ML23151A571
| ML23151A571 | |
| Person / Time | |
|---|---|
| Issue date: | 12/23/1991 |
| From: | NRC/SECY |
| To: | |
| References | |
| PRM-050-056, 56FR66377 | |
| Download: ML23151A571 (1) | |
Text
DOCUMENT DATE:
TITLE:
CASE
REFERENCE:
KEYWORD:
ADAMS Template: SECY-067 12/23/1991 PRM-050-056 - 56FR66377 - RICHARD P. GRILL PETITION FOR RULEMAKING PRM-050-056 56FR66377 RULEMAKING COMMENTS Document Sensitivity: Non-sensitive - SUNSI Review Complete
STATUS OP RULEMAltING PROPOSED RULE:
PRM-50-56 OPEN ITEM (Y/N) N RULE NAME:
RICHARD P. GRILL PETITION POR RULEMARING PROPOSED RULE PED REG CITE:
56FR66377 PROPOSED RULB PUBLICATION DATE:
12/23/91 ORIGINAL DATE FOR COMMENTS: 02/21/92 NUMBER OP COMMENTS:
5 EXTENSION DATE:
I I
PINAL RULE FED. REG. CITE: 58FR07757 FINAL RULE PUBLICATION DATE: 02/09/93 NOTES ON PET. REQUESTED AMENDMENT OF PART 50 REGULATIONS BY ADDING LIGHTNIN TATUS G INDUCED AND ELECTRICAL TRANSIENTS TO LIST OF SAFETY RELATED PHEN F RU'l,E OMENA. DENIAL SIGNED BY EDO.
FILE LOCATED ON Pl.
TO PINO THE STAFF CONTACT OR VIEW THE RULEMARING HISTORY PRESS PAGE DOWN KEY HISTORY OF THE RULE PART AFFECTED: PRM-50-56 RULE TITLE:
RICHARD P. GRILL PETITION FOR RULEMARING
.OPOSED RULE SECY PAPER:
FINAL RULE SECY PAPER:
PROPOSED RULE SRM DATE:
FINAL RULE SRM DATE:
DATE PROPOSED RULE I
I SIGNED BY SECRETARY:
12/17/91 DATE FINAL RULE I
I SIGNED BY SECRETARY:
01/08/93 STAFF CONTACTS ON THE RULE CONTACT1: MICHAEL T. LESAR CONTACT2:
MAIL STOP: P-223 MAIL STOP:
PHONE: 492-7758 PHONE:
DOCKET NO. PRM-50-56
{56FR66377)
In the Matter of RICHARD P. GRILL PETITION FOR RULEMAKING DATE DATE OF TITLE OR DOCKETED DOCUMENT DESCRIPTION OF DOCUMENT 08/19/91 08/19/91 PETITION FOR RULEMAKING SUBMITTED BY RICHARD P.
GRILL 12/18/91 12/17/91 FEDERAL REGISTER NOTICE - PROPOSED RULE 01/22/92 01/18/92 COMMENT OF MARVIN I. LEWIS {
- 1) 02/24/92 02/23/92 COMMENT OF OHIO CITIZENS FOR RESPONSIBLE ENG. INC.
(SUSAN L. HIATT) {
- 2) 02/24/92 02/19/92 COMMENT OF OMAHA PUBLIC POWER DISTRICT (W. G. GATES, DIVISION MANAGER) (
- 4) 02/25/92 02/17/92 COMMENT OF DOOLEY KIEFER (
- 3) 01/14/93 02/04/93 12/02/92 LTR. FROM RICHARD GRILL TO CHAIRMAN SELIN REQUESTING INFORMATION ON THE STATUS OF THE PETITION FOR RULEMAKING 01/08/93 DENIAL OF PETITION PUBLISHED ON 2/9/93 AT 58FR7757 02/08/93 01/27/93 COMMENT OF TOM MIZERACKI (
- 5)
U.S. Nuclear Regulatory Commission Washington, DC 20555 DOCKET NUMBER PETITION RULE PRM 50-St
( s 6 f Pt 6 {, 3 77_}
1-27-93
Subject:
R.P. Grill, Filing of Petition for Rulemaking Docket No. PRM-50-56 "93 FEB -8 P 4 :18 Dear Sirs; I would like to offer my comments on the proposed rule.
The power industry, including nuclear and non-nuclear utilities, has produced adequate evidence supporting the fact that exposure to lightning induced transients may affect generating station operation. Extensive research and testing, performed by utilities in the 1970's, provided the data and evaluated preventive measures to suppress transients transmitted from the switchyard to plant.
Generally, the grounding mat, when properly designed, provides protection against human contact and excessive step voltage for faults within the switch yard or outdoor high voltage substation. The protective grounding system will envelope switching and lightning-induced interference, and facilitate the resulting overvoltage transient's dissipation. If additional measures, i.e. proper interface between the plant and switchyard mats and other means against direct lightning strikes are considered, then the transient voltage entering the plant power and control systems may be substantially reduced.
Therefore, it would be imperative to emphasize in the proposed rule proper design and maintenance for the plant and switchyard's grounding system.
The following comments refer to other transient related problems:
The high frequency transients can enter the redundant safety related system via the shared sources. Verification of the harmonics produced by each major contributor, i.e. rectifier or inverter, and the content of harmonics in the power and control systems should be evaluated and controlled.
The effect of transient currents in DC and AC control and instrumentation circuits on the relay contacts should be evaluated.
Insufficient attention was given in the past to the effect of an electrical fault on the protective relaying coordination and performance. Evaluation of the current transformer burden and response to the maximum short circuit current should be required.
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M zeracki, Rt 3/Box 143B, Russellville, AR 72801 MAY 11 199l __ __
Acknowlodged by,.,,..., *--
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AGENCY:
ACTION:
SUMMARY
DOCKET NU ~1BER
' I, PET\\"'"iON RULE PRM 50;5
[56 Ffl 66371)
NUCLEAR REGULATORY COMMISSION 10 CFR Part 50
[Docket No. PRM-50-56]
DOCKETED us~ 690-01]
- 93 FEB - 4 P 4 :48 Richard P. Grill; Denial of Petition for Rulemaking Nuclear Regulatory Commission.
Denial of petition for rulemaking.
The Nuclear Regulatory Commission (NRC) is denying a petition for rulemaking (PRM 50-56) submitted by Richard P. Grill on August 16, 1991.
The petitioner requested that the ~RC amend 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," and issue new regulations, as necessary, to add lightning induced and other electrical transients to the required list of phenomena licensed nuclear power plants and other nuclear facilities must be designed to safely withstand.
The petition is being denied because the design and construction of existing nuclear power plants adequately protect plant electrical systems from the effect of electrical transients, and there is no evidence at this time that electrical systems and components were not designed to withstand the effects of electrical transients in such a manner as to require additional generic regulatory action.
ADDRESSES:
Copies of the petition for rulemaking, the public comments received, the NRC internal report "Report on the Sources and Effects of Electrical Transients on the Electrical Systems of Commercial Nuclear Power Plants," and the NRC's letter to the petitioner are available for public 1
inspection or copying in the NRC Public Document Room, 2120 L Street NW.
(Lower Level), Washington, DC, 20037.
FOR FURTHER INFORMATION CONTACT:
Chris Rourk, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555, telephone (301) 492-3938.
SUPPLEMENTARY INFORMATION:
I.
The Petition II.
Basis for the Petitioner's Request III.
Public Comments on the Petition IV.
Reasons for Denial I. The Pet it ion In a letter dated August 16, 1991, Mr. Richard Grill filed a petition for rulemaking with the NRC.
The petition requested that the NRC take the following actions:
(1) Amend the regulations or issue new regulations as necessary to add lightning-induced and other electrical tr-ansients to the required list of phenomena licensed nuclear power plants and other nuclear facil'ities must be designed to safely withstand, (2) Perform a comprehensive study to determine the current state of knowledge of electrical transients, 2
(3) Perform a study to identify and quantify potential consequences on licensed nuclear facilities from electrical transients, (4) Require each licensed facility to be analyzed and modified as necessary to prevent the compromise of safety-related electrical systems by electrical transients, (5) Develop regulatory guidance for the protection of safety-related control systems from electrical transients, and (6) Determine why this issue was not addressed and resolved in the past.
II. Basis for the Petitioner's Request The petitioner asserts that (1) because of the complexity of the electrical systems in nuclear facilities, there is a need for explicit requirements for protection of electrical systems from electrical transients in the provisions of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, (2) inadequacies exist in the analysis of the electrical system of each licensed facility regarding the effects of electrical transients, and (3) a large number of alternative paths for the entry of electrical transients into the safety-related electrical systems exist that can only be discovered by performing a thorough and rigorous analysis of the entire electrical system.
In support of his position, the petitioner states that the Defense Nuclear Agency (DNA) and the Defense Communications Agency {DCA) have developed computer programs that can be used to analyze the effects of nuclear electromagnetic pulse (EMP) on electrical systems.
The petition states that these programs can be used to determine the effect of electrical transients on safety-related electrical systems in NRC-3
licensed facilities.
The petition also refers to a draft regulatory guide that was issued for public comment in 1979. This draft guide concerned the protection of nuclear power plants from lightning. The petition requests information on the reasons the regulatory guide was never issued, even though a draft of it had been issued for public comment.
The petition also refers to potential improprieties in the manner that the petitioner was treated by the NRC and its predecessor, the Atomic Energy Commission in the 197Os.
These references are separable from the safety questions raised by the petition.
III. Public Comments on the Petition A notice of receipt of the petition for rulemaking was published in the Federal Register on December 23, 1991 (56 FR 66377).
Interested persons were invited to submit written comments or suggestions concerning the petition by February 21, 1992.
The NRC received four comments in response to the notice:
two from private citizens, one from a citizens group, and one from a public utility. Three of the commenters supported the petition. The main reasons cited by the commenters who supported the petition were:
One commenter feels that the changes in world conditions increase the likelihood of a nuclear device detonation and that nuclear power plants must be hardened against EMP from nuclear explosions.
One commenter believes that efforts by the national defense agencies to harden equipment from the effects of nuclear EMP indicate that similar efforts are required of civilian nuclear power plants.
4
One commenter, a citizen group, believes that electrical transients in nuclear power plants present a safety hazard, based upon NRC generic communications regarding operational events cause by radio frequency interference (RFI), lightning, geomagnetically induced currents (GIC), and battery failure.
In addition, they believe that the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities program should have included a review of the potential effects of lightning for all licensees, not just those licensees who have experienced adverse plant effects from lightning besides loss of offsite power.
Two of the above three commenters support the petition because of the perceived delicate nature of solid-state electronic devices, and the belief that these devices will not be adequately protected in the absence of regulation by the NRC.
One commenter, a public utility, was opposed to the petition because research has not yet proven the need for any rulemaking, or the extent of rulemaking if a need is shown.
If the order of proposed actions in the petition were accepted, licensees would be required to take actions prior to the issuance of any guidance.
IV.
Reasons for Denial The NRC has considered the petition, the public comments received, and other information and has concluded that the issues raised in the petition, though valid concerns, do not warrant new staff regulatory positions for existing plants. The following discussions address the issues raised in the petition.
5
Upon receipt of the petition from Richard Grill, the NRC staff reviewed all the General Design Criteria of Appendix A to 10 CFR Part 50 to determine whether any of them, not just those cited in the petition (Criteria 2, 13, 14, 17, 18, 19, 21, 22, 23, 24, 29, 63, and 64), should be modified as requested.
Design Criterion 2 states that "Structures, systems and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornados, hurricanes, *... without loss of capability to perform their safety functions." Although lightning is not specifically identified, it is implicitly included in the natural phenomena for which protection must be provided. Criterion 4 states that "Structures, systems and components important to safety shall be designed to accommodate the effects of and be compatible with the environmental conditions associated with normal operation, maintenance, testing.... These structures systems and components shall be appropriately protected against dynamic effects.... and from events and conditions outside the nuclear power unit.
11 The environmental conditions cited implicitly include electrical transients and their sources. Also, qualification of safety-related systems and components for the applicable environmental conditions is required for conformance with this criterion.
Design Criteria 2 and 4 apply to all safety-related instrumentation, control, and power systems.
Therefore, the staff finds that there is no need to modify any of the General Design Criteria in order to assure that the effects of electrical transients are considered in the design of these systems.
The NRC licensing review of operating plants for conformance to General Design Criteria 2 and 4 in regard to protection against lightning, switching surges, and other electrical transient phenomena was based on the knowledge that: (1) established industry design standards and practices were being 6
applied in the design of the electrical control and instrumentation systems; (2) the great majority of electrical systems and components in nuclear power plants were qualified for operability in the electromagnetic environment of these plants on the basis of prior operational experience in similar industry applications; and (3) the equipment and systems deemed to be particularly vulnerable, such as. those utilizing solid state components and circuitry, were required to be qualified for operability in the electromagnetic environment by appropriate type testing before being approved for-nuclear power plants.
The NRC next thoroughly reviewed the technical literature regarding sources of electrical transients. This review and other bases for the staff's conclusions are documented in an internal NRC report entitled "Report on the Sources and Effects of Electrical Transients on the Electrical Systems of Commercial Nuclear Power Plant, 11 which is availQble for public inspection or copying in the NRC Public Document Room.
It was determined that potentially dangerous electrical transients are not generally transmitted to electrical systems or components in the power generation plant from the power transmission system.
There are only four physical mechanisms by which an electrical transient can be transmitted_ to an electrical system or component, all of which are well documented in the technical literature and are generally considered in the design of nuclear safety-related electrical systems.
- First, the transient may enter via a transmission line that carries power or data to or from the system or component.
Second, the transient can enter via capacitive (electric field) coupling of the system or component to the source of the transi.ent. Third, the transient can enter via inductive (magnetic field) coupling of the system or component to the source of the transient.
Finally, the transient can be caused by ionized particles impinging *on the 7
. system or component.
The NRC find~ that the present consideration of these effects is sufficient to assure safe operation of nuclear power plants with analyses conducted on a system-or component-specific basis. There is no need to perform a comprehensive analysis of the entire electrical system of a nuclear power plant.
Based on a review-of the technical literature, it appears that analyses of components and systems have been conducted and have effectively prevented electrical transients from significantly affecting the operation of nuclear power plants for the electromechanical control's-based systems typically employed at licensed U.S. nuclear po~er plants.
In addition, the NRC has required licensees to perform additional testing of solid-state controls components and systems which specifically targeted the potential for problems to be caused by electrical transients. These considerations provide a
.sufficient basis for the *NRC to conclude that electrical transients have been adequately considered in the licensing of e~isting nuclear power plants.
The NRG theA reviewed 177 operating events that were attributed to lightning from 1980 to 1991, a period representing approximately 967 operating years, to determine whether any of these events might indicate that nuclear safety-related electrical systems and components have not been adequately protected from power line transients, capacitively coupled transients, and magnetically coupled transients. This review is also contained in the previously referenced internal report. Ten of these events were also analyzed in NUREG/CR-3591, "Precursors to Potential Severe Core Damage Accidents," vol.
1, July 1984, and NUREG/CR-4674, "Precursors to Potential Sever~ Core Damage Accidents, 11 vol. 2, December 1986;. vol. 6, May 1988; vol.. 8, July 1989; vol.
12, August 1990.
