Document: NUREG-0800
Document ID: 7e0d3b3e-62c3-4492-ba89-6cebb4e82234
Document Type: srp
Title: SECONDARY CONTAINMENT FUNCTIONAL DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340701.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.3
CFR Part: 
CFR Title: 

Content:
ered in the radiological analysis of a loss-of-coolant accident. The secondary containment consists of a structure which completely encloses the primary containment and can be maintained at a pressure lower than atmospheric so that primary containment leakage can be collected or processed before release to the environment. The secondary containment may include an enclosure building which forms an annular volume around the primary containment, the auxiliary building where it completely encloses the primary containment, and other regions of the plant that are provided with leakage collection and filtration systems. Depressurization systems are provided as part of the secondary containment to decrease or maintain the secondary containment volume at a negative pressure. All primary containment leakage may not be collected because (1) direct primary containment leakage can occur while the secondary containment is being depres- surized and (2) primary containment leakage can bypass the secondary containment through containment penetrations and seals which do not terminate in the second- ary containment. Direct leakage from the secondary containment to the environment can occur when- ever an outward positive differential pressure exists across the secondary con- tainment boundary. The secondary containment can experience a positive pressure transient following a postulated loss-of-coolant accident in the primary contain- ment as a result of thermal loading and infiltration from the environment and the primary containment that will occur until the depressurization systems become effective. An outward positive differential on the secondary containment wall can also be created by wind loads. In this regard, a "positive" pressure is defined as any pressure greater than -0.25 in. w.g. (water gauge), to account for wind loads and the uncertainty in the pressure measurements. Whenever the pressure in the secondary containment volume exceeds -0.25 in. w.g., the leakage- prevention