Regulatory Guide 1.32

Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants

ML13350A366
Person / Time
Issue date:	03/31/1976
From:	NRC/OSD
To:
References
RG-1.032, Rev. 1
Download: ML13350A366 (3)

U.S. NUCLEAR REGULATORY COMMISSIONREGULATORY GUIDEOFFICE OF STANDARDS DEVELOPMENTREGULATORY GUIDE 1.32CRITERIA FOR SAFETY-RELATED ELECTRIC POWER SYSTEMSFOR NUCLEAR POWER PLANTSRevision IMarch 1976

A. INTRODUCTION

General Design Criterion 17, "Electric Power Sys-tems," of Appendix A, "General Design Criteria forNuclear Power Plants," to 10 CFR Part 50. "Licensingof Production and Utilization Facilities," requires thatan onsite electric power system and an offsite electricpower system be provided to permit functioning ofstructures, systems, and components important tosafety. In addition, Criterion 17 contains requirementsconcerning system capacity, capability, independence,redundancy, availability, testability, and reliability. Gen-eral Design Criterion 18, "Inspection and Testing ofElectric Power Systems," of Appendix A to 10 CFR Part50, contains requirements concerning periodic in-spection, testing, and testability of electric powersystems important to safety. This guide describes amethod acccptable to the NRC staff of complying with..Criteria 17 and 18 with respect to the design, operation'.and testing of safety-related electric power systems' In alltypes of nuclear power plants.

