NRX

Surrounding the fuel element was an aluminium coolant tube with up to 250 litres per second (3,300 imp gal/min) of cooling water from the Ottawa River flowing through it.

Emerging from a World War II cooperative effort between Britain, the United States, and Canada, NRX was a multipurpose research reactor used to develop new isotopes, test materials and fuels, and produce neutron radiation beams, that became an indispensable tool in the blossoming field of condensed matter physics.

When the decision was made to build the NRX at what is now known as Chalk River Laboratories, the detailed engineering design was contracted to Canada's Defence Industries Limited (DIL), who subcontracted construction to Fraser Brace Ltd.

In the early days of cancer radiation therapy, the NRX reactor was the world's only source of the isotope cobalt-60, first used to bombard tumours in 1951.

[3] In 1994, Dr. Bertram Brockhouse shared the Nobel Prize in Physics for his work in the 1950s at NRX, which advanced the detection and analysis techniques used in the field of neutron scattering for condensed matter research.

[4] It is claimed that the term "crud" originally stood for "Chalk River Unidentified Deposit", used to describe the radioactive scaling that builds up on internal reactor components, first observed in the NRX facility.

[citation needed] On 12 December 1952, the NRX reactor suffered a partial meltdown due to operator error and mechanical problems in the shut-off systems.

The wrongly-opened valves were immediately closed, but some control rods did not reenter the core and were stuck in almost withdrawn positions, but still low enough for their status lights to indicate them as lowered.

Meanwhile, some fuel elements melted and were pierced in several places; the helium cover gas leaked, and the air was aspirated inside.

[6] To remove the fuel decay heat, the water cooling system was kept operating, leaking contaminated coolant to the reactor basement.

About 10 kilocuries (400 TBq) of radioactive materials, contained in about 4,500 cubic metres (1,200,000 US gal) of water,[6] collected in the basement of the reactor building during the next few days.

The US contingent included future US president Jimmy Carter, at the time a lieutenant in the US nuclear submarine program who was in charge of 12 men.