In 1957, in the very early days of power reactors, Christopher Hinton, head of reactor building in England, visited Sweden. On his return, he wrote to Frank Farmer, the UK expert on reactor safety. Sweden was planning to build a small reactor, of the sort then being built in Canada, to provide community heating by warming up water piped into a town. “It follows,” wrote Hinton, “from the fact that these stations are being designed for district heating that they must be located within the precincts of the city.” The Swedes planned to counter the dangerousness of such a close-up reactor by siting it underground, but they remained concerned.
I find it interesting that the Swedes asked the British, who in turn assiduously observed American safety theory and design. Theory and practice quickly spread from the largest and most knowledgeable countries to the smaller countries, sometimes being amended during passage. Hinton commanded Farmer: “I suggested that . . . it might be helpful to them if you arranged to visit Sweden to discuss some of their problems with them and to tell them of our general philosophy in relation to safety.”
Hinton, Christopher. 1957. Hinton to Farmer, Mar. 22, 1957. AB 19/23, National Archives, Kew, United Kingdom.