This is the Agesta nuclear reactor south of Stockholm, Sweden. It only operated for ten years, from 1964 to 1974. When my grandfather visited in 1967 it was billowing steam.
Kodachrome slide. Taken by my grandfather David C. Cook while visiting for an International Electrotechnical Commission, atomic test standards subcommittee meeting. Date stamp October 1967, photo taken in September. Slide cartridge "Stockholm Skansen". Unlabeled slide "05 W4".