1
Subsidy Project of Decommissioning and Contaminated Water Managementin the FY 2016 Supplementary Budgets

Development of Technology for Fuel Debris
Analysis and Characterization
Interim Report

April 2018
International Research Institute for Nuclear Decommissioning (IRID)©International Research Institute for Nuclear Decommissioning

CONTENTS

2

1. Research Background and Purposes
2. Project Goals
3. Implementation Items and Relations with Other Projects
4. Schedule
5. Project Organization
6. Implementation Details©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes
Background of Research
Accident at the Fukushima Daiichi Nuclear Power Station (1F)

3
(March 2011)

Investigate and sort out available knowledge about past incidents, including information on theaccident at Three Mile Island Unit 2 (TMI-2) research on severe accidents (SAs), and information
related to the 1F accident(2011–2012)✓

Not much has been known about boiling water reactors (BWRs) in the TMI-2 accident or SA research
conducted overseas.
✓ There is not much information on fuel debris relevant to 1F-specific events, such as the impact of exposure
to seawater and the Molten Core Concrete Interactions (MCCIs).

•

To execute nuclear decommissioning (retrieval, criticality control, collecting/transferring/storing,material accountancy, and final treatment) safely, steadily, and quickly, it is necessary to sortout and make available fuel debris information that can be leveraged in technical development.

•

If accurate fuel debris information cannot be obtained at an initial stage, it is necessary to setup (i.e., assume) fuel debris information based on existing knowledge and research anddevelopment projects conducted at home and overseas. This information should be updated
and shared among researchers/developers and field workers.

•

To determine specific information on fuel debris to be collected, it is necessary to sort out andconfirm sufficient project needs and timing requirements (retrieval methods & foundation,collecting/transferring/storing, and criticality control (hereafter referred to as "Information User
PJ")) that makes use of such information.
©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes
Purpose of Research: (1) Estimation of Fuel Debris Properties and(2) Characterization Using Simulated Debris

4[Purpose] To reflect research results to the “List of Fuel Debris Properties” and provide the updated
information to Information User PJ

Treatment of Fuel Debris

Information
User PJ

EstimateCollecting, Transferring,and Storing

Fuel Debris Retrieval

ProvideUpdate Fuel Debris Listof Fuel Debris Properties

Metal compounds(e.g., SUS-Zr-U alloy or ZrB2)

Test & research using simulated
debrisOxides(e.g., (U, Zr)O2)

Unmolten fuel pellet
CS system

Estimate Fuel Debris Properties

Feedwater
systemCrystals such as
borides
Structure materials(Metals)

Image of Fuel Debris

Reactant withconcrete (e.g.,silicate compounds)©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes
Purpose of Research: (3) Developing of Element Technologies for Analysis
on Fuel Debris and Other Materials

5[Purpose] To develop analytical technologies while studying transportation methods to analyze facilities for
speedy and steady fuel debris analyses
Before Operation
Startup in New Analysis& Research Facility

Sampling of Fuel Debris
Sampling of Fuel
Debris in PCV

Scope of Fuel Debris
Characterization Project⚫

⚫

Review Transportation
Methods➢ Review acceptability ateach analysis facility
Develop Element Technologies
for Analysis
0➢ Develop analytical0
technologies➢ Prepare analysis proceduresCollected
Debris Samples

MinimalSamples

Minimal Samples

After Operation Startup in
New Analysis & Research Facility(Transported)
Minimal Samples

Fuel Debris Retrieval
Collected Debris
Samples

Transportation(Transported)

Existing Analysis
Facility

Collected Debris
Samples(After FY 2021)(Analyzed)
Existing Analysis
Facility

New Analysis & Research
Facility(Facility within Fukushima
Daiichi Nuclear Power Station)(Analyzed)

New Analysis & Research Facility(Facility within Fukushima Daiichi Nuclear Power Station)

Characterize Fuel Debris©International Research Institute for Nuclear Decommissioning2. Project Goals
Scope and Timing

6

FY
Determine retrieval policy 

Investigation
Inside the PCVInformation User PJ

Technical Development &ReviewInformation based on Past Knowledge& Assumption (e.g., a Preliminary
Version of “Debris Standardization”)

Technical Development/ Design &Manufacture Equipment

Update List of Fuel Debris Properties
based on MCCI Characterization
and Dose Evaluation

Summarize Fuel Debris Update List of
Property Data
Fuel Debris
Properties

Fuel Debris
Characterization

 Confirm retrieval method for initial unit

A2 Inspection
On-site Inspection 
A2' Inspection 
Unit 3 Inspection 
B2 Inspection Prepare List of Fuel Debris Properties
To examine “Debris Standardization”
Information

Update Analysis Data, List of
Fuel Debris Properties, for Fuel
Debris Samples

Update Analysis Data, List of
Fuel Debris Properties, forCollected Debris Samples

FP Emission Behaviors
During Dry Heat
Treatment

Review “List of Fuel Debris Properties”
Estimate MCCI properties/ meet the project’s needs
for collecting, transferring, and storing

Coordinate 1F Sample
Analyses/Review
Transportation Methods

Fuel Debris Property
Analysis

Execution of Retrieval, etc.

Coordinate Future Debris
Sample Analyses

Review and Develop Items andTechnologies for Debris Analysis

Project Duration* Each implementation team’s
objectives are described in “6.
Project Items.”©International Research Institute for Nuclear Decommissioning3. Implementation Items and Relations with Other Projects(2)

Characterization Using
Simulated Debris[1]

Characterize MCCI Products in
Terms of Heterogeneous
Properties[2]

Evaluate Emission Behaviors ofFission Products During Drying
Heat Treatment(1)

Estimation of Fuel Debris
Properties(3)

Prepare List of Fuel
Debris Properties

Data from
Tests Using
Simulated
Debris, etc.

