Grain Subdivision Fission Gas Swelling Model for UO2

MRS Advances ◽  
2016 ◽  
Vol 1 (35) ◽  
pp. 2465-2470
Author(s):  
Thomas Winter ◽  
Richard Hoffman ◽  
Chaitanya S. Deo
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Gas Diffusion ◽  
Fine Grain ◽  
Fuel Pellets ◽  
Model And Simulation ◽  
Nucleation Sites ◽  
Fission Gas ◽  
High Burnup ◽  
Swelling Model

ABSTRACTUnder high burnup UO2 fuel pellets can experience high burnup structure (HBS) at the rim also known as rim effect. The HBS is exceptionally porous with fine grain sizes. HBS increases the swelling further than it would have achieved at a larger grain size. A theoretical swelling model is used in conjunction with a grain subdivision simulation to calculate the swelling of UO2. In UO2 the nucleation sites are at vacancies and the bubbles are concentrated at grain boundaries. Vacancies are created due to irradiation and gas diffusion is dependent on vacancy migration. In addition to intragranular bubbles, there are intergranular bubbles at the grain boundaries. Over time as intragranular bubbles and gas atoms accumulate on the grain boundaries, the intergranular bubbles grow and cover the grain faces. Eventually they grow into voids and interconnect along the grain boundaries, which can lead to fission gas release when the interconnection reaches the surface. This is known as the saturation point. While the swelling model used does not originally incorporate a changing grain size, the simulation allows for more accurate swelling calculations by introducing a fractional HBS based on the temperature and burnup of the pellet. The fractional HBS is introduced with a varying grain size. Our simulations determine the level of swelling and saturation as a function of burnup by combining an independent model and simulation to obtain a more comprehensive model.

scholarly journals Study on the erosion of Mo/ZrO2 alloys in glass melting process

2020 ◽  
Vol 39 (1) ◽  
pp. 595-598
Author(s):  
Cui Chaopeng ◽  
Zhu Xiangwei ◽  
Li Qiang ◽  
Zhang Min ◽  
Zhu Guangping
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Powder Metallurgy ◽  
Hydrothermal Synthesis ◽  
Grain Boundaries ◽  
Electrode Material ◽  
Glass Melting ◽  
Melting Process ◽  
Fine Grain ◽  
Conventional Electrode

AbstractThe Mo/ZrO2 electrode was prepared by combining hydrothermal synthesis with powder metallurgy, and this new electrode material has a totally different microstructure from the conventional electrode. The grain size of the new electrode was fine, and the size of ZrO2 in the alloy reached 200 nm. According to the results, the Mo–ZrO2 electrode has better performance, because the erosion occurs along the grain boundaries. Meanwhile, the new electrode, based on its fine grain, can effectively improve the corrosion resistance of the electrode.

Effect of grain size on recrystallization in high burnup fuel pellets

1997 ◽  
Vol 248 ◽  
pp. 196-203 ◽  
Author(s):  
K. Nogita ◽  
K. Une ◽  
M. Hirai ◽  
K. Ito ◽  
K. Ito ◽  
...  
Keyword(s):  
Grain Size ◽  
Fuel Pellets ◽  
High Burnup

scholarly journals Effect of Grain Size on Carburization Characteristics of the High-Entropy Equiatomic CoCrFeMnNi Alloy

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7199
Author(s):  
Hyunbin Nam ◽  
Jeongwon Kim ◽  
Namkyu Kim ◽  
Sangwoo Song ◽  
Youngsang Na ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Grain Sizes ◽  
Fine Grain ◽  
Cast Specimen ◽  
Vacuum Carburization ◽  
Cold Rolled ◽  
Face Centered

In this study, the carburization characteristics of cast and cold-rolled CoCrFeMnNi high-entropy alloys (HEAs) with various grain sizes were investigated. All specimens were prepared by vacuum carburization at 940 °C for 8 h. The carburized/diffused layer was mainly composed of face-centered cubic structures and Cr7C3 carbide precipitates. The carburized/diffused layer of the cold-rolled specimen with a fine grain size (~1 μm) was thicker (~400 μm) than that of the carburized cast specimen (~200 μm) with a coarse grain size (~1.1 mm). In all specimens, the carbides were formed primarily through grain boundaries, and their distribution varied with the grain sizes of the specimens. However, the carbide precipitates of the cast specimen were formed primarily at the grain boundaries and were unequally distributed in the specific grains. Owing to the non-uniform formation of carbides in the carburized cast specimen, the areas in the diffused layer exhibited various carbide densities and hardness distributions. Therefore, to improve the carburization efficiency of equiatomic CoCrFeMnNi HEAs, it is necessary to refine the grain sizes.

