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:
s. 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 assumption of 100% water entrainment. In addition, the selected vent critical flow correlation should be conservative with respect to available experimental data. Currently acceptable vent critical flow correlations are the "frictionless Moody" (Reference. 1613) with a multiplier of 0.6 for water-steam mixtures, 20 and the thermal homogeneous equilibrium model for air-steam-water mixtures. 5. At the construction permit or design certification stage, a factor of 1.4 should be 21 applied to the peak differential pressure calculated in a manner found acceptable to the SCSB for the subcompartment, structure and the enclosed components, 22 for use in the design of the structure and the component supports. At the operating license stage, the peak calculated differential pressure should not exceed the design pressure. It is expected that the peak calculated differential pressure will not be substantially different from that of the construction permit or design certification stage. However, improvements in the analytical models or 23 changes in the as-built subcompartment may affect the available margin. Technical Rationale:24 The technical rationale for application of the above acceptance criteria to PWR dry containments is discussed in the following paragraphs: 1. GDC 4 requires that structures, systems, and components important to safety be designed to withstand the environmental conditions and dynamic effects associated with normal operations, maintenance, testing, and postulated accidents. GDC 4 allows dynamic effects associated with postulated pipe ruptures to be excluded from the design basis when analyses reviewed and approved by the staff demonstrate that the probability of fluid system piping rupture is extremely low. Demonstration of extremely low probability pipe