'Three Mile Island': What Happened In the Chalk River Nuclear Accident?

Meltdown: Three Mile Island on Netflix brings to the small screen the terrifying reality of the Three Mile Island Nuclear accident on March 28, 1979.

At Three Mile Island Nuclear Generating Station in Pennsylvania, there was a partial meltdown of Unit 2 (TMI-2), marking the worst commercial nuclear accident on U.S. soil.

The Three Mile Island accident was (and indeed remains) the worst commercial nuclear accident to happen on U.S. soil, and as history has shown with Chernobyl in 1986 and Fukushima in 2011, accidents continue to happen.

However, 27 years before the Three Mile Island accident there was a serious accident at Chalk River Laboratories in Ontario, Canada, which is briefly mentioned in Netflix's Meltdown: Three Mile Island.

What happened in the Chalk River Nuclear Accident?

Newsweek has everything you need to know.

chalk river jimmy carter
(L-R) Plant Official, President and Mrs. Carter, Governor Thornburgh and NCR's Harold Denton at crippled Three Mile Island nuclear plant in 1979. Dirck Halstead/Getty Images

What Happened in the Chalk River Nuclear Accident?

In 1952 and 1958, the first nuclear reactor to exist outside of the United States, Chalk River Laboratories in Canada, found itself at the center of two potential nuclear disasters.

The first was known as the NRX Accident (National Research Experimental), and the second as The NRU Accident (National Research Universal Reactor).

1952 NRX incident

The first incident occurred on December 12, 1952, featuring a reactor meltdown and partial loss of coolant in the NRX reactor—at that time the world's most powerful nuclear research reactor.

The situation was made worse when the control rods could not be lowered into the NRX's core, with the incident further exacerbated by both mechanical and human errors.

The roof of the reactor was blown off, and over 1,200,000 U.S. gallons of radioactive water leaked, settling in the cellar of Chalk River Laboratories.

But, instead of the water being removed off-site, it was dumped into ditches 1,600 meters from the border of the Ottawa River, releasing 10 kilocuries (a unit and measure of radioactivity, equal to 1000 curies) of radioactive material into the area, details the Canadian Nuclear Society's report on the 1952 NRX Incident.

At the time of the first Chalk River Nuclear accident, future U.S. President Jimmy Carter, who was serving as a U.S. Navy officer, was part of the clear-up team which included U.S. Navy volunteers all helping to deal with the aftermath.

Journalist and author Arthur Milnes spoke to CBC News about the conditions Carter found himself in at Chalk River. For example, he and his men worked in shifts of 90 seconds due to the radioactivity risk.

He said: "By today's standards, there's no way that would have happened.

"In [Carter's] case, at least, he was lowered into the building ... with his wrench, and he had to run over to the reactor casing and he had one screw to turn. That was all the time he had. And then, boom, back up."

NRX resumed operations within two years.

When the accident at Three Mile Island occurred over 20 years later, Carter, who was now President, inspected the nuclear plant five days after the accident in a bid to reassure people in the area (and the world) that their lives were not in any danger.

His background in nuclear engineering and his experience of dismantling a reactor at Chalk River helped with this credibility.

In April 1979, he launched the President's Commission on the Accident at Three Mile Island in a bid to understand what went wrong.

1958 NRU incident

Six years after the first incident in Canada, in 1958, Chalk River experienced another serious incident when a damaged fuel rod caught fire and tore apart as it was being removed from the NRU core. As a result, there was a fuel rupture of the core and a large fire in the NRU building.

The whole building was contaminated with radioactive material, which leaked to a large area outside the building when the ventilation system kicked in. Thankfully, the fire was put out and nobody was harmed in the immediate aftermath.

There have been several other incidents at Chalk River Laboratories, including a 2008 radioactive leak from the NRU, but it was not deemed a risk to the public. In 2007 and 2009, the NRU was temporarily shut down but soon re-opened.

On March 31, 2018, the reactor at Chalk River was officially shut down and entered a decommissioning stage.

NRU may be shut down but the site at Chalk River is still in use, with some old buildings removed and new ones established. Today, it is the site of the Canadian Nuclear Laboratories Research Facilities.

Meltdown: Three Mile Island is streaming on Netflix now.