CTF RESIDUAL FORMULATION OF SOLID LIQUID COUPLING

摘要

Nuclear engineering codes are being used to simulate more challenging problems and at higher fidelities than they were initially developed for. In order to expand the capabilities of these codes, state of the art numerical methods and computer science need to be implemented. One of the key players in this effort is the Consortium for Advanced Simulation of Light Water Reactors (CASL) through development of the Virtual Environment for Reactor Applications (VERA). The sub-channel thermal hydraulic code used in VERA, COBRA-TF (Coolant-Boiling in Rod Arrays - Three Fluids), is partially developed at the Pennsylvania State University by the Reactor Dynamics and Fuel Management Research Group (RDFMG). The RDFMG version COBRA-TF is referred to as CTF. In an effort to help meet the objectives of CASL, a version of CTF has been developed that solves the residual formulation of the one-dimensional single-phase conservation equations. The formulation of the base equations as residuals allows the code to be run semi-implicitly or fully implicitly while clearly defining the original conservation equations. This paper outlines work to integrate one dimensional solid conduction equations into the residual formulation. This allows the coupling between the solid and liquid equations to be either explicit or implicit. A simple test problem consisting of a single liquid channel and fuel pin is used to compare the different numerical models available from the new residual formulation to an analytical solution. The methods are compared both for steady state and transient conditions to quantify the accuracy of each method. The ability to choose appropriate numerical methods allows for greater fidelity and decreases computational expenses. The comparison to an analytical solution helps to verify that the code is working properly. The residual formulation will be written into the current version of CASL CTF step by step with verification and validation practices along the way. The objective is to upgrade the different numerical methods available to CTF and increase software confidence.