Document: NRC Regulatory Guide
Document ID: 9c99a4b7-8619-41f0-b716-262bfdb03941
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:
l. Means shall be provided for detecting and, to the extent practical, identifying the location of the source of reactor helium leakage. Means shall be provided for detecting ingress of moisture, air, secondary coolant, or other fluids to within the reactor helium pressure boundary. “Reactor coolant pressure boundary” has been relabeled as “reactor helium pressure boundary” to conform to standard terms used for mHTGRs. 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. 31 Fracture prevention of reactor helium pressure boundary. The reactor helium pressure boundary shall be designed with sufficient margin to ensure that, when stressed under operating, maintenance, testing, and postulated accident conditions, (1) the boundary behaves in a nonbrittle manner and (2) the probability of rapidly propagating fracture is minimized. The design shall reflect consideration of service temperatures, service degradation of material properties, creep, fatigue, stress rupture, and other conditions of the boundary material under operating, maintenance, testing, and postulated accident conditions and the uncertainties in determining (1) material properties, (2) the effects of irradiation and coolant chemistry on material properties, (3) residual, steady-state, and transient stresses, and (4) size of flaws.