ML19269E493
| ML19269E493 | |
| Person / Time | |
|---|---|
| Issue date: | 02/09/1979 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-1604, NUDOCS 7906290173 | |
| Download: ML19269E493 (20) | |
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3 3 "jR EATE ISSUED:
2/9/79 LI lj d/7/77 MINUTES OF 'IHE ACRS SUBCOMMITTES MEETING ON U- /6Oy REGUIATORY ACTIVITIES WASHINGTON, D.C.
0 JANUARY 3, 1979 fpg g
he ACRS Regulatory Activities Subcommittee held a meeting on January 3, D79, at 1717 H Street, N.W., Washington, D.C.
he pJrpose of this meet-ins was to review:
proposed Regulatory Guides, A.
2.
revisions to the existing Regulatory Guides, and f'
3.
other matters pertinent to activities that affect the current licensing process or reactor operations.
Notice of this meeting was published on Tuesday, December 19, 1978, in the Federal Register, Volume 43, Number 244; a copy is included as Attachment A.
Mr. Gary Quittschreiber was the Designated Federal Employee for this meeting. A list of meeting attendees is incitxled as Attachment B.
INTRODUCTORY STATEMENT BY THE CHAIRMAN Dr. Siess, the Subcommittee Chairman, convened the meeting at 8:45 a.m.,
reviewed briefly the schedule for the mee, ting, and noted that the Sub-committee had received a request from a representative of the Yankee Atomic Electric Company for time to make oral statements in relation to the Draft Regulatory Guide 1.XXX, " Lightning Protection for Nuclear Power Plants". We Subcommittee had not received any written comments from the members of the public.
REGULATORY GUIDE 1.141, REVISION 1,' " CONTAINMENT ISCLATION PROVISIONS FOR FLUID SYSTEMS" Mr. Diab reviewed this Guide,. indicating that it endorses with certain exceptions ANSI N271-1976. %is Guide describes a method acceptable to the NRC Staff for complying with the Commission's requirements with re-spect to centainment isolation for fluid systems.
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Reg Act Mtg January 3, 1978 Mr. Diab noted that this Guide was issued for public comment in April, 1978. During the public comment period of this Guide, comments were received only from the General Electric (GE) Company.
'1he Subcommittee sought some clarification of the NRC Staff's resolution of GE's comments.
With regard to GE's concern about the application of the Appendices and footnotes of the ANSI N271-1976 Standard, Mr. Diab mted that the Appen-dices are not mandatory; the material provided in the Appendices are only for information and guidance. A sentence at the first page of the Appen-dices indicates clearly that these Appendices are not part of the Standard, but are included for information only.
In respanse to a question from Dr. Siess as to whether this procedure is applicable to all the other ANSI Standards which were endorsed by Regulatory Guides, Mr. Morrison noted that this Js not true in all cases; in some Regulatory Guides they endorse both the Standard and its Appendices.
Dr. Kerr exi assed concern about the fact that the information provided in some of t..e Appendices of the Standard ANSI N271-1976 are obsolete; he wondered how one can expect these Appendices to provide guidance to the Applicants which do not even reflect the current state-of-the-art.
In response to several questions from Dr. Siess, the NRC Staff noted that GE had originally forwarded their comments to the Standards Conmittee. Se NRC Staff does not know whether those comments had been accepted by the Standards Committee. However, GE had sent the same comments to the NRC Staff just for information. So far GE had not sent any reply to the NRC Staff's resolution of their comments. Se NRC Staff reiterated that these Appendices are non-mandatory; they will not hold the Applicants responsible for the requirements of these Appendices.
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Reg Act Mtg January 3, 1978 s
Dr. Kerr reiterated his concern about the obsoleteness of these Appendices. He suggested that some modifications to these Appen-dices, to make them more illustrative and also to make them reflect the current design practice, would be helpful.
We NRC Staff noted that the Standards are being continuously upgraded. Rey believe that these Appendices eventually will be modified to reflect the current state-of-the-art.
