ML19341D654
| ML19341D654 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/31/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| TASK-08-04, TASK-8-4, TASK-RR LSO5-81-03-076, LSO5-81-3-76, NUDOCS 8104080346 | |
| Download: ML19341D654 (7) | |
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Docket No. 50-155 LS05 03-076 t
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Mr. David P. tioffman Nuclear Licensing Administrator f.
Consumers Power Company
\\ D.' W I 0 212 West Michigan Avenue Jackson, Michigan 49201
Dear Mr. Hoffman:
SUBJECT:
SEP TOPIC VIII-4, ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT (BIGROCKPOINT)
Draft Technical Evaluation Reports (TER) on Topic VIII-4 have been prepared and fomarded to all SEP Licensees for coment. Coments from some licensees l
(e.g., Northeast Utilities letters dated August 29, 1980 and January 29, 1981) indicated concern with the model used and assumptions made in the initial conditions and material properties. Unfortunately, most respondents have not provided sufficient technical information nor detailed schematics to support their coments.
Our audit calculations failed to estabitsh that the fault current protection for containment electrical penetrations in SEP facilities is generally adequate.
Tnis does not necessarily mean that the protection is inadequate. Our calcula-l tions were simplified and conservative so that there is room to improve the result by using more realistic models.
In addition, licensee comments have l
indicated that there may be some errors in our calculations. Nevertheless, our audit did not put the matter to rest and, thus, you are requested to evaluate the ' adequacy of all electrical pen _etrations in your facility in accordance with the enclosed position.
Generally, where needed, our position calls for more realistic calculations l
than were used in our audit.
In relation to current licensing criteria, it provides relief from the need for redundant circuit protective devices in certain instances and specifically provides for using fuses as an alterna-tive to circuit breakers. Other straightfomard alternatives such as deenergizing circuits are also provided for.
If any instances arise where your calculations cannot demonstrate circuit protection in accordance with our position, you are requested to inform us of your intended corrective actions.
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< In order to complete our review of Topic VIII-4, please provide a report describing the calculations performed and criteria used for evaluating the penetrations for the specific circuits identified in the staff's previous report within 60 days of receipt of this letter.
The report as a minimum should address the following items:
1.
Protection for low voltage penetrations.
2.
Backup protection for de penetrations.
The requested information will be used to revise our topic Safety Evaluation Report and will be used in the preparation of the integrated assessment for your plant.
Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
As stated cc w/ enclosure:
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NUCLEAR REGULATORY COMMISSION 3.
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March 31, 1981 Docket No. 50-155 LS05 03-076 l
Mr. David P. Hoffman Nuclear Licensing Administrator Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201
Dear Mr. Hoffman:
SUBJECT:
SEP TOPIC VIII-4, ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT (BIG ROCK P0 INT)
Draft Technical Evaluation Reports (TER) on Topic VIII-4 have been prepared and forwarded to all SEP Licensees for coment. Coments from some licensees (e.g., Northeast Utilities letters dated August 29, 1980 and January 29, 1981) indicated concern with the model used and assumptions made in the initial conditions and material properties. Unfortunately, most respondents have not provided sufficient technical information nor detailed schematics to support their comments.
Our audit calculations failed to establish that the fault current protection ll for containment electrical penetrations in SEP facilities is generally adequate.
l This does not necessarily mean that the protection is inadequate. Our calcula-l tions were simplified and conservative so that there is room to improve the result by using more realistic models.
In addition, licensee comments have indicated that there may be some errors in our calculations. Nevertheless,
our audit did not put the matter to rest and, thus, you are requested to evaluate tne acequacy of all electrical penetrations in your facility,
in accordance with the enclosed position.
Generally, where needed, our position calls for more realistic calculations than were used in our audit.
In relation to current licensing criteria, it provides relief from the need for redundant circuit protective devices in certain instances and specifically provides for using fuses as an alterna-tive to circuit breatars. Other straightfordard alternatives such as deenergizing circuits are also provided for.
If any instances arise where your calculations cannot demonstrate circuit protection ir. accordance with our position, you are requested to inform us of your intended corrective actions.
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In order to complete our review of Topic VIII-4, please provide a report
- I describing the calculations performed and criteria used for evaluating the penetrations for the specific circuits identified in the staff's previous report within 60 days of receipt of this letter.
l The report as a minimum should address the following items:
l.
