BISON Capabilities for LWR Fuel Behavior Analysis During Accident and High-burnup Conditions

Abstract

The U.S. Department of Energy (DOE)'s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program aims to develop predictive capabilities using computational methods for the analysis and design of advanced reactor and fuel cycle systems. This program has been supporting the development of BISON, a high-fidelity and high-resolution fuel performance tool at the engineering scale. Recent increasing interest in applications at extended burnups motivated this study to incorporate more physically based models in BISON. This document details integration of newly implemented modeling capabilities for BISON. These include: (1) new thermal conductivity models that are valid up to 100 GWd/t, (2) models for the formation of the high-burnup structure (HBS), (3) two porosity correction methods applied to the thermal conductivity due to the conducting pores during the HBS formation. BISON's results are verified and validated to test the new modeling capabilities.

BISON Fuel Fragmentation Relocation and Dispersal (FFRD) Assessment Database for Eventual Use in Bayesian Calibration

“…Figure 5.3 presents the least squares fit currently employed in BISON for the HBS porosity. Couple this with the wealth of data and uncertainty associated with the thermal conductivity of UO 2 compiled by [48], and it becomes clear this is an area that would also benefit from Bayesian calibration. models follow a power law formulation, but the leading coefficients and activation energies differ and are a function of the Zircaloy-4 phase.…”

“…This is used to weigh the contributions of the non-restructured fuel thermal conductivity and thermal conductivity in the HBS pores. Details of the methodologies for computing the effective thermal conductivity can be found in Toptan et al [48]. Figure 5.3 presents the least squares fit currently employed in BISON for the HBS porosity.…”

Evaluation of Mechanistic and Empirical Models against Existing FFRD and LOCA Experimental Databases

“…If the HBS fraction is greater than 0.5 and the bubble pressure exceeds the critical bubble pressure, pulverization is permitted to occur. The models for determining the HBS volume fraction and porosity in the HBS were previously implemented in BISON [27] and have already been verified to be implemented correctly. Therefore, in the tests for the pulverization criterion, it is assumed that the computation of the HBS volume fraction and porosity in the HBS is correct, and those values are simply used in the studies here.…”

“…In particular, Rods IFA-650.2, IFA-650.4, IFA-650.9, and IFA-650.10 have been extensively used, given the BISON teams participation in the FUMAC project [33]. More recently [27,25], IFA-650.14 has been added to the validation suite to assess the impact of various model improvements on a rod that had extensive relocation but no cladding rupture. In particular, IFA-650.4 has been referred to as the experiment whose observations reignited the rapid investigation into FFRD by industry, national laboratories, and universities.…”