The Subcommittee commented that Regulatory Position C4 of this Guide is ambiguous. Bere are two separate thoughts combined (one ta.1ks about diversity in the means of actuation and the other talks about diversity in the parameters sensed); the way they are combined is confusing and some modification would be helpful.
The NRC Staff indicated that they would make appropriate changes to avoid the ambiguity.
We Subcommittee suggested several editorial changes, provided suggestions for clarification and improvement in seve'ral areas, and indicated that it would recommend this Guide to the full Committee for concurrence wi" the Regulatory Position of this C.uide during the 225th ACRS meeting.
DRAFT REGUIATORY GUIDE 1.XXX, " LIGHTNING PRCTI'ECTION FOR NUCLEAR PCfdER PLANTS" Eis draft Regulatory Guide on lightning protection wu reviewed by the Regulatory Activities Subcommittee at the May 3,1978 meeting.
During that meeting it was brought to the attention of the Subcommittee that there were some difference of opinions among the NRC Staff re-garding the technical adequacy of this Guide. We Subcommittee suggested that the NRC Staff try to resolve these differences prior to bringing it back to the Subcommittee for further action.
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mReg Act Mtg vanuary 3, 1978 The Subcommittee reconsidered this Guide at tle January 3, 1979 meeting.
The NRC Staff stated that all of the written technical comments based on dissenting views have been resolved with the exception of those from Mr. Rosa of the Division of Systems Safety.
Mr. Rosa still has some serious reservations regarding the technical contents of this Guide.
He has provided an alternate Regulatory Position. % is alternate approach proposed by Mr. Rosa will be attached along with this Guide, and public comments will be solicited on both this Guide and the alternate approach. Se NRC Staff noted also that the comments from Mr. Rosa represent only his individual view points. We Director of the Division cf Syst. ems Safety has concurred with the Regulatory Position of this Guide.
Mr. Marinos reviewed the changes made to this Guide subsequent to its review by the Subcommittee at the May 3,1973 meeting. Se changes include:
- 1. ' Addition of new references 2.
Rearrangement and clarification of some of the Regulatory Positions Identification of costs in tne VaJue/ Impact Section 3.
for installation and replacement of the necessary equipnent for lightning protection for the 40 year life time of the plant.
We NRC Staff indicated that this Guide will be reviewed by the Regulatory Requirements Review Committee (RRRC) after the p1blic ccament period, in accordance with the new procedures.
In response to a question from Dr. Siess as to why there is no implementation section incitried in this Guide, the NRC Staff noted that they intend to incitxie an implementation section in the future.
We reason for not incitxiing it now is that this Guide is btended for forward-fit only. However, the back-fit provision will be dis-cussed and decided durina the RRRC review.
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Reg Act Mtg January 3, 1978 With regard to the references listed in this Guide, Dr. Siess commented that they are not properly referenced; some of them seem to be' untraceable; any references used in this Guide should be re-trievable. If the ACRS full Committee is expected to use the references as a basis for its concurrence, then the NRC Staff should provide copies of these references to the ACRS; copies should also be placed in the public document room if necessary.
Suggesting that the Subecmmittee should try to let this Guide go out for public comment to get the public views on its technical adequacy, Dr. Siess solicited the opinion of the Subcommittee members.
Dr. Kerr commented that it seems that this Guide deals with a problem which has not been documented; there seems to be no strong evidence that lightning has caused any particular problems in nuclear systems.
Without any evidence this Guide seems to indicate that solid state equipnent is particularly vulnerable to lightning strikes. Although he is not that comfortable in issuing this Guide for public comment in its present form, he feels Gat it might be possible to find out the public need for this Guide by issuing it for public comment.
Mr. Ray commented that it seems that there is no demonstrated public need for this Guide; this Guide in its present form has several defi-ciencies.
Mr. Ray and Dr. Kerr sought some clarification of the term " separate grounds" used in one of the statements in the Discussion section which states " separate grounds may be necessary for some designs.....
transient currents".
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Reg Act Mtg January 3, 1978 The HEC Staff's response was very ambiguous. Se hRC Staff pointed out that there is no Regulatory Position corresponding to this state-ment.