Protection for low voltage penetrations.
2.
Backup protection for dc penetrations.
The requested information will be used to revise our topic Safety Evaluation Report and will be used in the preparation of the integrated assessment for your plant.
Sincerely,
,ng DenE E}i.'Crutchfield, ie Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
As stated cc w/ enclosure:
See next page I
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Mr. David P. Hoffman Cc Mr. Paul A. Perry, Secretary U. S. Environmental Protection Consumers Power Cocpany Agency 212 West Michigan Avenue Federal Activities Branch Jackson, Michigan 49201 Region V Office ATTN: EIS COORDINATOR Judd L. Bacon, Esquire 230 South Cuarborn Street Consumers Power Cocpany Chicago, Illinois 60604 212 West Michigan Avenue Jackson, Michigan 49201 Herbert Grossman, Esq., Chairman Atomic Safety and Licensing Board Joseph Gallo, Esquire U. S. Nuclear Regulatory Commission Isham, Lincoln & Beale Washington, D. C.
20555 1120 Connecticut Avenue Room 325 Dr. Oscar H. Paris Washington, D. C.
20036 Atomic Safety and Licensing Board U. 5. Nuclear Regulatory Commission Peter W. Steketee, Esquire Washington, D. C.
20555 505 Peoples Building Grand Rapids, Michigan 49503 Mr. Frederick J. Shon Atomic Safety and Licensing Board Alan S. Rosenthal, Esq., Chairman U. S. Nuclear Regulatory Commission Atomic Safety & Licensing Appeal roard Washington, D. C.
20555 U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Big Rock Point Nuclear Power Plant ATTN: Mr. C. J. Hartman Mr. John O'Neill,11 Plant Superintendent Route 2, Box 44 Charlevoix, Michigan 49720 Maple City, Michigan 49664 Christa-Maria Charlevoix Public Library Route 2, Box 108C 107 Clinton Street Charle voi x,' Michi gan 49720 Charlevoix, Michigan William J. Scanlon, Escuire 2034 Pauline Boulevard Chai rman County Board of Supervisors Ann Arbor, Michigan 48103 Charlevoix County Charlevoix, Michigan 49720 Resident Inspector Big Rock Point Plant Office of the Governor (2) c/o U.S. NRC Room 1 - Capitol Building RR13, Box 600 Lansing, Michigan 48913 Charlevoix, Michigan 49720 Director, Criteria and Standards Mr. Jim E. Mills Route 2, Box 108C Division Office of Radiation Progracs Charlevoix, Michigan 49720 (ANR-460)
U. S. Environmental Protection Thomas S. Moore Atomic Safety & Licensing Appeal Board Agency Washington, D. C.
20460 U. S. Nuclear Regulatory Commission Washington, D. C.
20555
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I Mr. David P. Hof fman CC Dr. John H. Buck l
Atomic Safety and Licensing Appeal Board U. S. Nuclear Regulatory Commi3sion Washington, D. C.
20555 l i Ms. JoAnn Bier 204 Clinton Street I
Charlevoix, Micnigan 49720 Herbert Sem:'el Council for Cnr1sta *. aria, et al.
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Urban Law Institute Antioch School of Law 263316tn St reet, N. W.
Washington, D. C.
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ENCLOSURE POSITION ON PROTECT]ON OF CONTAINMENT ELECTRICAL PENETRATIONS AGAIN51 r ALLURES CAUSED Bi FAULT AND OVERLOAD CURRENTS FOR SEP PLANTS Introduction As part of the Systematic Evaluation Program (SEP) the WRC staff performed an audit, conparing sample containment electrical penetrations in SEP facilities with current licensing criteria for protection against fault and overload l
currents following a postulated accident. The simplified and conservative model usec did not show that the SEP facilities meet current licensing criteria nor did it show the existing circuit protection to be adequate. Accordingly, the SEP licensees 4rt requested to demonstrate, using sore realistic calcula-l tions where necessary, that the circuit protection is adequate in accordance with the position described below.
Back erotmd In licensing new plants, the staff requires cor:;1iance with the recocrnendations of Regulatory Guide 1.63 or an acceptable alternative method.
l For each containment electrical penetratier., tne rctective systems provide primary and backup circuit protection devices to prevent a single failure in con-junction with a circuit overload from impairing containment integrity. The primary and backup protection devices have trip time vs. current response charac-teristics which assure protection against penetration failure.
