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Beginnings + 1945: ZEEP + 1947: NRX + 1957: NRU + 1994: Nobel Prize
In Canada following the outbreak of war, there was a scientist George Laurence, who had studied under Rutherford in the UK. After gaining his PhD he had joined the National Research Council, working on radium and x-rays. In the spring of 1940 having read about experiments in nuclear fission from others working in the field, Laurence built the first Canadian nuclear fission experiment. At that time Canada was one of only two significant sources of uranium in the world. Laurence recognized the advantage his country had, in pursuing this field of science. However it was not yet recognized as crucial to the war effort so his first experiment was assembled during weekends and spare time.
In a room inside the grand NRC building at 100 Sussex Drive in the centre of Ottawa, Laurence built a prototype nuclear reactor.
He wanted to see if he could create a continuous fission process. To do that he needed two materials. First of course he needed uranium. He borrowed half a ton of uranium oxide from Gilbert Labine of Eldorado mines. It was a waste product from the production of radium from the pitchblende deposits around Great Bear Lake in northern Canada. The second material Laurence knew he would need was something to slow down the neutrons from the fission process. It was already known that neutrons emitted from a uranium atom as it split, were moving too quickly to be captured by a neighbouring atom. They needed to be slowed by colliding with atoms of another material. Laurence chose carbon for this purpose, and consequently bought ten tons of coke from the graphite industry. He piled paper bags of uranium oxide in a regular pattern, each surrounded by the powdered coke, about a ton of material in total. In the middle of this pile he inserted a neutron source to initiate the nuclear reaction, which he measured using home-made Geiger counters. It was only the impurities in his raw materials that prevented Laurence from becoming the first to create a sustained nuclear reaction.
On the right is a diagram of the prototype nuclear reactor built on Sussex Drive in Ottawa in 1941-42. It did not achieve criticality, so the experiment is called a "sub-critical pile". However, at the time it was built, the US and UK had not yet started nuclear experiments of such a scale: another Canadian achievement. Laurence's lab was in the National Research Council's building at 100 Sussex drive, just a few minutes from the Byward Market and downtown Ottawa.
That first experiment predated similar work in the United States but it was not long before both the USA and the UK began to pursue in earnest a quest to unlock the large power contained within the atom. Through the early part of the war the three countries had periods of both cooperation and isolation between their nuclear programs. By 1944 however, with the US weapons program now developing in isolation, there came agreement that a large nuclear research facility should be built in Canada with involvement from the other allied nations. Ned Steacie and George Laurence of the NRC were both involved in the selection of Chalk River as the first choice of site, which was approved by the Canadian cabinet minister C.D. Howe in August 1944.
By October there were 350 men on site, clearing trees and farms on the banks of the Ottawa river, and constructing roads, water lines and essential services. Within a year there were over 3,000 working at the laboratory site. At Chalk River on September 5th 1945 the first nuclear reactor outside of the USA went critical. It was known as the Zero Energy Experimental Pile, ZEEP.
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George Laurence's pile circa 1941