ML13317A805
| ML13317A805 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/30/1981 |
| From: | Udy A EG&G Idaho |
| To: | Scholl R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13317A806 | List: |
| References | |
| CON-FIN-A-6425, TASK-08-04, TASK-8-4, TASK-RR EGG-EA-5648, NUDOCS 8201110005 | |
| Download: ML13317A805 (11) | |
Text
EGG-EA-5648 NOVEMBER.1981i SYSTEMATIC EVALUATION PROGRAM, TOPIC VIII-4, ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT,
- 2.
SAN ONOFRE NUCLEAR STATION, UNIT NO. 1 A.
C.,
Udy.
U.S.- Department of Energy Idaho Operations Office
- Idaho National Engineering Laboratory FI N.
A6425___
Ud ThsiPnifra eotItne o uea rlmnr rwrigdcmn PeAd frte UreS.
e Nuler Rheuaor onnsso Under DOE Contract No. DE-ACO7-76ID01570.,
FIN No. A6425 8211005 2i31 EEG Idaho
..PDR ADOCK 0500020 P.
PeGs Idaho. Inc.
M EG&G-398 INTERIM REPORT Accession No.
Report No.
EGG-EA-5648 Contract Program or Project
Title:
Electrical, Instrumentation, and Control Systems Support for the Systematic Evaluation Program (II)
Subject of 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 Date 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.
Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. DE-AC07-76IDO1570 NRC FIN No.
A6425 INTERIM REPORT
0095J SYSTEMATIC EVALUATION PROGRAM TOPIC VIII-4_
ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT SAN ONOFRE NUCLEAR STATION, UNIT NO. 1 Docket No. 50-206 November 1981 S. E. Mays A. C. Udy 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.
11t
CONTENTS
1.0 INTRODUCTION
2.0 CRITERIA.............
3.0 DISCUSSION AND EVALUATION..........................
2 3.1 Typical Low-Voltage (0-1000 V) Penetration (WPC-23)......
3.1.1 Low-Voltage Penetration Evaluation...........
3 3.2 Typical Medium-Voltage (>1000 V) Penetration.............
3 3.2.1 Medium-Voltage Penetration Evaluation..............
3 3.3 Typical DC Penetration.........
4 3.3.1 DC Penetration Evaluation.....................
4
- 4.
SUMMARY
4
- 5.
REFERENCES..........
4 4
_SYSTEMATIC EVALUATION PROGRAM TOPIC VIII-4 ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT SAN ONOFRE NUCLEAR STATION, UNIT NO. 1
1.0 INTRODUCTION
This review is part of the Systematic Evaluation Program (SEP), Topic VIII-4
-The objective ofithis 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 overload protection devices.
General Design Criterion 50, "Containment DesignBasis" of.Appendix A, "General Design Criteria for Nuclear Power.Plants" to10 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 the staff.
Specifically, this review will examine the protection of typical e ec 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 continuous 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."
This paragraph is augmented by Regulatory Guide 1.63, Para-.
graph C-1 -- "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 maximum duration of rated short circuit current shall be the maximum timethat the conductors of a circuit can carry rated short circuit current based on the operating'time of the backup protective device or apparatus, durng which the electrical integrity may be lost, but for which the penetration assembly shall maintain containment integrity."
3.0 DISCUSSION AND EVALUATION In thi evalationthe r
In this evaluation, the results of typical containment penetrations being at LOCA temperatureinitially 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 400aF (2040C)..
before seal failure for the low voltage penetration,3 a temperature limit of 842oF (450*C) for the medium voltage penetration, and a temperature limit of 300*F (149 0C) for the dc penetration based on the melting point of the material comprising the hermetical seal (manufacturer test for the low voltage penetration). Maximum short circuit current available (Isc was provi ed by Southern California Edison for a three-phase bolted fault.
Rated current*(Ir) for each penetration was also provided.
To evaluate 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 A2
[T2+234]
1.0297 log T1+234 (Formula 1) where t
=
time in seconds.
current in amperes-_
A
=
conductor area in circular mils T
=
initial temperature (133 0C LOCA condition),
T2
=
maximum penetration temperature before failure.
2.
