[Confidential]

Subsidy Project of Decommissioning and Contaminated Water
Management in the FY2017 Supplementary Budgets

Development of Analysis and Estimation
Technologies for
Fuel Debris Characterization
Results for FY2019
September 2020
International Research Institute for Nuclear Decommissioning (IRID)©International Research Institute for Nuclear Decommissioning1

[Confidential]

Contents
1. Research background and purposes
2. Project goals
3. Implementation items, their correlations, andrelations with other research
4. Implementation schedule

5. Project organization
6. Implementation details©International Research Institute for Nuclear Decommissioning2１． Research Background and Purposes
Background of Research[Confidential]

3

After the Fukushima Daiichi (1F) accident, knowledge such as accident information on Three Mile
Island Nuclear Power Station Unit 2 (TMI-2), research information on severe accidents (SA) , as well
as 1F accident information, were surveyed and organized.
✓ Not enough knowledge of boiling water reactors (BWR) in the TMI-2 accident and in SA research
conducted overseas.
✓ Not enough information on fuel debris related to the 1F specific events, such as the impact of
exposure to seawater and the Molten Core Concrete Interactions (MCCIs) .

•

•

•
•

To implement nuclear decommissioning (i.e. Fuel debris retrieval, criticality safety control,
containing, transfer and storage of fuel debris, nuclear material accountancy, and final treatment)
in a safe, steady, and prompt manner, it is necessary to provide and organize available
information on fuel debris that can be applied for technical development.
Until now, fuel debris information has been estimated based on existing domestic and overseas
knowledge and research and development using simulated substances, etc., but trial retrieval offuel debris will begin in 2021, and it is expected that information will be obtained from the actual
fuel debris in the future.
The fuel debris samples obtained in the initial stages are extremely limited in terms of quantity andlocations of collection, and how to extract effective information from them is important forproceeding with future decommissioning work.
Uranium-containing particles were detected from the results of analysis of the substances
adhering to the investigation devices and deposits collected during the investigation inside 1F
PCV, and it became clear that the fuel debris properties can be estimated by examining theseuranium-containing particles in detail.
©International Research Institute for Nuclear Decommissioning[Confidential]
1. Research Background and Purposes(1) Development of technology required for analyzing the estimation of fuel debris properties

4
List of fuel debris properties (Up to FY2018)
Results of tests and research
conducted by using simulated
debrisProperties of uranium(from past literature)

Severe accident
findings from TMI-2, etc.

SA researchfindings

Environment inside
the 1F reactor
situation during theaccident

Collection

Etc.

Fuel debris
tracesAnalysis
samples fromthe collected fueldebrisTransport

Reflection
Comprehensive Evaluation(Evaluation taking into account the generation process of fueldebris, the sedimentation and damage conditions of the fueldebris and constituent materials in the area of each Unit)

Existing analytical facilities

Analysis results

Updating the list of fuel debris properties

Provision of information〇 Information User PJ (Containing, Transfer and Storage PJ*1, Retrieval
PJ*2, Waste Management PJ*3)〇 Tokyo Electric Power Company Holdings, Inc.

Used for the review of analysis items

International conference
findings, etc.

*1 Development of Technology for Containing, Transfer and Storage of Fuel Debris PJ, *2 Development of Technology for Further Increasing the Scale of Retrieval of Fuel Debris and Internal Structures PJ,*3 R&D for Treatment and Disposal of Solid Radioactive Wastes PJ©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes(2) Development of estimation technology for particle behaviors of fuel debris[Confidential]

The fuel debris retrieval from the first Unit will start from FY2021. Although initially expected to be on a small scale,
gradually the fuel debris retrieval work will be carried out on an expanded scale.
During the full-scale fuel debris retrieval work, there is the risk of a significant rise in the amount of exposure to theworkers and the general public due to the particles generated by the handling of large quantities of fuel debris
which may deteriorate the working environment and cause leakages into the environment if confinement measures
are inadequate.
For studying appropriate confinement methods or methods for managing the work environment, it is important toestimate the behavior of the particles originating from fuel debris.
Inside the 1F reactor and PCV (inside RPV pedestal)

Dismantling during the gas phase

Transportation of radioactive
particles due to air current

Gas
phase

Generation ofGeneration of radioactive
radioactive particles particles (grinding swarf)(steam)Off-gas treatment
systemCollection rate of theradioactive particles

Dismantling during the liquid phase (in thevicinity of the gas-liquid interface)

Migration of the radioactive particles due toaerosol such as air bubbles during dismantling
Migration to the gas
phase due to the mist

Dismantling jig(thermal) (E.g.: Laser)

Dismantling jig(mechanical) (E.g.: Core
boring pit)

Liquid phase
Migration of radioactive
particles inside water

Liquid waste
treatment system
Collection rate of theradioactive particles

Fuel debris
Coagulation settlement
and refloating

Structural
material
Fig. Generation and migration route of the radioactive particles generated inside the 1F reactor and PCV (inside the RPV pedestal) during fuel debris
retrieval©International Research Institute for Nuclear Decommissioning5

2. Project Goals(1) Development of technology required for analysis of fuel debris properties[Confidential]

Relation between issues in this project and the "Road map for
Decommissioning"

FY

Up to 2018

Information user
PJs and TEPCO
HD

2019-2020

2021

Technological developments/
design and manufacturing of equipment

2022 onwards

Implementation of
retrieval work, etc.
△ Start of retrieval at the first Unit

Issues in thisproject(Development oftechnology
required foranalysis of fueldebrisproperties)

Preliminary
work

Updating the list of fuel debris
properties
・Estimating the fuel debris
characteristics for each area ineach Unit from a small sample.
(Estimating the most probablevalues and variations of theproperty values)

Reflection in device design, work
process control and safetymeasures, etc.

Proposal of analysis items andefficient analytical methods basedon the needs of thedecommissioning process

Reflection in the methods ofmanaging the fuel debris (labeling,etc.)©International Research Institute for Nuclear Decommissioning6

2. Project Goals(2) Development of estimation technology for particle behaviors of fuel debris[Confidential]

Relation between issues in this project and the "Road map for
Decommissioning"

FY

Information user
PJs and TEPCOHD

Up to 20182019-2020

2021

2022 onwards

Implementation of
retrieval work, etc.

Technological developments/
design and manufacturing of equipment

Expansion of scale△ Start of retrieval at the first Unit

Findings concerning generation
behavior and the properties ofparticles

Issues in thisproject(Development oftechnology for
estimating the
behaviors of fueldebris particles )Preliminary
work

Generalization of properties and migration
behavior of particles

Reflection in the confinement
and safety designs

Findings concerning migration
behavior©International Research Institute for Nuclear Decommissioning7

3. Implementation items, their correlations, and relations with other research(FY2019 to FY2020)・Information concerning the compositionand properties of fuel debris (Including theanalytical values of the fuel debris)
・Information on the behavior ofradioactive particles
Generation behavior, migration behavior

Development of Technology
for Increasing the Scale of Fuel
Debris Retrieval in Stages PJ#1・ Information concerning
fuel debris samples (state,amount, etc.)

Development of Analysis andEstimation Technologies for
Fuel Debris Characterization
PJ (Development of estimation
technology for aging propertiesof fuel debris)

Property data ofaged deteriorationand information

・ Information concerning the compositionand properties of fuel debris (Including theanalytical values of the fuel debris)
R&D for Treatment and Disposalof Solid Radioactive Wastes PJ: INPUT Information

Development of Analysis
and Estimation
Technologies for Fuel
Debris Characterization PJ

・Information about analysis
planning, etc.
・Engineering information andrelated technology development
information concerning the fueldebris retrieval system[Confidential]

Development of Technology for
Further Increasing the Scale ofRetrieval of Fuel Debris andInternal Structures PJ #2

・Engineering information and related
technology development information
concerning the fuel debris retrieval
system・ Information concerning the compositionand properties of fuel debris (Including
the analytical values of the fuel debris)

Development ofTechnology for
Containing, Transfer andStorage of Fuel Debris PJ
・Information concerning the composition andproperties of fuel debris (Including the analyticalvalues of the fuel debris)
・Improvement in the analytical efficiency (small
amounts of fuel debris sample)
・ Information on the behavior of radioactive particles
TEPCO HD
(Decommissioning operator): OUTPUT Information#1 Initially, at the start of the project, the project title was "Development of Sampling Technology for Retrieval of Fuel Debris and Internal Structures“, but it was changed to "Development of Technology for
Increasing the Scale of Fuel Debris Retrieval in Stages" following the FY2020 Decommissioning Research and Development Plan published at the 75th Secretariat Meeting of the Team for Countermeasuresfor Decommissioning and Contaminated Water Treatment.
#2 Initially, at the start of the project, the project title was "Development of Technology for Retrieval of Fuel Debris and Internal Structures“, but it was changed to "Development of Technology for Further
Increasing the Scale of Retrieval of Fuel Debris and Internal Structures" following the FY2020 Decommissioning Research and Development Plan published at the 75th Secretariat Meeting of the Team forCountermeasures for Decommissioning and Contaminated Water Treatment.
©International Research Institute for Nuclear Decommissioning

8

[Confidential]

4. Implementation Schedule (FY2019) (1/2)
項目
Items

April
4月

May
5月

June
6月

As of the end of March 2019
July
7月

2FY2019
0 1 9 年度
AugustOctober
8月 September
9月
10月 November
11月 December
12月 January
1月 February
2月

March
3月

9

備考
Remarks(1) 燃料デブリ性状の分析に必要な技術開発等
Development of technology required for analysis of fuel debris properties
Preparation サンプル輸送準備／分析準備
for sample transportation/ preparations for analysis

 Analysis of the

Sampleサンプルの輸送
transportation ▼for analysis
分析準備① 得られる燃料デブリサ Preparations
obtained fuel debris
ンプル等の分析及び分析
samples,
and
study
to
効率化の検討
分析実施
analysis
improve the efficiency Conductingof analysis

Completion of分析終了
analysis ▼Completion of分析終了
analysis ▼Completion検討終了
of study ▼Completion検討終了
of study ▼分析効率化検討
Study
to improve the efficiency
of analysis

Summarizing
成果とりまとめ the results
Completion of investigations
調査終了 ▼

Internal investigation results Improvement in the 内部調査結果・文献調査
and literature survey
estimationof fuel②
燃料デブリの性状推
定の高度化
debris properties
Discussions through experts’
専門家会議による議論
meetings

Completion of investigations
調査終了 ▼
Completion of discussions
議論終了▼

Summarizing
成果とりまとめ・the results and特性リスト改訂
revisionof the list of properties
 International③ 燃料デブリ分析の知and review of analysis
cooperation for gathering Study
分析項目検討・レビュー
見収集のための国際協 items
the knowledge on fuel力
debris analysis

1F Sample Evaluation
Committee
1F試料評価委員会▲(February 25) （2/25）（2）燃料デブリ微粒子挙動の推定技術の開発(2)
Development of technology for estimating the behaviors of fuel debris particles① Behaviors
燃料デブリの加工に伴う放射性飛散粒子の生成挙動
of airborne radioactive particles generated with the processing of fuel debris

-1.
①-1. Large-scale
ウラン含有模擬
契約手続き
Contract
procedures
デブリを用いた粒子生
testingof particle
成に関する大型試験
generationby using
Uranium-containing Execution
試験実施 of tests
simulated debris▼ Contract
契約▼ Contract
契約

Completion of manufacturing and installation of testing devices
for thermal and mechanical processing ▼加熱・機械的加工試験装置の製作・据付終了
Completion of manufacturing and installation of testing devices加熱・機械的加工試験装置の製作・据付終了
for thermal and mechanical processing ▼成果とりまとめ the results
Summarizing①-2. Basic
粒子生成挙動に-2.
testing
係る基礎試験
試験準備
Preparations
for testingofparticle
generation behavior

Conducting
tests
試験実施
Summarizing
成果とりまとめ the results

Completion of cold
test preparations ▼Completionホット試験準備終了
of hot test preparations▼
コールド試験準備終了
Completion of cold
test preparations ▼ Completionホット試験準備終了
of hot test preparations▼
コールド試験準備終了
コールド試験の実施
Executionof cold test ▼Executionof hot test ▼ホット試験の実施

Test試験の終了
completion ▼Executionof cold test ▼コールド試験の実施

Executionof hot test ▼ホット試験の実施

Test 試験の終了
completion ▼Black: Plan
Red: Actual©International Research Institute for Nuclear Decommissioning[Confidential]

4. Implementation Schedule (FY2019) (2/2)
Items
項目

As of the end of March 2019
FY20192019年度

April
4月

May
5月

June
6月

July
7月

August
8月 September
9月 October
10月 November
11月 December
12月 January
1月 February
2月

March
3月

10

Remarks
備考(2) Development of technology for estimating the behaviors of fuel debris particles（2）燃料デブリ微粒子挙動の推定技術の開発▼Contract
契約

