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:
intain a safe shutdown under design-basis event conditions. SECY-94-084, “Policy and Technical Issues Associated with the Regulatory Treatment of Non-Safety Systems in Passive Plant Designs” (Ref. 29), describes the characteristics of a safe shutdown condition as reactor subcriticality, decay heat removal, and radioactive materials containment. The staff replaced “postulated accident conditions” with “design-basis event conditions,” to emphasize that plants are required to maintain a safe shutdown following AOOs as well as postulated accidents. The second sentence of ARDC 26(2) refers to a means of achieving and maintaining shutdown that is important to safety but not necessarily safety related. The second means of reactivity control serves as a backup to the safety-related means and, as such, margins for malfunctions are not required but the second means shall be highly reliable and robust (e.g., meet ARDC 1 -5). “Independent” indicates no shared systems or components with the safety-related means and “diverse” indicates a different design than the safety-related means. The purpose of an independent and diverse means of controlling reactivity is to preclude a potential common cause failure affecting both means of reactivity control, which would lead to the inability to shut down the reactor. The second means of reactivity control does not have to demonstrate that design limits for fission product barriers are met. APPENDIX C. MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR DESIGN CRITERIA Appendix C to DG-1330, Page C-14 III. Reactivity Control Criterion mHTGR-DC Title and Content NRC Rationale for Adaptions to GDC Additionally, the current GDC 26, third sentence, states that the second reactivity control system shall be capable of reliably controlling the rate of changes resulting from planned, normal power changes (including xenon burnout) to assure acceptable fuel design limits are not exceeded. Staff has identified this as an operational