Document: NUREG-0800
Document ID: 63f62189-691f-402d-9ac9-41fb60ec2261
Document Type: srp
Title: DETERMINATION OF RUPTURE LOCATIONS AND DYNAMIC EFFECTS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1423/ML14230A035.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.6.2
CFR Part: 
CFR Title: 

Content:
justified. C. Dynamic Analysis Models for Jet Thrust Justified. i. The time-dependent function representing the thrust force caused by jet flow from a postulated pipe break or crack should include the combined effects of the following: the thrust pulse resulting from the sudden pressure drop at the initial moment of pipe rupture; the thrust transient resulting from wave propagation and reflection; and the blowdown thrust resulting from buildup of the discharge flow rate, which may reach steady state if there is a fluid energy reservoir having sufficient capacity to develop a steady jet for a significant interval. Alternatively, a steady state jet thrust function may be used, as outlined in Subsection III.5.C(iv), below. ii. A rise time not exceeding one millisecond should be used for the initial pulse, unless a combined crack propagation time and break opening time greater than one millisecond can be substantiated by experimental data or analytical theory based on dynamic structural response. iii. The time variation of the jet thrust forcing function should be related to the pressure, enthalpy, and volume of fluid in the upstream reservoir and the capability of the reservoir to supply a high energy flow stream to the break area for a significant interval. The shape of the transient function may be modified by considering the break area and the system flow conditions, the piping friction losses, the flow directional changes, and the application of flow-limiting devices. iv. The jet thrust force may be represented by a steady state function if the energy balance model or the static model is used in the subsequent pipe motion analysis. In either case, a step function amplified as indicated in Subsection III.5.B(ii) or III.5.B(iii), above, is acceptable. The function should have a magnitude not less than T = KpA where p = system pressure prior to pipe break, A = pipe break area, and K = thrust coefficient. To be acceptable, K values should not be less than 1.26 for