1,240,235. Detecting neutrons. NATIONAL NUCLEAR CORP. 12 May, 1969 [13 May, 1968], No. 24019/69. Heading G6P. In a non-destructive testing system, for nuclear reactor fuel elements, the element is neutron irradiated. The delayed and prompt fission neutrons are counted and compared with counts for a standard sample to provide a measure of the plutonium/uranium ratio in the element. The neutron beam employed has an energy lower limit above the large fission resonance of the fissionable material and an upper limit less than the fission threshold of the fertile element. The fuel element, 30, is irradiated in the neutron beam, 24, the delayed fission neutrons are detected at 32, 33 and prompt fission neutrons at 34. The neutron beam is formed in the accelerator, 21, employing a reaction of the type :- In an alternative form, an antimony-beryllium neutron source is employed.
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