Subsidy Project of Decommissioning and Contaminated Water Management
Started From FY2020

Development of Technologies for Containing,
Transfer and Storage of Fuel Debris(Treatment for Fuel Debris in Powder and Slurry/Sludge State)
Final Report for FY2021

August 2022
International Research Institute for Nuclear Decommissioning(IRID)All rights reserved.
©International Research Institute for Nuclear Decommissioning (IRID)

No.1

Contents
1. Background and purpose of the project
2. Goals
3. Implementation items, their correlations, and relations with other research
4. Implementation schedule
5. Project organization
6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or sludge
form
6.2 Identifying issues involving the storage of fuel debris in powder, slurry, or
sludge form
6.3 Performance assessment of canister filters
7. Summary©International Research Institute for Nuclear Decommissioning1. Background and purpose of the project

No.2

1.1 Background
For the decommissioning of the Fukushima Daiichi Nuclear Power Station (Fukushima
Daiichi), equipment and facilities (including collection containers) suitable for theconditions of fuel debris are required to safely and reliably collect, transfer, and store theretrieved fuel debris.
A contaminated water treatment (liquid system) is currently under review by the retrieval
side (Subsidy Project of Development of Technology for Further Increasing the Retrieval
Scale of Fuel Debris and Reactor Internals) and fuel debris in slurry and sludge state is
expected to be retrieved.
However, both collection containers and methods for transfer and storage of fuel debris
in slurry or sludge state have not yet been studied.

1.2 Purpose
The purpose of this subsidy project is to conduct case studies in Japan and abroad
involving containers for slurry or sludge, and transferring, collecting and storing of thecontainers for addressing one of technological issues. The technological issues are also
clarified in case of that applying existing technologies such as technology for transferringand storing the collection containers (canisters) of powdery and lump-like fuel debris.
Fuel debris is expected to spread easily because water lost in the fuel debris due todrying treatment against suppressing hydrogen generation, therefore, the impact on theperformance of filters (blockage, degradation, etc.) that are installed on the canister lid toprevent from dispersing dust outside the canister is studied.
©International Research Institute for Nuclear Decommissioning

No.3

1. Background and purpose of the project
Large(Supplementary)

Particle size

The collection of slurry or sludge fromcontaminated water is currently underreview, but a review of collection
containers, transfer methods, and storage
methods has not yet been undertaken.

- Investigation of collection containers, andtransfer and storage methods for slurry or
sludge should be conducted in Japan andabroad to collect information including
focusing points.
- Canisters can also be used as collection
containers. Issues are identified inmethods for transfer and storage of thecanister that the same method using thecanister for particulate and lump-like fueldebris is currently under review.
- The filters that are installed on thecanister lid are studied since the handlingof powdery fuel debris has issues.

Particle diameter: 100
mm or more
Requires processing
before collecting in a unit
canPlanned to collect by grabbing,scooping, etc.

Particle diameter: 0.1
mm or lessCollected through theliquid phase system

Particle diameter: 0.1 to
10 mmCollected by suction
because it is difficult tohandle with tools.

Particle diameter: 10 to
100 mmCan be collected in a unit
can without processing

Targetsubstance

Powdery fuel debris

Fuel debris in lump form Fuel debris in pebble form Fuel debris in particle form

Planned to collect throughthe liquid phase system(particle size: 0.1 mm or less)

Planned to develop asuction collection
system

7. Implementation details of this project2) Development of fuel debris handling technologies(ii) Technological development involving the treatment of fuel debris and deposits② Treatment technologies for deposits collected from PCV
The bottom row shows a conceptual diagram of the contaminated water treatment system during fuel debris retrieval.
: Equipment used in tests for tasks in this item
Item: ②a. Characterization of collectedliquids, liquid waste, etc.

Boric acid (silo)

CoolerSolublenuclideremovalSupernatant
water

Drain water/
backwash water

Sludgecollection

SludgeItem: ②b. Development of technologies forthe separation and collection of solids fromcollected liquids and liquid waste

Sludgecollection

Waste
treatment
facility

To watertreatment
facility/tank

Item: ①a. Conceptual system design of soluble nuclide
removal facility

Supernatantwater
SludgeConditioned
boric acid water

Item: ①b. Conceptual design of boric acidconditioning equipment

SolublenuclideremovalDrain water/
backwash water

Boric acidconditioning
facility

Tank

Waste
treatment
facility

Particle
removal

Pump

Boric acid watertank + pump

Pump

Particle
removalPump

Groundw
ater

Source: Extracted and processed from the results of the IRID HP
FY2019 research and development project “Developmentof Technology for Further Increasing the Retrieval Scale of
Fuel Debris and Reactor Internals”

Small

To watertreatment
facility/tank
Note: This conceptual diagram
is an example of facility
configuration (when there
is no leakage from PCV)

Figure. Liquid phase system (conceptual diagram) and target element test when retrieving fuel debris©International Research Institute for Nuclear Decommissioning2. Goals

No.4

The indicators for determining target achievement for the end of FY2021 are as follows.
1. Case study of handling radioactive materials in powder, slurry, or sludge form
• Overseas case study of handling powdery, slurry or sludge radioactive materials must be
analyzed. Specific precautions and a concept of ensuring the safety for radioactive materials in
powder, slurry, or sludge form must be clarified.
(Not subject to TRL* evaluation)
2. Identify issues involving the storage of fuel debris in powder, slurry, or sludge form
• Issues involving safe, reliable, and rational storage manners when fuel debris is stored in thedry condition using the same canister for particulate or lump-like fuel debris must be identified.
(Target TRL* upon completion: Level 1)
3. Performance assessment of canister filters• The environments and conditions that affect canister filter life must be understood andorganized. Also, the test methods and conditions for any item that are required to be tested forevaluation of the filter life must be studied and any relevant existing knowledge must beorganized.
(Target TRL* upon completion: Level 1)*TRL: Technology readiness level©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with No.5
other research
3.1 Implementation items
The following technological development issues were addressed for the engineering of transfer
and storage of fuel debris in the Fukushima Daiichi under this subsidy project.
(1) Case study of handling radioactive materials in powder, slurry, or sludge form
It is useful to collect and analyze experience, knowledge, and information on the handling andstorage of radioactive materials in powder, slurry, or sludge form when identifying issues
involving the storage of powdery, slurry and sludge form fuel debris (implementation items in (2)below). Therefore, case studies of handling powdery nuclear and radioactive materials in Japanand overseas, the storage methods and the facility size were investigated. Experience,
knowledge and information that are required to establish the system for containing, transfer andstorage of the fuel debris including precautions in handling powdery, slurry or sludge type fueldebris, concepts for ensuring safety, and methods for reflecting these concepts in the design,
etc. were analyzed and organized.
(2) Identifying issues involving the storage of fuel debris in powder, slurry, or sludge form
Based on the results of the analysis and organization of experience, knowledge, andinformation obtained from implementation items (1), issues involving safe, reliable, and rational
storage conditions were identified when fuel debris that is mainly powder, slurry or sludge form
is stored in drying conditions using the same canister for fuel debris in particle or lump form.
Also, technological issues were clarified to resolve from the perspective of whether thenecessary safety functions can be secured, whether storage can be stably conducted for long
periods of time, etc.
©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations with No.6
other research
3.1 Implementation items(3) Performance assessment of canister filters
In addition to verifying the necessary specifications for filters studied in other related
research and development projects, the required specifications were broadly reviewed andconsistency between the selection process for the filters and the evaluation results of thefilters were confirmed. Furthermore, failure scenarios (i.e., corrosion, etc.) that impact filter
performance were selected and the test conditions for evaluating those scenarios werestudied.

©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations withother research

No.7

3.2 Relevance between implementation items(Target schedule) B3④: Development of Technology for Collection, Transfer, and Storage of Fuel Debris

Item/FY

Period 2(The period until fuel debris retrieval begins)

Period 3-①
2023 onwards

Maintain and manage safe plant conditions
Major events in the current
Mid-and-Long-Term Roadmap▽ Begin retrieving fuel debris at the initial unit
Engineering for collection, transfer, and storage[Development of Technology forCollection, Transfer, and Storage ofFuel Debris]

0. Investigations and R&D
planning for collection,transfer, and storage
1. Development oftechnology for collection(implemented in
FY2020/21)
2. Development of drying
technology
3. Case study of handlingradioactive materials in
powder, slurry, or sludge
form (implemented in
FY2020/21)
Development oftransfer technology[Development of Technology
for Further Increasing the
Scale of Retrieval of Fuel
Debris and Reactor Internals]

Planning

Update plans based on related projects, etc.

Implementation item inthis subsidy project

Canister
specification
reviews andstructuralverification tests

Canister filter failure scenario selection
and consequence assessment

Development oftechnology for drying
treatment

Study of countermeasures against changes to canister
filter performance

Implementation item in related
subsidy projects

Expansion and enhancement of drying treatment methods and operational parameters

Analysis, organization, and comparison of caseinvestigation, knowledge, and information,

Clarification of issues with current canisters in thedry storage of fuel debris in powder, slurry, or
sludge form

Hydrogen gas
generation tests andinvestigation of transfer
conditions

Verification, etc. of dry storage withcurrent canisters

Implementation item inthis subsidy project
Alignment with related technological developments

Field work (including engineering)
R&D

Team Meeting for Countermeasures for Decommissioning and Contaminated Water Treatment / Secretariat Meeting (86th meeting) Materials “FY2021
Decommissioning R&D Plan,” Added to “(Target schedule) B3④: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris”©International Research Institute for Nuclear Decommissioning3. Implementation items, their correlations, and relations withother research

No.8

3.2 Relevance between implementation items
Tokyo Electric Power Company Holdings, Inc.

International Research Institute for Nuclear Decommissioning(IRID)[Project Management for theDecommissioning of the Fukushima
Daiichi Nuclear Power Station]
Fuel debris characterization project Note 1[Provide information for the canister(sludge) project]- List of fuel debris characteristics(Knowledge on their morphology,
properties, basic physical properties,
etc.)

Canister (sludge) project Note 1[Provide information to related projects]- Collected information and identified
issues involving the drying and storageof sludge

Project for further increasing retrieval
scale Note 1[Provide information for canister (sludge)
project]- Fuel debris collection and storage- Information related to criticality control(Constrained conditions, etc. formaintaining sub-criticality)

Canister project Note 1

Canister (drying) project Note 1[Provide information for the canister(sludge) project]- Canister shape- Processes from fuel debris collection
to storage[Obtain information from the canister(sludge) project]- Reference information for examining
drying technology

Note 1:
Project for further increasing retrieval scale: “Development of Technology for Further Increasing the Retrieval Scale of Fuel Debris and Reactor
Internals” Project
Fuel debris characterization project: “Development of Analysis and Estimation Technology for Fuel Debris Characterization” Project
Canister project: “Development of Technologies for Containing, Transfer, and Storage of Fuel Debris” Project
Canister (drying) project: “Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris)”
Project
Canister (sludge) project: “Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (for fuel debris in powder, slurry, or
sludge form)” Project

Consistent results can be obtained by sharing and coordinating
information from related projects within IRID and theinformation provided by this project.
©International Research Institute for Nuclear Decommissioning4. Implementation schedule

No.9

Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(for fuel debris in powder, slurry, or sludge form)
FY2020

FY2021

1. Investigation into cases of handling radioactive
materials in powder, slurry, or sludge form
① Investigation planning(examination of investigation
targets, investigation items, etc.)② Investigation③ Organization of investigation results

2. Identification of issues involving the storage of fueldebris in powder, slurry, or sludge form
① Identification of targets and items to organize② Identification of evaluations and issues③ Evaluation based on Japan and overseas
investigation results
3. Performance assessment of canister filters① Identification of environments and conditions② Study of filter life evaluation methods③ Study of test methods and conditions
4. Progress report, etc.
Planned schedule

Actual schedule©International Research Institute for Nuclear Decommissioning5. Project organization

Tokyo Electric Power Company Holdings, Inc.
〇 Project Management for the Decommissioning of
the Fukushima Daiichi Nuclear Power Station(As of the end of March 2022)

No.10

International Research Institute for Nuclear Decommissioning(IRID) (Head Office)○ Formulation of an overall plan and technology management○ Technology management such as the progress oftechnological developments

Related development projects
Toshiba Energy Systems &Solutions Corporation

Mitsubishi Heavy Industries, Ltd.

Hitachi-GE Nuclear Energy, Ltd.

Development of Analysis and Estimation
Technology for Fuel Debris Characterization(1) Case study of handlingradioactive materials in
powder, slurry, or sludgeform(1) Investigation into cases ofhandling radioactive
materials in powder, slurry,or sludge form

(1) Investigation into cases ofhandling radioactive
materials in powder, slurry,or sludge form

Development of Technology for Further
Increasing the Scale of Retrieval of Fuel
Debris and Reactor Internals(2) Identifying issues involving
the storage of fuel debris in
powder, slurry, or sludgeform(2) Identification of issues
involving the storage of fueldebris in powder, slurry, or
sludge form

(2) Identification of issues
involving the storage of fueldebris in powder, slurry, or
sludge form

R&D on Solid Waste Treatment and Disposal(3) Performance assessment ofcanister filters (review)(3) Performance assessment ofcanister filters(3) Performance assessmentof canister filters (review)

Development of Technology for Containing,
Transfer, and Storage of Fuel Debris (Drying
Technology for Fuel Debris)

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

MHI-NS- Literature translation and organization

MHI-NS: MHI NS Engineering Co., Ltd.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.11

6.1 Case study of handling radioactive materials in powder,slurry, or sludge form
6.2 Identifying issues involving the storage of fuel debris in
powder, slurry, or sludge form
6.3 Performance assessment of canister filters©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.12

① Purposes and goals
The purpose of the project is to investigate the cases necessary to obtain theinformation and knowledge for reviewing the experience, knowledge, and informationon the handling and storage of radioactive materials in powder, slurry, or sludge form,
and identify and organize precautions in the handling of the fuel debris.
② Comparison with existing technology
In the Development of Technologies for Containing, Transfer, and Storage of Fuel
Debris project conducted up to FY2020, technologies were developed for the safe
handling and storage of fuel debris in particle or lump form using canisters.
However, fuel debris in powder, slurry, or sludge form is expected to be collected whenretrieving fuel debris, so it is important to identify issues in safely storing them in thesame way as fuel debris in particle or lump form and to clarify the technological issues
to resolve.
From the perspective of implementing the above, it is useful to collect and analyze theexperience, knowledge, and information on the handling and storage of radioactive
materials in powder, slurry, or sludge form.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.13

③ Implementation items and resultsa. Investigation planning(1/2)
Potential investigation targets and items was reviewed to obtain the experience,
knowledge, and information on the handling and storage of radioactive materials in
powder, slurry, or sludge form.
<Potential investigation targets>
USA
Cases of radioactive materials discharged from contaminated water treatment during
retrieval of TMI-2 fuel debris
Cases of slurry and sludge in the decommissioning of the Hanford Site (K-Basin)
UK
Cases of slurry and sludge in the decommissioning of the Sellafield facility
Japan
Japan Atomic Energy Agency: Cases of radioactive materials discharged from liquid
waste treatment
Japan Nuclear Fuel Limited: Cases of radioactive materials discharged from liquid
waste treatment at a reprocessing plant©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.14

③ Implementation items and resultsa. Investigation planning(2/2)<Investigation items>
Investigation items from the perspective of safe transferring and storage
Shielding, maintaining sub-criticality, heat removal, confinement, structural integrity,
long-term integrity, hydrogen countermeasures, fire
Investigation items from the perspective of handling and processes
Specifications (structure, etc.) for canisters and handling equipment andspecifications for drying, etc. processes and the equipment for such processes©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form
③ Implementation items and resultsb. Investigation (1/2)

No.15

An investigation format was created to organize investigation items and cases involving thehandling and storage of radioactive materials in Japan and abroad were surveyed.

<Investigation format sample (example)>
Overview of the entire plant[Overview of the entire plant]- Basic information (background, purposes, information on target substance,etc.)[Outline of each process]- Overview of the process (purposes, flow, etc.)- Safety assessments (structure, heat removal, confinement, shielding, criticality,
heat removal, hydrogen countermeasures, etc.)- Permission and authorization (regulatory requirements, inspection items, etc.)
Investigation results (including ideas on the establishment, etc.)

①
a.
b.
c.

Source (related literatures)

Basic information
Background/Circumstances/Purposes, etc.
Positioning (Practical application complete In planning Research
purpose, etc.)
Information on the target substance (the source of the sludge)(a) Fuel type (plate fuel, uranium dioxide fuel, fuel debris, etc.)

d.
e.
②
a.
b.
c.
③
a.

(b) Chemical components and composition of sludge (assumed)(c) What kind of treatments were used in transferring and storing?
If drying was used, the specifications of components and the reason forthe process
Details of treatment for solidification, etc.
If concentrated, the specifications of components, etc.
Has the sludge been processed into a form for transferring and storing(d)(composition and moisture content)?
Method used to transfer (pipeline, etc.) sludge to the storage facility (tank,etc.)
Sludge storage method (storage inside a tank, etc.)
Permission and authorization
Whether regulatory requirements exist
Permission and authorization procedure and examination period
Inspection items before shipment or before/during storage
Planned schedule
Future plan
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.16

③ Implementation items and resultsb. Investigation (2/2)
Investigations on the handling and storage of radioactive materials, etc. in powder, slurry, or
sludge form have organized the following items from the perspective of both handling andprocesses and the safe transfer and storage of fuel debris in powder, slurry or sludge form.
<Investigation items>- Maintaining sub-criticality, shielding, heat removal, structure, hydrogen, fire, confinement, longterm integrity, drying<Investigation targets>
USA
A case of radioactive materials discharged from contaminated water treatment during retrieval of
TMI-2 fuel debris
A case of slurry and sludge in the decommissioning of the Hanford Site (K-Basin)UK
A case of slurry and sludge in the decommissioning of the Sellafield facility
FranceA case of slurry and sludge at the La Hague reprocessing plant
Japan
Japan Atomic Energy Agency: A case of radioactive materials discharged from liquid waste
treatment
Japan Nuclear Fuel Limited: A case of radioactive materials discharged from liquid waste
treatment at a reprocessing plant©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.17

③ Implementation items and resultsc. Organization of investigation results (1/8)
The main results from investigation into Japan and overseas cases involving
the handling and storage of radioactive materials, etc. in powder, slurry, or
sludge form are shown below.
Table Investigation results on the handling and storage of radioactive materials in powder, slurry,or sludge form (1/8)
Investigation
items

Investigation
targetInvestigation results

Maintaining
sub-criticality

TMI-2- Even when a coagulator was added to the canister (collection container), theboron materials installed inside the canister safely ensures criticality.
- The canister (collection container) can be transferred in a transfer cask.
Analysis using an evaluation model verified that sub-criticality for the canisterand transfer cask can be maintained.

Shielding

IAEA- Spent fuel/damaged fuel is mainly stored in wet storage, with more than 80% ofspent fuel stored in wet storage. Wet storage management primarily employs
shielding and cooldown and heat removal with pool water. Safety measures andcalibration inspections are easy to incorporate and it is assumed that
continuous SAFSTOR can be established through pool water conditions andanalysis.

©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.18

③ Implementation items and resultsc. Organization of investigation results (2/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry,or sludge form (2/8)
Investigation
items

Investigation
targetHeat removal

IAEA

Investigation results- Spent fuel/damaged fuel is mainly stored in wet storage, with more than 80% ofspent fuel stored in wet storage. Wet storage management primarily employs
shielding and cooldown and heat removal with pool water. Safety measures andcalibration inspections are easy to incorporate and it is assumed that
continuous SAFSTOR can be established through pool water conditions andanalysis.

Hanford (K- - It was verified that concentrically arranging highly radioactive waste that has
Basin)
undergone washing, dehydration, drying, etc. treatments in a scrap basket
facilitates heat removal.
Sellafield- It was verified that increasing the surface areas of fins on the Magnox fuelelement improved the efficiency of heat removal.

©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.19

③ Implementation items and resultsc. Organization of investigation results (3/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry,or sludge form (3/8)
Investigation
items

Investigation
targetStructure

Hanford (KBasin) [KWBasin]

Figure 1 Hose-in-Hose Note1 used
for sludge transportation

Investigation results- A separation treatment for sludge collected from the bottom of the Basin by using the pump
was conducted through the Integrated Water Treatment System (IWTS) (spent fuel: grains 1/4
inch (0.64 cm) or larger, powder (sludge) ): coagulation sedimentation, ions: ion exchange
resin) after transporting the sludge into the storage container through the transportation piping(Hose-in-Hose). Pu content in the collected sludge was verified below a certain value andthen cement solidification was carried out in drum cans.
- From the viewpoint of maintaining criticality, particles collected by coagulation sedimentation
were collected in tanks (settle tanks) with an outer diameter of 20 inches (0.5 m) and a lengthof 16 ft (5 m). Surplus water was discharged via high-pressure washing and 99.7% of sludge
was collected.

Figure 2 Overview of the sludge treatment and solidification systeminstalled at K-West-Basin Note 1

Figure 3 Settle Tanks Note 2

Note 1: From P.Knollmeyer et al. Waste Management 2006 Conference, February 26 - March 2, 2006, Tucson, AZ. Progress with K Basins Sludge Retrieval, Stabilization and Packaging at Hanford Nuclear Site, 2006
©International
Note 2: From Eric G et al. Waste Management 2011 Conference, February 27 - March 3, 2011, Phoenix, AZ. Sludge Retrieval from Hanford K-West Basin Settler Tanks,– 11449. Research
2011. Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.20

③ Implementation items and resultsc. Organization of investigation results (4/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry,or sludge form (4/8)
Investigation
items
Hydrogen

Investigation
targetHanford(K-Basin)

Investigation results- A physical model evaluated the possibility of gas accumulation in the solid-liquid bed when K-Basinsludge was stored in a high-level radioactive liquid waste storage tank, and the relational expressionof the hydrogen concentration is examined.
- The relational expression between the rate of hydrogen gas generation and temperature was
examined, factoring in the thermal decomposition of organic matter inside the high-level radioactive
liquid waste storage tank, the radioactive decomposition of water, corrosion of tank steel, and more.
- It was verified the event in which the gas generated by the radioactive sludge was capped by theradioactive sludge and was not released, resulting in a gas accumulation. Study of the relationshipbetween the volume of gas retained in sludge and the yield stress of sludge.

Gas
accumulation

Figure 1 Hydrogen discharge event(GRE: Gas Release Event) Note 1 in tanks at the Hanford Site

Radioactive
sludgeFigure 2 Gas accumulation formed by radioactive sludge within a sludge
bed Note 2

Note 1: From PA Gauglitz et al. PNNL-24255 WTP-RPT-238 Rev.0. Hydrogen Gas Retention and Release from WTP Vessels: Summaryof Preliminary
Studies,
2015.
©International
Research
Institutefor Nuclear Decommissioning
Note 2: From G.Terrones et al. PNNL-13805. Vessel-Spanning Bubble Formation in K-Basin Sludge Stored in Large-Diameter Containers, 2002.

6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.21

③ Implementation items and resultsc. Organization of investigation results (5/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry,or sludge form (5/8)
Investigation Investigation
Investigation results
items
targetHydrogen
Savanna River -When the agitator was suspended during treatment of high-level radioactive liquid waste, aSitebehavior model of hydrogen gas that accumulated in liquid waste and released upon theresumption of the agitator was evaluated.
Sellafield- In the hydrogen formed by the corrosion of shavings during the dismantling of Magnox fuel,the amount and form of hydrogen accumulated in the Mg(OH)2 slurry of corrosion products
were examined in the test.
JAEA- It was verified that gamma-ray irradiation causes hydrogen gas to accumulate within the
carbonic acid slurry, and that the volume expands.
Immediately before
irradiation

6 hours after
irradiation

22 hours after
irradiation

44 hours after
irradiation

Water level(Top surface ofsupernatant)

Static water level at the beginning: 100 mm
Water level after approx. 120 days: 99 mm

Energy absorbed
fraction
Slurry (95 g/L)

Solution 91.8%

Initial waterlevel

Suspendedmatter 8.2%(a) Gamma-ray
irradiation

Slurry height(Interface between
supernatant andslurry)(b) Non-irradiatedFigure 1 Rise in water level and increase in accumulated water from gamma-ray
irradiation to a simulated carbonate slurry in HIC Note 1

Figure 2 Relationship between absorbed dose and theamount of hydrogen generated from gamma-ray
irradiation to a simulated carbonate slurry in HIC Note 2

Note 1: From Takafumi Motooka et al., Atomic Energy Society of Japan Proceedings 2I20, Spring 2016, Irradiation Experiments of Simulated Carbonate©International
Slurry in HIC Research(2) Gas Retentionof Simulated
Institute forBehavior
Nuclear Decommissioning
Carbonate Slurry under Gamma Ray Irradiation, 2016.

6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.22

③ Implementation items and resultsc. Organization of investigation results (6/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry, or sludge form (6/8)

Investigation Investigation
Investigation results
items
targetFire
La Hague- Asphalt solidification with a large volume of waste filling was studied as a treatment
method for radioactive sludge, but French regulatory authorities did not allow permission
due to the issue of gas generation from the radioactive decomposition of asphalt. An
alternative measure, having the sludge dried via a Drying/Compress process, pelletized,
and then collected in a container with sand, is currently under consideration.
- Construction of a facility that is designed for retrieving the graphite and magnesium waste(approximately 600 m3) used in the uranium fuel cladding stored at the La Hague
reprocessing plant was completed and the retrieval begun.

