ML19282A034

Preliminary Value/Impact Assessment Supporting Draft Reg Guide,Lightning Protection for Nuclear Power Plants. Proposed Alternate Regulatory Position Encl

ML19282A034
Person / Time
Issue date:	12/12/1978
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
Shared Package
ML19281B333	List: ML19281B331 ML19282A031 ML19282A034
References
TASK-OS, TASK-RS-706-8 REGGD-01.XXX, REGGD-1.XXX, NUDOCS 7905090354
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l$h PRELIMI:3...Y VALUE/I" PACT ASSESSMENT 01 Ll'_91iSiM iE'u ECTIO" FOR ?.UCtEAR PCWER PLA.TS G

I.

The Procosed Action A.

Descriction Electrical transients, resulting from lightning phenomena ans switching of electrical circuits, have hampered the performan_e of sensitive electronic equipment and insulation systems,~.

The history of instrument failures (Refs. 3 thct many years.

18, 27, 28 & 29) blowing of fuses in control circuits anc im of insulation systems suggest that transients of electrical i....

can increase the risk of system unavailability beycad acceptacie levels.

The increasingly cc. men use of highly sensitive solid state T

logic systems for the protection of nuclear power plants ac:s.-

teates the need for clcser scrutiny in the method used fcr protecting such systems frem transient over-voltages.

- The staff has not reviewed the strge protection aspects of nuclear power plants and, therefore, is not thoroughly familiar with the present practices used for the protection of nuclear Puha I

syste.as imcortant to safety from transient over-voltages.

c lished literature and industry standards (Refs. 20 & 21) on the subject reveals that surge protection is based largely c.

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sc?.ib.* cui s...C.vds ULVL ICpCd. Or COnVenstlGna l non nuC ied:

systems on a princ.' pally cost-teaefit basis; no special -

-idoraticr. :ns baar, given for tne protection of nuclear p..;

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3 systems important to safety.

There is evidence to support the r,

concern that.::ma.on failure modes can exist, in the nuclear

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safety cystcas, whereby surges of a transient nature cculd 4j render redundant ccaponents inoperable.

For example, power 'c radundant safety systems is typically supplied from the ef s is 9.,

power transmission system through a transformer (with a ty; i

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transformation ratio of 345 kV/4.16 kV).

Therefore, a prim:

to secondary failure in the transformer could propagete the I,

primary voltage to the secondary, if the secondary is not pro-y perly designed (Ref. 29).

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Additicna11y, a surge originated ia the primary side of the transformer can prcpagate to tha redundant 1

j circuits in the secondary through capacitive ccupling in the transformer, with potentially damaging consequences.

Such high A

j voltages occurring even for short durations could destroy ser.si-3i tive equipment on onsite distribution buses and render onsite

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- power supplies incperable.

Additionally, protection system comoonents, electrically ccnnected to these supplies could be

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The frequency of induced o r direct lightning surge on the primery side of a transformer could be high, based on statistical data collected on strikes per mile of transmission line per yaar 4

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In the event of such occ.crence, the nr--

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of the transformer.

The propagation of high surges thr'iT 4

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transformer windings could occur as a result of the fel", "-

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If surge rise time is shorter than the arrester's r=e-i j

' f time, a significant amount of the surge will propagate r:

l the arrester before it is safely carried to the greu :..

4 the arrester (Ref. 35).

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In a successfully responding surge arrester the volta

'drep developed between phase to grcund is a functio s

. magnitude of the current surge arrested and the resista s

to ground (IR drop).

Therefore, a successful discharge of 3

a current surge of 2-00,000 amperes through 10 cha resistance will. develcp a voltage drop of 2,C00,000 volts on the i

primary side of the transformer with the prcpagation of approximately 50% cf that voltage (Ref.19), electrostati-cally, to the secondary through transformer capacitance with potentially damaging consequences to systems el cally connected to this secondary.