[1]
[2]

Develop Element
Technologies to Analyze Fuel
Debris and Related Materials

Prepare for Fuel Debris Sample Analysis
Develop Element Technologies Required
for Analysis

Prepare for Fuel
Debris Analysis

Update List of Fuel
Debris Properties

Analyze Actual Fuel Debris(Currently Out of Scope of This Project)

Analyze Data from a
Fuel Debris Sample

Provide List of Fuel Debris Provide

Characterization
Associated with Dried
Fuel Debris

OutputProperties(Property Data ofFuel Debris)

OutputInformation User: Project©International Research Institute for Nuclear Decommissioning

74. Schedule
Project Outline and Schedule FY 2017 & FY 2018
FY 20178FY 2018

 Update List of Fuel
Debris Properties(1) Estimate Fuel Debris Properties

Update (2) Characterization Using Simulated Debris[1] Characterize MCCI Products with Ununiform Properties[2] Evaluate Emission Behaviors of Fission Products During Dry Heat
Treatment(3) Develop Element Analysis Technologies on Fuel Debris and Other
Materials[1] Prepare for Fuel Debris Sample Analysis[2] Develop Element Technologies Required for Analysis

a. Develop Technologies for Dissolution and Multi‐Element
Analysis of Fuel Debrisb. Develop Fuel Debris Analysis Technologies Using X-Ray CT*
c. Develop a Multiple Nuclide Rationalization Analysis Technology
Using ICP-MS**d. Review Matters Related to Fuel Debris Sample Transportation(iii) Review Analytical Technologies(Where appropriate)(Where appropriate)* X-Ray CT: X-ray computed tomography** ICP-MS: High-frequency inductively coupled plasma mass spectrometry©International Research Institute for Nuclear Decommissioning5. Project Organization (FY 2017)9Tokyo Electric Power Company Holdings, Inc.
 Coordinate technical development
 Assist R&D management
Cooperative research contact• Waste Management Group, Project Planning Department,
Fukushima Daiichi D&D Engineering Company

Japan Atomic Energy Agency (JAEA)[1] Estimate Fuel Debris Properties[2] Characterization Using Simulated Debris[3] Develop Element Technologies Analysis on Fuel
Debris and Other Materials

International Research Institute for Nuclear
Decommissioning Draw up overall plan and oversee technology

management
 Manage technologies, including technicaldevelopment progress

Mitsubishi Heavy Industries, Ltd.

Hitachi-GE Nuclear Energy, Ltd.

[3]
DevelopElement Technologies Analysis on Fuel
Debris and Other Materials(Review analytical technologies)[3]
Developelement technology to analyze fueldebris and other materials (review
analysis technologies)

CEA (France) Analyze large-scale MCCI
products

Inspection Development Company
Ltd.
 Business contractor for evaluating
medium volatile FPs’ emissions

Yashima Denki Co., Ltd.
 Calibrate linear X-ray accelerators

CHINO Corporation
 Calibrate pyrometers

Ascend Co., Ltd.
 Business contractor to developelement technologies for analyzing
fuel debris

NIPPON STEEL & SUMIKINTECHNOLOGY Co., Ltd.
 Test for evaluating emission
behaviors using simulated FPs

SEIKO EG&G Co., Ltd.
 Install cold test facilities and adjust
ICP-AES spectrometers

PESCO Co., Ltd.
 Business contractor to characterize
and develop analytical technologies
for fuel debris
Hitachi Environment Development Co.,Ltd.
 Collect, transport, and dispose ofcold test liquid waste©International Research Institute for Nuclear Decommissioning6. Implementation Details

10

(1)

Estimate Fuel Debris Properties (Update Fuel Debris List of Fuel Debris Properties)(2)

Characterization Using Simulated Debris[1] Characterize MCCI Products with Heterogeneous Properties[2] Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment(3)

Develop Element Analysis Technologies on Fuel Debris and Other Materials[1] Prepare for Fuel Debris Sample Analysis[2] Develop Element Technologies Required for Analysis
a. Develop Technologies for Dissolution and Multi‐Element Analysis of Fuel
Debrisb. Develop Fuel Debris Analysis Technologies Using X-Ray CT
c. Develop a Multiple Nuclide Rationalization Analysis Technology Using ICP-MS©International Research Institute for Nuclear Decommissioning

(1) Estimation of Fuel Debris Properties (Update List of Fuel Debris Properties)11⚫Update List of Fuel Debris Properties(FY 2017 and FY 2018)[Objectives]
To estimate dose rates near fuel debris surfaces under typical conditions.
To reflect the latest results, including dose rate evaluation results, on the “Lists of Fuel Debris
Properties,” prepared based on findings over a period up to FY 2016 among other things.
[Criteria for Target Achievements]➢ “List of Fuel Debris Properties” was updated based on newly obtained knowledge in FY 2017. (End of FY 2017 Completed)➢ “Lists of Fuel Debris Properties” are updated based on newly obtained knowledge in FY 2018. (End of FY 2018)➢ Dose rates near the debris surfaces are estimated.(End of FY 2018)
Achievements in FY 2017

1. Evaluation of Surface Dose Rates of Debris
Added values calculated by an evaluation formula for surface dose rate, created based on calculation
codes.
2. Characterization of MCCI Products with Heterogeneous Properties
Reflected values in the List including property values based on the product analysis results in large-scale
MCCI tests performed in FY 2017.

©International Research Institute for Nuclear Decommissioning

(1) Estimation of Fuel Debris Properties (Update Fuel Debris List of Fuel Debris
Properties)◆ Evaluation of Debris Surface Dose Rates

12

To retrieve fuel debris, estimating fuel debris surface dose rates is important because it helps to develop a work plan that takes
exposure control into consideration (appropriate shields, task durations, etc.) for workers and other personnel during retrieval tasks.
⚫ Assuming typical fuel debris, based on the fuel debris distribution inside the reactor, the surface dose rate is evaluated for thissingle fuel debris (under a condition unaffected by radiation from other sources).

Achievements in FY 2017
A preliminary calculation was performed to find the surface dose rate of spherical debris using the Monte Carlo code particle transport code
(PHITS) under parameters of fuel debris properties, and the best ways to organize the data (charts and fitting formulas) was reviewed. In FY
2017, surface dose rate evaluation methods, selected a case of fuel debris were reviewed, and preliminary evaluations performed. Minimum
parameters were obtained to determine the surface dose rate, and a preliminary evaluation formula was created through function fitting.

