Regulatory Guide 1.169

(Draft Was DG-1055) Configuration Management Plans for Digital Computer Software Used in Safety Systems of Nuclear Power Plants

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Issue date:	09/30/1997
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DG-1055 RG-1.169
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U.S. NUCLEAR REGULATORY

COMMISSION

REGULATORY

September

1997 GUIDE OFFICE OF NUCLEAR REGULATORY

RESEARCH REGULATORY

GUIDE 1.169 (Draft was DG-1055) CONFIGURATION

MANAGEMENT

PLANS FOR DIGITAL COMPUTER SOFTWARE USED IN SAFETY SYSTEMS OF NUCLEAR POWER PLANTS

A. INTRODUCTION

In 10 CFR Part 50, "Domestic Licensing of Pro duction and Utilization Facilities," paragraph

55a(a)(1)

requires, in part, that systems and components be designed, tested, and inspected to quality standards commensurate with the safety function to be per forme

d. I Criterion

1, "Quality Standards and Re cords," of Appendix A, "General Design Criteria for Nuclear Power Plants," of 10 CFR Part 50 requires, in part, 1 that appropriate records of the design and testing of systems and components important to safety be .2 maintained by or under the control of the nuclear power unit licensee throughout the life of the unit. Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR Part 50 describes criteria that must be met by a quality assur ance program for systems and components that prevent or mitigate the consequences of postulated accidents.

In particular, besides the systems and components that directly prevent or mitigate the consequences of postu lated accidents, the criteria of Appendix B also apply to all activities affecting the safety-related functions of such systems and components, such as designing, pur chasing, installing, testing, operating, maintaining, or lln this regulatory guide, many of the regulations have been paraphrased;

see 10 CFR Part 50 for the full text.modifying.

A specific requirement is contained in 10 CFR 50.55a(h), which requires that reactor protection systems satisfy the criteria of IEEE Std 279, "Criteria for Protection Systems for Nuclear Power Generating Stations." 2 Paragraph

4.3 of IEEE Std 279-19713 states that quality of components is to be achieved through the specification of requirements known to promote high quality, such as requirements for design, inspection, and test. Many of the criteria in Appendix B to 10 CFR Part 50 contain requirements closely related to the con figuration management activity.

Criterion III, "Design Control," of Appendix B requires measures for design documentation and identification and control of design interfaces.

The same criterion also requires that design changes be subject to design control measures com mensurate with those used in the original design. Crite rion VI, "Document Control," requires that all docu ments that prescribe activities affecting quality, such as 2 Revision I of Regulatory Guide 1.153, "Criteria for Safety Systems," en dorses IEEE Std 603-1991,"Criteria for Safety Systems for Nuclear Pow er Generating Stations," as a method acceptable to the NRC staff for satis fying the NRC's regulations with respect to the design, reliability, qualifi cation, and testability of the power, instrumentation, and control portions of the safety systems of nuclear power plants. 3 1EEE publications may be obtained from the IEEE Service Center, 445 Hoes Lane, Piscataway, NJ 0885

4. USNRC REGULATORY

GUIDES The guides are issued in the following ten broad disions: Regulatory Guides re Issued to describe and make available to the public such Informa bon as methods acceptable to the NRC staff for hmplementing specific parts of the Com- 1. Power Reactors 6. Products mission's regulations, techniques used bythestaff inevaluating specific problemsor pos 2. Research and Tost Reactors 7. Trarsportation tulated accidents.

and data needed by the NRC staff in Its review of applications rper.- I Fuels and Mateials Facilities

8. Occupational Health mits and licenses.

Regulatory guides ae not substitutes foregulations, and compliance

4. Environmental end Siting 9. Anitrust and Financial Review withViem Isnotrelred.

Methods andisolutions different from thosesetoutinlheguldes

5. Materials and Plant Protection

10. General will be acceptable If they provide a basis for the findings requisite to the Issuance or oon tinuence of a permit or cense by the Commission.

Single copies of regulatory guides may be obtained free of charge bywrlilng the Printing, This guide was issued after consideration of comments received from the public. Corn- Graphics and Distribution Branch, Office of Adminisation.

