Las están desarrollando en Japón, con vistas a venderlas tanto en países del tercer mundo, como en USA, este de Europa, tigres asiáticos y otros voraces consumidores de energía. El sistema incluiría un mecanismo de bloqueo cuando se planteara algún problema:
Toshiba Corp. is developing an ultra-compact reactor with an output of about 10,000 kilowatts and has started procedures for approval in the United States, the Nikkei business daily said. The new reactor, the Toshiba 4S, is designed to minimise the need for monitoring and maintenance, with an automatic shutdown function to ensure safety in case of problems.
Toshiba plans to market the reactor first in the United States, while foreseeing demand from emerging countries in Southeast Asia and Eastern Europe as well as in Africa.
Mitsubishi Heavy Industries Ltd. has separately completed the concept design for a pressurised-water reactor with a power output of around 350,000 kilowatts.
Demand for nuclear power stations has been growing around the world. A total of 151 were under construction or slated for construction in 27 countries as of the end of 2008.