isexperienced the hydrogen explosion caused during the accident and may be damaged by the fallen
rubble.
3.4.3.4 Summary of key Technical issues
The major technical issues and future plans described in this section are summarized as shownin Fig. 19.

80

Fiscal Year

2019

2020

2021

2022

Milestone
Unit 1
Unit 2

2023

2024

2025

Start of fuel removal from Unit 1 (by FY2023)
Start of fuel removal from Unit 2 (by FY2023)
Cover installation, etc.

Rubble removal, etc.
Investigation ofoperating floor, etc.

Fuel removal

Dismantlement and modificationof upper part of the building, etc.

Fuel removal
Construction, etc.

(Selection of retrieval
plan for Unit 2)
Unit 3

Selection and examination
Submit/Approval request to
implementation plan/Preparation work

Fuel removal
On-site work

Disassembly of upper part of
exhaust stack for Units 1/2

Surrounding environment

Proper storage ofremoved fuelTechnical studies for on-site constructionin each item

Measures to preventsea contamination, etc

Procurement of dry cask
Transfer of dry casks from the common spent fuel storage poolto the dry cask temporary custody facility
Fuel removal from Units 5 and 6
Implemented to the extent not affectthe operations on Units 1 to 3
Installation of additional dry cask temporary custody facility

Study on future
treatment and storage
methods

Determination of future treatment and storing
method of removed spent fuel (around FY 2020)
Study on long-term integrity inconsideration of fuel of Unit 3
Study on treatment and storing methods

Fig.19 Technical issues and further plan on removing fuel from the spent fuel pool (Process chart)81

3.5 Other specific measures
3.5.1 Sustaining of reactor cold shutdown status
Currently, the plant conditions in Units 1, 2 and 3 are judged to be in a stable cold shut-down
status based on the internal PCV plant data monitored continuously since the accident, including
radiation dose, temperature, hydrogen concentration, pressure, and radioactive material
concentration, etc. As an example, the concentration of Xe-135, a continuously monitored shorthalf-life fission product, does not exceed the criticality level of 1 Bq/cm3, showing no signs ofcriticality 29 . Because fuel debris generates decay heat, it should be continued to monitor
parameters in PCVs and seal nitrogen to reduce a risk of a hydrogen explosion, while maintaining
and improving reliability through maintenance and management, to maintain the stable state in the
future.
Considering the fact that the decay heat of fuel debris seems to have decreased significantly, in
April 2019, a test was conducted at Unit 2 that is highly reliable in measuring the temperatures of
the RPV bottom surface and the PCV to halve the flow rate of reactor water injection for fuel debris
cooling for about a week. In May in 2019, a test was also conducted to stop the injection of water
into the reactor for about seven hours, and it was confirmed that there was no abnormality with thestatus of cooling reactors. With this, the actual condition of the cooling condition of fuel debris isgrasped, and improvements such as the optimization of the emergency response procedures are
expected to be made. From the viewpoint of reducing the burden of contaminated water
management and reducing the criticality risk, as alternatives for examination, cooling fuel debris by
air can be considered. However, the internal information on the plant that is available as of now is
considered to be still insufficient to judge the appropriateness, and this matter will continue to be
examined.
3.5.2 Radiation dose reduction and contamination expansion prevention all over the power
station
3.5.2.1 Prevention of sea contamination expansion
Immediately after the accident, radioactive materials flowed out to the port, as can be seen fromthe fact that high-concentration contaminated water in the turbine buildings flowed out through theunderground trenches. To tackle this problem, emergency measures were taken, such as soil
improvement in contaminated areas, pumping up of underground water, and removal of highconcentration contaminated water in trenches. Fundamental measures were also taken, such as
installation of the sea-side impermeable wall and covering of the seabed soil including radioactive

29

For example, refer to the in-core condition data and diagrams (at the portal website for Decommissioning R&D
Information) at http://www.drd-portal.jp/assets/files/current_data_jp.pdf. The website posts the in-core condition
data released by TEPCO regarding the Fukushima Daiichi NPS (each unit's in-core temperature, dose rate, feedwater rates, Xe concentration, etc.).

82

materials. As a result, the radioactive material concentration in the port was lowered to 10 Bq/L,
although it rises slightly when rain falls (in the open ditch, Pu-137) (20). It is lower than the limit
concentration specified by the radiation dose regulations announcement for the area outside the“warning area” (average three-month concentration: Cs-134, 60 Bq/L; Cs-137, 90 Bq/L). (Fig. 20)
Because of these various measures, the ingress of radioactive materials into the port water has
been strictly controlled; however, even today, the concentration of radioactive material in the portrises when it rains. It is therefore important to suppress the ingress of contaminated surface waterby way of drainages. In particular, the radioactive material concentration in drainage K, which runs
near the buildings, is higher than that in drainages A, B and C, and the concentration in drainage
K rises when it rains. Thus, the radioactive materials eluted from contaminated rubble or the laidsand on the top of the buildings or rubble on the Tokyo Peil (T. P.) 8.5-meter bed, and eluted
radioactive materials from the bed, are considered to be reaching the water in the port from thebranch pipes of drainage K. Based on this supply mechanism, measures for reducing theconcentration of radioactive material in the drainage channels that flow into the port need to becontinued to further reduce the concentration, such as installing a purification system in the Kdrainage and cleaning, measures against rainwater ingress from the top of the buildings, andpaving around the buildings.
Because soil near the port has contaminants in the shallow layers, the long-term environmental
impact evaluation involves technical challenges; namely, unlike the relocation analysis of thegeological disposal of high-level radioactive waste, knowledge of which been obtained, theinfluence of unsaturated layers and the effect of adsorption reaction rates need to be considered.
It is important to continue R&D such as understanding the migration mechanism of nuclides andrefinement of analytical models with a view to long-term impact assessment on the futureenvironment restoration30.

30

Refer to “(6) Environmental fate studies of radioactive materials generated during decommissioning” included in
Attachment 15.

83

Fig.20 Radioactive material concentration in seawater in the port
3.5.2.2 Management of gas and liquid waste
The Mid-and-Long-term Roadmap specifies that monitoring of gas and liquid waste should becontinued and its emission should be closely controlled to ensure that the concentration limits
defined in the Notification is strictly observed. With this view, proper countermeasures should betaken as their concentrations are made as low as possible based on a reasonable methods.
For the control of air release, centralized control by the monitoring system of exhaust stacks
cannot work because of the impact of the accident, the PCVs of Units 1 to 3 are continuously
monitored with gas control equipment (dust monitors and gas monitors), while the reactor buildingsof Units 1 to 4 are continuously monitored with equipment (dust monitors) installed in the upper
part of the building or nearby. The release control target from Units 1 to 4 is set to a total Cs-134
and Cs-137 of 1.0 x 107 Bq/h, and it is confirmed that the dust monitors near the boundaries of thepremises indicate values lower than the concentration limit for the outside the surrounding
monitoring area, and the radiation dose evaluation is conducted once a month. When the emissions

84

from Units 1 to 4 are 1.0 x 107 Bq/h, the effective radiation dose evaluation value near theboundaries of the site should be 3 x 10-2 mSv/year. The effective radiation dose (radiation exposuredose) evaluation based on the actual measurements of March in 2019 was about 2.2 x 10-4
mSv/year, indicating that air release is controlled at a sufficiently low level (Fig. 21).

Fig.21 Evaluation of annual radiation exposure dose at site boundaries due to radioactive
materials (Cesium) emitted from Units 1 to 4 reactor buildings31
Regarding drainage control of the water purified after being pumped up from the sub-drains andunderground water drains, four major radionuclides: Cs-134, Cs-137, Sr-90, and H-3, plus 44 otherradionuclides have been selected for control based on the core inventory and other related
information, as significant target radionuclides for radiation exposure evaluation.
 Before water drainage, it should be checked that the concentrations of four major nuclides
are below the standard values32.
 A monthly analysis with a lowered detection limit concentration should indicate no
significant increase for the six indicators, which are the four major nuclides, all beta and allalpha emitters.
 It should be checked quarterly that the sum of the ratios to the notified concentration limitsof all the target nuclides for confirmation is less than 0.21.
As described above, drainage is strictly controlled. In addition, nuclides with the notified
concentration limit ratio of 0.01 or less, isotopes of Cs-137 with very small radiation dose
contribution and daughter nuclides are excluded from the nuclides to be checked. In the application
for change in April 2017, the number of nuclides to be checked was 41, including the four major
nuclides.
The underground bypassed water pumped up on the mountain side before entering the reactor
buildings is temporarily stored in tanks, and is released after checking that it satisfies theoperational target; namely, the notified limit concentration rate of less than 0.22.
3.5.2.3 Radiation dose reduction through the site decontamination
Of primary concern immediately after the accident was the workers’ radiation exposure in the31

Reference 2 : Overview of decommissioning and contaminated water treatment from The secretariat Meeting of
69th Team meeting on decommissioning and contaminated water treatment, August 29, 2019,http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/08/2-1.pdf
32 The standard values are as follows: Cs-134 and Cs-137 < 1 Bq/L; Sr-90 < 5 Bq/L; and H-3 < 1500 Bq/L

85

Fukushima Daiichi NPS. Possible causes were fallout contamination across the entire site anddirect radiation from the plant. In March 2014, TEPCO formulated “Implementation Policy ofRadiation Dose Reduction on the Site of the Fukushima Daiichi NPS”33 and set target radiationdose rates in stages for each area in the sites to reduce the radiation dose. As a result of theremoval of high radiation dose rubble, decontamination and shielding by cutting down trees,
removing topsoil and facing, etc., the target radiation dose equivalent rate of 5 μSv/h was achievedat the end of FY 2015 in the areas around Units 1 to 4 as well as the areas where many workers
are working, excluding the waste storage area, and radiation dose reduction has been progressing
since then. In the vicinity of Units 1 to 4, the area where workers can work with general work clothes,etc. has expanded to about 96% of the entire site due to the identification of the radiation sourceby directional monitoring and the progress in the installation of shields. In addition, from October
2018, it became possible to move between the seismic isolation building, rest center near the west
gate, and access control building without additional equipment.
Improving the radioactivity environment and labor environment in the site is essential for
protecting workers’ health and safety (refer to Section 4.1). TEPCO should continuously maintainan average level of 5 µSv/h or under as specified in the Mid-and-Long-term Roadmap and should
gradually reduce the target radiation dose equivalent rate to ultimately reach the pre-accident level.
3.5.2.4 Reduction of environmental impact
As to the radiation dose evaluation at the boundary of the site (“effective radiation dose”),
encompassing additional emissions from the entire site, attained the target radiation dose of 1
mSv/year or less was attained at the end of FY2015, as a result of the previously described efforts
to reduce the radiation dose and prevent the expansion of contamination; namely the purificationof high-concentration contaminated water described in Section 3.3, adequate storage of solid waste
specified in Section 3.2, and the entire risk inspection including the inspections described below.
Since then, 1 mSv/year or less has been maintained, and at the end of FY 2018, it was 0.90
mSv/year (Fig. 22).

33 TEPCO, “Efforts for Dose Reduction inside the Fukushima Daiichi NPS”, presented as Handout 3-2 at the 19th
Meeting of The Committee on Supervision and Evaluation of the specified Nuclear Facilities (March 31, 2014).
http://www.nsr.go.jp/data/000051045.pdf

86

(Source : TEPCO)

Fig.22 Effective radiation dose evaluation at site boundaries34
Besides high-concentration contaminated water, other water with radioactive materials has beenthoroughly inspected as a risk that may have an impact on areas outside the site, and efforts suchas contaminant removal and drainage cleaning are being made. Solid waste such as rubble isreduced in volume where possible and is placed indoors to eliminate temporary outdoor storage
areas. The effective radiation dose at the boundary of the site contributes not only to the direct
radiation doses from radiation sources on the premises but also to the radiation emitted upwardfrom sources, dispersed in the air, and radiated down to the surface soil. It is therefore importantto adequately control and shield the radiation sources. Risk reduction outside the site of the
Fukushima Daiichi NPS is continued through such efforts, to retain the effective radiation dose ofunder 1 mSv/year.
The representative individuals in the radiation dose evaluation for public protection should beselected from among those with relatively high exposure, in consideration of actual lifestyle habits
and environmental conditions in the vicinity of the site. Intermediate radioactive waste storage
facilities are placed near the Fukushima Daiichi Power Station, and the representative individuals
should be realistically selected from this perspective. Setting control targets and evaluation
conditions is desirable. Discussion is desirable from the viewpoint of the possible integration of the2007 Recommendations35 of the International Commission on Radiological Protection (“ICRP”)
into Japanese law.

34 TEPCO, “Dose Conditions in the Fukushima Daiichi NPS Buildings”, presented as Handout 3-6 at the 65th

Meeting of the Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water
Treatment, April 25, 2019http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/04/3-6-2.pdf
35 The International Commission on Radiological Protection (ICRP), The 2007 Recommendations of theInternational Commission on Radiological Protection, ICRP Publication 103, Annals of the ICRP, 37 (2-4), (2007).

87

3.5.2.5 Comprehensive risk review
TEPCO conducted a comprehensive inspection of risk sources that may affect the outside of
the site, and systematically established the following six categories of additional measures mainly
for leakage passages (liquids confining radioactive materials) and for work (dust), and announced
them in April 2015: (1) Research required; (2) Measures required; (3) Measures being taken; (4)Conditions being observed after implementation of measures; and (5) Measures not presently
required. As a result, for the radiation sources requiring additional measures, specific measures
were discussed while taking priorities into consideration. They were reviewed as appropriate
reflecting environmental changes, and have been explained and announced at places such as the
local adjustment meeting for decommissioning and contaminated water management.
Also, the Nuclear Regulation Authority created a target map for reducing the mid-term risk of the
Fukushima Daiichi NPS in February 2015. This Mid-term risk reduction target map, which has been
updated from time to time, is characterized by a risk reduction work schedule of about three years
emphasizing the presentation of residual risk. In regard to this Target map for reducing the midterm risk of Fukushima Daiichi NPS, TEPCO reported the current approach, issues and responding
status according to the further schedule as needed after May 2018. In it, for example, a very large
floating structure (VLFS, Megafloat) can become a drifting object and damage nearby equipment
if hit by a tsunami; and therefore, it is positioned as a measure against earthquakes and tsunamis
in the target map for reducing the mid-term risk of Fukushima Daiichi NPS. TEPCO plans to movethis VLFS to the open ditch of the water intake channel for Units 1 to 4 and position it in contact
with the sea bottom, to effectively use it as a revetment and shallow-draft wharf for the preparationof a newly built port yard. To achieve this, TEPCO started construction in November 2018, with theaim of completing the reduction of tsunami risk by the end of the first half of 2020 and completionof construction within fiscal 2021.
Regarding to the other countermeasures against earthquake and tsunami, building of tideembankment is being studied at the sea side of Unit 1 to 4 buildings. TEPCO should continue thiskind of efforts for the purpose of avoiding increases in stagnant water as a result of water inflow
into the building due to tsunami, and reducing damage to essential facilities in preparation of a Kuril
Trench Tsunami, which was identified as a highly imminent possibility.
In the future, it will be important to comprehensively understand the risk sources and tocontinuously reduce the implementation of each measure while comprehensively considering thepositioning and priority in the overall decommissioning project of the Fukushima Daiichi NPS as
described in Section 3.6.
3.5.3 Plan for decommissioning measures for nuclear reactor facilities
In the Mid-and-Long-term Roadmap, TEPCO should formulate the decommissioning plan for
the Fukushima Daiichi NPS in phase 3 after commencing fuel debris retrieval, aiming at thecompletion of decommissioning in 30 to 40 years, depending on the progress of tasks such as fuel88debris retrieval, and R&D. NDF should provide multifaceted and expert advice and guidance basedon the progress and forecast of the decommissioning, the situation of the reactor buildings, and thetrends of R&D with wisdom and knowledge from around the world.
Based on the need to take prompt and efficient measures for reducing risks of the whole facility
in Fukushima Daiichi NPS, NRA is examining a review to regulate entire Fukushima Daiichi NPS
integrally mainly with the implementation plan, in order to put more effective regulation todecommissioning work into practice. Therefore, the provisions of “Plan for decommissioning
measures” are not to apply to Fukushima Daiichi NPS36,37.
3.5.4 Concrete efforts toward securing safety
3.5.4.1 Efforts to ensure work safety
In FY 2018, the average number of workers per day was 4000 - 5000, which is on a slightly
decreasing trend. Safety activities are being continued in order to reduce the number of accidents.
The number of accidents (number of people involved in disasters) was 20 in FY 2016 and 11 in FY
2017, but it was 13 in FY 2018. When analyzed the three causes of “people, facilities, andmanagement”, many accidents are caused by human factors (assumption and lack of risk
sensitivity). In particular, taking into account that there are many accidents involving workers withless than 1 year of experience, a safety policy has been formulated from the viewpoint of“Awareness, skill improvement and management” to reduce accidents and the work environment
is continuing to improve38.
Similar to fuel debris retrieval operations, for the work plans that require workers to intervene ina high radiation dose environment and for which complete remote-control system operation isdifficult, it is important to control the individual radiation dose, evaluate the environment according
to the resources introduced from the viewpoint of “justification and optimization”, examine
diversified approaches while noting the mid-to-long term radiation management, and aim to ensure
the safety of the work environment as much as possible. Particularly when the work is “for the firsttime”, “changed”, or “for the first time in a long time”, it is essential to fully implement work training
using a mock-up in order to design, implement and verify effective work procedures and test
methods. To prevent labor accidents, it is important to verify the procedures and at the same time
repeat preliminary training using a virtual reality (“VR”) system, and to map out a safe, reliable work
plan with clear hold points. Therefore, VR system reinforcement is effective, by updating the method
information and site conditions.
36

NRA, Direction of review for regulations concerning TEPCO Fukushima Daiichi NPS (draft), handout 4 of 10th
Nuclear Regulation Authority Meeting, May 29, 2019, http://www.nsr.go.jp/data/000271371.pdf
37 NRA, Maintenance of laws and regulations for introducing new inspection system (Nuclear regulation inspection)(First stage) and invitation for public comment, handout 6 of 20th Nuclear Regulation Authority Meeting, July 31,
2019, http://www.nsr.go.jp/data/000279077.pdf
38 TEPCO, “FY2018 Accident Occurrence Conditions in the Fukushima Daiichi NPS” and “FY 2019 Safety Action
Program”, Handout 3-7 of 65th Meeting of Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water Treatment, April 25, 2019.
http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/04/3-7-2.pdf

89On-site work including the preliminary work for retrieval of fuel debris is expected to include:
decontamination in reactor buildings; investigation of PCV leakage positions; repair of PCV lower
and upper sections; construction of a network system; preparations for the installation of fuel debris
retrieval devices and systems; fuel debris retrieval operation; and fuel debris containing,transferring and storing. Therefore, for each work stage, a detailed work plan should be prepared,
and in the case of an accident or problem, prevention measures should be taken based on theproper preliminary risk assessment and measures. It is necessary to examine how to handle anunexpected accident: in the event of an accident or problem, a maintenance work area should be
provided to deal with it quickly. In the future, it is necessary to review the radiation dose reduction
work in the reactor buildings conducted so far and the PCV internal investigation, and use theinformation for preliminary measures, such as preparations, planning, and training, for other work.
In January 2019, an event occurred in which the inspection scaffold of the Units 3 and 4 exhauststack fell. No work was being performed in the surrounding area, and there was no damage to
people. However, considering the passage of time since the accident, similar events may occur inother facilities. Therefore, it is important to consider measures to improve safety.
In line with the Mid-and-Long-term Roadmap, it is stated that measures for industrial accident
prevention (joint operation of the labor safety and health control system by TEPCO and the originalcontractors; risk assessment by TEPCO, etc.; thorough communication and coordination between
tasks; experience-based education and training facilities for improvement of new employees’ risk
expectations capability, etc.) will be taken and reviewed continuously, medical preparedness will
be planned in anticipation of industrial accidents, and measures will be taken to reduce
occupational risk exposure as much as possible. It is important to ensure a perfect system of worksafety by continuing these efforts.
3.5.4.2 Efforts for facility safety
In the Fukushima Daiichi NPS where there are various kinds of work and safety facilities, special
attention to the safety of facilities is also essential. TEPCO has been preparing a complete set of
information, such as databases, maintenance plans for individual tools and devices, and drawings39.
Measures for retaining and improving reliability will be taken in the future to ensure long-term use,
based on the maintenance plans for individual tools and devices, by steadily performing periodic
investigations, updating equipment at the proper timing, and making equipment permanent.
Particularly important safety assurance equipment, such as circulation system to cool fuel debris,
nitrogen gas separation system, and PCV gas control system, are operated, inspected, maintained,
remote-controlled, monitored, and otherwise properly managed by TEPCO, based on maintenanceplans and other schedules. It is important to continue thorough measures that will be taken toprevent their important function from stopping, not just from the standpoint of equipment servicing
39 TEPCO, “Development of Database and Maintenance Plan for equipment, etc.,” presented as Handout 1-6 at
the 23rd Decommissioning and Contaminated Water Treatment On-Site Coordination Meeting (July 27, 2015).
http://www.meti.go.jp/earthquake/nuclear/osensuitaisaku/committtee/genchicyousei/2015/pdf/0727_01k.pdf

90

but from management and operation standpoints as well.
When installed new equipment or facility, it is critical to avoid defects on site as much as possible,
and steady quality assurance should be conducted through design reviews and testing andexaminations.
In the last fiscal year, there was a malfunction with the fuel removal device at the time of theremoval of the fuel from the Unit 3 SFP. As a result, the start of the removal was significantly delayed
from the original plan. This malfunction was directly caused by insufficient quality control of products
procured from overseas. Therefore, TEPCO is taking measures to strengthen quality control toprevent recurrence.
While this response is of course necessary, we believe that this case should not be viewed asmerely a matters of quality control, but rather as an indication of the existence of an organizational
problem, i.e., a lack of broad technical response skills necessary to promote the project.
Considering that more difficult work, such as debris retrieval, is expected in the future, this caseshould be utilized in order to strengthen technical response skills as a decommissioning
organization in the future.
3.5.4.3 Security enhancement
At decommissioned nuclear power plants, appropriate fuel removal is conducted, and, when
nuclear material protection concerns are removed, dismantling and other decommissioning work is
performed. Because a great quantity of nuclear fuel material is stored in the Fukushima Daiichi
NPS, it requires particular attention to be paid for its security same as a normal nuclear plant,measures to confirm the reliability of each individual, enhance nuclear security training, prevent
unauthorized intrusion into the sites, etc. are being implemented.
Along with these measures to be continued, it is necessary to implement appropriate measuresin operation to allow accepting visits of inspectors including locals to see the progress of thedecommissioning work as it is, at the Fukushima Daiichi NPS on site, as described in Section 7.2,
because showing the progress with their own eyes is extremely valuable for building the public’s
understanding of the decommissioning operation. On the other hand, it is crucial to further
strengthen access control to the NPS in consideration of Olympic that will be held in 2020.

91

3.6 Comprehensive efforts for the decommissioning project of the Fukushima
Daiichi NPS
As mentioned in Chapter 2, in the decommissioning project of the Fukushima Daiichi NPS in the
future, it must be addressed more complex, uncertain challenges over the long term, such as fueldebris retrieval. For this reason, when making efforts in each of the fields listed in Sections 3.1 to
3.5, it is necessary to systematically promote efforts to resolve issues by looking ahead andsecuring lead time for sufficient preparation; though there had to carry out work while accumulating
work to respond to the challenges that are facing us in the short term as emergency responses
from right after the accident onwards.
Decommissioning of the Fukushima Daiichi NPS is a complex and multi-layered large-scale
project, and various efforts undertaken within the project are carried out simultaneously and inparallel and in a mutually related manner. In particular, when the retrieval of fuel debris is started
in the future, the relevance of the work in each field will be strengthened further, such as the issueof the treatment of cooling water used to cool debris, the issue of the establishment of storage
facilities to temporarily store the removed debris, and the issue of the space coordination for various
works such as the removal of fuel in SFP conducted in the upper part of the building and theinstallation of related facilities in the yard. In order to proceed the entire decommissioning projectin a stable manner over the mid-and-long-term in the context of increasing complexity in the relation
between the mutual work, it is important to optimize allocation of limited resources (people, goods,
money, time, and space) while ensuring the consistency and feasibility of these many related efforts
as a whole.
From the viewpoint of the necessity of the proactive and systematic work and the necessity of
coordinating the intricately-related work as a whole, to proceed with the decommissioning projectsteadily and efficiently in the future, it is necessary to formulate a consistent long-term plan for theentire decommissioning from the current state to the short, medium, and long terms, so that various
efforts can be managed comprehensively in accordance with this plan.
In addition, individual work in each field of decommissioning work is generally carried out
through processes such as technological development  conceptual design  detailed design 
production  site installation work inspection operation. In addition, safety inspections andother inspections by the Nuclear Regulation Authority will be conducted as necessary. In order tocarry out this series of processes without omission or delay, it is effective to set up the large work
flow defined in the long-term plan as an individual project as a management unit of appropriate
scale. IN addition, it is important to promote a comprehensive approach under a sophisticatedproject management system so that correlation and time-series relationships between the projects
can be optimized and risks inherent in the project can be appropriately managed.
Even if a long-term plan is drawn up, it is virtually impossible to draw up a plan with high accuracy
into the future at this point because there are still large uncertainties regarding the status of thedecommissioning of reactors in the distant future and the necessary work. Therefore, as a long92

term plan, it is considered to be practical to optimize the work plan for the longest possible range
where the work can be specified to a certain extent; from the viewpoint of showing the road todecommissioning inside and outside, though there are restrictions on the level of detail to suchspecification can be realized.
As to the decommissioning of the Fukushima Daiichi NPS, it is an unprecedented challenge anda project that needs to be carried out while accumulating experience and results, while improving
the site, investigating the situation, and developing technology, with limited information and asevere environment due to contamination and impact of tsunami. In order to safely and steadily
advance a decommissioning project that contains many uncertain elements, it is important to draw
up a plan based on the current information and assumptions, to incorporate new information andvarious knowledge gained as work progresses in a timely manner, and to review the plan flexibly
according to the situation that becomes clear. It should also be noted that over-adherence to a plan
after it has been developed may reduce the scope for choosing the best approach for the situationor the safest approach under the situation, thereby impeding the progress of safe and steady work.
Thus, while it is necessary to formulate a long-term plan and to proceed with the work in aplanned manner under the project management system, the formulated long-term plan should not
be rigidly positioned and operated. For concrete use of the long-term plan, it is more important to
set decision points in advance at an appropriate time so that new knowledge can be obtained,
evaluate the progress of work at that time and knowledge, consider how to proceed thereafter, andflexibly revise and operate the long-term plan based on that.
Fig. 23 shows the image of decision points and the review of the long-term plan.

Fig. 23 Decision points and review of the long-term plan93

4. Handling critical enablers for smooth operation of the project4.1 Actions toward improvement of working environment and conditions
The working environment of the Fukushima Daiichi NPS has been steadily improved. Needlessto say, this improvement is essential for protecting and respecting the rights of workers. For the
Fukushima Daiichi NPS decommissioning project, which will continue for a long period of time after
the end of the emergency status, a good working environment is the basis for ensuring safe andsteady implementation on a healthy foundation. To name a few typical efforts, TEPCO is improving
the working environment infrastructure by consolidating and removing existing rest stations andsetting up alternative rest stations, a cafeteria, convenience store, and shower booths, which are
infrastructure for improving the working environment. The company conducted a questionnaire
survey on the working environment for those working in plant, and is using the results to improve
the working environment40.
A variety of measures are taken to improve working safety and health, according to the“Guidelines for Safety and Health Control Measures for the TEPCO Fukushima Daiichi NPS” 41
established in August 2015 by the Japanese Ministry of Health, Labour and Welfare. Reinforcementof the safety and health control system that integrates TEPCO and the original contractors is
implemented, by designating necessary positions such as the safety and health supervisor and by
establishing a health cooperation organization, while proceeding with steady efforts, such as risk
assessments regarding dangers and hazards caused by on-site materials, working behavior orother duties; implementation of measures based on the risk assessment results; implementation ofhealth education for new staff members; centralized radiation exposure dose control; reinforcementof entry/exit control of those working in the station facilities; and integration of effective radiation
exposure reduction measures into the project plan at the stage of placing purchase orders.
As measures against heat attack, fixed WBGT42 indicators and clocks have been installed onsite, enhancing acclimation to heat, and medical history of heat attack and health conditions havebeen confirmed (early detection of poor physical condition). In fiscal 2018, the period forstrengthening measures to prevent heat attack was extended from April to October. As a result ofvarious measures, the number of heat attack patients increased by only two from fiscal 2017
despite the unusually hot weather (6 persons--> 8 persons). In fiscal 2019, the rules for preventing
heatstroke in fiscal 2018 will be continued, and because heat attack occurred in October for threeconsecutive years, a new rule was added to encourage workers to prevent heat attack in case40

TEPCO, “Results of Questionnaire for a Better Labor Environment (9th Meeting) and Future Improvement Plans”,
presented as Handout 3-7 at the 61th Meeting of the Secretariat of the Team for Countermeasures for
Decommissioning and Contaminated Water Treatment (December 27, 2018).
http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2017/12/3-07-02.pdf
41 “Reinforcing safety and health control measures for the TEPCO Fukushima Daiichi NPS”, Press release data
announced by the Ministry of Health Labour and Welfare, Aug.26, 2015,
http://www.mhlw.go.jp/stf/houdou/0000095466.html
42 Wet-bulb globe temperature : that incorporate humidity, radiant heat, and temperature, which have a significant
impact on the heat balance of the human body)94

temperature may change significantly by confirming weather forecast (WBGT and temperaturechange) in advance.43
As radiation exposure control, the monthly average radiation exposure dose in fiscal years 2014
to 2018 has been about 1 mSv/month or lower (Fig.24). The average radiation exposure dose in
FY2018 was about 2.4 mSv/year, individual maximum radiation exposure dose is low enough44 as
no worker radiation dose exceeded 20mSv/year. The radiation exposure dose of most workers islarge enough for the radiation dose limit. Furthermore, the ICRP's statement regarding theequivalent radiation dose limit for the lens of the eye45 was voluntarily adopted, and 150 mSv/year
was reduced to 50 mSv/year as voluntary control from April 2018, in addition, the limit radiationdose of 100mSv for five years has been applied since April, 2019. With the progress of the project,
work in a high radiation dose environment is expected to become more frequent. To comply withthe radiation dose limits of individual workers, a limit should be designated that will be lower thanthe legislated limit. When a worker’s radiation exposure is at or above, or may be above the limit,
such worker is to be excluded from engaging in radiation work or request that the worker preparesa radiation dose control plan where the radiation dose control methods will be determined in detail
and work according to the control plan to ensure that the radiation dose does not exceed thelegislated limit radiation dose. Such management needs to be carried out without fail.
Radiation exposure dose(monthly average radiation dose) mSv

35
被
ば
く
線
量

Partnercompany
協力企業

TEPCO
employee
東電社員

30
25

（

15
10
2019/6

5

2019/032018/112018/072018/032017/112017/072017/03

2016/112016/07

2016/03

2015/112015/07

2015/03

2014/11

2014/07

2014/032013/112013/072013/032012/112012/072012/03

2011/110

Average平均0.30mSv
of 0.30 mSv（暫定値）(provisional
value)

2011/07

）

m
S
v

20

2011/03月
平均線
量(Source : TEPCO)

Fig.24 Changes in workers’ monthly radiation exposure dose (monthly average radiation dose)(Radiation exposure dose by month after March 2011)46

43

TEPCO, “Status of accidents in FY 2018 and safety activity plan in FY 2019”, issued in FY2019, presented as
Handout 3-7 of 65th Meeting of for the study group on Countermeasures for Decommissioning and Contaminated
Water Treatment, April 25, 2019.
https://www.tepco.co.jp/decommission/iinformation/committee/roadmap_progress/pdf/2019/d190425_12-j.pdf
44 TEPCO, “Status of radiation exposure dose for radiation workers in Fukushima Daiichi NPS”, April 24, 2019https://www.tepco.co.jp/decommission/iinformation/newsrelease/exposure/pdf/2019/exposure_20190424-j.pdf
45 ICRP, ICRP Statement on Tissue Reactions and Early and Late Effects of Radiation in Normal Tissues andOrgans – Threshold Doses for Tissue Reactions in a Radiation Protection Context, ICRP Publication 118, Annalsof the ICRP,.41(1-2), (2012).
46 Reference 2 : Overview of decommissioning and contaminated water treatment from The secretariat Meeting of
69th Team meeting on decommissioning and contaminated water treatment, August 29, 2019http://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2019/08/2-1.pdf

95

As measures for radiation dose reduction on site, as described in Sub-section 3.5.2.3, highradiation dose rubble removal, surface soil removal, and decontamination by facing and shielding
have been performed, and as a result, the target radiation dose equivalent rate of 5 μSv/h wasachieved by the end of FY 2015 (excluding the vicinities of Units 1 to 4 and waste storage areas).
The area where workers can wear ordinary uniforms or similar attire has extended to approx.96%
of the entire premises. In addition, since March 30, 2017, the areas that have been confirmed tobe free from the spread of radioactive contamination within the areas in which it is permitted towork with general work clothes (Access Control Building, Rest Area, Seismic Isolation Building,etc.) was designated as areas where people can move around without a shoe cover and only withgloves. As a result of promoting environmental improvement of the areas only with gloves needed,those areas was designated as areas where additional protective cloths including even gloves are
not necessary for workers to move around after October 1, 2018. Such area has been enlarged
and it was apply to the pavement connected between surrounding Rest Area and Seismic Isolation
Building, too. Moreover, this was applied to the upland located on west side of Units 1 to 4 from
November 2018, it became possible for people to inspect only with the clothes as they wear.47. As
it is no longer necessary to wear protective masks and protective clothes, improvement has beenachieved in terms of narrowed sight, longer moving time due to the load on the body, and thepossibility of a heat attack. This has helped improve safety and health control measures not
associated with radiation.
In the future, while continuing the actions specified in Mid-and-Long-term Roadmap for
improvement in the working environment and conditions, it is needed to specifically design internalradiation exposure prevention measures in preparation for the fuel debris retrieval that will generate
α-dust, which contributes significantly to radiation dose in the event of internal radiation exposure.
Specifically, it is necessary to control signs through appropriate measurement and monitoring, inaddition to confinement in specific areas using contamination expansion prevention methods,
prompt contamination removal, and wearing of protective gear. Especially, at the entrance and exit
control (control of surface density), measures against the contamination of protective gear thathave direct contact with the body are important, because adhering radioactive materials may
indirectly contaminate the skin and may become airborne particles that could cause internalradiation exposure. TEPCO has an agreement with Japan Nuclear Fuel Limited regarding theradiation dose evaluation of internal radiation exposure due to α-nuclides derived from fuel debris,(internal radiation dose evaluation using bioassay analysis), and a system has been prepared toenable action. For further safety purpose, study on organizing a system to evaluate internalradiation exposure dose by themselves is being examined in considering further progress ofoperation.