Figure 1 Drying/Compress process Note 1

Figure 2 Magnesium waste storage container Note 2

Note 1: From Elisa LEONI et al. WM2019 Conference, March 3 – 7, 2019, Phoenix, Arizona, USA. La Hague STE2 Sludge Retrieval and Conditioning Strategy -19229. 2019.
©International
Research
for NuclearReducing
Decommissioning
Note 2: From Bruno VILTARD et al. WM2020 Conference, March 8 - 12, 2020, Phoenix, Arizona, USA. Start-up of Silo 130 Waste Retrieval
at La Hague:
1stInstituteStep Towards
LegacyInventory -20020. 2020.

6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.23

③ Implementation items and resultsc. Organization of investigation results (7/8)

Table Investigation results on the handling and storage of radioactive materials in powder, slurry, or sludge form (7/8)

Investigation Investigation
Investigation results
items
targetConfinement Hanford- A container called an MCO (Multi Canister Overpack) for collecting highly radioactive sludge has(K-Basin)been designed based on the ASME Class 1 vessels (equivalent to a reactor pressure vessel) andensures airtightness in the collection, transfer, and storage of sludge (in an interim storage
facility).
Sellafield- High-level radioactive liquid waste generated when reprocessing Magnox spent fuel and spentoxidized fuel is concentrated in an evaporator, denitrified, and then pulverized and vitrified. The
vitrified material is injected into a stainless steel container and the lid is welded shut to seal in theradioactive material.
TMI- After retrieving fuel debris, each target substance is packaged in a dedicated fuel debris canister.
- Analysis of pressure and temperature fluctuations when a canister was dropped or transported
verified that fuel debris would not leak.
Long-term
Hanford- The internal pressure load is an influential factor in the long-term integrity of MCO and reducing
integrity(K-Basin)
the temperature (maintaining temperatures below 60℃, including when drying), dehydration(adding magnesium oxide or calcium oxide as a dehydration agent), suppressing corrosive
reactions (adding nitrite or phosphate to the solution), and adding supplements (adding nitrate(NO3-) or nitrite (NO2-) to the solution) are recommended to reduce the generation of hydrogengas.
DryingHanford- Low-temperature vacuum drying (pressure conditions: 8 Torr (1 kPa), temperature conditions: 40(K-Basin)to 50℃, drying time: 50 hours) was used to limit fuel damage from the rapid oxidation of uranium
in collected sludge.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.24

③ Implementation items and resultsc. Organization of investigation results (8/8)

Figure 1 Hanford’s MCO (Multi Canister Overpack)and a scrap basket to be collected in the MCO
Note 1

Note 1: JCH2MH ILL (2012): “Knock Out Pot Material Multi-Canister
Overpack Proof of Dryness (OCRWM), Sludge Treatment Project
KOP Disposition, PRC-STP-00210, Revision 2”

Figure 2 TMI-2 filter canister Note 2(Size of collected particles: 0.5 to 800 μm)
Note 2: “THI-2 Defueling Canisters Final Design Technical Report” 771153937-04©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.25

④ Contribution of outcomes to relevant study areas
The results of investigations of cases involving the handling and storage of radioactive materials in
powder, slurry, or sludge form were summarized to contribute to identifying issues in the handlingand storage of powdery, slurry and sludge type radioactive materials.

⑤ Analysis with respect to the on-site applicability
These case investigations are useful references when examining the handling of fuel debris in
powder, slurry, or sludge form, which are the forms assumed to be collected during fuel debris
retrieval.

⑥ Goal achievement level
It can be concluded that goals have been achieved since the following indicator was met.
• Analyze overseas cases of handling radioactive materials in powder, slurry, or sludge form andorganize specific precautions, ways to ensure safety, etc. for the handling of radioactive materials
in powder, slurry, or sludge form.

⑦ Issues to be addressed
As examples of investigations on the handling and storage of radioactive materials in powder, slurry,or sludge form in Japan and abroad, the investigation was primarily conducted at TMI-2 and the
Hanford Site in the United States and the Sellafield facility in the United Kingdom. Further
information acquisition and analysis on the La Hague reprocessing plant in France and similar
facilities in Japan would be useful.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.1 Case study of handling radioactive materials in powder, slurry, or
sludge form

No.26

⑧ Summary- Case studies were conducted based on literatures regarding the handling andstorage of radioactive materials in powder, slurry, or sludge form at TMI-2 and the
Hanford Site in the United States, Sellafield in the United Kingdom, and others.

- Based on the results of the investigation, the evaluation items, evaluation methods,
and countermeasures necessary for safely handling and storing fuel debris in
powder, slurry, or sludge form are classified according to safety assessments andhandling for each item (maintaining sub-criticality, shielding, heat removal, structure,hydrogen, confinement, long-term integrity, drying), and organized by precautionary
points, etc.
- Further investigations of the experience, knowledge, and information regarding thehandling and storage of radioactive materials in powder, slurry, or sludge form will be
conducted in FY2022 and will target the La Hague reprocessing plant in France andsimilar facilities in Japan. Investigating this knowledge and information is planned asa continuation project of this subsidy project.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.27

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form

① Purposes and goals
The purpose and goals of the project is to identify issues involving safe, reliable, andrational storage conditions and clarify technological issues to resolve when using acanister for dry storing fuel debris in powder, slurry, or sludge form in a similar way asfuel debris lumps or fuel debris particles.

② Comparison with existing technology
In the Development of Technologies for Containing, Transfer, and Storage of Fuel
Debris project conducted up to FY2020, technologies were developed for the safe
handling and storage of fuel debris in particle or lump form using canisters.
However, fuel debris in powder, slurry, or sludge form is expected to be collected whenretrieving fuel debris, so it is important to identify issues in safely storing them in thesame way as particulate or lump-shaped fuel debris and to clarify the technologicalissues to resolve.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.28

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (1/8)

An issue identification format
that reflects evaluation items
and organizational methods

It is assumed that different type of issues exist between the containing, transfer, andstorage of powdery, slurry or sludge type fuel debris and particulate or lump shaped fueldebris. From the perspective of clarifying issues, items will be identified assuming transferof handling fueland storage using the same procedures, e.g. using the canisters for fuel debris in particle Flowdebris in particle or lumpor lump form, which are the result of FY2020 technological developments.
form(32 processes in total)
Therefore, a series of handling processes (see No. 29 and 30) for fuel debris inparticle or lump form were considered and organizational methods and items to evaluate
were examined for each handling process (a total of 32 processes, from retrieving fuelOther relevant
on sludge
debris in reactors to long-term storage), and also a format for identifying issues (see No. informationthat is being examined31) was formulated. These were conducted from the perspective of comprehensivelyin other related projects
identifying issues involved in bringing fuel debris in powder, slurry, or sludge form (SeeNo. 32 and 33) into safe and long-term stable storage, including sludge collected during
proposed retrieval task, coagulation sedimentation sludge in water circulation systems,
Identification ofissues (draft)matter captured on filters, oxide particles of various configuration materials, particles suchas processing abrasives and neutron absorbers for maintaining sub-criticality.

<Items to be evaluated>
1. Analysis and identifying of issues from the perspective of safe andlong-term stable storage
Evaluation perspectives: Shielding, maintaining sub-criticality, heat removal,
confinement (contamination), structural integrity, long-term
integrity, hydrogen countermeasures, fire

2. Analysis and identifying of issues from the perspective of handlingand processes
Evaluation perspectives: Canister structure (lid structure, filter, etc.), drying andhydrogen concentration measurements

Results of investigations
into cases of handlingradioactive materials in
powder, slurry, or sludge
form in Japan andabroad(See [6.1])- Selection of issues andconsideration of countermeasures- Clarification of technologicalissues(Technological issue solution
phase, solution period)

Issue identification flow
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.29

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (2/8)- A series of handling processes for fuel debris in particle or lump form
(Fuel debris retrieval from inside reactors ~ Transferring inside the premises: 17 processes)
Reactorbuilding<Area classification>
Red: High contaminated area, Unmanned operations (remote tasks controlled from outside the area)
Yellow: Area with medium radiation level (radiation level is controlled, but there is still a risk of harmful exposure)
Unmanned operations (remotely operated from outside the area in principle with limited occasions ofworkers working in it for maintenance and tasks.)
Green: Low contamination area (not substantially contaminated), Manned operation

Example handling flow using the side entry method
Extensionbuilding

Lifting machine

Manipulator

Lifting machine

Debris treatment cell

Fuel debris
retrievalequipmentWork
monitoring
camera

RPV

unit
can

Fuel debris

PCV

Port

Canister lid fastening system(Check surface contamination)
CanisterDrying apparatus

Lifting machine

Primary lid
fasteningmachine/gas
injector/leakdetector

Sealingcell

Gas injection
systemSecondary lid
fasteningmachine/gas
injectionsystem/leakdetection system

Preparation
cell

Transfertruck

Access tunnel

unit cantransfersystemInside the reactor

Access tunnel[1] Cut and process discharged
materials[2] Visually verify discharged
materials[3] Collect fuel debris with the fueldebris retrieval equipment and load
it into a unit can (hereafter “unitcan”)[4] Dewater and dry fuel debris[5] Transfer the unit can out of thereactor building (transfer out of thepedestal)[5] Transfer the unit can out of
the reactor building (passthrough the access tunnel) *1*1: In addition to fuel debris, waste suchas reactor internals moves from inside
the reactor to the extension building
through the access tunnel.

Dryingapparatus
Debris treatment cell[6] Dry fuel debris(Load the unit can into
the drying system ~Drying treatment)

Canister transfer
systemThe drying apparatus and theinside of the canister areclassified as an area with highradiation level

Transfer
Weight measuringsystemcask(Surface contamination
check)

Transport cask
transfer equipment

Sealing cell[7] Load the unit can into the (Dry fuel debris(Connect the canister to drying
canistersystem ~ drying treatment *2))
[8] Fasten the canister lid(Affix inner lid ~ Move to lid [10] Inject inert gas into the canister(Connectthe canister to the gas
fastening system ~ Fasten
injection system ~ Inject inert gas
lid - Verify lid seal)
into the canister~)[9] Verify surface[11] Measure the amount of hydrogencontamination on thegenerated *3
canisterTransferrack

Preparation cell[12] Verify that the canisterhas been delivered(Measure weight, etc.)[13] Load the canister into
the transfer cask
(Move the canister to the
top of the port)*2: Executed if drying within the fuel debris treatment cell is not possible*3: Considering executing this when injecting inert gas[13] Load the canister into the transfer cask
(assume they are stacked)[14] Fasten the transfer cask lid(Fasten lid (primary lid) ~ Inject inert gas(inside cavity) ~ Verify lid seal (primary lid)
~ Fasten lid (secondary lid) ~ Inject inert
gas (between primary and secondary lids)~ Verify lid seal (secondary lid))[15] Measure the amount of hydrogengenerated *4[16] Verify delivery of the transfer cask[17] Load the transfer cask onto the transfer
vehicleInside thepremise- Transfer inside thepremises*4: Considering executing thiswhen inert gas is injected
into the cavity

Figure Handling process for fuel debris in particle or lump form (1/2)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.30

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (3/8)- A series of handling processes for fuel debris in particle or lump form
(Bringing the transfer cask into the storage building ~ Long-term storage: 15 processes)
Example handling flow using the side entry method
Hydrogen gas treatment system
Lifting machine<Area classification>
Red: none
Yellow: Medium contamination area, unmanned operation (remote tasks
controlled from outside the area)
Green: Low contamination area, manned operation
Storage building

Area monitor
Ventilation
systemHandlingjigWorkShieldingmonitoring covercameraGas treatment system

Canister

Gate
Transfercask

Stored item
checking
equipment

Dryingapparatus

Storagecask

Scaffolding
for work

Primary
lid ofstoragecask

Secondarylid ofstorage cask

Vent pipe

Surfacetemperature
measuringequipment

Transfer
cask rack[18] Receive the transfer cask at thetruck bay door
[19] Unload the transfer cask fromthe transfer vehicle[20] Verify that the transfer cask has
been received[21] Measure the amount of hydrogengenerated *5[22] Open transfer cask lid(Remove secondary lid ~ Remove
primary lid)[23] Retrieve the canister from the transfer
cask *6[24] Verify that the canister has been received*5: Execute after removing the secondarylid*6: Cover the canister with a shield coverand move[25] Verify the stored
item*7(Load the canister
into the stored item
checking equipment~ Verify)

Dry fuel debris *8(Load the canister
into the drying
system ~ Drying
treatment)*7: Assume the dose ratemeasurement*8: Execute if drying isrequired prior to storage[26] Verify prior to storing canister[27] Load the canister into thestorage container(assume they are stacked)[28] Fasten the storage container
lid(Fasten lid (primary lid) ~ Inject
inert gas (inside cavity) ~ Verify
lid seal (primary lid))[28] Fasten the storage
container lid(Fasten lid (secondarylid) ~ Inject inert gas(between primary andsecondary lids) ~ Verify
lid seal (secondary lid))[29] Verify confinement[30] Connect a vent pipe to thestorage container[31] Verify vent pipe seal
[32] Long-term storage

Figure Handling process for fuel debris in particle or lump form (2/2)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.31

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize(4/8)[Components subject to evaluation]- Unit cans, canisters, unit can, and systems that
handle canisters[Evaluation perspective]- Design concepts, safety design policies, issues<Issue identification format>

Concepts and policies from a technological standpoint
Step

No

Locations

Details of
implementation

Technologicalelements① Structure② Heat removal

1

Inside thereactorCutting andprocessing ofdischarged
materials④ Shielding- The necessary shielding capabilities shall be in place toprevent radiation sickness.

⑤ Criticality- There shall be no risk of fuel debris reaching criticality.

⑥ Hydrogen- Hydrogen explosion shall be prevented.

⑦ Fire- Fires shall be prevented from occurring.

⑧ Measuring

Measures for the material accountancy and protection of
nuclear fuel materials shall be enacted.
- The basic requirements of ① to ⑧ shall be able to be
maintained even when accounting for aging.

① Structure② Heat removal

2- Leakage of radioactive materials shall be prevented.
- The necessary shielding capabilities shall be in place toprevent radiation sickness.

⑤ Criticality- There shall be no risk of fuel debris reaching criticality.

⑥ Hydrogen- Hydrogen explosion shall be prevented.

⑦ Fire- Fires shall be prevented from occurring.

⑧ Measuring

Measures for the material accountancy and protection of
nuclear fuel materials shall be enacted.

Identifying issues for eachfuel debris handlingprocess (32 processes)

unit canCanister

unit canCanisterOther components(Systems that handle components
other than unit can and canisters)

Identify issues ineach process fortarget components- Structural strength shall be able to maintain the basic
requirements in ② to ⑦ against loads from the assumed
events.
- Fuel debris shall not melt from decay heat.
- Heat removal functions shall be able to maintain the basic
requirements of ① and ③ to ⑦.

④ Shielding⑩ Other necessary items forhandling operations

Canister

Proposed issues- The necessary functions for fuel debris retrieval and collection
shall be in place.

③ Confinement(Contamination)⑨ Long-term integrity

unit canPermission and authorization(safety design) policies- Structural strength shall be able to maintain the basic
requirements in ② to ⑦ against loads from the assumed
events.
- Fuel debris shall not melt from decay heat.
- Heat removal functions shall be able to maintain the basic
requirements of ① and ③ to ⑦.
- Leakage of radioactive materials shall be prevented.

⑩ Other necessary items forhandling operations

Inside thereactorBasic requirements③ Confinement(Contamination)⑨ Long-term integrity

Visualverification ofdischarged
materials

Systems concepts

Considerations for thebasic requirements- The basic requirements of ① to ⑧ shall be able to be
maintained even when accounting for aging.
- The necessary functions for fuel debris retrieval and collection
shall be in place.

[Evaluation items] - Safety assessments(structure, heat removal, confinement(contamination), shielding, criticality,hydrogen, measuring, long-term integrity)- Requirements for handling operations©International Research Institute for Nuclear Decommissioning6. Implementation details

No.32

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (5/8)- Information on the fuel debris in powder, slurry, or sludge form that is expected to be discharged during fueldebris retrieval (characteristics, amount generated, properties, safety requirements, etc.) was exchanged at
joint project meetings.
<Summary of information on fuel debris in powder, slurry, or sludge form expected to be discharged during fuel debris retrieval (excerpt from the table)>
Properties of the target substance when collected in a collection container (including additives other than fuel debris)

No.

1

Types

Coagulation
sediment incoarse filter
liquid waste

Properties

High volume of particles
with large particle size andhigh specific gravity

Coagulation
sediment inHigh volume of particles
2 intermediate and with small particle size andfinal treatment
low specific gravity
filter liquid waste

3

4

Location ofgeneration

Amount generated

Timing ofgeneration

Contained materials(including percentage)

Shape (including
fuel debris size)

Density

Candidate collection
containers(unit cans, canisters,others)Moisturecontent

Void ratio

90 to 95 [vol%]Almost 0 [vol%]- Sludge collection
container (Φ200 ×
H400)- Waste storage
container

Existence ofcollection
container
treatment

If “yes” in the left
column, thetreatment method

Form ofcollection into
the collection
container

Location ofcollection into
the collection
container

Proposedtransfer routeof collection
container

Transferfrequency ofcollection
container

Safety requirements whenhandling collection
containers (including
storage)

None—

Direct collection

Sedimentation
separation tankin the extension
building

Transfer fromthe extension
building
through theinterior of the
hot cell

1 [pcs/day]- Control shape to maintain
sub-criticality- Use venting, etc. tomaintain hydrogenconcentration levels below
the explosion lower limit

0.055 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Molten fuel- Core structures- Concrete- Other solids (earth andsand, precipitates, insoluble - Particle form (particle
neutron absorbers,
diameter: 100 to
Approx. 1 [g/cm3]
solidified materials,
several tens of μm)
abrasives, etc.)- Aluminum sulfate(1000 ppm)
- Boric acid components

Sedimentation
separation
system inside the 54 to 7 [m3/y]
extensionbuilding

0.27 to 0.035 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Molten fuel- Core structures- Concrete- Other solids (earth and- Particle form (particle
sand, precipitates, insoluble
size: several tens toApprox. 1 [g/cm3]
neutron absorbers,
0.1 μm)solidified materials,
abrasives, etc.)- Aluminum sulfate(1000 ppm)

90 to 95 [vol%]Almost 0 [vol%]- Sludge collection
container (Φ200 ×
H400)- Waste storage
container

None—

Direct collection

Sedimentation
separation tankin the extension
building

Transfer fromthe extension
building
through theinterior of the
hot cell

1 to 8 [pieces/day]- Control shape to maintain
sub-criticality- Use venting, etc. tomaintain hydrogenconcentration levels below
the explosion lower limit

1.6 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Powder adsorbents (titanicacid, titanium silicate,- Particle form
activated carbon, hematite,(Particle size: several
magnetite)μm)- High base PAC (1000ppm)

Approx. 1 [g/cm3]

90 to 95 [vol%]Almost 0 [vol%]- Sludge collection
container (Φ200 ×
H400)- Waste storage
container

Yes

In technologicaldevelopment (target
moisture content of
60 vol% or less;provisional setting)Direct collection

Sedimentation
separation tankin the extension
building

Transfer fromthe extension
building
through theinterior of the
hot cell

111 [pcs/day]- Control shape to maintain
sub-criticality- Use venting, etc. tomaintain hydrogenconcentration levels below
the explosion lower limit

Further
Increase of
retrieval scale(1/3 units)- Dust debris- Others- Particle form (particle
size: unknown, but
assumed to beparticles that float in
the air)

Further
Increase of
retrieval scale(1/3 units)- Gd2O3- Bismuth borate glass(Glass material containing
B/Gd)- Sodium silicate (Na2O,
SiO2, CaO, Al2O3, Fe2O3,
CaSO4, NaH2PO4)- Gd particles: Particle
form(Particle size: up to
500 μm)- Glass material
containing B/Gd:
Particle form (particle
size: up to 1 mm)- Sodium silicate:
Sludge form after
solidification (particle
size: up to 100 μm)- Gd2O3 particles:
4.3 [g/cm3]- Glass material
containing B/Gd:
4.29 [g/cm3]- Sodium silicate:
2.1 [g/cm3] (M3V2019-000230,
rev1, The usage
methods of nonsoluble neutron
absorbers)

For Gd2O3 andglass material
containing B/Gd,water content is0%
Unknown for
sodium silicate,but thought to behigh(Will revise if data
is obtained in the2021-2022
project)

For Gd2O3 andglass material
containing B/Gd,void ratio is 0%
Unknown for
sodium silicate,but thought to be
low(Will revise if data
is obtained in the2021-2022
project)

There is no size limit forcontainers that collectabsorbents(Absorbents will not becollected separately after
retrieval, but will becollected along with fueldebris)

The containersthat collectabsorbents can bedisposed of as
general industrial
waste.

None (no need toconsider)No special treatment
is required forcollection containers
with added
absorbents.

None (no need toconsider)Collected alongwith debris.

None (no needto consider)Collected alongwith debris.

None (no needto consider)Collected
along withdebris.

- Gd particles:
Transfer 5.5 [L]once a year
1.5 E-5 [m3/day] ×
365 [days] = 5.5[L/year]- Sodium silicate:Transfer 11 [L]once a year
3.0 E-5 [m3/day] ×
365 [days] = 11
[L/year]None (no need to consider)
The government R&D project
verified the safety of theabsorbents and their impact
on collection and storage.
(M3V-2020-000265,
Summary of performanceassessment of insoluble
neutron absorber)

Sedimentation
separation
system inside the 11 [m3/y]
extensionbuilding

Coagulation
settings in RO
concentrated
water

Dominated by powder
adsorbents on the order ofseveral μm

Sedimentation
separation
system inside the 310 [m3/y]
extensionbuilding

Gas phasesludgeGenerated by collecting
dust debris floating in the
air with a metal HEPA filter
in a gas phase system andusing backwashing to
remove it.
Currently considering
treatment in a liquid phasesystem sedimentation
separation tank as one
proposal.

Metallic HEPA
filter in a gas
phase system

Solid-type absorbents (Gdparticles, glass materials
Neutroncontaining B/Gd) andabsorbers forsolidified-type absorbents
5
maintaining sub- (sodium silicate) that havecriticality
been processed together
with debris and changed toa powder or sludge form

Frequency of generation

Location ofdebris retrieval
task such aspedestal, etc.

The amount of Gd particles and glassmaterials containing B/Gd used is estimatedto be 2.5% of the volume of debris.
Assuming that an additional 1% of this turns
into sludge, the volume ratio to debris is2.5% × 1% = 0.025%.
The amount of sodium silicate used isestimated to be 5% of the volume of debris,so the volume ratio to debris is 5% × 1% =0.05%. (M3V-2019-000230, rev1, The
usage methods of non-soluble neutron
absorbers)

The amount of Gd particles and glassmaterial containing B/Gd used per day isestimated to be 1.5 liters (1.5 E - 3[m3/day]). Assuming that 1% of this turns
into sludge, then 1.5 E - 5 [m 3/day]
The amount of sodium silicate used per
day is estimated to be 3.0 liters (3.0 E - 3[m3/day]). Assuming that 1% of this turns
to sludge, then 3.0 E - 5 [m3/day] (M3V2019-000230, rev1, The usage methods of
non-soluble neutron absorbers)(Remarks) Classification of colored cells in the table: Items that can be provisionally set based on future desk studies, etc.

: Items that are considered difficult to judge (provisionally set) further (requires actual fuel debris information): Items that do not require further consideration (does not require criticality control and collection container)

Listing of the fuel debris in powder, slurry, or sludge form expected to be discharged (19 types) Assume theamount generated, properties, collection form, etc., and color-code according to the following classifications- Yellow: Items that can be provisionally set based on future desk studies, etc.
- Pink: Items that are considered difficult to judge (provisionally set) further (requires actual fuel debris
information)- Blue: Items that do not require further consideration (does not require criticality control and collection©International Research Institute for Nuclear Decommissioning
containers)

6. Implementation details

No.33

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (6/8)<Example of fuel debris in powder, slurry, or sludge form expected to be discharged when retrieving sorted fuel debris>
No.

Types

Coagulation
sediment in1coarse filter
liquid waste

Properties

Location ofgeneration

Amountgenerated

SedimentatioHigh volume ofn separation
particles with large
system inside 11 [m3/y]particle size andthe extension
high specific gravity
building

Coagulation
SedimentatioHigh volume of
sediment in
n separation
particles with small
2 intermediate andsystem inside 54 to 7 [m3/y]particle size and low
final treatment
the extension
specific gravity
filter liquid wastebuilding

3

No.

