Post-Test Simulation and Analysis of the Second Full Scale CHAN 28-Element Experiment (Validations of CHAN-II (Mod 6) Against Experiments)

Abstract

An experimental program, the CHAN Thermal Chemical Experimental Program, has been setup at WNRE under COG/CANDEV to assess and verify the physical and mathematical models of the CHAN codes. The program has been progressing from studying separate effects in single-element experiments to a full integrated mode in a CANDU 28-element bundle geometry. The CHM-11 series codes are used in the licensing analysis of CANDU reactors. The basic code provides an efficient tool to predict the thermal response of a fuel channel during postulated loss-of coolant accidents (LOCA) with and without a loss of emergency coolant injection (LOECI) in which the transport of heat by convection is greatly reduced. The code models the progression of the event including fuel channel geometry deformation due to severe overheating. It is the main objective of this paper to discuss further verification of the CHAN-I1 (MOD 6) computer code against the second fill scale 28-element experiment performed at WNRE under COG/CANDEV, designed to represent a Pickering type bundle geometry. The main models and assumptions used in the code will be briefly described. The objective of the experiments is to provide data for the assessment of the physical and mathematical models of the CHAN codes and produce data for code verification under integrated conditions with significant hydrogen production and flow rates similar to the LOCA/LOECI scenario. The issue of whether the Zr/steam reaction is sustainable in a full bundle geometry at elevated temperatures is also examined. A comparison between the predictions of CHM-II (MOD 6) and the experimental results is discussed.