ML20198C918
| ML20198C918 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 05/07/1986 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-84-02, IEB-84-2, NUDOCS 8605230092 | |
| Download: ML20198C918 (2) | |
Text
Y-w Northern States Power Company 414 Nicollet Mall Minneapohs. Minnesota 55401 Telephone (612) 330 5500 May 7, 1986 Mr J G Keppler Regional Administrator, Region III US Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 LICENSE NO. DPR-22 Additional Response to IE Bulletin 84-02. HFA Relay Failures The following additional information concerning the replace-ment schedule of coils for HFA relaye installed at the Monticello Nuclear Generating Plant is provided in response to NRC IE Bulletin 84-02.
All normally energized AC and DC General Electric HFA51 relay coils have been replaced with Century Series Tefzel coils.
Further investigation has indicated that two normally ener-gized DC relays in the reactor protection system (Model HFA65) do not require replacement.
The HFA65 coil spools are of different materials and design (copper core and glass polyester end discs versus nylon or lexan) than HFA51 coil spools.
The HFA65 relays have an integral rectifier which changes the alternating current used for the coil to direct current.
Because of the DC applied to the coil, HFA65 relays are not subject to mechanical and thermal stress that may lead to premature failure as identified in the bulletin.
General Electric reports no record of premature failures for this coil design.
Also, no Century Series Tefzel coil design is available for this model.
For these reasons, the two HFA65 relays coils will not be replaced and do not required continued monthly inspection.
In our response of July 17, 1984, we stated that normally de-energized safety related AC and DC relay coils were to be replaced during the next refueling outage.
However, in reviewing activities scheduled for the current outage, the Appendix R Alternate Shutdown System modification will require that the plant remain on Division I power sources for a major portion of the outage.
Insufficient time is available to replace the Division I relay coils.
The 8605230092 860507 PDR ADOCK 05000263 G
PDR MAY 151986 /O
'Ir Northem States Power Company Mr J G Keppler May 7, 1986 Page 2 Division II relay coils will be replaced.
We will replace the balance-of the normally de-energized AC and DC HFA relay coils during the outage in 1987.
The normally de-energized coils remaining to be replaced are not subject to the degree of thermal aging and stress as those which are normally energized.
Monticello has never experienced a failure of a normally de-energized HFA51 relay coil.
We believe that this revised schedule for relay coil re-placement will have no.effect on the safe operation of the Monticello plant.
Please contact us if you have any questions re ted our revised commitment.
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C E Lars Vice President Nuclear Generation c: Resident Inspector, NRC NRR Project Manager, NRC G Charnoff