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NRC proposes changes to its rules on nuclear materials
In response to Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” the NRC is proposing sweeping changes to its rules governing the use of nuclear materials that are widely used in industry, medicine, and research. The changes would amend NRC regulations for the licensing of nuclear byproduct material, some source material, and some special nuclear material.
As published in the May 18 Federal Register, the NRC is seeking public comment on this proposed rule and draft interim guidance until July 2.
R. E. Chrien, H. I. Liou, M. J. Kenny, M. L. Stelts
Nuclear Science and Engineering | Volume 72 | Number 2 | November 1979 | Pages 202-215
Technical Paper | doi.org/10.13182/NSE79-A19464
Articles are hosted by Taylor and Francis Online.
The cross sections for neutron interactions with thorium targets were measured at several energies. Capture cross sections at 0.0253 eV and at 2 and 24.3 keV were measured by activation techniques. Transmission measurements were made from 10 to 100 eV, and capture cross sections were determined from 0.03 to 15 eV by recording discrete lines for the (n,γ) spectrum. The measured thermal cross section is 7.41 ± 0.08 b, at 2 keV the cross section is 1.96 ± 0.10 b, and at 24.3 keV it is 0.540 ± 0.014 b. These values are reported relative to an assumed 231Pa branching ratio of 38.5% for the 311-keV gamma ray, and they do not include the branching ratio error. The results are fitted to R-matrix parameters. The transmission and (n,γ) measurements lead to parameters that give a somewhat higher epithermal capture than previously expected in thorium. This result brings the differential data into better agreement with experiments on subcritical assemblies.