By Visio Roughton
Nuclear power has had a significant impact on humanity and the science field in the past century, and humanity’s understanding of energy has only grown.
Today, it is utilized to power cities and medical treatment, and none of this could have been possible without decades of endless research to gain an understanding of it.
The development of nuclear technology has not been perfect, and has been marked by several infamous disasters; events such as the Three Mile Island, Chornobyl, and Fukushima Daiichi meltdowns are synonymous with the term ‘nuclear accident’.
However, they are far from the first events of their kind. Chalk River in Ontario, Canada is home to the first-ever nuclear accident though surprisingly, very few people seem to know about this historical accident.
Background – A Look at the Chalk River Site
Chalk River Laboratories, formerly known as Chalk River Nuclear Laboratories,
Is located in Deep River, Ontario, roughly 120 miles outside of Ottowa.
Defined by its rich history and influence on Canada’s nuclear research field, it has played an instrumental role in furthering the development of nuclear power since its establishment in 1944.
The facility’s focus on nuclear science was elicitated by a collaborative effort formed between Canada, the United Kingdom, and the United States during World War II that was aimed at advancing nuclear science and technology, along with scientists’ understanding of it.
The primary research focus initially conducted at Chalk River during its first years of operation was focused on the design and construction of nuclear reactors. In addition to this, researchers also studied plutonium production, and these concentrations in turn allowed them to contribute research toward the creation of nuclear energy and weapons.
In 1952, Atomic Energy of Canada Limited (AECL) was established, an organization aimed at encouraging the peaceful use of nuclear energy; it subsequently took over operations at Chalk River.
Under AECL’s management, the focus of research at Chalk River shifted to focus more on the civilian applications of nuclear technology (this included the development of, including the development of the CANDU reactor technology, a nuclear reactor that primarily uses water as a coolant while producing energy. To this day, the CANDU reactors are one of the safest nuclear reactor designs).
Throughout its long history, Chalk River has been instrumental in a number of scientific developments. One of its most notable mentions was the role it played in Professor Bertram Brockhouse’s work around neutron spectroscopy (a process of measuring kinetic and magnetic energy emitted by Neutrons), which he completed at the facility from 1950 to 1962. The work even earned him a Nobel Prize in Physics in 1994.
For a significant period of time, Chalk River was also one of the world’s leading producers and suppliers of medical isotopes.
Two events in the laboratory’s history marked dark moments for nuclear science, however, as it also played host to two of the world’s first known nuclear accidents.
The First Incident – the NRX Reactor Accident
On December 12, 1952, the NRX reactor, one of the nuclear reactors housed at the Chalk River Laboratories site, suffered a partial meltdown that after investigation, was found to be the result of largely human error, but also partially mechanical malfunctions.
The reactor was made up of a sealed aluminum silo that was roughly 26 ft tall by 9.8ft wide. Within this metal body of the reactor, there was an array of vertical metal tubes; out of the total 175 rods, 163 of them contained uranium fuel while the other twelve were control rods coated in boron carbide. The rods were essential to maintaining control of the reactor. The boron carbide-covered rods could absorb neutrons and were one of the forces that slowed a nuclear reaction, and if enough of those rods were inserted, they also had the potential to completely stop the nuclear reaction.
The water inside the reactor was another factor that worked to subdue nuclear reactions, as it could slow down the neutrons and increase their reactivity. It also acted as a coolant for the machine. During the final procedure in a series of planned tests on December 12th, some of that cooling water was drained from the reactor.
At the same time, one of the reactor operators removed four of the rods within the reactor, which further disrupted the balance within the core.
An on-duty supervisor was able to identify these mistakes as the cause of the reactor’s sudden spike in activity and called the control room to instruct operators on how to rectify their error. Whilst relaying the instructions he misspoke and accidently ordered the worker on the phone to push a button that would remove more rods from the reactor. While he was quick to clarify his mistake, the worker had already stepped away from the phone and pushed the wrong button.
