ML20077B863
| ML20077B863 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/13/1983 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-976, NUDOCS 8307250465 | |
| Download: ML20077B863 (4) | |
Text
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Jul 13 1983 STkL-AE-976 File Number:G12.'?5
%W@@MW Mr. John T. Collins Regional Administrator, Region IV s
Nuclear Regulatory Commission JR I 81983 611 Ryan Plaza Dr., Suite 1000 D'
Arlington, Texas 76012
Dear Mr. Collins:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Final Report Concerning Flashovers/ Failures of Non Safety-Related Insulators On June 16, 1983, pursuant to 10CFR50.55(e), Houston Lighting & Power Company (HL&P), notified your office of an item concerning flashovers/
failures of insulators that are not safety-related at the South Texas Project (STP) site. Attached is the Final Report concerning this item.
If you should have any questions concerning this matter, please contact Mr. Michael E. Powell at (713) 877-3281.
Very truly yours, hr
. W. Oprea, Jr.
Executive Vice President MEP/mg littachment 8307250465 830713 PDR ADOCK 05000498 1 L
,Q 7 G
PDR Il
r Ilouston Lighting & Power Company cc:
G. W. Oprea, Jr.
ST-HL-AE-976 J. H. Goldberg File Number: G12.135 J. G. Dewease Page 2 J. D. Parsons D. G. Barker M. R. Wisenburg R. A. Frazar J. W. Williams
~R. J. Maroni J. E. Geiger H. A. Walker S. M. Dew J. T. Collins (NRC)
A. Vietti (NRC)
W. M. Hill, Jr.
(NRC)
M. D. Schwarz (Baker & Botts)
R. Gordon Gooch (Baker & Botts)
J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)
STP RMS Director, Office of Inspection & Enforcement Nuclear Regulatory Commission Washington, D. C. 20555' G. W. Muench/R. L. Range Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washingtcn, D. C.
20555 H. L. Peterson/G. Pokorny Dr. James C. Lamb, III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonRosenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory P. O. Box 1771 University of California San Antonio, Texas 78296 P. O. Box 808, L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney General Harmon & Weiss for the State of Texas 1725 I Street, N. W.
P. O. Box 12548 Suite 506 Capitol Station Washington, D. C.
20006 Austin, Texas 78711 Lanny Sinkin Citizens for Equitable Utilities, Inc.
Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1, Box 1684 San Antonio, Texas 78233 Brazoria, Texas 77422 Robert G. Perlis, Esquire Hearing Attorney Office of the Executive Legal Director U. S. Nuclear Regulatory Comission Washington, D. C.
20555 Revision Date 07-05-83
Final Report Concerning Flashovers/ Failures of Non Safety-Related Insulators I.
Summary The South Texas Project (STP) 345kv substation has experienced several incidents of insulator flashover. One incident resulted in the loss of six of seven existing sources of offsite power to the switchyard. This incident represents the first indication of a common mode failure which potentially could result in the loss of all offsite power. The subject insulators.will be replaced prior to operation of the STP.
II. Description of the Incident On June 16, 1983, pursuant to 10CFR50.55(e), riouston Lighting & Power Company (HL&P), notified the NRC-Region IV of an item concerning flashovers of insulators at the STP 345kv substation.
Units 1 & 2 of the STP are served by a common 345kv switchyard.
Eight 345kv transmission circuits (one of which is a future circuit) rated from 850 to 1,080 mva connect the STP 345kv switchyard to the owner's respective systems. These eight 345kv circuits provide the source of AC power to the 345kv switchyard.
In addition, there is a 138kv line which supplies the STP.
This 138kv line is connected directly to an emergency transformer which can supply power to the Class 1E loads of either unit.
Some of the insulators utilized at the STP are supplied by the Lapp Bethea Interpace Corporation (hereafter, Lapp) of LeRoy, New York. These Lapp insulators are utilized in a non safety-related application and are not purchased under a 10CFR50 Appendix B Quality Assurance Program.
Lapp hollow core insulators, catalogue numbers 97592-70 and 91260-70, have flashed over at STP on four separate occasions since.1978. Of these four incidents of flashover, only one is considered to be a serious concern with respect to the total loss of offsite power. On April 21, 1983, l
flashover of 22 insulators on the transmission lines terminating in the l
switchyard at the STP site resulted in tripping of five of seven independent power sources to the switchyard.
Flashovers also resulted in intermittent operation of one of the two remaining transmission lines and deenergization of one of the two switchyard busses. During the flashover incidents, the 138kv line remained fully operational. On June 15, 1983, HL&P personnel became aware that Lapp hollow core insulators, catalogue number J-52591-PA70, were also being used on the 138kv line although no flashovers of ~ the 138 kv l
line insulators have been identified. Random single flashovers have occurred l-in the past, however, the flashovers of April 21, 1983 represent the first indication of a common mode failure which potentially could result in the loss of all offsite power. The failure mode of the insulators causing flashover has yet to be identified with certainty.
It is believed to be a l
I
ST-HL-AE-976 File Number: G12.135 Page 2 combination of environmental effects (i.e., heavy construction activity causing dust to build up on the surface of the insuiators during relatively long periods of dry weather followed by a condition of extremely high humidity) and the characteristics of the Lapp insulators. There has been no conclusive evidence of an insulator design problem.
III. Corrective Action coated with Dow-Corning Silicon grease (g Lapp insulators have either been As an interim measure, the remainin type SWS-295) or replaced with an insulator from a different manufacturer. The Dow-Corning grease appears to be effective since no greased insulators have flashed. The replacement insulators also have not experienced flashing. Although the grease appear:
effective in preventing flashover, it is not our preferred lo,'a-term solution. We will replace the current Lapp insulators with a different design (eitherfromLapporanothermanufacturer).
IV. Recurrence Control See discussion in Section III.
V.
Safety Analysis The plant engineered safety features have been designed to mitigate the consequences of design basis accidents concurrent with the total loss of all 345kv and 138kv transmission lines. However, the loss of offsite power is a severe challenge to'the safety systems. NRC General Design Criteria (GDC) 17 states that the probability of loss of the offsite power should be minimized.
Although not quantifiable, the probability of a loss of offsite power has not been minimized if the current type Lapp insulators were to remain in service. Therefore, HL&P conservatively concludes that the failures of these insulators could " adversely affect the safety of operations of the plant" and considers this matter reportable pursuant to 10CFR50.55(e).
. _-