United States Nuclear Regulatory Commission - Protecting People and the Environment

LICENSEE: FOXBORO COMPANY
SITE: FOXBORO COMPANY EN NUMBER: 36122
DOCKET: EVENT DATE: 09-03-99
RX TYPE: EVENT TIME:
VENDORS: NOTIFY DATE: 09-03-99
EMERGENCY CLASS: N/A REGION: 1 STATE: MA TIME: 14:00
OPS OFFICER: WILLIAM POERTNER
10 CFR SECTION: CCCC UNSPECIFIED PARAGRAPH

DEFECTIVE RELAYS PROVIDED TO FOXBORO BY VENDOR

Foxboro Co., has identified a potential failure with N-2A0-L2C-R and/or 2A0-L2C-R Contact Output Isolator cards. The subject cards may contain N0152CK relays supplied by Communications Instruments Inc. which may have been manufactured utilizing a repair residual on the contact armature plate. As a result, relays utilizing this repair residual have contacts that may not return to their normal de-energized position when the relay is de-energized (a condition known as contact hang-up).

Extensive analysis performed on a number of relays confirmed that utilization of this repair residual prevented the return of the contact armature (and contacts) to the normally de-energized position when the relay coil was de-energized after an energization period of at least one hour. Further analysis performed by the supplier of the relay confirmed the presence of this repair residual as the root cause for the relay failures. The supplier has determined that during assembly of the relays, this unauthorized repair procedure may have been utilized on 5 to 6 percent of the relays manufactured since manufacturing week 9834. Utilization of the repair residual has been halted by the manufacturer of the relay.

***Update on 09/13/99 at 1325 ET
by George Johnson taken by MacKinnon****

"Subsequent investigate analysis and an audit performed at the supplier's manufacturing facility, has determined that the utilization of Mylar repair residuals is present is present on relays displaying a manufacturer's date code of 9806 to 9933."

As we were investigating the Mylar problem, we identified another potential defect of substandard solder joints. Relays that were supplied with substandard (poorly wetted) solder joints could lead to cracked, or in extreme cases, intermittent solder connections. This potential defect could present itself as an intermittent connection to the common relay contact. Foxboro has determined that relays manufactured between 9801 and 9936 could display this potential defect.

"Foxboro is taking immediate corrective action to rectify the situation and will notify all Nuclear Utilities that have purchased this product from Foxboro during the time period affected and provide replacement relays" R1DO (Neil Della Greca) and NRR (Vern Hodge) notified.

Page Last Reviewed/Updated Thursday, March 29, 2012