1

Coagulation
settings in RO
concentrated
water

Types

Sedimentatio
Dominated byn separation
powder adsorbents
system inside 310 [m3/y]on the order ofthe extension
several μm
building
Candidate collection
containers(unit cans, canisters,others)- Sludge collection
Coagulation
container (Φ200 ×
sediment in
H400)
coarse filter liquid- Waste storage
waste
container

Frequency ofgeneration

Timing ofgeneration

Properties of the target substance when collected in a collection container (including additives otherthan fuel debris)
Contained materials (including
Shape (including
MoistureDensity
Void ratio
percentage)fuel debris size)
content

0.055 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Molten fuel- Core structures- Concrete- Particle form
- Other solids (earth and sand, precipitates,
Approx. 1(Particle size: 100 to
insoluble neutron absorbers, solidified[g/cm3]several tens of μm)
materials, abrasives, etc.)- Aluminum sulfate (1000 ppm)
- Boric acid components

90 to 95
[vol%]

Almost 0[vol%]

0.27 to 0.035 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Molten fuel- Core structures- Concrete- Particle form
- Other solids (earth and sand, precipitates,
Approx. 1(Particle size: several
insoluble neutron absorbers, solidified[g/cm3]tens to 0.1 μm)
materials, abrasives, etc.)- Aluminum sulfate (1000 ppm)
- Boric acid components

90 to 95
[vol%]

Almost 0[vol%]

1.6 [m3/day]Further
Increase of
retrieval scale(1/3 units)- Powder adsorbents (titanic acid, titanium
silicate, activated carbon, hematite,magnetite)- High base PAC (1000 ppm)

90 to 95
[vol%]

Almost 0[vol%]

Form ofcollection into
the collection
container

Location ofcollection
into thecollection
container

Proposedtransfer routeof collection
container

Transferfrequency ofcollection
container

Safety requirements whenhandling collection
containers (including
storage)- Particle form
Approx. 1(Particle size: several[g/cm3]μm)

Existenceofcollection
container
treatment

If “yes” in the left
column, thetreatment method

None

-

Directcollection

Sedimentation Transfer fromseparation
the extension
tank in thebuilding throughextension
the interior ofbuilding
the hot cell

1 [pcs/day]- Control shape to maintain
sub-criticality- Use venting, etc. to maintainhydrogen concentration levels
below the explosion lower limit

Coagulation
sediment in
2 intermediate andfinal treatment
filter liquid waste- Sludge collection
container (Φ200 ×
H400)- Waste storage
container

None-

Directcollection

Sedimentation Transfer fromseparation
the extension
tank in thebuilding throughextension
the interior ofbuilding
the hot cell

1 to 8[pieces/day]- Control shape to maintain
sub-criticality- Use venting, etc. to maintainhydrogen concentration levels
below the explosion lower limit

Coagulation
settings in RO
concentratedwater- Sludge collection
container(Φ200 × H400)- Waste storage
container

Yes

In technologicaldevelopment (target
moisture content of
60 vol% or less;provisional setting)Directcollection

Sedimentation Transfer fromseparation
the extension
tank in thebuilding through 111 [pcs/day]extension
the interior ofbuilding
the hot cell

- Control shape to maintain
sub-criticality- Use venting, etc. to maintainhydrogen concentration levels
below the explosion lower limit

3[Information on the organization of fuel debris in a
powder, slurry, or sludge form]- Type- Characteristics- Location of generation, amount generated,frequency of generation, time of generation- Properties(Contained materials, shape, density, moisture
content, void ratio)- Candidate collection containers- Existence of collection container treatment andtreatment method- Form of collection into collection container,
collection location- Collection container transfer route and transfer
frequency- Safety requirements when handling and storingcollection
containers©International
Research Institute for Nuclear Decommissioning6. Implementation details

No.34

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (7/8)- Information on the advantages and disadvantages of drying treatment for powdery fuel debris was exchanged at joint project
meetings
Items

Hydrogencountermeasures

Advantages

Disadvantages- Since the amount of hydrogen generated can be reduced byusing drying treatment to reduce the volume of watercontained in fuel debris, it can be collected in collection
containers (including canisters) to achieve values below thelower explosion limit of hydrogen (4 vol%).

- When fuel debris becomes clay-like due to residual moisture from insufficient drying, hydrogen pools
will form in the fuel debris, and one of the following reasons could cause hydrogen concentration to rise
sharply by hydrogen being suddenly discharged from hydrogen pools.
〇 Vibration caused by handling fuel debris〇 Discharge caused by the hydrogen pool expansion (depends on the viscosity of fuel debris)
In addition, because it is assumed that the hydrogen pools cause fluctuations in the hydrogenconcentration of the gas phase section, it may be difficult to understand the amount of hydrogengenerated based on results from hydrogen concentration measurements.

- By reducing the volume of water contained in fuel debris- There is a possibility that the drying treatment will disperse dried radioactive materials in powder form
through drying treatment, fuel debris can be collected ininside the canister and clog the hydrogen discharge filter installed in the lid.
collection containers (including canisters) and handled in a
- There is a possibility that an increase in the amount of dispersion of radioactive materials in powder form
Confinement
sealed state, and it is also possible to suppress the discharge
will require a larger off-gas treatment system. In addition, there is a possibility that the maintenance(Contamination) or radioactive materials.
(decontamination) frequency for equipment that handles canisters such as transfer casks and storage
containers will increase.
- Radioactive gas (FP) could be released from fuel debris if the drying temperature is high (200 to 300℃).
- Reducing the volume of water contained in fuel debris throughdrying treatment is advantageous from the viewpoint of―
Criticality
maintaining sub-criticality.
- Since the amount of moisture with shielding effect is reduced, less water will increase surface dose andexposure levels.
―
Shielding- There is a possibility that dispersion of radioactive materials in powder form will increase the dose inhandling areas.
- Reducing the volume of water contained in fuel debris throughLong-term
drying treatment can reduce the risk of corrosion during long―integrity
term storage.
- The drying treatment makes it easier for fuel debris in powder form to rise, which may increase the risk of―Firedust fires.
- The drying treatment reduces the volume of fuel debris, so- Drying treatment facility (drying system, off-gas treatment system, temporary storage system (areas)storage efficiency is expected to improve.
suitable for drying treatment speed, etc.) is required.
- Reducing the volume of water (ideally, completely drying)- There is a possibility that drying treatment will cause fuel debris in powder form to stick to the unit canOthersfacilitates uniform solidification, which increases stability andand canister, making it impossible to retrieve when the final treatment method is determined.
makes it easier to estimate properties, etc. compared to nonuniform solidification when not dried or partially dried.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.35

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsa. Identification of targets and items to organize (8/8)- Creation of a draft process flow that adds the handling of fuel debris in powder, slurry, or sludge form expected
to be discharged during fuel debris retrieval to the series of processes for handling fuel debris in particle or lumpform.
<Assumed process flow for fuel debris in powder, slurry, or sludge form (draft)>
Reactor building +extension building[Fuel debris retrieval process] (Cutting and processing of discharged materials ~ Unit can delivery)[Storage process] (Loading the unit can canister ~ Fastening the canister lid)

[Processes before canister delivery] (Verifying canister delivery ~ Verifying delivery)[Delivery process] (Loading the canister transfer cask ~ Delivering the transfer cask)[Transfer processinside the premises]

Canister lid
Empty
canister

Receive empty
canisterOpen lid

Empty canister(lid open)

Retrieve empty unit can

CanisterEmpty unit can

[7]
Load
Discharged
materials[1]Cut andprocess[2] Visualverification

Fuel debris[3] Collectand fill[4] Dewater* Sorting at the retrieval site and after retrieval will behandled in the future Reflected in this flow at the stageof examination.
As of FY2018, the scenario states that anything thatcan be clearly identified as waste via visual verification
will be sent to the waste treatment facility. (Theamount of generated material is unknown.)[5] Transfer
outside thereactor building[8] Fasten
lid・ MCCI crushed fragments in powder form [No.7]
・ MCCI crushed fragments in particle form [No.8]
・ Debris processing chips [No.10, 11, 12]・ Gas phase filter [No.18][9’]Decontamination

Receive empty
sealed container

Scenario
branches(Note) Individual types of waste do not require subcriticality control, but if they cannot be sorted
by visual verification then they must be
managed as fuel debris.

[12]
Verifydelivery

Empty transfer cask /Empty shielding container
Use a transfer cask
for transferring inside
the 1F premises?

Open lid

Generation in a liquid system(debris is collected in a sedimentation separation tank)・ Filter liquid waste coagulation settlings [No.1 and 2]
・ Coagulation settings in RO concentrated water [No.3]
・ Gas phase sludge [No.4][5] Transfer
outside the reactor
building

Dedicated
container[7] Load[6]
DryingIn addition, dedicated containers for the following fuel debris inparticle form with a particle size of 0.1 mm or more are assumed
Empty dedicated to be mesh-structured containers such as a unit can.
- MCCI crushed fragments in particle form [No.8]
container- Debris processing chips [No.11]- Deposits at PCV bottom [No.17][3] Collectand fill

Lid

Empty transfer cask (lidopen) /

Empty sealedcontainer

Empty sealedcontainer (lid
open)

Load

Open lid

Sealedcontainer(lid open)

Sealedcontainer lid

Fasten lid[14] Fasten
lid

Canister

Surface contamination
verification[4] Dewater[5] Transfer
outside thereactor building( No. 1 to 3 occur
in the extension
building)

Dedicated
container[6]
DryingTransfer
cask

Sealedcontainer
Shieldingcontainer[16] Verify
delivery

[17]
Load

Transfertruck

Gas phase sludge [No.4] [liquid system]

Abrasives [No.13] [Waste] (Note)

Neutron absorbers for maintaining sub-criticality (sludge form) [No.5] [Waste] (Note)

Solidified materials such as geopolymers [No.14] [Waste] (Note)

Neutron absorbers for maintaining sub-criticality (slurry form) [No.6] [Waste] (Note)

Fumes, etc. during cutting [No.15] [Waste] (Note)

MCCI crushed fragments in powder form (particle size: less than 0.1 mm) [No.7] [Liquid
system/gas system]

Bentonite heavy mud water [No.16] (particle size: several tens of μm to 5 mm) [Waste]

MCCI crushed fragments in particle form (particle size: 0.1 to 10 mm) [No.8] [Unit can]Deposits at PCV bottom [No.17] (Particle size 0.1 μm to 10 mm) [Canister (loaded in a
separator instead of a unit can)]Debris processing chips (laser gouging: 1 μm or less) [No.10] [Liquid system/gas system]

Empty canister

[7]
Load

[15] Measure
the amount ofhydrogengenerated

Transfer cask (lidopen) / Shielding
container (lid open)[13] Load

Generation in a liquid system (suction to collect debris underwater)

・ MCCI crushed fragments in powder form [No.7]
・ MCCI crushed fragments in particle form [No.8]
・ Debris processing chips [No.10, 11, 12]・ Deposits at PCV bottom [No.17]
・ Liquid phase filter [No.19]

Receipt of empty transfer cask /empty shielding container

Fuel debris in powder, slurry, or sludge form and waste expected to be generated in the reactor building- Inside RPV and PCV*: Processes that might not be implemented.
[3] Collectand fill[11]
Measurethe amountof hydrogengenerated

Scenario
branches[9] Verify
surfacecontamination

Waste treatment facility

Generation in a gas system (metallic HEPA filter, etc.)[10] Inject
inert gas

Decontamination-Neutron shielding material for maintaining sub-criticality[No. 5 and 6] (Note)- Abrasives [No.13] (Note)- Solidification material such as geopolymers [No.14](Note)- Fumes , etc. during cutting [No. 15] (Note)- Bentonite heavy mud water [No. 16] (Note)

Waste

Canister(lid open)[6]
DryingUnit canDryingExecute drying
treatment based on
canister condition?

Execute drying
treatment based onunit can condition?

Bring inside the pedestal

Scenario
branches

The following is the process flow for
the fuel debris in particle or lumpform listed above.
It is necessary to refer to (from [8]onwards) and determine theprocesses to be implemented fromthe viewpoint of safety and handling.

Debris processing chips (laser gouging: 250 μm to 1 m) [No.11] [Collection container](Note)

Gas phase filter [No.18] [Gas system (metallic HEPA filter, etc.)]
Liquid phase filter [No.19] [Gas system (metallic HEPA filter, etc.)]

Debris processing chips (disc cutter: 0.5 to 100 μm) [No.12] [Liquid system/gas system]

Fuel debris in powder, slurry, or sludge form expected to be generated in theextension building- Sedimentation separation system- Coagulation sediment in coarse filter liquid waste [No.1] [Sludge collection container/waste container](Note) Individual types of waste do not require
sub-criticality control, but if they cannot besorted by visual verification then they must
be managed as fuel debris.

- Coagulation sediment in intermediate and final treatment filter liquid waste [No.2] [Sludge
collection container/waste container]©International Research Institute for Nuclear Decommissioning- Coagulation settings in RO concentrated water [No.3] [Sludge collection container/waste container]6. Implementation details

No.36

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form

③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (1/6)- Issues in each process for handling fuel debris in powder, slurry, or sludge form were identified
based on the issue identification format.
<Example of issue identification based on the issue identification format>
Concepts and policies from a technological standpoint
Step
Technologicalelements
No

3

Locations

Inside thereactor

Details of
implementation

unit canProposed issues

Permission and authorization (safety design)
policies

Systems concepts
Basic requirements

Considerations for the basic
requirements
Canister

unit canCanister

unit canCanisterOther components (systems that handle components other than unit canand canisters)—- The current unit can structure proposal uses a meshstructure for dewatering, making it difficult to collect fueldebris in slurry or sludge form.
- Since the current unit can structure proposal does nothave a lid (the upper part is open), vibrations or shaking
may cause fuel debris in slurry or sludge form collected
inside the unit can to spill out of the unit can.

—

—

—

<Building issues>
Verify that there are no significant issues in using building ventilation toensure the permissible temperature for melting fuel debris, etc.
(Since the amount of heat generated is considered to be small, it is thoughtthat no significant issues exist.)—<Building (hot cell) issues>- Dried debris in powder form discharged outside the unit can is likely to bedispersed and it may be necessary to strengthen confinement performanceinside the hot cell.
(However, other projects are examining the handling of fuel debris in
powder form inside the reactor, so it may not be an issue.)① Structure- Structural strength shall be able
to maintain the basic requirements
in ② to ⑦ against loads from theassumed events.

- For the basic requirements in ② to⑦, guarantee either the unit can,canister, transfer cask, storage
container, or cell.

- Although the structure shouldbe able to maintain the basic
requirements of ② and ⑤, if theunit can is stored within thecanister, it will be maintained by
the canister.

—- Although it is assumed thatsystem redundancies, etc. will
prevent the assumed events
such as overturning or falling
during handling and the policy
is not to consider them, astructural strength evaluationmust be conducted if
becomes necessary toconsider them.

② Heat removal- Fuel debris shall not melt fromdecay heat.
- Heat removal functions shall beable to maintain the basic
requirements of ① and ③ to ⑦.

- The cells within the building havesufficient ventilation capacity toremove decay heat inside the unitcan.

- Because the amount of heatgenerated is small and heat isremoved by ventilation, active
heat removal is not guaranteed.

—- The amount of heatgenerated by fuel debris isconsidered to be small, so
verify that ventilation cansatisfy the permissible
temperature for melting fueldebris, etc.

—

③ Confinement(Contamination)- Leakage of radioactive materials
shall be prevented.

- The cells within the building havesufficient confinement performance
to prevent contamination(confinement).

- The unit can does notguarantee confinement
performance.

—- The unit can does notguarantee confinement
performance.

—④ Shielding- The necessary shielding
capabilities shall be in place toprevent radiation sickness.

- Cell shielding is designed toprevent radiation exposure toradiation personnel and the generalpublic caused by radiation emitted
from debris.
- Because the cell bears primary
responsibility shielding functions, thethickness of the canister should be
the thickness required from theperspective of structure, etc..

- There is no particularguarantee as it is provided by
the cell boundary.

—- There is no particularguarantee as it is provided by
the cell boundary.

—- No issue exists because there is no guarantee—<Building (hot cell) issues>
Verify the shielding guarantee at the cell boundary.
(However, other projects are examining the handling of fuel debris in
powder form inside the reactor, so it may not be an issue.)⑤ Criticality- There shall be no risk of fueldebris reaching criticality.

- Maintain sub-criticality in the unit
can geometrical shape.
- Maintain sub-criticality even in theevent of spillage, etc.

- Maintain sub-criticality in theunit can geometrical shape.
- It is assumed that measures
will be taken on the equipment
end to prevent the unit can fromoverturning.

—- Maintain sub-criticality in theunit can geometrical shape.

—- Verify the validity of the unit can’s assumed dimensions
with respect to criticality evaluation conditions (debris
distribution, arrangement, etc.)—- Verify that measures will be taken on the equipment end to prevent
overturning with the handling of unit can.

- Hydrogen is constantly
discharged inside the reactor
when the unit can is notcovered, so maintain hydrogenconcentration below the lower
explosion limit of 4 vol.% byventilating the inside of thereactor.
- When the unit can is covered,conduct hydrogen diffusion
evaluations, etc. to verify thathydrogen generated in the unit
can is discharged properly.

—- When the unit can is notcovered, hydrogenconcentration will bemaintained by ventilating theinside of the reactor.
- When the unit can iscovered, hydrogenconcentration will bemaintained by ventilating theinside of the reactor. Conducthydrogen diffusion
evaluations, etc. as necessary
to verify that hydrogengenerated in the unit can is
below the lower explosion limitof 4 vol.%.

—- As fuel debris becomes finer, the contribution rate of αrays, which have a large impact on water radiolysis,
increases, and there is a possibility that the amount ofhydrogen generated will increase compared to thecurrently assumed particle size of 0.1 mm or larger.
- There is no problem because the current unit canstructure proposal does not have a lid (the top is open),but if it is changed to one with a lid (sealed), it may bedifficult to achieve hydrogen concentration of less than 4
vol% in the unit can.
- Because fuel debris in slurry or sludge form is viscous, it
is possible that hydrogen pools will form in the interior andintermittently discharge hydrogen, causing hydrogenconcentration in the gas phase section inside the unit can
to rise suddenly.

Collect fuel debris
with the fueldebris retrieval
equipment and fillunit can⑥ Hydrogen- Hydrogen explosion shall be
prevented.

- Maintain hydrogen concentration
inside fuel debris collection, transfer,and storage containers below thelower explosion limit of 4 vol.%.

⑦ Fire- Fires shall be prevented fromoccurring.

- Fires are prevented by creating aninert gas atmosphere inside thereactor.

- Fires are prevented by creating
an inert gas atmosphere inside
the reactor.
- The high moisture content offuel debris is expected tosuppress dust fires.

—- Fires are prevented bycreating an inert gas
atmosphere inside the reactor.

—⑧ Measuring

Measures for the material
accountancy and protection of
nuclear fuel materials shall beenacted.

- Material accountancy will not be
conducted when handling unit cansthat have collected fuel debris.
(material accountancy will be
conducted after loading into thecanister)- All efforts will be made to
design the unit can so that fueldebris does not spill.

——⑨ Long-term integrity- The basic requirements of ① to
⑧ shall be able to be maintainedeven when accounting for aging.

- There is no problem with material
integrity caused by corrosion, etc. of
structural components in theenvironment during handling.

- Select materials that canmaintain structural integrity forthe expected unit can usage
environment.

—- Select materials (SUS316L,etc.) considering
environmental conditions anduse analysis and testing toevaluate integrity.

⑩ Other necessary
items for handling
operations- The necessary functions for fueldebris retrieval and collection shallbe in place.

- The amount of heat generated by fuel debris is small
and the ventilation should be able to remove it, but verify
that there are no significant issues on the heat removal
side.

- There is no issue because the confinement performance
is not guaranteed.

Yellow markers indicate issues
selected from issues (draft) for eachfuel debris handling process (32processes)——- There is no issue, because fuel debris in slurry or sludge
form contains moisture and so will suppress dust fires.

—

—

—

- There is no issue because material accountancy is notconducted with the unit can.

—<Issues with material accountancy and nuclear fuel material
measuring equipment>- It is possible that measuring nuclear fuel materials (including fuel debris inslurry or sludge form) collected in the canister may not be correct becauseof other materials such as concrete and moisture contained in the fueldebris.
(However, other projects are examining methods for measuring nuclear
materials, so it may not be an issue.)—- The retrieval period is short and corrosion risk is notassumed to materialize.

—<Building (hot cell) and related component issues>- There is the possibility of problems with material integrity caused bycorrosion, etc. of structural components in the environment during
handling.
(However, other projects are examining the handling of fuel debris in
powder form inside the reactor, so it may not be an issue.)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.37

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (2/6)<Main issues identified involving the storage of fuel debris in powder, slurry, or sludge form>[Target equipment: unit can (unit can)]Hydrogen

Structure

Items

Selected issues

Proposed measures

Technological issues, solution phase, andsolution period Note1- Since the current unit can structure proposal uses a meshstructure for dewatering, it is difficult to collect fuel debris in
powder, slurry, or sludge form (hereinafter referred to as“powdery fuel debris”).

- Study of containers without mesh structureinteriors for filling powdery fuel debris.

- Since the current unit can structure proposal does not have a lid(the upper part is open), powdery fuel debris may spill out during
handling.

- Implement countermeasures to prevent spills,
such as a unit can structure with a lid.

- Because powdery fuel debris has a very small particle size, it isdifficult to dewater by having water fall from the unit can’s meshpart via gravity.

- Develop drying procedures or dewatering
methods because it is difficult to dewater via
gravity.

- Study of drying systems for powdery fuel debris⇒ Study of using related subsidy project (drying project)- In case of fine fuel debris, the contribution rate of α-rays, whichhave a large impact on water radiolysis, increases, and there is apossibility that the amount of hydrogen generated will increase
compared to the currently assumed particle size of 0.1 mm orlarger.

- Verify whether the amount of hydrogengenerated from powdery fuel debris is greaterthan that from fuel debris in particle or lumpform.
- Study of the discharge characteristics ofhydrogen generated from powdery fuel debris.
- Measure hydrogen concentration anddetermine the subsequent handling methods(reducing the amount of collection, etc.) basedon results of actual measurements.

- Study of the amount of hydrogen generated and hydrogen
discharge characteristics of powdery fuel debris⇒ Study of using subsidy project starting in FY2022 andactual machine engineering- Study of methods for measuring hydrogen concentration in
powdery fuel debris⇒ Study of using actual machine engineering- Because powdery fuel debris is viscous, it is possible thathydrogen pools will form in the interior and intermittently
discharge hydrogen, causing hydrogen concentration in the gas
phase section inside the unit can to rise suddenly.

- Study of the discharge characteristics ofhydrogen generated from powdery fuel debris.

- Study of discharge characteristics of hydrogen generated
from powdery fuel debris⇒ Study of using subsidy project starting in FY2022 andactual machine engineering- If the unit can is changed to the one with a lid (sealed), it may bedifficult to achieve hydrogen concentration of less than 4 vol% in
the unit can.

- If unit can structure will have a lid, examine
using a lid with a vent.

Note 1: - Related subsidy project (drying project)- Subsidy project starting in FY2022- Actual machine engineering- Study of container interiors for powdery fuel debris(alternative containers for unit can)⇒ Study of using related subsidy project (drying project)and subsidy project starting in 2022** It is also necessary to examine the safety requirements for handling
unit cans and canisters in related subsidy projects that are
reviewing the discharge of fuel debris in powder, slurry, or sludgeform.

- Study of container interiors for powdery fuel debris(alternative containers for unit can)⇒ Study of using related subsidy project (drying project)and subsidy project starting in FY2022: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris): Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(development of the necessary technologies to the storage of fuel debris in powder, slurry, or sludge form): Study of after the characterization of fuel debris in powder form*©International Research Institute for Nuclear Decommissioning(*in the subsidy project, the properties of fuel debris in powder form were examined under assumed conditions)6. Implementation details

No.38

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (3/6)<Main issues identified involving the storage of fuel debris in powder, slurry, or sludge form>[Target equipment: canister] (1/2)
Proposed measures- When powdery fuel debris is dried, drying could blow the finely
powdered fuel debris and disperse it inside the cell, increasing
contamination. In addition, because the fine powder passes throughthe canister’s vent filter, the risk of the canister filter clogging could
increase.

- Development of a method forsolidifying powdery fuel debris that
becomes finer powder after drying
treatment. However, considering final
disposal, a reversible solidification
method is required.

- Study of a solidification method for powdery fueldebris⇒ Study of using subsidy projects (TBD) or
actual machine engineering- When powdery fuel debris is dried, drying could blow the finely
powdered fuel debris, which could then pass through the canister’svent filter, resulting in high radiation contamination of the drying
equipment and the equipment that handles the canister.

- Evaluation of the behavior of fine
powdery fuel debris during drying
treatment (e.g., floating up) and theamount of filter clogging and material
that passes through.

- Study of the dispersion characteristics of powdery
fuel debris in canisters during drying⇒ Study of using subsidy project starting in
FY2022- Study of a drying method to suppress
the amount of powdery fuel debris thatthe fuel debris can pass through thefilter, or containing and handling
methods that do not involve drying
treatment (such as a packaging
method for stable storage).

- Study of drying systems for powdery fuel debris⇒ Study of using related subsidy project (drying
project) and subsidy project starting in FY2022- Study of handling methods (packaging methods)
for powdery fuel debris⇒ Study of using subsidy project starting in
FY2022- Response to hydrogen generation byusing the canister, which is the samemeasure using the unit can.
(See No. 37)- Response to hydrogen generation by using thecanister, which is the same measure to solve
technological issues of the unit can at the period ofsolution. (See No. 37)

HydrogenConfinement(Contamination)

Selected issues

Structure

Technological issues, solution phase,and solution period Note1

Items- When fuel debris becomes fine, the contribution rate of α-rays, whichhave a large impact on water radiolysis, increases, and there is apossibility that the amount of hydrogen generated will increase
compared to the currently assumed particle size of 0.1 mm or larger.
- Because powdery fuel debris is viscous, it is possible that hydrogenpools will form in the interior and intermittently discharge hydrogen,causing hydrogen concentration in the gas phase section inside thecanister to rise suddenly.

Note 1: - Related subsidy project (drying project)- Subsidy project starting in FY2022- Subsidy project (TBD)- Actual machine engineering: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris): Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(development of the necessary technologies to the storage of fuel debris in powder, slurry, or sludge form): A subsidy project not currently planned that may be conducted in the future©International Research Institute for Nuclear Decommissioning: Study of after the characterization of fuel debris in powder form*(*in the subsidy project, the properties of fuel debris in powder form were examined under assumed conditions)6. Implementation details

No.39

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (4/6)<Main issues identified involving the storage of fuel debris in powder, slurry, or sludge form>[Target equipment: canister] (2/2)
Items

Selected issues

Proposed measures

Fire- The risk of dust fires may increase when drying powdery - Maintaining of an inert gas atmospherefuel debris because drying makes it easier for fuel debris inside the cell.
to rise.

Technological issues, solution phase,and solution period Note1- Study of the atmosphere inside cells forhandling powdery fuel debris⇒ Study of using actual machineengineering

Measuring- Depending on the properties of the powdery fuel debris
collected in the canister, nuclear fuel materials may bedischarged outside the canister, making appropriatematerial accountancy impossible.