Substantial effort is being expended for determining a con erva-tive " design basis surge" for lightning and scme switchi -n 3

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The significant parameters that define a sur a are (a) r 8

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to peak value, (b) peak value, and (-) tire tc half ;cn i<

Rise times, peak values and frequency distribution of ':

. ga.n1 surges are presently unde, study by NRC, by NASA ar.d er., <-r i q of Florida and by 00E (Refs. 26, 35 & 28).

However, the inwe -

nationally accepted rise times appear accept:ble at thi

c.... e for our purposes, and when results are made availabl:

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above studies we will re evaluate our present position a

The frequency of thunderstorm days for various locations i

depicted in an isokeraunic map, of unknown origin i

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, widely '

by meteorologists (Ref.1).

However, an updating of this ---

may be necessary at this time in order to assure its va (Refs. 26 & 35).

Surge protection for safety systems, in nuclear power p n s.

can be achieved if the following system protection is im e:

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Installation of suitable ground wires, running the len of the transmission line, covering a reasonable distance from the plant site to protect against direct lightning strikes en power transmission lines.

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Conventional lightning rods strategical'ly located to picc..,

switchyards, of f gas : tacks, eteorological towers, rue; tanks and other components whose functional integrity e.

important for maintaining safe plant operation.

3.

Installation of high enercy absorption surge arresters ua

. critical lines entering the plant.

4.

Installaticn of surge arresters on the primary and so-sides of power transfer ers.

5.

Installation of low energy absorption surge suppressors i onsite distribution systems and critical instrument power

. - supplies.

The preposed action is the develc; ment of design guidance on acceptable criteria for the prctaction of nuclear systems important to safety from surges that can appear en the ccaponents and systems listed abcve.

The likeliheed of damaging surges

. propagated through field wirir.g, te redundant systems importart to safety, is extremely 1cw and r. sed not be addressed.

Elevated ground potentials, resulting frca the discharge of high current surges to ground, may ad.ersely affect the performance of sensitive integrated circuit cceponents used in reactor pre-tection systems (Refs. 35 & 37).

Therefore, designs th * 'ise

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designs that use integrated circuit components must be evaluatec and designed tr 3cs re that ground potentials do.ct adve

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af fect their performance.

B.

Need for the Procosed Action The potential consequences on the public safety are of such significance that it seems imperative for the staff to include in their review, of systems important to safety, the protectia:.

of such systems frcm electrical surges externally or internal Y

generated.

To acccmplish this goal, general guidance is regt-to bring to the attention of the' design engineer and the NRC reviewer the significant areas that need particular scrutiny 1..

the design of systems important to safety, and to provide accep-table methods for surge protection for such systems.

'C.

Value/Imoact of the Procored Action 1.

NRC Oceraticns The benefit gained by the proposed action is to secure additional staff awareness of the significant areas that require additional review, and assure that current kncwl-gdge in su ge phencmena are considered in the design of nuclear systems important to safety.

4 Additional review time will be required and the reviewir staff should become thcrcughly familiar with the technica.

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aspects of surge protecticn and its compatibility with tne systems bcina orotected.

9 The Inspection and Enforcement staff should also beceme familiar with the staff requirements to ascertain that installations are impiecented in accordance "ith acceptac design criteria.

Research, to support our proposed action, is currently under way (Ref. 26, 35 & 38) to ascertain equipment tolerance to surges, surge characteristics, surge ampi -

tudes and frequency.

Also, funding for technical assist-ance may be required to evaluate the level cf protectior afforded by present designs.

2.

Other Government Acencies TheactivitiesofFAA,hASAand00Eisbeingevaluated (Refs. 26, 25 & 3S) for the purpose of cbtaining in'or~"-

tion on efforts exper.ded by these agencies in addressing protection against electrical surge phencmena for their respective concerns.

Information available at these agencies is being utilized as background for our effort.

