Document: NUREG-0800
Document ID: 9c7116dd-39cd-47a9-b121-dce6f51adc77
Document Type: srp
Title: SUBCOMPARTMENT ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070620009.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.1.2
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as follows for the review described in this SRP section. The SRP is not a substitute for the NRC’s regulations, and compliance with it is not required. However, an applicant is required to identify differences between the design features, analytical techniques, and procedural measures proposed for its facility and the SRP acceptance criteria and evaluate how the proposed alternatives to the SRP acceptance criteria provide acceptable methods of compliance with the NRC regulations. 1. Nodalization Schemes. Subcompartment nodalization schemes should be chosen so that there is no substantial pressure gradient within a node. A sensitivity study which includes increasing the number of nodes until the peak calculated pressures converge to small resultant changes should be used to verify the nodalization scheme. The guidelines of Section 3.2 of NUREG-0609 (Ref. 1) should be followed and a nodalization sensitivity study should be performed, which should include the consideration of spatial pressure variations (e.g., pressure variations circumferentially, axially, and radially within the subcompartment). These variations are use to calculate the transient forces and moments acting on components. 2. Initial Thermodynamic Conditions. The initial atmospheric conditions within a subcompartment should maximize the resultant differential pressure. An acceptable model would assume air at the maximum allowable temperature, minimum absolute pressure, and zero percent relative humidity. If the assumed initial atmospheric conditions differ from this model, the selected values should be justified by the applicant. Another acceptable model that may be used for a restricted class of subcompartments involves simplifying the air model outlined above. In this case, the initial atmosphere within the subcompartment is modeled as a homogeneous water-steam mixture with an average density equivalent to the dry air model. This approach should be limited to subcompartments that have choked flow