Measurements were performed with 1.05 and 3.15 kg plutonium blocks with known (nominal) 239Pu fractions 88.7, 91.0, 93.2, and 95.2% in order to check the possibility of determining their mass and enrichment by using a neutron detector – an active well coincidence counter (AWCC). Analysis of double and triple neutron-neutron coincidences was performed taking spatial effects into account. The intensity of the source of spontaneous fissions in the block and thereby the effective mass of 240Pu were determined on the basis of the requirement that the neutron multiplicities obtained from double and triple coincidences are the same. The 239Pu content was determined to within 0.003–0.004 (1σ), which makes it possible to reliably determine the 239Pu content in the blocks, equal to 91% (power-grade) and 93% (weapons-grade). The plutonium mass in a block is determined to within ±2–3% from the obtained effective neutron multiplication factor.
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Translated from Atomnaya Énergiya, Vol. 118, No. 1, pp. 38–41, January, 2015.
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Dulin, V.A., Dulin, V.V. Determination of the Parameters of Plutonium Blocks Placed Inside Containers. At Energy 118, 52–56 (2015). https://doi.org/10.1007/s10512-015-9955-z
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DOI: https://doi.org/10.1007/s10512-015-9955-z