First Principal Active Neutron Coincidence Counting Measurements of Uranium Oxide

Uranium is present in most nuclear facilities ranging from uranium mines, enrichment plants, fuel fabrication facilities, nuclear reactors, and reprocessing plants. The isotopic, chemical, and geometric composition of uranium can vary significantly between these facilities, depending on the application and type of facility. Examples of this variation are: enrichments varying from depleted (0.270 wt% 235U) to high enriched (95 wt% 235U); compositions consisting of U3O8, UO2, UF6, metallic, and ceramic forms; geometries ranging from plates, can, and rods; and geometries masses which can consist of a several kilogram can down to a few gram fuel pellet. Because 235U can be used to make a nuclear explosive device, it is routinely safeguarded in these facilities. Current techniques of quantifying the 235U mass in a sample include neutron coincidence counting. One of the main disadvantages of this technique is that it requires a known standard of similar geometry and composition for calibration. By assuming a known geometry and composition of the unknown uranium sample this allows for possible misdeclaration by the State, and thus the effectiveness of safeguards is weakened. In order to address this weakness, the authors have developed a neutron coincidence counting technique which uses the first principal point-model developed by Boehnel instead of the “know standard” method. This technique was primarily tested through simulations using the Monte Carlo N-Particle eXtended (MCNPX) code. The results of these simulations showed good agreement between the simulated and exact 235U sample masses.

GODDARD Braden;  CHARLTON William;  PEERANI Paolo; 

2014-01-16

ELSEVIER SCIENCE BV

JRC81825

0168-9002,   

http://www.sciencedirect.com/science/article/pii/S0168900213016665,    https://publications.jrc.ec.europa.eu/repository/handle/JRC81825,   

10.1016/j.nima.2013.11.101,