ML20070M349
| ML20070M349 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/14/1994 |
| From: | Miller D NORTHEAST NUCLEAR ENERGY CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| MP-94-266, NUDOCS 9404260110 | |
| Download: ML20070M349 (2) | |
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}g Nuclear Energy Northeast Rope Ferry Rd. (Route 156), Waterford. CT 06385 Millstone Nucicar Power Station Northeast Nuclear Energy Company
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t RO. Box 128
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Waterford, CT D6385-0128 (203) 447 - 1791 Fax (203)444-4277 The Northeast Utilities System i
Donald B. Miller, Jr.
Senior Vice President - Millstone
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Docket No. 50-423 Re: 10CFR50.36 April 14, 1994 MP-94-266 4
1 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Millstone Nuclear Power Station, Unit No. 3 Train B Emergency Diesel Generator Start Failure I
Gentlemen:
This special report is being submitted within thirty days pursuant to Technical Specifications 4.8.1.1.3 and 6.9.2. Technical Specification 4.8.1.1.3 requires that a special report be submitted to the NRC within 30 days for any valid or nonvalid emergency diesel generator (EDG) failure. This Specification also requires information recommended in Regulatory Guide 1.108, Revision 1, Regulatory Position C.3.b, August 1977, to be included in the report.
On March 18,1994, at 1803 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.860415e-4 months <br />, with the plant in Mode 1 at 100% power,2253 psia and 587 degrees Fahrenheit (Tave), a monthly operational test was be' ng perform 3d on the "B" train EDG following maintenance. While conducting this test, the "B" diese!
started and the generator came up to speed. However, the generator exciter field did not flash which resulted in an unsuccessful loading of the generator. The "A" train EDG i
was unaffected and remained operable.
l This failure was the first (1$ start failure in the last 100 valid tests. The current EDG start surveillance test interval is once per 31 days, under Technical Specification 4.8.1.1.2.
This interval conforms with the 31-day schedule of Regulatory Guide 1.108, Regulatory Position C.2.d. Since no other failures have occurred in the sc1100 tests, the surveillance interva! will remain at 31 days.
The "B" EDG had already been placed in an inoperable status in order to conduct the monthly surveillance. As immediate action, it was determined that no alarms had annunciated to indicate any problems. However, it was found that an indicating lightfor the " Diesel Ready to Auto Start," had blown on the local control panel. A check of fuses for this light circuit found that one fuse had blown. A replacement light and fuse were installed, and the monthly EDG surveillance test was successfully completed at 0226 hours0.00262 days <br />0.0628 hours <br />3.736772e-4 weeks <br />8.5993e-5 months <br /> on March 19,1994. The total time that the diesel was inoperable due to the start failure was 8.38 hours4.398148e-4 days <br />0.0106 hours <br />6.283069e-5 weeks <br />1.4459e-5 months <br />.
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As further corrective action, an investigation was conducted in order to determine the effect of the blown light and fuse. The diesel had started and achieved rated speed.The licht had failed in a closed-short manner that created an overcurrent condition in the circuit, which exceeded the fuse capacity. The blown fuse resulted in the loss of the "B" EDG governor control circuit. This, in turn led to the fallure of the generator field to flash and an unsuccessful generator loading. As action to prevent recurrence, a new light fixture with a current-limiting resistor has been installed for each EDG, so that a shorted indicating light cannot cause an overcurrent condition.
The spurious failure of the indicating lightis a random single event. There have been no other cases of a spurious failure of an indicating light resulting in a diesel start failure.
The licensee contact for this special report is W. J. Temple, who may be contacted at (203) 437 - 5904.
Very truly yours, NORTHEAST NUCLEAR ENER COM ANY Donald B. Miller, Jr.
Senior Vice President - Millstone Station
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DBM/RLM:ljs cc'.
T. T. Martin, Region 1 Administrator P. D. Swetland, Senior Resident inspector, Millstone Unit Nos.1,2, and 3 V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 1
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