Improved LWR Fuel Rod Mechanics Models

Abstract

There has been an ongoing effort to improve the mechanical constitutive models used in the BISON fuel performance code to improve their robustness and accuracy. This report documents recent work that was directed at improving the smeared cracking model used to represent fracture, especially for application to axisymmetric two-dimensional representations of light water reactor (LWR) fuel. It also demonstrates the application of this model in axisymmetric fuel rod simulations, including an example problem and a full-length axisymmetric LWR fuel rod model with available profilometry data in the BISON assessment test suite. The work described in this report was performed under funding from the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. This report is issued in satisfaction of the Level 3 milestone M3MS-18IN0201015 on improving light water reactor (LWR) fuel rod mechanics models in the INL Engineering-Scale Fuel Performance (BISON) Work Package.

Implementation and testing of physics-based pulverization model in BISON

“…The orientation of the crack is fixed, and additional cracks can form if the tensile stress in a direction orthogonal to the first crack direction exceeds the tensile strength. An exponential softening law is used for cracks that form in the plane of a Cartesian model, while a power-law model is used for out-of-plane cracks in lower-dimensional models, based on the findings in [39]. the perimeter of the pellet in the case that included pore pressurization than in the case that excluded that effect.…”