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NRC to add new items to categorical exclusions list
The Nuclear Regulatory Commission has identified five categories of action to add to its list of categorical exclusions to reduce its documentation work under National Environmental Policy Act (NEPA) procedures.
These revisions are included in the final rule, “Categorical exclusions from environmental review,” which was published in the Federal Register on March 30. The final rule will become effective on April 29.
S. Kitsos, A. Assad, C. M. Diop, J. C. Nimal, P. Ridoux
Nuclear Science and Engineering | Volume 117 | Number 1 | May 1994 | Pages 47-66
Technical Paper | doi.org/10.13182/NSE94-A13568
Articles are hosted by Taylor and Francis Online.
Exposure and energy absorption buildup factors for aluminum, iron, lead, and water are calculated by the SN1D discrete ordinates code for an isotropic point source in a homogeneous medium. The calculation of the buildup factors takes into account the effects of both bound-electron Compton (incoherent) and coherent (Rayleigh) scattering. A comparison with buildup factors from the literature shows that these two effects greatly increase the buildup factors for energies below a few hundred kilo-electron-volts, and thus the new results are improved relative to the experiment. This greater accuracy is due to the increase in the linear attenuation coefficient, which leads to the calculation of the buildup factors for a mean free path with a smaller shield thickness. On the other hand, for the same shield thickness, exposure increases when only incoherent scattering is included and decreases when only coherent scattering is included, so that the exposure finally decreases when both effects are included. Great care must also be taken when checking the approximations for gamma-ray deep-penetration transport calculations, as well as for the cross-section treatment and origin.