High Explosive Research

High Explosive Research was the British project to independently develop atomic bombs after the Second World War. This decision was taken by a cabinet sub-committee on 8 January 1947, in response to apprehension of an American return to isolationism, fears that Britain might lose its great power status, and the actions by the United States to unilaterally withdraw from sharing of nuclear technology under the Quebec Agreement. The decision was publicly announced in the House of Commons on 12 May 1948.

The project was a civil, not a military one. Staff were drawn from and recruited into the Civil Service, and were paid Civil Service salaries. It was headed by Lord Portal, as Controller of Production, Atomic Energy, in the Ministry of Supply. An Atomic Energy Research Establishment was located at a former airfield, Harwell, in Berkshire, under the direction of John Cockcroft. The first nuclear reactor in the UK, a small research reactor known as GLEEP, went critical at Harwell on 15 August 1947. British staff at the Montreal Laboratory designed a larger reactor, known as BEPO, which went critical on 5 July 1948.

Production facilities were constructed under the direction of Christopher Hinton, who established his headquarters in a former Royal Ordnance Factory at Risley in Lancashire. These included a uranium metal plant at Springfields, nuclear reactors and a plutonium processing plant at Windscale, and a gaseous diffusion uranium enrichment facility at Capenhurst, near Chester. The two Windscale reactors became operational in October 1950 and June 1951. The gaseous diffusion plant at Capenhurst began producing highly enriched uranium in 1954.

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