Nathan Capps

TL;DR: The Severe Accident Test Station at Oak Ridge National Lab as mentioned in this paper provides various temperature profiles, steam, and thermal shock conditions necessary for integral loss of coolant accident testing, defueled oxidation quench testing, and high-temperature beyond design basis accident testing.

TL;DR: The approach exploits advanced modeling and simulation at the outset to inform constituent and system selection and to enable integral fuel performance analyses to reduce the time for development and qualification of a new fuel system and to reduce associated costs.

Abstract: High burnup fuel fragmentation, relocation, and dispersal is one of the largest hurdles for the nuclear industry to clear before rod average burnup can be increased beyond 62 GWd/MTU. This objective of this work is to inform the high burnup loss-of-coolant-accident (LOCA) safety case for a core containing high burnup fuel to help accelerate the nuclear industry’s goals to (1) extend cycle lengths to 24 months and (2) increase peak rod average burnup to 75 GWd/MTU. The results of this analysis will define realistic, prototypic LOCA conditions to design subsequent separate effects and integral testing and will inform advanced modeling and simulation to develop mechanistic models. US Department of Energy tools were used to evaluate commercial pressurized water reactor (PWR) fuel susceptible to fragmentation under high burnup conditions. Realistic, rather than bounding, 24-month core designs and operating conditions (power history, axial profile, thermal boundary condition, flux, etc.) for VERA depletion analyses were provided by an industry partner. RELAP5-3D provided LOCA transient conditions (decay heat, thermal hydraulic conditions, etc.) for a core containing high burnup fuel (i.e., over 62 GWd/MTU with peak rod being 75 GWd/MTU). These operating conditions were entered into BISON to evaluate the evolution of the high burnup fuel under steady-state and transient conditions. BISON was used to determine the limiting fuel rod in each high burnup assembly and to evaluate the impact of pretransient fuel conditions (i.e., radial temperature profile), clad strain, ballooning behavior, and burst timing on the fuel’s susceptibility to high burnup fuel fragmentation. These efforts culminated in this summary of the potential impacts of high burnup fuel fragmentation, relocation, and dispersal and definition of prototypic LOCA conditions.