Document: NUREG-0800
Document ID: b6b57a00-5b85-4f0c-965c-ca89ef4265e7
Document Type: srp
Title: DETERMINATION OF RUPTURE LOCATIONS AND DYNAMIC EFFECTS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1608/ML16088A041.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.6.2
CFR Part: 
CFR Title: 

Content:
internal and external to the piping. However, following interactions with the Advisory Committee on Reactor Safeguards (ACRS) on the jet models described in ANSI/ANS 58.2 by ACRS the staff determined that there were potential nonconservatisms in these models with respect to the (a) strength, (b) zone of influence, and (c) space and time-varying nature of the loading effects of postulated pipe ruptures on neighboring structures, systems, and components (SSCs). Blast Waves In the event of a high-pressure pipe rupture, the first significant fluid load on surrounding SSCs would be induced by a blast wave. A spherically expanding blast wave is reasonably approximated to be a short duration transient and analyzed independently of any subsequent jet formation. However, the expansion of blast waves in an enclosed space is not purely spherical, and reflections and amplifications may need to also be accounted for. Blast waves are not considered in the ANSI/ANS 58.2 Standard for evaluating the dynamic effects associated with the postulated pipe rupture. Jet Plume Expansion and Zone of Influence In the characterization of supersonic jets given by the ANSI/ANS 58.2 Standard, some physically incorrect assumptions underlie the approximating methodology. The model of the supersonic jet itself is given in Figures C-1 and C-2 of the ANSI/ANS 58.2 Standard. The standard assumes that a jet issuing from a high pressure pipe break will always spread with a fixed 45 degree angle up to an asymptotic plane and subsequently spread at a constant 10 degree angle. The characteristics of the jet, however, are not universal. Initial jet spreading rates are highly dependent on the ratio of the total conditions of the source flow to the ambient conditions. Subsequent spreading rates depend, at a given axial position, on the ratio of the static pressure in the outermost jet flow region to the ambient static pressure. In the ANSI/ANS 58.2 Standard, the asymptotic plane is described as the point at