Determination of the Parameters of Plutonium Blocks Placed Inside Containers

• Published in: Atomic energy (New York, N.Y.) Vol. 118; no. 1; pp. 52 - 56
• Main Authors: Dulin, V. A., Dulin, V. V.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2015; Springer Nature B.V
• Subjects: Approximation; Coincidence circuits; Coincidences; Containers; Efficiency; Experiments; Fission; Hadrons; Heavy Ions; Measurement techniques; Multiplication; Neutron detectors; Neutrons; Nuclear Chemistry; Nuclear Energy; Nuclear Physics; Nuclear reactors; Physics; Physics and Astronomy; Plutonium; Sensors; Spontaneous; Storage; Studies; United States > US; Subcritical State; Plutonium; Neutron Multiplication; Spontaneous Fission; Neutron Multiplicity
• ISSN: 1063-4258; 1573-8205
• DOI: 10.1007/s10512-015-9955-z

Measurements were performed with 1.05 and 3.15 kg plutonium blocks with known (nominal) 239 Pu 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 240 Pu were determined on the basis of the requirement that the neutron multiplicities obtained from double and triple coincidences are the same. The 239 Pu content was determined to within 0.003–0.004 (1σ), which makes it possible to reliably determine the 239 Pu 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.