FX2-POOL—A Two-Dimensional Coupled Hydrodynamic Thermodynamic and Neutronic Computer Model for Hypothetical Core Disruptive Accident Analysis

Abstract

Subroutine POOL was developed for the study of hypothetical core disruptive accidents in nuclear reactors and, as such, is set up for use as a subroutine in the FX-2 Dynamic Neutronics Code. This combination permits scoping studies of the total neutronic/hydrodynamic interactions and is capable of performing phenomenological investigations of hypothetical problems ranging from the high ramp disassembly calculations, performed in the past by the Lagrangian code VENUS, to the study of recriticality in boiling pools of fuel and steel. POOL specifically includes, in at least parametric fashion, the following phenomena: (1) intra- and inter-element heat transfer by diffusion, convection, and radiation for both fuel and steel inside the pool and at the boundaries; (2) local vapor generation and concurrent local pressurization; and (3) hydrodynamic behavior using the inviscid Navier-Stokes equations in a Eulerian formulation. Sample results are shown for boil-up of an initially quiescent dense pool of fuel and steel. Subroutine POOL was modified by removing the free surface portion of the calculation and the associated expansion of the Eulerian Grid. The combined code, known as FX2-POOL, was used to perform prompt burst calculations for two comparison cases for a 1000-MW(t) demo-like reactor. Good agreement is shown between FX2-POOLmore » and VENUS II for these two hypothetical situations, indicating that the hydrodynamic and thermodynamic assumptions made in POOL are accurate enough for prompt burst analysis and compare well with the VENUS models.« less