Reactor Kinetics Study in Candu-6: A 3-D Versus Point Kinetics Comparison for Loss of HTS Flow Events

Abstract

This paper describes a series of coupled neutronic-thermalhdyraulic simulations of postulated loss of primary circuit flow events occurring in CANDU 6 Nuclear Power Generating Station. The full-core time-dependent neutron kinetic calculation was performed using the *CERBRRS module in physics code, RFSP-IST. *CERBRRS solves the time-dependent neutron diffusion equation with delayed neutrons using the Improved Quasistatic Methodology. In addition, it incorporates Reactor Regulating System (RRS) capabilities, which makes it suitable for analysis of slow transients. Dynamic coupling of the thermalhydraulic code CATHENA version Mod3.5dRev.1 with RFSP was automated using RCCTS, a PERL-based script. For these coupled simulations, a full 2-energy-group WIMS-IST Simple Cell Model (SCM) approach was used with 2-group device incrementals from DRAGON. A “point reactor” model was also used in simulation, with incorporation of reactivity coefficients and delayed-neutron data from the RFSP model.A "point reactor" version of the RRS controller, used in *CERBRRS, was incorporated in the “point reactor” model. A three dimensional (3-D)versus "point neutronics" comparison is thus established as it pertains to loss of heat transport system (HTS) flow.