Heavy Water Reactor Moderator Effectiveness as a Backup Heat Sink During Accidents

The IAEA organizes international collaborative standard problems (ICSP) to facilitate the development and validation of computer codes for design and safety analysis of nuclear power plants, which usually includes an experimental investigation of important phenomena and simulation of the experiment with computer codes. This ICSP investigated phenomena that determine the thermo-mechanical behaviour of heavy water reactor fuel channels during a fuel overheating scenario. The publication summarizes the experiment, the complex and transient nature of phenomena interactions that ultimately determine fuel channel behaviour, the simulation methods and results, and the lessons learned from the ICSP. It provides a comparison of the results obtained from eight participating organizations from five countries, utilizing different methods and computer codes. General conclusions drawn and recommendations made for future developments are also included.