There is no impact antici-pated to there agencies as a result of our proposed action.*

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Industry A close scrutiny in the surge protection for sensitivs instrumentation, adequate insulation coordination ano sufficient conventional lightning protection for components exposed to direct lightning will reduce inadvertent failurr.

of plant equipment anc allcw plant availability to increasa Surge protection is assumed an integral.part of a good engineering design.

Therefore, the differential cost fn implementing all cur proposed provisicns for a 200,000 ampere level of protection, at a 345kV ~ 4tchyard, will be as follows:

1.

Purchase cost of arresters for start-up and unit auxiliary transformers and'onsite switchgear at $25/kV - $31,000 2.

Approximate installation cost -

$31,000 3.

Approximate cost for periodic surveillance per olant site at $25,000/ test for 40 years

$175,000 TOTAL S227,000 A more accurate cost evaluation could be made if the present protection level were known.

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P: N' i c Tna value to the public will be in the direction of cree reliable and safe nuclear power at a ecce. ate financ.

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D.

Decision en the Procesed Action Guidanc2 should be issued, in view of the potential risks associated with electrical surges on equipment, to identity acceptable design criteria for consideration in the desi1. _..

installation of nuclear systems important to safety.

II.

Technical Accroach A.

Technical Alternatives Alternative tethods for addressing surge protection, f:r re^ -

dant systems important to safety, that could limit cc :.cn mcd >

failures resulting frca high energy surges on single transmis-sion lines would require; 1.

strict implementatior of electrical indepen:ence of cffsite as well as ensite transmission and distribution syst:Tr.

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assure that single surge events do not prcpagate to redon-dant trains of systems important to safety, and/or 2.

underground transmission of offsite powar to plant systccs 4

to minimize the likelihood of direct lightning strikes from entering the plant distributica systems.

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Discussion and Comoarison of Technical Alternatives

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Redundant Offsite Pcwer Sources The implementation of redundant offsite pcwer scurces w limit the protection systems' exposure to certain cc. mon T

mode failures resulting frca surges initiated in (a) prict rf to secondary transformer failures, (b) switching at the primary side of the transformer and (c) lightning surgas r

the primary side of the transformer.

2.

Underground Transmission The underground transmission will limit the direct stri<.

on the pcwer transaission to plant auxiliaries.

However,

...the common =cde failures asscciated with transformer failures and switching will not be eliminated with this alternative design unless redundancy is also maintained in the underground circuits.

C.

Decision en Technical Accreach

~ 'The proposed action discussed in part I above should be under-taken.

The technical alternati ces described in iten IIB above are not feasible at this time in view of the limitations in

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' independence requirements expressed in the General Design Criterion 17, of the 10 CFR Part 50 Appendix A. '

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edural Accroach rncedural A1+ce,ati"es that may be used to promulgate the otential 50 proccdurc3 precoced action and technical approach include the f ollowing:

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Regulation "b N W W 4%4we Regulatory Guide ANSI Standard, endorsed by a Regulatory Guide Branch Position NUREG Value/Incact of Procedural Alternatives A NUREG is not a viable alternctive because it will not contain the kind of guidance required to interpret the existing regu-General Design Criterion 2, Appendix A, 10 CFR 50 is lations.

Therefore.

the regulation covering the subject technical issue.

a Regulatory Guide is required to provide the staff acceptable

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methods for implementing this regulatica.

How-At present there is no ANSI standard under preparation.

ever, a standard would be the most viable cption for future considera'. ion, because industry technical resources and exper"-

ences will provide a valuable contribution in the development of mc - i.r.,_ _ __

consistent requirements for all plant designs.

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limited scope and distribution.

C.

Decision on Procedural Accroach A Regulatory Guide should be prepared and licensees as weli c.s applicancs should be requested to evaluate their surge pro-tection and make appropriate modifications, if needed, to assur.:

minimum protection requirements.

IV.

Statutory Considerations A.

tiRC Autnority Thi, guide would f all under the authority and safety requirements of the Atomic Energy Act.

