Document: NRC Regulatory Guide
Document ID: da269da5-7390-4252-b08f-bdb7aeb8beaf
Document Type: regulatory_guide
Title: Developing Principal Design Criteria for Non-Light Water Reactors + HISTORY - HISTORY 02/2017 – DG-1330 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1630/ML16301A307.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.232
CFR Part: 
CFR Title: 

Content:
ems as required for mHTGR-DC 34. The list of examples was deleted, as they apply to LWR designs and each specific design will have different important components associated with residual heat removal. 37 Testing of passive residual heat removal system. The passive residual heat removal system shall be designed to permit appropriate periodic functional testing to ensure (1) the structural and leaktight integrity of its components, (2) the operability and performance of the system components, and (3) the operability of the system as a whole and, under conditions as close to design as practical, the performance of the full operational sequence that brings the system into operation, including operation of associated systems and interfaces with an ultimate heat sink and the transition from the active normal operation mode to the passive operation mode relied upon during postulated accidents, including the operation of applicable portions of the protection system and the operation of the associated structural and equipment cooling water system. Criterion 37 has been renamed and revised for testing the passive residual heat removal system required by mHTGR-DC 34. Section 2.3.4 of INL/EXT-10-17997, “Mechanistic Source Terms White Paper,” (Ref. 33) notes that the passive reactor cavity cooling system (RCCS) (using either air or water as heat transfer fluid) contributes to the mHTGR safety basis and is subject to component integrity testing. However, Section 6.1 of INL/EXT-11-22708, “Modular HTGR Safety Basis and Approach,” (Ref. 34), indicates that RCCS performance does not require “leaktight” conditions. For an RCCS which is an “open system”, the normal and expected loss of RCCS coolant through the exhaust structure would not be considered leakage. Abnormal leakage of RCCS coolant to locations other than the exhaust structure may be acceptable provided that (1) the RCCS leakage does not impact safety functions under all conditions, and (2) functional