Subsidy Project of Decommissioning and Contaminated Water
Management in FY 2018 Supplementary Budget

Development of Technology for Containing, Transfer
and Storage of Fuel Debris
FY 2019 Research ReportAugust 2020
International Research Institute for Nuclear Decommissioning (IRID)
All rights reserved.
©International Research Institute for Nuclear Decommissioning (IRID)

Contents

No.1
1. Research background and purpose
2. Project goals
3. Implementation items, their correlations, and relations with other research
4. Implementation schedule
5. Project organization chart
6. Implementation details
6.1. Investigation and research plans for containing, transfer and storage of fueldebris
6.2. Development of technology for containing of fuel debris
6.3. Development of technology for transfer of fuel debris
6.4. Development of drying technology and systems
6.5. Evaluation and summary
7. Overall summary[Supplement-1] Basic conditions of development of the canister[Supplement-2] Design conditions of the canister regarding safety requirements[Supplement-3] Design conditions of the canister regarding handling requirements[Supplement-4] Specification plan for the canister[Supplement-5] Investigation results of hydrogen concentration measurement technology(details)[Supplement-6] Principles of hydrogen concentration measurement technology(heat conduction type)[Supplement-7] Principles of hydrogen concentration measurement technology(proton conductor)©International Research Institute for Nuclear Decommissioning1. Research background and purpose

No.2

1.1. BackgroundFor decommissioning of the Fukushima Daiichi Nuclear Power Station (hereinafter called the 1F), technology
for containing, transfer and storage of fuel debris to be retrieved in a safe and effective manner is required.
Fuel debris contains nuclear fuel material, therefore, it is necessary to consider, in particular, confinement ofradioactive materials (preventing the spread of contamination) and sub-criticality in the handling of the debris.
When the Three Mile Island Nuclear Power Station Unit 2 (TMI-2), in the US, was decommissioned, fueldebris was retrieved and put into specialized containers (canisters) and handled by the canister. Thiseffectively fulfilled requirements, such as confinement of radioactive materials, by using existing technologies
for transfer and storage of spent nuclear fuel and management of radioactive waste. This example led tothe belief that it is reasonable to use existing technologies effectively by developing canisters to satisfy
individual conditions. Based on this approach, it has been decided to focus the development of canisters for thedecommissioning of the 1F.
The plant type of the 1F is different from that of TMI-2. In addition, seawater was injected during the initial
phase of the accident, and the molten core reached the pedestal at the bottom of the reactor pressure vessel.
Therefore, the requirements for the 1F canisters are more complex and advanced compared to TMI-2.
Development of specialized canisters for the 1F is required to contain, transfer, and store fuel debris safely andeffectively.
•1.2. Purpose
In this project, fuel debris canisters applicable to the 1F conditions and technology for handling thecanisters will be developed. To do that, the information and requirements provided from the related IRID
projects (input conditions) and those provided from this project to the related IRID projects (output
conditions) will be organized and clarified by close cooperation with the related projects.

©International Research Institute for Nuclear Decommissioning1. Research background and purpose
1.3 Previous studies and remaining issues (1/4)

No.3

The process for fuel debris containing, transfer and storage, and issues therein are shown below.
Reactorbuilding<Area classification>
Red: Highly contaminated area, unmanned operations (remotely operated by operations fromoutside the area)
Yellow: Medium-contaminated area (area that is controlled, but is likely to be contaminated)
Unmanned operations (the principle is to remotely operate by operations from outside the area,
but people may enter for maintenance etc.)
Green: Less contaminated area (area with virtually no contamination), manned operations

Example of handling flow during side-access retrieval method
Expandedbuilding

Lifting
machineManipulator

Debris treatment
cell

UC

Fuel debris

Inside thereactorHeat removal
Confinement

Safety design

Note: RPV (abbreviation for reactor
pressure vessel)
PCV (abbreviation for primarycontainment vessel)
UC (abbreviation for unit can)Area

Subcriticality

Black text: Indicates that technologicaldevelopment is not required based on
past results, etc.
Blue text: Indicates study has been
completed
Red text: Indicates that issues remain ⇒under study in this PJ

Dryingapparatus

Gas injection
systemSecondary lid
fastening system/
Gas injection
system/leakage checking
facility

Preparation
cell

TransfervehicleDryingapparatus

Access tunnel
CanisterCanisterPort

Primary lid
fastening system/
Gas injection
system/leakage checking
facility

Sealingcell

Access tunnel

UC transfer
system

PCV

Note: Safety design and handleability
from "inside the reactor to debris
treatment cell" will be studied in the“Project of further increasing thescale of fuel debris retrieval"

Canister lid fastening system(Implementation of surface
contamination inspection)Work monitoring
cameraRPV

Fuel debris
retrieval
deviceLifting machine

Lifting machine

Shielding
Structure
Material

HydrogenFire prevention
Handleability
Improvement in storage
workability

Canister transfer
systemDebristreatment cell

Drying apparatus and theinside of the canisters arehighly contaminated areas

Weight measuring system(Implementation of
surface contamination
inspection)

Transfer
cask

Transfer cask
transfer system

Preparation
cell

Sealing cell

Sealing cell

Transferrack

Inside thepremises

Preparation cell (excluding drying apparatus)

Subcriticality can be maintained by the geometrical shape ofcanister

Inside the premises

Subcriticality can be maintained by the geometrical shape of the canister and the arrangement inside
the transfer cask

Canisters can be naturally cooled using normal in-cell
ventilation

Each transfer cask can be naturally cooled bynormal building ventilation

Each transfer cask can be naturally cooled by
the outside air

Confinement using the sealing material of canister, study offilter and sealing cell.
(Gas is released in a controlled manner)

Confinement using the sealing material ofcanister, study of filter and preparation cell.
(Gas is released in a controlled manner)

Confinement using the sealing material ofcanister, study of filter and transfer cask (Gas isreleased in a controlled manner)

Shielding in sealing cell

Shielding in preparation cell

Shielding in transfer cask

Study to maintain safety function against damage caused by drop from up to 9m/ drop of canister within transfer
cask

Can withstand accidents during transfers(Designed to be encapsulated during fall)

Safety function can be maintained against aging (As a prerequisite, the corrosion of the metal is studied. Also, as the neutron flux density is small, irradiation does notaffect the material)

Study on the vent diameter used for release of hydrogen from the canister’s vent hole with filter to the cell/ the cell
can control the hydrogen concentration to the lower explosion limit or lower by ventilation.
・Study on the reduction of water content of fuel debris by early drying of fuel debris, as hydrogen countermeasuresduring sealed transfer. (The top priority in debris treatment cell is the drying timing)
・ Study of hydrogen concentration measurement inside transfer cask to ensure that the hydrogen concentration is 4
vol.% or less at the time of transfer

・ Study for sealing the canister/ transfer cask
for up to 7 days
・ Study of method to predict hydrogengeneration at the time of transfer (byevaluation formula)・ Study on recombination catalyst

Can maintain the inside of sealing cell/ preparation cell/ transfer cask at an inert atmosphereCan be remotely transported and closed with a lid
The storage work efficiency can be improved by expanding
the inner diameter of the canisterCan be remotely transported

Can be stored in transfer cask
None©International Research Institute for Nuclear Decommissioning1. Research background and purpose

No.4

1.3 Previous studies and remaining issues (2/4)

The process for fuel debris containing, transfer and storage, and issues therein are shown below.
<Area classification>
Yellow: Medium-contaminated area (area that is controlled, but is likely to be contaminated)
Unmanned operations (the principle is to remotely operate by operations from outside thearea, but people may enter for maintenance etc.)
Green: Less contaminated area (area with virtually no contamination), manned operations

Example of handling flow during side-access retrieval method

Hydrogen gas
treatment system
Lifting machine

Storage building

Area monitor

Ventilation
system
Work
Shieldingmonitoring covercameraCanisterHandling jig

Gate
Scaffolding
for work

Transfer cask

Gas treatment system

Stored item
checking
equipment

Dryingapparatus

Storagecask

Secondarylidof storage
cask

Primary lidof storage
cask

Surfacetemperature
measuring
deviceVent pipe

Transfer caskrack

Carry-in entranceof storage facility

Receivingarea ①

Canister

Note: Drying area shall be set
up when drying
apparatus cannot be
installed inside thedebris treatment cell

Safety design

Black text: Indicates thattechnological development is not
required based on past results, etc.
Blue text: Indicates study has been
completed
Red text: Indicates that issues
remain ⇒ under study in this PJ

AreaStored items
checking area

Drying area

Storagepreparation area

Receivingarea ②

Receiving area ① ~ Receiving area② (Excluding drying area)

Storage area

Storage preparation area

Storage area

Subcriticality

Subcriticality can be maintained by the geometrical shape ofcanister

Subcriticality can be maintained by the geometrical shape of the canister and the arrangement
inside the storage cask

Heat removal

Can be naturally cooled using normal in-cell ventilation

Each storage cask can be naturally cooled using normal building ventilation

Confinement

Confinement using the sealing material of canister, study of filterand building(Gas is released in a controlled manner)

Confinement using storage cask/ building(Gas is released in a controlled manner)

Shielding in the cell

Shielding in storage cask/ building

Shielding
Structure
Material
HydrogenFire prevention

Handleability
Improvement in storage
workability

Study to maintain safety function against damage caused by drop from up to 9m/ drop of canister within storage cask

Can withstand accidents during storage(Designed to be encapsulated during fall)

Safety function can be maintained against aging including corrosion
Study on the vent diameter used for release of hydrogen from the canister’s vent hole with filter to the cell/ Can bescavenged inside the building

Can be vented/ scavenged inside the storagecask

Can maintain the building/ inside of transfer cask at an inert atmosphereCan be remotely transported

Can be stored in a storage cask
None©International Research Institute for Nuclear Decommissioning1. Research background and purpose

No.5

1.3 Previous studies and remaining issues (3/4)

The table below shows the results of the study on safety design of fuel debris canister conducted up to FY 2018, and the remaining
issues to be studied.
Canister specifications

Safety design

Suspending
part
Vent plug(Including
filter)Catalyst

Study up to FY 2018

Issues to be studied (in FY 2019 and FY 2020)

・ The inner diameter of the canister was set (φ220 mm)
based on the subcriticality maintenance evaluation
method considering the fuel debris particle size andwater content, so that the canister itself can maintainsubcriticality.

－

Heat removal

・ No problem.

－

Confinement

・ A filter and an outlet to prevent hydrogen retention(vent plug) are installed to prevent the spread ofcontamination during actual operation.

Shielding・ No problem.

Structure・ The integrity was checked by conducting element
tests for lid, body, and buffer structure against the
impact load during the drop on the canister inside thetransfer or storage cask, and during the tumbling or
dropping while handling the canister.

Material integrity

・ The validity of the canister material (SUS316L
material) was confirmed assuming the water quality
environment of 1F and the handling process, etc., of
the canister.

－Hydrogen・ Hydrogen generation amount： The validity of the Gvalue was confirmed through gamma irradiation test
considering the 1F water quality (iodine, etc.). In
addition, the effect of alpha rays was confirmed
through a hydrogen generation test using spent
nuclear fuel.
・ Catalyst： Identification of catalyst candidates capableof hydrogen recombination in a canister environment(presence of low temperature, high humidity anddose).
・ As a result of the drying element test conducted forporous bodies that may exist as a form of fuel debris,the phenomenon of equilibrium moisture content notreaching zero (drying stops with water remaining)
was confirmed.

・ Study of method to predict hydrogen generation suitable for fueldebris condition in 1F.
・ Collection of detailed data on catalyst performance and evaluationof effectiveness when the catalyst is installed inside a canister.
(Studied as “development of transfer technology”)
・ Study on vent diameter(Studied as “development of storage technology”)
・It is necessary to develop a drying method that keeps the equilibrium
moisture content at or below the target moisture content within thetarget time. In addition, it is necessary to set the basic
specifications of drying apparatus considering maintainability, etc.
・ As the purpose of drying fuel debris is to reduce the amount ofhydrogen generation, a technology for measuring hydrogenconcentration is required as a means of confirmation.
(Studied as “development of drying technology and systems”)

Fire prevention

・ No problem.

Subcriticality

Cooling

Confinement

Canister lid
Φ220 mm

Canister body
Other
(Maintaining the
shutdown,
Buffer structure cooling andconfinement
functions)(Canister Material: SUS316L)

Figure: Structural plan for canister(Provisional structural plan set in FY 2018)

・ Study of sealing material/ filter (except during storage)(Studied as “development of storage technology”)－・ It is necessary to confirm the structural integrity when the entire
canister is integrated.
(Studied as “development of storage technology”)－©International Research Institute for Nuclear Decommissioning1. Research background and purpose

No.6

1.3 Previous studies and remaining issues (4/4)

The table below shows the results of the study on the fuel debris canister specifications up to FY 2018,
and the remaining issues to be studied.
Handleability/
rationalization

Canister specifications
Study up to FY 2018

Issues to be studied (In FY 2019 and FY2 020)

・ Remote lid closing andremote lifting of canister・ Study on the structural plan for the lid fastening device
and hanging jig required for remotely handling thecanister-・ Increasing the innerdiameter of the canister・As a mitigation measure, the conditions that allow the
inner diameter to be expanded (φ400 mm) were set.

(Decision on acceptance or rejection basedon the actual fuel debris results)©International Research Institute for Nuclear Decommissioning2. Project Goals

No.7

The indicators for determining achievement of target at the end of FY 2020 are as follows.
1. Investigation and research plan of containing, transfer, and storage of fuel debris• The latest study status and findings of related projects and actual projects have been collected, overseas
safety-related technical requirements have been additionally analyzed and organized based on alreadyobtained information, and have been reflected in the research plan along with the opinions of experts.
(Not subject to TRL evaluation)

General2. Development of technology for containing of fuel debris① Study of canister specifications andstructure• The structural integrity of the canister as per the provisionally set specifications and structural plans has been
confirmed using structural verification tests or analysis.
• The specifications and structural plans for the canister have been proposed based on the results of structural
integrity verification.
(Target TRL at the end of the project: Level 6)

3.Development of technology for transfer of fuel debris① Study on methodhydrogen generation

topredict② Study on hydrogen measures• A method to predict hydrogen generation suitable for the fuel debris condition has been proposed.
• The transfer condition plan has been presented based on the evaluation results of the proposed method topredict hydrogen generation.
(Target TRL at the end of the project: Level 6)• The resistance to chloride ion, which is a candidate catalyst and a typical toxic substance, etc., have been
evaluated.
• The flow inside the canister has been evaluated, and the validity of hydrogen measures using catalyst, etc.,
has been evaluated.
(Target TRL at the end of the project: Level 6)

4. Development of drying technology and systems① Study on the basic specifications ofdrying apparatus• The first draft of the basic specifications for the fuel debris drying system has been proposed.
(Target TRL at the end of the project: Level 4)② Study on hydrogen concentration
measurement technology• Selection of candidates for hydrogen concentration measurement technology applicable to the canister has
been completed.
(Target TRL at the end of the project: Level 3)

5. Evaluation summary• Participation in and cooperation with fuel debris and waste sorting technical surveys upon request.
(Not subject to TRL evaluation)©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with No.8
other research
3.1 Implementation Items
This subsidy project plans to work on the following technological development issues related to transfer and storageengineering of fuel debris in 1F.
(1) Investigation and research plan of containing, transfer and storage of fuel debris
To collect the latest study status and findings of related projects and actual projects, perform additional analysis andorganize overseas safety-related technical requirements based on already obtained information, and to reflect this in
the research plan.

(2) Development of technology for containing of fuel debris
To maintain and confirm the safety functions (criticality prevention and confinement) during evaluation events withthe entire canister in an integrated state, through a structural verification test using a real-size canister.
(3) Development of technology for transfer of fuel debris
To analyze the existing methods to predict hydrogen generation and the factors that impact the generation, etc., andto predict the amount of hydrogen generated by acquiring data by conducting tests, if necessary.
As catalyst-based hydrogen measures, acquire performance data for the candidate catalyst in consideration of thecanister environment and confirm the effectiveness considering the diffusion of hydrogen inside the canister.
(4) Development of drying technology and systems
To propose a sample drying system arrangement for drying fuel debris, considering the basic concept of drying
apparatus and its maintenance, by organizing the safety requirements of the drying system itself, identifying theapplicable candidate technologies, and by collecting drying behavior data using a real-size test device.
To ensure that the hydrogen concentration in the transfer cask does not exceed the lower explosion limit during the
expected transfer period before allocating the transfer cask, investigate the hydrogen concentration measurement
technology, and identify and propose the applicable candidate technologies for the canister.

©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with other research
Safety (overall)Ａ
Safety requirements
Review of criteria

Fuel debris transfer and storage system

Containing,transfer andfuel debrisの収納・移送・
storage保管計画検討
plan for fuel debris

Fuel debris quantity setting
Storage location candidates,
etc.

Setting and reviewing oftransfer and storage methods,
and storge location Note 1

Physical properties andcharacteristics of fuel debris

Setting criteria forsafety requirements

Setting and reviewing oftransfer and storage contents

Setting functional
requirements

Setting and reviewing theprocess for transfer andstorage systems Note 3

Compatible with retrieval
requirements

・ Note 2：
Specific storage methods such as driedand-vented storage and dried-and-sealed
storage:
Related technology development:
Hydrogen generation amount evaluation,
Hydrogen measures
・ Note 3：
Processes such as drying that are required
for transfer and storage
Related technology development:
Drying apparatus, Hydrogenmeasurement technology

Process
Reflected in retrieval method
and process settings
Requirement setting

Note2

Operational
requirements for fueldebris retrieval
No

Yes・ Note 4：
Safety evaluations
Related technology development:
Structural evaluation, Hydrogengeneration amount evaluation
・ Note 5：
Go up for “Setting and review of transfer
Note 5 and storage contents”, and go down for“Review of overall safety criteria”
If it is both the cases, go up and down

Safety (safety evaluation of transfer and storage systems)

・ Note 6：
When studying the overall safety bytemporarily setting the criteria, the criteria
for overall safety may be reviewed asnecessary by enhancing knowledge
through R&D and incorporating the
progress of the study

Safety evaluation and review at
the time of transfer and storage
Note 4Compliance with safety
evaluation standards
Yes

Proposed containing,transfer and storage planfor fuel debris

No.9

・ Note 1：
Setting basic storage policies such as wet
storage and dry storage in new facilities

Environment, physical properties,
etc.

Note 5No
Note 6Ａ©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with other research
No.10
3.2 Relation of Implementation Items (1/2)(Target process) 2 - (3) Development of Technology for Containing, Transfer and Storage of Fuel Debris
Stage 3 – Period (1)Stage 2 (Period until the start of fuel debris retrieval)

Items/ Year

After FY 2022

Maintaining and managing the stable state of the plant
Major events in thecurrent mid-and-long term
▽Confirmation of fuel debris retrieval method for the first Unit
roadmap[Development ofTechnology for Containing,
Transfer and Storage ofFuel Debris]▽Start of fuel debris retrieval in first Unit

Engineering for containing, transfer and storage

Drafting of plan

Modification of plan based on related projects, etc.
1. Investigation andresearch/development planof containing, transfer, andSetting the basic specifications of canisters
storage of fuel debris
Drafting of test plan

2. Development oftechnology for containingof fuel debris

Optimizing thecanister
specifications

3. Development oftechnology for transfer offuel debris

Clarifying thesafetyrequirements

Implementation and evaluation of structural verification test
Prototyping

Test, analysis and investigation for clarifying the transfer conditions

4. Development of drying
technology and systems[Development of technology
for further increasing the scaleof retrieval of fuel debris andreactor internals] etc.

Study on transfer methods

Development of drying technology
Development of evaluation technology for treatment used in storage

Onsite operations (includes engineering)

R&D©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with other researchesNo.11
3.2 Relation of Implementation Items (2/2)
TEPCO Holdings, Inc.
【 Coordination for the site application 】
・Coordination to reflect the status ofreceiving approvals and authorizations
・ Coordination to reflect the conditions of
the decommissioning site

Fuel Debris Characterization Project*2[Information provided to the Canister
Project Team]・Knowledge of fuel debris shape
・Knowledge of fuel debris properties
・Knowledge of basic physical propertiesof fuel debris
・ Knowledge of thermal properties of fueldebris・Knowledge of chemical properties offuel debris

Waste Project *3[Information provided to the Canister
Project Team]・ Information of canister related totransfer and storage

International Research Institutefor Nuclear Decommissioning(IRID)
Canister Project *4[Information provided to related project
teams](1) Study of safety requirements,
specifications and storage systems forthe transfer and storage of fuel debris
canisters
・Details of inspections for safety assessment(2) Study of fuel debris containing method
・Canister specifications
・Conditions of structure, weight, dimensions,etc.
・Basic canister handling method
・Canister handling device* specifications
・Handling method of canister handlingdevices** Canister lid fastening device, canistersuspending device, etc

Project of further increasing thescale of fuel debris retrieval *1[Information provided to the Canister ProjectTeam]
Constrained conditions while handling fueldebris・ Conditions for dimensions and weight limitations

Fuel debris containing location andprocedures・ Canister installation location
・ Canister lifting information

Fuel debris collecting method

・Knowledge of fuel debris cutting, particle size, etc.
・Collection method (for example, pump suction)

Handling procedure of special tools
Information on criticality control
・ Constrained conditions to maintainsubcriticality
・To be used for maintaining subcriticality
・Neutron absorbent
Investigation of sorting technology for fueldebris and waste
・To be participated and cooperated

Note)*1: Project of further increasing the scale of fuel debris retrieval: Development of technology for further increasing the scale of retrieval of fuel debris andreactor internal structures**2: Fuel debris characterization project: Development of technology for analysis and estimation of fuel debris characterization*3: Waste Project: Research and development of treatment and disposal of solid waste*This project was called as Development of Technology for Retrieval of Fuel
*4:Canister Project : Development of technology for containing, transfer, and storage of fuel debris
Debris and Internal Structure, when the project started. According to theConsistent results should be obtained by sharing information provided from
IRID’s related projects as well as information delivered by this project, working
in cooperation and coordinating with those projects.

development plan of decommissioning research in FY 2020 disclosed at
the 75th Secretariat Team Meeting for Countermeasures for
Decommissioning and Contaminated Water Treatment, the project namewas changed to Development of Technology for Further Increasing the
Scale of Retravel of Fuel Debris and Internal Structures.
©International Research Institute for Nuclear Decommissioning4. Implementation schedule

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

No.12

FY 2019

Items

First half

4.1 Investigation and research plan of containing, transfer
and storage of fuel debris

Plan

FY 2020

Second halfFirst half
Plan

Investigation

Remarks

Second half
Investigation

Drafting of structural verification test plan

4.2. Development of technology for containing of fuel debris

Designing the canister (canister for testing)
Prototyping the canister (canister for testing)
Implementation of structural verification test
Evaluation of structural verification test

Including material procurement

Including pre-analysis of confirmation test
If necessary

Study of canister specifications and structure

Study of implementation content necessary
for setting the transfer conditions plan

4.3 Development of technology for transfer of fuel debris(1) Study on method to predict hydrogen generation

Implementation of hydrogen generation test
Study on method to predict hydrogen generation
Estimation of hydrogen generated in canister

Study of transfer conditions
Study of catalyst

4.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures

Extended to study methods for measuring low
concentrations of hydrogen

Detailed study of flow characteristics inside the canister

Incorporate the catalyst study results (Catalyst
performance)

Study on catalyst allocation

4.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus

Study on basic conditions
Collection of drying behavior data (including preparation of test equipment)
Basic plan for drying system (Study on maintenance plan/ devices and systems/ equipment configuration)
Basic plan for drying system (Study on basic specifications of devices)

4.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement
technology

Study on required technicalspecifications and applicability criteria
Investigation of the hydrogen concentration measurement technology
Implemented if necessary
Feedback on progress and results

4.5 Evaluation summary：Plan：Actual：Reviewed plan

©International Research Institute for Nuclear Decommissioning5. Project Organization Chart
Tokyo東京電力ホールディングス株式会社
Electric Power Company Holdings, Inc.

(as of the end of March 2020)

No.13

International Research Institute for Nuclear Decommissioning
技術研究組合 国際廃炉研究開発機構（本部）(Head Office)of overall plan and technical management○ Development
全体計画の策定と技術統括
Technical
management,
including technical development progress○ 技術開発の進捗など技術管理

三菱重工業株式会社
Mitsubishi
Heavy Industries, Ltd.

Toshiba
Energy Systems and東芝エネルギーシステムズ
株式会社
Solutions Corporation

Hitachi-GE
Nuclear Energy,
日立ＧＥニュークリア・
Ltd. エナジー株式会社(1)収納・移送・保管に係る調査及び研究計画立案(1) Investigation and establishment of research plans for containing, transfer and storage of fuel(2)収納技術の開発
debris(2) Development of containing technology(3)移送技術の開発(3) Development of technology for transfer of fuel debris(4)乾燥技術／システムの開発(4) Development of drying technology and systems(5)評価まとめ(5) Evaluation and summary

連携する開発Relevant projects
プロジェクトDevelopmentof Technology for Analysis
燃料デブリの性状把握のための分析・推定
and Characterizationof Fuel Debris
技術の開発
燃料デブリ・炉内構造物の取り出し規模のDevelopmentof Technology for Further Increasing the
Scale of更なる拡大に向けた技術の開発
Retravel Debris and Reactor Internals
R&D for Treatment and Disposal of Solid Waste
固体廃棄物の処理・処分に関する研究開発

MHI-NS
MHI-NS 社• Investigation of technological
・技術開発に関連する調査
development•・水素ガス対策のための収納缶構
Study on the canister structure formeasures
造検討 against hydrogen gas
generation
Soltec 社
Soltec• Study on catalyst performance
・水素ガス対策のための触媒性能
formeasures against hydrogenの検討
gas generation
RSG
RSG 社
•・乾燥のための乾燥チャンバー内のStudy (analysis) of drying
検討（解析）
chamberinterior

NDC
NDC 社• Study of convection flow in the・水素ガス対策のための収納缶内のcanisterfor measures against
hydrogengas generation (evaluation
対流検討（水素量評価）
on hydrogen volume)

MHI-NS 社
MHI-MS• Study on basic specifications and・乾燥装置の基本仕様、構造の検討
the structure of drying apparatus

Toko Corporation• 東鉱商事株式会社
Investigation of the canister lid test
・収納缶蓋構造試験体の調査
structure
Company
A*
Ａ社＊• ・収納缶試験体の製作
Manufacturing of the test canister
Ceres
Inc.
株式会社セレス• Verification test of the canister
・収納缶構造検証試験
structure
Company
B*
Ｂ社＊ of methods to predict• Study
・水素発生予測法の検討
hydrogen generation*:*：一般競争入札等により決定
Determined by open bidding
NDC: Nuclear Development Corporation
NDC：ニュークリア・デベロップメント株式会社
MHI-NS: MHI-NS Engineering Co., Ltd.
MHI-NS：MHI NS エンジニアリング株式会社
MHI-MS:
Mitsubishi Heavy Industries Machinery
MHI-MS：三菱重工機械システム株式会社
Soltec：MHI
Systemsソリューションテクノロジーズ株式会社
Ltd.
RSG：株式会社菱友システム技術
Soltec: MHI Technologies Co., Ltd.
RSG: Ryoyu System Engineering Co., Ltd.
.

