GBR-4 protection systems: failures and their consequences

In the GBR-4 design of a gas-cooled fast breeder reactor, emphasis is placed on using to advantage the single-phase character of the coolant. Specific features of the protective systems are fail-safe neutron absorption, permanently operating auxiliary supplies, and atmospheric-pressure cooling. A computer program that uses a point reactor model for heat transfer and neutron kinetics is used for transient analysis, and a steam-generator dynamics code is used to describe secondary side effects. Anticipated disturbances in operation are reactivity insertion, loss of supplies, and loss of coolant pressure. Failures in reactor protection systems are postulated for these disturbances in decreasing order of probability, and the consequences are analyzed and discussed. The results lead to the conclusion that, owing to the inherent characteristics of the system and to the specific design, occurrences are well within the limits of a typical probability release criterion. (U.S.)