Document: NUREG-0800
Document ID: 824740ba-eb51-4b24-bd6f-df01c35d75f3
Document Type: srp
Title: LOSS OF NONEMERGENCY AC POWER TO THE STATION AUXILIARIES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550008.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.2.6
CFR Part: 
CFR Title: 

Content:
d be maintained by keeping the minimum departure from nucleate boiling ratio (DNBR) above the 95/95 DNBR limit for PWRs and the critical power ratio (CPR) above the minimum critical power ratio safety limit for BWRs based on acceptable correlations (see SRP Section 4.4). 3. An incident of moderate frequency should not generate a more serious plant condition without other faults occurring independently. 4. For the requirements of GDCs 10 and 15, the positions of Regulatory Guide (RG) 1.105, "Instrument Setpoints for Safety-Related Systems," have impact on the plant response to the type of transient addressed in this SRP section. 5. The most limiting plant system single failure, as defined in the "Definitions and Explanations" of 10 CFR Part 50, Appendix A, must be assumed in the analysis and must satisfy the positions of RG 1.53. The applicant's analysis of the loss of ac power transient should be based on an acceptable and NRC-approved model. If the applicant proposes analytical methods not approved, these are evaluated by the staff for acceptability and approval. For new generic methods, the reviewer requests an appropriate evaluation. The parameter values in the analytical model should be suitably conservative. The following values are acceptable: A. The initial power level is taken as the licensed core thermal power for the number of loops initially assumed to be operating plus an allowance of 2 percent to account for power measurement uncertainties unless the applicant can justify a lower power level. The number of loops (RCS loop requirements as applicable for BWR design) operating at the initiation of the event should correspond to the operating condition which maximizes the consequences of the event. B. Conservative scram characteristics are assumed (i.e., for a PWR maximum time delay with the most reactive rod held out of the core and for a BWR a design conservatism factor of 0.8 times the calculated negative reactivity insertion rate). C. The core burn-up