Company
C*
Ｃ社＊• Evaluation
test of hydrogen
・水素発生評価試験
generation©International Research Institute for Nuclear Decommissioning

Contents

No.14

6. Implementation Details
6.1. Investigation and Research Plans for Containing, Transfer and Storage of Fuel
Debris

6.2. Development of technology for containing of fuel debris
6.3. Development of Technology for Transfer of Fuel Debris(1) Study of methods to predict hydrogen generation(2) Study on measures against hydrogen generated
6.4. Development of Drying Technology and systems(1) Study on basic specification of drying device(2) Study on hydrogen concentration measuring technology
6.5. Evaluation and summary©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.15
6.1 Investigation and research plan for containing, transfer, and storage of fuel debris① Purpose and Goal
To obtain the latest trends of related PJs and the latest trends of on-site operations and work
together to make technology development useful, and in addition, to improve the efficiency oftechnological development by collecting information from overseas.
② Implementation items and results (Estimated and actual)a. Reflection of latest trends in research plan (FY 2019, FY 2020)
In order to make the technological development useful from the viewpoint of consistency with related
PJs and site application, the latest knowledge and study status of the project of further increasing thescale of fuel debris retrieval, fuel debris characterization project, waste project, etc., were obtained
through joint meetings, and the status of coordination related to on-site work at TEPCO Holdings andlatest trend/ information such as the status of coordination related to licensing were obtained, andincorporated in the research plan.
For example, the plan for the current unit can shape was obtained from the project of further
increasing the scale of fuel debris retrieval and reflected in the drying test plan.
b. Investigation of overseas information (FY2019, FY2020)
The already obtained literature on the drying of TMI-2 fuel debris was re-evaluated for an efficientdevelopment plan. (Described in 6.4 Development of drying technology and systems (1) Study on
the basic specifications of drying apparatus)©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.1 Investigation and research plan for containing, transfer, and storage of fueldebris

No.16③ Contribution of the results to the areas where they can be reflected
The implementation results will be reflected in the study items of this subsidy project.
④ Analysis from the perspective of site application
The latest on-site trends are reflected in the study items of this subsidy project, which
is useful.
⑤ Issues
There are no issues in executing the current plan.
⑥ Level of achievement
The latest study status and findings of other projects and actual projects were collected
and overseas safety-related technical requirements, etc., were additionally analyzed
and organized based on already obtained information. In the future, it is expected thatthe specified results will be obtained by reflecting these along with the experts’opinions in the respective research plans.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.17
6.1 Investigation and research plan for containing, transfer, and storage of fuel debris⑦ Future plans
Table

Study schedule for the investigation and research plan for containing, transfer, and storage

FY 2019Items
6.1 Investigation and researchplan for containing, transfer, andstorage of fuel debris

First
half

FY 2020

Second
half

Plan

First
half

SecondhalfRemarksPlan

a. Reflection of latest trends inresearch plan

The plan will be reviewed as appropriate
according to the situation.

Investigationb. Investigation of overseas
information: PlanInvestigation

Investigation/ evaluations of generaldrying apparatus.

: Actual©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test -No.18① Purpose and Goal
To propose the specification and structural plan of the canister.
To review the specification and structural plans of the canister that were provisionally set in FY 2018,
and to make a prototype of the real-size canister, for that purpose. Also, to conduct a structuralverification test using the prototype canister to confirm the maintenance of the safety functions(criticality prevention and confinement) during evaluation events.
In addition, to confirm the applicability of the analysis methods that can simulate the structural integrityof the canister in various events, by comparing and evaluating with the results of the structuralverification test.
② Comparison with existing technology
Among the lid structures studied in FY2018, the bolt structure is a method of fastening the lid bytightening the bolts, and it is considered possible to be designed within the application range of theexisting technology.
Meanwhile, the simple mounting structure is a method of fastening the lid by turning the lid. Although it
has a proven track record in ultra-high pressure vessels, there are concerns about the structural
integrity of the entire canister (an integrated state with the lid structure, body, buffer structure, etc.) in
the event of dropping or tumbling, etc. Hence it is necessary to ensure the structural integrity based on
the handling of canisters in 1F.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test -No.19③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY 2019) (1/10)(i) Selection of events to be tested (1/4)

Events from each operation of the latest handling flow of canister (side-access retrieval method, dry storage, metal
cask storage) were identified as the targets for event selection.

Loading fuel debris into UC - Transfer inside premises (method ofaccessing from the side of nuclear reactor)
Reactorbuilding<Area classification>
Red: Highly contaminated area, unmanned operations (remotely operated by operations from outside the area)
Yellow: Medium-contaminated area (area that is controlled, but is likely to be contaminated)
Unmanned operations (the principle is to remotely operate by operations from outside the area, but people may
enter for maintenance etc.)
Green: Less contaminated area (area with virtually no contamination), manned operations

Expanded Lifting machine Manipulator
building

Sealingcell

Debristreatment cellWorkmonitoring
cameraFuel debris
retrieval
deviceFueldebrisPort

Lifting machine

Lifting machine

Canister lid
fastening systemGas injection system
CanisterDrying apparatus

Primary lid fastening Secondary lid
Preparation
fastening system/
system/cell
Gas injection system/ Gas injection system/leakage checking
leakage checking
facility
facility

TransfervehicleAccess tunnel

UC transfer
systemInside the reactor[1] Cutting and processing of discharge[2] Visual confirmation of the discharge[3] Collection of fuel debris by fuel debris
retrieval device and filling in UC[4] Draining of water present in the fueldebris[5] Carrying-out the UC outside the reactor
building (transported outside the pedestal)

Access tunnel[5] Transporting UC outside thereactor building (through the accesstunnel) *1*1 In addition to the fuel debris,
wastes such as internal structures
will also be transferred from inside
the reactor to the expanded building
through the access tunnel.

Carrying transfer cask into the storage building - Storage
Lifting machine

Hydrogen gas treatment system

Dryingapparatus

Debris treatment
cell[6] Drying of fuel debris(loading of UC into drying
apparatus - Drying
treatment)

Canister transfer
systemWeight measuring Transfer Transfer cask transfer
system cask system

Sealing cell[11] Measurement of amount of[7] Loading of UC into canister (Drying of fuel debrishydrogen generated *3[8] Fastening the lid of canister (Connecting the canister to[12] Confirmation of canister(inner lid installation ~ transfer drying facility ~ drying
allocation (weight measurement ,treatment*2))
to lid fastening device ~
etc.)
[10]
Injecting
inert
gas
into
the
fastening the lid ~ confirmation[13] Loading of canister into
canister(connecting
theof lid being fastened)transfer cask (transferring thecanistertothegas
injection[9] Checking for surface
canister up to the top of the port)
facility~
injecting
inert
gas
into
contamination of canister
the canister ~ )<Area classification>
Yellow: Medium-contaminated area (area that is controlled, but is likely to becontaminated)
Unmanned operations (the principle is to remotely operate by operations from outside thearea, but people may enter for maintenance etc.)
Green: Less contaminated area (area with virtually no contamination), manned operations*2 Implemented when drying cannot be performed in debris
treatment cell
*3 Study on implementing it along with inert gas injection

Transferrack

Preparation cell

Inside the[13] Loading of canister into transfer cask (stacking
premisesassumed)[14] Fastening the lid of transfer cask (fastening the Transfer inside thelid (primary lid) ~ injecting inert gas (inside thepremisescavity) ~ confirmation of lid being fastened (primarylid) ~ fastening the lid (secondary lid) ~ injecting
inert gas (between the primary and secondary lid) ~confirmation of lid being fastened (secondary lid) )[15] Measurement of amount of hydrogen*4 Study on implementing
generated *4
it while injecting inert gas[16] Confirmation of transfer cask allocation
inside the cavity[17] Loading of transfer cask into transfer vehicle

Storage building

Area monitor
Ventilation system

HandlingjigWorkShielding covermonitoring
CanistercameraGate

Transfer cask

Scaffolding for work

Gas treatment system

Stored item
checking
equipment

Dryingapparatus

Storagecask

Primary lid ofstorage cask

Secondarylid ofstoragecask

Vent pipe

Surface temperature
measuring device

Transfer cask rack

Carry-in entrance of storage
facility[18] Receiving transfer cask at carry-in
entrance[19] Unloading transfer cask from transfer
truck[20] Confirming the receipt of transfer cask

Receiving area (1)[21] Measurement of amount of hydrogen
Stored items
Drying area *8
generated *5checking area (Drying of fuel debris[22] Opening the lid of transfer cask (Removal of(Loading the canister into the[25] Checking the stored
secondary lid ~ removal of primary lid)
items *7 (Loading thedrying facility ~ drying[23] Removing canister from transfer cask *6
canister into the stored items treatment) )[24] Confirming the receipt of canisterchecking facility ~ checking)*5 Implemented after the removal of secondary lid*6 Covering the canister with shielding cover and *7 Dose rate measurement is *8 Implemented when drying
assumedis required before storagetransferring

Receiving area (2)[26] Checking the canister before storing[27] Loading the canister into the storage
cask (stacking is assumed)[28] Fastening the lid of storage cask
(Fastening the lid (primary lid) ~ Injecting
inert gas (inside the cavity) ~ confirmingthat the lid is fastened (primary lid) )Storage preparationarea[28] Fastening the lid of storage cask
(Fastening the lid (secondary lid) ~Injecting inert gas (between the primaryand secondary lids) ~ confirming that thelid is fastened (secondary lid)[29] Confinement confirmation

Figure. Handling flow of canister

Storage area[30] Connecting vent pipe to storage cask
[31] Checking vent pipe confinement[32] Long term storage<Definition of events>① Abnormal events
Refers to the events caused by a single failure or
malfunction of the equipment handled or by a single
incorrect operation by the operator, in each operation in thehandling flow of canister② Accident events
Refers to events that exceed the abnormal events in each
operation in the handling flow of canister. It is an event thatis technically expected to occur, and when it does occur, it
may release radioactive materials, and is important fromthe perspective of radiation exposure of the general public.
③ Design events
Of the above abnormal events/ accident events, design
event refers to events, the occurrence and spread of whichshould be prevented by the design of the facilities/
equipment, and which should be considered in the design.
④ Evaluation event
Refers to events that are not expected to occur as they canbe dealt with by equipment or operations, however, theimpact of these events needs to be evaluated from a safety
viewpoint.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.20

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY 2019) (2/10)(i) Selection of events to be tested (2/4)

Design events were identified from each operation based on the latest handling flow of a canister.
Table Results of identification of design events (typical example)
Design events

No.

1

Abnormal landing ofcanister inside thetransfer or storage
cask, etc.

Diagram showing the events

Possibility of
event
occurrence Note1

Impact on basic
safety functions
and structural
strength Note2

Events for which structural verification test is implemented
Accepted/
Rejected

Approach to selectionx

As the collision velocity in the evaluation event "No. 5 drop ofcanister" is faster than the lowering velocity at the time ofcollision (assuming about 0.025 m/s), it is assumed to becovered under that event, and not considered as an event tobe tested.

x

As the collision velocity in the evaluation event "No. 6 drop ofcanister on top of another canister" is faster than the lowering
velocity at the time of collision (assuming about 0.025 m/s), it
is assumed to be covered under that event, and notconsidered as an event to be tested.

x

As the collision velocity in the evaluation event "No. 5 drop ofcanister" is faster than the lowering velocity at the time ofcollision (assuming about 0.025 m/s), it is assumed to becovered under that event, and not considered as an event tobe tested.

Suspending
deviceAn event where the canister
being loaded inside the transfer
or storage cask, etc., collides
with the bottom of the transfer orstorage cask at a lowering
velocity due to an incorrect
operation by the worker.

Canister○△BasketTransfer orstorage cask

2

3

Abnormal landing ofcanister on top of
another canister

Abnormal landing oftransfer or storage
cask on transfer rackAn event where the canister
being loaded inside the transfer
or storage cask, collides with the
top of an already loaded canister
inside the transfer or storage
cask at a lowering velocity due toan incorrect operation by theworker.

An event where the transfer orstorage cask to be placed on thetransfer rack, collides with thetransfer rack at the lowering
velocity due to the incorrect
operation by the worker.

Suspending
deviceCanister○△BasketTransfer orstorage cask
Transfer caskorstorage cask

Suspending
deviceBasketCanister○△Transferrack

Transfer vehicle
Note 1： Possibility of event occurrence
x： The occurrence of event can be avoided by handling it with equipment or operations.
○： Occurrence of event cannot be avoided
Note 2： Impact on basic safety functions and structural strength
x：Events that do not have an impact△： Events that have an impact, but are not expected to lead to criticality or the release of radioactive
materials Research○： Eventsthat forhave
an impact
and are©International
Institute
NuclearDecommissioning
expected to lead to criticality or the release of radioactive materials

6. Implementation Details

No.21

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY2019) (3/10)(i) Selection of events to be tested (3/4)

Evaluation events were identified from each operation based on the latest handling flow of a canister.
Table Results of identification of evaluation events (typical example)

No.

Evaluation events

Diagram showing the events

Possibility of
event
occurrence
Note1

Impact on
basic safetyfunctions andstructural
strength Note2

Events for which structural verification test is implemented
Accepted/
Rejected

Approach to selectionx

The result of preliminary analysis showed that the collisionvelocity from the side when a canister falls in the obliqueorientation in the evaluation event “No. 5 drop of canister”
was faster than tumbling (tumbling: about 7 m/s, droppingin the oblique orientation: 18 m/s). So, it is assumed to becovered under that event, and not considered as an event
to be tested.

Canister4

An event where the canister being
moved tumbles due to damaged
fixing mechanism of the canistertransfer device, etc.

Tumbling of canisterx○

Canister transfer
deviceSuspending
device5

6

An event where the canister being
lifted falls due to the damage inthe suspending device, etc.

Dropping of canister

Fall of canister on topof another canister

An event where the canister being
loaded inside the transfer orstorage cask, falls on top of analready loaded canister due todamage in the suspending device,
etc.

x

○

○

① Canister dropping in the vertical orientation: Comparedto other events, the impact load received at the bottom of
the canister is supposed to be the largest, so it is considered
as an event to be tested.
② Canister dropping in the oblique orientation：Comparedto other events, the impact load received from the sides of
the canister is supposed to be the largest, so it is considered
as an event to be tested.

x

○

○

Compared to other events, the impact load received at the
top of the canister is supposed to be the largest, so it isconsidered as an event to be tested.

Canister

Suspending
devicebasketcanisterTransfer orstorage cask

Note 1：Possibility of event occurrence
x： The occurrence of event can be avoided by handling it with equipment or operations.
○： Occurrence of event cannot be avoided
Note 2： Impact on basic safety functions and structural strength
x： Events that do not have an impact△： Events that have an impact, but are not expected to lead to criticality or the release of radioactive materials
radioactive materials©International
fortoNuclear
Decommissioning○： Eventsthat have anResearch
impact andInstituteare expectedlead to criticalityor the release of

6. Implementation Details

No.22

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY 2019) (4/10)(i) Selection of events to be tested (4/4)

Among the identified design events and evaluation events, the events of the canister dropping in the vertical orientation, the canister
dropping in the oblique orientation, and the canister dropping on top of another canister in the vertical orientation, which are considered
to have a large impact on the structural strength, were selected as the events for which the structural verification test will be performed.
The dropping height was set in consideration of the dimensions of the building and transfer cask. The oblique angle was provisionally
set to 60º, which has a large impact based on the preliminary analysis.

(Supplement *1)
The port is assumed to
open/close or slide in
the orientation opposite
to the moving
orientation of thecanister, and is notincluded in the
dropping height.

Lifting
machineHandling jig
Canister

Port *1

Unit canTransfer cask
Canistertransfer
devicea. Dropping in the verticalorientationb. Dropping in the obliqueorientation(Height 8.4 m ⇒ 9 m)

Figure. Canister handling flow planc. Canister dropping on
top of another canister inthe vertical orientation(Height 6.5 m ⇒ 7 m)

Shieldingwall

CanisterTransfer cask
transfer system

Figure. Approach to setting of the dropping height©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY 2019) (5/10)(ii) Test cases

No.23

For each event, a test was planned with a combination of test conditions and a real-size canister (canister for testing) structure.
Testing conditions

No.

EventsDropheight

Drop
angle

Inner
Air
diameter supply No. of
No. ofLid
tests structure of the mechan unitsbodyismSimplemountin
400 mmg
structure

1

2

Canister
dropping in
the verticalorientation

9m

0º

Once

9m

60º
(Tentativ
e)

Once
Bolt
structure 220 mm

5Simplemountin
220 mmg
structure

6

1

Yes

1

No

2

Simplemountin
400 mmg
structure

4

Canister
dropping
on top ofanother
canister inthe verticalorientationNo
Bolt
structure 220 mm

3
Canister
dropping in
the obliqueorientation

Structure of real-size canister(Canister for testing)

7m

0º

Once
Bolt
structure 400 mm

Table Test cases (Plan)
Main goal of the test

Approach to selection of combination for real-size canister (canister for testing)structure

・ Two types of lid structures, simple mounting structure and bolt structure, are chosen,
to check the effect on each lid structure (including confirming the validity of analysis).
・ The main purpose is to confirm theeffect of vertical drop on the body of・ Two types of inner diameter of body, 220 mm and 400 mm Note 1, are chosen as thecanister (confirming the amount ofcondition for different weight/ buffer structure, to confirm the effect of vertical drop on
deformation of the inner diameter of the the body of canister (confirming the amount of deformation of the inner diameter ofbody) and to confirm the effectivenessthe body) and to confirm the effectiveness of the buffer structure (includes confirmingof buffer structure (includes confirming
the effect of preventing the collision of stored items with the inner surface of the lid).
the effect of preventing the collision of ・ As there is no air supply mechanism in the main plan (the main process involves
stored items with the inner surface ofdrying the fuel debris in the unit can, so the air supply mechanism is absent), air
the lid).
supply mechanism is considered absent (if there is an air supply mechanism, it will be
evaluated by analysis).
・ Two types of lid structures, simple mounting structure and bolt structure, are chosen,
to check the effect on each lid structure (including confirming the validity of analysis).
・ The main purpose is to confirm the・ Two types of inner diameter of body, 220 mm and 400 mm Note 2, are chosen as theeffect of dropping in the obliquecondition for different weight/ bottom plate structure/ air supply mechanism structure,orientation (including collision of
to confirm the effect of dropping in the oblique orientation (including collision of thecanister on the floor surface after
canister on the floor surface after dropping in the oblique orientation) on lid, bottom
dropping in the oblique orientation) on
plate and air supply mechanism of the canister (confirmation on the sealability of thethe lid, bottom plate and air supply
lid, confirmation on the integrity of the bottom plate and air supply mechanism).
mechanism of canister (confirmation ofsealability of lid, integrity of air supply ・ Though there is no air supply mechanism in the main plan (the main process involves
drying the fuel debris in the unit can, so the air supply mechanism is absent), airmechanism).
supply mechanism is considered present to confirm the impact of collision with thefloor surface.
・Twotypes of lid structures, simple mounting structure and bolt structure, are chosen,
・ The purpose is to confirm the effect of a to checkthe effect on each lid structure (including confirming the validity of analysis)
canister dropping on top of another・Two types of inner diameter of body, 220 mm and 400 mm Note 2, are chosen as thecanister in the vertical orientation, on
for different weight/ buffer structure, to confirm the effect on the bodythe body of the canister (confirmation of condition(confirmation on the amount of deformation of the inner diameter of body) and to
deformation of inner diameter of body)confirm the effectiveness of the buffer structure (including the deformation of theand to confirm the effectiveness of
suspending part and the effectiveness of countermeasures for the event where thebuffer structure (including deformationbuffer structure enters the suspending part)of suspending part and confirmation on
・ As there is no air supply mechanism in the main plan (the main process involves
effectiveness of countermeasures fordrying the fuel debris in the unit can, so the air supply mechanism is absent), air
the event where the buffer structure
supply mechanism is considered absent (if there is an air supply mechanism, it will beenters suspending part).
evaluated by analysis).

Note 1: For simple mounting structure, the inner diameter is set to 400 mm (and for bolt structure, it is set to 220 mm), since the feasibility verification test of the canister lid structure in FY 2018 confirmed that the lid cannot be
opened in a simple mounting structure of inner diameter φ400 mm.
Note 2: When the inner diameter of body is 400 mm, the lid should be a simple mounting structure for conditions of heavy weight and heavy impact load (for body with inner diameter of 220 mm, the lid should have a bolt structure).
Note 3: As a test for an impact load in the vertical orientation, consider a combination opposite to that of the test for canister dropping in the vertical orientation,that is, innerdiameterof simple
is set to 220 mm©International
Research
Instituteformounting
Nuclearstructure
Decommissioning
and for bolt structure, it is set to 400 mm.

6. Implementation Details

No.24

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY2019) (6/10)(iii) Test system

The structural verification test was planned to be carried out by preparing the test equipment shown in the image
below to reproduce the events that occur in actual operations.

Mobile crane

Detachment device

Mobile crane

Real-size canister

Guide(Simulated basket dimension)

Detachment
deviceMobile craneMeasuring
instrument

Measuring cable
7m
Measuring
instrument(a) Canister dropping in the vertical orientation

Real-size canister(Upper side)

Rack

Real-size canister

Measuring cable

9m

Detachment device

9m

Measuring
instrument

Measuringcable

Real-size canister(Lower side)(b) Canister dropping in the oblique orientation(c) Canister dropping on top of another canister in the vertical orientation

Figure. Image of structural verification test of a real-size canister©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.25

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test -③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY2019) (7/10)(iv) Safety function requirement related items to be confirmed during tests (1/3)

The items to be confirmed by the structural verification test were set based on the safety function requirements of canisters.
Table

Safetyfunctions
Confinement

Safety function
requirements
Confinement ofradioactive
materials

Canister requirements

Safety requirements and items to be confirmed during testing (plan) (1/3)
Items to be confirmed during the test
Details

PeriodApproach to selection of confirmation items

Evaluation criteria

Prevention of leakage ofradioactive materials frominside the canister except
via the vent mechanism.

Leakage test

Before the test

・Leakage rate: Impact evaluation by actual measurement ・ Confinement in the normal state (pre-test state) is
confirmed through leakage test
(Target：3 x 10-2 (ref cm3/s) or less Note1)

Appropriate reduction inleakage of radioactive
materials associated withthe release of hydrogengas from the ventmechanism.

Appearance check

After the test

・Filter, coupler: Check the degree of damage andevaluate the impact

Appropriate reduction inleakage of radioactive
materials even in the eventof occurrence of dropping
events that must be
expected.

Leakage test

After the test

・Leakage rate： Impact evaluation by actual
measurement(Target: 3 x 10-2 (ref cm3/s) or less Note1)

Appearance check

After the test

Dimension check (Checking the Before the test
dimensional difference of O
After the test
ring seal part before and after
the test)

・ Though evaluation events (canister dropping in thevertical orientation, etc.) are events that are notexpected to occur, the extent of damage to the filterand coupler after receiving the impact load of theevaluation event are checked from a safety point ofview, to evaluate the impact on the confinement ofradioactive materials when the event occurs.

・ Though evaluation events (canister dropping in thevertical orientation, etc.) are events that are notexpected to occur, the leakage rate after receiving theimpact load of the evaluation event, and the・Lid: Lid does not come off
dimensional difference/ presence or absence of plastic
・Lid, main body (body, bottom plate), air supply
deformation/ relative displacement of the O ring seal
mechanism (piping)： Absence of serious damages
before and after the test are checked from a safetyleading to large leaks (such as cracks penetrating
point of view, to evaluate the impact on theinside and outside)
confinement of radioactive materials when the event
・ Others (hook , bolt, stopping pin, O ring, coupler, air
occurs.
supply mechanism (cover) ): The extent of damage is・ Though evaluation events (canister dropping in the
checked and impact is evaluatedvertical orientation, etc.) are events that are notexpected to occur, lid detachment and serious damage
・Difference in dimension before and after the test: Impact(cracks that penetrate inside and outside) leading toevaluation by actual measurement
leakage of large amounts of radioactive materials shall(Target: ±0.5 mm Note2)
not be allowed from a safety point of view.

Distortion time history
measurement (Checking thepresence or absence of plastic
deformation near the O ring
seal surface)

During the test

・Distortion: Impact evaluation by actual measurement(Target: 9 x 10-4 or less Note 3)

Momentary opening of the
openings (measurement ofrelative displacement of the O
ring seal before and after the
test)

During the test

・Relative displacement measurement (or pressurechange measurement) of lid and body ： Impact
evaluation by actual measurement

Note 1：Set with reference to the maximum allowable air leakage rate of the NFT-22B type spent nuclear fuel transport cask
Note 2：Set with reference to the O ring squeeze rate (0.6 mm)
Note 3： From the ratio of the yield stress σ to the longitudinal elastic modulus E of SUS316L, ε is set as ε ＝ σ/ E ＝ 175/195000 ≒ 9 x 10-4

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.26

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY2019) (8/10)(iv) Safety function requirement related items to be confirmed during tests (2/3)

The items to be confirmed by the structural verification test were set based on the safety function requirements of canisters.
Table

Safetyfunctions

Safetyfunctionrequirements

Criticality
prevention

Preventionof additional
nuclearfissionreactionHeatremovalPreventionof abnormal
overheating

Canister requirements
The shape should be able toprevent criticality.

The canister should be able tomaintain the temperature of
the fuel debris at theappropriate level.

Safety requirements and items to be confirmed during testing (plan) (2/3)
Items to be confirmed during the test
Details

Approach to selection of confirmation items

PeriodEvaluation criteria

Appearance check

After thetest

・ Lid: Lid does not come off
・Lid, main body (body, bottom plate), air supply
mechanism (piping): Absence of serious
damages leading to large leaks (such as cracks
penetrating inside and outside)・ Other (hook , bolt, stopping pin, O ring, coupler,
air supply mechanism (cover) ): The extent ofdamage is checked and impact is evaluated.

Dimension check(dimensional check of
inner diameter of body)

After thetest

・Dimension of inner diameter of body (220 mm):
245 mm or less Note1 (Target: 232.5 mm or lessNote2)
・ Dimension of inner diameter of body (400 mm) :Impact evaluation by actual measurement

Appearance check

After thetest

・Lid, main body (body, bottom plate): Check thedegree of damage and evaluate the impact

・Though evaluation events (canister dropping in thevertical orientation, etc.) are events that are notexpected to occur, the extent of damage to the lid
and main body after receiving the impact load ofthe evaluation event are checked from theviewpoint of safety, to evaluate the effect onnatural heat dissipation when the event occurs.

－－

・There are no items to be confirmed in the test asother equipment and building air conditioning aredesigned not to let the canister exceed thepermissible temperature even in the event of lossof external power or other expected events.

The design should be such
No items to be tested
that the internal temperatureof the canister does notexceed the permissible
temperature even if there is an
expected rise in the building
temperature.

・Though evaluation events (canister dropping in thevertical orientation, etc.) are events that are notexpected to occur, large deformations that makes
subcriticality maintenance impossible, lid
detachment and serious damages (such as
cracks penetrating inside and outside) that lead toleakage of large amounts of radioactive materials
shall not be allowed from a safety point of view.

