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:
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 isolation test verifies safe preparation for maintenance on the reactor pressure vessel and steam generators by draining down and isolating the RCS. During small-break LOCAs and safe-shutdown seismic events, when the residual heat removal (RHR) is in service and the chemical volume and control system letdown is isolated from the RCS, the ELS provides water to the refueling water storage pit (RWSP). Water from the RWSP then flows to the safety injection system (SIS) pumps. (1) Flow and Isolation Test—Cold Conditions. This test should verify the ELS flow and isolation functions. Flow testing should be conducted in a manner similar to that for the LPSI system (see Regulatory Position C.1.c.(1) above). (2) Flow and Isolation Test—Hot Conditions. This test should demonstrate the ability of the ELS gate and globe valves to control and throttle flow to the RWSP and supply depressurized water to the SIS. The test should successfully demonstrate a controlled cooldown of the RCS from hot-shutdown to cold-shutdown conditions while maintaining an adequate RCS water level in the pressurizer. When the system design includes isolation requirements for inservice conditions, this function test should include actuation methods and actuation completion time requirements. f. Passive Core Cooling System—Safety Injection (AP1000)2 (1) Flow Tests—Cold Conditions. This test should verify the ability of the passive core cooling system (PCCS) components (core makeup tanks (CMTs), accumulators, in-containment refueling water storage tank (IRWST), containment sump, automatic depressurization system (ADS), and their associated piping and valves) to perform their intended safety function: (a) Verify design acceptance criteria are met for flow resistance of each CMT injection line,