Document: NUREG-0800
Document ID: 02fef38f-79ed-4d55-825f-81551bcfdcdc
Document Type: srp
Title: LOSS-OF-COOLANT ACCIDENTS RESULTING FROM SPECTRUM OF
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550016.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.6.5
CFR Part: 
CFR Title: 

Content:
le need for pump overspeed protection. The review of the applicant's analysis of the spectrum of postulated loss-of-coolant accidents is closely associated with the review of the ECCS, as described in SRP Section 6.3. As a portion of the review effort described in this SRP section and in SRP Section 6.3, the appropriate reactor systems reviewer evaluates whether the entire break spectrum (break size and location) has been addressed; whether the appropriate break locations, break sizes, and initial conditions were selected in a manner that conservatively predicts the consequences of the LOCA for evaluating ECCS performance; and whether an adequate analysis of possible failure modes of ECCS equipment and the effects of the failure modes on the ECCS performance have been provided. For postulated break sizes and locations, the reactor systems review includes the postulated initial reactor core and reactor system conditions, the postulated sequence of events including time delays prior to and after emergency power actuation, the calculation of the power, pressure, flow and temperature transients, the functional and operational characteristics of the reactor protective and ECCS systems in terms of how they affect the sequence of events, and operator actions required to mitigate the consequences of the accident. A spectrum of both large and small break LOCAs are to be evaluated and the limiting break identified through sufficient analyses to determine the worst break peak clad temperature (PCT), the worst local clad oxidation, and the highest core wide oxidation percentage. The small break spectrum should have sufficient resolution to locate these limiting conditions. In the analysis of small breaks, evaluating integer diameter break sizes (i.e., 1, 2, 3, 4-inch, etc.) is considered insufficient to determine the worst break because the break areas associated with these integer diameters are too coarse to adequately identify the highest PCT. The analyses must also be