Document: NUREG-0800
Document ID: 243e1ce7-857c-48e4-9eb7-6125311da9be
Document Type: srp
Title: RESIDUAL HEAT REMOVAL (RHR) SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070437.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.4.7
CFR Part: 
CFR Title: 

Content:
cceptable if suitably justified. 4. The system(s) shall be capable of bringing the reactor to a cold shutdown condition, with only offsite or onsite power available, within a reasonable period of time following shutdown, assuming the most limiting single failure. B. RHR System Isolation Requirements The RHR system shall satisfy the isolation requirements listed below. 1. The following shall be provided in the suction side of the RHR system to isolate it from the RCS. (a) Isolation shall be provided by at least two power-operated valves in series. The valve positions shall be indicated in the control room. (b) The valves shall have independent diverse interlocks to prevent the valves from being opened unless the RCS pressure is below the RHR system design pressure. Failure of a power supply shall not cause any valve to change position. (c) The valves shall should have independent diverse interlocks to protect against one or both valves being open during an RCS increase above the design pressure of the RHR system, to the extent that such interlocks will not degrade high system reliability during shutdown operations (see Reference 14).175 2. One of the following shall be provided on the discharge side of the RHR system to isolate it from the RCS: (a) The valves, position indicators, and interlocks described in item 1(a) through 1(c) above, (b) One or more check valves in series with a normally closed power-operated valve. The power-operated valve position shall be indicated in the control room. If the RHR system discharge line is used for an ECCS function, the power-operated valve is to be opened upon receipt of a safety injection signal once the reactor coolant pressure has decreased below the ECCS design pressure. DRAFT Rev. 4 - April 1996 5.4.7-24 (c) Three check valves in series, or (d) Two check valves in series, provided that there are design provisions to permit periodic testing of the check valves for leak tightness and the testing is performed at least