契約手続き
Contract
procedures
-3.
of①-3 Investigation
国内外の原子力casesof airborne
施設における放射性国内調査
Investigations in Japan
粒子の飛散事例の調
radioactive
particles査in nuclear facilities inOverseas investigations
Japan and overseas 海外調査

▼Contract
契約

国内情報調査・整理
Investigationand organization of information in Japan▼ Completion
調査終了 of investigation▼ Completion
調査終了 of investigation

Investigation and organizationof overseas information ▼ Completion
海外情報調査・整理
調査終了 of investigation▼ 調査終了Completion of investigation

成果とりまとめ
Summarizing the results
 微粒子の気相・気液界面及び液相におけるMigration behavior of particles in the gas phase, gas②
liquidinterface, and liquid phase
移行挙動▼ Contract
契約▼Contract
契約

Completion of test試験準備終了▼
preparations

Preparation and Procurement-1. 気相・気液界面
Evaluation of 準備・調達②-1における微粒子挙
particle
behavior in
the動評価gas phase andConducting tests
gas-liquid interface 試験実施

Completion of test試験準備終了▼
preparations

Execution of the移行率測定試験の実施
migration rate measurement test
解析モデルの検討
Studyof the analysis model▼

Completion of the migration
移行率測定試験の終了
rate measurement test▼

Execution of the migration移行率測定試験の実施
rate measurement test ▼ Completion of the migration
rate measurement test ▼移行率測定試験の終了

Summarizing the results
成果とりまとめCompletion of test試験準備終了▼
preparations

-2. 液相におけるEvaluation of②-2
微粒子挙動評価
particle
behavior in
the liquid phase

準備・調達
Preparation and Procurement

試験実施
Conducting tests

Completion of test試験準備終了▼
preparations
Execution of the sedimentation
rate measurement test
沈降率測定試験の実施
Verificationシミュレーションの適用性確認
of the applicability of simulation ▼Execution of the sedimentation 沈降率測定試験の実施
rate measurement test ▼Completion of the sedimentation
沈降率測定試験の終了
rate measurement test▼

Completion of the sedimentation rate
沈降率測定試験の終了
measurement test ▼成果とりまとめ
Summarizing the results
Overall
Summary
全体とりまとめ

Summary
とりまとめ
第1回中間報告会▲
First interim
report meeting

Major
milestones
主要なマイルストン(October（10/3）3)

第2回中間報告会▲
Second interim
report meeting(Scheduled for（4/20予定）
April 20)

Black: Plan
Red: Actual©International Research Institute for Nuclear Decommissioning[Confidential]

5. Project Organization (FY2019)
IRID Headquarter
Tokyo Electric Power Company Holdings, Inc. (TEPCO HD) Various coordination from the viewpoint of site
applicability• Coordination for reflection of the licensing status• Coordination for reflection of the status ofdecommissioning site, etc.

International Research Institute for Nuclear
Decommissioning (IRID)

 Drafting of overall plans and consolidation ofengineering management
 Overview of technology management such as
progress of technological developments.

Japan Atomic Energy Agency (JAEA)ATOX Co., Ltd.

1) Development of technology required for analysis of fuel debris
properties
2) Development of estimation technology for particle behaviors
of fuel debris

E&E Techno Service Co., Ltd.
 Contract work related to the analysis of fuel debris
samples. (FMF)

1) Development of technology required for analysis offuel debris properties(Preparation for transportation of analytical samples)

PESCO Co. Ltd.
 Contract work related to the development oftechnology for the characterization and analysis of fueldebrisNippon Nuclear Fuel Development Co., Ltd. (NFD)
 Work contract related to the analysis of test samples
collected from the Fukushima Daiichi Nuclear Power
Station*Kensakaihatsu Co., Ltd.
 Contract work related to the analysis of fuel debris
samples. (AGF)

Hitachi Transport System, Ltd.
 Contract work related to the transportation of fueldebris samples.

PESCO Co. Ltd.
 OECD/NEA* “PreADES” Meeting-related venue
preparations and administrative work

ONET Technologies CN, France (Agency: Marubeni
Utility Services Co. Ltd.) Testing of particle generation behavior due to cuttingof large-scale simulated fuel debris

Radwaste and Decommissioning Center (RANDEC)
 Contract research on investigation of cases ofairborne radioactive particles in nuclear facilities inJapan and overseas*PreADES: Preparatory Study on Analysis of Fuel Debris

University of Tokyo, Designated National University Corp.
 Contract research on migration behavior of particles in
the gas phase, gas-liquid interface, and liquid phase©International Research Institute for Nuclear Decommissioning

11

[Confidential]

6. Implementation Details

12

Implementation Achievements of FY2019(1) Development of technology required for analysis of fuel debris properties
 Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
 Improvement in the estimation of fuel debris properties
 International cooperation for gathering the knowledge on fuel debris analysis(2) Development of technology for estimating the behaviors of fuel debris particles

 Behaviors of airborne radioactive particles generated with the processing of fuel debris
-1. Large-scale testing of particle generation by using Uranium-containing simulated debris
-2. Basic testing of particle generation behavior
-3. Investigation of cases of airborne radioactive particles in nuclear facilities in Japan andoverseas [RANDEC]
 Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase[University of Tokyo] (FY2019 to FY2020)
-1. Evaluation of particle behavior in the gas phase and gas-liquid interface
-2. Evaluation of particle behavior in the liquid phase©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for analysis of fuel debris properties[Confidential]

13
Overall plan for the development of technology required for analysis of fuel debris properties
 Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis.

a. Transportation and analysis of target analytical samples from the Fukushima Daiichi NPS
Deposit accumulated in the reactor and sediment samples during investigation inside PCV[FY2019]
Samples for small-amount sampling (fuel debris sampling)[FY2020]b. Study on improving the efficiency of analysis[FY2019]
 Improvement in the estimation of fuel debris properties
Evaluation of fuel debris properties for each area and revision of the “List of fuel debris
properties” for each area through experts’ meetings based on the results of . [FY2019,
FY2020] International cooperation for gathering the knowledge on fuel debris analysis
Review of the analysis items for the fuel debris samples from b. by an experts’ meeting while
incorporating the knowledge from international conferences organized by the OECD/ NEA*.
[FY2019]Note) The underlined parts are highly relevant and hence with be reported together. (→Pages
46-50)*OECD/NEA: The Organization for Economic Co-operation and Development, Nuclear Energy Agency©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for analysis of fuel debris properties[Confidential]

14
Positioning, purpose and correlation of the issues (Conceptual drawing of theentire output)
 Analysis of the obtained fuel debris samples,etc., and study to improve the efficiency ofanalysis• Results of analysis of fuel debris and deposits, etc.

 International cooperation for gathering theknowledgeon fuel debris analysis*
・ Analysis items for fuel debris samples (plan) andinternational cooperation
p.50
p.15-39

Reflected in analysis workAnalysis data

Improvement in the estimation of fuel debris properties•

Formation of Japan-expert meeting

Knowledge and analysis items
from international projects (plan)

Task force (Task leader: Masaki Kurata, JAEA)
Analysis and insights on 1F sample analysis results and internal observation data p.42

Study on the improvement of the list of fuel debris properties p.43-44
Study on the risks in the fuel debris retrieval process Internal study by JAEA (Non-subsidy project)

Presentation of study results

Review of study results

1F Sample Evaluation Committee(Chairman: Professor Uno, Fukui University) p.42•
Review of knowledge obtained from analysis results, etc. (plan)•
Review of analysis items for the fuel debris samples
Participatingorganizations

Fukui University, Tokyo Institute of Technology, Osaka University, Tohoku
University, TEPCO HD, Toshiba ESS, Hitachi GE, CRIEPI, GNF-J, IRID, NDF*,
JAEA. *Participation as observer

Reflection
Revision of the list of fueldebris properties
To be described after the
resolution of the issues©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]

15① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Plan for FY2019
1. Analysis of fuel debris samples

Investigation of issues related
to analysis, sample preparation,and transportation➢ The following samples will be transported to the hot laboratory in the JAEA Oarai R&D
Institute for destructive and non-destructive analysis (figure on the right).
a.

Smear sample of PCV insertion device during the investigation of Unit 2 conductedin the second half of FY2018b.

Deposit samples that will be collected during the internal investigation of Unit 1
scheduled to be implemented in the first half of FY2019c.

Additional analysis using the samples transported until last year (confirmation ofanalysis methods, analysis of insoluble substances, etc.)➢ Systematic organization of analysis resultsi.

Listing up data (composition, element map) for each measurement site in thesampleii.

Standardization of various FPs with respect to U concentration, U: Zr ratio, (U + Zr):
Fe ratio, etc.

Transportation* and reception*: Transportation of fuel debris by
TEPCO HDSample preparation
JAEA: Alkali fusion
NFD: Hydrofluoric acid + aqua regia
dissolution

Analysis of sample
JAEA: FE-SEM / WDS etc.
NFD: FE-TEM / EDX etc.

2. Study on improving the efficiency of analysis
A case study was conducted on efficient analysis methods for the fuel debris samples
retrieved initially on an experimental basis, by hearing opinions from stakeholders such as
NDF and TEPCO HD. (See pages 49 and 50 for study results)

Organization of analysis
results©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis -Achievements of FY20191. Analysis of fuel debris samples➢The following destructive and non-destructive analysis was conducted in the Oarai hot laboratory, the JAEA R&D Institutea. Smear sample of PCV insertion device during the investigation of Unit 2 conducted in the second half of FY2018(Partially implemented#1 )b. Deposit samples that will be collected during the internal investigation of Unit 1 scheduled to be implemented in the firsthalf of FY2019 (Not implemented#2 )c. Additional analysis using the samples transported until last year (confirmation of analysis methods, analysis of insoluble
substances, etc.)
・ SEM / EDX analysis of insoluble substances present on the Unit 2 operation floor curing sheet (implemented), alkali
fusion treatment and analysis of insoluble substance samples from inside the Unit 1, 2 PCV (Not implemented#3 )・ Confirmation of Gd separation process through a cold test (Implemented)#1 Due to the delay in sample

d. Analysis of additional samples (Newly implemented based on request from TEPCO)
・ Unit 1 Smear of deposit removal jig in X-2 penetration, smear of operation floor well plug・ Unit 2 Filtration of stagnant water inside torus room

carrying-in period#2 As the investigation inside Unit 1

had not been implemented#3 Due to the delay in restarting ofcell glove box work due to thehorizontal dissemination ofproblems

・ Unit 3 Filtration of stagnant water inside torus roome. Confirmation of analysis accuracy of U isotope ratio, confirmation of Gd separation process (implemented)➢ Systematic organization of analysis resultsi. Listing up data (composition, element map) for each measurement site in the sample
ii. Standardization of various FPs with respect to U concentration, U: Zr ratio, (U + Zr): Fe ratio.

©International Research Institute for Nuclear Decommissioning

16

(1) Development of technology required for the analysis of fuel debris properties[Confidential]

17① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis●: Analysis completed in FY2017 / FY2018〇: Analyzed in FY2019*

Sampling position and analysis details (Initial plan for FY2019)
Unit 1
Inside PCV

Analysisfacility

Outside PCVUnit 3Inside PCV

Outside PCVInside PCV

Samples ofdeposits frominvestigation
inside pedestal

Smear sample
Samples ofSamples offrom side wall
Samples
deposits from
Curing sheet on concrete ofdeposits fromadhering to TIP
investigation
operation floor operation floor investigation
inside PCV
inside pedestal
and itssurroundings

Muddy
samplesfrom D/W

Deposit samples
from D/W

Samples fromairlock room

Samples ofdeposits from
CRD
replacementrail area
investigation

Image plate

●

〇

●

●

●

〇

●

●

●

●

FE-SEM (whole image)

●

〇

●

●

●

〇

●

●

●

●

Alpha nuclide analysis

●

〇

●

●

〇

●

●

●

Gamma nuclide analysis

●

〇

●

●

〇

●

●

●

ICP-MS (nitric acid solution)

●

●

●

●

●

●

Measurement item

JAEA

〇

ICP-MS (alkali fusion)

NFD**

Unit 2〇

FE-SEM(U-containing particles)

●

〇

●

〇

●

●

TEM-EDX(after FIB adjustment***)

●

〇

●

〇

●

●

ICP-MS (Aqua regia, etc.)〇

Evaluate the average properties and variations of Unit 1 D/W deposits
by analyzing the chemical properties of Unit 1 D/W deposits and theproperties of U particles contained in them and by comparing andexamining them with conventional data.

〇

Gain knowledge on sample representativeness and diversity andproceed with the characterization of Unit 2 fuel debris, by analyzing
samples at various positions inside Unit 2 PCV and by comparing
and examining them with conventional data.

