ML18046A723
| ML18046A723 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/15/1981 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-08-04, TASK-8-4, TASK-RR NUDOCS 8106180170 | |
| Download: ML18046A723 (5) | |
Text
'1. -'-\\
p consumers Power
- company General Offices:* 212 West Michigan Avenue, Jackson, Michigan 49201 * (517) 788-0650 June 15, 1981 Director, Nuclear Reactor Regulation Att Mr Dennis M Crutchfield, Chief Operating Reactors Branch No 5 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - SEP TOPIC VIII-4, ELECTRICAL PENETRATIONS OF REACTOR CONTAINMENT By letter dated July 11, 1980, the NRC transmitted a draft technical evaluation of SEP Topic VIII-4, Electrical Penetrations of Reactor Containment.
This report provided a contractor's evaluation of three penetration types represen-tative of those penetrations installed at Palisades and identified several unresolved issues.
In a subsequent letter dated March 26, 1981, the NRC reiter-ated the unresolved issues and requested further information to specifically address the staff concerns.
The attached information is provided in response to that request and provides our. comments on the July 11, 1980 evaluation.
Robert A Vincent Staff Licensing Engineer CC Director, Region III, USNRC NRC Resident Inspector - Palisades pages 81061801/0
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RESPONSE TO OPEN ITEMS NRC LETTER DATED MARCH 26, 1981 Item 1 Backup Protection for Low-Voltage AC and DC Penetrations Neither the typical low-voltage ac penetration nor the de voltage penetration complies with the acceptance criteria as described in Section 2.0 of the sub-ject SEP topic.
In both cases, the primary interrupter opens the circuit prior to the time at which the penetration reaches its limiting temperature.
The primary interrupters open in approximately five cycles (0.08 seconds).
The secondary (backup) interrupt devices, however, would fail to trip prior to the penetration reaching its limiting temperature of 302°c with the postu-lated combination of faults and failure of the primary interrupters.
In the case of the low-voltage ac penetration, the time required for the penetration to heat up to its limiting temperature during the fault has been calculated to be 1.14 seconds.
The secondary interrupter actuates approxi-mately 200 seccind.safter the fault occurs. - -
In the case of the de penetration, the time required for the penetration to heat up to. it3 limiting temperature during the fault condition has been cal-culated to be 8.95 seconds.
The secondary interrupter actuates approximately 23 seconds after the fault occurs.
Because the probability that a primary interrupter will fail is low (approxi-mately lo-3/year from WASH-1400), and because the probability of a LOCA occur-ring and creating condt tions which could lead. to short. circuiting is low (approximately4 x 10- /year from WASH-1400), the likelihood of a* condition
- which would challenge a secondary interrupter is low enough so that immediate installation of backup penetration protection is unwarranted.
We have concluded, however, that an analysis of at least power and control circuits which penetrate containment is appropriate to determine the extent of the question and to evaluate the possiole need for modifications. *. Accordingly, Consumers Power Company*has,initiated a program* to evaluate overload pro-*
tection for all electrical containment penetrations in the Palisades Plant.
The elements of this program and our expected schedule are as*follows:
- 1.
A determination of maximum fault currents, penetration heatup times and an evaluation of the adequacy of backup circuit pro-tection including trip signal power supply independence will be performed for each power circuit which penetrates containment.
This effort is expected to be completed by August l, 1981.
- 2.
Control and instrument circuits which penetrate containment will be divided into groups of similar circuits and a repre-sentative. sample will be selected from each group.
For each sample circuit an eYaluation similar to that described above for power circuits will be performed.
In addition, indepen-dence of power supplies used for tripping primary and backup devices will be assessed for control and instrument circuits.
These efforts will follow the power circuit eiraluations, ar-d are expected to be completed by October 1, 1981.
- 3.
An evaluation of the adequacy of the Palisades Plant overcurrent protection surveillance testing program will be performed to verify that all appropriate circuit protective devices are in-cluded and that testing methods and frequencies are adequate.
This effort is expected to be completed by October 1, 1981.
- 4.
Following the evaluations discussed above, a summary of the results, our conclusions and their bases, and a discussion of any modifications which may be deemed necessary will be sub-mitted to the NRG.
This report is expected to be submitted by October 15, 1981.
2 It is our belief that the above program is fully responsive to.the NRC's concerns.
We also feel that even though the schedule will require a sub-stantial effort to assemble the necessary data, develop necessary computer models, and perform and review the analyses, it is a schedule which will allow our conclusions to be based en detailed technical evaluations rather than subjective judgements.
