Steady-State Analysis of the APR1400 Benchmark using STREAM/RAST-K Two-step code

Abstract

STREAM/RAST-K two-step code has been verified and validated several times using different benchmarks, but the continuous improvements made to the code arise the need for the continuous verification and validation. That’s why this thesis is focused on validating the STREAM/RAST-K code system against the recent APR1400 Benchmark. STREAM, which stands for “Steady State and Transient Reactor Analysis code with Method of Characteristics”, is used to generate different cross- sectional data, so it could be fed to RAST-K “Reactor Analysis code for Steady state and Transient- KEPRI”, to get the results of the calculations. Using different options such as the inflow and outflow transport cross-section correction methods and different “Method of Characteristics” (MOC) parameters, STREAM generated two-group transport cross-sections (tr_maXS), absorption cross- sections (a_maXS), fission cross-sections (f_maXS) and down-scattering cross-sections(s_maXS). The APR1400 benchmark has 6 sets of problems, ranging from 2-D fuel pin problems to 3-D core depletion calculations. Before modeling the problems that require a lot of computational power, the optimal parameters and options ought to be found, that’s why for the fuel pin problems, fuel assembly problems and the 2-D core problems, a steady-state analysis was conducted to find the best combination of parameters. An in-out tilt was found when running the 2-D core problems, that’s why a new approach in modelling was used, where the cross-sections for the peripherical assemblies (near reflector) were generated using a different transport correction method than the rest of the assemblies that make up the core. The best combination was then used to simulate the rest of the benchmark and the obtained results shows good agreement with those provided in the benchmark, which proves that STREAM/RAST-K could be used for assessing advanced pressurized water reactor (PWRs) like the APR1400 reactor (Advanced Power Reactor 1400) in different sets of conditions.