Secure reactors

The principle of Process Inherent Ultimate Safety (PIUS) is a new approach to Light Water Reactor (LWR) safety that could represent a solution to the present problems of public distrust, regulatory maze and plant design complexity plaguing the nuclear industry in many countries. A unique thermohydraulic design of the primary system ensures core integrity, and thereby guarantees freedom from significant releases of radioactive matter, in all credible emergencies. This is accomplished entirely without reliance on potentially failure prone engineered safety systems and with immunity to operator mistakes. The potential for human fallibility to cause accidents is thereby drastically reduced in an easily understood way. Plant design can be greatly simplified because redundant, diverse safety systems are no longer needed. The paper briefly describes the PIUS design principle and the two SECURE reactor designs based on it, i.e. SECURE-H for district heating and process steam and SECURE-P (usually known simply as PIUS) for electric power generation. Demonstration of simulated system over-all thermohydraulic function and transient response in a large electrically heated test loop is described and results from some component development work is given