ML20039G814
| ML20039G814 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/30/1981 |
| From: | Udy A EG&G, INC. |
| To: | Scholl R Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6425, TASK-08-04, TASK-8-4, TASK-RR EGG-EA-5648, NUDOCS 8201190174 | |
| Download: ML20039G814 (9) | |
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This is an informal report intended for use as a preliminary or working document Prepared for the U.S. Nuclear Regulatory Commission Under DOE Contract No. DE-AC07-761001570 FIN No. A6425 b O E b idaho I74 811130 p
h EGsG.....-
FORM EG&G 398 c ii m INTERIM Rl! PORT Accession No.
EGG-EA-5648 Report No.
- Contract Program or Project Tille:
i Electrical, Instrumentation, and Control Systems Support for the Systematic Evaluation Program (II)
Subject cf this Document:
Systematic Evaluation Program, Topic VIII-4, Electrical Penetrations of Reactor Containment, San Onofre Nuclear Station, Unit No. 1 Type of Document:
Informal Report Author (s):
A. C. Udy D te of Document:
November 1981 Responsible NRC Individual and NRC Office or Division:
Ray F. Scholl, Jr., Division of Licensing This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes, this document should not be considered final.
EG&G Idaho, Inc.
i Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. ggC07 76tD01570 NRC FIN No. A INTERIM REPORT 1
0095J l
SYSTEMATIC EVAllMTION PROGRAM l
i TOPIC VIII-4 ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT SAN ONOFRE NUCLEAR STATION, UNIT NO. 1 l
l Docket No. 50-206 l
November 1981 S. E. Mays A. C. Udy i
i l
l l
l l
l l
i 10-27-81
ABSTRACT This SEP technical evaluation, for the San Onofre Nuclear Station, Unit No. 1, reviews the capability of the overcurrent protection devices to protect the electrical penetrations of the reactor containment for postu-lated fault conditions concurrent with an accident condition.
FOREWORD This report is supplied as part of the " Electrical, Instrumentation, and Control Systems Support for the Systematic Evaluation Program (II)"
being conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Licensing by EG&G Idaho, Inc.,
Reliability & Statistics Branch.
The U.S. Nuclear Regulatory Commission funded the work under the authorization B&R 20-10-02-05, FIN A6425.
/
11 u
9A CONTENTS 1
1.0 INTRODUCTION
~
1 2.0 CRITERIA........................................................
?
3.0 DISCUSSION AND CVALUATION.......................................
3.1 Typical Low-Voltage (0-1000 V) Penetration (WPC-23).......
3 3.1.1 Low-Voltage Penetration Evaluation.................
3 3
3.2 Typical Medium-Voltage (>1000 V) Penetration..............
3.2.1 Medium-Voltage Penetration Evaluation..............
3 4
3.3 Typical DC Penetration....................................
3.3.1 DC Penetration Evaluation..........................
4 4
4.
SUMMARY
4 5.
REFERENCES......................................................
e 0
iii
SYSTEMATIC EVALUATION PROGRAM TOPIC VIII-4 ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT SAN ON0FRE NUCLEAR STATION, UNIT NO. 1
1.0 INTRODUCTION
O This review is part of the Systematic Evaluation Prog' ram (SEP), Topic VIII-4. The objective of this review is to determine the capability of the electrical penetrations of the reactor containment to withstand short cir-cuit conditions *of the worst expected transient fault current resulting from single random failures of circuit overloac protection devices.
General Design Criterion 50, " Containment Design Basis" of Appendix A,
" General Design Criteria for Nuclear Power Plants" to 10 CFR Part 50 requires that penetrations be designed so that the containment structure can, without exceeding the design leakage rate, accommodate the calculated pressure, temperature, and other environmental conditions resulting from any loss-of-coolant accident (LOCA).
IEEE Standard 317, " Electric Penetration Assemblies in Containment Structures for Nuclear Power Generating Stations", as augmented by Regula-tory Guide 1.63, provides a basis of electrical penetrations acceptable to l
the staff.
Specifically, this review will examine the protection of typical elec-trical penetrations in the containment structure to determine the ability of the protective devices to clear faults prior to exceeding the penetra-tion design rating under LOCA temperatures.
2.0 CRITERIA IEEE Standard 317, " Electric Penetration Assemblies in Containment Structures for Nuclear Power Generating Stations" as supplemented by Nuclear Regulatory Commission Regulatory Guide 1.63, " Electric Penetration Assemblies in Containment Structures for Light-Water-Cooled Nuclear Power Plants" provides the basis acceptable to the NRC staff. The following criteria are used in this report to determine compliance with current licensing requirements:
(1)
IEEE Standard 317, Paragraph 4.2.4 - "The rated short circuit current and duration shall be the maximum short circuit current in amperes that the conductors of a circuit can carry for a specified duration (based on the operating time of the primary.
overcurrent protective device or apparatus of the circuit) fol-lowing continuous operation at rated contiruous current without the temperature of the conductors exceeding their short circuit design limit with all other conductors in the assembly carrying their rated continuous current under the specified normal environmental conditions."
l
This paragraph is augmented by Regulatory Guide 1.63, Para-graph C "The electric penetration assembly should be designed to withstand, without loss of mechanical integrity, the maximum possible fault current versus time conditions that could occur given single random failures of circuit overload protection devices."
(2)
IEEE Standard 317, Paragraph 4.2.5 - "The rated maximuin duration of rated short circuit current shall be the maximum time that the conductors of a circuit can carry rated short circuit current based on the operating time of the backup protective device or apparatus, during which the electrical integrity may be lost, but for which the eenetration assembly shall maintain containment integrity."