Fuel Debris Property Parameters
Composition of irradiated fuel(At the Accident)(i) Type of fuel debris: Melted, MCCI, or metallic debris(ii) Density and porosity (bulk density)(iii) Volatile FP emission rate (high to low)

Nuclide Mixture, FP Emission, andDecay Calculations(iv) Size of retrieved debris (about 10 cm or less in diameter)(v) Primary nuclide composition ratio
Identify Major
SourceNuclide(vi) Evaluation period
105
104
103
102
101

φ 10 cm
Debris

100
10−1
10−1
10−3

Dose Rate (mSv/h)

1m

Atmospheric
Condition

Calculate Debris Source

Figure 1 - Example of Dose
Rate Calculation under Molten
Debris Layer Conditions
Using PHITS

Surface Dose Rate
Self-Shielding Effect

Dose Rate Calculation (PHITS)

Parameter
Dependence of
Dose Rate

Organize Data (Charts and Formulas)
Figure 2 - Evaluation Flow
©International Research Institute for Nuclear Decommissioning

(1) Estimation of Fuel Debris Properties (Update Fuel Debris List of Fuel Debris
Properties)

13◆ Evaluation of Debris Surface Dose Rates⚫

A unitarily applicable evaluation method was established to estimate molten debris (UO 2-ZrO2) surface dose rates, including MCCI
debris (multiple compositions based on the accident progress analyses), and metallic debris (a metallic layer formed at the bottom
due to density differences). This method is applicable to fuel debris with diverse element compositions and properties.
=> Through trial and error in combining various property parameters in radiation source and PHITS calculations, minimum
parameters were obtained to determine the surface dose rate, and a preliminary evaluation formula was created through function
fitting. (See Formula 1 and Figure 3)
 Example of minimum parameter estimation(Formula 1)

When r = 3 cm and u = 8.9 wt%
2.4E-07

Ri
i
r
p
u
t
Np

⚫

Surface dose rate (Sv/h): Evaluated amount
Photon emission rate function (number of photons/sec): Fitting formula based on combustion, FP
emission, and decay calculations
Surface dose rate response function: Fitting formula based on PHITS calculation
FP volatilization model (low emission, most probable, or high emission): Selected according to theintended purpose
Debris radius (cm): Set based on the sampling plan
Bulk density (g/cm3): Estimated from TMI debris measurements, simulation tests, etc.
Uranium concentration (wt. %): Estimated from accident progress analysis and simulation test
results, etc.
Elapsed time (year): Determined based on the sample analysis plan
Proton number density (number of: Estimated from accident progress analyses, simulation test
protons/cm3)
compositions, etc.

The preliminary surface dose rate was evaluated for case of fuel debris based on theestablished evaluation formula.
−
Example of surface dose rate estimation (average composition of Unit 1, diameter of
6 cm, volatile FP low emission model, 2021)
Molten debris: 56 Sv/h
MCCI debris: 6 Sv/h

The different marker colors representchanges in density.
(Porosity: 0–99%)
Preliminary Ri
evaluation formula(A second degree
polynomial dependent
on r and u)

2.3E-07
2.2E-07

R (mSv/h)
R [mSv/h/(amount/sec)]

DiPi

2.1E-072.0E-07
1.9E-07
1.8E-07

1.7E-07

Molten debris
The rest are MCCI debris
with different compositions.

1.6E-07
1.5E-07
0.0E+00

4.0E+23

8.0E+23

1.2E+24

1.6E+24

2.0E+24

Np

Figure 3 - Correlation between Surface Dose Rate
Response Function (Ri) and Proton Number
Density (Np) for Debris with Various Properties⇒ The impact of elemental compositions and porosity on Ri
can be roughly represented as a function of Np.

What to Expect in FY 2018
In FY 2018, the evaluation formula will be finalized by increasing the number of cases using different FP volatile models and otherparameters. The data and evaluation formula to estimate the sampled debris surface dose rates for various cases will be provided to otherprojects. -> Debris surface dose rates will be reflected in the List of Fuel Debris Properties.
©International Research Institute for Nuclear Decommissioning

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties

14⚫Characterization of MCCI Products with Heterogeneous Properties (FY 2017)[Objectives]
To analyze a large-scale MCCI test product produced in FY 2016 at a test facility owned by France's CEA (taking the 1F conditions into
account) and understand its layer structures, formed phases, and hardness, etc. To analyze measurement data from the MCCI test and clarify
temporal changes in concrete erosion.

[Criteria for Target Achievements]➢ The layer structures of the MCCI test product are illustrated.
➢ Typical formed phases and hardness are shown for each layer with different characteristics.
➢ Temporal changes in concrete erosion from the MCCI tests are shown.

(End of FY 2017 - Completed)(End of FY 2017 - Completed)(End of FY 2017 - Completed)• In the 1F's Primary Containment Vessel, reactions (MCCI) occurred between molten core fuel and concrete on the vessel floor. Core
materials, such as uranium dioxide, zircaloy, and stainless steel, were melted and mixed with concrete components, producing
various compounds (MCCI products).
• Since there is no knowledge about MCCI products even in TMI-2, their behaviors and properties must be reviewed.
• MCCI products’ properties, such as formed phase and hardness, are expected to vary depending on their locations in the vessel,
and information on such “heterogeneity of properties” is extremely important to understand fuel debris conditions inside the vessel
as well as to review retrieval tools and methods.

Large-Scale MCCI Test in FY 2016
• In this large-scale MCCI test, MCCI
products were produced while taking
the 1F conditions into account and the
profile (range of concrete erosion andoverview of erosion profile) was
obtained for the final test section.
• Metals/oxides were identified based on
the obtained products’ characteristics,
test sample’s dismantling status, etc.

Initial loadingmaterial (UO2 +ZrO2+Zr +stainless steel)

Cylindermade of
ZrO2

Coil for highfrequency
induction
heatingCavityLayer of lower
density oxides

Layer of higher
density oxides

Concrete specimen

Layer with a lot of
metals and metallic
luster, adhered withmagnets

Figure 1 - Cross-Section of Testing Equipment Figure 2 - Cross-Section of MCCI
Test Product and Concrete Test
samples©International Research Institute for Nuclear Decommissioning

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties
Large-Scale MCCI Test in FY 2016

<Large-scale MCCI Test: Product Appearance>

Glass, Orange-Colored Phase

State Before Dismantlement (After
Removing Upper Cylinder)

Metal Particles

Layer Structures

Image of Product Cross-Section

After Removing Majority of Molten
Substances©International Research Institute for Nuclear Decommissioning

15

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties

Particulate• Outflowed andscattered powder

Crust

Heat Deterioration Layer• Solidified
surfaces• Thin heat-deteriorated portion

Composite Phase• Metal particles of a few
millimeters and glass phases
are contained in various places.

Air Holes & Stratification
Cavity• A low-density molten oxide layer witha number of air holes that is slightly
hard to crush.

Air Holes & Stratification• A high-density molten oxide layer
with a few air holes that is hard to
crush.

Air Holes & Stratification

Separated Oxide and Metallic Layer• A layer with many metals thatis hard to crush.

