Double beta decay of Uranium-238: Proton reactions of 238U in 5--12 MeV range. Final report, April 15, 1987--March 31, 1992

This report is in two parts. The first part reports on the experimental work determining the half-life for double beta decay of 238U to 238PU to be (2.0 ± 0.6) x 1021 years. This is the first evidence for a third mode of decay of this heaviest naturally occurring nucleus. This rate is about 106 times slower than spontaneous fission, which itself is about 106 times slower than alpha decay. The implication of this double beta decay to neutrino masses depends on uncertain theoretical calculations of the rate for such a heavy nucleus. The second part reports on yields of principal fission products from 5.6, 7.3, 9.4, and 11.5 MeV proton interactions with 238U. The yields at 11.5 MeV are similar to those from 14 MeV neutron fission of 238U. At the same time, the production cross sections of 238Np at the same energies are determined. This nuclide is produced as often as fission at the lowest energy but only 3.8% as often at the highest energy