U.S. Nuclear Regulatory Com mens and suggestions for Improvenents In these guides re encouraged stall tines, and mission. Washington, OC 20555-0001;

or by fax at (301)41515272.

guides will be revised, as eppropriae.

to accommodate comments :nd to reflect new in Ion~on or experience.

Issued guides may also be purchased from the National Technical Information Service on Written comments may be submitted to the Rules Review and Diectives Branch DFIPS, a standing order basis. Details on this service may be obtained by writing NTIS, 5285 Port ADM, U.S. Nuclear Regulatory Commission, Washington.

DC 20555-0001.

Royal Road, Springfield, VA 22161.

instructions, procedures, and drawings, be subject to controls that ensure that documents, including changes, are reviewed for adequacy and approved for release by authorized personnel.

Criterion VIII, "Identification and Control of Materials, Parts, and Components," requires, in part, that parts and components be identi fied to prevent the use of incorrect or defective parts or components.

Criterion XVI, "Corrective Action," requires that conditions adverse to quality, such as fail ures, malfunctions, deficiencies, and others, be identi fied, and that the cause be determined, the condition be corrected, and the entire process be documented.

Crite rion XVII, "Quality Assurance Records," requires in part that sufficient records be maintained so that data that is closely associated with the qualification of per sonnel, procedures, and equipment be identifiable and retrievable.

This regulatory guide, which endorses IEEE Std 828-1990, "IEEE Standard for Software Configuration Management Plans," 3 and ANSI/IEEE Std 1042-1987, "IEEE Guide to Software Configuration Manage ment," 3 with the exceptions stated in the Regulatory Position, describes methods acceptable to the NRC staff for complying with the NRC's regulations for pro moting high functional reliability and design quality in software used in safety systems.4 In particular, the methods are consistent with the previously cited Gener al Design Criteria and the criteria for quality assurance programs of Appendix B as they apply to the mainte nance of appropriate records of, and control of, soft ware development activities.

The criteria of Appen dices A and B apply to systems and related quality assurance processes and, if those systems include soft ware, the requirements extend to the software elements.

In general, information provided by regulatory guides is reflected in the Standard Review Plan (NUREG-0800).

The Office of Nuclear Reactor Regu lation uses the Standard Review Plan to review applica tions to construct and operate nuclear power plants. This regulatory guide will apply to the revised Chapter 7 of the Standard Review Plan. The information collections contained in this regu latory guide are covered by the requirements of 10 CFR Part 50, which were approved by the Office of Manage ment and Budget, approval number 3150-0011.

The NRC may not conduct or sponsor, and a person is not 4 The term "safety systems" is synonymous with "safety-related systems." The General Design Criteria cover systems, structures, and components "important to safety." The scope of this regulatoty guide is, however, lim ited to "safety systems," which are a subset of "systems important to safety." required to respond to, a collection of information un less it displays a currently valid OMB control number.

B. DISCUSSION

The use of industry consensus standards is part of an overall approach to meeting the requirements of 10 CFR Part 50 when developing safety systems for nuclear power plants. Compliance with standards does not guarantee that regulatory requirements will be met. However, compliance does ensure that practices accepted within various technical communities will be incorporated into the development and quality assur ance processes used to design safety systems. These practices are based on past experience and represent in'dustry consensus on approaches used for development of such systems.

Software incorporated into instrumentation and control systems covered by Appendix B will be referred to in this regulatory guide as safety system software.

For safety system software, identification, control, and documentation of the software must be accomplished as part of the effort to achieve compliance with the NRC's requirements.

In addition to the record mainte nance requirement of Criterion

1 of Appendix A, Appendix B to 10 CFR Part 50 provides detailed quali ty assurance criteria, including criteria for administra tive control, design documentation, design interface control, design change control, document control, identification and control of parts and components, and control and retrieval of qualification information asso ciated with parts and components.