3.0 DISCUSSION AND EVALUATION In this evaluation, the results of typical containment penetrations being at LOCA temperature initially concurrent with a random failure of the circuit protective devices will be analyzed.
Southern California Edison provided information (References 1 and 2) on typical penetrations. No evaluation of the data was provided.
Southern California Edison has established a temperature limit of 400*F (204*C) before seal failure for the low voltage penetration,3 a temperature limit of 842*F (450 C) for the medium voltage penetration, and a temperature limit of 300*F (149*C) for the dc penetration based on the melting point of the material comnrising the hermetical seal (manufacturer test for the low Maximum short circuit current available I was provi ed by Southern California Edison for a three-phase bolted (fE t.
volta 0epenetration).
Rated current (Ir) for each penetration was also provided.
To evaluat'e the ability of the penetration to withstand a LOCA environ-ment, the following formula was used to determine the time allowed before a short circuit would cause the penetration to heat up to the temperature limit.4
-A-2+234-2 t=
.0297 log (Formula 1) 234-5 where time in seconds t
=
6 current in. amperes I
=
conductor area in circular mils A
=
initial temperature (133 C, LOCA condition)
Tj
=
1' maximum penetration temperature before failure, i
T2
=
i 2
This is based on the heating effect of the short circuit current on the conductor and does not take into account heat losses of the conductor.
For times less than several seconds, this heat loss is negligible.
In evaluating the capability of the penetration to withstand LOCA temperature with a short circuit current, Formula 1 was used to calculate e
the time required to heat the conductor from the LOCA temperature to pene-tration failure temperature for currents from rated current to maximum short circuit current in 20% increments. Times for the primary and secon-dary overcurrent devices to interupt these fault currents were determined.
3.1 Typical Low-Voltage (0-1000V) Penetrations (WPC-23).
This penetration provides 480 V ac power to Residual Heat Removal Pump B, and uses 4/0 conductors that have a rated continuous current capacity of 188 amps. The temperature limit for the hermetic seal of this penetration is 204*C. SCE has calculated the maximum available short circuit current to be 27,530 amps.
Using formula 1, this current can be carried for 0.135 second before the penetration conductor temperature exceeds the 400'F test limit. The primary circuit breaker responds within this time, while the secondary circuit breaker does not. For smaller fault currents, both the allowable time before the hermetic seal is damaged increases and the fault clearing time increases. At all fault current levels, the primary breaker cleared, while the secondary breaker did not clear the fault within the allowable time.
3.1.1 Low-Voltage Penetration Evaluation. Since all vice,gtainment compongnts are environmentally qualified for class lE ser-in-co a NRC position 20 can be applied. This position requires only a single class lE circuit breaker for penetration protection where all com-ponents served by that penetration are qualified to class lE requirements.
3.2 Typical Medium-Voltaae (> 1000 V) Penetration.
Penetration number JBlA0 has been identified by Southern California Edison as'being typical of medium-voltage penetrations. This penetration provides 4160 V ac power to Reactor Coolant Pump A.
SCE determined that the maximum short circuit current for the penetration is 43,825 amperes, and at this current, the penetration limiting temperature is reached in 4.18 seconds. Rated current is 565 amps and the penetration uses 500 MCM cable.
The primary breaker will operate to clear this fault current in 0.1 second. The secondary breaker will operate to clear the same level of fault current in 0.95 second. The secondary breaker used with the start up i
transformer will operate to clear this level of fault current in 0.35 sec-4 i
ond. At all levels of fault current all of these protective devices will I
clear the fault in sufficient time to prevent damage to the hermetic seal of the penetration.
4 i
3.2.1 Medium Voltage Penetration Evaluation.
Penetration JBlA0 is designed and utilized within the criteria described in Section 2.0 of this report.
4 3
4
3.3 Typical DC Penetration.
Penetration nunher EPC-6 has been iden-tified by Southern California Edison as being typical of direct current penetrations. This penetration is used to provide 125 V de power to Emer-gency RCP Thermal Cooling Pump.
The maximum available short circuit cur-rent has been determined by SCE to be 5953 amps. At this current the penetration temperature limit will be exceeded in 0.27 second. The rated current is 116.7 amps and the penetration uses 2/0 cable.
The primary breaker will operate to interrupt any short circuit cur-
~
rent prior to reaching the 149 C penetration temperature limit from LOCA temperature initially. The secondary breaker will not operate to prevent the penetration seal temperature limit from being exceeded for any fault current.
3.3.1 DC Penetration Evaluation. Penetration EPC-6 does not meet current requirements of RG 1.63 and IEEE Std. 317 for any short cir-cuit conditions with a failure of the primary breaker.
4.0
SUMMARY
From LOCA temperatures initially, penetrations WPC-23 and JBlA0 meet current licensing requirements for a short circuit fault and random failure of the primary circuit breakers. Penetration EPC-6 does not.
5.0 REFERENCES
1.
SCE letter, J. G. Haynes to Director of Nuclear Reactor Regulation, NRC, dated June 15, 1979.
2.
SCE letter, W. C. MooJy to Director, Office of Nuclear Reactor Regulation, NRC, " Systematic Evaluation Program," June 17, 1981.
3.
Telecon, A. C. Udy, EG&G Idaho, Inc., T. Lawerence, SCE, October 23, 1981.
4.
IPC&A Publication P-32-382, "Short Circuit Characteristics of Insu-lated Cable."
5.
Telecon, A. C. Udy, EG&G Idaho, Inc., T. Lawerence, SCE, October 27, 1981.
6.
NRC letter to SCE, "SEP Topic VIII-4," March 30, 1981.
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