A Semi-Analytical, Inherently Parallel Method for LWR Thermal-Hydraulic Feedback

Abstract

A new, semi-analytical, method for the fast and accurate computation of temperature and void distributions in Light Water Reactors has been developed and implemented in the code SAMOVAR. The model used is that of a smeared assembly channel. In this model all the flow properties are assumed to be constant (i.e. averaged) over the cross section of any given channel. Simplified conservation laws and correlations are used to yield a formulation amenable to analytical solution within each axial node. The model thus devised is functionally similar to the one used for thermalhydraulic feedback in the EPRI code SIMULATE-E. The spatial discretization method follows the practice previously adopted for nodal neutron diffusion methods and the solution algorithm is bared on local piece-wise analytical solutions of the conservation equations and related correlations. The new method accepts as input a flux or power in analytical or polynomial representation (as normally obtained from advanced nodal neutron diffusion computations). The method is inherently parallel and has been implemented on a CRAY X-MP/48. The results obtained demonstrate a high level of accuracy in comparison with operating data for a BWR as well as a very high computational efficiency: convergence of the full computation, to better than 1% maximum error on the flow rates, is achieved in approximately 2 seconds for a realistic representation of the Illinois Power Clinton Reactor.