47

TEPCO, Status of improvement in the work environment at the Fukushima Daiichi NPS, Handout 3-7 of The 60th
Meeting of Secretariat of the Team for Countermeasures for Decommissioning and Contaminated Water Treatment,
November 29, 2018,https://www.meti.go.jp/earthquake/nuclear/decommissioning/committee/osensuitaisakuteam/2018/12/3-7-3.pdf

964.2 Enforced management structure for steady mid-and-long-term
decommissioning
TEPCO Fukushima Daiichi Decontamination and Decommissioning Engineering Company(hereinafter referred to as “Decommissioning Company”), established in April 2014, has introduced
a project system to promote the safe and steady decommissioning of reactors, and is working totransform from the conventional routine-based operation management to project-based operation
management. With the introduction of the project system, targets and deadlines are clearer than
before, and certain achievements have been obtained in the work of contaminated water
management and removal of fuel in SFPs. However, as difficult tasks such as fuel debris retrieval
are scheduled in the future, the project management function is needed to be enhanced more,rather than satisfied with previous achievements.
To that end, the Decommissioning Company restructured its project framework last October andis preparing to shift to a framework in which project managers have sufficient responsibilities andauthority. Program Management Office (PMO) has been established for the overall managementof the related projects and line operations, and the PMO is in charge of promoting the enhancementof project management functions.
<Examples of enhancing Project Management functions>(1) Empowering Project Managers(2) Integrated management of all projects utilizing project management tools(3) Visualize projects with the Earned Value Management (EVM)(4) Decision-making based on stage gate process(5) Preparation of long-term plan and project management based on the long-term plan(6) Improving (kaizen) Supply Chain Management (Procurement based on long-term plans)
On the other hand, the NDF, which manages and supervises TEPCO's decommissioning work,
established the Program Supervision and Support Office (PSO) in February 2018 to support thestrengthening of TEPCO's project management functions in cooperation with the TEPCO PMO.
The cooperation between the two organizations is also strengthened in the implementation of
the project. In the NDF, counterparts are assigned to coordinate with the program manager (PGM)
and the project manager (PJM) of the Decommissioning Company, and the NDF counterpartsattend project-related meetings hosted by the Decommissioning Company to share issues specificto the project and provide technical support to resolve issues as necessary (Fig. 25).
In addition, program projects implemented by TEPCO need to be clearly defined as plans under
the decommissioning Reserve Fund System. In the Policy for Preparation of Withdrawal Plan, NDF
has recently shown TEPCO, which is the licensed decommissioning company, the following: 1) the
status quo of the decommissioning project and operational targets for the mid-and-long-term
perspective based on the planning of the project; and 2) the tasks to be implemented and their
purposes, as well as the targets and major tasks for the three years to come, as activities to be97

incorporated in the Withdrawal Plan. (Table 3 shows the preparation policy issued to TEPCO on
October 2, 2018.)
TEPCO is to submit the “Decommissioning Implementation Status, Decommissioning
Implementation Plan, and Other Items Specified by the Ordinances of the Minister in Charge” every
year via the NDF to the Minister of Economy, Trade and Industry, who is in charge ofdecommissioning. TEPCO and the NDF jointly prepared the Withdrawal Plan and obtained
approved from the Minister of Economy, Trade and Industry to withdraw from the fund. These
documents have been created according to the planning of the ongoing program and project fromthe viewpoint of making steady progress in the decommissioning.
The implementation of the plan (implementation of decommissioning work) will be carried out
by TEPCO, and the NDF will manage and supervise the status of how TEPCO is implementing theplan. For this reason, the NDF, in the process of preparing the Withdrawal Plan with TEPCO, notonly confirms that the costs necessary for decommissioning work are appropriately budgeted by
TEPCO, but also receives monthly reports from TEPCO on the status of use of the reserve funds
for decommissioning and confirms the appropriateness of the use status.

Tokyo Electric Power Company Holdings, Inc.

Nuclear Damage Compensation and Decommissioning Facilitation Corporation

Fukushima Daiichi D&D Engineering
Company (General Director : CDO)
Safety andQuality Control
Division[PG1]
Contaminated
Water
Solution PG

Project Management
Office (PMO)[PG2] Pool
Fuel Removal
PG[PG3] Fuel
DebrisRetrieval PG[PG4] Waste
Management
PG[PG5] Site
Area/Work
Environment
Improvement
PG

Decommissioning support division(General Manager: President)

Overall management of PG & PJ

[PG6] Unit 5/6
Response PG

Program Supervision andSupport Office (PSO)

Technological Strategy G
Contaminatedwater
management
team

NuclearDamageCompensation
OfficePool fuelremoval team

Fuel debris
retrieval teamInternational
AffairsG

Decommissioning
Management G

Waste
strategy teamThe same as PG1The same as the contaminated water management team

Program Manager (PGM)

Coordination between PGs

Program leader

Project Manager (PJM)

Coordination between PJs

Project Leader

Project Member

In charge of project* CDO, Chief Decommissioning Officer, in charge of decommissioning and contaminated water management; PG, program; and G, group.

Fig.25 NDF and TEPCO organizational system for Project Control

98

Table 3 Description of the Projects included in the Withdrawal Plan
Program

Objectives

Three-year targets

Major tasks (for the coming three years)(1) Contaminated water• Implementation of
fundamental
measures against
contaminated water• Removal ofcontaminants that may
have an impact on the
Fukushima Daiichi
NPS boundaries• The effective radiation dose at
the boundaries of the site should
be maintained at a level below 1
mSv/year.
• The total volume ofcontaminated water under an
average rainfall amount should
be controlled (no greater than
150 m3/day in total).
• Tank capacities should besecured according to a plan.
• While the difference in level
between stagnant water in thebuildings and underground water
is retained, the water level in thebuildings should be lowered(keeping a situation to preventthe outflow of stagnant waterfrom the reactor buildings into
other buildings).

• Reinforcing sub-drain and land-side
impermeable wall related operation• Measures to prevent the inflow ofgroundwater/storm sewage into thebuildings• Installation of welded tanks andremoving of flange tanks, etc.
• Transferring stagnant water inbuildings and installation of
purification equipment• Purification process of stagnant
water in buildings• Measures for stable storage ofsludge from decontaminationequipment• Spent fuel removalfrom Units 1 to 3
• Storage in common
spent fuel storage
pool, etc. in stablecondition• Installation of Unit 1 fuel removal
covers should be started in FY
2021.
• Unit 2 buildings upper part
dismantling and related work
should be able to be completed
in FY 2022.
• Fuel removal from Unit 3 SFP
shall be complete.
• Improvement of surrounding
environment of Unit 2 shall becompleted.

• Unit 1 operating floor rubble removal• Unit 2 internal investigation ofoperating floor of R/B and building
upper part dismantling• Installation of cover for fuel removal,
fuel removal and stable storage at
Unit 3• Dismantling of upper part of Units 1
and 2 exhaust stack• System establishment
for fuel debris retrieval
methods from Units 1,
2 and 3• Retrieving, containing,transferring and storingof fuel debris of Units 1
to 3• The fuel debris retrieval methodof the first implementing unit has
been
determinedanditsengineering work behind themethod should be implemented.
Then, preparation for retrieval is
to be made.

(4) Waste management
program• Formulation of waste
storage management
plan and appropriate
waste storage• Solid waste is safely andreasonably stored andcontrolled, and the required
storage capacity should besecured.
• Steady implementation of efforts
to reuse, recycle and reducevolume of waste(5) Site area / working
environment
improving program• Formulation of siteuse plan andestablishment of the
management
processes• Improving working
environment forworkers(6) Management of• Maintenance of Units
5 and 6 equipment• Decommissioning
planning and its
implementation• Various measures fordecommissioning are being
steadily implemented throughthe operation of the site use
plan.
• Infrastructure is in place tomaintain and improve theworking environment within the
power station• Spent fuel shall be stably kept
cooled.

• Examination of fuel debris retrieval
methods for each unit (Steady
implementation of engineering, etc.)• Detailed investigation of theconditions in the PCVs
• Preparatory work for fuel debris
retrieval• Technology development led by
TEPCO HD
• Installation of waste storage andvolume reduction treatment
equipment (incinerators, etc.)• Formulation of Mid-and–long-term
Storage plans (Including Storage ofadsorption vessels, concentrated
waste liquid and slurry)• Technology development led by
TEPCO HD• Retention of buildings in good order• Improvement of decommissioning
infrastructure• Provision of buildings and rest
facilities

management
program(2) Program for removalof fuel in SFPs

(3) Fuel debris retrieval

programUnits 5 and 6
program• Appraisal and implementation ofother risk reduction measures• Maintaining cooling equipment• Decommissioning planning andproposal development• Relocation of VLFS

In the second withdrawal plan approved by the Ministry in April this year, costs related todecommissioning work for three years from FY 2019 to FY 2021 are included. As thedecommissioning progresses, it is expected that various things would be clarified with the progress99

of work and technological studies. For this reason, the following points should be fully consideredin the subsequent withdrawal plan.
In order to proceed with safe and steady decommissioning work, in addition to enhancing the
project management function mentioned above, it is essential to develop human resources toaccomplish the project. In particular, since it is important to enhance project management skills,
as well as engineering capabilities, specific plans should be drawn up for this purpose andefforts should be accelerated.

As for R&D, some projects are carried out by TEPCO on its own, but most of them are carriedout by the Government-led R&D program on Decommissioning and Contaminated Water
Management. However, with the progress made in TEPCO’s engineering, it is expected that
there will be an increase in the number of field-oriented research and technology developmenttasks that could not be found by this Government-led R&D program. The R&D with hightechnical difficulties that require the support of the government should be carried out by thegovernment-led decommissioning and contaminated water management projects as before.
As for technology improvement to apply the achievements of those R&D to the site and new
R&D tasks the necessities of which were found by TEPCO engineering, TEPCO should takethe initiative.



In addition, coexistence with the local community is indispensable to continue
decommissioning for a long time. To achieve that, it is important for TEPCO to create morecontacts with local communities through procurement of goods and services associated withdecommissioning from them and employment of human resources in these regions. For
instance, the technology developed by a local company was applied to the field for thedismantling of the exhaust stack of Units 1/2, and it is desirable to increase such good practices.
TEPCO should proactively improve the environment that more local enterprises can participate
in the decommissioning work through engineering support, while balancing the safe andsteady decommissioning with the priority given to local communities.

Column : What is “Project Management” ?
What is a project in the first place? PMBOK (Project Management Body of Knowledge), aninternational standard for project management, defines projects as follows.
“It’s a temporary endeavor undertaken to create a unique product, service or result” (citedfrom the 5th edition of PMBOK)
Every job has a goal. However, when it is called a project, it is characterized by being“temporary (it has a defined beginning and end in time)” and “unique (it is not a routine
operation)” in addition to setting a goal. To put it simply, a project can be said to be “a nonroutine operation designed to accomplish a singular goal on time”.

100Now that’s the question. Which of the followings can be called a project?
1. It’s hard for my mom to do housework while working outside. In order to reduce the burdenof mom's housework, we decided to share the housework among the whole family.
2. 23rd of the next month is my daughter's 7th birthday. This year, I wanted to celebrate herbirthday with her friends in commemoration of Shichigosan, so I decided to hold herbirthday party, inviting her friends.
3. My child will go to a private school next year. I wanted to reduce my household waste asmuch as possible, so I decided to keep a household account book next month.
The answer is 2. 1 has a goal (= to reduce the burden on the mother) but no end (= untilwhen) or it is not unique (= no routine operation). 3 is the same. On the other hand, in addition
to the goal (= to celebrate a birthday with friends), there are a period (= birthday of 23rd of thenext month) and uniqueness (= as a memorial of Shichigosan) in (2).
How did you understand what a project is? Next, let's consider what “project management”
is.
If you read it literally, it will be “to conduct management of a project”. So what does
management in this case mean? When management is translated into Japanese, it becomes“an activity to control or organize works”, but in the Japanese business scene, management isoften used as it is without translation.
In short, project management is a collective term for “project activities* to meet the projectrequirement”. If these activities are not coordinated, you cannot accomplish a goal of project. It
is the role of a project manager to lead to accomplishment of a goal by organically bringing them
together.
* In project management, these activities are defined by WBS (Work Breakdown Structure: adiagram that organizes project activities in a tree structure <Level1-Level2-Level3-…>). In large
projects, this number of WBSs range over thousands to tens of thousands.
Now let's move on to the story to Fukushima Daiichi decommissioning.
TEPCO Fukushima Daiichi Decontamination and Decommissioning Engineering Company(“Decommissioning Company”) was established in April 2014, three years after the accident. It
has adopted a project system. Why did Decommissioning Company adopt the project system(← here is the point)?
Normally, once a nuclear power station shifts from construction phase to operation phase,works of the electric power company will be to maintain facilities in line with operations of thepower plant and periodic inspections. Since the time required for a periodic inspection is
stipulated by law as one year, power plants alternate between inspection (periodic inspection)and operation in a one-year cycle. For this reason, power plants are generally organized by101

“functional organizations” (also called sectoral organizations) such as power generation
department, maintenance department, radiation management department, et al. Functionalorganizations are based on the concept that when each plays its own role, an overall goal of apower plant can be accomplished.
In addition to TEPCO, other electric power companies often adopt functional organizations at
power plants. This is because the business cycle has been settled, and it is judged that anorganization according to functions is most suitable for executing routine works efficiently without
sacrificing safety and quality.
In turn, what about the decommissioning of Fukushima Daiichi NPS? Can you say that thesame business style and organization as a power plant are suitable? Of course, somedecommissioning operations are routine like works in power plants. However, the weight of suchroutine works are small, and the large portion of the main subjects are unprecedented anddifficult tasks such as countermeasures against contaminated water after the accident, fuelremoval from SFP, and fuel debris retrieval. Nevertheless, it is necessary to complete thedecommissioning within the scheduled period. Moreover, the resources that can be used fordecommissioning (people, goods, money) are limited.
In order to proceed with decommissioning in a safe and steady manner under the limited
resources and to finish it within the period, Decommissioning Company decided that the projecttype work style and organization, that can respond to major changes and uncertain factors
flexibly and promptly, were more suitable for the decommissioning of Fukushima Daiichi NPS as
compared with the routine and stable work style and organization at power plants.
◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇ ◇Decommissioning Company is steadily preparing for enhancing its project management
function and engineering capabilities to transform into a genuine project-type organization fromFY2020. On the other hand, NDF is in a position to manage and supervise the decommissioning
conducted by Decommissioning Company. For this reason, NDF reviews the Withdrawal plan
through the process of jointly developing it with TEPCO whether the expense, though which is
not for the decommissioning operation itself but is required for ensuring the safety and quality ofdecommissioning including ones for enhancing project management functions and engineering
capabilities, is properly recorded into the plan.

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4.3 Developing and securing human resources
4.3.1 Developing and securing operators and engineers
The decommissioning project of the Fukushima Daiichi NPS requires completely different skills
from the technologies related to the construction and operation of NPSs that TEPCO has
accumulated to date as well. Furthermore, the technical challenges posed by the existence ofenormous amounts of groundwater and others, the uncertainty of the internal site, and highradiation due to α- nuclides and fission products, etc. compose a very different condition from thedecommissioning of normal reactors.
For this reason, the Decommissioning R&D Partnership Council has prepared a draft technology
map in order to understand the overall image of core technology necessary for decommissioningof the Fukushima Daiichi NPS and the image of required decommissioning personnel (Attachment13). As a result, it has become clear, for example, that there are fields in which it is possible toprocure human resources through training, etc. by utilizing the existing pool of technology andhuman resources in the nuclear industry, such as analytical engineers whose necessity is now clear,and fields in which it is necessary to seek and systematically train technical human resources froma wide range of sectors other than the existing nuclear industry. It is expected for related institutions
to utilize this map for developing and securing human resources in ways such as (1) to clearlygrasp the overall picture of the technologies required for the decommissioning of the Fukushima
Daiichi NPS; (2) to clearly understand the strength of their own personnel; (3) to prepare training
programs; and (4) to plan recruiting strategy aiming wider areas not limited to the conventional
nuclear industry. In addition, the NDF is preparing to provide opportunities for engineers and others
working at the Fukushima Daiichi NPS to learn common technologies required for decommissioningwork.
In handling a complex, large-scale project like the decommissioning of the Fukushima Daiichi
NPS that involves many related factors, it requires special personnel who are not only able todemonstrate expertise in their assigned area, but also have the ability to manage projects from acomprehensive perspective, including the consideration of relationship between the projects basedon the overview of the entire decommissioning process. In the second test of the qualifying examfor Professional Engineers (PE) for the fields of nuclear power/radiation, from FY 2019, “Reactor
Decommissioning (including handling after Severe Accident)” was added to the content of optional
subject “reactor systems and facilities” and that “processing and disposal of fuel/radioactive waste
after decommissioning and sever accidents of reactors” was added to the content of anotheroptional subject “processing and disposal of nuclear fuel cycle and radioactive waste”. Accordingly,
in the Government-led R&D program on Decommissioning and Contaminated Water Management,
the main persons in charge are supposed to describe the status of their related qualifications for
professional engineers when applying from the public offering conducted in March 2017. It is
expected that companies will continue to make effort to expand the employees’ capabilities by103

encouraging them to acquire related qualifications such as PE, Chief Engineer of Reactors, orRadiation Protection Supervisor, etc.
The forecast of the number of workers expected to be required for the upcoming three years isshown in the Mid-and-Long-term Roadmap, however, as newer tasks will be implemented such asfuel debris retrieval required number of workers may change. Therefore, it is necessary to grasp
the amount of required personnel of each field on a timeline basis by imaging a long-term prospect
for the project of decommissioning of the Fukushima Daiichi NPS. According to this, the required
number of personnel having sufficient skills should be steadily and systematically developed andrecruited. Such long-term prospect is to be examined through the entire decommissioning plan
described in Section 3.6.
4.3.2 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 andto continue R&D activities for a long period of time, it is essential to train and secure future
researchers and engineers. It is important for industrial-academic-governmental institutions as awhole related to nuclear power to steadily promote efforts for this purpose.
Specifically, industry and educational institutions should cooperatively continue the activities toenhance students' understanding of the nuclear power industry and show the attractiveness of theindustry. They should also convey to students that the decommissioning of the Fukushima Daiichi
NPS is an extreme technological challenge unprecedented anywhere in the world, as well asbuilding and showing a variety of career paths for researchers and engineers to take part.
In addition, the stable development of researchers and engineers is of fundamental importance.
From this perspective as well, the Project for the Promotion of Nuclear Science, Technology and
Human Resource Development (hereinafter referred to as “the World Intelligence Project”), which
mobilizes the wisdom of the Ministry of Education, Culture, Sports, Science and Technology, waslaunched in FY 2015. In particular, from FY 2018, a common platform nuclear research programfor young human resources such as universities has been implemented. The program sets up ayoung research quota for which members of the research group, including research representatives,
are eligible if they are 39 years old or younger. In this program for enhancing the decommissioning
research and human resource development that has been carried out since FY 2015, not only thecourses related to decommissioning prepared under this program are counted in the units requiredfor graduation, but also the program provides students with the opportunity to study
decommissioning through their graduation research and to foresee future career paths. The“Conference for R&D Initiative on Nuclear Decommissioning Technology by the Next Generation(NDEC)”, intended for students, and the “Creative Robot Contest for Decommissioning”, intended
for college students are held. Students exchange opinions with researchers and engineers involvedin the Project of Decommissioning of the Fukushima Daiichi NPS, and those with excellent resultsreceive awards at the events. In addition, for human resources retention and expansion through104the entire industry, various initiatives such as “Nuclear Dojo” providing nuclear education programsin collaboration among 16 universities in Japan and “Nuclear Facilities Tour for College/High SchoolStudents towards Brighter Future” have been carried out. It is necessary to further promote andstrengthen measures for securing human resources at universities, etc.
For the decommissioning of the Fukushima Daiichi NPS is difficult operation that has never been
experienced, accordingly, knowledge in a variety of field is required. It is essential to cultivate
human resource through R&D activities including wide range of areas not only nuclear field but
mechanical, chemical, civil or material engineering, etc. Furthermore, in long-term and large-scale
projects such as the decommissioning of the Fukushima Daiichi NPS, it is essential to develop corepersonnel for R&D who can perform scientific and engineering investigation from an academic
perspective and personnel with a panoramic perspective (system integrators) who can integrate
individual technology seeds into a system with practical functionality. This activity is being
implemented by R&D themes described next in Chapter 5.
These activities for fostering next-generation decommissioning personnel should not be
considered just as an effort to supply researchers and engineers. Approaching to a wider layer ofpeople should be considered to enable the large cyclic rotation of personnel, from a long-term
viewpoint. The previously described programs for developing decommissioning R&D personnel has
brought in solid results, such as graduates joined the nuclear power industry engaged indecommissioning, while many students decided to study further at graduate schools, joined
regulating authorities, and were admitted to local municipalities. It is expected that their experiencein decommissioning as a student and a wide range of experience in society may provide a newperspective to the project of Decommissioning of the Fukushima Daiichi NPS and drives the project
forward.

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5. R&D initiatives
5.1 Basic policy for R&D
5.1.1 Basic policy
Decommissioning of the Fukushima Daiichi NPS is technically extremely difficult and involves
many challenging issues never dealt with before. In order to implement various countermeasures
steadily in accordance with the Mid-and-Long-term Roadmap, development of new technologies tosolve such issues and of reliable technologies aiming at on-site application is indispensable.
Therefore, R&D projects aiming at practical application, construction of research centers andfacilities by JAEA, basic and generic research as well as applied research at researching
institutions including universities have been conducted under the governmental subsidized orcommissioned project and facility buildings of R&D center. At the same time, TEPCO has beenworking by itself.
NDF has determined the R&D duties implementation policy48 based on the NDF Act. According
to this policy, the NDF has been gathering expertise of R&D institutions and managing a variety of
R&D projects, such as clarifying the inner reactor conditions, feasibility studies on fuel debris
retrieval methods that support steady implementation of the Mid-and-Long-term Roadmap.
The phase of decommissioning work is shifting to a mid-and-long-term response, as seen in fullscale engineering for fuel debris retrieval, etc., and the R&D process will enter a new phase in the
future. As detailed processes towards the decommissioning becomes clearer, the role of each R&D
player should also be more clarified. Here, it is necessary to allocate the division of roles between
the enterprise and the relevant researching institutions in an appropriate manner in order toimplement R&D results on the decommissioning site steadily. To back up the implementation of the
mid-and-long-term decommissioning project, it will be further expected that the government andthe relevant researching institutions should establish centers of basic research/research
infrastructure based on a mid-and-long-term perspective. At the same time, it is expected that withthe progress of engineering, R&D tasks that are to be applied to the field will be identified, andTEPCO will be required to make efforts to put more weight on developing its own technology thatis directly linked to be applied to the field to achieve decommissioning work.
For this challenge entering into an the pathless field, it is important to further enhance many
approaches from different angles through the collective effort of Japan such as realizing effective
R&D, cooperation between the related organizations including those overseas, utilization ofresearch facilities, and human resources development.

48

Policy for conducting business related to research and development concerning the technology necessary to
implement decommissioning, etc. (R&D duties implementation policy for technology such as decommissioning)
http://www.dd.ndf.go.jp/jp/committee/policy/index.html

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5.1.2 Entire perspective of R&D
Various issues involving difficult R&D elements exist in the decommissioning of the Fukushima
Daiichi NPS. R&D activities for solving these problems are being conducted by a variety ofindustrial-academic-governmental institutions engaged with the Fukushima Daiichi NPS
decommissioning R&D projects through the areas of basic/fundamental research, applied research,and development/utilization (Fig. 26 and Fig.27). To organically link these activities and efficiently
solve the on-site problems through the R&D, it is important to understand and share of theinformation of R&D activities conducted by the related organizations and to cooperate andcoordinate between the decommissioning site and research site. Therefore, NDF holds meetingsof the Decommissioning R&D Partnership Council according to the decisions of the Team forCountermeasures for decommissioning and contaminated water management. The members of
the Council are NDF, JAEA, TEPCO, IRID, plant manufactures, the experts concerned and theministries concerned. The main task of the Council is to tackle with the issues such as sharing
information on R&D needs and seeds, coordinating R&D based on the needs of decommissioning
work, and promoting cooperation in R&D and human resource development in matters ofcollaborating with related organizations, gathering international expertise and promoting itcomprehensively and systematically. Moreover, NDF provides information about the activities
performed by researching institutions, universities and business operators inside and outside thecountry through the web portal in order to enable centralized acquisition of R&D information on
decommissioning. This is used by many people including access from overseas. Through these
activities, NDF is working on overall optimization to promote the R&D activities of relatedorganizations effectively and efficiently.

107

108

Support

※８
※９

※７

NDF

Request for study and Support

Platform of Basic
Research for
Decommissioning

Fukushima Environmental
Safety Center

Okuma Analysis andResearch Center

Naraha Center for Remote
Control Technology
Development

Project
Management
Operation

CLADS

Sector of Fukushima R&D

JAEA

Management
Expenses Grant

Cooperative
relationship

Human Resource
Development andResearch
Program for
Decommissioningof
Fukushima
Daiichi NPS
Adopteduniversities, etc.

Domestic
universities,
Research
institutes, etc.

Acceleration
Program for
Reactor
Decommission
ing
Adopteduniversities,
etc.

Joint
Research

Foreign
Universities/
Research
Institutes

Foreign
Governmental
Agencies

Cooperation

Administering

Project
Management
OfficeAssignment

Commissioned Research Institutes※６

Contract/
collaborative
Research※７

Funding

Center of World Intelligence
Project for Nuclear S&T and
Human Resource Development

MEXT

Fig. 26 Whole picture of R&D structure of the decommissioning of the Fukushima Daiichi NPS (As of FY 2019)

Decommissioning R&D Partnership was established in NDF according to a decision of Team for Countermeasures for Decommissioning and Contaminated Water Treatment.
Bold solid arrows mean supplies of R&D and management expenses (except for facilities expense).Light solid arrow means cooperation. Dotted line arrow means participation in
Decommissioning R&D Partnership Council.
Some institutions including JAEA are at the multiple positions.
Each institution has their own cooperation with foreign institution based on MOU, etc.
R&D activities by other institutions including Central Research Institute of Electric Power Industry are abbreviated.
Among the promotion projects of nuclear energy science technology/human resource development that require collective know‐how, the adopted projects up to 2017
were entrusted by MEXT to the trustee, which are not shown in this figure.
Subsidies for the promotion projects of nuclear energy science technology/human resource development that require collective know‐how are delivered to JAEA, but expressed
as being delivered to CLADS for the sake of clarity here.
For Decommissioning and Contaminated water treatment subsidy project, NDF drafts the next R&D plan and METI determines it based on the policies on Roadmap and the Strategic Plan and R&D progress.
NDF participates in the steering committee of human resource development promotion project of Nuclear Science Technology that gathers wisdom and intelligence, as a constituent.

TEPCO

Sharing/planning
R&D information(Member） NDF,JAEA,TEPCO, IRID, Plant Makers,
Related Experts, METI, MEXT

Decommissioning※１
R&D Partnership Council※９

SupportExchange of researchneeds/seeds

※３
※４
※５
※６

※８

SupportDecommissioning Strategy Committee

Commission

Information
sharing※１※２

Domestic / Foreign Enterprises

National R&D Agency
Plant makers
Electric power Companies, etc.

IRID

Subsidized Project Operating Entities

Administering

Project
Management Office

Othermakers, etc.
(including
foreignenterprises)

Funding

Assignment

Fund for Decommissioning andContaminated Water Management

Fund Establishment Organization

Funding

The Government-led R&D
Program on Decommissioning
and Contaminated Water
Management

METI

Cooperation
Participation

Decommissionin
g of 1F
R&D
organizations,e.g. IRID

Development andpractical application

Tokyo ElectricPower
Company
Holdings, Inc.

Applied research
Basic researchorganizations,e.g., universities

Basic research

Collaborative Laboratories for
Advanced Decommissioning
Science, Japan Atomic Energy
AgencyFundamental research (development of common
fundamental technology, improvement of
infrastructure and management of basic data)

Fig.27 A conceptual picture of the division of roles among main R&D institutions for thedecommissioning of the Fukushima Daiichi NPS

5.2 R&D of decommissioning required for on-site work/engineering
5.2.1 Promotion of effective R&D
There are two types of R&D activities towards their practical use for the accomplishment of thedecommissioning of the Fukushima Daiichi NPS: the engineering activities including technologicaldevelopment implemented by TEPCO and the Government-led R&D program on Decommissioning
and Contaminated Water Management carried out by selected subsidiary companies (Attachment
14).
In particular, aiming at the overall optimization of the entire decommissioning project as
described in Section 3.6, project-based R&D management will be important. R&D tasks that areraised as necessary through the engineering considerations conducted by TEPCO should beshared with the NDF. An appropriate implementing institution takes over the implementation of such
R&D tasks in a timely and accurate manner under the coordination of the NDF. Then, the result of
the R&D will be accurately provided to the site in a timely manner. As mentioned in Section 1.1, theNDF was designated to oversee and supervise the project management of TEPCO under theReserve Fund system, it is important to achieve effective R&D management through the system.
Specifically, according to the progress of the engineering work implemented by TEPCO, R&D
tasks that are newly needed will be identified, and the timing to implement such R&D tasks will be
determined through considerations of the project management. To operate an R&D management
system on a project-basis like this in an effective manner, appropriate information sharing on the
progresses of R&D implementation by TEPCO and engineering considerations and on the R&D
tasks for which the necessity became clear should be carried out under the project management
system enforced jointly by the NDF and TEPCO. To this end, it is necessary to marshal the R&D
tasks currently in progress, and R&D tasks required in the future then to manage the project under
the project management system, while clarifying in which project and until when the problem must
be solved.
In this regard, even including implementing the tasks in the Government-led R&D program on

109Decommissioning and Contaminated Water Management, implementation of R&D tasks should beconsidered in line with the basic concept of an appropriate division of roles between the government
and TEPCO according to the substances of the tasks. Specifically, R&Ds that need supports by thegovernment should target those with high technical difficulties that require the support of thegovernment, and it would be appropriate that R&D with many engineering elements will be
conducted by TEPCO.
Based on this concept, TEPCO is required to: (1) position necessary R&D tasks in theengineering schedule, including projects to be implemented in this Government-led R&D program;(2) actively commit to the management of overall processes in this Government-led R&D program,mainly in the stage leading to engineering by TEPCO; and (3) extract R&D tasks from engineeringstudies and steadily advance R&D.
5.2.2 Future approach to R&D
As a result of the R&D conducted through the Government-led R&D program on
Decommissioning and Contaminated Water Management, definite results have been obtained, forinstance, the internal condition of PCVs by have been gradually clarified by implementing elemental
technology development and developing investigation equipment. As mentioned above, as theconcrete process for full-scale decommissioning has become clearer, the R&D directly related tothe on-site application of decommissioning to realize decommissioning work will be required in the
future. For this purpose, it is essential for TEPCO, while performing actual work on the site, to planout and manage R&D, based on their own operations and measures for securing safety, as well as
the overall picture of decommissioning. Accordingly, for the effective implementation of R&D that is
directly linked to application in the field, TEPCO is required to put more weight on them, while
establishing a system in which TEPCO will plan and manage R&D by itself. As mentioned above,
regarding R&D activities, including fundamental ones, which require an approach on a mid-andlong-term basis and thus, are difficult for TEPCO to implement, the governmental support should
be provided.

5.3 Enhancement of basic study and R&D infrastructure for the success of thedecommissioning project
For decommissioning of the Fukushima Daiichi NPS, which is a large-scale project involving
opacity and uncertainty, predicting what would be the critical technical challenges in the future is avery difficult task. Based on the available information at the moment, precedents and experts’knowledge and experience, R&D tasks which might become critical in the future should be
extracted. At the same time, the infrastructures of personnel, organization and facilities should bemaintained and expanded on a long-term basis so that forthcoming cross-sectional technologicalchallenges can be managed. These are the major elements to secure smooth execution of the
project.

110

5.3.1 Essential R&D Themes and its strategic promotion derived from the needs
While universities and public research institutes in charge of basic research are expected tomaintain and develop human resources, knowledge, and infrastructure that can promptly respondto technical issues requiring science and engineering knowledge when they arise in the future, it isalso important for them to share their awareness for the issues the decommissioning sites arefacing.
In addition, facilitate the decommissioning project of the Fukushima Daiichi NPS in a safely
steady and effective manner, it is essential to develop mid-and-long-term R&D strategies including
scientific and technological investigation based on understandings of the principles and theories.
For this purpose, NDF has built a task force on research collaboration and specified the 6 Essential
R&D Themes that should be preferentially and strategically targeted based on the discussions at
the Decommissioning R&D Partnership Council. Moreover, the Platform of Basic Research for
Decommissioning49 was investigated and R&D strategies for the Themes, based on which the
R&D to be executed immediately was initiated in FY2017.
Furthermore, on the occasion of transition of the World Intelligence Project into a subsidy
program described in the following sub-section, the Ministry of Education, Culture, Sports, Scienceand Technology (MEXT) showed NDF their intention to discuss how to proceed with the future R&Dof the World Intelligence Project. This included selection of the theme for the call for proposal
considering the Essential R&D Themes from the perspective of propulsion of basic and genericresearch based thoroughly on necessity. Therefore, the NDF has compiled its basic direction for
the future to carry out six important R&D tasks, including the background of the issues, awarenessof the problems by the consumer-side and the image of the research assumed, and presented it to
the Ministry of Education (Attachment 15). This basic direction has been utilized for the public
offering of the World Intelligence Project that was started by JAEA in FY 2018.
5.3.2 Construction of basic research center and R&D infrastructure for mid-and-long-term
prospects
In order to make the long-term decommissioning project of the Fukushima Daiichi NPS proceedsteadier in technical aspects, it is essential to work on developing R&D infrastructure andaccumulating technological knowledge, developing generic technologies and collecting basic data,
including the Essential R&D Themes described in the preceding sub-section, building up research
centers, facilities and equipment, and human resource development. Decommissioning of the
Fukushima Daiichi NPS is an opportunity for trial of state-of-art science and technology and suchthe accumulation of such activity is expected to become a source of innovation.
The building for International Research Collaboration of the Collaborative Laboratories for

49 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.