None of these incidents resulted in a significant risk of 8
core damage.
Based on this review, it was determined that the existing level of protection against electrical transients is sufficient to protect against failure of nuclear safety-related electrical systems.
It should be noted that the electrical transients created by lightning can be more severe than any other source of electrical transient except nuclear EMP.
The effect of nuclear EMP on nuclear safety-related electrical systems has been studied by the NRC.
This investigation is documented in NUREG/CR-3069,* "Interaction of Electromagnetic Pulse with Conunercial Nuclear Power Plant Systems," February 1983.
It was detennined that a high-altitude nuclear explosion would not prevent the safe shutdown of a nuclear power plant.
Therefore, it 1s not necessary' to analyze nuclear safety-related electrical systems with the programs developed by the ONA and DCA.
In addition, these programs were written to determine the effects of ionizing radiation on electrical systems and components, an effect known as system generated EMP (SGEMP).
A civilian nuclear power plant would only be exposed to SGEMP in the event of a near or direct strike with a nuclear weapon.
Nuclear power plants are not required to be designed to survive the effects of a near or direct nuclear weapon strike.
Some of the petitioner's concerns will be further addressed in the individual plant IPEEE reviews.
Because the NRC has previously determined that additional regulation of lightning protection is not cost-justified, lightning is not required to be specifically,considered in the IPEEE program unless there have been plant-specific effects. For those licensees where, based on operating experience, lightning strikes are likely to cause more than just loss of offsite power, further examination of lightning effects is expected, including a determination of whether any plant modifications are 9
required.
Licensees have been notified of this position by Supplement 4 to Generic Letter 88-20, which includes NUREG-1407, "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities," June 1991, as guidance.
However, operating events which have been studied to date have not revealed any significant concerns. Therefore, there is no need to extend the IPEEE review to consider other potential-effects besides loss of offsite power to plants which have had no operating experience with such effects, as requested by one commenter.
The on-going staff reviews of advanced light water designs are more focused in regard to the application of General Design Criteria 2 and 4 in the review of these designs for protection against electrical transient phenomena.
The NRC staff is reviewing the advanced designs against the Electric Power Research Institute's (EPRI) requirements that address lightning protection, grounding, surge withstand capability, electromagnetic interference (EMI) and electrostatic discharge.* EPRI's requirements are based upon good engineering practices and established industry standards. The NRC staff is also evaluating the above criteria for inclusion in the 11 Inspection, Tests, Analyses, and Acceptance Criteria/Design Acceptance Criteria (ITAAC/DAC)"
verification programs that will be implemented on advanced designs.
More information on this subject is provided in SECY-92-53, 11Use of the Design Acceptance Criteria during io CFR Part 52 Design Acceptance Reviews, 11 which is also available in the NRC Public Document Room.
Copies of NUREG-1407, NUREG/CR-3591, NUREG/CR-4674, and NUREG/CR-3069 may be purchased from the Superintendent of Documents, U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20013-7082.
Copies are also available from the National Technical Information Service, 5285 Port Royal 10
Road, Spr-ingfiel.d, VA 22161.
A copy is also available for inspection and copying for a fee in the NRC Public Document Room, 2120 L Street, NW. (Lower level), Washington, DC.
The petitioner also requested the reason that the Draft Regulatory Guide RS 705-4, "Lightning Protection for Nuclear Power Plants," was never issued in final form.
The Advisory Committee for Reactor Safeguards (ACRS) requested on February 3, 1981, that a risk assessment be perfonned to determine whether the draft regulatory guide would be cost effective. This risk analysis indicated that implemehtation of the guide would not be cost effective.
In addition, measurements of surge arrester current magnitude which are reported in the technical literature indicate ~hat there is no apparent basis for the position adopted in the guide that a 120,000-ampere surge arrestor is required to protect nucl~ar safety-related electrical systems and components from power line transients.
For example, one study (Gaibrois, G. L., "Lightning Current Magnitude. Through Distribution Arresters," IEEE Transactions* on Power Apparatus and Systems, Vol. PAS-100, No. 3 March 1981) indicates that 0.07% of measured surge arrester currents exceeded 100,000 amperes for a sample size of 2488 distribution surge *arresters. These currents would be higher than transmission line surge arrester currents because distribution lines do not typically have shield wires.
Implementation of the draft regulatory guide would have imposed an economic burden on licensees, and the staff did not find sufficient safety benefit to justify such a burden on them or-their ratepayers.
On the m~tter of the potential improprieties in the treatment of the petitioner or his concerns by the NRC or its predecessor, the questions raised have been referred to the Office of the Inspector General for appropriate.
11
consideration and disposition.
For the reasons cited above, Dated at Rockville, Maryland the NRC denies the petition.
~
this 8" day of~. 199.i.
For the NucleVRegu{atory Commission.
for Operatiorys.
12
DOCKET NUMBER 1,
- ? 11 ** ULE PRM 5 5 C_S ~ P fl-6 6 377)
Department of Energy Washington. DC 20585 J)_EC_ O 2 1992 Dr. Ivan Selin, Chairman Nuclear Regulatory Commission Washington, D.C. 20555
Dear Dr. Selin:
uU-.L 1 LD USNi{C
- 93 JAN 14 P 4 :Q1 I am writing to you to request a status report on the progress, if any, of the Petition for Rulemaking I submitted to the Nuclear Regulatory Commission (NRC) on August 16, 1991, as a private citizen. The Petition was received by the Commission on August 19, 1991, and a Notice of Receipt was published in the Federal Register on Monday, December 23, 1991.
Other than the transmittal on March 9, 1992, of comments received to the Notice, I have not heard from the NRC regarding the disposition or progress of this Petition.
My request is that I be informed of: 1) what actions have been taken to assign this Petition to technically competent staff, 2) what NRC organization has been assigned the action, 3) what individual staff member is assigned the lead, 4) what further actions have been planned to resolve the issues raised, and 5) the projected completion date(s) for resolution milestones.
The purpose of these requests is twofold.
Firstly, it was my practice when I worked for the Commission to make an initial contact with the petitioner after I was assigned responsibility for a petition.
I would follow this by periodic updates as the resolution of the Petition proceeded to discuss progress. This was ooviously not a requirement but I felt, as did most of my colleagues, that it was a courteous and necessary response of a governmental body to any citizen petitioning that Agency.
! wcuid appreciate the same courtesy.
Secondly, since assessment of the safe design of nuclear facilities is part of my duties, I would like to inform you of the interest that has been generated within the Department of Energy (DOE) in the effects of natural phenomena in general and lightning in particul ar on the safety or our facilities, partly due to my activity since joining DOE.
As a result of this interest, and a great number of lightning related disruptions of our operations, a Workshop has been planned by DOE for February 17-19, 1993.
The title of the Workshop is "Ljqhtninq Hazards for Nuclear and Other Energy Facilities." The meetings are open to DOE, its contractors, industry, private concerns, and other Government agencies will be held in Cocoa Beach, Florida, and will be hosted
2 by the Lawrence Livermore National Laboratory.
I will be addressing this workshop and would like to inform them of the progress being made on my Petition by the Cormaission.
Should you think it appropriate for your technical staff to attend the Workshop, I suggest they contact Lili an Decman, Lawrence Livennore National Laboratory, 7000 East Avenue, L-193, Livermore, California 94550.
She can be reached on (510) 294-4576 or by fax on (510) 423-2163.
- cerely,
(~'
Richard P. Grill Safety and Health Division of Regulatory Compliance Offi ce of Waste Management Tel: (301) 903-7145
45-5124 February 19, 1992 LIC-92-069R Omaha Public Power District 444 South 16th Street Mall Omaha, Nebraska 68102-2247 402/636-2000 Mr. Samuel J. Chilk Secretary of the Commission U.S. Nuclear Regulatory Commission Washington, DC 20555 Attention: Docketing and Service Branch ieference: Docket No. 50-285
Dear Mr. Chilk:
"92 FEB 24 Al 1 :40
~fF!C£ OF SEC1 E !ARV iocKET ING i.tNICf.
BRANCH
SUBJECT:
Comments on Petition for Rulemaking: Effect of Electrical Transients on the Operability and Reliability of Nuclear Safety Related Systems Omaha Public Power District (OPPD) has reviewed the subject petition for rulemaking as published in the Federal Register on December 23, 1991 (56 FR 68377) and provides the following comment.
As with any potential safety concern, it is important that the NRC research the issue and provide adequate guidance to licensees before proposing any regulatory requirements.
The order of proposed actions in the "solution" portion of the petition suggests licensees take actions prior to issuance of detail ed guidance by the NRC. This would be an inefficient use of resources by both licensees and the NRC, s i nee research has not yet proven the need for and the extent of rulemaking.
If you should have any questions, please contact me.
Sincerely
~..,ll. ~
W. G. Gates Division Manager Nuclear Operations WGG/sel c:
LeBoeuf, Lamb, Leiby & MacRae D. L. Wigginton, NRC Project Manager S. D. Bloom, NRC Project Engineer R. D. Martin, NRC Regional Administrator, Region IV R. P. Mullikin, NRC Senior Resident Inspector Document Control Desk Employment with Equal Opportunity Male/Female APR 1 5 1992 Acknowledged by card......... -......... _.. _..
U.S. NUCLEAR REGULATORY COMMISSION DOCKETING & SERVICE SECTION OFFICE OF THE SECRET ARY OF THE COMMISSION Document Statistics
Secretary U.S. Nuclear Regulatory Connnission Washington, DC 20555 Dear Sir/Madam;
'92 FEB 25 A10 :36 in re Docket No. PRM-5 QJF.P-fu:" !}~~'tm: TARY (i)
P. Grill petitiQ10CKETING & SEftVICf.
BRANCli I write in support of Mr. Grill's request that the NRCMamend its regulations to establish general design criteria for nuclear power plants, as necessary, to add lightning-induced and other electrical transients to the required list of phenomena that licensed nuclear power plants and other nuclear facilities must be designed to withstand safely Y Although I write as a layperson, I have folmowed nuclear power issues for about 25 years, and feel qualified to comment.
Efforts in tlie area of national defense to ensure that basic communications and functioning of equipment not be disrupted by electromagnetic pulses have gotten significant publicity over the years.
The same attention shold be paid to nuclear facilities, where health and safety may also be at stake.
It seems obvious that as control rooms and safety-related systems have gotten more complex, and now utilize more delicate solid-state systems, they, too, need protection -- not just from EMPs but, as Mr. Grill enumerates, from any number of possible sources of electrical transients.
If, as Mr. Grill asserts, it is true that the NRC does not even require existing conventional standards for protection of electrical and electronic circuits, then I am almost speechless.
How could this be?
Please act expeditiously on Mr. Grill's petition and grant his request for (1) bringing your knowledge of surge protection up to date, (2) concurrently identifying and quantifying the the potential consequences of all types of electrical transients, and then (3) developing electrical transient protection guidance, and requiring nuclear to be designed and/or backfitted accordingly.
Thank you for the opportunity to comment.
Sincerely,
~~
629 Highland Rd.
Ithaca, NY 14850 Acknowledged by card~~!:...:,~"'~...:;;
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U.S. NLCLEAf{ REGULATORY COMMISSION DOCKETING & SERVICE SECTION OFFICE OF THE SECRETARY OF THE COMMISSION Document Statistics Postmark Date
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OOCKEiED USNRC 1J.<3 February 23, 1992 t:,. cf JI.* /5
'92 FEB 28-- A~
COMMENTS OF OHIO CITIZENS FOR RESPONSIBLE ENERGY, INC. o#',~~flWs~CR 11\\R',.,
ON PRM-50-56, FILED BY MR. RICHARD P. GRILL, 56 FED. REG.HJCKfff(iNi,7.ll SEi!VICf:
(DECEMBER 23, 1991)
Bkt-NC'i ~
In this petition, the petitioner requests that the NRC a mend its lo/
regulations to require nuclear power plants to withstand electri-cal transients induced by lightning and other phenomena.
OCRE supports this petition for rulemaking and urges the NRC to take the actions requested by the petitioner without delay.
OCRE finds that the petition is well-supported and that the petitioner, formerly employed by the NRC and AEC, possesses the utmost credibility and authority.
The NRC's refusal to address this issue through the years, as thoroughly documented by the petitioner, constitutes a reprehensible neglect of statutory responsibilities.
The vulnerability of solid-state electronic devices to transients is well-known.
The undersigned holds an degree in electronic engineering and has experience with the design and construction of analog and digital electronic circuits using semiconductor devices.
While specific maximum values of voltage and current are dependent on the particular device, it can be said with certainty that semiconductor devices are much more vulnerable to malfunction and even destruction from transient voltages and currents that would be of little or no concern in circuits em-ploying vacuum tubes or relay logic.
Some semiconductor devices, such as integrated circuits utilizing CMOS technology, must be carefully protected from discharges of static electricity, which can destroy the device.
Typical precautions which are taken include storing the ICs on conductive foam to ensure that all leads are at the same electrical potential and grounding the work surface, soldering iron, and persons handling the ICs.
The fact that semiconductor circuits are low voltage circuits means that induced transients do not have to be of a large magnitude to act as false signals.
The vulnerability of semiconductor devices to transient surges is so well-known that surge suppressors are widely available for the protection of consumer electronics.
It is indeed surprising that nuclear power plants do not have com-parable protection for their sensitive circuits.
That surge suppressor technology is widely available suggests that protec-tion for nuclear power plants can be achieved at low cost.
It is necessary for this issue to be resolved as soon as possible 1
APR 15 1992 Acknowledged by card" *** "..... ___ ---..
U.S. NUCLEAR RtGULATORY COMMISSION DOCKETING & SERVICE SECTION OFFICE OF THE SECRETARY OF THE COMMISSION Document Statistics Postmark Date A ><-.
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because of the likelihood that new nuclear plant designs will extensively utilize solid-state circuitry.
Under 10 CFR Part 52, standardized designs are to receive early approval before any plants using the design are actually constructed; thus this issue needs to be addressed now and the appropriate regulatory require-ments established at the earliest opportunity to support the review of standard design applications.
Existing plants are also upgrading their circuits to solid-state; for example, see 57 Fed.
Reg.
1930 (January 16, 1992), which describes an operating li-cense amendment for the Zion plant which will upgrade the process protection system from an analog system to a digital system.
It is likely that many licensees will choose to incorporate solid-state circuitry in existing plants as part of plant refurbishment for operating license renewal.
This again shows the need for prompt resolution of this issue.
It is incredible that the draft regulatory guide on lightning protection, attached to the petition, has been neglected for over a decade.
The draft value/impact statement for the guide (writ-ten in 1979) showed a compelling need for action:
"There is evidence to support the concern that common failure modes can exist in the nuclear plant safety systems whereby surges of a
transient nature could render redundant components inoperable."
(draft guide, p. 10); "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 protection of such systems from electrical surges generated externally or internally." (draft guide, p. 12); "Failures in a number of installations (Refs. 1 through 17 and 19 through
- 29) suggest that the high energies released by lightning have the potential to cause severe damage to sensitive systems important to protect the health and safety of the public." (draft
- guide,
- p. 17).
Operating events have not shown that the need for action has diminished since the draft regulatory guide was issued for com-ment.
OCRE's review of generic communications issued since 1979 reveals that the hazard from transients continues:
Information Notice 83-83, "Use of Portable Radio Transmitters Inside Nuclear Power Plants," December 19, 1983, which describes system malfunctions and spurious actuations caused by the use of walkie-talkies in the plants. Four separate incidents are cited.
