ML19290C580

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Responds to IE Bulletin 79-25, Failures of Westinghouse Bfd Relays in Safety-Related Sys. Over 300 Bfd Relays in Use.Tests Showed No Relay Degradation or Excessive Coil Temps.Replacement to Begin W/Unit 2 Jan 1980 Outage
ML19290C580
Person / Time
Site: Prairie Island  Xcel Energy icon.png
Issue date: 12/20/1979
From: Wachter L
NORTHERN STATES POWER CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-25, NUDOCS 8001220108
Download: ML19290C580 (2)


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NSP NORTHERN STATES POWER COMPANY M I N N E A PO LI S. M I N N E S OTA 55401 December 20, 1979 Mr. James G. Keppler Director - Region III Office of Inspection and Enforcement United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT Dockets No. 50-282 and No. 50-306 In response to IE Bulletin No. 79-25, the following information is offered:

A total of 320 BFD relays, Style No. 766A235, coil style 503C428G21, or equivalent are presently in use at Prairic Island. There are 41 in each train of Reactor Protection Logic and 39 in each train of Safeguards Logic.

Subsequent to Westinghouse NSD-TB-76-2 of February 18, 1976, addressing BFD relay degradation due to overheating, extensive time response and thermal testing was conducted on these relays from March through July of 1976. Westinghouse recommended replacement of failed relays with Style No. 5069A95, Coil No. 1259C71G19. The problems addressed in that manufacturer's bulletin became the subject of IE Bulletin 76-J5. Our test results revealed no relay degradation or excessive coil temperatures.

Meanwhile, Westinghouse NSD-TB-76-5 of April 30, 1976, was issued addressing a problem with sticking BF and BFD relays. By the date of this bulletin, this problem would relate to the newer Style No. 5069A95 relay recommended by NSD-TB-76-2. This became the subject of IE Circular 76-02. Relay performance was checked at Prairie Island and again no problems were found.

The sticking problem was reported in Westinghouse NSD-TB-76-16 of November 22, 1976, to have been an isolated case.

Westinghouse NSD-TB-76-16 recommended replacement of all BFD relays with their latest Style No. 5072A49, Coil No. 1271C50G01 - the NBFD relay.

Since our original relays have established reliable performance and wholesale replacement presents significant testing probicas, it was decided to forego replacement until adequate assurance was received that the replacement relays were indeed a significant improvement over the originals. This was received in January, 1979. It was decided at that time to replace our BFD relays with NBFD relays over two refueling outages per unit with the reactor protection relays being replaced first.

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NORTHERN STATES POWER COMPANY lir. James G. Keppler December 20, 1979 Page 2 This replacement schedule is based on two factors. First, demonstrated reliability of the BFD relays implies a shorter schedule is unnecessary.

Second, there are significantly more normally energized relays in the reactor protection logic than in the safeguards logic (31 per train as opposed to 2 per train) . Sufficient replacements for the reactor protection trains were ordered, but not received in time for the spring, 1979, Unit 1 outage. They are on hand now.

As advised by Westinghouse NSD-TB-79-05 of August 14, 1979, 129 affected NBFD relays were tested for insufficient overtravel of which 50 failed.

They will be replaced. Replacement relays for the safeguards logic trains have been ordered, but not received. They will be tested upon receipt.

We expect to begin replacement of BFD relays on a refue. ling outage basis beginning with the Unit 2 outage scheduled for January, 1980. Expected

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completion of replacement is December 31, 1981.

Yours very truly, h

L. J. Wachter Vice President - Power Production cnd System Operation cc: Ftr. G. Charnoff NRC Of fice of Inspection and Enforcement Washington, D.C.

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