111

Advanced Decommissioning Science of JAEA (JAEA/CLADS) has opened in April 2017 in Tomiokamachi, Fukushima prefecture as a location for universities, research institutes and industries insideand outside the country to create a network to integrally promote R&D and human resources
development. TEPCO and some universities have moved into the building to undertake researchand so on. It is expected that, in the future, interaction between various talents in universities,
research institutes, industries inside and outside the country will make JAEA/CLADS a central
organization acting as a hub of such activities. Following this idea, the Ministry of Education, Culture,
Sports, Science and Technology (MEXT) reformed the Center of World Intelligence Project for
Nuclear S&T and Human Resource Development into a subsidy project intended for JAEA
according to a proposition by NDF. The project is currently implemented by the system centered on
JAEA/CLADS from the newly adopted tasks in FY2018. Moreover, “Program for Decommissioning
Research by Human Resource Development” was newly established in the Center of WorldIntelligence Project in 2019. It created a basis of research and human resource development(Collaboration laboratory)50 in both of educational research institutions and JAEA/CLADS, and has
started R&D and human resource development project that connects these organizations by crossappoint system. It contributes to functional enhancement of JAEA/CLADS.
It is also important to develop research infrastructure of hardware. JAEA put the Naraha Remote
Technology Development Center in full service in April 2016 in Naraha-machi, Fukushima
Prefecture. It is a facility with a variety of equipment for development and experiment of remotely
controlled devices and installations. Specifically, prior to sending the devices into the harshenvironment inaccessible for people, testing in a real-scale mock-up is indispensable for
performance verification as well as for training and establishment of the operating procedure. It is
desirable that the enterprises and so on utilize the mock-up actively. In order to proceed withsmooth decommissioning of Fukushima Daiichi NPS, it has become even more important toeffectively use this facility, e.g. mock-up test with arm-typed accessing equipment for fuel debris
retrieval is scheduled.
Moreover, Fukushima Prefectural Centre for Environmental Creation where Fukushima
Prefecture, JAEA, and the National Institute for Environmental Studies have their offices (Miharumachi, Fukushima Prefecture) opened in July 2016, serving as a comprehensive center ofcollaboration of the three agencies. In addition, JAEA opened the facility management building of
the Okuma Analysis and Research Center (Radioactive Material Analysis and Research Facility)(Okuma-machi, Fukushima Prefecture) in March 2018. For the 1st building, where low radiationdose samples such as rubble will be handled mainly, the frame construction of the third floor isbeing carried out. For the 2nd building, where high radiation dose samples such as fuel debris will
be handled, detailed design is being carried out.
As seen above, R&D infrastructures related to decommissioning, contaminated water
management and environmental decontamination measures are being set up mainly in Fukushima

50

JAEA can use the bases in Tokai and Oarai as well as the base in Fukushima,

112

Prefecture. These research facilities are formulating a global center of decommissioning R&D
aiming at the mid-and-long-term vision.

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6. Enhancement of international cooperation
6.1 Significance 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. Furthermore, there is significant uncertainty in the management of various
radioactive substances in past nuclear development facilities called “legacy sites” which are locatedin the UK, US and France etc. In these sites, there are implemented decommissioning andenvironmental remediation over a long period of time. These countries have continued to bechallenging to issues such as technological difficulties called “unknown unknowns” (don’t knowwhat is unknown) associated with these decommissioning and environmental remediation, project
management for several decades, and securing of large amount of funds.
In order to make steady progress on the decommissioning of the Fukushima Daiichi NPS, that
deals with the advanced engineering issues, as a risk reduction strategy, it is important to learn
from the measures taken for the preceeding damaged reactors and from the lessons acquired
through decommissioning activities of the legacy sites, and to apply them to the actual
decommissioning, while utilizing excellent technologies and human resources that each county
have fostered. In addition, to maintain and develop understanding, interests and relationship frominternational communities on decommissioning, it is also important to give the knowledge gained
from the accident and decommissioning of Fukushima Daiichi NPS proactively and strategicallyback through international joint activities related to decommissioning; then to engage in mutually
beneficial decommissioning open to international societies.
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 be interpreted as which the decommissioning of Fukushima Daiichi NPS may be an influential
ground to create innovation. Assembling diverse wisdom and experiences to Fukushima from allover the world is primary an important effort to steadily proceed with decommissioning itself ofFukushima Daiichi NPS. It is also an important effort from the perspective of that innovation to becreated through the decommissioning process leads to the reconstruction of the local industries
and to establish the local community engagement that is essential to continue decommissioning
over a long period of time.
In moving international cooperation forward specifically, it is also important to utilize multilateral
cooperation framework through the international institutions such as IAEA, Organization for
Economic Co-operation and Development/Nuclear Energy Agency (hereinafter referred to as the“OECD/NEA”), as well as to promote bilateral cooperation according to the circumstances of each114

country. These international institutions have roles of contribution for designing the international
standard, sharing the knowledge and experiences among nations, and forming internationalcommon understanding concerning decommissioning. To proceed with the decommissioning of the
Fukushima Daiichi NPS in an internationally open manner, it is crucial for Japan to participate in
the activities of these institutions. At the same time, it is also expected to fulfill a part of responsibility
to the international society through sharing the Fukushima experience with memberships of theinstitutions through participating in the discussion for designing the international standard.

6.2 Facilitation of international cooperation activities
6.2.1 Enhancement of partnership with overseas decommissioning agencies
Because the decommissioning of the Fukushima Daiichi NPS continues over a long time
period, it is required to establish the definitive basis of international cooperation, as well as to build
long-term and continuous partnership with overseas decommissioning agencies.
Especially, the decommissioning of legacy sites would serve, as a model for approach
preceding to the Fukushima Daiichi NPS decommissioning, in many knowledge in accordance withtechnology and management. Each country has established its own public decommissioning
organization to promote decommissioning of legacy sites because the decommissioning requires
the expertise, concept, and new technologies which are different from the operation/maintenancefor nuclear reactor and nuclear fuel cycle facility. Therefore, it is important for NDF to build andreinforce a long-term partnership with these institutions such as Nuclear Decommissioning
Authority (NDA), Commissariat a l’energie atomique (CEA), United States Department of Energy,
Office of Environmental Management (DOE/EM) that deliver decommissioning of legacy sites ineach country under government-level framework. TEPCO should also establish and reinforce along-term partnership with overseas decommissioning operators, and these should be broadcooperation-based.
On that ground, NDF has concluded memorandums of cooperation with the NDA and the CEA,
while TEPCO has concluded agreements with Sellafield Ltd. in the U.K. and so on, to construct aframework of constant exchange of opinions as shown in table 4. In the future, it is also importantto learn technologies and lessons from various countries to utilize it for the decommissioning of the
Fukushima Daiichi NPS, in using these framework. Moreover, with a view to reinforcing thepartnership, it is also important for our country to share the technology and experience derived fromthe decommissioning of the Fukushima Daiichi NPS to develop an interactive cooperative
relationship.
6.2.2 Integrating and utilizing wisdom in the world
In regard with the decommissioning of the Fukushima Daiichi NPS, Japan should gather andlearn the wisdom in the world on a variety of approaches not only in technical aspect, but also
operational aspect such as system/policy, providing strategy, project plan/operation, securing safety,

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regional communications, and so on. On the other hand, there are opportunities to support thedecommissioning of the Fukushima Daiichi NPS by international society, and Japan has received
several kinds of supports by overseas governmental institutions and experts including DAROD
project led by IAEA and collaboration projects promoted by OECD/NEA.
In the technical aspect on the decommissioning of the Fukushima Daiichi NPS, while learning
the use situation of technologies in the decommissioning of legacy sites among other things in eachcountry, many suggestions from joint research by governmental projects and universities have beenobtained. For example, referring also to the information that fuel debris in Chernobyl has been
pulverized due to aging, the “To identify process of characteristic changes in fuel debris over time”
has been extracted as the Essential R&D Themes, which should be addressed strategically andpreferentially, and its R&D project has proceeded. In addition, an international tendering system
was applied to the Government-led R&D Program on Decommissioning and Contaminated Water
Management of the Ministry of Economy, Trade and Industry (METI) and foreign companies are
participating in the project as subsidized operators. Moreover, as with the World Intelligence Project
by MEXT, international joint research are implemented as well with the cooperation of overseasorganizations in the U.K., the U.S.A. and universities in Japan. In addition, our country
independently participates in the international joint research PreADES, “Preparatory study on
Analysis of fuel DEbriS”, project led by the OECD/NEA from the viewpoint of characterizing fueldebris and so forth. As described in Chapter 5, the country and the operator must divide the roles
appropriately to proceed steadily with on-site application of the R&D results and, for this purpose,
it is also important to refer to the principles of the R&D system for decommissioning overseas.
In the management aspect, as for system and policy, information exchange with various
countries by means of intergovernmental meetings, commissioned research on the system
structure to overseas organizations has been conducted as shown in Table 4. Specifically, welearned from opinion exchanges with the NDA, case studies, and the efforts of overseas
engineering firms. To give a practical use example, the project management techniques wasintroduced into the actual formulation of strategies and planning/management of projects. Moreover,as for securing safety, we have been studied the information on international regulations obtained
through activities in international organizations and the regulatory activities related to the overseas
reactors suffered from accidents and the legacy sites. We will have used them as a reference toformulate the institution for decommissioning in our country and the idea of ensuring safety
described in Sub-section 2.3.3.4.
Japan has to keep on proceeding with the decommissioning of the Fukushima Daiichi NPS
while gathering and utilizing global knowhow from both of technological and management aspects.
For this purpose, while encouraging participation in the activities of international organizations andintergovernmental meetings and promoting international joint research, experts from overseas areto be invited to receive advice and evaluations and gather knowhow and experience with regard todecommissioning and so on overseas. As for gathering wisdoms on basic and fundamental R&D,
it should collect and interact with a variety of ideas and human resources, and it is necessary to116

improve its environment and fields appropriately. ,As described in Chapter 5, JAEA/CLADS is oneof the important base to provide such environment and fields, it is essential to reinforce the function
to integrate the wisdom from in and out of Japan more in regard to further decommissioning.
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. Under the circumstance that decommissioning isbeing conducted across by many companies across countries, it is crucial to understand the latest
status for effectively utilizing excellent technologies and human resources of the world.
Table 4 Cooperative relationship among the institutions for the decommissioning of the
Fukushima Daiichi
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 February 2012).

Japan-US Decommissioning
and Environmental
Management Working Group

After the Fukushima Daiichi NPS accident in March 2011, theestablishment of the US-Japan Bilateral Commission on Civil
Nuclear Cooperation (the Bilateral Commission) wasannounced in April 2012 based on the relationship between
Japan and the US to further reinforce bilateral cooperation.
Under this commission, “the Decommissioning andEnvironmental Management Working Group (DEMWG)” wasestablished (Since December 2012).

Japan-Russia Nuclear
Working GroupThe Nuclear Working Group was established after confirmingthat Energy is one of the eight areas of cooperation plan
approved at the Japan-Russia top-level meeting in September
2016, (Since September 2016).
Inter-organizational Cooperation Agreement

Domestic

International

Descriptions

NDF

NDA

Exchange of information for various technical knowledge on
decommissioning, etc. and personal exchange are provided.
(Concluded in February 2015)

NDF

CEA

Exchange of information for various technical knowledge on
decommissioning, etc. and personal exchange is provided.
(Concluded in February 2015)

TEPCO

DOE

Umbrella Contract was made and information is exchanged asneeded. (Concluded in September 2013)

TEPCO

Sellafield, Ltd.

Information Exchange Agreement for site’s operation, etc. wasconcluded. (September 2014)

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TEPCO

CEA

Information Exchange Agreement on for decommissioning was
concluded. (September 2015)

JAEA

NNL

Comprehensive Agreement for advanced technology on
nuclear R&D, advanced fuel cycles, fast reactor, radioactive
waste

JAEA

CEA

Cooperation Agreement for specific technical issues on molten
core-concrete interaction, etc.

JAEA

Belgium Nuclear
Research Center

Agreement of Cooperation for Nuclear R&D and Research on
the accident of the Fukushima Daiichi

JAEA

Nuclear Safety
Research Center(Ukraine)

Memorandum for decommissioning research, etc. of the
Fukushima Daiichi NPS and Chernobyl was concluded.

JAEA

IAEA

Research Agreement on characterization of fuel debris

6.2.3 Dissemination of information to the global society
As Japan’s responsibility to the international global society for having caused the accident at
the Fukushima Daiichi NPS, also from the viewpoints of keeping concerns of human resource whowill be able to lead decommissioning from the world and contributing to gather wisdom andknowledge, it is important to proceed with the decommissioning in a manner open to theinternational community. It is needed to prevent reputational damage as described in Section 7.3;
therefore, the dissemination of clear information should be strengthened to formulate a precise
understanding in the international community.
Accordingly, NDF takes dissemination of information about the situation of the Fukushima
Daiichi NPS decommissioning globally through holding side events of the IAEA General
Conference, by taking the platform at major international conferences such as OECD/NEA Steering
Committee, Nuclear Safety Regulatory Information Conference (RIC) sponsored by the U.S.
Nuclear Regulatory Commission’s (NRC’s) and Decommissioning Forum in France, and throughpresentations at intergovernmental meetings. Moreover, in order to clearly report the situation of
the decommissioning of the Fukushima Daiichi NPS to the world, and to work on dialogue forsymbiosis with the local community, NDF has held the “International Forum on theDecommissioning of the Fukushima Daiichi NPS” every year since 2016. This Forum is a trial for
global dissemination of the way to communicate about decommissioning through dialogue with thelocal residents, which is evaluated as an important event internationally.
Furthermore, it is also important to make the latest information on the decommissioning of the
Fukushima Daiichi NPS available throughout the world through publicity in foreign languages,
English websites, mailing lists and other means; therefore, this efforts must be continued to provide
clear information utilizing videos and so on. (Refer to Table 5, Approach for dissemination of
information to the world)118

6.2.4 Participation in international cooperative activities
Eight years have passed since the Fukuoka Daiichi NPS accident, there have been moves
outside Japan, which are to scientifically verify and analyze this accident and the decommissioning
process and to apply the knowledge gained from the result to other issues. Decommissioning as arisk reducing strategy is top priority issue for our country, it is also important to keep concerns ofFukushima Daiichi NPS high from the viewpoint of gathering wisdom and knowledge from the world
in order to proceed with decommissioning. For this reason, it is essential to promote international
joint research, and it is also necessary to pursue in a beneficial manner to each side, not only to
pay attention to Japan’s needs but overseas demand that is newly generated. It is important tobring the wisdom and knowledge gained through decommissioning as a result of these efforts backto overseas cooperation organizations properly.
Therefore, keeping in mind that Japan actively responds to these new concerns from the world,
our country has launched projects including PreADES/TCOFF and taken the initiative in discussing
positively, as well as joined the studies at SEREF, which was established by OECD/NEA with theaccident of Fukushima Daiichi as the starting point. NDF proactively participates in international
joint activities such as “Committee on Decommissioning of Nuclear Installations and Legacy
Management” (CDLM, established in April 2018), that is a committee to exchange opinions on
decommissioning organized in OECD/NEA, “Expert Group on Characterisation Methodology of
Unconventional and Legacy Waste” (EGCUL, established in November 2018) to study
characterization methodology of large amounts of waste generated from accident site under“Radioactive

WasteManagement

Committee”(RWMC),

and“Improved

NuclearSitecharacterisation for waste minimisation in Decommissioning and Dismantling operations underconstraint EnviRonment” (INSIDER, established in June 2017), that is an R&D project of EU withthe aims of improving waste management cost reduction and efficiency through the analysis of theactual cases. Then, NDF provides information about the accident of Fukushima Daiichi NPS, andit should be continued in the future in cooperation with the related organizations.

6.3 Close cooperation with relevant domestic organizations
As described in Sub-section 6.2.1, the related domestic organizations are proceeding withefforts to construct and strengthen partnerships with overseas related organizations in accordancewith respective roles. On the other hand, with regard to decommissioning R&D, as shown in Fig 28,
cooperation such as joint research between research institutes and universities is in progress.
Since sharing knowhow and personal relationships obtained through these activities is importantfor our country also in the context of ensuring consistency with international cooperative activities
and realizing effective international cooperation, cooperation between related domesticorganizations must be promoted to be tighter than ever.

119

Table 5 Approach for dissemination of information to the world
Holding or attending International Conference (from April 2018 to August 2019)
Conference Name

PeriodOrganization

TOTAL-DECOM Forum (UK)

April, 2018

NDF

INSIDER Project Meeting

June, 2018

NDF

The 3 International Forum on the Decommissioning of the
Fukushima Daiichi NPS

August, 2018

NDF

The 62nd IAEA Conference Side event

September, 2018

NDF, METI

Nuclear Decommissioning Forum 2018 (France)

October, 2018

NDF

Workshop on development of containing, transferring and storing
technologies for fuel debris

December, 2018

NDF

The 1st G7 Nuclear Safety Security group (NSSG)

February, 2019

METI

UKAEA Workshop on Remote Technology (UK)

February, 2019

NDF

The 3 UK-Japan Nuclear Industrial Forum

February, 2019

NDF, METI

Waste Management (WM) Symposium 2019 (US)March, 2019

NDF

NRC Regulatory Information Conference (RIC) 2019

March, 2019

NDF

OECD/NEA Symposium on Decommissioning and Food Safety ofFukushima Daiichi NPSMarch, 2019

METI, MAFF

International Meeting on Fukushima Decommissioning Research2019 (FDR2019)

May, 2019

METI

WTO/SPS Committee, Briefing for EU countries

July, 2019

METI

The 4 International Forum on the Decommissioning of the
Fukushima Daiichi NPS

August, 2019

NDF

Fukushima Research ConferenceYear round

JAEA

rd

rd

th

Dissemination of information 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 fromthe 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

TEPCO CUUSOO（https://tepco.cuusoo.com/）TEPCOManagement Office for the Government-led R&D program on Decommissioning andContaminated Water Management(https://en.dccc-program.jp/)

MRI

120

7. Local community engagement
7.1 Approaches for local community engagement
In order to steadily implement decommissioning of the Fukushima Daiichi NPS that spans long
periods of time, decommissioning that moves forward together with the local restoration must be
aimed under the recognition that “Decommissioning and the reconstruction of Fukushima are an
indispensable pair”.
On that account, understanding and cooperation of the region are essential as it is the first priority
to proceed with efforts toward decommissioning in a safe and steady manner. Accurate information
concerning decommissioning should be disseminated at the right time and appropriately. In addition,
it is important to respond to the voices by communicating carefully through dialogues to listen to
the voice of anxieties or questions from the local communities and various standpoints sincerely.
Moreover, we believe that decommissioning can be trusted by the community and co-existedwith the regions, while effectively utilizing the local resources and developing decommissioning ora variety of its relevant activities along with the restoration of the region.

7.2 Actual effort for better Communication
As decommissioning operation, including fuel debris retrieval, proceeds, it is necessary to put
into practice information providing or interactive communication in a further well thought-out manner,with proper cooperation between the related organizations such as the government, NDF andTEPCO referring to the various overseas experiences.
The government will work 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 and website that summarize the decommissioning approach and thebrochure “Important Stories on Decommissioning” as well as by active explanations to andconversations 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 the local residents every year, provides clear
information on the decommissioning, and exchanges honest opinions with the participants, while
sharing the latest progress and the technical results of the decommissioning efforts among both
Japanese and foreign experts. Besides, NDF makes efforts to have attentions and interests indecommissioning by holding workshops and sessions targeted at future generations who are to
face decommissioning. In addition, the brochure “Hairo no Iroha (ABCs of decommissioning)” hasbeen prepared to disseminate accurate and clear information on the decommissioning in a simple
way. Also in the future, it has been decided to continue interactive conversational activities morevigorously to seek establishment of trustful relations with the local residents.

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TEPCO is continuously working on explanations and conversations through management andthe risk communicators and on the explanations to and conversations with the local representatives
regarding the progress of the Mid-and-Long-term Roadmap 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.
Moreover, the Decommissioning Communication Center was established in November 2017, tobuild a trusting relationship with the regions. The center integrates management between
decommissioning section and communication section facing the regions and the community under
the chief executive of decommissioning.
While strengthening the structure, TEPCO seeks dissemination of clear information through PR
tools such as regular press conference on nuclear, scheduled lectures to Fukushima Prefectural
Government Press Club, information dissemination on decommissioning status in the conferencesthat TEPCO participates in at right time and accurately, disclosure on website, and magazine on
decommissioning “Hairo Michi” (the way to decommissioning). In particular, the website,“Fukushima Daiichi Decommissioning Project” has been completely updated in August 2018, to
make it easy to obtain desired information from the standpoint of viewers.
Upon formulating a common understanding of decommissioning, it is very effective to havepeople observe the real state of progress of the decommissioning task on the site. TEPCO has
been proactively accepting visitors to the Fukushima Daiichi NPS, including evacuees, and 18,886
visitors were accepted in FY2018. In the future, setting the acceptance level at 20,000 visitors per
year in FY2020 as a target, a further increase of the acceptance level will be attempted.
In November 2018, “TEPCO Decommissioning Archive Center” has opened as a place whereenables visitors to know the fact of the nuclear accident and the progress of decommissioning
operation, it drew about 21,000 visitors as of the end of May, 2019. While coordinating with therelevant facilities and surrounding regions, it is important to continue to enhance the contents andto disseminate clear information in maintaining its endeavor and to gather wisdom and knowledge
from around the world by making use of these facilities.

7.3 Measures against reputational damages
Reputational damage can be caused only with the presence of anxiety even if the risk is not
actualized. Moreover, it is pointed out that, even though eight years have passed since the accident,
the image immediately after the accident still remains without being erased and has an influence.
The delay in responding to the reputational damage, occurrence of troubles in decommissioning
operations, radiation exposure of operators and the cost increase may damage the social
evaluation of the decommissioning effort, which might lead to a vicious circle of further delays indecommissioning activities. In order to avoid a vicious cycle like this, it is important to promptly
reduce existing risks as top priority while proceeding with decommissioning approach in a safe andsteady manner. Besides, it is crucial to establish trustful relationship by communicating regularly

122

with local residents, as disseminating information on decommissioning should be made at the righttime and accurately.
In order to prevent reputational damage, the government held “Task Force on the Nuclear
Hazard’s Influence Including the Negative Reputation Impact”, as it requires to expand
communications with wider range of people. The concerned government agencies are working on
it in an integrated manner, based on the three enhanced guidelines which are “Eliminate source ofnegative reputation”, “Prevent negative reputation by providing accurate and clear information” and“Support damaged industries due to negative reputation”. In December 2017, the government
formulated the “Strategies to Eliminate Negative Reputation and to Strengthen Risk
Communication”, and has made efforts against eliminating negative reputation.
TEPCO formulated “Action Plan to Combat Reputational Damage” in January 2018, and has
made efforts to promote distribution of prefectural products of Fukushima and to provide accurate
information concerning their safety.
In accordance with these, it is important for the concerned organizations to continue theirconcerted efforts.

7.4 Decommissioning moves forward together with the recovery of thecommunity
Under the recognition of “Decommissioning and the reconstruction of Fukushima as an
indispensable pair”, it is important to work for developing human resources that will engage
decommissioning in the region and for integrating its relevant industries, to recover the industry in
Hamadori region of Fukushima prefecture where was lost by The Great East Japan Earthquake
and nuclear disaster, in conjunction with “Fukushima Innovation Coast Framework (Fig. 28)” as anational project aimed to establish new industrial infrastructure.
For proceeding with decommissioning along with the local reconstruction, it is important toincrease contact with the region, for instance, TEPCO procures materials and services associatedwith decommissioning from the local vendors and employs the local workers. On the other hand, it
is necessary to achieve not only safe and steady decommissioning but giving priority to the local
product and services, based on the need to safely proceed with decommissioning as early as
possible. In Fukushima Daiichi NPS, managing cafeteria and shops of the new office building andmaintaining infrastructure including electricity and air conditioning facility on site are conducted withthe cooperation of the local companies. In the aspect of employment, sixty percent of workers,
including TEPCO employees and partner company operators, etc., are the local human resources.
There are some examples of utilizing technical capabilities of local companies for decommissioning
work, include cases where a company with local offices is involved in the development of full-facemasks that improve safety of workers, and where a local company with high engineering
capabilities on remote operations plays an active role in dismantling of the exhaust stack in123cooperation with TEPCO. These technical capabilities of local companies play a part of thedecommissioning work.
In the future, attracting business operators and projects associated with decommissioning, andprocuring from enterprises within Fukushima prefecture will be promoted actively, it is expected tocontribute to the reconstruction of the region as well, while supporting the local companies, incooperation with Fukushima SoSo (Soma and Futaba regions) Reconstruction Promotion Agency
which has a strong network and Fukushima Innovation Coast Framework which supports
decommissioning-related industries by matching their needs with seeds.
In order to achieve decommissioning that moves forward together with the recovery of thecommunity, it is strongly expected that TEPCO addresses various issues by working together
between Fukushima Daiichi Decontamination and Decommissioning Engineering Company andthe Fukushima Revitalization Headquarter in TEPCO, and coordinates with the government, NDF
and the relevant organizations of the local government.
Furthermore, promotion of safe and steady decommissioning requires appropriateness on quality
and price for goods and services to be procured, its environment should be improved which enables
many of the local companies to participate in decommissioning work from the long-term perspective
through use of resources and know-hows obtained by the relevant organizations and technologicaland business supports.

Fig. 28 Overview of Fukushima Innovation Coast Framework

124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

NRC

Nuclear Regulatory Commission

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

VR

Virtual Reality

X-6 penetration

PCV X-6 penetration

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.

125

Withdrawal Plan

Withdrawal plan for reserve fund

The Policy of
Preparation ofWithdrawal Plan

The Policy of preparation of withdrawal plan for reserve fund fordecommissioning

Fukushima Daiichi NPS

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

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

Preliminary
engineering

Engineering operation to determine the feasibility of engineering work
preliminary in advance of basic design that is conducted at the beginningof general construction126

Well shieldplug

Operating floor
Spent
Fuel
Pool
(SFP)

Component
Pit

4th floor

Primary
Containment
Vessel (PCV)
ReactorPressure
Vessel (RPV)

3rd floor

2nd floor

Pedestal
Vent Tube

1st floor
1st basement Fl.

Suppression
Chamber (S/C)

Torus room

Courtesy
IRID（IRID of提供）

Fig. 29 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 guide
Differential pressure detector/
Piping of Boric acid solution
injection system

Jet pump
Control Rod Drive Mechanism
Pedestal for RPV

Courtesy
IRID（IRID of提供）

Fig. 30 Structural drawing inside Reactor Pressure Vessel (RPV)127

List of Attachment
Attachment 1

Revision of the Mid-and-Long-term Roadmap and the earlier publishedstrategic plan

129

Attachment 2

Major risk reduction measures performed so far and future course of action 131

Attachment 3

Overview of SED indicator

Attachment 4

Risk sources that include radioactive materials exists in site of Fukushima

137

Daiichi NPS except for major risk sources

144

Attachment 5

Change in risk over time146

Attachment 6

Coverage of fuel debris retrieval

147

Attachment 7

Strategic recommendation for determination of fuel debris retrieval methods forthe first implementing unit

149

Attachment 8

Analysis and investigation plan

191

Attachment 9

Reduction of liquid phase and contaminated water (Water balance around thereactor buildings)

200

Attachment 10

Study on the water level at the bottom of PCV during fuel debris retrieval

202

Attachment 11

Terms related to radioactive waste management

206

Attachment 12

Overall image of Storage Management Plan for the Fukushima Daiichi NPS
207

Attachment 13

Draft of technical map toward human resource development fordecommissioning reactors

Attachment 14

209

Current Progress of the Government-led R&D program on Decommissioning
and Contaminated Water Management

210

Attachment 15

Basic Direction of 6 Essential R&D Themes

248

Attachment 16

Record of collaborative activities with foreign organizations

256

128

Attachment 1 Revision of the Mid-and-Long-term Roadmap and the earlier published strategicplan[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 the 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; theperiod up to spent fuel removal start (1st period), the period up to fuel debris retrieval start from completionof the 1st period (2nd period) and the period up to completion of decommissioning from completion 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 theabove.
[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.

129

[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
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 treatment and disposal of radioactive waste” which is expected
to be 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 technical recommendations.
 Basic concepts concerning solid waste treatment and 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.

130

Attachment 2 Major risk reduction measures performed so far 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. A2-1. The vertical axis in the top graph in the figure
shows the risk level in common logarithmic scale and the horizontal axis shows number ofyears after the accident.
Although the risk level at the time of zero year after the accident was at high level causedby the fuel 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 inboth Hazard Potential and Safety Management, because of implementation of safetymeasures including cooling function restoration of the fuel pool, cooling of fuel debris withwater injection by core spray system, nitrogen injection, etc. (in 2011) as well as thecontribution of inventory and decay heat decrease due to decay of radioactive materials.
The risk level in 0.5 to 2.5 years after the accident is shown in the enlarged graph (thevertical axis is in linear scale) with the breakdown of major risk source (fuel debris, fuel in
SFP and contaminated water) at the bottom left in the figure and the similar graph since 3
years after the accident is given in the bottom right with the risk level multiplied by 10.These0

Fuel removal from
Unit 4 SFP started

1

2

3

4

5

CF of fuel in
SFP reviewed

6

7

Risk level (linear scale)

Risk level (linear scale)

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

8

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

Fuel debris

Fuel in SFPs

Fig. A2-1

Contaminated water

5

6

7

Year after accident

Year after accident
Fuel debris

Fuel in SFPs

Contaminated water

Reduction of risks contained in the Fukushima Daiichi NPS(Same of Fig.4 of p.16)
131

8

Change in the risk level with further breakdown of major risk source over the time since 0.5
years after the accident is shown in Fig. A2-2. In using with logarithmic scale, risk sources
can be indicated that are too small to be displayed in the linear scale of Fig. A2-1. Fuel inthe common spent fuel storage pool and fuel in dry cask temporary custody facility are notshown which stay in the region of sufficiently stable management.
Reasons of change in the risk level of every major risk source shown above are as follows,
and the summary of the risk reduction measures described below is shown in Table A2-1.
CF of fuel in SFP
reviewed

Risk level (logarithmic scale)

Total
Fuel in SFPs
Progression ofProcessing

Fuel debris
Stagnant water in bldgs
Contaminated water in trenches
Stored water in tanks
Secondary waste
Contaminated structures in bldgs
Rubbles, etc.

0

1

2

3

4

5

6

7

8

Years after accident

Fig. A2-2

Change in the risk level of every major risk source(1) Fuel in SFPs
Since one year after the accident, removing rubble and installing the fuel removal coverwere implemented as preparations of fuel removal in Unit 4. Fuel removal in SFP in Unit 4
was started 2.5 years later after the accident by transportation to the common spent fuelstorage pool with low Safety Management, resulting in the risk level reduction (completion in2014). Except reduction due to decay of the radioactive materials, it is this fuel removal from
SFP in Unit 4 that contributes most so far to the risk level reduction of the total site.
In Unit 3, rubble removal has been conducted as preparations of fuel removal from SFP,
and the cover for fuel removal was installed in 2018. Moreover, fuel removal from SFP wasstarted from April 2019, resulting in reduction of risk level. In addition, fuel removal in SFP in
Units 1 and 2 is scheduled to start by 2023 to reduce the risk level.
In light of the evaluation of eight years after the accident, as a result of incorporating theinsight that the rise in water temperature after cooling shutdown was slower than expected,
132

the risk of fuel in SFPs is lower than previously estimated, because the time margin before
this risk becomes apparent increases.
(2) Fuel debris
Although fuel debris was at an high risk level just after the accident because it was at
molten state, and in addition, the release risk of radioactive materials was realized, the risk
level was reduced, not only by decay of the radioactive materials, but also by reduction ofHazard Potential and Safety Management because of restoration and strengthening ofcooling function.
Although the risk level reduction effect was observed because of Safety Management
reduction caused by diffusion control function with the building cover in Unit 1 (in 2011), thiseffect currently disappeared due to removal of the building cover (in 2015) to prepare for fuelremoval from SFP.
(3) Stagnant water in the buildings
Stagnant water in the buildings is generated by cooling water for fuel debris and leakageof groundwater into the buildings, and its treatment has been progressed because of thestarting of operation of the cesium adsorption apparatus (KURION and SARRY) (in 2011). In
addition, due to the effects of sub-drain systems and land-side impermeable walls, thegroundwater level was lowered and the inflow amount of groundwater into the buildings was
reduced, resulting in achievement of lowering of the water level in the buildings. This also
helped progress of treatment of the stagnant water. Moreover, draining of the condensers
has been completed (in 2017). This stagnant water treatment in the buildings so far
significantly contributes to risk level reduction of the total site following contribution by fuelremoval from SFP.
This treatment of the stagnant water in the buildings resulted in generation of secondary
waste from water treatment systems described in (6) below to which most inventory wastransferred and the stored water in the tanks described in (5) below as the treated water.
In 2018, an increase in radioactive material concentration in the stagnant water in thebuilding of Unit 3 is observed and the risk level of total stagnant water in the buildings has
risen. This is considered as an effect that isolated water, etc., which was not included in therisk assessment, has leaked in, and the investigation and the study are underway. In recent
days, the risk level of total stagnant water in the buildings is slightly decreasing due to the
reduction of storing amount.

133(4) Contaminated water in trenches
Although the high concentration of contaminated water has been stagnated since just after
the accident in the seawater pipe trenches in Units 2 to 4, treatment of the stagnant water
has been completed and trenches were blocked (in 2015).
Treatment of stagnant water in the seawater pipe trench in Unit 1 with lower concentrationcompared to those in Units 2 to 4 is ongoing continuously, and it is scheduled to complete in
2019.
(5) Stored water in tanks
In each tank, there are several types of stored water with different radioactive material
concentration. Although concentrated liquid waste generated by operation of the evaporative
concentration system (in 2011) just after the accident had high concentration of radioactive
materials, the evaporative concentration system stopped after a short period of operation (in2011) and concentrated liquid waste is not generated at present. In addition, the concentrated
liquid waste slurry was separated from this concentrated liquid waste and has been regarded
as secondary waste from water treatment system (in 2014). The risk level of the residual
concentrated liquid waste was decreased because of reduced inventory and transfer to thewelded tanks that is secured more.
Processing of the concentrated salt water generated by the cesium adsorption apparatus
has been completed in 2015 by operation of the Advanced Liquid Processing System(ALPS)(in 2013 with the existing system and in 2014 with the expanded system) and the highperformance ALPS (in 2014).
Reduction of risk level is devised by raising and duplicating the weir (completed in 2014
for existing tanks) and replacing tanks from flanged type to welded type (completed in
FY2018). Whether it is concentrated salt water, Sr treated water or treated water, there is asmall amount of residual water left at the bottom of the flange tanks, and the process is inprogress to dismantle those tanks.
(6) Secondary waste from water treatment
Many radioactive materials have moved from contaminated water to secondary waste
through water treatment. Secondary waste from water treatment system includes the waste
sludge, waste adsorption columns by operation of the cesium adsorption apparatus (KURION
and SARRY) (in 2011), HIC slurry by operation of the Advanced Liquid Processing System(in 2013), waste adsorption columns by operation of the high-performance ALPS (in 2014),
waste adsorption columns by the mobile type treatment equipment that processedcontaminated water in the seawater pipe trenches, etc. Although the contribution level of the134waste sludge is higher as the risk level, currently the waste sludge is not newly generated.
Therefore, the risk level of the total secondary waste from water treatment system does nottend to increase.
Although the concentrated liquid waste slurry separated from the concentrated liquid waste(in 2014) was stored in the welded type horizontal tanks without the weir and placed on the
ground without the base, its risk level was reduced due to implementation of safety measuresby installation of the reinforced-concrete base and the weir (in 2017).
(7) Contaminated structures, etc. in the buildings
There is no significant change at the present moment in the risk level of contaminatedstructures, etc. in the buildings comprised of structures, piping, components, etc. in thereactor buildings, PCVs or RPVs that are contaminated by dispersed radioactive materials
caused by the accident since fuel 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 been enhanced by soil covered temporary storage facilities (in 2012), felledtree temporary storage pool (in 2013), expansion of solid waste storage facilities (in 2018),
etc. Furthermore, outdoor temporary storage is planned to dissolve by increasing incinerator
facility, volume reduction facility and solid waste storage, etc. by 2028 in accordance with thesolid waste storage management plan.

