Document: NUREG-0800
Document ID: 7a841760-7020-433b-b182-63af2e6f5e72
Document Type: srp
Title: OVERPRESSURE PROTECTION
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340596.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.2.2
CFR Part: 
CFR Title: 

Content:
erpressure protection system prevents overpressurization of the reactor coolant pressure boundary under the most severe transients and limits the reactor pressure during normal operational transients. Overpressure protection is provided by safety and relief valves located on the four main steam lines between the reactor vessel and the first isolation valve inside the drywell. The relief and safety valves are distributed among the four main steam lines such that a sin- gle accident cannot disable the automatic overpressure protection function. The valves discharge through piping to the suppression pool. 5.2.2-4 Rev. 2 - November 1988 The valves have setpoints that range from to _psig. Their total capacity at their setpoint is % of rated steam flow. To determine the ability of the overpressure protection system to prevent overpressurization, the applicant has analyzed the most severe overpressure transients. The analysis was performed assuming that: (a) the plant is in operation at design conditions *% of rated steam flow and a reactor vessel dome pressure of * psig), and (b) the reactor is shut down by _ The calculated peak pressure at the bottom of the vessel is _ psig, a value within the code allowable of psig (110% of vessel design pressure). 2. PWRs The overpressure protection system prevents overpressurization of the reactor coolant pressure boundary under the most severe transients and limits the reactor pressure during normal operational transients. Overpressurization protection is provided by safety valves. These valves discharge to the pressurizer quench tank through a common header from the pressurizer. The safety and relief valves in the primary, in conjunction with the steam generator safety and relief valves in the secondary, and the reactor protection system, will protect the primary system against overpressure in the event of a complete loss of heat sink. The peak primary system pressure following the worst transient is limited to the ASME Code