Long-term
integrity- Development of a method to solidify powdery - Study of a solidification method for powdery
fuel debris that becomes finer powder after
fuel debris
drying treatment. However, considering final ⇒ Study of using subsidy projects (TBD)
disposal, a reversible solidification method is or actual machine engineering
required.

- Short-term handling, such as transfer using canisters- Evaluation of the possibility of canister(material SUS316L) collecting powdery fuel debris, iscorrosion occurring, factoring in the storage
considered to have a low risk of corrosion, but with long- method and environment assumed during
term storage, environmental conditions like temperature, long-term storage of powdery fuel debris. If
residual water, and moisture within ingredients
there is a risk of corrosion occurring,increases the risk of canister corrosion.
countermeasures such as corrosion control
are considered.

Note 1: - Related subsidy project (drying project)- Subsidy project starting in FY2022- Subsidy project (TBD)- Actual machine engineering- Study of material accountancy procedures
based on nuclear fuel materials being
discharged outside the canister.

- Study of material accountancy proceduresfor canisters⇒ Study of using actual machineengineering- Study of assumed environment andcorrosion countermeasures during long-term
storage of powdery fuel debris⇒ Study of using subsidy projects (TBD)
or actual engineering: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris): Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(development of the necessary technologies to the storage of fuel debris in powder, slurry, or sludge form): A subsidy project not currently planned that may be conducted in the future: Study of after the characterization of fuel debris in powder form*(*in the subsidy project, the properties of fuel debris in powder form were examined under assumed conditions)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.40

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (5/6)<Main issues identified involving the storage of fuel debris in powder, slurry, or sludge form>[Target equipment: other equipment]

HydrogenConfinement(Contaminati
on)Structure

Items

Selected issues

Proposed measures- The flow of drying gas could disperse a large amount offine powder inside the unit can into the drying equipment(including the exhaust gas treatment system).

- Drying treatment at a slow flow rate that does notdisperse fine powder.
- Assuming that a large amount of fine powder isdispersed, develop equipment where filters can be
replaced quickly and remotely, with a multi-line filter
configuration.

Technological issues, solution phase, and solution
period Note1- Study of drying systems for powdery fuel debris⇒ Study of using related subsidy project (drying project) or
actual machine engineering- Study of the dispersion characteristics of powdery fuel debris incanisters during drying⇒ Study of using subsidy project starting in FY2022- Study of the system of each component and the dispersion
characteristics of fine powdery fuel debris within each component⇒ Study of using actual machine engineering- When powdery fuel debris is dried, a large amount of fine - Development of a method to solidify powdery fuelpowder within a canister could be dispersed insidedebris that becomes finer powder after drying
handling components (transfer casks, storage containers,
treatment. However, considering final disposal, aetc.) and equipment used in preparing canisters (inert gas
reversible solidification method is required.
injection equipment, hydrogen concentration measuring
equipment, etc.).

- Study of a solidification method for powdery fuel debris⇒ Study of using subsidy projects (TBD) or actual machineengineering-

When powdery fuel debris is dried, a large amount offine powder within a canister could disperse inside
canister handling areas (expansion building hot cells,etc.) and handling components (transfer casks, storage
containers, etc.), possibly creating high radiation
contamination.

- Evaluation of the behavior (floating up, etc.) of fine
powdery fuel debris during drying treatment. Basedon the results of these evaluations, the confinement
performance of each area and component,
countermeasures to prevent the spread ofcontamination, maintenance methods, etc. areconsidered.

- Study of the dispersion characteristics of powdery fuel debris ineach area and component, and the confinement performance,
countermeasures to prevent the spread of contamination, andmaintenance methods⇒ Study of using actual machine engineering- As fuel debris becomes finer, the contribution rate of αrays, which have a large impact on water radiolysis,
increases, and there is a possibility that the amount ofhydrogen generated will increase compared to thecurrently assumed particle size of 0.1 mm or larger.
- Because powdery fuel debris is viscous, it is possible thathydrogen pools will form in the interior and intermittently
discharge hydrogen, causing hydrogen concentration in
the gas phase section inside each component to risesuddenly.

- Response to hydrogen generation by using the- Response to hydrogen generation by using the canister, whichcanister, which is the same measure using the unit
can.

is the same measure to solve technological issues of the unit
can at the period of solution.

(See No. 37)(See No. 37)

Note 1: - Related subsidy project (drying project)- Subsidy project starting in FY2022- Subsidy project (TBD)- Actual machine engineering: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris): Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(development of the necessary technologies to the storage of fuel debris in powder, slurry, or sludge form): A subsidy project not currently planned that may be conducted in the future: Study of after the characterization of fuel debris in powder form*©International Research Institute for Nuclear Decommissioning(*in the subsidy project, the properties of fuel debris in powder form were examined under assumed conditions)6. Implementation details

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,No.41
or sludge form
③ Implementation items and resultsb. Evaluation/issue identification (including evaluations based on Japan and overseas
investigation results) (6/6)- The solution phase and solution period for the selected issues are shown below.
(Target schedule) B3④: Development of Technology for Collection, Transfer, and Storage of Fuel Debris
Period 2 (period until fuel debris retrieval starts)

Actual machineengineering Note 1

Period 3-①

Item/FY

2023 onwards
Maintain and manage safe plant conditions

Major events in the current
Mid-and-Long-Term
Roadmap▽ Begin retrieving fuel debris at the initial unit
Engineering for collection, transfer, and storage[Development ofTechnology for Collection,
Transfer, and Storage ofFuel Debris]
0.

1.

Investigations and R&D
planning for collection,transfer, and storage
Development oftechnology for collection(implemented in
FY2020/21)

Planning
Update plans based on related projects, etc.

This subsidy

Canister
specification
reviews andstructuralverification tests

project
Canister filter failure scenario selection andDevelopment ofDevelopment of drying
technology for drying
This subsidy
technology
treatment

3.

Case study of handlingradioactive materials in
powder, slurry, or sludge
form (implemented in
FY2020/21)
Development of transfer
technology

Expansion and enhancement of drying treatment methods and operational parameters

Analysis, organization, and comparison of caseinvestigation, knowledge, and information,
Clarification of issues with current canisters
in the dry storage of fuel debris in powder,slurry, or sludge form

Hydrogen gas
generation tests andinvestigation oftransfer conditions[Development of Technology
for Further Increasing the
Scale of Retrieval of Fuel
Debris and Reactor Internals]- Subsidy project (TBD)- Actual machine engineering

Verification, etc. of dry storage withcurrent canisters

Alignment with related technological developments

Field work (including engineering)

Team Meeting for Countermeasures for Decommissioning and Contaminated Water Treatment / Secretariat
Meeting (86th meeting) Materials “FY2021 Decommissioning R&D Plan,” Added to “(Target schedule) B3④:
Development of Technologies for Containing, Transfer, and Storage of Fuel Debris”

Note 1: - Related subsidy project (drying project)- Subsidy project starting in FY2022

Related subsidy project(drying project) Note 1[Implementation items]- Acquisition of drying data for difficult-to-dry
materials (slurry, sludge, concrete)- Expansion of drying data from canisters- Clarification of drying equipment concepts(Demands on canisters in terms of drying
treatment)

consequence assessment

2.

project

Study of countermeasures against changes
to canister filter performance[Implementation items (example)]- Study of the design and operation(including rationalization) of eachcomponent based on the results ofsubsidy projects and the data following
collection of powdery fuel debris

R&D

Subsidy project starting in
FY2022 Note 1[Implementation items]- Case study of handling radioactive materials in
powdery fuel debris- Study of hydrogen gas generation anddischarge characteristics- Evaluation of the behavior of powdery fueldebris within canisters- Conceptual study of powdery fuel debris
collection methods

Subsidy project (TDB)
Note 1[Implementation items (example)]- Study of a solidification method for powdery fueldebris- Study of the assumed environment and long-term
integrity when handling powdery fuel debris: Development of Technologies for Containing, Transfer, and Storage of Fuel Debris (Drying Technology for Fuel Debris): Development of Technologies for Containing, Transfer, and Storage of Fuel Debris(development of the necessary technologies to the storage of fuel debris in powder, slurry, or sludge form): A subsidy project not currently planned that may be conducted in the future©International Research Institute for Nuclear Decommissioning: Study of after the characterization of fuel debris in powder form*(*in the subsidy project, the properties of fuel debris in powder form were examined under assumed conditions)6. Implementation details

No.42

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
④ Contribution of outcomes to relevant study areas

The results of identification of issues related to the storage of fuel debris in powder, slurry, or sludge
form were summarized to contribute to the clarification of technological issues to resolve in order toensure the necessary safety functions and implement long-term stable storage. For example,
reference information on the drying and storage of sludge.

⑤ Analysis with respect to the on-site applicability
Solving the technological issues related to the storage of fuel debris in powder, slurry, or sludge form
assumed to be collected during fuel debris retrieval is beneficial because it will lead to technologies
that can be applied on-site.

⑥ Goal achievement level
It can be concluded that TRL Level 1 was achieved as planned because the following indicator tojudge goal achievement was satisfied:• Identification of issues involving safe, reliable, and rational storage conditions when using acanister for dry storing fuel debris similar to that for fuel debris in particle or lump form.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.43

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
⑦ Issues to be addressed

Issues and countermeasures for each process up to storage were examined for dry storage of fueldebris using similar canisters to those used for fuel debris in particle or lump form, and the following
technological issues to resolve were clarified.
(See No. 37 to 40)
In addition, related subsidy project and the continuation project of this subsidy project are planned tosolve the above technological issues after FY2022.
[Technological issues]✓ Study of the interior of containers for powdery fuel debris (alternative containers for unit can)✓ Study of the amount of hydrogen generated and the discharge characteristics of hydrogen generated frompowdery fuel debris✓ Study of methods for measuring hydrogen concentration in powdery fuel debris✓ Study of drying systems for powdery fuel debris✓ Study of the dispersion characteristics of powdery fuel debris in canisters during drying✓ Study of the systems in each component✓ Study of the dispersion characteristics of powdery fuel debris in each area and component, and theconfinement performance, countermeasures to prevent the spread of contamination, and maintenancemethods✓ Study of handling methods (collection methods) for powdery fuel debris✓ Study of the atmosphere inside cells for handling of powdery fuel debris✓ Study of assumed environment and corrosion countermeasures during long-term storage of powdery fueldebris✓ Study of material accountancy procedures for canisters✓ Study of a solidification method for powdery fuel debris©International Research Institute for Nuclear Decommissioning6. Implementation details

No.44

6.2 Identifying issues involving the storage of fuel debris in powder, slurry,or sludge form
⑧ Summary- To comprehensively identify issues involved in safe and long-term stable storage offuel debris in power, slurry, or sludge form, evaluation items and organizational
methods for a series of handling processes and the canisters for particulate or lumpshaped fuel debris were studied and the issue identification format was created .
- Information was exchanged at joint meetings with the related project, and information
involving fuel debris in powder, slurry, or sludge form expected to be discharged during
fuel debris retrieval was organized.
- Based on the above information and issue identification format, the technologicalissues related to the storage of fuel debris in powder, slurry, or sludge form as well as
their solution phases and solution periods were clarified.
- Related subsidy project and the continuation project this subsidy project are planned tosolve the above technological issues after FY2022.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.45

6.3 Performance assessment of canister filters① Purposes and goals
Although it is assumed that the powdery fuel debris collected in canisters alongside fueldebris in particle or lump form will be blown around the inside of the canister during various
handling and treatments (drying treatment, inspection, measurement, etc.) until final storage ina storage facility, designs are progressing so that this dust will be captured by a filter installedon the lid of the canister. Depending on the amount of powdery fuel debris captured, the flowrate of hydrogen gas discharged outside the canister may decrease, or in the worst casescenario, the canister may become clogged and the concentration of hydrogen gas inside thecanister may exceed the standard value.
In addition to the verification of the required specifications for filters that has been studied in
the related R&D project, “Development of Technologies for Containing, Transfer, and Storageof Fuel Debris,” a broad range of the required specifications is reverified under this project.
Concepts of selecting filters that are being considered and consistency with evaluation resultsof the filters are examined.
Furthermore, failure scenarios (i.e., corrosion, etc.) that impact filter performance are
selected and test conditions for evaluating those scenarios are considered.

② Comparison with existing technology
The TMI-2 case study of vent filters was conducted to acquire knowledge, but information on
the effects of degradation due to a long-term use on filter performance is insufficient.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.46

6.3 Performance assessment of canister filters③ Implementation items and results
Setting of a study flow and study of each implementation item
a. Identification of environments/conditions- Examine general concepts for selecting filter specifications

Filter requirements

Factor identification in filter
degradation- Identify factors that may cause filter degradation by referring to the scenario development
process for safety assessment (FEP Note 1) used in designing disposal facilities- Refer to and organize the environment, fuel debris properties, andcanister specifications as input conditions from past projects(canisters and fuel debris properties)- Select degradation factors that match input conditions from among filter degradation
factors and identify possible degradation events

Organization of input conditions

Selection of degradation
factorsb. Study of filter life
evaluation methods

Organization of filter categories

Select ion of degradation
events based on canisterenvironmentc. Study of test
methods andconditions- For each type of filter, examine the possibility that the degradation events identified ina. will occur under the following input conditions from retrieval to storage, and selectdegradation events with high probability of occurringY*
N- Sort general filter properties- Sort necessary requirements for evaluating each filter life

Evaluation of filter degradation - Use a theoretical formula to evaluate filter performance affectedusing a theoretical formulaby degradation from retrieval to storage* A method for estimating degradation events in canister environments has been established
Note 1:

Study of filter degradation simulation
methods- Study of filter degradation simulation methods- Study of methods for determining the degree of degradation- Investigate general filter performance assessment methods (JIS, etc.)

Study of filter performance assessment - Study of the applicability of general methods (inapplicable ⇒ consider
methods
amendments)- Organize parameters (inputs) and issues required for testing

A method of organizing
individual events bysummarizing scenario
characteristics (Feature), events(Event), and processes(Process) in a list

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.47

6.3 Performance assessment of canister filters③ Implementation items and resultsa. Identification of environments and conditions (1/11)(i) Filter requirements
Aerosol- Functions that confine fuel debris
particles

Wavelength ofelectromagnetic
waves X-rays

Cigarette smoke
Combustion nucleus
Carbon black
Viruses
Soot
Ultraviolet rays

Compatible
air filter

Bacteria

PollenCement powder
Fly ashFlour
Fog

Visible light

Dripping
water

Infrared

ULPA filter
HEPA filter
Medium efficiency filter
Coarse dust filter

Particle size (μm)

- Functions that release hydrogen generated by waterradiolysis→ Selected a filter with a hydrogen permeation performance thatallows the generated hydrogen to escape by diffusion so thathydrogen concentration in the canister remain below the lower
explosion limit (4 vol% or less at room temperature and pressure).

Lower limit

Figure 1 Filter unit performance and particle size captured Note 1

Pressure [kg/cm2G]→ Selected a filter with a capture rate that canguarantee the set DF for the fuel debris
particle size to be captured.

Hydrogen concentration (vol%)Note 1: Kamishima, “Performance of Air Filter Units” Aerosol Research Vol.4, No.4 (1989)
Note 2: Yagyu et al., “Effect of High Pressure on the Flammability Limits of Hydrogen,” Safety Engineering Vol.8, No.5 (1969)

Figure 2 Flammability limit of binaryhydrogen-air system Note 2©International Research Institute for Nuclear Decommissioning6. Implementation details

No.48

into 5 environmental categories with
6.3 Performance assessment of canister filters - Arranged
regard to the scenario development process for③ Implementation items and resultsa. Identification of environments and conditions (2/11)(ii) Identifying factors in filter degradation

Environmental
category

Radiation
environment

CauseRadiolysis

EventsHydrogengeneration
Embrittlement

Radiation

Radiation
degradation

safety assessment (FEP)(radiation environment, thermal environment,
stress environment, chemical environment,
external environment)- Arranged possible causes and events of filter
degradation for each environmental category

Event details
Radiolysis of fuel debris generates hydrogen and particles are blown into the atmosphere, clogging the filter.
Radiolysis of fuel debris generates hydrogen and particles are blown into the atmosphere, clogging the filter and thereby
increasing internal pressure and filter damage.
Prolonged exposure to hydrogen generated by the radiolysis of the water that accompanies waste causes hydrogen
embrittlement and filter damage.

Stressenvironment

Chemicalenvironment

External
environment

Decay heat

Vibration duringtransportation or from anearthquake

Corrosion

Differences between thecanister interior and theoutside environment

UV in the environment

The temperature of fuel debris rises due to decay heat and heat conduction causes the temperature of the filter to rise,

DamagedImpacts such as collisions and drops during transportation or earthquakes can deform or damage the container and filter,
resulting in the loss of filter functionality.

Dust generated byVibrations caused by transportation or earthquakes cause fuel debris particles to rise and clog the filter.
vibration
Thickness reduction Corrosive substances attaching to the filter cause corrosion and wastage.
Oxide film
Corrosion on the surface of filter fibers causes an oxide film to form, which increases fiber diameter (decreases pore
diameter) and results in clogging.
generation
Prolonged exposure to vapors containing corrosive substances causes the accumulation of corrosive substances on theSalt precipitation filter, resulting in clogging.
A potential difference is created between the filter and the contact surface of the container or metal fuel debris, resulting
Electric corrosion in electric corrosion of the filter and weakening or damage.
Microorganisms such as mold grow inside and outside the filter, forming a biofilter that clogs the filter and prevents
Microbial membrane hydrogen permeation.
Temperature differences between the inside and outside of the filter cause a film of water to form on the surface of theWater film
filter that clogs the filter and prevents hydrogen permeation.
Aerosol deposition Aerosols such as sea salt particles are dispersed and deposited on the outer surface of the filter, clogging it.
Pressure differences between the inside and outside of the filter generate an air flow, causing powder to fly around andPowder dispersion clog the filter.

UV degradation

DamagedDamagedThermalThe temperature of fuel debris rises due to decay heat and heat conduction causes the temperature of the container todeformation
rise, exerting stress on and damaging the affixed filter.
(container)
Thermal convection Thermal convection causes powder of fuel debris to rise in the atmosphere and clog the filter.
ImpactDamagedRadiation of fuel debris causes filter material to degrade and become damaged.

Thermal alteration resulting in thermal alteration and filter damage.
Thermalenvironment

Degradation
mode
CloggedDamaged
CloggedDamaged
CloggedDamaged
Clogged
CloggedDamaged
Clogged

Clogged
Clogged
CloggedDamagedUV in the environment degrades and damages filter material.

17 degradation events in total were identified.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.49

6.3 Performance assessment of canister filters③ Implementation items and resultsa. Identification of environments and conditions (3/11)
Input conditions (fuel debris properties, container(iii) Organization of input conditions (1/3) specifications, environment conditions inside and outside
canisters) were identified from information in past projects.

Table Results of identifying fuel debris properties
6. Implementation details of this project6.2 Implementation details
1) Technological developments to prevent fuel debris diffusion① Development of a fuel debris collection system

Properties

Remarks 2

Molten fuel debris Main component 1

Items

UO2

Data obtained from accident progression analysis of Unit 1

Molten fuel debris Main component 2

ZrO2

Data obtained from accident progression analysis of Unit 1

MICCI Main component 1

SiO2

Data obtained from accident progression analysis of Unit 1

MICCI Main component 2

Fe2O3

Data obtained from accident progression analysis of Unit 1*3

MICCI Main component 3

UO2

Data obtained from accident progression analysis of Unit 1*4

Metal fuel debris Main component 1

Fe

Data obtained from accident progression analysis of Unit 1

6. Implementation details*1: Fuel debris smaller than 0.1 mm is collected by suction using the liquid phase circulation system as the debris will
likely float and not settle at the bottom.
*2: Particle fuel debris which is relatively small is collected by suction using a pump as this method is likely to be fasterthan collecting by scooping or grabbing.
*3: There are two types of fuel debris in lump form that can’t be sucked by a pump: one that requires processing andanother that does not. Those that do not require processing are generally collected using a clamshell-bucket-like
tool. Those near structures that cannot be grabbed by fuel debris, etc. are collected by picking them up with a
Manipulator
Pressure
tong-like tool.
Spent fuel*4: A larger fuel debris that needs to be processed beforeindicator
being collected
in a unit can is processed into a size that canpellet particle
fit inside(spenta unit canfueland collected(i) Test conditions for hydrogen generation tests
tests) by methods *1 to *3 depending on its size after processing.

Metal fuel debris Main component 2

Ni

Data obtained from accident progression analysis of Unit 1

6.3 Development of technology for transfer of fuel debris(1) Study of methods to predict hydrogen generation③ Implementation items and results (estimated and actual)b. Performing hydrogen generation tests (1/3)

Metal fuel debris Main component 3

Ru

Data obtained from accident progression analysis of Unit 1

Component

a. Methods and procedures for collecting fuel debris (suction, grabbing, etc.)○ Classification of fuel debris by size and method of collecting
Classificat
ion

Particle size

PowderSmaller than 0.1 mm

Particle

Lumps

Case 4

Particle size:
approximately 0.1 mm,
pure water

Case 5

Particle size:
approximately 0.1 mm,
no agitation

Case 6

Blank test

Test
environment

Test period*4of pellet particles (the- The amountof hydrogen generated in a canister that
contains
fuel debris was estimated using a linear<Initial
inneramount of water thatpressure>model.
can be agitated) Halogen ions No Note 3
10 and 20 days
2
- The following condition was used for fuel debris: itapproximately
consists 1only of UO 2 fuel debris that originates in fuel0.123 mmatm
loaded in the 1F-1 (a burnup of 40GWd/t and 10-year cooling period).
- 50 vol% for the volume of dewatering and None
1.1 vol%
(≒
0.1
wt%)
for31the<Temperature>
daysvolume of
1 moisture to be dried
Halogen ions Yes
Room
were used for the volume of waterin
PHITS
calculation.
2,
Note
3
Note

No

-

6 to 11 g/cm3

Data obtained from accident progression analysis of Unit 1

Molten and resolidified material Bedrock form

6 to 11 g/cm3

Data obtained from accident progression analysis of Unit 1

MCCI product Powder or pebble form

6 to 11 g/cm3

Data obtained from accident progression analysis of Unit 1

MCCI product Lump form

2 to 11 g/cm3

Data obtained from accident progression analysis of Unit 1

MCCI product Bedrock form

2 to 11 g/cm3

Data obtained from accident progression analysis of Unit 1

Water

Particle size (powder form)

Smaller than 0.1 mm

Fuel Debris Retrieval (Fundamental Technology) Project FY2018 Final Report Material No.21

Particle

Particle size (particle form)

0.1 mm to 10 mm

Fuel Debris Retrieval (Fundamental Technology) Project FY2018 Final Report Material No.21

Particle size (lump form)

10 mm to 100 mm

Fuel Debris Retrieval (Fundamental Technology) Project FY2018 Final Report Material No.21

5.6 × 10^-4 mol/L

Canister Project FY2020 Final Report Material No. 46

Iodide ion

1.0 × 10^-4 mol/L

Canister Project FY2020 Final Report Material No. 46

pH

9 to 10

Canister Project FY2020 Final Report Material No. 46

Moisture content (before drying)

50 vol.%Canister Project FY2020 Final Report Material No. 50

Moisture content (after drying)

0.1 wt%Canister Project FY2020 Final Report Material No. 50

Hydrogen generation rate (before drying)

1.6 × 10-16 L/h/Bq

Canister Project FY2020 Final Report Material No. 50

Hydrogen generation rate (after drying)

2.3 × 10-18 L/h/Bq

Canister Project FY2020 Final Report Material No. 50

Total inventory

2.18 × 10^15 Bq/t

JAEA/CRIEPI “Research on the Sophistication of Statistical Inventory Estimation Method”

Numberof tests2, Note 3

Approxima
tely 10 g

Data obtained from accident progression analysis of Unit 1

Molten and resolidified material Lump form

Figure: Photos of the hydrogen generation testwith spent fuel*1

Similar to Cases 1 to5
Estimation scenarios

temperature
Table Conditions Yes
and resultsof the estimation10of dayshydrogen generation
amount1
P1

Note 1: Particle sizes below are volume average diameters derived from the results of SEM analysis performed on spent fuel pellet particles before the tests.
Note 2: Artificial seawater (equivalent to a chloride ion concentration of 5.6 × 10−4 mol/L, 20 ppm) and sodium iodide (1.0 × 10−4 mol/L in iodide ion concentration) are used asadditives.
Note 3: The pH value of the test water is controlled between 9 and 10 by adding a pH adjusting agent (NaOH) to suppress the c lumping of particles.
*2
Note 4: The pellet particles used in the tests of cases 4 and 5 are reused.

