Document: NRC Regulatory Guide
Document ID: c256f223-ee35-43e0-82e7-aa7b14469259
Document Type: regulatory_guide
Title: Preoperational Testing of Emergency Core Cooling Systems for Pressurized Water Reactors + HISTORY - HISTORY DG-1253 , Proposed Revision 2 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1101/ML110110480.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.79
CFR Part: 
CFR Title: 

Content:
any pressure up to normal precharge pressure. Test results for flow rates should be adjusted for the actual test pressure and temperature versus the design temperature and pressure. These tests apply to all passive injection systems. (2) Isolation Valve Test. At some facilities, the accumulator isolation valves receive a confirmatory open signal whenever the safety injection signal is activated. This ensures that inadvertent valve closures do not prevent operation of the core flooding system. At facilities that have this design feature, testing should demonstrate that the valve will open under the maximum differential pressure conditions and maximum expected accumulator precharge pressures. This test should be conducted using both normal and emergency power supplies. (3) Flow Test—Hot Conditions. This test should verify that check valves subject to higher- than-ambient temperatures during power operation will function properly at the higher temperatures. Any planned or unplanned actuation of core flooding that results in the injection of cold fluid into the hot RCS should be documented in the preoperational test records discussed in Regulatory Position C.3 of this RG. (a) Initially, the RCS and the accumulators should be at their normal operating temperature and pressure, with the RCS pressure higher than the accumulator pressure. Each accumulator injection train should be tested individually or simultaneously by opening the isolation valve and then slowly decreasing RCS pressure and temperature until the check valves operate as indicated by a decrease in the fluid level of each accumulator. To minimize the thermal cycling, the isolation valve should be closed as soon as check valve operation is verified. (b) If the operability of these valves at high temperature is demonstrated during a different phase of the testing program, this specific test may be eliminated. DG-1253, Page 6 e. Emergency Letdown System (US-APWR) The emergency letdown system (ELS) flow and