Document: NRC Regulatory Guide
Document ID: d6326081-f430-476d-8098-4edf00868dd9
Document Type: regulatory_guide
Title: Verification, Validation, Reviews, and Audits for Digital Computer Software Used in Safety Systems of Nuclear Power Plants + HISTORY - HISTORY 08/2012 – DG-1267 , Proposed Revision 2 01/2003 – DG-1123 , Proposed Revision 1 08/1996 – DG-1054 , Proposed Revision 0 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1031/ML103160431.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.168
CFR Part: 
CFR Title: 

Content:
These methods are often used in association with software quality assurance activities. The annexes to IEEE Std. 1012-2004 and IEEE Std. 1028-2008 contain information that may be useful. However, the information in these annexes should not be viewed as the only possible solution or method. Since the nuclear industry has not reached a consensus regarding the use of these methods, the NRC staff does not endorse the use of these annexes, except as noted below. 1. Software Integrity Clause 4 of IEEE Std. 1012-2004 defines an acceptable four-level method of quantifying software integrity levels, in which level 4 is the highest and level 1 the lowest. The standard uses software integrity levels to determine the minimum V&V tasks to be performed. The applicant or licensee may either use the method in the standard or define another method and provide mapping between the applicant’s or licensee’s method and the method defined in the standard. Software used in nuclear power plant safety systems should be assigned integrity level 4 or the equivalent, as demonstrated by a mapping between the applicant or licensee approach and integrity level 4 as defined in IEEE Std. 1012-2004. 2. Software Reliability In its discussion of component and integration test plans in Table 1, IEEE Std. 1012-2004 identifies the measurement of software reliability as a criterion for determining whether software elements “correctly implement software requirements” (5.4.3, “Activity: Design V&V,” Task 5, “Component V&V test plan generation,” and Task 6, “Integration V&V test plan generation”). Consistent with the staff’s position on reliability measures for digital safety systems contained in other agency guidance, the NRC staff’s acceptance of quantitative reliability goals for computer-based safety systems is predicated on deterministic criteria for the computer system in its entirety (i.e., hardware, system software, firmware, application, and interconnections). 3.