The notice states that "to date, solid state devices installed in nuclear power plants have been responsible for all of the known cases of radio frequency interference (RFI) generated by portable radio transmitters."
2
Information Notice 85-86, "Lightning Strikes at Nuclear Power Generating Stations," November 5, 1985, which describes incidents at five plants. The event at Zion resulted in noise spikes and damage to a 24-V power supply, such that it had to be replaced.
The event at Byron caused the failure of four rod drive power
- supplies, including a redundant pair.
Lightning protection at both plants was improved as a result of the events.
At
- Salem, lightning struck main steam vent pipes which extend above the
- roof, and the surge was carried through the piping into the
- building, where it caused a transient on seven main steam pres-sure transmitters, damaging two of them, which had to be re-placed.
The notice states that "since solid state circuitry designs are being increasingly employed in safety related sys-
- tems, the impact of lightning induced line surges on those cir-cui ts is emphasized in this notice."
Information Notice 90-42, "Failure of Electrical Power Equipment Due to Solar Magnetic Disturbances," June 19, 1990, which de-scribes damage to electrical equipment and systems, including the total blackout of the Hydro-Quebec system, due to geomagnetic storms.
The notice states that such disturbances "may produce equipment
- damage, loss of electrical power, and problems with voltage control in transmission systems connected to nuclear power plants."
Information Notice 91-64, "Site Area Emergency Resulting from a
Loss of Non-Class lE Uninterruptible Power Supply, October 9,
- 1991, which describes the August 13, 1991 event at Nine Mile Point Unit 2, which was initiated by a voltage transient.
Had the licensee performed proper maintenance on the power
- supplies, the event probably would have been avoided.
Nonetheless, this event demonstrates that such transients, when coupled with other failures, can lead to unanticipated plant conditions.
Incredibly, the problem of lightning-induced transients will not even be addressed by all licensees in the IPEEE program.
Generic Letter 88-20, Supplement 4 only requires licensees to address seismic events, internal fires, high winds and tornadoes, exter-nal floods, and transportation and nearby facility accidents.
NUREG-1407, "Procedural and Submittal Guidance for the Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities,"
explains why lightning was excluded as a
re-quirement for the IPEEE.
The reasoning is that the primary effect of lightning is loss of offsite power, which is addressed as part of the internal events IPE program.
"The staff has concluded that, in general, other effects of lightning on nuclear power plants are insignificant.
However, further examination of lightning effects may be warranted for certain sites where, based 3
on past operating experience, lightning strikes are likely to cause more than just loss of offsite power; for example, they may also affect safety-related instrumentation and control systems."
- p.
- 4.
The staff concludes that consideration of lightning effects should be performed only for plant sites where lightning strikes are likely to cause more than just loss of offsite power or a scram.
Not only does this ignore the adverse events documented in the generic communications listed above, this approach misses the point of performing the IPEEE.
If a nuclear plant has never been struck by lightning, how will the licensee know if more severe effects than a scram or loss of offsite power will occur?
Even for those plants which have been struck, the event may have occurred before making changes to plant systems involving re-placement of components with solid-state devices.
The plant's reaction before these changes may not be indicative of the post-change behavior.
The whole point of the IPEEE is to perform a
plant-specific systematic search for risk outliers from external phenomena.
How can one rule out the effects of lightning without conducting a plant-specific analysis of its effects?
The staff did not restrict the consideration of seismic events to only those plants which have already experienced an earthquake with adverse consequences.
Excluding lightning from the IPEEE might be acceptable if, like most of the other external phenomena considered, lightning had been part of the plant's design basis and the IPEEE only consid-ered events beyond the design basis envelope.
(Seismic events are an example; nuclear plants are designed to withstand the SSE, but the IPEEE is to examine earthquakes greater than the SSE.)
- But, as Mr. Grill's petition clearly sets forth, lightning was never part of the design basis for nuclear power
- plants, but should have been.
The fact that the staff has chosen to essen-tially exclude lightning from the scope of the IPEEE means that this issue has never been, and never will be, addressed, unless Mr. Grill's petition is granted.
On the technical issue of lightning and other electrical tran-
- sients, Mr.
Grill's petition is factually accurate and well-supported.
But apparently facts aren't enough for the NRC.
The petition raises another issue which also needs to be explored; the fifth recommended action listed in the petition is "in order to assure prompt resolution of other nuclear safety issues, determine why the NRC was so reluctant to face and dispose of this one."
OCRE has also had experiences with the NRC where the agency refused to face the facts.
(This problem is not unique to the NRC, or even to government agencies.)
There needs to be an 4
investigation of the psychological, political, and institutional factors that led to this situation.
Mr. Grill's petition reveals some of them: resistance to change, the desire to maintain con-
- formity, and the avoidance of controversy ("don't make waves,"
Attachment 1 to the petition at 2); and the inordinate power of the nuclear industry over the agency (petition at 6-7).
Unfortu-
- nately, the developments of the last decade (e.g.,
the Backfit Rule) give the industry even more influence than it had in the 1970s.
Ironically, it is probably easier to solve the technical issue raised in PRM-50-56 than to solve the institutional issues implicated.
But, it appears that the technical issue won't be resolved until the institutional problems are.
In conclusion, OCRE urges the NRC to finally face the facts on this issue.
PRM-50-56 should be granted expeditiously.
Respectfully submitted, Susan L. Hiatt Director, OCRE 8275 Munson Road Mentor, OH 44060-2406 (216) 255-3158 5
UUlii\\i:'f NUMBER Pl WI § O __,,..5 (:,
PROPOSED RULE_ I' I 7 7, (5bFf< 3
/
l JLI\\[; t.D U~NRC "92 JAN 22 P 4 :26 Mcirvin I. Lewis 7801 Roosevelt Boulevard Suit£,) 62
- f F!C'" UF SE.CR.f 1 Y
uOCKCilNG >.. Su<VICf BRANCH Phila., PA 19152 (E~15)624-157l~
Secretary USNf-<C Washington, D. C. 20555 Dear Mr. Secretary; A
.... cc,*,~lease iE1ccept this le:*tter as my comments on Dockeit Number PRM
'-'-1" I agree with Mr. Grill, the Petitioner, that electrical transients must be part of the phenomenon required for nuclear plant licensing. I am especially concerned since the USSR is no longer an *enemy*, much of the nuclear capability of the USSR will be on the World market. Anyone will be able to buy a nuclear device. The likelihood of a nuclear device detonating anywhere in the World has gone up astronomically while the chance of a World wide nuclear holocaust has fallen.
At this time, the obvious need for hardening of nuclear power plants against EMP electrical transients from nuclear explosions is immediate and paramount.
bl~
Acknowfedged by card.:.:~11~2!,,;~:,x,a CD
U.S. NUCLEAR REGULATORY COMMISSION DOCKETING & SERVICE SECTION OFFICE OF THE SECRET ARY OF THE COMMISSJON Do<:urnent Statistics a --z..,
Poatmark Dall _.... ~
<J _
Coi-s ReoeiYed_...__ ____ _
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Specill Distribution 1:. b 5
NUCLEAR REGULATORY COJDIISSIOB 10 CFR Part so (Docket No. PRM-50-56]
DOCKETED USNRC
- 91 OEC 18 A11 :OO Richard P. Grill; Filing of a Petition for Rulemakirig AGENCY:
Nuclear Regulatory Commission.
ACTIOB:
Notice of receipt of petition for rulemaking.
SUMMARY
Mr. Richard P. Grill requests that the Nuclear Regulatory Commission (NRC) amend its regulations that establish general design criteria for nuclear power plants, as necessary, to add lightning induced and other electrical transients to the required list of phenomena that licensed nuclear power plants and other nuclear facilities must be designed to withstand safely.
The petitioner requests that the NRC require licensees of nuclear power plants and other nuclear facilities to consider the effect of electrical transients on t he operability and reliability of nuclear safety related systems and potential accident scenarios analyses.
2./11 /1~
DATES:
Submit comments by {60 days following publication in the Federal Register).
Comments received after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except as to comments received on or before this date.
ADDRBSSIIBS&
SUbmit comments to:
Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555.
Attention:
Docketing and Service Branch.
For a copy of the petition, write:
Rules Review section, Regulatory Publications Branch, Division of Freedom of Information and Publications Services, Office of Administration, Washington, DC 20555.
FOR ~UR'l'BBR ?HJ'ORKATIOH CONTACT:
Michael T. Lesar, Chief, Rules Review Section, Regulatory Publications Branch, Division of Freedom of Information and Publications Services, Office of Administration, Washington, DC 20555, Telephone:
(301) 492-7758 or Toll Free:
800-368-5642.
SUPPLBKml'l'l\\RY INFORMATION:
Background
The NRC has received a petition for rulemaking submitted by Richard P. Grill.
The petition was assigned Docket No. PRM 56 on August 19, 1991.
The petitioner has requested that the NRC amend Appendix A to 10 CFR Part so, "General Design Criteria for Nuclear Power Plants," to add lightning induced and other electrical transients to the required list of phenomena that licensed nuclear power plants and other nuclear facilities must be designed to withstand.
The petitioner has requested that the NRC modify Design Criteria 2, 13, 14, 17, 18, 19, 21, 22, 23, -24, 29, 63 and 64 of Appendix A to 10 CFR Part 50 to require licensees of nuclear power plants and other nuclear facilities to consider the effect of electrical transients on the operability 2
and reliability of nuclear safety related systems and potential accident scenarios analyses.
The requested amendment would also require licensees to take whatever actions are necessary to assure that electrical transients cannot compromise the safety of the facility and the health and safety of the public.
The petitioner requests that these design requirements be mandatory for all new license applications as well as for license renewal for operating plants.
The petitioner requests that the commission first conduct the research necessary to develop a technical basis for issuing the regulations and for supplying guidance to its licensees.
The Petitioner The petitioner was formerly the Chief, Site Safety Branch, Division of Reactor Licensing, U.S. Atomic Energy Commission in the late 1960 1 s and early 1970 1s.
In 1976, petitioner accepted a position with the NRC, in the Environmental Standards Branch.
The petitioner contends that some members of the staff of the Atomic Energy Commission and the Nuclear Regulatory Commission have urged that a comprehensive study be conducted to quantify the potential risk and consequences from electrical transients since the late 1960 1 s.
As the Branch Chief responsible for analysis of the hazards posed by natural phenomena on nuclear power plants, the petitioner actively sought to have the electrical transient issue addressed.
After joining the NRC in 1976, the petitioner renewed efforts to have the issue addressed.
These efforts included a direct appeal to the 3
co-isaion.
As a result, a Draft Regulatory Guide and Value/Impact Statement, entitled "Lightning Protection for Nuclear Power Plants," was issued for public collllllent by the Commission in August 1979.
The draft guide was submitted to the Advisory cOJIIDlittee on Reactor Safeguards (ACRS) for review and a final draft version was submitted to the ACRS in February 1981.
The guide (which had not received NRC Staff-consensus) was discussed at the February 5-7, 1981, ACRS meeting.
The ACRS e
returned the regulatory guide to the staff for further action and recommended that the NRC Staff utilize consultants to provide the necessary expertise for this specialized subject.
A final version of this Regulatory Guide was never published.
The petitioner contends that the draft Regulatory Guide was weak on justification because the studies necessary to show whether or not electrical transients posed a threat had not been done.
In fact, page 10 of the guide states "The staff has not reviewed the surge protection aspects of nuclear power plants and, therefore, is not thoroughly familiar with the present practices used for the protection of systems important to safety from transient overvoltages."
Need for the suggested Amendments The petitioner believes that potential effects of transient electrical surges on the integrity of safety related control and monitoring systems have not been rigorously analyzed nor have any implications for safety been factored into preventative design conservatisms.
The petitioner states that, to his knowledge, no 4
commercial nuclear power plant design in the United States has ever been thoroughly studied to see what effect the range of electrical transients from lightning strikes, switching surges, or other sources, might have on the facility.
The petitioner asserts that a complete analysis of this issue has never been conducted by the NRC.
The petitioner contends that because the effects of lightning and other electrical transients have not been analyzed, 4t the effects were not considered in the development of General Design Criteria or Safety Class 1 specifications.
Therefore, the design of electrical safety sensing and control systems may not have utilized equivalent levels of conservatism now found in the remainder of the facility.
According to the petitioner, lightning strikes and switching surges are relatively common occurrences at or near electrical generating stations and their associated transmission lines.
Generating station designers have long known electrical transients could damage generators or other equipment and interrupt electrical service.
All generating stations are protected to some level against a transient's gross effects as a matter of prudent economics.
Lightning arresters, for example, are provided to decouple massive electrical surges on a transmission line resulting from a lightning strike.
Protective devices, however, do not assure protection of more delicate control circuits or instrumentation from the pulse the arrester allows to pass before interrupting the transient.
5
The petitioner states that transients can also enter the circuitry by any number of alternate paths from outside or inside the plant.
These transients can enter directly on electrical supply and instrumentation lines from direct contact with a source of electricity or by induced currents generated by electromagnetic impulse (EMP) phenomena in the atmosphere (lightning, nuclear detonations), switching procedures, ferromagnetic effects or electromagnetic emission from other adjacent equipment, i.e., radio or radar transmitters, arc welders, thyristor dimmer switches, radio frequency heaters, electric motors, etc.
These transients are not considered crucial for conventional generating stations as the maximum consequence is plant shutdown and a resultant loss of revenue.
The transients could be extremely important for a nuclear powered
\\
station, however, as the bottom line in this case could be the health and safety of the public, not dollars.
The petitioner also states that as safety related control systems at nuclear facilities have become more complex and sophisticated, their vulnerability to electrical transients has increased.
Relatively sturdy vacuum tubes used in earlier plants have been replaced, first by transistors and more recently by solid state integrated logic systems.
These later systems can be disrupted by quite small fluctuations of current.
The petitioner contends that industry standards have been developed for protection of conventional electrical and electronic circuits because of the vulnerability of these electronic systems.
According to the petitioner, the NRC does 6
not require the use of even these conventional standards much less require more rigorous standards commensurate with the safety consequences of failure of nuclear power plant protective systems.
Therefore, the petitioner doubts that the electrical/electronic definition of "Safety Class 1 11 is as equally rigorous and reassuring as that for other design parameters.
The petitioner contends that members of the NRC staff have indicated that they are aware of several incidents which have occurred in nuclear power plants that can be attributed to lightning effects such as the shut down of the Humbolt Bay plant and the explosion in the off-gas system of Vermont Yankee.
The Solution The petitioner requests that the NRC amend its regulations pertaining to General Design Criteria for Nuclear Power Plants, as necessary, to add lightning induced and other electrical transients to the required list of phenomena that licensed nuclear power plants and other nuclear facilities must be designed to safely withstand.
The petitioner requests licensees be required to take whatever actions are necessary to assure such transients cannot compromise the safety of the facility and the health and safety of the public.
According to the petitioner, other Government agencies, such as the Defense Nuclear Agency and the Defense Communications Agency, have devoted significant resources to investigation of surge disruption in similarly complex electronic circuitry.
7
While the transients investigated in these studies originate from sources other than natural phenomena, such as EMP from postulated nuclear explosions, the effects on circuitry are similar.
