ML20205B840

Part 21 Rept Re Chattering of Wilmar Electronics Underpower monitor-type Relay Circuit Boards,Model 21-171.Caused by Overheated Components,Damaged Circuit Boards & Bad Solder Connections.Defective Relay Replaced

ML20205B840
Person / Time
Site:	Rancho Seco
Issue date:	07/30/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
REF-PT21-86, REF-PT21-86-280-000 JEW-86-271, PT21-86-280, PT21-86-280-000, NUDOCS 8608120179
Download: ML20205B840 (2)

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SACRAMENTO MUNICIPAL UTILITY DISTRICT 6201 s Sireet. P.O. Box 15830. Sacremento CA 95852 183o.(5161452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CAUFORNIA T

JEW 86-271 , , LOG, S H, tdo 1D July 30,1986 S EC 8 A' Ma 96-22 -Po J B MARTIN REGIONAL ADMINISTRATOR REGION V 0FFICE OF INSPECTION AND ENFORCEMENT U S NUCLEAR REGULATORY COMMISSION 1405 MARIA LANE SUITE 210 WALNUT CREEK CA 94596 DOCKET NO. 50-312 LICENSE ~NO. DPR-54 10 CFR 21 REPORT, DEFICIENCIES IN WILMAR UNDERPOWER RELAYS In accordance with 10 CFR 21.21 (b) (2), the Sacramento Utility District hereby submits a written report concerning the discrepancies found between the Wilmar Electronics Underpower Monitor type relay circuit boards, model 21-171, and the schematic drawings in the manufacturer's instruction book, E10.07-20. -

While investigating the cause of a reactor coolant pump (RCP) underpower relay monitor chatter which caused soltage fluctuations on a 120 volt bus, several components on the underpower relay circuit board appetred to be severely overheated. The defective underpower relay, 637-8 serial No. 10, was replaced with another relay, serial No. 12, and the chattering stopped.

An inspection of the RCP underpower relays discovered several discrepancies such as overheated components, damaged circuit boards, bad solder connections

.- and circuit boards that did not match the vendor supplied schematic drawings.

Two nonconformance reports (N'CR) were written, NCR S-5557'on flay 6,1986 arid NCR S-5598 on May 23, 1986, to address the discrepancies identified during the inspections. The NCRs were assigned to the Nuclear Engineering Department ,

for resolution. During the investigation by Nuclear Engineering, a repre-sentative of the Sacramento Municipal Utility District visited Wilmar -

Electronics on June 11, 1986. During the visit, our represen':ative came to the opinion that Wilmar Electronics does not appear to havis an adequate Quality Assurance program required for the supply of equipmen: to nuclear ,

power plants (ANSI N45.2-1977). Most of the relays, which havin been repaired at different times without any record of changed components, have .

. different component ratings. As a result, there is not any single electrical schematic diagram applicable for all relays.

Upon review of the NCRs by the Quality Assurance Department, two internal Occurrence Description Reports (ODR) were initiated on July 17, 1986, requesting the Plant Review Committee (PRC) to evaluate the nonconformante for 10 CFR 21 reportability. The PRC in a meeting held July 23, 1986 deternined the discrepancies identified in the nonconformance reports constituted a defect in a basic '

component and recommended a report be made pursuant to 10 CFR 21.

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The defect identified by the PRC was a deviation in a basic conponent (i.e.,

RCP underpower monitor. relays) in that each reactor coolant punp motor power supply is monitored by two types of power monitors: an underpower monitor and a phase balance monitor. Detection of an abnormal condition by either monitor will provide a trip signal to the pump power monitor circuit of the Reactor ProtectionSystem(RPS).

Apparently Rancho Seco Generating Station Unit No. 1 is the only nuclear plant using Wilmar Electronics underpower relays. Nuclear Engineering has submitted a purchase order to replace all of the Wilmar Electronics underpower relays with Brown Boveri undercurrent relays. Additionally, the Regulatory Compliance staff has initiated a proposed amendment, No.150, to the Technical Specifications ammending Table 3.5.1-1 to reflect the use of Brown Boveri undercurrent relays instead of Wilmar Electronics underpower relays.

If there are any questions, please contact Ron W. Colombo at Rancho Seco Nuclear Generating Station Unit No. 1. .

JO ' E WARD PUTY GENERAL Mn.AGER NUCLEAR CC: NRR e

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