Three-dimensional moderator circulation experimental program for validation of CFD code MODTURC-CLAS

Detailed predictions of moderator flow patterns and the associated temperature distributions in the calandria of Ontario Power Generation Inc. (OPGI) reactors are performed for safety analysis of certain accident scenarios. The specialized computational fluid dynamics (CFD) code MODTURC-CLAS-IST V2.9 has been selected as the Canadian nuclear industry tool for performing these predictions. To close all gaps in the validation data base, a robust program of three-dimensional moderator circulation experiments is being conducted for OPGI at AECL's Chalk River Laboratories. The program is divided into a separate-effect and component-testing stage, and a quarter-scale, calandria model, integral testing stage. The separate-effect and component experiments, performed in specially designed test sections and test loop configurations, include the round jet development test, moderator inlet diffuser characterization, tube bank pressure loss experiments, wall jet development studies and buoyant-jet experiments. The main Moderator Test Facility (MTF) will be used to conduct the integral quarter-scale calandria flow experiments. A series of such tests will be conducted, covering reactor conditions representative of 0 to 100% full power, with both 8 and 12 moderator inlet nozzle configurations. Transient tests are being devised that will provide data for the validation of the transient modeling capabilities of MODTURC-CLAS-IST V2.9. The first series of separate-effect tests, involving pressure drop measurements for tube bundles accurately representing the CANDU calandria tube arrangement, has been completed and the results will be presented. (author)