Former President Jimmy Carter reacts as his wife Rosalynn Carter speaks during a reception to celebrate their 75th wedding anniversary Saturday, July 10, 2021, in Plains, Ga. The now-98-year-old Carter started hospice care at his home this weekend, prompting a rush of remembrances, including a consequential piece of international nuclear history that played out at Ontario's Chalk River Laboratories more than 70 years ago. THE CANADIAN PRESS/AP Photo/John Bazemore, Pool

It was December 1952, the Cold War was raging and in a rural Ontario community a nuclear reactor had just partially melted down – the first serious reactor accident in the world.

The partial meltdown at the experimental Chalk River Nuclear Laboratories, about 200 kilometres northwest of Ottawa, was significant for the changes to reactor safety and design it helped usher in.

More than 70 years later, it's also being remembered as the event where a young U.S. naval officer who went on to become president helped disassemble parts of the reactor facility under intense radiation.

Jimmy Carter, best known for being the 39th president of the United States, was at that time Lt. James Earl Carter Jr., a 28-year-old officer who arrived with a team in the aftermath of the accident to help.

The now-98-year-old Carter started hospice care at his home this weekend, prompting a rush of remembrances, including a consequential piece of international nuclear history that played out at Chalk River decades earlier.

"It was very valuable," Morgan Brown, a recently retired Chalk River reactor safety engineer and president of the Society for the Preservation of Canada's Nuclear Heritage, said of the American assistance.

"Personally I'm very grateful to these other (U.S.) teams who were able to come up here."

The accident took place on Dec. 12, 1952, when a series of failures led to a brief surge, melting some of the nuclear reactor's fuel rods and maxing out at about three times the facility's power, Brown says. No one was killed or seriously injured, and contamination was closely monitored in the aftermath, he said.

In his 1975 autobiography, Carter recounted how he was part of a U.S. military contingency who helped dismantle parts of the reactor facility, donning white protective equipment and working in 90-second shifts to reduce radiation exposure.

His team would first practice their maneuvers on a replica reactor constructed nearby before going in to the real facility.

"There were no apparent aftereffects from this exposure – just a lot of doubtful jokes among ourselves about death versus sterility," Carter wrote in the autobiography.

Carter would later say the cleanup was an indication of the close ties between Canada and the U.S., a relationship he would look to as president during the 1980 Iranian hostage crisis.

Brown noted that records suggest U.S. military personnel arrived several weeks after the accident.

"There would've been contamination," he said. "There would have been relatively high radiation fields and that's why they had limited time to go in and do their job."

Carter was one of the 150 U.S. military personnel who worked on the cleanup alongside roughly 860 facility staff, 170 Canadian military personnel, and 20 construction contractors.

A speech delivered by U.S. Admiral Hyman Rickover in 1978 indicates he asked Canada for permission to send a group of naval officers to help, but also to gain experience.

Rickover said Carter did "an outstanding job," according to a copy of his remarks, published to Carter's presidential library website.

Brown said the Chalk River accident is well-remembered in the nuclear community for the changes it brought about, including improved shutdown systems and clearer control room operation standards.

This report by The Canadian Press was first published Feb. 20, 2023.

Note to readers: This is a corrected story. A previous version incorrectly described Chalk River as north of Ottawa.

News from © The Canadian Press, 2023