Thi.s 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 an7'-_
In evaluating the capability of the penetration to withstand LOCA7::
temperature.with a short circuit current, Formula 1 was used to calculate the time required to heat the conductor from the LOCAtemperature 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 (0-100V) 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 2040C. 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 in-containment compongnts are environmentally qualified for class 1E ser vice, 5 NRC position 2 can be applied. This position requires only-a single class 1E circuit breaker for penetration protection where all com ponents served by that penetration are qualified to class 1E requirements.
3.2 Typical Medium-Voltage (> 1000 V)Penetration. Penetration number 381Ay has been identified by Southern Californa 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 transformer will operate to clear this level of fault current in 0.35 sec ond. At all levels of fault current all of these protective devices will clear the fault in sufficient time to prevent damage to the hermetic seal of the penetration.
3.2.1 Medium Voltage Penetration Evaluation. Penetration JB1AO is designed and utilized within the criteria described in Section 2.0-of this report.
.3
3.3 Typical DC Penetration._ Penetration number EPC-6 has been iden tified by Southern California Edison as being typical of direct current i penetrations. This penetration is used to provide 125 V dc power to Ener 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 trcuit 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 JB1AO 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. Moody to Director, Office of Nuclear Reactor Regulation, NRC, "Systematic Evaluation Program," June 17, 1981.
- 4. IPC&A Publication P-32-382, "Short Circuit Characteristics of Insu lated Cable."
4 ENCLOSURE E SEP TOPIC VIII-4 ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT I.
INTRODUCTIO*
The safety objective of Topic VIII-4, "Electrical Penetrations of Reactor, Containment," is to assure that all electrical penetrations in the contain ment structure are designed not to fail from electrical faults during a high energy line break..
As part of the Systematic Evaluation Program (SEP) the NRC staff performed an audit, comparing sample containment electrical penetrations in SEP facilities with current licensing criteria for protection against fault and overload currentsfollowing a postulated accident.
II.
REVIEW CRITERIA The review criteria are presented in Section 2.0 of EG&G Report EGG-EA-5648, "Electrical Penetrations of the Reactor Containment."
In addition, in licensing new plants, the staff requires compliance with the recommendations of Regulatory Guide 1.63 or an acceptable alternative method.
For each containment electrical penetration,.the protective systems should provide primary and backup circuit protection devices to orevent a single.
failure in conjunction with a circuit overload from impairing containment integrity. The primary and backup protection devices must have trip time vs. current response characteristics which assure protection against penetra tion failure.
The protection devices are to be periodically tested to verify trip setpoints and adequacy of response.
No single failure should allow excessive currents in the penetration conduc tors that will degrade the penetrations'seals. Where external control power is used for actuating the protection systems the power for primary and backup breakers should be derived from separate sources. Overcurrent signals for tripping primary and backup system devices should be electrically in dependent and physically separated.
Ill.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under the related Topic 111-12, Environmental Qualification.
The related topic report contains the acceptance criteria and review guidance for its subject matter.
-2 Theoretically, there are no safety topics that are dependent on the present topic information for their completion; however, the results of the present topic have a definite impact upon the capability of equipment inside of containment to function after a high energy line break.
IV. REVIEW GUIDELINES The review guidelines are presented in Section 3.0 of EG&G Report EGG EA-5648. "Electrical Penetrations of the Reactor Containment.
V. EVALUATION As noted in the EG&G Report on this topic, with a LOCA environment inside containment, the backup protection for some penetrations does not conform to the current licensing criteria. Since the licensee has not evaluated backup protection for electrical penetrations as proposed by our July 30, 1981 letter, the staff must assume that the alternative approaches recommended do not provide adequate protection.
VI.
CONCLUSIONS As a result of our review, we have concluded that a suitable program is not in place to assure that all penetrations conform to current licensing criteria.
Furthermore, we conclude that -no other equivalent protection exists.
The staff proposes that the design of backup protection-for most low voltage (less than 1000 v.) ac and all dc penetrations be modi fied to provide adequate, coordinated protection against all postulated faults inside of containment assuming the failure of the primary protec tion device.
As noted in our July 30, 1981 letter, removal of power, tripping on ESF initiation, and provision of additional interrupting devices are accep table alternatives.,