Decay Constant and Mass-Yield Curve for the Spontaneous Fission of Uranium-238

Abstract

The equilibrium ratio of ${\mathrm{Te}}^{132}$/${\mathrm{U}}^{238}$ in nonirradiated natural and depleted uranium was measured to be (2.2\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ disintegrations per second per gram of uranium. This value was used to normalize the mass-spectrometric data for the relative yields of krypton and xenon isotopes from the ${\mathrm{U}}^{238}$ spontaneous fission. Combining the mass-spectrometric and radiochemical data obtained by previous investigators, a mass-yield curve for the spontaneous fission of ${\mathrm{U}}^{238}$ was constructed in which the equilibrium ratios of the fission products in nonirradiated uranium were plotted against the mass numbers. By summing the area under the curve, a value of (7.8\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{yr}}^{\ensuremath{-}1}$ was obtained for the ${\mathrm{U}}^{238}$ spontaneous fission decay constant. This value is intermediate between the values reported by Fleischer and Price and by Segr\`e.