DEPENDENCE OF FISSION FRAGMENT KINETIC ENERGIES AND NEUTRON YIELDS ON NUCLEAR STRUCTURE
Technical Report
·
OSTI ID:4635449
It is suggested that the dip in kinetic energy and the sawtooth structure in the prompt neutron yields for thermal neutron fission of U/sup 235/ result from the influence of the shell structure of the eventual fragments on the deformations at the scission configuration. A simple model embodying this assumption was explored in order to clarify the effects involved. Fragments that have a closed shell structure prefer to retain a spherical shape at the scission configuration, whereas fragments which are soft with respect to deformation are more distorted at the scission configuration. From such a model, it is seen how rather modest variations in the deformation energy as a function of distortion are exploited by the Coulomb repulsion between the eventual fragments to produce much larger effects on kinetic energies and neutron yields. This model, utilizing parameters determined from the U/sup 235/ experimental data, accounts for the qualitative features of ihe kinietic energy release and neutron yields for other fissioning nuclei from Bi to Cf. It is concluded that the structure in the kinetic energy release and neutron yields is primarily related to the shell structure of the final fragments rather than to differences associated with hypothetical symmetric and asymmetric modes. The large deficit in kinetic energy observed for U/sup 235/ near symmetry is attributed to the fact that both of the neutron-rich primary fission fragments for these mass divisions lie in a region characterized by an unusually low resistance towards deformation. 28 references. (auth)
- Research Organization:
- Copenhagen. Universitet. Institut for Teoretisk Fysik; Argonne National Lab., Ill.
- DOE Contract Number:
- W-31109-ENG-38
- NSA Number:
- NSA-17-038090
- OSTI ID:
- 4635449
- Report Number(s):
- TID-17663; UAC-6965
- Country of Publication:
- United States
- Language:
- English
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