Consideration of grain size distribution in the diffusion of fission gas to grain boundaries

2013 ◽  
Vol 440 (1-3) ◽  
pp. 435-439 ◽  
Author(s):  
Paul C. Millett ◽  
Yongfeng Zhang ◽  
Michael R. Tonks ◽  
S.B. Biner
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Fission Gas

Identification of Radial Position of Fission Gas Release in High-Burnup Fuel Pellets under RIA Conditions

2010 ◽  
Vol 47 (2) ◽  
pp. 202-210 ◽  
Author(s):  
Hideo SASAJIMA ◽  
Tomoyuki SUGIYAMA ◽  
Toshinori CHUTO ◽  
Fumihisa NAGASE ◽  
Takehiko NAKAMURA ◽  
...  
Keyword(s):  
Radial Position ◽  
Gas Release ◽  
Fuel Pellets ◽  
Fission Gas ◽  
High Burnup ◽  
Fission Gas Release

Powder Leaching Study for Grain Boundary Inventory of Two High Burnup Fuels

MRS Advances ◽  
2019 ◽  
Vol 4 (17-18) ◽  
pp. 981-986
Author(s):  
Alexandre Barreiro Fidalgo ◽  
Olivia Roth ◽  
Anders Puranen ◽  
Lena Z. Evins ◽  
Kastriot Spahiu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Spent Fuel ◽  
Short Period ◽  
Fission Gas ◽  
Leaching Solution ◽  
Significant Release ◽  
Leaching Experiments ◽  
High Burnup ◽  
Fission Gas Release

ABSTRACTIn the context of safety assessment, the fraction of inventory that is expected to rapidly dissolve when water contacts the spent fuel is called the Instant Release Fraction (IRF). Conceptually, this fraction consists of radionuclides outside of the uranium dioxide matrix and therefore the fraction can be further divided into the radionuclides in the fuel/cladding gap and radionuclides in the grain boundaries. The relative importance of these two fractions is investigated here for two Swedish high burnup fuels through simultaneous grinding and leaching fuel fragments in simplified groundwater for a short period of time. The hypothesis is that this will expose grain boundaries to leaching solution and provide an estimate of the release of the grain boundary inventory upon contact with water. The studied fragments were used in previous leaching experiments and thus pre-washed to remove any pre-oxidized phases. The results showed a significant release of iodine, cesium and rubidium and to a lower extent molybdenum and technetium. The fraction of inventory in the aqueous phase of actinides and lanthanides was 1-2 orders of magnitude lower than for the elements associated to the IRF. Both fuels displayed a very similar behavior and no correlation as a function of burnup or fission gas release was found.

scholarly journals Effect of Annealing on Microstructure and Tensile Behavior of CoCrNi Medium Entropy Alloy Processed by High-Pressure Torsion

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 849 ◽  
Author(s):  
Praveen Sathiyamoorthi ◽  
Jae Bae ◽  
Peyman Asghari-Rad ◽  
Jeong Park ◽  
Jung Kim ◽  
...  
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Tensile Strength ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Face Centered Cubic ◽  
Kernel Average Misorientation ◽  
Fine Grain ◽  
Fcc Phase

Annealing of severely plastic deformed materials is expected to produce a good combination of strength and ductility, which has been widely demonstrated in conventional materials. In the present study, high-pressure torsion processed CoCrNi medium entropy alloy consisting of a single face-centered cubic (FCC) phase with a grain size of ~50 nm was subjected to different annealing conditions, and its effect on microstructure and mechanical behavior was investigated. The annealing of high-pressure torsion processed CoCrNi alloy exhibits partial recrystallization and near full recrystallization based on the annealing temperature and time. The samples annealed at 700 °C for 2 min exhibit very fine grain size, a high fraction of low angle grain boundaries, and high kernel average misorientation value, indicating partially recrystallized microstructure. The samples annealed for a longer duration (>2 min) exhibit relatively larger grain size, a low fraction of low angle grain boundaries, and low kernel average misorientation value, indicating nearly full recrystallized microstructure. The annealed samples with different microstructures significantly influence the uniform elongation, tensile strength, and work hardening rate. The sample annealed at 700 °C for 15 min exhibits a remarkable combination of tensile strength (~1090 MPa) and strain to failure (~41%).

