Abstract

During operation of light water reactors hydrogen from the primary coolant is absorbed within the zirconium cladding and is able to migrate and redistribute within the cladding. The hydrogen in solid solution is able to precipitate, forming zirconium hydrides which results in a decrease of ductility of the cladding and ultimately an increase in likelihood of cladding failure, especially in conditions such as transport or storage of nuclear fuel rods. In collaboration with other universities, industries, and national laboratories the overarching goal of this project is to enhance the development for modeling hydride behavior to be implemented into the BISON fuel performance tool. The University of Tennessee-Knoxville (UTK) has been tasked with quantifying the uncertainty in the models developed within this project as well as quantifying the sensitivity to the most significant parameters of uncertainty.

The BISON fuel performance code has been shown to overpredict the total concentration of hydrogen at cold regions of a temperature profile, thus a sensitivity study was performed to quantify the impact that key diffusion parameters have on the local concentration of hydrogen at the cold end of a 1-D model subjected to an asymmetric temperature profile. It is shown within this document that the diffusion activation energy and the pre-exponential factor, values within the diffusion coefficient of hydrogen, have a large impact on the local concentration of hydrogen and their importance increases for an increase in annealing time.

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