ML050700046

Part 21 Report Re Abnormal Contact Response Was Observed During pre-installation Testing of Allen-Bradley 700RTC Relays

ML050700046
Person / Time
Site:	North Anna
Issue date:	03/09/2005
From:	Hartz L Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
05-069
Download: ML050700046 (5)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 2326 1 March 9 , 2005 U.S. Nuclear Regulatory Commission Serial No.05-069 Attention: Document Control Desk NL&OS/ETS Rev. 1 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 N PF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNITS 1 AND 2 PART 21 NOTIFICATION - IDENTIFICATION OF DEFECT Pursuant to 10 CFR 21.21.d, Dominion is providing the required 30-day written notification of the identification of a defect. This information was initially reported to the NRC Operations Center on February 10, 2005. During pre-installation testing of Allen-Bradley 700RTC relays, abnormal contact response was observed. The attachment to this letter provides the information requested by 10 CFR 21.21.

This letter does not establish any new commitments. Should you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, W

Leslie N. Hartz Vice President - Nuclear Engineering Attach ment

cc: U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. M. S. King NRC Senior Resident Inspector North Anna Power Station Mr. S. R. Monarque NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike MaiI Stop 8- H12 Rockville, Maryland 20852 Mr. J. E. Reasor Old Dominion Electric Cooperative lnnsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060

Attachment 10 CFR 21.21 Notification Allen-Bradley 700RTC Relays Virginia Electric and Power Company (Dominion)

North Anna Power Station Units 1 and 2

Part 21 - Regarding the abnormal response of Allen-Bradley 700RTC relays when configured with the NC contact in the C5C6 position.

Responsible Officer: W. R. Matthehs. Senior Vice President - Nuclear Operation 5000 Dominion I3lvd.

Glen Allen. Virginia, 23060 Event Date: February 8. N O 5 Unit Name: North Anna Power Station Component Information (as applicable):

Manufacturer: Allen-Bradley Part Number: 700RTC I I I IOU1

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Description:==

Abnormal contact response was observed during pre-installation testing of Allen-Bradley 700RTC relays. The 700RTC relays are solid state timing relays used in several Safety Related applications at North Anna. The 700RTC relay provides a wide time adjustment. The relay has two timed contact positions and two instantaneous contact positions. The relays are ordered to a part number that specifies a certain contact arrangement, but the contacts are fully interchangeable and may be configured by the end user in any combination of Normally Open/Normally Closed (NO/NC). Removable contact cartridges mount in the contact slots. At North Anna, Allen-Bradley part number 700RTC11 I IOU I i s used, which is a contact configuration of NO, NC, NO, NC.

The relays were setup and tested in a NO, NO, NC, NC configuration when it was discovered that the instantaneous contact (CS-C6 position), with a NC contact cartridge installed, behaved like a timed contact. The CS-C6 position changed state according to the setting of the timer. All other contact positions worked properly. With a NO contact installed in the C5-C6 position, the contact position behaved as expected (as an instantaneous contact). Different NC contact cartridges were installed in the C5-C6 position of the relay and the anomaly still occurred. Forty-five (45) relays were tested for this anomaly. Twelve of 45 relays failed testing (C5-C6 with NC contact behaved like a timed contact). The relays were returned to Allen-Bradley for failure analysis. Allen-Bradley has duplicated the anomaly using the returned relays and one from their stock. This defect could cause the failure of a safety system to actuate or perform its intended safety function.

The 700RTC relays are used as replacements for Agastat Relays in certain safety-related applications. Over the past twelve years, 700RTC relays have been installed in various locations at North Anna. There are 88 installed timers in two circuits - SBO Diesel and EDG Load Sequencing circuits affecting several plant safety systems. In addition, six timers are installed in the non-safety related instrument air system.

At North Anna, the 700RTC relays are purchased commercial grade then upgraded for safety-related use using the commercial grade dedication process. The upgrade is performed by the North Anna Materials Verification Lab using an approved commercial grade dedication plan. Prior to identification of this anomaly, the dedication testing verified proper contact operation of the contact cartridges in the as-received configuration. The dedication process now verifies proper contact operation in all possible contact configurations.

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Current and planned 700RTC relay installations were reviewed. The majority of installed 700RTC relays are configured with the contact cartridges arranged according to the 700RTClll lOUl part number (NO. NC, NO, NC). In a few locations, the contact cartridges are configured NO, NO, NC, NC. North Anna does not utilize the CS-C6 position with the NC contact cartridge in any of 700RTC locations.

Prior to installation, 700RTC relays are bench tested for satisfactory operation.

Causes: Cartridge tolerance is not fully compatible with the relay causing the normally closed instantaneous contact to act as a timed contact. This is generally due to the variation in sensitivity to the eddy currents developed in the relay field poles that operate the contacts. In addition, the contacts do not always have consistent sensitivity, so when their positions are changed there can be incompatibilities between field poles and contacts.

Immediate Corrective Actions: Nine of the relays that failed bench testing were sent back to Allen-Bradley for analysis.

Industry Notification: OE notification No. 19273 - Abnormal response of Allen-Bradley 700RTC relays when configured with the NC contact in the CS-C6 position Page 2 of 2