According to the BBC (and The Scotsman and probably others) it’s 50 years today since Scotland’s (and Britain’s) first experimental fast breeder achieved criticality; there are plans to turn the complex into the UK’s first nuclear heritage site.
BBC: First nuclear heritage site bid
Wikipedia gives a somewhat different story, stating the first, Dounreay Materials Test Reactor achieved criticality as early as in May 1958, and in November 1959 the second, Dounreay Fast Reactor came online. Well, whatever.
Note: two days later Sue Thompson (http://www.dounreay.com/) kindly explained:
“Oddly enough, both sources are correct.
The Dounreay Materials Test Reactor achieved criticality first, but was not a fast breeder reactor. The Dounreay Fast Reactor was the UK’s first fast breeder reactor.”