A High Fidelity Multiphysics Framework for Modeling CRUD Deposition on PWR Fuel Rods.

CRUD deposition;Multiphysics;Reactor physics;CFD;Modeling and simulation;Fuel failure;Nuclear Engineering and Radiological Sciences;Engineering;Nuclear Engineering and Radiological Sciences

Walter, Daniel JohnKendrick, Brian K ;

University of Michigan

关键词: CRUD deposition;    Multiphysics;    Reactor physics;    CFD;    Modeling and simulation;    Fuel failure;    Nuclear Engineering and Radiological Sciences;    Engineering;    Nuclear Engineering and Radiological Sciences;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/120638/djwalter_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Corrosion products on the fuel cladding surfaces within pressurized water reactor fuel assemblies have had a significant impact on reactor operation. These types of deposits are referred to as CRUD and can lead to power shifts, as a consequence of the accumulation of solid boron phases on the fuel rod surfaces. Corrosion deposits can also lead to fuel failure resulting from localized corrosion, where the increased thermal resistance of the deposit leads to higher cladding temperatures. The prediction of these occurrences requires a comprehensive model of local thermal hydraulic and chemical processes occurring in close proximity to the cladding surface, as well as their driving factors. Such factors include the rod power distribution, coolant corrosion product concentration, as well as the feedbacks between heat transfer, fluid dynamics, chemistry, and neutronics. To correctly capture the coupled physics and corresponding feedbacks, a high fidelity framework is developed that predicts three-dimensional CRUD deposition on a rod-by-rod basis. Multiphysics boundary conditions resulting from the coupling of heat transfer, fluid dynamics, coolant chemistry, CRUD deposition, neutron transport, and nuclide transmutation inform the CRUD deposition solver. Through systematic parametric sensitivity studies of the CRUD property inputs, coupled boundary conditions, and multiphysics feedback mechanisms, the most important variables of multiphysics CRUD modeling are identified. Moreover, the modeling framework is challenged with a blind comparison of plant data to predictions by a simulation of a sub-assembly within the Seabrook nuclear plant that experienced CRUD induced fuel failures.The physics within the computational framework are loosely coupled via an operator-splitting technique. A control theory approach is adopted to determine the temporal discretization at which to execute a data transfer from one physics to another. The coupled stepsize selection is viewed as a feedback control problem, and a controller of the type integral is utilized. The temporal discretization adapts with the problem solution to maintain a user-prescribed tolerance of specific solution variables. Predictor-corrector algorithms enable convergence error estimates. The highly nonlinear precipitation rate of solid boron phases, and their dependence on the local thermal hydraulic conditions, is the primary motivation for seeking an automated and adaptive stepsize selection algorithm.