The protection devices are periodicallj tested to verify trip setpoints and adequacy of response.
No single failure allows excessive currents in the penetration conductors which will degrade the penetration seals. Where external control power is used for actuating the protection systems the power for primary and backup breakers are derived from separate sources. Overcurrent signals for tripping primary and i
l backup system devices are electrically independent and physically separated.
Staff Audit The safety objective of SEP Topic VIII-4, " Electrical _ Penetrations of Reactor Containment," is to assure that all electrical penetrations in the containment structure are designed not to fail from electrical faults during a high energy line break (LOCA or secondary system line break).
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I We have perforred preliminary evaluations, on a conservative basis, cf th: f ault current protection for three sa:ple containment electrical penetrations for each of the eleven SEP plants. The entire penetration was assumed to be initially at the peak calculated LO~A te perature. Then, for a given f ault current, tne time to heat the wire to the limiting raterial terperature (usually the celting point of the seal raterial) was calculated.
This time was comared to the tice for the protective device (s) to interrupt the fault current.
On this basis, several penetrations exceed limiting te peratures if the prica y prote: tion device f ails.
Others do so without postulating prirary device failure.
Tw0 of the sarple penetrations even have melting terperatures less than the peak I
LO*.A te perature and thus ex:eed the limits of this codel even if there is no f ault current.
(References I through 11)
This does not necessarily mean that the penetrations would actually fail.
The analysis was conservative, particularly in assuming that the penetration 1 mas initially r. the pe2L calculated contain:ent te.perature. Tne penetratierts would not reach such a te cerature folicwing an accident.
In addi* ion, licensee co. rents have indicated that there ray be so e errors in the calculations.
(For exacple, Northeast Utilities letter date:: Aug.:st 29,1950 Do:Let ho. 50-245, providing co rents on the staff calculations for Millstone. Unit 1). Ne ver*.heless,
this audit clearly did not put the ratter to rest.
Position Each SEP licensee is requested to evaluate the adequacy of the existing fault current protection for containrent ele:trical penetrations in accordan:e with the position discussed in ecre detail below and to propose recedies where neeoed in order to neet the position.
1.
The basic requirement of Regulatery Guide 1.63 that all penetration c.ircuits, Class IE or non-Class IE, be provided with overcurrent prote: tion in conforr.ance with the redundancy anc testability requirements of IEEE Std 279-1971 should l
be met; 2.
A single circuit breaker to protect a penetration serving a Class IE circuit or a non-safety circuit containing only components that are qualified to Class IE requirements is acceptable provided that each component of such circuit is qualified to the accident environment; 3.
A circuit whose loads inside containment are not required to mitigate the l
consequences of accidents may be automatically disconnected from its power source on receipt of an accident signal or it may be maintained dcenergized by positive means such as those outliend in Brancn Technical Position ICSB I
18 (PSB) of Appendix 8A to the Standard Review Plan whenever contain:.:ent integrity is required.
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,. Notes i
Tor the purpose of evaluating the adequacy of protection for containrent protection, f aults should be postulated up to a bolted cabic fault inside contain ent at the penet. ration (a bolted three phase f ault for three phase circuits). The prir.ary protection device should have a trip tirne vs. current response characteristic that assures against penetration failure under all fault conditions.
Circuit breakers should be tested periodically to verify their trip setting value and response tirm.
Breakers should be designed to interrupt the sexinum possible fault current for the circuit or backup protection fast response current limiting fuses should be provided.
In addition, fuses r.ay be used Un lieu of circuit breakers as protective devices.
Where fuses are used, do:urentation of their response characteristics derived f rom production testing shosld be available for audit.
It is acceptable to use less conservative rodels than were used in our preliminary evaluations provided that they address f ault currents up to bolted faults and still provide reasonable assuran:e that the penetration will not f ail.
For exarple, a rore realistic initial terperature of the cor.tainrent penetration could be determined rather than assuming the penetration has reached the peal calculated containrent att:csphere te:p-e rature.
Circuits may be modified to redu:e the shcrt circuit current to acceptable values by the use of current lir.iting devices (such as resistors, isolation transformers, and changing transformer taps) external to the containment, l
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