ST-HL-AE-5153, Discusses Review of Preliminary Accident Sequence Precursor Analysis
| ML20091S127 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/31/1995 |
| From: | Martin L HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ST-HL-AE-5153, NUDOCS 9509070313 | |
| Download: ML20091S127 (3) | |
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rject ectr c Generat g Stadon P. O. Box m Wadsworth, Texas N llouston Lighting & Power August 31, 1995 ST-HL-AE-5153 File No.: G25 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498; STN 50-499 Review of Preliminary Accident Sequence Precursor Analysis of Condition at South Texas Project. Unit 2
Reference:
Letter from Mr. T. W. Alexion, Nuclear Regulatory Commission to Mr. W. T. Cottle, Houston Lighting & Power dated July 17,1995 (ST-AE-HL-94253)
The Preliminary Accident Sequence Precursor Analysis as described in enclosure 1 of the referenced correspondence was reviewed in accordance with the guidance for licensee review. Houston Lighting & Power does not regard this event as a precursor, as the modeling of the event is not consistent with the events that occurred or that had the potential to occur.
The analysis was overly conservative in that a probability of "one" was assigned to events that did not happen or which were assumed without adequate basis. These included:
NRC Modeline Assumption: "It was assumed that the piston failure of EDG 22 occurred sometime during the last successful surveillance of the diesel" HL&P Response: Although the 4R piston was damaged, all indications are that it was still functioning at the time of the 18 month inspection. It is not known how long the piston skirt had been broken, but the damage had not progressed to the point of disabling the cylinder. Since the damage did not cause failure, there is nothing to indicate when it had occurred.
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Misc-95\\5153 Project Manager on Behalf of the Part.icipants in the South Texas Project 9509070313 950831 PDR ADOCK 05000498
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Houston Lighting & Power Company ST-HL-AE-5153 South Texas Project Electric Generating Station Page 2 of 2 1
NRC Modeline Assumption: "EDG 22 would have subsequently failed during any attempt to run the diesel" HL&P Response: The broken piston would not necessarily have caused engine failure, as it did not cause failure during the latest test. It would be accurate to say that the diesel was in a degraded condition, and to postulate that the probability of failure was higher than average while this condition existed. But the failure probability was demonstrably not equal to one, as the damage was found only by inspection of the piston, not by failure of the engine.
NRC Modeling Assumption: "It was also assumed that the piston failure would not be detected unless EDG 22 was run" HL&P Response: HL&P disagrees with this statement. The failure was detected by a teardown inspection, and not by running the engine. In fact, in previous tests with the engine running, the cylinder gave normal test indications.
NRC Modeline Assumption: "Although this event occurred during an extended shutdown, it was assumed that the 4R piston failure associated with EDG 22 could have occurred while Unit 2 was at power. Therefore, this event was modeled as a long term (720 h) unavailability of a single EDG while at power."
HL&P Response: HL&P disagrees with the logic applied here. The unit was not at power, but was in a shutdown that had lasted for almost one year. No fuel was in the vessel during the time the event occurred and considering the low level decay heat in the spent fuel pool, a loss of AC power would have had to last a long time to have any consequence.
In summary, the referenced letter describes an analysis which is inappropriate to the events that actually occurred. The event analyzed ilid not happen, i.e. a 30 day unavailability of an EDG at power. The unit was shut down, and HL&P's surveillance program was successful in that it detected an adverse situation before it led to equipment failure. The status of EDG 22 will continue to be closely monitored to assure that any uncorrected problem with this machine will be diagnosed and eliminated.
If you should have any questions, please contact Mr. A. W. Harrison at (512) 972-7298 or me at (512) 972-8686.
L. E. M. in Genera Manager, Nuclea Assurance & Licensing KJT/lf Misc-95\\5153
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Houston Lighting & Power Company ST-HL-AE-5153 South Texas Project Electric Generating Station File No.:
G25 Page 3 c:
Leonard J. Callan Rufus S. Scott Regional Administrator, Region IV Associate General Counsel U. S. Nuclear Regulatory Commission Houston Lighting & Power Company 611 Ryan Plaza Drive, Suite 400 P. O. Box 61067 Arlington, TX 76011-8064 Houston, TX 77208 Thomas W. Alexion Institute of Nuclear Power Project Manager Operations - Records Center U. S. Nuclear Regulatory Commission 700 Galleria Parkway Washington, DC 20555-0001 13H15 Atlanta, GA 30339-5957 i
David P. Loveless Dr. Joseph M. Hendrie Sr. Resident Inspector 50 Bellport Lane c/o U. S. Nuclear Regulatory Comm.
Bellport, NY l1713 P. O. Box 910 Bay City, TX 77404-0910 Richard A. Ratliff 4
Bureau of Radiation Control J. R. Newman, Esquire Texas Department of Health Morgan, Lewis & Bockius 1100 West 49th Street 1800 M Street, N.W.
Austin, TX 78756-3189 Washington, DC 20036-5869 U. S. Nuclear Regulatory Comm.
K. J. Fiedler/M. T. Hardt Attn: Document Control Desk City Public Service Washington, D. C. 20555-0001 i
P. O. Box 1771 San Antonio, TX 78296 J. C. Lanier/M. B. Lee J. R. Egan, Esquire City of Austin Egan & Associates, P.C.
Electric Utility Department 2300 N Street, N.W.
721 Barton Springs Road Washington, D.C. 20037 Austin, TX 78704 C. A. Johnson J. W. Beck Central Power and Light Company Little Harbor Consultants, Inc.
P. O. Box 289, Mail Code: N5012 44 Nichols Road Wadsworth, TX 77483 Cohassett, MA 02025-1166 p
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