SAFETY CONCEPTS AND SYSTEMS OF THE CANADIAN SCWR

摘要

Canada is developing a next generation (Gen IV) reactor, the Canadian Super-Critical Water-cooledReactor (SCWR) which will meet the goals of the Gen IV International Forum (GIF). These includeenhanced safety features (inherent safe operation and deploying passive safety features), improvedresource utilization (~40% more efficient than current nuclear power generating stations, sustainablefuel cycle (will burn thorium, which is three times more abundant than uranium), and greaterproliferation resistance than Gen III reactors. The Canadian SCWR concept is a heavy-watermoderated pressure-tube type reactor that uses supercritical water as a coolant, a separate heavy watermoderator, and a direct steam power cycle. One of the major design goals of the Canadian SCWR isto enhanced safety such that the risk of core damage and release of radiation to the environment issignificantly reduced. The unique features of the pressure tube based design allow for an optimumbalance of passive safety features on the moderator systems for emergency heat removal (such as aprolonged station blackout event) and a combination of active and passive safety systems in the maincooling system. The primary system components are selected to provide multiple and redundantdecay heat removal paths; these defence-in-depth concepts should provide improvements in plant riskover existing designs. However, there is a transformative improvement in core damage risk byincluding a further passive decay heat removal pathway for emergencies. This capability is possiblethrough a combination of a natural circulation driven moderator cooling system, the High EfficiencyChannel concept, and direct radiation heat transfer from the fuel to the HEC components. The paperpresents the preliminary safety concepts and systems proposed for the Canadian SCWR design, anddiscusses how the passive moderator cooling system significantly reduces core damage frequency.