Ground-state spontaneous-fission half-lives of uranium isotopes

The ground-state spontaneous-fission half-lives of /sup 233/U, /sup 234/U, /sup 235/U, and /sup 236/U were redetermined using solutions of highly enriched uranium in spinner detectors. The following values were obtained: >2.7 x 10/sup 17/ years for /sup 233/U; (1.42 +- 0.08) x 10/sup 16/ years for /sup 234/U; (9.8 +- 2.8) x 10/sup 18/ years for /sup 235/U; (2.43 +- 0.13) x 10/sup 16/ years for /sup 236/U. The values for /sup 234/U and /sup 236/U are in agreement with the systematics for spontaneous-fission half-lives of even-even nuclides. The spontaneous-fission of the odd-A uranium isotopes 233 and 235 is considerably hindered (hindrance factors >1.3 and 3, respectively).