Note 1： In the criticality evaluation in FY 2016, when SUS material was considered, the inner diameter equivalent to Keff = 0.925 was evaluated as 245 mm. So, that value was set.
Note 2： In the criticality evaluation in FY 2016, when SUS material was not considered, the inner diameter for Keff = 0.925 was evaluated as 220 mm, and it was confirmed that increasing the inner diameter by 10 mm increases Keff by 0.02. Therefore, the innerdiameter when Keff = 0.95, which is the upper limit of the criticality safety design evaluation standard, can be calculated as 232.5 mm. The 232.5 mm, which was the value when not considering SUS material, was conservatively set as the target value withrespect to design.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.27

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY2019) (9/10)(iv) Safety function requirement related items to be confirmed during tests (3/3)

The items to be confirmed by the structural verification test were set based on the safety function requirements of canisters.
Table

Safetyfunctions

Safety function requirements

Safety requirements and items to be confirmed during testing (plan) (3/3)
Canister requirements

Items to be confirmed during the test
Details

PeriodEvaluation criteria

Approach to selection of confirmation items

Shielding

Prevention of excessive exposure
and internal exposure due toradiation(No requirements)

No items to be tested－－

・ As there are no requirements related to shielding function of
the canister, there are no items to be confirmed in the test.

Prevention ofhydrogen
explosion

Response to fires and explosions
caused by flammable gas due toradiolysis of water (response tohazards)

The design should besuch that theconcentration ofhydrogen inside thecanister can be
maintained below thedesign value.

No items to be tested－－

・ As the design allows the release of hydrogen generated inside
the canister through the vent mechanism, there are no items
to be confirmed in the test.
・ As reduction of hydrogen concentration by catalyst is evaluatedseparately as part of the “Study on hydrogen measures”, there
are no items to be confirmed in the test.

The design should besuch that the hydrogenconcentration does notexceed the specified
value even in the eventof occurrence of an
expected event.

Appearance check

After the test

・Filter, coupler: Check the extent of damageand evaluate the impact

・Though evaluation events (canister dropping in the verticalorientation, etc.) are events that are not expected to occur, theextent of damage to the filter and coupler after receiving theimpact load of the evaluation event is checked from a safety
point of view, to evaluate the effect on hydrogen release whenthe event occurs.

Prevention ofdust fires

Response to fires caused by thereaction of oxygen and metal dust
generated during debris retrieval
and cutting (response to hazards)

To prevent ignition bycreating an inert gas
atmosphere inside.

Leakage test

Before thetest

・Leakage rate： Impact evaluation by actual
measurement(Target: 3x10-2 (ref cm3/s) or less Note 1)

・Assuming that the inside of the canister is replaced with an inert
gas atmosphere, the confinement property under the normal
state (pre-test state) is confirmed by the leakage test.

-≪Handling function requirements≫

The lid can be fastened
and opened by remote
operations.

Confirmation of lid fastening/ lid
opening (Including theconfirmation of lid rotation
during lid fastening and lid
opening, and bolt fastening/rotation torque)

Before thetest
After the test

・Lid fastening/ lid opening (Before the test):
Must be possible
・Opening the lid (After the test): Check if it ispossible or not, and evaluate the impact

・Use manual tools to confirm that the lid can be fastened andopened under normal conditions (pre-test state).
・Though evaluation events (canister dropping in the verticalorientation, etc.) are events that are not expected to occur, thepossibility of opening the lid after receiving the impact load ofthe evaluation event is confirmed using manual tools to serve
as information for studying the treatment method after theoccurrence of the event.

Note 1: Set with reference to the maximum allowable air leakage rate of the NFT-22B type spent nuclear fuel transport cask

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.28

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)a. Drafting of structural verification test plan (FY 2019) (10/10)(v) Items to be confirmed during test to check the applicability of analysis method

Items to be confirmed by the structural verification test were set to obtain the data necessary to confirm the applicability of the analysis
method by comparing with the test results.
Table

Data items related toconfirming theapplicability ofanalysis method

Items to be confirmed during test to check the applicability of analysis method (plan)
Items to be confirmed during the test

Details

PeriodAcquired data

Approach to selection of confirmation items

External appearance Appearance check

Before thetest
After thetest

・ To confirm the accuracy of the analysis, the changes during the test are measured and a
・ Key external appearances of the lid (including hook),
comparative evaluation is performed between the deformation state obtained from themain body (including flange, body, bottom plate, hook),analysis and the test results.
bolt, buffer structure and air supply mechanism (piping)(focus on observation of parts where deformation was
confirmed in preliminary analysis)

Dimension

Dimensional check

Before thetest
After thetest

・ Key dimensions of the lid (including hook), main body(including flange, body, bottom plate, hook), bolt,
buffer structure and air supply mechanism (piping)(focus on measuring the parts where deformation was
confirmed in preliminary analysis)

・To confirm the accuracy of the analysis, the amount of change (dimensions) during thetest is measured and a comparative evaluation is performed between the amount of
deformation obtained from the analysis and the test results.

Distortion

Distortion time
history measurement

During thetest・Distortions in the key parts of the lid (including hooks),main body (including flanges, body, bottom plate,hooks), bolts, buffer structure, and air supply
mechanism (piping) (focus on measuring the parts
where a large (characteristic) distortion was confirmedin the preliminary analysis)

・To confirm the accuracy of the analysis, the distortion during the test is measured and acomparative evaluation is performed between the distortion obtained from the analysis
and the test results.

Acceleration

Acceleration time
history measurement

During thetest

・Acceleration of lid, main body, buffer structure

・To confirm the accuracy of the analysis, the acceleration during the test is measured anda comparative evaluation is performed between the acceleration obtained from theanalysis and the test results.

Velocity

Velocity
measurement

During thetest

・ Velocity of canister just before the collision

・To confirm the accuracy of the analysis, the velocity during the test is measured and acomparative evaluation is performed between the velocity used as input conditions foranalysis and the test results.

Relativedisplacement of lid
and body

Displacement time
history measurement

During thetest

・Relative displacement of lid and main body duringcollision・To confirm the accuracy of the analysis, the relative displacement of the lid and the main
body during the test is measured and a comparative evaluation is performed between therelative displacement obtained from the analysis and the test results.

Video (high-speed
camera video)High-speed camera
video shooting

During thetest

・High-speed camera video at the time of collision (nearthe colliding part)・To confirm the accuracy of the analysis, a picture of the deformation behavior during thetest is taken and a comparative evaluation is performed between the deformation
behavior obtained from the analysis and the test results.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test -No.29③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (1/7)(i) Canister specification plan
The design conditions/ design policy for canister were re-organized, and the canister specification plan was set considering the latest
canister handling flow and the status of study of project of further increasing the scale of fuel debris retrieval, etc.
Suspending part・A structure that allows lifting without being affected by the shape of the storage space (square prism,
cylinder, plate (drilled hole) ), by providing a groove inside the lid of the canister for lifting and making
the suspending device smaller than the outer diameter of the canister lid.
・A structure where the buffer structure does not enter the suspending part by not installing thesuspending part that was earlier installed in the center of the upper surface of the lid.

Lid・Two types of lids were designed as remotely operable structures: a simple mounting structure that can be
opened and closed by turning the lid, and a bolt structure that has a proven track record in remote controlled
operation in TMI-2, etc.
・The structure does not cause detachment of the lid or damage leading to a large amount of leakage anddoes not generate continuous leakage from the seal even when it receives an impact load such as a drop in
the vertical orientation.

Seal

Vent mechanism

To ensure the confinement function at the storage facility during storage, elastomer
gasket (EPDM: ethylene propylene diene rubber) was used prioritizing on the storage
efficiency (minimization of lid outer diameter), lid fastening workability, and applicability toa simple mounting structure.

The inner diameter of the coupler was set to 1 inch by conducting diffusion evaluation considering the coupler
and filter for the amount of hydrogen generated based on actual measurements in the presence of water(since it dries, the amount of hydrogen generated is assumed to reduce to a value lower than that based on
actual measurements in the presence of water). Also, a coupler was installed in normally-open state based on
the risk evaluation conducted for vent opening and closing operations when handling canisters.

Method of sealing the port between cells and the canister

Air supply mechanism

・A structure where the upper end plane of the canister body is pressed and sealed
against the seal part of the port between cells, as a method to prevent contamination as
much as possible at the area boundary between cells.
・ A structure with an inner lid (with a filter for hydrogen venting) is installed on thecanister body to prevent contamination as much as possible during handling of thecanister from the port between cells to the fastening of the lid.

・ When fuel debris is dried in the unit can, the air supply mechanism is not installed in the canister, but whenfuel debris is dried in the canister, it was decided to install air supply mechanisms at two locations (couplers
for air supply) on the body flange. A coupler that is normally-closed is installed in each air supply mechanism
so that hot air flows from the bottom to the top of the canister in the order of air supply coupler (air supply port)⇒ piping ⇒ inside the canister ⇒ air supply coupler (exhaust port). To prevent clogging, it was decided to
install a filter on the system side equipment and not on the air supply coupler.

Filter・ The release of hydrogen was evaluated by the hydrogen diffusion evaluation formula, and it was
confirmed that the hydrogen concentration was less than 4 vol% when using a wire mesh type SUS316
filter having a mesh diameter of 0.3 μm (suitable for HEPA). So, it is a structure which is less susceptible
to clogging by increasing the filter diameter and increasing the surface area of the flow path.

Body
・Two types of bodies were designed, 220 mm, which can maintain subcriticality, and 400 mm, which has an
expanded inner diameter for improved workability.
・The internal height of the canister was set taking into account the catalyst case thickness (20 mm(temporarily set)) and height of two unit cans it will store (400 mm per can), in addition to considering amargin on the thermal expansion of the unit cans, the manufacturing tolerance, and the total dimension of theheight when the unit cans are stored at an angle.
・ A tapered portion is provided at the joint between the body, the flange, and the bottom plate to relieve stresswhen an impact load is applied.

Catalyst
・ Assuming that catalyst will be installed, it was temporarily installed under
the inner lid.

Buffer structure

Material
It was decided to use SUS316L in consideration of SCC resistance, procurement, workability,
etc.
Note 1: In the cross-sectional view, the components
are color coded for identification.

Figure. Canister specification
plan Note 1(Structural plan with bolt structure/ innerdiameter 220 mm/ air supply mechanism)

・A structure with a buffer structure installed to prevent collision of stored
items with the inner surface of the lid due to shooting up during drop events,
and to reduce deformationof thebody ofInstitutethe canister.
The Decommissioning
DOE (skirt) type
©International
Research
for Nuclear
was selected because of its good manufacturability.

6. Implementation Details

No.30

6.2 Development of technology for containing of fuel debris③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (2/7)(ii) Canister structural plan

Eight types of structural plans were selected for the canister: two types of lid structures (simple mounting structure and bolt
structure), two types of inner diameter of body (220 mm and 400 mm), and with/ without air supply mechanism.
Lid (simple mounting structure)

Body

Lid (bolt structure)

Air supply mechanism

Unit canFuel debris

Buffer structure

Simple mounting structure Note 1(Inner diameter of body is 220 mm/ without air supply mechanism)

Main dimensions
・Outer diameter: About 0.3 m
・Inner diameter： About 0.2 m
・Height： About 1 m

Bolt structure Note 1(Case where inner diameter of body is 220 mm/ with air supply mechanism)

Figure. Real-size canister structural plan

Note 1: In the cross-sectional view, the lid, body, unit can, fuel debris, etc. are color coded for identificationof the components©International
Research Institute for Nuclear Decommissioning6. Implementation Details

No.31

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (3/7)(iii) Main specification plan (1/5)

1) Lid・ Two types of lids were designed as remotely operable structures: a simple mounting structure that can be opened and closed
by turning the lid, and a bolt structure that has a proven track record in remote controlled operation in TMI-2, etc.
・ The structure does not cause detachment of the lid or damage leading to a large amount of leakage and does not generatecontinuous leakage from the seal, even when it receives an impact load such as a drop in the vertical orientation.

Suspending part

Lid

Lid
Vent mechanism (coupler)

Suspending part

Vent mechanism (coupler)FilterFilter

Lid bolt

Inner lid (with filter)

Inner lid (with filter)

O ring (plane)
Catalyst

Catalyst

O ring (plane)

O ring (cylindrical surface)
Unit can
Hook

Unit canBody

Simple mounting structure(Inner diameter of body is 220 mm/ without air
supply mechanism)

Body
Figure. Structural plan of the lid Note 1

Bolt structure(Inner diameter of body is 220 mm/
with air supply mechanism)©International Research Institute for Nuclear Decommissioning
Note 1: In the cross-sectional view, the lid, body, vent mechanism, filter, catalyst, and O ring are color coded for identification of components

6. Implementation Details

No.32

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (4/7)(iii) Main specification plan (2/5)
2) Body
・ Two types of bodies were designed, 220 mm, with a geometricalshape, which can maintain subcriticality irrespective of the particle
size and moisture content of the fuel debris, and 400 mm, which has
an expanded inner diameter for improved workability.
・ Referencing the ¼ inch (6.35 mm) shell thickness of the TMI-2
canisters, the shell thickness was designed to be 10 mm for acanister with an inner diameter of 220 mm, which had a structurestrong enough not to cause serious damage leading to a large
amount of leakage, even if it receives an impact load such as a dropin the vertical orientation, and which deforms within the range inwhich it can maintain subcriticality.

・ The inner space of the canister body was designed to have astructure ,which can contain two unit cans (outer diameter 210 mm
and height 400 mm) stacked one on top of the other.

Tapered portion

Body(Inner diameter 220
mm, 400 mm)(Shell thickness 10
mm)
Unit can(Storage for 2 cans)

Tapered portion

・ A tapered portion is provided at the joint between the body, theflange, and the bottom plate to relieve stress when an impact load,such as drop in the vertical orientation, is applied.

Note 1: In the cross-sectional view, the components are color coded for identification.

Figure. Structural plan for body Note 1(For a bolt structure, inner diameter of body 220 mm, and with air supply mechanism)©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (5/7)(iii) Main specification plan (3/5)

No.33

3) Seal (1/2)
・The canister seal is required to provide the confinement function during transfer and handling (assuming a period of about 7 days)
while the confinement function is not required during storage (assuming a period of about 50 years) (during storage, theconfinement function will be ensured in the storage facility).

・For this purpose, the elastomer gasket (EPDM) was adopted from among the candidates to fulfill the requirement of confinementand durability during transfer and handling (assuming a period of about 7 days) along with prioritizing storage efficiency(minimization of outer diameter of lid), lid fastening workability, and applicability to a simple mounting structure.
・ During storage (assuming a period of about 50 years), the confinement function may be lost due to aging of the seal, but it isunlikely that a large amount of fuel debris will be released from the seal of the canister during stationary storage. Even if the fueldebris is released, it will remain in the storage cask (in the case of the metal cask method), so it will not impair the confinement
function as a storage facility.
・ As a means for improving the confinement function during storage (and after storage), adoption of a metal gasket could have been
considered, but it has the following issues and was not adopted for the canister (canister for testing) used in the structuralverification test. However, with a view to considering its adoption in the future, the metal gasket (bolt structure) has been retained
as an alternative idea.
(i) Cannot be applied to the simple mounting lid structure.
(ii) Can be applied to a bolt lid structure, but since a large fastening force is required compared to the elastomer gasket, the lidouter diameter/ bolt diameter becomes large, which increases the weight of the canister and reduces the storage efficiency.
(iii) Compared to the elastomer gasket, careful consideration is required for cleaning of the sealing surface (prevention ofscratches and management of foreign material intrusion) and management of bolt fastening work.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.34

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (6/7)(iii) Main specification plan (4/5)
3) Seal (2/2)

Table
Elastomer gasket

Confinement

・Can ensure short-term confinement.

Long term integrity of ・Although there is no issue during transfer,sealing material/difficult to guarantee the same during
surfacestorage.

Comparison of various types of seals for the canister lid
Metal gasket

・Can ensure long-term confinement.

Metal touch

Welded type・Difficult to guarantee both short-term or
long-term confinement.

・Can ensure long-term confinement.

・No issues during both transfer and storage. ・Since the sealing surface is metallic, there is ・No issues during both transfer and storage.
no issue.

・About two years Note 1 for the irradiation (up ・There is no issue at the irradiation (up to 30 ・There is no issue at the irradiation (up to 30 ・There is no issue at the irradiation (up to 30
Radiation resistanceto 30 Gy/h) assumed for the seal duringtransfer or storage.

Gy/h) assumed for the seal during transfer
or storage.

Gy/h) assumed for the seal during transfer
or storage.

Gy/h) assumed for the seal during transfer
or storage.

・There is no issue in the temperature range ・There is no issue in the temperature range ・There is no issue in the temperature range ・There is no issue in the temperature range
Heat resistance(up to 200C Note 2) assumed for the seal
during transfer or storage.

・It is comparatively easy.
Workability

Ease of removal

・Constant fastening force is necessary (lessthan that for the metal gasket).

・As compared to the elastomer gasket,

precaution is necessary during fastening.
・Constant fastening force is necessary(larger than the one required for theelastomer gasket).

・Removal is possible
・Removal is possible
・Gasket must be replaced depending on its ・Metal gasket must be replaced.
condition.

・It can be adopted for a simple mounting
Effect on lid design(up to 200C Note 2) assumed for the seal
during transfer or storage.

structure, but precaution is necessary if
there are lapping sections.

(up to 200C Note 2) assumed for the seal
during transfer or storage.

・It is easy.

(up to 200C Note 2) assumed for the seal
during transfer or storage.

・Welding work at the Reactor Building(including the Expanded Building) is difficult.

・Removal is possible
・Removal is possible
・Ensuring the same confinement capability ・It cannot be re-used.
all the time is difficult.

・It cannot be adopted for a simple mounting ・It cannot be adopted for a simple mounting
structure.
structure.
・The outer diameter of the lid becomes larger(larger than that for the elastomer gasket).

・Wider extent of freedom for overpack welds.

Note 1: When it is assumed that all the fuel debris in the unit cans is UO2, and the burn-up of 41 GWd/t and the cooldown period of 10 years has been set from the burn-up of the sixth batch irradiation fuel considering the irradiation history of burn-up of fuel debris (from September 2012 Fukushima Daiichi Fuel Composition
Evaluation by Japan Atomic Energy Agency JAEA-Data/Code2012-18 by Nishihara Kenji, Hiroki Iwamoto, Kenya Suyama). Note that it has been evaluated to be around 5 years when the average burn-up inside the reactor of 26 GWd/t and the cooldown period of 10 years was used for evaluation.
Note 2: As a result of heat removal analysis FY 2014, the temperature of the seal is assumed to be up to 200℃ under the conditions when there is the highest burn-up (41 GWd/t) in a canister and the filling rate of fuel debris is 30% and when the centre of the fuel debris is 209℃ and the canister body heats up to about 90℃.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.35

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)b. Designing the canister (canister for testing) (FY 2019) (7/7)(iii) Main specification plan (5/5)

FilterHydrogenCoupler4) Vent mechanism
Unit canFigure. Diffusion Evaluation Model

Hydrogen concentration inside the canister [%]・By using an evaluation formula that is similar to the diffusion evaluation formulaused for evaluation at TMI-2, the hydrogen concentration inside the canister
was calculated considering the coupler and filter, etc., on the vent flow path,and a one inch coupler was selected as a specification so that the lower
explosion limit is 4 vol.% or less.
・The following three conditions were considered for the hydrogen generation
rate. Since there is a plan to dry the fuel debris (target value of dryness 0.1
wt.%), condition ② was selected as the evaluation condition assuming that thehydrogen generation rate can be reduced to less than the actual measurementsfrom the test of immersing spent nuclear fuel in water.
Condition ①: Estimated on the basis of the TMI-2 evaluation formula of
FY 2018 (particulate transport calculation):1.3x10-16[L/h/Bq]
Condition ②: Value that considers any measurement error or variation in theactual measurements in the FY 2018 hydrogen generation test using
spent nuclear fuel:1.2x10-17 [L/h/Bq]
Condition ③: Actual measurements in the FY 2018 hydrogen generation test
using spent nuclear fuel：5.1x10-18 [L/h/Bq]
・For canisters with inner diameter φ 220 mm which are supposed to be usedduring the initial period of retrieval, a coupler with a size, which has tolerance
for the lower explosion limit of 4 vol.%, was selected considering the uncertain
factors such as the clogging of the filter, etc.

hydrogen generation rate: 1.3 x 10-16 [L/h/Bq](Condition ①: Estimated from TMI-2 evaluation formula(particulate transport calculation))hydrogen generation rate: 1.2 x 10-17 [L/h/Bq](Condition ②: Test measurement values (value
considering measurement errors and variation) )hydrogen generation rate: 5.1 x 10-18 [L/h/Bq](Condition ③: Test measurement values)

The selection criteria for the coupler is ahydrogen concentration which is equal to or
lower than the lower explosion limit of 4vol.%at the hydrogen generation rate based on
actual measurement (Condition ②)

Size of coupler (in inches)
Figure. Results of evaluating the hydrogen concentration in the canister bymeans of the diffusion evaluation formula (inner diameter 220 mm)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.36

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ③ Implementation items and results (Estimated and actual)c. Prototyping the canister (canister for testing) (FY 2019, FY 2020)

Based on the canister (canister for testing) design implemented in point b., preparations such as material procurement, etc. for the
prototyping of real-size canister (canister for testing) are underway. The prototyping will start in FY 2020.

d. Implementation of structural verification test (FY 2020) [Scheduled]

The structural verification test will be carried out on the basis of the structural verification test plan studied in point a. using the canister(canister for testing) prototyped in point c. Note that at the time of executing the structural verification test, data that can help in theverification of the structural integrity concerning the maintenance of safety functions, etc., will be acquired.

e. Evaluation of structural verification test (FY 2020) [Scheduled]

From the results of the structural verification test executed as per point d., evaluation will be conducted from the view point ofmaintenance of safety functions of the canister (subcriticality maintenance, fuel debris confinement). Moreover, based on the structural
analysis methods studied till FY 2018, the structural analysis will be conducted by simulating the structural verification tests, and bycomparing and evaluating the results of the structural verification tests, the feasibility of the canister specifications and structure will beverified along with verifying the applicability of the analysis methods.

f. Study of canister specifications and structure (FY 2020) [Scheduled]

Incorporating the evaluation results of the structural verification tests conducted as per point e., the canister specifications andstructure will be reviewed and studied as necessary.

Based on the above-mentioned study, the specification and structural plan (structural drawing) of the canister will be proposed at the endof FY 2020.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.37

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test ④ Contribution of the results to the areas where they can be reflected

On the basis of the proposed specification and structural plan for canisters, it is believed that it should be possible to contribute to thedesigning or manufacturing of the real-size canister. Moreover, it should also be possible to contribute to the study of the related facilities
for the canister (expanded building, storage facilities, handling devices etc.).

⑤ Analysis from the perspective of site application

The specifications and structure of the canisters are being studied in consideration of the handling right from containing to storage of thecanisters in 1F and the evaluation events assumed during handling, and it is believed that there are no issues in the applicability to thesite.

⑥ Issues

There are no issues in the execution of the present plan.

⑦ Level of achievement in light of the goal

The processes up to the drafting of structural verification test plan are complete, and the prototyping of the canister (canister for testing) is
underway. The progress is almost as planned, and it is expected that the target results can be achieved by the end of FY2020.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.38

6.2 Development of technology for containing of fuel debris- Prototyping of real-size canister and structural verification test Summary
In FY 2019, in view of developing containment technology, a plan was drafted for the test items to be implemented
during the structural verification test of the canister, and the canister (canister for testing) was designed based on thesafety requirements of the canister. Moreover, material procurement, etc. was carried out for the prototyping of thecanister (canister for testing).
In FY 2020, real-size canister (canister for testing) to be used in the structural verification test will be prototyped, andthe structural verification test will be carried out to verify the maintenance of the safety functions (criticality prevention,
confinement). Moreover, the structural analysis will be compared and evaluated with the results of the structuralverification test, and the applicability of the analysis methods will be verified. Note that the canister specifications andstructure will be reviewed or studied as necessary.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.39

6.2 Development of technology for containing of fuel debris - Prototyping of real-size canister and structuralverification test -⑧ Future Schedule

Table. Schedule for the development of containment technology

FY 2019

Items

First half

Second half

FY 2020First half

Second half

Remarks

6.2. Development of technology for containing offuel debrisa. Drafting of structural verification test planb. Designing the canister (canister for testing)c. Prototyping the canister (canister for testing)

Includes material procurement

d. Implementation of structural verification test
e. Evaluation of structural verification test

Includes the preliminary
analysis for the verification
tests

f. Study of canister specifications and structure

As necessary：Plan：Actual©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation

No.40① Purpose and Goal
To propose a method to predict hydrogen generation suitable for 1F fuel debris conditions, to propose a predictedvalue of hydrogen generated in a canister using the method to predict hydrogen generation, and to propose atransfer condition plan based on the predicted value of hydrogen generation.
For this purpose, in addition to the results of studies conducted so far, the results of past research will be
investigated and analyzed, the past methods to predict hydrogen generation will be analyzed, and the factors
greatly affecting hydrogen generation gas will be analyzed. Moreover, as necessary, the data to be used forevaluation will be obtained by means of testing.
② Comparison with existing technology
The effect of alpha rays during the radiolysis of water has been confirmed, but there are few reported findings on asystem coexisting with beta rays and gamma rays, including those from TMI-2. Therefore, a study must be
conducted considering the conditions peculiar to 1F.
It is particularly necessary to study the method for setting the energy absorption rate and its validity verification
method, since it is believed that this factor has a large effect on the evaluation of the hydrogen generation amount.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.41

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (1/14)(i) Establishing the evaluation method study flowStart
The study of various implementation items was conducted by establishinga study flow for the evaluation methods.

① Study of evaluation methods

Table. Implementation details of the study of methods to predict hydrogen generation (plan)
Study items
Major items

Minor items[Output] Evaluation method plan

Implementation details (plan)② Study of input values

Investigation of evaluation
methods

Investigation of other domestic and overseas evaluation
methods (evaluation methods for waste etc.) (Refer to 6.3 (1) ③
a. (ii) a.)

Study of evaluation methods

Deciding the evaluation methods based on the investigation
results of the evaluation methods and the availability of dataetc. (Refer to 6.3 (1) ③ a. (ii) b.)

When the validity
cannot be verified

Study of methods forevaluating the input values

Evaluation of the energy absorption rate using the particulatetransport calculation results (Refer to 6.3 (1) ③ a. (iii))[Output]
Input value (maximum value)③Verification ofvalidity of input
valuesStudy of methods to verify the Confirming that the evaluation of the amount of energy
validity of input values
absorption using the particulate transport calculation for theenergy absorption rate is moderately conservative with
Verification of validity of input respect to the results of the test using single radiation sourceor test using spent nuclear fuel (Refer to 6.3 (1) ③ a. (iv))
valuesWhen the applicability cannot
be verified④Verification of
applicability ofevaluation
methods

Study of methods to verify the Confirming that the hydrogen generation rate as per the linear
applicability of the evaluation model is moderately conservative with respect to the results ofmethods
the test using spent nuclear fuel (Refer to 6.3 (1) ③ a. (v))[Output]
Method to predict hydrogen generation(Input value is the maximum value)①Study ofevaluation
methods②Study of input
values[Output] Input value plan

③ Verification of validityof input values
When the validity can be verified

Evaluation of input values

Verification of applicability ofevaluation methods[Output] Input value④ Verification of
applicability of evaluation
methods
When the applicability can be verified[Output] Method to predict hydrogengeneration
End

Figure. Study flow of the evaluation methods©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation

No.42③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY2019) (2/14)(ii) Study of evaluation methods (1/2)
a. Investigation of evaluation methods

Domestic and overseas evaluation methods were investigated in order to select the evaluation methods that
could be applied to the methods of estimating the hydrogen generation at 1F.
[Investigation Results]
Evaluation method A: Evaluation method in which the hydrogen generation rate does not depend on the time period(Linear model)• Concise evaluation formula of "Amount of energy absorbed per unit time" x "G-value of hydrogen generation"• There are two types of "Amount of energy absorbed per unit time”
A-1： "Released energy" x “Energy absorption rate "Actual evaluation results are available for the amount of hydrogen generated at the TMI-2 (fuel debris), at theSavannah River National Laboratory (radioactive sludge and slurry), and at the U.S. Nuclear Regulatory
Commission (TRU waste)
A-2： "Absorbed dose rate" x "Weight of absorption medium"
Actual evaluation results are available for the amount of hydrogen generation at the TMI-2 (Filling for the low-level
radioactive material removal device)Evaluation method B: Evaluation method using the radiolysis model (Radiolysis model)•
It is possible to consider a change in various chemicals due to the passage of time, and in particular, the hydrogengeneration rate can be reduced by considering the recombination reaction.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.43

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (3/14)(ii) Study of evaluation methods (2/2)
b. Study of evaluation methods
Based on the investigation results of the evaluation methods, the “Evaluation method A: Linear model", which enables
conservative evaluation because the recombination reaction is not considered, and in this, "A-1: "Released energy" x "Energy
absorption rate"", which has a proven track record in TMI-2 (fuel debris), were adopted.

