Abstract
Measurements have been made of the absolute values of the effective fission cross sections in U233, U235, Pu239 and Pu240, using as photoneutron sources Sb + Be (∼ 30 kev), Na + D2O (∼ 250 kev), Na + Be (∼ 900 kev), a source with a simulated fission-neutron spectrum and Po-α-Be. The fission cross sections for 30 kev-neutrons are 3.06 ± 0.16, 2.21 ± 0.12 and 1.79 ± 0.11 barns for U233, U235 and Pu239, respectively. As the neutron energy Is increased from 30 kev to 250 kev the cross sections in U233 and U235 fall off by approximately 35% and then remain almost constant while the cross section in Pu239 falls off by 12% and then increases. The effective cross sections for fission in Pu240 for 900-kev and 5-Mev neutrons is ∼ 1.4 barns and the threshold for fission in Pu240 lies within the limits 250 and 900 kev.
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Additional information
In conclusion the authors wish to express their gratitude to P. E. Spivak for help in formulating the problem and a discussion of the results.
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Dorofeev, G.A., Dobrynin, Y.P. Effective cross sections for fission of U233, U235, Pu239 and Pu240 by neutrons with energies from 30 kev to 5 Mev. The Soviet Journal of Atomic Energy 2, 9–16 (1957). https://doi.org/10.1007/BF01480700
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DOI: https://doi.org/10.1007/BF01480700