133Ba as a gamma-ray surrogate source for 1kg HEU and 10g 239Pu and 252Cf as a Neutron Surrogate for Pu

Pohl, Bertram A. ; Archer, Daniel E.

Lawrence Livermore National Laboratory

关键词: Uranium;    Testing;    Shielding;    Half-Life;    Impurities;   

DOI  :  10.2172/15009812
RP-ID  :  UCRL-TR-202871
RP-ID  :  W-7405-ENG-48
RP-ID  :  15009812

美国|英语

来源: UNT Digital Library

【 摘 要 】

Monte Carlo was performed for the purpose of relating gamma-ray signal strength from 1kg of HEU and 10g of {sup 239}Pu (as described in the ASTM standards) to the radiation emitted from an amount of {sup 133}Ba. A determination was made on the amount of {sup 133}Ba that could act as a surrogate for the specified amounts of HEU and Pu. {sup 133}Ba is not the ideal source to use as a surrogate for HEU because of its higher energies. {sup 133}Ba was chosen as the surrogate since it has a half-life of 10.54 years, rather then the more ideal surrogate of {sup 57}Co which has a half-life of 271 days. A similar Monte Carlo was performed for the purpose of relating neutron signal strength from 200g of Pu (as described in the ASTM standards) to the radiation emitted from an amount of shielded {sup 252}Cf. A determination was made on the amount of {sup 252}Cf necessary to act as a surrogate for the 200g of Pu. An ASTM standard source is a metallic sphere, cube, or right cylinder of SNM having maximum self-attenuation of its emitted radiation. For plutonium, the source should be at least 93% {sup 239}Pu, less than 6.5% {sup 240}Pu, and less than 0.5% impurities. A cadmium filter of at least 0.08cm thick should be used to reduce the impact of {sup 241}Am. For uranium, the source should contain at least 95% {sup 235}U and less than 0.25% impurities. For neutron detector testing, the neutron source shall be placed in a lead shielding container that reduces the gamma radiation from the source to 1% of its unshielded value.