ML20099B068
| ML20099B068 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 07/24/1992 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-92-006, CP-92-6, TXX-92339, NUDOCS 9207300146 | |
| Download: ML20099B068 (5) | |
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Log # TXX-92339
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File # 10110 j
Ref. # 10CFR50.55(e)
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7UELECTRIC July 24, 1992 Wimam J. Cahill. Jr.
Grmer Vut President U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 2 DOCKET NO. 50-446 ISOLATION OF NON-1E COMPONENTS IN CLASS 1E BATTERY CHARGERS SDAR: CP-92-006 REF:
Notice of Reportable Condition SDAR-CP-92-006, dated, June 26, 1992 Gentlemen:
On June 26, 1992, via the referenced facsimile, TU Electric notified the NRC of a condition where redundant fuses were not provided by Power Conversion Products in their design to isolate non-safety related components from a class 1E power supply (transformers T1A, T1B, and T1C secondaries).
Subsequent to the referenced facsimile TU Electric has revisited the specifics of this deviation and have concluded tnat for CPSES, a substantial safety hazard could not exist. This conclusion is based in part on the specific configuration of the battery chargers and associated batteries.
Nevertheless, despite the conclusion that a substantial safety hazard could not exist at CPSES, a deviation in a basic component has been identified.
As a result, TU Electric is providing the information required by 10CFR50.55(e) such that other users with configurations different than CPSES may. perform any reviews they believe appropriate.
Attached is TV Electric's voluntary report for CPSES Unit 2 whicn is submitted per the requirements of 10CFR50.55(e). The report has been formatted to correspond to the specific information requested by subparts (i) through (viii) of paragraph 10CFR50.55(e)(8). except for that portion of i
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DR ADOCK 050004 6 400 N. otive stree Ls, si Dattai. Texas 75201 (j
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,Page 2 of 2 subpart (vi.') regarding the advice that has been or will be given to other facilities outside of TU Electric.
Such advice would be dependent on the facilities' specific use and operating / maintenance history of the subject components. Therefore, the content of item Iriii) is limited to CPSES Unit 1.
. A *If Sincerely,
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William J. Cahill, Jr.
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Attachment 4
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c - Mr. J. L. Milhoan, Region IV Resident inspectors, CPSES (2)
Mr. B. E. Holian, NRR 7
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i Attachment to TXX-92339 Page 1 of 3 10CFR50.ES(e) VOLUNTARY REPORT INVOLVING ISOLATION OF NON 1E COMPONENTS IN CLASS 1E BATTER) GARGERS, SDAR CP-92-006 (i)
Infccmation supplied by:
William J. Cahill, Jr.
TU Electric 400 North Olive Street, L. B. 81 Dallas, Texas 75201 (ii)
The basic components are Power Conversion Products bat *ery chargers model 350-130-225.
(iii)
The battery chargers described in (ii) were qualified and supplied to TU Electric by Power Conversion Products, Crystal Lake, Illinois.
(iv)
Description FSAR Section 8.3.1.3.2a(5) requires that two circuit breakers, two fuses or a breaker and a fuse in series, both coordinated with an upstream circuit breaker be provideo to isolate non-class 1E from class 1E circuits.
This is to conform +o Reg. Guide 1.75 position on separation between IE and non IE deviccs and circuits.
Contrary to the above, the vendor, Power Conversion Products (PCP),
did not provide redundant fuses to isolate the non-safety related 120 VAC "Under Voltage Alarm Relay" (device 2/AC) and timer from the 1E power supply. Although the relay and timer do not perform a safety function, their failure could impact the internal safety related transformers and consequently the charger safety function.
PCP performed a Failure Modes and Effect Analysis (FMEA) to declassify the non-safety related components cranected to the 1E power supply internal to the class 1E battery.aargers. The FMEA identified the following discrepancies associated with the isolation of the AC undervoltage relay and the timer relay circuitry:
- 1. PCP has taken credit for blowing fuse F17, to isclate the non-safety AC undervoltage alar, relay from the IE power supply.
However, a thr6e phase fault postulated at the input terminals of the AC relay will result in blowing additional fuses in the transformer secondar," delta winding, thus collapsing the entire control voltage of the battery charger.
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- 2. The non-safety timer is attached to the 1E power supply through only or? protective device.
Attachment to TXX-92339 Page 2 of 3 Site Specific Summary The above deviations involving inadequate isolation of non-safety related comporents were found as part of the seismic equipment qualification effort. These deviations apply '
all CPSES class 1E battery chargers.
There e.re eight class 1E battery chargers in Unit 2.
Two battery chargers are available for each class 1E battery (one normally con ected and one re).
No failure has occurred to date due to this cor.dition.
Site Specific Imolications The safety function of the battery chargers is to maintair. the Train A and Train B safety related batteries in a fully charged condition.
In the Urlikely event of a loss of all AC power, which would render all battery chargers inoperable, the safety related batteries will provide vital DC and vital AC power (via the inverters) during the time the plant is taken to and maintained in a safe shutdown condition.
Even though the deviation described in this evaluation could (in the event of a three phase fault in the non IE relay circuit) result in the-less of safety function of a single charger, there is no credible failure mechanism that could cause a three phase fault in multiple battery chargere simultaneously.
In addition, eny loss of a battery charger would bc annunciated in tne control room.
Each_ safety ralated battery (four total, two in Train A and two in Train B) has two full capacity chargers available.
If any of the four batteries are left without at least one charger and at least one charger cannot be restored within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, then the technical specifications require that the plant be placed in a safe shutdown condition within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and cold shutdown within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
lhese required actions of the plant technical specificacions preclude the development of unsafe conditions in the unlikely event of loss of charging capability to a single battery.
Based on the above, the loss of a single charger (or in an incredible event, two chargers) would not result in a major reduction in the degree of protection provided to the public heaith and safety.
Therefore, no substantial safety hazard could result from this deficiency at CPSES.
(v)
The3e discrepancies were identified as part of the Seismic Equipment Qualification documentation review on April 8, 1992, i
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, to TXX-92339
, Page 3 cf 3 (vi)
CPSES utilizes 16 class 1E battery chargers in Units 1 and 2.
The tag numbers are CP1/2-EPBCE0-01 through -08.
All these chargers are located in the control buildings at elevation 792.
(vii)
TV Electric's corrective action will be as follows:
- 1. Add additional fuses to properly 1solate the undervoltage alarm re'ay.
(This work is being performed based on Power Conversinn Products' reevaluation of the FMEA).
- 2. Disconnect the timer circuitry to ensure that this non-safety device cannot impact the 1E power supply (this 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> timer relay is not used at CPSES).
Unit 2 work will be completed by Power Conversion Products prior to obtaining Unit 2's operating license.
(viii) The deviations discussed above are applicable to the eight class IF battery chargers in CPSES Unit 1 (CP1-EPBCED-01 through 08).
A Unit 1 non-conformance document has been initiated to evaluate the deviation.
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