B. DISCUSSION

IEEE Sid 308-1974' is a revision of IEEE Std308-1971 and was prepared byWorking Group 4.1 of theNuclear Power Engineermig Cobilnittee (NPEC) of theInstitute of Electrical and .Ele6tr6udlcs Engineers (IEEE).IEEE Std 308-1974--was .approv'ed by NPEC at itsmeeting on Mayf A.18.7':J973 itnd subsequently by theIEEE Standards Bard on December 13, 1973.'IEEE Std"3(8-"974, "-lrF Standard Criteria for Class I-Power Sysiemti'for Nuclear Power Generating Stations," may beobtained from Institute of Electrical and ElectronicsEngineers. United Eingineering Center. 345 East 47th Street.New York, New York 10017.This revision to IEEE Std i08-_ ,)71 has made thestandard consistent with the require ment ij- Criterion 17for two circuits to the uffsite network, each designed tobe available in sufficient time following a loss of onsitealternating current power supplies and the other ofl'sltt,electric power circuit. However. two potential conflictswith Criterion 17 remain unresolved: one in the area ofavailability of offsitc power (Item I) and the other inbattery charger supply requirements (Item 2). In addi-tion. an inconsistency. exists between I EEI Std308-1974 and IIEEE.SId 450-1975 (Itiem 3).1. IEEE Standard 308-1974. Section 5.2.3(4). firstparagraph. requires that off'site power be available withinan acceptable tine following a loss-of-coclarrt accident..ii, contrast, Criterion 17 requires that offsite power beavailable within a few seconds following a loss-of-coolantlccident.; Thus a potential for misunderstanding existswi.vith regard to t[le maximum permissible time for access,tro the offsite network in the event of a loss-of-coolantaccident, and further guidance is needed.2. Section 5.3.4 of IEEE Std 308-1974 requires. inpart. that each battery charger supply (a) furnish electricenergy for 'he steady-state operation of connected loadsrequired duial normal and postaccident oplration whileits battery is to turned to or maintained in a full!y chargedstate and (b) have sufficient capacity to restore thebatter)y from the design mninimum charge to its f'ullycharged state while supplying normal and postaccidentsteady-state loads. In contrast, the equivalent position ofCriterion 17 requires that the onsite electric powersupplies, including the batteries and the onsite electricdistribution system. have sufficient independence, re-dundancy. capacity. and testability to perform theirsafety functions assuming a single failure. Criterion 17.USNRC REGULATORY GUIDES Comments should be sent to the Sectetaty of the Comrnison U S Nuclea,Rfqulatoty Guides ,..e ...ued to describe and niafke dvuilable to th, pulibtc Regulatory Ctoniison Washiglon DC 2M56 Attention Oocketing &tidnt-thods acceptlble to ftle NRC Stall of implemtenting iSpecific prl,. tit tieoConim-issin s teguldtions. to detineale lechniques used by the staff in avalo Ihe guides ate issued in the following ten broad divisionshlunq specitic ptiiblents or poItulated accident,. or to provide guidance lu apphcants Reguldtoiv Guides at. not substitutes tot regulations. and comph.ance I Power React.is 6P'odutctswith them is nut tequtoedl MeIthods and solutions different fion, those %el out 2t% 2 Research aid Test Reactots 7 Ttansporalatonthe guides will be accept.iblr it they provide a basis tot the fitdings requisite to J Fuels and Matetiats facilities 8 Occupational Heallhthe isslance tit ciinlinuttsce il d p-totit os license by the Comntmission nvtonmental and Siting 9 Antitrust ReviewComntits asd -iilqestii s ll i oinigtist ntit l III ttieh e guides aie encouraged 5 MuterldJs and Plant Protection t0 Genertaat alt ltii. inld qiljes will li tev i-d. is iltptopriale to 4tccuntndalole con.noe,,fs a,, sit new tttliltli ittnot rit esgtellrent However. Ill Copies ot published guides may be obtained by written tequest indicating thethi. ,utitfe. if rii, wiitthi .httiiI utw toilithtl otter its issuartce. he pat divisions desired to the U S Nucleat Regulatory Commission, Washingtoin 0 Cticulltai useful ... etlittiiqltil the iln-d fill .ill eily oI vitool l 20556, Attention Ditector. OfiIce of Standards Development therefore, does not restrict the battery charger supplyloads to normal and postaccident steady.state loads. Aconflict may therefore exist for those plants in whichother loads (e.g., loads required during hot or coldshutdown, large startup loads during an accident, orother design basis events) are greater than the normaland postaccident steady-state loads.3. Table 2, "illustrative Periodic Tests," of IEEE Std308-1974 lists a test interval of 3 years for the batteryperformance discharge test and refers to IEEE Std450-1972, "Recommended Practice for Maintenance,Testing, and Replacement of Urge Stationary TypePower Plant and Substation Lead Storage Batteries," fordetails regarding performance of such tests. Subsequentto the publication of IEEE Std 308-1974, IEEE Std450-1972 was revised and published as IEEE Std450.1975, "IEEE Recommended Practice for Mainten-ance, Testing, and Replacement of Large Lead StorageBatteries for Generating Stations and Substations."IEEE Std 450.1975 specifies a battery performancedischarge test within the first two years of service andthereafter at intervals of 5 years until the battery showssigns of degradation or until 85% of expected service lifeis reached, at which time annual tests are required. The3-year interval specified in IEEE Std 308-1974 conflictswith these requirements. IEEE Std 450-1975 alsodescribes a battery service test, but no test frequency isspecified. IEEE Std 308-1974 does not specificallymention the battery service test.It should be noted that the scope of IEEE Std308-1974 is more limited than that of Criteria 17 and18. For example. the scope of IEEE Std 308-1974excludes the unit generator(s) and th"ir buses; step-up,auxiliary, and startup transformers; connections to thestation switchyard. switchyard; transmission lines; andthe transmission network. Except for the unit genera-tor(s), these are all included within the scope of Criteria17 and 18.In the foreword to IEEE Std 308-1974 it is notedthat certain areas of this standard neee more extensivetreatment. These include shared systems in multi-unitstations, independence between redundant standbysourcem, connection of non-Class I E equipment to ClassI E systems, and the definition of design basis events.Some of these topics have been the subject of otherregulatory guides, e.g., Regulatory Guide 1.6 (SafetyGuide 6), "Independence Between Redundant Standby(Onsite) Power Sources and Between Their DistributionSystems," which is concerned with electrical independ-ence. Regulatory Guide 1.75, "Physical Independence ofElectric Systems," which is concerned with physicalindependence of Class I E systems and the connection ofnon-Class I E equipment to Class I E systems; andRegulatory Guide 1.81, "Shared Emergency and Shut.down Electric Systems for Multi-Unit Nuclear PowerPlants." Other matters of importance to the regulatoryprocess for electric power systems in nuclear powerplants have been the subject of such regulatory guides asRegulatory Guide 1.9 (Safety Guide 9), "Selection ofDiesel Generator Set Capacity for Standby PowerSupplies," and Regulatory Guide 1.93, "Availability ofElectric Power Sources."The criteria and requirements in IEEE Std 308-1974are indicated by the verbs "shall" and "must", andrecommendations are indicated by the verb "fhould".The terms "may", "suggested", and "illustrative" indi-cate optional practices.

