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:
ems reviewer); 15.6.5-11 Revision 3 - March 2007 and carryover fraction (if it is not an input to the calculations). The boric acid concentration should be shown as a function of time for the limiting large and small breaks. For small breaks where simultaneous injection is unable to flush the core, other procedures must be employed to show that the boric acid concentration does not achieve precipitation limits. New reactor designs may base their ECCS and reactor coolant system designs on prevention of core uncovery. Should that be the case, the reviewer should compare the applicant’s analysis with the staff independent analysis to determine if the predicted level of core coverage is consistent. 8. The calculated peak clad temperature, maximum local oxide thickness, and core average zirconium-water reaction meet the acceptance criteria for ECCS given in 10 CFR 50.46(b). Boric acid concentration should be shown to be controlled prior to reaching the precipitation limit and all equipment and operator action times identified for inclusion in the EOPs. 9. The applicant's analysis addresses the full LOCA sequence of events, for the full spectrum of break sizes and locations, to the point where the plant is in the long-term cooling mode and removal of decay heat has been well established for both large and small breaks. The reviewer checks the assumed sources of coolant water, redundancy of delivery routes, alignment of valves, control of boron concentration (PWR) and all required operator actions. 10. TMI action item II.K.3.5 “Automatic RCP Trip during a LOCA” requires reactor coolant pump trip following all small breaks. While II.K.3.5 requires trip, restart of the RCPs should only be attempted based on explicit guidance in the EOPs dealing with a safe restart of the pumps. This will ensure SBLOCA ECCS performance is not later degraded and pump damage is also avoided. The following steps shall be included in PWR emergency operating procedures as a condition for