Item 2 Protection of Parallel Conductors and Seals if an Open Circuit Should Develop The Technical Evaluation of Topic VIII-4 indicates that tw~ parallel pene-trations are used to supply power to each.primary coolant pump motor.
In reality, each primary coolant pump motor utilizes a single penetration separate from the penetratio~s.that supply the other three pump motors (see Reference 2).
As a result, the overload concerns as described in the SEP evaluation do not apply to the Palisades Plant.
Item 3 Basis for Continued OperationWith Medium-Voltage Penetrations Using Butyl Rubber Insulation The Technical Evaluation of Topic VIII-4 indicates that the typical medium-voltage ac penetration is constructed-of a.1500 Mcm copper conductor with Butyl rubber insulation passing through the ceramic bushings.
In addition, the evaluation indicates that the Butyl rubber will melt at 120°C, and that this temperature should be used as the limiting temperature in the short circuit analysis; The paragraphs conclude that the qualification limit of the penetration will be.exceeded in the event of a LOCA (given a peak LOCA temperature of 140°c) even without experiencing a fatil.ted circuit.
A review of the applicable penetration drawings showed no evidenc.e of a conductor jacketed with Butyl rubber passing through the ceramic bushing.
Instead, Reference 3 shows the conductor jacket removed prior to the con.:..
ductor entering the ceramic bushing.
Reference 4 describes the hermetic connector primary seal for canisters P-1 and P-2 (medium-voltage type canis*ters) as a cerami*c-to-metal type of seal.
Considering then a conductor-to-ceramic interface, the time required to heat the ceramic beyond its temperature rating during the postulated fault condi~
tion can be computed.
Utilizing the same copper conductor temperature
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formula ceramic as of t
that used in the SEP evaluation, and a temperature rating for 650°c (.Reference 5)' the heatup time is calculated as:
= (0.0297)A2 Log T2 + 234 I
2 (T
+ 234) 1 SC
= (0.0297) (1500 x 103)2 448102 Log (650 + 234) 140 + 234
= 12.4 Seconds Where:
A
= Conduc.tor Area (cm)
I
= Fault Current (Amperes)
SC Tl = Initial Operating TemperatlJ!e (LOCA, oC)
T2 = Maximum Insulation Temperature (OC) 3 It should be noted that both the typical* medium-voltage ac primary and second-ary interrupter trips occur in less time than that required to exceed the ceramic temperature rating.
The instantaneous primary interrupting device 252-103 will trip in approximately 0.08 seconds (five cycles).
The secondary.-
interrupting device 252-101 will trip in approximately 0.27 seconds.
The secondary device.trip time consists of a fault detection and trip signal generation time of 0._19 seconds and a breaker operating time of O. 08 seconds (see Reference 6).
Given the foregoing analysis, it is concluded that both the primary and second-ary interrupters will open a faulted circuit prior to the typical medium.-
voltage ac penetration losing its mechanical integrity.
This conclusion is considered conservative since an init.ial canister temperattire of 140°C and a rn.8.ximum short circuit current of 44,870 amperes' (asymmetrical) was assumed::
As a result, the typical medium-voltage ac penetration does conform to the criteria described in Section 2.0 of the SEP ev8.luation.
Reference Number 1
2 3
4 5
6 REFERENCES Reference Description WASH-1400, "Reactor Safety Study," October 1975, USNRC, Appendix III, Table III 2-2 (Page III-11/12)
Consumers Power Company Drawings E-31, Sh 28, Rev l; E-610, Sh 10, Rev l; E-610, Sh 11, Rev O; E-610, Sh 14, Rev l; E-610, Sh 15, Rev O; E-610, Sh 12, Rev l; E-610, Sh 13, Rev O; E-610, Sh 6, Rev 1 and E-610, Sh 7, Rev 0 (Attached)
Consumers Power Company Drawing E20*950 BB2, Sh. 1-3 (.Viking Industries, Inc Drawing 23,0000-0005C) "Electrical Penetration Types P-1 and P.:...2, Master" (Attached)
Viking Industries Inc Engineering Information and Price Proposal for Electric. Penetrations per Bec.htel Specification 5935-E-20, Section 3, "Design Discussion" Standard Handbook for Electrical Engineers, Fink and Carroll, 10th Edition, Page 4-198, Tabel 4-80 "Some Typical Enamel-Insulated Wires" "MA-250 Air Magnetic Circuit Breaker Design Test Data", Allis-Chalmers Switchgear Division as Signed by W H Lane, PE, Manager of Engineering, September 9, 1975