In particular under General Design Criterion 2, Appendix A, 10 CFR 50, whica requires, in part, that structt.res, systems and components important to safety be designed to withstand natural phencmene.

2 The design bases for these structures, systems, and components shall refTect:

(1) apprcpriate consideration of the most severe j

cf the natural phenomena that have been historically reportea 3j for the site and surrcunding area, with sufficient margin for

, the limited accuracy, quantity, and period of time in which the 1

1 historical data have been accumulated, (2) appropriate ccm-binations of the effects of normal and accident conditions with the effects of the natural phenomena and (3) the importance of l

the safety functions to be performed.

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f:eca ice iMPA Assessment The pec;;used action is r.ot an actica defined by 10 CFR 51, 5(a)(10), and does not require an environmenta'. impact stete e3 V.

f.elationshic to Other Existina cr Precosed Reculations or Policies The p cposed action is considered as part of the implementation of the require..ents set forth in General Design Criterien 2 of Appen-dix A to 10 CFR Part 50.

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The're are no potential conflicts or overlaps with other agencies anticipated as a result of the proposed action.

The Standard Format and Content of Safety Analysis Reports, and the Standard Review Plan should be revised to address the necessity for evaluation of surge protection for the nuclear safety systems.

Eackfitting requirements should be determined upon ccepletion of the guide with priority placed on plants located in areas of high frocuen v thunderstorm activity.

VI.

Summary and Conclusions Failures in a number of installations (Refs. 3 :: u 18, 27, 28) sug-gest that the high energies released by lightning have the potential to cause severe damage to sensitive nuclear systems impcrtant t' 13

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protect the health and safety of the public.

Therefore, a Regulatory Guide identifying a censistent set of design criteria for surge protection for. power plants is appropriate at this time.

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c-re-evaluation may be necessary at a later date upon c:: pietion o' liRC DOE and the NASA-University of Florida Studies which are aimin; te more accurately define "ise times, peak values and frecuency for lightninc surges.

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e REFERENCES Westinghouse - Transmission and Distribution Refercnce Book,1954.

1.

R. H. Golde - The Frequency of Occurrence and the Distribution of 2.

Lightning Flasnes to Transmission Lines,1945.

QUAD CITIES Of fgas Sys.am Explosion (Lightning) 1973.

3.

0YSTE? CREEK Three Power Transformer Fuses for Diesel Generator 4.

No. 2 Were Slown (Lightning), 1973.

5.

Vermont Yankee Offgas System Explcsion (Lightning),1972.

6.

Ft. Calhoun Less of Of fsite Power (Lightning),1973.

7 Ft. Calhoun Less of Offsite Pcwer (Lightning),1977.

8.

Millstone Less of Offsite Pcwer (Lightning),1971.

9.

Monticello Loss of Offsite Power (Lightning),1976.

10.

Pilgrim Loss of Offsite Power (Lightning),1974.

11.

Vermont Yankee Process Computer and miscellaneous equipment rendered incperable, Unit Scram..ed (Lightning),1974.

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12.

Yankee Rowe - Actuation of Overcurrent Relays on two Main Ccolant Leops Resulted in Reactor Scram (Ligh ning),1972).

13.

Unusual cccurrence - PNO-77-126, Indian Point 2, dated July 14, '. 7" 14.

Unusual occurrence - PNO-77-170, Palisades, dated September 24, 1977 15.

Unusual occurrence - P"0-77-171, Indian Point 2 & 3, dated Septer.cer 21, 1977.

16.

Farley Less of Off site Power and Less of Reactor Ccclant Flow and Rcd Position Indication (Lightning),1977.

17.

Farley Loss of Offsite Power and Inadvertent Safety Injection (Lightning),1E78.

Rancho Seco - Lightning on main transformer (damaged winding), 1978.'

18.

19.

A. Greenwood - Electrical Trcasients in Power Systems,1971.

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ANSI CG2.1 std., 1973 - Surge Arreste:- for Al terncting-Current Fc..'er Circuits.

