ML18052A387
| ML18052A387 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 04/15/1986 |
| From: | Kuemin J CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8604170433 | |
| Download: ML18052A387 (3) | |
Text
consumers Power POWERING MICHIGAN'S PROGRESS General Offices: 1945 West Parnall Road, Jackson, Ml 49201 * (517) 788-0550 April 15, 1986
- Director, Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
LOSS OF OFFSITE POWER EVENTS -
CORRECTION TO APRIL 10, 1986 LETTER Our letter of April 10, 1986, which sought to correct previous information contained incorrect dates in the first and third paragraph and the attachment.
Included below is the corrected letter and attachment.
We apologize for any inconvenience this may have caused.
Consumers Power Company and the NRC met on January 8, 1986 to discuss the reliability of the Palisades Auxiliary Feedwater System.
The discussions included a summary o~ loss of offsite power events.
A January 31, 1980 Consumers Power Company letter was used as the basis for the summary of loss of offsite power events which stated that Palisades had a total of five such events.
Four events are noted in the January 31, 1980 letter and one event occurred on January 8, 1984.
A recent review of plant files has shown that there have been two additional loss of offsite power events to those provided in the summary given on January 8, 1986, and in the January 31, 1980 letter.
The two events occurred on May 17, 1972 and October 17, 1974 and each was initiated by overly sensitive differential relaying.
These events were reported to the NRC in letters dated May 26, 1972 and November 15, 1974.
Our January 31, 1980 letter states that no loss of offsite power occurred on October 17, 1974, but that the unit was shutdown for AEC Operator's examinations.
This is incorrect.
The unit was shutdown as stated however the loss of offsite power occurred later that same day.
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OC0486-0073-NL04
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Director, Nuclear Reactor Regulation Palisades Plant Loss of Offsite Power Events - Correction April 15, 1986 2
An additional error, in the previous information provided, is that the recovery time for the November 25, 1977 event was reported, in the January 31, 1980 letter, to be 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and 30 minutes.
Both the log books and the LER associated with this event, dated December 16, 1977 show the recovery time to be 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 16 minutes.
Attached is a revised summary of loss of offsite power events.
r.1.~
James L Kuemin Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident inspector - Palisades Attachment OC0486-0073-NL04
PALISADES TOTAL LOSS OF OFFSITE POWER
SUMMARY
There have been seven total loss of offsite power events at Palisades.
One event was purposely initiated so that' switchyard breaker maintenance could be performed.
The three events that occurred in late 1977 were suspected to be caused by seepage of water into a sudden pressure auxiliary relay or one of the startup transformers.
Since that time, the relay and conduit into the control cabinet were replaced.
Also, separate lockout relays for each transfer trip system were added so that a single mistrip would not result in the loss of the "R" bus.
There has been no reoccurrence of this type of event since the above modifications.
The two events which occurred in 1972 and in 1974 were also initiated by a single cause; in this case, differential relaying which was overly sensitive.
Even though the intentional event in early 1984 resulted in a loss of onsite AC power, there was never an increased threat to public health or safety because there was no fuel in the reactor.
The potential for a loss of offsite power was realized before maintenance began.
If there had been any reason to suspect a safety hazard, the maintenance would not have been started.
The averag~ time that it took to regain offsite power was three hours and six minutes.
The maximum time the plant was without offsite power is eight hours and twenty-two minutes.
TABLE 3 Palisades Total Loss of 'Offsite Power Events Event No Date Time Power Was Off (hr:min) 1 09/02/71 0:56 2
05/17/72 8:22 3
10/17/74 0:30 4
09/24/77 4:45 5
11/25/77 2:16 6
12/11/77 1:30 7
01/08/84 3:23 MI0386-0009A-NL01-NL04