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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.
Jin Beak Park, Yong Soo Hwang, Chul Hyung Kang
Nuclear Science and Engineering | Volume 142 | Number 2 | October 2002 | Pages 165-176
Technical Paper | doi.org/10.13182/NSE02-A2297
Articles are hosted by Taylor and Francis Online.
Matrix diffusion into a rock matrix has been regarded to retard radionuclide migration in a fracture. Recent field findings on a fractured system indicate that only a small portion of the rock in a fractured porous medium contributes to holding a radionuclide by matrix diffusion. To understand this effect, radionuclide migration in a fracture and diffusion from a finite rock matrix to a fracture are discussed with limited matrix diffusion under solubility-limited boundary conditions of a target radionuclide for the band-type release. Numerical inversion of the Laplace transform method is applied to estimate concentrations in a fracture and a finite rock matrix and fluxes at the fracture surface. Matrix diffusion into a finite rock matrix shows enhanced radionuclide migration and a higher concentration profile in a fracture. Diffusive flux from a finite rock matrix into a fracture after the end of leaching time shows higher peak values than flux from an infinite rock matrix because of (a) higher saturation of a radionuclide in a finite rock matrix and (b) increase of a radionuclide concentration in a fracture. Therefore, it is more realistic and conservative to apply the finite matrix diffusion for the overall assessment in a potential repository embedded in a fractured porous medium.