Dr. Siess remarked that, theoretically, any infonnation in the Discussion section is either supposed to explain the Regulatory Positions or justify, them. %is particular statement under discussion does not seem to do either one.
Including certain things in the Discussion section without including a Regulatory Position corresponding to them will create confu-sion. He suggested that the NRC Staff think about this and decide whether to add a corresponding Regulatory Position to this statement or to delete it from the Discussion section.
The Subcommittee asked several questions to determine the technical adequacy of the requirement that lightning arresters be designed for discharging current of no less than 200,000 amperes.
In response to a question from Dr. Kerr as to whether there is any evidence that lightning strokes will bypass the grounding systems and hit the transmission lines, Mr. Marinos noted that there is no such evi a ce.
In response to another question from Dr. Kerr, Mr. Marinos noted that they have evidence that lightning strokes hit electrical systems; however, it is hard to determine whether they are direct strokes or induced.
Dr. Kerr remarked that it is important to know whether the lightning strokes are direct or induced.
If it is not direct, it may not be necessary to design lightning arresters to withstand 200,C00 amperes.
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Reg Act Mtg January 3,1978.
Indicating that some of the information in the Discussion Section of this Guide gives the implication that there are data available to substantiate that lightning arresters with a discharge current-withstand-ing capability of 200,000 amperes may be needed to protect the electrical systems, Dr. Kerr asked whether any such data actually indicate that a lightning arrester will see such a high current.
Mr. Marinos responded that there is no strong evidence to supprt this issue. Ibwever, the preliminary results of some study indicate that 0.1% of the lightning strokes exceeds 200,000 amperes. Some other recent studies indicate that 3% of the lightning strokes may exceed 200,000 amperes. Based on such available information, the NRC Staff has chosen this specific number, 200,000 amperes.
Mr. Ray remarked that electrical equipent has been protected adequately by the state-of-the-art; there has been no evidence to indicate that lightning arresters need to be designed to withstand a current of 200,000 ampheres.
In response to another question from Dr. Kerr concerning the basis for the selection of 200,000 amperes, Mr. Marinos noted that, on the basis of the available data and also by using the logic adopted by the Industry in its selection of lightning arrester rating (63,000 amperes), this number (200,000 amperes) was selected.
Dr. Kerr asked whether the Industry is using surge current or stroke current to determine the lightning arrester rating.
Mr. Marinos responded that the Industry calls it resurge current; however, he is not sure exactly what it represents.
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Reg Act Mtg January 3, 1978 Dr. Kerr commen*
that it does not seem appropriate to compare stroke current with surge current, if the Industry is using surge current to determine the rating of the lightning arresters.
After further discussion on this issue, the Subcommittee got the impression that the 200,000 amperes was chosen arbitrarily; there is no strong documented evidence for the selection of this number.
With regard to paragraph 2.11.1 of the Regulatory Position which implies that a lightning arrester demonstrated by test to withstand 200,000 ampere current should not be reused, the Subcommittee wondered why a perfectly good, tested arrester should be thrown away.
In relation to the paragraph 2.11.2 of the Regulatory Position, Dr. Siess suggested that the phrase " including those 5 years later" n'eeds further clarification.
The, NRC Staff indicated that they will give consideration to the Subcommittee's concerns and make some changes to these paragraphs as appropriate.
In relation to the paragratt 3.2 of the Regulatory Position which states " Adequate shielding of the line conductor should be achieved by maintaining a nominal 30 angle of protection," Mr. Ray commented that this may not be applicable to all the systems. 'Ihe angle of pro-tection may very well be dictated by the configuration of the components and the distance between them.. Specifying a certain angle may interfere with the design and reliability of some systems. He suggested that some modification to this paragraph would be helpful.
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' Reg Act Mtg January 3, 1978 Mr. Marinos indicated that he would make appropriate changes to this paragraph.
With reference to the requirement of Regulatory Position 4.2 that copper down-conductors should be used to connect the air terminal to the plant grounding system, Dr. Kerr wondered why copper down-conductors are speci-fically required for. He feels that any down-conductors that will carry the current and that has a low enough resistance and reactance should be acceptable.
The NRC Staff did rot argue this point.