135

Table A2-1

Major efforts affected directly to the risk level implemented up to today andfuture actions

Year

Fuel debris

2011

 Starting water
injection by corespray system
 Starting
Nitrogeninjection
 Installation ofbuilding cover(Unit 1)

Fuel in SFP

Contaminated water Investigation ofinternal pool（Unit 4）
 Removing rubbles inoperation floor（Unit4）
 Installation of fuelremoval cover (Unit 4)
 Removing large
rubbles in pool (Unit 4)
 Removing rubbles inoperation floor (Unit 3)
 Start of fuel removal(Unit 4)
 Completion of fuelremoval (Unit 4)

2012

2013

2014

 Removal ofbuilding cover(Unit 1)

 Removing large
rubbles in pool (Unit 3)
 Investigation ofinternal pool (Unit 3)

2015

2016
2017
 Installation of fuelremoval cover (Unit 3)

 Start of Unit 3 removal

2019

Futureactions

 Receipt start ofsoil covered
temporarystorage facility
 Operation start of ALPS
 Starting transfer to weldedtank Start of retrieval
from first
implementing
unit in 2021

 Start of Units 1 and 2
removal, aiming by
FY2023136

 Receipt start offelled tree
temporarystorage pool

 Completion of raise andduplication of weir for existingtanks
 Operation start of expanded
ALPS and high-performance
ALPS Operation start of mobile-type
strontium removal equipment Separation of concentrated
liquid waste slurry fromconcentrated liquid waste Adding Sr-removing function
to SARRY Adding Sr-removing function
to KURION
 Completion of concentrated
salt water treatment
 Completion of seawater pipe
trench blockage (Units 2 to 4)
 Start of pumping up by subdrain system Closure of sea-side
impermeable walls Completion of condenser
drainage (Units 1 to 3)

2018

Solid waste

 Operation start of KURION
and SARRY Operation start and shutdownof AREVA Decontamination
System Operation start and shutdownof evaporative concentration
system Cooling function
restoration

 Closure of land-side
impermeable walls, mostly
completed Completion of transfer of Srtreated water to welded tanks
 Completion of transfer oftreated water to welded tanks
 Blockage of seawater pipe
trench at Unit 1 in 2019
 Completion of stagnant water
treatment in the buildings in2020

 Completion ofsafety measuresfor concentrated
liquid waste
slurry Installation of
new solid waste
storage facility

 Storing of solid
waste in thestorage facility inaccordance withsolid waste
storage plan by
FY2028

Attachment 3 Overview of SED indicator
Risk analysis targeting various risk sources, which have diverse characteristics and exist
all over the site, was conducted in reference to the SED indicator51 developed by the NDA.
The SED indicator is an important factor to decide priority to implement risk reduction
measures. It was partially modified (refer to the following pages) so that uniquecharacteristics 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 are described below.

The SED indicator is expressed by the following formula. The first formula is the one widelyused for waste assessment and the second is for contaminated soil assessment. In each
formula, the first 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 thechemical 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 dose52. The STP is defined as thevolume of water required to dilute 1TBq of radioactive materials and corresponds to theradiation dose coefficient. Ingestion of a certain amount of such diluted water throughout the51
52

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.

137

year will result in a radiation exposure dose of 1mSv. The SED indicator conservatively uses
the larger radiation dose coefficient between ingestion and inhalation.
⁄
Form Factor (FF), as shown in Table A 3-1, is an indicator representing how much
radioactive material is actually released depending on material form, such as gas, liquid, solid,
etc. The indicator is set assuming that 100% of radioactive material is released in the caseof gas and liquid when containment function is totally lost and that 10% of radioactive material
is released in the case of powder based on the measurement data. Because of no clear basis,the indicator in case of solid is set to a sufficiently small value assuming that the solidmaterials are less easily released.
In Table A 3-1, several expected forms, especially for fuel debris, are added to the definition
used by the NDA. The scores for the form of No.4 and No.5 are newly established.
Control Factor (CF), as shown in Table A 3-2, is an indicator representing time allowanceavailable 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 defined by the NDA.
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

138

Table A 3-2

Definition and score of CFNo.

Time allowance available before any risk is realized

CF

1

Hours

1

2

Days

10

3

Weeks

100

4

Months

1,000

5

Years

10,0006

Decades

100,000(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 thefactors including integrity of the facility, redundancy of containment function, safety measurecondition, 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 scorebased on 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 usedas defined by the NDA, they are re-defined as shown in Table A 3-3 and Table A 3-4
respectively.

139

Table A 3-3
Category

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, no assessment forcontainment function is available.

100

2“Safety assessment criteria*2” are not satisfied at “the time of assessment*1” causedby 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 “safety assessment criteria”
exists at “the time of assessment”.

52

5

Integrity of diffusion control function has been assessed and “safety assessment
criteria” are satisfied until “the time of work (such as transfer, treatment, recovery,etc.)” for the risk source.
Frequency of occurrence of “contingency*4” is high, and when contingency 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 as transfer,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 as transfer,treatment, recovery, etc.)” for the risk source.
Facilities dissatisfying “safety assessment criteria” exist in the surrounding area, andthe 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 as transfer,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 as transfer,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 as transfer,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 which measures should betaken” or “securing of diffusion control function within the scope of design basis event”.

*3 This refers to the time of “recovery” of the risk source for disposition and carrying out for which SED score shallbe 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.

140

Table A 3-4

Criteria(NDA definition is modified to enhance applicability to the caseof the Fukushima Daiichi NPS)

Category*1*2

Criteria and score of WUD
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 of reasons
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. is insufficient, andcontrol and surveillance are unavailable.
Handling is practicable for the current form or condition because of reasons 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. is insufficient.

74

4

The material is fuel and active (which has fissile properties).
Necessary information for work including treatment, recovery, etc. is obtained (canbe confirmed or estimated), and control and surveillance with monitoring, etc. areavailable.
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, andcontrol 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 geometrical instability.
Handling is impracticable for the current form or condition.

98

Although the material is inactive, it has physical or geometrical instability.
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“Active” refers to possession of activity defined by CF at such a significant level as that activity affects control
and work.
“Inactive” refers to non-possession of activity or possession of sufficiently low level of activity.

(3) Safety Management - SSR, BER and CU
The definition of SSR, BER and CU used for Safety Management assessment forcontaminated soil is the same as the one defined by the NDA and each score is shown in
Table A 3-5.
Speed to Significant Risk (SSR) is an indicator concerning the time until the public isaffected through such as distance to the site boundary, groundwater flow conditions, etc. andto assess urgency of taking measures.
141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 therisk assessment model.

Table A 3-5
Indicator

SSR

BER

CU

Definition and score of SSR, BER and CU

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 of magnitude or canfacilitate control stepwise.

4

Implementation of measures can reduce risks by 1 or more order of magnitude, 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 6 points

4(1)+(2)=3 to 4 points

1(1)+(2)=
2 points(1) Assessment for the present state
1 point:
Major nuclear types and diffusion pathways are monitored.
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 for construction ofassessment model.
2 points: Major characteristics representing the site are obtained.
3 points: There is no model usable for future prediction

142

Table A 3-6 shows the overview of containment function, safety equipment, the state ofcontrol and surveillance, etc. of each risk source used when Safety Management wasassessed.
Table A 3-6 Characteristics of each risk source concerning Safety Management
Risk source

Characteristics

Fuel debris

No significant damage has been observed in the PCV and redundancy of criticality
control, cooling system and hydrogen explosion prevention system is secured. In addition,
important parameters including Xe concentration, temperature, hydrogen concentration,etc. are being monitored.

Spent fuelThe spent fuel pool of each unit is designed to maintain subcriticality, and redundancy ofthe cooling system is also secured. Some units have experienced falling rubble and heavy
weight objects, ceiling defects of the buildings, seawater injection, etc.
Common spent fuel storage pool and dry cask temporary custody facility, as well as thebuildings are not damaged by the earthquake and the tsunami.

Contaminated water,etc.

For stagnant water in the buildings, containments of the contaminated water are
maintained by management of the water level difference between the contaminated waterand ground water.
The water treated by the purified equipment was stored either in flange tanks or weldedtanks, and transfer from flange tanks to welded tanks was completed. (residual water is
excluded)

Secondary wastefrom water treatment
systems

The waste adsorption column is a shielded carbon-steel vessel storing Cs-adsorbed
zeolite, which is contained again in a shielded vessel, and is mounted on the box culvert
or the frame. Any control of decay heat removal, etc. is not required.
Waste sludge is stored in the agglomeration pit integrated in the process main building,where leak monitoring, decay heat removal, and hydrogen exhaust operations are
performed.
HIC slurry is stored in the polyethylene container, which is further contained in the SUS
reinforced vessel, and is stored in the box culvert. Although decay heat removal is not
required, measures against hydrogen generation is continuously taken. Concentrated
liquid waste is the liquid waste generated by concentrating the concentrated saltwater
through the evaporative concentration system and has a high concentration of radioactive
material and salinity. Its precipitation is extracted as a concentrated liquid waste slurry andstored in welded tanks within the weir.

Rubbles, etc.

Rubbles, etc. that is stored in the solid waste storage facility is waste which has a highconcentration of radioactive material, etc. and is contained in the container. Special
control is not required for this waste.
Temporally stored rubbles, etc. are waste which has various concentrations of radioactive
material and is stored outdoor in various forms, then monitoring and such is required forthis waste.

Contaminatedstructures, etc. in thebuildings

They are a variety of structures and the like in the buildings that were contaminated with apart of fission products like Cs which was released from fuel due to molten core at theaccident. The location and from of the contaminants are still investigation.

143

Attachment 4 Risk sources that include radioactive materials exists in site of Fukushima
Daiichi NPS except for major risk sources
Items

Descriptions

Exhaust stack for

Dismantling is ongoing, Radiation level : 0.22 to 0.51mSv/h at the height of 115m

Units 1 and 2

above ground level and 0.76 to 1.50mSv/h at the height of 35m above ground level.53
Construction of fender banking was completed. Treatment of ballast water, internal

VLFS (megafloat)

decontamination and grounding mound building in the sea bottom are in operation.
Radioactivity concentration in ballast water : Cs-134 (5.49×10-2 to 0.315Bq/L ) and Cs137 (0.456 to 3.20Bq/L).54

Underground water

Collection of residual water in all the underground water tanks were completed.

tankDismantling and removal policies are under consideration).55

Rainwater inflow
into buildings

Rubble removal and additional water seal on the roof floor, Installation of purificationmaterial into rain gutters, Installation of backflow valves into drain pipes, and Repair
and blockage of roof drains.56

Accumulated water

Extracted by risk overhaul performed in 2015. Concentration of radioactive materials

on siteand volume of water are confirmed appropriately on and after.57

α-sludge

Waste before theearthquake

R/B of Unit 2

Cs-137：9.35×107Bq/L, α:13.6Bq/L in total, in a decreasing trend58

R/B of Unit 3

Cs-137：1.66×108Bq/L, α:4.52×105Bq/L, in an increasing trend.54

Stored in 185,816 drums59, Major nuclide is Co-60.

53) “Response to the risk overhaul may affect outside the site boundary of Fukushima Daiichi NPS”, Handout

1-2 provided in The 36th The local coordination meeting for decommissioning and contaminated water
management54) NRA, Interview material with licensees “Changes to the implementation plan associated with risk reducing
measurement against tsunami for VLFS”, November 22, 201855) “Reference 1 : Process chart of the consideration and instruction items based on Target map for Reducing
the mid-term risk of Fukushima Daiichi NPS”, The 69th Specified nuclear facility monitoring andassessment meeting56) “Reference 2 : Status of countermeasure against storm sewage inflow”, The 70th Specified nuclear facility
monitoring and assessment meeting57) “Reference 1 : Status of the residual water on site including contaminated water (as of July 18, 2019)”
from The secretariat Meeting of 68th Team meeting on decommissioning and contaminated water
treatment58) “Reference 3-1 : Analytical results of α-nuclide” from The secretariat Meeting of 67th Team meeting on
decommissioning and contaminated water treatment59) TEPCO, NRA, Interview material with licensees “Status of monitoring exhausted radiation of common
facilities for supporting operation of SFP and recovery of air conditioning systems in fuel storage area of
Fukushima Daiichi NPS” issued on September 21, 2018144

As a result of the topsoil analysis, more than half of the samples are in excess of theContaminated soil

designated standards (8,000Bq/kg) provided for in the act on special measuresconcerning of handling contamination by radioactive materials.60

Deposits on the

Deposits such as zeolite sandbags put on the lowest floors of process main building

floor

and high-temperature incinerator building.

Spent control rods

Spent control rods, etc. : 24,0307, Fragments of core shroud : 193m3 7, Major nuclide is
Co-60.

In-pool water

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

Rubbles on

Investigation was conducted in Unit 1 and Unit 3. Scattered radiation of Cs-134 andoperating floor

Cs-137 were measured.61

Dust in operating

Less than the target value of release control (1×107Bq/h). Gradually in decreasing

floor

trend.
Cs-137 decreased to ND to 23Bq/L in Drainage A62, same in Drainage K decreased toDrainage

67Bq/L by removing contamination source on the roof of R/B in Unit 263. Additional
measures were taken, including installation of purification materials.64

Rubbles aroundbuildings

Dismantling of rubbles scattered on the roof floor of the buildings due to hydrogen
explosions is now in operation and planned.12) The physical quantity has not been
confirmed.

60) TEPCO, Analytical results of daily radioactive materials in Fukushima Daiichi NPS (Website)61 ) “Reference 5-3 : Dose report in operating floor of reactor building in Unit 3 (Flash report)”, The 38th

Specified nuclear facility monitoring and assessment meeting62) “Reference 2 : Status of measures for reducing the concentration of effluent in K drainage”, The 32nd

Specified nuclear facility monitoring and assessment meeting63 ) “Reference 4 : Status of measures for reducing the concentration of effluent in drainage”, The 34th

Specified nuclear facility monitoring and assessment meeting64) “Reference 2 : Storm sewage inflow suppression countermeasures (Status of storm sewage draining inturbine buildings and installation of clarification materials”, The 63rd Specified nuclear facility monitoring
and assessment meeting145

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 notmean such risk level can always be accepted over time, but the time will come when suchrisk level cannot be accepted in the future (yellow region). In addition, as time passes, therisk level may increase caused by degradation of facilities and risk sources (represented by
the dotted line). On the other hand, when risk reduction measures are taken, the risk levelcan be reduced so that it may not reach the unacceptable region (red region) with careful
preparation and thorough management, although it may be temporarily increased. In this way
the risk level shall be targeted to be sufficiently reduced (represented by the solid line) sothat 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 ismade whether the risk levelis acceptable or not withclose examination ofdifficulty of risk reduction

Broadly acceptable area

Time
Reference: 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 Regulation of Decommissioning and Associated Waste Management” 1st International Forum on theDecommissioning of the Fukushima Daiichi Nuclear Power Plant (April 2016).

Fig. A5-1

Change in risk over time146

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 resolidified”, namely, fuel debris is “fuel assembly, control rod and structures inside reactor
have melted and solidified together” according to the report by IAEA65,66.
The condition inside PCV is as shown in Fig.A5-1, as the comprehensive estimations
from the inside investigation of reactor, the past accidents including TMI-2 or ChNPP-4, andthe result of the simulation test. It does not show any of specific unit. For more detail, as
shown in the Fig. fuel debris 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

65

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

147

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 theothers. The one that 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 asshown in Fig. A5-2. Objects generated by core damage have been classified depending onnecessity of criticality measures and the content of fuel, in spite that a lot of names are usedaccording to the content of fuel component or form in appearance.

Fig. A6-2

An example of organized concept of fuel debris as fuel debris retrieval target atthe Fukushima Daiichi NPS【Glossaries and Terms】
FCM : Fuel Containing Materials. It refers broadly that molten fuel component comes to solidify
in conjunction 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 fuelcomponent other than using by electron microscope because particle of adhered fuelcomponent is extremely small and whit.

148

Attachment 7: Strategic recommendations for determination of fuel debris retrieval methods
for the First implementing unit
To determine fuel debris retrieval methods for the first implementing unit, the NDF
investigated the first implementing unit and its fuel debris retrieval methods. The results ofthe study are summarized as a strategic recommendation for “determination of fuel debris
retrieval methods for the first implementing unit” (hereinafter referred to as “strategic
recommendation”), which is described below.
This Attachment corresponds to the Strategic Plan as follows:

Strategic Recommendation

Strategic Plan

(this Attachment)

3.1.2.1

A. Policy of study to determine fuel debris

Approach to risk reduction in fuel debris

retrieval methods for the first implementing

retrieval workunit

3.1.2.2

B. Recommendations for determination of

Fuel debris retrieval methods for the first

fuel debris retrieval methods for the first

implementing unit (outline of the strategic

implementing unit

recommendation for determination of fueldebris retrieval methods for the first
implementing unit)
3.1.3.1

C. Initiatives after determination

Technical issues and plans related to thefuel debris retrieval from the first
implementing unit

149

Strategic recommendation for“Determining fuel debris retrieval methods
for the first implementing unit”

Table of Contents
A.Policy of study to determine fuel debris retrieval methods for the first implementing
unit ............................................................................................................................... 151
B.Recommendations for determination of fuel debris retrieval methods for the first
implementing unit ......................................................................................................... 155
B.1 Status of investigation ............................................................................................. 155
B.1.1
Research and Development ........................................................................ 155
B.1.2
Internal Investigation of PCVs (Internal status of the PCV) ......................... 159
B.1.3
Improvement of working environment .......................................................... 161
B.1.4
Site-wide planning ....................................................................................... 163
B.1.5
Study through the preliminary engineering .................................................. 164
B.2 Comprehensive Evaluation and Recommendations................................................ 179
B.2.1
Comprehensive evaluation .......................................................................... 179
B.2.2
Recommendations for determining the fuel debris retrieval method for the first
implementing unit ........................................................................................ 180
C.Initiatives after Determination ........................................................................................ 184
C.1 Initiatives toward start of retrieving fuel debris from the first implementing unit ...... 184
C.2 Initiatives for expanding retrieval scale and retrieval in units other than the first
implementing unit .................................................................................................... 189

150

A. Policy of study to determine fuel debris retrieval methods forthe first implementing unit
The intention of fuel debris retrieval is to reduce risk, and for the stable management offuel debris distributed at each location of Units 1, 2and 3, and fuel debris retrieval is to be
conducted continuously using retrieval devices, transfer equipment, storage equipment, andsafety equipment for safety operation. In executing, because of the difficulty of handling fueldebris, it is essential to build a plan based on the on-site situation by working with highly
reliable means after ensuring safety.
In the strategic recommendation, the scientific evidence for the fuel debris retrieval
methods of the first implementing unit and the path forward are indicated, based on theinformation revealed so far towards “determination of fuel debris retrieval methods for the
first implementing unit” by the government as well as towards fuel debris retrieval from thefirst implementing unit by TEPCO.
“Determination of fuel debris retrieval methods for the first implementing unit” is understudy based on the “Policy on Fuel Debris Retrieval” presented in 2017 in the Mid-and-Longterm Roadmap of the Inter-Ministerial Council for Contaminated Water and Decommissioning
Issues. The “Policy on Fuel Debris Retrieval” and its immediate actions are as follows:

Policy on Fuel Debris Retrieval[1] Step-by-step approach[2] Optimization of the overall decommissioning work
[3] Combination of multiple methods[4] Approach focused on partial submersion method[5] Prioritizing fuel debris retrieval by access to the bottom of the PCV from the side

“Immediate actions based on the policy on fuel debris retrieval”[1] Implementation of preliminary engineering[2] Continued internal investigation and accelerated/prioritized R&D(1) Step-by-step approach
At present, the condition of the internal environment of each unit is gradually revealed
by improved working environment in the field and internal investigations that have been
conducted since the earthquake disaster happened. However, as the reactor building(R/B) is a high radiation dose environment and it is difficult to conduct an investigation in
the vicinity of the PCV, information on the fuel debris to be retrieved is not yet sufficient.
151

Therefore, in the “Policy on Fuel Debris Retrieval”, the importance of the “step-by-step
approach” is described, in which determination of fuel debris retrieval method to be started
in advance is important to reduce the risk at an early stage, then, the direction will be
adjusted in a flexible manner based on the information that will be obtained gradually. Itshould be recognized that the fuel debris retrieval work is not a simple, stepwise expansion
or a routine project, but it has a character requiring constant reassessment based on thecurrent technology development and the project-oriented viewpoint, while assessing the
updated situation.
The “Step-by-Step Approach” is described in the Mid-and-Long-term Roadmap: “Fueldebris retrieval will start on a small-scale and the scale of retrieval will be expanded instepwise revising operations flexibly based on new findings obtained from thecharacteristic of the fuel debris and working experience”. This fuel debris retrieval work isunprecedented attempt, and the first step is value to assess the internal situation byinternal investigations, etc., to accumulate work experience inside PCV, and to use it indesigning the fuel debris retrieval methods and devices. Then, as for the fuel debris
retrieval, it should be conducted carefully little by little while ensuring safety at the initialstage. After taking procedures to verify debris retrieval steps, to check the engineering
reliability of devices, and to check the environmental impact of the work, etc., the retrieval
scale should be expanded gradually by using the knowledge and experiences obtained to
be incorporated into the work of retrieval.
In the same way, the Approach is described as “determination of fuel debris retrieval
methods to be started in advance to reduce risks at an early stage, then, the direction
should be adjusted in a flexible manner as retrieval proceeds, based on information thatwill be obtained gradually”. In examining fuel debris retrieval methods, the conditions
inside the PCV and RPV and the properties of the fuel debris have been gradually clarified,
but it is still difficult to say completely clarified. It is expected such information will be
gradually revealed through access to the inside. Based on this, make assessment
regarding the internal conditions and debris properties to be revealed in steps by theinternal investigations and characterization of debris to be conducted in the future. Whenthe next step in the plan is affected, the next step in the plan including the method andschedule (ex. expansion of scale, review of system capacity, etc.) is to be reviewed.
(2) Internal investigation and fuel debris retrieval
In the “Policy on Fuel Debris Retrieval”, it is stated that internal investigations and fueldebris retrieval should be performed in a coordinated and integrated manner. Workelements related to the fuel debris retrieval for each unit need to be examined in detail,and the examples of the concept are shown below.
152 Internal investigation (investigation of internal situation and characterization of fueldebris)For the internal condition of PCV and damage to internal structure, investigation andobservation are to be made provided that on-site environment has not changed. This will
provide information for checking the distribution and accessibility of fuel debris and for
judging safety of fuel debris retrieval work, which is used for examining the fuel debris
retrieval method. Fuel debris will also be collected from inside PCVs through sampling and
be transferred to the facility for analysis to identify the properties of fuel debris, including
the shape, existing state, composition, and mechanical/chemical properties, etc.
On the premise that analyses and investigations on decommissioning andcontaminated water management to be conducted for the safe and steadydecommissioning of the Fukushima Daiichi NPS, consideration shall be paid for thenecessity from the viewpoint of investigating the cause of the accident and improving
nuclear safety in the future.
 Fuel debris retrieval
In the fuel debris retrieval, to reduce risks of fuel debris, a series of operations should
be carried out continuously, starting with the preparatory work, followed by retrieving,
containing, and transferring fuel debris to stable storage. At the initial stage of fuel debris
retrieval, small-scale fuel debris retrieval (hereinafter referred to as “small-scale retrieval”)
will be conducted without significantly changing the on-site situation, and internal
investigations and analysis will be performed as well. It is expected the small scale
retrieval will provide important prediction on the following expanded-scale retrieval andretrieval from units other than the first implementing unit in the future. The scale of retrieval
and the area of retrieval will be gradually expanded based on new findings from theproperties of fuel debris and work experience while reviewing the work in a flexible manner(hereinafter referred to as “expanded-scale retrieval”). Otherwise, retrieval from units otherthan the first implementing unit is to be commenced.
With regard to expanded-scale retrieval and retrieval from units other than the first
implementing unit, the on-site situation can be significantly changed depending on the newsafety devices suitable for the expansion of the scale, the extension of existing openings
according to their needs, and the installation of new openings and so on. Such work should
be carefully carried out after enough examination on safety based on the information
obtained from small-scale retrieval.

153

(3) Effect of small-scale fuel debris retrieval from the first implementing unit
It is expected that the small-scale fuel debris retrieval from the first implementing unit
will provide important suggestions for subsequent expanded-scale retrieval and for the
retrieval from units other than the first implementing unit. In particular, as the initial stageof fuel debris retrieval, to obtain and verify information for determining the subsequent
retrieval work and devices, without causing irreversible changes of state in PCVs, thefollowing effects are expected:[1]

Enables verification of devices, facilities and safety systems, including remote
operations in the phase of small-scale retrieval by obtaining information (including therelease ratio of radionuclides into the air and water) on the effectiveness and work
efficiency reviews of devices, facilities, and safety systems from fuel debris retrieval tocontainment, transfer, and storage.

[2]

Enables use of work experience gained from fuel debris retrieval to containment,
transfer, and storage, including remote operations, as the process to master fuel debris
retrieval operations for TEPCO.

[3]

Enables obtainment of information that contributes to understanding the situation inside
the PCV (fuel debris distribution [Including characteristics], information on accessroutes, information on structural conditions, etc.).
The above mentioned information and the experience are expected to be obtained
firstly by TEPCO, which is the main operator of fuel debris retrieval work. By reflecting
these information in engineering, it is expected that the subsequent fuel debris retrieval
plan will become more rational. However, since the content and timing of the informationand experience are different depending on the progress of the work, it is necessary to start
retrieval for the units other than the first implementing unit or switch to the expanded scale
retrieval as it becomes required timing, checking whether the necessary information andexperience were obtained from the viewpoint of overall optimization.

154

B. Recommendations for determination of fuel debris retrieval
methods for the first implementing unit
B.1 Status of investigation
Based on the “policy on fuel debris retrieval”, the following is presented for “determinationof fuel debris retrieval methods for the first implementing unit”:•

Specific methods for the first implementation of fuel debris retrieval (“fuel debris retrieval
methods”)“Fuel debris retrieval methods” will be selected considering the progress in preliminary
engineering as well as research and development based on the “policy on fuel debris
retrieval”.

•

The unit at which the first retrieval will be carried out (“the first implementing unit”)
The “First implementing unit” candidate will be selected from Units 1, 2, and 3. The
advantages and disadvantages of each unit will be considered in accordance with thecurrent status of each unit and the progress of the PCV internal investigation.
In addition, the practical feasibility of the selected candidate unit will be examined. The
step-by-step approaches should be also indicated such as setting hold-points leading to
the start of retrieval, as well as after the start of retrieval at the first implementing unit.
The process of determining the first implementing unit and its retrieval method is

described below Based on the R&D results and the PCV internal investigation results, etc.,
obtained so far, the conceptual design of fuel debris retrieval system, scenario of fuel debris
retrieval (work schedule) of each unit and study on its applicability to the actual site need tobe evaluated in the preliminary engineering by TEPCO. Then, the overall optimization
combining the scenario of each unit and the arrangement plan for the whole site is to be
examined, and finally, recommendations for determination of fuel debris retrieval methods forthe first implementing unit will be presented. The correspondence with Fig. 6 in this thestrategic plan is shown in the reference figure at the end of this report.

B.1.1

Research and Development

In the Government-led R&D program on Decommissioning and Contaminated Water
Management, R&D related to the PCV internal investigations and the retrieval of fuel debris
has been carried out. Table 1 shows an overview of this program.

155

(1) Development related to internal investigation
Currently, as part of the Development of Technology for Detailed Investigation inside
the PCV, an arm-type access equipment that enables access to the inside of the pedestal
through an X-6 penetration (Unit 2) and an submersible ROV to confirm the condition of
the submerged portion of outside of the pedestal by accessing through X-2 penetration(Unit 1) have been developed. In particular, with regard to the arm-type access equipment,a cell (enclosure) storing the arm-type access equipment is installed outside the PCV
which has the function of PCV internal investigation, removal of obstacles, picking a fueldebris sample and carrying it out from the PCV, consistently. Methods and systems forpicking fuel debris samples such as gripping, sucking, and crushing are being developed.
In addition, for development of technologies for analyzing and characterizing properties offuel debris, a plan related to the off-site transportation of samples is being investigated.
These results contribute to the preliminary engineering.
(2) Development related to fuel debris retrieval
Development on the fuel debris retrieval is mainly aimed at the expanded-scale
retrieval and the progress is currently at the stage of conceptual studies and element tests.
In the future, it will be necessary to evaluate the actual site applicability of these results
and apply them to the design of actual fuel debris retrieval equipment/system. These
actions have just started as a part of the preliminary engineering.

156

Table A7-1

Overview of the state of review in the Government-led R&D program on
Decommissioning and Contaminated Water Management

Development related to fuel debris retrieval

Development related to RPV/PCV internal investigation

Items

The Government-led
R&D program on
Decommissioning andContaminated Water
Management
Development ofTechnology for Detailed
Investigation inside the
PCV

Development oftechnology forinvestigation inside the
RPVDevelopment ofTechnologies for
Retrieving Sampling ofFuel Debris and Internal
Structures
Development oftechnologies foranalyzing andcharacterizing propertiesof fuel debris

Upgrading of methods
and system for retrievalof fuel debris andinternal structures
Upgrading offundamental
technologies for retrievalof fuel debris andinternal structures
Development of closed
circulation systems forwater through inside the
PCV

Development oftechnology forcontaining, transferringand storing of fuel debris

Overview of status of review (as of March 2019)

To obtain more detailed information on the distribution ofdeposits and fuel debris inside the PCV, investigation
devices (underwater ROV for Unit 1 and arm-type accessequipment for Unit 2) tailored to the condition of Units 1
and 2 will be developed and actual investigation will be
carried out.
An investigation methods by side access and top accessare being developed and the development will be
continued.
A fuel debris sampling plan will be developed anddevelopment of sampling devices and systems will befollowed.

Retrieved fuel debris and deposits samples will beanalyzed in the future, and the properties of fuel debris willbe estimated based on the analysis results. Then, the fueldebris characteristics list will be enhanced. In addition, thedevelopment of technology for estimating the aging of fueldebris and for estimating the behavior of fuel debris
particles will be continued.
Development of various systems necessary for
maintaining safety functions during the retrieval work anddevelopment of elemental technology for the fuel debris
retrieval have been carried out.
In the future, the new project will be continued to resolve
the technical issues identified during the previous projects,
recognized by TEPCO's engineering activities, andpresented in the Strategic Plan 2018.
To build a new circulation system of water via the PCV,
technical specifications for building accessing andconnecting path to the PCV will be prepared. Then, theirdevelopment plans will be drawn up, and finally,
development of elemental technologies for building
accessing and connecting path to the PCV and verificationof them by using full scale of PCV will be continued.
Technology development was carried out for a system forcontaining, transferring, and storing including storage
containers for retrieved fuel debris safely, reliably, andefficiently, and technical issues were identified.
Development will continue to address them.
157

(3) Status of review in preliminary engineering
Preliminary engineering is being carried out by TEPCO based on the “policy on fueldebris retrieval” in the Mid-and-Long-term Roadmap. The preliminary engineering is theaction of preliminary assessment of the practical feasibility of studied fuel debris retrieval
concept from the view point of engineering aspects prior to starting the basic design. To
assess the practical feasibility of studied fuel debris retrieval concept derived from theresults of R&D, the work schedule of the fuel debris retrieval operation needs to be put inshape. Specifically, the arm-type access equipment and the air tightened enclosure storing
it, which have been developed and their actual site applicability was in sight by theGovernment-led R&D program on Decommissioning and Contaminated Water
Management, are being investigated to apply to the actual small-scale fuel debris retrieval.
The study on the expanded-scale retrieval method/equipment have just started by taking
the results obtained in this Government-led R&D Program into account.
The retrieved fuel debris is currently considered to be contained in to the canister which
has been developed and its actual site applicability was in sight in the Government-led
R&D Program, and the canister is to be stored in the storage facilities installed within the
Fukushima Daiichi NPS. Study on the expanded-scale retrieval has just been started byincorporating the results of this Government-led R&D Program. Securing an area to be
used for stable storage is the one of issues to be addressed.
The status of preliminary engineering results is presented in Sub-section B. 1.5.

158

B.1.2

Internal Investigation of PCVs (Internal status of the PCV)The current situation of the estimated fuel debris distribution, access routes andsurrounding structures of Units 1 to 3 are shown in Fig. A7-1.

(Prepared by Achievement Report 2017 Subsidy for “the Government-led R&D program on Decommissioning and Contaminated Water
Management by the supplementary budget (Advancement of comprehensive internal PCV condition analysis)” (June 2018) provided by IRID, The
Institute of Applied Energy), etc.

Fig. A7-1

Estimated fuel debris distribution, access route and surrounding structuresof Units 1 to 3
159

PCV internal investigations to verify the condition inside the PCV are also important forfuel debris retrieval from the lower PCV according to the Fuel Debris Retrieval Policy. Table
7-2 shows the current status.
Table A7-2
Unit

PCV internal investigation status

Inside the pedestal

Outside the pedestal• Deposits on grating and in the lower

Unit 1• Not yet performed

pedestal were investigated in• It may be possible to verify theInvestigation B2 (March 2017).

condition in part by Investigation B3 • Investigation B3 (scheduled) will access(scheduled).

the outside of the pedestal to verify
deposits near the access opening.

• The condition inside the pedestal
was verified in Investigation A2’• Conditions from X-6 to near the CRD(January 2018).
Unit 2railing were verified in Investigations A2’• Contact survey on deposits at thePCV bottom was performed in(January 2018) and A2’’ (February2019).

Investigation A2’’ (February 2019).
• Detailed conditions will be verified in• Verification on access routes will beplanned in Investigation A3 (scheduled).

Investigation A3 (scheduled).
• The condition inside the pedestal
Unit 3• Conditions of the access routes to thewas verified in the ROV

pedestal CRD opening were verified ininvestigation (July 2017).

ROV investigation (July 2017).

* A2, B2, etc., indicate the position and order of internal investigations in the Governmentled R&D program on decommissioning and contaminated water management. A2means the 2nd investigation inside the pedestal (A), while B2 means the 2nd
investigation outside the pedestal (B). Since Investigations A2’ and A2’’ were performed
with the same equipment used for Investigation A2 after improvement, they are
considered as a series of investigations.
In Investigation A2’’ performed at Unit 2 in February 2019 (contact survey on deposits), in
particular, it was identified that some deposits could be moved by gripping. Based on the
results of this Government-led R&D Program, in addition, Investigation A3 is planned(scheduled) to identify the structures and distribution of deposits inside the pedestal, followed
by a small amount of sampling.
160

The assessment status of on-site conditions is as follows. Though the conditions differ byunit, acquiring the information on side-access is in progress (Refer to Fig. 3 in Sub-section
B.1.3, for the current status of the radiation dose rate by unit).
Unit 1: Since there is a significantly high radiation dose on the southeast side, where the X-6
penetration is located, operations are difficult to perform so the self-propelled survey
equipment was inserted from the X-100B penetration on the northwest side, where
the radiation dose rate was relatively low (Investigation B2: March 2017). As thecondition of the pedestal opening is still uncertain, an investigation with access fromthe X-2 penetration is planned (Investigation B3: Scheduled). The outside of thepedestal is covered with deposits, and the condition at the PCV bottom has not been
observed yet.
Unit 2: The telescopic survey equipment was inserted from the X-6 penetration on thenorthwest side. The results reveal the damaged condition from the pedestal opening
to the internal grating, etc., as well as the limited damage on the CRD housing(Investigation A2’: January 2018). It has been confirmed that deposits that might befuel debris at the PCV bottom could be moved (Investigation A2’’: February 2019).
Unit 3: Because of the high water level inside the PCV and the submerged X-6 penetration,
the underwater ROV was inserted from the unsubmerged X-53 penetration on thesame northwest side to observe and enter the inside of the pedestal opening. Damageon the CRD housing was significant, and damage on the CRD switching equipment
and deposits covering collapsed equipment were observed (ROV survey: July 2017).
Conceptual examinations for the RPV internal investigation are underway in the
Government-led R&D Program. Prior to practical application, further examinations areneeded including adjustment based on on-site conditions (including work interference with
fuel removal from SFP).
As for the amount of fuel debris, it is estimated that 279 ton in Unit 1, 237 ton in Unit 2,
and 364 ton in Unit 3 as a result of comprehensive analysis by analyzed result and the data
investigated with actual equipment67.

B.1.3

Improvement of work environment

In order to retrieve fuel debris, radiation exposure among workers needs to be managed
appropriately. Therefore, appropriate work planning and radiation dose reduction in theworking environment through decontamination, shielding, and other means as needed are

67

IRID, Overview of research and development addressed by IRID, August 4, 2016161

required. As described in Sub-section B.1.5, side-access from the R/B to the PCV is under
examination in preliminary engineering studies for small-scale retrieval. Fig. A7-2 shows theradiation dose rate on the first floor of the R/B by unit as the working environment.

Fig. A7-2

Radiation dose rate on the R/B 1st floor by unit (mSv/h) (Source TEPCO)

The following describes the status of work environment development in each unit, basedon Fig A7-2.
Unit 1: Although the radiation dose on the northwest side is relatively low, it is 630 mSv/haround the X-6 penetration (southeast side), making it difficult for workers to approach.
Since the AC system piping may be the radiation source, countermeasures such as
removal or shielding are necessary to secure the working environment. The radiationdose on the south side is also high, which may be affected by the DHC system. Thus,
similar countermeasures are required.
Unit 2: Along with the improvement of the working environment, the radiation dose has been
reduced to approx. 5 mSv/h overall. It is possible for workers to work with limitations.
Further environmental improvement has been made for the scheduled Investigation
A3.
Unit 3: As the working environment, the radiation dose from the southwest side, where theequipment hatch is located, to the northwest side with the X-6 penetration ranges from
6.4 to 11.5 mSv/h. Therefore, manned working hours are limited. While the radiationdose exceeds 10 mSv/h in other areas, it is difficult to execute manned operations. At
Unit 3, as shown in Fig. A7-2, the current water level inside the PCV is higher than thefirst floor surface of the R/B. To secure the working environment, it is necessary to162reduce radiation dose on the first floor of the R/B first so that workers can installdrainage systems.

B.1.4

Site-wide planning(1) Fuel removal from spent fuel pools
As the site-wide plan, the status of fuel removal from SFP, where operational
interference with fuel debris retrieval is expected, is shown below.
Unit 1: Removal of rubble from the operating floor is underway. Fuel removal from the SFP
is planned to be initiated in 2023 subsequent to the maintenance of the operating
floor and installation of the fuel removal equipment.
Unit 2: The operating floor investigation is ongoing. Fuel removal from the SFP is planned
to be initiated in 2023 subsequent to the improvement of environment on theoperating floor and installation of the fuel removal equipment.
Unit 3: Fuel removal started in April 2019 and is scheduled to be completed in FY 2020.
Fuel removal operation from SFP completes in Unit 3 first. Fuel debris retrieval workand fuel removal work from SFP can be done in parallel at every unit.
(2) Contaminated water management
Treatment of stagnant water in the buildings of each unit is scheduled to be completed
within FY 2020. In small-scale retrieval, the existing water circulation system will be used.
In association with retrieval, sampling from stagnant water transfer lines and water
treatment systems is planned for verification on the effect of fuel debris outflow from thedrywell. The impact on the water treatment systems should also be verified. In expandedscale retrieval, required safety systems will be examined. With consideration for systemdevelopment to achieve containment functions during fuel debris retrieval, from now it
should be coordinated with contaminated water management.
(3) Waste management
It is necessary to consider storage of waste generated along with fuel debris retrieval.
Because of the limited size of the containers to be carried out of the PCV in small-scale
retrieval, basically, the amount of waste for off-site transfer is also limited. Scale of retrieval
is small and existing systems such as safety systems are repurposed, so no significant
change in the amount of waste is expected from maintenance, inspection and otheractivities. In expanded-scale retrieval, the amount of waste to be carried out, including
obstacles, and the system scale are large, so a plan to calculate the amount of waste andstore it needs to be implemented in alignment with the retrieval plan.
163

B.1.5

Study through the preliminary engineering

There are two phases of fuel debris retrieval; Small-scale retrieval and expanded-scale
retrieval. As mentioned in Sub-section B. 1.1 (3), investigation on small-scale retrieval areongoing through the preliminary engineering, and actual site applicability are getting in sight.
For expanded-scale retrieval, the methods (side-access, upper-access) forward effective fueldebris retrieval are under investigation through the Government-led R&D program on
decommissioning and contaminated water management. However, it is requested toaccumulate safety system operation experiences (containment function (gas, liquid),
criticality) and information of the circumstances inside the PCV (including characteristics offuel debris), also requested to conduct further R&D activities in order to realize safe andreliable retrieval of fuel debris.
The following shows that the progress of each technical requirement based on the study
for fuel debris retrieval method as well as actual site applicability so far, through preliminary
engineering.
(1) Establishing the containment functions
At present, the containment functions are stably maintained by using existing gas andliquid phase systems (gas management systems, water circulation systems, etc.). To
establish concerned systems for fuel debris retrieval, the impact analysis on the existing
containment functions should be performed. Fuel debris retrieval work will lead to changes
the condition of fuel debris. In particular, there is a risk regarding dispersion of radioactive
airborne particles due to fuel debris crushing work. Therefore, safety analysis andmeasures are required.
As for the gas phase, it has been confirmed that airtightness in Unit 2 is the highest of
the three units according to operating experience so far (airtightness in Unit 1 is slightly
lower than Units 2, Unit 3 is the lowest). Small-scale retrieval work in Unit 2 will start using
equipment such as gripping and sucking as shown in (6). With regard to gripping andsucking, no significant impact on the atmosphere was observed A2’’ investigation(February 2019) which contacted with deposit inside the pedestal. Therefore, the risk offuel debris dispersion might be low. Thus, it has evaluated that the containment functions
in each unit can be secured by existing safety systems. In preliminary engineering, PCVs
depressurization by the existing gas management system and dust monitoring for theinside/outside R/B are planned because the pressure inside of the PCVs are positive asshown in Fig.A7-3. Then, safety environment will be enhanced. Regarding crushing work
such as cutting fuel debris, safety analysis and study on the necessity of concerned safetysystems depending on the scale of fuel debris retrieval should be conducted ON the other164

hand, detailed study regarding the expansion of the access area inside the pedestal will
be required due to the possibility of removing obstacles as shown in (5).
As for the liquid phase, no significant impact on the outside was identified while
Investigation A2’’ (February 2019) as well as gas phase. Therefore, it has evaluated thatthe containment functions in each unit can be secured by existing safety systems. The
design concept that enables strict monitoring has been established, where dedicatedmonitoring system for contaminated water installed in the existing water treatment system
as shown in Fig. A7-4.
Preparation of safety analysis and safety systems according to the fuel debris retrieval
method is mandatory in order to ensure containment functions in expanded-scale retrieval.
In this case, safety analysis should be performed properly based on input data in line withthe conditions at Fukushima Daiichi NPS.

Fig. A7-3

Fig. A7-4

Outline of safety system study on small-scale fuel debris retrieval(Data provided by TEPCO)

Outline of safety system study on small-scale fuel debris retrieval(Data provided by TEPCO)

165

(2) Maintaining cooling functions
The fuel debris cooling around several cubic meters per hour as injection flow ratecontinues in each unit by using the existing water recirculation system. Therefore, thecooling functions are basically maintained by continuous water injection. Even if current
operation has no impact on existing systems during small-scale retrieval, appropriate
management (i.e. maintenance or preparation of procedure) is strictly requested to ensure
continuous operation.
In order to secure cooling functions while expanded-scale retrieval, dedicated studies
should be performed depending on the retrieval method to be applied in each unit.
(3) Ensuring structural integrity of the PCVs and buildings
It is considered that PCVs and the buildings of each unit are not in a situation thatwould immediately pose a problem in terms of structural integrity. In the present smallscale retrieval plan, the equipment with a weight that is within the acceptable building floorloads will be used without modification, such as expanding existing penetration. Therefore,
no impact on the structural integrity of the PCVs and buildings is expected.
On the other hand, there is a possibility of modification because the equipment to be
used for expanded-scale retrieval affects the structural strength of existing structures andbuildings. For assessment on actual site applicability for each unit, therefore, modificationof the equipment itself and PCVs/buildings associated with equipment installation should
be considered.
(4) Criticality control
Although fuel debris currently remains in a subcritical state, it is necessary to analyze
and evaluate the possibility of criticality due to retrieval or its influence when changing thestate of fuel debris caused by retrieval, and to examine necessary and sufficientcountermeasures.
With high uncertainty in fuel debris properties and limitations in control by priorcalculation, design and engineering, it is important to ensure prevention of criticality withcombination of monitoring and judgment during retrieval.
In the case of gripping/sucking without fuel debris crushing, criticality is unlikely to occur.
As shown in Fig. A7-5, however, examinations should be made on criticality prevention,
detection methods, impact of criticality if it occurs, and countermeasures during fuel debris
fabrication.

166

Fig. A7-5

Outline for safety system study on small-scale fuel debris retrieval(Data provided by TEPCO)(5) Establishment of access routes to fuel debris
Based on the “Policy on Fuel Debris Retrieval”, when retrieving fuel debris by the partial
submersion method accessing the bottom of the PCV from the side, there are candidate
access penetration openings such as X-1, X-2 and X-6, it is considered most efficient toaccess the inside of the pedestal linearly from the existing X-6 penetration through the
CRD opening of the pedestal based on the structure of the bottom of PCV.
Although it is necessary to establish appropriate access routes for each unit, as shownin Sub-section B. 1.2, currently, available information on access routes to fuel debris(access routes from the pedestal opening to the pedestal bottom, etc.) is limited to only for
Unit 2 and Unit 3. (Fig. A7-6 shows an image of small-scale fuel debris retrieval using an
X-6 penetration). However, according to the results of the internal investigation of Unit 2
and Unit 3, the access range within the pedestal may be restricted due to obstacles suchas gratings and frame structures. Therefore, it is necessary to examine the removal of the
obstacles as well to secure the access range within the pedestal.
Methods of expanded-scale retrieval (side access and top access methods) are still at
the stage of studying the concept. Therefore, further study is required to establish accessroutes on the device for expanded-scale retrieval in accordance with the application of theretrieval method of each unit.

167

Fig. A7-6

Image of small-scale fuel debris retrieval with X-6 penetration(provided by TEPCO)(6) Development of fuel debris retrieval devices and equipment
For retrieval of fuel debris, it is necessary to continuously retrieve fuel debris from thePCV. Retrieval devices and equipment for the purpose should be capable of getting closer
to the location of fuel debris relatively easily and need to have a certain level of load
capacity and containment function.
Access devices such as ROV-type, telescopic-type and arm-type have been developed
as a part of the Governmental-led R&D program on Decommissioning and Contaminated
Water Management (sampling technology for retrieval of fuel debris and internal
structures), device to be used for small-scale retrieval is planned in the preliminary
engineering based on the arm-type access equipment being developed, such as ROV-type,telescopic-type and arm-type as a part of the Government-led R&D program on
Decommissioning and Contaminated Water Management (sampling technology for
retrieval of fuel debris and internal structures). The arm-type access equipment is basedon the boom-type arm proven in JET (Joint European Torus), UK, and the same device isscheduled to be used for the detailed internal investigation in this Government-led R&D
Program. This method was chosen as the best for accessing inside and outside of thepedestal in the PCV without affecting the structure and using the existing X-6 penetration
and CRD opening (See Fig. A7-7 for the conceptual diagram.).
The arm-type access equipment is designed to be stored in the enclosure withcontainment performance shown in Fig. A7-8 and be installed on the 1st floor of R/B.

168

Review is underway for the tools for gripping and sucking as shown in Fig. A7-9 basedon the results of the A2’’ investigation (February 2019), and they are designed to be
attached to the arm-type access equipment respectively.
As for maintainability, it is designed such that parts can be cleaned and replaced during
operation in the enclosure. Specifically, when the arm-type access equipment that wasused for the work inside the PCV is returned to the enclosure, it can be cleaned to remove
contamination, and as shown in Fig. A7-8, the enclosure is equipped with a double arm
manipulator to replace tools, measuring instruments, cameras, lighting fixtures, and partsof the arm-type access equipment.
A system is being studied in which the debris retrieval container to be carried into theenclosure from inside the PCV will be placed in a sealed container inside the enclosureand delivered to a shielded on-site transport container. It is possible to carry in the parts
and the like to be replaced inside the enclosure through the port. However, in the event ofa failure of the arm-type access equipment itself, the arm-type access equipment needs tobe removed for maintenance by a means that will prevent contamination from fuel debris
from spreading inside and outside the R/B. In the preliminary engineering, the area andequipment for carrying out the enclosure for maintenance are under study. In addition, theresponse in the event of an abnormal situation is examined on the assumption of an
accident scenario.

Fig. A7-7

Conceptual diagram of small-scale retrieval devices(TEPCO materials edited by NDF).

169

Fig. A7-8

Conceptual diagram of enclosures (for storing arm-type access equipment)(provided by TEPCO)
Crushing tools (example)

Gripping tools (example)
Bucket tool

Drilling and recovery tool

Gripper tool

Cutting tools (example)
Obstacle removal* tool
(Mechanical cutting)Sucking tools (example)

Fig.A7-9

Gripping, Sucking, and Cutting Tools (example) (provided by TEPCO)

Operation of retrieving fuel debris has the following unique difficulties.
[1] Retrieval period will be long.
[2] Harsh environment and many uncertainties such as working in a high radiation dose
environment.
[3] Having no prior example, technical difficulties are high.
[4] Preparation for retrieval work needs to be conducted while developing the methods.
In light of these issues, in order to ensure technical safety and reliability of thedecommissioning project at the Fukushima Daiichi NPS, it is necessary to develop amethod for retrieving fuel debris and establish reliable operation procedures andmaintenance methods prior to the introduction of remote control equipment at the site for
retrieving fuel debris. In addition, it is necessary to utilize mock-up tests (hereinafter
170referred to as “remote mock-up test”) and VR (virtual reality) of the remote equipment inorder to carry out the field work accurately. What is important about the remote mock-up
tests for the retrieval of fuel debris at the Fukushima Daiichi NPS is, from the viewpoint ofconfirming the performance of remote equipment as well as training and development ofoperators, aligning the facilities appropriately before the tests are conducted so that theon-site conditions can be reproduced. For this purpose, planning shall be made rationallybased on risk assessment, and considerations shall be made about the environment thatwill be revealed gradually over the long period of fuel debris retrieval period and maychange unexpectedly.
Also, when retrieving fuel debris, through cutting, etc., α-nuclides diffuse into the air andwater, causing internal exposure to workers. For this reason, it is necessary to establish
criteria for air and water concentrations of α-nuclides, conduct appropriate monitoring, anddetermine necessary protective equipment. Furthermore, work efficiency can be lowered
when handling heavy or long objects such as constructing work cells due to protective
equipment, and safety management for workers is also necessary. Therefore, it is desirable
to conduct a risk assessment before starting the work and to educate and train workers.
As for the development of devices and equipment for expanded-scale retrieval,conceptual studies and element technology development are being carried out in the
Government-led R&D Program. However, further R&D, such as the development oftechnology to control dust scattering during retrieval is required, and engineering based onsuch R&D results will be necessary going forward. Fig. A7-10 shows an example ofexpanded-scale retrieval device and equipment.

Partial submersion –side accessFig. A7-10

An example of expanded-scale retrieval device and equipment(Provided by IRID)

171

(7) Establishment of system equipment and working areas
For system equipment to be prepared to ensure required safety functions, it is planned
that the existing safety systems will be used for small-scale retrieval. In addition,
strengthening of monitoring (radiation, water sampling, etc.) is planned in order to ensure
the change of retrieval work.
* Gas management system, water circulation system and emergency boric acidinjection system (some parts will be modified), as described in (1)At present, safety requirements for the expanded-scale retrieval are being investigated.
For establishing area to install the retrieval equipment and system equipment, requirement
for the area is now being calculated. Dedicated study on the possibility of using areas
outside of the existing buildings is ongoing, and also application of high radiation doseareas in the reactor building and interference with other projects are under study.
(8) Development of methods for containing, transferring and storing retrieval fuel debris
Preliminary engineering is studying a series of operations from retrieval of fuel debris
to their temporary storage for a small-scale retrieval as shown in Fig. A7-11.

Fig. A7-11
Working image for small-scale retrieval(TEPCO material edited by NDF)
Concepts as of today are as follows.
1) Fuel debris retrieved from the bottom of the PCV is contained in a small debris
container and transferred into an enclosure tightly connected to the PCV.
2) The fuel debris contained in a small debris container is then contained into a transfer
container connected to the enclosure, and transferred to the acceptance/measurement cell by an on-site transfer vehicle.
3) The transferred transfer container is connected to the acceptance/ measurement
cell and the fuel debris is taken out from the transfer container into theacceptance/measurement cell together with the small debris container. In the172acceptance/measurement cell, the fuel debris contained in a small debris container
is measured (weight, radiation dose rate, surface nuclide composition, etc.) andtreated (drying, etc.) as required for temporary storage. Thereafter, the fuel debris
in a small debris container is moved from the acceptance/measurement cell to thedelivery cell. There, it is contained in a canister for temporary storage, and moved
and stored in a temporary storage cell using the lifting tool with radiation shield.
4) Some fuel debris are moved from a delivery cell to an delivery cell for analysis,
where samples for analysis are taken out from the small debris container to be filled
into a sampling confinement bottle, and the sampling confinement bottle iscontained in a sampling container, then the sampling container is contained in an
off-site transport cask and transported to the analytical facility.
Basic design of facilities and equipment shall be made based on these concepts, andthey shall be available for use at the start of the small-scale retrieval. As for the storage
location, preliminary engineering is studying candidate areas for the temporary storage
inside of the Fukushima Daiichi NPS.
At present, conceptual study on storage facilities for expanded-scale retrieval isongoing in preliminary engineering. The issue is to secure a space stable storage of theretrieved fuel debris, and required facilities shall be prepared through detailed study.
(9) Fuel debris retrieval scenario for each unit
In the process of determining the method of retrieving fuel debris for the first
implementing unit, basic elements constituting the fuel debris retrieval scenario are site
environment preparation (dose reduction, water level lowering in PCV, etc.), PCV internal
investigation, small-scale retrieval (horizontal access), and expanded-scale retrieval(horizontal access, top access). The following describes the scenarios based on theconditions of each unit. Since the expanded-scale retrieval method is still in the conceptual
study stage, access route construction of the expanded-scale retrieval equipment should
be studied in accordance with the application of the retrieval method of each unit.
Unit 1: Radiation dose around the X-6 penetration, which has linear access to the inside of
the pedestal and is considered useful for retrieving fuel debris in the pedestal, is high,and radiation dose reduction should be done if this penetration is to be used. Once
access routes are secured, PCV internal investigations will start, followed by smallscale retrieval and expanded-scale retrieval. Research development and technology
development are required going forward as well for the expanded-scale retrieval, and173

actual site applicability needs to be examined based on these studies in order tomaterialize it.
Unit 2: PCV internal investigation is in progress, and improving site work has advanced themost.
Furthermore, there is a prospect that the small-scale retrieval can be possible
considering situations surrounding the X-6 penetration, so it will start from small-scale
retrieval (Horizontal Access). In order to make the long-term field work possible,
improvement of the working environment needs to be made continuously. R&D andtechnology development are required going forward as well for the expanded scale
retrieval, and actual site applicability needs to be examined based on these studies inorder to materialize it.
Unit 3: PCV water levels must be lowered in order to use the X-6 penetration. In addition,
radiation dose reduction in the R/B is required in order to implement the work in the
R/B continuously. Once access routes are secured, PCV internal investigations will
start, followed by small-scale retrieval and expanded-scale retrieval. R&D andtechnology development are required going forward as well for the expanded-scale
retrieval, and actual site applicability needs to be examined based on these studies inorder to materialize it.
Based on the preliminary engineering results described in (1) to (9) above, Table A7-3 andTable A7-4 show results of the conceptual study of retrieval as well as results of actual site
applicability study for each unit from the point of interest based on the guiding principles of
NDF, which consists of 5 viewpoints “safe”, “proven”, “efficient”, “timely”, and “field-oriented”.

174

Table A7-3 Retrieval Concept Study Results (1/2)
Expanded-scale retrieval (Horizontal Access,Viewpoints

Point of interest

TargetSmall-scale retrieval (Horizontal Access)

Top Access)(Retrieval work without significant change of the site condition)(Retrieval that significantly changes conditions of
the site)

Establishment of
the containment
function forradioactive
materials

Maintaining thecooling functions

Since the radioactive materials concentration inside
PCV may change due to the retrieval of fuel debris,

Since the fuel debris retrieval will start from gripping and sucking at the beginning,

perspective of applicability on the containment function

the risk on dispersion of dust might be low. In addition, depressurization inside theagainst the radioactive materials shall be investigated

PCV and monitoring of concerned parameters (i.e. PCV internal pressure, dust

from the view point of radiation exposure on the public

monitoring, etc.) during retrieval work will be conducted.

and workers.
Prospect of applicability on the fuel debris cooling

Application of the arm-type access equipment enables to maintain the operation offunction that can secure current condition shall be

existing water injection cooling system during retrieval work. Thus, the coolinginvestigated.

function is to be maintained.

Prospects shall be obtained that impact on theSafe

structural strength of existing PCVs and buildings by

Although conceptual studies and element

retrieval related equipment, which is planned to betechnology development have been carried out

Ensuring the

installed anew, is allowable value.

Since the arm-type access equipment is brought in from the existing large

for the expanded-scale retrieval method,

structural integrity

When an existing facility is changed from the present

equipment carrying-in opening without expanding the existing X-6 penetration, no

technical issues remain to be solved, and furtherof PCVs andstate, such as openings are enlarged, the prospects of

new opening is generated and the equipment is installed within the allowable floor

R&D and engineering work are required. Further

buildings

the structural integrity shall be obtained regarding theload of the existing building, so there is no impact on the integrity.

understanding of the inside of the PCV as wellenlarged opening (such as X-6 penetration) or a newly

as feedback from the experiences of small-scaleinstalled device in design case and beyond-design

retrieval work are also necessary. For thiscase.

reason, evaluation of the expanded scale

Prospects shall be obtained that criticality monitoring
Criticality control

and prevention measures at the time of fuel debris
retrieval are valid.

Since no new criticality risk exists at the initial stage of small-scale retrieval of fuelretrieval method will be conducted when thedebris (gipping and sucking), no particular change from the current situation isdetails of the retrieval method are determined.

considered necessary. However, when the retrieval includes working on fueldebris, such as cutting and fuel debris retrieval, it is desirable to limit the volume of
the work or have the work conducted under neutron monitoring until the propertiesof fuel debris are confirmed.

Prospects shall be obtained that labor safety issecured and radiation exposure of workers is

At present, environmental improvement plans such as radiation dose reduction in

Securing laborreasonable considering as well the viewpoint of

the R/B for each unit have been drafted and started. Also, the arm-type accesssafetyestablishing working environments (radiation dose

equipment is the same device as investigated in the A3, and the learning effectreduction) at the time of preparatory construction work

such as mock-up training is expected.

and retrieval work.

175

Table A7-3 Retrieval Concept Study Results (2/2)

Viewpoints

Small-scale retrieval (Horizontal Access)(Retrieval work without significantly change conditions of the site)

Point of interest

TargetDevelopment ofequipment/device
for fuel debris
retrieval

Prospects shall be obtained for securing required
functions and capabilities on devices and equipmentused for fuel debris retrieval.

Prospects have been obtained that it will be applicable to the field, as specificdesign work is in progress for works such as fuel debris gripping, sucking,removing obstacles, and cutting by the similar equipment as A3 investigationequipment (arm-type access equipment.).

Establishment ofsystem/equipment
and working
areas

Prospects of applicability of system/equipment for safe
operation (modification of existing facilities, etc.) during
fuel debris retrieval shall be investigated and required
working areas for retrieval work can be secured.

The safety evaluation study has been performed and verified that the early phaseof small scale retrieval work (by gripping and sucking) can be done. Removal or
obstacles or fuel debris retrieval by crushing might require detail safety evaluation
and additional safety system depending on the evaluation results.

Establishment ofmethods forcontaining,transferring andstoring retrieved
fuel debris

Prospects shall be obtained that the method ofcontaining and transferring retrieved fuel debris canreally be available and that the temporary storage
facilities can really be ready. In addition, prospects
shall be obtained that waste generated at the time of
retrieval can be stored appropriately.

Designs are in progress for transfer method for retrieved fuel debris includingtransfer containers, as well as a cell for receiving the transferred fuel debris anddelivering a storage container and an analysis sample. Plans of a temporarystorage facility for retrieved fuel debris is being examined. TEPCO is considering
area for temporary storage within site. The volume of generated waste is not
significant matter at the initial stage of the small scale fuel debris retrieval becausea volume of fuel debris is not large at this stage and retrieval operation will bedone by using existing safety equipment.

Efficient

Validity of the fueldebris retrieval
plan

Plans to be utilized for the next step (including transfer
knowledge to the other units) shall be confirmed
depending on the information (applicability oftechnology, impact on environment, etc.) through thefirst implementing unit retrieval work.

In order to accumulate necessary information for the expanded-scale retrieval andthe retrievals in units other than the first implementing unit, dedicated impact
analyzes on various operations, crushing work and securing safety will be
performed through the first implementing unit retrieval work.

TimelyEarlycommencementof fuel debris
retrievalPossibility of early commencement of fuel debris
retrieval shall be confirmed.

Small scale debris retrieval work in the first implementing unit enables to get
fruitful information and experience for the expanded-scale retrieval work and theunits other than the first implementing unit. Thus, the risk of fuel debris will be
reduced.

Maintainability(maintenance andtroubleshooting)

Maintainability and troubleshooting availability at thetime of an anomaly, adjustable for the length of
retrieval duration, for each device, and waste
generated at the time of maintenance are considered,since it is not easy for a person to directly perform
maintenance on devices used for the fuel debris
retrieval.

The small-scale retrieval device (arm-type access equipment) is assumed to be
used for an order of several years, and maintainability is considered. Further,since the device is same as the one used for the internal investigation, it isexpected to have a proficiency effect such as mock-up training.

Operability

In order to ensure stable operation of fuel debris
retrieval, consideration shall be given to securing
operability, validating through mock-ups, and securing
operator expertise, for remote operation of devices
used for fuel debris retrieval.

With regard to the small-scale retrieval device (arm-type access equipment),
feedback from results of the A3 investigation and a proficiency effect such as
mock-up training are expected.

ProvenFieldoriented

176

Expanded-scale retrieval (Horizontal Access,
Top Access)(Retrieval that significantly changes conditions of
the site)

Although conceptual studies and element
technology development have been carried out
for the expanded-scale retrieval method,technical issues remain to be solved, and further
R&D and engineering are required. Further
understanding of the inside of the PCV as well
as feedback from the experiences of small-scale
retrieval work are also necessary. For thisreason, evaluation of the expanded-scale
retrieval method will be conducted when thedetails of the retrieval method are determined.
At present, concept of storage facilities for
expanded-scale retrieval has been studied inpreliminary engineering. The issue is to secure
an area that can be used stably, and details forstorage facility shall be determined and required
facility shall be prepared going forward.

Table A7-4 Study result of actual site applicability for each unit (1/2)
Viewpoints

Point ofinterest

Details

Evaluation

Unit 1

Unit 2

Unit 3

Reduction ofradiation
exposure ofworkers(radiationdose in theworkplace)

Prospects shall beobtained that labor safety
is secured and radiation
exposure of workers is
reasonable considering
as well the viewpoint of
establishing working
environments (radiationdose reduction) at thetime of preparatory
construction work andretrieval work.

Radiation dose rate around the X-6
penetration, which is suitable for the armtype access equipment, is high (630mSv/h).

As radiation dose rate on the first floorof the R/B is about 5 mSv/h, theworking environment in which workers
carry out their work is expected to be
secured even though with some
limitations.

Environmental radiation dose rate on thefirst floor of the R/B is several to several
tens of mSv/h or more, making it difficult
for workers to work there.

Radiation dose at the workplace of Unit
2 is considered to be the lowest
compared to other units. For Unit 2,
further radiation dose reduction has
been implemented for the A3
investigation (which is to be conductedgoing forward).

• Currently, air tightness is slightly
secured. It is estimated that air tightness
might be kept after the water level in
PCV comes down.
• At present, opening area of the liquid
phase is assumed to be same as the gas
phase.

• At present, air tightness is highly
secured. It is the reason why Unit 2
was not affected by the hydrogen
explosion and integrity of the building is
still maintained. On the other hand,when the PCV water level will comedown, reduction of air tightness shall betaken into consideration.
• Currently, it is assumed that opening
area is in the liquid phase (S/C
submerged portion).

• At present, the air tightness is less thanthat of Units 1 and 2. And the opening
area has not been evaluated.
• Dedicated test to accumulate
necessary data for calculating opening
area and evaluation is required.

It is established that the function ofcontaining radioactive materials in Unit 2
is the highest compared to other units.

Securing afunction ofcontaining
radioactive
materials

Since the radioactive
materials concentration
inside PCV may change
due to the retrieval of fueldebris, perspective of
applicability on thecontainment function
against the radioactive
materials shall be
investigated from theview point of radiation
exposure on the public
and workers.

Based on the analysis conducted so far,
it is assumed that a small amount of fueldebris is present at the bottom of thepressure vessel, that most of the fueldebris is present at the bottom of thePCV, and that fuel debris may havespread to the outside of the pedestal
through the worker entrance. On theother hand, at present, no information on
deposits that are thought to be fueldebris has been obtained from internal
investigations, etc.

Based on the analysis conducted sofar, it is assumed that a large amount offuel debris is present at the bottom of
the pressure vessel, that a certain
amount of the fuel debris is present at
the bottom of the PCV, and that fueldebris spread to the outside of thepedestal through worker entrance isestimated to be small. At the bottom of
the PCV, part of fuel assemblies was
identified, and deposits thought to befuel debris are confirmed to be
movable.

Based on the analysis conducted so far,
it is assumed that some amount of fueldebris is present at the bottom of thepressure vessel, that a larger amount of
the fuel debris compared with Unit 2 ispresent at the bottom of the PCV, andthat fuel debris may have spread to theoutside of the pedestal through worker
entrance. At the bottom of the PCV,
deposits that may be fuel debris havebeen identified.

As for Units 2 and 3, information on thestatus of fuel debris is available, andprospects are considered to be obtained
regarding risk reduction effects bycarrying out the retrieval work. In Unit 2,part of the fuel assemblies was found at
the bottom of the PCV, and it issomewhat more likely than at Unit 3 thatthe deposits at the bottom of the PCV
are fuel debris.

Safe

ProvenConditions of each unit

Status of fueldebris

Prospects shall beobtained regarding risk
reduction effects from
retrieval work execution,
based on theinvestigation of fueldebris status in the target
area for fuel debris
retrieval.

177

Table A7-4 Study result of actual site applicability for each unit (2/2)
Viewpoints

Point of interest

Details

Prospects shall beobtained for the feasibilityof routes inside andoutside the building toaccess the fuel debris.

ProvenEstablishmentof accessroutes to fueldebrisTimelyPossibility of earlycommencement of fuelEarlydebris retrieval shall becommencement
confirmed based on theof fuel debris
evaluation of preparatory
retrieval
work volume andschedule.

Fieldoriented

Workability (siteconditions,consideration
for surrounding
construction)

The impact of field
conditions of each unit
(impact on fuel removalfrom SFP, etc.) andinterference withsurrounding construction,etc., shall be adjustable
and consideration shallalso be given to waste
generated during thework.

Conditions of each unit
Unit 1

Unit 2

Unit 3• Situations surrounding the X-6
penetration have not been identified forboth inside and outside of the PCV, butaccess to the bottom of the PCV outside
the pedestal is possible from the top of
the grating outside the pedestal.
• However, situations surrounding the
CRD rail that connects the X-6
penetration and the inside of thepedestal and situations surrounding theworker entrance have not been
confirmed, and currently no information
is available about access routes to theinside of the pedestal where most of thefuel debris is thought to be present.
• From the analysis and the estimation
based on the results of the internal
investigation of other Units, damage andfalling objects equivalent to those of Unit
3 are expected to exist in the internal
structure of the reactor.

• Situations surrounding the X-6
penetration have been identified both
inside and outside the PCV, andsituations surrounding the CRD railthat connects the X-6 penetration andthe inside of the pedestal have also
been identified, providing informationon the access routes to the inside of
the pedestal where a certain amount offuel debris presumed to exist.
• Damage to the reactor internals(CRD housings, CRD exchangers,
platforms, etc.) are limited, but there
are obstacles on the access route, andmany items such as CRD exchangers
and gratings become obstacles when
the retrieval scope is expanded.

As a preparatory work for the fuel debris
retrieval, reduction of the radiation dosearound the X-6 penetration is necessary(removal of high radiation dose piping,etc.) for the installation of the arm-typeaccess equipment. But this preparatory
work may take a long time because
careful work is mandatory.
• There is a concern about interferencewith the fuel removal work from SFP, but
it is considered to be avoidable byadjusting the work of the upper side andlower side.
• There is a concern about interferencewith environmental preparation work(radiation dose reduction, removal of
obstacles, etc.) on the first floor of the
R/B.

Establishment of work area is inprogress for the fuel debris retrieval.
And it is evaluated that preparation for
the environment around the X-6
penetration is the most advanced.

• Regarding the situations surrounding
the X-6 penetration, the radiation dose
outside the PCV is higher than that ofUnit 2.
• Situations surrounding the CRD railthat connects the X-6 penetration andthe inside of the pedestal have been
identified, and information on accessroutes to the inside of the pedestal
where many fuel debris may be present
has been available.
• On the other hand, there are many
fallen objects, the bottom of the PCV iscovered with deposits, and there aremany obstacles. In addition, due to thehigh water level inside the PCV, it isnecessary to lower the water level inorder to use the X-6 penetration for
retrieval.
• PCV water level is high, and loweringof the water level is necessary to use theX-6 penetration.
Lowering the water level of the PCV isrequired as preparatory work for the fueldebris retrieval. As reduction of theradiation dose around the X-6
penetration is required in order to install
the arm-type access equipment, and the
preparation is expected to take time.

• There is a concern about interferencewith the fuel removal work from SFP,
but it is considered to be avoidable byadjusting the work of the upper side
and lower side.
• Preparation of the environment on
the first floor of the R/B (radiation dose
reduction, removal of obstacles, etc.) ismost advanced, and concern about
interference with the work is the least
there.

178• There is a concern about interferencewith the fuel removal work from SFP, but
it is considered to be avoidable byadjusting the work of the upper side andlower side. The adjustment period forthe upper side work and lower side work
will be the shortest as the fuel removalfrom SFP is expected to be completed
earliest.
• There is interference between
environmental preparation work(radiation dose reduction, removal of
obstacles, etc.) on the first floor of the
R/B and water level lowering work in
PCV.

Evaluation
For Units 2 and 3, information on accessroutes to fuel debris is available, and theprospects are believed to be clear
regarding the routes inside and outside
the buildings for access to fuel debris.
However, in both Units 2 and 3,
obstacles exist on the access route, and
it is necessary to remove them. There
are more fallen objects and moreobstacles in Unit 3.

Since the establishment of the work area
is most advanced in Unit 2, earlycommencement of the fuel debris
retrieval can be possible.

• Interference with the fuel removal workfrom SFP in each unit are thought to be
avoidable by adjusting the work of theupper side and lower side. The concern
about interference with environmental
preparation work on the first floor of the
R/B is the smallest in Unit 2.

B.2 Comprehensive Assessment and Recommendations
B.2.1 Comprehensive assessment
To “determine the fuel debris retrieval method for the first implementing unit”, a comprehensive
evaluation for “the fuel debris retrieval method” and “the first implementing unit” should be
performed based on the considerations given in Sub-section B.1. Also, based on the Mid-and-Longterm Roadmap, the study on fuel debris retrieval should be promoted as a comprehensive plan
aiming at overall optimization, including coordination with other work at the site, from the viewpointof optimizing the entire decommissioning work. In addition, it is necessary to take into account thepeculiarity of the unprecedented fuel debris retrieval work in the uncertain situation of the site at
Fukushima Daiichi NPS. Furthermore, experience and information accumulated in advancethrough the handling of fuel debris from retrieval to storage at the first implementing unit will be
expected to be used (feedback) in the planning of the expanded-scale retrieval. Therefore, a highly
reliable retrieval method and the first implementing unit should be selected as soon as possible
under the condition that safety is secured.
“Method of fuel debris retrieval”
As a “fuel debris retrieval method”, the overall risk resulting from fuel debris at Units 1 to 3 will
be reduced by “Promptly” starting a small-scale fuel debris retrieval operation while minimizing theincrease in risks associated with the retrieval work, and “Promptly” obtaining information andexperience toward the expanded-scale retrieval and the retrieval at units other than the first
implementing one. Specifically, “Safe”, “Reliable”, and “Prompt” fuel debris retrieval operation ispossible, based on the use of the existing safety systems without significant modification to the site
condition, by starting from the methods such as gripping and sucking by employing the arm-typeaccess equipment and air tightened enclosures to contain this equipment, which actual site
applicability is getting in sight. In addition, fuel debris retrieval by crushing or cutting other thangripping and sucking also need to be performed without significant modification of existing safetysystem. Moreover, proposed method of containing, transferring and storing of retrieved fuel debris,that retrieved fuel debris firstly contained in the small container is transferred and contained in thecanister and stored in dry condition at the temporary storage facility built within Fukushima Daiichi
NPS site, is also judged to be able to contain, transfer and storing the retrieved fuel debris “safely”,“reliably” and “promptly”.
“First implementing unit”
From the viewpoint of optimization of entire decommissioning work of Fukushima Daiichi NPS,
Unit 2 is currently judged to be appropriate for the first implementing unit. Its reasons are thatsufficient information on PCV internal condition and the site condition (radiation dose, degree of air
tightness of the existing safety systems) has been obtained as well as that information andexperience on fuel debris retrieval work can be promptly obtained by starting its fuel debris retrieval
work “safely”, “surely” ad “promptly” based on the site condition such that fuel debris retrieval work
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and fuel removal work from SFP can be done in parallel. Small-scale retrieval operation starting at
Unit 2 enables to reduce risks existing in Units 1, 2 and 3.
In Unit 2, in this way fuel debris will be retrieved by using the arm-type access equipment, anda series of operations of containing, transferring, and storing should be continued safely and reliably,
and then information and experience required for further implementation can be accumulated
promptly.

B.2.2 Recommendations for determining the fuel debris retrieval method for the
first implementing unit
Based on the comprehensive evaluation, the recommendations are given below for determining
the fuel debris retrieval method applicable for the first implementing unit.
[1] Fuel debris retrieval work is to start from small-scale operation such as gripping andsucking by using the arm-type access equipment that actual site applicability is gettingin sight and the air tightened enclosure that contains the arm-type access equipment
combined with existing safety system without significant modification.
 From the viewpoint of performing the fuel debris retrieval work safely and reliably, actions
that lead to change in the site condition should be refrained from as much as possible
when the site condition is uncertain. From this point of view, a small-scale retrieval by asystem (an arm-type access equipment), whose performance is expected to be verified
through the detailed investigations of PCV internal, can minimize the impact on the existing
systems, since it does not need significant modification such as expansion., of the existingX-6 penetrations.
 In addition, at the initial stage, fuel debris retrieval should start with small-scale retrieval bymethods such as gripping and sucking without cutting/crushing of fuel debris.
Consequently, scattering of fuel debris due to such operation and a possibility of criticality
can be suppressed, and the impact on existing facilities can be minimized.
 Because a part of fuel assemblies was found at the bottom of the PCV of Unit 2, fuel debris
is considered to be present in a certain form, as well as fuel debris (deposits, etc.) may
also be present on the grating. These deposits should also be considered as potential fueldebris and the retrieval of them should be considered as well.
[2] Using information and experiences accumulated through fuel debris retrieval
operations by gripping and sucking, crushing method for fuel debris retrieval work andremoving method of obstacles are to be studied. Fuel debris retrieval work by crushingor cutting during the small-scale fuel debris retrieval work phase is also to be performed
under without significant modification of existing safety system.
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

From the viewpoint of carrying out fuel debris retrieval safely and reliably, it is consideredappropriate at present that fuel debris retrieval will be conducted by using the existing
safety systems with minimum changes. Then, it is important to take necessary measuresin accordance with the confirmed site condition.



Crushing/cutting work will definitely be required at a certain stage of the fuel debris
retrieval, because some deposits are identified not to be gripped during the deposit
contact investigation conducted at Unit 2. Further consideration for crushing/cutting work
is required.

Some obstacles such as gratings and frame structures inside the pedestal are assumed
at Unit 2, which is considered to have the best accessibility to the bottom of the PCV. An
arm-type access equipment should have functions/capabilities to remove such obstacles.

Safety equipment for the crushing/cutting of fuel debris and removal of obstacles is also
required. Based on safety assessments for this work, preparation of safety system
including utilizing of existing safety systems should be studied.

[3] Retrieved fuel debris firstly contained in the small container is transferred, contained in
the canister and stored in dry condition at the temporary storage facility built within
Fukushima Daiichi NPS site.
 Facilities and equipment for storing the retrieved fuel debris will be designed by considering
the properties/characteristics of the fuel debris. A step-by-step approach needs to be taken
for the design of the storage facilities. The storage facilities for a small-scale retrieval at
the first implementing unit needs to be designed with safety margin derived fromconservative estimation on the properties/characteristics of fuel debris. Therefore, it isconsidered appropriate that data obtained during storage of the fuel debris at small-scale
retrieval (the amount of hydrogen generated, and so on), will be used for supporting theconsiderations on an expanded-scale retrieval work as well as for improvement andstreamlining of safety assessment of the design of storage facilities at the next unit.
 The dry type is deemed appropriate storage method because it can be placed without
being lifted to a high place (superior in terms of securing safety), and it can also restrict
contaminated areas (excellent in terms of waste reduction). Specific containers for fueldebris are under development, whose actual site applicability is getting in sight. The drytype storage is also deemed reasonable for storage facilities for small-scale retrieval at thefirst implementing unit, because of the same reasons and from the viewpoint of obtaining
useful data for the design of storage facilities for a subsequent expanded-scale retrieval
work and the retrieval at the next unit.
 Fuel debris handling facility with safety system is also necessary for the transporting of fueldebris samples to an analysis facility.
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 Discussions on licensing and safeguards, as well as obtaining the understanding from local
communities and the general public need to be performed before starting the fuel debris
retrieval work, since fuel debris to have been located in one place, so called within the
PCV would be moved and stored in storage facilities separately from PCV by fuel retrieval
work, that is some kind of handling of nuclear material.
[4] From the viewpoint of optimization of entire decommissioning work of Fukushima
Daiichi NPS, Unit 2 is currently judged to be appropriate for the first implementing unit.
Thus, a series of operations from fuel debris retrieval to containing, transferring andstoring of the retrieved fuel debris will be continued at Unit 2, and information andexperiences will be accumulated necessary for expanded-scale retrieval work in the
future. However, certain hold points should be appropriately defined on the process ofnecessary study or planning to start fuel debris retrieval work for verifying theappropriateness of current study/planning.
 Unit 2 is appropriate as the first implementing unit, from the viewpoint of optimizing theentire decommissioning work. Its reasons are that fuel debris retrieval work can be started“Promptly”, “Safely” and “Reliably”, information and experience on the fuel debris retrieval
operation can be obtained “Promptly”, the risk derived from overall fuel debris at Units 1 to
3 can be reduced “Promptly”, and the removal of fuel from SFPs can be carried out inparallel with the fuel debris retrieval by paying attention to operations at both upper andlower locations.
 The retrieved fuel debris from Unit 2, will continuously contained, transferred and stored,
and the effectiveness of required systems for further implementation can be promptly
confirmed through this series of operations. In addition, accumulated experiences throughthe series of small-scale retrieval operations including maintenance by using remotecontrol equipment is expected to contribute to making considerations on the expandedscale retrieval work efficiently.
 To determine the method of fuel debris retrieval at the first implementing unit, it is essential
to conduct in-depth examinations of the fuel debris retrieval work schedule based on themeasures to address the issues revealed through PCV internal investigations, etc., and to
examine the interference of fuel removal work from SFP with the fuel debris retrieval workin detail.
[5] Retrieval methods including containing, transferring and storage of the retrieved fueldebris applicable for the expanded-scale of fuel debris retrieval work phase or otherthan the first implementing unit need to be established by proceeding with PCV internal
investigation, necessary R&D and improvement of working environment such as PCV
water level lowering, radiation dose reduction, and securing working space, as well as
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engineering of new safety system, fuel debris retrieval and storage facility using
accumulated information and experiences through fuel debris retrieval work of the first
implementing unit including study on safety evaluation and actual site applicability ofabove mentioned engineering results.
 As mentioned above, the fuel debris retrieval work is recommended to start by the methodsof gripping and sucking using a small-scale device through the existing X-6 penetration at“Unit 2”. The fuel debris retrieval work should be gradually expanded based on the policythat the information and experiences accumulated during current fuel debris retrieval workneed to be used for improvement of the next step of fuel debris retrieval work. In addition,
the fuel debris retrieval at units other than the first implementing one need to be considered.
 On the other hand, a suitable safety equipment should be prepared for expanded-scale
retrieval work because it may require a significant alteration of the site condition. In addition,
modification of existing facilities may impact on current confinement capability maintainedby existing facilities. Therefore, the expanded-scale retrieval work shall be considered andestablished to have safety function by using feedback from the information and experienceon the retrieval of fuel debris at the “first implementing unit”.
 Since the expanded-scale retrieval work requires not only the increased amount of
retrieved fuel debris but also the wider area for necessary facilities around the reactor
building, the needs for adjustment/coordination with other works would be increased, andthe need for cooperation with other works would also be increased, such as contaminatedwater or waste management during the fuel debris retrieval work. In addition, the area
needs to be secured for stable storage of the retrieved fuel debris. Consequently, theactivities and organization to consider the expanded-scale retrieval work should beenhanced for the purpose of optimizing the entire decommissioning work.

183

C. Initiatives after Determination
C.1 Initiatives toward start of retrieving fuel debris from the first implementing
unit(1) Setting of hold points before the start of retrieving
The Mid-and-Long-term Roadmap stipulates that the “start of retrieving fuel debris from thefirst implementing unit” should be carried out in 2021. To this end, discussions should be madein accordance with the recommendations of “Determination of the method of fuel debris retrieval
for the first implementing unit”.
Specifically, it is necessary to clearly define the process leading to actual site application,
detail of the tasks, and the system to materialize and realize the management guidelines, and tocontinue the project activities among the engineering activities promoted mainly by TEPCO. In
the process designed for the implementation before the “start of retrieving fuel debris from thefirst implementing unit” in the project activities, it is necessary to set hold points appropriately,
considering the following elements.


Results of detailed internal investigation (equipment, verification of accessibility)

Results of improvement of the site environment (status of radiation dose reduction, etc.)

Verification of actual site application of small-scale retrieval equipment (when the mock-up
completes)Results of study on the modification of safety system (including safety assessment)

Results of study on storage facility (temporary storage, plan for the storage)

Establishment of organization and securing human resource, etc.

Application and approval of licensingCoordination for safeguards

Feasibility of parallel operations with fuel removal from SFP, etc.
To make decision on the method of fuel debris retrieval of the first implementing unit, it is also

required to pay attentions to the work schedule examination based on the issues through PCVinternal investigations and work interference examination based on the considerations on thefuel removal method from SFP as mentioned followings.


It becomes apparent through PCV internal investigation that there are obstacles in theaccess route to the fuel debris and improvement of measures to prevent dust diffusion isnecessary when removing such obstacles. Accordingly detail planning and examination on
work schedule aiming at start of fuel debris retrieval shall be promoted considering removal
method of the obstacles including enhancement of prevention of radioactive airborne
material diffusion during obstacles removal work

184



It becomes apparent through PCV internal investigation, research and development andpreliminary engineering by TEPCO that the works such as the installation of the enclosure
require many human works at the site. Accordingly detail planning and examination on work
schedule aiming at start of fuel debris retrieval shall be promoted, considering further
reduction method of the radiation dose rate at the first floor of the reactor building (about 5
mSv/h), where most human works take place.



It is observed through the investigation of operating floor of Unit 2 that the radiation dose
rate is decreased so that human works would be available to some limited extent. Several
plans are considered on the fuel removal from SFP with the method to reduce risks of dust
diffusion. Accordingly, coordination of work interferences when making parallel works both
fuel removal from SFP and fuel debris retrieval including preparation works shall be well
examined based on the progress of engineering on method of fuel removal from SFP.
Toward start of retrieving the fuel debris for the first implementing unit, TEPCO announced aplan of the future internal investigations in July, 2018. For Unit 2, it is scheduled to conduct [1]deposit contact investigations and [2] investigation to grasp the distribution of deposits as well
as sampling in small amount of deposits, and [3] sampling in larger amount of deposits. The
status and purpose of each investigation and sampling are as follows:[1] A deposit contact investigation was conducted in February 2019. The purpose is to contact
the deposits and to check the changes in the state before and after contacting. As results, it
is confirmed that deposits which are considered as the fuel debris are able to be moved bygripping.
[2] The investigation to grasp the distribution of deposits as well as sampling in small amount ofdeposits is scheduled to be conducted in the future, and it is appropriate to conduct it before
start of retrieving the fuel debris for the first implementing unit. The purposes are : a) to
confirm that the arm-type access equipment can go into PCV, and b) to characterize the fueldebris by analysis.
[3] The plan of sampling in larger amount of deposits is now under consideration. The purposes
are : a) to confirm that the fuel debris retrieval can be carried out, and b) to characterize thefuel debris by analysis using larger amount of deposits.
Though start of retrieving fuel debris was scheduled after confirming a) of [3], it is evaluatedthat can be obtained by the confirmations in [1] and [2]. Specifically, fuel debris retrieval in small
amount is scheduled to start by gripping and sucking, and the data required for assessment of
cutting the fuel debris, etc. is evaluated so for to be obtained by sampling in larger amount of fueldebris by using the same equipment as that for fuel debris retrieval in small amount. Thus, fueldebris retrieval for the first implementing unit is possible to be integrally conducted with [3], andby this procedure it is possible to reduce the total amount of workers’ radiation exposure and185waste. Therefore, it is appropriate to revise a plan that the fuel debris retrieval for the first
implementing unit and [3] is scheduled to be integrally carried out.
Fig. A7-12 shows a roadmap as one of example based on these findings.

Fig. A7-12

Roadmap toward “the fuel debris retrieval at the first implementing unit” (example)

186

(2) Continuous implementation of a small-scale fuel debris retrieval
In a small-scale fuel debris retrieval, in order to retrieve fuel debris from the bottom of the
PCV at Unit 2, the task of removing obstacles such as gratings will be carried out, and a scenario
of retrieval depending on the site conditions shall be developed in the future. Basically, thescenario shall be updated as the site condition is confirmed, a scenario needs to be developed
as shown in Fig. A7-13 as an example of the current situation.

Fig. A7-13

Retrieval scenario during a small-scale retrieval (example)

Furthermore, since the tasks such as the removal of obstacles are also carried out in theinitial stage of the retrieval, investigations and sampling as well as the removal of obstacles, shallbe carried out in an integrated manner during the small-scale retrieval, in addition to the retrievalof fuel debris itself.
With regard to the continuation of fuel debris retrieval, scenarios as mentioned above andmaintenance/inspection plans are also required and, thus, it is essential to consider a specificwork plan. It is also necessary to give attention to flexibly revising and continuously updatingthese plants according to the situation after work commencement.
(3) Information obtained through small-scale retrieval and the shift to the expanded-scale retrieval
For the following information obtained during small-scale retrieval, it is expected that it will bereflected in the planning of expanded-scale retrieval and the examination of rationalizing the site
situation and tasks, etc.
[1] Verification of equipment, facilities and safety systems at the small-scale retrieval stage
 Confirmation of retrieval equipment installation and the status of operations (including
technical review)187 Verification of measuring equipment
 Efficiency of retrieval and the throughput up to storage Status of equipment maintenance (frequency of filter replacement, radiation exposure
conditions, etc.)
 Contamination status of retrieval equipment and the work environment (changes)
 State of the environment (changes) inside the PCV, R/B and surrounding areas (safetyrelated)[2] Verification of the process to master the fuel debris retrieval operation

Fostering and securing of operators (including analysts) engaged in a long-term
retrieval task, and mastering of the retrieval operation[3] Acquisition of data related to examinations on the expanded-scale retrieval(Data related to the fuel debris composition, impact on the surrounding environment, storage
and transportation, etc.)
 Distribution of fuel debris within the PCV
 Properties (hardness, etc.) and shape of debris affecting to retrieval
 Conditions within the PCV (radiation dose, quantity and state of structures (obstacles)) Conditions of R/B and surrounding areas (radiation dose, quantity and state of structures(obstacles)) Properties, shape, composition, etc. of the debris retrieved Checking the dust transfer rate during retrieval
 Conditions of draining water, hydrogen generation, etc.
 Identification of impact on the surroundings (analysis of the transfer to the basement of
the building and the water treatment facility due to retrieval)Consideration should be given to the future taking into account of the efficiency and system
life of small-scale retrieval operations: In which stage and to what extent above information
should be obtained, and in which stage a shift may be made to the next step.

188

C.2 Initiatives for expanding retrieval scale and retrieval in units other than thefirst implementing unit
Retrieval will start from small-scale with no significant changes in the state of the site in using
existing safety system as a base, and expand the scale or retrieve fuel debris of units other than
the first implementing unit based on new findings including information and experiences acquired
from the small-scale retrieval operation. To allow for this, following activities are necessary.
a) Consideration of actual site applicability based on such as conceptual study on safety systemb) Information organization such as radionuclide airborne release fractions for examining
necessary and sufficient safety systemsc) Site environment preparation such as radiation reduction, water level lowering in PCV and areaplanningd) Further understanding of inside condition of PCV and RPVe) Technologies to make efficient fuel debris retrieval including removing obstaclesf) Technologies to reduce dispersion of radionuclide airborne particles during fuel debris retrievalg) Consideration on sorting and distinction of fuel debris and radioactive wasteh) Technologies to analyze and estimate fuel debris properties and distributions for understanding
In this regard, improving site work environment, PCV internal investigation and R&D arecontinued, regarding to the retrieval method in case of expanding the scale or applied to the units
other than the first implementing unit. The retrieval method in conjunction with containing,transferring and storage should be determined after proceeding with engineering to examine newsafety system, retrieval facilities and the prospect of their actual site applicability which is based on
the information and experiences obtained through fuel debris retrieval in the first implementing unit.
Since fuel debris retrieval is carried out in parallel with other works, it is necessary to revise thework plan in accordance with the overall situation of decommissioning activities. Especially, in orderto realize the regular full-scale fuel debris retrieval safely and smoothly, efficient site space planwith appropriate margin is an important issue by keeping stably available area in the site.
Furthermore, the way of fuel debris retrieval shall be flexibly considered in view of optimization of
total decommissioning activities, as example the retrieval at the units other than the first
implementing unit can start if prepared well, even though the retrieval of the first implementing
unit is still continuing.

189

Sub-sections B.1.1 and B.1.2
Progress of ancillary R&D and
PCV internal investigation

Sub-section B.1.3
Progress of work environment
improvement

Sub-section B.1.4
Progress of site-wideplanning•••

It was observed that there are some
movable pebble size deposits in
Unit 2.
Get development of arm-typeaccess equipment and the canisterfor retrieved fuel debris into shape.

•

In contrast with relatively low radiationdose in Unit 2, radiation dose
reduction is needed in Units 1&3 aswell as lowering of water level in PCV
in Unit 3.

Sub-section B.1.5, Table A7-3

Study on concept of fuel debris retrieval••••

Use of existing safety system.
Use of arm-type access equipment that actual site
applicability is getting in sight and use of air-tightend
enclosure which contains it.
Start from small-scale retrieval by such gripping or
sucking, and progress to plan fuel debris retrieval bycrushing.
Contain retrieved fuel debris in a small canister,transfer it, contain it in a canister and stored it in dry
condition at the temporary storage facility within site

Fuel removal operation from
SFP completes in Unit 3 first.
Fuel debris retrieval work andspent fuel removal work can bedone in parallel at every unit.

Sub-section B.1.5, Table A7-4

Study result of actual site applicability of fueldebris retrieval work by Unit•••

Unit 1: Maintaining relatively high airtightness with current
safety system, but the radiation dose is high in working
environment and deposits potential of fuel debris andaccess route to reach them are unidentified.
Unit 2: Maintaining high airtightness with current safetysystem and the radiation dose is relatively low in working
environment, deposits potential of fuel debris is movable
and access route to reach them has been identified.
Unit 3: Deposits potential of fuel debris and access routeto reach them has been identified, but airtight level withcurrent safety system is lower than Units 1&2, theradiation dose is relatively high in working environment.

Sub-section B.2.1
Comprehensive assessment【 Fuel debris retrieval method】 →The arm-type access equipment & the canister enables to retrievefuel debris safely, reliably and promptly.
- Actual site applicability of the arm-type access equipment/canister for retrieved fuel debris are getting in sigh.

【 The first implementing unit】 → Unit 2 is judged to be appropriate because fuel debris retrieval can bestarted “safely”, “reliably” and “promptly” and overall
decommissioning work can be optimized.
- Safe: The radiation dose in working environment is relatively lower than other units and the airtightness with existing
safety system is higher than other units.
- Reliable : Some deposits with potential for fuel debris are movable, and access route to reach them has been identified.
- Prompt : It has a possibility to start fuel debris retrieval work promptly, as well as to accumulate information andexperiences on fuel debris retrieval work.

Unit 2 has potential to reduce risks resulted from entire fuel debris at unit 1, 2 and 3 promptly because theessential information and experiences will be accumulated necessary for expanded scale of fuel debris
retrieval work in the future through a series of operations from fuel debris retrieval by using the arm-typeaccess equipment to containing, transfer and storage of the retrieved fuel debris safely, reliably and promptly.

Sub-section B.2.2
The points to be recommended for determining fuel debris retrieval method of the first implementing unit
① Fuel debris retrieval work is to start from small-scale operation such as gripping and sucking by using the arm-typeaccess equipment that actual site applicability is getting in sight and the air tightened enclosure that contains the armtype access equipment combined with existing safety system without significant modification.
② Using information and experiences accumulated through fuel debris retrieval operations by gripping and sucking,crushing method for fuel debris retrieval and removing of obstacles are to be studied. Fuel debris retrieval by crushingor cutting during the small-scale fuel debris retrieval work phase is also to be performed under without significant
modification of existing safety system.
③ Retrieved fuel debris firstly contained in the small container is transferred, contained into the canister and stored in dry
condition at the temporary storage facility built within Fukushima Daiichi NPS site.
④ From the view point of optimization of entire decommissioning work of Fukushima Daiichi NPS, unit 2 is currently
judged to be appropriate for the first implementing unit. Thus, a series of operations from fuel debris retrieval tocontaining, transferring and storing of the retrieved fuel debris will be continued at unit 2, and information andexperience will be accumulated necessary for expanded-scale of fuel debris retrieval work in the future. However,certain hold points should be appropriately defined on the process of necessary study or planning to start fuel debris
retrieval work for verifying the appropriateness of current study/planning.
⑤ Retrieval methods including containing, transferring and storing the retrieved fuel debris applicable for the expandedscale of fuel debris retrieval work phase or other than the first implementing unit need to be established by proceedingwith PCV internal investigation, necessary R&D and improvement of working environment such as lowering of PCV
water level, radiation dose reduction and securing working space, as well as engineering of new safety system, fueldebris retrieval and storage facility using accumulated information and experience through fuel debris retrieval work of
the first implementing unit including study on safety evaluation and actual site applicability of engineering results.

Reference Figure: Flow of Strategic Proposal Review(Section numbers corresponding to this Attachment are added to Strategic Plan, Fig. 6)
190

Attachment 8

Analysis and investigation plan

1.1 Objectives
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 three areas,
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, processing and disposal.
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 the knowledge
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. A8-1 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.

191

Past
Accident
occurrence

Present
Estimation of fuelInternal
debris distribution investigation

Accident history
investigation


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

FutureSampling

Fuel debris analysis
RPV internal investigation
PCV internal and external
investigations

Dismantlingof facilities

Containmentand storage

Fuel debris
retrieval

Accomplishment of
decommissioning

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

management

StorageCountermeasures against
criticality

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

Processing anddisposal

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

Fig. A8-1

Countermeasures against
criticality
Nuclides and the amountof radioactivity
Chemical stability

Clarification of accident
cause

Improvement of nuclear safety

Where analyses and investigation results are reflected and their relationships

1.2 Difficulty in unraveling the overall picture of the accident at Fukushima
Daiichi NPS
The accident at Fukushima Daiichi NPS caused core damage and fuel melting at 3 reactors,
thereby allowing the encapsulated FPs release into the environment. This is the world’s first boilingwater reactor (BWR) accident. A BWR is composed of core support structures such as core shrouds
and fuel supports, to secure the flow path of cooling water within the RPV and to support the steamwater separator. Zircaloy alloy, which is a cladding tube material, is supposed to lower the melting
point by way of the eutectic reaction with stainless steel68,69. It has also been reported that thecontrol rod uses boron carbide (B4C) as a neutron absorber, and that the control rod is dissolved
with stainless steel and zircaloy alloys in the vicinity, lowering the melting point70. Since the loweringof the melting point depends on the mixing ratio of elements, it defers from locations of inside
reactor and there was no record of the thermos sensors furnished at the RPV flange and at thebottom of RPV head due to electricity failure on the site during the accident. Owing to these factors,
it is difficult to understand the situation at the time of the accident and the melting and mixing stateof fuels.

68

Nuclear Fuel Engineering - Current Status and Prospects, the Atomic Energy Society of Japan (1993)
Practical Text Series No. 3: Behavior of LWR Fuel, Nuclear Safety Research Association (2008)
70 T. Hastea et. al., “Study of boron behavior in the primary circuit of water reactors under severe accident
conditions: A comparison of Phebus FPT3 results with other recent integral and separate effect data”, Nuclear
Engineering and Design, 246 (2014).
69

192

As a measure to bring the accident under control, water was injected by way of fire engines.
However, it has not been made clear how much water actually reached the inside of the RPV or
when the injected water arrived, because many branches, solenoid valves, pumps, etc., were
present on the route of the water being injected from the outside to the inside of the RPV. As
seawater was also injected in addition to fresh water, there is a concern about the influence of salt
(NaCl) contained in the seawater. Since NaCl is water soluble, it is thought that most of it does notremain within the RPV due to subsequent water injection and purification, but some of it may becontained in fuel debris. In an environment containing Cl, pits (pitting corrosion) are formed in theoxide film of stainless steel and this causes deterioration events such as stress corrosion cracking,which may affect future storage.
As described above, for the accident at Fukushima Daiichi NPS, it is extremely difficult tounderstand and evaluate the composition and properties of fuel debris and the operating conditionsof equipment because of the unprecedented reactor type, complexity of the structure, melting
behavior, lack of data during the accident, and the peculiarity of measures taken to settle a severe
accident. To carry out decommissioning safely and reliably, it is important to correctly understandthe current situation and what has happened at Fukushima Daiichi NPS through analyses of fueldebris and investigations of the on-site condition.

2

Fuel debris analysis items
A boiling water reactor is, roughly classified, composed of fuel assemblies that generate heatfrom nuclear fission, control rods that absorb neutrons, water that decelerates neutrons andremoves heat, and components of structural materials that make up the reactor structure. During
the accident, because water reacted or was discharged as steam, the remaining three components
were melted, mixed and solidified. Therefore, as it drips down onto the core, the bottom of the RPV,
the CRD housing, and the PCV pedestal floor, it is considered that the surrounding structural
materials are involved, and the content rate of nuclear fuel and FPs relatively decreases. The key
analysis items are listed in 2.1 to 2.3 below. Since the results should be reflected in criticality control
and safeguards, the measurement will basically focus on fuel components, components with alarge section area of neutron absorption, and the isotope ratio of fuel components. For waste
management, the radioactivity of Cs-137, which has a half-life of about 30 years due to high ɤ-rays,
should also be measured. For some FPs, the analysis priority may be required to be lowered. Thisis because, among FPs, the content of some nuclides is originally below 1%, and it is assumed thatthe structural materials were involved during the severe accident, and that the content rate has
decreased further due to attenuation caused by the time spent until the analysis of samples was
conducted, resulting in a fall below the detection limit (ND). For nuclides with low contents, thepriority of analysis should be determined by comprehensively examining the importance of thenuclide, where the results obtained will be reflected, inventory, and the dilution degree dependingon the sampling site, etc.

193

2.1 Fuel debris analysis items in Unit 1
In Unit 1, 400 fuel assemblies are loaded into the core. Assuming that the mass of 1 fuelassembly is approximately 300 kg, the content of U and Pu are estimated to be 55.4 mass% and
0.4 mass%, respectively, based on the inventory 71 contained therein. As the fuel melts andcomponents other than the fuel such as control rods and stainless steel are mixed, the content
rates relatively decrease. Fig. A8-2 shows the key items to be confirmed by analysis of fuel debris
in Unit 1.
(1) Fuel debris at the bottom of the RPV• Confirmation of fuel constituents and the chemical form of fueldebris in a small amount adhering to the bottom of the RPV.
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Checking for the presence of boride phase (possibility ofincreased hardness).
• Confirmation of the amount of fuel debris adhering to andinvading into the CRGT and CRD housings.
(2) Fuel debris at the bottom of the pedestal• Checking of the components of the fuel assembly (U, Pu, Gd,Zr), control rods (B, C, Fe, Cr, Ni) and structural materials (Fe,Cr, Ni) at each position.
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Checking for the presence of boride phase (possibility ofincreased hardness).
• Confirmation of the concrete components (Ca, Si, etc.).
• Confirmation of erosion depth by MCCI.
(3) Others• Checking for the presence of the effects of seawater injection(Na, Mg, and Cl).
• Confirmation of the form of adhering or remaining Cs-137 andCs-134 and the residual amounts.
• Checking of the degree of oxidation of U (the degree of
secular change).
• For nuclides with a high possibility of becoming ND based on
the inventory quantity, it is necessary to examine theappropriateness of analysis.
• The nuclides related to the storage, processing and disposalof waste are discussed in Stage 3.
Fig. A8-2

Items to be confirmed by analysis of fuel debris in Unit 1

71

Kenji Nishihara et al., “Evaluation of fuel composition at Fukushima Daiichi NPS”, Japan Atomic Energy Agency,
JAEA-Data/Code 2012-018 (2018).

1942.2 Analysis items of fuel debris in Unit 2
In Unit 2, 548 fuel assemblies are loaded into the core. Assuming that the mass of 1 fuelassembly is approximately 300 kg, the contents of U and Pu are estimated to be 55.4 mass% and
0.4 mass%, respectively, based on the inventory contained therein. As the fuel melts andcomponents other than the fuel such as control rods and stainless steel are mixed into the RPV,the content rate is relatively low. However, because the RCIC was operating for three days at thetime of the accident, the heat removal was more advanced than at Units 1 and 3 and, thus, it has
been pointed out that unmelted fuel may remain in the RPV. Fig. A8-3 shows the key items to be
confirmed by analysis of fuel debris in Unit 2.
(1) Fuel debris at the bottom of the RPV• Checking of the components of the fuel assembly (U, Pu, Gd,Zr), control rods (B, C, Fe, Cr, Ni) and structural materials (Fe,Cr, Ni) at each position.
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Checking for the presence of boride phase (possibility ofincreased hardness).
• Checking for the presence and the quantity of FP nuclides inunmelted fuel.
• Confirmation of the amount of fuel debris adhering to andinvading into the CRGT and CRD housings.
(2) Fuel debris at the bottom of the pedestal• Confirmation of the components of fuel assemblies, control
rods and structural materials (fuel components may be 10% orless).
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Confirmation of the concrete components (Ca, Si, etc.).
• Confirmation of the components of objects fallen onto thegrating.
• Confirmation of the loading position and the falling path of theupper tie plate that has fallen.
• Confirmation of the invasion of fuel debris into the drain sumppit.
• Confirmation of erosion depth by MCCI.
(3) Others - items in common• Checking for the presence of the effects of seawater injection(Na, Mg, and Cl).
• Confirmation of the adhering and residual form and theresidual amounts of Cs-137 and Cs-134.
• Checking of the degree of oxidation of U (the degree of secularchange).
• For nuclides with a high possibility of becoming ND based on
the inventory quantity, it is necessary to examine theappropriateness of analysis.
• The nuclides related to the storage, processing and disposal ofwaste are discussed in Stage 3.
Fig. A8-3

Items to be confirmed by analysis of fuel debris in Unit 2

1952.3 Fuel debris analysis items in Unit 3
In Unit 3, as with Unit 2, 548 fuel assemblies are loaded into the core. The inventory thereinshows that the content rate of U is 55.4 mass%, and that of Pu is 0.4 mass%. As with Unit 1, thecontent rate will decrease due to the mixing of control rods, stainless steel, etc. Although 32 MOX
fuel assemblies were loaded, the inventory evaluation indicates that the Pu concentration wasalmost the same as that of Unit 2.

(1) Fuel debris at the bottom of the RPV• Checking of the components of the fuel assembly (U, Pu,
Gd, Zr), control rods (B, C, Fe, Cr, Ni) and structural
materials (Fe, Cr, Ni) at each position.
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Checking for the presence of boride phase (possibility ofincreased hardness).
• Confirmation of the amount of fuel debris adhering to andinvading into the CRGT and CRD housings.
(2) Fuel debris at the bottom of the pedestal• Confirmation of the components of fuel assemblies, control
rods and structural materials.
• Confirmation of the isotope ratio of U and Pu.
• Density and particle size.
• Checking of the buildup in the center (CRD exchanger?).
• Checking for the presence of boride phase (possibility ofincreased hardness).
• Confirmation of the concrete components (Ca, Si, etc.).
• Confirmation of erosion depth by MCCI.
(3) Others• Checking for the presence of the effects of seawater
injection (Na, Mg, and Cl).
• Confirmation of the form of adhering or remaining Cs-137
and Cs-134 and the residual amounts.
• Checking of the degree of oxidation of U (the degree of
secular change).
• For nuclides with a high possibility of becoming ND basedon the inventory quantity, it is necessary to examine theappropriateness of analysis.
• The nuclides related to the storage, processing anddisposal of waste are discussed in Stage 3.
Fig. A8-4

Items to be confirmed by analysis of fuel debris in Unit 3

196

2.4 Representativeness of samples
In general, in order to improve the representativeness of analysis results, a large number ofsamples are taken to reduce the standard deviation. However, if the number of samples isincreased, the number of analyses to be conducted is also increased, requiring a lot of time, labor,
and expense, and eventually generating delays in processes, which may arouse concern that theresults of analysis would not be available in a timely manner.
Fig. A8-5 shows a schematic of the composition of fuel debris. Fuel debris is shown enlarged as
the molten fuel has flown down with structures involved. It is assumed that the concentrations of
the components vary seamlessly, depending on their location, temperature, and reaction process,eventually becoming heterogeneous. In particular, a concrete component is included at thepedestal bottom, which acts as a boundary, and then the composition changes greatly. Thus,
increasing the number of samples does not reduce the standard deviation.
Since the analysis results indicate the composition and physical properties specific to thesampling site, the analysis results should be combined with the positional information to make acomprehensive judgment. It is desirable to combine the results of fuel debris analysis, including thepositional information, with severe accident analysis codes, criticality assessment, etc., to evaluate
safety during retrieval and storage, and to optimize equipment specifications.
Top
Fuel

Vertical direction

Zirconium and iron
Concrete
Since they are not homogeneous, thecomposition will be varied even with a small
difference in position.

Center of thepoint of fall

Bottom of thepedestal
BottomHorizontal direction

Fig. A8-5

Peripheral partof the pedestal

Schematic diagram of the composition of fuel debris

The distribution and chemical composition of fuel debris in Unit 4 of the Chernobyl Nuclear
Power Plant are shown in Fig. A8-6 and Table A8, respectively72. In Unit 4 of the Chernobyl Nuclear
Power Plant, the state has changed into the black FCM, the brown FCM, and a mixture of them,
depending on the horizontal and vertical directions from which fuel debris was sampled. The
chemical composition in the FCM has also varied and is not homogeneous.

72

B. Burakov, “Study of Chernobyl [lava], corium and hot particles: experience of V.G. Khlopin Radium Institute(KRI)”, Data from the 2nd International Forum on the Decommissioning of the Fukushima Daiichi NPS, Day 2,(2017).

197

Fig. A8-6
Table A8

Fuel debris distribution67 in Unit 4 of Chernobyl NPP

Chemical composition67 of fuel debris in Unit 4 of Chernobyl NPP

3. Investigations on decommissioning and for clarification of the accident
process
3.1 How to proceed with the investigation
Considering that the accident had developed with the fuel damage, the analysis of fuel debris
described above is particularly important from the viewpoint of investigating the cause of theaccident. However, the traces of the accident as a result of the accident progression, such as
melting, solidifying, breaking, and falling, have been left in RPV, PCV, and reactor buildings, andthis information is necessary for clarifying the cause of the accident.
Since many of the traces can be used as direct inputs to the decommissioning work, including
debris retrieval, i.e., “What is located where?”, “How has the situation changed since before theaccident?” and “How much is the radiation dose?”, investigations should be rationally conductedfrom the viewpoint that they often overlap with the subject of “investigations for the purpose of
decommissioning”.
However, unlike experiments that are carried out in a planned manner, some of theinvestigations extracted to be conducted in order to clarify the cause of the accident are difficult in
realization because of their significant impact on the decommissioning process, human resources,
costs, etc., even if they are of high importance. Therefore, “investigations for clarifying the causeof the accident” should be carried out in a planned manner, considering feasibility.

198

Investigations for clarifying the cause of the accident are classified into the following fivecategories:[1] Since we have already acquired materials for examinations, we are only required to think hard.
 Investigations have already been completed.
[2] Since there is a similar plan that can be used for investigations for the purpose of
decommissioning, samples should be taken in an expanded form for solving issues by thinking
them through.
 At this point, a research plan is in progress, which can be relatively easily extended. The
burdens on the technology development required for expansion and on the budget are small.
[3] Items for which a plan for the current decommissioning process is not developed and that require
planning from scratch, such as determining an investigation period, securing human resourcesand expenses, and solving technical issues.
 Priority is given to establishing objectives, resources, and research methods(countermeasures against high radiation doses), etc.
[4] Due to the decommissioning schedule, no investigations have been planned over the past 10
years.
 Since no concrete investigation plans are developed at this point and distinguishing theaging degradation from the accident effect would become more difficult, investigations should
be carried out as soon as possible.
[5] An experiment to verify examinations that were conducted by thinking hard
 As this is an experiment, this is not included in the investigation of the accident history.

199

Attachment 9

Reduction of liquid phase and contaminated water (Water balance around thereactor buildings)

The containment function in the liquid is required to contain radioactive material to restrict therelease of the uncontrolled radioactive material from the reactor buildings with the objective ofminimizing the effect of radiation exposure to the liquid the on the public as with the exposure to
the gas.
However, since the PCVs and buildings (torus rooms) are found to be pierced and damagedby the earthquake, it is difficult to statically confine the liquid to perfection. For this reason,containing radioactive material is planned by maintaining the difference in level between thecontaminated water and groundwater to prevent water containing radioactive material from being
released from the reactor buildings to soil outside the buildings.
Due to the difference in level between groundwater and the water inside the reactor buildings,
groundwater flows into the buildings. In the torus rooms, this groundwater is mixed with coolingwater coming out of the PCVs and then discharged, treated, and stored in a planned way. Still, theemergence of contaminated water should be desirably minimized to the extent possible. Fig. A9-1
shows the current mass balance of water around the reactor buildings and the mass balance thatwill be achieved in the future if a water circulation system is built. From the viewpoint of water massbalance, it is possible to reduce the emergence of contaminated water possible by:(1) Reducing the inflow of the groundwater
It is important to take measures to prevent rainwater from flowing into the reactor buildings
and to set an appropriate groundwater level.
and/or(2) Reducing the emergence of contaminated waterThis method reduces the amount of the PCV cooling water that flows out into the torus rooms
to reduce the amount of contaminated water by setting the level of water inside the PCVs (drywell sections) and building system for directly recovering PCV cooling water with a combinationof the reduction of PCV cooling water and water stopping (whether it is feasible or not must be
determination).
In the future, in reviewing in details of the method for removing fuel debris in light of theengineering of the undertaker, it is necessary to identify how the water level inside the PCVs should200be set, whether or not it is possible to stop water, the system for directly recovering cooling waterfrom the PCVs (dry wells), and so on.

Fig. A9-1

Water balance around the reactor buildings

201

Attachment 10 Study on the water level at the bottom of PCV during fuel debris retrieval
Assuming that control of the water level can be performed by installation of underwater pumps,
state of the water level during fuel debris retrieval at the bottom of the PCV is illustrated in theconceptual diagram (Fig. A10-1) with grouping of the following cases. Each low of the diagramshows the expected result on the water level in the following cases; the 1st low shows the case ofpresent state, the 2nd low shows the case when water stoppage is performed by injection of thewater stoppage material inside the vent pipe (vent pipe water stoppage), the 3rd low shows thecase when water stoppage is performed by burial of the downcomer tip with filling of the highly
workable concrete inside the S/C (Suppression Chamber) (downcomer water stoppage), and the
4th low shows the case when water stoppage is not performed. Since it is desirable to maintain thewater level inside the S/C as low as possible from the viewpoint of earthquake resistance during
fuel debris retrieval, it was assumed that lowering of the water level inside of the PCV down to thelowest part of the vent pipe joint can prevent water from flowing inside the S/C when water stoppage
is not performed in each Unit.
Furthermore, development of water stoppage technology has just been started with installationof the water stoppage plate at the jet deflector and installation of the weir inside the D/W (Dry Well)in addition to the conventional vent pipe water stoppage, etc. as development of the water stoppage
technology conducted in the Government-led R&D Program on Decommissioning andContaminated Water Management. While considering these situations described above, it isnecessary to perform setting and control of the water level based on implementation or nonimplementation of water stoppage.
Progress of the study on each Unit is shown below.
A.

Study on the water level in the PCV in Unit 1
Current water level in the PCV is assumed to be about 2m and most part of fuel debris at thebottom of the PCV is considered to be submerged under water. In addition, leakage of the coolingwater in the PCV is found to the S/C through the vacuum break line (about 1.1m high from thebottom of the PCV) and to the torus room through the sand cushion drain pipe.
Therefore, it is necessary to lower the water level of the PCV to the level of the vacuum breakline or lower before applying the water stoppage technology between the PCV and the S/C (ventpipe water stoppage or downcomer waster stoppage) or the water level in the PCV is required tobe maintained at the level of the lowest part of the vent pipe joint or lower when water stoppage is
not performed. In addition, even in the case of performing either measure described above, it isconsidered to become necessary to take action against the cooling water flowing into the torus
room through the sand cushion drain pipe when retrieving fuel debris in the water or under the202cooling water being kept flowing on the fuel debris. Furthermore, installation of the drain receiverby means of the remote technology at the sand cushion drain part is considered necessary.
When either vent pipe water stoppage or downcomer water stoppage is performed, as the waterlevel in the PCV is maintained to the level of the vacuum break line or lower as described above,
the amount of the cooling water stagnating in the PCV is not large. Therefore, even if the coolingwater in the PCV leaks out to the torus room supposedly in case of damage at the vent pipe joint
part, the water level in the torus room can be maintained at the groundwater level or lower. In
addition, as the measures to prepare against leakage of the cooling water to the S/C from inside of
the PCV supposedly in case of damage of the downcomer joint part, it is being studied to takemeasures by collecting the cooling water with pumps installed in the S/C.
When water stoppage is not performed, the water level in the PCV will be maintained at the levelof the lowest part of the vent pipe joint or lower and fuel debris retrieval will be performed in the air
while the poring cooling water is kept flowing on fuel debris. In this case, it is necessary to study inadvance on the decay heat of fuel debris, required amount of the cooling water, etc., because apart of fuel debris will be expected to be exposed in the air.

B. Study on the water level in the PCV in Unit 2
Current water level in the PCV is assumed to be about 0.3m and most part of fuel debris at thebottom of the PCV is considered not to be submerged under water. In addition, occurrence ofleakage is assumed from the S/C to the torus room because both water levels in the S/C and thetorus room are almost the same.
When either vent pipe water stoppage or downcomer water stoppage is performed, the waterlevel in the PCV can be raised and fuel debris retrieval at the bottom of the PCV will be able to be
performed in the water. In this case, expected measures to be taken when the cooling water leaks
out from inside of the PCV are the same as ones taken in case of Unit 1.
When water stoppage is not performed, the water level in the PCV will be maintained at the samelevel of the current one and fuel debris retrieval will be performed in the air while the cooling water
is kept flowing on fuel debris. In this case, it is necessary to identify and repair the damaged partof the S/C to prevent leakage of the cooling water from inside of the PCV to the torus room via S/C.

C. Study on the water level in the PCV in Unit 3
The current water level in the PCV is assumed to be about 6m and is higher compared to thoseof Units 1 and 2. Therefore, fuel debris at the bottom of the PCV is assumed to be submerged
under water. On the other hand, the water level in the PCV is required to be lowered for the side
entry method to be performed from the viewpoint of leakage prevention of the cooling water fromthe access part.

203

When either vent pipe water stoppage or downcomer water stoppage is performed, fuel debris
retrieval can be performed in the water, although the water level in the PCV is required to belowered to almost the same level (about 2m) of the current one in Unit 1 due to the reason describedabove. In this case, measures expected to be taken when the cooling water leaks out from insideof the PCV are the same as ones taken in case of Unit 1.
When water stoppage is not performed, the water level in the PCV will be maintained at the levelof the lowest part of the vent pipe joint or lower and fuel debris retrieval will be performed in the air
while the cooling water is kept flowing on fuel debris. In this case, it is necessary to study in advanceabout the decay heat of fuel debris, required amount of cooling water, etc., because a part of thefuel debris will be expected to be exposed.

204• Current water level in the PCV is as follows; Unit 1: about 2m water depth, Unit 2: about 0.3m water depth and Unit 3: about 6m water depth.
• When vent pipe water stoppage is performed, fuel debris retrieval can be performed in the water at each unit. Operation of the collection system from D/W (DryWell) is started to control the water level in the PCV, for example, the water level at Unit 2 is raised and lowered at Unit 3. When the water level is lowered, fueldebris retrieval can be performed in the air while the cooling water is kept flowing on the fuel debris.
• As for water stoppage other than vent pipe water stoppage, downcomer water stoppage is performed at Unit 1 and water inside of the S/C is collected from theviewpoint of seismic resistance. At Units 2 and 3 the downcomer water stoppage is performed to separate the D/W from the S/C. Operation of the collection
system from the D/W and the S/C is started to control the water level, and fuel debris retrieval is performed in the water or the air while the cooling water is
kept flowing on the fuel debris.
• When water stoppage is not performed, the water level in the PCV is very low at the bottom and fuel debris retrieval is performed in the air while the coolingwater is kept flowing on the fuel debris.

Fig. A10-1

Water level at the bottom of the PCV and water stoppage in the PCV(Conceptual diagram with assumed results)
205

Attachment 11 Terms related to radioactive waste management
IAEA Safety Requirements GSR-Part 5 73 explains that predisposal of radioactive waste
encompass all stages of radioactive waste management from generation to disposal, including
processing, storage and transportation. Terms related to the management of radioactive waste as
defined in the IAEA glossary are shown in Fig. A11-1. Within the pre-disposal management,
processing of radioactive waste is classified into pretreatment, treatment and conditioning.
Processing is carried out to be in the form of waste suitable for selected or anticipated disposal
options. Radioactive waste may also be stored in for its management, therefore it is thought to benecessary that the form is suitable for transportation and storage.
Processing: a generic terms used to refer to the following
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. A11-1

Terms related to radioactive waste management (IAEA)74 and their translation
examples (For the Japanese translation example, refer to the materials of theAtomic Energy Society of Japan (AESJ) 75,76

73

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)74 IAEA, p.216 of IAEA Safety Glossary Terminology Used in Nuclear Safety and Radiation Protection 2007 Edition,(2007).
75 AESJ, The Report of 2013, - Organizing information of radioactive waste and matters to be considered for solving
the issues (p.7), March 2014, the Expert Committee, “Processing/disposal of radioactive waste generated by theaccident of Fukushima Daiichi NPS”
76 AESJ, Seiya Nagao and Masafumi Yamamoto, “Introduction to radioactive waste – Management of radioactive
waste from operation and decommissioning of nuclear and other facilities (1) Perspective of radioactive waste
management”, the 56 of (9) of Journal of the Atomic Energy Society of Japan, p.593, (2014).

206

Attachment 12

Overall image of Storage Management Plan for the Fukushima Daiichi NPS77

77 TEPCO, Solid Waste Storage Management Plan for Fukushima Daiichi Nuclear Power Station of Tokyo ElectricPower Company Holdings, Inc., June 2018 edition (issued in June 28, 2018)207

(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.A12-1

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

208

Attachment 13 Draft of technical map toward human resource development for decommissioning
reactors
Field Related to Electrical andMechanical Engineering

Stages of
NuclearIndustries

Nuclear Power
Station (fromPlanning andConstruction to
Operation)

Nuclear Fuel andWaste (from
Front-end to
Back-end of Fuel
Cycle)

Decommissioningof Nuclear
Facilities such as
Non-accidental
nuclear Power
Plant

Field Related to Plant Engineering

Field Related to Civil, Geotechnicaland Architectural Engineering

Field Related to Chemical andMaterial Engineering

Field Related to Nuclear Engineering(including Environment andRadiation)

Other Fields(Examples of Field)
Mechanical Engineering,Electrical and Electronic Engineering,Electronic Material,
Instrument Engineering and System
Control Engineering,
Signal and Image Processing,Information Engineering(Examples of Field)
Chemical Engineering,
Industrial Chemistry,
Chemical Plant,
Plant Engineering,
Process Engineering,
Water Chemistry(Examples of Field)
Civil Engineering,
Geotechnical Engineering,Architectural Engineering,
Groundwater Engineering,
Deep Geological Science,
Geohydrology, Soil Science,
Solid State Engineering (Concrete,etc.)(Examples of Field)
Material Engineering,
Solid State Engineering (Metal, etc.),
Metal Corrosion Engineering,
Nuclear Fuel Engineering,
Actinoid Chemistry,
Radiation Chemistry(Examples of Field)
Nuclear Reactor Physics,
Nuclear Reactor Design and
Structure,
Simulation Engineering,
Criticality Control,
Maintenance Engineering,
Radiation Science,
Radiation Effects,
Radiation Protection,
Environmental Radiation,
Kinetics theory(Examples of Field)
Project Management,
Legal Affairs,
Labor Management,
Financial Affairs, PA,
Risk Communication,
External Relations,
Information System,
Radiation Management

Features

Work Process(Examples of Basic Technology)
Electric System Design Engineering(Instrument Engineering and System
Control Engineering, Heavy Current
and Weak Current ElectricalEngineering, MechanicalEngineering),
Imaging,
Human Interface,
VR Technology,
Visualization Technology and
Recognition Support,
Mechanical Crafting (Cutting,
Shearing, etc.),
Remote-control Systems (Robotics),
Resistance to Radiation(Examples of Basic Technology)
Plant Designing,
Manufacturing,
Construction,
Assembly,
Piping,Plant Design,
Systems Designing,
Plant Instrumentation,
Boundary Building,
Negative Pressure Management,
Filter Design,
Engineering Flow

(Examples of Basic Technology)
Architectural Design,
Building and Construction Diffusion,
Demolishing Technology,
Non-destructive Inspection(Concrete, etc.),
Structural Soundness,
Boring,Underground Diffusion Control andEnvironment Restoration,
Property of Concrete(Examples of Basic Technology)
Welding, Corrosion Evaluation,
Metal Physics,
Nuclear Reactor Material,
Fuel Design, Radiolysis,
Rust Prevention,
Long-term Soundness Evaluation,
Volume Reduction and Stabilizationand Solidification,
Metal Recycling Technology,
Property Grasping(Examples of Basic Technology)
Designing, Operation,
Subcriticality Monitoring and Control,
Analysis Codes and Simulation,
Human Factor, Burn-up Analysis,
Nuclide Identification, Protection,
Environmental Impact Assessment,
Exposure Evaluation,
Radiation Evaluation,
Evaluation of Emission/Scatteringand Migration,
Future Estimation (Long-term
Dynamics),
Transfer Behavior(Examples of Basic Technology)
Project Management (Planning, Risk Evaluation andManagement, Resource Evaluation, EVM, etc.),
Laws and Ordinances,
Public Administration Affairs,
Accounting, Procurement, Contract, Workforce Estimation,
Labor Safety,
Management of Records, Documents and Knowledge,
Decision Making, Problem Solution, Strategic Thinking,
Leadership, Communication Capability,
Negotiation and Influence,
Presentation Capability, Coaching,Foreign Language Ability,
ICT and Systems Engineering,
Facility Maintenance and Management,
Other sorts of Back-office Operation,
Nuclear Material Accounting/Nuclear Material Control/
Safeguards and Inspection Affairs

Sustaining of
Criticality/Subcriticality,
Existence of Defense in Depth,
Remote Controlling in Some
Parts,High Temperature and High
Pressure,
Long-term Operation

Design and Construction,
Equipment Design,
Manufacturing and Assembly,
Power Generation (Turbine, etc.),
Operation and Maintenance,
Fuel Replacement and Storage

Electrical System (Heavy Current andWeak Current),
Instrumentation System,
Electricity Generators (Turbine, etc.),
Maintenance and Checkup (Electrical
Equipment, etc.),
Non-destructive Inspection andAnalysis (Devices)

Systems Designing (Process
Design),Layout Design,
Structure Design (Process
Equipment, Piping, etc.),
Thermal Hydraulics Design,Circulation System for Power,
Generation (Heat Exchanger, etc.),
Confinement System (without αnuclides),Air Conditioning Design

Geotechnical Evaluation,
Seismic Design (Structural
Soundness),
Large-size Equipment Assembly,
Maintenance and Inspection of
Buildings, etc.

Reactor Design (Materials),
Systems Designing (Materials),
Structural Soundness of Structures,
Maintenance and Checkup(Structures and Systems)

Core Design,
Safety Design,
Shielding Design,
Thermal Analysis and Cooling
Evaluation,
Plant Operation,
Response to Emergency,
Fuel Storage (Dry and Wet)

<Legal Affairs, Finance, and Back-office>Financial Management, Contract Administration,
Purchase Administration, Electricity/Gas/Water Supply,Intellectual Property Management,
Information System Development and Operation, Security,
Management of Records and Documents

Keep Criticality;
Existence of Defense in Depth;High Radiation Field;
Basically Remotely Controlled,
Long-term Operation;
Mechanical Crafting in Some
Parts;
Emission of Dusts Containing αnuclides;
Numerous Chemical Processes

Design and Construction,
Equipment Design,
Manufacturing and Assembly,
Operation and Maintenance,
Transportation of Nuclear Materials
and Fuels,
Fuel Processing and Manufacturing,
Fuel Storage (Dry and Wet),
Spent Fuel Reprocessing,
Waste Processing and Disposal

Electrical System (Heavy Current andWeak Current)
Instrumentation System
Nuclear Fuel and Spent Fuel Handing
Equipment
Remote Crafting and Measuring
Instruments
Cutting and Dismantlement (Spent
Fuel, etc.)
Waste Vacuuming and Removal
Equipment
Decontamination Technology (Device
Development)

Systems Designing (Process
Design),Layout Design,
Structure Design (Process
Equipment, Piping, etc.),
Confinement System (for α-nuclides)
Measures for Scattered Particle
Dusts (as System Development),
Air Conditioning Design,
Spent Fuel Reprocessing,
Decontamination of Systems (Using
Chemical Methods),
Waste Processing (Volume
Reduction and Stabilization),
Maintenance and Inspection of
Systems

Geotechnical Evaluation,
Seismic Design (Structural
Soundness),
Large-size Equipment Assembly,
Decontamination Technology(Concrete, etc.),
Cement and Asphalt Solidification,
Storage Facility and Disposal Site
Design (Thermal Design, etc.),
Maintenance and Inspection of
Buildings, etc.

Fuel Design (Material),
Fuel Processing and Manufacturing
Systems Designing (Material),
Maintenance and Inspection of
Systems,
Decontamination Technology of
Systems,
Material Design of Storage Cans,
Waste Storage Management(Chemical Stability and Long-term
Change Prediction)

Fuel Design (Heat, Neutron),
Safety Design,
Shielding Design,
Thermal Analysis and Cooling
Evaluation,
Criticality Control,
Radiation Measurement,
Radiation-resistant Design,
Nuclear Material Accounting(Criticality),
Measures for Scattered Particle
Dusts (Against Exposure) ,Heat Calculation of Waste,
Waste Shielding Storage andManagement (Criticality),
Radioactivity and Material BalanceManagement (Inventory Evaluation)

Known Internal Conditions,
Gradual Removal of Defense in
Depth,
Remote Controlling in Some
Parts,
A lot of Mechanical Crafting,
Emission of Dusts,
Long-term Project

Retrieval of Spent Fuel,
Decontamination of Inside of
Buildings,
Waste Sampling,
Dismantlement of Reactor Area
Dismantlement of Buildings, etc.,
Waste Processing and Disposal,
Environment Restoration (Soil
Restoration, etc.)

Remote Crafting and Measuring
Instruments,
Cutting and Dismantlement(Structures),
Waste Vacuuming and Removal
Equipment,
Decontamination Technology (Device
Development),
Non-destruction Inspection andAnalysis (Devices),
Waste Sampling Devices,
Dismantlement of Steel and Concrete
Structures

Confinement System (Without αnuclides),Decontamination Systems (Using
Chemical Methods),
Measures for Scattered Particle
Dusts (as System Development),
Waste Processing (Volume
Reduction and Stabilization)

Structural Soundness of Buildings,
Decontamination Technology(Concrete, etc.)
Recycling of Concrete, etc.,
Dismantlement of Buildings, etc.,
Storage Facility and Disposal Site
Design (Thermal Design, etc.),
Environment Restoration (Soil, etc.)

Decontamination Technology(Structures),
Property Grasping of Waste (Radiochemical Analysis),
Waste Storage and Management(Chemical Stability and Long-term
Change Prediction)

Radiation Measurement (Handling
Operations, etc.),
Radiological Protection,
Nuclide Identification,
Shielding Design,
Measures for Scattered Particle
Dusts (Exposure Prevention),
Heat Calculation of Waste,
Waste Storage Management(Criticality, Shielding),
Radioactivity and Material BalanceManagement (Inventory Evaluation),
Clearance Level Assessment<Labor, Organization Management, Safety Management>
Labor Safety,
Response to Emergency and Accident,
Fire and Explosion Prevention,
Failure Protection Measures,
Operation Risk Assessment,
Crisis Management, Assessment (Audit),
Organization Management,
Equipment Management (Operation),
Maintaining Motivation, Incentive Design,
Technology Succession, Education and Training, HR(human Resource Management and Development Plan)<Project Management>
Strategic Vision Formulation, Scenario Study,
Overall Plan Formulation, Planning and Application of
Decommissioning Plan of the Site,
Cost Evaluation and Management, Time Management,
Risk Assessment and Management, Process Control,
Material Amount Management, Material Procurement,
Expenditure Prioritization, QA, Land Planning,Work Space Management, Special Procurement (Planningand Implementation),
Redundancy Securing, Construction Management,
Quality Control<Engineering>
Process Planning, Construction Plan, Maintenance,
Operation Instruction, Planning and Training Simulator,(Remote-controlled) Equipment Operation,
High-place Work Plan
<Matters Common to Nuclear Power Facilities>
Site Planning and Regional Relations,
Environmental Impact Assessment,(Environmental) Monitoring,
Exposure Management and Assessment,
Radiation Management Equipment,
Anti-terrorism Measures and Nuclear Material Protection,
Designating and Canceling Radiation Controlled Areas,
Equipment Maintenance,
Planning, Managing and Implementing Fuel and Waste
Transportation,
Compliance with Safety Regulations and Permission andAuthorization,
Safeguards Administration<Research and Development Environment>
Precedent Case and Studies, Environment for Innovation,
Development and Maintenance of Foundations for R&D,
Strategy for Mock-up Facilities and Testing,
Collaboration with Researching Institutions<Social Relations>
Securing Consistency with Past Cases,
Relations with Stakeholders, Social Impact,
Public Relations, Treating Visitors

Decommissioningof Fukuoka
Daiichi NPS andOther Accidentdamaged NPS

Keep Criticality,
High Radiation Field,
Basically Remotely Controlled,
Loss of Defense in Depth,
Unclear Internal Conditions,High Uncertainty,
A lot of Mechanical Crafting,
Emission of Dusts Containing αnuclides,
Long-term Project,
Large-scale Project<Site Stabilization>
Countermeasures for Groundwaterand Contaminated Water,
Securing Cooling Function (Water
Circulation),
Retrieval of Spent Fuel
<Improvement of Operation
Environment>
Decontamination of Inside of
Buildings,
Structuring Inside PVC

Spent Fuel Handling Equipment

Measures for Cooling Water andContaminated Water (Circulation
System)Electrical System (Heavy Current and Decontamination of Systems (Using
Weak Current),
Chemical Methods)
Instrumentation System,
Decontamination Technology (Device
Development)<Investigation andRemote Crafting and Measuring
Preparation for Fuel Debris Instruments (Investigating
Retrieval>Instruments)
PCV/RPV Internal
Investigation,
Waste Sampling,
Fuel Debris Sampling

Systems Designing (Process
Design),Layout Design
Structure Design (Process
Equipment, Piping, etc.),
Confinement System (for α-nuclides)
Measures for Scattered Particle
Dusts (as a System Development)
Air Conditioning Design<Fuel Debris Retrieval>
Fuel Debris Retrieval,Transportation and Storageof Fuel Debris,
Processing and Disposal of
Fuel Debris

Radiation Measurement (System
Development),
On-site Sample Analysis
Non-destructive Inspection andAnalysis (Devices),
Remote Crafting and Measuring
Instruments (Retrieving Instruments),
Cutting and Dismantlement(Structures),
Sampling Devices for Fuel Debris,
Retrieving Devices for Fuel Debris,
Waste Sampling Devices,
Waste Vacuuming and Removal
Equipment

Fuel Debris Processing
Waste Processing (Volume
Reduction and Stabilization)<Dismantlement andEnvironment Restoration>
Reactor Area Dismantlement
Dismantlement of Buildings,
etc.,
Waste Processing andDisposal,
Environment Restoration(Soil Restoration, etc.)

Remote Crafting and Measuring
Instruments (Dismantling Devices)
Cutting and Dismantlement(Structures)
Waste Sampling Devices
Waste Vacuuming and Removal
Equipment

Waste Processing (Volume
Reduction and Stabilization)

Measures for Groundwater

Measures for Contaminated Water(Processing)

Thermal Analysis and Cooling
Evaluation

Decontamination Technology(Concrete, etc.)

Unravelling Contamination
Mechanism,
Decontamination Technology(Structures),
Investigating the Chemical Effect of
Seawater,Corrosion Prevention (PCV/RPV)

Making Contamination Maps

Systems Designing (Material)
Property Grasping of Fuel Debris(Chemical Analysis)
Material Design of Storage Cans

Severe Accident Progression
Analysis,
Property Grasping of Fuel Debris,
Thermal Analysis and Cooling
Evaluation,
Radiation-resistant Design,
Measures for Scattered Particle
Dusts (Against Exposure)

Radiation Measurement(Development of Components),
Aging Characteristics of Fuel Debris,
Property Grasping of Waste(Radiochemical Analysis),
Waste Storage and Management(Chemical Stability and Long-term
Change Prediction)

Radiation Measurement (Handling
Operations, etc.),
Radiological Protection,
Nuclide Identification,
Criticality Control,
Radioactivity and Material BalanceManagement (Inventory Evaluation),
Fuel Debris Storage andManagement (Criticality, Shielding),
Heat Calculation of Waste,
Waste Storage and Management(Criticality, Shielding)

Property Grasping of Waste(Radiochemical Analysis),
Waste Storage and Management(Chemical Stability and Long-term
Change Prediction)

Heat Calculation of Waste
Waste Storage and Management(Criticality, Shielding) ,Clearance Assessment

Structural Soundness of Buildings,
Structural Soundness ofContainment Vessels,
Water Sealing at Building Borders,
Water Sealing at PCV Borders

Dismantlement of Buildings, etc.,
Cement and Asphalt Solidification,
Storage Facility and Disposal Site
Design (Thermal Design, etc.),
Environment Restoration (Soil, etc.)Implementation of all the above actions, keeping in
mind Safe, Proven, Efficient, Timely, and Fieldoriented work under the environment anduncertainty at 1F that are different from normal
environment, with unknown shape, composition, andinternal condition (especially, Project Management)

Response to unprecedented regulations andSafeguards



Players well-versed in more than one field arenecessary, considering that necessary humanresources differ and processes change dependingon the period.

