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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.
Zelmo Rodrigues de Lima, Aquilino Senra Martinez, Fernando Carvalho da Silva, Antonio Carlos Marques Alvim
Nuclear Science and Engineering | Volume 170 | Number 1 | January 2012 | Pages 66-74
Technical Note | doi.org/10.13182/NSE10-67TN
Articles are hosted by Taylor and Francis Online.
Cross sections are homogenized over an entire node in nodal model implementation. The presence of a control rod (CR) partially inserted in the node has occasioned axial heterogeneity and generates a homogenization problem. If the homogenization process is only the volume-weighted average for nuclear parameters, the calculation of the multiplication factor and power in steady-state problems may mean relevant errors and for time-dependent problems may have caused the well-known cusping problem, which arises in three-dimensional transient simulations with CR motions. The major purpose of this technical note is to introduce an alternative method, based on the nodal expansion method, to deal with partially inserted CRs in nodes. One-dimensional equations, acquired through transverse integration of the neutron diffusion equation, have been modified to formulate the alternative method, which was evaluated in a transient problem. Furthermore, the alternative method gives satisfactory results and corrects the cusping effect in the case analyzed in this technical note.