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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.
C. Y. Fu
Nuclear Science and Engineering | Volume 109 | Number 1 | September 1991 | Pages 18-25
Technical Paper | doi.org/10.13182/NSE91-A23841
Articles are hosted by Taylor and Francis Online.
Pairing corrections in particle-hole (exciton) state-density formulas used in precompound nuclear reaction theories are, strictly speaking, dependent on the nuclear excitation energy U and the exciton number n. A general formula for (U, n)-dependent pairing corrections was derived earlier for the exciton state-density formula for a system of one kind of fermion. A similar derivation is made for a system of two kinds of fermions, a system in which neutrons and protons occupy different sets of single-particle states. It is shown that the constant-pairing-energy correction used in standard statedensity formulas, such as U0 in Gilbert and Cameron, is a limiting case of the present general (U, n)-dependent results. Spin cutoff factors are calculated using the same pairing theory and parameterized into an explicit (U, n)-dependent function, thereby defining the exciton level-density formula for two kinds of fermions. The results show that the ratios in the exciton level densities in the one- and two-fermion approaches vary with both U and n, thus, most likely leading to differences in calculated compound-to-precompound ratios. However, the differences in the spin cutoff factors in the two cases are found to be rather small.