Evaluation conditions

Case 3

Molten and resolidified material Particle or pebble
6 to 11 g/cm3
form

Properties

Test
container

Particle size
Amount of waterType of test water
6.3
Developmentof technology
for transfer of fuel debris
0.0085mm(1)
Studyof methods to predict hydrogen generation
10 and 20 days
4
Halogen ions Yes
0.123mm
10 and 31 days
3
③ Implementation
items
Noteand results (estimated and actual)
Approximately 30<Gas phase> air
0.415
times the totalYes
and 31 days
4d. mm
Estimation
ofvolumehydrogen generation
amount in10,a20,canister

Energy absorption
rate (evaluatedusing PHITS
calculations)

Amount ofmoisture(Volume ratio)
Particle size
distribution

Evaluation
results (F) Note 1
Decay heat (E)Peaking factor (P)Weight of fuel debris (M)P2

Accompanying
Chloride ion
liquidFigure PHITS calculation system

P4

P5

Volume of dewatering
Target volume of moisture Target volume of moisture
Volume of dewatering(Particles: water =to be dried
to be dried(Particles: water = 1:1 *2)
1:1*2)(Particles: water = 91:1 *3)(Particles: water = 91:1 *3)
Particle size distribution
Particle size distribution (powder
Particle size distribution(powder with 0.1 mm with 0.1 mm and a few mm particles(powder with 0.1 mm
PowderPowder*4*5,
6
particles mixed in)mixed in)particles mixed in)*4
α-ray: 0.250
α-ray: 0.133
α-ray: 0.021
α-ray: 0.004
α-ray: 0.004
β-ray: 0.160
β-ray: 0.142
β-ray: 0.064
β-ray: 0.002
β-ray: 0.002
γ-ray: 0.158
γ-ray: 0.134
γ-ray: 0.058
γ-ray: 0.002
γ-ray: 0.002
Estimates based on burnup calculation results (α-ray: 0.113 W/kg UO2, β-ray: 0.383 W/kg UO2, and γ-ray: 0.221 W/kg UO2)Note 7
Estimates based on burnup calculation results (α-ray: 2.35, β-ray: 1.56, and γ-ray: 1.56)*8
Design value (72.9 kg for a canister with an inner diameter of 220 mm)

Ratio of fuel contained in fuel debris(C)

Hydrogen generation rate (RH2)

P3- A pellet particle is placed in the exact center of acube
- Each nuclide is uniformly distributed in the pellet
particle- The target volume of moisture to be dried issimulated by placing a water film with the same
volume around the particle

Volume of dewatering(Particles: water = 1:1 )Max. value (1)Values cited from literature (α-ray: 1.3 molecules/100 eV and β-ray and γ-ray: 0.45 molecule/100 eV)*9

Hydrogen generation G value (G)

Esti
matio
n
resul
ts

Case 2*2

Test water

Agitation

Particle size:
approximately 0.015 mm
Particle size:
approximately 0.1 mm
Particle size:
approximately 0.3 mm*1Sucked by pump.

Test container

6. Implementation details

Outlines
WeightCase 1

Sucked by waterborne system.

0.1 mm to 10 mmTable Test conditions of the hydrogen generation tests with spent fuelSpent fuel pellet particle

Remarks

10 mm to 100 m
Grabbed by a clamshell-bucket-like tool(a size that can be collected in a unit canor tong-like tool.
without processing)
Larger than 100 mm
Processed into a size that would fit in a(a size that needs to be processed before being unit can and collected by methods *1 to *3collected in a unit can)depending on its size after processing.

Tests are conducted using particle size as a parameter to verify the particle
size dependence. To eliminate the influence of the contact between pellet
particles and air bubbles in the boundary bed between the pellet particles
and test water, the water will be agitated to cause the particles to float in thewater. In addition, two types of test water are prepared to verify the influenceof the recombination of generated hydrogen into water: one withrecombination inhibitor halogen ions added in it and the other without such
halogen ions. Further, tests with and without agitating the test water areplanned to verify the influence of agitation.

Case No.

Method of collecting

1.6 × 10-16 L/h/Bq

1.1 × 10-16 L/h/Bq

3.4 × 19-17 L/h/Bq

2.3 × 10-18 L/h/Bq

Hydrogengeneration

2.2 × 10-18 L/h/Bq

Note 1: A margin of error of ±1% was set for estimates because calculation was performed so that the statistical error of PHITS calculation results was less than 1%.
Note: This ratio was set based on the result of dewatering tests in FY2016 (maximum amount of residual water).
Note 3: This volume ratio was set based on 0.1 wt% for the target volume of moisture to be dried, 11 g/cc for the density of the pellet particles, and 1 g/cc for water density.
Note 4: It was assumed that particles with a size of 0.1 mm were collected in a canister to its maximum capacity and powder filled the gap between the particles. (The composition ratios of powder and 0.1 mm particles were 26% and 74%, respectively)
Note 5: This particle size distribution was hypothetically used based on the particle size distribution obtained from simulant fuel debris (the composition ratios of powder, 0.1 mm particles, 1 mm particles, and 4 mm particles being 4%, 8%, 12%, and76%, respectively) that was reported in the Subsidy Project of “Decommissioning and Contaminated Water Management: Characterization of Fuel Debris” in the FY2014 Supplementary Budgets, Final Report, published by the International
Research Institute for Nuclear Decommissioning (IRID), in May 2017.
Note 6: It was considered to be difficult to verify the energy absorption rate of particles with a size of a few mm by tests.
Note 7: The calorific values of main nuclide in the 1F-1 for each type of rays were quoted from Tables 5, 8, 11, 43, 45, and 47 in the report below and summed up: Nishihara, K., Iwamoto, H. and Suyama, K., Estimation of Fuel Compositions inFukushima-Daiichi Nuclear Power Plant, JAEA-Data/Code. 2012–18, published by the Japan Atomic Energy Agency in September 2012. Note that no margin of error was set because the values of decay heat used in the estimate were those for the
maximum burnup by applying peaking factors to make the estimate conservative.
Note 8: These peaking factors were set for each type of rays taking into account those for each type of nuclides derived based on the data described in the report cited in Note 7 above. (The ratio of the maximum decay heat to the mean decay heat for
α-ray and the ratio of the maximum burnup to the mean burnup for β- and γ-rays)
Note 9: These G values were set by reference to Hilbert Christensen and Erling Bjergbakke, Nuclear and Chemical Waste Management, Vol.6, pp. 265–270, Table 2, Apprication of Chemisimul for Groundwater Radiolysis (1986). Note that a margin oferror of ±10% was set taking into account variation in data among different literatures.

OthersExtracted from
Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing, Transfer andStorage of Fuel Debris)” in the FY2018 Supplementary Budgets, Final Report, June 2021
Subsidy Project of “Decommissioning and Contaminated Water Management (Upgrading of Fundamental Technology for Retrieval of Fuel
Debris and Reactor Internals)” in the FY2016 Supplementary Budgets, Final Report, July 2019
JAEA/CRIEPI “Research on the Sophistication of Statistical Inventory Estimation Method”©International Research Institute for Nuclear Decommissioning6. Implementation details

No.50

6.3 Performance assessment of canister filters③ Implementation items and resultsa. Identification of environments and conditions (4/11)(iii) Organization of input conditions (2/3)
Table 1 Results of identifying canister specifications
Items

Specifications

Material

Stainless steel (SUS316L)

Seal material

Elastomer resin (EPDM)

Heat removal
methodDryingInternal diameter

220 mmHeight

800 mmUnit can outer
diameter

210 mmUnit can height

400 mmCapacity

0.03 m3

Filling rate

30% (Fuel debris capacity: 0.01
m3)

Confinement
function
Gas processing
function

Filter installation
Recombination catalyst

Remarks
June 2021 Canister Project Final Report
Material No.112
June 2021 Canister Project Final Report
Material No.115
June 2021 Canister Project Final Report
Material No.106
June 2021 Canister Project Final Report
Material No.114
June 2021 Canister Project Final Report
Material No.114
June 2021 Canister Project Final Report
Material No.114
June 2021 Canister Project Final Report
Material No.114
Approximate value from the above
dimensions
June 2021 Canister Project Final Report
Material No.26
June 2021 Canister Project Final Report
Material No.108
June 2021 Canister Project Final Report
Material No.112

Vent filter (temporary values)
Items

Specifications

Material

SUS316

Mesh diameter

0.3 μmRemarks
June 2021 Canister Project Final Report
Material No.108
June 2021 Canister Project Final Report
Material No.108

Recombination catalyst (temporary values)
Items

Specifications

Material

Platinum catalyst (TKK H1P)

Catalyst bed
thickness

20 mm

Remarks
June 2021 Canister Project Final Report
Material No.120
June 2021 Canister Project Final Report
Material No.112

Table 2 Results of identifying transfer cask specifications
Items

Specifications

Remarks

Material

Not specified―

Seal material
Heat removal
methodNot specified

Internal diameter

1700 mm

Height1200 mm

Capacity

12 canisters can be enclosed―
June 2021 Canister Project Final Report
Material No.94
June 2021 Canister Project Final Report
Material No.94
June 2021 Canister Project Final Report
Material No.94
June 2021 Canister Project Final Report
Material No.94
June 2021 Canister Project Final Report
Material No.52
June 2021 Canister Project Final Report
Material No.52

DryingConfinement function Sealing
Gas processing
functionNo

Table 3 Results of identifying storage container specifications
Items

Specifications

Remarks

Material

Not specified―

Seal material
Heat removal
methodInternal diameter

Not specified

Not specified―
June 2021 Canister Project Final Report
Material No.5―

HeightNot specified―

Capacity
Confinement
function
Gas processing
function

Not specified―
June 2021 Canister Project Final Report
Material No.5
June 2021 Canister Project Final Report
Material No.5

DryingVent pipe
There is a gas treatment systemin the later stage

Extracted from the Subsidy Project of “Decommissioning and Contaminated Water Management (Development ofTechnologies for Containing, Transfer and Storage of Fuel Debris)” in the FY2018 Supplementary Budgets, Final
Report, June 2021

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.51

6.3 Performance assessment of canister filters③ Implementation items and resultsa. Identification of environments and conditions (5/11)(iii) Organization of input conditions (3/3)
Table Results of identifying environmental conditions inside and outside canisters
Canisterinterior

Process

Sealing cell

Drying treatment

Preparation cell

Receiving area

Storage area

Remarks

Temperature

Up to 300℃

Up to 300℃

Up to 300℃

Up to 300℃

Up to 300℃

March 2017 Canister Project Final Report Material No.50

Pressure
Humidity (before
drying)Humidity (after
drying)Negative pressure

Not specified

Normal pressure

Negative pressure

Not specified

June 2021 Canister Project Final Report Material No.4-5

100 %

―

100 %

100 %

―

June 2021 Canister Project Final Report Material No.4-5

Sufficiently low value

Sufficiently low value

Sufficiently low value

Sufficiently low value

Sufficiently low value

Same as building
atmosphere
Dry natural cooling―

Inert gas injection

Inert gas injection

Inert gas injection―

Dry natural cooling

Dry natural cooling

Building

Drying apparatus

Building → transfer cask

Dry natural coolingTransfer cask → building →storage container

June 2021 Canister Project Final Report Material No.4-5,
98
June 2021 Canister Project Final Report Material No.4-5,
100-101
June 2021 Canister Project Final Report Material No.4-5

Storage cask

June 2021 Canister Project Final Report Material No.4-5

Atmosphere gas
Cooling method
Exterior
environment

Exterior
environment

Confinement
function

FilterFilterAssumed period

Not stated (expected to bea few days)

Up to 10 days

Filter + seal

FilterNot stated (expected to be Not stated (expected to be a few
a few days)
days)

From the vent pipe tothe outside of theJune 2021 Canister Project Final Report Material No.4-5
building through the gas
treatment system
Maximum 50 years

June 2018 Canister Project Final Report Material No. 49

Process

Sealing cell

Drying treatment

Preparation cell

Receiving area

Storage area

Temperature

Room temperature

200℃

Room temperature

Room temperature

Room temperature

Remarks
June 2021 Canister Project Final Report Material No.4-5

Pressure

Negative pressure

Not specified

Normal pressure

Negative pressure

Negative pressure

June 2021 Canister Project Final Report Material No.4-5

Humidity

Properly managed―

Properly managed

Properly managed

Properly managed

June 2021 Canister Project Final Report Material No.4-5

Extracted from
Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing, Transfer andStorage of Fuel Debris)” in the FY2014 Supplementary Budgets, Final Report, March 2017
Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing, Transfer andStorage of Fuel Debris)” in the FY2015 Supplementary Budgets, Final Report, March 2018
Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing, Transfer andStorage of Fuel Debris)” in the FY2018 Supplementary Budgets, Final Report, June 2021

©International Research Institute for Nuclear Decommissioning6. Implementation details- Sealing cell

6.3 Performance assessment of canister filters

Sealingcell③ Implementation items and resultsa. Identification of environments and conditions (6/11)

Port

No.52

Lifting
machineCanister(iv) Selection of degradation factors (1/6)
Canister transfer
systemHydrogenembrittlement

Radiation
Degradation

Amount of hydrogengenerated
Moisture content
Temperature
Time

Amount ofAmount ofhydrogenhydrogengenerated
Radiation dose generated
Moisture content Radiation dose
Moisture content
Filter pore
Filter pore
diameterdiameter
Filter strength
Powder particle Powder particle
size
size
Powder density Powder density

Gas generation

Thermalalteration

Radiation dose
Irradiation time
Filter material
Time

Thermaldeformation(Container)

Temperature
Filter strength

ImpactTemperature
Filter strength
Filter thermal
expansion coefficient
Filter material
Container thermal
expansion coefficient

Weight measuring system(Surface contamination check)

Electric
corrosion

Thickness
reduction

Generated stress
Filter strength
Fuel debris
composition
Fuel debris shape(lump)
Container strength
Container material

Corrosive ion
concentration
Temperature
Humidity
Moisture content
TimeUV
degradation

Container material
Filter material
Fuel debris
composition
Moisture content
Temperature
HumidityTime

UV intensity
Irradiation time
Filter material
Time

Damaged

CloggedTemperature
Container shape
Fuel debris shape
Fuel debris position in
the canister
Powder particle size
Powder density

Thermalconvection

Frequency and Internal andCorrosive ion
Corrosive ion
amplitudeconcentration
external
concentration
Acceleration
Temperaturepressure
Temperature
Filter pore
Humiditydifference
Humidity
diameterPowder particle Moisture content
Moisture content
Powder particle size
Filter pore diameter Filter poresize
Powder density TimediameterPowder density
Time

Dust
generatedby vibration

PowderDispersion

Excluded because the event progresses slowly and does not lead to damage or
clogging while in the area
Excluded because there is no difference in pressure between the inside andoutside of the canister in the area
Excluded because the area is indoors

Oxide film
generation

Salt
precipitation

Temperature
Humidity
External wind
speed
Aerosol particle
size
Aerosol density

Aerosol
accumulation

Temperature
Temperature
Humidity
Moisture
Moisturecontent
Microorganisms content
Time

Microbial
membrane

Water film

Excluded because the salt concentration is adequately low based on fuel debris
properties

17 degradation events ⇒ 10 items excluded, so 7 items to be examined.
©International Research Institute for Nuclear Decommissioning6. Implementation details- Preparation cell

6.3 Performance assessment of canister filters

Primary lid
fasteningmachine/gas
injector/leakdetector③ Implementation items and results

No.53

Lifting
machineSecondary lid
Preparation
fasteningcellmachine/gas
injectionsystem/leakdetection systema. Identification of environments and conditions (7/11)
Transfer
truck(iv) Selection of degradation factors (2/6)
Transfer
cask

Hydrogenembrittlement

Radiation
degradation

Amount of hydrogengenerated
Moisture content
Temperature
Time

Thermalalteration

Radiation dose
Irradiation time
Filter material
Time

Amount ofAmount ofhydrogenhydrogengenerated
Temperature
Radiation dose generated
Moisture content Radiation dose Container shape
Moisture content Fuel debris shape
Filter pore
Filter pore
Fuel debris position indiameterdiameterthe canister
Filter strength
Powder particle Powder particle Powder particle size
size
size
Powder density
Powder density Powder density

Gas generation

Thermalconvection

Thermaldeformation(Container)

Temperature
Filter strength

ImpactTemperature
Filter strength
Filter thermal
expansion coefficient
Filter material
Container thermal
expansion coefficient

Transport cask
transfer
equipment

Electric
corrosion

Thickness
reduction

Generated stress
Filter strength
Fuel debris
composition
Fuel debris shape(lump)
Container strength
Container material

Transferrack

Corrosive ion
concentration
Temperature
Humidity
Moisture content
TimeUV
degradation

Container material
Filter material
Fuel debris
UV intensity
composition
Irradiation time
Moisture content Filter material
Temperature
Time
HumidityTime
Damaged

CloggedFrequency andCorrosive ion
Corrosive ion
Internal andamplitudeconcentration
concentration
external pressure
Acceleration
Temperature
Temperature
difference
Filter pore
Humidity
Humidity
Powder particle
diameterMoisture content
Moisture content
size
Powder particle
Filter pore diameter Filter pore
Powder density
size
Time
diameterPowder density
Time

Dust
generatedby vibration

Powderdispersion

Excluded because the event progresses slowly and does not lead to damage
or clogging while in the area
Excluded because there is no difference in pressure between the inside andoutside of the canister in the area
Excluded because the area is indoors

Oxide film
generation

Salt
precipitation

Temperature
Humidity
External wind
speed
Aerosol particle
size
Aerosol density

Aerosol
accumulation

Temperature
Temperature
Humidity
Moisture
Moisturecontent
Microorganisms content
Time

Microbial
membrane

Water film

Excluded because the salt concentration is adequately low based on fuel debris
properties

17 degradation events ⇒ 10 items excluded, so 7 items to be examined©International Research Institute for Nuclear Decommissioning6. Implementation details- Receiving area

No.54

6.3 Performance assessment of canister filters③ Implementation items and results

Hydrogen gas
treatment systema. Identification of environments and conditions (8/11)

Ventilation
systemWork
monitoringShielding
camera cover

Canister

Stored item
checking
equipmentGate(iv) Selection of degradation factors (3/6)

Dryingapparatus

Storagecask

Primary lidof storage
cask

Scaffolding
for work
Transfer caskrack

Hydrogenembrittlement

Radiation
degradation

Amount ofhydrogengenerated
Moisture content
Temperature
Time

Thermalalteration

Radiation dose
Irradiation time
Filter material
Time

Amount ofAmount ofhydrogenhydrogengenerated
Temperature
Radiation dose generated
Moisture content Radiation dose Container shape
Moisture content Fuel debris shape
Filter pore
Filter pore
diameter
Fuel debris position indiameter
Filter strength
the canister
Powder particle Powder particle Powder particle size
size
size
Powder density
Powder density Powder density

Gas generation

Thermalconvection

Thermaldeformation(Container)

Temperature
Filter strength

Temperature
Filter strength
Filter thermal
expansion coefficient
Filter material
Container thermal
expansion coefficientElectric
corrosion

Thickness
reduction

ImpactGenerated stress
Filter strength
Fuel debris
composition
Fuel debris shape(lump)
Container strength
Container material

Corrosive ion
concentration
Temperature
Humidity
Moisture content
Time

Frequency
Corrosive ion
Corrosive ion
and amplitudeconcentration
concentration
Acceleration
Internal andTemperature
Temperature
Filter poreexternal pressure Humidity
Humidity
diameterdifference
Moisture content
Moisture content
Powderparticle size Powder particle Filter pore diameter Filter poresize
diameterTime
PowderPowder densityTimedensityDust
generatedby vibration

Powderdispersion

Oxide film
generation

Salt
precipitation

UV
degradation

Container material
Filter material
Fuel debris
composition
Moisture content
Temperature
HumidityTime

UV intensity
Irradiation time
Filter material
Time

Damaged

CloggedTemperature
Humidity
External wind
speed
Aerosol particle
size
Aerosol density

Aerosol
accumulation

Temperature
Temperature
Moisture
Humidity
content
Moisture
Microorganisms content
Time

Microbial
membrane

Water film

Excluded because the event progresses slowly and does not lead to damage or clogging while in the area

Excluded because the area is indoors

17 degradation events ⇒ 9 items excluded, so 8 items to be examined

Excluded because the salt concentration is adequately low based on fuel debris properties©International Research Institute for Nuclear Decommissioning6. Implementation details- Drying treatment

6.3 Performance assessment of canister filters

No.55

Vacuum exhaust(inner pressure)
Radiation
heating③ Implementation items and resultsa. Identification of environments and conditions (9/11)
Hydrogen gas
treatment system

Heater(Heating
temperature)

Ventilation
system
Work
Shieldingmonitoring covercamera(iv) Selection of degradation factors (4/6)

Hot air(Heating
temperature)

Canister
Stored item
checking
equipment

Gate

Dryingapparatus

Storagecask

Primary lidof storage
cask

Scaffolding
for work

Chamber or canister(capacity)
Figure Basic concept of the drying apparatus

Transfer caskrack

Hydrogenembrittlement

Radiation
degradation

Amount ofhydrogengenerated
Moisture content
Temperature
Time

Thermalalteration

Radiation dose
Irradiation time
Filter material
Time

Amount ofhydrogenAmount ofgeneratedhydrogenRadiation dose generated
Temperature
Moisture content Radiation dose Container shape
Filter pore
Moisture content Fuel debris shapediameter
Filter pore
Fuel debris position in
Filter strength
diameterPowder particle Powder particle the canister
Powder particle size
size
size
Powder density Powder density Powder density

Gas generation

Thermalconvection

Thermaldeformation(Container)

Temperature
Filter strength

ImpactTemperature
Filter strength
Filter thermal
expansion coefficient
Filter material
Container thermal
expansion coefficientElectric
corrosion

Thickness
reduction

Generated stress
Filter strength
Fuel debris
composition
Fuel debris shape(lump)
Container strength
Container material

Corrosive ion
concentration
Temperature
Humidity
Moisture content
TimeUV
degradation

Container material
Filter material
Fuel debris
composition
Moisture content
Temperature
HumidityTime

UV intensity
Irradiation time
Filter material
Time

Damaged

CloggedFrequency andInternal andamplitude
external
Accelerationpressure
Filter poredifference
diameterPowder particle
Powdersize
particle size
Powder density Powder density

Dust
generatedby vibration

Powderdispersion

Corrosive ion
Corrosive ion
concentration
concentration
Temperature
Temperature
Humidity
Humidity
Moisture content
Moisture content
Filter pore
Filter pore diameter diameter
Time
Time

Oxide film
generation

Salt
precipitation

Temperature
Humidity
External wind
speed
Aerosol particle
size
Aerosol density

Aerosol
accumulation

Temperature
Temperature
Humidity
Moisture
Moisturecontent
Microorganisms content
Time

Microbial
membrane

Water film

Excluded because the event progresses slowly and does not lead to damage or clogging while in the area
Excluded because the area is indoors

17 degradation events ⇒ 9 items excluded, so 8 items to be examined

Excluded because the salt concentration is adequately low based on fuel debris properties©International Research Institute for Nuclear Decommissioning6. Implementation details- Storage area

No.56

6.3 Performance assessment of canister filters

Area monitor③ Implementation items and resultsa. Identification of environments and conditions (10/11)(iv) Selection of degradation factors (5/6)

Hydrogenembrittlement

Radiation
degradation

Amount ofhydrogengenerated
Moisture content
Temperature
Time

Amount ofhydrogenAmount ofgeneratedhydrogenRadiation dose generated
Moisture content Radiation dose
Filter pore
Moisture content
diameter
Filter pore
Filter strength
diameterPowder particle Powder particle
size
size
Powder density Powder density

Gas generation

Thermalalteration

Radiation dose
Irradiation time
Filter materialTime

Temperature
Container shape
Fuel debris shape
Fuel debris position in
the canister
Powder particle size
Powder density

Thermalconvection

Thermaldeformation(Container)

Temperature
Filter strength

Temperature
Filter strength
Filter thermal
expansion coefficient
Filter material
Container thermal
expansion coefficientFrequency andamplitude
Acceleration Internal andexternal
Filter porepressure
diameterdifference
PowderPowder particle
particle size
size
PowderPowder density
densityDust
generatedby vibration

ImpactPowderdispersion

Gas treatment
systemElectric
corrosion

Thickness
reduction

Generated stress
Filter strength
Fuel debris
composition
Fuel debris shape(lump)
Container strength
Container material

Surfacetemperature
measuringequipment

Vent
pipe

Secondarylid ofstoragecask

Corrosive ion
concentration
Temperature
Humidity
Moisture content
TimeUV
degradation

Container material
Filter material
Fuel debris
composition
Moisture content
Temperature
HumidityTime

UV intensity
Irradiation time
Filter material
Time

Damaged

CloggedCorrosive ion
Corrosive ion
concentration
concentration
Temperature
Temperature
Humidity
Humidity
Moisture content
Moisture content
Filter pore
Filter pore diameter diameter
Time
Time

Oxide film
generation

Salt
precipitation

Temperature
Humidity
External wind
speed
Aerosol particle
size
Aerosol density

Aerosol
accumulation

Temperature
Temperature
Moisture
Humidity
content
Moisture
Microorganisms content
Time

Microbial
membrane

Water film

Excluded because the area is indoors
Excluded because the salt concentration is adequately low based on fuel debris properties

17 degradation events ⇒ 4 items excluded, so 13 items to be examined©International Research Institute for Nuclear Decommissioning6. Implementation details

No.57

6.3 Performance assessment of canister filters③ Implementation items and resultsa. Identification of environments and conditions (11/11)(iv) Selection of degradation factors (6/6)
Process

Sealing cell

Drying treatment Preparation cell

Receiving area

Storage area

Hydrogen generation
×

×

×

×

×

×

×

×

ImpactDust generated byvibration
Thickness reduction

×

×

×

×

Oxide film generation

×

×

×

×

Salt precipitation

×

×

×

×

Electric corrosion

×

×

×

×

Microbial membrane

×

×

×

×

×

Aerosol deposition

×

×

×

×

×

Powder dispersion

×

UV degradation

×

×

×

Hydrogenembrittlement
Radiation
degradation
Thermal alteration
Thermal deformation(container)
Thermal convection

×

Water film
×××

×: Items determined to
not require examination
based on the input
environmental conditions

Since salt precipitation, microbial membrane, aerosol deposition, and UV degradation
are excluded from all processes, they are excluded from examinations after 6.3 ③ b.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.58

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (1/27)(i) Organization of filter categories
Manufacturingmethod and filter
media

Primary manufacturer

Atomic filters
USA WIPP
France La Hague
Japan 1F HIC

Nuclear Filter Technology, Inc.
(NFT)
Ultra Tech, Inc.
Poral etc.

