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1999
Conference Paper
Titel
Measurement of delayed neutrons after induced fission of special nuclear material
Abstract
Nondestructive measuring capabilities for the in situ detection and analysis of nuclear material are considered as possible measures to discover illicit trafficking of nuclear material and to prohibit nuclear proliferation. Therefore, we performed measurements on the time structure of delayed neutrons after the induced fission of nuclear material by a pulsed 14 MeV neutron tube. The measured decay curves were fitted to the well known six groups of delayed neutrons. The relative strengths of the different groups were reproduced well for the measurements with the long irradiation time (60 s) and the long counting time (approx. 200 s) for the delayed neutrons. For shorter irradiation or measuring times only some of the relations could be reproduced. Our measurements show that a clear detection of the delayed neutrons is possible, even in presence of a high neutron background. So the measurements are not disturbed by neutrons from (alpha, neutron) reaction inside uranium oxide or from spontaneous fission of plutonium isotopes. Thinking of verification of weapons materials this measurement method allows confirmation of fissile materials content without disclosing sensitive information (like geometry). These experiments show that fissionable material can be detected clearly and easily in a suspicious box with a pulsed neutron generator within a very short time (several minutes).
Author(s)