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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.
L. A. Hageman, J. B. Yasinsky
Nuclear Science and Engineering | Volume 38 | Number 1 | October 1969 | Pages 8-32
Technical Paper | doi.org/10.13182/NSE38-8
Articles are hosted by Taylor and Francis Online.
Alternating-direction implicit (ADI) time-differencing approximations are developed for the two-dimensional neutron group-diffusion equations. These methods are analyzed for accuracy and stability relative to the implicit-difference approach used in the TWIGL program. It is shown that for model problems (bare homogenous reactors with constant material properties) the ADI method is as accurate as the TWIGL method and much faster computationally. However, several numerical comparisons show that the ADI approach is asymptotically unstable for non-model problems unless extremely small time-steps are used. Such comparisons show the ADI methods (considered in this paper) to be inferior to the TWIGL method for realistic reactor-dynamic problems. A variant on the ADI scheme (ADI-B2) is developed and for a class of delayed supercritical problems shown to be potentially superior to all methods considered.
