ML20136G235

Reg Guide 1.152,Task IC 127-5, Criteria for Programmable Digital Computer Sys Software in Safety-Related Sys of Nuclear Power Plants

ML20136G235
Person / Time
Issue date:	11/30/1985
From:	NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:
References
TASK-IC-127-5, TASK-RE REGGD-01.152, REGGD-1.152, NUDOCS 8511220286
Download: ML20136G235 (4)

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[%,, U.S. NUCLEAR REGULATORY COMMISSION Ncvember 1985

%'#) REGULATORY GUIDE

\ ...*+ OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 1,152 (Task IC 127-5)

CRITERIA FOR PROGRAMMABLE DIGITAL COMPUTER SYSTEM SOFTWARE IN SAFETY RELATED SYSTEMS OF NUCLEAR POWER PLANTS A, INTRODUCTION 10 CI R Part 50, which proshles the regulatory hasn f or r

this guide. The information sollettmn r equiremen t s in j Criterion 21, " Protection sy stem rehabihry and 10 CFR Part 50 hase been sicarest under mtit clear-testabihty," of Appendis A. " General Design Critena for ance No. 3150 0018.

Nuclear Power Plants " in 10 CFR Part 50, "Domestie

) Licenung of Productmn and Utduatioa l'a c ih t ie s," 8. DISCUSSION

! requires, among other things, that protestion systems be

] leugned for high functional rehabihty com menuarate Computer technology can proude new tarabibhes to -

j with the ufety function to be performed. Cottrion Ill, nuclear power plant protection amt sontrol sptcms the j "Deug i Control," of Appendis ll, "Quahty A ssurance NRC staff encourages the a pphca t io n of adsanced

} Criteria for Nuclear Power Plants and Fuel Reprocesung tet h nology sush as programrnable digital computers m j Pla n t s," of 10 CI R Part 50 requires, among other the operation of nuclear power plants if such adiansed j things, that quahty standards be specified ar d that technology serves to enhan6e ufct),

des.gn control ment.res he provided for ver f? ing or thecke.g the adequaq of design in 19 7ft , a joint working group sonsatmg of mem-j hers of the American Nuticar So icty ( ANS) and of the 1

This guide destabes a method acceptable to the NRC Institute of I lettncal and I let tronu s I ngmeen til i I l staf f for complying with the Commisuon's regulations was formed with a charter to develop a runt standad for promoting high functional rehabiht) for sa fe t y- mntaining general guida ni.e for sntem deugn and j related o st em s uung programmable digit al wmputer specific gubiante on stage-bystage testmg, overall per-1 systems in the operation of nu6 lear power plants. This formanse anurans e, and dos umentation of sof tw are for

! rnet hod is appheable to deug mng sof tware, serifying programmable digit al mmputer 9 stenn m ufety related i sof tw are, tmilementmg sof t w are, and wahdating mm- systems of nuclear power plants lietause of the unique puter systems.

f nature of programtnable digital m m puter n st ems, e specially with respett to sof t w are, the standad was

} Structures, spt em s, and com pone nt s are "utet)

I intended to supplement li l l. sht r>03-leo, " Standard related" if they are tehrd upon to rernun fun 6tional Criteria for Safety Systems for Nusicar Powcr Generat.

] during and following drugn basis events to ensure (1) ing S t a tio n s,"I w hic h estahinhes the f u ra tional and the integrity of the rentor coolant preuure boundary, design triteria for the power, wntrol, and instrumenta-

(2) the upabihty to shut down the rentor and main- tion portion of safety related spf ems for enulcar power l tain it in a ufe condition, or (3) the arabihty to plants. T his jomt standard w.n approved h the il I l l prevent or mitigi,te the cornequences of autdents that Nudear l'ow er I ngineering Co m nnt t ee and the ANS

} muld result m potential offute exposurce comparable to I the 10 01 R Part 100 guidthnes Nudcar Power Plant Standards Comnnttee and has been i

pubbshed as ANSI /II I I?ANS 7-4 3 Lin?, "Apphtation Cnteris for Programmable theital Computcr $> urnn m l 't he Adtnory Committee on Rentor Safeguards has I

