ML20206N147
| ML20206N147 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 06/12/1986 |
| From: | Foster D GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-86-240-000 GN-941, PT21-86-240, PT21-86-240-000, NUDOCS 8607010388 | |
| Download: ML20206N147 (7) | |
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Georgia Fower Company Put Office Box 282 wVaynesborn Georgia 30830 Telephone 404 5549M1, Ext. 3360 404 724-8114. Ext. 3360 Re Georgia Power m,,,
Vice Pres. cert tre soortem elatoc system vogne noiect June 12, 1986 M
United States Nuclear Regulatory Commission Region II File: X7BG031M103 Suite 2900 Log:
GN-941, 101 Marietta Street, Northwest 53 Atlanta, Georgia 30323 Vogtle Electric Generating Plant-Units 1 and 2; 50-424, 5b25;
Reference:
Separation of Field Wires in Isolation Transformers; Letter GN-891 dated May 1,1986 Attention: Mr. J. Nelson Grace In previous correspondente on this subject, Georgir. Power Company indicated the NRC would be informed of the results of the evaluation of this condition on or before June 13, 1986.
Georgia Power _ Company has completed its evaluation and concluded that a reportable condition as defined by the reporting criteria of Parts 10 CFR 50.55(e) and 10 CFR 21 does exist.
Based upon gui. dance in NUREG-0302, Revision 1 and other NRC correspondence conce'ning duplicate reporting, Georgia r
Power Cr.mpany is reporting this condition per the reporting criteria of Part 10 CFR 50.55(e). A summary of our evaluation is attached.
This respolise contains no proprietary information and may be placed in the NRC Public Document Room.
Your truly,[
/
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, 0. Foster Attachment xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 J. H. Miller R. A. Thomas L. T. Gucwa J. P. O'Reilly D. R. Altaan C. W. Hayes G. F. Head P, R. Bemis G. A. McCarley R. E. Conway J. A. Bailey D. S. Road J. T. Beckham
- 0. Batum Sr. Resident (NRC)
R. H. Pinson G. Bockhold C. S. McCall (OPC)
P. D. Rice C. E. Belflower J. E. Joiner (TSLA)
B. M. Guthrie J. F. D'Amico D, C. Teper (GANE)
D. E. Dutton E, D. Groover N0PJ45 8607010388 860612 PDR ADCCK 05000424 W-.N s
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EVALUATION OF A POTENTIALLY REPORTABLE CONDITION SEPARATION OF FIELD WIRING IN ISOLATION TRANSFORMERS Initial Report:
On April 3,1986, Mr. R. E. Folker, Vogtle Project Quality Assurance Engineer, informed Mr. W. H. Rankin of the USNRC Region II of a poten-tially reportable condi tion concerning the separation of field wires in isolation transformers.
In our letter GN-891 dated May 1,
- 1986, Georgia Power Company indicated the NRC would be informed of the results of the evaluation of this condition by June 13, 1986.
Background Information:
Section 8.3.1.4 of the Vogtle Electric Generating Plant - Final Safety Analysis Report (FSAR) addresses the independence of redundant systems.
Section 8.3.1.4.3.C addresses cable routing within panels and control boards.
This section states that the minimum spatial separa-tion between components or cables of different separation groups (both field-routed and vendor-supplied internal wiring) is six inches.
Where it is not possible to maintain this separation, barriers are installed i
between components and wiring of different separation groups, or analysis is performed to determine the minimum separation requirements.
This is consistent with the requirements of IEEE-384 (1974) Standard Criteria for Separation of Class 1E Equipment and Circuits.
Readiness Review Findings 6-14 and 6-16 identified a violation of the separation distance (six inches) between the primary (input) and secondary (output) wiring of the isolation transformers.
Acditionally, Readiness Review Finding 6-14 identified a concern regarding a " hot short" on the secondary side of the transformer.
This condition was discussed in the FSAR in the response to NRC Question PSB Q430.61C in Amendment 15 dated March 7,1985.
An attempt was made to justify less than six inches of separation between the primary and secondary field wiring of the isolation trans-formers by the use of a test program.
The test program was intended to demonstrate that under transformer secondary short circuit conditions, the primary and secondary cables would not exceed the 90 degrees Centi-grade continuous duty rating.
These tests indicated that the cable used for the input and output wiring of the transformers is not rated for the temperatures that will exist inside the transformer wiring com-partment under normal full load operating conditions.
Engineering Evaluation:
Specification X3AA04 - (Paragraph 3.2.E and Table 1) identified the Class 1E transformer to be used for lighting is an isolation transformer.
This type of transformer was specifically chosen because of its inherent isolation capability (ferro-resonant transformers).
Regulatory Guide 1.75 was listed as a design requirement in the specification.
Data sheets from vendor catalog 923-25-230-3 dated January 25, 1980, was L
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Page Two submitted as part of the vendor equipment qualification submittal.
As a result of conditions previously described, additional tests were performed on Sola Electric Model 23-28-275.
The test data was evaluated and also used for evaluating model 923-28-275.
A comparison of the two models is included as Attachment 1.
The transformers are used to distribute and isolate power between different safety and non-safety related systems (e.g.,
from a Class 1E power source on the primary to non-Class 1E loads connected to the secondary).
The design of the isolation transformers limits the flow of current in the transformer primary and secondary circuits if a short were to occur in the secondary circuit.
The current limiting feature is required to prevent unacceptable degradation in the transformer primary circuit as a result of problems in the transformer secondary circuit.
Failure of these transformers would result in the loss of the following:
(1) Backup Power for the Class 1E 120V Vital AC Buses
( 2) Emergency Lighting in Critical Plant Areas (3) Plant Vent Radiation Monitoring Equipment (4) Reactor Control Rod Position Indication System A listing of the transformers ano application is provided in Table 1.
