a second reactor, but to proceed with the first one "with the highest urgency and importance". Reactors were built at the former ROF Sellafield. To avoid any confusion with Springfields, where uranium metal was produced, the name was changed to Windscale. Gaseous diffusion facility A few months later, Portal, who had not been appointed when this decision was taken, began to have doubts. Word reached him of problems with the Hanford Site reactors, which had been all but completely shut down due to Wigner's disease. On a visit to the United States in May 1946, Groves advised Portal not to build a reactor. By this time, there was interest from the scientists in making better use of uranium fuel by re-enrichment of spent fuel rods. A gaseous diffusion plant was costed at somewhere between £30 and £40 million. The Gen 75 Committee considered the proposal in October 1946. Michael Perrin, who was present, later recalled that: The Gen 75 Committee thereupon approved the construction of the proposed gaseous diffusion plant, which was built on the site of an old Royal Ordnance Factory at Capenhurst, near Chester. Gen 163 Committee In July 1946, the Chiefs of Staff Committee considered the issue of nuclear weapons, and recommended that Britain acquire them. This recommendation was accepted by the Cabinet Defence Committee on 22 July 1946. The Chief of the Air Staff, Lord Tedder, officially requested an atomic bomb on 9 August 1946. The Chiefs of Staff estimated that 200 bombs would be required by 1957. Despite this, and the research and construction of facilities that had already been approved, there was still no official decision to proceed with making atomic bombs. Dissent came from Patrick Blackett, who submitted a paper to the Gen 75 Committee that forcefully argued against Britain acquiring atomic bombs. The Foreign Office, however, labelled his ideas "dangerous and misleading rubbish", and rejected a characterisation of the Soviet Union as a peace-loving state with no expansionist ambitions whereas the United States was an aggressor predisposed towards preemptive war. Portal submitted his proposal to proceed with the manufacture of nuclear weapons at the 8 January 1947 meeting of the Gen 163 Committee. This was a smaller committee, consisting of Attlee, Morrison, Bevin, Wilmot, the Secretary of State for Dominion Affairs, Lord Addison, and the Minister of Defence, A. V. Alexander. It was this committee, which met only once, that agreed to