Oral Statement by Yankee Atomic Electric Comoany - Mr. Baxter Mr. Baxter, representing Yankee Atomic Electric Company and an IEEE Committee, stated that the
- aents made by him on this Guide at the May 3, 1978 meeting are still valid. He feels that the lightning protection technology has been treated in a superficial and simplistic manner; the technical adequacy and accuracy of this Guide are questionable. He feels that this Guide in its present< form should not be issued for public comment.
Mr. Baxter reviewed briefly some of the comments made by the Surge Protective Devices Committee and the Nuclear Power Engineering Committee of the IEEE (Attachment C).
After the oral statements by Mr. Baxter, Dr. Siess asked the NRC Staff whether any attempt has been made to analyse this issue on a probabi-listic basis.
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e Reg Act Mtg January 3, 1978 Mr. Varinos responded that he has given some thought to resolve this issue on a probabilistic basis. As a matter of fact, he responded to one of Mr. Rosa's comments on a probabilistic basis. 'Ihe probabilistic approach used by him reveals that the risk associated with lightning strikes are much higher than that predicted by Mr. Rosa.
Indicating that a considerable amount of sttdy has been performed on the propagation of electromagnetic disturbances associated with weapons effects and on the protection of electrical atomic equipment against surges, Dr. Kerr suggested that the NRC Staff consult some of the consultants involved in that study to get their opinions on the technical contents of this Guide.
Mr. Grill, NRC Staff, indicated that during the developnent stage of the lightning issue, he contacted the Defense Nuclear Agency and the Defense Communications Agency and some people at the Lawrence Livermore Laboratory doing work in the weapons system on propagating currents. 'Ihey believed that they have computer programs and model available to perfom an analysis to determine the magnittde of risk associated with lightning strikes.
In response to a question from Dr. Siess as to whether it is appropriate to have such a unifom requirement for all parts of the country, in view of the fact that there is a difference in the probability of lightning strikes in different parts of the country, Mr. Marinos noted that the difference is not significant enough to justify having different require-ments for different parts of the country.
Dr. Siess requested that the NRC Staff provide the Subccomittee with all the Licensee Event Reports referenced in this Guide.
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Reg Act Mtg January 3,1978 After further discussion, the Subecmmittee suggested several editorial changes, provided suggestions for clarification and guidance for im-provements in several areas, and indicated that the NRC Staff could issue this Guide for public comment.
Dr. Siess thanked all the participants and adjourned the meeting at 11:53 a.m.
- us ICTE: For additional details, a complete transcript of the meeting is available in the NRC Public Document Room, 1717 H St., N.W.,
Washington, D.C. 20555, or from Ace-Federal Reporters, Inc.,
444 North Capital Street, N.W., Washington, D.C.
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NOTICIS I
[7593-01-M]
NUCLEAR REGULATORY Guide 1.141. Revision 1. may do so by COMMISSION providing a readily reproducible copy to the Subcommittee at the beginnmg ADVISOtY COMMITT!! ON ttACTOR SAFE.
of the meeting. However, to insure GUAtOS $UsCOMM4TTit CN EtGULATORY that adequate time is availabic for full ACTIVITits consideration of these comments at the meeting, it is desirable to send a M**8 readily reproducible copy of the com.
The ACRS Subcommittee on Regu.
ments as far in advance of the meeting latory Actisities will hold an open as practiesble to M r.
Gary R.
, meeting on~ January 3.1979 in Room Quittschreiber ( ACRS), the Designat.
104c.1717 H St N.W., Washington, ed Federal Employee for the meetme,
' DC 20555. Notice of this meeting was it' care of ACRS. Nuclear Regulatory published in the Frota.u. Rrcism on Commission Washmgton. D.C. 20555 October 20 and November 20,1978 (43 or telecopy them to the Designated FR 49080 and 5411(7. respectively).
Federal Employee (202-634-3319) as In accordt.nce with the procedures far in advance of the meeting as prac.
outlined in the Ftorut. Rectstra on ticable. Such comments shall be based October 4,1978 (43 FR 45925) oral or upon documents on file and available written statements may be presented for public inspection at the NRC by members of the public, recordings Public Document Room. 1717 H will be permitted only during those Street. N.W. Washington. DC 20555.
portions of the meeting when a tran.