For software, these activities are often called, in aggregate, "software con figuration management" (SCM). SCM is identified as a safety system criterion by the industry standard, IEEE Std 7-4.3.2-1993, "Standard Criteria for Digital Com puters in Safety Systems of Nuclear Power Generating Stations," 3 which is endorsed by Revision I of Regula tory Guide 1.152, "Criteria for Digital Computers in Safety Systems of Nuclear Power Plants." Configuration management is a significant part of high quality engineering activities and is already re quired by the NRC staff for structures, systems, and components important to safety. While the principles and intentions of traditional configuration management apply equally to software, there is also a significant change in emphasis for which traditional hardware con figuration management systems might not be suffi cient. This is because with software there is a greater emphasis on design process and the deliverable product is more like a design output. In the production of engi neered hardware, design outputs are inputs to a manufacturing process, and configuration management

1.169-2 activities focus on ensuring that design outputs and manufacturing process variables are traceable to identi fiable manufactured products.

In contrast, with engi.> neered software, a large amount of design process in formation and many intermediate design outputs are associated with the final design output. Relatively many software engineering changes are expected and encountered.

Consequently, although similar in intent to hardware configuration management, software con figuration management requires a change in emphasis, with expansion of the importance of intermediate de sign baselines and associated design process informa tion. The needs for robust change management and identification and control of product versions are also substantially increased.

One consensus standard on software engineering, IEEE Std 828-1990, "IEEE Standard for Software Configuration Management Plans," and one IEEE guide, ANSI/IEEE Std 1042-1987, "IEEE Guide to Software Configuration Management" (reaffirmed in 1993), describe software industry approaches to SCM that are generally accepted in the software engineering community.

They provide guidance for planning and executing an SCM program. Together, this IEEE stan dard and guide elaborate on the important features required in an SCM program that may be under>j emphasized in traditional hardware configuration man agement programs.

The relationship of IEEE Std 1042-1987 to IEEE Std 828-1990 is important.

IEEE Std 1042-1987 is a tutorial guide that explains how to comply with IEEE Std 828-1990.

Section 1.1, "Scope," of IEEE Std 1042-1987 states that the guide provides suggestions and examples and "presents an interpretation of how IEEE Std 828-1983 [since updated to IEEE Std 828-1990]

can be used for planning the management of different kinds of computer program development and maintenance activities." The actual criteria to be met for compliance with the standard are contained in IEEE Std 828-1990..

Both the standard and the guide apply to general purpose software development and mainte nance efforts, and they do not have specific criteria for safety system software.

C. REGULATORY

POSITION IEEE Std 828-1990, "IEEE Standard for Software Configuration Management Plans," provides an approach acceptable to the NRC staff for meeting the ./ requirements of 10 CFR Part 50, as applied to software, in planning configuration management of safety sys tem software, subject to the provisions listed below.ANSI/IEEE Std 1042-1987, "IEEE Guide to Soft ware Configuration Management," subject to the pro visions listed below, provides guidance acceptable to the NRC staff for carrying out software configuration management plans produced under the auspices of IEEE Std 828-1990.

IEEE Std 1042-1987 should be used with the definitions of IEEE Std 828-1990 to implement the details of plans prepared pursuant to IEEE Std 828-1990.

In the provisions listed below, ref erence is made to explanatory sections of IEEE Std 1042-1987 where appropriate to clarify SCM concepts.

To meet the cited requirements of Appendix A to 10 CFR Part 50 by complying with the cited criteria of Appendix B, the following exceptions are necessary and will be considered by the NRC staff in the review of submittals from applicants and licensees. (In this Regu latory Position, the cited criteria are in Appendix B to 10 CFR Part 50 unless otherwise noted.),

1. DEFINITIONS

IEEE Std 828-1990 refers to IEEE Std 610.12-1990, "IEEE Standard Glossary of Software Engineering Terminology," for definitions of the tech nical terms that are enumerated in section 1.3 of IEEE Std 828-1990.

These definitions are acceptable with the following clarifications and additions:

1.1 Baseline Meaning (1) of baseline is to be used in IEEE Std 828-1990.

Formal review and agreement is taken to mean that responsible management has reviewed and approved a baseline.

