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| Entered date | Event description | |
|---|---|---|
| ENS 42151 | 17 November 2005 16:25:00 | The following information was received via facsimile: On 11/2/05 SGT LLC, primary contractor for Steam Generator replacements at Callaway Plant, received notification from PRIME Measurement Products, (formerly ITT Barton) of a manufacturing defect in Model 763, 763A, and 764 pressure transmitters involving use of Zener diodes that were not in compliance with purchase specifications. Subsequently, on 11/3/05 SGT LLC notified AmerenUE Callaway Plant of the potential manufacturing defects involving the aforementioned transmitters. These transmitters provide input to steam generator level indication and control functions. The notification provided by PRIME stated the purchasing specifications required JANTX components, but in some cases commercial variations of the required parts were used to manufacture some transmitters. This condition was potentially reportable under 10 CFR 21, depending on the specific application at facilities using these instruments manufactured by PRIME Measurement Products. The following is a summary of the information obtained from PRIME Measurement Products: 1. This notification involves 76 specific transmitters manufactured between 2/10/04 and 9/19/05. 2. Each transmitter contains two Zener diodes which may not comply with purchase specifications. 3. The JANTX Zener diodes are different in appearance with respect to the commercial variations. Some JANTX Zener diodes used in the recent past have bodies that are solid orange or light blue in color or clear glass. The commercial Zener diodes in question have a clear glass body. The commercial Zener diode is larger (0.095" diameter X 0.275" long) than the smaller JANTX Zener diode (0.072" diameter X .155" long). 4. The existence of the commercial Zener diode can be confirmed by removal of the transmitter electronics cover and observing the Zener diodes at locations CR2 and CR3, as shown on manufacturer supplied circuit board drawings. 5. The Zener diodes are not field replaceable, as it is necessary to electronically reestablish the calibration zero which will likely necessitate replacement of a calibration resistor. This calibration resistor is located in a temperature sensitive portion of the electronic circuit and requires thermal performance validation. 6. PRIME believes that transmitters with commercial Zener diodes that are currently installed in a plant can be relied upon to continue to operate and perform their safety-related function in the event of an accident. This belief is based on the facts that the commercial Zener diodes installed in any transmitter have been shown to be functional at the accident maximum sustained temperature and because the radiation effects on commercial Zener diodes are known to be within the margin of the original Barton qualification. SGT LLC purchased 22 of the suspect transmitters for use in the Callaway Plant Steam Generator replacement project. Additionally, 6 suspect transmitters had been supplied directly to Callaway Plant. Physical inspections by SGT LLC and Callaway Plant staff determined 21 of the transmitters had the commercial Zener diodes installed. These transmitters were returned to PRIME where the commercial Zener diodes were replaced with qualified Zener diodes and proper transmitter operation was verified. The affected transmitters have since been returned to Callaway as fully qualified for safety related use in nuclear applications. On 11 /16/05, Callaway Plant personnel completed evaluations and determined the use of commercial Zener diodes constituted a defect per 10 CPR 21, requiring initial notification to the NRC within two days. Per the information provided by PRIME, all other affected customers have been notified. The concern was identified while Callaway Plant was shutdown for a refueling outage when the transmitters were installed, and prior to being returned to service. Therefore, no other reporting criteria apply. The NRC Resident Inspectors have been notified of this issue. |