Spontaneous Fission Xenon in Natural Gases

Isotopic enrichments of Xe¹³², Xe¹³⁴, and Xe¹³⁶ were found in a number of natural gases and are attributed to the spontaneous fission of U²³⁸. The ratio of spontaneous-fission xenon to atmospheric xenon and the ratio of spontaneous fission xenon to He are discussed in terms of a solubility model. It is shown that the isotopic enrichments can be explained in terms of the solubility model and a preferential release of He as compared to XegF by a factor ranging up to three. An estimate is made of the present flux of spontaneous-fission.