Elements in Region of Platinum Formed by Fusion in Fission Explosions

Abstract

The fission products in a fission explosion at the time of the last few generations before explosion are sufficiently numerous that the probability of reaction with each other becomes measurable. In this paper the probability of fusion is calculated. It is found that the fusion of two light fission fragments is the only possible process of this type. For explosion of a mass of 14 kg of uranium or plutonium having a 25% efficiency the yield of platinum group elements is estimated as 1.2\ifmmode\times\else\texttimes\fi{}${10}^{14}$ atoms. Although the kind of nucleus produced instantaneously with highest probability has $Z=75$ and $A=190$, the excess of kinetic energy is such as to boil off between 9 and 18 neutrons forming elements $A=175 \mathrm{to} 182$, on the low side of the stability curve. In view of the recently developed theories of supernovae explosion, involving production of ${\mathrm{Cf}}^{254}$ and other fissile nuclei, it may be important to consider the subsequent fusion of fission fragments in supernovae. If this process is sufficiently important, it may affect the astrophysical abundances of elements in the region of platinum.