ML20076K471
| ML20076K471 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/28/1994 |
| From: | Link B WISCONSIN ELECTRIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CON-NRC-94-081, CON-NRC-94-81 VPNPD-94-118, NUDOCS 9411010178 | |
| Download: ML20076K471 (2) | |
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Wisconsin Electnc POWER COMPANY 231 W MicNgon, PO Box 2046. Mdmukee. WI 53201-2046 (414)221 2345 VPNPD-94-118
.NRC-94-081 October 28, 1994 Document Control Desk U.S. NUCLEAR REGULATORY COMMISSION Mail Station P1-137 Washington, DC 20555 Gentlemen:
DOCKETS 50-266 AND 50-301 DEGRADED GRID VOLTAGE SETTING LIMIT STATUS UPDATE POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 In a letter dated March 30, 1994, we provided information about the status of analyses and evaluations that are being performed to establish the appropriate Technical Specifications for the degraded voltage setting limit.
In that letter, we stated that we expected to provide a Technical Specifications change request by November 1, 1994.
In further evaluations, we have discovered additional enhancements associated with the degraded voltage setting limit, time delay, and reset value that need to be implemented prior to proposing amendments to our Technical Specifications.
The actions that we have completed to date include raising the low voltage station auxiliary transformer output voltage tcp settings by about 2% for both units and replacing the ITE 27D degraded voltage relays with ABB 27N relays.
The low voltage station auxiliary transformer output voltage tap settings were raised to increase the plant electrical distribution system voltages.
This change allows reset of the degraded voltage relays following short duration degraded voltage situations with the expected system voltage recovery.
This change also allows the degraded voltage setting limit to be raised further, if necessary, without significantly increasing the chance that the safeguards buses will automatically be isolated from off-site power unneces-sarily.
The replacement of the ITE 27D relays with ABB 27N relays was initiated because the ABB 27N relays are more accurate and have better reset characteristics.
The reset characteristics are better because the ABB 27N relays can be set with a reset value closer to the setpoint than the ITE 27D relays.
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e Document Control Desk October-28, 1994 Pagd 2 Additionally, we are currently modifying the degraded voltage protection logic to include a shorter time delay if the degraded voltage condition occurs coincident with a safety injection signal.
We expect the modifications to be completed for Unit 1 during the spring refueling outage 1995 and for Unit 2 during the fall refueling outage 1995.
In the interim, we have reduced the time delay setting to 10 seconds to provide appropriate compensation for this situation until these modifications are completed.
The calculations to determine the appropriate Technical Specifi-cations setting limit, with these enhancements included, are in progress.
We are also continuing to verify and validate the inputs and assumptions used in the calculations of the setting limit.
The interim operability determination provided in the letter dated February 16, 1994, and the conclusion that the degraded voltage protection function is operable remain valid.
We are currently in the process of completing the necessary calcu-lations to determine the appropriate setting limit, time delay, and reset value for the degraded voltage protection function.
It is expected that these efforts will be completed by April 1995.
Therefore, we expect to provide a Technical Specifications Change request for degraded voltage by April 28, 1995.
Please feel free to contact us if you have any questions.
Sincerely
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g 1t ob Link Vice President Nuclear Power CAC/jg cc:
Regional Administrator, Region III NRC Resident Inspector i
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