Concrete• Increased number of air holes atthe concrete boundary

Figure - Layer Structure Drawing of MCCI Test Product(Large-Scale MCCI Test Product in FY 2016)©International Research Institute for Nuclear Decommissioning

16

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties

17◆ Analysis of Large-Scale MCCI Test ProductAchievements in FY 2017•

As the main objects of analysis, 10 samples were sampled from each structural layer (see Figure 1) to determine each layer’s
tendencies in formed phase, hardness, etc.
Upper Crust
Upper Oxide Layer/Top
Table 1 - Analysis Items and Methods

Analysis Item

MethodMicrostructure & Local
Composition

SEM/EDS

Crystalline Structure

XRD

Microhardness

Indenter Indentation
MethodBulk Density

Dipping Method

Average Composition

Dissolution & Solution
Analysis

Particle Size Distribution(For particles generated bysevering with a grinder)

Upper Oxide Layer/Dust
Accumulated During
Dismantlement

CavityUpper Oxide Layer/Bulk

Upper Oxide
Layer/Concrete Side
Boundary

Lower Oxide Layer/Bulk

Lower Oxide
Layer/Concrete Side
Boundary
Concrete

Screening
Bottom
Metallic Layer

Lower Oxide
Layer/Metallic Layer
Boundary

Lower Oxide
Layer/Concrete Bottom
Boundary

Figure 1 - Test samples Sampling Positions©International Research Institute for Nuclear Decommissioning

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties◆ Analysis of Large-Scale MCCI Test ProductAnalysis Results• Gas pockets of roughly 5 mm were distributed (porous)in every portion.
Upper Crust• In test samples mainly consisting of oxides, such as
upper crust and upper/lower oxide layers, U-Zr oxide, andSide
oxides composed mainly of Cr, were deposited in a
Boundary
matrix composed predominantly of Si (and includes Ca
and Al). With XRD, compounds were found, including
Bottom Boundary(Metallic)cubic crystal (U1-xZrx)O2, tetragonal ZrO2, spinel phase(e.g., FeCr2O4), and SiO2 (cristobalite) in qualitative
analysis.
• The metallic layer at the bottom boundary was an alloy
composed mainly of Fe.
• No significant differences were found in both formed
phases and hardness for different sampling positions.
• For physical properties (e.g., hardness), roughly thesame values were obtained as the “Fuel Debris List of
Fuel Debris Properties”.

Element Mapping for Bottom
Boundary Cross-Section

Upper Oxide
Layer
Lower Oxide
Layer

Element Mapping for Upper Crust CrossSection

Element Mapping for Lower Oxide Layer CrossSection

In the large-scale MCCI test that takes the 1F conditions into account, it was confirmed that no significant differences were found interms of formed phases and physical properties between this test and assumptions that had been made based on the past fundamental
test results, etc.
©International Research Institute for Nuclear Decommissioning18

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties◆ Temporal Change in Concrete Erosion Profiles

10:28 (62 min after heating)
10:31 (65 min after heating)
10:33 (67 min after heating)

Cylinder made of ZrO2

10:36 (70 min after heating)

Simulated fuel material

10:44 (when heating ended)
Thermocouples

Thermocouples

Coil for highfrequency
induction heating

10:26 (60 min after heating)

Thermocouples

Concrete specimen (1F
concrete components are
simulated)

Power (kW)Figure - Large-Scale MCCI Test Equipment---- Initial Position of Concrete Wall･: Initial Position of Thermocouple (Orientation: 0–180°), ･: Initial Position of Thermocouple (Orientation: 90–270°)○: Broken Thermocouple (Orientation: 0–180°), ∆: Broken Thermocouple (Azimuth: 90–270°)

Figure - Positions of Broken Thermocouples at Each Point in Time

[Heating Started at 9:26 and Ended at 10:44]➢ Inspected temporal changes in thermocouples installed in the test equipment(inside the concrete portion) as they broke (melted) to understand the stateof erosion in the concrete portion.
=> It was discovered that erosion proceeded radially (i.e., laterally) at the initialstages of fusion and erosion proceeded axially (i.e., downward).
New knowledge has been acquired the state (progress) of erosion under the 1F
conditions.

Figure - Changes in Heating State of Corium by Induction Heating (FY 2016)©International Research Institute for Nuclear Decommissioning

19

(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties

20◆ Recommendations for Decommissioning Work(Cutting and Processing the Fuel Debris) Based on
Test Results
Based on the characteristics of the appearance and changes in the working environment observed during the dismantling process,recommendations on how to retrieve fuel debris using mechanical methods while supplementing the sample analysis results were summarized.

Characteristics Observed During
Dismantling Process(Appearance & Working Environment)

Sample Analysis Results of This Test
(Formed Phases, Hardness, Compositions, etc.)

Recommendations

The debris is highly porous andappears to be brittle, but is actually
very tough.

Gas pockets of roughly 5 mm are distributed
throughout. Hardness is 5–22 [GPa] for the oxide
phase and 1–3 [GPa] for the metallic phase.

It is difficult to select optimal tools based only on observing the air holes. Therefore, itis thought to be necessary to refer to the maximum hardness values obtained in thistest and select components made from materials with equivalent hardness (stainlesssteel or alumina).

Significant quantities of powder dust
were generated during the dismantlingprocess.

Properties of a powder dust sample:
Particles smaller than 1 [mm] take up about 40% of thepowder dust sample’s weight. Contains 20–33 [wt%] ofU.

During dismantling in atmospheric conditions, measures against rapid visibility
deterioration caused by fine powder dusts, including nuclear materials, must be taken,
as well as against the possible impact of powder dusts on radiation monitoring.

Crust formation

Properties of upper crust sample: Deposits such as(U,Zr)O2 and (Cr,Fe)Ox are present in a Si-Al-Ca oxide
matrix. Hardness is 5–18 [GPa]. Formed phases andhardness are roughly the same as other samples.

In this test, microstructures and hardness of the crust turned out to be similar to thoseof the molten pool area. However, in an actual accident progression scenario, where
surfaces are rapidly cooled by water injection, harder phases may be formed
compared to the molten pool portion.

Particulate debris was observed.

-

Handling tools (for suction or scooping) and separation of solid‐liquid in the water
treatment system may be necessary.

A heat deteriorated concrete layer ispresent.

-

Not suited for grabbing due to its brittleness.

Air holes & stratification wereobserved.

Air holes of roughly 5 mm are distributed in both theupper and lower parts.

It is necessary to check for the impact that different degrees of air holes
sparsity/density will have on the criticality evaluation.

Oxide and metallic layers wereseparated.

Metallic layer: Mainly comprised of Fe-Ni alloy.
Hardness is up to 3 [GPa]. It is hard to crush this layer
while preprocessing analysis samples.
Oxide layer: (U,Zr)O2 and (Cr,Fe)Ox were deposited in
the Si-Ca-Al oxide matrix (hardness: 5–12 [GPa]).

