Recent experimental data on sub-barrier fission of light actinides

Abstract Neutron induced fission cross-section and fission fragment angular distribution data for the light actinide elements are reviewed and examined to see how well some of the data can be explained in terms of the properties of the fission potential barrier. Our understanding is at a stage where the 'thorium anomaly', which arises when certain cross-sections are interpreted in terms of a double-hump fission potential barrier, has been removed by interpreting the data in terms of a shallow third minimum. The data for 230Th provide a sensitive test for this model and their interpretation is examined in detail. The data available for the target nuclei 227Ac, 228Th, 232Th, 231Pa and the sub-actinide 226Ra are also noted.