Extension of integrated neutronic and thermal-hydraulic analysis capabilities of the "numerical nuclear reactor" software system for BWR applications

The Numerical Nuclear Reactor is a software analysis system based on the integration of high fidelity models of neutronic, thermal-hydraulic and thermo-mechanical phenomena. Originally developed for pressurized water reactors (PWRs), the current version has been extended to treat neutronic and thermal-hydraulic issues in boiling water reactors (BWRs). The neutronic module is an extension of the DeCART whole core neutron transport code, which is capable of generating three-dimensional sub-pin level power distributions with the thermal feedback effect incorporated directly during the whole core calculation. The original cell based modular ray tracing scheme has been extended to an assembly modular ray tracing to address the complex geometry of a BWR. Thermal-hydraulic analyses are performed with computational fluid dynamics (CFD) solutions based on the STAR-CD code which has been extended to treat boiling two-phase flow, along with conjugate heat transfer, for expected BWR conditions. Verification and validation of the neutronics and thermal-hydraulics modules are described. Results of integrated calculations are illustrated. A review of the numerical performance on parallel computing system is also provided.