A long time ago, as part of a "Industry Study Visits"-course at university, we went to visit Asea-Atom and were told about the "PIUS" reactor ("Process Inherent Ultimate Safety"). Supposedly the construction was "passively safe" (i.e., breakdown of cooling pumps etc would not matter.) The idea was to have the reactor encased in an open pipe contained in a larger (closed) tank with borated water. Using stable stratification, the non-borated water was more or less
kept contained in the inner pipe using density locks; if something would go wrong the borated water would get sucked in and and shut the reactor down.
The engineers were very optimistic about selling this even as small municipal thermal power plants (for heating water) very close to city centers. The idea of passive safety is quite beatiful, but it seems
no PIUS reactors were produced. Rosatom seems to have had some success.
The engineers were very optimistic about selling this even as small municipal thermal power plants (for heating water) very close to city centers. The idea of passive safety is quite beatiful, but it seems no PIUS reactors were produced. Rosatom seems to have had some success.
More info about PIUS can be found at
https://www.iaea.org/sites/default/files/publications/magazi...
https://www.euronuclear.org/e-news/e-news-17/nps-kth.htm