Sintered metal
Carbon composite> 99.97% for 0.3 to 0.5 μm particles(example from WIPP)

1.85 - 92.5 × 10-6
(m/s/mf) @NFT
3.66 × 10-6
(m2/s) @Poral

Fuji Filter Manufacturing Co., Ltd.
Nippon Seisen Co., Ltd. etc.

Powdered sinteredbodyLong-fiber sintered
body
Short-fiber sinteredbody
Multilayered metal
sintered body

0.1 to 1000 μm
Controllable depending on filter type
No specification for accuracy

Based on the filter specifications(pressure loss), the hydrogen
permeation performance isassumed to be about the sameas that of atomic filters

NGK Insulators, Ltd.
Ibiden Co., Ltd. etc.

Aluminum oxide
ZeoliteCordierite

Lower capture efficiency for 0.1 to
0.3 μm particles
It is estimated that HEPA-equivalent
performance can be achieved bycontrolling pores

Based on the filter specifications(pressure loss), the hydrogen
permeation performance isassumed to be about the sameas that of atomic filters

Japan Air Filter Co., Ltd.
Cambridge Filter Japan Ltd. etc.

Glass fiber
Polypropylene
OlefinPTFEHEPA: 99.97% or better for 0.3 μm
particles
ULPA: 99.9995% or better for 0.15μm particles

Based on the filter specifications(pressure loss), the hydrogen
permeation performance isassumed to be about the sameas that of atomic filters

Metal gas filters

Ceramic gas filters

Glass or resin gas
filters

Particle capture function

Hydrogen permeation
performance

Intended use

The biggest difference in filter specifications is the quality of the filter media.
The required particle capture performance determines the manufacturing method and configuration of the filter media.
Filter life depends largely on the quality of the filter media.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.59

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (2/27)(ii) Selection of degradation events based on canister environment (1/26)
Scenarios that would lead to degradation for each degradation process are organized.
A broad range of degradation scenario conditions were examined by considering two stages of conditions (moderate and severe).
Degradation
process

Hydrogengeneration

Scenarios leading to degradation
Scenario 1 (moderate conditions)

Scenario 2 (severe conditions)Hydrogen is generated via radiolysis ofresidual moisture within waste after
drying and fuel debris particles rise,
clogging the filter and causing it to lose
its functionality.

Collecting undried or insufficiently dried waste
generates more hydrogen than when dried,causing fuel debris particles to rise, clogging
the filter and causing it to lose its functionality.

The generated hydrogen is absorbed
The generated hydrogen is absorbed andHydrogenand reaches a concentration thatmoisture is generated, reaching a concentration
embrittlement causes embrittlement within the storage that causes embrittlement within the storage
period, destroying the filter.
period, destroying the filter.
Radiation
degradation

Thermalalteration

Thermaldeformation(Container)

Thermalconvection

ImpactFilter material absorbs radiation energy
Filter material absorbs radiation energy andand degrades, reducing the strength ofdegrades, damaging the filter material.
the material.
The temperature of fuel debris rises due The temperature of fuel debris rises due toto decay heat. When the temperature decay heat. When the temperature reaches
reaches 200℃ (the temperature during 300℃ (the temperature specification of thedrying), the filter deforms and loses its canister), the filter deforms and loses its
functionality.
functionality.
The temperature of fuel debris rises due The temperature of fuel debris rises due toto decay heat. The temperature reaches decay heat. The temperature reaches 300℃,
200℃, the temperature during drying. the temperature specification of the canister.
The container is thermally deformed and The container is thermally deformed and thethe affixed filter becomes stressed,
affixed filter becomes stressed, resulting inresulting in damage.
damage.
Thermal decay raises the temperature
Thermal decay raises the temperature of theof the fuel debris to 200℃ and heat
fuel debris to 300℃ and heat convection occurs
convection occurs inside the container,
inside the container, leading to fuel debris
leading to fuel debris particles rising andparticles rising and clogging the filter, which
clogging the filter, which causes the filter
causes the filter to lose its functionality.
to lose its functionality.
The container and/or filter become
The container and/or filter become deformed ordeformed or damaged from a mild
damaged from a collision or from being
collision or impact during transportation dropped from a height of several meters during
or an earthquake and the filter loses its transportation or an earthquake and the filter
functionality.
loses its functionality.

Degradation
process

Scenarios leading to degradation
Scenario 1 (moderate conditions)

Scenario 2 (severe conditions)
The container overturns during
Vibrations during transportation or antransportation or an earthquake, causing
Dustearthquake cause waste particles to rise,
waste particles to press against the filter
generated by covering and/or blocking the filter surface
surface, covering and/or blocking the filter
vibrationand causing the filter to lose its
surface and causing the filter to lose its
functionality.
functionality.
Condensation, etc. brings moisture into theCondensation, etc. brings moisture into
filter, causing a phenomenon like a large
the filter and a phenomenon like chloride
Thicknessamount of powder from the waste adhering
ions adhering to the filter occurs, causing
reduction
to the filter, which causes crevice corrosion
pitting corrosion that generates corrosionthat generates corrosion products that clog
products that clog the filter.
the filter.
The temperature of fuel debris rises due The temperature of fuel debris rises due toto decay heat. When the temperature
decay heat. When the temperature reaches
Oxide film
reaches 200℃ (the temperature during 300℃ (the temperature specification of thegeneration
drying), an oxide film forms and clogs the canister), an oxide film forms and clogs thefilter.
filter.
Condensation, etc. brings moisture into theCondensation, etc. brings moisture into filter, causing a phenomenon like chloride
Electric
the filter, causing a phenomenon likeions adhering to the filter and corroding a
corrosion
chloride ions adhering to the filter.
portion of the filter, leading to a difference inelectrical potential in the area.
Water film

Condensation creates a water film thatblocks part of the filter, reducing flow
path surface area.

Powderdispersion

Differential pressure caused by
Ventilation in the canister storage building
ventilation in the canister storage building and the exhaust operations of the transfer
generates a flow inside the storage
cask generate a flow inside the storage
container, which causes fuel debris
container, which causes fuel debris particles
particles to rise and clog the filter.
to rise and clog the filter.

Condensation creates a water film thatblocks the entire filter.

The necessity for selection as a degradation event was examined foreach degradation process.
©International Research Institute for Nuclear Decommissioning6. Implementation details

Canister

No.60

6.3 Performance assessment of canister filters③ Implementation items and results

HydrogenstreamFuel debrisb. Study of filter life evaluation methods (3/27)

Height
400 mm(ii) Selection of degradation events based on canister environment (2/26)
Event: Hydrogen generation Degradation mode: Clogged & Damaged

Inner diameter: 210 mm
Figure 1 Unit can schematic diagram⇒ The hydrogen generation rate and particle settling
velocity are calculated and evaluated.
◼ Flow rate from hydrogen generation
From input conditions, the flow rate from hydrogen generation
was calculated to be 9.03 × 10-5 [L/h](Calculation formula)
Hydrogen generation rate [L/h/Bq] × total inventory [Bq/ton] × fuel debris
density [ton/m3] × fuel debris volume [m3])(Input conditions)- Hydrogen generation rate: 2.3 × 10−18 [L/h/Bq] (moisture content after
drying is 0.1 wt%)
- Total inventory: 2.18 × 1015 [Bq/ton],- Fuel debris density: 4.0 [g/cm 3] (MCCI average density)- Fuel debris volume: 0.0045 [m3] (30% of unit can volume)

Hydrogen rises 0.038 [m2] in a cross section of a canister with an innerdiameter of 210 mm
The hydrogen flow velocity is calculated at 6.6 × 10-10 [m/s].

The hydrogen flow velocity is sufficiently smaller thanthe particle settling velocity, so filter degradation fromhydrogen generation can be ignored.

◼ Rising velocity of powder
The settling velocity of the particles is calculated by using the
Stokes’ law.
Initial ascension speed (m/s)◼ Evaluation of filter clogging caused by powdery fueldebris increasing due to hydrogen generation.

Settling velocity > Hydrogengeneration flow velocity

Particle size (μm)

Figure 2 Results of calculating the settling velocity(Calculation formula) Stokes’ law vs = DP2 (ρP - ρf) g/18η
(Input conditions)- Terminal velocity vs [m/s]- powder diameter DP [m]: 0.1 to 100 [μm]Upper limit: 0.1 mm or less according to the definition of particles
Lower limit: Set with regard to filter performance regulations (HEPA 0.3 μm,
ULPA 0.15 μm)- Particle density ρP [kg/m3]: Fuel debris density 4.0 [g/cm 3]- Fluid density ρf [kg/m3]: 1.205 (20℃ atmosphere)- Fluid viscosity η [Pa·s]: 1.82 × 10-5 (20℃ atmosphere)- Gravitational acceleration g[m/s2]: 9.8©International Research Institute for Nuclear Decommissioning6. Implementation details

No.61

6.3 Performance assessment of canister filters(ii) Selection of degradation events based on canister environment (3/26)
Event: Hydrogen embrittlement Degradation mode: Damaged••

Evaluation of hydrogen partial pressure in a container
To examine hydrogen solubility in various materials, the hydrogen partial pressure inside a storage container
for each hour was obtained from the hydrogen generation rate and the proportion of hydrogen in theatmosphere.
Hydrogen pressure in the storage container = hydrogen in the atmosphere + hydrogen generated in thestorage container, so (the ratio hydrogen pressure outside the container) : (the ratio of hydrogen in theatmosphere) equals 0.00005%, meaning that hydrogen pressure is 0.05 Pa.
Hydrogen pressure in the container: PV = nRT (calculated using P: pressure, V: volume, n: mol, R: gasconstant, T: temperature.
Assuming that the temperature is 300℃, hydrogen partial pressure in the storage container is 1.4 Pa using
the hydrogen generation rate.
Therefore, hydrogen pressure inside the container at a temperature of 300℃. is 1.45 Pa (1.4 × 10−5
atm).

Hydrogen pressure

Figure 1 Relationship between hydrogen solubility andhydrogen pressure for 304 L Note 1

Contraction ratio of hydrogen andatmosphere (%)

b. Study of filter life evaluation methods (4/27)

Hydrogen solubility (ppm)③ Implementation items and results

SSRT in room
temperaturehydrogen gas

Hydrogenabsorption →Atmospheric SSRT
SSRT during cathodic
charging

Atmospheric
SSRT

For stainless steels and Ni-based alloys- As Figure 1 shows, considering the hydrogen pressure inside the container, the hydrogen solubility of
SUS304L is lower than 5 ppm even at a temperature of 300℃ Note 1. Since the hydrogen solubility of
austenitic stainless steel shows virtually no difference between steel type, SUS316 and SUS316L can beconsidered to have the same solubility.
- Hydrogen embrittlement does not occur with SUS316L, even if it absorbs several hundred ppm at room
temperature, and several tens of ppm at 85℃ Note 2.
Surface hydrogen concentration (ppm)- The solubility of Ni-based alloys varies depending on the composition, but the amount of Ni at a
Figure 2 Effect of surface hydrogentemperature of 400℃ is approximately 85%, which is about five times that of Fe. Since it has been
concentration on hydrogen embrittlementNote3reported that the solubility of hydrogen in Fe does not differ much from that of SUS, it is estimatedcharacteristics Note 2that the hydrogen solubility of 85% Ni at a temperature of 300℃ is 30 ppm or less.
Note 1: Nomura et al., Journal of the Japan Institute of Metals and Materials, Vol. 15, No. 9, p.563-570 (1976)
The same can be assumed for SUS316.
Note 2: Ohmura, Nakamura, Materials and Environments, 60, 241-247 (2011)
At these concentrations, hydrogen embrittlement is unlikely to occur.
Note 3: Yoshida et al., Journal of the Japan Institute of Metals and Materials, Vol. 11, No. 7, p.533-548 (1972)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.62

6.3 Performance assessment of canister filters③ Implementation items and results(ii) Selection of degradation events based on canister environment (4/26)
Event: Hydrogen embrittlement Degradation mode: Damaged- For Ti
From Figure 1, the hydrogen solubility of Ti is approximately 10 ppm
at room temperature and 100 mass ppm for industrial Ti (containing Fe:0.3%). Considering that the concentration at which hydrogen
embrittlement occurs is 100 to 300 ppm, hydrogen embrittlement may
occur at room temperature depending on type Note 1.

Temperature/℃

b. Study of filter life evaluation methods (5/27)
α + residual β

α + γ (hydride) + residual βFigure 1 Hydrogen content and phase composition ofcommercially pure titanium ASTM Gr.3 containing 0.3%
Fe

Since the hydrogen solubility exceeds 1000 ppm at the high-temperature of 300℃, embrittlement may occur
if used for a long periods of time in an environment where hydrogen is generated constantly. In addition,
hydrides are formed when the temperature falls below 300℃, which may cause embrittlement Note 1.
• For ceramics
Table 1 shows reported examples of films that function as hydrogenbarriers Note 2. Alumina, a ceramic, has the property of reducing thehydrogen permeation levels, and its application as a film for suppressinghydrogen embrittlement for metals, etc. is being examined. It has also
been reported that embrittlement of crystalline alumina does not occur ina hydrogen environment Note 3. No reports on hydrogen embrittlement ofcordierite and zeolite were found.

Table 1 Reported examples of films
that function as hydrogen barriersType of film

Hydrogen permeation
reduction rate

AI2O3

10 to 10000

TiC

10 to 10000

TiN

10 to 10000

Cr2O3

10

BN

100

Note 1: Fujii et al., Materials and Environments, 60, 248-253 (2011)
Note 2: NEDO “Fundamental Research Project on Advanced Hydrogen Science Interim Evaluation Report (2008)”
Note 3: JST/ Funds for Promoting Science and Technology, “Research on Function of Hydrogen in Environmental Embrittlement ofStructural Materials” 2001-2002: 2nd term)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.63

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (6/27)(ii) Selection of degradation events based on canister environment (5/26)
Event: Hydrogen embrittlement Degradation mode: Damaged- Glass fibers
No reports on the degradation behavior of hydrogen with glass fibers
were found. There are reports that crystalline silica glass fibers do notembrittle in a hydrogen environment*1.
However, since the heat resistance of glass fibers varies dependingon the product, the maximum temperature of 300℃ within the storage
container must be considered when selecting materials.

Joint material
Perm
SUS3 SUS
Brass eable
04 316
●
●
●
●
●
●
△
△
△
●
●
●
●
●
―

LiquidPTFE

Diisobutylene
Diethyl phthalate
Carbonic acid tetrachloride
Dioctyl phthalate
Cyclohexanone

―
●
●
●
●

―
―
×
●
―

Cyclohexane
Dimethylaniline
Dimethyl phthalate
Potassium dichromate

●
●
●
●

●
―
―
―

●
―
―
●

●
―
―
●

●
●
●
―

Oxalic acid
Bromine water
10% Nitric acid
70% Nitric acid
Ferrous nitrate
Ferric nitrate

●
●
●
●
●
●

×
×
×
×
―
×

△
×
△
△
●
●

●
×
△
△
●
●

×
×
×
×
―
―

Potassium nitrate
Calcium nitrate
Silver nitrate
Sodium nitrate
Zinc acetate
Zinc chloride
VinegarMercury

―
●
●
●
●
●
●
●

×
●
△
●
●
×
×
●

△
●
●
△
●
△
△
●

●
●
●
△
●
●
●
●

―
●
△
△
●
×
×
×

Magnesium hydroxide

●

●

●

●

●

Hydrogen gas
Steam

●
●

●
△

●
―

●
△

●
△

CS

- Macromolecules
There are no reports on polypropylene and its behavior is
unknown
The High Pressure Gas Safety Institute of Japan has reported thatpolyethylene can be used for hydrogen gas piping and that it does
Figure Usability of PTFE in each environment Note 3
not embrittle Note 2.
PTFE is generally approved for use in a hydrogen gas
Note 1: Funds for Promoting Science and Technology, “Research on Function of Hydrogen in Environmental Embrittlement
environment and does not embrittle Note 3.
● : GoodC
A△: Can be used for limited periods of time × : Not recommended ― : No test dataof Structural Materials” 2001-2002: 2nd term)
Note 2: Tabata, Hydrogen Energy Systems, Vol.35, No.4 (2010)
Note 3: From the Chunichi Giken Products website→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.64

6.3 Performance assessment of canister filters
b. Study of filter life evaluation methods (7/27)(ii) Selection of degradation events based on canister environment (6/26)
Event: Radiation degradation

Degradation Mode: Damaged

Study of the possibility that irradiation from radiation generated by
the fuel debris changes the mechanical characteristics of the filter
material after fuel debris is collected in a canister.

Radiation generated by fuel debris•••

Range in air (cm)

③ Implementation items and results

Alpha rays
Beta rays

Radiation energy (MeV)

Figure Range of alpha and beta rays in air

Alpha rays, beta rays, and gamma rays derived from actinides, fission products, and activation materials aredischarged from fuel debris.
The range of alpha rays from actinide (approximately 5 to 7 MeV) is several centimeters in air and several micrometers
in solids and water. They are discharged only from the surface of fuel debris. They do not impact anything other thanfuel debris near the filter, and even if they adhere to the filter, they will not affect anything other than the surface of thematerial.
Beta rays and gamma rays have a longer range than alpha rays, and since gamma rays have particularly highpermeability, they are also irradiated from fuel debris far away from the filter.

Tasks that may cause radiation degradation
Constantly irradiated after fuel debris is collected in a canister.

The effects of radiation on filters
The mechanical characteristics of materials can change when exposed to irradiation from radiation.
If an impact is applied to a filter whose mechanical characteristics have been changed by irradiationfrom radiation, the filter may be damaged and lose its functionality.

→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.65

6.3 Performance assessment of canister filters③ Implementation items and results

Study ofd the possibility of the temperature of fuel debris
rising due to decay heat and heat conduction causing thetemperature of the filter to rise, resulting in thermal
alteration and filter damage.
(ii) Selection of degradation events based on canister environment (7/26) Evaluation was performed by comparing the maximum
temperature with the melting point and softening point ofEvent: Thermal alteration (maximum temperature 200℃) Degradation the filter media. If available, information on the heat
resistance temperature, etc., was also taken intomode: Clogged & Damaged
consideration.

b. Study of filter life evaluation methods (8/27)

Metal

Ceramics

Glass

Macromolec
ules

Melting point[℃]

Softening
point [℃]

Other [℃]

SUS3041398 to 1453 Note 1——

SUS3161370 to 1397 Note 1——

Alloy600

1371 to 1427 Note 1

—

—

Ti

1668 Note 2

—

—

SiC

—

—

Heat resistance temperature
1600 Note 4

Al2O3

2015 Note 3——

Cordierite——

Fire resistance 1400 Note 3

E-glass—

840 Note 5

Maximum operating temperature
280 Note 6

C-glass—

749 Note 5—

S-glass—

970 Note 5—

D-glass—

771 Note 5—

Polyethylene

65 to 140 Note 7—

Normal heat resistancetemperature 70 to 110 Note 8

Olefin

65 to 168 Note 7—

Normal heat resistancetemperature 70 to 140 Note 8

PTFE (Teflon)

327 Note 7—

Normal heat resistancetemperature 260 Note 8

Evaluation
Melting point is sufficiently high for 200℃ and thermal alteration does
not occur. Filter damage is unlikely.

〇

〇

(〇)

Melting point, heat resistance temperature, and fire resistance aresufficiently high for 200℃, and thermal alteration does not occur. Filter
damage is unlikely.

Softening point and maximum operating temperature are sufficiently
high for 200℃, and thermal alteration does not occur. Filter damage isunlikely.
Attention must be paid to the maximum operating temperature of eachindividual product.

×

Melting point is less than 200℃ and normal heat resistancetemperature is less than 200℃, so they cannot withstand use at
200℃.

〇

Melting point and normal heat resistance temperature are high for
200℃, and thermal alteration does not occur. Filter damage is unlikely〇: No need to consider the test method because there is no possibility of occurrence ×: Need to consider the test method
Note 1: Handbook of Stainless SteelNote 2: Daido Steel: https://www.daido.co.jp/products/titanium/properties/index.html
Note 3: Inorganic Chemistry Handbook, Gihodo Shuppan Co., Ltd.

Note 4: Ceramic New Materials of SiC System, Japan Society for the Promotion of Science
Note 5: Central Glass Fiber Co., Ltd.: http://www.centralfiberglass.com/jp/glass_fiber/outline/index.html
Note 6: For filter bags - Nitto Boseki (nittobo.co.jp): https://www.nittobo.co.jp/business/glassfiber/industrial/heatresistant/filter.html

Note 7: New Edition Points for Selecting Plastic Materials, Japanese Standards Association
Note 8: The Japan Plastics Industry Federation: http://www.jpif.gr.jp/2hello/conts/youto.pdf→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.66

6.3 Performance assessment of canister filters③ Implementation items and results

Study ofd the possibility of the temperature of fuel debris
rising due to decay heat and heat conduction causing theb. Study of filter life evaluation methods (9/27)
temperature of the filter to rise, resulting in thermal
alteration and filter damage.
(ii) Selection of degradation events based on canister environment (8/26) Evaluation was performed by comparing the maximum
temperature with the melting point and softening point of
the filter media. If available, information on the heat
Event: Thermal alteration (maximum temperature 300℃)
resistance temperature, etc., was also taken into
Degradation mode: Clogged & Damaged
consideration.

Metal

Ceramics

Glass

Macromolec
ules

Melting point[℃]

Softening
point [℃]

Other [℃]

SUS3041398 to 1453 Note 1——

SUS3161370 to 1397 Note 1——

Alloy600

1371 to 1427 Note 1

—

—

Ti

1668 Note 2

—

—

SiC

—

—

Heat resistance temperature 1600

Al2O3

2015 Note 3—-

Cordierite——

Fire resistance 1400 Note 3

E-glass—

840 Note 5

Maximum operating temperature
280 Note 6

C-glass—

749 Note 5—

S-glass—

970 Note 5—

D-glass—

771 Note 5—

Polyethylene

65 to 140 Note 7-

Normal heat resistancetemperature 70 to 110 Note 8

Olefin

65 to 168 Note 7-

Normal heat resistancetemperature 70 to 140 Note 8

PTFE (Teflon)

327 Note 7-

Normal heat resistancetemperature 260 Note 8

Evaluation
Melting point is sufficiently high for 300℃, and thermal alteration does
not occur. Filter damage is unlikely.
〇

Note 4〇(X)

Melting point, heat resistance temperature, and fire resistance aresufficiently high for 300℃, and thermal alteration does not occur. Filter
damage is unlikely.

Softening point is sufficiently high for 300℃, and thermal alteration offilter media does not occur.
Some materials have a maximum operating temperature of less than
300℃, so attention must be paid to the maximum operating
temperature of each individual product.

Melting point is less than 300℃ (type 2) and normal heat resistancetemperature is less than 300℃, so they cannot withstand use at
300℃.
×〇: No need to consider the test method because there is no possibility of occurrence ×: Need to consider the test method
Note 1: Handbook of Stainless SteelNote 2: Daido Steel: https://www.daido.co.jp/products/titanium/properties/index.html
Note 3: Inorganic Chemistry Handbook, Gihodo Shuppan Co., Ltd.

Note 4: Ceramic New Materials of SiC System, Japan Society for the Promotion of Science
Note 5: Central Glass Fiber Co., Ltd.: http://www.centralfiberglass.com/jp/glass_fiber/outline/index.html
Note 6: For filter bags - Nitto Boseki (nittobo.co.jp): https://www.nittobo.co.jp/business/glassfiber/industrial/heatresistant/filter.html

Note 7: New Edition Points for Selecting Plastic Materials, Japanese Standards Association
Note 8: The Japan Plastics Industry Federation: http://www.jpif.gr.jp/2hello/conts/youto.pdf→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.67

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (10/27)(ii) Selection of degradation events based on canister environment (9/26)
Event: Thermal deformation (container) Degradation mode: Clogged & Damaged

Study of the possibility of the temperature of fuel debris rising due to decay
heat and heat conduction causing the temperature of the container to rise,
exerting stress on and damaging the affixed filter and causing it to losefunctionality.

Ventmechanism

LidCanister and filter media: Assuming the following conditions
Body- The canister is made of SUS316L (linear thermal expansion coefficient,16.2 × 10-6 [/℃] Note 1) and has a cylindrical shape- The same material is used for canister and the outer frame of the filter- The filter is fixed rigidly to the canister- Outer diameter of filter media is 200 mm and the outer diameter ofcanister (and filter frame) is 300 mm- The filter media is dense

Bufferstructure

Inner diameter: 220 mm

Figure Canister (assumed) Note 2

The thermal stress on the filter media at maximum operating temperature for eachscenario was evaluated based on the above assumptions.
Note 1: Japan Stainless Steel Association: http://www.jssa.gr.jp/contents/faq-article/q6/
Note 2: Taken from the Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing, Transfer and Storage of Fuel Debris)” in the
FY2018 Supplementary Budgets, Final Report, June 2021
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.3 Performance assessment of canister filters

rc0 rf0

b. Study of filter life evaluation methods (11/27)

Canister (and filter frame)
Room temperature(ii) Selection of degradation events based on canister environment (10/26)
Event: Thermal deformation (container) (maximum temperature200℃) Degradation mode: Clogged & Damaged

Metal

Ceramics

Glass

Macromolec
ules

SUS316rch
Wo③ Implementation items and results

Linear thermal
Young’s
expansion
modulus ofcoefficient of filter filter media
Note 14
media Note 14 , αf [10-6
Ef [GPa]
/ ℃]

No.68

Filter media

Stress on filter Tensile strength ofmedia
filter media Note 14
σc [MPa]σ [MPa]16.2 Note 1

193 Note 10

470 Note 4

SUS30417.8 Note 1

193 Note 1-36

470 Note 4

Alloy600

13.3 Note 2

157 Note 256

600 to 1200 Note 2

Ti

8.4 Note 3

106 Note 3112

240 Note 5

SiC

3.7 Note 6447 Note 8447

390 Note 10

Al2O3

7.7 Note 6

370 Note 9277

120 Note 11

Cordierite

1.1 Note 7

88 Note 7

188

25 to 40 Note 7

E-glass

5.5 Note 12

72.5 Note 12

1133430 Note 12

C-glass

7.3 Note 12

68.6 Note 12902744 Note 12

S-glass

2.9 Note 12

84.3 Note 121594655 Note 12

D-glass

3.1 Note 12

51.9 Note 121042450 Note 12

Polyethylene

—

—

—

—

Olefin

—

—

—

—

PTFE

100 Note 13

0.4 Note 13-6

14 Note 13

r
rfh

Wh

200℃

<Model>- Impacts from thickness are not taken into consideration (filter thickness = canister thickness)- The filter media and filter frame as well as the filter outer frame and the inner diameter of the canister are rigidly
connected- The filter material is dense (no gaps).
- The outer frame of the filter and the canister are made of the same material.
- The outside diameter of the filter media is 200 mm, and the outside diameter of the canister (and filter frame) is
300 mm.
- Evaluate the stress (as thermal stress) required to extend the radius of the filter media (rfh) after free expansion to
the equilibrium position (r)Impact assessment Note 15

If the canister is not made of SUS316L (thermal expansion is not the same), thermal stress will occur andthere is a possibility of damage.
××

If the canister is made of SUS316L, the thermal expansion of the filter media and the canister are thesame, stress applied to the filter media is low, and the tensile strength of the filter media is low, so theimpact is considered to be small. However, stress will increase if the volume ratio of the filter media
decreases and there will be a possibility of damage.

