Document: NUREG-0800
Document ID: 4f141c71-35ca-4353-9047-a13efe6d56b7
Document Type: srp
Title: Revision 6 - August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A308.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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d data or code has the potential to propagate a common-cause or common-mode failure via software errors, thus defeating the redundancy achieved by the hardware architectural structure. Greater sharing of process equipment among functions within a channel, that is, the same processing equipment will be performing a number of different safety functions, increases the consequences of the failure of a single hardware module and reduces the amount of diversity available within a single safety channel. Because of these concerns, the staff review of digital I&C systems emphasizes quality, diversity, and defense-in-depth as protection against common-cause failures within and between channels. Software quality is an important element in preventing the propagation of common- cause failures. The development of safety system software should progress according to a formally defined life cycle. Many life cycles have been defined in the technical literature and in national and international standards. These differ in the definitions of life cycle activity groups and in the order in which life cycle activities are performed. The software developer should select and document the software life cycle, and specify the products that will be produced by that life cycle. The software developer can be the applicant or licensee, the vendor, a company working on behalf of either, or a commercial software development company. All software development life cycles share certain characteristics. The activities that will be performed can be grouped into a number of categories (termed activity groups here); the activity groups are common to all life cycles. Life cycle activities produce process documents and design outputs which can be reviewed and assessed. Further information on life cycles, activity groups, and document contents can be found in NUREG/CR-6101. BTP 7.14-10 Revision 6 - August 2016 B.2 Information to be Reviewed The information to be reviewed is subdivided into three topic areas: