The Measurement of Absolute Delayed-Neutron Yields from 3.1- and 14.9-MeV Fission

Christopher F. Masters; M. M. Thorpe; Darryl B. Smith

doi:dx.doi.org/10.13182/NSE69-A19717

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The Measurement of Absolute Delayed-Neutron Yields from 3.1- and 14.9-MeV Fission

Christopher F. Masters, M. M. Thorpe, Darryl B. Smith

Nuclear Science and Engineering / Volume 36 / Number 2 / May 1969 / Pages 202-208

Technical Paper / dx.doi.org/10.13182/NSE69-A19717

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A new method, utilizing a modulated neutron source operated in antisynchronism with a long counter, has been used to measure the absolute and relative delayed-neutron yields of five fissionable isotopes for neutron-induced fission at 3.1 and 14.9 MeV. The results, in units of delayed neutrons per fission, for 14.9-MeV fission are:

²³⁹Pu	0.0043 ± 0. 0004
²³³U	0.0043 ± 0.0004
²³⁵U	0.0095 ± 0. 0008
²³⁸U	0.0286 ± 0. 0025
²³²Th	0.031 ± 0.003

The measured ratios of delayed-neutron yields at 3.1-MeV to those at 14.9-MeV fission are:

²³⁹Pu	1.60 ± 0.09
²³³U	1.79 ± 0.10
²³⁵U	1.89 ± 0.11
²³⁸U	1.71 ± 0.10
²³²Th	1.94 ± 0.11

These new delayed-neutron yield data are in accord with qualitative theoretical predictions but are in marked disagreement with earlier measurements.