Document: NUREG-0800
Document ID: 6de5c1bb-88d0-4d17-8255-a248a8db304a
Document Type: srp
Title: SUBCOMPARTMENT ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070487.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.1.2
CFR Part: 
CFR Title: 

Content:
ompartments, involves simplifying the air model outlined above. For this model, 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 within the vents. However, the adequacy of this simplified model for subcompartments having primarily subsonic flow through the vents has not been established. 2. Subcompartment nodalization schemes should be chosen such that there is no substantial pressure gradient within a node, i.e., the nodalization scheme should be verified by a sensitivity study that includes increasing the number of nodes until the peak calculated pressures converge to small resultant changes. The guideline of Section 3.2 of NUREG-0609 (Reference 27) should be followed 18 and a nodalization sensitivity study should be performed which includes consideration of spatial pressure variation, e.g., pressure variations circumferentially, axially and radially within the subcompartment, for use in calculating the transient forces and moments acting on components. 3. If vent flow paths are used which are not immediately available at the time of pipe rupture, the following criteria apply: a. The vent area and resistance as a function of time after the break should be based on a dynamic analysis of the subcompartment pressure response to pipe ruptures. b. The validity of the analysis should be supported by experimental data or a testing program should be proposed at the construction permit or design certification stage that will support this analysis. 19 c. In meeting the requirements of GDC 4 the effects of missiles that may be generated during the transient should be considered in the safety analysis. 4. The vent flow behavior through all flow paths within the nodalized compartment model should be based on a homogeneous mixture in thermal equilibrium, with DRAFT Rev. 3 - April 1996 6.2.1.2-4 the