* If additional analysis might be effective for the samples analyzed until FY2018, then additional analysis shall be implemented for them as well**NFD: Japan Nuclear Fuel Development Co., Ltd.
***FIB adjustment: Exposing the cross section of samples with Focused Ion Beam

©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for the analysis of fuel debris properties

18① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis●: Analysis completed in FY2017 / FY2018〇: Analyzed in FY2019*
Sampling position and analysis details (Achievements of FY2019 1/2)■: To be implemented in FY2020

Unit 1
Inside PCV

Analysisfacility

Outside PCVUnit 3Inside PCV

Outside PCVInside PCV

Samples ofdeposits frominvestigation
inside pedestal

Smear sample
Samples ofSamples offrom side wall
Samples
deposits from
Curing sheet on concrete ofdeposits fromadhering to TIP
investigation
operation floor operation floor investigation
inside PCV
inside pedestal
and itssurroundings

Muddy
samplesfrom D/W

Deposit samples
from D/W

Samples fromairlock room

Samples ofdeposits from
CRD
replacementrail area
investigation

Image plate

●

■

●

●

●

〇

●

●

●

●

FE-SEM (whole image)

●

■

●

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●

〇

●

●

●

●

Alpha nuclide analysis

●

■

●

●

〇

●

●

●

Gamma nuclide analysis

●

■

●

●

〇

●

●

●

ICP-MS (nitric acid solution)

●

●

●

●

●

●

Measurement item

JAEA

■

ICP-MS (alkali fusion)

NFD**

Unit 2■

FE-SEM(U-containing particles)

●

■

●

■

●

●

TEM-EDX(After FIB adjustment***)

●

■

●

■

●

●

ICP-MS (Aqua regia, etc.)■

Sampling of Unit 1
deposit was notconducted. (FY2020)■

Gain knowledge on sample representativeness and diversity and proceedwith the characterization of Unit 2 fuel debris, by analyzing samples atvarious positions inside Unit 2 PCV and by comparing and examining themwith conventional data.
As sample aggregation at 1F and adjusting the transportation
implementation plan took time, there was delay in bringing in the samples,so the alkali fusion and analysis by NFD was carried over to next year.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for the analysis of fuel debris properties

19① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis●: Analysis completed in FY2017 / FY2018〇: Analyzed in FY2019*

Sampling position and analysis details (Achievements of FY2019 2/2)
Unit 1
Inside PCV

Analysisfacility

JAEA

Measurement item

Unit 2

Outside PCVInside PCV

Outside PCV

Samples ofdeposits from
Samples ofSmear samples ofSamples
Muddy
Samples
Smear samples
CRD
deposits fromX-2 penetration
adhering tosamples from from airlockof operation replacement rail investigation
deposit removal
TIP
D/W
room
floor well plugarea
inside pedestal
jig
investigation

Curing sheet
on operation
floor

Inside PCV

Samples ofSamples ofSmear sample Samples ofdeposits
filter paper,from side wall filter paper,from
filtrate, andconcrete of filtrate, andinvestigation
stagnant
operation floor stagnant
insidewater ofand its
water ofpedestal
Unit 3surroundings
Unit 2

Image plate

●

●

○

○

●

●

●

●

●

○

●

○

FE-SEM (whole image)

●

●

○

○

●

●

●

●

●

○

●

○

Alpha nuclide analysis

●

●

○

○

●

●

●

○

●

○

Gamma nuclide analysis

●

●

○

○

●

●

●

○

●

○

ICP-MS (nitric acid solution)

●

●

○

○

●

●

●

○

●

○

Additional analysis in FY2019

ICP-MS (alkali fusion)

NFD**

Unit 3

FE-SEM(U-containing particles)

●

〇

○

●

●

○

●

○

TEM-EDX(After FIB adjustment***)

●

〇

○

●

●

○

●

○

ICP-MS (Aqua regia, etc.)○

Proceed with the characterization of Unit 1 fuel debris properties
by analyzing the samples of deposits at locations near Unit 1
D/W and samples from locations where the deposits may havepassed through the atmosphere inside the PCV (accessroute),and by comparing and examining with conventional data.

○○

Gain knowledge on sample representativeness and diversity andproceed with the characterization of Unit 2 and Unit 3 fuel debris, byanalyzing the filtrates of high-dose stagnant water in Unit 2 and Unit 3
and by comparing and examining them with the conventional data.
Conduct a detailed analysis of the conventional sample for comparison.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for the analysis of fuel debris properties

20① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Needs for analyzing 1F sample〇 Items required from other decommissioning-related PJs# for fuel debris analysis• Fuel debris retrieval: Fuel debris distribution and quantity, corrosion range, chemical properties#, mechanical properties, thermal
properties, dose and heat generation, reactivity to high temperature#, drying properties, hydrogen generation properties, device
verification and mock-up#• Measurement control and safeguards: Concentration of U and Pu in fuel debris, isotopic composition of U and Pu• Criticality control: Coexistence of U and Pu, coexistence of U and Gd, mixture ratio of Fe and Cr, concentration and distribution of Gd,
Fe and Cr in fuel debris, concentration of Gd-155, isotopic composition of U, composition of (Pu+Am-241) / U, concentration of Cm244
The data that can be obtained at• Dose evaluation: Cs-137 dose (concentration), Sr-90 dose (concentration)• Containing, transfer and storage: Items related to criticality safety control (described above)Items related to corrosion and long-term stability (chemical forms of fuel debris#, chlorine concentration)
Items related to hydrogen generation (porosity, moisture content, chlorine concentration)
Indicators of fuel debris quantity (Quantity of Eu-154 and its coexistence with U)

the existing facilities from 1F
deposit samples is highlighted
blue and the analysis items
under this project are underlined.

• Waste: Inventory of 38 nuclides related to safety evaluation for geological disposal〇 Requirements from the viewpoint of reliability of analysis data and representativeness of sample (Discussion in JAEA and task
force)• Reliability of analysis data: Dissolution technology, analysis of insoluble components, light elemental analysis, interfering elements
and nuclides, detection limits and threshold conditions, error evaluation# Items that can be partially evaluated byunderstanding the mechanism are highlighted green.

• Representativeness of sample: Understanding of fuel debris formation mechanism(It is possible to reduce uncertainty of sample representativeness by understanding the mechanism)〇 Accident progression analysis and understanding the conditions inside the reactor©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Evaluation of 1F sample analysis data (FY2019)〇 Update on the findings on fuel debris• By observing the inside of the 1F building and analyzing the understanding the condition of the reactor, it has
become clear that the 1F fuel debris properties vary more than expected from the conventional findings of TMI-2
fuel debris.
➢ Substances with varied properties (oxides, metals and alloys, compounds, etc.) are mixed in different
states in each Unit and region.
• Therefore, it is necessary to proceed with the evaluation of the analysis data considering the reliability of theanalysis data and the representativeness of the samples for each Unit and area according to the analysis
requirements (refer to a previous slide).
〇 Analysis procedures• Prioritize items that can be analyzed even with a small amount of sample while responding to the requirements on
the previous slide (in particular, regarding the analysis focusing on U particles, which are expected to be seamlessly
linked to the fuel debris findings).
• Identify the issues such as sample melting conditions, analysis accuracy (data reliability), threshold conditions /detection limits, interfering elements and nuclides, error evaluation, etc., and develop an analysis environment forfuel debris analysis.
• Obtain knowledge on the U particle formation mechanism, which may provide knowledge on sample
representativeness.
• Furthermore, systematically organize the obtained analysis results by comparing with the past knowledge andsummarize it in “Improved list of fuel debris properties" for each Unit and area in a format that is easy for theoperator to utilize.
©International Research Institute for Nuclear Decommissioning

21

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

22

Overview of the objectives of analysis and utilization of analysis results
Sampling position

Analysis objectives

Utilization of analysis results

RelatedslidesOperation floor plug smear

I. Quantity of alpha dust and distribution inside thebuilding
II. Properties of U-containing particles (coexistencewith Pu, U isotope ratio, chemical properties)
III. To compare with the Unit 2 operation floor samples

I. Fuel debris retrieval (dose and heat generation, risk), waste
II. Criticality safety control, fuel debris retrieval (chemical
properties, risk)
III. Accident progression analysis and understanding theconditions inside the reactor

23
24

X-2 penetration deposits smear

I. To confirm the difference in distribution andproperties of U particles depending on their position
inside PCV
II. Properties (same as above), formation mechanism
and characteristics of sub-components of U-containing
particles

I. Fuel debris retrieval (fuel debris distribution and quantity,chemical properties, risk), sample representativenessII. Fuel debris retrieval (fuel debris distribution and quantity, doseand heat generation, risk), waste

25
26

Above the curing sheet on operation
floor(Additional analysis of FY2018
samples)

I. To confirm the diversity of U-containing particles
II. To estimate the impact of accident scenarios on
debris properties(Analyzing the 2 unanalyzed groups among the 4groups of U particles identified in FY2018)
III. To study the analysis methods of nitric acidinsoluble substances

I. Fuel debris retrieval (Fuel debris distribution and quantity)
II. Accident progression analysis and understanding theconditions inside the reactor
III. Reliability of analysis data28
29Internal investigation device sealing
smear

I. To compare with the smear of the internal
investigation device body
II. To confirm the variations in sample properties

I.II. Fuel debris retrieval (Fuel debris distribution and quantity,chemical properties, risk), sample representativeness30

Filtration of torus room stagnant water

I. To compare with the PCV samples and operation
floor samples (check the variation in properties)
II. To gain knowledge on the corrosion of debris andstructural materials

I. Fuel debris retrieval (Fuel debris distribution and quantity(regarding torus deposits), dose and heat generation), long-term
stability, waste
II. Long-term stability, fuel debris retrieval (risk)

31
32
36

Internal investigation device smear(Additional analysis of FY2018
samples)

I. To analyze in detail the U-containing particles having
a dense structure unique to Unit 3 samples
II. To study about debris formation mechanism, andthe possibility of metal phase formation
III. To compare with Unit 1 and Unit 2

I.II. Fuel debris retrieval (Fuel debris distribution and quantity,
dose and heat generation, chemical properties, risk), criticality
safety control
III. Accident progression analysis and understanding theconditions inside the reactor

33
34

Filtration of torus room stagnant water

I. To compare with the PCV sample and operation
floor sample (check the variation in properties)
II. To gain knowledge on the corrosion of debris andstructural materials
III. To compare with Unit 2

I. Fuel debris retrieval (Fuel debris distribution and quantity(regarding torus deposits), dose and heat generation), long-term
stability, waste
II. Long-term stability, fuel debris retrieval (risk)
III. Accident progression analysis and understanding theconditions inside the reactor

35
36

Unit 1

Unit 2

Unit 3©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

23

Overview of the sample and objective of the analysis (Unit 1: Operation floor well plug smear)〇 Overview of the sample
Location from where
sample was taken

External appearanceof the smear sample

Imaging plate picture (Exposed for 30 seconds)• U particle density (FE-SEM / WDX): About 1 particle/cm 2• Important detected components (ICP-MS): Fe, Cr (structural materials), Pb, Zn(paint), Te, Mo, Cs, Ba, Sr, Sb (FP), traces of U
• Dose: High dose detected due to Cs-137〇 Objective of the analysis• Migration route of U particles from PCV to operation floor

Knowledge on the distribution of alpha dust inside the building [Fuel debris retrieval, dose]• Composition of U particles and structural materials, coexistence of U / Pu, formation
mechanism
Knowledge on the chemical properties of fuel debris [Fuel debris retrieval]
Coexistence of U / Pu, isotopic composition [Criticality safety control, material accountancy]
Predicted maximum reachable temperature, state of fuel debris phase [Fuel debris retrieval,risk]• To compare with the Unit 2 operation floor samples
Impact of different accident scenarios on fuel debris properties
Unit 1: Slow cooling from high temperature melting state (2500 ℃ or higher)
Unit 2: Rapid cooling from a solid-liquid mixed state (about 2000-2300 ℃)[Fuel debris retrieval, risk, accident progression analysis]©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

24

Analysis results (Unit 1: Operation floor well plug smear)

FE-SEM / WDX analysis

TEM analysis

SEM/EDX

Pu

5µm(U, Fe) O2(Reference) Unit 2
operation floor sample

Fe3O
Selection of TEM analysis field of view 4
Zn
Low

5µm

High

Unit 1 operation floor well plug smear

Angular shape (slow cooling from liquid phase)Round shape (transportation in gas phase or liquid
phase, and rapid cooling and condensation)

Strength❑ Properties of U particles (FE-SEM/WDX): U particles with a size of several μm (about 1 particle/cm2) were detected. Coexistence of U and Pu wasconfirmed. The structural material components and paint components formed different phases in the surroundings. Overview evaluation of the U isotope
ratio (to be described later) was conducted. Zr was at the detection limit level (possibility that only ZrO2, which has low vapor pressure, was nottransferred).
❑ Comparison with Unit 2 operation floor sample (TEM)
Unit 1 (2019): It is presumed that it slowly cooled and deposited from the U-Fe-O liquid phase that does not contain Zr.
Unit 2 (2018): 4 types of U particles with different Zr concentrations were confirmed, and it is presumed that they each cooled rapidly and got deposited.

