He proposed cooling the reactor with ordinary water instead of using helium at a relatively high temperature. It was not that Wigner thought the problems were insoluble, but rather that solving them for such a hot reactor would take a very long time. That would mean immense materials problems. He argued that if helium were the coolant, then the reactor would have to run at a very high temperature, perhaps 400–500☌. Wigner, with his chemical engineering background, objected very strongly to helium cooling. Weinberg, ed., The Collected Works of Eugene Paul Wigner, vol.

He later wrote that he had no reason for specifying five years, but he was confident that the nuclear community would discover a neutron-initiated nuclear reaction that would produce both energy and neutrons. He decided as early as 1936 that no such law existed, and in his unpublished speech that year to the Gamma Alpha Society at the University of Wisconsin, he said that within five years scientists would figure out how to release nuclear energy. The memoir is an excellent history of the origins of Hanford. Wigner kept a diary, beginning in 1941, which is published as Memoir of the Uranium Project in A. He says in his memoirs that he thought long and hard to see whether some kind of law of nature-somewhat like the law of conservation of energy-would preclude the possibility of a nuclear chain reaction. Wigner was impressed with Szilard’s general idea.

Space engineers where to find uranium