This combination of errors resulted in a partial meltdown of the NRX reactor, and as the heat within its system increased, a series of pipes that supplied water to the reactor ruptured and spilled a flood of radioactive water down through the basement of the facility.
After about one minute, operators were able to get the cooling system back online and drain water out of the reactor’s core. While they had prevented a full-scale meltdown, they were still now tasked with an extensive clean-up.
The cleanup efforts took over a year to complete, and around 800 employees of the facility were tasked with contributing to this effort. The damage to the reactor was irreparable, thus it was disassembled and buried, a venture that proved difficult as workers were not allowed to be in contact with the reactor for more than 90 seconds.
To remedy this, a replica of the reactor was built on the playground of the town established near the Chalk River site, which allowed workers to train for their shift with the real reactor.
In addition to the employees of Chalk River, many members of the US Army and Navy also helped contribute to the cleanup. One of the most notable participants was then Navy Lieutenant Jimmy Carter, who would go on to be the 39th president of the United States.
After continuous efforts, the reactor was disassembled and buried in a remote area.
As the cleanup effort reached its end, the research that was so intrinsic to Chalk River’s operation resumed.
The Second Accident – the NRU Reactor Fire
Six years after the NRX incident, Chalk River faced its second nuclear accident. On May 24th, 1985, scheduled maintenance work began on a newer, much more powerful reactor that had been installed in the site’s National Research Universal reactor (NRU) building the previous year.
Some of the fuel rods within the reactor had become overheated, and as a result, they needed to be removed via a robotic crane. While completing this task, the robotic arm pulled away from the reactor too fast while still holding one of the rods, subsequently damaging it even further.
When the rod bent, the uranium caught fire and fully snapped the rod, which led to one of its largest portions falling back down into the reactor, while still burning.
A cloud of radioactive dust and smoke was sent rushing through the entire building and many of the workers and reactor operators fled the sudden wave of contamination.
To combat the fire, scientists, maintenance workers, and even members of the admin staff dawned protective gear and returned to the reactor with buckets of sand that were then used to extinguish the flames.
They continued to dump sand on the fire, running back and forth over the flaming rod via a catwalk until it had been fully extinguished.
Once again, a large clean-up effort was initiated— hundreds of workers operated in ten-minute shifts to minimize exposure to the radioactive materials. Some 1,200 workers participated in the clean up for the NRU incident, and this time the operation to clear away all the contaminated materials only took about 6 months.
In the years following the incident, new safety measures were put in place and these major improvements have made it so that since the 1950s, Chalk River has not experienced any more major accidents at its facilities.
Aftermath – the Effects of Chalk River Decades Later
While the 1952 and 1958 Chalk River nuclear accidents did not result in any immediate deaths, many of the workers and military personnel who responded to the incidents and participated in the clean-up efforts would suffer long-term health consequences in the years following the events at Chalk River.
The Canadian Coalition for Nuclear Responsibility notes that many members of the military who were part of the clean-up efforts were repeatedly denied disability pay due to health damages they suffered and continue to suffer from their radiation exposure.
Those who responded to the accidents also suffered a much higher risk of cancer later in life, four times more than is expected for the population at large.
It was not until the early 2000s, after years of denial, that members of the Canadian Military could claim around $20,000 that would recognize their service at Chalk River. Furthermore, it took until 2021 before civilian employees were promised monetary compensation for the damages they suffered as a result of their exposure to nuclear radiation in the Chalk River incidents.
In 2005, the cleanup at Chalk River during the 1952 incident was reviewed, with the focus especially turning to the decision to bury radioactive waste. It should be mentioned that most of the waste, especially the radioactive fuel rods, was buried in wooden crates, which had long since decayed leaving the soil to be contaminated by the radioactive materials. However, this choice to use wooden crates and the overall lack of caution regarding disposal of the nuclear waste is largely attributed to the limited knowledge of radiation at the time.
After this review, the waste was excavated and moved to a different location and fitted with a more adequate setup that would better contain the radioactive material.
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