❑ Migration route of U particles (Consideration from analysis results): May differ between Unit 1 and Unit 2. The maximum reachable temperature of
U particles may be different.
❑ Fuel debris formation mechanism (Same as above): The melting and solidification paths of fuel debris in Unit 1 and Unit 2 may be different. It may
have an impact on the chemical properties, mechanical properties, reactivity to high temperature, hydrogen generation properties, handling risk, etc., offuel debris.
➔ Various properties of oxide-based fuel debris may differ.
©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Overview of the sample and objective of the analysis (Unit 1: X-2 penetration deposits smear)〇 Overview of the sample

External appearanceof the smear sample

Location from where
sample was taken

Imaging plate picture(Exposed for 60 seconds)• Amount of U particles (FE-SEM/WDX): About 0 ~ 2 particles/cm 2• Important detected components (ICP-MS): Fe, Cr (structural materials), Pb,
Zn (paint), Ba, Sr, Sb (FP), traces of U
• Dose: High-dose parts detected at pinpoints in contaminated areas〇 Objective of the analysis• Similarity of the samples inside PCV (Comparison with D/W muddy deposits)
Variation of U particles and matrix components [Representativeness, fuel debris
distribution]
Knowledge on the distribution of alpha-dust in the building [Fuel debris retrieval]• Composition of U particles, coexistence of U / Pu, formation mechanism
Knowledge on the chemical properties of debris [Fuel debris retrieval]
Coexistence of U / Pu, isotopic composition [Criticality safety control, material
accountancy]
Predicted maximum reachable temperature, state of fuel debris phase [Fuel debris
retrieval]• Sub-components: Knowledge on the paint material (Zn) and structural materials
Phase state of sub-components (Possibility of obtaining knowledge on fuel debris
properties)[Fuel debris retrieval]©International Research Institute for Nuclear Decommissioning25

[Confidential](1) Development of technology required for the analysis of fuel debris properties

26① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis results of Unit 1 sample (E.g. X-2 penetration deposits smear)
TEM analysis (By cutting out some of the U particles)

FE-SEM / WDX analysis

SEI

3µ
m

U

3µm
m

Pu

SS components(unidentified)

Fe

Cr

Ni

Monoclinic crystal ZrO2
(low-temperaturephase)

Cubic crystal (U, Fe) O2(possibility of low-temperature phase)❑ Properties of U particles (FE-SEM/EDX): U particles with a size of several μm were detected. U and Pu coexist. Separate layers of structural
materials components were formed in the surroundings (The site of existence of Fe, Cr and Ni were different ⇒ suggests steel components
once melted)❑ Matrix components (ICP-MS): Steel components, Si, other light elements (Al, Ca, Na, Mg, etc.)❑ Comparison with the muddy samples from D/W (TEM)
X-2 penetration (2019): Low-temperature phase (Monoclinic crystal ZrO2) was detected, possibility of slow cooling from U-Zr-Fe-O liquidphase
D/W mud (2018): Low-temperature phase (alpha-Zr (O)) was detected, possibility of slow cooling from U-Zr-Fe-O liquid phase➔ The level of fuel debris oxidation depends on the position of sedimentation [possibility of impact on the chemical properties,
mechanical properties, risks, etc.]❑ Formation mechanism (consideration): Suggests slow cooling of fuel debris during the accident progression ⇒ Phase separation,
component separation©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis(Reference) Impact on the chemical properties of fuel debris due to the difference in melting and solidification paths of fuel debris

Average composition of molten fuel (corium)
VULCANO test

TMI-2 accident

Corium

Rapid cooling: Maintains
high temperaturehomogeneous phase(yellow)

Slow cooling: Phase /component separation in
low-temperature phase(blue)〇 Molten fuel (corium) formation conditions (red)Temperature: About 2800 K or higher
Composition: Slightly Zr-rich dioxide
General trend〇 Fuel debris formed by rapid cooling (yellow)
Phase: Maintains a homogeneous single phase of the hightemperature stable phase (fcc, fct).
Components: The important components (U, Zr, Pu, Gd, etc.) were
homogeneously distributed.
Structure: Relatively dense (particulate in reaction with coolingwater)
Large particle size crystals (20 to 30 μm or more)〇 Fuel debris formed by slow cooling (blue)
Phase: Low temperature stable phase (U-rich cubic, Zr-rich mono)
Components: Phase separated into U-rich, Zr-rich, etc.
Pu, Gd, etc. were also phase separated.
Structure: Fine crystal grains (2-3 μm or less), can be powderedeasily.
〇 Conditions where corium is not formed
Temperature: About 2200 ~ 2500 K
Composition: Mixture of solid (UO2, ZrO2) and liquid (U-Zr-O melt)(not homogeneous naturally)
Components: U and Zr are largely phase-separated
Structure: Liquid phase components are separated into metalbased and oxide-based components
Dense, easy to powder and crush, active residues# When corium is not formed, evaluation using a U-Zr-O ternary
system is required.

UO2-ZrO2 binary system status diagram(P.Piluso, JNM 344 (2005) 259.)©International Research Institute for Nuclear Decommissioning27

[Confidential](1) Development of technology required for the analysis of fuel debris properties① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

28

Overview of the sample and objective of the analysis (Unit 2: Sample from the curing sheet on operation floor)〇 Overview of the sample• Amount of U particles (FE-SEM /WDX) : 226 particles/cm2• Important detected components(ICP-MS):
Fe, Cr (structural materials),
Pb, Zn (paint),
Location from where Ba, Sr, Sb (FP),sample was taken
traces of U
• Dose: Localized high dose

Green (FY2018)
Red (FY2019)
Unit 2 Operation
floor area 04

Cubic crystal (hightemperature phase)

UO2 + SS
components

Tetragonal (hightemperature phase)i)# Figure on the right: Of the 2 samples
outside the composition range,i) will be analyzed in detail as neededin the future, and data for ii) is being
inspected for particles containing
uranium.

ii)
Unit 2 Operation floorarea 30

Unit 2 Operation floor area 20

Identification of U particles in 4 groups# (2018)〇 Objective of the analysis (Additional measurement of
FY2018 sample)• Migration route of U particles from PCV to operation floor
Knowledge on the distribution and adhesion status of alpha-dust in the building [Fuel debris retrieval]
Knowledge on the diversity of fuel debris [Sample representativeness, accident progression](Detection of different particles of 4 groups (2018), implementation of additional analysis (FY2019))• Comparison with the Unit 1 operation floor well plug sample
Impact of different accident scenarios on fuel debris properties [Fuel debris retrieval]• Identification and dissolution process of insoluble substances
Knowledge related to the development of fuel debris analysis technology [Fuel debris analysis
technology]©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for the analysis of fuel debris properties

29① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis results of Unit 2 samples (E.g. Additional analysis of the sample from the curing sheet on operation floor)
TEM analysis (2019, Group d)

Green (FY2018)
Red (FY2019)

Unit 2 Operation floor area 04

b. Cubic crystal (hightemperature phase)(U, Zr) O2c. (U, Fe) O2+ SS components

a. Tetragonal (high temperaturephase)(Zr, U) O2＋Spineld①②④ (U, Zr) O2+FeCr2O4 or Fe3O4③
FeCr2O4⑤ (U, Zr) O2+FeCr2O4 or Fe3O4

Unit 2 Operation floor area 30

Unit 2 Operation floor area 20

Identification of U particles (4 groups) on the Unit 2 operation floor❑ Identification of chemical characteristics of the 4 groups of U particles
Group a: high temperature phase fct- (Zr, U)O2, FeCr2O4, Fe3O4Group b: high temperature phase fcc- (U, Zr, Fe)O2
Group c: high temperature phase fcc- (U, Fe)O2, FeCr2O4, Fe3O4Group d: high temperature phase fcc- (U, Zr)O2, FeCr2O4, Fe3O4❑ Formation mechanism (consideration): U, Zr oxide maintained the high temperature phase (however, multiple hightemperature phases were formed), and iron oxide phase (spinel) was deposited.
⇒ Iron oxide solid solution may affect chemical properties and mechanical properties of fuel debris.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for the analysis of fuel debris properties

30① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Overview of the sample and objective of the analysis (Unit 2: PCV internal investigation device sealing smear)〇 Overview of the sample

Low

Location from where
sample was taken

External appearanceof the smear sample

Dose rate

High

Imaging plate picture(Exposed for 30 seconds)• Amount of U particles (FE-SEM/WDX): Not detected so far• Important detected components (ICP-MS): Fe, Cr (structural
material), Pb, Zn (paint), Ba, Sr, Zr, Sb (FP), traces of U
• Dose: High-dose parts detected at pinpoints in contaminated areas〇 Objective of the analysis• Similarity of samples inside PCVComparison with the internal investigation device smear [Sample
representativeness]
No significant difference was seen in bulk components (ICP-MS).
Search for U particles to continue (FY2020).
©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Overview of the sample and objective of the analysis (Unit 2: Filtration of torus room stagnant water)〇 Overview of the sample

External appearanceof the smear sample

Imaging plate picture(Exposed for 30 seconds)• Amount of U particles (FE-SEM/WDX): About 10 ~ 15 particles/cm2• Important detected components (ICP-MS): Fe (rust), Pb, Zn (paint), Cs, Sb(FP), traces of U
• Dose: Extremely high-dose parts detected at pinpoints in contaminated areas
Location from where
sample was taken〇 Objective of the analysis• Comparison of properties with the samples from operation floor and inside PCV
Knowledge on the diversity of fuel debris properties [Fuel debris retrieval,representativeness]
Knowledge on the migration mechanism via aqueous phase [Long-term
deterioration]
Knowledge on the distribution of alpha dust [Fuel debris retrieval, risk]• Properties of fuel components and sub-components
Knowledge on the degree of corrosion of fuel debris and structural materials[Corrosion, long-term deterioration]©International Research Institute for Nuclear Decommissioning

31

[Confidential](1) Development of technology required for the analysis of fuel debris properties

32① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis results of Unit 2 samples (E.g. Filtration of torus room stagnant water)
FE-SEM / WDX analysis

TEM analysis (By cutting out some of the U particles)
U particles with high Zr
concentration
Cr2O3
Fe3O4
UO2
High temperature
phase(U, Zr) O2
Fe2SiO4
U particles with low
Zr concentration

Low

StrengthHigh

FE-SEM / WDX currently detects
particles with low Zr concentration only.

❑ Properties of U particles (FE-SEM/WDX, TEM): Two types of U particles with a size of several μm were detected. U and Pu coexist. Fe
was detected in the surroundings (assumed to be rust).
❑ Matrix components (ICP-MS): Steel, Si, Zn, Pb, Cs, Sn, Sb, etc. were detected.
❑ Comparison with samples from inside the PCV and operation floor (consideration): The mixability of fuel components with steel
components or Si might differ.
➔ Formation mechanism might differ from that of samples inside PCV and operation floor, chemical properties andmechanical properties might differ.
❑ Other findings: No evidence of corrosion (U (VI) formation) was observed on the surface of U particles.
➔ Suggests long-term stability of fuel debris©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Overview of the sample and objective of the analysis (Unit 3: PCV internal investigation device smear)〇 Overview of the sample region

SparseDense region• Sparse area: High temperature phase fcc- (U, Zr) O2• Dense area: High temperature phase fct- (Zr, U) O2 + alpha-Zr (O)Study in progress on the➔ Possibility of cooling from solid-liquid mixed state, separated into phases and components➔ Possibility of rationally eliminating residual active metal components
Location from where
sample was taken〇 Objective of the analysis (additional measurement of
FY2018 samples)• Detailed analysis of U particles with mixed dense areas, which is specific to Unit 3
samplesIn the Unit 3 accident process, fuel debris was separated into components and phases
at a relatively low maximum reachable temperature and a slow solidification rate,
resulting in diversified properties [Fuel debris retrieval, risk, criticality evaluation, longterm stability, material accountancy, containing and storage, etc.]• Comparison with the samples from other Units
Impact of different accident scenarios on fuel debris properties [Accident progression]©International Research Institute for Nuclear Decommissioning

33

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis results of Unit 3 samples (E.g. PCV internal investigation device smear)
Sample with highZr concentration

Sample with low
Zr concentration

High temperature
phase(U, Zr) O2

Coexistence of hightemperature phase (U, Zr) O2
and Fe3O4(U, Fe)O2
High
temperaturephase (Zr, U) O2❑ Properties of U particles (TEM): In the additional analysis, residues of alpha-Zr (O) were not identified, and properties of the two groups ofparticles were evaluated.
Particles with high Zr concentration: Slow cooling from U-Zr-Fe-O liquid phase is presumed, and the maximum reachable temperature for fueldebris may be low (solid-liquid mixture).
Particles with low Zr concentration: Possibility of slow cooling from U-Fe-O liquid phase, suggests multiple fuel debris formation mechanisms.

