Analyses of hot channel fuel conditions and loss of regulation accident for CANDU-SCWR fuel channels

Safe reactor operation relies on remaining below certain thermal limits during normal operation, anticipated operating occurrences and during accidents. With the very high temperature and pressure conditions proposed for the supercritical water reactor (SCWR), ensuring adequate cooling of fuel is of paramount importance. This study focuses on determining the pin temperatures, namely peak clad and fuel centerline temperatures, during normal operation conditions and reactivity induced accidents (RIA) in the most limiting fuel channel. The analysis has been performed using the FUELPIN point kinetics and heat transfer code which has been previously used in CANDU safety and licensing. The study was performed using proposed CANDU-SCWR conditions and operating parameters. Examined is the effect of various reactivity insertion rates on hot channel temperatures. As well, current CANDU neutronic trip coverage setpoints are examined to see how adequately current shutdown systems would perform in the CANDU-SCWR. The results of this analysis shows the response of the key parameters to reactivity insertion as well as the sensitivity to fuel pin diameter, normal operating power, sheath thickness and fuel-clad gap. (author)