Further information regarding script is being kcot. and Questions may topics to be discussed. Whether the be asked only by memb2rs of the Sub.
meeting has been cancelled or resched-committee. Its consultants, and Staff.
uled. the Chairman's ruling on re.
Persons desiring to make oral state.
quests for the opportunity to present men' thould notify tht: Designated o"' statements and the time allotted Federal Employee as far in advance as therefor can be obtained by a prepaid practicable so that appropriate ar.
telephone call to the Designated Fed.
rangements can be made to allow the eral Employee for this meeting Mr.
neces:ary time during the meeting for Gary R.
Quittschreiber. (telephone such statements.
202/634 3267 between 8:15 a.m. and The agenda for subject meeting 5.00 p.m.. EST.
shall be as follows Wednesday. Janu.
ary 3.1979. 8:45 a.m.-12:00 noon.
Dated. December 14.1978*
The Subcommittee will hear presen-Jonx C. HOYLE.
tations from the NRC Staff and will Advisory Committee, hold discussions with this group perti.
Mencremenf O//scer.
nent to the following:
(FR Doe. T8 35192 Piled 1218.T8. 8:45 arnl (1) Draf t Regulatory Guide 1.XXX.
" Lightning Protection for Nuclear Power Plantr."
(2) Regulatory Guide 1.141. Revision
- 1. " Containment Isolation Provisions for Fluid Systems" Other matters which may be of a predec:sfor:al nature relevant to reac-tor operation or licensing activities may be discussed following this ses.
sion.
Persons wishing to submit written
, statements regarding Regulatory FlottAt atGISTit. VOL 43. NO. 244--tut 1 DAY. DECEMBla 19. 1978
'D "
- lD
- M
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ATTACHMENT A 9
o e N s I W In L
ACRS SUBCOMMITTEE ON REGULATORY ACTIVITIES WASHINGTON, D.C.
JANUARY 3, 1979 ATTENDEES LIST ACRS NRC C. P. Siess, Chairman E. C. Marinos, OSD H. Etherington, Member S. W. Brown, CSB W. Kerr, Member D. F. Sullivan, OSD J. Ray, Member R. G. Fitzpatrick, DSS /PSB W. Mathis, Member R. Z. Kornasiewicz, OSD G. Quittschreiber, Staff
- R. P. Grill, EPSB S. Duraiswamy, Staff S. S. Diab, RSB/ DOR J. A. Norberg, OSD
- Designated Federal Employee W. Morrison, OSD J. Shapaker, CSB PUBLIC SERVICE GAS &
J. R. Levine, HMB ELECTRIC, N.J.
A. Smith, OSD G. Sen YANKEE ATOMIC ELECTRIC C0 GE.
F. Baxter F. Gruscavage i
N. Shirley ACE - FEDERAL REPORTERS BECTEL B. Whitlock B. Montgomery I. Thomas B&W R. Borsum ATTACHMENT B 2145 190
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$@C0EVY Please add,ess,qiy los Mr. A. Simmons Philadelphia Electric Co.
2301 Market Street Philadelphia, PA 19101 September 8, 1978 U.S. Nuclear Regulatory Commission i
Washington, D.C.
20555 Attention:
Office of Docketing & Service Section Regulatory Guide 1.XX Lightning Protection for i
Nuclear Power Plants l
(Draf t dated 3/9/78)
Dear Sir:
l The Surge Protective Devices Committee and the Nuclear Power Engineering Committee of the IEEE are pleased to have an opportunity to comment on the pro-posed Regulatory Guide 1.XX - Lightning Protection for Nuclear Power Plants (Draf t dated 3/9/78).
The topics of lightning theory, surge protection and grounding are complex subjects. As the authors of the Regulatory Guide have shown, much has been g
written on these subjects. Although there are many references, application of surge protection requires the use of knowledge extrapolated from engineering i
experiences.
