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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.
Yasuki Kowata, Nobuo Fukumura
Nuclear Science and Engineering | Volume 99 | Number 4 | August 1988 | Pages 299-312
Technical Paper | doi.org/10.13182/NSE88-A23560
Articles are hosted by Taylor and Francis Online.
Using the substitution method combined with the pulsed neutron technique, coolant void reactivities of PuO2-UO2 fuel lattices in pressure-tube-type heavy water reactors have been determined as functions of PuO2 enrichment in PuO2-UO2 (0.54 and 0.87 wt%), fissile content of plutonium (91 and 75% fissile plutonium), lattice pitch (Vm/Vf: 7.4 and 9.9), and coolant void fraction (0, 30, 70, 87, and 100%). The reference loading of 1.2 wt% enriched UO2 clusters was progressively replaced by PuO2-UO2 test clusters. The void reactivities were obtained from Simmons and King’s formula in which correction was made for a change of the prompt generation time. As decay constants can be maintained invariable due to substitution, buckling differences were analyzed by the first-order perturbation method, on the assumption that lattices are homogeneous and no difference in diffusion coefficients exists between the two lattices. Void reactivities of test lattices were determined with an accuracy of ∼10% when the minimum number of test fuel clusters was ∼5% of the total. The void reactivity shifted farther to the negative side as the proportion of fissile plutonium was increasingly in the PuO2-UO2 fuel of the same enrichment of plutonium.