21.

e..:51 JG2.2 sts.,13a; - Guide f or opplicacion ci vei,e-type i i w cr..-

arresters for alternating-current systems.

" LIGHTNING," - U.S. Department of Cor.merce Environmental Sciences 22.

Services Administration, Decemoer 1966.

Electrical Prctection Guide for Load-Eased Radio Facilities,

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-;;, 2 23.

Bodle, dated 1971.

24.

THE SELL SYSTEM - TECHNICAL JOURNAL, Volume XXVIII,1949, G. A. Brcwn, " Joint Frequency Distribution of Stroke Current Rise

_-d 25.

Crest Magnitude to Transmission Lines," IEEE Power Engineeriag '.

mittee, January / February, 1978.

26.

"An Unusual Lightning Flash at Kennecy Space Center," Science, 7.. I 1978.

27.

Piigric Loss of Offsite Power (Lightning), August 6,1978.

Crystal River 3 - Meteorological Instrumentation Failure (Lightr.:. 3,,

28.

July 15,1978.

3 29.

Beaver Valley Transformer Failure, July 28, 1978.

30.

J. C. Cronin, R. G. Colelaser,-R. F. Lehman - Transient Lightning Overvoltage Protection Requirements for a 500kV Gas-Insulated Sub-station.

IEEE, PAS, Jan/Feb., 1978.

l 31.

G. St-Jean, Y. Latour, J. G. Pincault, M. Roy - Aging Tests on Full H. V. arresters.

IEEC & E, 1977.

1 32.

M. Kebayashi, M. Mizuno, T. Aizaua, M Hayashi, K. Mitani - Develcp.r,en-of Zinc-Oxide Non-Linear Resistors Arresters.

IEEE, PAS, July /Aug.. '"Mi 33.

E. C. Sakshaug, J. S. Kresge, S. A. Miske, Ur. - A New Concept In Station Arrester Design.

IEEE, PAS, March / April, 1977.

34.

Stanislaw 5:por - Comparison of Polish Versus American Lightning Records.

IEEE, PAS, May 1969.

35.

H. Wayne Beaty - Researchers gather lightning data.

Electrical War,ld, August 1, 1978.

Letter frem Lcwell E. Rock (Toledo Edison) to James C. Kep;'er (hm.,

36.

dated August 3, 1977 - Grounding for Davis-Sesse Unit 1.

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Letter from Jar.cs H. Tay, r (EDI) to Ernst Voleca'.' G:P.C) dated Marcn 9,1978. - Groundirig for Occ ce 1, 2, 3; lt',I 1, 2; f.::0-1; i

R;.-ncho Seco; Da. i s-iiesee 1; Crystal _.. ver a; m..c.cnc, 1, c.

Report frca P.icnael W. Maier (10AA) to R. Abbey (NRC) dat'ed Jcrua;.

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e Oraccsed Al tere.a+ e R cul atcev Posi tion C.

F.egulatory Position Conforcance with the erinciples and requirements of the fciicwinc ctandards (as apoiicable) cravide acceptable methods for cc:;1ying with General Cesign Criteria.2 and 15 of Appendix A cnd with Acr.:ndix B to 10 CFR Part 50 with respect to the design, cualific:-

tien, construction, inst:llatica and te..ing of systems and cccrcrent providing protection agains: lightning for light-water-cooled nuclear pcwer plants. subject to the follcwing:

NFPA (National Fire Protectica Associa:icn) No. 72-1975; Lightning Protection Ccde, ? art II - Protection of Build-ings and Miscellaneous Prc;erty, and Part III - Protecticn of Structures Ccataining Flammable Liquids and Gasses; ANSI C62.1-1975, American National Standard - Surge Arresters for Alternating - Current ?cwer Circuits; and ANSI C52.2-1969, American National Standard Guide for Applicatien of Valve-Typ2 Lightning Arresters for Alternat-ing - Current Systems; t

