ANALYSES OF TRACE-PARCS COUPLING CAPABILITY

In the nuclear reactor analysis studies, the best-estimate thermal-hydraulic and threedimensional neutron kinetic codes have given a valuable contribution in improving design, optimization and safety analyses. In order to model the interaction between neutron kinetic and thermal hydraulic phenomena and its spatial distribution in a more accurate way, advanced techniques have been developed by coupling best estimate thermal hydraulic and three-dimensional neutron kinetic codes. These techniques allow to reduce uncertainties and, giving a more realistic analyses of transient phenomena, to carried out a more realistic study of the accident sequence. Therefore, three-dimensional coupling analyses permit a better estimation of the safety margins and can increase the operational flexibility of a Nuclear Power Plant (NPP). In the last years, in order to analyze the thermal hydraulic behavior of Light Water Reactors (LWR), the USNRC is developing an advanced best estimate thermal hydraulic system code called TRAC/RELAP Advanced Computational Engine (TRACE) that can be run coupled with the 3D reactor kinetics Purdue Advanced Reactor Core Simulator (PARCS) code. This paper presents a study of the coupling capability of the TRACE and PARCS codes by analyzing the “Main Steam Line Break (MSLB) benchmark problem”, consisting in a double-ended MSLB accident assumed to occur in the Babcock and Wilcox Three Mile Island Unit 1. The analyses of the TRACE/PARCS calculated data show that the codes are able to predict the expected phenomena typical of this transient and the related thermal hydraulic neutronic feedback. The graphical capability of SNAP has been useful to have a direct visualization of selected calculated data.