C. REGULATORY POSITION

1. For the portion of safety-related electric powersystem within its scope, the criteria, requirements, andrecommendations in IEEE Std 308-1974 are generallyacceptable to the NRC staff and provide an adequatebasis for complying with the Commission's GeneralDesign Criteria 17 and 18 of Appendix A to 10 CFRPart 50 %k ith respect to the design, operation, and testingof e!ectric power systems, subject to the following:a. Availability of Offsite Power. Consistent withthe requirements of Criterion 17, the phrase "within anacceptable time" in Section 5.2.3(4), first paragraph, ofIEEE Std 308.1974 should be construed to mean"within a few seconds". A preferred design wouldinclude two immediate access circuits from the trans-mission network. Detailed guidance for operating pro-cedures and restrictions acceptable to the staff, appli.cable where two immediate access circuits are available,is contained in Regulatory Guide 1.93, "Availability ofElectric Power Sources." An acceptable design wouldsubstitute a delayed access circuit for one of theimmediate access circuits provided the availability of thedelayed access circuit conforms to Criterion 17.b. Battery Charger Supply. The capacity of thebattery charger supply should be based on the largestcombined demands of the various steady-state andtransient loads and the charging capacity to restore thebattery from the design minimum charge state to thefully charged state, irrespective of the status of the plantduring which these demands occur.c. Battery Performance Discharge Tests. The testinterval for the battery performance discharge testshould be as specified in IEEE Std 450-1975 instead ofthe 3 years specified in Table 2 of IEEE Std 308-1974,"Illustrative Periodic Tests." The battery service testdescribed In IEEE Std 450-1975 should be performed inaddition to the battery performance discharge test. Thebattery service test should be performed during refuelingoperations or at some other outage, with intervalsbetween tests not to exceed 18 months. The notefollowing Table 2 of IEEE Std 308-1974 should refer-ence IEEE Std 450-1975 rather than IEEE Std450-1972.1.32-2 d. Independence of Redundant Standby Sources.Electrical independence between redundant standby(onsite) power sources should be in accordance withRegulatory Guide 1.6. Physical independence should bein accordance with Regulatory Guide 1.75.e. Connection of Non-Class IE Equipments toClass IE Systems. The guidance presented in RegulatoryGuide 1.75 should be followed.f. Selection of Diesel Generator Set Capacity forStandby Power Supplies. The guidance presented inRegulatory Guide 1.9 should be followed.2. The following optional practices are considered tobe unacceptable as given below:a. Shared Electric Systems for Multi-Unit NuclearPower Plants. The provisions of Section 8.2 of IEEE Sid308.1974, which permit sharing of standby powersupplies among units of a multi.unit station, are un-acceptable except as specified in Regulatory Guide 1.81.The provisions of Section 8.3.1 of IEEE Std 308-1974that permit sharing of battery supplies among units at amulti.unit plant are considered unacceptable and shouldbe supplanted by tne recommendations of RegulatoryGuide 1.81.b. Availability of Electric Power Sources. Table 3,"Suggested Operating Alternatives with Degraded ClassIE Power System Conditions," of IEEEStd 308.1974 isconsidered unacceptable and should be supplanted bythe recommendations of Regulatory Guide 1.93.

D. IMPLEMENTATION

The purpose of this section is to provide informationto applicants reg-irding the NRC staff's plans for usingthis regulatory guide.Except in those cases in which the applicant proposesan acceptable alternative method for complying withspecified portions of the Commission's regulations. ( I )the methods described in portions of this guide thatreference other regulatory guides are being and willcontinue to be used in the evaluation of submittals forconstruction permit applications and (2) the methodsdescribed in other portions of this guide will be used inthe evaluation of submittals for construction permitapplications docketed after November 1. 1976, unlessthis guide is revised as a result of suggestions from thepublic or additional staff review.If an applicant wishes to use this regulatory guide indeveloping submittals for applications docketcd on orbefore November 1, 1976, the pertinent portions of theapplication will be evaluated on the basis of this guide.1.32-3