❑ Comparison with the samples from other Units (consideration): All of the U particles detected in Unit 3 have a more complicated structure
than those of other Units and suggests that the fuel debris may have been separated into phases and components and diversified in the process ofmelting, migration, and solidification of fuel debris.
©International Research Institute for Nuclear Decommissioning34

[Confidential](1) Development of technology required for the analysis of fuel debris properties① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

35

Objective of analysis of each sample (Unit 3: Filtration of torus room stagnant water)〇 Overview of the sample

Low
External appearanceof the smear sample

Dose rate

High

Imaging plate picture(Exposed for 30 seconds)• Amount of U particles (FE-SEM/WDX): Not detected• Important detected components (ICP-MS) : Fe (rust), Pb, Zn (paint), Cs, Sb (FP),traces of U
• Dose: Contamination had spread over the entire filter paper and high dose was
detected.
(Might have been powdered due to the stagnant water filtrate in Unit 2)〇 Objective of the analysis
Location from where
sample was taken• Comparison of properties with the samples from operation floor, inside PCV and Unit 2
Knowledge on the diversity of fuel debris properties [Fuel debris retrieval,representativeness]
Knowledge on the migration mechanism via the aqueous phase [Long-term
deterioration]
Knowledge on the distribution of alpha dust [Fuel debris retrieval, risk]• Properties of fuel components and sub-components
Knowledge on the extent of corrosion of fuel debris and structural materials [Corrosion,
long-term deterioration]©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis results of the stagnant water filtrate in Unit 2 and 3 torus room (Summary of the results so far)
Unit 2• U particles (FE-SEM/WDX): Approximately 10 ~ 15 particles/cm2• Important detected components (ICP-MS): Fe (rust), Pb, Zn (paint), Cs, Sb, traces of U
• U235/ (U-235+U-238): 0.018 (Derived from fuel)• Dose: Extremely high-dose parts detected at pinpoints in contaminated areas.
• Similarity of U particles: May differ from the PCV investigation (Feb 2018) device smear sample.
•
Planned to be compared with the PCV investigation (Feb 2019) device smear.
(The 2018 sample did not touchdown to the pedestal.)
Unit 3• U particles (FE-SEM/WDX): Not detected.
Very little uranium adhered to substances believed to be organic matter or paintcomponents.
• Important detected components (ICP-MS): Fe (rust), Pb, Zn (paint), Cs, Sb, traces of U
• U235/ (U-235+U-238): 0.018 (Derived from fuel)• Dose: Contamination had spread over the entire filter paper and high dose was detected. (Possibility ofaccumulation of fine powder)• Similarity of U particles: May differ in Units 2 and 3©International Research Institute for Nuclear Decommissioning36

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Analysis of insoluble substances and development of dissolution treatment technology
Purpose: To identify the main components of nitric acid insoluble substances for the establishment of fuel debris analysis flow.
To confirm the feasibility of dissolution technology for insoluble substances (technology other than alkaline fusion method(aqua regia / hydrofluoric acid))
Nitric acid insoluble substances containing Si as the main component

Block-like residue

SEI

Si

U

Nitric acid insoluble substances containing light elements as main
components

SEI

Si

U

5µm

Fiber residue

SEM analysis of the residue of Unit 1 operation floor
sample after dissolution with aqua regia / hydrofluoric acid

SEM/WDX analysis of Unit 2 operation floor sample residue❑ The main component in the insoluble substances in the Unit 2
operation floor sample was presumed to be SiO2 and light elements
such as C.
❑ However, U particles that cannot be completely dissolved with nitricacid remained inside.
⇒ Requires advanced dissolution treatment technology (alkali fusion,aqua regia / hydrofluoric acid treatment).

❑ Successful in almost completely dissolving thesamples from Unit 1 operation floor and residues ofstagnant water in Unit 2, 3 torus room using aquaregia / hydrofluoric acid treatment.

❑ The traces of residues were identified as filter
paper components and insoluble oxides such as Cr.
©International Research Institute for Nuclear Decommissioning37

[Confidential](1) Development of technology required for the analysis of fuel debris properties

38① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Confirmation of Gd separation process
Background: Neutron poison (Gd) is an interfering element in the analysis of rare earth elements FP (Ce, Pr, Nd, Sm, Eu, etc.) by
ICP-MS.
Purpose: To select the appropriate ion exchange resins and adjust the dissolution conditions with reference to technology forseparating Gd from irradiated fuel (existing literature: Bowers et al., 2008).
1
Gd

20% 0.9M-HNO3
80% CH3OH

Washed
水洗with water

10% 0.13M-HNO3
90% CH3OH
Ce, Pr,
Nd

0.8

Eu

Relative concentration

Sm

Ba

0.6

Ce

Pr
Nd

Sm

0.4

Eu
Gd

0.2

0
0

10

20

30

40

50

60

Eluent / mL

❑ To improve the accuracy of rare earth FP analysis, the separation process of the interfering element Gd was investigated,and prospects were gained as to the possibility of separation using the ion exchange method.
# Nd, which is a part of rare earth elements, may be used as an indicator of burnup, and requires high-precision analysis.
# Similarly, Eu could be used as an indicator of fuel debris amount in material accountancy.
©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for the analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
Method for systematic organization of analysis results (Utilization of composition triangle of major components)
Plot the U: Zr ratio and (U + Zr): Fe ratio obtained by SEM / EDX measurement on the composition triangle

Unit 1 plug 2 area 06

Unit 2 torus area 01
Unit 1 plug 2 area 07

Unit 2 torus area 02
Triangular diagram of the ratio of major
elements near U particles present in thestagnant water filtrate in Unit 2 torus room

Triangular diagram of the ratio of major
elements near U particles present inside theUnit 1 operation floor well plug smear sample

It is possible to classify fuel debris by systematically organizing the composition ratio of the major components in fuel debris and U particles[U: Zr ratio]: Melting and solidification conditions of U particles (maintenance of homogeneous high temperature phase or component / phase separated
in low-temperature phase)[ (U+Zr): Fe ratio]: Level of fuel debris oxidation (possibility of residual active metal component), level of mixing of fuel and steel⇒ Also used for comparison with existing findings (TMI-2 fuel debris, etc.). (By determining which of the various fuel debris in 1F are similar to which of
the existing findings, it is possible to utilize the existing findings to gain knowledge on mechanical properties that require relatively large samples.)©International Research Institute for Nuclear Decommissioning39

(1) Development of technology required for analysis of fuel debris properties[Confidential]

40② Improvement in the estimation of fuel debris properties
Plan for FY2019
・ Brainstorming by experts in Japan (Utilizing the results for (1) ①, 1F internal observation, related literature, etc.)
a. Evaluation of fuel debris generation process (preparatory implementation for Units 1, 2 + Unit 3 as well#)b. Estimation of damage and sedimentation condition of fuel debris and structural material, and evaluation offuel debris properties for each area in every Unit
c. Revision of “List of fuel debris properties”, and their organization from the viewpoint of the analysis needs

1F Sampling Evaluation Committee (Lead Researcher:
Professor Uno, Fukui University)➢

Participating organizations: Fukui University, Tokyo Institute ofTechnology, Osaka University, TEPCO HD, Toshiba
ESS, Hitachi GE, CRIEPI, GNFJ, IRID, NDF*, JAEA.

➢*Participation as observer

Frequency of meeting: Around thee times a year
Presentation of proposal for
list of fuel debris properties

Instructions on study policy

Task Force (Lead Researcher: Div. Chief Kurata of JAEA)
Participants: Sample analysts, Young members from theorganizations participating in the Committee
Frequency of meeting: As required

➢
➢
➢
➢

Review of the proposed list of fuel debris
properties by the experts of nuclear fuel,plant, SA analysis
Mapping of the analysis needs identified
by the JAEA experts and the list of fueldebris properties, and study of utilization
methods
Evaluation of analysis data
Improvement in the evaluation accuracy of theproperties of Unit 1 D/W deposits and Unit 2
pedestal deposits
Preparation of a proposed list of fuel debris
properties
Organization from the viewpoint of analysis needs# Sample analysis is not scheduled in this project, but a preliminary study will be conducted with reference to the in-core status estimation diagram.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for analysis of fuel debris properties② Improvement in the estimation of fuel debris properties (Overview of implementation)
Current list of fuel debris properties
Micro properties

Estimated drawing of the conditions
inside the reactor

41

Sample analysis and evaluation results

Residual fuel rods and their debris

Assumption of debris shape

Oxide debris (porous)
Particulate debris
Fuel debris (containing a lot of metal)
Concrete-mixed debris

Macro properties
Damaged CRGT
CRD (with debris inside)
ShroudPellets
Damaged RPV opening
Upper tie plate
Deposits (Material unknown)➢ Reference value (known substances suchas uranium)➢ Knowledge based on severe accident
research referencing TMI-2 and TMI-2
accident➢ Estimation based on test data using
simulated substances (MCCI products, etc.)

U-Zr-O formation mechanism➢ Estimation of the conditions inside thereactor for each Unit using the 1F
accident progression analysis based on
the site situation.

Estimated phase separation
during solidification
Composition
range of U-Zr-O

U-Zr-O status diagram (2200℃)

As the basic database for the system design of the fuel debris retrieval process, the list offuel debris properties can be updated and improved in accuracy by the exchange of
opinions between experts, taking into account the results of internal investigations and theanalysis results of the conditions inside the reactor, in addition to the results of on-site
sample analysis.

➢ Sample analysis results (measurement facts)➢ Analysis and evaluation (evaluation basis)➢ Expected fuel debris properties©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for analysis of fuel debris properties

42② Improvement in the estimation of fuel debris properties
Achievements in FY2019
The 1st 1F Sample Evaluation Committee (July 17, 2019)➢ Sharing awareness about the purpose and plans of the 1F Sample Evaluation Committee➢ Introduction to the related information (list of fuel debris properties, estimated drawing of the conditions inside the reactor, analysis resultsof 1F samples, and so on)• Evaluation of the fuel debris generation process is important in the analysis of 1F samples.
• The list of fuel debris properties should be in a form that is easy for the decommissioning operators to use. It is extremely important towork closely with the users on this.
• Coordination with the Treatment and Disposal of Solid Radioactive Waste Project, etc., and sharing of the analysis results is essential.

The 2nd 1F Sample Evaluation Committee (February 25, 2020)➢ Technical review including international discussions on analysis items suitable for small amount of fuel debris samples
・It was confirmed that the analysis items selected in this project are identified as having a high level of importance internationally as well.

Task Force (Conducted as requested from November 20, 2019)➢ Discussion on the focus points of the generation mechanism for this fiscal year's analysis samples and the previous samples
・ The Cs chemical species (Cs2MoO4, CsBO2, etc.) in the gas phase reflect the conditions inside the reactor during the accident, andshould be organized with the focus on Mo and B as well.
・ Even if the U particles are minute, their chemical state is highly likely to seamlessly reflect the fuel debris formation mechanism (rapid
cooling or slow cooling, diversity of fuel debris, etc.). The same applies to the structural material attached to the U particles.
Understanding the U particle formation mechanism would be effective to leverage the knowledge obtained from the small
amount of fuel debris samples for the evaluation of risks in debris retrieval.
・ The chemical analysis data must be organized paying constant attention to the detection limit, intrusion of fine powder, insoluble
residues, etc.
➢ Verification of reliability and quality control of this fiscal year's sample analysis data
・Opinions were exchanged on detection limits, threshold conditions for obtaining reliable data, evaluation methods for heavy elements
above Np and Pu, etc., in ICP-MS analysis and radiation analysis, and systematic data organization methods were summarized.
・The measurement error factors in FE-SEM/WDX and FE-TEM/EDX were examined, and important data to be used for the study of theformation mechanism of U particles which will be carried out in the next fiscal year, was selected.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for analysis of fuel debris properties② Improvement in the estimation of fuel debris properties
Overview of study[Policy for improvement of list of properties]
Link the information that can be used and organize the characteristics of fuel debris andstructural materials for each Unit and area. Identify and examine the level of importanceof risks (proposed as analysis needs at the time of planning) in fuel debris retrieval,storage, treatment, etc., so that they can be used by the decommissioning operators.

[List improvement work]
The Study TF developed the concept of an improved properties list, and conducted astudy on the information links for each Unit and area, and a study on the fuel debris
generation mechanism.

Information contributing to the revision of the list of fuel debris properties• Analysis data obtained with “① Analysis of the obtained fuel debris samples
and study to improve the efficiency of analysis”• Initial quantity and materials of the plant[Information provided by TEPCO HD and the plant manufacturer]• Estimation diagram of fuel debris distribution[Upgrading of the Comprehensive Identification of Conditions inside Reactor
Project implemented in FY 2016-2017]• Current list of fuel debris properties[Fuel Debris Characterization Project implemented from FY2013 to FY2018]• Details of the study conducted by JAEA subcommittee for the study on fueldebris research strategy [Internal study by JAEA - Non-subsidy project](On the analysis of fuel debris at TEPCO Holdings’ Fukushima Daiichi NPS)[Study of retrieval risks]
Identification of fuel debris retrieval risks was undertaken based on the improved list.

