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Chadwick’s Role in Canada’s Nuclear Heritage

Written by
Jim Ungrin
the North Renfrew Times
2022 Jun 15

Many Canadian, British and European scientists played important roles in the beginnings of Canada’s nuclear story and have received various degrees of credit for their contributions. Les Cook was the Director of the Chemistry and Metallurgy Division of CRNL from 1945 to 1956. He also was the host for the only visit of Sir James Chadwick to Chalk River. His evaluation of the critical role Chadwick played in the origins of the “Canadian project” that led to CANDU are documented in his unpublished book “Birthpangs of CANDU”. The following is Cook’s version of the visit and of Chadwick’s role in the beginnings of Canada’s nuclear program.

“Sir James Chadwick, the Cambridge physicist who discovered the neutron in 1932, came once to visit Chalk River. Rutherford had guessed that such a particle existed, had sought it for years and almost given up, when Chadwick realized he had it. The discovery of this particle, one of which forms the essential key that triggers the fission of each uranium or plutonium atom in a nuclear reactor or bomb, was a critical step towards the discovery of fission by Otto Hahn in Berlin six years later.
Sir James had come to the US as head of the British group of scientists who were partners in the Manhattan District project. He actually had the same status in the Manhattan District project as General Groves, who had great faith in Chadwick and consulted him on all important technical matters.

So Chadwick’s visit was a major and welcome event, an opportunity to meet a great scientist, an influential and fine man, and to discuss our work with him.
Since we had no reasonable public facilities for entertaining guests in Deep River, or anywhere closer than Ottawa (125 miles away), we had to lay on parties and receptions in our own homes, small and inadequate though they were. Thus it came about that Chadwick was entertained in the evening in my basement at 34 Parkdale, which I had set up as a study but with a little extra furniture could serve for a modest gathering.

For some reason, at such gatherings the senior Chalk River staff usually got into busy discussions among themselves, and I found myself alone in a delightful discussion with our honoured guest. Chadwick told me two things of considerable and lasting interest.

The first concerned the origin of the Canadian project. He told me he had agreed completely with the decision to use graphite as the moderator for the Hanford plutonium production reactors, because graphite was adequate as a moderator, and commercially available in adequate quantities (such graphite is used for electrodes in electrolytic aluminum production). However, he was convinced that the exploration of the superior moderating characteristics of heavy hydrogen should not be allowed to fallow, even during the war. He urged on Groves that a high-power heavy-water experimental reactor should be committed.

Groves agreed to have his staff look into the pros and cons and make a report with recommendations. Chadwick said that the report had been well done. All he had to do, he said, was make a few changes in the recommendations, turning a few of the negatives into positives, to make it an excellent report. He told me that Groves accepted it as modified – and it remained only to work out the details where the reactor should be located, and the division of responsibilities. The UK was ruled out because of the bombing risk. The US was ruled out because it was viewed as an undesirable diversion of manpower from its focus on the bomb. Accordingly, it was proposed that it be located in Canada: that the UK would be responsible for staffing; and the US would provide essential technical information, uranium fuel, heavy water, and any other necessary materials. Fuel processing technology was not included, but it was agreed that irradiated uranium and thorium would be supplied so that the process R&D could be done.

This proposal went to Churchill, Roosevelt and McKenzie King at their famous Quebec City meeting. King agreed to it all, with the proviso that Canada would supply the money and administration, “own” the project and take it over completely after the war.

Thus was the “Canadian” nuclear project initiated, according to Chadwick.

Chadwick’s second comment concerned the superb accomplishment of Dr. J. “Mac” Lounsbury in designing, building and successfully operating a mass spectrometer for analyzing the isotopic composition of different samples of uranium and plutonium.”

After several more pages on mass spectrometers Cook adds a final paragraph:

“I never met Sir James again, but I remember him as one of the finest, quickest and most perceptive and honest minds I have been privileged to know. If anyone should be designated the father of Chalk River, of NRX and of CANDU, it is Sir James Chadwick. His share in their creation was never widely known, and has long been forgotten with the demise of those few who really know. May this story set the record straight.”