Prompt Neutron Emission Multiplicity Distributions and Average Values, <ν>, at 2200 Meter per Second for the Fissile Nuclides

Norman E. Holden and Martin S. Zucker

Brookhaven National Laboratory
Upton, New York 11973, USA

The prompt neutron emission multiplicity distribution, Pν, is of interest for methods of self-calibration and for auto-correlation to assay fissionable material for nuclear safeguards. <ν>, the average value of Pν, is of interest at neutron thermal energies since it is related to the neutron multiplication factor and it is used as a normalizing point for energy dependent values of <ν>. Values of Pν and <ν> have been determined at the standard neutron energy of 0.0253 ev for the neutron induced fission of the four fissile nuclides, 233,235U, and 239,241Pu. Revised <ν> values have been obtained by re-evaluating <ν> experiments measured at 2200 meter/second relative to the <ν> from the spontaneous fission of 252Cf. These revised values of <ν> have been used to renormalize the measured Pν values. The revised values of <ν> are all about 1/4% to 1/2% smaller than the corresponding values of ENDF/B-V.

KEYWORDS: <ν>, Pν, En = 0.025 ev, 233U, 235U, 239Pu, 241Pu