Silver Release from Coated Particle Fuel

Nabielek, H.; Brown, P. E.; Offermann, Peter

doi:10.13182/nt35-483

Cited by 112 publications

(95 citation statements)

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“…Using the analytical solution for release from a thin spherical shell, the "diffusion" coefficient necessary to produce that silver release can be calculated for each heat treatment as follows (Crank 1956). The effective mass transport coefficients calculated from the mass loss data for the current silver experiment are plotted along with the diffusion coefficients reported in the literature in Figure 3-2 (Nabielek, Brown, and Offerman 1977, Brown and Faircloth 1976, Förthmann et al 1982, Amian and Stöver 1983. The calculated diffusion coefficients from the complete set of experiments continue to appear higher than the literature band, but there is overlap between the data sets.…”

Section: Mass Lossmentioning

confidence: 75%

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Development of Improved Models and Designs for Coated-Particle Gas Reactor Fuels (I-NERI Annual Report)

Petti¹,

Maki²,

Languille³

et al. 2002

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The objective of this INERI project is to develop improved fuel behavior models for gas reactor coated particle fuels and to develop improved coated-particle fuel designs that can be used reliably at very high burnups and potentially in fast gas-cooled reactors. Thermomechanical, thermophysical, and physiochemical material properties data were compiled by both the US and the French and preliminary assessments conducted. Comparison between U.S. and European data revealed many similarities and a few important differences. In all cases, the data needed for accurate fuel performance modeling of coated particle fuel at high burnup were lacking. The development of the INEEL fuel performance model, PARFUME, continued from earlier efforts.The statistical model being used to simulate the detailed finite element calculations is being upgraded and improved to allow for changes in fuel design attributes (e.g. thickness of layers, dimensions of kernel) as well as changes in important material properties to increase the flexibility of the code. In addition, modeling of other potentially important failure modes such as debonding and asphericity was started. A paper on the status of the model was presented at the HTR-2002 meeting in Petten, Netherlands in April 2002, and a paper on the statistical method was submitted to the Journal of Nuclear Material in September 2002. Benchmarking of the model against Japanese and an older DRAGON irradiation are planned. Preliminary calculations of the stresses in a coated particle have been calculated by the CEA using the ATLAS finite element model. This model and the material properties and constitutive relationships will be incorporated into a more general software platform termed Pleiades. Pleiades will be able to analyze different fuel forms at different scales (from particle to fuel body) and also handle the statistical variability in coated particle fuel. Diffusion couple experiments to study Ag and Pd transport through SiC were conducted. Analysis and characterization of the samples continues. Two active transport mechanisms are proposed: diffusion in SiC and release through SiC cracks or another, as yet undetermined, path. Silver concentration profiles determined by XPS analysis suggest diffusion within the SiC layer, most likely dominated by grain boundary diffusion. However, diffusion coefficients calculated from mass loss measurements suggest a much faster release path, postulated as small cracks or flaws that provide open paths with little resistance to silver migration. Work is ongoing to identify and characterize this path. Work on Pd behavior has begun and will continue next year. INTRODUCTIONThe objectives of this INERI project are to:develop improved fuel behavior models for gas cooled reactor particle fuels (initially for TRISO-coated fuels), develop improved gas cooled reactor particle fuel coating materials and designs that will reliably reach very high burnups, assess the extension of the particle fuel concept to hard spectrum gas-cooled cores, and develop an irradiati...

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Section: Mass Lossmentioning

confidence: 75%

“…Second, we are proceeding to establish what the actual diffusion coefficient is for Ag in SiC. The single literature source that is available that addresses this issue (Nabielek, Brown, and Offerman 1977) is inconclusive. In this work ion implantation was used in an effort to identify the diffusion coefficient.…”

Section: Ag Release-path Forwardmentioning

confidence: 99%

Development of Improved Models and Designs for Coated-Particle Gas Reactor Fuels (I-NERI Annual Report)

Petti¹,

Maki²,

Languille³

et al. 2002

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“…23,25,253,254] that the only radioactive isotope which escapes from TRISO particles in significant quantities during normal reactor operating conditions is silver m 110 Ag. For most of the other radiologically important nuclides (e.g.…”

Section: Silver Diffusionmentioning

confidence: 99%

“…[254], and especially from the newer silver implantation studies in single crystal SiC at elevated temperatures where the SiC remains crystalline [100 -105, 270, 283] and ab initio simulation studies [277,278,282] it is clear that the volume diffusion coefficient of silver in SiC is too low to account for the silver release data. In one of the early studies [254] it was proposed that the release was associated with the migration of silver through grain boundaries of the coated polycrystalline SiC enhanced by traces of free silicon. The influence of Si has been completely refuted by microscopy studies [274 -276].…”

Section: Silver Diffusionmentioning

confidence: 99%

Diffusion of fission products and radiation damage in SiC

Malherbe

2013

J. Phys. D: Appl. Phys.

109

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A major problem with most of the present nuclear reactors is their safety in terms of the release of radioactivity into the environment during accidents. In some of the future nuclear reactor designs, i.e. Generation IV reactors, the fuel is in the form of coated spherical particles, i.e. TRISO (acronym for Triple Coated Isotropic) particles. The main function of these coating layers is to act as diffusion barriers for radioactive fission products, thereby keeping these fission products within the fuel particles, even under accident conditions. The most important coating layer is composed of polycrystalline 3C-SiC. This paper reviews the diffusion of the important fission products (silver, caesium, iodine and strontium) in SiC. Because radiation damage can induce and enhance diffusion, the paper also briefly reviews damage created by energetic neutrons and ions at elevated temperatures, i.e. the temperatures at which the modern reactors will operate, and the annealing of the damage. The interaction between SiC and some fission products (such as Pd and I) is also briefly discussed. As shown, one of the key advantages of SiC is its radiation hardness at elevated temperatures, i.e. SiC is not amorphized by neutron or bombardment at substrate temperatures above 350°C. Based on the diffusion coefficients of the fission products considered, the review shows that at the normal operating temperatures of these new reactors (i.e. less than 950°C) the SiC coating layer is a good diffusion barrier for these fission products. However, at higher temperatures the design of the coated particles needs to be adapted, possibly by adding a thin layer of ZrC.

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“…2. 17. Microstructure of Sic coating from Triso-coated U02 particle doped with silver and annealed for 2000 h at 1450°C in a thermal gradient of 275"C/cm (transmission electron micrograph).…”

Section: Ye-i 1771mentioning

confidence: 99%

Gas-cooled reactor programs: high-temperature gas-cooled reactor technology development program. Annual progress report for period ending December 31, 1981

1982

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Silver Release from Coated Particle Fuel

Cited by 112 publications

References 2 publications

Development of Improved Models and Designs for Coated-Particle Gas Reactor Fuels (I-NERI Annual Report)

Development of Improved Models and Designs for Coated-Particle Gas Reactor Fuels (I-NERI Annual Report)

Diffusion of fission products and radiation damage in SiC

Gas-cooled reactor programs: high-temperature gas-cooled reactor technology development program. Annual progress report for period ending December 31, 1981

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