Baselines are subject to change control. Acceptable baseline change approval authority is described in Exception

2 below. 1.2 Promotion The term "promotion," as defined in Section 1.4 of IEEE Std 1042-1987, is added to the list of defined terms. 1.3 Interface All four variations of the meaning of interface are to be used in IEEE Std 828-1990, depending upon the context. Meaning (1), "A shared boundary across which information is passed," is interpreted broadly according to Criterion III to include design interfaces between participating design organizations.

1.4 Configuration Audit IEEE Std 610.12-1990

refers the definition of con figuration audit to two other audits without specifying whether one or both definitions are meant. In the 1.169-3 context of an audit for delivery of a product, a configu ration audit includes both a functional configuration audit and a physical configuration audit.

2. AUTHORITY

LEVELS Section 2.2.4 of IEEE Std 1042-1987 is modified to permit hierarchies of change approval authority lev els, as described in that section and discussed in section 3.3.2.1, provided the required authority level is com mensurate with life cycle stage (nearness to release) and product importance to safety. The promotion of a soft ware product might involve a change in level of control and responsible individual.

3. ACCEPTANCE

CRITERIA Criterion II, "Quality Assurance Program," states that activities affecting quality are to be accomplished under suitably controlled conditions.

Criterion V, "Instructions, Procedures, and Drawings," states that instructions, procedures, or drawings are to include appropriate quantitative or qualitative acceptance crite ria for determining that important activities have been satisfactorily accomplished.

Section 1.3 of IEEE Std 828-1990 defines "control point." The software con figuration management (SCM) plan should describe the criteria for selecting control points and establish the correspondence between control points identified in the plan and baselines, project milestones, and life cycle milestones.

4. CONFIGURATION

MANAGEMENT

Section 2.3 of IEEE Std 828-1990 describes four functional areas under which configuration manage ment activities are grouped: configuration identifica tion, configuration control, status accounting, and con figuration reviews and audits. However, while IEEE Std 828-1990 requires that SCM plans describe provi sions for these activities, it has no minimal set of activi ties for safety system software.

Criterion II, "Quality Assurance Program," states that activities affecting quality are to be accomplished under suitably con trolled conditions.

Criteria III, "Design Control";

VI, "Document Control";

VII, "Control of Purchased Ma terial, Equipment, and Services";

VIII, "Identification and Control of Materials, Parts, and Components";

XVII, "Quality Assurance Records";

and XVIII, "Au dits," address various aspects of the need for control ling designs, documentation, and materials.

For safety system software, the minimal set of activities must ac complish the following- identification and control of all software designs and code, identification and control of all software design interfaces, control of all software design changes, control of software documentation (user, operating, and maintenance documentation), control of software vendors supplying safety system software, control and retrieval of qualification informa tion associated with software designs and code, soft ware configuration audits, and status accounting.

Some of these functions or documents may be per formed or controlled by other quality assurance activi ties; in this case the SCM plan should describe the divi sion of responsibility.

5. CORRECTIVE

ACTION Criterion XVI, "Corrective Action," requires that conditions adverse to quality, such as failures, malfunc tions, deficiencies, and others, be identified, the cause be determined, the condition be corrected, and the en tire process be documented.

In software development or maintenance, the responsibility for these activities is often distributed among several organizations, possi bly leading to a fragmented view of the correction process. Section 2.3.2 of IEEE Std 828-1990 requires a partial description of the correction process, including change requests, change evaluation, change approval, change implementation, change verification, and changed-version release. The preliminary steps leading to a change request should also be described, including responsibility for executing and documenting anomaly reports, problem analyses, and statistical monitoring of software performance.

If these activities are described by other documents, the descriptions may be included by reference.

6. DOCUMENTATION

Section 2.3.1.1 of IEEE Std 828-1990 requires, as a minimum, that all configuration items that are to be delivered be listed in the SCM plan. This fulfills the in tent of Criterion VIII, "Identification and Control of Materials, Parts, and Components," with regard to safety system software if all software deliverables are identified and controlled as configuration items. Crite rion III, "Design Control," requires measures for de sign documentation, identification and control of de sign interfaces, and control of design changes.