The petitioner further states that the analytical tools already developed by these agencies could be modified for use by the NRC and the commercial nuclear industry to determine the magnitude of this potential threat and to suggest remedial courses of action, should they be necessary.
Petitioner suggests that the NRC answer a simple question posed over 20 years ago "Do electrical transients produced by lightning or other causes present a significant hazard to the safety of nuclear facilities?" Specifically, the petitioner suggests that the NRC take the following actions:
- 1. Initiate a research study to determine the current state of knowledge of lightning and other electrical surge protection.
Assemble the results of this study into a comprehensive reference report.
- 2.
Initiate another study to identify and quantify potential consequences of all types of electrical transients on licensed nuclear power plants and other nuclear facilities.
- 3.
Prepare and publish a rule in the Federal Register to require that each relevant NRC licensee analyze and modify, if necessary, its facility to assure safety related nuclear systems will not be compromised by electrical transients.
- 4.
Utilizing these studies, licensee experience and analysis, and relevant industry standards, develop electrical 8
transient protection guidance specifically tailored to the exceptionally high reliability requirements of nuclear facility safety related control systems.
- 5.
In order to assure prompt resolution of other nuclear safety issues, determine why the NRC was so reluctant to address this issue.
The Petitioner's suggested Amendments The petitioner has requested a generic amendment to the general design ~riteria provisions for nuclear power plants, 10 CFR Part 50.
I.
The amendment would --
- 1.
Revise Design Criteria 2, 13, 14, 17, 18, 19, 21, 22, 23, 24, 29, 63 and 64 of Appendix A, to require licensees of nuclear power plants and other nuclear facilities to consider the effect of electrical transients on the operability and reliability of nuclear safety related systems and potential accident scenario analyses.
- 2.
Require licensees to take whatever actions are necessary to assure such transients cannot compromise the safety of the facility or the health and safety of the public; and
- 3.
Be mandatory for all new license applications as well as for license renewals of existing plants.
II.
The petitioner suggests that prior to proceeding with the suggested amendments the commission must first conduct the 9
research necessary to develop a technical basis for issuing the regulations and for supplying guidance to its* licensees.
Request for Comments Interested persons are invited to submit written data, views and arguments concerning the foregoing discussion.
~
Dated at Rockville, Maryland, this \\1 -day of December 1991.
For the Nuclear Regulatory Commission.
the\\Commission.
10
DOCKET NUMBER 5 O _ §,6 PETlTlON RULE PRM
( r;' 6 F-Yl-66371)
Secretary U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Chief, Docketing and ch DOCKETED AUG 19 1991 DOCKETING &
SERVICE BRANCH SECY-NRC
~
PETITION FOR RULEMAKING s
4:
RECEIVED AUG 1 5 19.91 Off ice of the 16 August, 1991 i p~~~ ~* n the Nuclear Regulatory Commission to amend Part 50 of your r egulat i ons and/or issue new regulations, as necessary, to add lightning induced and other electrical transients to the required list of phenomena licensed nuclear power plants and other nuclear faci l ities must be designed to safely withstand. In particular, Design Criteria 2, 13, 17, 14, 18, 19, 21, 22, 23, 24, 29, 63 and 64 of Appendix A to 10 CFR 50 should be modified to require licensees of nuclear power plants and other nuclear facilities to consider the effect of electrical transients on the operability and reliability of nuclear safety related systems and potential accident scenarios analyses and to take whatever actions are necessary to assure such transients cannot compromise the safety of the facility or the health and safety of the public. These design requirements for lightning protection should be mandatory for all new license applications as well as for license renewals.
In order to do this, the Commission must first conduct the research necessary to develop a technical basis for issuing the regulations and for supplying guidance to its licensees.
Justification:
My concern has been, for many years, that the ~ovisions of 10 CFR 50, "General Design Criteria for Nuclear Power Plants", has not been implemented fully in the Commission's licensing procedure, in that the potential effects of transient electrical surges on the integrity of safety related control and monitoring systems has not been rigorously anal yzed nor any implications for safety factored into preventative design conservatisms. To my knowledge, the design of no commercial nuclear power plant in the United States has ever been thoroughly studied to see what effect the range of electrical transients from lightnfng strikes, switching surges, or other sources, might be. Certainly, such a 1
U.S. NUCLEAR REGULATORY COMMISSION DOCKETING & SERVICE SECTION OFFICE OF THE SECRETAR¥ OF THE COMMISSK>N Document Statistics Postmark Date _.d:
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complete analysis has never been conducted by the NRC. Since the details of this potential mechanism for compromising plant safety has never been thoroughly investigated and is thus essentially unknown, I request NRC regulations be amended to require this possible unreviewed safety question be scoped, reviewed and resolved for all nuclear power plants on a generic basis and for any individual plants, as required.
The Commission has often pridefully made statements that the analyses utilized in scoping nuclear power plant accidents caused by both natural and man-made phenomena has been done in an extremely conservative manner in that they include accidents resulting from events of extremely low probability. Earthquake, flood, tornado, tsunami, extreme snow loading, aircraft crashes, transportation accidents, toxic fumes, etc., are all required to be addressed in Safety Analysis Reports and any adverse conclusions of the analyses of these low probability events are reflected in conservative designs. One of the natural events of highest probability, lightning, has not been addressed, however.
Because of the conservatism required by the Commission in analyzing these rare events and because of other conservatisms contained in the General Design Criteria required by the Commission, safety related systems at nuclear power plants have been designed and constructed to meet a rigid set of specifications known as "Safety Class l". Containments, for example, are oesigned to withstand the impact of tornado generated. missiles and crashing aircraft. Intake structures are designed to accommodate extremely low coolant water levels.
Machinery and piping is designed to safely withstand the effects of the highest expected earthquake loading. Safety related equipment is conservatively designed, constructed, installed ano tested of only carefully selected and inspected materials subject to meticulous quality assurance checks to assure it will continue to operate reliably throughout the life of the plant.
Because the effects of lightning and other electrical transients have not been analyzed, and therefore not considered in development of the General Design Criteria or in developing Safety Class 1 specifications, the design of electrical safety sensing and control systems may not have been designed utilizing an equivalent levels of conservatism now found in the remainder of the facility.
Lightning strikes and switching surges are relatively common occurrences at or near electrical generating stations and their associated transmission lines. All such stations are protected to some level against a transient's gross effects. Lightning arresters, for example, are provided to decouple massive electrical surges on a transmission line, resulting from a lightning strike, since generating station designers have long known such transients could damage generators or other equipment 2
and thus interrupt electrical service. It is only prudent economics to provide such devices. These protective devices, however, do not assure protection of more delicate control circuits or instrumentation from the pulse the arrester allows to pass before interrupting the transient.
Transients can also enter the circuitry by any number of alternate paths from outside or inside the plant. Such transients can enter directly on electrical supply and instrumentation lines from direct contact with a source of electricity or by induced currents generated by electromagnetic impulse (EMP) phenomena in the atmosphere (lightning, nuclear detonations), switching procedures, ferromagnetic effects or electromagnetic emission from other adjacent equipment,i.e., radio or radar transmitters, arc welders, thyristor dimmer switches, radio frequency heaters, electric motors, etc. These transients are not considered crucial for conventional generating stations as the maximum consequence is plant shutdown and a resultant loss of revenue. Transients could be extremely important for a nuclear powered station, however, as the bottom line in this case could be the health and safety of the public, not dollars.
As safety related control systems at nuclear facilities have become more complex and sophisticated, their vulnerability to electrical transients has increased. Relatively sturdy vacuum tubes used in earlier plants have been replaced, first by transistors and more recently by solid state integrated logic systems. These later systems can be disr-upted by quite small fluctuations of current.
Because of the vulnerability of these electronic systems, industry standards have been developed for protection of conventional electrical and electronic circuits. If these standards are followed in nuclear facilities, and analysis can show failure of the systems is always in a safe direction, a regulator could have some basis for assuming nuclear safety related systems would remain operable during events involving unplanned fluctuations of current. The NRC, however, does not require the use of even these conventional standards, much less require more rigorous standards commensurate with the safety consequences of failure of nuclear power plant protective systems. There is doubt, therefore that the electrical/electronic definition of "Safety Class l is as equally rigorous, and reassuring as that for other design parameters.
More importantly, the Commission has never systematically investigated postulated failure scenarios or the potential consequences of transient events at a single nuclear power plant and cannot, thus, judge what margin of safety, if any, exists at operating plants today.
Other Government Agencies such as the Defence Nuclear Agency and 3
the Defence Communications Agency have devoted significant amounts of resources to investigation of surge disruption in similar complex electronic circuitry. While the transients investigated in these studies originate from sources other than natural phenomena, such as EMP from postulated nuclear explosions, the effects on circuitry are similar. The results of these studies show the phenomena are not simple ones nor are the effects simple to predict. The surges can cause complex interactions among adjacent circuits and systems by failing insulation and by causing high transient voltages between points that are normally at or close to the same poten~ial.
Electromagnetic compatibility (EMC) modeling and testing are particularly complex. None-the-less, the analytical programs have-proven both valuable and workable. I have been informed the analytical tools already developed by these Agencies could be modified for use by the NRC and the commercial nuclear industry to determine the magnitude of this potential threat and to suggest remedial courses of action, should they be necessary.
Some members of the staff of the Atomic Energy Commission, and later the Nuclear Regulatory Commission, have urged since the late 1960's that a comprehensive study be conducted to quantify the potential risk and consequences from electrical transients.
Those staff members felt such a study would allow intelligent choices to be made for what additional regulatory requirements, if any, need be imposed on licensees. I, as a Branch Chief responsible for analysis of the hazards posed by natural phenomena on nuclear power plants, was active in the effort to surface the issue; at one point (1976) appealing directly to the Commission. Partly as a result of my urging, a commitment was made by NRC management to do the necessary research and to develop regulatory guidance. Subsequently, studies were conducted to determine lightning strike frequency and the magnitude of the expected maximum pulse, and a "lightning relate~d" category was added to the system used for keeping records of nuclear power plant incidents. A Regulatory Guide on lightning protection also prepared. It was issued for public comment in 1979 and completed in 1981, but the Reg. Guide was never issued.
The draft Regulatory Guide was weak on justification because the studies necessary to show whether or not electrical transients, in fact, posed a valid threat had not been done. In fact, the draft Guide states on page 10, "The staff has not reviewed the surge protection aspects of nuclear power plants and therefore is not thoroughly familiar with the present practices used for the protection of systems important to safety from transient overvoltages. Published literature and industry standards on the subject reveal that surge protection is based largely on statistical methods developed for conventional non-nuclear systems principally on a cost-benefit basis; no special consideration has been given for the protection of nuclear plant systems important to safety."
4
Requested Action:
I request the Commission do several things in preparation for amending the regulations. They are:
- 1) Initiate a research study to determine the current state of knowledge of lightning and other electrical surge protection. Assemble the results of this study into a comprehensive reference report.
- 2) Initiate another study to identify and quantify potential consequences on licensed nuclear power plants and other nuclear facilities from electrical transients of all types.
One way to do this would be to choose a representative sample of "typical" nuclear power plants and other nuclear facilities and, using available analytica~ techniques, modified as necessary, investigate the effect of various plausible electrical transients on the safety related control systems of the facility. Any failure modes discovered should be used to modify the probabalistic risk assessment and safety analyses of the facilities.
- 3) Prepare and publish a Rule in the Federal Register to require each relevant NRC licensee analyze and modify, if necessary~ his facility to assure safety related nuclear systems will not be compromised by electrical transients.
- 4) Utilizing the above, licensee experience and analysis and relevant industry standards, develop electrical transient protection guidance specifically tailored to the exceptionally high reliability requirements of nuclear facility safety related control systems.
- 5) In order to assure prompt resolution of other nuclear safety issues, determine why the NRC was so reluctant to face and dispose of this one.
It has been over twenty years since the issue w.,.as raised. The question, a simple one, was: "Do electrical transients produced by lightning or other causes present a significant hazard to the safety of nuclear facilities?"
The question still has not been answered.
Additional
Background:
I first surfaced this concern in the late 1960's and early '70's as Chief, Site Safety Branch, Division of Reactor Licensing, U.S.
Atomic Energy Commission. The job of my Branch, among other things, was to assess nuclear accident consequences and to 5
determine the effects of natural phenomena on the safety of nuclear power plants. Once these potential effects were determined, guidance was prepared to assist licensees in designing the facilities and preparing license applications for our later review.
From previous work experience, I was aware of problems resulting from electrical surges caused by lightning and from other sources. I was also aware that nuclear weapons testing required elaborate safety procedures be followed to prevent inadvertent currents capable of affecting instrumentation or other critical circuits. Some sites used detectors capable of sensing differences in atmospheric electrical potential, indicating incipient lightning strikes. All operations were secured during these conditions. I was also familiar with an incident (then highly classified) in which the onboard computers of a missile, in a silo, had been incapacitated by the effects induced currents from a lightning strike a quarter of a mile away.
We reasoned: If an induced transient could damage a missile control system, it might conceivably damage the. safety control systems of a nuclear reactor or possibly the structure itself. My Branch prepared a series of questions on lightning surge protection for a particular power plant applicant (Farley). This plant was chosen because it was sited in a region of the country with the highest reported incidence of lightning strikes.
The applicant was surprisingly uncooperative. A strong protest was lodged with my management by the applicant's representative to the effect that: 1) there was no lightning problem, 2) the AEC staff was unreasonably adding another burdensome analytical requirement on the applicant, for another wildly improbable phenomenon such as meteor strikes, earthquakes and airplane crashes on containment, and 3) "Get off our backs 1" Our staff response was: 1) The probability and magnitude of a lightning strike and its consequences for the safety of the reactor are unknown, 2) the lightning protection design of the power plant is also unknown to the staff, 3) questions to the licensee, intended to provide assurance of safety, are reasonable and assist the staff in developing technical positions, 4) The general location of this particular plant site was within one of the highest frequencies of recorded lightning ~trikes in the U.S., 5) if an accident from such a source is so incredible as to be dismissed from consideration in licensing, we owe it to the public and to future licensees to address the issue and document the reasons for doing so in the same manner we had put the meteor issue to bed, 6) We are willing to be convinced, however we, as regulators must be "from Missouri. Show us."
The nuclear industry apparently decided to "hang tough" on this issue. I was told privately by senior industry representatives, 6
"This was the straw that broke the camel's back. We have decided to take a stand. We will not allow the AEC to go further down the road of exploring ever more remote accident sceparios. I have talked to the 'powers that be' and I guarantee you will never ask another lightning question."
The applicant submitted answers to our original list of questions. The answers were brief. They essentially said, "We have provided lightning rods. Our analysis shows the plant is safe. "
No details of this analysis, design assumptions or details were submitted.
My management would not allow me to submit a more detailed follow-up list of questions to that applicant and would not allow me to ask similar questions of other applicants. I was told the matter was not technically the concern of my Branch. The issue was to be transferred to the Electrical Safety Branch. This branch would take responsibility for following the issue and
- assu-ring -it wa-s --resolvea, -r was told-. -
Shortly thereafter, in 1972, I left the AEC to work for private industry, mostly in Europe, and lost track of the issue. Four years later, in 1976, I took a job with the NRC and asked how the "lightning issue" had been resolved. I was tolff the matter had not been addressed. The issue was exactly where I had left it.
