Learning the hard way - an early accident at the NRX reactor led to improved design of subsequent reactors and the development of a distinct Canadian approach to reactor safety

On a Friday December afternoon just over 50 years ago an event occurred which would have a significant effect on the Canadian nuclear program, especially on the development of reactor safety philosophy. During preparation for reactivity measurements at low power, on 12 December 1952, 'a complex concurrence of mechanical defects ... and operating errors ... resulted [in] a power surge in the NRX reactor. This major accident, the most serious in the history of the Canadian nuclear program, resulted in melting of some of the uranium metal fuel and the release of an estimated 10,000 curies (about 4x108 MBq) of fission products into about 1,000,000 gallons (over 4,000,000 litres) of (light) water which was contained in the basement of the NRX reactor building. The following accounts (and the quote above) are taken from the official report on the accident by Dr. W.B. Lewis, issued in 1953, and a 1955 paper by G.W. Hatfield. (author)