It is difficult to crush the metallic layer by impact. Since oxide and metallic layers havedifferent mechanical properties, it is necessary to detect the change in layers whendifferent tools are required for each layer.

©International Research Institute for Nuclear Decommissioning

(2) Characterization Using Simulated Debris(ii) Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment⚫Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment (FY 2017 and FY 2018)[Objectives]
For a drying facility under consideration as a preprocessing facility before storing fuel debris, basic data is required on fission
products (FPs)’ heat emissions. The data will be used as a basis for considering the design of the off-gas processing facility
including its safety.
Behaviors of volatile FPs during the drying treatment are important information when considering the need for, and processing
methods of, collected FPs’ off-gas processing. Therefore, this evaluation sorts out information on volatile FPs (especially medium
volatile FPs with high environmental toxicity) and off-gas design collections of existing plants, and evaluates emission behaviors
of medium volatile FPs based on tests, etc.
[Criteria for Target Achievements]➢ Medium volatile FPs with high environmental toxicity are identified.
(End of FY 2017 - Completed)➢ Emission behaviors of medium volatile FPs, such as emission start temperature and emission speed, are evaluated.
(End of FY 2018)

 Highly volatile FPs -> The entire amount is emitted.
✓ Cs, I, noble gases, etc.
✓ Design based on the assumption that FPs are emitted
 Medium volatile FPs -> Partially emitted.
✓ FPs which are highly likely to be emitted under dry heat treatment conditions✓ It is necessary to consider design loads, etc. caused by emission for each FP
 Low volatile FPs: Not emitted.
✓ FPs which are highly unlikely to evaporate due to their high melting points, such as Ac and its compounds©International Research Institute for Nuclear Decommissioning

21

(2) Characterization Using Simulated Debris(ii) Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment
Achievements in FY 2017

Table 1 - Evaluation of Nuclides1) with High Environmental Toxicity (Unit 3)➢ Evaluation of FP Emission Behaviors
NuclidesEvent Specific to 1F (Differences with TMI-2)

22

Radioactivity [Bq]
After 10 Years fromthe Accident

Dose
Coefficient[mSv/Bq]

Environmental
Toxicity(Exposure
Dose) [mSv]

Compounds2) estimated to begenerated*1(From a viewpoint of impacts on FP emission behaviors)◆ The fuel burnup is higher, and the fuel has a higher
FP content, in the 1F accident.
◆ Fuel debris containing concrete is present due to MCCI.

*2*3⚫The same drying conditions as TMI-2 are highly unlikely to be applicable.
⚫It is essential to enhance basic data to cover a wider range.
Example: From room temperature to 1,000°C strong (assuming the reduction of concrete's
moisture content)➢Selection of Nuclides with High Environmental Toxicity
Environmental Toxicity = (Inventory [Bq] After 10 Years from the
Accident) x (Dose Coefficient [mSv/Bq]) ----- (Table 1)

*4

*5

*6

In addition, compounds with greater impacts were identified bycomparing the following conditions and vapor pressure.

H*7◆ Nuclides that can be emitted entirely without any problem: Excluded◆ Conditions of compound with lower vapor pressure than UO3: Excluded

Candidates are Ag, Te, and oxides of Te, Sn, and Cd*1 Pu238, Am241, Pu241, Pu240, Cm244, and Pu239*2 Am243, Am242m, and Cm243*3 Eu154, Pu242, Pm147, Cs134, and Cm242*4 Eu152, Zr93
*5 Fe55 Np239*6 H3, Ni63, Co60, Sn121m, Pm146, Kr85, U237, and Pr144*7 Sn119m, Sn121, Rh106, Sb126, Np238, Pr144m, Sb126m, Mn54, Gd153, and Rh102

1) Nuclides whose impact on the environment is negatively evaluated when emitted
Specifically, for each nuclide, the product of the mount of radioactivity in fuel debris after ten years
and the dosimeter count were calculated and compared.
2) Compounds that may be generated under severe accident conditions©International Research Institute for Nuclear Decommissioning

(2) Characterization Using Simulated Debris(ii) Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment➢ Review Methods for Measuring FP Emission Behaviors
Test methods were reviewed using simulated debris manufactured with Ru, whose
behaviors are well known.
==> Confirmed that FP emission behaviors and emission speed can be measured
using TG-DTA*.
Test results: Heating test under air atmosphere (See Figure 1)◆ By measuring the temperature at the point when a specimen’s weight starts to decrease==> Possible to evaluate the emission start temperature◆ By measuring temporal changes in a specimen’s weight ==> Possible to evaluate theemission speed

23

Weight reduced due to
Ru emission

Weight increased due tooxidation of Ru and UO2Temperature range where
the weight starts to decrease

As part of our review of emission behavior evaluation methods, a method using vapor
pressure, etc., based on the existing evaluation formula, is under consideration.
Figure 1 - Weight Change by Heating the Simulated Debris
Containing Ru under Air Atmosphere

What to Expect in FY 2018
➢ Obtain & Evaluate Emission Behavior Data for Medium Volatile FP⚫ Emission Behavior Evaluation Test
Emission behaviors will be measured and evaluated formedium volatile FP nuclides(candidates: Ag, Te, and oxides of Te, Sn, and Cd) by applying the technology describedabove. Figure 2 shows the vapor pressure curve of candidate oxides.
⚫ Analyze Emission Behaviors
In response to our evaluation method review, as mentioned above, a better understandingof FP emission behaviors and evaluating FP nuclides that are hard to experiment on will becontributed to.
* Thermogravimetry/differential thermal analyzer: Measures weight changes in a specimen when its
temperature increases at a constant rate.
By looking at weight changes, it is possible to estimate the specimen's behaviors, including
volatilization/evaporation and oxidation.

Figure 2 - Vapor Pressure (Calculated Value) ofMajor Compounds in Nuclides with High©International Research Institute for Nuclear Decommissioning
Environmental Toxicity

(3) Develop Element Technologies for Analysis on Fuel Debris and Other Materials
24(i) Prepare for Fuel Debris Sample Analysis⚫Prepare for Fuel Debris Sample Analysis (FY 2017 and FY 2018)[Objectives]

To analyze a very small amount of fuel debris that is expected to be obtainable from inside the reactor bysampling before the Okuma Analysis and Research Center starts operating a facility currently under preparation,
it is necessary to make preparations so that 1F samples including fuel debris can be analyzed in the existing
analysis facility.
To this end, analysis items (including fuel debris composition and mechanical properties) to be conducted in theexisting facility are reviewed and appropriate procedures for each item prepared.
[Criteria for Target Achievements]➢ Appropriate procedures are prepared for each analysis item to be conducted in the analysis facility. (End of FY 2018)

Achievements in FY 2017
Prepare Procedure Documents for Existing Analyzers & Methods• Of all candidate analysis items, the preparing of procedure documents for 12 highpriority items (3 preprocessing items and 9 analysis items, as shown in the table
to the right) was started, reflecting considerations and information applicable todebris analyses.
Prepare Procedure Documents for Analysis Methods Developed through Element
Development• Analysis procedure documents for each technical development item of debris
specimen dissolution methods, quantitative element analysis using ICP-AES*,
porosity measurement using X-ray CT, and measurement of γ ray nuclide
distribution were prepared.