The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. Although the thermal stress is low compared to the material strength, stress will increase if thevolume ratio of the filter media decreases and there will be a possibility of damage.

×

The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. The thermal stress is high compared to the material strength, and there is a possibility ofdamage.

×

The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. Although the thermal stress is low compared to the material strength, stress will increase if thevolume ratio of the filter media decreases and there will be a possibility of damage .

×

Thermal stress (compression) occurs in PTFE because the thermal expansion of the filter media is greaterthan that of the canister. Compressive stress will rise if the volume ratio of the filter media decreases
and there will be a possibility of damage.

〇: No need to consider the test method because there is no possibility of occurrence ×: Need to consider the test method
Note 1: Japan Stainless Steel Association: http://www.jssa.gr.jp/contents/faq-article/q6/
Note 2: Takayama Co., Ltd.: http://www.takayama-industry.com/inconel/
Note 3: Daido Steel: https://www.daido.co.jp/products/titanium/properties/index.html
Note 4: Handbook of Stainless SteelNote 5: Kobe Steel: https://www.kobelco.co.jp/products/titan/files/details.pdf
Note 6: Kyocera: https://www.kyocera.co.jp/prdct/fc/list/tokusei/bouchou/Note 7: Inorganic Chemistry Handbook, Gihodo Shuppan Co., Ltd. (as cordierite porcelain,linear thermal expansion is the value between 20 to 100℃)

Note 8: Ferrotec Material Technologies Corporation:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwioqeK3xcTzAh
WdwosBHZa-CKkQFnoECAQQAQ&url=https%3A%2F% 2Fftmt.co.jp%2Fassets%2Fpdf%2Fjp%2Fcvd_sic%2Fcvd_sic_performance.pdf&usg=AOvVaw0eZTi5AELcG7hFkH0TsKj0
Note 9: Japan Fine Ceramics Co., Ltd.: https://www.japan-fc.co.jp/products/cate01/cate0101/al2o3-995-al2o3-999.html
Note 10: Fujisawa, Matsusue, Takahara: Tensile Strength of Engineering Ceramics Vol.35, No.397 (1986) p. 1112
Note 11: Sakaguchi E.H VOC Corp.: https://sakaguchidennetsu.co.jp/assets/files/PDF/lineup/other/taikabutsu_sankou.pdf

Note 12: Nanjo, Journal of the Japan Society for Composite Materials, Vol.33, No.4 (2007) p.141 - 149
Note 13: Kayo Corporation:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiLi4DdttjzAhW
SHXAKHStnCScQFnoECAYQAQ&url=https%3A%2F%2Fkayo-corp.
co.jp%2Fcommon%2Fpdf%2Fpla_propertylist01.pdf&usg=AOvVaw2Vxk2pSVEW3Vcqf-4O4ONL
Note 14: Underlined figures may be data for temperatures other than 200℃
Note 15: Differs depending on design conditions→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details
6.3 Performance assessment of canister filters

rc0 rf0

b. Study of filter life evaluation methods (12/27)

Canister (and filter frame)
Room temperature

Event: Thermal deformation (container) (maximum temperature 300℃)
Degradation mode: Clogged & Damaged

Ceramics

Glass

Macromolec
ules

SUS316

Stress on filter Tensile strength ofmedia
filter media Note 14
σc [MPa]σ [MPa]16.2 Note 1

193 Note 10

470 Note 4

SUS30417.8 Note 1

193 Note 1-56

465 Note 4

Alloy600

13.3 Note 2

157 Note 2

88

600 to 1200 Note 2

Ti

8.4 Note 3

106 Note 3

177

170 Note 5

SiC

3.7 Note 6447 Note 8705

385 Note 10

Al2O3

7.7 Note 6

370 Note 9437

120 Note 11

Cordierite

1.1 Note 7

88 Note 7296

25 to 40 Note 7

E-glass

5.5 Note 12

72.5 Note 121783430 Note 12

C-glass

7.3 Note 12

68.6 Note 121412744 Note 12

S-glass

2.9 Note 12

84.3 Note 122514655 Note 12

D-glass

3.1 Note 12

51.9 Note 121632450 Note 12

Polyethylene

—

—

—

—

Olefin

—

—

—

—

PTFE

100 Note 13

0.4 Note 13-9

14 Note 13

r
rfh

Wh

300℃

<Model>- Impacts from thickness are not taken into consideration (filter thickness = canister thickness)- The filter media and filter frame as well as the filter outer frame and the inner diameter of the canister are rigidly
connected- The filter material is dense (no gaps).
- The outer frame of the filter and the canister are made of the samematerial.
- The outside diameter of the filter media is 200 mm, and the outside diameter of the canister (and filter frame) is
300 mm.
- Evaluate the stress (as thermal stress) required to extend the radius of the filter media (rfh) after free expansion to
the equilibrium position (r)(ii) Selection of degradation events based on canister environment (11/26)

Metal

rch
Wo

③ Implementation items and results

Linear thermal
Young’s
expansion
modulus ofcoefficient of filter filter media
Note 14
media Note 14 , αf [10-6
Ef [GPa]
/ ℃]

No.69

Filter media

Impact assessment Note 15

If the canister is not made of SUS316L (thermal expansion is not the same), thermal stress will occur andthere is a possibility of damage.
××

If the canister is made of SUS316L, the thermal expansion of the filter media and the canister are thesame, stress applied to the filter media is low, and the tensile strength of the filter media is low, so theimpact is considered to be small. However, stress will increase if the volume ratio of the filter media
decreases and there will be a possibility of damage.
The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. The thermal stress is high compared to the material strength, and there is a possibility ofdamage.

×

The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. The thermal stress is high compared to the material strength, and there is a possibility ofdamage.

×

The thermal expansion of the filter media is smaller than that of the canister, so thermal stress (tensile) is
generated. Although the thermal stress is low compared to the material strength, stress will increase if thevolume ratio of the filter media decreases and there will be a possibility of damage.

×

Thermal stress (compression) occurs in PTFE because the thermal expansion of the filter media is greaterthan that of the canister. Compressive stress will rise if the volume ratio of the filter media decreases
and there will be a possibility of damage.

〇: No need to consider the test method because there is no possibility of occurrence ×: Need to consider the test method
Note 1: Japan Stainless Steel Association: http://www.jssa.gr.jp/contents/faq-article/q6/
Note 2: Takayama Co., Ltd.: http://www.takayama-industry.com/inconel/
Note 3: Daido Steel: https://www.daido.co.jp/products/titanium/properties/index.html
Note 4: Handbook of Stainless SteelNote 5: Kobe Steel: https://www.kobelco.co.jp/products/titan/files/details.pdf
Note 6: Kyocera: https://www.kyocera.co.jp/prdct/fc/list/tokusei/bouchou/Note 7: Inorganic Chemistry Handbook, Gihodo Publishing Co., Ltd. (as cordierite porcelain.
Linear thermal expansion is the value of 20-100℃)

Note 8: Ferrotec Material Technologies Corporation:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwioqeK3xcTzAhWd
wosBHZa-CKkQFnoECAQQAQ&url=https%3A%2F% 2Fftmt.co.jp%2Fassets%2Fpdf%2Fjp%2Fcvd_sic%2Fcvd_sic_performance.pdf&usg=AOvVaw0eZTi5AELcG7hFkH0TsKj0
Note 9: Japan Fine Ceramics Co., Ltd.: https://www.japan-fc.co.jp/products/cate01/cate0101/al2o3-995-al2o3-999.html
Note 10: Fujisawa, Matsusue, Takahara: Tensile Strength of Engineering Ceramics Vol.35, No.397 (1986) p. 1112
Note 11: Sakaguchi E.H VOC Corp.: https://sakaguchi-dennetsu.co.jp/assets/files/PDF/lineup/other/taikabutsu_sankou.pdf

Note 12: Nanjo, Journal of the Japan Society for Composite Materials, Vol.33, No.4 (2007) p.141 - 149
Note 13: Kayo Corporation:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiLi4DdttjzAhW
SHXAKHStnCScQFnoECAYQAQ&url=https%3A%2F%2Fkayo-corp.
co.jp%2Fcommon%2Fpdf%2Fpla_propertylist01.pdf&usg=AOvVaw2Vxk2pSVEW3Vcqf-4O4ONL
Note 14: Underlined figures may be data for temperatures other than 300℃
Note 15: Differs depending on design conditions→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.70

Unit can

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (13/27)

Fuel debris(Filling rate:30%)(ii) Selection of degradation events based on canister environment (12/26)
Event: Thermal Convection Degradation Mode: Clogged & Damaged

ThermophoresisFuel debris - 280 mm fromthe top part of the unit can(= 280 x (1 - 0.3))

Height: 400 mm

Inner diameter: 210 mm

Figure 1 Dust generation by thermophoresis••

When the maximum temperature of fuel debris is assumed to be 300℃ and the upper part of the unit can is room
temperature, creating a temperature gradient in the gas phase section of the unit can where a force toward the lowtemperature side (thermophoresis) is exerted on the particles contained in the fuel debris, evaluate whether an event that
degrades the filter occurs by comparing it against the settling velocity of particles.
The rising velocity of the particles and the thermophoretic velocity in the unit can environment caused by thermophoresis
were evaluated, which were compared with the settling velocity based on Stokes’ law.

Thermophoretic velocity
The Waldmann equation Note 1
UT = Kth• v• ∇T / T*About the thermophoretic coefficient Kth- It depends on the degree of coarseness when the particles are agglomerated. Coarseness isexpressed by the degree of dimensionless, which is the ratio of bulk density to true density. The
smaller the degree of dimensionless (the coarser the aggregation of the particles), the more likely itis that particles will be affected by thermophoresis, and thermophoretic coefficient K th will be larger.
- Since the degree of dimensionless for fuel debris particles inside the canister is unknown, K th = 1 isconservatively set here in order to increase thermophoretic velocity.
- This should be re-evaluated as soon as details on fuel debris information become available.

UT: Thermophoretic velocity [m/s]Kth: Thermophoretic coefficient*
v: Kinematic viscosity coefficient of gasses [m2/s]= Viscosity coefficient of fluids [Pa·s] / Density of fluids [kg/m3]⇒ 20℃, use the value for air∇T: Temperature gradient [K/m]⇒ Fuel debris surface at 300℃, upper part of unit can at 25℃ (roomtemperature)
Use the value 982 K/m divided by 280 mm, the distance between
the fuel debris and the top of the unit can
T: Absolute temperature [K]Note 1: Suzuki, Dobashi, et al., Estimation Method of Thermophoretic Behavior of Soot, Journal of the Combustion
Society of Japan, Vol.52, No.59 (2010) p. 68 - 75

Kth = -0.49 DD + 0.89

Figure 2 Correlation between the degree ofdimensionless and the thermophoretic coefficient Note 1©International Research Institute for Nuclear Decommissioning6. Implementation details

No.71

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (14/27)(ii) Selection of degradation events based on canister environment (13/26)
Event: Thermal Convection Degradation Mode: Clogged & Damaged•

The thermophoretic velocity is 5 × 10-5 m/s, which exceeds the particle rising velocity for particles of 1 μm or less (particles
are dispersed by thermophoresis).

•

The travel distance of particles dispersed by thermophoresis is 1 × 10−8 mm, which is a very small distance and less thanthe distance to the filter.

The reach of particles dispersed by thermophoresis isvery small and is less than the distance to the filter.

Settling speed
Particle size range
in which particles
are dispersed
Thermophoretic
velocity

Distance to reach filter [mm]Initial ascension speed (m/s)⇒ The distance particles rise due to thermal convection is sufficiently small, so filter degradation from thermal
convection can be ignored.

Particle size (μm)

Figure 1 Comparison of thermophoretic velocity and settling velocity

Particle size [mm]Figure 2 Result of evaluation on distance reached by particles©International Research Institute for Nuclear Decommissioning6. Implementation details

No.72

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (15/27)(ii) Selection of degradation events based on canister environment (14/26)
Event: Impact Degradation Mode: Clogged & Damaged
Ventmechanism

Study of the possibility of loss of filter functionality anddeformation or damage to containers and filters from impacts
such as collisions and being dropped during transportationand earthquakes.

53

114

Lid
Lid

75
Φ240
Φ220

Canister weight

Body- The following specifications were assumed for the metal part.
Interference
structure

Body
840

Lid

Body

SUS316L(Density:
8.0 g/cm3)

SUS316L(Density:
8.0 g/cm3)

SUS316L(Density:
8.0 g/cm3)

SUS316L(Density:
8.0 g/cm3)

Outer
Φ300 mmdimensions × 114 mm

Φ240 mm
× 840 mm

Φ240 mm
× 840 mm

Φ210mm× 400 mmThickness 50 mm

10 mm

2.8 mm

6 mmMaterial

Φ300
Φ200

Unit can30
Unit can
Φ198
Φ210

400

Bufferstructure
Fuel debris
10

Inner diameter: 220 mm

2.8

30

115
- Fuel debris is assumed to have a filling rate of 50% and aΦ216.3Figure 1 Canister structureInterference
density of 11 g/cm3.
example Note 1
10Φ240
structure
The above specifications were used to calculate the weight of the unit canFigure 2 Assumed canisterand the canister containing the fuel debris.
structure
The canister weight is assumed to be approximately 300 kg.
Note 1: Taken from the Subsidy Project of “Decommissioning and Contaminated Water Management (Development ofTechnologies for Containing, Transfer and Storage of Fuel Debris)” in the FY2018 Supplementary Budgets, Final Report, June 2021

©International Research Institute for Nuclear Decommissioning6. Implementation details
6.3 Performance assessment of canister filters③ Implementation items and results

Debris treatment
cellb. Study of filter life evaluation methods (16/27)(ii) Selection of degradation events based on canister environment (15/26)

No.73

Lifting machine

Sealing cellGas injection
systemPrimary lid
fasteningmachine/gas
injector/leakdetector

Event: Impact Degradation Mode: Clogged & Damaged

Tasks that may cause an impact- Falls after lifting a canister (including earthquakes)- Collision to the side of the canister caused by shaking whentransferring a canister or shaking due to an earthquake

Weight measuring system Transfer(Conduct a surface
cask
contamination inspection)

Transport cask
transfer equipment

Figure Example task during the canister
handling flow (assumed) Note 1

The effects of impacts on filters- When a canister (approximately 300 kg) is dropped from a height of several meters, the impact anddeformation of the canister could deform or damage the filter and cause it to lose functionality. The
state of deformation and/or damage depends on the height of the fall, movement speed, point of impact(dropped from the bottom of the canister, overturning, etc.), and how the filter is affixed.
- The filter may become deformed and/or damaged and lose its functionality during an impact. In
addition, the state of deformation and/or damage depends on the movement speed at the time of impact,
the point of impact, how the filter is affixed, etc.
- Depending on the specifications of the unit can and the specifications of the filter mounting part (the shapeof the mounting part, any baffle plates and their specifications, etc.), deformation, damage, and/or
clogging of the filter due to unit cans or splashing of fuel debris must be considered.

→ Test methods and conditions are studied as degradation events that should be considered.
Note 1: Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing,
Transfer and Storage of Fuel Debris)” in the FY2018 Supplementary Budgets
Extracted and edited from Final Report Material June 2021

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.74

Maximum seismic acceleration
during the Great East Japan
Earthquake = 29.33 m/s 2 Note 1

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (17/27)(ii) Selection of degradation events based on canister environment (16/26)
Event: Dust generated by vibration Degradation mode: Clogged& Damaged- When the initial velocity (determined by earthquake motion and seismic cycle) acts
perpendicularly to the particles, the dust generated by earthquake motion is considered tohave an effect when the height reached by the particles exceeds the distance between thefuel debris and the filter.
- Using the below formula, the initial velocity of the Great East Japan Earthquake was 4.4 m/s.
Initial velocity [m/s] = Maximum seismic acceleration of 29.33 [m/s2]× (Seismic cycle 1/3.3 [s] × Time period of upward force 0.5 [-])- The height to reach pores with an initial velocity of 4.4 m/s was evaluated by solving theequation of motion Note 2 for the rising and settling of a particle
Unit canFigure 1 Strong vibrations from the Great East
Japan Earthquake Note 1

Highest point
Fluid- Equation of motion for a particle during rising

𝜌𝑃 𝑉𝑃

𝑑𝑣
= −𝜌𝑃 𝑉𝑝 𝑔 + 𝐹𝑏 − 𝑅𝑓 …(1)𝑑𝑡

𝜌𝑃 , 𝑉𝑃 , 𝑣 are particle density, volume, and velocity, respectively
𝑡 is time, 𝑔 is gravitational acceleration,
𝐹𝑏 is buoyancy, 𝑅𝑓 is fluid resistance

Fuel debris(Filling rate:
30%)(Positive indicates upward movement)
Note 1: Kunugi et al., Strong Motion Characteristics of the 2011 Tohoku-Oki Earthquake, National ResearchInstitute for Earth Science and Disaster Resilience Major Disaster Investigation No. 48 (2012)
Note 2: Kohei Ogawa, Series <New Chemical Engineering> 1, “Fluid Transport Analysis” First Edition,
Asakura Publishing Co., Ltd., (2011) p. 58

Upwardinitial velocity
fromvibration

Distance between fuelresistancedebris and the top partforce Rfof the unit can
280 mm (= 400 × (10.3))
Initial velocity

Height
400 mmInner diameter: 210 mm

Schematic of Unit canv0 fromvibration

Buoyancy
force Fb

GravityFine
powderFuel debris surface

Physical model

Figure 2 Unit can schematic and physical model of dust
generation from vibration©International Research Institute for Nuclear Decommissioning6. Implementation details

No.75

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (18/27)(ii) Selection of degradation events based on canister environment (17/26)

Event: Dust generated by vibration Degradation mode: Clogged & Damaged••

The distance reached by fuel debris’ upward motion is calculated when receiving an initial vertical velocity of 4.4
m/s from earthquake motion.
The reach for target particles of 100 μm or less is generally small, approximately 320 mm for 100 μm particles.
Because this result returns a similar distance, the influence of the earthquake motion cannot be ignored.
Distance between fuel debris and the top partof the unit can: 280 mm

Distance to reach filter [mm]•Particle size [mm]Figure Result of calculations on the maximum height reached by particles from vibration→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.76

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (19/27)(ii) Selection of degradation events based on canister environment (18/26)
Event: Thickness reduction Degradation Mode: Damaged

26Cr-1Mo steel
No crevice
corrosion
Corrosion potential
in an open
atmosphere [2]Corrosion potential in an
open atmosphere(SUS403)

Chloride ion concentration (ppm)
Pitting corrosion resistance index PRE(Cr+3Mo (+10 N))

Figure 1 Pitting corrosion potential and pitting
corrosion resistance index of various
stainless steels

Corrosion
Usable resistance

316 stainless steel

Figure 2 Relationship between crevice
corrosion potential and chloride ion
concentration Note 1
Note 1:Central Research Institute of ElectricPower Industry Report Q12001 April
2013

Titanium

20Cr-24Ni-6Mo
steel
29Cr-2Ni-4Mo
steel

Crevicecorrosion
occurs

Ni content (%)

Degassed artificial
seawater, 80℃,
Potential feed rate:
20 mV/minCrevice corrosion potential (V (based on saturated
calomel electrodes))Pitting corrosion potential V′c (V vs. SCE)

Moisture evaporates at temperatures above 100℃, so the events here examined a scenario below 100℃.
- For metal filters
The pitting corrosion potential and pitting corrosion resistance index of various stainless steels shown in Figure 1 show that thecorrosion resistance is that of a 625 alloy, which is SUS304 < SUS316L < Ni-based alloy. Figure 2 shows that crevice corrosion does notoccur in SUS as long as the chloride ion concentration remains under 300 ppm. Figures 3 and 4 show that Ni-based alloys and Ti have ahigher resistance to crevice corrosion than SUS, so it is assumed that corrosion is less likely to occur.
However, condensation always generates moisture, and particles derived from chlorides and waste adhere locally, which will increase thecorrosion potential in that area only. Corrosion can occur if the pitting corrosion potential or crevice corrosion potential is exceeded.
The possibility exists with SUS, which has a relatively low corrosion resistance, and so test evaluations should be conducted.
There is almost no difference between SUS316 and SUS316L in terms of pitting corrosion resistance index and corrosion potential, so
evaluations on wastage are considered to be the same.

825 Ultra Mo

Corrosion
occurs

Note 3:
Proceedings of
the Japan
Concrete
Institute, Vol.30,
No.1 (2008)

904 ultra Mo

Temperature (℃)
Pitting corrosion resistance index PRE (Cr+3.3Mo)
Figure 3 The maximum occurrence of
crevice corrosion in Ti and
Figure 4 Relative comparison of applicability of various
various stainless steels inside
Ni alloys and stainless steels to stressa saturated sodium chloride
corrosion cracking and crevice corrosion inaqueoussolutionenvironment
Note 2cooling zone lines Note 3
Note 2: Hiroshi Sato et al., The Piping
Engineering, 24, 66 (1982)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.77③ Implementation items and resultsb. Study of filter life evaluation methods (20/27)

MgO, ThO2 weakly basic
BeO amphoteric, more basic than Al2O3
MgAl2O4 more basic than Al2O3(ii) Selection of degradation events based on canister environment (19/26) Al O , Cr O , ZrO amphoteric2

Event: Thickness reduction Degradation Mode: Damaged

3

2

3

2

SiO2, TiO2, SiC, B4C , Si3N4 weakly acidic

Acid resistance→ Large
Large ← Baseresistance

6.3 Performance assessment of canister filters- For Ceramics
Aluminum oxide (Al2O3)
Good corrosion resistance in acid solutions, but poor corrosion
resistance in alkaline solutions.
The higher the purity, the better the corrosion resistance (reported inhigh-temperature water).
Cordierite (2MgO • 2Al2O3 • 5SiO2)
Reports state that it has less corrosion resistance than aluminumoxide and is strong against alkalis.
Zeolites (based on SiO4 and AlO4 tetrahedral structures)
There are no reports on its corrosion resistance, and its behavior
is unknown.

Weight reduction, ΔW (mg·cm-2)

Figure 1 Corrosion resistance of ceramics against
acids and bases Note 1

Reaction time (days)

Figure 2 Relationship between weight change andreaction time due to corrosion of alumina ceramics
in 300℃ water Note 1- For Glass
E, C, S, and D types of glass fiber filters exist, but only C-type ismanufactured with corrosion resistance in mind. There are no reports
on its corrosion resistance, and its behavior is unknown.

Note 1: Yoshio et al., Materials and Environments, 44, 405 - 415(1995)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.78

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (21/27)(ii) Selection of degradation events based on canister environment (20/26)
Event: Thickness reduction Degradation Mode: Damaged- For Macromolecule filters
Polyethylene, polypropylene and PTFE show good corrosion resistance to salt water as shown in the table.
Therefore, they can be used so long as attention is paid to the operating temperature (polyethylene: max. 130℃,
polypropylene: max. 160℃, PTFE: max. 260℃).
Table 1 Corrosion resistance of polyethylene, polypropylene, and PTFE Note 1
Polyvinyl alcohol

Polyvinyl acetate

Polystyrene

ABS

Polyethylene

Polypropylene

Polyisobutylene

Polyamide (Nylon)

Polyoxymethylene(Paraformaldehyde /Polyoxymethylene)

Methacrylic (acrylic)

Polycarbonate

Fluorine (Teflon)

Type of plastic material

Polyvinylidene chloride

Thermal grease

PVC

PVdC

PVA

PVAc

PS

ABS

PE

PVC

PIB

PA

POM

PMMA

PC

PIFE

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Polyvinyl
chlorideSoft

Oil/Solvent/Chemicals (arranged phonetically)
PVC
Temperature/Weight % & Temperature ℃
Potassium chloride◎
Calcium chloride◎
Mercuric chloride○
Stannic chloride○
Ferric chloride◎
Copper chloride○
Thionyl chlorideх
Nickel chloride◎
Barium chloride◎
Benzyl chlorideхMagnesium chloride◎
Methyl chlorideхHydrochloric acid[10•RT] ○Hydrochloric acid
[20•RT] ○Hydrochloric acid[20•80]хHydrochloric acid
[38•RT] △◎Salt water
Chlorine gas (dry)△
Chlorine gas (wet)△Chlorinated solvents
х

Hard

х
◎
х
х
х

◎ represents that corrosion
resistance is particularly good forpolyethylene, polypropylene, andPTFE (○: good; △: not good; х:bad)Note 1: Excerpt from Kayo
Corporation
http://www.kayo-corp.co.jp/→ Test methods and conditions are studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.79

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (22/27)
Event: Oxide film generation Degradation mode: Clogged
Macromolecule materials cannot be used because theyexceed the heat resistance temperature.
Evaluate metal filters, ceramics, and glass fibers.
- Metal filters
High-temperature oxidation of alloys containing Cr increases
slightly up to 700℃.
It is several nanometers for Ti, even after one hour of oxidation
treatment. However, keeping the filter at 200 to 300℃ for 50
years may cause an oxide film to grow and clog the filter.
- Ceramics
Ceramics have excellent heat resistance, so they almost neverform an oxide film in an environment of 200℃ or 300℃.
- Glass fibers
The table shows the characteristics of various glass fibers. They
have a high softening point, but general heat resistancetemperature is between 250 and 350℃ and so the possibilityof use in this temperature range is low.

