Hans Bethe, Manhattan Project scientist and Nobel laureate, calculated in 1956 that if a breeder's liquid
sodium coolant leaked out, it could melt in 40 seconds, become a small unintended atom bomb and spontaneously explode.
Superphenix the French fast - breeder reactor shut down in 1990 because air
leaked into its liquid
sodium coolant, can not start up again until a public inquiry has been held, Prime Minister Pierre Beregovoy announced this week.