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:
nd components. Same as GDC II. Multiple Barriers Criterion mHTGR-DC Title and Content NRC Rationale for Adaptions to GDC 10 Reactor design. The reactor system and associated heat removal, control, and protection systems shall be designed with appropriate margin to ensure that specified acceptable system radionuclide release design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences. The concept of specified acceptable fuel design limits, which prevent additional fuel failures during anticipated operational occurrences (AOOs), has been replaced with that of the specified acceptable system radionuclide release design limits (SARRDL), which limits the amount of radionuclide inventory that is released by the fuel and surfaces within the helium coolant boundary under normal and AOO conditions. The “system” refers to the components and internals of the mHTGR helium pressure boundary. Design features within the reactor system must ensure that the SARRDLS are not exceeded during normal operations and AOOs. APPENDIX C. MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR DESIGN CRITERIA Appendix C to DG-1330, Page C-4 II. Multiple Barriers Criterion mHTGR-DC Title and Content NRC Rationale for Adaptions to GDC The tristructural isotropic (TRISO) fuel used in the mHTGR design is the primary fission product barrier and is expected to have a very low incremental fission product release during AOOs. As noted in NUREG-1338 (Ref. 3) and in the NRC staff’s feedback on the Next Generation Nuclear Plant (NGNP) project white paper, “Next-Generation Nuclear Plant – Assessment of Key Licensing Issues” (Ref. 11) the TRISO fuel fission product transport and retention behavior under all expected operating conditions is the key to meeting dose limits, as a different approach to defense in depth is employed in an mHTGR. The SARRDL concept allows for some small increase in circulating radionuclide inventory during