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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.
K. V. Subbaiah, A. Natarajan, D. V. Gopinath
Nuclear Science and Engineering | Volume 101 | Number 4 | April 1989 | Pages 352-370
Technical Paper | doi.org/10.13182/NSE89-A23624
Articles are hosted by Taylor and Francis Online.
Modifications to the computational scheme of the existing slab geometry gamma-ray transport code ASFIT are introduced to facilitate the inclusion of coherent scattering contributions. The revised code is tested with two model problems and subsequently is used to investigate quantitatively the transport effects of coherent scattering as a function of the incident photon energy and the atomic number Z of the medium. The shield materials studied in this respect are beryllium, aluminum, iron, molybdenum, tin, tungsten, lead, and uranium, and the incident photon energies range between 0.015 and 0.3 MeV. The system studied is a 48-mfp-thick slab, embedding a thin strip of isotropic source located 4 mfp from the left boundary. Plane parallel incident fluxes have also been studied in certain instances. The results of the computation are presented in the form of scattered flux spectra and dose rates, both at several depths inside the media. Tables of point isotropic source buildup factors including coherent scattering are also presented. It is observed that the addition of coherent scattering does not alter the shape of the flux spectrum significantly, but changes only the magnitude. Except for a small distance near the source, these changes in flux and hence dose are downward at all depths, becoming appreciable at large depths. Furthermore, the magnitude of the reduction varies essentially according to the ratio of the coherent scattering to the total cross section (ΣR/Σt)