First, I made contact with other Agencies to see their progress.
Both the Defense Nuclear Agency and the Defense Communications Agency told me they had developed elaborate computer programs to model the propagation, effects and interactions of transients in their systems. They felt these programs could be modified fairly easily for modeling the safety related systems used in nuclear power plants. They were willing to actively pursue a cooperative research effort with the NRC.
I tried to resurface the matter within NRC but, getting no response from my management and t-here being no formal process for submitting a Differing Technical Opinion (DPO) at that time, wrote a letter to the Chairman of the NRC. The letter expressed my opinion lightning effects were a potentially unreviewed safety question that should be addressed by the Commission (Attachment 1). I received a prompt response from Chairman Rowden and a number of meetings were held to discuss the matter over the next few years. A Commissioner's assistant, Hugh Thompson, was assigned to check on the progress of the issue resolution.
In the final meeting, Roger Mattson, then a Division Director in the Office of Standards Development, asked me to stay for a private discussion. He said, "Grill, if you will shut up about this matter, I promise I will "fix it". I will get a Regulatory 7
Guide published on the subject."
"It's a deal," I replied. Roger Mattson's word was (and is) his bond. I withdrew from the controversy and, aside from checking from time to time with the staff member assigned to write the Guide, following the meteorological research on lightning that was started and assuring Hugh Thompson from time to time I felt the NRC was behaving responsibly, I assumed the.problem was being solved.
I was asked to review a draft version of the Guide in 1977, and supplied comments at that time (Attachment 2). In 1979 a draft Guide was issued for public comment (Attachment 3). I felt the Guide represented a competent but limited job, in that it did not address my principal concern, i.e., an independent critical assessment of lightning and other transient protection designs of operating reactors. After that, I know the Guide was submitted to the Advisory Committee on Reactor Safeguards at least twice. A final version was submitted to the ACRS in 1981.
Some time af.teriiards, four tl1ings happene_d_: 1 f Roger Mattson le-ft -
the NRC. 2) The staff member responsible for developing the Guide was given another assignment. 3) The Guide disappeared from sight. It has never been published. 4) Most of the files on this matter were discarded.
I gave up.
I have kept in touch with some of the principals in this issue, over the years. They assure me the lightning ispue remains dead at the NRC and they see no hope of reviving it from within the NRC. Most of the files on the issue have been discarded except for my personal copies. We, collectively, had trouble even finding a copy of the draft Lightning Protection Guide as even the author had discarded his. Only the 1979 public comment draft could be found.
I am no longer employed by the NRC. I feel I have unfinished business in this area, however. Many of us who worked on this problem plan to leave Government service within a few years and feel the same way. There is a reluctance among those still employed by the NRC to become involved in another futile round of discussion, but all of us, I think, feel this issue was never given a fair or complete hearing. We remain technically convinced the matter deserves a more focused and dispositive treatment. We would like to see the matter addressed responsibly and finally put to bed.
If there is a suspicion that a mechanism exists, capable of circumventing the redundant safety features of a nuclear power plant, and those responsible for assuring public safety have not thoroughly examined the issue; they have not fulfilled their duty 8
to that public. No one could be happier than I if, after careful study, we conclude there is no problem. My point is; the NRC has not done a careful, thorough and documented study on which to base this conclusion.
I stand ready to answer any questions you may have on this matter or to supply any documentation still in my possession.
Sincerely, V:L~~
Richard P. Grill 19305 Frenchton Place Gaithersburg, MD 20879 Tel: (301) 330-8589 (h)
(301) 353-3355 (w) 9
To:
Chairman Rowden Commissioner Mason Commissioner Gilinsky Commissioner Kennedy From:
R. Grill
Subject:
LIGHTNING PROTECTION - POSSIBLE UNRESOLVED SAFETY_ ISSUE I am taking the unusual step of writing directly to you as I assume that the statement of ex Chairman Anders of an "Open Door Policy" is still supported by Chairman Rowden.
The reasons for my doing so are:
- 1. I believe that a possible safety issue exists which has never been properly addressed, much less resolved.
- 2. This issue could prove embarassing to the Commission in the future.
- 3. I feel some residual responsibility for this matter.
- 4. I am experiencing some quilt feelings for not remaining within the AEC to fight more strongly for the resolution of this issue.
- 5. My repeated attempts at resolution, over the years, in dealing with those lower in the organizational structure have met with no results.
- 6. I do not wish to place intermediate levels of management and staff in a defensive posture for fear of a "witch hunt" to assess blame.
- 7. I do wish to handle the matter responsibly within the organization with a minimum of publicity.
- 8. The final reason is that I am both angry and resentful that action has not been taken to resolve my concerns *
Background
- At one point during my employment with the AEC (1969/1972) I had the responsibility for analysis of site safety and environmental concerns in the Division of Reactor Licensing.
For a time, before the appointment
The Commissioners 2
of an Assistant Director I supervised the entire group and was appointed Chief of the Site Saftty Branch on his assumption of duties.
In such p~sitions I was responsible for identification and analysis of all phenomena which could compromise the safety of the plant and calculations of consequences to the environs.
I continued in the above capacity until I resigned on March 1972.
l.remained in Europe until March 1976 when I accepted a position with the Environmental Standards Branch.
History of Problem Early in my tenure in the AEC I became concerned with the possible effects of lightning upon the safet:y of nuclear power plants.
I
.expressed my concerns to my superiors and attempted to ask relevant questions of applicants. I, was told that 1. The division had no tine to waste on "marginal issues",
- 2. The issue was probably not a
__ real-one-, -3. -A.dd-i-t-iona-1--q~s--tions -to-- *the-app1:ic*an-t-Wott!d-only slow -
down the licensing process further and
- 4. "Don't make waves".
I continued to make contacts with knowledgeable persons to assess the po~sible extent and probability of lightning effects. This inquiry led into areas of classified information through contacts from 1llY prior work with National Laboratories.
The information I gathered was enough for me to conclude that the issue warranted at least sufficient investigation and discussion*by the staff to be able to dismiss the concern on technical grounds or to indicate further investigations be carried out.
I documented my concerns to Dr. Morris and made enough of a pest of myself verbally that my Branch was allowed to ask a question of a single plant, James T. Farley, conceming the level of lightning protection provided in their design.
The reply to this query was inadequate but I was not allowed to ask further questions.
The net result of my effort was that I was told: 1. The area of concern was not in my jurisdiction, 2. The issue was probably not valid, but 3. The matter was to be formally assigned to the Electrical Projects Branch for assessment and resolution and 4.
"Go away and don't bother me".
(Unfortunately the correspondence on this issue has become misplaced.
The Branch files have been destroyed, a search of central files has failed to unearth copies, Electrical Projects remembers but cannot find the memos and my personal files were ruined by sea water during a storm in the Mediterranean two years ago.
I have tried to reconstruct my concerns in the addendum to this letter q.v.)
The Commissioners Shor,tly after this period I resigned (only partly due to this issue).
When I returned I made inquiries to find out what conclusions were reached and how the matter was resolved.
The answer was that 3
essentially nothing has been done in the intervening six years!
Members
..of my old branch have continued to ask questions* of applicants but no programs of information gathering or research activities have been started.
Meni:iers of the Sta£ f tell me that they are aware of several incidents which have occurred in.nuclear power plants which can be attributed to lightning effects such as the shut down of the Rumbolt Bay plant,and the explosion in the off-gas system of Vermont Yankee.
Suggea tions A
I believe that either an actual lightning related incident-or an inquiry by citize,n s-soups (particularly if my earlier correspondence is llllcovered)
- could place the Staff and Com:nission in the position.of appearing
_________ ~-~.I\\egle~t,ful _of __their-responsibility~-to-~rot~t -the-public..saf..eey,.----1~ i-&-------~----
therefore my suggestion that you do:
- 1. Establish a group to investigate the *extent of this problem by:
A. Collecting data on frequency of occurrence and consequences of lightning related incidents at power generating facilities. Also, data should be collected from incidents involving a combination lightning and failure of electronic control systems for other than power generation.
B. Postulate the effects on nuclear,power generating facilities of lightning related phenomena with special emphasis on the effect of failure or maifunction of integrated circuitry associated with engineered safety features.
C. Analyse data on frequency of lightning strikes related to location of nuclear power plants so that probability estimates may be developed.
- 2. Based ppon any need indicated by the above, initiate appropriate research activities.
- 3. Reach early conclusions on this issue and if necessary require that corrective measures be taken.
It is my suggestion that you do not:
- 1. Attempt to assign blame for the delay in addressing this matter.
- 2. Dismiss my concerns without documented technical justification.
It is my hope that in bringing this matter to your attention my involvement can be terminated as my present responsibilities are not involved with
The Commissioners 4
this issue.
I am, however, at your disposal for any further discussion or clarification you should wish.
Addendum:
As stated Sincerely, R. P. Grill Environmental Standards Branch Office of Standards Development,
ADDENDUM Lightning Phenomena and Nuclear Power Plant Safety The following is a rough reconstruction (from memory) of the concerns
.I repeatedly expressed to AEC Management and Staff in 1970/72.
_Problem:
Lightning is a natural phenomenon about which little information is available.
Applicable research which has been done and can be found outside classified literature is scarce.
On the assumption that the iarge quantities of energy transferred during a lightning strike could conceivably affect a nuclear power station we can justify exploring possible effects. If this exercise shows chains of events whic.,;, could conceivably result in compromising the integrity of engineered safety features a more detailed examination seems warranted.
Possible Effects
- 1. Direct Strikes: One would assume that electrical and other components within a nuclear reactor would be shielded from the effects of a direct strike by the conductive steel reinforcing bar> liners, etc. acting as a Farraday cage.
Several considerations make this a less tenable assumption.
- a. Constructors will not guarantee the electrical continuity nor complete grounding of the "rebar".
- b. A strike could travel along a conductive portion of the containment, reach an area of high resistence, the resultant heat generation could produce steam from the water of hydration in the surrounding concrete and either spall or penetrate the containment.
This might not be noticed until this engineered safety feature was called upon to fulfill its function, at which point it might fail.
- c. Auxilliary generators and other critical structures are not always within containment and these could be disabled by direct strikes.
The massive grounding system required by any electrical generating station plus* a system of lightning rods would seem to greatly minimize this 1:1.Spect of concern if we had assurance that the system was designed and constructed on sound principles. I'm not certain that we can feel confident of this in present plants.
- 2. Indirect "Strikes
- a. Strikes on transmission lines, auxilliary generating facilities etc. could cause large surges to enter the plant, possibly damaging critical equipment or electrical circuitry.
All electriCc\\l generating plants have interruptors installed to prevent damage from just such an event. Unfortunately these mechanisms are installed to protect the generators, transforroor~ and other large pieces of expensive gear from damage from massive charges.
They are not set sensitively
)
411 2 -
enough to protect the type of electronic equipment now being used in engineered safeguard controls and instrumentation.
In
- addition the "reaction time" of the interruption is much too slow to prevent short duration pulses from entering the system.
The above insensitive settings are understandable as the operators of a plant do not wish it to be shut down unnecessarily or frequently.
A thorough analysis of the effects of surges on the control instrumepts of a nuclear plant has. not been conducted, to my knowledge.
- b. Magnetic Fields: Electronic circuitry, particularly integrated circuitry, is susceptable to magnetic influence.
Lightning strikes produce significant perturbations in the earths magnetic field. Many modern designs of engineered safeg~rd systems are using integrated circJ.its.
The eff'9ects of lightning strikes near a nuclear power plant on these circuits ia unknown but probably significant.
Frequency Little data is available about strike frequency but data on thunderstorm activity indicates that the Gulf Coast of the U.S. and the Bay of Beagal coast nave the highest frequencies in the world.
As a large number of U.S. Nuclear Reactors are located in the South Eastem U.S. where thunderstorm activity is high I feel we have presumptive cause to feel some conce m.
Cursory examination of reliability records of a southern utility indicated that a very high percentage of their outages (over 85% as I recall) were caused by lightning strikes on transmission lines. Thunderstorms can obviously occur in almost any location in the U.S. as indicated by the incident that caused serious disruption of the Rumbolt Bay plant in Califomia and the Verioont Yankee incident.
Experience:
A few incidents that I am aware of may give some insight to the magnitude of the possible problem.
- 1. Careful reading of the classified literature concerning the
~.... ~~ s' "decoupling" simulation experiments in Mississippi will probably cit..~ u~......,."l.J,"aeveal the extent of the problems encountered in unplanned pre-
.,., t,~ ~
C, etonations of explosive gas mixtures caused by lightning.
e, __......,.Ali.l:.lil 2. Analysis of the lightning problem has led to elaborate precautions
~:()_'*~,,
being taken during weapons testing.
Instrumentation to detect
~~J impending lightning strikes has been long developed and is
-T... L. tt"f-,
routinely deployed.
Detailed procedures have been worked out
-~
to prevent the obviously unacceptable results of a strike during
~
testing.
Not only safety, of course, but also reliability of data is involved here.
411
.. 3 -
- 4. European experience is hard to gather but I have been told by safety personnel that it is a concern and that "elaborate lightning protection schemes have been employed for many years" for nuclear test and power reactors.
- 5. Several U.S. reactors have experienced "scrams" and other incidents which could be attributed to lightning.
The Vermont Yankee plant, for example, had an explosion in the gas holdup system caused by lightning.
The Humbolt Bay plant was shut down in 1970 by a lightning strike which caused concern of blowdown stresses on the plant.
As far as I know, no systematic collection of lightning related incidents has been initiated among our licencee~.
Possible Consequences I am not qualified to postulate all possible series of events which could follow a lightning strike which could effect a nuclear reactor *
.Some possibilities are obvious, however.
A few might be:
- 1. A strike could put the emergency generating equipment out ol:
action.
- 2. Control instrumentation could be damaged so that reactivity is added at the same time that 11scram" systems are disabled.
- 3. If a lightning induced power surge could cause a turbine trip with simultaneous loss of auxilliary power we might be well on our way toward an event which could lead to a reactivity surge resulting in steam generator tube failure with resultant release of radioactivity.
- 4. If surges or magnetic field fluxuation disable the overload or overspeed controls on the turbine, a runaway turbine condition could develope.
- 5. Surges etc. could cause instrumentation to falsly represent operating conditions causing plant operators to take inappropriate or dangerous actions.
- 6. Alarms or automatic scram controls might be disabled in a tnanner which leaves the operator unaware of impending problems.
Conclusions and Suggestions Based upon the, admittedly, not very thorough or scientific speculation above I would conclude that there is enough. presumptive justification to initiate a more thorough investigation to determine if a real problem exists or not.
My suggestions would be the same now as they were six years ago i.e.
- 1. Start a program of data collection for lightning related incidents involving both conventional and nuclear power generating stations.
Disruption of other electronically controlled installations could also be included.
,;w
4 -
- 2. Start a data collection program to determine the relative and actual frequency of lightning strikes.
- 3. Do a literature search (both classified and open) regarding lightning phenomena and its effects.
(I know that Los Alamos did a great deal of this work about 10 years ago with a view to differentiating lightning from nuclear explosions by sattelite observation)
- 4. Have knowledgeable personnel construct "scenarios" to see if the safety of a plant could possibly be violated by lightning phenomena and, if possible, try to attach rough probabilities.
