PRACTICAL ELIMINATION OF LARGE OR EARLY RADIOACTIVE RELEASES - APPROACH FOR IMSR400

Abstract

One essential objective of the design of a new Nuclear Power Plant (NPP) is to limit, in the event of a severe accident, the radiological consequences. In this context, one of the most important requirements of CNSC REGDOC-2.5.2 and IAEA SSR-2/1 for new NPP designs is for “practical elimination” of the accident conditions that could lead to significant radioactive releases. This paper presents the “practical elimination” approach for Terrestrial Energy’s IMSR400 design in the context of defence in depth, taking into account the requirements of CNSC and IAEA. The IMSR400 achieves excellence in nuclear safety with its inherent safety characteristics of the design. The IMSR400 design has implemented the necessary provisions for mitigation of severe accidents and “practical elimination” of the accident conditions that potentially lead to a large or early release. The paper also presents the preliminary assessment demonstrating that accident conditions potentially leading to a significant radioactive release are physically impossible or extremely unlikely to occur. As a Generation IV reactor, the IMSR400 is designed to eliminate the need for offsite emergency response.