1985•University of North Texas Digital Library (University of North Texas)Open access
Mean fission neutron spectrum energies for /sup 252/Cf and fissile nuclides, /sup 233/U, /sup 235/U, /sup 239/Pu and /sup 241/Pu
Norman E. Holden
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Abstract
The international standard for a neutron spectrum is that produced from the spontaneous fission of /sup 252/Cf, while the thermal neutron induced fission neutron spectra for the four fissile nuclides, /sup 233/U, /sup 235/U, /sup 239/Pu and /sup 241/Pu, are of interest from the standpoint of nuclear reactors. There have been many data sets produced in recent years which deal with the shape of these spectra, particularly at both the low energy and the high energy portions of the curve. However, our interest here is in the average neutron energies of these spectra. We have tabulated all measurements for the five nuclides of interest. The individual measurements are recorded with the neutron energy range measured, the method of detection as well as the average neutron energy for each author. Fortunately, the measurements have been performed with a number of techniques, which allows one to estimate the systematic error from the spread in the results for the different techniques. An attempt has been made to renormalize results when the neutron spectrum used for normalization purposes has been given. In addition to the tables of mean energy measurements, we have also tabulated the measurements of the ratio of mean energies for pairs of fission neutron spectra. The following items were considered, where possible, in the analysis of the mean energies of the neutron spectra: the energy scale of the measurement, the determination of the detector efficiency, the sample size and the sample thickness and the scattering corrections made. The recommended mean energies for the spectra considered are shown. The uncertainty listed attempts to estimate the systematic error as well as merely the precision in each of the experiments. The recommended values for /sup 233,235/U, /sup 239,241/Pu, and /sup 252/Cf are 2.02 +- 0.03 MeV, 1.98 +- 0.03 MeV, 2.06 +- 0.04 MeV, 2.05 +- 0.05 MeV, and 2.14 +- 0.03 MeV, respectively. 73 refs.
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