The Montreal Laboratory in Montreal, Quebec, Canada was established by the National Research Council of Canada to undertake nuclear research, and to take over some of the scientists and projects from the Tube Alloys nuclear project in Britain. The laboratory was associated to the American Manhattan Project, and was the result of a collaboration between the United Kingdom and Canada.
Foundation of Montreal Laboratory 
The British Government wanted the Cavendish Laboratory team at the University of Cambridge to be relocated in Chicago, where the American research was being done but the Americans had become very security-conscious. Only one of the six senior scientists in the Cambridge group, which had originated in Paris, was British. They were therefore sent to the Montreal Laboratory.
Emerged with Université de Montréal 
The first eight staff arrived in Montreal at the end of 1942, and occupied a house belonging to McGill University. Three months later in March 1943 they moved into a 200 square metre area in a new building at the Université de Montréal, which had been built for a new medical school, but through lack of funds had not been fitted out.
Manhattan Project 
The laboratory grew quickly to over 300 staff; about half were Canadians recruited by George Laurence. A subgroup of theoreticians was recruited and headed by a Czechoslovak physicist George Placzek. Placzek proved to be a very capable group leader, and generally regarded as the only member of the staff with the stature of the highest scientific rank and close personal contacts to many key physicists involved in the Manhattan project. The Director of the laboratory was Hans von Halban, but he proved to be an unfortunate choice as he was a poor administrator, and did not work well with the National Research Council of Canada. The Americans saw him as a security risk, and objected to the French atomic patents claimed by the Paris Group (in association with ICI). One other scientist at the laboratory was later found to be a security risk: Alan Nunn May. Bruno Pontecorvo, who defected to the Soviet Union in 1950, has long been suspected of having been involved in espionage, but passed all security tests at the time, and no evidence that he was a Soviet agent has ever been established.
Nuclear Research at Montreal Laboratory 
The Montreal team in Canada depended on the Americans for supplies of heavy water from the US heavy water plant in Trail, British Columbia (which was under American contract), as well as technical information about plutonium. The Americans said that they would give heavy water to the Montreal group only if it agreed to direct its research along the limited lines suggested by du Pont, . Despite doing much good work, by June 1943 work at the Montreal Lab had come to a complete standstill. Morale was low and the Canadian Government proposed cancelling the project. The Quebec Agreement in 1943 had led to more cooperation with America, though most of the British Mission scientists were based at Berkeley or Los Alamos.
Development of Atomic Bomb 
In April 1944 a Combined Policy Committee meeting at Washington agreed that Canada would build a heavy water reactor. Scientists who were not British subjects would leave, and John Cockcroft would become the new Director of the Montreal Laboratory. This was also because following the Liberation of Paris in August 1944, Halban returned on a visit to London and Paris, where he saw Joliot-Curie for the first time since leaving France. While he maintained that he did not divulge any nuclear secrets to his previous boss (although he had discussed patent rights), Halban was not allowed to work or to leave North America for a year, by General Groves, head of the Manhattan Project.
When Cockroft took over, the Americans fully supported the reactor project with information and visits. They also supplied material e.g. uranium and heavy water. The project developed the ZEEP reactor and then the NRX reactor. Lew Kowarski of the Paris group who had not wanted to work for Halban joined the Laboratory.
The Chalk River Laboratories opened in 1944, and in 1946 the Montreal Laboratory was closed.
See also 
- The Quebec Conference: Agreement Relating to Atomic Energy
- Early Years of Nuclear Energy Research in Canada by George C. Laurence
- How it All Began in Canada - The Role of the French Scientists by Bertrand Goldschmidt