fitt heating tests and 3d image analysis of agr-2 particles
TRANSCRIPT
art.inl.gov
• Advanced Reactor Technologies
• Idaho National Laboratory
Gas-Cooled Reactor
Fuels and Methods Program Review
June 18-19, 2019
FITT Heating Tests and 3D Image
Analysis of AGR-2 Particles
Tyler Gerczak
ORNL R&D Staff
FITT Heating Tests
2
Furnace for Irradiated TRISO Testing (FITT)
• Safety-testing provides valuable insight on the integral release behavior of fission products from compacts (diffusive release and particle failure) in particular:
Continued release of Ag-110m and Eu-154 at 1800oC
“Goldilocks” release of Ag-110m in Compact 4-2-2 at 1150–1300oC (Multi-temperature test)
• CCCTF Safety-testing has limitations:
Does not allow for direct confirmation of diffusive release from intact particles (release occurs simultaneously from Matrix, OPyC, and particle)
Long duration operation is not feasible due to planned work scope and cost
• A need exists to provide long term thermal exposures to observe release from intact particles below 1800oC
Supplement safety-testing observation to provide insight on diffusion kinetics to support fuel performance models
3
Fractional release measurements of 154Eu
from AGR-1 Compacts exposed to 1800oC
for 300 hours, Compacts 4-4-1 and 4-3-2
were AGR-1 V3, while Compacts 3-2-3 and
5-1-3 were AGR-1 V1 and showed a
difference in release behaviors.
R.N. Morris et al., “Performance of AGR-1 high-
temperature reactor fuel during post-irradiation
heating tests,” Nucl. Eng. Des., 306, 24-35
(2016).
FITT: Intentionally Simple
• Flexible, intentionally-simple, cost-effective capability to heat small batches of irradiated TRISO particles up to 1700oC
System is ceramic tube in box furnace containing 10-30 particles in a graphite holder under flowing Ar
Two systems have been installed in the Irradiated Fuels Examination Laboratory (IFEL) at ORNL
Expands testing envelop established by the integral release tests in the Core Conduction Cooldown Test Facility (CCCTF) and Furnace Accident Condition Simulator (FACS) to observe fission product release over a broader range of conditions
• Fission product release experiments
Isolate release from intact particles by exploring “burn-back” particles (no OPyC or matrix release) via individual particle gamma analysis before an after exposure
Currently exploring long term thermal exposures to measure 154Eu release from AGR-2 Compact 542 burn-back particles
Plan to measure 110mAg release from AGR-5/6/7 particles
4
Image of FITT system in IFEL
hood
Status of FITT Effort
• Testing initially focused on exploring the elevated release of Ag-110m in the “Goldilocks” temperature regime and continued release at long term thermal testing at 1600oC for both Ag-110m and Eu-154
• Initially planned to explore silver release, but this is no longer viable due to decay (little EOL inventory remains for AGR-2 Ag-110m)
5
Temperature (oC) T1 (h) T2 (h) T3 (h)
1150 100 500 1000 (in progress)
1300 100 500 1000 (in progress)
1600 100 500 1000
FITT Test Matrix
Initial Results: Eu-154 release
• Focusing on Eu-154
Average particle release of 13% at 1300oC, 500 h
2% total inventory at 1150oC, 500 h
Indication of matrix’s ability to hold onto Eu-154?
• FITT operational feasibility has been demonstrated
Established process is ready for exploring silver release in AGR-5/6/7
• Continuing planned exposures to understand europium release/diffusion
6
1300oC, 500 h exposure of AGR-2 Compact 542
particles showing relative change in inventories of Ru-
106, Cs-137, and Eu-154. Initial results indicate
(diffusive) release of Eu-154.
3D Image Analysis of AGR-2 Particles
7
Understanding fission product distribution at IPyC/SiC using 3D reconstruction image analysis
• The IPyC/SiC interface is a sink for fission products and actinides (FP&A)
• The IPyC/SiC interface plays an important role in governing local SiC corrosion (SiC failure) and FP&A uptake and diffusion across the SiC
• The nature of FP&A interaction at the IPyC/SiC interface varies considerably
• Defining the role of IPyC open porosity and interfacial stitching in FP&A distribution can provide insight on factors influencing FP&A interactions with the SiC layer and potential for mitigating approaches
8
542-RS01; 110mAg M/C 0.18 542-RS07; 110mAg M/C 0.19
542-RS25; 110mAg M/C = 1.03
Local SiC corrosion
Variation in FP interaction
Backscattered Electron Micrographs of the IPyC/SiC Layers of Compact 542 TRISO Particles
The Why?
Serial Sectioning Image Analysis
•A dual beam scanning electron microscope (SEM) / focused ion beam (FIB) is used to mill material
• Image after each milling slice with SEM
– Depth resolution on the nanoscale allows resolution of fine scale interfacial variation and co-location of FP&A features
– Can be coupled with analytical techniques such as energy dispersivex-ray spectroscopy (EDS) or electron backscatter diffraction (EBSD)
•A systematic approach to studying the IPyC/SiC interface in irradiated TRISO fuel (compared to the as-fabricated case)
• Initial shake down: compare as-fabricated Compact 542 particles with low-Ag and high-Ag retention
ROI+
Pt Cap Spacing of 25-30 nm between
each slice
Top schema
Slice schema
Example of ROI and pre-milled region
SiC
IPyC
IPyC
Pre-milled region to allow for appropriate imaging conditions
Targets and Status
•Slice and view data acquisition has been completed on 67% of the targeted
locations
•Data processing and handling is ongoing – exploring what properties can be
measured and how to accurately define/report
– Accurately define the “interface”
– Measure the spatial distribution of FP&A within the interface and it's components (e.g.
open porosity, SiC stitching)
Particles DescriptionMinimum targeted number of
locations FY19 (completed)
As-fabricated UCO (LEU09) Unirradiated Baseline 2 (2)
D51 (542-RS01 & RS07) Low-Ag (110mAg M/C 0.18) 2 (2)
D55 (542-RS25 & RS33) High-Ag (110mAg M/C = 1.03–1.23) 2 (0)
Test Matrix
AGR-2 Compact 5-4-2 Exampleparticle with Low-Ag retention
Quantification of Interfacial Properties
-0.2
0
0.2
0.4
0.6
0.8
1
0 2 4 6 8 10 12 14
Volu
me F
raction
Distance (um)
Material vs. Depth
FP Porosity PyC SiC
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0 2 4 6 8 10 12 14
Volu
me F
raction
Distance (um)
Material vs. Depth
FP Porosity
• Initial observations: interface is a diffuse region, FPs are not directly concentrated in open volume – segregated to IPyC/SiC boundary?
• Takeaway: Considerable opportunity to correlate structure with local FP behavior, to quantify the nature of the IPyC/SiC interface (or other layers too), determine concentration profiles in 3D space… Lots to learn.
– Continuing work this FY: complete High-Ag particles and data analysis
