The Concentration of (236)Pu Daughters in Plutonium for Application to MOX Production from Plutonium from Dismantled US Nuclear Weapons

Sampson, T.E. ; Cremers, T.L.

Los Alamos National Laboratory

关键词: 98 Nuclear Disarmament, Safeguards, And Physical Protection;    Radiation Doses;    Spectra;    Thallium 208;    Daughter Products;   

DOI  :  10.2172/781473
RP-ID  :  LA-13762-MS
RP-ID  :  W-7405-ENG-36
RP-ID  :  781473

美国|英语

来源: UNT Digital Library

【 摘 要 】

The isotope {sup 236}Pu in the weapons-grade plutonium to be used in the US MOX (mixed-oxide) plant is of concern because the daughter products of {sup 236}Pu are sources of high-energy gamma rays. The {sup 208}Tl daughter of {sup 236}Pu emits intense, high-energy gamma rays that are important for radiation exposure calculations for plant design. It is generally thought that the concentrations of {sup 236}Pu and its daughters are well below 10{sup {minus}10}, but these concentrations are generally below the detection limits of most analytical techniques. One technique that can be used to determine the concentration {sup 208}Tl is the direct measurement of the intensity of the {sup 208}Tl gamma rays in the gamma-ray spectrum from plutonium. Thallium-208 will be in equilibrium with {sup 228}Th, and may very well be in equilibrium with {sup 232}U for most aged plutonium samples. We have used the FRAM isotopic analysis software to analyze dozens of archived high-resolution gamma ray spectra from various samples of US and foreign plutonium. We are able to quantify the ratio of minor isotopes with measurable gamma-ray emissions to the major isotope of plutonium and hence, through the measurement of the plutonium isotopic distribution of the sample, to elemental plutonium itself. Excluding items packaged in fluoropolymer vials, all samples analyzed with {sup 240}Pu < 9% gave {sup 228}Th/Pu ratios < 3.4 e-012 and all samples of US-produced plutonium, including {sup 240}Pu values up to 16.4%, gave {sup 228}Th/Pu ratios < 9.4 e-012. None of these values is significant from a radiation dose standpoint.