Document: NUREG-0800
Document ID: bfe08773-10ce-45c6-9767-3cbe51c1726f
Document Type: srp
Title: - 12.4
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070720019.pdf
Revision Date: 2023-06
Chapter: 12
Section ID: 12.3
CFR Part: 
CFR Title: 

Content:
ievable, and a total person- sievert (person-rem) dose that is ALARA. Based on current operating experience and 12.3-12.4-10 Revision 3 - March 2007 on predictions being made for new plant designs, it is expected that the plant shielding can be designed, the plant can be zoned, and sufficient radiation protection design features can be incorporated, such that individuals in shielded areas would receive a small fraction of the 10 CFR Part 20 limits. All vital areas, in which radiation may unduly limit personnel occupancy during operations following an accident resulting in a degraded core, should be identified. Personnel access to these areas under accident conditions should be demonstrated in accordance with 10 CFR 50.34(f)(2)(vii), using the methods listed in Section II.B.2 of NUREG-0737. The analysis should consider access to, stay time in, and egress from these vital areas. 2. Shielding The staff will evaluate the shielding design in terms of the assumptions used to calculate shield thickness, the calculational methods used, and the parameters chosen. A number of acceptable shielding calculational codes are available that are effective for determining the necessary shield thickness for gamma ray and combination neutron- gamma sources. The code description file of the Radiation Safety Information Computational Center (formerly the Radiation Shielding Information Center) at Oak Ridge National Laboratory includes most of the codes used by shield designers, which means that the codes have been tested and authenticated for operation but not for reliability and accuracy. Radiation shielding codes vary in complexity and accuracy from the relatively simple point-kernel methods, to the more complex discrete ordinates methods, to the still more rigorous Monte Carlo methods. The staff may use these codes, as necessary, to calculate dose rates for given shield designs and source strengths as a confirmation of the applicant’s method. The applicant’s shielding design is