Weight increase (mg/cm2)(ii) Selection of degradation events based on canister environment (21/26)

Oxidation temperature (℃)

Figure 1 Oxidation behavior ofvarious stainless steels in theatmosphere Note 1

Note 1: Ryohei Tanaka, Ed.: Data Sheet for High-Temperature Characteristics of Heat-Resistant Steel,Japan Stainless Steel Association (1978)
Note 2: Shimada et al., Yamaguchi University Joint Research, H23-012
Note 3: Fiber Overview [General Characteristics of Long Glass Fibers] | Central Glass Fiber Co., Ltd.
Long fiber site (centralfiberglass.com)

Figure 2 Surface roughness andthickness of surfaceoxide layer oftitanium samples with various
oxidation conditions Note 2

Table Characteristics of glass fibers Note 3
Glass typeE-glass

C-glass

S-glass

D-glass

SiO2

53

64

72

AI2O3

15

65
4

25

1

Chemical CaO
composition MgO
(wt%)
B2O3

21
2

14
3

1.0
-

Na2O+K2
O
Specific
gravity
Softening
point (℃)
Dielectric
Properties constant
1 MHz
22℃
Young’smodulus(GPa)
Properties

8

6

10
-

0.3

8

0.3

2.5

2.55

2.49

2.49

2.16

840

749

970

771

6.13

6.79

5.21

4.00

72.6

68.6

8S.3

52.0

Electricalinsulation,
generalpurposeAcid
resistanceHighstrengthLowdielectric
constant

23©International Research Institute for Nuclear Decommissioning6. Implementation details

No.80

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (23/27)(ii) Selection of degradation events based on canister environment (22/26)
Event: Electric corrosion Degradation mode: Damaged

Electric corrosion occurs only in metal filters and not in
insulators such as ceramics, glass fibers, andmacromolecules. Therefore, only metal filters are examined.
Figure 1 shows an example of filter structure. Electric
corrosion does not occur when the filter housing is made ofan SUS or Ni-based alloy. Ti has electropositive potential, so
Ti housing sides will corrode.
This can be explained by the potential difference of various
metals in seawater.
Corrosion
potential

Noble (+)

Container exterior
Filter housing

Negative(-)

Platinum
Titanium

Silver solder
Lead

Filter lid

BronzeAluminum brass
SolderCopperTin
Brass

FilterContainer interior

Low carbon steel
Mild steel, cast iron
Aluminum, Al alloys
Zinc

Figure 2 Potential difference of metals in seawater(temperature 25℃) Note 1

Figure 1 Example of the filter structure

Note 1: Urban Steel Study Group, “Guide to Iron and Steel Landscape
Materials” 1997.7©International Research Institute for Nuclear Decommissioning6. Implementation details

No.81

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (24/27)(ii) Selection of degradation events based on canister environment (23/26)
Event: Water film Degradation mode: Clogged

When humidity around the filter is high and there is a large temperature difference caused by anabnormality in the air conditioning system, moisture in the air will condense and form a water filmon the surface of the filter, which will in turn block the filter.
Condensation conditions• The presence of condensation and the volume of water generated by condensation depend
on humidity and temperature.
• Condensation occurs when the temperature drops below the dew point temperature (thesaturation temperature of vapor in the air).
• M1 (g/m3) is the amount of vapor in the air at temperature T1 (℃) and M2 (g/m3) is the amountof saturated vapor at temperature T2 (℃) (T2 < T1). If M2 < M1, then (M1 − M2) amount ofcondensation occurs.
• Condensation does not occur if M2 > M1, even with large changes in temperature.
• The presence of condensation depends on environments, therefore, it is different from timerelated degradation events.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.82

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (25/27)(ii) Selection of degradation events based on canister environment (24/26)
Event: Water film Degradation mode: Clogged

Operations that may generate water films
Operation when fuel debris is stored in the canisters. When an abnormality occurs in the air
conditioning system in the winter and the temperature around the canister changes.
The effects of water film on filters
When condensation creates a water film that covers the filter surface, flow path area isreduced and that could reduce hydrogen discharge performance. The degree of
performance degradation depends on the area covered.

→ Test methods and conditions shall be studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.83

6.3 Performance assessment of canister filters③ Implementation items and results

Area monitor

b. Study of filter life evaluation methods (26/27)
Gas treatment
system(ii) Selection of degradation events based on canister environment (25/26)
Event: Particle dispersion Degradation mode: Clogged & Damaged•

Occurrence of particle dispersion caused by the air supply is evaluated.

•

When storing canisters, configurations that allow for the venting and supply
of hydrogen is being considered, and two types of canister configurations are
anticipated, one with an air supply mechanism and one without (the figure on
the right is a type with an air supply mechanism).

•

Figure 1 Canister and air supply
system Schematic diagram
Flow of gas
Lid(Bolt structure)

When the hydrogen inside the canister is supplied to the gas treatment
system via a gas flow, gas flows from the bottom to the top of the canister,which could cause particles to rise, depending on the flow velocity.

•

With particles 100 μm or less (powdery fuel debris), the ease with which
particles will float increases with particle size. As a result, the air supply
velocity for 100 μm particles to reach the distance between the fuel debris
and the filter was evaluated at 5 m/s.

•

Therefore, air flow velocity of 5 m/s or higher presents a possibility of filter
degradation from the dispersion of particles.

Surfacetemperature
measuringequipment

Vent pipe

Air supply
mechanism

Canister(Body)
Unit canFigure 2 Schematic diagram :Canisterwith air supply mechanism→ Test methods and conditions shall be studied as degradation events that should be considered.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.84

6.3 Performance assessment of canister filters③ Implementation items and resultsb. Study of filter life evaluation methods (27/27)(ii) Selection of degradation events based on canister environment (26/26)

Summary
Degradation
factors

Metal

Ceramics

Glass

Macromolecules

Stainlesssteel

Nickel-basedalloy

Titaniumalloy

Aluminumoxide

Cordierite

ZeoliteE-glass

C-glass

S-glass

D-glass

Hydrogengeneration
Hydrogenembrittlement
Radiation
degradation

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Dust generated
by vibration
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generation
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Powderdispersion

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Polyethylene Polypropylene

PTFE

Study of test methods based on the combination of degradation
factors and materials to be considered.

◎: Study of test methods is required for both Scenarios 1 and 2○: Study of test methods is required for Scenario 2 only--: Study of test methods is not required because there is no possibility that either Scenario 1 or 2 will occur©International Research Institute for Nuclear Decommissioning6. Implementation details

No.85

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (1/13)(i) Study of filter degradation simulation methods (1/10)
Event: Hydrogen embrittlement
Test overview (draft)- Hydrogen is charged under 2 to 3 conditions based on the amount of hydrogen generated ineach material during using the filter and then materials are placed on the filter performanceassessment equipment and tested. The appropriate method is used for each material
though there are a variety of charging methods, including an electrolytic method, a highpressure method, and other such methods. (Figure 1)- Performance assessment and the amount of charged hydrogen are verified. Thermal
desorption analysis is used as the method. (Figure 2)

Thermocouple

Thermocouple
Vacuum chamber

Potential and current control equipment
SampleQuadrupole mass
spectrometer
Quartz transparent dishQuartz sample stage
Thermocouple(for the stage
temperature)

Antipole

Referenceelectrode

Test
piece

Quartz column for
introducing infrared
light
Infrared

Figure 1 Example of hydrogen charge(example of electrolytic hydrogen charging)

Figure 2 Example of thermal desorption
analysis system©International Research Institute for Nuclear Decommissioning6. Implementation details

No.86

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (2/13)(i) Study of filter degradation simulation methods (2/10)
Event: Radiation degradation
TensileIrradiation is simulated assuming that fuel debris iscollected in the canister and changes in mechanicalcharacteristics are verified.

Destruction

InitialTest overview (draft)• The target material is irradiated with the assumed
radiation dose and the mechanical characteristics
before and after irradiation are investigated.
• The assumed stress when using a filter is investigatedto satisfy the above mechanical characteristics.
• JIS stipulates tension tests for organic substances(plastics) and materials are evaluated in accordancewith the stipulated method.
(JISK7161:2014 Plastics - Determination of tensile
characteristics)

The specimen
becomes extremely thinafter passing the yield
point. (necking)

Stres
s

Elongation increases ,but stress does notincrease.
Auxiliary line for tensile elasticity

Point ofdestruction

Upper yield point (JISstandard: yield point)
Lower yield point

Proportional limit

StrainFigure 1 Example of a stress-strain diagram from a tensile test

Figure Example of a stress-strain chart from atension test Note 1

Note 1: DJK Corporation website
https://www.djklab.com/service/koubunshibussei/323©International Research Institute for Nuclear Decommissioning6. Implementation details

No.87

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (3/13)(i) Study of filter degradation simulation methods (3/10)
Event: Thermal deformation (container), Thermal alteration
It is assumed that the filter is exposed during a work flow of the canister
handling.
The integrity of the filter is verified in the temperature environment.

Test overview (draft)• A filter is fixed to the structure that simulates the canister (hereinafter referred to as asimulated canister).
• Heating mechanism is installed with the simulated canister or the simulated canister
is installed in heating equipment.
Simulatedcanister• The simulated canister is heated up to the predetermined temperature.
Figure Overview of heating tests• The integrity of the filter is verified after heating. (appearance, filter performance
tests, etc.)
An analysis using FEM (finite element method) to gauge the influence of thermal deformation (container)
can be carried out before conducting the test.
The test results may differ depending on a method for fixing the canister lid, the shape and dimensions of
the storage container, the method for fixing the canister lid, the shape of the inner container, etc. and sotests should be conducted after the detailed specifications have been determined.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.88

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (4/13)(i) Study of filter degradation simulation methods (4/10)
Event: Impact

ReleaseCrane
equipment
Full-scale canistersampleMeasuring cable

Crane

The filter is subjected to an impact assumed possible
to occur during a work flow of canister handling. The
integrity of the filter is verified after impact.

Test overview (draft)• A filter is fixed to the structure that simulates thecanister (hereinafter referred to as a simulated
canister).
• A lifting tool raises the simulated canister to apredetermined height.
• The simulated canister is separated from the hanger
and allowed a free fall.
• The integrity of the filter is verified after the fall.
(appearance, filter performance tests, etc.)

Releaseequipment
Full-scale
canister sample
Measuring cable

Measuringequipment(a) Dropping the canisterfrom a vertical positionGuide(basket dimensions)
Crane

Measuringequipment(b) Dropping the canister from an
inclined position
Release equipment
Full-scale canister sample(upper surface)
Platform
Measuring equipment

Full-scale canistersample (bottom
surface)

Measuring cable(c) Dropping a canister onto the top of the anothercanister from a vertical position

Figure Examples of falling orientation for a simulated
canister object in an impact test
(Test system diagram for structural verification tests offull-scale canister samples*)The test results may differ depending on a method for fixing the canister lid, the shape and dimensions of thestorage container, the method for fixing the canister lid, the shape of the inner container, etc. and so tests should
be conducted after the detailed specifications have been determined.
Note 1: Subsidy Project of “Decommissioning and Contaminated Water Management (Development of Technologies for Containing,
Transfer and Storage of Fuel Debris)” in the FY2018 Supplementary Budgets
Extracted from the Final Report Materials June 2021

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.89

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (5/13)(i) Study of filter degradation simulation methods (5/10)
Event: Dust generation from vibration (dust generation from earthquake motion)
An unit can containing fuel debris (simulated) that includes powdery fuel debris in a canister with a filter is placed. Then avibration test simulating earthquake motion is conducted to simulate filter degradation caused by dust generated by earthquake
motion.
Test overview (draft)- Fuel debris (simulated) that includes powdery fuel debris is filled in the unit can.
(The fuel debris density, particle size, and filling volume are simulated.)- The unit can is placed in a canister and then the canister lid is closed

Canisterafter installing a filter.
- The canister is attached on a vibration table that can simulate earthquake motion.

Filter- The canister is fixed on the vibration table with a fixing jig to prevent thecontainer from overturning.
- A vibration test that simulates earthquake motion is conducted.
(The input ground motion should be implemented based on the storage areaand equipment environment, for example, input ground motion should be awave equivalent to the design basis earthquake motion.)

Unit canPowdery
fuel debris

Fixing jig

Vibrationtable- After the vibration test, the canister lid is opened to remove the filter. The deposition
amount can be evaluated by the weight of the filter.
- A performance assessment is conducted to evaluate the performance accordingly.

Figure Overview of filter degradation simulation
test caused by dust generation due toearthquake motion

The test results may differ depending on a method for fixing the canister lid, the shape and dimensions of the storage
container, the method for fixing the canister lid, the shape of the inner container, etc. and so tests should be conducted after thedetailed specifications have been determined.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.90

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (6/13)(i) Study of filter degradation simulation methods (6/10)
Event: Thickness reduction
Test overview (draft)
The following two types of thickness reduction evaluation can be considered.
- The filter is immersed in the assumed environment, and the corrosion rate is calculated from the amount of change inweight over time to predict the state of thickness reduction- Assuming that corrosive ions will adhere as the wet/dry environment cycle repeats, a combined cycle test (JIS K
5600_7_9) is used to repeat a salt spray, drying, and humidification as one cycle
In the combined cycle test, a filter is installed in the equipment shown in the Figure below and then corroded.
However, as a foundation for the performance assessment, filters with different corrosion progressions rates must be
manufactured and tested to evaluate whether filter performance can be maintained.
Examining corrosion rates and results of combined cycle tests together with the above performance assessment results
make it possible to determine whether a filter can be used as a filter in a canister storage container.
Test piece

Figure Example of combined cycle test equipment

A filter is installed in theequipment shown in the left
side of the Figure.The filter iscorroded through a combined
cycle.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.91

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (7/13)(i) Study of filter degradation simulation methods (7/10)
Event: Oxide film generation
Thermocouple

Test overview (draft)
Oxide film measurement test
The oxide film growth rate on the applicable filter material ismeasured at a temperature of 300℃ in normal atmosphericconditions.
The materials to be measured are placed in the heat treatment
furnace. The oxide film growth rate is measured from theincrease in weight before and after heat treatment, setting threeor more conditions for the heat treatment period.
The oxide film thickness 50 years later is calculated based on
those values. Then, a performance assessment on the filter isconducted under accelerated conditions (excessively highoxygen conditions) where calculated values of the oxide film
thickness is added.

Test piece

Test piece
tableElectric
furnace
Figure Example of a heat
treatment furnace©International Research Institute for Nuclear Decommissioning6. Implementation details

No.92

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (8/13)(i) Study of filter degradation simulation methods (8/10)
Event: Water film
Air permeability is verified under conditions that simulate theformation of a water film due to condensation on the filter.

Test overview (draft)• The pressure to emit gases inside the container isinvestigated when a water film is formed on the filter.
• The filter can be evaluated by applying a method for fiber
waterproof test. (See the Figure on the right)• The fixed filter is pressurized with water, then the pressure
at the time of emitting air is measured.

Supportplate

SampleWater
pressure
Figure: Illustration of an air permeability
test for a clogged filter Note 1

Note 1: W. L. Gore & Associates. materials (https://www.gore.co.jp/sites/g/files/ypyipe116/files/2016-04/PTV-TechInfo-WEP-Testing-US.pdf)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.93

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (9/13)(i) Study of filter degradation simulation methods (9/10)
Event: Powder dispersion (dust generation due to ventilation)
The canister with filters is contained with fuel debris (simulated) that includes powdery fuel debris and filled withupward air flow simulating supplying air in the canister. Then filter degradation can be simulated by air supply fromupstream caused from dust generation during ventilation.
Test overview (draft)- Preparation of a vertical reaction tube with a powder support plate, filter, andparticle concentration counter as shown in the right Figure on the right.
- Reaction tube filling with powdery fuel debris (simulated) and installation of afilter.
- Air supply at a flow rate equivalent to ventilation (use the air supply gas).
- Verification of the particle dispersion by counting particles during gas flowusing the particle concentration measuring instrument placed in front of thefilter based on the number of particles before testing.
- When particles disperse, filter performance could be affected. In such cases,
the lid of the canister is opened to remove the filter after ventilation andparticle adhesion can be evaluated from measurement of the filter weight.
- The filter performance is evaluated by evaluation tests accordingly.

Particle
concentration
measuring
instrument

FilterPowdery fueldebris (simulated)

Particle collection
tube

Powder support
plate
Air supply gas
Figure Overview of a test system forsimulating dust generation from vibration

Test results may differ depending on the ventilation flow rate, the location where air supply mechanisms are
installed, the configuration of the container such as its shape and dimensions, the fuel debris filling method, etc. andso the test should be conducted after the detailed specifications have been determined.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.94

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (10/13)(i) Study of filter degradation simulation methods (10/10)
Summary- A test method to simulate filter degradation for each degradation process
was organized because it is difficult to evaluate the degree of degradation in
the 10 identified degradation processes from theoretical formulas.

- It is difficult to simulate filter degradation without inputs (environmental
conditions, fuel debris properties, etc.), treatment process, detailed
specifications, required performance, and filter type. Once these information
are consolidated, it is necessary to re-evaluate the possibility of degradation
occurrence at each process and conduct degradation simulation tests forevaluation of degradation rate, and evaluate the life of various filters in order
to select a filter.

©International Research Institute for Nuclear Decommissioning6. Implementation details
6.3 Performance assessment of canister filters

No.95③ Implementation items and resultsc. Study of test methods and conditions (11/13)(ii) Study of filter performance assessment methods (1/3)
Particle capture performance assessment method- Particle capture performance assessment method is stipulated for general filter performance assessment methods,
and JIS includes the following:
JIS B 9908-2: 2019 Test method of air filter units for ventilation and electric air cleaners for ventilation - Part 2: Measurement of
fractional efficiency and air flow resistance- Based on this method, as shown in the Figure on the right, the particle capture performance of a filter can beevaluated by running an airflow that contains particles through the filter and measuring the particle concentration
before and after.
Particle generator
Manometer for static(Test method)
Filterfor testing
differential pressure- Temperature and humidity maintains constant, and a blower pushes
measurementsa dry current through the filter at a constant flow rate.
From theExhaust- Particles adjusted to a certain particle size are used as test particles
blowerin the air flow.
Particle collection tube
Rectifier- The particle number concentration before and after filtering is
Particle concentration
measured to evaluate the capture efficiency rate of the filter.
counter for testing
Figure Filter performance assessment test Overview(Assessment criteria)- Assessment criteria is determined by satisfying the specified performance of the particle capture efficiency.
- References of a performance guideline results equivalent to a JIS HEPA filter (capture performance 99.97% @0.3 μm) or a HIC vent filter (NucFil® 019-HCR, particle capture performance > 99.97% @ 0.3 to 0.5 μm DOP,
specified flow rate: 210 ml/min @ 330 Pa).

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.96

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (12/13)(ii) Study of filter performance assessment methods (2/3)
Hydrogen permeation performance assessment method (general industry)
1) General filter performance evaluation method- JIS stipulates the following for general filter performance assessment test methods:
JIS 9908:2011 Test method of air filter units for ventilation and electric air cleaners for ventilation
This standard is a performance assessment method for air filters that remove dust floating in air and does
not describe the assessment of hydrogen permeation performance.
- The following regulation pertains to filters for nuclear facilities:
JISZ 4812-1995 HEPA Filters for radioactive aerosols
This standard is used for the purpose of removing radioactive aerosols in the exhaust systems, ventilation
air conditioning systems, etc. of nuclear facilities.
It stipulates that high-performance air filters (hereafter referred to as high-performance air filters) must be
flame-retardant to protect against fire. Assessment of hydrogen permeation performance was notdescribed in the standard.
In this investigation, any JIS standard regarding the assessment method for hydrogen permeability was notfound.

©International Research Institute for Nuclear Decommissioning6. Implementation details

No.97

6.3 Performance assessment of canister filters③ Implementation items and resultsc. Study of test methods and conditions (13/13)(ii) Study of filter performance assessment methods (3/3)
Hydrogen permeation performance assessment method (nuclear)
2) Method for assessing hydrogen permeation performance of filters
In the United States, test methods have been established for hydrogen discharge filters used in radioactive waste andTRU waste containers Note 1. A container with filter is filled with hydrogen at a specified concentration (4%), and thehydrogen concentration in the static container is measured 7 times every 5 minutes.
Nitrogen gas
A permeability performance assessment is made based
Hydrogen 4% +on hydrogen diffusivity (D) obtained from the following
nitrogen 96%
formula.

𝐷=

𝑃𝑉
𝑡𝑅𝑇

𝐿𝑛𝐻
0𝐻𝑡

D: hydrogen diffusion coefficient (mol/sec/mol fraction)
P: pressure (atm), V: container volume (L), t: time (seconds),
R: gas constant of an ideal gas (0.082 Latm/molK),
T: temperature (K), H0: initial hydrogen concentration,
Ht: Hydrogen concentration at time t

Argon gas

FilterContainer

1 mL
Sample loop

Purge
valve

Gas
chromatographIn the United States, the WIPP (Waste Isolation Pilot Plant)
stipulates the performance of filters used in waste containers
Figure Schematic diagram of hydrogen diffusivity test equipment
Note 1: Terry Wickland and John Schierloh Hydrogen Diffusivity through Drum and Liner Venting Filters WM98
(http://archive.wmsym.org/1998/html/sess27/27-37/27-37.htm)©International Research Institute for Nuclear Decommissioning6. Implementation details

No.98

6.3 Performance assessment of canister filters④ Contribution of outcomes to relevant study areas
This data is useful when selecting filters in the design phase.

⑤ Analysis with respect to the on-site applicability
In terms of on-site applicability, the effects of degradation are evaluated based on test resultsfrom the filter degradation simulation methods and filter performance assessment methods thatare the outcomes of this project, and those evaluation results are used to select filters thatsatisfy performance requirements even after degradation.

⑥ Goal achievement level
It can be concluded that TRL Level 1 was achieved as planned because the following
indicator to judge goal achievement was met:
• The environments and conditions that affect canister filter life must be understood andorganized. Also, the test methods and conditions for any item that must be tested toevaluate filter life must be examined and any relevant existing knowledge must beorganized.

⑦ Issues to be addressed
Once information such as inputs (environmental conditions, fuel debris properties, etc.),
treatment processes, required filter performance, etc. is aggregated, it is necessary toreevaluate of the possibility of each degradation process occurring, evaluate the effect ofsuperimposed processes, conduct degradation simulation tests to evaluate the rate ofdegradation, etc., before evaluating the life of each filter and finally selecting a filter.
©International Research Institute for Nuclear Decommissioning6. Implementation details

No.99

6.3 Performance assessment of canister filters⑧ Summary• The functions for confining fuel debris particles and functions for releasing hydrogengenerated by the radiolysis of water were identified as filter requirements.
• The filter degradation factors were figured out and 17 degradation processes wereidentified. Using existing knowledge as input conditions, the four processes of salt
precipitation, microbial membrane, aerosol deposition, and UV degradation were excluded
from the target processes based on fuel debris properties, container specifications, andenvironmental conditions inside and outside the canister. Scenarios were defined in which
the selected 13 processes lead to degradation based on the canister environment.
• Among the degradation processes, the three events of hydrogen generation, thermal
convection, and electric corrosion were evaluated as not occurring, and the evaluations offilter degradation using theoretical formulas were attempted for the other 10 events, butsince no method for estimating degradation events has been established, testing methods
for simulating degradation were examined and filter degradation simulation methods foreach degradation process were presented.
• As methods for determining degrees of degradation, particle capture performance andhydrogen permeation performance, both of which are required as filter performance, were
examined and developed as general assessment method proposals.
• Once information such as inputs (environmental conditions, fuel debris properties, etc.),
treatment processes, required filter performance, etc. is aggregated, it is necessary toreevaluate of the possibility of each degradation process occurring, evaluate the effect ofsuperimposed processes, conduct degradation simulation tests to evaluate the rate ofdegradation, etc., before evaluating the life of each filter and finally selecting a filter.
©International Research Institute for Nuclear Decommissioning7. Summary

No.100• The experience, knowledge, and information on the handling and storing ofradioactive materials, etc. in powder, slurry, or sludge form at TMI-2 and the
Hanford Site in the US, Sellafield in the UK, and other sites, which areconsidered to be useful for identifying issues related to the storage of
powdery, slurry or sludge fuel debris, were collected and analyzed.
• Issues and countermeasures in each process up to storage when
conducting dry storage with canisters similar to those for fuel debris inparticle or lump form were examined. The technological issues related tothe storage of fuel debris in powder, slurry, or sludge form as well as theirsolution phases and solution periods were also clarified.
• Potential degradation processes were identified from the environment andconditions in which the canister filters are placed. A simulated degradation
method was provided for each degradation process and performanceassessment test method plan were proposed.
©International Research Institute for Nuclear Decommissioning