Note that only the beta rays and gamma rays are considered at TMI-2 (fuel debris), so the amount of energy absorbed per unit
time is multiplied with the G-values of hydrogen generation of the beta rays and gamma rays. Meanwhile, since there is thepossibility of impact of alpha rays at 1F, the hydrogen generation rate was calculated from the amounts of energy absorbed perunit time and the G-values of hydrogen generation of the alpha, beta and gamma rays respectively, and these hydrogen generation
rates were added up.

[Evaluation method: Linear model]
𝑅𝐻2= 𝐸 x 𝑃 x 𝑀 x 𝐶 x 𝐹 x 𝐺
ReleasedenergyEnergyabsorption
rate

Amount of energy absorbed per unit time

RH2：Hydrogen generation rate, E：Decay heat,
P：Peaking factor, M：Weight of fuel debris
C ：Fuel content ratio, F：Energy absorption rate,
G：G-value of hydrogen generation

G-value of hydrogen generation

Since it was not possible to verify the actual results which would confirm the applicability of the evaluation method (Linear model)
to a coexisting system of alpha, beta and gamma rays, the applicability must be confirmed considering the individual input values.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.44

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (4/14)(iii) Study of input values (1/4)
a. Overview of input value settings
Each input value for the evaluation method (Linear model) was set on the basis of the following policy.

Table. Policy for input value settings
SymbolInput value

Setting policy

E

Decay heatSet for each type of ray after adding up the decay heat of the nuclides based on theliterature Note 1.

P

Peaking factor

Set the ratio of maximum decay heat and average decay heat OR set the ratio of maximum
burn-up and average burn-up based on the literature Note 1.

M

Weight of fuel debris

Set the design value.

C

Fuel content ratio

Assume that the entire fuel debris is made up of spent nuclear fuel.

F

Energy absorption rate

Set the ratio of the amount of energy absorbed by water and the energy amount containedin the fuel debris.
With an aim to ease the transfer conditions, the policy is to evaluate the amount of energy
absorbed by water by means of the particulate transport calculation so as to get closer tothe real state. (Refer to 6.3 (1) ③ a. (iii) b. for details)

G

G-value of hydrogengeneration

Set the initial G-value of hydrogen generation for each type of ray based on the literature
Note 2.

Note 1: Fukushima Daiichi NPS Fuel Composition Evaluation, September 2012, Tables 5, 8, 11, 43, 45, 47 by the Japan Atomic Energy Agency, JAEA-Data/Code2012-18 by Nishihara Kenji, Hiroki
Iwamoto, Kenya Suyama.
Note 2: Hilbert Christensen and Erling Bjergbakke, NUCLEAR AND CHEMICAL WASTE MANAGEMENT, Vol.6, pp.265-270, TABLE 2，APPRICATION OF CHEMISIMUL FOR GROUNDWATERRADIOLYSIS, 1986

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.45

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (5/14)(iii) Study of input values (2/4)
b. Energy absorption rate (1/3)

The evaluation of the hydrogen generation amount using the energy absorption rate (F max) for the instance when all the energy
contributes to the radiolysis of water, can explain the situation well, but is excessively conservative, so the fuel debris transfer
conditions become very severe (Refer to 6.3(1)③a.(iii)b.(2/3)).
Therefore, in order to ease the transfer conditions, the energy absorption rate (F (calc.)d) that is close to the real state was evaluated on
the basis of the results of the particulate transport calculation, wherein self-shielding can be considered, thereby, easing the transfer
conditions.

Energy absorption rate

Fmax
Energy absorption rate when all the energy contributes
to the radiolysis of water (Fmax)
Energy absorption rate evaluated from the particulatetransport calculation result (amount of moisture is theextent of drainage) (F(calc.)d)F(calc.)dEnergy absorption rate evaluated from the measurement
results of the FY 2018 hydrogen generation test using the
spent nuclear fuel (F(test))

F(calc.)powder

F(calc.)0.1mm
F(test)0.0001

0.001

0.01

0.1

1

10

Particle size d [mm]Figure. Relation between the particle size and the energy absorption rate (Image diagram)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.46

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (6/14)(iii) Study of input values (3/4)
b. Energy absorption rate (2/3)
The aim is to ease the transfer conditions to be evaluated on the basis of the energy absorption rate using theparticulate transport calculation, solely with the method for predicting hydrogen generation, without relying on otherhydrogen measures (drying, measurement of hydrogen concentration, and catalyst).
Table. Energy absorption rate and transfer conditions Note 1 studied in FY 2018
Calculation results

Evaluation
methods

TMI-2
Evaluation
Model

Energy absorption rate

Transfer conditions(Evaluation conditions: Hydrogen concentration is less than 4vol.%Time required for theTime required for theand the transfer period is 7 days)
concentration of hydrogen inside concentration of hydrogen inside
the canister to reach 4 vol.%the transfer cask to reach 4 vol.%Total absorption(Fmax equivalent)Approx. 0.04 day(Approx. 1.0 hour)

Approx. 0.3 day(Approx. 7.1 hours)

Sealed transfer of the canister is not possible. In case of a sealedtransfer via a transfer cask, it is necessary to decrease the numberof canisters to one Note 2 along with decreasing the amount of fueldebris contained to about 50 percent.

Transfer calculation(F(calc.)0.1mm equivalent)Approx. 0.2 day(Approx. 5.5 hours)

Approx. 1.7 days
(Approx. 41 hours)

Sealed transfer of the canister is not possible. In case of a sealedtransfer via a transfer cask, it is necessary to decrease the numberof canisters to two Note 2.

Test results(F(test) equivalent)Approx. 5.8 days
(Approx.139 hours)

Approx. 43 days
(Approx. 1029 hours)

The sealed transfer of canisters is possible if the amount of fueldebris contained is reduced to about 80 percent when there are still
12 canisters Note 2. Sealed transfer of the transfer cask is possible.

Note 1: International Research Institute for Nuclear Decommissioning (IRID), FY2016 Supplementary Budget "Subsidy Project of Decommissioning and Contaminated Water Management (Development of Technology for Containing, Transfer and Storage of Fuel
Debris)" FY 2018 Final report, June 2019
Note 2: It is assumed that the number of canisters stored in the transfer cask is 12©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.47

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (7/14)(iii) Study of input values (4/4)
b. Energy absorption rate (3/3)
Although fuel debris of size 0.1 mm or more (standard) is to be stored in the canister, considering that fuel debris
less than 0.1 mm could unintentionally be stored with the other fuel debris during actual operations, the hydrogengeneration rate is calculated from the energy absorption rate based on the transport calculation result taking theparticle size into account. Therefore, it is necessary to verify the validity of the energy absorption rate
corresponding to the particle size that is evaluated on the basis of the particulate transport calculation result.

•

When the entire fuel debris has a particle size of 0.1 mm or more

𝑅𝐻2 = 𝐸 x 𝑃 x 𝑀 x 𝐶 x 𝐹 𝑐𝑎𝑙𝑐. 0.1𝑚𝑚 x 𝐺•

When a% of the fuel debris has a particle size of 0.1 mm or more AND b% of the fuel debris has a particle size of less than
0.1 mm𝑏

𝑅𝐻2= 𝐸 x 𝑃 x 𝑀 x 𝐶 x (𝐹 𝑐𝑎𝑙𝑐. 0.1𝑚𝑚 x 𝑎 + 𝐹(𝑐𝑎𝑙𝑐.)𝑝𝑜𝑤𝑑𝑒𝑟 x 100)x𝐺
100

RH2：Hydrogen generation rate，E：Decay heat，P：Peaking factor，M：Weight of fuel debris
C ：Fuel content ratio，F：Energy absorption rate，G：G-value of hydrogen generation
a: Ratio of particles whose size is 0.1 mm or more, b: Ratio of particles whose size is less than 0.1 mm©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.48

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (8/14)(iv) Verification of validity of input values (1/5)
a. Verification of validity of the energy absorption rate (1/2)
The particulate transport calculation code, "PHITS Note 1", which isused for the evaluation of the energy absorption amount, is theMonte Carlo calculation code that simulates various radiation
behavior in matter using the nuclear reaction model and nuclear data,
but it could not verify the results of evaluation of amount of energy
absorbed by water for the alpha, beta and gamma rays in a complex
system in which solids and liquids are mixed.
Note that, if the validity of the energy absorption amount evaluatedbased on the calculation result of PHITS cannot be verified, then thetransfer conditions become severe due to the use of energy
absorption rate Fmax Note 2, which is excessively conservative, hence
the verification of validity of PHITS is necessary in order to ease thetransfer conditions.
Therefore, the policy of verifying the validity of PHITS by acomparative evaluation of the energy absorption amount obtained
from the test and the calculation results of PHITS, and by checking
the extent of maintainability of the calculation result of PHITS withrespect to the actual phenomenon, was adopted.

Single radiation source test/
Spent nuclear fuel test

Particulate transport
calculation/
Linear model calculation[Output]
Energy absorption amountOr hydrogen generation
rate(Calculated value)[Output]
Energy absorption amount Orhydrogen generation rate
(Test value)
Test value under all
conditions < Calculated
value

Comparative evaluation ofenergy absorption amount andhydrogen generation rate

Upper limit of all test values >Upper limit of all calculated values

Upper limit of all test values< Upper limit of all
calculated values
AND

Test value under any of theconditions > Calculated
value

The amount of energy absorption
is a value that corresponds to theparticle size evaluated from theparticulate transport calculation
result (Equivalent to F(calc.)d in theenergy absorption rate Note 1)

The amount of energy
absorption is the maximum
value evaluated from theparticulate transport
calculation result (Equivalentto F(calc.)powder in the energy
absorption rate Note 1)

The amount of energy
absorption is the maximum
value (Equivalent to Fmax in theenergy absorption rate Note 1)

Figure. Study flow (plan) for the verification of validity of input values (Energy absorption rate)
Note 1: Particle and Heavy Ion Transport code System, the Monte Carlo calculation code which simulates various radiation behavior in matter using the nuclear reaction model and nuclear data, etc.
Note 2: F(calc.)d, F（calc.）powder, and Fmax are the energy absorption rates described in the graph in 6.3 ③ (1) a. (iii) b.(1/3)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.49

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (9/14)(iv) Verification of validity of input values (2/5)

a. Verification of validity of the energy absorption rate (2/2)
The test results of the hydrogen generation test conducted using spent nuclear fuel in FY 2018, were considered as theexisting test results, which could be used for the verification of validity, but upon re-evaluation (refer to 6.3③(1)a.(iv)b.),
it was found that the test results also included the effect of contact between particles and the effect of air bubbles in thepellet pieces-test water layer, and that the test results of FY 2018, which might have been less conservative, were notsuitable for verifying the validity of the evaluation of energy absorption amount.
When verifying the validity through tests, the following tests (Test plan 1 Or Test plan 2) are believed to be necessary
wherein, by using a particle size or a radiation source whose radioactivity is already known, the test water is stirred inorder to eliminate the effect of contact between particles or the effect of air bubbles in the particles-test water layer,
thereby suspending the particles.

Test water
Test plan 1: Conduct a test using a single radiation source (Single radiation
source test) where it is comparatively easy to make the particle size
uniform and it is easy to evaluate the radioactivity, and confirm thatthe evaluation of energy absorption amount using the particulate
Single radiation source ORtransport calculation is moderately conservative with respect to the Spent nuclear fuel pellet pieces
test results.

Test plan 2: By means of test using spent nuclear fuel pellet pieces (Spentnuclear fuel test (The same test as the spent nuclear fuel test usedfor verifying the applicability of the evaluation methods (Refer to 6.3③ (1) a.(v))), confirm that the particulate transport calculation
results are moderately conservative even in case of a coexisting
system of alpha, beta and gamma rays.

Test cask(a) Single radiation source test OR spent nuclear
fuel test

Single radiation source OR
spent nuclear fuel pellet piece
Water(b) Particulate transport calculation model

Figure. Image of the test system©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.50

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (10/14)(iv) Verification of validity of input values (3/5)

b. Re-evaluation of hydrogen generation test (Summary of re-evaluation results)
The results of the hydrogen generation test (conducted in FY 2018) using spent nuclear fuel were re-evaluated and it was presumed
that the main causes for the difference between the calculated results and the test results are the air bubbles inside the pellet pieces
layer and the contact between the pellet pieces.

Table. Results of re-evaluation of differences between the calculated results (evaluation result by means of the particulate transport calculation) and the test results

Causes of difference studied

Extent of impact
Small diameter (average particle size 0.04 mm) Large diameter (average particle size 2.5 mm)

Maximum about 10%

Particulate transport
calculation

Test
results① Release of nuclides due to the washing of pellet pieces② Burn-up distribution of pellet pieces

Almost none

③ Uneven distribution of elements in the gas during the gaseous phase

Almost none

④ Residue of generated gas in the pellet pieces - test water layer

Almost none

⑤ Error by measurement devices

Maximum about 10%① Overestimation of radioactivity of the pellet pieces

Maximum about 5%② Effect of dissipation of the alpha, beta and gamma rays

About 10%

About 30%

③ G-value of hydrogen generation considering the LET Note 1 of alpha rays

About 10%

About 3%④ Particle size distribution of pellet pieces

About 10%

Almost none

⑤ Collection of air bubbles on pellet pieces - test water layer (Refer to 6.3 (1) ③ a. With a rise in the air bubble content percentage, the extent of impact increases Note 2(iv) c. for details)
up to several tens of percent points
As the contact increases, the extent of
impact increases Note 3 up to several tens of
Not evaluated⑥ Contact between the pellet pieces (Refer to 6.3 (1) ③ a. (iv) d. for details)
percent points
Note 1: Linear Energy Transfer. Energy lost on average per unit length of range as radiation passes through matter
Note 2: The extent of impact is about 20% when the air bubble content ratio is 0.3 with respect to the hydrogen generation rate considering the impact of particulate transport calculation ②
Note 3: The extent of impact is about 70% when the void size generated due to the contact between pellet pieces is 0.3 mm with respect to the hydrogen generation rate considering the impact of©International Research Institute for Nuclear Decommissioning
particulate transport calculation ②

6. Implementation Details

No.51

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (11/14)(iv) Verification of validity of input values (4/5)

c. Example 1 of re-evaluation of the hydrogen generation test (Impact verification of collection of air bubbles on pellet
pieces - test water layer)
When the particulate transport calculation was used to verify the impact of the collection of air bubbles due to the gas (oxygen andhydrogen) generated as a result of water radiolysis, and due to the residual gas after the injection of test water, it was confirmed thatthe hydrogen generation rate decreased as the air bubble content percentage increased (For instance, at an air bubble content ratioof 0.3, the hydrogen generation rate decreased by about 20%).

Mixture of waterand air bubbles

Pellet pieces

2.5E-04
Considering the impact of
air bubbles Note 1

Water
Air
bubbles

Hydrogengeneration rateL/(100gUO2・h)

2.0E-04

Test results
Test errors 1σ Note 2

1.5E-04(a) Collection of air bubbles during test

・Particle size 0.04 mm
・Consideration of the dissipation ofradiation from the test cask
・Non-consideration of impact of LET
and the particle size distribution(b) Collection of air bubbles in re-evaluation

Figure. Image of collection of air bubbles

1.0E-04

Pellet pieces
Mixture of water and gas(Water and gas are uniformly
distributed)

5.0E-05
0.0E+00

・The pellet pieces and mixture
have the same volumes
Figure. Image of single particle system for particulate transport calculation

0

0.2

0.4

0.6

0.8

1

1.2

Air bubble content ratio [-]Figure. Evaluation results from the particulate transport calculation: Air
bubble content ratio and hydrogen generation rate

Note 1: The hydrogen generation rate is calculated by multiplying the G-value of hydrogen generation with the amount of energy absorbed by water calculated using particulate transport
calculation. (The peaking factor is not considered for the calorific value in the TMI-2 evaluation formula)©International Research Institute for Nuclear Decommissioning
Note 2: Variation in the test results of four cases using pellet pieces with small particle size

6. Implementation Details

No.52

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (12/14)(iv) Verification of validity of input values (5/5)

d. Example 2 of re-evaluation of the hydrogen generation test (Impact verification of the impact of contact between thepellet pieces)
The variation in particle size distribution of small particle sizes (0.02 to 0.3 mm) is large and the particles differ in shape anddimensions, so the pellet pieces tend to come in close contact with each other, and when the impact of this contact was verified bymeans of the particulate transport calculation, it was confirmed that the hydrogen generation rate decreased with the decrease in thecontact area (For instance, when the void diameter (water pooling) was 0.3 mm, the hydrogen generation rate decreased by about70%).

2.5E-04

Void(water pooling)

Considering the impact ofcontact Note 1

Pellet pieces

Hydrogengeneration rateL/(100gUO2・h)(a) Contact between the pellet pieces
during test(b) Contact between the pellet pieces inre-evaluation

Figure. Image of contact between
particles

2.0E-04

Test results
Test errors 1σ Note 2

1.5E-04

・Consideration of the dissipation of radiation
・Non-consideration of impact of LET and theparticle size distribution

1.0E-04
Water

5.0E-05

Pellet pieces

・Pellet pieces and water have thesame volumes
Figure. Image of single particle system for particulate transport calculation

0.0E+00
0.01

0.1

1

10

Void (water pooling) diameter [mm]Figure. Evaluation results from particulate transport calculation: Void (water pooling)
diameter and hydrogen generation rate

Note 1: The hydrogen generation rate is calculated by multiplying the G-value of hydrogen generation with the amount of energy absorbed by water calculated using particulate transport
calculation. (The peaking factor is not considered for the calorific value in the TMI-2 evaluation formula)©International Research Institute for Nuclear Decommissioning
Note 2: Variation in the test results of four cases using pellet pieces with small particle size

6. Implementation Details

No.53

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY 2019) (13/14)(v) Verification of applicability of evaluation methods (1/2)
The actual results verifying the applicability of theevaluation method (Linear model) to a system containingalpha, beta and gamma rays could not be verified, so it isnecessary to verify the applicability after consideringLinear model
Spent nuclear fuelindividual input values.
calculation
test
It is believed that the comparison with the hydrogengeneration rate by means of the actual fuel debris is mostappropriate to verify the applicability to the 1F conditions,but it is difficult at the present moment from the viewpointof availability.

Therefore, the policy that was adopted to verify theapplicability of the evaluation method (Linear model) byconfirming that the hydrogen generation rate calculated by
the Linear model, which uses the energy absorption rateevaluated from the particulate transport calculation result
as the input value, was moderately conservative withrespect to the test results in case of a coexisting system ofalpha, beta and gamma rays simulating the fuel debris.

[Output]
Hydrogen generation rate
(Calculated value)[Output]
Hydrogen generation rate (Testvalue)
Test value under all
conditions < Calculated value

Comparative evaluation of
Hydrogen generation rate

Upper limit of all test values >Upper limit of all calculated
valuesUpper limit of all test values <Upper limit of all calculated
valuesAND
Test value under any of
the conditions > Calculated
value

The energy absorption rate is avalue that corresponds to theparticle size evaluated from theparticulate transport calculation
result(F(calc.)d Note 1)

The energy absorption rate is
the maximum value
evaluated from theparticulate transport
calculation result(F(calc.)powder Note 1)

The energy absorption rate is
the maximum value(Fmax Note 1)

Figure. Study flow (plan) for the verification of applicability of evaluation methods (Linear model)

Note 1: F(calc.)d, F（calc.)powder, Fmax are the energy absorption rates described in the graph in 6.3③(1)a.(iii)b.(1/3)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.54

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)a. Study of implementation details necessary for setting the transfer conditions plan (FY2019) (14/14)(v) Verification of applicability of evaluation methods (2/2)

The test results of the hydrogen generation test conducted in FY2018 using spent nuclear fuel were considered as theexisting test results that could be used for the verification of applicability of evaluation method, but upon re-evaluation(refer to 6.3③a.(iv)b.), it was found that the test results also included the effect of contact between particles and the effectof air bubbles in the pellet pieces-test water layer, and that the test results of FY 2018, which might have been lessconservative, were not suitable for verifying the applicability of the evaluation method (Linear model).
When verifying the applicability through tests, the following test is believed to be necessary wherein, by using fuel debris
simulants (radiation source) containing of alpha, beta and gamma rays, the test water is stirred in order to eliminate theeffect of contact between simulants or the effect of air bubbles in the simulant-test water layer, thereby, suspending theparticles.

Test plan: By means of the test using spent nuclear fuel pellet pieces (spent nuclear fuel test (the same test as
the spent nuclear fuel test used for the verification of validity of the energy absorption rate (refer to 6.3③
(1)a.(iv)a.))), confirm that the hydrogen generation rate calculated by the Linear model, which uses theenergy absorption rate evaluated from the particulate transport calculation result as the input value, ismoderately conservative with respect to the test results in case of a coexisting system of alpha, beta andgamma rays.
Test water

Test cask
Spent nuclear fuel pellet
piecesSpent nuclear fuel pellet
piecesWater(a) Spent nuclear fuel test(b) Particulate transport calculation model

Figure. Image of the test system©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.55

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (Estimated and actual)b. Implementation of hydrogen generation test (to be implemented if necessary) (FY 2020)[Scheduled]

Based on the results of the study in point a., a study will be conducted in view of executing the hydrogengeneration test in FY 2020. The study results will be evaluated using the evaluation formula and analysis, etc.,
and the results will be compared. Moreover, even while evaluating the results of this test, expert opinions will beheard as appropriate.

c. Study of method to predict hydrogen generation (FY 2019, FY 2020)

The proposed methods to predict hydrogen generation are being studied on the basis of the test results in point a.
During the study, the hydrogen generation test results (if the tests were conducted) from point b. will also bereferenced. In addition, if necessary, evaluation will also be carried out by means of analysis.

d. Estimation of hydrogen generated in canister (FY 2020) [Scheduled]

The amount of the hydrogen generation under the 1F canister conditions will be presumed on the basis of the
proposed methods to predict hydrogen generation studied in point c.

e. Study of transfer conditions (FY 2020) [Scheduled]

Based on the study results of point d., the hydrogen generation countermeasures (study of recombination
catalyst) implemented separately and the study results of the drying technology, etc., transfer condition plans forcanisters will be studied and proposed so that the canisters can be transferred safely from the viewpoint ofhydrogen measures.

Based on the above-mentioned study, a method to predict hydrogen generation suitable in the 1F fuel debris
conditions will be proposed along with proposing the conditions, restrictions, and additional countermeasuresnecessary for the transfer of fuel debris.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation

No.56④ Contribution of the results to the areas where they can be reflected

On the basis of the presumed amount of hydrogen generation and the proposed transfer condition plans, it is believed that it should
be possible to contribute to the drafting of operation plans for transfer and storage of actual canisters, designing and manufacturing of
the vent mechanism for the actual canisters, and the study of hydrogen gas treatment facility.

⑤ Analysis from the perspective of site application

For application to the site, in addition to the method to predict hydrogen generation, which will be the outcome of this project, it isnecessary to conduct studies combining the drying treatment to reduce the amount of hydrogen generation, ensuring tolerance bymeans of a hydrogen catalyst, and checking if transfer is possible by means of actual measurement of hydrogen concentration prior totransfer, etc.

⑥ Issues

There are no issues in the execution of the present plan.

⑦ Level of achievement in light of the goal

As a study for the implementation details necessary for setting the transfer condition plans, the method of verifying the validity of the
input values for the method to predict hydrogen generation and the method of verifying the applicability of evaluation methods, arebeing studied. The progress is almost as planned, and it is expected that the target results can be achieved by the end of FY2020.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation

No.57

Summary

For the development of technology for transfer of fuel debris, in FY2019, the study items
and implementation details required for setting the transfer condition plans were studied
by investigating domestic and overseas findings and by hearing expert opinions on themethods to predict hydrogen generation.
In FY 2020, the study of methods to predict hydrogen generation will proceed, wherein
the amount of hydrogen generated inside the canisters will be presumed on the basis of
the results of hydrogen generation tests implemented as needed, and transfer condition
plans to enable safe transfer will be studied.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.58

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation⑧ Future plans

Figure. Schedule for development of technology for transfer of fuel debris/ study of methods to predicthydrogen generation

FY 2019

Items

First half

Second half

FY 2020First half

Second half

Remarks

6.3. Development of technology for transfer offuel debrisa. Study of implementation details
necessary for setting the transfer
conditions planb. Implementation of hydrogen generation
testc. Study of methods to predict hydrogengenerationd. Estimation of hydrogen generated incanistere. Study of transfer conditions:Plan: Actual©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures

No.59① Purpose and Goal

• Studies are being conducted centering on early drying treatment in order to control the hydrogen generated from fuel debris duringtransfer, but as a backup the method of recombining hydrogen with oxygen by means of a catalyst will be studied.
• As per the studies conducted so far, it is necessary to consider the following as the environment inside the canister:○ Humid environment: To continue the recombination reaction, it is necessary to promptly remove the moisture generated by hydrogen
recombination.
○ Room temperature environment: The recombination reaction cannot take place easily.
○ High radioactivity: The water-repellent treatment for removing moisture tends to deteriorate easily.
• The studies conducted up to FY 2018 have revealed that the catalyst applied during the water-repellent treatment may be able to handle
the environmental conditions inside the canister as well.
• Based on the above, the hydrogen recombination performance of the catalyst (platinum-based catalyst with a particle size of
about 3 mm and water-repellent treatment applied) identified in the study last year, will be evaluated mainly focusing on the flow
velocity of the gas passing through the catalyst.

• The amount of hydrogen generation or the internal structure of canisters, etc. was not determined in the recent studies, but case studies
were conducted in accordance with the hydrogen generation amount for the current canister design and the effectiveness ofhydrogen measures has been exhibited.

② Comparison with existing technology• In case of the TMI-2 fuel debris canisters, the catalyst believed to be effective at that point in time was adopted, but water-repellency was
not considered.
• Various catalysts have been developed in Japan, and last year, operation tests were conducted under humid and room temperatureenvironments for catalysts available in Japan, a catalyst with a powerful water-repellent treatment was selected, and radiation resistanceof 7 days or more, which is the transfer period, was confirmed.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures

No.60③ Implementation items and results (Estimated and actual)
Canister Lid

Gas flow

Diameter of catalyst layerΦ220 mm

The hydrogen which reaches
the vicinity of the catalyst
layer reaches the surface ofthe catalyst due toconvection and diffusion of
the combustion heat ofhydrogen and burns up
there.