Criterion VI, "Document Control," requires that all documents that prescribe activities affecting quality, such as instructions, procedures, and drawings, be sub ject to controls that ensure that documents, including changes, are reviewed for adequacy and approved for release by authorized personnel.

Criterion XVII, "Quality Assurance Records," requires in part that suf ficient records be maintained so that data that is closely associated with the qualification of personnel, proce dures, and equipment will be identifiable and retriev able. This regulatory guide applies to all aspects of the software life cycle within the system life cycle context.1.169-4 Therefore, for safety system software, configuration items or controlled documents should include the fol lowing:

• Software requirements, designs, and code a Support software used in development (exact ver sions) a Libraries of software components essential to safety

• Software plans that could affect quality

• Test software requirements, designs, or code used in testing a Test results used to qualify software

• Analyses and results used to qualify software

• Software documentation

• Databases and software configuration data

• Commercial software items that are safety system software

• Software change documentation Items that could change because of design changes, review, or audit should be configuration items subject to formal change control. Other items that may not change but are necessary to ensure correct software pro duction, such as compilers, should also be configura tion items, thereby ensuring that all factors contribut ing to the executable software are understood.

This also is useful in areas such as maintenance, future software development, and tracing the impact of reported bugs. Items that are retained for historical or statistical pur poses may be controlled documents.

7. CONTROL OF PURCHASED

MATERIALS

Criterion VII, "Control of Purchased Material, Equipment, and Services," requires measures to ensure that purchased material conforms to procurement docu ments. Criterion VIII, "Identification and Control of Materials, Parts, and Components," requires measures to be established for the identification and control of materials, parts, and components.

Contractually devel oped or qualified commercial software products that are safety system software must be taken under control by an SCM program that complies with IEEE Std 828 1990 as endorsed by this regulatory guide. This means, for example, that the exact version of the product is .2 identified and controlled according to the change con trol procedures applied to other configuration items and that its usage is tracked and reported.

8. DEVELOPMENT

TOOLS Tools used in the development -of safety system software should be handled according to IEEE Std 7-4.3.2-1993, "Standard Criteria for Digital Comput ers in Safety Systems of Nuclear Power Generating Sta tions," as endorsed by Revision 1 of Regulatory Guide 1.152. In particular, tools must be taken under control (i.e., treated as a configuration item) by an SCM pro gram operated by the using organization that complies with IEEE Std 828-1990 as endorsed by this regulatory guide.

9. ACCEPTANCE

CRITERIA Criterion V, "Instructions, Procedures, and Draw ings," requires that instructions, procedures, and draw ings include appropriate quantitative or qualitative ac ceptance criteria for determining that important activities have been satisfactorily accomplished.

In addition, Criterion VIII, "Identification and Control of Materials, Parts, and Components," requires measures to be established for the identification and control of materials, parts, and components;

and Criterion II, "Quality Assurance Program," states that activities af fecting quality must be accomplished under suitably controlled conditions.

In order to maintain acceptance criteria established in accordance with Criterion V and suitably controlled conditions (in accordance with Cri teria II and VIII) for safety system software, section 3.2 of IEEE Std 828-1990 is not endorsed by this regulatory guide. 1

0. DESIGN VERIFICATION

IEEE Std 828-1990, in paragraph

2.3.2(4), re quires a definition of the verification, implementation, and release of a change. The criteria for verification must be consistent with Criterion III, "Design Con trol," which requires that design changes be subject to design control measures commensurate with those ap plied to the original design. This encompasses the re examination of any appropriate safety analysis related to the change. 1U. SCM PLAN IEEE Std 828-1990, in paragraph

2.1(7), requires the SCM plan to address the assumptions upon which the plan is based, including assumptions that might have an impact on cost and schedule.

Any use of cost and schedule criteria must be consistent with the re quirement of 10 CFR 50.57(aX3)

that there be reason able assurance that the activities authorized by the oper ating license can be conducted without endangering the health and safety of the public.1.169-5

12. BACKFIT CLARIFICATION

Section 1.1 of IEEE Std 828-1990 states "It also applies to non-critical software and to software already developed." Such statements in the standard should not be interpreted as requirements for backfit. See the Im plementation section of this regulatory guide for the NRC staff's position on backfitting regarding this guidance.