- 5. If the above actions indicate any cause for concern, or if the basic information is lacking with which to make a judgement, initiate a research effort to develop the necessary information so that this matter may be "put to bed" one way or the other
- My only concern is to define whether a problem exists or not. If it does not we should be able to issue a report which classifies lightning dong with "gremlins" an-d meteorites -a:s 11noii-probTems". If it does -
prove a problem we had better fix it -- now.
I
UMITEO STATES NUCLEAR REGULATOnY COM:\\11SSION WASHINGTON, D. C. 20555 OCT 2 5 1977 MEMOM:-IDUN F0~:
Wilber M. Morrison, Chief, Reactor Systems Standards Branch~ SD FR0-;1:
R. P. Grill, Environmental Standards Branch, SD
SUBJECT:
REVIEW OF DRAFT GUIDE:
?OHER PLANTS".
"LIGHTNING PROTECTION FOR NUCLEAP. *
+
~
At the reauest ::r~ !.. C. Roberts I have reviewed the subject draft Gu1cm and *
- have the follo*ii.iJ comnents and suggestions to offer for your consideration.',.
- General* *..
This Guide, in Gj 0pinion, represents a significant step tcrn~rd resolution of the.problem.of. ass:.ir_ing.tha _ _s_afety and rel_iabj]j_1_:,y of fu_ture f!llClear pm,rer.
stations. It does not, however, relate directly tm*iard resolution~*ot*my*-:_-*-
primary concern, i.e. an independent critical assessment of the light?Jing
- protection designs of operating reactors and those now under construction.
I realize that this larger concern is outside the scope of the efforts currently undeniay within your Branch and that any actions to upgrade the protective systems of these reactors would d2pend upon a careful and deliberate considera-tion by other portions of NRC management and the RRRC.
l*ly concern is that,,
without the rasu1ts of such a detailed assessment involving 0 fau1t tree analysis" or si;;;i1ar studies, NRC management will not have the tools avail-able to rr.ake t~~;e decisions.
The second s~~~:*~1 cbservation is that several of.the numerical criteria within. this ~~-a-:~ ze::ra to have inade~uate justification presented \\'lithin the Guice. :..,::-=*~ available, this should be presented either.\\'1ithin.th2 Guide.,
itself or a.5 :.;t ::=:e.11:fum..
Where such justification is unavailable studies should be unrle::;;.i:n to d2velop defensable backup for all components of
- the Gui de.
- Specific p~l.XX-i', last p!ra:* insert "nor cause spurious or inappropriate function ofn.
- after the word ir.operable.
Inoperability of a safety related system* may be of less concern t.";an operation of a system out of proper sequence or a spurious signal causing an::rther* system or op2rator to take inappropriate actions.
p.1.XX-3,' para.. 3:
R~place the word 11high 11 jn the first sentence with usignificant 11 ** Change the \\*mrds 11 reasonable assurancen in the second sentence with "reasonably conservative assurance."
J*kjlber M. Morrison 2
This section s~~uld also be rr~dified to indicate: (l) that higher amperages are pJssible, (2) the degree of conservatism represented by the 200,000 ampere figure in relation to the consequences of failure of a safety related syste.~,
and (3) t1hich ether groups have adopted this figure where loss of systems.
were judged u:-12.:.ceptable. {It is my understanding that it is, primarily, defense relate..: zctivities which use this design figure. They, correctly, have judged -:r:::: the 0industry 11 standard which allows the choice of design parameters so"l-::y on a basis of "cost-benefitiality 11 are inadequate when the
. consequenses *=*f failure are considered.)
- p. 1.XX-4, para. 2: Substitute* the phrase. n1n this type of. system 11 *for_ *.. '
- . the word athar~f::rre" in the. fourth sentence.
- ," ~
, (
1* *
- p. T.XX-5, para. l: The relevance of the' phrase "surge wave.of the 1.2 x* 50 usec shapeu_ shc!.i1c be more c~letely explained and the source re~e~nced_.,. __.:
- p. 1.XX-5, pcra. 2:
The second sentence could be improved by changing it -
-'ta -read,. ~Ade.q.uat!;_ PD!t?ction can be provided *** " The second sentence could be clarified by h~ving it read ":~.these* arrestors -ean.-** ~-- _.. *
- p. lXX-6, para. 2:
In the position on Design Basis Surge, a second sentence should be added:
11Unusually, if analysis of local conditions indicate t.iat higher surges ara more significantly probably, selection of a higher design value may be necessary.
11
- p. 1.XX-7, para *. l: The word 11meteorological n.shoula be substituted for-,.
r.radiological.
11 It should be noted somewhere in the _Guide that columns of ionized gas~es co~ing from stacks and vents can form conductive paths and thus pres:n: ~referential poi~ts for lightning strikes. Additional protection klcf ~~=~ to be designed for these locations.
- p. l.XX-7, i::::i::...1: The raference here, and elsewhere in the Guide> troubles.
ma.
Is visua: -~~~ection sufficient, as opposed to actual.:testing of.
- electrical co~~:-~~ty, in viett of the consequenses of faiTure7.
- p. 1~.XX-7, pare:.~ Zt 6:, Should not fault tree studies be conducted~in.all cases, not jGt ~:>r-justification of lower rating arrestors? Recent experience with 7cilures in transmission systems would seem to mandate this.*
~
~
I
- t. ~
\\
~
~
- p. 1.XX-9, para.. 1: Why \\'fas the figure. of *five years chosen for* testing ** '*
of arrestors? This r.iay well be a proper interval, but some justification should be preser.teci. If no defensible basis is available7 perhaps a special appeal for technical input could be written into the Guide or the explanatory discussion when it goes*out for public comment.
A third paragraph could be* added to.this position: "(3) In safet'f related statiun control systems which a detailed analysis indicates "to be "criticaln, all arrestors must be tested or replacec at intervals of _____....;*"
~~8~
R. P. Grill
j.
C C
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF STANDARDS DEVELOPMENT DRAFT REGULATORY GUIDE AND VALUE/IMPACT STATEMENT LIGHTNING PROTECTION FOR NUCLEAR POWER PLANTS A.
INTRODUCTION August 1979 Division 1 Task RS 705-4
~
General Design Criterion 2, "Design Basis for Pro~ainst Natural Phenomena, 11 of Appendix A, "General Design Criteria ~
Power P1ants,'1 to 10 CFR Part SO, "Domestic Licensing of Productio lization Facil-to safety be designed-to withstand -natural ph!i_
me_*-
he desi_gn bases for these structures, systems, and components a e u
d to reflect (1) appro-priate consideration of the most severe o **
a ral phenomena that have been historically reported for the sit r unding area, with sufficient margin for the limited accuracy,.q6an it n period of time in which the historical data have been accumula d; -
appropri~te combinati~ns of the effect of normal and accident cond 1th the effects of the natural phenomena; and (3) the irnportPo~the safety fun~tions to be performed.
General Design Criterion Vspection and Testing of_ Electric Power Systems," of Appendix A to 10 CFR Part 50, requires, in.part, that electric power systems important to safety be designed with a capability to test periodically the ope~and functional performance of _their components.
This regulacs~ ~escribes criteria acceptable to the NRC staff for the design, appl a
, and testing of lightning protection systems to erisure that electr~c s ts resulting from lfghtniQg phenomena do not render systems imp a
to safety inoperable or cause spurious operation of such systems.
This regulatory guide 1nd the 11socilted value/flll)llct stateinent are befng fssued fn draft fot"III to involve the public fn the early stages of the develop111ent of a regulatory position tn this area. They have not receiYed camplete staff review. have not been reviewed by the NRC Regulatory Requfrement.s Review COllllft-ta. and do not represent an official NRC staff posftfon, Public coaments are being solfcfted on both drafts. the guide (including any f111Plementatfon schedule) an~
the vilue/fmpact statement. COll'l'lllnts on the value/i~t statement should be accOIIIJ)ln1ed by supporting data. Caaments on both drafts should be sent to the Secratary of the C01111issfon, U.1 HycleafgBl9ulltory to.naissfon, Washington, D.C. 20555, Attention: Docketing and Service Branch. by UwT l l I~
Requests for single copies of fssued guides and draft guides (which *1 be reproduced) or for placement on an aut01111t1c*dfstr1but1on 11st for single copies of future guides and draft guides in specific d1v1s1ons should be 1111de in writing to thl U.S. Nuclear Regulatory Com1ss1on, Washington, D.C. 20555, Attention:
Director, Division of Technical lnfonnat1on and Document Control.
- 8.
DISCUSSION To ensure the continuous and reliable functioning of systems important to safety, protection against lightning-induced transients must be provided for the components and structures of these systems fn the plant. Properly placed lightning rods and masts have been proven effective against direct strokes.
Further, electric systems must also be protected from lightning and other elec-trical transients (for example, switching surges) to ensure that these systems and protection systems electrically connected to them are not damaged.
Surge arresters, which function to limit overvoltages, are applied for protection against surges entering the plant site through connected transmission lines.
Surge transient periods, regardless of cause, are usually very short.
- However, these periods are extremely important, s'fnce -f.t -i-s at such-times that circuit components are subjected to the greatest stresses from excessive cur-rents or voltages and damage to components or systems important to safety could result.
During abnormal conditions, when transient currents take unusual paths,
)
high transient voltages can appear between points that are normally at or close
\\
- to the same potential. This can cause electrical stresses that damage equipment;11uJ thereby adding considerably to the effects of the inftial disturbance.
Adverse consequences of abnormal voltage disturbances can be greatly reduced by correct design.
The object of this design is to reduce transient potential gradients as much as possible. Therefore, special grounding methods must be applied where soil conditions are particularly adverse and low ground resistance cannot easily be achieved.
These grounding methods s0111etimes aust take the form of a counterpoise, a continuous ground mat laid underground.
The principal goal of any ground 111at design is to provide as low a resistance path to ground fault currents as 1s necessary to prevent discharge voltages and reflected waves fro causing transient overvoltages in sensitive equipment.
A high frequency of induced or direct lightning surges on power transmis-sion lines and transformers suggests that protection must be provided to ensure that high-energy surges do not propagate into plant distribution and 2
)
C C
protection systems and cause damage to redundant systems important to safety.
Direct strokes at the plant site are of concern only if the shielding masts are bypassed and the stroke terminates on electrical equipment.
In this case 1 the arrester, following sparkover, would be subjected to surge discharge cur-rents of large magnitude and short duration which. -because of the-short time of application, ay not stress a properly applied arrester to its thermal limit.
line surges entering as a result of shielding or backflash failures wtll also result in short-time current discharges that, again, do not thermally stress the arrester. The longer-lasting switching surge stresses the thermal capabil-ity, as do several cycles of follow (power) current subsequent to arrester sparkover.
Available data suggest a significant frequency of lightning surges with currents on the order of 200 1000 &.11peres.
Therefore, we have concluded that protection against a postulated design basis discharge surge of this current magnitude will provide a reasonably conservative assurance that nuclear systems important to safety will be protected against the most severe anticipated lightning-induced surges.
Lightning surges with currents larger than 200,000 amperes do occur, but at a lower frequency.
The consequences of these larger surges on plant systems I
important to safety would be as severe as those of any surge that is greater than the design capability of the systems being.protected.
However, transmis-sfon line and switchyard protection will further reduce the probability of such surges from reaching the.plant systems important to safety.
Electrical transients generated from lightning phenomena and switching of electric circuits have been 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 power plan~s have increased the unavailability of systems important to safety.
The increasingly connon use of highly sensitive solid state logic systems far the protection of nuclear power plants accentuates the need for closer scrutiny 1n the methods used for protecting such systems from transient over-voltages generated externally and propagated into the plant.
Co111110n failure IIOdes whereby surges of a transient nature could render redundant components af systems important to safety inoperable can be eostulated.
For example, power to redundant onsite electric distribution systems 1s typically supplied 3
from the offsite transmission system through a power transformer with a typi-cal transformation ratio of 345 kV to 4.16 kV.
In this type of system, a pri-mary-to-secondary failure in the transformer as a result of lightning or other causes could propagate the primary voltage to the secondary if the secondary fs not properly grounded to hold the voltage at near normal secondary voltage.
Additionally, a lightning-induced surge originating in the primary side of the transformer can propagate to the redundant circuits in the secondary through capacitive coupling in the transformer with potentially damaging consequences ta the redundant circuits in engineered safety feature sequence logics and pro-tection systems electrically connected to the offsite power system.
Insulation coordination between protector and protected equipment is of great importance in power systems.
An arrester with an impulse characteristic that is higher than that of a transformer would not be effective in protecting the transformer even at the first surge. Therefore, ft is essential that the boundary impulse voltage characteristic curve for the insulation of the pro-tected equipment be greater than the impulse voltage characteristic curve of the protective equipment. for a voltage wave of the J.2 x 50 µsec shape. i.e.,
LZ µsec to reach peak value and 50 µsec to decay to half peak.
The impulse voltage characteristic curve for the maximum surge.that the protector must control can then be completely contained within the boundary impulse voltage characteristic curve of the protected equipment.
Care must be exercised in the selection of surge arresters for applica-tion fn electric power systems.
Adequate protection can be provided by modern Tfghtning arresters. These arresters can be applied to protect the insulation and divert surges fro111 propagating to sensitive equipment in the plant. Under certain conditions, however, an arrester can be subjected to sustained rms avervoltages from which ft cannot recover, thereby subjecting the power system ta additional faulted conditions. Therefore, the arrester voltage rating ust be higher than the maximum expected rms line-to-ground voltage under any normal or faulted condition.
Lightning arresters for a.c. power systems are rated according to the maxiLIII line-to-ground system voltage they are expected to withstand. Of the three types of surge arresters (distribution, intermediate, and station),
tha station type offers the best protective characteristics. Its higher discharge-current capacity and fts essentially flat voltage-time character-istic make ft particularly suited for protecting transformer insulation 4
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where_the margin between operating voltage and surge strength is relatively low.
ANSI C62.l-1975, "Surge Arresters for Alternating-Current Power Circuits, 111 describes procedures for the qualification of lightning arresters used in elec-tric power systems.
This standard, although not specifically developed for use in nuclear service, provides guidelines for the performance qualification of arresters that can be used in nuclear service.
Additionally, some sections of ANSI C62.2-1969, 11Guide for Application of Valve-Type Lightning Arresters for Alternating-Current Syst81ls, 111 provide guidelines for the application of lightning arresters in nuclear service. This standard also was not developed for nuclear service, and use can be ade of selected sections only.
The statistical data on surge characteristics relied upon for the devel-opment of the above standards were collected in the 1940's by instrumentation of limited and questionable accuracy.
Therefore, 1complete endorsement of these standards is not possible at this time.
C.
REGULATORY POSITION Lightning protection for systems important to safety in nuclear power plants should conform to the design, inspectiorr,*and testing criteria presented below.
- 1.
DESIGN BASIS SURGE Surge protection equipment should be designed for a discharge-current surge of no less than 200,000 amperes with an 8 x 20 µsec wave shape.
If analyses of local conditions indicate a high frequency of larger surge currents, selection of a larger design basis surge should be considered.
Z.
SURGE ARRESTERS FOR TERMINAL EQUIPMENT PROTECTION 2.1.
Surge arresters with a rating of 100 percent of normal line-to-line voltage should be provided to protect against any anticipated overvoltage 1copies may be obtained from the American National Standards Institute, 1430 Broadway, New York, New York 10018.