Dimensions of the catalyst
layer

Lid

The concentration of hydrogen on
the surface of the catalyst layer isobtained from the amount ofhydrogen generated (set on thebasis of the test)

Diffusion

Main
canister body
Unit can(Collection of fueldebris)The performance of the catalyst (reaction rate coefficient) depends on theparameters such as the flow velocity. Hence evaluate the effectiveness ofthe catalyst by understanding about it from the flow-type reaction rateevaluation test.

Study methodology
a. Study of Catalyst

Set the necessary amount as per
the performance of the catalyst.

Hydrogen concentration on
the catalyst layer

Catalyst

Basic approachb. Detailed study of flow
characteristics inside thecanister

Distribution of hydrogenconcentration

The concentration of hydrogen in thefuel debris is obtained from the amountof hydrogen generated (calculated byevaluating diffusion)

Expansion of hydrogen

The hydrogen in the debris will mainly
diffuse and reach the vicinity of thecatalyst layerc. Study on catalyst allocation: Determine catalyst performance underenvironmental conditions such as the flow velocity
conditions, etc. by means of tests.
: Based on the restrictions of the placement locationand conditions such as the canister shape and theamount of hydrogen generated, etc., evaluate the
distribution of hydrogen concentration inside thecanister from the viewpoint of flow/diffusion, andselect the predominant location from the viewpointof concentration.

: Based on the study of catalyst allocation and catalystamount in points a. and b. above, set up an effective
placement from the viewpoint of hydrogenconcentration inside the canister.

Location of catalyst allocation(to be added if required)Figure. Image diagram of hydrogen diffusion inside the canister©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.61

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures③ Implementation items and results (Estimated and actual)a. Study of catalyst (1/2)
In a test where a catalyst is filled in a void tower and gas is circulated (flow-type reaction rate evaluation test), obtain the overall reaction
rate coefficient data by varying the conditions of the circulated gas (flow velocity (superficial velocity), gas temperature, hydrogenconcentration, toxic components), and derive an estimation formula for the overall reaction rate coefficient of the catalyst forenvironmental conditions such as flow velocity.
ReactorGas
Hydrogen and
水素、酸素
oxygen
mixed
gas
混合ガス

Hydrogen
水素濃度
concentration
measurement
計測

Reactor
反応器
Exhaust
排気

Hydrogenconcentration
水素濃度
measurement

計測

Catalyst(Installed inside)

触媒
Catalyst

Thermostatic
恒温槽
chamber

Figure. Concept of flow-type reaction rate evaluation test

Refer the following slides (Supplements) on the detailed procedure for calculating the overall reaction
rate coefficient from the reaction rate obtained by the flow-type reaction rate evaluation test.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.62

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures(Supplement) Method for calculating the reaction rate formula and overall reaction rate coefficient
The formula for calculating the overall reaction rate coefficient K from the reaction rate (concentration change amount
per unit time) and reaction efficiency rate η is shown below:
Reaction equation： H2 ＋ 1/2O2 → H2O

reaction rate when expressed as primary Note 1： − 𝑟 = 𝐾𝐶𝐻2

⇒ 𝐾 = 𝑆𝑉𝑙𝑛11−𝜂-r： reaction rate
K：Overall reaction rate coefficient CH2：Hydrogen concentration
CO2： Oxygen concentration
CH20：Inlet hydrogen concentration η：Reaction efficiency rate
SV： Space velocity (=Q/Vcat) Q： Gas flow rate
Vcat： Volume of catalyst layer
As space velocity (SV) is the ratio of gas flow rate (Q) and amount of catalyst (Vcat: volume of catalyst layer), the effectiveness ofhydrogen measures can be evaluated or confirmed by setting the amount of catalyst and its placement according to the following
procedure.
・Testing stage：As reaction rate coefficient depends on environmental conditions such as temperature and flow velocity, the estimation
formula of the overall reaction rate coefficient is constructed by calculating the overall reaction rate coefficient from the reaction rate
corresponding to the space velocity and these conditions.
・ Amount of catalyst in canister / placement study stage: The required reaction rate is set based on the hydrogen gas concentration andhydrogen generation amount inside the canister, and the amount of catalyst is temporarily set based on the estimation method of thereaction rate coefficient. As the environment inside the canister is also affected by the amount of catalyst and its arrangement, theeffectiveness of hydrogen measures is confirmed by evaluating the hydrogen concentration in the canister under the set catalyst
conditions. Also, the amount of catalyst and its placement are reviewed and re-evaluated or confirmed as necessary.

Note 1：Y.IWAI et.al, Journal of NUCLEAR SCIENCE and TECHNOLOGY, vol.48, No.8, P.1184-1192©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.63

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures(Supplement) Approach to laminar gas film mass transfer and overall reaction rate coefficientStages of hydrogen transfer andreaction in the vicinity of the catalyst

Hydrogen gas concentration CH2

Catalyst

Laminargas film

Gas

CH2b
CH2s

①

○ The reaction of hydrogen by a catalyst can be explained in thefollowing two stages:① Mass transfer from fluid to catalyst surface② Reaction on the catalyst surface○ Depending on the conditions of use, the velocity of both ① and ②change, and the stage where the velocity is relatively low becomesthe rate-determining step and this determines the overall velocity.
○ The mass transfer rate from the fluid to the catalyst surface isexpressed by laminar film mass transfer (laminar gas film masstransfer).
rG = kG (CH2b- CH2s)②○ The reaction rate on the catalyst surface is expressed by thefollowing equation:rR = kRCH2s
Distance
Figure. Concept of hydrogen transfer andreaction in the vicinity of the catalyst Note 1○ Based on the above, the overall reaction rate coefficient K isexpressed by the following equation:

1
1
1
=
+
𝐾 𝑘𝑅 𝑘𝐺

K: Overall reaction rate coefficient
kR：Catalyst reaction rate coefficient
kG：Laminar gas film mass transfer coefficient

Note 1： Created from Pg. 183 of Reaction Engineering, Baifukan, by Kenji Hashimoto©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.64

6.3 Development of technology for transfer of fuel debris(Supplement) Approach to collection of performance data of catalyst
As described above, the reaction rate equation of the hydrogen recombination
reaction is expressed by the following equation:
reaction rate equation
Reaction when expressed as primary： −𝒓 = 𝑲𝑪𝑯𝟐
r： reaction rate CH2: Hydrogen concentration CO2 : Oxygen concentration
K: Overall reaction rate coefficient✓✓

The prerequisite for the above relation is similar environment conditions suchas temperature and gas flow velocity. As the overall reaction rate coefficient(K) depends on these environmental conditions, it is necessary to collect dataso that these conditions can be dealt with. In particular, it is necessary to consider
that the gas flow velocity forms a laminar gas film on the catalyst surface.
Therefore, when setting K, it was decided to acquire data through flow-type
reaction rate evaluation test so as to focus individually on the reaction
velocity coefficient of the catalyst itself (kR: catalyst reaction rate coefficient)and the effect of diffusion inside the laminar film (kG: laminar gas film masstransfer coefficient), and estimate K for any flow velocity condition.

1
1
1
=
+
𝐾 𝑘𝑅 𝑘𝐺

The effect on kR is checked usinghydrogen concentration and gas
temperature as parameters.

kG is estimatedfrom K and kR

Overall reaction rate coefficient K(2) Study on hydrogen measures

kR
K

Diffusion rate-limiting← →Reaction rate-limiting
Presence ofAbsence oflaminar film
laminar film
resistanceresistance

Impact
of kG

1
1
1
=
+
𝐾 𝑘𝑅 𝑘𝐺

u4

Superficial velocity ug(kR： Catalyst reaction rate coefficient,kG： Laminar gas film mass transfer coefficient)Figure. Approach to obtaining reaction rate coefficient(K: Overall reaction rate coefficient, kR: Catalyst reaction rate coefficient, kG: Laminargas film mass transfer coefficient)©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris

No.65(2) Study on hydrogen measures③ Implementation items and results (Estimated and actual)a. Study of catalyst (2/2)
The superficial velocity (flow velocity) dependence data of overall reaction rate
coefficient is being collected through tests.
b. Detailed study of flow characteristics inside the canister
Based on the study in FY 2018, it was found that the flow inside the canister was very
little and diffusion was dominant, so it was decided to carry out the evaluation
focusing on diffusion.
c. Study on catalyst allocation
The hydrogen concentration in the sealed canister will be evaluated with respect tothe catalyst allocation and amount of catalyst set based on the results of points a. andb., and the effectiveness of catalyst-based hydrogen measures will be confirmed.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.3 Development of technology for transfer of fuel debris

No.66(2) Study on hydrogen measures④ Contribution of the results to the areas where they can be reflected
Investigated as one of the candidate plans for hydrogen measures during canister transfer.
(It is a back-up for hydrogen measures by means of time management (mitigation measures) especially when drying
before transfer is not possible)⑤ Analysis from the perspective of site application
Ensure that it does not become a burden during actual application, by incorporating the environment assumed in the
catalyst performance study related to catalyst installation.

⑥ Issues
As a result of preliminary tests while acquiring catalyst performance data, the hydrogen concentration after passing
through catalyst was low, and a method for precisely measuring low-concentration hydrogen was required tounderstand catalyst performance. Therefore, it was decided to collect catalyst performance data in FY 2020 after
determining the method.
⑦ Level of achievement in light of the goal
After doing the needed measures to collect more precise catalyst performance, we would like to proceed with a study
that will collect the catalyst performance including the impact of iodine (as a toxic catalyst substance) and will obtain thedesired results by evaluating the validity of catalyst-based hydrogen measures.
SummaryIn FY 2019, the flow inside the canister was studied as catalyst-based hydrogen measures. The study on the method
for obtaining catalyst performance is underway.
In FY 2020, the required amount of catalyst and its installation position will be studied, and the hydrogen concentration
inside the canister will be evaluated to confirm the effectiveness of the catalyst, based on the catalyst performance dataobtained through tests and the evaluation of flow inside the canister.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.67

6.3 Development of technology for transfer of fuel debris(2) Study on hydrogen measures⑧ Future plans

Table. Schedule for development of technology for transfer of fuel debris/ study on hydrogen measures

Items

FY 2019First half

Second half

FY 2020First half

Second half

Remarks

6.3 Development of technology
for transfer of fuel debris(2) Study on hydrogenmeasuresa. Study of catalyst

Study of catalyst

b. Detailed study of flow
characteristics inside thecanister

Detailed study of flow characteristics
inside the canisterc. Study on catalyst allocation

Extended to study methods formeasuring low concentrationhydrogen

Study on catalyst allocation(Effectiveness evaluation): Plan: Actual

Incorporating the catalyst study
results (Catalyst performance): Reviewed plan
©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus

No.68① Purpose and Goal
• During the inter-building transfer of fuel debris up to the storage facility, the sealing of fuel debris is essential as theaccumulation of hydrogen due to the moisture content of the fuel debris is an issue. Hence, moisture removal by
drying is considered to be effective in reducing the amount of hydrogen generation.
• Therefore, in this technological development, for the purpose of safer transfer, the goal is to propose a draft on thebasic specifications of a drying apparatus for 1F fuel debris by setting the parameter conditions that are effective fordrying with the focus on the drying behavior of the porous material, which may be a possible form of fuel debris, andalso considering the maintenance and handling of even fuel debris substitutes in contaminated areas.
• It is expected that these results will be utilized as the base for the verification tests using actual fuel debris
performed at the stage of engineering work for the actual equipment or for the design of actual equipment based on
the test results.
② Comparison with existing technology• The purpose of drying the fuel debris in TMI-2 is to remove free water to ensure subcriticality and it is not atreatment method aimed at advanced drying. Meanwhile, as the purpose in 1F is to reduce the hydrogen generation
amount, it is necessary to determine concrete details of a treatment method that can achieve a low moisture
content. Also, the findings (contamination measures, etc.) related to heated vacuum drying selected for TMI-2 areconsidered to be useful information.
• There are various methods used for drying in general industries, and it is believed that there are methods other thanthe methods used in TMI-2, which would be effective for 1F fuel debris. Meanwhile, there are problems in applying
them to the drying of fuel debris as is, in terms of maintenance and handling, etc., in contaminated areas.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus

No.69③ Implementation items and results (Estimated and actual)
Study methodology
a. Study on basic conditions(i) Study on performance requirements (target items, target time, target moisture content)• Set the targets to be dried, the target time, and the target moisture content, and organize the requirements of drying apparatus
performance.
(ii) Study on safety requirements• Clarify the safety requirements and organize the functional requirements of drying apparatus.
(iii) Investigation and analysis of existing drying technology• Investigate the drying technologies used in TMI-2, organize the drying technologies used in general industries, and study their applicability
to debris drying.
(iv) Study on the device concept• Study on the concept of drying apparatus (including maintenance plan, equipment systems, equipment configuration) based on (i)-(iii) andelement tests Note 1.

b. Collection of drying behavior data

Note 1: Implemented as needed(i) Preparation of test equipment• Identify the items to be collected / verified on a real-size (canister or / and unit can) and formulate a test plan
Element tests are conducted as necessary.
(ii) Collection of drying behavior data (including maintainability, etc.)• Perform data collection / verification including operability and maintainability required for b.(i) and c.(i) using a real-size test equipment.

c. Basic plan for drying system(i) Study on maintenance plan / equipment systems / equipment configuration• Specify the functional requirements and study the system concepts, identify the items that need to be collected / verified and reflect themin section b.
(ii) Formulation of basic specifications of the equipment (after reflecting the data)• Reflect the test results and come up with the basic specifications (plan) of drying apparatus and the configuration (plan) of ancillaryfacilities©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.70

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a. Study on basic conditions (1/8)(i) Organizing performance requirements (1/3)
As performance requirements of the drying system, the standard values of the target items,
drying time, and moisture content were set as follows:(Target items) Porous materials(Target time) Receiving to allocation 24 hrs(Target moisture content) 0.1 ｗｔ.% Note 1

Table. Evaluation for performance requirements
Performance requirements

Note 1: Moisture content based on
the density of fuel debris. The
target moisture content in thetest should be reviewed basedon the density of the test
specimen.

Target items

Response policy planCan deal with the propertiesof fuel debris collected at the
retrieval side

The target is porous material having small pores.
Although slurry might be subject to drying,considering the fact that their current properties are
unknown, the applicability of drying technologies thatare under study as the main targets will be studied
using element tests, etc.

Can be handled by a method
allocated from the retrieval
side

Considering their handling in unit cans or canisters.

Target time

Can dry within the timecorresponding to thethroughput of debris retrieval

The assumed target time from receiving to allocationis 24 hours.

Targetmoisturecontent

Reduces the amount of waterremaining after drying as
much as possible

The target moisture content is set to 0.1 wt.%
estimating a margin on the moisture content (1.5
wt.%) where the hydrogen concentration in thecanister reaches the lower explosion limit (4 vol.%)during the transfer period of 7 days.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.71

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a. Study on basic conditions (2/8)(i) Organizing performance requirements (2/3)
Following are the main collections that were identified as drying targets during the study.
Table. Main collections to be studied
Generation
sourceName

Overview

Part of the fuel assemblies that remained
intact without melting

Block-like fuel debris,
MCCI

Fuel debris that cooled slowly to become
like a block

Pebble or powder-likefuel debris

Molten core material that cooled rapidly
and fragmented

Structureswithdeposits of nuclear
fuel material

Structures that remained without melting
and on which fuel debris has depositedWater
treatment systemSlurryPowdery, fine particulate debris

OthersFilters

Filters present in water treatment system/ gas treatment process

Retrieval process

Stump fuel debris

Image

Features・ Debris collected from the retrieval process isthe main target for drying.
・ Oxide debris is presumed to be porous
material in the study for the Characterization
PJ.

・Fine particulate debris may be a target fordrying.
・ However, the detailed properties are
unknown.
(Therefore, applicability of drying technologies
studied using porous materials is considered)©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus

No.72③ Implementation items and results (Estimated and actual)a. Study on basic conditions (3/8)(i) Organizing performance requirements (3/3)

In the Fuel Debris Characterization Project, the following results were collected until FY 2016 by conducting the“Evaluation of moisture content and drying properties of fuel debris” :✓ In the case of porous materials, the drying rate at the end of the drying process becomes slow when theimpact of small pores is large.
✓ In the case of powdered granular material, when fine particles are moistened, they become clay-like and thedrying rate decreases.
From the above, it is assumed that properties such as porous materials containing small pores and fine particles
containing moisture (slurry) affect the drying behavior.
From the above, the development of the targets to be dried will be carried out as per the below policy, based on theorganized results on the targets and their features for each retrieval process (previous slide).
✓ The main target is porous material with small pores. (Typical porous material ⇒ Zeolite test specimen)✓ Although slurry might be a target for drying, considering the fact that current properties of the slurry are
not known, the applicability of drying technologies to be studied with porous materials as the main
target, will be studied using element tests, etc.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.73

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a.Study on basic conditions (4/8)(ii) Organizing safety requirements
The requirements of drying apparatus with respect to the safety functions being considered in this development are similar to those of
the canisters, and are set as follows.
Table. Required functions of drying apparatus with respect to the safety functions

Safety functions

Design goals

Division of safetyfunctions

CanisterOtherequipment

OO

Subcriticality

To maintain subcriticality

CoolingHeat removal

To prevent the impact on physicalproperties of canisters, fuel debris, etc.

-

O

Confinement

To prevent exposure of workers andpublicO

O

Shielding

To prevent exposure of workers andpublic-

Structure

To achieve the structural strength formaintaining the safety functions

Confinement

Other(Maintaining the
shutdown, coolingand confinement
functions)

Material integrity To maintain the structural strength

HydrogenTo prevent the explosion of hydrogengenerated by the radiolysis of waterFire prevention

To prevent fire caused by residual
zirconium

Required functions
Dryingapparatus

RemarksO
O(Additional)

Heated by drying
treatment(Prevention ofabnormal heating)O

Preventing the
spread ofcontaminationO-

Installed inside the
cell

O

O

O

O

O

O

O
(Catalyst)

O

O(Drying)-

O©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.74

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a.Study on basic conditions (5/8)(iii) Investigation and analysis of existing drying technologies (1/2)

The drying methods used in general industries were organized, and the drying methods applicable to the drying of fueldebris were selected.
Table. Investigation and analysis of drying apparatus in general industries

Drying method

Level of difficulty in responding to safety requirements
Maintaining subcriticality

Confinement function

Prevention of spread ofcontamination

Prevention of abnormal
heating

Warm air (carrier gas)

O

O

O

O

Heat conduction medium

O

O

△

O

Radiation

O

O

O

O

Microwave

O△ (Increase in size ofcell)

x (Waveguide sealing)O

Induction heating (IH)

O

O

O

O

Superheated steam

Remarks

As heat is input by directly touching the heat transfer
surface, the maintenance target becomes a directcontaminant.

As the waveguide cannot be sealed during drying, themicrowave generating equipment is also subject tocontamination.

(Not applicable as it will bring in moisture)

Depressurization

O

O

O

O

Stirring

x (UC retrieval)Ox (Expansion ofcontaminated area)O

Suspension flowx (UC retrieval)△ (Increase in size ofcell)x (Expansion ofcontaminated area)O

Legend: O…Low level of difficulty△…Medium level of difficulty

The fuel debris is retrieved from the UC and stirringand suspension flow is carried out on it to whirl up thepowder.

x… High level of difficulty

Approach to narrowing down the methods• As a prerequisite fuel debris is handled in unit cans (UC).
• Ensures safety (maintaining subcriticality) by handling UC.
• Stirring and suspension flow requires retrieval from UC and necessitates further contamination measures and subcriticality evaluation.
• In the case of microwaves, as the waveguide and the inside of the drying apparatus have the same atmosphere, further contamination
measures are required in consideration of maintainability.
[Drying methods] Warm air, Heat conduction medium, Radiation, Induction heating (IH),
Depressurization©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.75

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a. Study on basic conditions (6/8)(iii) Investigation and analysis of existing drying technologies (2/2)
The drying performance of TMI-2 fuel debris was evaluated and its applicability to the development of thistechnology was studied.
Table. Study on the applicability of TMI-2 fuel debris drying technology to this development

Items

DesignSafetymeasures

Targets forinvestigation and study

Performance with TMI-2 fuel debris

Purpose / Goal

Purpose: Maintaining subcriticality
Target: Water removal between particles,
and the allowable water content is set to 8ℓ/can (42 cm3/ℓ per canister internal volume)

Material under test for
preliminary study

Sand, pumice (porous materials)

Policy of using porous materials that are more difficult to dry than that in TMI-2

Drying method

Heated vacuum(temperature limit of sealing material
150 ℃)
Heated gas (used only in test)

・It is expected that the method used in TMI-2 can be applied to the drying of free water
between particles.
・It is necessary to consider the optimum drying conditions, and decide on them by conducting
surveys on heating, depressurization, air speed, etc.

Subcriticality

No information available on the evaluation
conditions for drying furnace

Requires study

Cooling

No information available on design approach

Requires study

Contamination measuresfor drying apparatus(system)

Installation of metal filter in canister

Applicability to this development

The purpose of this development is to control the hydrogen generation gas, and the drying
target is strictly set to 1/20 or less (2 cm3/ℓ or less) of TMI-2.

The lesson learned that installing a metal filter in a canister is effective in controlling
equipment contamination is useful information.

[Summary] ・ The results of TMI-2 can be used as a reference for removing free water between particles.
・ As the goals set for drying in this development are strict, their direct application is difficult.
・ The installation of a filter in the canister as a measure against system contamination in the device isuseful information.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.76

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a. Study on basic conditions (7/8)(iv) Conceptual study of the device (1/2)◆ Subcriticality is maintained by handling fuel debris in unit cans
◆ The unit can is a netted-caged structure made of a mesh that allows easy flow ofwater / air ⇒ Assuming that it facilitates the draining and drying of fuel debris◆ Elements that facilitate drying are evaporation facilitation, mass transfer
facilitation, area improvement ⇒ Combined for maximum use◆ Evaporation facilitation: Direct heating method (warm air) anddepressurization method are used to reach the boiling point efficiently◆ Mass transfer facilitation: In principle, the concentration gradient is secured byscavenging◆ Area improvement: Ensure as much surface area as possible by providing
gaps between the unit cans when stacking, etc.
◆ As latent heat of vaporization needs to be input in the depressurization method,an external heat source (heater) is added◆ Basically, the confinement property is secured in the chamber or canister (reduces
the load in the later stage)◆ Design parameters•
Heating temperature•
Internal pressure•
Flow velocity of warm air•
Chamber capacity

Depressurized exhaust(Internal pressure)
Radiant
heating

Warm air(Heating temperature)

UC

UC

UC

Flow velocity
of warm air
Heater(Heating temperature)

UC

Chamber or canister(capacity)

Figure. Basic concept of drying apparatus©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.77

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)a. Study on basic conditions (8/8)(iv) Conceptual study of the device (2/2)
The basic specifications of the device are set as follows based on the safety requirements:(1) Heating temperature
The equipment capacity of the heat source is selected so that the chamber or canister can be heated up to
200 ℃.
✓ Heat resistant temperature of canister sealing material for 1F ⇒ About 200 ℃✓ Behavior of radionuclides ⇒ Released above 200 ℃(2) Consideration for maintenance
The number of parts installed inside the cell and chamber, which need to be maintained are minimized.
(3) Shape
For maintaining subcriticality, the maximum inner diameter of the treatment device used for filling debris is
set to φ 220 mm.
(4) Flow velocity
An upper limit for flow velocity is set in consideration of the scattering of debris particles. A negative pressure
is maintained inside the chamber or canister to ensure safety.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.78

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)Table. TG-DTA test conditions

Pressure

RIGAKU TG TG-DTA8122(OT6800049)
Time, mass, temperature
Retained at 200 ℃ for 10 hours(After that, hold at 300 ℃ for 1 hour todry completely)
Atmospheric pressure

Gas used

Dry-N2 100 mL/min

Shape of chamber

Rectangular 15 mm x 10 mm

Sample cask
Name of sample

Platinum crucible
Synthetic zeolite (HiSivTM-3000 1.6)

Amount of sample

About 16 mg

b. Collection of drying behavior data (Study in FY 2019 and FY 2020) (1/2)

Equipment name(i) Element tests

Measurement items◼ Collect the data on drying properties of synthetic zeolite as a
typical porous material◼ The moisture content should be 0.22 wt% at 10 hours and
200 ℃

Moisturecontent
Temperature

Drying rate

Time (h)Figure. Test result (change in moisture content)

Temperature
Temperature (℃)

Drying rate (mg / min)Temperature (℃)

Moisture content (wt%)◼ In the future, basic data on the drying properties will beobtained, with the operating conditions and characteristics ofthe materials to be dried as parameters.

Temperature

Moisture content (wt%)

Figure. Test result (drying properties curve)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.79

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)b. Collection of drying behavior data (Study in FY 2019 and FY 2020) (2/2)(ii) Preparation of test equipment

Identification of items to be collected / verified in real size (canister / unit can). The specific details of the test plan
will be determined in the future.
Table. Full-scale drying test items

Test items

Goal

Remote operation andoperability test

As operations and maintenance are oriented toward remote operations from the viewpoint ofsafety, operations using a manipulator are required. For these operations, confirm that onethrough operations and maintenance operations by remote control are possible by verifying theoperability and visibility in the same space dimensions as the actual equipment.
<Checklist>① Possibility of removing foreign materials from inside the drying apparatus chamber② Possibility of wiping decontamination inside the drying apparatus③ Replacement of drying apparatus seal (under study)

Full-scale drying test

To comprehensively confirm the applicability of the design methods created on the basis ofelement tests.
<Checklist>①
Drying time (residual heat ~ drying ~ cooling)②
Final moisture content③
Decision criteria for completion of drying(iii) Collection of drying behavior data

Collection of data that contributes to the actual drying system, including maintainability and operability required inpoint c., by conducting a drying test using real-size test equipment©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.80

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus③ Implementation items and results (Estimated and actual)c. Basic plan of the drying system (Study in FY 2019 and FY 2020)(i) Study on maintenance plan / equipment systems / equipment configuration

Study on the system concept (plan) by creating a system design for drying facilities. Also, study on the remote maintenance policy.
[Approach to system design](1) Possibility of switching between warm air heated drying / heated vacuum drying(2) A filter is installed in the later stage of the drying apparatus to minimize the spread ofcontamination(3) The water vapor during drying is collected using a cold trap / gas-liquid separation tank ora wet scrubber(4) Exhaust gas filter installed in off-gas system

Cell
Nitrogen

Used during warm air heateddryingCanister

Used during heated vacuum drying
In-cell crane

Heater

Maintenancearea

Equipment
repairing box

Decontamination
line

NitrogenCold trap *2

Vacuum pump

Filter *1
Heated vacuum drying
apparatus

Gas-liquid
separationtank

Condensate receiving tank
HeaterCondenser Demister

Range that can be
maintained using
remote operations

Exhauster
Wet scrubber

Exhaust gas filter

When remote maintenance isdifficult, decontaminate, carryout, and maintain throughmanual operations outside thedrying apparatus cell
(Drain treatment)
Exhaust system of
the building
The equipment insidethe drying apparatus
cell is maintained
remotely

Off-gastreatment unit

*1 Can be installed in canister or drying apparatus*2 The necessity is decided based on the vacuum pump model

Figure. Drying apparatus - Conceptual example of system
diagram (Example: During heated vacuum drying operation)(ii) Study on basic specifications of the equipment

Targets to be
maintained are placed
as much as possible
outside the cell

Dryingapparatus cell

Equipment that is difficult tomaintain remotely includes
structures that can be remotely
removed (quick connector, etc.)

