NSUF 10-281: Microstructural and Irradiation Effects on Ag and Cs Diffusion in CVD-SiC
An understanding of the diffusion of Ag and Cs in the SiC layer of TRIstructural ISOtropic (TRISO) fuel is necessary for development of the Very High Temperature Reactor as identified by the Department of Energy’s Next Generation Nuclear Plant initiative. In TRISO fuel the SiC layer serves as the main fission product barrier, however, at normal and accident conditions 110mAg and 137Cs have been observed to be released from intact particles. The release of the fission products causes immediate maintenance and safety concerns ultimately limiting the lifetime of the fuel. In order to predict fuel lifetimes and ensure safe and efficient operation accurate diffusion coefficients for Ag and Cs in SiC are required. Diffusion coefficients from fractional release plate-out experiments have been reported for Ag and Cs in SiC with orders of magnitude variation in reported diffusion coefficients. It has also been shown that fractional release is microstructurally dependent where particles with large columnar grains releasing more of their Ag and Cs inventory than particles with lamellar grained SiC layers.[1] Although fractional release measurements provide a rough transport result on the permeability of SiC, the effects of the detailed microstructure on the transport has not been illuminated. This research proposes to investigate the transport mechanism and microstructural effects on Ag and Cs diffusion in SiC and irradiated SiC. CVD-SiC and 6-H single crystal SiC will be implanted with Ag and Cs at The University of Michigan’s Michigan Ion Beam Laboratory with the 400 kV ion implanter. Following implantation the samples will be exposed to temperature (1200-1600oC) to induce thermal diffusion. A set of samples will also be proton irradiated to measure irradiation enhanced diffusion at the ion beam user facility at the University of Wisconsin-Madison which is capable of high temperature irradiations up to 1400oC. Ag/SiC and Cs/SiC Depth profiles will be obtained by secondary ion mass spectroscopy to measure diffusion coefficients and solubility limits. Scanning transmission electron microscopy (STEM) with energy dispersive x-ray spectroscopy (EDS) will be conducted on the CVD-SiC samples to determine preferential diffusion along specific grain boundaries as defined by the coincidence site lattice model. The as-implanted samples will also serve as standards for determination of k factors for EDS analysis and relative sensitivity factors for SIMS analysis. These experimental efforts are proposed to be a one year project. This investigation will serve to determine the active transport mechanisms for Ag and Cs diffusion in TRISO fuel materials and to determine the contributions of specific microstructural features. To the authors knowledge this work is the first to measure Cs diffusion coefficients from implantation experiments and to directly investigate irradiation enhanced diffusion of Ag and Cs in CVD-SiC. The resulting diffusion coefficients will allow for accurate prediction of fuel lifetimes and efficient operation, and to reduce safety and maintenance concerns through determination of fission product release from TRISO fuel, while, the transport mechanism must be understood to develop an engineering solution to improve the retention of fission products by the SiC layer. maintenance concerns through determination of fission product release from TRISO fuel, while, the transport mechanism must be understood to develop an engineering solution to improve the retention of fission products by the SiC layer.
Información adicional
| Campo | Valor |
|---|---|
| Awarded Institution | University of Wisconsin |
| Embargo End Date | 2026-02-27 |
| Facility Tech Lead | Adrien Couet, Kory Linton |
| NSUF Call | FY 2010 RTE Solicitation |
| PI | Izabela Szlufarska |
| Project Member | Dr. Tyler Gerczak - Oak Ridge National Laboratory (https://orcid.org/0000-0001-9967-3579) |
| Project Member | Izabela Szlufarska - University of Wisconsin |
| Project Type | RTE |
| Publication | Observations of Ag diffusion in ion implanted SiC Todd Allen, Tyler Gerczak, bin leng, Kumar Sridharan Journal of Nuclear Materials 461 2015-06-01 https://www.sciencedirect.com/science/article/pii/S0022311515001749#! |
| Publication | Effect of exposure environment on surface decomposition of SiC–silver ion implantation diffusion couples Todd Allen, Kevin Field, Tyler Gerczak, Guiqiu Zheng Journal of Nuclear Materials 456 2015-01-01 https://www.sciencedirect.com/science/article/pii/S0022311514006631#ak005 |
| Publication | Cesium and Silver Diffusion in SiC for TRISO Applications Todd Allen, Tyler Gerczak Transactions of the American Nuclear Society 104 2011-06-01 http://epubs.ans.org/?a=11785 |
| Publication | Effect of exposure environment on surface decomposition of SiC–silver ion implantation diffusion couples Tyler Gerczak, Guiqiu Zheng, Kevin Field, Todd Allen Journal of Nuclear Materials 456 2015-01-01 https://www.sciencedirect.com/science/article/abs/pii/S0022311514006631 |
| Publication | Observations of Ag diffusion in ion implanted SiC Tyler Gerczak, bin leng, Kumar Sridharan Journal of Nuclear Materials 461 2015-06-01 https://www.sciencedirect.com/science/article/abs/pii/S0022311515001749 |
| Publication | Effect of carbon ion irradiation on Ag diffusion in SiC Tyler Gerczak, bin leng Journal of Nuclear Materials 471 2016-04-01 None |
| RTE Number | 281 |