5
conditions in grounded neutral power systems unless a lower rating is justi-fied by calculations based on position 2.2.
2.2.
For use of surge arresters with a lower rating than 100 percent in grounded neutral power systems, detailed system fault calculations should be perfor11ed to determine the maximum line-to-ground voltages (where zero-sequence resistance to positive-sequence reactance ratios are positive and 1.0 or less and zero-sequence reactance to positive-sequence reactance ratios are positive and 3.0 or less).
2.3. The provisions for determining maximum line-to-ground voltages identi-fied in section 3.1 of ANSI C62.2-1969 should be followed.
For effectively grounded neutral systems, the arrester selection curves (Fig. 1 of the standard),
may be used for estimating purposes only.
2.4. Selection of surge arrester ratings for isolated neutral systems.
should be based on calculations taking into account the constants of the system, the type of fault considered, and the fault resistance.
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2.5. Station-type surge arresters with a current-discharge capability of 200,000 amperes should be installed on the primary and secondary sides of startup and unit auxiliary transformers shared by redundant systems.
For redundant systems that do not share transformers, the discharge c~pability reconmended in section 5 of ANSI C62.l-1975 is acceptable.
2.6. Station-type surge arresters with a current-discharge capability of 200,000 amperes should be installed at the electrical switchgear upstream of the feeder breaker connected to startup and unit auxiliary transformer second-aries that are shared by redundant systems.
For redundant systems that do not share transformers, the discharge capability recommended in section 5 of ANSI C62.l-1975 is acceptable.
2.7. If n arresters are used in parallel to meet the 200,000-ampere recom-mendation of items 2.5 and 2.6, each arrester should be capable of withstanding
'l!lll.l 200,000/n amperes in service.
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2.8. Qualification testing for surge arresters should be conducted in accordance with the requirements specified in ANSI C62.l-1975.
2.9.
Design tests included in section 7 of ANSI C62.1-1975 should be used but should be supplemented to include high-current-discharge tests of 200,000 amperes for arresters (or parallel comb4nations of arresters, see item 2.7) used to protect redundant systems important to safety that share startup or unit auxiliary transformers. For redundant systems that do not share trans-formers, the high-current-discharge tests recommended in the standard are acceptable.
2.10.
The provisions recommended in section 3.5 of ANSI C62.2-1969 for insulation coordination of transformers external to systems 11RJ)ortant to safety, namely unit auxiliary and startup, are acceptable at a design basis discharge-c:urrent surge best suited for the partic~lar application. However, for redun-dant systems important to safety electrically connected to these transformers, the arrester discharge voltage from a design basis discharge current of 200,000 amperes reaching these systems should not exceed their withstand capability.
2.11.
Periodic testing of surge arresters.should be conducted as follows:
2.11.1. At intervals not to exceed ten years, a surge arrester of the oldest installed group of each type and rating should be removed and repl~ced.
The removed arresters should be tested fn accordance with the performance test requirements specified 1n section S of ANSI C62.l-1975.
2.11.2. If the tests discussed 1n item 2.11.1 reveal unsatisfactory r
performance that is attributed to c0111D0n design or aging defects, all arresters of the sue type and rating, including those installed ten years after the oldest fnstalled group, should be replaced. If, however, the unsatisfactory performance is attributed to a rand011 failure unique to the arrester under test, additional replacements should not be required.
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GROUND WIRES FOR TRANSMISSION LINE SHlELDING 3.1. Ground wires should be provided for a sufficient distance, as deter-mined by analysis. along the transmission lines.
3.2. Transmission lines should be shielded to maintain an angle of pro-tection that does not exceed 30°.
Shielding at an angle of protection greater than 300 _should be justified by analysis.
3.3. Tower footing resistance to ground should be maintained low enough to ensure that lightning discharge transient voltages do not exceed the voltage withstand level of the insulation between tower and conductor.
3.4. Visual inspections of ground wire continuity consistent with other planned periodic inspection programs for outdoor electrical installations should be conducted.
- 4.
CONVENTIONAL LIGHTNING RODS (AIR TERMINALS) FOR PROTECTION OF STRUCTURES 4.1. Air terminals should be installed to protect switchyards. offgas stacks, fuel tanks, meteorological towers, and other.components whose functional 4lt integrity fs important in 1tafntaining the safety of the plant. 2 4.2. The air terminals should be connected to the plant grounding system by electrical bonding. 2 4.3. Air terminals should be located in such a way that all items *to be pro-tected are included in a cone of protection with a nominal angle of 40°.
4.4. Visual inspections and conductor continuity tests consistent with 1 other planned periodic inspection programs for outdoor electrical installations should be conducted.
2National Standard NFPA No. 78-1968, Ulfghtnfng Protection Code,N Part II, Protection of Buildings and Miscellaneous Property, provides acceptable methods for the detailed installation of lightning rods.
Copies may be obtained front the National Fire Protection Association, 470 Atlantic Avenue, Boston, Massachusetts 02210.
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D.
IMPLEMENTATION This proposed guide has been released to encourage public participation in its development.
Except in those cases in which an applicant proposes an acceptable alternative method for complying with specified portions of the COlmlfssion's regulations, the method to be described in the active guide reflecting public comments will be used 1n the evaluation of applications for construction permits docketed after the implementation date to be specified in the active guide.
Implementation by the staff will in no case be earlier than April 1980.
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DRAFT VALUE/IMPACT STATEMENT
- 1.
THE PROPOSED ACTION I.1 Description Electrical transients resulting from lightning phenomena and switching of electrical circuits have hampered the perfomanca of sensitive electronic equfpment and insulation systems for many years.
The history of instrument failures (Refs. 1 through 29), blowing of fuses in control circuits, and failures of insulation systems suggest that transients of electrical nature can increase the risk of system unavailability beyond acceptable levels.
The increasingly common use of highly sensitive solid state logic systems for the protection of nuclear power plants accentuates the need for closer scrutiny in the method used for protecting such systems from transient over-voltages.
The staff has not reviewed the surge protection aspects of nuclear power plants and therefore is not thoroughly familiar wf~h the present practices' used for the protection of systems important to safety from transient over-vattages. Published literature and industry standards (Refs. 30 and 31) on the subject reveal that surge protection is based largely on statistical nthods developed for conventional nonnuclear systems principally on a cost-benefit basis; no special consideration has been given for the protection of nuclear plant systems important to safety. There fs evidence to support the concern that c011111on failure modes can exist in the nuclear plant safety systeas whereby surges of a transient nature could render redundant components inoper-able. For example, power to redundant safety systems is typically supplied frcm'the offsite power transmission system through a transformer with a typical transformation ratio of 345 kV/4.16 kV.
Therefore, a primary-to-secondary faflure in the transformer could propagate the primary voltage to the secondary, tf the secondary is not properly designed (Ref. 18). Additionally, a surge arfginatad fn the primary side of the transformer can propagate to the redun-dant circuits in the secondary through capacitive coupling in the transformer, with potentially damaging consequences.
Such high voltages occurring even for shart durations could destroy sensitive equipment on onsfte distribution buses 10
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and render onsite power supplies inoperable.
Additionally, protection system components electrically connected to these supplies could be rendered inoperable.
The frequency of induced or direct lightning surge on the primary side of a transformer could be high, based on statistical data collected on strikes per mile of transmission line per year (Refs. 32 and 33).
In the event of such occurrence, the propagation of the surge to plant distribution systems is a certainty if appropriate protection is not installed on both sides of the transformer.
The propagation of high surges through transformer windings could occur as a result of the following:
- a.
If the surge rise time is shorter than the arrester's response time, a significant amount of the surge will propagate past the arrester before it is safely carried to the ground by the arrester (Ref. 34).
- b.
In a successfully responding surge arrester the voltage drop devel-oped between phase and ground is a function of the magnitude of the current surge arrested and the resistance to ground (IR drop).
Therefore, a successful discharge of a current stirge of 200,000 amperes through a 10-ohm resistance will develop a voltage drop of 2,000,000 volts on the primary side of the transformer with the propagation of a significant fraction of that voltage (Ref. 35), electrostatically, to the secondary through transformer capacitance
{ff the secondary is not properly grounded) with potentially damaging conse-quences to systems electrically connected to this secondary.
Substantial effort is being expended to detemfne a conservative adesign basis surge" for lightning and some switching surges (Refs. 34 and 36-39).
The significant parameters that define a surge are rise time to peak value, peak value, and time to half-peak value.
Rise times, peak values, and frequency dfstrfbution of lightning surges are presently under study by NRC, by NASA and the University of Florida, and by DOE (Refs. 34 and 37).
However, the internationally accepted rise times appear acceptable at this time for our purposes, and when results are made available from the above studies, we wfll reevaluate our present position.
The frequency of thunderstorm days for various locations fs depicted tn an isokeraunfc map of unknown origin widely used by meteorologists (Ref.
32). However, an updating of this map may be necessary at this time in order to ensure its validity (Refs. 34 and 37).
Surge protection for safety systems in nuclear power plants can be achieved ff the fQllowing system protection is implemented:
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- a.
Installation of suitable ground wires running the length of the transmission line for a reasonable distance fro* the plant site to protect against the effects of direct lightning strikes on power transmission lines.
- b.
Conventional lightning rods strategically located to protect switchyards, offgas stacks, meteorological towers, fuel tanks, and other com-ponents whose functional integrity is important for maintaining safe plant operation.
- c.
Installation of high-energy-absorption surge arresters on cri-tical lines entering the plant.
- d.
Installation of surge arresters on the primary and secondary sides of power transformerR.
- e.
Installation of low-energy-absorption surge suppressors in onsite distribution systems and critical instrument power supplies.
The proposed action is the development of design guidance on accept-able criteria for the_protection of nuclear systems important to safety from surges that can appear on the components and systems listed above.
The likeli-hood of damaging surges*propagated through field wiring to redundant systems important to safety is extremely low and need not be addressed.
Elevated ground potentials resulting from the discharge of high current surges to ground may adversely affect the performance of sensitive integrated circuit components used in reactor protection systems. Therefore, designs that use integrated circuit components must be evaluated and designed to ensure that ground potentials do not adversely affect their performance.
LZ Need for the Proposed Action The potential consequences on the public safety are of such significance that ft seems imperative for the staff to include in their review of systems important to safety the protection of such systems from electrical surges gen-erated externally or internally.
To accomplish this goal, general guidance is required to bring to the attention of the design engineer and the NRC reviewer the significant areas that need particular scrutiny in the design of systems fmpartant to safety and to provide acceptable methods for surge protection for such systems.
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Additional review time will be required and the reviewing staff should become thoroughly familiar with the technical aspects of surge protection and its compatibility with the systems being protected.
The Inspection and Enforcement staff should also become familiar with the staff requirements to ascertain that installations are made in accordance with accepted design criteria.
Research to support our proposed action is currently under way (Refs. 34 and 37) to ascertain equipment tolerance to surges, surge characteristics, f
surge amplitudes, and frequency.
Also, funding for technical assistance may 1
be required to evaluate the level of protection afforded by present designs.
t 1.3.2 Other Government Agencies r
The activities of FAA, NASA, and DOE are being evaluated (Refs. 34 and 37) for the purpose of obtaining information on eff.orts expended by these agencies 1
fn addressing protection against electrical surge phenomena.
The information available at these agencies is being used as background for our effort.
There is no i,npact anticipated on these agencies as a result of OU! proposed action.
1.3.3 Industry A close scrutiny of surge protection for sensitive instrumentation, ade-quate insulation coordination, and sufficient conventional lightning protection for components exposed to direct lightning will reduce inadvertent failures of plant equipment and thus increase plant availability.
Surge protection 1s assumed an integral part of good engineering design.
Therefore, the differential cost for implementing all our proposed provfsfons for a 200,000-ampere level of protection at a 345 kV swftchyard will be as follows:
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- a.
Purchase cost of arresters for startup and unit auxiliary transformers and onsita switchgear at $25/kV:
- b.
Approxinate installation cost:
- c.
ApproxiB1ata cost for periodic surveillance par plant site at $25,000/tast for 40 years:
TOTAL
$31,000
$31,000
$175,000
$237,000 A more accurate cost evaluation could be made if the present protection level were known.
- 1. 3. 4 Puhl ic The value to the public will be in the direction of more reliable and safe nuclear power at a moderate financial cost.
1.4 Decision on the Proposed Action In view of the poten~ial risks associated with electrical surges on equip-ment, guidance should be issued to identify acceptable design criteria for consideration in the design and installation of nuclear systems important to safety.
- 2.
TECHNICAL APPROACH 2.1 Technical Alternatives Alternative methods for addressing surge pr~tection for redundant systems tmportant to safety that could limit co1D1ROn-mode failure~ resulting from high-energy surges on single transmission lines would require:
- a.
Strict implementation of electrical independence of offsite as well as onsite transmission and distribution systems to ensure that single surge events do not propagate to redundant trains of systems important to safety, or
- b.
Underground transmission of offsita power to plant systeas to Mini-mfze the likelihood of direct lightning strikes entering the plant distribution syste11s.
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2.2 Discussion and Comparison of Technical Alternatives 2.2.1 Redundant Offsfte Power Sources The implementation of redundant offsite power sources will limit the expo-sure of protection systems to certain common-mode failures resulting from surges tni~iated in (a) primary-to-secondary transformer failures,*(b) switching at the primary side of the transformer, and (c) lightning surges on the primary sfde of the transformer.
2.2.2 Underground Transmission Underground transmission will limit the direct strikes on the power trans-mission to plant auxiliaries. However, the common-110de failures associated with transformer failures and switching will not be eliminated with this alter-native design unless redundancy is also maintained fn the underground circuits.
2.3 Decision on Technical Approach The proposed action discussed in.Part 1 should be undertaken.
The tech-nical alternatives described fn ftea 2.2 are not feasible at this tiae in view af the limitations in independence requirements expressed in General Design Criterion 17 of Appendix A to 10 CFR Part 50.
- 3.
PROCEDURAL APPROACH 3.1 Procedural Alternatives Potential SD procedures that may be used to promulgate the proposed action and technical approach include the following:
Regulation Regulatory guide ANSI standard, endorsed by a regulatory guide Branch position NUREG report 15 l
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3.2 Value/Impact of Procedural Alternatives A NUREG fs not a viable alternative because ft will not contain the kind of guidance required to interpret the existing regulations. General Design Criterion 2 of Appendix A to 10 CFR Part 50 fs the regulation covering the sub-ject technical issue. Therefore, a regulatory guide is required to provide the staff acceptable methods for implementing this regulation.
At present there is no ANSI standard addressing surge protection for redund-ant systems important to safety that could limit common-mode failures resulting from high-energy surges on single transmission lines. However, a standard would e
be the most viable option for future consideration because the technical resources and experience of industry will provide a valuable contribution in the develop-11ent of consistent requirements for all plant designs.
A branch position will not be a viable alternative because of its limited scope and distribution.
3.3 Decision on Procedural Approach A regulatory guide should be prepared, and licensees as well as applicants should be requested to evaluate their surge protection and make appropriate modifications, if needed, to ensure minimum protection requirements.
- 4.
