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Home / Store / Journals / Electronic Articles / Nuclear Science and Engineering / Volume 90 / Number 4

Exciting Years!

Arthur H. Snell

Nuclear Science and Engineering

Volume 90 / Number 4 / August 1985 / Pages 358-366


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An account is given of some nuclear measurements that apparently had some importance in the early days of the nuclear chain reaction. These include measurements of the decay periods and the intensity of the delayed neutrons (important for the control of the chain reaction), and the first measurements relative to a fast-neutron chain reaction in uranium metal. The latter showed that normal uranium would have to be enriched by a factor of more than 12 in order to sustain a fast-neutron chain reaction in a finite geometry, and that high enrichment would be needed for a nuclear weapon. They also suggested to reactor theorists that the interaction fast effect might make an important contribution to a controlled slow-neutron chain reaction using natural water as moderator/coolant. (In the capable hands of others, this perception of the theorists led eventually to most of the civilian and naval power reactors.) Items of personal research are briefly mentioned, viz., observation of the radioactive decay of the free neutron, of nuclear recoil due to neutrino emission, and of the atomic consequences of radioactive decay. The periods covered are 1940–1944 with the Cyclotron Group at the Metallurgical Laboratory, Chicago, and 1944–1968 at Oak Ridge, Tennessee.

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