Document: NUREG-0800
Document ID: 087cef2c-a084-4143-84b9-9f1ba68e1851
Document Type: srp
Title: MASS AND ENERGY RELEASE ANALYSIS FOR POSTULATED SECONDARY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340662.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.1.4
CFR Part: 
CFR Title: 

Content:
- July 1981 If no liquid entrainment is assumed, a spectrum of the steam line breaks should be analyzed beginning with the double-ended break and decreasing in area until it has been demonstrated that the maximum release rate has been considered. A single active failure in the steam or feedwater line isolation provisions or feedwater pumps, such that the containment peak pressure and temperature are maximized, should be assumed to occur in steam and feedwater line break analyses. For the assumed failure of a safety grade steam or feedwater line isolation valve, operation of nonsafety grade equipment may be relied upon as a backup to the safety grade equipment. In this event, the CSB reviewer will confer with the ASB and MEB reviewers to ensure a consistent staff position regarding the acceptability of the design criteria for the nonsafety grade equipment. Feedwater flow to the affected steam generator should be calculated considering the diversion of flow from the other steam generators, feed- water flashing and increased feedwater pump flow caused by the reduction in steam generator pressure. An acceptable method for computing feedwater flow is to assume all feedwater travels to the affected steam generator at the pump runout rate before isolation. After isolation, the unisolated feedwater mass should be added to the affected steam generator. The RELAP4 code may also be used to compute feedwater flow. Operator action to terminate auxiliary feedwater flow will be reviewed by ASB. (See SRP Section 10.4.9.) Acceptable computer codes for calculating mass and energy releases for steam line breaks are SGN-III (Ref. 19) and TRAP-2 (Ref. 31). Other methods will be acceptable if they are found by CSB to be conservative for these calculations. III. REVIEW PROCEDURES The procedures described below are followed for the review of the mass and energy release analysis of secondary coolant systems pipe breaks. The reviewer selects and emphasizes material from these procedures as