Prompt-fission-neutron spectra of /sup 233/U, /sup 235/U, /sup 239/Pu and /sup 240/Pu relative to that of /sup 252/Cf. [550 and 850 keV]

The prompt-neutron-induced-fission spectra of /sup 233/U, /sup 235/U, /sup 239/Pu, and /sup 240/Pu are measured relative to the prompt-spontaneous-fission-neutron spectrum of /sup 252/Cf. The fission of /sup 233/U, /sup 235/U, and /sup 239/Pu is induced by approx. = 550-keV neutrons, and that of /sup 240/Pu, by approx. = 850-keV neutrons. The emitted fission neutrons are observed over the energy range less than or equal to 0.5 to 10.0 MeV by use of time-of-flight techniques. Analysis of the measured values indicates that the average-fission-neutron energies are -123 +- 30 (/sup 233/U), -157 +- 24 (/sup 235/U), -76 +- 29 (/sup 239/Pu), and -46 +- 29 (/sup 240/Pu) keV relative to the energy for /sup 252/Cf. The experimental results are compared with those of ENDF/B-V, and a simple behavior of average-prompt-fission-neutron energies is suggested