List of fuel debris properties to be revised (Conceptual diagram of configuration based on the study undertaken by the Study Task Force)
Comprehensively evaluate the information obtained on the fuel debris generation process (basic mechanism and migration behavior) and distribution and create aprovisional list.
Estimate the composition and structural materials in each area as well as propose issues pertaining to fuel debris retrieval.
(1) Fuel debris generation process
Describe the basis that the state
described in (2) will be reached.
(2) Estimating the composition andstructural materials in each area

Unit 2: Oxide debris (porous): Particulate debris: Fuel debris (containing a lot of metal): Concrete-mixed debris: Deposits (Material unknown)◼ Phase status, distribution, and quantity of main
components◼ Chemical form, distribution, and content of FP◼ Degree of oxidation, mixing, and homogeneity◼ Mechanical properties◼ Dose rate
◼ Surface deposits
Etc.

Pre-accident
information

Initial quantity andmaterials[RPV]・Reactor vessel, standard, X
kg・Insulating material, standard,
X kg
[PCV]
・Concrete[Core]
・Fuel etc.

Elapsed time

Migration behavior ofreactor core materials◼Inverse problem analysis
of solidification path

Reference information(Internal study by JAEA - Nonsubsidy project)

Identification ofConditions inside Reactor
Project◼Plant data
◼SA analysis

Proposal Issues related to fuelCurrent information

Analysis data
◼ FE-SEM◼ Alpha-nuclide
analysis◼ Gamma-nuclide
analysis◼ ICP-MS◼ TEM-EDS, etc.

Obtained knowledge

Current list of fuel debris
properties (knowledge from
TMI-2 accident)+
Examples of past accidents
in nuclear facilities andknowledge from simulated
tests, etc.
◼ Table of micro properties◼ Table of macro properties◼ Assumption of shape◼ Dose rate near thesurface◼ Behavior of radiation
particles◼ Aging etc.

debris retrieval◼Fuel debris re-criticality
evaluation◼Scattering of alpha dust,
Pu / Am properties,
evaporation of U
particles, diffusion ofresidual FP during the
cutting of fuel debris◼Study of risks in fueldebris retrieval, etc.
Reference information(Internal study by JAEA Non-subsidy project)©International Research Institute for Nuclear Decommissioning

43

[Confidential](1) Development of technology required for analysis of fuel debris properties

44② Improvement in the estimation of fuel debris properties
Improved list of fuel debris properties (E.g. Bottom of Unit 2 pedestal)

Each related information card that serves as the basis
for decision was organized and a database was created.
Basis for decisionInterpretation of fuel debris distribution and generation process
No.

Area
2号機ペデスタル床部
Bottom of Unit 2 pedestal

1

Estimation of the composition and structural materials in each area
Composition and structural
Fuel debris generation processmaterials■ Phase status and quantity of main
components■ Chemical form and content of FP■ Extent of oxidation, mixing, andhomogeneity■ Mechanical properties■ Dose rate
■ Surface deposits, etc.

Estimated drawing of the conditions inside the reactor

Reflection(Example)
The analysis of samples collected from the [area]
reveals the [analysis data]. Comprehensive
evaluation of [internal investigation], [accident
progression], [previous knowledge], and [initialquantity and materials] suggests that fuel debris of[composition and structural materials] exists in thevicinity of the [area]. The risk of retrieving this fueldebris contains [issues related to fuel debris
retrieval].

Uncertainty

Describes theuncertainty in estimationand the requirement for
future sample analysis
to reduce theuncertainty

Related information
Initial quantity and Core materialInternal
materials
migration behavior investigation■ Quantity in eachregion■ Standard ofstructural materials■ Physical propertiesetc.

■ Plant data
■ SA analysis■ Status diagram■ Inverse problem
analysis ofsolidification pathetc.

■ Date of investigation■ Overview ofinvestigation■ Results ofinvestigation etc.

Analysis data

Previous
knowledge■ Information on
location ofcollection■ Mechanism■ FE-SEM■Alpha-nuclide
analysis■ Gamma-nuclide
analysis■ ICP-MS■ TEM-EDX etc.

Examples of past
accidents in nuclear
facilities and knowledge
from simulated tests:■ Table of microproperties■ Table of macro
properties■ Assumption of shape■ Dose rate near thesurface■ Behavior of radiation
particles■ Aging etc.

Related information card (example)
Micro properties

Residual fuel rods and their debris
Oxide debris (porous)
Particulate debris

Assumption of debris shape

Fuel debris (containing a lot of metal)
Concrete-mixed debris
Damaged CRGT
CRD (with debris inside)
ShroudPellets

Deposits (Material unknown)

Risk■ Issues related tofuel debris retrieval■ Analysis needs

Reflects the study
results of JAEA's Fuel
Debris TF and thestudy results of theStudy TF in this project

Composition rangeof U-Zr-O

U-Zr-O status diagram (2200oC)

Damaged RPV opening
Upper tie plate

Macro properties

Estimated phase separation
during solidification

Risk

Study of debris
solidification mechanism
using materials science
database and SA analysis

Evaluation of the average degree ofoxidation of fuel debris, which is an
important factor, from the fuel melting
mechanism during the accident andthe sample analysis results.

Evaluationofthesimilarities with fuel debris
properties obtained fromprevious knowledge suchas the TMI-2 accident[Summary]
・ A plan was prepared for the revision of the list of fuel debris properties. (In FY2020, the plan is to organize the improved list into an easy-to-use
format. Page 67 shows the consolidated format as a reference.)
・ In FY2020, the basis for decision will be improved, a property list reflecting all the knowledge obtained currently will be consolidated, information
will be exchanged with decommissioning operators, and the fuel debris retrieval risks will be identified, and the level of importance evaluated. In
addition, the obtained knowledge will be reflected in the estimated drawing of the conditions inside the reactor.
©International Research Institute for Nuclear Decommissioning[Confidential](1) Development of technology required for analysis of fuel debris properties45
 b. Study to improve the efficiency of analysis and Review of analysis items by experts’ meetings

Since this content is highly relevant, it will be reported together in the following order:(Pages 46-50)
 Analysis of the obtained fuel debris samples and study to improve the efficiency of analysisb. Study to improve the efficiency of analysis
・ Study of analysis items for small amount of fuel debris samples

・ Study to improve the efficiency of analysis
 International cooperation for gathering the knowledge on fuel debris analysis©International Research Institute for Nuclear Decommissioning

(1) Development of technology required for analysis of fuel debris properties[Confidential]① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

Study of analysis items for small amount of fuel debris samples
Background: JAEA study on fuel debris (Non-subsidy project)
From the viewpoint of the need to safely and steadily proceed with the decommissioning work at 1F, JAEA has summarized theissues in the management and analysis of processes from retrieval to treatment and disposal of fuel debris, and has consolidated
the analysis needs and methods for their resolution.[1]Based on this principle, the identification of focus points for analysis, and the evaluation items and analysis items were studied
using a small amount of fuel debris sample as an example.
[1] See JAEA-Review 2020-004 for the analysis of the fueldebris at TEPCO Holdings’ Fukushima Daiichi NPS

Conditions of study➢ Study of analysis items for the initially presumed case of retrieval of small amount of fuel debris
・ Transportation of a small amount of retrieved fuel debris is assumed to be A-type transportation
・ The amount that can be transported in an A-type container is not determined by the shape and weight, but in consideration of
the difficulty of analysis, it is assumed that the shape is a sphere of about 1 mm or a square of about 5 mm, and the weight isabout 0.5 g or less.
・ Items that are thought to be feasible at the current existing facilities (JAEA + NFD) in the Ibaraki area will be studied.
➢ Focus points for the study of fuel debris analysis items
・ Focus on the needs of related projects when analyzing the fuel debris samples at the current existing facilities in the Ibaraki
area.
・ Consider the generation mechanism, which is important information for estimating the properties of the 1F fuel debris, basedon the evaluation results of deposit and sediment accumulated in 1F, which have been obtained in recent years.

1F Sample Evaluation
Committee

Status of studies at OECD/NEA
International Conferences©International Research Institute for Nuclear Decommissioning46

[Confidential](1) Development of technology required for analysis of fuel debris properties① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis

Analysis items for small amount of fuel debris samples
・ Presuming a small amount of fuel debris samples (A-type transport container), analysis items that can be
implemented with the analytical equipment of the existing facilities (JAEA＋NFD) were identified for each of thestages of A) Acceptance analysis and non-destructive analysis, B) Physical property measurement andinstrumental analysis, and C) Chemical analysis ⇒ Can be incorporated into the fuel debris analysis needs

A : Acceptance analysis and non-destructive analysis
A-1 Observation of appearance (periscope)
A-2 Weight measurement
A-3 Dose measurement
A-4 Imaging plate
A-5 Gamma ray measurement (scan)
A-6 X-ray CT*
B : Physical property measurement and instrumental
analysis
B-1 Metallurgic observation (Optical microscope)
B-2 Crystal structure and phase identification (XRD)
B-3 Constituent elements / impurities (SEM/EPMA)
B-4 Crystal structure and phase identification (TEM)

B-5 Density measurement (immersion scales)
B-6 Hardness and toughness (Vickers hardness tester)B-7 Moisture measurement (Karl Fischer moisture meter)

C : Chemical analysis
C-1 Elemental analysis (ICP-AES)
C-2 Nuclide analysis (ICP-MS)
C-3 Alpha-ray emitting nuclide analysis (Alpha-ray spectrometer)
C-4 Beta-ray emitting nuclide analysis (Liquid scintillation)
C-5 Gamma-ray emitting nuclide analysis (Gamma-ray
spectrometer)
C-6 Nuclide analysis (TIMS)**Optional: Items that are not mandatory but can be expected toacquire more advanced data

©International Research Institute for Nuclear Decommissioning47

[Confidential](1) Development of technology required for analysis of fuel debris properties① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
2. Study to improve the efficiency of analysis➢Policy for the study to improve the efficiency
・ NDF, TEPCO HD, MRI, and JAEA agreed to hold a liaison meeting on improvement of analysis efficiency, and to conduct acase study on the small amount of fuel debris samples expected from the trial debris retrieval.
✓✓✓✓Analysis items that answer the needs of decommissioning
Take into account the fuel debris formation mechanism based on the evaluation results of 1F deposits and sediments
Take into account the status of equipment at the existing Ibaraki area facilities (JAEA, NFD).
Study analysis items and flows to get as much data as possible➢Case study (Weight and shape)
Case 1: One spherical particle of 4 mm Φ and 0.447 g (Assuming spherical UO2 particles at the maximum loading capacityof the A-type transport container)
Case 2: One spherical particle of 1 mm Φ and 0.006 g (Assuming recovery of one spherical UO2 particle by gold brushsampling)
Case 3: Powdered sample (Assuming recovery of about 0.1 g on a 3 cm Φ filter paper by the vacuum blood collection tube
method of sampling)➢Case study (Days required for analysis)
・ Assuming that the analysis is carried out within the project period, the implementation items of cases, where the number ofdays taken for analysis is limited to 1 month or 2 months, are compared with the cases where all the analysis items listed in
the above study policy are analyzed.
・ In the actual analysis work, it can be assumed that hold points will be set for the analysis sample processing methods suchas non-destructive analysis, physical property measurement, chemical analysis, and also for verification of results, etc., anddiscussions will be held among the stakeholders, but the schedule is not taken into consideration.

©International Research Institute for Nuclear Decommissioning48

[Confidential](1) Development of technology required for analysis of fuel debris properties① Analysis of the obtained fuel debris samples and study to improve the efficiency of analysis
・ Study to improve the efficiency of analysis➢Summary of the study
As a study to improve the efficiency of analysis, case studies were conducted on the presently existing
facilities in Ibaraki Prefecture, using sample weight / shape and analysis period as parameters.
The summary of the consolidated results is as follows:・ When the fuel debris sample is relatively large (Case 1), the assumed fuel debris analysis items arealmost feasible. (JAEA Nuclear Science Research Institute and the Oarai R&D Institute)・ When the fuel debris sample is relatively small (Case 2, Case 3), there are analysis items that are
difficult to implement in the physical property measurement and instrumental analysis.

In the future, this result will be reflected in the study on the analysis plan, and necessary studies will be
additionally implemented in consultation with NDF and TEPCO HD.

©International Research Institute for Nuclear Decommissioning49

(1) Development of technology required for analysis of fuel debris properties[Confidential]

50
 International cooperation for gathering the knowledge on fuel debris analysis
The status of studies at OECD/NEA International Conferences waspresented to the 1F Sample Evaluation Committee, which reviewed theabove-mentioned fuel debris sample analysis items, and provided an
overview and the following comments:

・ It is necessary to create guidelines regarding which samples are to becollected by the site and the guidelines should make the analysis work
post collection smooth.
・ Since there is still time, it is important to create optimum guidelines bycontinuing the discussions.
➢Summary
Based on the present results of review by the 1F Sample Evaluation
Committee, the scrutiny of the analysis items will continue.

