Search for spontaneous fission of \(^{234}\)U, \(^{235}\)U, \(^{236}\)U, and \(^{238}\)U by gamma spectrometry

Experimental search for spontaneous fission and cluster decays of \(^{234}\)U, \(^{235}\)U, \(^{236}\)U and \(^{238}\)U was carried out with a certified 230-g uranium oxide sample enriched in \(^{235}\)U to 93.2%. The sample was measured over 46.3 days by using a 70 cm\(^3\) broad energy germanium detector. The search for the fission fragments and their daughters was performed by using \(\gamma \) quanta of energy \(>1.5\) MeV expected in \(\beta ^-\) decays. No such \(\gamma \) peaks were observed in the experimental data, thus, upper limits on the fragments’ yields are set. The lower limits on partial half-lives are obtained at the level of \(5.0\times 10^{10}-2.6\times 10^{17}\) years for the corresponding cold fission and cluster decay channels. In particular, 5 limits for \(^{235}\)U and \(^{238}\)U cold fission exceed the prediction made by S.B. Duarte et al. in framework of the effective liquid drop model by a factor of 1.6–227. Therefore, the obtained results can be used to improve the theoretical frameworks to study the cold fission processes.