PIUS on the move in Italy

It is almost ten years since ABB Atom began working on the PIUS reactor design, aiming to improve Lighter Water Reactor (LWR) safety characteristics with inherent and/or passive features based on simple natural laws such as gravity and thermohydraulics. Many versions have been studied, but recently efforts have been concentrated on a 600MWe unit with four-loops. Basically, PIUS is a passive, simplified PWR, based on well-established LWR technology. In conventional LWRs, severe accidents with major releases to the environment can occur following core meltdown. The main safety aim, therefore, is to protect the core and its fuel. In PIUS, this is accomplished by submerging the core in a large pool of borated water, and by ensuring that the cooling capability of this water is greater than the power of the core. The detailed design work for PIUS is progressing, with a final design verification experimental programme planned. An NRC licensability review will begin this year and the design certification process, which should aid any decision to construct the first plant, may well start in 1992/93. (author)