Industry standards have been developed which recognize that surge protection is to be applied to mininize damage to the protected equipment. There is no furdamental difference in the exposure to lightning or the equipment to be protected in nuclear power plants, and therefore, these standards are applicable to nuclear power plants.
A long list of referencer provided with the regulatory guide alludes to examples of lightning initiated problems in nuclear power plant safety systems.
An investigation of a number of these incidents has revealed that there has not been an incident which has involved a degradation of the safety shutdown equip-ment damaged by lightning. There is no reason to believe that if the position of this regulatory guide was implemented that there would have been an improve-ment in the protection over that provided by existing standards.
The proposed position promulgated by the guide is grossly understated, since there would be a need for additional testings, a need to develep ne' <
protective equipment and a reduction in plant availability.
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The NRC is encouraged to recognize the existence of IEEE Power Engineering Society as a body of experts in surge arrester standard development and saf ety system protection. In particular the IEEE Surge Protective Devices Ccnmittee works closely with ANSI Committee C62, which is responsible for U.S. standards dealing with surge arresters and their application. These Cormittees stand ready to work with the NEC to identify those items which may require special attention in nuclear power plants.
The content of this regulatory guide should be limited to an endorsement of ANSI, IEEE and NFPA Standards with the stipulation that they be utilized in the design of nuclear power plants.
Detailed comments on the various sections of the regulatory guide are attached as Appendix A.
The f act that ecements have not been made on certain sections should in no way be interpreted to represent IEEE concurrence.
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W. Simmons S. S. Kershaw Chairman of Nuclear Power Chair =an of SPD, IEEE Engineering Committee, IEEE
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./ J. L. Keepfitger./
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Chairman of; ANSI C62 r
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APPENDIX A Comments on Regulatory Guide 1.XX Lightning Protection for Nuclear Power Plants 1)
General The term " Lightning Arrester" has been superseded by the term " Surge Arrester" which is now internationally accepted.
2)
Page 1.XX-3 The statement " Numerous publications suggest a high probability of lightning surges of current magnitude on the order of 200,000 numbers (References 1, 2, 16, 19, 20, 21 and 22)." is totally erroneous. None of the references suggest that there is a high probability of obtaining surge currents of this magnitude.
Using modern reference data developed by the Stanford Research Institute Report titled "A GrouM Lightning Environment for Engineering Usage" by N. Cianos and E. T. Pierce, it can be shown that a typical plant in a high lightning incident j
area may experience no more than one stroke of 200 kA within its anticipated 40 year life.
With lightning protections designed in accordance with existing standard practices, there is no reason to believe that a 200 kA stroke woult' result in 7
damage. The shielding system, when properly designed, will reduce, the current MF' impressed I:pon a modern arrester to a value which it is capable of withstand.
3)
Page 1.XX-3
'the statement that " separate ground mats may be necessary for some designs to assure that redundant systems important to safety are not simultaneously ex-posed to damaging flashovers generated from ground fault transient currents" demonstrates a lack of understanding of power system grounding.
Such a scheme would be physically impossible to construct, since it would require insulating rot only the ground cables of one redurdant system from the other, but also of piping, structural steel, fourdations, and fluid systems as well in order to maintain the integrity of such a grounding system.
4)
Page 1.XX-4 It is stated that:
" Electrical transients, generated from lightning phenemena and switching of electrical circuits, has bcen a source of concern for many years.
Instrument failures, blowing of fuses in control circuits, and failures of insulation systems as a result of transients of electrical nature in nuclear j-power plants has increased unavailability of systems important to safety
-p (References 3 through 15)".
J.d g An investigation of a number of these incidents has indicated that there has g'p not been an instance which has involved the degradation of safety shutdown equipment being damaged by lightning. F ur thermore, af ter review of this Regulatory Guide, it was also apparent that none of the proposed regulatory positions, if implemented, would have prevented the equi;rnent f ailures frem occurring.
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4 The inference that highly sensitive solid state logic systems used for protection of nuclear power plants accentuates the need to protect this equipment from external generated surges does not justify a change in the application of surge arresters or station grounding.
