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:
to reflect the use of the mHTGR functional containment. See the mHTGR-DC 16 rationale. 14 Reactor helium pressure boundary. The reactor helium pressure boundary shall be designed, fabricated, erected, and tested so as to have an extremely low probability of abnormal leakage, of rapidly propagating failure, “Reactor coolant pressure boundary” has been relabeled as “reactor helium pressure boundary” to conform to standard terms used for mHTGRs. APPENDIX C. MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR DESIGN CRITERIA Appendix C to DG-1330, Page C-6 II. Multiple Barriers Criterion mHTGR-DC Title and Content NRC Rationale for Adaptions to GDC of gross rupture, and of unacceptable ingress of moisture, air, secondary coolant, or other fluids. The mHTGR-DC 14 addresses the need to consider leakage of contaminants into the helium used to transport heat from the reactor to the heat exchangers for power production, residual heat removal, and process heat. The phrase “reactor helium pressure boundary” encompasses the entire volume containing helium used to cool the reactor, not just the volume within the reactor vessel. For consistency, a specific requirement is appended to mHTGR-DC 30 for a means of detecting ingress of moisture, air, secondary coolant, or other fluids. Although “other fluids” could be interpreted as including water and steam, for emphasis, the word “moisture” is included in the list of contaminants in both mHTGR-DC 14 and mHTGR-DC 30. 15 Reactor helium pressure boundary system design. All systems that are part of the reactor helium pressure boundary, such as the reactor system, vessel system, and heat removal systems, and the associated auxiliary, control, and protection systems, shall be designed with sufficient margin to ensure that the design conditions of the reactor helium pressure boundary are not exceeded during any condition of normal operation, including anticipated operational occurrences. “Reactor coolant system” has been