After isolating the systemfrom the drying apparatus
and decontaminating it, it
is maintained by theoperators

Figure. Concept of drying system

Reflect the test results, and come up with the basic specifications (plan) of drying apparatus and the configuration (plan) of ancillaryfacilities©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.81

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus④ Contribution of the results to the areas where they can be reflected
A summarization of the concept of the fuel debris drying apparatus should contribute to hydrogen measures duringtransfer.
⑤ Analysis from the perspective of site application
Included in study items assuming hot handling and maintenance.
The plan is to decide on the applicability using the process to determine specific details in the future.
⑥ Issues
There are no issues in the execution of the present plan.
⑦ Level of achievement in light of the goal
A study is underway to present the basic specifications plan for the fuel debris drying system, and it is expected thatthe desired results will be obtained as per the plan.
SummaryIn FY 2019, as the development of drying technology and system, the functional requirements of the drying
apparatus, investigation on existing technologies, and planning for element tests required for the conceptual designof the drying apparatus were studied, and studies were conducted for the tests.
In FY 2020, the drying behavior data will be collected by planning a drying test with real-size test equipment basedon the concept of drying apparatus, and in addition, the basic specifications plan of the drying apparatus for 1F fueldebris will be proposed by studying about maintenance and handling, etc., inside the contaminated areas.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.82

6.4 Development of drying technology and systems(1) Study on the basic specifications of drying apparatus⑧ Future plans

Table. Schedule for the study on the basic specifications of drying apparatus

FY 2019

Items

First half

FY 2020

Second halfFirst half

Second half

Remarks

6.4. Development of drying technology andsystems(1) Study on the basic specifications ofdrying apparatus
a. Study on basic conditions

Study on basic conditions

b. Collection of drying behavior data

Device arrangement / data collection

c. Basic plan for drying system

Study on maintenance plan/ devices and systems/ equipment configuration
Study on basic specifications of devices: Plan: Actual©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.83

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology① Purpose and Goal
To prevent hydrogen combustion or explosion during transfer inside 1F premises, measure the hydrogenconcentration in the canister and (or) transfer cask, and confirm that the hydrogen concentration in thecask stays below the lower explosion limit (4 vol.％) for 7 days Note 1, before delivering the canister to thestorage building.
For this, investigate hydrogen concentration measurement technologies, and select and propose
applicable candidate technologies.
Note 1： Set in consideration of the actual transfer time of removed spent nuclear fuel, and the time required for the expected recovery from a failure
occurring during transfer in Unit 4 of 1F.

② Comparison with existing technology
Existing technologies can be used for hydrogen concentration measurement. However, there is little
knowledge about hydrogen concentration measurement in a high-dose environment. It is necessary to
study the applicability, etc., of the technologies in consideration of the storage and transfer process offuel debris, the interaction with the canister and transfer cask, and the environmental conditions in 1F, etc.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.84

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (1/12)✓ Study on the points for hydrogen concentration measurement from the perspective of “continuous monitoring” and “sequential
monitoring”.
✓ “Sequential monitoring” helps in identifying the work processes with which hydrogen concentration can be measured withminimum equipment support, in the work processes from fuel debris retrieval to transfer cask allocation ([1] to [32] in the
below figure)
Reactorbuilding
Expandedbuilding

Port

Lifting machine

Lifting machine

Debristreatment cellWorkmonitoring
cameraFuel debris
retrieval
deviceManipulator

Lifting machine

Primary lid fastening Secondary lid
system/fastening system/
Gas injection
Gas injection
system/system/leakage checking
leakage checking
facility
facility

Sealingcell

Canister lid
Gas injection
fastening systemsystemDryingCanisterapparatus

Preparation cell

TransfervehicleAccess tunnel

Fuel debris

Inside thereactor[1] Cutting and processing the discharge[2] Visually checking the discharge[3] Collecting fuel debris by means of fueldebris retrieval device and filling it in UC[4] Draining the entrained water from fueldebris[5] Transporting UC to the access tunnel
outside the pedestal

UC transfer
systemAccess tunnel[6] Transferring UC to the
expanded building *1*1 Besides UC, fuel debris blocks andstructures are transferred from inside thereactor through the access tunnel to the
expanded building. The transfer of UC isillustrated as a representative example.

Drying apparatus

Debristreatment cell[7] Loading UC into drying
equipment[8] Drying fuel debris

Canister transfer
system[9] Loading UC into the canister[10] Temporarily closing thecanister lid[11] Transferring the canister tothe lid closing area
[12] Closing the lid of thecanister[13] Confirming that the canister
lid is closed[14] Checking for contaminationon the back side of the canister

weight measuring system(Implementation of surface
contamination inspection)

Transfer cask
transfer systemtransfer
cask

Sealing cell[19] Placing the canister on the([15] Connecting the canister toweight measuring system
drying equipment*2)[20] Measuring the weight of the([16] Drying the canister *2)
canister[17] Connecting the canister to the [21] Confirming allocation of thegas injection system
canister[18] Injecting inert gas into the[22] Transferring the canister on tocanisterthe port*2 Implemented when drying cannot be performed indebris treatment cell

Transfer rack

Preparation cell[23] Loading the canister into the transfer cask[24] Opening the canister vent pipe[25] Closing the lid of the transfer cask (primary lid)[26] Injecting inert gas (inside the cavity)[27] Confirming that the lid of the transfer cask is closed (primarylid)[28] Closing the lid of the transfer cask (secondary lid)[29] Injecting inert gas (between the primary and secondary lids)[30] Confirming that the lid of the transfer cask is closed(secondary lid)[31] Confirming allocation of transfer cask[32] Loading the transfer cask on to the transfer truck

Within thepremises[35] Transferring
within the premises

Figure. Example of expanding the fuel debris retrieval process flow to the handling flow of the side-accessretrieval method©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.85

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (2/12)(i) Hydrogen measurement points for continuous monitoring
Study on the applicability (installation) of hydrogen densitometer to unit cans (UC), canisters, and transfer casks.
⇒ From the table below, it was decided that the densitometer can be applied (installed) to the transfer cask.
As it is only necessary to confirm that hydrogen is below the lower explosion limit, the existing general-purposehydrogen densitometer can be applied in continuous monitoring. Note that it is necessary to separately evaluate theeffect of installation of hydrogen densitometer on the strength of the transfer cask.
Table. Shape of each cask and amount generated

Target cask
Unit can(UC)

Structure

Mesh shape

Amountgenerated
Maximum

Signaltransmission

Continuous monitoringxx
Due to the structure of the cask,
hydrogen escapes from the cask,
making measurement impossible.

Unit canCanister

Sealed(presence of ventpipe with filter)

Many

x

x
Signal transmission during storage intransfer cask is difficult. Also, as large
number of canisters is expected,
installation on all canisters will be
expensive.

Transfer cask

SealedLess

OOCanisterTransfer cask

Figure. Image of transfer cask
allocation©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.86

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (3/12)(ii) Hydrogen measurement points for sequential monitoring (Process) (1/2)
The following were the necessary conditions used as the criteria for identifying hydrogen measurement
technology in sequential monitoring:✓ In a process where sequential monitoring is performed, the hydrogen concentration obtained fromthat process, and the hydrogen concentration in the cask near the fuel debris when the amount ofhydrogen generated per hour (calculated from the gas flow rate of that process) continues for 7days, should be 4 vol.% or less.
✓ It should not affect the throughput of fuel debris (Must be a hydrogen concentration measurement
technology that can measure hydrogen concentration without involving any new processes or taking
extra analysis time)
From the above,
Work processes that can replace the gas inside the canister or transfer cask, or processes
where there are no dynamic operations that could cause gas leakage within the process, wereselected as candidate processes.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.87

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (4/12)(ii) Hydrogen measurement points for sequential monitoring (Process) (2/2)
Select from・Fuel debris drying process
・ Inert gas injection process (canister)・ Inert gas injection process (transfer cask)
・ Combination of the above.

✓✓

Evaluate the required measurement range from the expected hydrogengeneration amount (rate) in each selected work process.
Study whether or not the required measurement range can be met withthe lower measurement limit of general-purpose hydrogen densitometeras the criteria.

Table. Study results on work processes for sequential monitoring
No.

Work process【8】

Drying of fuel debris

Handled item

Reason for decision

Decision

Unit can / Drying
chamber○

Since gas is replaced inside the drying chamber along with the drying treatment, it was
decided that the hydrogen concentration can be measured at that time.

－【16】 Drying of fuel debris

Canister○【18】

Canister○Canister

×

【24】

【26】

Inert gas injection
Opening of canister
vent pipe
Inert gas injection

Transfer container(inside the cavity)

Since gas is replaced inside the canister along with the drying treatment, it was decided thatthe hydrogen concentration can be measured at that time.
Since gas is replaced inside the canister along with the injection of inert gas, it was decided
that the hydrogen concentration can be measured at that time.
Since just opening the vent pipe does not completely replace the gas inside the canister, it
was decided that the measurement of hydrogen concentration is difficult.
As gas is replaced inside the transfer container along with the injection of inert gas into the○transfer container, it was decided that the hydrogen concentration can be measured at that
time.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.88

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (5/12)(iii) Result of selection of candidate hydrogen concentration measurement points for “continuous monitoring” and“sequential monitoring” (Process) (Summary)<Continuous
monitoring>Transfer cask

Reactorbuilding

Expandedbuilding

Lifting machine

Manipulator

Lifting machine

Debristreatment cellWorkmonitoring
cameraFuel debris
retrieval
devicePrimary lid fastening Secondary lid
system/fastening system/
Gas injection
Gas injection
system/system/leakage checking
leakage checking
facility
facility

Sealingcell

Canister lid
Gas injection
fastening systemsystemDryingCanisterapparatus

Port

Lifting machine

Preparation cell

TransfervehicleAccess tunnel

Fuel debris

UC transfer
systemInside thereactor[1] Cutting and processing the discharge[2] Visually checking the discharge[3] Collecting fuel debris by means of fueldebris retrieval device and filling it in UC[4] Draining the entrained water from fueldebris[5] Transporting UC to the access tunnel
outside the pedestal

Access tunnel[6] Transferring UC to the
expanded building *1*1 Besides UC, fuel debris blocks andstructures are transferred from inside thereactor through the access tunnel to the
expanded building. The transfer of UC isillustrated as a representative example.

<Sequential
monitoring>[8] Drying of fueldebris (UC)

Drying apparatus
Debristreatment cell[7] Loading UC into drying
equipment[8] Drying fuel debris

weight measuring transfer
cask
systemCanister transfer
system[9] Loading UC into the canister[10] Temporarily closing thecanister lid[11] Transferring the canister tothe lid closing area
[12] Closing the lid of thecanister[13] Confirming that the canister
lid is closed[14] Checking for contaminationon the back side of the canister<Sequential
monitoring>[16] Drying of fueldebris (canister)

Transfer cask
transfer system

Sealing cell[19] Placing the canister on the([15] Connecting the canister weight measuring system
to drying equipment*2)[20] Measuring the weight of thecanister([16] Drying the canister *2)[17] Connecting the canister to [21] Confirming allocation of thecanister
the gas injection system
Transferring the canister on to[18] Injecting inert gas into the [22]the port

canister*2 Implemented when drying cannot be performed indebris treatment cell

<Sequential
monitoring>[18] Inert gas injection(canister)

Transfer rack

Preparation cell[23] Loading the canister into the transfer cask[24] Opening the canister vent pipe[25] Closing the lid of the transfer cask (primary lid)[26] Injecting inert gas (inside the cavity)[27] Confirming that the lid of the transfer cask is closed(primary lid)[28] Closing the lid of the transfer cask (secondary lid)[29] Injecting inert gas (between the primary and secondarylids)[30] Confirming that the lid of the transfer cask is closed(secondary lid)[31] Confirming allocation of transfer cask[32] Loading the transfer cask on to the transfer truck

Within thepremises[35] Transferring
within the premises<Sequential monitoring>[26] Inert gas injection(transfer cask (inside thecavity))©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.89

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (6/12)(iv) Hydrogen generation amount (rate) expected in the hydrogen measurement process selected by sequential
monitoring (1/3)
The maximum value (Case I) and the minimum value (Case VI) of hydrogen generation amount (rate) from past evaluation
results, which are indicated in the table below, are used.
Table. Evaluation result of hydrogen generated per hour Note 1
Inner
収納缶内径
diameter
of
ケース
Case
canister(mm)(mm)

Amount of hydrogen
収納缶当たりの単位時間でHydrogen generation
水素発生速度を定義した

debris（wt.％）

model with defined
水素発生モデルhydrogengeneration rate

Energyエネルギー
absorption
吸収率
rate

generated per unit timeの水素発生量per storage can (m3 / h /（m3canister)/h/収納缶）デブリ中UOUO2 rate in2率

Ⅰ

220

26

TMI評価式
TMI evaluation
model

Total
全吸収
absorption

2.15×10-4

Ⅱ

220

26

TMI評価式
TMI evaluation
model

Transfer
輸送計算
calculation

3.83×10-5

Ⅲ

220

26

TMI評価式
TMI evaluation
model

Test
results
試験結果

1.50×10-6

Ⅳ

220

26

放射線分解モデル
Radiolysis model

Total
全吸収
absorption

1.09×10-4

Ⅴ

220

26

放射線分解モデル
Radiolysis modelTransfer
輸送計算
calculation

1.30×10-5

Ⅵ

220

26

Radiolysis model
放射線分解モデル

試験結果
Test
results

7.36×10-7

Note 1: Referenced from the FY 2018 study results of the Canister Project. The hydrogen generation amount will be reviewed in FY 2020 based on the
progress and outcome of the “Study of method to predict hydrogen generation”.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.90

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (7/12)(iv) Hydrogen generation amount (rate) expected in the hydrogen measurement process selected by sequential monitoring (2/3)
Based on the cask volume (see next slide) in each work process for the selected hydrogen concentration measurement, evaluate theallowable hydrogen generation rate at which the inside of the target cask (drying chamber, canister, transfer cask) is less than the lower
explosion limit concentration of 4 vol.% for 7 days.

Table. Evaluation results on the allowable hydrogen generation rate Note 5Work process No.

【8】

【16】

【8】

【16】

Operations in the

Drying process (heated vacuum

Drying process (warm airprocess

drying)heated drying)Work target
Number of canisters
inside the work target
Gas phase volume inwork target (m3)Drying chamber(unit can)
5

0.356

Note 1

Canister1

0.02

Note 2

Drying chamber(unit can)

5

0.356

Note 1【18】

Inert gas injection process

CanisterCanister

1

1

0.02

Note 2【26】

0.02

Note 2

Transport
container cavity

12

1.78

Note 3

Allowable hydrogengeneration rate Note 4

8.4×10-5

4.7×10-6

8.4×10-5

4.7×10-6

4.7×10-6

4.2×10-4

3(m /h)

Note 1: Set by assuming the dimensions of drying chamber referencing the FY 2018 study results of the Canister Project
Note 2: Referenced from the FY 2018 study results of the Canister Project
Note 3: Set by assuming the dimensions of transfer cask referencing the FY 2018 study results of the Canister Project
Note 4: Allowable hydrogen generation rate va = Volume of work target cask Vg x Lower explosion limit concentration 4 vol.% / storage duration168 h
Note 5: The drying chamber gas phase volume, etc., will be reviewed in FY 2020 based on the progress and results of the “Study on the basic specifications ofdrying apparatus”.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.91

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (8/12)(iv) Hydrogen generation amount (rate) expected in the hydrogen measurement process selected by sequential monitoring (3/3）
The assumed volumes of the drying chamber, canister, and transfer cask cavity are shown below.
The shapes and dimensions will be reviewed in FY 2020 based on the
progress and results of the "Study on the basic specifications of drying apparatus"
Secondary lid

1500

Volume between
the lids is 0.02 m3

Primary lid

Unit can

760

Unit can storage
compartment

Gas phase volume360

Fuel debris fillingrate is 30%

O.D. 210
I.D. 198

Drying chamber
Entire volume

840

1480 L356 L(a) Unit can drying chamber

Cavity 1.78 m3

Transfer cask

Housing volume

11.1 Lcask volume

1.80 m3

Volume of fuel debris

3.33 L

Cavity volume

1.78 m3

Gas phase volume

7.77 L

Volume between the lids

0.02 m3(b) Unit can(c) Transfer cask

Figure. Overview of the unit can drying chamber, unit can, and transfer cask••

The gas phase volume in the unit can drying chamber has been calculated by referencing the FY 2018 study results of the Canister Project. For trial calculation, the height of the unit canstorage compartment, which is not mentioned, is assumed to be equal to two unit cans with the external diameter of the unit can storage compartment being equal to the internal diameterof the drying chamber, and the trial calculation is carried out assuming that the height of the drying chamber is 10% the height of the compartment.
Referencing the FY 2018 study results of the Canister Project, the gas phase volume of the transfer cask is 1.80 m 3, and the volume between the primary and the secondary lids is set byreferring to the volume ratio of the cask capacity used for both transport and storage.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.92

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (9/12)(v) Decision on the required measurement range and the applicability of general-purpose hydrogen densitometer in sequential
monitoring (1/4)
Hydrogen concentration was calculated on a trial basis after 7 days inside the target (drying chamber, canister, transfer cask) by assuming
the hydrogen generation rate cases I and VI, and that hydrogen is continuously generated at the allowable hydrogen generation rate (Refer tonext slide).
The applicability of the existing hydrogen densitometers was determined from the concentration of hydrogen at the allowable hydrogengeneration rate based on the following criteria.
[Criteria]
Concentration of hydrogen at the allowable hydrogen generation rate - 100 ppm or more:  (General-purpose hydrogen densitometercan be used)
Concentration of hydrogen at the allowable hydrogen generation rate - 1 to 100 ppm:
 (High-sensitivity hydrogen densitometeris necessary)
Concentration of hydrogen at the allowable hydrogen generation rate - Less than 1 ppm:
 (Difficult to handle with the existing hydrogendensitometers)[Results]
・Drying process✓ Warm air heated drying: The hydrogen concentration is less than 1 ppm and is difficult to handle with the existing hydrogen densitometers.
✓ Heated vacuum drying: The hydrogen concentration is between 1 to 100 ppm and a high-sensitivity hydrogen densitometer is necessary.
・Inert gas injection process✓ The hydrogen concentration is 100 ppm or more at the allowable hydrogen generation rate in both canister and transfer cask
and a general-purpose hydrogen densitometer can be used.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.93

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (10/12)(v) Decision on the required measurement range and the applicability of general-purpose hydrogen densitometer in sequential
monitoring (2/4)
Table. Result of evaluation of hydrogen concentration Note 6
Process
No.

Process

Work target

Gas replacementrate(m3/ｈ)
@0℃

[8]
[16]
[8]
[16]
[18]
[26]

Drying of fuel debris(Heated vacuum drying)
Drying of fuel debris(Heated vacuum drying)

Drying of fuel debris(Warm air heated drying)
Drying of fuel debris(Warm air heated drying)
Inert gas injection

Inert gas injection(Inside the cavity)

100 kPa
Note 1

Amount of hydrogen generation per unit
time (m3/h)

Hydrogen concentration (ppm) Note 5

Decision

Case I

Case VI

Allowablehydrogengeneration rate

1.07E-03

3.68E-06

8.48E-05

3.6E+02

1.2E+00

2.9E+01△

Case I

Case VI

Allowablehydrogengeneration rate

Drying chamber

2.95E+00

Canister

5.90E-01

Note 2

2.15E-04

7.36E-07

4.76E-06

3.6E+02

1.2E+00

8.1E+00△

Drying chamber

1.22E+03

Note 3

1.07E-03

3.68E-06

8.48E-05

8.8E-01

3.0E-03

7.0E-02x

Canister

2.43E+02

Notes 2,3

2.15E-04

7.36E-07

4.76E-06

8.8E-01

3.0E-032.0E-02x

2.15E-04

7.36E-07

4.76E-06

1.1E+04

3.7E+01

2.4E+02

O

2.58E-03

8.84E-06

4.24E-04

1.5E+03

5.0E+00

2.4E+02

O

Canister

1.98E-02

Transfer
cask

1.76E+00

Note 4Note 4Note 1: Referencing the FY 2018 study results of the Canister Project, the gas replacement rate is calculated on a trial basis for 0℃ 100 kPa.
Note 2: The gas replacement rate of the drying chamber in Note 1 is proportional to the number of unit can storage compartments, and the gas replacement rate of one compartment is equivalent to the gas replacement rate of a canister.
Note 3: Referencing the FY 2018 study results of the Canister Project, the gas replacement rate is calculated on a trial basis for 0℃ 100 kPa assuming that a vacuum pump with specifications similar to the one used for heated vacuum drying is also
used for warm air heated drying.
Note 4: Flow rate when the inside of the cask is vacuumed once for an hour before injecting the inert gas.
Note 5: Hydrogen concentration (ppm) = Amount of hydrogen generation per unit time (m3/h) / Gas replacement rate (m3/h) x 106
Note 6: The gas replacement rate will be reviewed in FY 2020 based on the progress and results of the "Study on method to predict hydrogen generation" and "Study on the basic specifications of drying apparatus“.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.94

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (11/12)(v) Decision on the required measurement range and the applicability of general-purpose hydrogen densitometer in sequential

monitoring (3/4)
The following work processes were selected as the first candidate assuming that the application of a general-purpose hydrogendensitometer is possible from the viewpoint of the required concentration range. As there is almost no oxygen in the measured atmosphere
due to the injection of inert gas, the hot-wire semiconductor type, etc., which does not need oxygen, is considered as the main target
for investigation.
Table. Evaluation results of the inert gas injection process
Work processes[18] Inert gas injection(Canister)[26] Inert gas injection(Inside the transfer cask
cavity)Assumed atmospheric conditions

Applicability criteria
Measurement in flow field is possible

Measurement target Note1

Gas discharged during replacement/ pump exhaust gas

Atmosphere

Room temperature Note2, atmospheric pressure

Operating temperature 10 to 40℃
Operation at atmospheric pressure

Gas element

Nitrogen/ Steam/ Hydrogen

240 ppm is detected in the said atmosphere

Measurement target Note1

Gas discharged during replacement/ pump exhaust gas

Atmosphere

Room temperature Note2, about atmospheric pressure

Operating temperature 10 to 40℃
Operation at atmospheric pressure

Gas element

Nitrogen/ Steam/ Hydrogen

240 ppm is detected in the said atmosphere

Measurement in flow field is possible

Note 1: The method of injecting the inert gas is unclear, so the assumed method is also described.
Note 2: About 10 to 40℃©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.95

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)a. Study on required technical specifications and applicability criteria (FY 2019) (12/12)(v) Decision on the required measurement range and the applicability of general-purpose hydrogen densitometer in sequential
monitoring (4/4)
The following work processes were selected as the second candidate assuming that the application of a high-sensitivity hydrogendensitometer is possible from the viewpoint of the required concentration range. The presence of an applicable high-sensitivity hydrogendensitometer was investigated based on the atmospheric conditions presumed in the drying treatment (heated vacuum drying).

Table. Evaluation results of the drying process (Heated vacuum drying)Work processes[8] Drying of fuel debris(Heated vacuum drying - Drying
chamber)[16] Drying of fuel debris(Heated vacuum drying - Canister)

Assumed atmospheric conditions

Applicability criteria
Measurement in flow field is possible

Measurement target

Pump exhaust gas

Atmosphere

Room temperature Note 1, below the atmosphericpressure

Operating temperature 10 to 40℃
Operation below the atmospheric pressure

Gas element

Steam/ Nitrogen/ Hydrogen28 ppm is detected in the said atmosphere
Measurement is possible around the dew point

Measurement target

Pump exhaust gas

Atmosphere

Room temperature Note 1, below the atmosphericpressure

Operating temperature 10 to 40℃
Operation below the atmospheric pressure

Gas element

Steam/ Nitrogen/ Hydrogen8.1 ppm is detected in the said atmosphere
Measurement is possible around the dew point

Measurement in flow field is possible

Note 1: 10 to 40℃ is assumed©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.96

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)b. Investigation of the hydrogen concentration measurement technology (FY 2019) (1/4)

Based on the results organized in section a., the technologies to measure hydrogen concentration were investigated extensively with thefocus on the existing technologies.
In addition, the selected targets (casks and work processes) for measuring the hydrogen concentration were classified into the following A, B,
and C types from the viewpoint of assumed atmosphere and assumed range of hydrogen concentration, and the hydrogen concentration
measurement technology applicable to each condition was selected.
Table. Classification and assumed environment for hydrogen concentration measurement points (processes)
Classif
icationMonitoring
methodSelected hydrogen concentration
measurement points (processes)

A

Continuous
monitoring

Transfer cask

B

Sequential
monitoring

Drying process (Heated vacuum drying)
C－1 Drying chamber
C－2 CanisterC

Sequential
monitoring

Inert gas injection process
B－1 Canister
B－2 Transfer cask cavity

Assumed atmosphere

Assumed rangeof hydrogenconcentration

Measurement methods

Room temperature andatmospheric pressure
Nitrogen/ Steam/ Hydrogen0 to 4 vol.%By installing a sensor in the transfer
cask

0 to 100 ppm

Gas sampling from the measurementtarget by means of a pumpOrby installing a sensor in the piping

100 ppm or more

Gas sampling from the measurementtarget by means of a pumpOrby installing a sensor in the piping

Room temperature andbelow the atmosphericpressure
Nitrogen/ Steam/ Hydrogen
Room temperature andaround the atmosphericpressure
Nitrogen/ Steam/ Hydrogen

A: Continuous monitoring in the transfer cask, B: Sequential monitoring during the drying treatment,
C: Sequential monitoring during inert gas injection©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.97

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)b. Investigation of the hydrogen concentration measurement technology (FY2019) (2/4)
Table. Investigation results of hydrogen concentration measurement technology (Overview) (1/2)
Sensor principle

1. Heat conduction type2. Contact combustion
type

3. Hot-wiresemiconductor type

4. New ceramic type

5. Semiconductor typeMeasuring range andaccuracy

0 to 100 vol%0 to 100 LEL

0 to 2000 ppm

ppm to 100% LEL

0 to 200 ppm

About  2% FS

About  5% FS

A

Installed in transfer cask

Installed in transfer cask

Installed in transfer cask

Installed in transfer cask

Installed in transfer cask

B

Installed in the exhaust gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas lineC

Installed in the exhaust gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas line

Installed in the exhaust
gas line

Applicable to continuous monitoring

Oxygen is needed in
the gasOxygen is needed in
the gasOxygen is needed in
the gasVerification of durability
in the usage
environment required

Installation method

Comprehensive
evaluation

A











B



















C

 (Prior gas separation)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.98

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)b. Investigation of the hydrogen concentration measurement technology (FY2019) (3/4)
Table. Investigation results of hydrogen concentration measurement technology (Overview) (2/2)
Sensor principle

6. Light wave interference type

7. Non-dispersed infrared ray
type

8. Difference absorption
spectroscopy (DOAS)

9. Gaschromatography type

10. Proton conductor(proton conductive
solid electrolyte)

Measuring range andaccuracy

0 to 100 vol%About  1% FS to  4% FS

Several hundred ppm toseveral tens of vol%1000 ppm to several vol%0 to 100 vol%About  10% FS

0 to 100 vol%1%  0.1%
10%  1%
100%  3%

A

Installed near the cask tocollect gas

Installed near the cask tocollect and analyze gas

Installed in transfer cask
(light source and detector)

Installed near the cask
to collect and analyzegasInstalled in transfer
cask

B

Installed near the exhaustline to collect gas

Installed near the exhaust line
to collect gas

Installed in the exhaust line

Installed near theexhaust line to collectgas

Installed in the exhaustline

C

Installed near the exhaustline to collect gas

Installed near the exhaust line
to collect gas

Installed in the exhaust line

Installed near theexhaust line to collectgas

Installed in the exhaustline

Low concentration anddepends on CCD
resolution: Difficult

Interference gas filter
regeneration required

Adjustment of optical path
length and filter for dust, etc.

