Document: NUREG-0800
Document ID: 42e7682f-df25-4a6a-94f4-7d44ea029702
Document Type: srp
Title: STEAM SYSTEM PIPING FAILURES INSIDE AND OUTSIDE OF CONTAINMENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070677.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.1.5
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Content:
erest consequences has been identified. The topics reviewed include: – Postulated initial core and reactor conditions pertinent to the steam line break accident; – Methods of thermal and hydraulic analyses, including the effects of hydraulic instabilities; – Postulated sequence of events, including analyses to determine the time of reactor trip and time delays prior to and subsequent to initiation of the reactor protection system; – Assumed responses of the reactor coolant and auxiliary systems; – Functional and operational characteristics of the reactor protection system in terms of its effects on the sequence of events; – Operator actions required to secure and maintain the reactor in a safe shutdown condition; – Core power excursion due to power demand created by excessive steam flow out the break; and – Variables influencing neutronics.5 The results of the analyses are reviewed to ensure that pertinent system parameters are within expected ranges. The parameters of importance for these transients include: – Reactor coolant system (RCS) pressure, – Steam generator pressure, – Fluid temperatures, – Clad temperatures, – Discharge flow rates, – Steam line and feedwater flow rates, – Safety and relief valve flow rates, – Pressurizer and steam generator water levels, – Reactor power, – Total core reactivity, – Hot and average channel heat flux, and – Minimum departure from nucleate boiling ratio (DNBR).6 The sequence of events described in the applicant's safety analysis report (SAR) is reviewed by both RSBSRXB and ICSB the Instrumentation and Control Branch (HICB). The RSBSRXB 7 8 reviewer concentrates on the capability of the reactor protection system, the engineered safety systems, and operator action to secure and maintain the reactor in a safe condition. The analytical methods are reviewed by RSBSRXB to ascertain whether the mathematical modeling and computer codes have been previously reviewed and accepted by the staff. If