Document: NUREG-0800
Document ID: 3b714304-f91e-4999-917a-7d27866735e3
Document Type: srp
Title: STEAM SYSTEM PIPING FAILURES INSIDE AND OUTSIDE OF CONTAINMENT (PWR)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350117.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.1.5
CFR Part: 
CFR Title: 

Content:
uld be used. f. The core burnup (time in core life) should be selected to yield the most limiting combination of moderator temperature coefficient, void coeffi- cient, Doppler coefficient, axial power profile, and radial power distribution. 15. 1. 5-4 Rev. 2 - July 1981 g. The initial core flow assumed for the analysis of the steam line rupture accident should be chosen conservatively. If the minimum core flow allowed by the technical specifications is assumed, the minimum DNBR margin results, but for the analysis of steam line break accidents this may not be the most conservative assumption. For example, maximum initial core flow results in increased reactor coolant system cooldown and depres- surization, decreased shutdown margin, and an increased possibility that the core will become critical and return to power. Since it is not clear what initial core flow is most conservative, the assumed value should be justified. h. For postulated pipe failure in nonseismically qualified portions of the main steam line (outside containment and downstream of the MSIVs) due to a seismically initiated event, only safety grade equipment should be assumed operative to mitigate the consequences of the break. i. For postulated instantaneous pipe failures in seismically qualified portions of the main steam line (inside containment and upstream of the MSIVs), only safety grade equipment should be assumed operative. If, in addition, a single malfunction or failure of an active component is postulated, credit may be taken for the use of a backup nonsafety grade component to mitigate the consequences of the break. j. During the initial 10 minutes of the transient, should credit for operator action be required (i.e., RCP trip), an assessment for the limiting conse- quence must be performed in order to account for operator delay and/or error. III. REVIEW PROCEDURES The procedures below are used during both the construction permit (CP) and operating license (OL) reviews. During the CP