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PDR HEGOD 01,152 R PDR

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l It should be noted that the standard does not valuable in f or ma tio n. it the referenced standards are address any follow -o n a c tivities such as testmg and used, they should be used m a mann(r consatent with )

vahdation of computer systems beyond the deogn, current regulations, w hith include but are not hmited to 1 un plement at i in, and integration p ha se s. As with any 101:1 Std 27419 71, "Criteru for Prot ect io n Sy stems j other ufety sy stem, there is legitim a t e cor.cern that for Nutlear Power Generatmg Stations "' and Appendis l measures be prostJed to ensure that computer sy stems 11 of 10 Cl'R Part 50. I will continue to perform as Jeugned thtoughout the hfe of the plant. \ssurance of sontmued performan6e a i normally aaom plahed for other safety -related sy ste ms D. IMPLEMENTATION  !

by periodic t est mg The requirements for pe r iod a t e st ing of hardware and witw are (r eu hJ at io n ) are The purpose of tha section a to proude information l contamcJ in the t es h nical sp ec ifica t ion s. A Jdit ional to apphcants and hs e n sees regarJ mg the NRC staf t's I guidance on p eriodic testmg h is been prouded in plans for usmg tha regulatory guiJc. l Regulatory Guide 1.118, " period a Testing of l lettra  !

Pow er and Protection S y stemsf 1 % ept in t hose ca se s in whah an apphtant or l heensee p ro po ses an acsertable alternatne in e t hod for i C. REGULATORY POSITION complyng with specified portions of the CommasionN regula t io n s, the method dewribed in tha guide will bc )

I he r eq uir e m en t s set for t h in AN51/II L t -ANS '- used by the staff in its evaluation of sof tw are for all  !

4..) 2 l % 2 e<tablah a met hod actertable to the NRC

. a pphcations in whuh programmable digital computers i st af f for deuemrg s. >f t w are, venf > ing of tw are. im ple- are used in safet> related sy stems of nuticar pow er I menting s.if tw are, an ! uhdating computer systems used plants submitted af ter Novemler 1985. Licensees and i in safet> idated sy stems of nuclear pow er plant s. A l- applicants may use tha guide as justification of current- I though \MI 111 I eS-7-4 3 2-l%2 referenses IF I 1, ty rending applications for use of programmable digital StJ t 01-iWO, ANst! \SMI. NQA t 1979, and 111.1 Std computers; howeser, the staff does not intend to apply {

Jr?-! % 0 these ref erenseJ standards are not endorsed this guide to appheations currently under review or to l by thn reg o!at. t r> /nte 1 hey do ho w es er. contam operating plants.  !

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VALUE/ IMPACT STATEMENT

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1. BACKGROUND 2.1.1 l'alue Compared to current analog methods of processing The standard endorsed by this regulatory guide variables, digital computers are considered to offer represents national consensus on methods to ensure the advantages in accuracy, rehabdity, and versatility, even accuracy and reliability, but not necessari!y the security, though they are more vulnerable to subtle failure modes of programmable digital computer system software as and unauthorized manipulation. Merit is seen in their applied to safety-related systems. The security aspects of appication to safety-related variables and processes. such systems will be treated on a case-by-case basis during the review process.

General guidance for the design of protection system hardware is provided in IEEE Std 6031980, " Standard This guide provides a standardtzed approach so that Criteria for Safety Systems for Nuclear Power Generat- industry and the NRC staff may have a common under-ing Stations." lieretofore there has been no such guid- standing on software verification and validation proce-anee for the design of protection system software. d ures, thus minimizing relevant ensmeeting costs for flowever, a joint working group consistmg of members industry and review costs for the NRC staff. Also, of the American Nuclear Society and the Institute of errors detected during the design phase through the Electrical and Electronics Engi teers has developed a verification process will be far less expensive than if standard, ANSI /IEEE ANS44.3.2-1982, that contains they were not detected until the operation phase.

general guidance for system design and spectfic guidance on stage-by-stage testing, overall performance assurance, 2.1.2 Impact and documentatio.: of software for programmable digital computer systems in safety related systems of nuclear There should be no impact beyond the positive power plants. This action is to endorse the standard indications in the value statement. This is the only developed by the joint working group. regulatory guide that specifically addresses software development. The guidar.cc was developed through the national consensus standards process jointly by ANS and IEEE and was accepted by ANSI.

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2. VALUEllMPACT ASSESSMLNT 2.1 General It is beheved that plants currently in the licensing process that utilize programmable digital computers for l

This regulatory guide endorses the guidance of ANSI / safety-related functions have been reviewed in a manner i IEEE-ANS4 4.3.21982, " Application Criteria for Pro- consistent with this regulatory guide. The review of l grammable Digital Computer S) stems in Safety Systems current and future submittals will benefit from this of Nuclear Power Generating Stations." documentation.

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