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:
esign 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 relabeled as “reactor helium pressure boundary” to conform to standard terms used for mHTGRs. 16 Containment design. A reactor functional containment, consisting of multiple barriers internal and/or external to the reactor and its cooling system, shall be provided to control the release of radioactivity to the environment and to ensure that the functional containment design conditions important to safety are not exceeded for as long as postulated accident conditions require. The term “functional containment” is applicable to advanced non-LWRs without a pressure retaining containment structure. A functional containment can be defined as “a barrier, or set of barriers taken together, that effectively limit the physical transport and release of radionuclides to the environment across a full range of normal operating conditions, AOOs, and accident conditions.” Functional containment is relied upon to ensure that dose at the site boundary as a consequence of postulated accidents meets regulatory limits. Traditional containment structures also provide the reactor and SSCs important to safety inside the containment APPENDIX C. MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR DESIGN CRITERIA Appendix C to DG-1330, Page C-7 II. Multiple Barriers Criterion mHTGR-DC Title and Content NRC Rationale for Adaptions to GDC structure protection against accidents related to external hazards (e.g., turbine missiles, flooding, aircraft). The mHTGR functional containment safety design objective is to meet 10 CFR 50.34, 52.79, 52.137, or 52.157 offsite dose requirements at the plant’s exclusion area boundary (EAB) with margins. The NRC staff has brought the issue of functional containment to the Commission, and the Commission has found it generally acceptable, as indicated in the