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Chalk River Nuclear Accident - Ontario, Canada

Chalk River Nuclear Accident - Ontario, Canada

Chalk River Laboratories is a facility located in Ontario, Canada. During the 50s, these facilities suffered two major nuclear accidents.

The first Chalk River nuclear disaster occurred in 1952 when the NRX reactor suffered a violent explosion that destroyed the reactor core. The explosion of the reactor caused the fusion of nuclear fuel. The descent of the control rods failed so that nuclear chain fission reactions could not be stopped. As a result, thousands of radioactive particles were released into the atmosphere.

The second nuclear accident at the Chalk River facilities took place 5 years later. In this case, several uranium nuclear fuel rods overheated and broke inside the NRU reactor core. Due to the breakage of the fuel rods they caught fire causing serious consequences in the Canadian installation.

Chalk River Laboratories

The Chalk River Laboratories or Chalk River Labs and previously called Chalk River Nuclear Laboratories are facilities located near the Chalk River, Ontario (Canada) population dedicated to the investigation of nuclear reactions.

The installation was born in 1942 as a result of collaboration between British and Canadian nuclear researchers. In 1944 the Chalk River Laboratories were inaugurated and in September 1945 the installation put into operation the first nuclear reactor outside the United States.

The NRX is a nuclear research reactor, moderated by heavy water, cooled by light water. It was built in a time of war with the aim of using it for military purposes, although the designers contemplated many other civil applications. At present, the Chalk River Laboratories are of great importance in the medical applications of nuclear energy.

First nuclear accident in Chalk River

The first accident occurred on December 12, 1952. The NRX reactor suffered a shutdown failure that, together with several bad decisions of the facilities operators, caused a nuclear fission chain reaction that increased the power by more than double of the nuclear reactor.

Operators opened the 4 pressure containment valves in the cooling system of the nuclear power plant, which caused an explosion that destroyed the core of the nuclear reactor, causing a spill of nuclear fuel.

Inexplicably, the closure of the control rods did not descend completely into the reactor core. A series of hydrogen gas explosions (or steam explosions) launched the four-ton dome through the air. Thousands of nuclear fission particles were released into the atmosphere along with a million liters of radioactively contaminated water. Contaminated water had to be pumped out of the basement and poured into shallow ditches, near the Ottawa River.

The NRX reactor core could not be decontaminated, but had to be buried as a radioactive waste. A new nuclear reactor, even more powerful, was placed in its place to continue its operation.

Jimmy Carter's role in Chalk River, Ontario

Jimmy CarterAs a curiosity, a young Jimmy Carter (a nuclear engineer from the US Navy) was one of the hundreds of Canadian and US military who were ordered to participate in the NRX cleanup as a result of this nuclear accident. Later he would be president of the USA.

At that time the INES Scale (International Nuclear Event Scale) had not yet been created, but at present, due to the characteristics of the accident it would be located at level 5 of the INES scale (accident with off-site risk).

Second Chalk River nuclear accident

Five years later, in 1958, several metal rods of uranium nuclear fuel from the NRU reactor overheated and broke inside the reactor core. One of the damaged bars caught fire and broke in two, while it was being removed from the base by a robotic crane. It fell into a shallow maintenance pit.

The burning of nuclear fuel remained there, laying deadly nuclear fission products and the emission of alpha particles throughout the Chalk River reactor building. The ventilation system was stuck in the "open" position, which contaminated the building's access areas, as well as an important area in favor of wind at the reactor site.

A relay team of scientists and technicians finally extinguished the fire. More than a thousand men were involved in cleaning operations after these two accidents at Chalk River.

Consequences of Chalk River nuclear accidents

More than 600 men were needed only to clean the NRU. The official reports of the AECL (Atomic Energy of Canada Limited) highlight that very few of these men were exposed to excessive radiation, that is, most of the radioactivity doses recorded did not exceed the levels that were considered admissible for workers in nuclear facilities at that time. Reports also indicated that there were no adverse health effects caused by the radioactive exposures received.

However, no medical follow-up has been performed to see if the population of men involved in Chalk River accidents in the future showed a higher than normal incidence of cancer.

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Last review: January 22, 2020