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

COMMISSION

REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 1.32 CRITERIA FOR SAFETY-RELATED

ELECTRIC POWER SYSTEMS FOR NUCLEAR POWER PLANTS Revision I March 1976

A. INTRODUCTION

General Design Criterion 17, "Electric Power Sys-tems," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50. "Licensing of Production and Utilization Facilities," requires that an onsite electric power system and an offsite electric power system be provided to permit functioning of structures, systems, and components important to safety. In addition, Criterion

17 contains requirements concerning system capacity, capability, independence, redundancy, availability, testability, and reliability.

Gen-eral Design Criterion

18, "Inspection and Testing of Electric Power Systems," of Appendix A to 10 CFR Part 50, contains requirements concerning periodic in-spection, testing, and testability of electric power systems important to safety. This guide describes a method 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 all types of nuclear power plants.

B. DISCUSSION

IEEE Sid 3 08-1 9 7 4' is a revision of IEEE Std 308-1971 and was prepared byWorking Group 4.1 of the Nuclear Power Engineermig Cobilnittee (NPEC) of the Institute of Electrical and .Ele6tr6udlcs Engineers (IEEE).IEEE Std 308-1974--was

.approv'ed by NPEC at its meeting on Mayf A.18.7':J973 itnd subsequently by the IEEE 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 be obtained from Institute of Electrical and Electronics Engineers.

United Eingineering Center. 345 East 47th Street.New York, New York 10017.This revision to IEEE Std i08-_ ,)71 has made the standard consistent with the require ment ij- Criterion

17 for two circuits to the uffsite network, each designed to be available in sufficient time following a loss of onsite alternating current power supplies and the other ofl'sltt, electric power circuit. However. two potential conflicts with Criterion

17 remain unresolved:

one in the area of availability of offsitc power (Item I) and the other in battery charger supply requirements (Item 2). In addi-tion. an inconsistency.

exists between I EEI Std 308-1974 and IIEEE.SId

450-1975 (Itiem 3).1. IEEE Standard 308-1974.

Section 5.2.3(4).

first paragraph.

requires that off'site power be available within an acceptable tine following a loss-of-coclarrt accident..ii, contrast, Criterion

17 requires that offsite power be available within a few seconds following a loss-of-coolant lccident.;

Thus a potential for misunderstanding exists wi.vith regard to t[le maximum permissible time for access ,tro the offsite network in the event of a loss-of-coolant accident, and further guidance is needed.2. Section 5.3.4 of IEEE Std 308-1974 requires.

in part. that each battery charger supply (a) furnish electric energy for 'he steady-state operation of connected loads required duial normal and postaccident oplration while its battery is to turned to or maintained in a full!y charged state and (b) have sufficient capacity to restore the batter)y from the design mninimum charge to its f'ully charged state while supplying normal and postaccident steady-state loads. In contrast, the equivalent position of Criterion

17 requires that the onsite electric power supplies, including the batteries and the onsite electric distribution system. have sufficient independence, re-dundancy.

capacity.

and testability to perform their safety functions assuming a single failur

e. Criterion

1

7. 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

&tid nt-thods acceptlble to ftle NRC Stall of implemtenting iSpecific prl,. tit tieo Conim-issin s teguldtions.

to detineale lechniques used by the staff in avalo Ihe guides ate issued in the following ten broad divisions hlunq specitic ptiiblents or poItulated accident,.

or to provide guidance lu apph cants Reguldtoiv Guides at. not substitutes tot regulations.

and comph.ance I Power React.is 6P'odutcts with them is nut tequtoedl MeIthods and solutions different fion, those %el out 2t% 2 Research aid Test Reactots 7 Ttansporalaton the guides will be accept.iblr it they provide a basis tot the fitdings requisite to J Fuels and Matetiats facilities

8 Occupational Heallh the isslance tit ciinlinuttsce il d p-totit os license by the Comntmission nvtonmental and Siting 9 Antitrust Review Comntits asd -iilqestii s ll i oinigtist ntit l III ttieh e guides aie encouraged

5 MuterldJs and Plant Protection t0 Generta at 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 the thi. ,utitfe. if rii, wiitthi .httiiI utw toilithtl otter its issuartce. he pat divisions desired to the U S Nucleat Regulatory Commission, Washingtoin

0 C ticulltai 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 supply loads to normal and postaccident steady.state loads. A conflict may therefore exist for those plants in which other loads (e.g., loads required during hot or cold shutdown, large startup loads during an accident, or other design basis events) are greater than the normal and postaccident steady-state loads.3. Table 2, "illustrative Periodic Tests," of IEEE Std 308-1974 lists a test interval of 3 years for the battery performance discharge test and refers to IEEE Std 450-1972, "Recommended Practice for Maintenance, Testing, and Replacement of Urge Stationary Type Power Plant and Substation Lead Storage Batteries," for details regarding performance of such tests. Subsequent to the publication of IEEE Std 308-1974, IEEE Std 450-1972 was revised and published as IEEE Std 450.1975, "IEEE Recommended Practice for Mainten-ance, Testing, and Replacement of Large Lead Storage Batteries for Generating Stations and Substations." IEEE Std 450.1975 specifies a battery performance discharge test within the first two years of service and thereafter at intervals of 5 years until the battery shows signs of degradation or until 85% of expected service life is reached, at which time annual tests are required.