©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]

51

Overall plan for the research on fuel debris particle behavior① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-1. Large-scale testing of particle generation by using Uranium-containing simulated debris (ONET/CEA/IRSN, France)➢ Preparation of the U and Hf-containing simulated debris samples and the design, manufacture, and installation of thesampling line and analysis system for the radioactive particles generated during the heating and mechanical cutting of thesamples [FY2019]➢ Execution of large-scale testing and result evaluation using the above-mentioned samples, sampling line and analysis
systems [FY2020]①-2. Basic testing of particle generation behavior (JAEA)➢ Establishment of an experiment and collection system in order to carry out the light-concentrated heating and mechanicalcutting test using Pu-containing samples [FY2019]➢ Execution of the light-concentrated heating and mechanical cutting test using Pu-containing samples, and Pu contingency
evaluation [FY2020]①-3. Investigation of cases of airborne radioactive particles in nuclear facilities in Japan and overseas (RANDEC)➢ Investigation and summarization of cases pertaining to the nuclear facilities in Japan, and study of applicability to the actual
work processes [FY2019]➢ Investigation and summarization of cases pertaining to the nuclear facilities in Europe and in the US, and study of applicability
comprehensively including the case investigation results [FY2020]② Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase (University of Tokyo)②-1. Evaluation of particle behavior in the gas phase and gas-liquid interface➢ Selection of particles for testing, deciding the water quality conditions, measurement of the migration rate in the gas-liquidinterface, and study of the analysis model [FY2019]➢ Measurement of the migration rate in the gas-liquid interface and applicability evaluation of the analysis model [FY2020]②-2. Evaluation of particle behavior in the liquid phase➢ Selection of particles for testing, deciding the water quality conditions, measurement of the sedimentation rate, and study ofsimulation for evaluation [FY2019]➢ Measurement of the sedimentation rate, applicability evaluation of CFD simulation, and evaluation of migration rate [FY2019
to FY2020]©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]
52

Overview of implementation
Knowledge and information believed to be necessary for the study of safety design and confinement
measures for the radioactive particles generated during 1F fuel debris retrieval and processing
Needs on the information user
<Off-gas Treatment System>
Migration to
the gas phase

Generation ofradioactive particles

Study issue example 1
Expected performance from the particle removal andcollection equipment and its maintenance frequency, etc.

Study issue example 2
Possibility of adhesion or adsorption to the off-gas
piping material, etc. (Optimization of pipe design)<Liquid Waste Treatment System>
Study issue example 1
Required performance from the particle removal andcollection equipment and its maintenance frequency, etc.

Image of the processing method under study(Top: Boring, Bottom: Laser gouging)(FY2014 Subsidy Project for Development of Fundamental
Technology for Retrieval of Fuel Debris and Internal Structures)

Migration to theliquid phase

Study issue example 2
Possibility of adhesion, adsorption or sedimentation on
the water treatment system piping material, etc.
(Optimization of pipe design)

Knowledge and information necessary andindispensable for study

Results achieved by executing these issues(Output)

1. Generation behavior and amount of generation
2. Physical properties (particle size, specific gravity, etc.) andchemical properties (elemental composition, etc.)
3. Particle migration and transportation behavior in each of the phasesof the particles generated due to the processing method that is under
study©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]<FY2019 Overview of Results and Complementary Relationship Between Various Issues>① Behaviors of airborne radioactive particles generated with the processing of fuel debris<Understanding the generation behavior (Amount of generation and particle properties)>

-1. Large-scale testing of particle generation byusing Uranium-containing simulated debris①-2 Basic testing of particle generation behavior• Preparation of specimens, and completion ofdesign and installation of the sampling andanalysis system necessary for testing in FY2020• Understanding the generation behavior andproperties of the U-containing simulated debris
particles• Establishment of the sampling and analysis system to be
used during the testing in FY2020 and completion of its
performance evaluation• Understanding the behavior and properties of U/Pu in theparticles of oxide-based simulated debris((U,Pu,Zr)O2-x)

Supplementation
with Pu
information② Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase<Understanding the migration behavior>②-1 Evaluation of particle behavior in the gas phase andgas-liquid interface• Measurement of particle migration rate from the gas phaseto the liquid phase, and evaluation of the influence of water
quality conditions, etc.
• Development and optimization of the model to evaluate thegas phase to liquid phase migration phenomenon②-２ Evaluation of particle behavior in the liquid phase• Measurement of particle sedimentation rate in the liquid phase,and evaluation of the influence of water quality conditions, etc.
• Development and optimization of the model to evaluate theliquid phase migration phenomenon①-3 Investigation of cases of airborne radioactive
particles in nuclear facilities in Japan and overseas• Literature survey of the diffusion cases in Japanand overseas

Information
supplementation

Proposal of estimation and evaluation technology for the generation and migration behavior of particles derived from fuel debris
Provision of knowledge in a format (basic data, trends, etc.) which enables the sharing of information with otherprojects (Retrieval PJ, etc.)©International Research Institute for Nuclear Decommissioning53

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]

54① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-1. Large-scale testing of particle generation by using Uranium-containing simulated debris(ONET/CEA/IRSN, France)
Actual Results in FY2019➢ Study of sample specifications (study of manufacturing methods and specimen composition),and completion of manufacturing of all 8 samples➢ Completion of designing of the heat test system, completion of the optimization and installation
work, execution of preliminary testing, verification of atmosphere (N2) in which testing can be
carried out. Testing is scheduled for next fiscal year under N2 atmosphere.
➢ Decision on specifications for the processing tool to be used during the mechanical cutting test,completion of optimization of the cutting test system design, and execution of preliminary test
FY2019July

Sample manufacturing

AugustSeptember October November December January February

March

Verification of sample specifications
In-vessel sample manufacturing and supply
Ex-vessel sample manufacturing and supply

Development of VITI
(heat test device/facility)

Remodeling and updating of the existing facilities
Designing and verification of the sampling line
Device assembly, installation, and commissioning

Development of the cutting test
device/facility

Designing of the cutting test system
Assembly and verification of the cutting test
chamber and test system©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-1. Large-scale testing of particle generation by using Uranium-containing simulated debris(ONET/CEA/IRSN, France)
FY2019 Results (test samples)
Table: Basis for the decision on the specifications, manufacturing method, and composition of the specimens used in this project
Sample No.

Sample name

Weight of theSpecimen

Pu/FP simulated
body*existence

ManufacturingmethodTest items

Actual MCCI reaction Heating/Cutting
Heating in crucible

Heating

Sample manufacturing
Done (January 2017)
To be manufactured
during this activity

Refer to the composition of Sample No. 1 (MCCI at 1F Unit 1)

Heating in crucible

Heating/Cutting Done (Prior to FY2016)

Heating in crucible

Heating/Cutting Done (Prior to FY2016)

Heating in crucible

HeatingHeating in crucible

CuttingHeating in crucible

HeatingHeating in crucible

Cutting

To be manufactured
during this activity
To be manufactured
during this activity
To be manufactured
during this activity
To be manufactured
during this activity

Grounds behind deciding the composition
MCCI reaction with the molten material or the MCCI reaction with the concreteelements inside the reactor core at 1F (Unit 1)

Average composition of the molten material inside the reactor core at 1F Unit 2
by means of the BSAF calculation

BSAF calculation + MCCI calculation of the US-DOE/NRC (Unit 2)
Average composition of the molten material inside the reactor core at 1F Unit 2
by means of the BSAF calculation
Average composition of the molten material inside the reactor core at 1F Unit 2
by means of the BSAF calculation

BSAF calculation + MCCI calculation of the US-DOE/NRC (Unit 2)
BSAF calculation + MCCI calculation of the US-DOE/NRC (Unit 2)* Pu is simulated with Ce, and the FP composition was decided on the basis of the computed values taking into account lapse of 10 years and disintegration with respect to the average values ofUnits 1 to 3, which are in turn based on the fuel composition evaluation values at 1F (Fuel composition (JAEA-Data/Code 2012-018) as of March 11, 2011 using the ORIGEN2 code).

The specifications of the test samples are set in such a way that it is possible to compare and study the representative
composition (Corium based, MCCI reaction products, existence of FP element) assumed for the actual fuel debris. Preparationof all the eight test samples have completed.

External appearance of the UO2_MCCI sample (No. 1)

External appearance of the UO2_In-vessel sample (No. 6)

External appearance of the UO2_In-vessel sample (No. 8)©International Research Institute for Nuclear Decommissioning55

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-1. Large-scale testing of particle generation by using Uranium-containing simulated debris (ONET/CEA/IRSN, France)

FY2019 Results (Heat test device and sampling and analysis system)

Optimized Heat Test System, and Sampling and Analysis Line
The Chamber, and the Sampling
and Analysis Line for the Heat Test
(Figure above), Diagram of theinternal structure of the heating
chamber (Figure below);
The deposition of particles
generated due to heating, duringtransportation, was kept to theminimum by optimizing the designof the heating furnace, and thetransportation, sampling, andanalysis line.

Evaluation of the migration and deposition behavior of particles inside
the sampling and analysis line for heat test using CFD simulation©International Research Institute for Nuclear Decommissioning56

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-1. Large-scale testing of particle generation by using Uranium-containing simulated debris (ONET/CEA/IRSN, France)
FY2019 Results (Mechanical cutting (core boring) test device and the sampling and analysis system)

Chamber, and sampling and analysis line for the mechanical cutting test
(Final study of design is underway)
System for performance testing of the device (core boring)
to be used in the mechanical cutting test

Performance test result of theabove-mentioned cutting device(Test of cutting a ZrO2 block by adiamond-coated bit)
It was confirmed that a diamondcoated bit is more effective forcutting and particle generation
than a diamond bit<Analysis items for the collected particles>(Information to be acquired in FY2020)➢ Amount of particle generation➢ Changes in concentration of the generated
particles with time
➢ Particle shape➢ Particle composition, density, and estimatedradioactivity©International Research Institute for Nuclear Decommissioning57

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]

58① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-2. Basic testing of particle generation behavior (JAEA)
Actual Results in FY2019➢ Heating device (light-concentrated heating device) and mechanical cutting device (low-speed
rotating and cutting machine) to be used during tests, have been set up inside the glove box at
the in-house facility of JAEA (Pu Fuel Technology Development Center).
➢ Performance verification tests of the above-mentioned testing devices have been conductedusing simulated material (Fe2O3,U3O8).
➢ Pu-containing simulated debris sample ((Pu, Zr)O2-x) manufactured➢ The heat test and mechanical cutting test were executed using the above-mentioned Pucontaining simulated debris samples.
➢ It was confirmed that Pu fumes can be generated by the heating device used, and thegenerated fumes can be solidified into particles. It was also confirmed that the particle (cutparticles) samples generated by the mechanical cutting device can be collected and analyzed.

©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-2. Basic testing of particle generation behavior (JAEA)

FY2019 Results (Creation of simulated debris samples and development of particle collection system)

Produced (Pu, Zr) O2-x
simulated debris

Light-concentrated
heating device(Thermal processing test)

Low-speed cutting machine set up
inside the glove box (Mechanicalprocessing test)

Thermal processing: The fumes (steam) generated due to heating come in contact with the container surface
and solidify into particles which are then collected.
Mechanical processing: Collection of particles (cut particles) that are generated by cutting

The collected samples are identified using EPMA and powdered XRD to understand the properties(elemental composition, shape etc.) of the generated particles.
©International Research Institute for Nuclear Decommissioning

59

[Confidential](2) Development of technology for estimating the behaviors of fuel debris particles

60① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-2. Basic testing of particle generation behavior (JAEA)
FY2019 Results (Performance verification of test device and analysis of samples)
W

Pu

Zr

Secondaryelectron image

Solidified material (white material in the photograph on the left)formed from the fumes generated when the (Pu, Zr)O2-x sample
is heated with the light-concentrating method, and the EPMA
measurement results of this solidified material (photograph on
the right)

W

Pu

Zr

Secondaryelectron image

The cross-section (photograph on the left) of the (Pu, Zr) O2-x
sample after it has been cut mechanically, and the EPMA
measurement results of the cut particles (particles) generated during
cutting (photograph on the right)<Summary of FY2019 Results>
・ The heating device and the mechanical cutting device were set up inside the glove box used for the JAEA hot test.
・ The performance verification test of the heating device was executed using Fe2O3 and U3O8, and the fume-derived particle
sample was collected and analyzed.
・ Pu-containing simulated debris (Pu, Zr)O2-x was produced.
・The heat test and the mechanical cutting test were executed using the (Pu, Zr)O2-x sample, and the collected samples wereanalyzed.
(It was confirmed that Pu and Am evaporate more easily than Zr on heating, that there is no element dependency on theparticle composition generated in mechanical cutting, and so on.)©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-3. Investigation of cases of airborne radioactive particles in nuclear facilities in Japan andoverseas (RANDEC)
Achievements in FY2019
1. Summary of cases and reports for Japanese nuclear facilities➢ Investigation of case reports of a total of 13 facilities in the following 4 fields:① Cases of decommissioning of reactor facilities (old JAERI/ “JPDR”, new model ATR “Fugen”)② Cases of operation and decommissioning of nuclear fuel handling facilities (JAEA Oarai/ FMF, AGF/
MMF, JMTR Hot Laboratory, WDF, JAEA Nuclear Science Research Institute/ Reactor FuelExamination Facility, hot laboratory facilities of the Tokai Research Establishment)③ Mixed-oxide (MOX) fuel manufacturing facilities (JAEA Nuclear Fuel Cycle Engineering Laboratories,
Pu Fuel Technology Development Facility, co-conversion development facility)④ Cases of decommissioning of reprocessing plants (JAEA Nuclear Science Research Institute/ JRTF)➢ Information specifically related to the generation and diffusion of particles was identified in light of theinvestigated cases, and studies are being conducted on the relevance and adaptability to the evaluationof the generation and migration behaviors of radioactive particles during the fuel debris retrieval work in
1F.

