Half-life of 238U spontaneous fission and its fragment kinetic energies

The kinetic energy spectrum of fragments from 238U spontaneous fission has been measured by using a cylindrical gridded ionization chamber with a source area of 5000 cm2. By comparing with the energy spectrum of fragments from 235U thermal-neutron-induced fission, the average kinetic energies are determined to be (97.6+-0.7)MeV for light fragment group and (67.0+-1.2)MeV for heavy fragment group. The half-life of 238U spontaneous fission is (8.43+-0.21)X1015 years, which is consistent with the results recently obtained by the spinner methods. (Auth.)