The 3-year interval specified in IEEE Std 308-1974 conflicts with these requirements.

IEEE Std 450-1975 also describes a battery service test, but no test frequency is specified.

IEEE Std 308-1974 does not specifically mention the battery service test.It should be noted that the scope of IEEE Std 308-1974 is more limited than that of Criteria 17 and 18. For example. the scope of IEEE Std 308-1974 excludes the unit generator(s)

and th"ir buses; step-up, auxiliary, and startup transformers;

connections to the station switchyard.

switchyard;

transmission lines; and the transmission network. Except for the unit genera-tor(s), these are all included within the scope of Criteria 17 and 18.In the foreword to IEEE Std 308-1974 it is noted that certain areas of this standard neee more extensive treatment.

These include shared systems in multi-unit stations, independence between redundant standby sourcem, connection of non-Class I E equipment to Class I E systems, and the definition of design basis events.Some of these topics have been the subject of other regulatory guides, e.g., Regulatory Guide 1.6 (Safety Guide 6), "Independence Between Redundant Standby (Onsite) Power Sources and Between Their Distribution Systems," which is concerned with electrical independ-ence. Regulatory Guide 1.75, "Physical Independence of Electric Systems," which is concerned with physical independence of Class I E systems and the connection of non-Class I E equipment to Class I E systems; and Regulatory Guide 1.81, "Shared Emergency and Shut.down Electric Systems for Multi-Unit Nuclear Power Plants." Other matters of importance to the regulatory process for electric power systems in nuclear power plants have been the subject of such regulatory guides as Regulatory Guide 1.9 (Safety Guide 9), "Selection of Diesel Generator Set Capacity for Standby Power Supplies," and Regulatory Guide 1.93, "Availability of Electric Power Sources." The criteria and requirements in IEEE Std 308-1974 are indicated by the verbs "shall" and "must", and recommendations 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 power system within its scope, the criteria, requirements, and recommendations in IEEE Std 308-1974 are generally acceptable to the NRC staff and provide an adequate basis for complying with the Commission's General Design Criteria 17 and 18 of Appendix A to 10 CFR Part 50 %k ith respect to the design, operation, and testing of e!ectric power systems, subject to the following:

a. Availability of Offsite Power. Consistent with the requirements of Criterion

17, the phrase "within an acceptable time" in Section 5.2.3(4), first paragraph, of IEEE Std 308.1974 should be construed to mean"within a few seconds".

A preferred design would include 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 of Electric Power Sources." An acceptable design would substitute a delayed access circuit for one of the immediate access circuits provided the availability of the delayed access circuit conforms to Criterion

17.b. Battery Charger Supply. The capacity of the battery charger supply should be based on the largest combined demands of the various steady-state and transient loads and the charging capacity to restore the battery from the design minimum charge state to the fully charged state, irrespective of the status of the plant during which these demands occur.c. Battery Performance Discharge Tests. The test interval for the battery performance discharge test should be as specified in IEEE Std 450-1975 instead of the 3 years specified in Table 2 of IEEE Std 308-1974,"Illustrative Periodic Tests." The battery service test described In IEEE Std 450-1975 should be performed in addition to the battery performance discharge test. The battery service test should be performed during refueling operations or at some other outage, with intervals between tests not to exceed 18 months. The note following Table 2 of IEEE Std 308-1974 should refer-ence IEEE Std 450-1975 rather than IEEE Std 450-1972.1.32-2 d. Independence of Redundant Standby Sources.Electrical independence between redundant standby (onsite) power sources should be in accordance with Regulatory Guide 1.6. Physical independence should be in accordance with Regulatory Guide 1.75.e. Connection of Non-Class IE Equipments to Class IE Systems. The guidance presented in Regulatory Guide 1.75 should be followed.f. Selection of Diesel Generator Set Capacity for Standby Power Supplies.

The guidance presented in Regulatory Guide 1.9 should be followed.2. The following optional practices are considered to be unacceptable as given below: a. Shared Electric Systems for Multi-Unit Nuclear Power Plants. The provisions of Section 8.2 of IEEE Sid 308.1974, which permit sharing of standby power supplies 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 308-1974 that permit sharing of battery supplies among units at a multi.unit plant are considered unacceptable and should be supplanted by tne recommendations of Regulatory Guide 1.81.b. Availability of Electric Power Sources. Table 3,"Suggested Operating Alternatives with Degraded Class IE Power System Conditions," of IEEEStd 308.1974 is considered unacceptable and should be supplanted by the recommendations of Regulatory Guide 1.93.

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants reg-irding the NRC staff's plans for using this regulatory guide.Except in those cases in which the applicant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations. ( I )the methods described in portions of this guide that reference other regulatory guides are being and will continue to be used in the evaluation of submittals for construction permit applications and (2) the methods described in other portions of this guide will be used in the evaluation of submittals for construction permit applications docketed after November 1. 1976, unless this guide is revised as a result of suggestions from the public or additional staff review.If an applicant wishes to use this regulatory guide in developing submittals for applications docketcd on or before November 1, 1976, the pertinent portions of the application will be evaluated on the basis of this guide.1.32-3