Document: NUREG-0800
Document ID: 41b2cf88-b6dc-4005-939a-cf3fb1a561d2
Document Type: srp
Title: INADVERTENT DECREASE IN BORON CONCENTRATION IN THE REACTOR
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0703/ML070380222.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.6
CFR Part: 
CFR Title: 

Content:
ower operation, hot standby, shutdown (hot and cold), and refueling modes. Because of the frequency of boron dilution events (one or more times during the life of the nuclear power unit) without other concurrent failures or incidents, regulatory requirements for AOOs apply to their analyses or evaluations. RCS pressure transients of power increases caused by postulated boron dilution events are analyzed for whether pressure limiting design features, including conservatively assumed responses of control and protection systems, maintain pressures below the RCPB design pressure limits for transients. Uncertainties of quantification or measurement of relevant boron dilution event parameters are verified by analyses including appropriate design margins. Thus, GDC 15 assures that analyses demonstrate, under conditions of normal operation, including the effects of postulated boron dilution events, design of the RCS and its auxiliary, control, and protection systems with sufficient margin to maintain RCPB integrity. 4. GDC 26 requires control rods to control reactivity changes to assure that acceptable fuel design limits are not exceeded under normal operation, including AOOs, and with appropriate margin for malfunctions such as stuck rods. Fuel design limits are established to assure the integrity of fuel cladding as a FP barrier. In PWRs, a control rod system is provided for reactivity control. Boron is also added to the reactor coolant in sufficient concentrations for reactivity control. PWR conditions of normal operation include startup, power operation, hot standby, shutdown (hot and cold), and refueling modes; however, the control rods may reduce reactivity only when withdrawn and operable (i.e. during startup and power operation). Because of the frequency of boron dilution events (one or more times during the life of the nuclear power unit) without other concurrent failures or incidents, regulatory requirements for AOOs apply to their analyses or evaluations.