Current practice treats differently surges which enter the control circuits from that experienced on high tension facilities, g "
IEEE standards have been developed and are being developed which address the surge protection on withstand capability of solid state equipment (IEEE 472/
ANSI C37.90a, IEEE P465 and IEEE P587).
- 5) Page 1.XX-5 It is stated that:
"In this type of system a primary to secondary failure in the transformer could propagate the primary voltage to the secondary, if the secondary is not properly grounded..."
The transformer electric characteristic provides a significant attenuation to surge transferred through the transformer. If the high voltage winding is t.,
properly protected in accordance with current practices, surge transferred through the transformer w$ 11 not overvoltage the secondary winding. If current (J, vill also be adequately protected. practices are applied in connecting equipnent to the seco q
vf 6)
Page 1.XX-5 The paragraph which discusses insulation coordination is too brief to be of value in providing surge protection to transformers. It f ails to recognize the existence of ANSI C62.2 which gives detailed guidance on this topic.
7)
Page 1.XX-6 It is stated that only portions of ANSI C62.2-1969 and ANSI C62.1-1975 are applicable to nuclear power plants.
We believe that there is nothing unique or special about nuclear power plants which change the nature of lightning or switching surges to which their systems may be exposed or which dictate a special or unique approach to surge protection.
The above referenced documents together with other ANSI and IEEE Standards give more than adequate guidance to all plants affected by lightning and other surges.
8)
Page 1.XX-7, Position Cl This position requires surge arresters designed for discharging currents of no less than 200,000 amp eres.
In coment 2 it was indicated that this requirement is excessive. ANSI Standard
[ C62.1 recently, due to vast research and field experience, reduced the high current short-duration withst.tnd value of valve arresters from 100 KA to 65 KA.
I Arresters used for high tension circuits are not available with discharge with-stand of 200 KA.
Da ta on arrester disenarge current recorded in both field and model studies show that arrester currents rarely exceed 20 KA.1, 2 1f.ig,htning Current in Arresters at Stations, 2 ightning overvoltage Entering A 7
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- . Gross and W.
A. Morris, A.I.E.E.
Transaction, Vol. 59,1940, pg. 417 Station and Lightning Currents Through Arresters, CIGRE Study Committee V33: Overvoltage and C
Insulation Coordi.tation, London 4
Cb lieguin, 33-77 2145 M4
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This Regulatory Guide proposes that arresters bs applied to withstand direct
', stroke. The essence of surge protection as 4:xemplified in ANSI C62.2 is to provide adequate shielding such that there is negligible probability of an arrester being called upon to discharge a direct stroke.
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Even in this remote contingency should the az ' ester fail the arrester will still perform its intended function of limiting voltege. A simple continuous test circuit is available to monitor a deteriorating crrester.
11 9)
Page 1.XX-L Position GGb
- 3. 1 This position specifies a 30* angle of protection in the design of overhead ground wires.
The requirement for a 30* angle of protection may be or may not be optimum.
The shielding angle to be used for a particular design is dependent on many f actors. Many alternative designs are presently in use. No universal statement can be made to substantiate one angle over another argie of protection.
Shielding performance must be related to the overall design and reliability goal of the power system; use of 30' shielding angles in an attempt to be overly
)Nr conservative can.seriou_s1_y interfere with station design reliability and reduce reliability. The correct shielding angle whatever it might be must be deter-mined with a sufficient degree of confidence and justified.
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Page 1.X.hS, Position 3a I /
This position gives criteria for air terminal installation that is inconsistent with good engineering practice.
Air terminals or alternative methods should be installed for the purpose of protecting all buildings contained in the facility. The criteria for air terminal installation should be no different from that of any other building being protected l Jainst lightning. !TPA-78-1977 provides guidelines on air terminal application. To single out a few selected buildings and structures for air terminal installation would result in a poorly designed lightning pro-tection system for the nuclear facility.
It should, however, be noted that depending on the individual design, air terminals may be supplemented in part or whole by overhead ground wires.
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11)
Page 1.X% Position %
This position requires copper down-conductors to connect the air terminal to the plant grounding system.