STATUTORY CONSIDERATIONS
- 4.1 NRC Authority Authority for this guide would be derived from the licensing authority and safety requirements of the At0111ic Energy Act through the NRC regulations, 1n particular, General Design Criterion 2 of Appendix A to 10 CFR Part 50, which requires, in part, that structures, systems, and components important to safety be designed to withstand natural phenomena.
The design bases for these struc-tures, systems, and components are requir~d to reflect (a) appropriate consid-eration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data 16
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4.2 Need for NEPA Assessment The proposed action is not a major action as defined by 10 CFR § 51.S(a)(lO),
and does not require an environmental impact statement.
- 5.
RELATIONSHIP TO OTHER EXISTING OR PROPOSED REGULATIONS OR POLICIES The proposed action is considered as part of the implementation of the requirements set forth in General Design Criterion 2 of Appendix A to 10 CFR Part 50.
There are no potential conflicts or overlaps with other agencies antici-pated as a result of the proposed action.
The Standard Format and Content of Safety Analysis Reports and the Stand-ard Review Plan should be revised to address the necessity for evaluation of surge protection for safety-related systems.
Backfitting requirements should be determined upon completion of the guide, with priority placed on plants located in areas with a high frequency of thun-derstorm activity.
- 6.
SUMMARY
AND CONCLUSIONS Failures in a number of installations {Refs. 1 through 17 and 19 through Z9) suggest that the high energies released by lightning have the potential to cause severe damage to sensitive systems important to protect the health and safety of the public. Therefore, a regulatory guide fdentffyfng a consistent set of design criteria for surge protection for nuclear power plants 1s appro-priate at thfs time.
However, a reevaluation ll8Y be necessary at a later date upon completion of the NRC, DOE, and the NASA-University of Florida Studies, which are aiming to more accurately define rise tf1Res 1 peak values, and fre-quency for lightning surges.
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- 7.
ALTERNATIVE REGULATORY POSITION During the preparation of the proposed guide; a differing technical position was developed by a staff member of the Division of Systems Safety, Office of Nuclear Reactor Regulation.
The staff member has expressed hfs technical position as a proposed alternative regulatory position, which is included as Attachment A to this draft value/1,npact statement.
Public review of, and cements on, the proposed alternative regulatory position are also requested.
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REFERENCES
- 1.
QUAD CITIES 2, "Offgas System Explosion (Lightning),u BBS-73-44, March 3, 1973.*
- 2. OYSTER CREEK 1, "Three Power Transformer Fuses for Diesel Generator No. 2 Were Blown (Lightning),
11 Rept. 73-13, June 21, 1973.
- 3.
VERMONT YANKEE 1, 110ffgas System Explosion (Lightning)," LER A0-73-16, June 12, 1973.
- 4.
FT. CALHOUN 1, "Loss of Offsfte Power (Lightning)," Rept. 73-4, September 26, 1973.
- 5.
FT. CALHOUN 1, "Loss of Off site Power (Lightning) 1 11 LER 50-285fl7-4, February 10, 1977.
- 6. MILLSTONE 1, 11Loss of Offsite Power (Lightning),
11 Rept. 71-12, June 25, 1971.
- 7.
MONTICELLO 1, 11loss of Offsite Power (Lfghtning), 11 Rept. 76-8, June 26, 1976.
- 8.
VERMONT YANKEE 1, "Process Computer and Miscellaneous Equipment Rendered Inoperable, Unit Scrammed (Lightning)," LER A0-74-11, July 5, 1974.
- 9.
YANKEE ROWE, "Actuation of Undercurrent Relays on Two Main Coolant Loops Resulted in Reactor Scram (Lightning), 11 Rept. 50-29/72-08, August 27, 1972.
- 10.
INDIAN POINT 2, Unusual Occurrence, PN0-77-126, July 14, 1977.
ll. PALISADES, Unusual Occurrence, PNO-n-170, September 24, 1977.
- 12. INDIAN POINT 2 and 3, Unusual Occurrence, PNO-n-172, September 26, 1977.
- 13.
FARLEY 1, "Loss of Offsite Power and Loss of Reactor Coolant Flow and Rod Position Indication (Lightning), 11 LER 77-012/0lT-O, September 16, 1977.
- 14.
FARLEY 1, "Loss of Offsite Power and Inadvertent Safety Injection (Lightning)," LER* 78-033/0lT-O, June 6 1 1978.
- 15.
RANCHO SECO, "Lightning on Main Transformer (Damaged Winding),"
January 14, 1978.
- 16. PILGRIM 1, "Loss of Offsite Power (Lightning)," LER 78-035-0lX-O, August 6, 1978.
Reports of events submitted to the NRC by licensees of nuclear power plants are available for inspection at or may be obtained by written request to the C0111aission 1s Public Document Room, 1717 H Street, NW., Washington, D.C.
Z0555.
19
- 17.
CRYSTAL RIVER 3, 11Meteorologfcal Instrumentation Failure (Lightning), 11
):
LER 78-036/03L-0, July 16, 1978.
- 18.
BEAVER VALLEY 1, "Transformer Failure, 0 LER 78-043/0lT-0, July 28, 1978.
- 19. MONTICELLO 1, 11Power to Reserve Transfomer Lost (Lfghtning), 11 Rept. LER 78-012/03L-0, June 16, 1978.
20..
VERMONT YANKEE 1, "Air Samplers Inoperable; Fuses Blown (Lightning),"
Rept. RO 78-18/3L, June 25, 1978.
- n. VERMONT YANKEE l, "Battery Charger CA-1 Failure; Stack Gas Monitoring System Failure; Motor Control Center 898 Failure (Lightning)," Repts.
78-13/3L, 78-14/3L, and 78-15/3L, June 19, 1978.
Z2.
INDIAN POINT 3, "Loss of Offsite Power (Lightning)," Rept. 77-3-5, May 6, 19n.
Z3.
VERMONT YANKEE 1, 110ffgas System Explosion (lightning), 11 August 31, 1973.
letter from R. T. Carlson (NRC, IE) to G. W. Reinmuth (NRC, IE) dated September 18, 1973.
Z4.
VERMONT YANKEE 1, "Off gas System Explosion (Lightning), 11 September 3,.
1973.
Letter from R. T. Carlson (NRC, IE) to G. W. Reinmuth (NRC, IE)
- 1~'
dated September 18, 1973.
ZS.
PEACH BOTTOM 2 and 3, "Stack Flow Transmitters Failure (Lightning), 11 Rept. 50-277-75-54 and A0-75-54.
z5_ 0. C. COOK 1, "Seismic Recorders Failure (Lightning}, 11 Rept. A0-50-315/
75-16, April 24, 1975.
- u. PEACH BOTTOM 2, "Blown Fuses 1n Stack Sampling System (ligh~ning), q Rept. 2-76-51/lT, July 17, 1976.
za..
PEACH BOTTOM 2, 11Stack Flow Recorders Failure (Lightning)," Rept. 2-76-45/
3L, June 20, 1976.
29-. -0.t. coo1r1--and 2,..,Loss ofllffsfte-Power (Lightning), 11 September r,
'1977.
Memoranduna from Executive Director for Operations to Co111111issioners Hendrie, Gilinsky, Kennedy, and Bradford dated September 6, 1977.
- 30. ANSI C62.l-1975, "Surge Arresters for Alternating-Current Power Circuits,"
American National Standards Institute, New York, N.Y.
3L ANSI C62.2-1969, "Guide for Application of Valve-Type Lightning Arresters for Alternating-Current Systems," American National Standards Institute, New York, N. Y.
- 32. Westinghouse Electric Corporation, Transmission and Distribution Refer-1, ence Book, East. Pittsburgh, PA, 1964.
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- 33.
R. H. Golde, "The Frequency of Occurrence and the Distribution of Lightning Flashes to Transmission Lines," American Institute of Electrical Engineers, Transactions, Vol. 64, pp. 902-910, 1945.
- 34.
H. Wayne Beaty, 11 Researchers Gather Lightning Data, 11 Electrical World, pp. 52-54, August 2, 1978.,
- 35.
A. Greenwood, Electrical Transients fn Power Systems, Wiley, New York, 1971.
- 36.
G. A. Brown, 11Joint Frequency Distribution of Stroke Current Rise and Crest Magnitude to Tr~nsmission Lines, 11 IEEE Power Engineering Convnfttee, Power Apparatus and Systems, No. F77017-7, January/February, 1978.
"51.
11 An Unusual Li ghtnfng Fl ash at Kennedy Space Center, 11 Science, Vo 1. 201, No. 4350, July 7, 1978.
- 38. J. C. Cronin, R. G. Colclaser, and R. F. Lehman, "Transient Lightning Overvoltage Protection Requirements for a 500 kV Gas-Insulated Substation, 11 IEEE, Power Engineering Committee, Power Apparatus and Systems, Vol. 97, No. 1, pp. 646-652, January/February 1978.
- 39. S. Szpor, "Comparison of Polish Versus American Lightning Records,"
IEEE Power Engineering Comnittee, Power Apparatus and Systems, Vol. 88, No. 5, pp. 646-652, May 1969.
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C C
ATTACHMENT A C.
REGULATORY POSITION Conformance with the principles and requirements of the following standards (as applicable) provides acceptable methods for complying with General Design Criteria 2 and 18 of Appendix A and*with Appendix B to 10 CFR Part 50 with respect to the design, qualification, construction, installation, and testing of systems and components providing protection against lightning for light-water-cooled nuclear power plants, subject to the following:
National Fire Protection Association (NFPA) No. 78-1975, ulightning Protection Code,t'* Part II, Protection of Buildings and Miscellaneou~
Property, and Part III, Protection of Structures Containing Flammable Liquids and Gasses; ANSI C62.1-1975, American National Standard, "Surge Arresters for Alternating-Current Power Circuits 11 ;***and ANSI C62.2-1969, American National Standard, 11Guide for Application of Valve-Type Lightning Arresters for Alternating-Current Systems. 11**
- 1.
PROTECTION OF STRUCTURES Lightning protection should be provided against direct strokes to struc-tures and exposed equipment installations, including containment, auxiliary buildings, off-gas stacks, fuel tanks, meteorological towers, and other compo-nents important for maintaining the safety of the plant.
The systems and equipment that provide this protection should conform with the principles and Copies may be obtained from the National Fire Protection Association, 470 Atlantic Avenue, Boston, Massachusetts 02210.
Copies may be obtained from the American National Standards Institute, 1430 Broadway, New York, New York 10018.
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requirements of NFPA No. 78-1975, subject to the following:
Sections 210l(d),
)
2102(c) through (i), and 2122(b) should be replaced by the following:
Aluminum should not be used as a conductor or structural support member.
Z.
PROTECTION OF SWITCHYARD EQUIPMENT AGAINST DIRECT STROKES Overhead ground wire shielding, augmented by air terminals and masts as necessary, should be-provided to protect all switchyard components of the power system (including overhead-line power circuits from the swftchyard to other plant structures) against direct-lightning strokes.
The complete shielding system, including the overhead components, interconnecting conductors, and ground-ing systera, should be designed and installed in accordance with established conservative design principles and practices of the electric utility industry, and the ground resistance should not exceed one ohm.
In addition, the design should provide a shielding effectiveness such that shielding failure stroke current (!max' the current in a lightning strike that bypasses the shielding I
and strikes a live component directly) will not exceed 15,000 amperes as defined I
by the rel at ion
- r
=
h + Y
= 7.1 I~ax* 75 s max 2(1 - sin 85 )
m where the maximum strike distance (r5 max> is a function of shield wire height (h), live component height (y), and shield angle (85 ). All dimensions are in meters; Imax is in kA.
- 3.
PROTECTION OF TRANSMISSION LINES AGAINST DIRECT STROKES Overhead ground wire shielding should be provided to protect all transmis-sfon lines terminating in the switchyard against direct lightning strokes.
Thfs shielding system should be provided over the entire length of the line; however.* ft should definitely be provided for a minimU11 distance of one-half Details for determination of shielding effectiveness using this method are con-tained in a paper by G. W. Brown, HLfghtning Performance - I Shielding Failures Si111plified 1 11 IEEE Transactions on Power Apparatus and Systems, Vol. PAS-97 1 No.
January/February 1978.
This paper specifically addresses transmission line shielding, but the methodology fs readily applicable to switchyard shielding.
2
.)
C C
ile from the switchyard terminus of the lines.
The complete shielding system including overhead ground wire, tower components, interconnecting conductors, and tower grounding system should be designed and installed in accordance with established conservative design principles and practices of the electric utility industry.
The overhead ground wires should be carried into the switchyard and tied to the switchyard ground system.
In addition, for each transmission line for a minimum of one-half mile from the switchyard, the design should provide a shielding effectiveness such that shielding.failure stroke current (Imax>
will not exceed 15,000 amperes as defined in Regulatory Position C.2 above.
- 4.
SURGE PROTECTION FOR SWITCHYARD TERMINAL EQUIPMENT Station-type surge (lightning) arresters should be installed on both the high-and low-voltage sides of all unit and startup or station service trans-formers in accordance with the following provisions:
4.1. The arresters should conform to all the applicable requirements of ANSI C62.l-1975, including design, construction, and qualification testing with the following exception:
In Section 7.5.1, High Current Short-Duration Test, the test surge current wave shape should be at }~ast 8 x 20 µsec (instead of the less conservative options also permitted by the standard).
4.2. The arresters should be provided with a discharge counter and a leakage grading current meter to facilitate surveillance and assessment of the functional capability of the installed arrester.
4.3. The arresters should be selected and applied in accordance with con-servative application of the principles and methodology contained in ANSI C62.2-1969, including the following:
4.3.1. Insulation coordination should be performed at a discharge current of 20,000 amperes minimum.
(See Sections 3.2.1 and 3.2.2 of ANSI C62.2.)
4.3.2. The protective ratio (margin) for. i11pulse coordination should be 1.2 inimum; for switching surge coordination, it should be 1.15 minim1.111.
(See Section 3.5.1 of ANSI C62.2.)
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- 5.
SURGE PROTECTION FOR CLASS IE SWITCHGEAR
)
Station-type surge arresters should be provided for all Class 1E switchgear components that are connected to exposed overhead lines either directly or through a short length of cable. These arresters should confom to the following:
5.1. The arresters should be selected and applied in conformance with Regu-latory Positions C.4.1, C.4.2, and C.4.3 above.
5.2. The arresters should be installed in the circuit upstrea11 of the feeder breaker; and the physical arrangement should be such as to preclude damage to the switchgear fn the event of arrester failure.
- 6.
PERIODIC SURVEILLANCE OF LIGHTNING PROTECTION SYSTEMS Periodic surveillance of lightning protection systems and components addressed in Regulatory Positfons_C.1 through C.5 should be performed, consistent wfth other planned periodic surveillance programs for outdoor electrical fnstallatfons)
As a minfmun, this periodic surveillance should include:
6.1. Visual inspection augmented by conductor continuity tests and ground resistance measurements as deemed necessary to ascertain the functional capability of the systems provfdfng protection.against direct strikes to structures, switchyard components, and transmission lines.
6.2. Visual fnspectfon of the surge arrester installation to detenaine ff there fs evidence of physical damage, surface contaafnatfon, or other deteriora-tiory fn the arrester or fts line and ground connections that could result fn failure of surge protection.
The visual inspection should be augmented by con-ductor continuity tests and ground resistance measurements as deemed necessary to ascertain the functional capability of the surge arrester installations.
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)