Multiplexing forcontinuous monitoring

The temperature of thepart to be measured ishigh. Heat shockcountermeasuresrequiredInstallation method

Comprehensive
evaluation

A







 (Suction pumprequired) (Damagecountermeasuresrequired)

B







C








(Sensitization device
required)(Concentration
measurement
required)©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.99

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)b. Investigation of the hydrogen concentration measurement technology (FY 2019) (4/4)

As a result of investigating the technologies to measure hydrogen concentration, the applicable hydrogen concentration
measurement technologies were evaluated under the conditions A, B, and C and the following candidates wereselected:
A Continuous monitoring: Heat conduction type

B Sequential monitoring during the drying process (heated vacuum drying): Gas chromatography type, Or
Proton conductor
C

Sequential monitoring during the inert gas injection process: Gas chromatography type, Or Proton
conductor©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.100

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology③ Implementation items and results (Estimated and actual)c. Feedback on progress and results of development of related technologies (FY 2020 [Scheduled])
In FY 2020, feedback on the progress and results of the "Development of technology for transfer of fuel debris" and the"Study of drying systems" conducted under the "Development of drying technology and systems“, which are being
pursued in parallel under this Project, will be provided in the Annual Research Report 2019.
④ Contribution of the results to the areas where they can be reflected
The studied hydrogen concentration measurement technologies should contribute to ensuring the safety of a canisterduring transfer.
Moreover, the technologies might also be able to contribute to the presumptions about the fuel debris drying states.
⑤ Analysis from the perspective of site application
Based on the currently assumed atmospheric conditions at the hydrogen concentration measurement points in 1F, ahydrogen concentration measurement technology suitable to these atmospheric conditions has been selected, andalthough it is necessary to address the issues mentioned on the following slide, the technology is believed to be
applicable.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.101

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology⑥ Issues
The hydrogen concentration measurement technology selected at present has the following issues in actual application:
A Continuous monitoring inside the transfer cask
✓There is no issue specifically related to the measurement technology. It is, however, necessary to study the impactof the installation of a sensor on the structural strength of the transfer cask.
B Sequential monitoring during the drying process (heated vacuum drying)✓Gas sampling is necessary for gas chromatography.
⇒A gas sampling line (for the facility) must be connected to the exhaust line of the drying facility (after the filter).
It must be installed in a shielded, uncontaminated area that can be directly operated by the workers.
Measures to improve the sensitivity of the measuring devices are necessary.
✓In the case of the proton conductor, the verification of sensitivity in low concentrations is essential.
C Sequential monitoring during the inert gas injection process✓ Gas sampling is necessary for gas chromatography.
⇒ A gas sampling line (for the facility) must be connected to the exhaust side of the inert gas injection line.
It must be installed in a shielded, uncontaminated area that can be directly operated by the workers.
✓No specific requirements in the case of the proton conductor.
As several of the site conditions of the drying apparatus (shape, flow velocity, pressure etc.) are undetermined, it isnecessary to verify and study the need to provide feedback to the selected hydrogen concentration measurement
technology as and when the site conditions become clear.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology

No.102⑦ Level of achievement in light of the goal
The selection of candidate hydrogen concentration measurement technology, applicable to canisters, was completed as
per the goal.
SummaryIn FY2019, the required technical specifications and applicability criteria for hydrogen concentration measurement werestudied and set up. Furthermore, technical investigations were conducted based on these results, and the targets forcontinuous monitoring and sequential monitoring (casks and work processes) and the candidates for the applicablehydrogen concentration measurement technology were selected as follows:[Continuous monitoring]Target cask: Transfer cask
Candidate technology: Heat conduction type
[Sequential monitoring]Target work processes: Inert gas injection process (first candidate), drying process (heated vacuum
drying) (second candidate)
Candidate technology: Gas chromatography type or proton conductor
In FY 2020, based on the estimations about the amount of hydrogen generated and the progress and results of the study
on the drying apparatus, the required technical specifications will be reviewed as appropriate, and if necessary, thecandidate technologies will be re-selected.
©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.103

6.4 Development of drying technology and systems(2) Study on hydrogen concentration measurement technology⑧Future plans
Table. Schedule for study on hydrogen concentration measurement technology
FY 2019

Items

First half

Second half

FY 2020First half

Second half

Remarks

Study on hydrogen concentration measurement
technology
a. Study on required technical specifications andapplicability criteriab. Investigation of the hydrogen concentration
measurement technology
c. Feedback on progress and results ofdevelopment of related technologies

Implemented if necessary: Plan: Actual©International Research Institute for Nuclear Decommissioning6. Implementation Details
6.5 Evaluation Summary

No.104① Purpose and Goals

To review the implementation items of the related projects and reflect the implementation items mentioned in Sections 6.1 to 6.4. The
goal is to also participate and cooperate, based on requests, in the investigation of technologies for sorting the objects retrieved frominside the PCV into fuel debris and radioactive wastes, which will be implemented under the Project of Further Increasing the Scale of
Fuel Debris Retrieval, as a part of the development of related technologies.

② Implementation items and results (Estimated and actual)a. Investigation of sorting technology (Implemented as required on the basis of requests from the Project ofFurther Increasing the Scale of Fuel Debris Retrieval)Based on the request from the Project of Further Increasing the Scale of Fuel Debris Retrieval, the requirement for sorting waspresented from the viewpoint of fuel debris storage. The Project of Further Increasing the Scale of Fuel Debris Retrieval consolidated
the required details as investigation results on the sorting requirements from other related projects.

b. Evaluation summary (Implemented at the end of FY 2019 and FY 2020)

The study of canister specifications and structures was conducted under the development of technology for containing of fuel debris;the study on method to predict amount of hydrogen generation and the study on hydrogen measures was conducted under thedevelopment of technology for transfer of fuel debris; and the study on the basic specifications of drying apparatus and the study onhydrogen concentration measurement technology was conducted under the development of drying technology and systems. In future,
the latest findings will be incorporated to advance research and development, and studies will continue to be conducted in FY 2020 as
well.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.105

6.5 Evaluation Summary③ Contribution of the results to the areas where they can be reflected
The implementation results will be reflected in the study items of this subsidy project.
④ Analysis from the perspective of site application
The investigation of sorting technologies undertaken by the Project of Further Increasing the Scale of Fuel Debris
Retrieval is conducted to reduce the amount of fuel debris, which is more difficult to handle as compared toradioactive wastes, from the viewpoint of criticality safety control, and the participation in and cooperation with theCanister Project is beneficial.
The summary of the evaluation clarifies the outcome of this subsidy project and is beneficial.
⑤ Issues
There are no issues in the execution of the present plan.
⑥ Level of achievement in light of the goal
It is expected that the defined results will be obtained by conducting joint meetings with related projects,
cooperating in the investigation of sorting technologies, and by summarizing the evaluation of individual
implementation items at the end of each fiscal year.

©International Research Institute for Nuclear Decommissioning6. Implementation Details

No.106

6.5 Evaluation Summary⑦ Future plans

Table. Schedule of study on evaluation summary
FY 2019

Items

First half

Second half

FY 2020First half

Remarks

Second half

Evaluation summarya. Investigation of sorting technology

Joint meetings with related projects

Criteria and advantages of sorting
were presented to the Project ofFurther Increasing the Scale of
Fuel Debris Retrieval from theviewpoint of efficiency of transfer
and storageb. Evaluation summary
Evaluation summary: PlanEvaluation summary: Actual©International Research Institute for Nuclear Decommissioning7. Overall Summary

No.107<Outcomes in FY 2019>• For the Development of Technology for Containing of Fuel Debris, a plan was drafted for the test items to be
implemented during the structural verification test of the canister, and the canister (canister for testing) was designed
based on the safety requirements of the canister. Moreover, material procurement etc. was carried out for the
prototyping of the canister (canister for testing).

• For the Development of Technology for Transfer of Fuel Debris, the study items and implementation details required forsetting the transfer condition plans were studied by investigating domestic and overseas findings and by hearing expert
opinions on the methods to predict hydrogen generation. Moreover, the flow inside the canister was studied as acatalyst-based hydrogen measure. In addition, a study of methods to acquire the performance of a catalyst is underway.
• For the Development of Drying Technology and Systems, the functional requirements of the drying apparatus,
investigation on existing technologies, and planning for element tests required for the conceptual design of the drying
apparatus were studied, and studies for the tests are underway. Moreover, upon studying and specifying the required
technical specifications and applicability criteria for hydrogen concentration measurements, a technical investigation
was carried out and the candidate hydrogen concentration measurement technologies were selected.
• The advantages and conditions effective in improving the efficiency of transfer and storage with respect to the sortingof fuel debris and radioactive waste, were presented to the Project of Further Increasing the Scale of Fuel Debris
Retrieval.
• As the subsidy project continues to make progress, the effective findings will be incorporated, and studies will continue
to be conducted in FY 2020 as well.

©International Research Institute for Nuclear Decommissioning7. Overall Summary

No.108<Plan for FY 2020>• The real-size canister (canister for testing) to be used in the structural verification test will be prototyped, and thestructural verification test will be carried out to verify the maintenance of the safety functions (criticality prevention,
confinement). Moreover, the structural analysis will be compared and evaluated with the results of the structuralverification test, and the applicability of the analysis methods will be verified.
• The study of methods to predict hydrogen generation will proceed wherein the amount of hydrogen generated inside
the canisters will be presumed on the basis of the results of hydrogen generation tests implemented as needed, andtransfer condition plans to enable safe transfer will be studied. Moreover, the placement of the catalyst will be studied
based on the evaluation of flow inside the canister by acquiring data on catalyst performance.

• The drying behavior data will be collected by planning a drying test with real-size test equipment based on the conceptof drying apparatus, and in addition, the basic specifications plan of the drying apparatus for 1F fuel debris will be
proposed by studying about maintenance and handling inside the contaminated areas.
With reference to the hydrogen concentration measurement technology, based on the estimations about the amount ofhydrogen generated and the progress and results of the study on the drying apparatus, the required technicalspecifications will be reviewed as appropriate, and if necessary, the candidate technologies will be re-selected.
• If there are any fresh requests, etc., from the Project of Further Increasing the Scale of Fuel Debris Retrieval,pertaining to the sorting of fuel debris and radioactive wastes, those requests will be dealt with.

©International Research Institute for Nuclear Decommissioning[Supplement-1] Basic conditions of development of the canister (1/4)

No.109The canister specifications have been set mainly from the viewpoint of safety evaluation based on the information on the fuel debris
properties obtained so far, the requirements from the fuel debris retrieval methods, and the information offered by the Fuel Debris
Characterization Project, etc. As these conditions also contain assumptions, it is necessary to verify and review them on the basis of theoutcomes of the Fuel Debris Characterization Project and the Project of Further Increasing the Scale of Fuel Debris Retrieval.
[Fuel debris properties]• Fuel debris composition (Excluding MCCI products):
The components assumed to be currently present inside the RPV/ PCV (uranium dioxide (including FP associated with irradiation),zirconium alloy, stainless steel, low-alloy steel, nickel-based alloy, concrete, and B4C)
• Salinity: About 100 ppm max.
The salinity of stagnant water was set conservatively to 10 to 20 ppm. Note that in the corrosion evaluation, it was realistically set toabout 3 ppm based on the actual results of the water inside the reactor.
• Zirconium: Small amounts of residue in metallic state

To consider the possibility of fire.
• Physical properties of MCCI products: Concrete mixed with the above-mentioned fuel debris
It is believed that the heat of fuel debris caused reactions such as loss of water of crystallization and generation of gas, but theconcrete components were assumed to be physically turbid in the evaluation.
• Stability of fuel debris: Stable at -20 to 300℃ (nitrogen atmosphere)
It was assumed that there is no occurrence of behaviors that would significantly affect safety, such as significant volume fluctuations
due to vaporization of the elements contained in the fuel debris, etc., or the release of large amounts of corrosive substances andradioactive gases, etc.
• Shape: Block-like, particulate, and powdered solids• Rust inhibitor/ neutron absorber: Sodium pentaborate
It is assumed that adoption of sodium pentaborate is being studied at the present time. Note that it was assumed that the insoluble
neutron shield material will be studied when the specific details are determined.
©International Research Institute for Nuclear Decommissioning[Supplement-1] Basic conditions of development of the canister (2/4)

No.110For setting the shape of the canister, the following conditions were assumed based on the Project of Further
Increasing the Scale of Fuel Debris Retrieval and the opinions of experts.
[Fuel debris containment methods]• Block-like and particulate fuel debris: To be collected and stored by gripping, scooping etc.
• Canister dimensions: Internal diameter is 220 mm and 400 mm and total length is 1000 mm
The canister internal diameter of 220 mm and 400 mm was assumed on the basis of studies conducted until
FY 2018. The total length of the canister was set based on the approx. 1 m assumed by the Project ofFurther Increasing the Scale of Fuel Debris Retrieval.
• Powdered fuel debris: Collected in a mesh-like drainable unit can and each unit can is stored in the fuel debris
canisterIn the general water treatment, a metal strainer-shaped filter is used, and it is assumed that a unit can withthe same structure is used for the collection of powdered fuel debris by a pump. The unit can is assumed to
be of a size that can be stored inside a canister, and the unit can is made of thermally stable material suchas stainless steel and sintered stainless steel net. Since the shape of the unit can is being studied under the
Project of Further Increasing the Scale of Fuel Debris Retrieval, a unit can with a net structure having amesh size of 0.1 mm has been assumed at present in light of the fact that the said project is targeting thecollection of fuel debris up to size Φ0.1 mm.
• Storage location: Storage work is non-flooding. Work is carried out in a space with a boundary such as a hot cell.
• Procedures from containing to carrying out the fuel debris: The fuel debris retrieval-related work is bifurcated into
half day for cutting work and half day for fuel debris collection, containment in canisters, and carrying out work.
[Fuel debris transfer methods]• Transfer method: Casks
As there are precedents in TMI-2 or proven track record with spent nuclear fuel.
• Requirement of filling water in the transfer cask: The restrictive conditions for the transfer casks have been
assumed in this project on the basis of technical studies.

©International Research Institute for Nuclear Decommissioning[Supplement-1] Basic conditions of development of the canister (3/4)

No.111

The following conditions were assumed based on discussions with experts:[Storage of fuel debris]• Storage method
Wet storage: Optional as of now
Wet storage utilizing the existing 1F pool is optional as of now because the expected profit issmall and the method is not highly reasonable considering the converting cost, period, level oftechnical difficulty, and so on.
Dry storage: Basic storage method
The dry storage method is considered as the basic storage method because dry storage isconsidered to be a reasonable method for storage of spent nuclear fuel in terms of operation
management, such as maintenance in addition to safety, and it is considered to be advantageous
for fuel debris as well. Note that concrete casks, etc., are also used overseas for the dry storageof spent nuclear fuel, however, since the requirements for stored items are the same, storage inmetal casks with a track record in Japan shall be used as a typical example.
• Drying of fuel debris: Minuscule amount of water content remains
The studies on transfer and storage assumed that some water remained in the fuel debris evenafter conservative drying.
• Storage period of fuel debris using canisters: 50 years
The storage period of fuel debris using canisters was set to 50 years to cover the 30-year period
until the final treatment or disposal decision of fuel debris specified in the roadmap. Note that the
spent nuclear fuel dry storage facility maintains data on long-term integrity assuming a 50-year
storage period and 10 years for carrying in and out, and this data is available for reference.
©International Research Institute for Nuclear Decommissioning[Supplement-1] Basic conditions of development of the canister (4/4)

No.112

During the development of the canister, the handling flow on the next slide was assumed and division of functions was set
tentatively to ensure reasonable safety.
Division of safety functions
Safety functions

Design goals

Subcriticality

To maintain subcriticality

CoolingHeat removal

To prevent the impact on
physical propertiesof canisters, fuel debris,
etc.

Confinement

To prevent exposure ofworkers and public

Canister

O

-

O

Other
equipment
O・The subcriticality of a single canister is maintained by the geometrical shape (inner diameter) of thecanister. (Refilling of fuel debris is a large-scale process and is unreasonable)
・The subcriticality of an array of canisters is maintained by using other equipment (e.g. ensuring anappropriate distance between the canisters in the temporary storage rack).

O・Since the calorific value is less than that of the same level of spent nuclear fuel and the canistercan be cooled by static natural cooling, no special heat removal device is installed in the canister ortransfer cask.
・ The fuel debris is handled at a temperature that is lower than the upper limit for the fuel debris
temperature that does not inhibit safety (such as generation of toxic gases), including during thedrying process of fuel debris.

O・Since the canister is provided with an outlet to prevent hydrogen retention, a filter is installed in theoutlet in order to prevent the spread of contamination during actual operations. The canister andother facilities (storage facilities, transfer casks) should be able to carry out the confinement
function (or control the release of gases).

・Adding a shielding function to the canister increases the weight, which leads to an increase in thesize of the handling equipment and a decrease in storage efficiency. Since there is a proven recordof the same idea in TMI-2 and no major disadvantages were found in the assumed handling flow, theshielding function is not added to the canister and it is secured using other equipment (transfer cask,building).

Confinement

Other(Maintaining the
shutdown,
cooling andconfinement
functions)

Approach

Shielding

To prevent exposure ofworkers and public-

O

Structure

To achieve the structural
strength for maintaining
the safety functions

O

O

Material
integrity

To maintain the
structural strength

O

O

・The canister should have the necessary strength against postulated abnormal events while taking
into account streamlining of canister handling equipment, etc.
・Other equipment is used to ease the load conditions and corrosion conditions on the canister.

HydrogenTo prevent the explosionof hydrogen generated
by the radiolysis of waterO(Catalyst)

O・ During transfer between buildings (transport at the site), hydrogen countermeasures (catalyst,
operation management, etc.) should be undertaken assuming that hydrogen cannot be released
outside the transfer cask.
・ Since the space inside the canister is small and the hydrogen concentration rises, scavenging, etc.,
is performed using another equipment as a structure that can release hydrogen outside the canister(outlet to prevent hydrogen retention).

Fire prevention

To prevent fire caused byresidual zirconium-

O・ The inside of the canister or cell has an inert gas atmosphere to prevent ignition.

#: The division of safety functions may be reviewed because it is affected by the fuel debris properties and canister handling procedures.
©International Research Institute for Nuclear Decommissioning[Supplement-2] Design conditions of the canister for safety
requirements (1/3)

No.113

Table. Setting up design conditions of the canister for safety requirements (1/3)
SafetySafety function

functionsrequirements

Confinement

Confinement ofradioactive
materials

Canister requirements

Canister design conditions
Lid

Main Body

Prevention of leakage of As a measure to prevent the spread of contamination, The main body of the canister should have a structureradioactive materials fromthe structure should be such that fuel debris pieces

whereby the airtightness is maintained by a welded

inside the canister except via(solid)Note 1 passing through the gaps between the

structure, etc.

the vent mechanism.

canister body and lid are not released. Note thatliquid and gas confinement should be ensured by acell or transfer cask and not by the canister.
 The integrity of the seal should be maintained-

against aging due to the corrosion and radiation
expected during the transfer period.

 The integrity of the strength members should be maintained against aging due to the corrosion and radiation
expected during the transfer and storage periods.
Appropriate reduction in As a measure to prevent the spread of contamination,

leakage of radioactive

the structure should be such that the release of fuelmaterials associated with thedebris pieces (solid)Note 1 passing through the ventrelease of hydrogen gas frommechanism is suppressed.

-

the vent mechanism.
Appropriate reduction in The structure should be such that serious damage such

 The main body of the canister should have aleakage of radioactive

as detachment or breakage of the canister lid does not

structure that does not incur serious damage suchmaterials even in the event of

occur even if it receives an impact load from dropping or

as breakage even if it receives an impact load fromoccurrence of dropping

tumbling, and from the perspective of preventing the

dropping or tumbling, and from the perspective of

events that must be expected

spread of contamination, the structure should be suchpreventing the spread of contamination, thethat fuel debris pieces (solid)Note 1 passing through thestructure should be such that fuel debris pieces

gaps between the canister body and lid are not released.

(solid)Note 1, liquids, and gases are not released.

Note that liquid and gas confinement should be ensured
by a cell or transfer cask and not by the canister.
Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris(collected by suction, etc.): 0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-2] Design conditions of the canister for safety requirements No.114(2/3)
Table. Setting up design conditions of the canister for safety requirements (2/3)

Safetyfunctions
Criticality
prevention

HeatremovalSafetyfunctionrequirements
Prevention of
additional
nuclearfissionreaction

Prevention ofabnormaloverheating

Canister requirements
The shape should be able
to prevent criticality.

Canister design conditions

Lid

Main Body-

 The structure should be such that the
subcriticality of fuel debris is maintained by thegeometric shape of the inner diameter of thecanister.

- In the case of an array of canisters, thesubcriticality should be maintained by retaining
the array dimensions using other equipment(metal cask basket, etc.).

 The structure should be such that serious
damage such as detachment or breakage of thecanister lid does not occur even if it receives animpact load from dropping or tumbling, andfrom the perspective of maintaining
subcriticality, the structure should be such that
fuel debris pieces (solid)Note 1 passing throughthe gaps between the canister body and lid are
not released. Note that liquid and gas
confinement should be ensured by a cell ortransfer cask and not by the canister.

⑪ The structure should be such that the innerdiameter of the canister can maintain thegeometric shape that can maintain subcriticality
even if it receives an impact load from droppingor tumbling. The structure of the main body of thecanister should be such that it does not incur
serious damage such as breakage, and from theperspective of maintaining subcriticality, thestructure should be such that fuel debris pieces(solid)Note 1, liquids, and gases are not released.

The canister should be
able to maintain thetemperature of the fueldebris at the appropriate
level.

⑫ The structure should be such that integrity is maintained using the natural heat dissipation of thecanister.

The design should be suchthat the internal
temperature of the canister
does not exceed thepermissible temperatureeven if there is an
expected rise in thebuilding temperature.

⑬ The internal temperature of the canister should not exceed the permissible temperature even in theevent of loss of external power or other events that must be expected.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris (collected by suction, etc.): 0.1 mm to 10 mm, blockdebris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-2] Design conditions of the canister for safety
requirements (3/3)

No.115

Table. Setting up design conditions of the canister for safety requirements (3/3)
Canister design conditions

Safetyfunctions

Safety function
requirements

Canisterrequirements

Shielding

Prevention ofexcessive exposure
or internal exposuredue to radiation(No requirements)⑭ The shielding function should be ensured by the building or transfer cask, etc., and not by thecanister.

Preventionof hydrogen
explosion

Response to fires
and explosions
caused byflammable gas
generated due toradiolysis of water(response tohazards)

The design should
be such that theconcentration ofhydrogen inside thecanister can be
maintained below
the design value.

⑮ The structure should be such that hydrogen generated by radiolysis of water due to fuel debris isappropriately discharged outside the canister.

Preventionof dust fires

Response to fires
caused by thereaction of oxygenand metal dust
generated during
debris retrieval andcutting (response tohazards)

Conduct studies on
measures to prevent
ignition due to thefine zirconium
powder expected infuel debris.

⑰ The inside of the canister or cell should have an inert gas atmosphere to prevent ignition.

Lid

Main Body⑯ The structure should be such that the hydrogen generation by the radiolysis of water due to fueldebris is suppressed.

©International Research Institute for Nuclear Decommissioning[Supplement-3] Design conditions of the canister for handlingrequirements

No.116

Table. Setting up design conditions of the canister for handling requirements
Handling
functionrequirements
Handleability

Canister design conditions

Canister requirements

Lid

Main body

The lid can be fastened and opened byremote operation.

(a) The lid structure should allow lid fastening
and opening by remote operation.

－

From the perspective of workability, thelid can be fastened and opened by asimple operation.

(b) The lid structure should allow lid
fastening and opening by simple operations,such as turning the lid.

－

The handling related to other operations
such as fuel debris containing, transfer,and storage should be possible.

(c) The canister should have a liftable structure.
(d) The structure should enable connection with the (drying facility and) inert gas injection
facility, etc.
(e) The structure should allow alignment of the lid and the bottom structure of the canister
so that stacking is possible during transfer and storage.

(f) The size and structure should take into account the workability in the handling flow ofcanisters.

Reactor
原子炉建屋
building
Expanded
増設建屋
building

Manipulator
マニピュレータ

揚重機machine
Lifting

揚重機
Lifting
machineDebris
デブリ処理セルtreatment cell

Fueldebris
燃料デブリ
retrieval
取り出し装置device

RPV
Port
ポート
U
C

燃料デブリ
Fuel
debris

PCV

揚重機
Lifting
machineSecondarylid
二次蓋蓋締めfastening system/
装置/
Gas
injectionsystem/
ガス注入設備/leakage checking
漏洩確認設備facility

Sealing
封缶セル
cell

Gas injection
収納缶 lid
Canistersystemfasteningsystem
ガス注入設備
蓋締め設備
DryingCanister
収納缶
乾燥設備
apparatus

仕立てセル cell
Preparation

Transfer
移送車
vehicleAccess tunnel
アクセストンネル

UC transfer
UC移動設備systemDryingapparatus
乾燥設備

Canistertransfer
収納缶移動設備
system

移送容器
weight measuringsystem transfer
重量測定設備cask

Transfer cask
移送容器移動設備
transfer system

Transferrack
移送架台

Figure. Canister handling flow plan (Example of side access)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (1/10)

No.117

Table. Design conditions and specifications for the canister (plan) (1/10)
Part

Safety functions
andfunctional requirements

Lid

Confinement

Design conditions⑥

The structure should be such that serious damage
such as detachment or breakage of the canister lid
does not occur even if it receives an impact load fromdropping or tumbling, and from the perspective ofpreventing the spread of contamination, the structure
should be such that fuel debris pieces (solid)Note 1
passing through the gaps between the canister bodyand lid are not released. Note that liquid and gas
confinement should be ensured by a cell or transfer
cask and not by the canister.

Criticality prevention⑩

The structure should be such that serious damage
such as detachment or breakage of the canister lid
does not occur even if it receives an impact load fromdropping or tumbling, and from the perspective of
maintaining subcriticality, the structure should besuch that fuel debris pieces (solid)Note 1 passing
through the gaps between the canister body and lid
are not released. Note that liquid and gas confinement
should be ensured by a cell or transfer cask and notby the canister.

Handleability(a)The lid structure should allow lid fastening andopening by remote operation.

(b)

The lid structure should allow lid fastening andopening by simple operations, such as turning the lid.

(f)

The size and structure should take into account theworkability in the handling flow of canisters.