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-_Pretectinn of Structures

?r tection snceld be provided again;t direct s te-3 Lightning to :t'ructures and expcsed equipm.cnt installations including contaiam:nt, auxiliary acildings, off-gas stacks, fuel t2n'<s.

metecrological t:wers ar.d other ccmpenents imper; ant fer The systems aad 2 quip-maintaining the safety of the plant.

ment that orovide this protection shall ccafor.a wi;h

'.'.2 principles and racuirements of NFPA No. [8_I975, subject ta Secticas 2101(d), 2102( ) through (i) an.

t."e follcwing:

I, Alumi um s. l' 5

2122(b) shall be replacec by the foi. cuing:

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ccncoctor or structural sup;crt member.

not te us2d as

. Protecticn of Ssitchvard Ecuicment Acainst Direct Stro 2.

- Overhead ground wire shielding, augmented by air terminais and masts as necessary, ih;uld be provided to protect ali f

l switchyard comp 6nents Of the pcwer syste'n (including overhea line pcnar circuit: fr a tne switchyard t: other plant 1

j The compleue structures) against direct lightning strokes.

1j shielding systcm incitcing the overhead ccmponents, inter-connecting conductors and grounding system shculd be designec and installed in ac::rdance with established conservativ design principics and prcctices of the electric utility industry; and the ground resistance should not exceed cne In additien, the design shculd provide a shiciding effectiveness such that shiciding failure stroke cureer.t the current in a lightning strike.hich bypasses (I ma x,

)w the shielding and st-ikes a live cer.;:nent directly i

not exceed 15,;c0 am; res as defined by the relatico y

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Frotection of Transmissien Lines Acainst Dire:t Scrokes 3

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Overhead grcund wire shielding shcuid bc provided to prntec t.-;.nsmission lines terminating in the switchyard acainst direct lic.htning strokes. This shielding svstam should be erc nded cver the entire length of the line, however, it should definetly be nravided for a minimt:1 distance of ene-half mile frca the switch The complete shielding system includ-ycrd terminus cf the lines.

ing overhead grcund wire, tower ccmpenents, interconnecting cen-ducters, and tower grounding system shcuid be designed and installed in acccrdance with established ccnservative design The principles and pra,tices of the electric utility industry.

overhead cround wires shculd be carried into the switchyard anc In addicion, for each tied to tSe switchyard ground system.

transm:ssien linc for a minimum of enc-half mile frca the swic yard, the d2 sign should provide a shielding effectiveness such that shielding failure stroke current (I,x),ill not exceed m.

15,000 amperas, as delined in Positicn C.2 abcve.

i "Etails for de:cnninaticn of shielding effectiveners usino thir retbed are cantained in a paper by G. W. Erewn, Ligntninn Ferfer4.:nce - !

Shielding Failures Simplifiec, IEEE Trar.sacticns en Powcr A,arnus

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.w Paper specifically addresses transmissicn lir.e shielcine but the methodolcgy is readily applicable to switchyard shieldinc.

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Sur;c pr:ceccinn :]r %itchyard Tem.inal Ecuit en:

Station t pe surge (lightning) arresters should be instalhd on

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bc-h the high and low voltage sicas of all unit, and start-up or station service transformers in accordance with the folicwing provisiens:

a.

The arresters should conform to all the applicable require-ments of AftSI C52.1-1975 including cesign, construction and qualification testing with tha follouir.g excepticn:

In Section 7.E.1, F.igh Current Short-Duratien Test, the test surge current wave-shape should be at least 8 x 20psac (insted of the less conservative options also permitted by the standard).

b.

The arresters shculd be provided wi-h a discharge counter anc a leakage grading current meter to facilitate surveiiiance and assessment of the functional capability of the installed arrester.

c.

T1e arresters should be selected and applied in accordance with conservative application of the principles and f.eth dci~cg.5 -

conuinec in MSI C62.2-1969, includinc the fn11nwing:.

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