Chalk River Accidents, Canada (1952 and 1958)

The Chalk River accidents in 1952 and 1958 involved partial meltdowns of the NRX and NRU research reactors. The 1952 incident released 10,000 curies of fission products into the Ottawa River, contaminating a 2-kilometer stretch of shoreline, with future U.S. President Jimmy Carter leading a 150-person cleanup team. The 1958 NRU incident, caused by a broken fuel rod, resulted in a fire that contaminated the reactor building for years, yet no direct fatalities occurred—a stark contrast to the one death from Castle Bravo's fallout.