In radiation treatment, a tumour is irradiated from several different directions to insure that it receives a high dose of radiation while the surrounding healthy tissue receives as small a dose as possible. The source, mounted on a wheel, could be turned to align with an opening in the shield, providing for precisely controlled emission of radiation. Probably nicknamed the cobalt bomb because atomic bombs of all kinds were very much in the news in those years immediately after the Second World War, it consisted of a cylindrical cobalt-60 source, about 3 cm in diameter and 5.5 cm long, inside a lead shield. He had his design built by John MacKay, owner of Acme Machine and Electric Co. Johns began developing a machine that could direct cobalt-60 radiation to tumours in a safe, calibrated way. Inside the reactor, cobalt, atomic weight 59, picked up an extra neutron in its nucleus to become the unstable isotope cobalt-60, 100 times more radioactive than radium–and far cheaper.ĭr. However, scientists operating the National Research Council’s heavy water reactor in Chalk River, Ontario, had created a better source of radiation. This generated powerful X-rays that could be used to treat cancer, but the machine was too expensive to operate for large-scale use, and the X-rays it produced weren’t always strong enough to reach tumours deep in the body. A precursor to the Canadian Light Source synchrotron now located at the university, the betatron used magnets to accelerate electrons to an energy level of 25 million electron volts.
Herrington, the head of the U of S Physics Department in the 1940s, had begun research in the 1920s into the medical use of radiation, and it was thanks to him that the U of S was at the forefront of nuclear physics in Canada in the post-war years, and received Canada’s first betatron in 1948. Harold Elford Johns, who had come to the U of S from the University of Alberta at the end of the Second World War.ĭoctors had been using radiation to kill cancer cells since shortly after the discovery of X-rays and radium in the 1890s, but X-ray machines were expensive and complicated, and radium, formed into thin needles and implanted near tumours, was expensive and not powerful enough to be completely effective.Į. It was the brainchild of physics professor Dr. In fact, to any reader of the pulp science fiction magazines of the day, it probably looked more like a super-powerful ray gun-which is just what it was. Installed in Room 167 of the newly constructed cancer wing adjacent to the medical college at the University of Saskatchewan on August 17, 1951, the device didn’t actually look like a bomb. Tell them the first cobalt bomb was built and tested right here in Saskatchewan, and they’ll wonder what kind of crazed conspiracy theorist you are.īut the first cobalt bomb was indeed built and first tested here, 55 years ago–and far from being a weapon, it marked a milestone in the medical treatment of cancer. Mathematically, one can go to ever higher and higher assumed tonnage and cobalt-60 production until a lethal range is reached.To most people, “cobalt bomb” sounds like some super-powerful weapon of mass destruction.
Thus, the estimated doses could be significant in long-term effects but not lethal in the sense of wiping out a worldwide population. Other doses may be calculated as a linear function of the tonnage assumed.
Decontamination measures could reduce this dose further. One megaton (total yield) detonated in the air might create enough cobalt-60 to produce a theoretical total dose of 0.17 r in the most heavily contaminated band of the earth f 30 0-60 0 north latitude), with weathering and shielding effects reducing this by as much as a factor of 10. fission yields and position of firing, would be more critical in determining the external y-hazard than the added cobalt-60. Based on stated assumptions, the ratio of potential external energy releases from fission products in “local” fallout compared to the cobalt-60 that may be produced can vary from a factor of 40, based on an exposure period from 1 hr to 1 month after a detonation, to 0.17 based on an exposure period from the twenty-fourth hour to 35 years.
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