Preprocessing Items
Cut out and powderize debris samples
Embed resin and mirror polish debris
Preprocess various analysis samples with solutions
Analysis of Items
Observe shape and measure dimensions with an optical microscope
Observe surfaces/cross-sections using SEM/EPMA and analyze
elements qualitatively/quantitatively
Measure chemical structures using X-ray diffraction analysis (XRD)
Determine powder classification and particle size distribution
Analyze elements qualitatively/quantitatively using TIMS
Quantitatively analyze α nuclides
Quantitatively analyze γ nuclides
Measure hardness and toughness
Measure uniaxial compressive strength* High-frequency inductively coupled plasma emission spectrometry©International Research Institute for Nuclear Decommissioning

(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
a. Develop Technologies for Dissolution and Multi‐Element Analysis of Fuel Debris

25⚫Develop applicability of a dissolution method, using alkali fusion and a multi‐elementary analysis technology, using ICP-AES(FY 2017)[Objectives]
To ensure proper elementary analysis in fuel debris, it is necessary to develop a dissolution method for fuel debris with poor solubility and an analysis
technology for such solutions. To this end, the applicability of a dissolution method is reviewed, using alkali fusion in preprocessing, for analyzing
compounds contained in fuel debris, which have not been reviewed so far. A multi‐elementary analysis technology for fuel debris solutions after alkali
fusion using ICP-AES is also developed. Note that target elements are 13 elements* that need to be analyzed (U, Pu, Zr, Fe, Gd ,Al, B, Ca, Cr, K, Mg,
Ni, and Si).
[Criteria for Target Achievements]➢ The conditions are identified for simulated materials to be completely dissolved. For undissolvable materials, complementary treatment methods areprovided, including acidic dissolution.
(End of FY 2017 - Completed)➢ Analysis procedures are provided for elementary analysis using ICP-AES.
(End of FY
Completed)
Test Target Substances
Time 2017
to Fusion-(min)Tested Year
OxidesAchievements in FY 2017
◆ Dissolution of Fuel Debris
Of all simulants (test target substances) listed in the List of Fuel Debris Properties, those that
had not been tested by FY 2016 (Cr2O3, Fe3O4, ZrSiO4, B4C, ZrB2, and Fe2B) were reviewed
for the applicability of alkali fusion (sodium peroxide) and their conditions were identified.

Major fusion conditions
Test samples particle size: 90 μm or less
Fusion agent ratio: 10(Fusion agent (sodium peroxide) 0.5 g : specimen 0.05 g)
Fusion temperature: 750°C

ZrO2

15

2015

(U,Zr)O2
SiO2
Al2O3

30
15
15

2016
2015
2015

Cr2O3

15

2017

Fe3O4

15

2017

ZrSiO415

2017(U,Pu,Zr)O2
MetalsZircaloy 2Zr(O)SUS316Fe2Zr
Borides, etc.
B4C

30

2017

30
15
60
15

2016
2016
2016
2016

15

2017

ZrB2

15

2017

Fe2B
Mixtures
ZrO2+SUS316(U,Pu,Zr)O2+SUS316

15

2017

15

2016

30

2017

Table 1 - Test Target Substances and Time to Fusion* Derived from reactor core fuel: U and Pu; from cladding/structural materials: Zr, Fe, Gd, Al, B, and Ni; from concrete: Ca, Cr, K, Mg, and Si©International Research Institute for Nuclear Decommissioning

(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
a. Develop Technologies for Dissolution and Multi-Element Analysis of Fuel Debris
Simulated Debris Test
samples◆ Developing a Multi-Element Analysis Technology

Crushed with stamp
mill: 300 or more times

Simulated MOX* debris samples were prepared and tested for
applicability of alkali fusion (using sodium peroxide) to acquire dataon debris dissolution.

Particle size: ≤ 90 [μm]Dispensed amount:
50-100 [mg]Heating

U (wt%)

Transfer the specimen to anothercontainer using water and diluted
nitric acid (about 15 ml in total)

Dissolving with Acidand Heating

Dissolve the specimen withapproximately 4 mol/L of nitric acid

Measuring a
Fixed Volume

Zr (wt%)Round 1

1.1

30.8

43.3

Dispensing

Round 2

1.1

31.8

43.4

Diluting

Round 3

1.1

42.0

Average

1.1

30.9

42.9

Cv

2.8%

1.5%

1.9%

Pu
ICP-AES Measurement
Procedures

Adjusting Acid
Concentration
Nitric acid concentration:
8 [mol/L]

Extracting Solid
Phase
Calculating Si and Pu
by correction

Quantitative Analysis on 9
elements*
Provisional measurement of 4
elements**

Resin: U/TEVA-Resin

Adjusting Acid
Concentration*9 elements:**4 elements:* Mixed Oxide: U-Pu mixed oxide fuelTemperature:
750[C]
Time: 30 [min]Retrieving Melt

Basic
Measurement

31.4

Crucible: Ni or Al2O3

Cooling

Table 1 - Alkali Fusion Analysis Results for Simulated MOX Debris (Example)

Pu (wt%)Fusion agent: Na2O2
Input amount: 0.5–1.0 [g]Dispensing

Mixing Test
samples and Fusion
Agent==> It was confirmed that dissolution and elementary analysis using
ICP-AES measurement are possible with MOX-simulated
debris based on established analysis procedures.