The testing program performed by Sola Electric discovered that under full load - normal operating conditions, the temperature at the surface of the conductor insulation inside the wiring compartment of the transformer was as high as 116 degrees Centigrade for the field cables that were used as recommended by Sola Electric.
Under short-circuit conditions, conductor insulation surface temperature reached 137 degrees Centigrade.
The resulting normal or short circuit tempera-tures could cause accelerated aging of the primary and secondary cables, and could cause premature failure of the cables and possible degradation of the power sources.
The field cables referred to this evaluation are those that run from a local splice box near the transformer.
The field cable, which is #6 AWG, 90 degrees Centigrade rated field cable, was procured based upon the manufacturer's recomendation.
Evaluation of Breakdown in a Quality Assurance Program:
A review of the quality assurance program at Sola Electric was conducted and it was determined that this condition associated with the transformers did not constitute a quality assurance program breakdown.
==
Conclusion:==
Georgia Power Company has concluded its evaluation of this condition and determined that a reportable condition as -defined by the reporting criteria of Parts 10 CFR 50.55(e) and '10 CFR 21 does exist. This condi-tion represents one that could potentially affect the safety of operations of the nuclear power plant at any time throughout its expected lifetime k
Page Three and a significant deviation from performance specifications. This condi-tion also constitutes a Part 10 CFR 21 based upon the failure of the vendor to supply a component that met the specification requirements of the purchase order.
Georgia Power Company, based upon guidance in NUREG-0302, Eevision 1, and other NRC correspondence, is reporting this condition pursuant to the requirements of Part 10 CFR 50.55(e).
Corrective Action:
Bechtel Power Corporation has located a cable type (captan) that will satisfy the high temperature and short circuit requirements of the field connected cable. A Change Control Package (CCP) will be issued to replace short lengths of field cable at each transformer. By replacing the existing cables with cables rated to carry the short circuit current of the transformer indefinitely, separation of the primary and secondary cables for the isolation transformers is not required since there is no degradation of the insulation of the cables in this condition.
Malfunctions in the secondary, therefore, cannot have an unacceptable influence on the primary circuit. This satisfies IEEE-384 (1974).
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ATTAChinEGT I
t 2.0 COMPARE 50N CHART
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C: __; -t Between Cat. Nos. 23-28-275 and 923-28-275 (Comparison of Core /CoR AssemMies)
Top Level C1sas 1E Seismic Unit Tested Standard Unit Catalog No.
Cat. No. 923-28-275 Cat. No.13-28-275 Electrical Ratings Mentical Identical Transformer C/C Assy.
3 required 3 required (T2) Transformer C/C No.
923-26-250-0E 23-26-250-ZE (TI) (T3) Transformer C/C No.
923-26-250-1E 23-26-250-3E (See Note 1)
Lamination (Core) P/N 11150-2 11150-4 Lamination Material 26 ga., M36, CRS 26 ga., M36, CRS (See Note 2)
Fully processed Semi-processed AAS Transformer Core Stack Size 4.69 inches 4.69 inches Coil P/N used in C/C Assy.
(TI) (T2) (T3)
"A" Coil 23-26-250-A4 23-26-250-A4 "B" Coil (See Note 3) 23-26-250-B3 23-26-250-B5 "C" Coil 23-26-250-C3 23-26-250-C3 C/C Insulation Materials Identical Identical C/C Impregnation Identical Identical C/C AC Capacitors Identical Identical Notes:
1.
(T2) C/C assembly is identical to the (TI) and (T3) assemblies except for the terminal block mounted in the (T2) wiring compartment.
2.
Laminations are identical except that -2 is a fully < processed material which has 10 war core loss and the c/c temperatures will be typically (5 to 10 C) cooler than the -4 lamination.
3.
The "B" coils have different coil magnet wire sizes as follows:
-B3 has size 9 AWG round copper and -B5 has 8 AWG round copper
-B3 coil temperatures will be typically (5 to 10 C) hotter than the -BS.
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2.0 COMPARISON CHART (Caet.)
Completed Thanfeemer Construction Comparison Data (Ref.: Assembly Drawings 23-24-275'and 923-2&-275)
The overall transformer construction is identical for both units which includes the wiring compartment housings, covers, mounting channels, and terminal blocks except as follows:
4.
The 23-28-275 uses one (1) wiring terminal block for both input and output terminations. The 923-28-275 uses two (2) terminal blocks, one for input and one for output wiring with a small metal barrier strip between them to separate the high and low voltage circuits.
5.
The 923-28-275 has a rubber pad mounted underneath the AC capacitors.
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1 TABLE 1 TRANSFORMERS TAG NUMBER APPLICATION lABA07X l-1807-Y3-03 ISOLATION
!BBC09X 1-1807-Y3-04 ISOLATION 1ABC23X 1-1808-T3-lO3 ISOLATION 1BBC.33X l-18808-T3-104 ISOLATION
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1ABF13X l-1808-T3-105 ISOLATION 1BBF13X l-1808-T3-lO6 ISOLATION lABC20X 1-1807-Y3-RX11 ISOLATION 1BBC20X l-1B07-Y3-RX12 ISOLATION 1ABC09X l-1807-Y3-Ol REGULATING 1BBA07X l-1807-Y3-02 REGULATING 1BBC42X l-1807-Y3-05 REGULATING 1ABE51X 1-1807-Y3-06 REGULATING-IBBB40X 1-1807-Ye-RX7 REGULATING 1ABB40X l-1807-V3-RXB REGULATING e
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