The challenge of licensing a reactor with passive safety characteristics

Special emphasis has been placed on establishing safety criteria and a safety design philosophy for the Modular High Temperature Gas-Cooled Reactor (MHTGR) which enhances public acceptance while also permitting the presentation of a simple safety case to the regulator. However, the MHTGR safety approach and its characteristics as a gas-cooled reactor move it beyond the existing light water reactor-based regulatory framework. The design selected utilizes an entirely passive decay removal process and ensures inherent safety response to positive reactivity insertion events in order to assure retention of radionuclides by the coated fuel particles even under accident conditions. This obviates the need for a pressure-retaining containment structure and post-accident operator intervention. The challenge for the MHTGR has been to demonstrate its safety capabilities within the existing regulatory regime while retaining the advantages accruing from its unique inherent characteristics ad passive design features