Simulated MOX
Debris Test
samples

FusionProcedures

Crushing
Dispensing andClassification

26

Quantitative Analysis
on Si, Al, and Ni

Basic Procedures of Sodium Peroxide©International ResearchInstitutefor Nuclear Decommissioning
Fusion
Method(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
b. Developing Fuel Debris Analysis Technology Using X-ray CT

27⚫Establish a Porosity Measurement Technology (FY 2017)[Objectives]
To establish a porosity measurement technology. Porosity information is reflected in the estimation of the water and other material
content in air holes and contributes to the evaluation of hydrogen generation and criticality control.
⚫Establish a Fuel Debris Component Identification Technology (FY 2017)[Objectives]
To establish a technology for identifying components with nondestructive measurement methods to confirm fuel debris components inadvance.
[Criteria for Target Achievements]➢ Analysis procedures are provided that enable the measurement of porosity using X-ray CT.
(End of FY 2017 - Completed)➢ Analysis procedures are provided that enable component (material) identification by comparing density evaluation results from X-ray
CT and nuclide distribution evaluation results from γ ray tomography measurement.
(End of FY 2017 - Completed)

Achievements in FY 2017
◆ Establish a Porosity Measurement Technology

Porosity Evaluation Formula Based on X-Ray CT Image(created in FY 2016)

Porosity (%) = 1 −Gas Pocket

𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐶𝑇𝑉𝑎𝑙𝑢𝑒 𝑜𝑓 𝑇𝑎𝑟𝑔𝑒𝑡 𝑆𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒𝐵𝑎𝑠𝑒𝑙𝑖𝑛𝑒𝐶𝑇 𝑉𝑎𝑙𝑢𝑒

Baseline CT Value: CT value of a portion (base material) without air holes

Base Material (Metal Portion)

Appearance of Simulated Debris Test samples X-Ray CT Image of Simulated Debris Test samples

It was confirmed that porosity can be measured using X-ray CT with anequivalent accuracy to the conventional method that uses optical
microscopes.

Porosity Evaluation Results
X-Ray CT Image
Optical Microscope
Image (for reference)

22%
23%

©International Research Institute for Nuclear Decommissioning∗ 100

(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
b. Developing Fuel Debris Analysis Technology Using X-ray CT
Achievements in FY 2017
◆ Establish Fuel Debris Component Identification Technology
Fuel debris components are difficult to determine by appearance alone. Understanding their distribution, using nondestructive
technologies and reviewing them in relation to their detailed sampling positions, made identifying fuel debris components more accurate.
Density (g/cm3)

Metallic Holder
Crucible

Molten ZircaloyArea

CT Value Is
Converted
into Density

Unreacted
Fuel Area

Test samples*
Appearance

X-Ray CT Image

Density Distribution

γ Ray Intensity
High

Test samples: Crushed fuel and shredded cladding (zircaloy)
are placed into a crucible, in that order, and heated to a hightemperature.

It was confirmed that components of test samples (fueland cladding portions) can be identified based on the
combination of density distribution from X-ray CT
image and γ ray emission nuclide distribution from γ
ray tomography measurement.

Low(Eu-154: 1274 keV)

(Co-60: 1332 keV)

γ Ray Emission Nuclide Distribution (γ Ray Tomography Measurement)©International Research Institute for Nuclear Decommissioning28

(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
c. Develop Multiple Nuclide Rationalization Analysis Technology with ICP-MS⚫Impact Assessment and Removal Test of Interfering Ions (FY 2017 and FY 2018)[Objectives]
When analyzing a particular nuclide contained in a fuel debris sample using ICP-MS, other nuclides in thesample may interfere with analysis. The new model ICP-MS reviewed in this project may reduce the impact
from interfering nuclides significantly. To this end, interfering nuclides need to be identified, their impact on theanalysis (i.e., the type and degree of interference) understood, and appropriate analysis conditions to remove
their influence reviewed. Furthermore, in cases where their impact cannot be ignored, the interfering nuclides
need to be properly removed.
In this project, the impact of interfering ions is evaluated and removal methods for ions established, whennecessary, based on the review conducted in FY 2016.
 Overview of New Model ICP-MS (ICP-QQQ-MS)
Ionization andIntroductionof Ions

After passing through the first quadrupole, ions react with gas in the reaction cell to change the mass-to-charge ratioof their chemical forms and separated again in the second quadrupole.

1Q

Reaction Gas (O2)2Q

Detectionof Ions

Interface &IonizationPart

Detection
Part
First quadrupole (m/z 80): All ions are
removed except those at m/z 80.

Cell

Second quadrupole (m/z 96): All ionsare removed except those at m/z 96.

Through Q1, only ions at m/z 80 ions may enter the cell. Consequently, Zr, Mo, and Ru do not pass through Q1. 80Se reacts with
O2 gas to produce SeO+. In 2Q, SeO+ are measured at m/z 96.
(Source: Agilent 8800 Triple Quadrupole ICP-MS Catalogue, Agilent Technologies)©International Research Institute for Nuclear Decommissioning29

(3) Developing Element Technologies Analysis on Fuel Debris and Other Materials(ii) Developing Element Technologies Required for Analysis
c. Develop Multiple Nuclide Rationalization Analysis Technology with ICP-MS

30[Criteria for Target Achievements]➢ Ions that need to be removed are identified. Target removal rates are set.

(End of FY 2017 - Completed)➢ Methods for removing the above-mentioned ions are identified and the feasibility of such removal methods is verified.

(End of FY 2018)

Achievements in FY 2017

◆ Test to Identify Interfering Nuclides
Using ICP-QQQ-MS and solutions that contained potential interfering nuclides, including matrix components reviewed in FY 2016,any peak that affected the mass number of target nuclides was checked for and ions requiring removal were identified.
• Sorted out information on the presence of interfering
nuclides and isotopes and lower limits of detection fortarget nuclides. Target concentrations for removing
interfering nuclides were calculated to be 1/10 of thevalues listed in “Baseline Dose Equivalent
Concentration in Vertical Shaft Disposal.” (Table 1)• Sorted out information on potential interfering ions fortarget nuclides. (Table 2)• Gained an outlook that, for Zr, measurements could bemade while removing interference from Nb and Mo
through a mass shift using NH3 gas.

Table 1 - Concentration List for Removing Interfering Nuclides (No Gas
Mode) using Lower Limit of Detection and the “Baseline Dose Equivalent
Concentration in Vertical Shaft Disposal” as Indexes
Target Nuclide

Minimum Baseline Dose
Equivalent Concentration(Rubble/Vertical Shaft) (ppb)

Interfering
Nuclidederived ions(%)

Lower Limit ofDetection (ppb)

Lower Limit ofDetection (ppb)

Se-79

Concentration for
Removing Interfering
Nuclides (ppb)

Table 2 - Interfering Ions andInterfering Ion
Generation* Rate
Generation Rate
Shown in red are FPTarget Nuclide

1.57E-01(Se-78)0.01 or less0.01 or less0.01 or less0.01 or less0.01 or less

I-129

What to Expect in FY 2018
• In succession to Zr, tests for removing
interfering nuclides for target nuclides analyzed
including Ni‐59 and Ni-63 will be conducted to
identify appropriate removal methods.