2. Preliminary investigation of information and details of cases in European and US facilities① Preliminary investigation was conducted for the presence of facilities and reports on cases of airborne
radioactive particles in Europe, and four German facilities were selected.
② Preliminary investigation was conducted in the target facilities in the US for the above-stated details,
and U.S. Department of Energy's Post-Irradiation Examination facility was selected.
③ The need for re-investigating and re-acquiring information on the Chernobyl nuclear accident inUkraine and the TMI-2 nuclear accident in the US was studied.
©International Research Institute for Nuclear Decommissioning61

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]
62① Behaviors of airborne radioactive particles generated with the processing of fuel debris①-3. Investigation of cases of airborne radioactive particles in nuclear facilities in Japan andoverseas (RANDEC)
Examples of case investigation results for Japanese nuclear facilities

Investigation of the relationship between the cutting methods and the particles generated during dismantling Fugen✓ In the case of thermal processing, the particle size distribution of the generated particles differs depending on
the processing method, but there is not much difference based on the material.
✓ The exhaust system and HEPA filter that are being used from the past are quite sufficient as the collection
system for the generated particles (up to 100 nm or more).
✓ Upon investigation of water-to-air migration rate of particles when processing (plasma arc, AWJ) is performed inwater, the relationship between the processing conditions and the migration rate (in processing that involved
increase in cutting speed (increase in the amount of particles generated) or heat input (high temperature
conditions), the migration rate of particles into the air increases, etc.) was identified.

Investigation of particles generated during GB mechanical cutting and dismantling at a MOX fuel manufacturing facility✓ The particles generated when mechanical cutting is performed with a tool such as a band saw or nibbler are in
the order of magnitude of μm, which is larger than the particles (in the order of nm) generated during thermal
processing.
✓ Although there are some differences depending on the tool and the material properties of the object to be cut,the size and distribution of particles generated during mechanical cutting and processing are basically in theorder of μm.
✓ No dependence was seen on the type of radionuclide in the particle size distribution of the generated particles.

©International Research Institute for Nuclear Decommissioning

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]② Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase(University of Tokyo)②-1. Evaluation of particle behavior in the gas phase and gas-liquid interface②-2. Evaluation of particle behavior in the liquid phase
Achievements in FY2019②-1. Evaluation of particle behavior in the gas phase and gas-liquid interface➢ Selection of particles and water quality conditions to be used in the test
➢ Measurement of particle migration rate in the gas-liquid interface under varying water quality conditions(amount and size of bubbles, pH, and particle surface charge)➢ Implementation of tests using nano bubbles and micro bubbles for changing the physical properties ofwater, such as the surface tension, and for basic evaluation focusing on the influence of bubbles thatcan be generated by various disturbances during debris retrieval, especially the remaining time in theliquid phase and the bubble size that is important when considering the interaction with particles➢ Study of an analysis model for the evaluation of the particle migration phenomenon in the gas-liquidinterface②-2. Evaluation of particle behavior in the liquid phase➢ Selection of particles and water quality conditions to be used in the test
➢ Measurement of sedimentation rate in the liquid phase under varying water quality conditions (pH,electrolyte concentration)➢ Study of simulation for the evaluation of the particle sedimentation phenomenon under flow conditions©International Research Institute for Nuclear Decommissioning63

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]② Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase (University of Tokyo)②-1. Evaluation of particle behavior in the gas phase and gas-liquid interface
Achievements in FY2019[Common] Selection of particles to be used in tests, and specification of water quality conditions:•

Based on the results of the laser cutting test conducted by ONET, ZrO 2 particles (100, 200 nm), and low-density TiO2 particles(4.2 g/cm3, 100, 200 nm) were selected, and their particle size was verified and zeta potential was evaluated using laser
diffraction and DLS.
Considering that particle density is the main factor governing migration behavior, the two samples of ZrO 2, which is believed to
be one of the main components of 1F fuel debris, and TiO 2, which has a lower density, were selected.
Ion-exchanged water (distilled water) was selected as thedispersion medium for the gas phase, gas-liquid interface, andliquid phase tests based on the water quality measurement results(neutral pH) for the stagnant water in 1F PCV.

••➢[②-1: Gas phase and gas-liquid interface] Measurement ofparticle migration rate in the gas-liquid interface•

The gas phase → liquid phase migration rate and particle size
distribution was measured using the light scattering method, andthe effect of bubble properties and concentration, electrification ofparticles, etc., on the migration rate was evaluated (for example,
migration to the liquid phase is accelerated as the amount and sizeof bubbles increase, the migration rate increases due to the increasein particle surface charge, and so on).

Gas-liquid migrationrate➢

Co-existent with nanobubbles

In pure water

Co-existent with micro
bubbles

Co-existent with nano bubbles(low concentration)
Particle size (μm)

Example of measurement results for the gas-liquid➢[②-1: Gas phase and gas-liquid interface] Study of a model for the
migration rate of ZrO2 particles (100 nm)
evaluation of the aerosol migration phenomenon in gas-liquid interface•

Multiple models (Fuch model, Friedlander model, etc.) for evaluating particle
migration behavior in the gas phase → liquid phase confirmed in the test are being reviewed and compared with theexperimental results.
©International Research Institute for Nuclear Decommissioning64

(2) Development of technology for estimating the behaviors of fuel debris particles[Confidential]② Migration behavior of particles in the gas phase, gas-liquid interface, and liquid phase(University of Tokyo)②-2. Evaluation of particle behaviors in the liquid phase
Achievements in FY2019 (continued)

65➢[②-2: Liquid phase] Measurement of particle sedimentation rate in the liquid phase
Using the ZrO2 particles dispersed in ion-exchanged water (pH = 4, 7, 10), a preliminary test was conducted to verify
the validity of the experimental method, and it was confirmed that particle sedimentation is slow under low pH/ lowelectrolyte concentration conditions.
Particle sedimentation rate (%)•

Fitting 1, sedimentation coefficient 0.00758

Time (h)Images of the sedimentation rate measurement test: Change in the ZrO2 particle sedimentation over time undervarying water quality conditions (right-side sample: pH = 6, left-side sample: pH = 7) (Photograph in the top left
corner: Sample at the start of measurement, photograph in the bottom right corner: Sample after 280 hours)➢

Example of calculation of sedimentation rate
based on the data on the left[②-2: Liquid phase] Evaluation of particle migration distance in the liquid phase•

An environment was established for CFD calculation (computer system, CFD software development), and thepreliminary calculation test was implemented.
Particle size = 10 μm

50 μm

100 μmPreliminary test results of CFD simulation for the
sedimentation behavior of ZrO2 particles withvarying particle sizes in a flow with an average flow
velocity of 0.1 m/s©International Research Institute for Nuclear Decommissioning[Confidential]

66

Reference(1) Development of technology for analysis of fuel debris

properties② Improvement in the estimation of fuel debris properties
Improving the list of fuel debris properties (Example oflist of fuel debris properties)©International Research Institute for Nuclear Decommissioning(Reference Material) Improving the list of fuel debris properties (Examples of formats to be summarized in the future)

Detailed information page for each Unit/ area 67

Top page
Classification of major debris and deposits (definition)
Initial material and quantity for each UnitClassification of deposit areas of debris for each Unit

Properties of major debris and deposits (overview)(Current draft only states information on peripheral substances and particles containing uranium)(For fuel debris, the estimated findings are described utilizing the estimated drawing of theconditions inside the reactor)(Past findings: Illustrations of similar substances obtained in TMI, Chernobyl, and in simulation
tests)Classification of Unit 1 debris and deposit sedimentation areas(Estimates and defines areas with different sedimentation statuses
based on site data, accident progression analysis, etc.)(Describes the initial material and quantity for each area)(Provides illustrations if the site photograph data is available)[Confidential]

State of the site in each area
(photographs)
Properties of debris and deposits
Quantity, chemical and mechanicalproperties
FP content, chemical state of FP
Dose, surface adhesion
Evaluation of the uncertainties of
the above
Sample analysis data
Analysis data information(collection region/time, sample
amount, etc.)
Analysis flow/ method (illustration)
Analysis results (Organizedgraphically in light of the above
properties)
Migration behavior of core material
Overview of accident progression
for each area
Debris melting/solidifying behavior
Effect on fuel debris properties
Debris handling risks
Related findings
Previously reported similar
substances estimated from theproperties of each area
Old debris property list
Other evaluation evidence

Outlines the main points of evaluation results and analysis data
(In addition, links to evaluation/data details, related findings/evidence PDFs)(Adds a direct link and comments to the relevant page of evidence)©International Research Institute for Nuclear Decommissioning

Definition of major technical terms, abbreviations, etc. (1)Technical terms/
Abbreviations[Confidential]
68

Definitions

Fuel debris

Melted fuel and other solidified substances that are produced under high temperatures through melting with control rods andstructures inside the primary containment vessel and reactor pressure vessel, after which they cooled and re-solidified.

1F

Fukushima Daiichi Nuclear Power Station

RPV

Reactor Pressure Vessel

PCV

Primary Containment Vessel

D/W

Dry Well: among PCV, a flask-shaped vessel that is designed to contain RPV

S/CSuppression Chamber: Donut-shaped container on the basement of the reactor building

AWJ

Abrasive Water Jet: A method of spraying and machining with an abrasive mixed into a water jet in order to increase the cutting
capability

Torus room

A room containing the torus-shaped (doughnut-shaped) S/C located in the basement of the reactor building

CRD

Control Rod Drive

TIP

Traversing Incore Probe, or Transverse Incore Probe

Operation Floor

Reactor building operation floor is on the top floor of the reactor building, where refueling work is performed during scheduled
outagePedestal

A pedestal is the foundation that supports the reactor body. It is a structure in which concrete is filled inside a steel plate cylindrical
shell

FP

Fission Products: Nuclides produced by fission, or nuclides produced by radioactive decay from such a nuclide (fission fragment)

BSAF

The Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station: One of the OECD/ NEA projects(November 2012 to March 2014)

SA research

Study of a Severe Accident

VULCANO test

France CEA Versatile UO2 Lab for Corium ANalysis and Observation: Large-scale MCCI (Molten Core-Concrete Interaction) test at
the CEA VULCANO facility

CFD simulation

Computational Fluid Dynamics (A method that analyzes various flow properties and phenomena such as substance transport and©International Research Institute for Nuclear Decommissioning
thermal transport in a fluid by numerically solving the basic equations of fluid phenomena)

Definition of major technical terms, abbreviations, etc. (2)[Confidential]

69
Technical terms/
Abbreviations

Definitions

FE-SEM

Field Emission (Type) Scanning Electron Microscope

FE-SEM/WDX

FE-SEM: Field Emission (Type) Scanning Electron Microscope
WDX/ WDS: Wave-length Dispersive X-ray Spectroscopy

FE-TEM/EDX
TEM-EDX

FE-TEM: Field Emission (Type) Transmission Electron Microscopy
EDX/ EDS: Energy Dispersive X-ray Spectroscopy
Transmission Electron Microscopy Energy Dispersive X-ray Spectroscopy

SEM/EDX

Scanning Electrode Microscope - Energy Dispersive X-ray Spectrometer

TEM

Transmission Electron Microscope

ICP-MS

Inductively Coupled Plasma Mass Spectroscopy

ICP-AES

Inductively Coupled Plasma Atomic Emission Spectrometry

TIMS

Thermal Ionization Mass Spectrometry

X-ray CT

X-ray Computed Tomography

EPMA

Electron Probe Micro Analyzer

Alpha-rayspectrometer

Alpha-ray spectrometer. Device that measures the energy spectrum of alpha rays

Gamma-rayspectrometer

Gamma-ray spectrometer. Device that measures the energy spectrum of gamma rays

©International Research Institute for Nuclear Decommissioning[Confidential]

70©International Research Institute for Nuclear Decommissioning