Document: NUREG-0800
Document ID: 55d768d1-b37e-4411-a262-f2276e26f3e7
Document Type: srp
Title: 15.3.2.-5
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550010.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.3.1
CFR Part: 
CFR Title: 

Content:
Revision 2 - March 2007 7. The performance of nonsafety-related systems during transients and accidents and of single failures of active and passive systems (especially the performance of check valves in passive systems), must be evaluated and verified by the guidance of SECY 77-439, SECY 94-084 and RG 1.206. 8. The applicant's analysis of the most limiting AOOs should use an acceptable model. Unapproved analytical methods proposed by the applicant are evaluated by the staff for acceptability. 9. Parameter values in the analytical model should be suitably conservative. The following values are acceptable: A. Initial power level is rated output (licensed core thermal power) for the number of loops initially assumed operating plus an allowance of 2 percent to account for power measurement uncertainty unless (i) a lower number can be justified through the measurement uncertainty methodology and evaluation or (ii) the uncertainty is accounted for otherwise (see SRP 4.4). The number of loops 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 (e.g., maximum time delay with the most reactive rod held out of the core for a PWR, a design conservatism factor of 0.8 times the calculated negative reactivity insertion rate for a BWR), unless (i) a different conservatism factor can be justified through the uncertainty methodology and evaluation or (ii) the uncertainty is accounted for otherwise (see SRP Section 4.4). C. The core burn-up is selected to yield the most limiting combination of moderator temperature coefficient, void coefficient, Doppler coefficient, axial power profile, and radial power distribution. D. Mitigating systems should be assumed as actuated in the analyses at setpoints with allowance for instrument uncertainty in accordance with RG 1.105 and as determined by the organization responsible for instrumentation and controls.