Canister specifications (plan)
Simple mounting structure
・ Integral method-based lid fastening structure (equipped with a stopping mechanism)
・ Lid outer diameter 300 mm (for a canister with inner diameter 220 mm), 500 mm (for acanister with inner diameter 400 mm)
Bolt structure
・ Bolt-based lid fastening structure (equipped with a guide pin)
・ Lid outer diameter φ300 mm (for a canister with inner diameter 220 mm), φ500 mm (for acanister with inner diameter 400 mm)[Approach to selection of specifications]・ The structure has a structural strength that does not cause detachment of the lid or serious
damage leading to a large amount of leakage and does not create a continuous gap in theseal even when it receives an impact load such as a drop in the vertical orientation.
・ Two types of remotely-operable structures were selected: a bolt structure that has a proventrack record in remote operation of a similar lid, and a simple mounting structure that allows
the lid to be opened and closed by simple operation (turning of the lid).
・ Considering workability and containing efficiency, the outer diameter of the lid was kept as
small as possible, and the size used was such that a canister with inner diameter 220 mm
could be contained in a basket with a 310 mm opening, and a canister with inner diameter
400 mm could be contained in a basket with a 510 mm opening.
・ The installation of a buffer structure prevents the stored items from shooting up andcolliding with the inner surface of the lid, so the lifting of the lid due to the collision need not
be considered and the processing time (processing amount) is reduced by using a structure
where the amount of fitting required to attach the lid to the cask is as small as possible.
・ In the unlikely event that a bolt wears away, it will be cut from the side of the lid with a
special tool (assuming a disk-shaped cutter), and to reduce the amount of cutting of the lid,
it was decided to place the bolt as farther outside as possible.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris (collected by suction, etc.):
0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (2/10) No.118
Table. Design conditions and specifications for the canister (plan) (2/10)
Part
Vent
mechanism

Air supply
mechanism

Safety functions
andfunctional
requirements

Design conditions

Confinement⑤

As a measure for preventing the spread ofcontamination, the structure should be such that therelease of fuel debris pieces (solid)Note 1 passing
through the vent mechanism is suppressed.

Prevention ofhydrogen explosion⑮

The structure should be such that hydrogengenerated by radiolysis of water due to fuel debris isappropriately discharged outside the canister.

Handleability(d)

The structure should enable connection with the(drying facility and) inert gas injection facility, etc.

Handleability(d)

The structure should enable connection with the(drying facility and) inert gas injection facility, etc.

Canister specifications (plan)・ Opening/ closing method: Coupler method (normally-open coupler)・ Coupler size: 1 inch type (Minimum cross-sectional area: Approx. 452 mm2)
[Approach to selection of specifications]・ The structure is such that the release of fuel debris pieces (particle size 0.1 mm or more)is suppressed by a filter installed in the vent mechanism.
・ A specification (coupler size) that keeps the hydrogen concentration inside the canister
below the lower explosion limit of 4 vol.% was selected, based on the release of hydrogen
evaluated using the diffusion evaluation formula considering the effect of the filter andcoupler on the vent flow path, for the amount of hydrogen generated based on actual
measurements in the presence of water.
・ Based on the evaluation of the risk of increase in hydrogen concentration during thevent opening and closing operation when handling canisters, a coupler with a normallyopen vent was selected to reduce the risk.
・ The inert gas injection facility was connected with one vent mechanism coupler creatinga structure that allows gas replacement inside the canister by alternately performing air
supply and exhaust.
・ Drying fuel debris in a unit can: Air supply mechanism absent
・ Drying fuel debris in a canister: Air supply mechanism present (Two connection ports
for air supply and exhaust)[Approach to selection of specifications]・ The heated vacuum drying method and the warm air heated drying method are being
studied as the methods of drying fuel debris, and the unit-can-state and canister-state
are being studied as the drying states, but the method has not been selected. Therefore,
structures with and without air supply mechanism, which can handle either of themethods or states, were studied.
・ When drying the fuel debris in the unit can, the unit can is placed in a drying chamber toimplement the drying process, so the air supply mechanism need not be installed. In thecase of canister drying (heated vacuum drying), by alternating the air supply andexhaust operations with the vent mechanism (one connection port), it may be possible
to eliminate the need to install an air supply mechanism.
・ In the case of canister drying (warm air heated drying), since the vent mechanism (oneconnection port) cannot be used, it is necessary to install an air supply mechanism inthe canister.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris(collected by suction, etc.): 0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (3/10) No.119
Table. Design conditions and specifications for the canister (plan) (3/10)
Part

Safetyfunctionsandfunctional
requirements

Body

Confinement

Criticality
prevention

Handleability

Design conditions②

The main body of the canister should have a structure
whereby the airtightness is maintained by a welded
structure.

⑦

The structure of the main body of the canister should
be such that serious damage such as breakage does
not occur even if it receives an impact load fromdropping or tumbling, and from the perspective ofpreventing the spread of contamination, the structure
should be such that fuel debris pieces (solid)Note 1,
liquids, and gases are not released.

⑧

The structure should be such that the subcriticality offuel debris is maintained by the geometric shape of
the inner diameter of the canister.

⑨

In the case of an array of canisters, the subcriticality
should be maintained by retaining the array
dimensions using other equipment (metal cask basket,etc.).

⑪

The structure should be such that the inner diameterof the canister can maintain the geometric shape thatcan maintain subcriticality even if it receives animpact load from dropping or tumbling. The structureof the main body of the canister should be such that
serious damage such as breakage does not occur,and from the perspective of maintaining subcriticality,
the structure should be such that fuel debris pieces(solid)Note 1, liquids, and gases are not released.

(f)

The size and structure should take into account theworkability in the handling flow of canisters.

Canister specifications (plan)

・ Inner diameter: 220 mm, 400 mm
・ Plate thickness: 10 mm
・ Internal height: 840 mm (for a canister with inner diameter 220 mm), 845 mm (for a canister with
inner diameter 400 mm)
・Welded structure: Butt-joint full penetration weld
[Approach to selection of specifications]・Temporarily considered equivalent to a Class 3 cask, the structure of the welded part was
adopted in accordance with JSME “Design and Construction Standard PVD-4000
Manufacturing of casks".
・ Since the wall thickness of TMI-2 canisters was ¼ inch (6.35 mm), the canister wall thickness
was taken as 10 mm to be on the safe side. The structure is strong enough not to cause
serious damage leading to a large amount of leakage even if it receives an impact load such asa drop in the vertical orientation. In addition, a hub (tapered part) was installed at the joint
between the body and flange to ease stress in the event of a lid collision. The shape of the hub(tapered part) conformed to JSME “Design and Construction Standards PVD-3000 Class 3 cask
Design”.
・ The inner diameter was set to 220 mm, which has been confirmed by subcriticality evaluation
to be able to maintain subcriticality regardless of the fuel debris particle size and moisture
content, and to 400 mm temporarily set in consideration of expansion of the inner diameter toimprove workability.
・ The array size was temporarily set to 330 mm or more, which has been confirmed to be capableof maintaining subcriticality based on the results of criticality evaluation for canister innerdiameter of 220 mm with uranium enrichment 4.9 wt%, water volume percent 0.2, and finite
array (10 x 10).
・ The structure is such that even if it receives an impact load of a drop in the vertical orientation,a canister of inner diameter 220 mm is deformed within the range that can maintainsubcriticality due to the installation of a buffer structure.
・ The internal height of the canister was set to 840 mm (for a canister with inner diameter 220mm) and 845 mm (for a canister with inner diameter 400 mm) taking into account the catalyst
case thickness (20 mm (temporarily set)) and height of two unit cans it will store (400 mm percan), in addition to considering a margin on the thermal expansion of the unit cans, themanufacturing tolerance, and the height when the unit cans are stored at an angle, as well as
allowing space above the unit cans.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris(collected by suction, etc.): 0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (4/10) No.120
Table. Design conditions and specifications for the canister (plan) (4/10)
Part
Heat
removalstructure

Safety functions
andfunctional
requirements
Heat removal

Canister specifications (plan)

Design conditions⑫

The structure should be able to maintain integrity

・ No heat removal structure (cooling fin, etc.)

using the natural heat dissipation of the canister.
[Approach to selection of specifications]⑬

The internal temperature of the canister should notexceed the permissible temperature even in the eventof loss of external power or other events that must be
expected.

・ As a result of an evaluation conducted in a heat removal study in FY2014, assuming
the handling of heat removal in the air, it was confirmed that when the block-likefuel debris with the highest burnup was placed at a filling rate of 50%, the fueldebris limit temperature of 300ºC, set with reference to TMI-2, was not exceeded, so
it was decided not to provide a special heat removal structure (fins, etc. to improveheat removal).
・ The temperature environment around the canister would be ensured through heatremoval by other equipment (transfer cask/ storage cask basket, cooling fins, etc.)
and air conditioning in the facility, and it was decided that the canister would not beprovided with a special heat removal structure (fins, etc. to improve heat removal).

Shielding
structure

Shielding⑭

The shielding function should be ensured by the・ No shielding structurebuilding or transfer cask and not by the canister.
[Approach to selection of specifications]・ In order to avoid a decrease in workability due to an increase in the weight of thecanister and a decrease in handleability due to the installation of a shielding
structure, no shielding structure was installed on the canister.
Inert
atmosphere

Prevention of dust
fires

⑰

The inside of the canister or cell should have an inert
gas atmosphere to prevent ignition.

・ Installation of a coupler (shared with the coupler of the vent mechanism) that can beconnected to the inert gas injection facility[Approach to selection of specifications]・ The measures to prevent ignition by fine zirconium powder have not been decided,
but assuming that the inside of the canister has an inert gas atmosphere to prevent
ignition, a coupler (shared with the coupler of the vent mechanism) is provided forthe canister so that it can be connected to the gas injection facility.
©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (5/10)

No.121

Table. Design conditions and specifications for the canister (plan) (5/10)
Part
Suspending
part

Safety functions
andfunctional
requirements
Handleability

Design conditions(c)

The structure of the canister should be such that it canbe lifted.

Canister specifications (plan)

・Structure to lift the canister by gripping the lifting groove provided inside thelid(Note that if the storage space is a square prism (or unrestricted), thecanister can also be lifted by gripping the body flange)[Approach to selection of specifications]・ By providing a lifting groove inside the lid and making the hanging jig of thecanister suspending device smaller than the outer diameter of the canister
lid, the structure allows lifting without being affected by the shape of thestorage space (square prism, cylinder, plate (drilled hole)).
・ The structure is such that by not installing the suspending part that was
installed in the center of the upper end plane of the lid, the event of entry of
the buffer structure into the suspending part, which was seen in the FY
2018 feasibility verification test for canister lid structure, does not occur.

Sealing
method forcanisters andthe port
between cells

Handleability(f)

The size and structure should take into account theworkability in the handling flow of canisters.

・ Structure that can be sealed by pressing against the seal installed in theport between cells by using a planar structure for the upper end of thecanister body・ Structure in which the inner lid (with filter) is installed on the canister body[Approach to selection of specifications]・ As a method of preventing contamination as much as possible at the areaboundary between cells in the handling flow of canisters, the structure issuch that the upper end plane of the canister body can be pressed against
the seal of the port between cells to seal it.
・ As a method of preventing contamination as much as possible during thehandling of canisters from the port between cells to lid fastening, thecanister body was installed with an inner lid. Note that the inner lid wasprovided with a filter on par with the vent mechanism for hydrogen venting.

©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (6/10)

No.122

Table. Design conditions and specifications for the canister (plan) (6/10)
Part
FilterSafety functions
andfunctional
requirements
Confinement

Design conditions⑤

As a measure for preventing the spread ofcontamination, the structure should be able toprevent the release of fuel debris pieces(solid)Note 1 passing through the vent mechanism.

Canister specifications (plan)・ Mesh diameter: 0.3 μm (suitable for HEPA)
・ Type: Wire mesh type・ Material quality: SUS316[Approach to selection of specifications]・ While selecting the filter specifications, the requirements for safetyfunctions were organized and set as a design policy plan for the filter.
(1) The particle size of the fuel debris to be handled in a canister has
been specified as 0.1 mm or more, so the mesh diameter was set toless than 0.1 mm.
(2) The mesh diameter should be such that the hydrogen generated
inside the canister can be released appropriately.
(3) From the viewpoint of fire resistance, heat resistance, and aging ofmaterial, the filter material shall be the same material as the canister.
・ From the above design policy plan, release of hydrogen was
evaluated based on the hydrogen diffusion evaluation formula withthe minimum mesh diameter assumed currently (0.3μm (suitable forHEPA)), and it was confirmed that the concentration of hydrogen
inside the canister could be kept at the lower explosion limit of 4vol.%or less, so 0.3 μm was selected as the mesh diameter for the filter.
・ The wire mesh type and the sintered metal powder type were the two
types of filters considered, but the wire mesh type was selected inconsideration of the results of BWR filter vents, etc.
・ The material used for the filter was SUS316, which is the samematerial as that of the canister.
・ As measures against clogging of the filter, the surface area of thefilter was increased by making the diameter of the filter as large as
possible, and the structure was made less susceptible to clogging. In
the unlikely event that the filter becomes clogged, it is assumed thatthe filter will be replaced by replacing the lid.
©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (7/10)

No.123

Table. Design conditions and specifications for the canister (plan) (7/10)
Part
Seal

Safety functions
andfunctional
requirements
Confinement

Canister specifications (plan)

Design conditions③

The integrity of the seal should be・ Elastomer gasket (EPDM: Ethylene Propylene Diene monomer)

maintained against aging due to the
corrosion and radiation expected[Approach to selection of specifications]

during the transfer period.

・ Since the storage facility ensures the confinement function during storage, the confinement function
during storage is not expected for canisters, for which it is difficult to maintain and confirm sealing
during storage (regular leak inspection, etc.). Therefore, elastomer gasket (EPDM) was adopted
prioritizing storage efficiency (minimization of outer diameter of lid), lid fastening workability, andapplicability to a simple mounting structure.

・ The radiation resistance is approx. two years as per a rough evaluation when all the fuel debris in
the canister was temporarily set to UO2 with fuel debris burnup 41 (GWd/t), and there was noproblem with durability during transfer and handling (assumed to be about 7 days).
・ During storage, which is estimated to be about 50 years, the confinement function may be lost due toaging, but even if the confinement function is lost, it is unlikely that a large amount of fuel debris
pieces will be released from the seal during stationary storage, and even if they are released, they
will remain in the storage cask (in the case of the metal cask method) that ensures the confinement
function, so it will not impair the confinement function as a storage facility.
・ As a means for ensuring the confinement function during storage (and after storage), adoption of ametal gasket may be considered, but it has the following issues and was not adopted in the current
design:(i) Cannot be applied to the simple mounting lid structure.
(ii) Can be applied to a bolt lid structure, but since a large fastening force is required, the lid outer
diameter/ bolt diameter becomes large, which increases the weight of the canister and reduces
the storage efficiency.
(iii) Compared to the elastomer gasket, careful consideration is required for cleaning of the sealing
surface (prevention of scratches and management of foreign material intrusion) andmanagement of bolt fastening work.

©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (8/10)

No.124

Table. Design conditions and specifications for the canister (plan) (8/10)
Part
Seal
(continued)

Safety functions
andfunctional requirements
Confinement

Criticality prevention

Design conditions①

As a measure to prevent the spread of contamination,
the structure should be such that fuel debris pieces(solid)Note 1 passing through the gaps between thecanister body and lid are not released. Note that liquidand gas confinement should be ensured by a cell ortransfer cask and not by the canister.

⑥

The structure should be such that serious damage
such as detachment or breakage of the canister lid
does not occur even if it receives an impact load fromdropping or tumbling, and from the perspective ofpreventing the spread of contamination, the structure
should be such that fuel debris pieces (solid)Note 1
passing through the gaps between the canister bodyand lid are not released. Note that liquid and gas
confinement should be ensured by a cell or transfer
cask and not by the canister.

⑩

The structure should be such that serious damage
such as detachment or breakage of the canister lid
does not occur even if it receives an impact load fromdropping or tumbling, and from the perspective of
maintaining subcriticality, the structure should besuch that fuel debris pieces (solid)Note 1 passing
through the gaps between the canister body and lid is
not released. Note that liquid and gas confinement
should be ensured by a cell or transfer cask and notby the canister.

Canister specifications (plan)
Simple mounting structure
・ Outer cylindrical surface: Elastomer (EPDM) O ring・ Upper end plane (O ring is installed on the lid): Elastomer (EPDM) O ring
[Approach to selection of specifications]・ From the lid structure, the position for installing the O-ring as aconfinement boundary can be considered to be the upper end plane andthe outer cylindrical surface of the canister, but if the O ring is installed on
the upper end plane, it is difficult to manage the O-ring squeeze rate due tothe structure of the lid, so the O ring was installed on the outer cylindricalsurface setting it as the confinement boundary.
・ Due to the structure of the lid, the simple mounting structure has arelatively large gap between the mating parts of the lid and the body, andwhen there is an impact load such as that caused by tumbling, there may
be a momentary gap in the outer cylindrical surface seal, so an O ring is
also installed on the upper end plane to suppress momentary leakage.
・ The O ring on the upper end plane was installed on the lid side so that the
O ring could be replaced in light of the measures to be taken when the seal
can no longer function due to the effects of aging, etc.
Bolt structure
・Upper end plane (O ring is installed on the lid): Elastomer (EPDM) O ring
[Approach to selection of specifications]・ Since the squeeze rate can be controlled by fastening bolts and the target
size of the outer diameter of the lid is restricted, the O-ring on the upper
end plane of the canister body was set as the confinement boundary.
・ The O ring on the upper end plane was installed on the lid side so that the
O ring could be replaced in light of the measures to be taken when the seal
can no longer function due to the effects of aging, etc.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris(collected by suction, etc.): 0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (9/10)

No.125

Table. Design conditions and specifications for the canister (plan) (9/10)
Part
Bufferstructure

Safety functions
andfunctional
requirements
Confinement

Criticality prevention

Handleability

Design conditions⑥

The structure should be such that serious damage such as detachment or
breakage of the canister lid does not occur even if it receives an impact
load from dropping or tumbling, and from the perspective of preventing the
spread of contamination, the structure should be such that fuel debris
pieces (solid)Note 1 passing through the gaps between the canister body andlid are not released. Note that liquid and gas confinement should beensured by a cell or transfer cask and not by the canister.

⑦

The structure of the main body of the canister should be such that serious
damage such as breakage does not occur even if it receives an impact loadfrom dropping or tumbling, and from the perspective of preventing the
spread of contamination, the structure should be such that fuel debris
pieces (solid)Note 1, liquids, and gases are not released.

⑩

The structure should be such that serious damage such as detachment or
breakage of the canister lid does not occur even if it receives an impact
load from dropping or tumbling, and from the perspective of maintaining
subcriticality, the structure should be such that fuel debris pieces (solid)Note
1 passing through the gaps between the canister body and lid are notreleased. Note that liquid and gas confinement should be ensured by a cellor transfer cask and not by the canister.

⑪

The structure should be such that the inner diameter of the canister canmaintain the geometric shape that can maintain subcriticality even if it
receives an impact load from dropping or tumbling. The structure of themain body of the canister should be such that serious damage such as
breakage does not occur, and from the perspective of maintaining
subcriticality, the structure should be such that fuel debris pieces (solid)Note
1, liquids, and gases are not released.

(e)

The structure should allow alignment of the lid and the bottom structure of
the canister so that stacking is possible during transfer and storage.

(f)

The size and structure should take into account the workability in thehandling flow of canisters.

Canister specifications (plan)
・DOE (skirt) type
[Approach to selection of specifications]・ A buffer structure was installed to deal with events such as theevent that occurred in the FY 2018 feasibility verification test
for canister lid structure in which the simple mounting
structure lid could not be opened due to the stored items
shooting up and colliding with the inner surface of the lid when
the canister fell, and in order to reduce the deformation of the
body of the lower canister in the event of a canister dropping
on top of another canister.
・ The buffer structures being considered included the existing
TMI (concave) type, Paks (doughnut) type, and DOE (skirt) type.
The DOE (skirt) type was selected in consideration of its simple
structure, good manufacturability, ease of canister stacking
and ease in provision of holes for preventing retention ofhydrogen gas.
・ Although there are difficulties in decontamination work by
wiping and surface contamination density measurement bysmearing, it is assumed that structural measures (such as nothaving an uneven shape on the inner surface) and measures toprevent contamination during handling (such as placing the lidon openings and covering) can be used to deal with theseissues.
・ In order to have a structure that prevents deformation of thebuffer structure when handling the canister, the lower end ringis installed as reinforcement.

Note 1: The particle size of fuel debris pieces (solid) is set to 0.1 mm or more (Definition of debris: Powder debris (collected by suction, etc.): less than 0.1 mm, particulate debris(collected by suction, etc.): 0.1 mm to 10 mm, block debris (collected in unit cans): more than 10 mm)©International Research Institute for Nuclear Decommissioning[Supplement-4] Specification plan for the canister (10/10)

No.126

Table. Design conditions and specifications for the canister (plan) (10/10)
Part
Catalyst

Qualityofmaterial

Safety functions
andfunctional requirements

Design conditions

Prevention ofhydrogen
explosion⑯

Confinement④

Canister specifications (plan)

The structure should be able toprevent the hydrogen generationby the radiolysis of water due tofuel debris.

・ Catalyst case (disk-shaped, 20 mm thick) is installed on thebottom of the inner lid

The integrity of the strength
members should be maintained
against aging due to the
corrosion and radiation expectedduring the transfer and storage
periods.

・ SUS316L[Approach to selection of specifications]・ As a measure to prevent hydrogen generation, theeffectiveness, required amount, installation position, etc. of
the catalyst is being studied separately, but as a provisional
specification, a catalyst case (disk-shaped, 20 mm thick) is
installed on the bottom of the inner lid.

[Approach to selection of specifications]・ At present, it is difficult to predict the environment inside thecanister, but in general, austenite stainless steel was selected
as a material that has excellent corrosion resistance and isrelatively easy to procure and process. Of this, SUS316L wasselected in consideration of its superiority in SCC resistancecontrol (chloride ion concentration, humidity control) over
SUS304L. In order to avoid SCC sensitization due to welding,
low carbon steel material (L material) was used.
・ Scenarios were created taking into account the viewpoints ofoperation and design, and based on the evaluation of crevice
corrosion and stress corrosion cracking on the presumptionof operation in dry conditions, it is projected that the material
can be adopted.

©International Research Institute for Nuclear Decommissioning[Supplement-5] Investigation results of hydrogen concentration measurement technology (details) (1/2)

No.127

A: Continuous real time monitoring in thetransfer cask
©International Research Institute for Nuclear Decommissioning[Supplement-5] Investigation results of hydrogen concentration measurement technology (details) (2/2)
6. Light wave interference type

7. Non-dispersed infrared ray type

8. Difference absorption spectroscopy (DOAS)

10. Proton conductor (proton conductive solid
electrolyte)

Utilizes the separation of H2 fromother flammable gases by gas
chromatography.

Measurement method using an inorganic
proton conductor. Using the Nernst equation,
the potential difference is converted tohydrogen partial pressure ratio between thereference gas and the measurement gas.

Sensor Principle
Utilize the fact that the refractive index of H2 is smaller The target gas is passed through the Gas concentration is measured by utilizing the fact thatthan that of air, etc.
measurement cell, infrared rays arelight of the wavelength determined for each gas type isirradiated, and the concentration isabsorbed. Measure the concentration of gas present
obtained from the amount of change in between the light source and the detector.
The LED light is split into two, and after passing
infrared rays due to absorption.
through the sample gas and standard gas, they are

Principle

combined and the position of the interference fringes ismeasured by CCD.
0 to 100 vol.%Hundreds of ppm to tens of vol.%1000 ppm to several vol.%No.128

9. Gas chromatography type

H2 is separated by gas
chromatography and then detected bya metal oxide semiconductor.
0 to 100 vol.%0 to 100 vol.%Measuring range and accuracy
About ±1%FS to ±4%FS
A
Evaluation

About ±10%FS

1%±0.1%; 10%±1%; 100%±3%
O

O

O

O

O

B

x

∆ (Preliminary gas separation)∆ (Adjustment of optical path length required)∆ (Additional sensor required)∆ (Verification required)C∆O
Gas that absorbs large amount of
infrared rays

O
Dust, fume, mist, etc. that cause light scattering andabsorption

O

O

None

Oxygen gas (combustion)

O2 (0.16vol.%),CO2 (－0.96vol.%),(H2O, Co2, etc.)
Interfering gas

Evaluation

Cl2, etc.

A
B
C

ResponsivenessA
Installation method

B

C* Values in parentheses show changes in indicatedvalues due to +1 vol.% fluctuation (approximate
values)O
OO
Scattered (also continuous)A
B
C

ContinuousO∆ (Preliminary gas separation)∆ (Preliminary gas separation)

Installed near the cask to collect gas

Installed near the cask to collect andanalyze gas

Installed near the exhaust line to collect gas

Installed near the exhaust line to collect Exhaust line installationgas
Installed near the exhaust line to collect Exhaust line installationgas
Interference gas filter regeneration
Adjustment of optical path length and filter for dust, etc.
requiredInstalled near the exhaust line to collect gas
Low concentration and depends on CCD resolution:
DifficultComprehensive evaluationO∆ (Preliminary gas separation)∆ (Preliminary gas separation)
Continuous (Filter regeneration
required)

x
x
∆

x
x
∆

Transfer cask installation (light source and detector)

∆
∆
∆

O
O
O
Scattered (1 data/ 10 mins)O
OOContinuous – Response time 1s or lessInstalled near the cask to collect and Installation of transfer cask
analyze gas
Installed near the exhaust line to
Exhaust line installationcollect gas
Installed near the exhaust line to
Exhaust line installationcollect gas
Multiplexing for continuous monitoring The temperature of part to be measured ishigh. Heat shock countermeasures required∆ (Suction pump required)∆ (Additional sensor required)O∆ (Damage countermeasures required)∆ (Concentration measurement required)O

B: Sequential monitoring in the drying process (decompression heating)
C: Sequential monitoring in the inert gas injection process©International Research Institute for Nuclear Decommissioning[Supplement-6] Principles of hydrogen concentration measurement
technology (heat conduction type)１)
Sample gas

No.1292)[Sensor structure]

Comparison chamber

Measurement chamberCap
Detectorelement
Compensation
element

Sintered metal[Bridge circuit]
Change in heat conduction →Change in resistanceCompensation
element

Detectorelement

DC
constant
current

SensoroutputFixed
resistanceDCamplification

Edge
resistance R
Sensor voltage
Vs

Figure. Diagram showing the principle of the heat conduction type analysis device
Uses the fact that the heat transfer coefficient differs depending on the gas type.
The difference in temperature of platinum wire heated with a constant current in the reference gas atmosphereand the gas atmosphere to be measured, is measured as the difference in electric resistance.
Source:1) Fuji Electric Co., Ltd. HP “Thermal Conductivity Gas Analyzer - Optimum for concentration measurement for H2, Ar, and He; Type: ZAF”
https://www.fujielectric.co.jp/products/instruments/products/anlz_gas/ZAF.html
2) RIKEN KEIKI Co., Ltd. Document “Riken Sensors - Introduction to Technology”
https://www.rikenkeiki.co.jp/cms/riken/pdf/support/PC9-0314-180610S.pdf©International Research Institute for Nuclear Decommissioning[Supplement-7] Principles of hydrogen concentration measurement
technology (proton conductor)

No.130Electromotive
properties

Application example: Hydrogen sensor

Figure. Diagram showing the principle of a proton conduction-type hydrogen sensor
A solid that selectively permeates hydrogen ions (protons) is called a proton conductive solid electrolyte,
and when the hydrogen gas concentration at both ends of the proton conductive solid electrolyte isdifferent, an electromotive force is generated according to the partial pressure.
The generated electromotive force can be converted to concentration by the formula in the figure.
Source: TYK Corporation; HP “Hydrogen Sensor for Gas – NOTORP-G”
http://www.tyk.co.jp/02ProductInfo/product02-04/details01.html©International Research Institute for Nuclear Decommissioning