There is no justification for requiring copper conductors. Dcwn-conductors may be made of copper, copper-clad steel, aluminum or any other metallic conductor deemed suitable for the application and environment as approved in IEPA-78-1977.
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Pace 1.XX-% Positien t Sce Comment No. 9 for comments on shielding angle.
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Pye 1.XX-8, Position Q This position gives criteria for the rating of surge arresters.
The selection of surge arresters should be based on insulation coordination studies amongst other factors. Arbitrary selection of 100% rated arresters indicates extremely poor engineering practice and can result in less than optimum protection.
The voltages as limited by the arresters are related to their rating. The use of a higher voltage rating arrester than necessary 9131 reduce the protective margin which the arrester is to provide to the equipent it protects.
F 14)
Page 1.XX-% Position % ?., 6~
The requirement of 200 KA arrester en both sides of a start-up and unit auxiliary transformer is without justification.
(See item 8)
No attempt has been made to disti.guish between transformers which are connected to overhead line ard those which are not.
Depending upon specific plant design, these transformers may have no exposure to lightning, and, therefore, may not require surge arresters on their primary side. This can be easily verified by studies that indicate that the transferred surce is of lesser magnitude and of such slope that neither surge arresters or capacitors are needed.
Surge arresters on the secondary side of these transformers are not required even when the primary side may be connected to overhead lines because:
a)
The failure mode of the primary surge arrester is such that it protects the transformer.
It may fail to seal off, but it will not fail to spark-over.
b)
The primary surge arrester sufficiently reduces the surge to protect the transformer secondary.
c) The transmission lines and transformer yard structures are shielded, thus direct stroke to equipent can be discounted.
If surge arresters are used on the secondary, they should be justified on some other basis.
O 15)
Page 1.XX-1, Position 44. Ab This pcsition calls for the application of surge arresters at the switchgear in order to protect equipment in the reactor containment.
g" Surge protection should be considered if studies disclose that the equipment
.,'. i ^
can be subjected to surges cf a greater magnitude than that for which they are
', ?',
designed.
Surge protection may be in the form of surge arresters, surge capaciters, or both. The type and location of surge protection used will V'gg ( depend upon the magnitudes and rate of rise of the surge and the characteristic f
of the equipment to be prctected.
y' lb l9b b
~
.p Surge arresters may be required when the equipment is connected to overhead lines, or where extremely high surge voltages can eppear directly at the equip-ment terminals. Surge capacitors may be required for lesser ragnitude surges which are expected to damage the motor. In any event the surge capacitor pro-tection equipnent, if used, should be connected as close to the motor terminals as possible and not at the switchgear.
Indiscriminate application of surge protection equipment in nuclear power station auxiliary power distribution systems is of particular concern because it may result in a decreue in overall nuclear plant safety.
16)
Page 1.XX-10, Position 44-2.//
This position requires surge arresters to be renoved periodically from service and subjected to testing to ascertain functional capability. This is both an
- ); f abnormal and totally unnecersary requirement without any technical justification.
The tests specified in ANSI C62.1 are design tests and will usually give no 4
g indication of deterioration with age, o
Simple means for determining when arrester replacement is necer,sary includes normal inspection, maintenance tests and leakage current measurements or where failure is obvious.
- 17) value/ Impact Assessment This value/ imp,act assessment is grossly underestimated.. The requirement promul-gated by this guide would result in expenditures per plant which are several million dollars more than those given in the proposed guide due to added costs of testing, a need to develop new protective equipnent and a reduction in plant availability.
As stated earlier, 200 KA surge arresters for high voltage application are not currently available. Development costs for these arresters wodd have to be taken into consideration. Assuming that such arresters were available, the cost together with other equipment would likely arount to over $2,000,000 per plant.
Plant down time to conduct the testing required of this guide is assumed to be a minimum of 1 day per year, which over the life of the plant would arount to
$50,000,000 using today's cost of replacement power.
Prepared by:
M. Beachy E. J. Cbhtn J. A. Hetrick D. W. Jackson S.
S. Kershaw J. L.
Koepfinger J. D. M. Phelps J. J.
Schlee, Jr.
2145 197 C
.