0.01 or less

1.42E-03(I-127)

Eu-151

5.91E-05

2.33E+01 2.33E+00

0.01 or less* Concentration of interfering nuclides when the signal strength is at 10% of thebaseline dose, the equivalent concentration of nuclides being analyzed

Note Percentage of interfering ions generated in target nuclides calculated
based on detected signals (i.e., the number of counts)* The evaluation is based on estimates using stable nuclides since
the tests were conducted in a cold environment.
Measurements
not been madefor α nuclides.
©International ResearchInstitute havefor Nuclear
DecommissioningProject Summary (1/3)31(1) Estimation of Fuel Debris Properties
 Estimate Dose Rate Near the Surfaces of Debris
By conducting γ ray source calculations based on nuclide decay generation calculations and numerous γ raytransportation calculations simulating sampled fuel debris, dominant factors of the surface dose rate including fueldebris properties were identified, and an evaluation formula to estimate the surface dose rate using these factors as
variables was developed. Using this evaluation formula, surface dose rates of Unit 1 fuel debris and MCCI debris
were calculated.
 Update the “Fuel Debris List of Fuel Debris Properties”
The “Fuel Debris List of Fuel Debris Properties” in FY 2016 was updated, with calculated surface dose rates of fueldebris and property data (e.g., hardness) obtained through analyzing the product of a large-scale MCCI test
conducted at CEA in France.
(2) Characterization Using Simulated Debris(i) Characterization of MCCI Products with Heterogeneous Properties
10 test samples collected from various portions of the product obtained in the large-scale MCCI test conducted at
CEA in France in FY 2016 were analyzed for their phase state, hardness, etc.
It was confirmed that all product portions were porous and had a structure that contained fine particles, including UZr oxide and oxides composed mainly of Cr, in a matrix of Si-Ca-Al oxides. It was also confirmed that the metallic
layer near the bottom boundary consisted mainly of Fe alloys.
Physical properties were roughly the same as those listed in the “Fuel Debris List of Fuel Debris Properties.”
The greater tendency for erosion in the axial direction by estimating temporal changes in the concrete’s erosion
profile during the MCCI test based on data from thermocouples installed in the concrete samples was also
confirmed.
Recommendations were put together for reactor Decommissioning Work(cutting and processing fuel debris) basedon the working conditions observed during a dismantling process for the MCCI test product in FY 2016 and analysis
results from this year.
©International Research Institute for Nuclear DecommissioningProject Summary (2/3)32(2) Characterization Using Simulated Debris(ii) Evaluate Emission Behaviors of Fission Products During Dry Heat Treatment
 Select Medium Volatile FPs with High Environmental Toxicity
Nuclides whose public exposure dose limit exceeds 1 mSv/year according to the ICRP recommendation were definedas “nuclides with high environmental toxicity.” Data on these nuclides based on radioactive nuclides’ activity after ten
years from the 1F accident was sorted out. Meanwhile, data on compound forms under dry heat treatment conditions
was sorted out, and vapor pressures calculated and compared. FPs whose vapor pressure is higher than that of actinideoxide (UO3) used as the fuel and lower than that of highly volatile Cs were defined as “medium volatile FPs.”
Based on the evaluation results above, Ag, Te, and oxides of Te, Sn, and Cd were selected as candidates for “medium
volatile FPs with high environmental toxicity.” Confirm Evaluation Methods for FP Emission Behaviors
Differential thermal/thermogravimetry measurement were selected as an evaluation method for emission speed, taking
dry heat treatment conditions into account. To validate the differential thermal evaluation method, a test using a
differential thermal/ thermogravimetry measurement on simulated debris containing FPs with a mixture of UO2-ZO2 andRu was conducted. It was confirmed that the emission start temperature and emission speed could be evaluated.
It was confirmed that, with the differential thermal/thermogravimetry measurement, the evaporation start temperature
could be obtained based on weight changes in test samples during a constant-rate heating test where the specimen’stemperature increased at a constant speed. It was also confirmed that the evaporation speed at a specific temperature
could be obtained based on the slope of weight changes during an isothermal heating test where a specimen is heatedat a constant temperature.
(3) Develop Element Technologies Analysis on Fuel Debris and Other Materials(i) Prepare for Fuel Debris Sample Analysis
The preparation of procedural documents for analyzing fuel debris, etc. was started at existing analysis facilities using
such facilities’ equipment with proven records and applicability for fuel debris analysis.

©International Research Institute for Nuclear DecommissioningProject Summary (3/3)(3) Develop Element Technologies Analysis on Fuel Debris and Other Materials(ii) Develop Element Technologies Required for Analysis
a. Develop Technologies for Dissolution and Multi‐Element Analysis of Fuel Debris
To verify the applicability of alkali fusion for substances listed in the “Fuel Debris List of Fuel Debris Properties,” analkali fusion test was conducted with sodium peroxide on six types of substances, including chrome oxide, and theconditions that allowed full dissolution of these substances was confirmed. Following the prepared analysis flow, anelementary analysis was conducted using ICP-AES measurement on MOX-simulated debris after dissolving it, thealkali fusion method, and our analysis flow were validated.
b. Develop Fuel Debris Analysis Technologies Using X-Ray CT
To establish a quantitative porosity evaluation technology using X-ray CT, it was confirmed that the technology wasapplicable to fuel debris with a complex profile. It was also confirmed that, based on the porosity evaluation results,
the technology enabled quantitative evaluation with an accuracy equivalent to the conventional evaluation methodthat uses optical microscopes.
For establishment of a fuel debris component analysis technology using X-ray CT and γ ray tomography, X-ray CT
scanning and γ ray tomography measurement on test samples containing a mixture of fuel and cladding components
were conducted, and it was confirmed that the technology could be used to analyze fuel and cladding components.
c. Develop a Multiple Nuclide Rationalization Analysis Technology with ICP-MS
In reviewing an analysis technology using ICP-MS, information on interfering nuclides and molecular ions thatinterfere with measurement of target nuclides was sorted out, and, as an objective for removing interfering nuclides,
reference values were set at 1/10 of those listed in the “Baseline Dose Equivalent Concentration in Vertical Shaft
Disposal.” Whether the interfering nuclides and molecular ions that were generated interfered with target nuclides
was also checked.
Zr is difficult to separate as a target nuclide, and Nb and Mo are interfering nuclides for Zr. It was found that Zr
could be measured separately by removing interference from Nb and Mo through a mass shift caused by introducing
NH3 gas during ICP-QQQ-MS measurement.
©International Research Institute for Nuclear Decommissioning

33