Document: NRC Regulatory Guide
Document ID: fc586342-92f7-4c77-ae76-79e3674cf288
Document Type: regulatory_guide
Title: Criteria for Programmable Digital Devices in Safety-Related Systems of  Nuclear Power Plants + HISTORY –HISTORY 02/2023 – DG-1374, Proposed Revision 4 Prior to issuance of DG-1374, RG 1.152 was entitled, “Criteria for Use of Computers in Safety-Systems of Nuclear Power Plants” 06/2010 – DG-1249, Proposed Revision 3 – Revise 12/2004 – DG-1130, Proposed Revision 2 – Revise 05/1995 – DG-1039, Proposed Revision 1 03/1983 – DG-1130, Proposed Revision 2 – Revise (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2301/ML23012A242.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.152
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CFR Title: 

Content:
d also consider the cybersecurity guidance in RG 5.71 in preparing a design certification under 10 CFR Part 52. Within such consideration, measures should be included to ensure that safety-related I&C systems do not present an electronic path that could enable unauthorized access to the plant’s safety-related system (e.g., the use of a hardware-based unidirectional device is one approach the NRC staff would consider DG-1374, Page 11 acceptable for implementing such measures). (4) Common-Cause Failure 4.1 CCFs have been identified as a type of hazard to which PDDs in safety-related digital systems could be more susceptible, due to the integration capabilities provided by the technology and its inherent complexity compared to analog technologies. PDDs in safety-related systems can be vulnerable to a CCF due to defects in the devices’ hardware or to latent defects in the software or software-based logic. A CCF of PDDs within a DI&C system can either (1) result in loss of capability to perform a safety function concurrent with an anticipated operational occurrence, a postulated accident, or normal operations, or (2) initiate the operation of a function without a valid demand or cause an erroneous (i.e., spurious) system action. The latter is typically referred to as “spurious operation” or “spurious actuation.” 4.2 Clause 5.16 of IEEE Std 7-4.3.2-2016 provides criteria that the NRC staff finds acceptable for addressing potential CCFs in PDDs of safety-related systems. In addition, the NRC staff uses the guidance in BTP 7-19 to evaluate the applicants’ defense in depth and diversity assessment as a means to address CCFs due to latent design defects in digital safety-related systems. (5) Use of Commercial Digital Equipment 5.1 Clause 5.17 of IEEE Std 7-4.3.2-2016 provides criteria that the NRC staff finds acceptable for addressing the use of commercial digital equipment in safety-related systems of nuclear power generations. Clause 5.17 references Annex C