13. OTHER CODES AND STANDARDS

IEEE Std 828-1990 and IEEE Std 1042-1987 ref erence other industry codes and standards.

These refer ences to other standards should be treated individually.

If a referenced standard has been incorporated separately into the NRC's regulations, licensees and applicants must comply with that standard as set forth in the regulation.

If the referenced standard has been en dorsed in a regulatory guide, the standard constitutes a method acceptable to the NRC staff of meeting a regu latory requirement as described in the regulatory guide. If a referenced standard has been neither incorporated into the NRC's regulations nor endorsed in a regulatory guide, licensees and applicants may consider and use the information in the referenced standard, if appropri ately justified, consistent with current regulatory prac tice.

D. IMPLEMENTATION

The purpose of this section is to provide informa tion to applicants and licensees regarding the NRC staff's plans for using this regulatory guide. No backfit ting is intended or approved in connection with this guide. Except in those cases in which an applicant or li censee proposes an"acceptable alternative method for complying with the specified portions of the NRC's regulations, the methods in this guide will be used in the evaluation of submittals in connection with applica tions for construction permits and operating licenses.

This guide will also be used to evaluate submittals from operating reactor licensees that propose system modi fications voluntarily initiated by the licensee if there is a clear nexus between the proposed modifications and this guidance.1.169-6 BIBLIOGRAPHY

Hecht, H., A.T. Tai, Y.S. Tso, "Class 1E Digital Sys tems Studies," NUREG/CR-6113, USNRC, October 1993.1 Institute of Electrical and Electronics Engineers, "Stan dard Criteria for Digital Computers in Safety Systems of Nuclear Power Generating Stations," IEEE Std 7-4.3.2, 1993. Lawrence, J.D., "Software Reliability and Safety in Nuclear Reactor Protection Systems," NUREG/ CR-6101 (UCRL-ID-117524, Lawrence Livermore National Laboratory), USNRC, November 1993.1 lCopies may be purchased at current rates from the U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20402-9328 (tele phone (202)512-2249);

or from the National Technical Information Ser vice by writing NTIS at 5285 Port Royal Road, Springfield, VA 22161. Copies are available for inspection or copying for a fee from the NRC Public Document Room at 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555-0001;

telephone

(202)634-3273;

fax (202)634-3343.

Lawrence, J.D., and G.G. Preckshot, "Design Factors for Safety-Critical Software," NUREG/CR-6294, USNRC, December 1994.1 Seth, S., et al., "High Integrity Software for Nuclear Power Plants: Candidate Guidelines, Technical Basis and Research Needs," 1 NUREG/CR-6263, USNRC, June 1995.1 USNRC, "Criteria for Digital Computers in Safety Systems of Nuclear Power Plants," Regulatory Guide 1.152, Revision 1, January 1996.2 USNRC, "Standard Review Plan," NUREG-0800, February 1984. 2 Single copies of regulatory guides may be obtained free of charge by writ ing the Office of Administration, Printing, Graphics and Distribution Branch, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001;

or by fax at (301)415-5272.

Copies are available for in spection or copying for a fee from the NRC Public Docunient Room at 2120 L Street NW, Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555-0001;

telephone

(202)634-3273;

fax (202)634-

334

3. REGULATORY

ANALYSIS A separate regulatory analysis was not prepared for this regulatory guide. The regulatory analysis prepared for Draft Regulatory Guide DG-1055, "Configura tion Management Plans for Digital Computer Software Used in Safety Systems of Nuclear Power Plants," provides the regulatory basis for this guide. A copy of the regulatory analysis is available for inspection and copying for a fee at the NRC Public Document Room, 2120 L Street NW., Washington, DC; the PDR's mailing address is Mail Stop LL-6, Washington, DC 20555-0001;

phone (202)634-3273;

fax (202)634-3343.

1.169-7

)UNITED STATES NUCLEAR REGULATORY

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