Optical Property of Spark Plasma Sintered Translucent AlN Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 545-548
Author(s):  
Y. Xiong ◽  
Zheng Yi Fu ◽  
Hang Wang
Keyword(s):  
Grain Size ◽  
Optical Property ◽  
Grain Boundaries ◽  
Spark Plasma Sintering ◽  
Secondary Phases ◽  
Fine Grain ◽  
Sintering Additive ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Good Optical Property

Translucent AlN ceramics were fabricated using spark plasma sintering (SPS) technique with 3wt% CaF2 as sintering additive. The samples achieved 52.4% maximum transmittance in medium IR region after 10 min holding time by spark plasma sintering at 1800°C and 30 MPa pressure in N2. The results from XRD, SEM, TEM and EDX showed that the sintered bodies were densely compacted and highly pure with fine grain size and uniform microstructures. No secondary phases were observed at the grain boundaries and triple grain junctions, which guaranteed good optical property of the sintered bodies.

scholarly journals Iodine release from high-burnup fuel structures: Separate-effect tests and simulated fuel pellets for better understanding of iodine behaviour in nuclear fuels

MRS Advances ◽  
2021 ◽  
Author(s):  
Janne Heikinheimo ◽  
Teemu Kärkelä ◽  
Václav Tyrpekl ◽  
Matĕj̆ Niz̆n̆anský ◽  
Mélany Gouëllo ◽  
...  
Keyword(s):  
Fission Product ◽  
Nuclear Fuel ◽  
Chemical Species ◽  
Outer Edge ◽  
Fuel Pellet ◽  
Fuel Pellets ◽  
Simulated Fuel ◽  
Fission Gas ◽  
High Burnup ◽  
Iodine Release

Abstract Iodine release modelling of nuclear fuel pellets has major uncertainties that restrict applications in current fuel performance codes. The uncertainties origin from both the chemical behaviour of iodine in the fuel pellet and the release of different chemical species. The structure of nuclear fuel pellet evolves due to neutron and fission product irradiation, thermo-mechanical loads and fission product chemical interactions. This causes extra challenges for the fuel behaviour modelling. After sufficient amount of irradiation, a new type of structure starts forming at the cylindrical pellet outer edge. The porous structure is called high-burnup structure or rim structure. The effects of high-burnup structure on fuel behaviour become more pronounced with increasing burnup. As the phenomena in the nuclear fuel pellet are diverse, experiments with simulated fuel pellets can help in understanding and limiting the problem at hand. As fission gas or iodine release behaviour from high-burnup structure is not fully understood, the current preliminary study focuses on (i) sintering of porous fuel samples with Cs and I, (ii) measurements of released species during the annealing experiments and (iii) interpretation of the iodine release results with the scope of current fission gas release models. Graphical abstract

The Effect of Grain Boundaries and Second-Phase Particles on Hydride Precipitation in Zirconium Alloys

MRS Advances ◽  
2018 ◽  
Vol 3 (31) ◽  
pp. 1749-1754 ◽  
Author(s):  
Said El Chamaa ◽  
Mitesh Patel ◽  
Catrin M. Davies ◽  
Mark R. Wenman
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Zirconium Alloys ◽  
Second Phase ◽  
Distribution Profile ◽  
Grain Sizes ◽  
Hydride Precipitation ◽  
Nucleation Sites ◽  
Wide Range ◽  
Pure Zirconium

ABSTRACTUnderstanding the precipitation of brittle hydride phases is crucial in establishing a failure criterion for various zirconium alloy nuclear fuel cladding. Accordingly, it is important to quantify the sensitivity of hydride precipitation to the component microstructure. This experimental investigation focuses on two microstructural characteristics and their role as hydride nucleation sites: The grain size and the alloy chemical composition. Samples of commercially pure zirconium (Zr-702) and Zircaloy-4, each with a wide range of grain sizes, were hydrided to 100 ppm and micrographs of the hydride distribution were optically analyzed for inter-granular and intra-granular precipitate sites. For most grain sizes, it was found that a significantly lower fraction of the precipitated hydrides nucleated at grain boundaries in Zircaloy-4 than in Zr-702, suggesting that a higher SPP content encourages the formation of intra-granular hydrides. Moreover, this effect became more prominent as the grain size increased; large-grain specimens contained a higher fraction of intra-granular hydrides than small-grain specimens of both Zr-702 and Zircaloy-4, highlighting the potency of grain boundaries as nucleation sites and how SPPs can influence the hydride distribution profile.

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