(Note) In the section of “Decommissioning of the Fukushima Daiichi NPS and other Accident-damaged NPS”, technical issues that have
similar entries in the other stages of nuclear industries are highlighted by yellow color, and other issues that have similar entries aswell but have different preconditions or require higher levels of response are highlighted by green color. Technical issues with nosimilar entries are highlighted by red color. (The corresponding entries in the other stages of nuclear industries are also highlighted byyellow or green colors.)(Source: Material 2-4-2, 6th Meeting of Decommissioning R&D Partnership Council (December 12, 2017)209

Attachment 14 Current Progress of the Government-led R&D program on Decommissioning andContaminated Water Management
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) (Fig. A141-(1))(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 technologies for analyzing and estimating characterization of fuel debris(FY 2019) (Fig. A14-1-(2))(Related projects) Development of technologies for characterization and processing of fueldebris using mock-up debris (FY 2011 - 2014)
Property analysis of actual debris (FY 2014)
Grasping properties of fuel debris (FY 2015 - 2016)
Development of technologies for grasping and analyzing fuel debris (FY 2017
- 2018)Construction of material accountancy method related to fuel debris (FY 2011 2013)
1-(3) Development of technologies for in-depth investigation of PCV inside (FY 2017 - 2019) (Fig.
A14-1-(3))(Related projects) Development of investigation technology of inside of PCV (FY 2011 - 2013)
Development of investigation technology of inside of PCV (FY 2014 - 2015)
Development of investigation technology of inside of PCV (FY 2016 - 2017)
1-(4) Development of investigation technology inside RPV (FY 2016 - 2019) (Fig. A14-1-(4))(Related projects) Development of investigation technologies inside RPV (FY 2013 - 2015)
1-(5) Development of sampling technologies for retrieving fuel debris and internal structures (FY2017 - 2019) (Fig. A14-1-(5))1-(6) Development of technologies for the detection of fuel debris inside reactors (using muon)(FY 2017 - 2019) (Fig. A14-1-(6))
2. Retrieval of fuel debris
2-(1) Development of technologies for retrieving fuel debris and internal structures (FY2019)(Fig.A14-2-(1))
210Advancement of retrieval method and system of fuel debris and internal structures (FY2015 - 2018)(Related projects) Development of technologies for retrieval of fuel debris and internal structures(FY 2014)
2-(2) Advancement of fundamental technologies for retrieval of fuel debris and internal structures(FY 2017 - 2018) (Fig. A14-2-(2))(Related projects) Development of fundamental technologies for retrieval of fuel debris andinternal structures (FY 2015 - 2016)
2-(3) Development of closed circulation systems for water inside PCV (FY 2018 - 2019) (Fig. A142-(3))2-(4)-1 Development of repair methods for leak spots in PCV (FY 2016 - 2017) (Fig. A14-2-(4)-1))(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-(4)-2 Full-scale test of repair methods for leak spots in PCV (FY 2016 - 2017) (Fig. A14-2-(4)-2))(Related projects) Full-scale test of repair methods for leak spots in PCV (FY 2014 - 2015)
2-(5) Development of evaluation methods of seismic performances of RPV and PCV and theimpacts of the damages (FY 2016 - 2017) (Fig. A14-2-(5))(Related projects) Development of evaluation methods for the structural integrity of RPV andPCV (FY 2011 - 2013)
Development of evaluation methods for the structural integrity of RPV andPCV (FY 2014 - 2015)
2-(6) Development of corrosion inhibition technology for RPV and PCV (FY 2016) (Fig. A14-2-(6))2-(7) Development of criticality control technologies of fuel debris (FY 2012 - 2017) (Fig. A14-2-(7))2-(8) Development of technologies for non-destructive detection of radioactive material depositedin S/C, etc. (FY 2014) (Fig. A14-2-(8))2-(9) Development of remote decontamination technology in the reactor building (FY 2014 - 2015)(Fig. A14-2-(9))(Related projects) Development of remote decontamination technology in the reactor building(FY 2011 - 2013)
2-(10) Formulation of comprehensive radiation dose reduction plan (FY 2012 - 2013) (Fig. A14-2(10))
2-(11) Development of technologies for containing, transferring and storing fuel debris (FY 2016 2019) (Fig. A14-2-(11))(Related projects) Development of containing, transferring and storing technologies of fueldebris (FY 2014 - 2015)

211

3. Waste management
3. Research and development of processing and disposal of solid waste (FY 2017 - 2019) (Fig.
A14-3)(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)
4. Spent fuel management
4-(1) Evaluation of long-term integrity of fuel assembly retrieved from spent fuel pool (FY 20152016) (Fig. A14-4-(1))(Related projects) Evaluation of long-term structural integrity of fuel assemblies removed fromspent fuel pool (FY 2012 - 2014)
4-(2) Investigation of method for processing damaged fuel, etc. removed from spent fuel pool (FY
2013 - 2014) (Fig. A14-4-(2))
5. Contaminated water management
5-(1) Verification tests of tritium separation technologies (FY 2014 - 2015) (Fig. A14-5-(1))5-(2) Verification of technologies for contaminated water treatment (FY 2014) (Fig. A14-5-(2))5-(3) Large-scale verification of impermeable walls (frozen wall) (FY 2014) (Fig. A14-5-(3))5-(4) Development and verification of high-performance multi-nuclide removal equipment (highperformance ALPS) (FY 2014) (Fig. A14-5-(4))

212Fig. A14-1-(1)Upgrading level of grasping state inside reactor

213

Fig. 14-1-(2)Development of technologies for analyzing and estimating the characterization offuel debris
214

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Fig.14-1-(3)Development of technologies for in-depth investigation of PCV inside217

Fig.14-1-(4)Development of investigation technology inside RPV
218

Fig.14-1-(5)Development of sampling technologies for retrieving fuel debris and internal
structures219

Fig.14-1-(6)Development of technologies for the detection of fuel debris inside reactors(using muon)

220

Project objectives
Based on the research and development results obtained so far, the necessary elemental technological development and testing will be carried out for theequipment, devices and systems related to the removal of fuel debris and reactor internal structures, as well as technologies for ensuring safety during
removal. Mainly, with regard to various technologies required for establishing the access, such as the technology for removing interference existing in the R/B
and PCV, and the technology for collecting and recovering fuel debris, technological development will be carried out taking into consideration remote
operations under high doses, high contamination, and environmental conditions including uncertain factors, ensuring safety such as maintaining thecontainment function, and continuous operations during the fuel debris retrieval period. In addition, each elemental technology related to the system forensuring safety when removing fuel debris and reactor internal structures will be developed.

1. Project details and progress
The following development will be carried out by reflecting and integrating the results of the related projects and the results of the "upgrading of
the fundamental technologies for retrieval of fuel debris and internal structures" as bellow section 2:(1) Development of fuel debris retrieval method
Based on the on-site information, etc., the technology will be developed to construct the access route necessary for the removal of fuel debris
existing in the reactor pressure vessel (RPV) and PCV. In particular, with regard to the technology for removing interference that can reduce
the fuel debris removal process, the feasibility of the technology for removal is supposed to be confirmed by considering situations of slippage,
deformation, damage, etc., based on the results of the investigation of the facilities in the R/B and PCV, and conducting element tests asnecessary.
In addition to the technologies for removal of interference, technological development will be carried out for the systems that support theoperation of remote equipment, the methods for maintenance of equipment inside the PCV, the technologies for preventing contamination fromspreading outside the PCV, and the technologies considered necessary for the construction of access routes that take into account theconstruction of shields to reduce exposure inside the R/B.
Equipment considered to become interference in each access method are as follows:[1] Top access method to RPV: Reactor well shield plug, PCV head, RPV head, internal structures, etc.
[2] Side access method to PCV: Equipment, systems and piping inside and outside the pedestal in the R/B (especially around thepenetration)(2) Development of fuel debris handling technology[1] Development of technologies for the system of collecting and recovering fuel debris dust inside the PCV
a. Development of dust collection system for the dust to be generated during fuel debris processing
For processing such as cutting fuel debris, mechanical methods including core boring, disc saw, chisels, etc., thermal methods such as lasers,
etc., and high pressure jet blasting methods have been studied for the application and are being developed in consideration of the requirementof workability according to the characteristics of fuel debris and the impact of dust generated by the processing. In accordance with thecharacteristics of dust generated by these various processing methods and processing environments, dust collection systems for the area
where dust is generated in the air or in liquids will be developed. In addition, a system will be developed to minimize the dispersion of dust
inside the PCV as much as possible, which complements the dust collection in the vicinity of the area where dust is generated.
b. Development of methods and systems for recovering and containing according to the condition of fuel debris
In addition to the melt-damaged fuel inside the RPV, there are fuel debris deposits at various locations on the structure, such as the pedestal
bottom in the PCV in various states (loose debris, sludge-like debris, fine (powder) debris, debris by processing such as crushing/cutting, etc.).
In order to improve the efficiency of fuel debris retrieval, recovery methods and a method of putting debris into the containers and systems
according to the state of fuel debris will be developed.
[2] Development of technologies related to purification and treatment of fuel debris and deposits inside the liquid phasea. Development of technologies to remove soluble nuclides
Regarding the technology for removing dissolved nuclides that are considered to leach into circulating cooling water from fuel debris, elemental
tests will be conducted on the alpha nuclides of adsorbents for removing dissolved nuclides to select the most suitable adsorbents, and theconceptual system of the facility for adsorption and removal will be designed.
b. Development of technologies for treating deposits recovered from inside the PCVWhen recovering deposits containing fuel debris present at bottom of the inside of the PCV, a recovery liquid containing the deposit will be
generated and, when a filter of the circulation cooling water system is backwashed during a fuel debris retrieval operation, a waste liquidcontaining solid matter or the like will be generated. In handling and storing these, it is necessary to separate the solid components from theliquid from the viewpoint of safety, volume reduction, etc. For the treatment technology to separate the solid matter from the liquid to put itaway, a technology considering the efficiency of containing, remote operation, maintenance, etc., will be developed, and a conceptual systemof the waste liquid treatment facility will be designed.
[3] Surveillance of technologies for separating fuel debris from waste
The technology, which will be necessary to divide the matter taken out of the inside of the PCV into fuel debris and radioactive waste material,
will be studied. Additionally, a method for separation will be examined. Then, the feasibility for the related projects such as “development oftechnology for containing, transferring and storing fuel debris” as well as “R&D for Treatment and Disposal of Solid Waste” will be assessed.
(Notes)As for technological development for equipment, devices and systems related to fuel debris retrieval, the following technologies will be
developed in consideration of the ease of handling and maintenance methods for systems to be used for remote operation:• Since the system is installed in high dose areas, maintenance will be conducted by remote operation in principle.
• It is necessary to consider contamination of equipment and required decontamination.
• Work area for maintenance is limited.
• It is necessary to minimize radioactive waste to be generated by maintenancework as much as possible.
Rail• It is necessary to consider the installation and handling of a criticalitydevice
monitoring system.
(3) Development of technologies related to ensuring safety during fuel debris retrieval work
Arm[1] Development of technologies related to the containment function
a. Development of technologies related to the prediction of dust behavior for the containment function
The containment function is important from the viewpoint of ensuring the safety of the public and workers. Research and development will be
carried out for the combination of the airflow analysis inside the PCV and the aerosol behavior analysis technology necessary for the predictionof the behavior of dust containing alpha nuclides to be generated during fuel debris processing inside the PCV. Additionally, the extension of
the analytical model for the prediction of the behavior in the R/B will be developed.
b. Development of containment technology for the existing connecting portion in the new large-scale facilities
For large new facilities to be installed in the R/B, such as a working cell for removing fuel debris, the structure, construction method,
inspection, maintenance of sealing materials, etc., of the connecting parts, etc., will be examined as technological development to ensure thecontainment function of the connecting parts with existing structures such as the PCV. Then, the validity of the technology will be confirmed byconducting necessary element tests.

221

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Fig. 14-2-(1)Development of technologies for retrieving fuel debris and internal structures

223

Fig. 14-2-(2)Advancement of fundamental technologies for retrieval of fuel debris and internal
structures

224

Fig. 14-2-(3)Development of closed circulation systems for water inside PCV

225

Fig.14-2-(4)-1

Development of repair methods for leak spots in PCV

226

Fig. 14-2-(4)-2

Full-scale test of repair methods for leak spots in PCV

227

Fig.14-2-(5)Development of evaluation methods of seismic performances of RPV and PCV andthe impacts of the damages

228

Fig. 14-2-(6)Development of corrosion inhibition technology for RPV and PCV
229

Fig.14-2-(7)Development of criticality control technologies of fuel debris

230

Fig. 14-2-(8)Development of technologies for non-destructive detection of radioactive material
deposited in S/C, etc.

231

Fig. 14-2-(9)Development of remote decontamination technology in the reactor building232

Fig. 14-2-(10)Formulation of comprehensive radiation dose reduction plan233

Fig. 14-2-(11)Development of technologies for containing, transferring and storing fuel debris
234

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237

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(4) Integration of R&D results[Achievements to date]* Regarding the waste stream, latest results derived from previous research are reflected in it, and establishment of methodology to integrate
progress, consistency of results, and remaining issues, is made to start. Operational issues are also summarized through trial.
[Current initiatives]* With incorporation of the results gained from studies, we continue to evaluate progress, consistency in the results, and remaining issues in acomprehensive manner. For this evaluation, issues will be summarized to contribute to further R&D activities.

Implemented byInternational Research Institute for Nuclear Decommissioning (IRID) (FY 2013 -)(Partly proposed by) IHI Corporation (From FY 2018)
Orano ATOX D&D Solutions Co., Ltd. (From FY 2018)
Kurion Japan Co., Ltd. (From FY 2019)

2. Related projects
The following describes the results of previous related projects.
 Development of technologies for processing/disposal of secondary waste generated by treatment of contaminated water (FY 2012)(1) Characterization of spent adsorbers, sludge, etc.
• Nuclides in contaminated water and treated water were analyzed, and progress was pursued in the analysis of nuclides that are difficult to measure.
• Work continued in estimating the distribution of cesium adsorbed into the adsorber inside an adsorption tower and in performing tests to characterize theproperties, such as the thermal stability of spent zeolite. It was not possible to perform sampling and analysis according to the schedule due to the high dose
rate from the sludge itself and in the surrounding area.
• Progress was made in the collection of information regarding the basic properties of secondary waste from newly employed contaminated water treatment
systems (cesium adsorption system No. 2 and multi-nuclide removal system).
(2) Studying long-term storage• Corrosion testing was performed on sludge storage container material and cesium adsorption apparatus material to collect electrochemical data, etc.,
pertaining to container corrosion that could contribute to the evaluation of long-term storage.
• Based on the results of spent zeolite property characterization, the hydrogen concentration and the temperature inside adsorption towers were estimated assafety-related information.
• Heat flow analysis was performed on sludge under the current storage conditions, and the appropriateness of measures that had been taken to address theissue of heat was verified.
• A literature search was begun on adsorbers used in the multi-nuclide removal system, etc.
(3) Research on the conditioning techniques• The results of research conducted were compiled on techniques used for conditioning of spent zeolite, sludge, etc.
• By conducting basic experiments on conditioning such as using the cement solidification technique, progress was made in the collection of data required forassessing the implementation feasibility of conditioning techniques.
• Information was obtained about secondary waste from the multi-nuclide removal system (types, predicted quantities, etc.).
 Development of technologies for processing/disposal of radioactive waste (FY 2012)(1) Characterization of “rubble, etc.”• The radioactivity of rubble and felled trees was analyzed to collect analysis data required to know features on the contamination status of waste.
(2) Development of techniques to analyze nuclides that are difficult to measure• To address nuclides such as Zr-93 and Mo-93 that are difficult to measure and therefore require the development of analysis techniques, literature searches
were performed and analysis flows were studied.
(3) Study on the development of infrastructure for R&D on waste processing/disposal• The study was conducted on the components of R&D as well as those solutions necessary to obtain prospects of a processing/disposal method and technology
related to its safety. In addition to that, information was compiled such as needs of users, future possibility of developing a database, and conceptual design
was implemented for its setting up.
(4) Establilshing an R&D program on waste processing/disposal techniques• Referring to a technical development program discussed within the special expert committee of the Atomic Energy Society of Japan, a draft R&D program for
waste processing/disposal techniques was produced.
 Research and development of processing/disposal of solid waste (FY 2013 - 2014)(1) Characterization• Rubble, felled trees and secondary waste generated by water treatment were transported to JAEA for radioactivity analysis. A proportional relationship was
found between Cs-137 and Sr-90 in rubble and felled trees in terms of radioactivity concentration.
• The radioactivity (i.e. the inventory of radioactive nuclides) in secondary waste generated by water treatment (cesium adsorption apparatus, etc.) was estimatedbased on the concentration analysis data of treated water.
(2) Studying long-term storage• The conditions inside cesium adsorption apparatus were estimated based on data from simulation test. It was noticed that corrosion was suppressed by thecoexistence of zeolite.
• The technique to be used to stabilize slurry from the multi-nuclide removal system was selected, and test was conducted using simulated samples.
(3) Studies on waste processing• Experiments were conducted with the solidification of slurry and spent adsorber from the multi-nuclide removal system using solidifiers of various types.
• A catalog of existing waste processing and conditioning techniques was compiled.
(4) Studies on waste disposal• Assuming the application of existing disposal concepts to the disposal of waste generated by the accident, safety assessment methods (scenarios, etc.) in
consideration of the features of waste was provisionally defined.
• In defining analysis cases for the postulated scenarios, provisional assessment was performed for the safety of disposal of different types of waste.
(5) Studying postulate of R&D• Waste generated by the accident was classified by property, contamination history, etc. And an example of handling flow consisting with storage, processing,and disposal and those may realize safe disposal was defined for each classification of waste.
• The collection of analysis data was expanded or updated with newly obtained data. In addition, the relationships between major development tasks ofprocessing/disposal techniques and various information items were defined to prepare for the development of information management tools.

240

Fig. 14-3

Research and development for processing/disposal of solid waste

241Fig. 14-4-(1)Evaluation of long-term integrity of fuel assembly retrieved from spent fuel pool242

Fig. 14-4-(2)Investigation of method for processing damaged fuel removed from spent fuel pool243

Fig. 14-5-(1)Verification tests of tritium separation technologies
244

Fig. 14-5-(2)Verification of technologies for contaminated water treatment245

Fig. 14-5-(3)Large-scale verification of impermeable walls (frozen wall)246

Fig. 14-5-(4)Development and verification of high-performance multi-nuclide removal
equipment (high-performance ALPS)

247

Attachment 15 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
center with 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 researcheswith satisfactory understanding of the Needs.
Therefore, concerning the 6 Essential R&D Themes which are described in the interim report of the Task
Force on Research Collaboration (November 30, 2016), the Basic Direction of the 6 Essential R&D Themes wascompiled 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 fueldebris 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 retrieved debris must be stored safely. Choosing the best possible
methods of retrieve/transmission/storage of fuel debris requires predictions ofcharacteristic changes of fuel debris over time.
In relation to the accident of Chernobyl nuclear power plant, detection ofparticulates of the micron order which contain fuel components from around thefuel debris has been reported and the national report of the Ukrainian government
showed concerns about the increase risk of radioactive dust emergence over timethrough self-decay. One of the possible reasons is that the fuel debris with highradioactivity exposed to rich humidity caused rapid progress of aging which quite
slowly proceeds with normal uranium mineral in the geological environment. It

Basic direction248

results in oxidation activated by radioactive dissolution and generate hexavalenturanium 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 the fuel debris. Since the radiation level is about oneorder higher in 1F than that of the fuel debris in the case of the Three Mile Island
Unit 2 (TMI-2) accident (occurred in a short time after the operation started), it isunder unexperienced condition. In addition, it should be noted that it will take alonger period to complete the retrieval of the fuel debris from the time of accident
than in the case of TMI-2.
Various factors are involved in the aging of such fuel debris in addition to theoxidation described above. Roughly classifying, those factors may include thechemical 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 αray), 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, thecontainment 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-and-Long-term Roadmap, while theprocessing and disposal method of the fuel debris will be decided in the third
period (from 2022) after the retrieval of the fuel debris is started, obtaining theaging information of the fuel debris is an urgent issue. While taking into
consideration the permission and authorization about the safety regulation, toprovide sufficient prediction and explanation of the risk changes resulted from theaging of the fuel 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 the matrix pattern of parameters (temperature, pH, etc.) to collectbasic data, and it needs to establish the prediction method of aging. In this case,
it is important to maintain the foundations for advancement of the actinoid
chemistry, which provides the basis for examination of the physical property of fueldebris. In addition, heat analysis for 1F should be included in the basis ofinvestigation since the temperature distribution of the fuel debris has to beunderstood 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 highradiation levels and unsteady routes of cooling water in order to prepare forpotential corrosion during decommissioning.
A boiling water reactor (BWR) consists of various metallic material. While
stainless steel, which is corrosion resistant, is used inside reactor where it is hightemperature and high oxidizing environment, carbon steel, which is not corrosion

Basic direction249

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, and especially, data has been collected being
focused on the corrosion data in the environment of high radiation, hightemperature, 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 have been generated through radiolysis of water.
Currently, since nitrogen has been injected into PCV to prevent hydrogen
explosion and the oxygen density has been decreased, the densities of the oxygen
and the hydrogen peroxide are considered to be decreased in the water andcorrosion 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 soundnessof the structure and pipes that form the boundary for confinement of radioactive
materials and it is also important to prepare countermeasures based on theknowledge on corrosion in such environment.
Since the corrosion is essentially a kind of battery reaction, it is likely tohappen if the electric conductivity of water raises, pH falls, and the electric
potential raises under the condition 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 factors that promotes corrosion suchas a formation of liquid film of dew, a humid environment that repeats wet and dry
conditions near the water surface, an irregular flow of cooling water, convection
flow, or backwater due to irregular paths created by gaps between various shapesof fallen objects or deposited materials, a progress of corrosion on the anode side
between different kinds of metals touching each other, a progress of acid-basereaction 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 the corrosion progresses over time during the decommissioning works
under the special environmental conditions, estimation of corrosion phenomenon
and investigation of countermeasures 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 ofcorrosion phenomena and systematically clarify and understand the phenomena
in order to provide satisfactory prediction and explanation of the risk changes that
follow corrosion of structures taking the permission and authorization of the safety
regulation into account with giving priority to the factors of higher needs that may
have critical impacts on the decommissioning works from the viewpoint of theprobability of occurrence such as the factors above and the impacts on thefunctionality (parts and severity), the scale and the timing. In this case, in order toexamine various approaches including not only the use of existing anti-corrosive
agents but also electric protection, it is important to accumulate and maintain theknowledge related to the corrosion phenomena in addition to the electronic state250

of materials in a special environment through principle analysis and clarification 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 tothe accident and the existing measurement devices do not meet thecapability/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 ofradiation measurement products using various principles or materials including
ionization chambers, counting tubes, semiconductor detectors, and scintillation
detectors are already offered. However, it is very important to develop the humanresources for measurement since it is necessary to understand the principles ofthe equipment in order to interpret the measurement data and address possible
troubles such as the case of the disorder (inversion of data value) between the all
β-radioactivity value and the value of Sr-90 because miss-counting has not beentaken into account for the resolution time in the analysis of the sampled water atthe 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 performed by remote operation since the radiation level is extremely
higher than the one in the work environment of existing nuclear facilities. It isnecessary 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 resistant sensors andcircuits. As for the specific examples of sensor development, it is necessary todevelop 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, and ɤ-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, high radiation resistance, energy discrimination, spaceresolution (identification of radiation source position), ease of operation, andmaintainability. As for the composition of the measurement targets, developmentof the technology so-called “on-site analysis” is required since there are needs offunctions that can be used to analyze the target without transferring a sample toother facility or equipment and obtain rough results used to promptly judge if thetarget is debris or not, and if the target is debris, the function to judge co-existenceof reactor internals and neutron poison is required.
In addition, effective support tools for the decommissioning can be provided
by developing the technology to visualize the radiation field and the contamination
situation and clarify the profile of the fuel debris based on the information of thestrength and the direction of the radioactive sources.
It is necessary to develop the generic technologies for innovative
measurement of radiation using new ideas and principles by considering on-sitemeasurement requirements.

Basic direction

251

Theme(4) To clarify behavior of radioactive airborne particle generated duringdecommissioning (incl. α-dust treatment)“Descriptions /Background issues”
on the interim report

Basic direction

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 to understand physical/chemical properties of α-dust, to predict theamount of dust to be produced for each method, and to consider how to seal thedust according to the results in order to make sure the retrieval will be conductedin a safe and effective manner.
As the fuel debris retrieval work will start, cutting the fuel debris will create alot of radioactive airborne particles (α-dust) that contain α-nuclide and they will bedispersed within the boundary. When retrieving the fuel debris, since the work will
be performed in the confinement boundaries which are the broken buildings, it isimportant to understand the property of the α-dust for studying how to secure theconfinement capability, designing the filtering system, and performing theexposure evaluation of the surrounding environment and workers including thetime of accident.
With regard to the data about the scattering rate when α-dusts are generated,
there is the data obtained at the decommissioning of JAEA’s JPDR and thedismantling of glove box of JAEA’s Nuclear Fuel Cycle Engineering Laboratories.
However, the data has not been collected just for the nuclear fuels but collected
for the objects polluted by the nuclear fuels, and the data has been collected forthe amount of the radioactive materials and their densities from the viewpoint ofradiation exposure control and it is not systematically organized.
On the other hand, the radioactive airborne particles in 1F will be generated
directly from the fuel debris when retrieving the fuel debris and from the polluted
objects in the decommissioning process. The types of radioactive materials are αnuclides and β (ɤ)-nuclides. While the α-nuclide of which typical element isplutonium is important from the viewpoint of internal exposure, the β(ɤ)-nuclide
such as cesium should be well considered as well from the viewpoint of the total
exposure evaluation.
In order to study on collection of radioactive airborne particles, efficientfiltering and purification, criticality prevention, etc., it is necessary to grasp theamount of generated particles, distribution of particle diameters, radioactive
diameters, and the physical and chemical property of particles according to thedifferences of the target objects and the method of cutting. It is also important tounderstand the behavior of the generated particles in the gas phase, at the airliquid interface, and in the liquid phase during transportation or transition. For
example, it is important to understand the growth of particles through coagulationin the gas phase, evaluation of mist generation from the air-liquid 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 fromthe fuel debris, especially the one of α-nuclides. In this case, it is important todecide 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 by plutonium is consistent with the ones that have been usedas the criteria of internal exposure evaluation for plutonium.

252

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 ofdecontamination based on the mechanism of the contamination to radiation
sources, and to decrease the volume 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 so on, paints, and concretes of the walls or floors. The contamination source
includes molten high temperature fuels at the time of accident, steams that containradioactive materials such as Cs leaked in consequence of hydrogen explosion
and so on, dusts and contaminated water that contain radioactive materials.
Currently, as for radiation reduction in the buildings on 1F, decontamination offloors 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 stepin the long decommissioning process, it is expected that many situations that
require decontamination will arise, therefore, effective and efficientdecontamination is considered highly necessary. With regard to decontamination,
not only reduction of radiation but also reduction of wastes should be taken into
consideration.
For decontamination, while engineering approaches are required, including
physical methods 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 areused in pipes, tanks and so on to confine radioactive materials. However, there isalmost no research on the concrete of structures or radiation shields that does notdirectly touch radioactive materials.
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 is important 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, the contamination mechanism must be clarified inprinciple on the concrete exposed to the accident and the subsequentenvironment 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-long-term viewpoint,
it is necessary to establish the evaluation method based on the understanding 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 mechanismof the metal of the piping and equipment in the environment of the 1F. While it isconsidered necessary to clarify the contamination mechanism inside PCV or RPV
exposed to the high temperature environment at the time of accident, it is notnecessary to take into consideration a special contamination mechanism such as
penetrate into metals outside PCV. As for the decontamination mechanism of

Basic direction253

resins and paints of cables, it is considered that it not necessary to conduct a
special research on decontamination since they can be replaced or removed.

Theme(6) Environmental fate studies of radioactive materials generated duringdecommissioning“Descriptions /Background issues”
on the interim report
Basic direction

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 theenvironment.
In order to properly evaluate and reduce the risk of future environmental
impact caused by radioactive materials in the Fukushima Daiichi NPS site, it isnecessary to provide proper evaluation and estimation of the environmental fateof radioactive materials around the site via the shallow underground water and thesurface 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 thatpoured into the ports in past and accumulated on the bottom of the sea (137Cs,
90Sr, etc.), and (3) the radioactive materials that are contained in the contaminatedwater that will be generated as the result of retrieval of the fuel debris ordecommissioning and dismantling of the buildings (including ion such as actinide
and suspended solids) that can be the future source 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 thetransport behavior of the radioactive materials as the required basic knowledge.
Specifically, the targets 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 anddiffusion in the surface layer, the existence form and the molten and diffusion
behavior of the radioactive materials in the seawater in the port and on the bottomof 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
the property 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 asimilar environment.
In addition, in order to provide the accurate future estimation of theenvironmental fate, it is also necessary to develop the monitoring technology toidentify the accurate contamination condition and the analysis technology tosimulate the transportation behavior of the radioactive materials. As for themonitoring technology, the technology for long term and continuous remotemeasurement and the mapping and behavior identification technology using thebig data are expected. As for the simulation technology, the creation model thatcan be used to analyze the behavior (influence of unsaturated layer, kinetic
evidence, etc.) specific to shallow underground and the estimation 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 including control of the amount of underwater, soil improvement,
stabilizing agent, adsorbent for purification of contaminated materials, and the254permeable reaction wall, it is necessary to examine the factors that have priority
since they may have critical influence 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 ofenvironmental influence so the development of the evaluation method related to
the risk of environmental influence has to be taken into account from thisviewpoint.

255

Attachment 16 Record of collaborative activities with foreign organizations
Activity

Contents

Participating
Organization

IAEA ProjectThe 4th IAEA
Review Mission

IAEA side event

DAROD

CRP T13015

・International review was made by accepting IAEA
inspection team regarding decommissioning efforts ofFukushima Daiichi NPS (November 2018)
・The received final report was released received in
January 2019.
・Side events are held every year along with the IAEA
General Conference and explanation of the latest
progress in decommissioning was made in order togain an understanding of the Fukushima Daiichi
decommissioning.
・In the 62nd IAEA General Conference, description videos
for the current status of the decommissioning andcontaminated water management were presented at theJapan booth while holding the side concerning thepresent situation of Fukushima Daiichi. (September,
2018)
・In the 63rd IAEA General Conference, description videos
for the current status is planned at the Japan booth andthe side event on Fukushima reconstruction and foodsafety of Fukushima Daiichi will be held. (September
2018)

METI
NDF
TEPCO
IRID
JAEA
METI
NDF
TEPCO
IRID (for data
provision)

・Knowledge and experience obtained from the efforts
on challenges of decommissioning and recovery ofdamaged nuclear power facilities (regulations,
technologies, systems, and strategies) are shared
among the relevant countries.
・Sharing information regard to the management ofseverely damaged spent fuel and corium

NDF

・This symposium was held for the purpose of sharing theefforts of safety management on food in regions affectedby radioactive materials including Fukushima as well as
cultivating a better understanding of current
decommissioning status and food safety of Fukushima
Daiichi NPS for food safety experts from each country,(March, 2019)
・A reception making use of ingredients produced in
Fukushima was also held after the symposium.
・From the point of view of whether it may contribute topromoting industrial cluster in Fukushima, a dialogue
with government was made concerning industrial
clusters. A side event is scheduled to be held with theattendance of invited the local officials by utilizing
network of OECD and collecting referential examples.
(The 1st event held in February 2019, The 2nd event in
September 2019).

METI
MAFF
TEPCO

・Research organizations and governmentalorganizations from eleven countries joined to conduct
benchmark study using severe accident analysis
codes developed by these organizations to find out
how the accident in the Fukushima Daiichi NPS
256

JAEA
IRID
TEPCO

IRID
JAEA

OECD/NEA Project
Symposium on
Decommissioning
and Food Safety ofFukushima Daiichi
NPS

Dialogue withgovernment on
industrial clusters
by ORCD

BSAF

METI

PreADESWGAMA-LTMNPP

TCOFF

EGFWMD

NEST

EGCUL

TAF-ID (reference)progressed and how the fuel debris and FPs spread
inside the reactors. Knowledge and findings related tothe 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
are shared.
・Sharing characteristics information that helps tounderstand properties of fuel debris such as its phasestate and composition.
・Enhancing “Fuel debris Analytical Chart” that summarizes
needs and priority of fuel debris analysis.
・Maintenance of tasks after analysis and analysis facility
information
・Regulations and standards in various countries andoperators’ efforts are shared and summarized on how
to ensure safe and stable status in the nuclear power
plants in which fuel remains after severe accidents.
・In reference to the accident progression of the
Fukushima Daiichi NPS, (1F) advancing molten coreand molten fuel models, FP migration behavior modeland thermodynamic database as their basis. Based on
the material scientific knowhow, evaluating details ofmolten core and fuel on condition of 1F accident, andcharacteristics of fuel debris and its producing
mechanism. Then, providing material scientificknowhow and result of detail evaluations tointernational cooperation project including PreADES,
ARC-F, TAF-ID, and domestic decommissioning project
like IRID.
・Project budget for 2017 to 2019 was contributed from
MEXT.
・Expansion of knowledge for waste management anddecommissioning at the Fukushima Daiichi NPS・Advice to Japan’s R&Ds regarding waste in the
Fukushima Daiichi NPS
・Establishing international network among universities,
researching institutions and industries in each country
through executing projects which young researchers andengineers participate in.
・Practical education on interdisciplinary science
technology that focused on advanced remote operation
technology by inviting young researchers and engineers.
・Discussing on characterization method for waste fromunknown derivation
・Maintenance and enhancement of thermodynamics on
Atomic Fuel database (TAF-ID) for advanced fuel anddamaged fuel and its application
・TCOFF is used for analysis as a major user of TAF-ID
Database. Conversely, knowhow from TCOFF is used foradvancement of TAF-IS Database.

257

METI
NRA
IR
JAEA
IRID
NDF
TEPCO
NRA
NDF
TEPCO
MEXT
JAEA
IR
Tokyo Instituteof Technology

NDF

JAEA
The Universityof Tokyo

METI
NDF
JAEA
TEPCO
JAEA
IR

Inviting International Expert

・To integrate and utilize a wide range of wisdom andknowhow, NDF invites the experts in strategy
development, R&D, program/project management andsafety regulation as the International Special Advisorsfrom UK, US, France, and Spain.
・ISA participates in the Decommissioning Strategy
Committees and makes advises based on theirexperiences in other countries.
International
・To obtain advice to contribute to the safer and more
Expert Groupefficient decommissioning of the Fukushima Daiichi(TEPCO)and its R&D, TEPCO invites experts with international
expertise and experience from UK, US, France, andUkraine.
International Advisors
・To gain the evaluation on the implementation status of(IRID)
the R & D design review being undertaken,
enhancement of information dissemination andcommunication, and acquire knowledge including
failure experience, IRID invites the prominent experts
from the UK, US, and Spain.
Activities by each organizations

NDF

Cooperation withoverseasorganizations at
the stage of IRID’s
practical
application
research

IRID

International
Special Advisors(NDF)

・Development of internal investigation technologies

TEPCO

IRID

（UK, France, Russia）
・Development of fuel debris and structural component

retrieval technologies（US,UK）
・Development of fuel debris criticality control technology(US, UK, France）

INSIDER Project
participation

TOAL DECOM
participation

ATOMEXPO
participation

The 4th Fukushima/
Chernobyl/ Three
Mile Island
International
Symposium・Development of Solid waste processing and disposal
technology (US, France)
・In order to optimize waste management, this project aims
at establishing common method applicable to the specificcases by evaluating cost effective analysis andmeasurement methods for nuclear R&D facility anddamaged reactor, etc.
・Participating in the kick-off meeting of this project, andgathering the information.
・Participating in the workshop held in Spain in May, 2019.
・Participating in meetings of nuclear and non-nuclear
companies related to decommissioning, held mainly
by British companies, and gathering information onefforts of each company. (April, 2018)
・Participating in a forum where nuclear powercompanies related mainly to Russia and Europe, held
mainly by ROSATOM, and exchanging views withlocal stakeholders. (May, 2018 and April, 2019)・Based on the lessons and cases learned from theaccidents of Three Mile Island and Chernobyl Nuclear
Power Plant, studies have been made for controlling theaccident of the Fukushima Daiichi NPS. (May, 2019)

258

NDF

METI
NDF

METI
JAEA
TEPCO
NDF
JAEA
TEPCO