ENS 54674
ENS Event | |
|---|---|
06:00 Apr 20, 2020 | |
| Title | Part 21 Report - Defect in Thermocouple Low Level Amplifier Modules |
| Event Description | The following is a summary of information received from Curtiss-Wright, Nuclear Division:
Three RTL modules [thermocouple low level amplifiers] have been delivered to clients that may have included faulty resistors that could have remained undetected during functional testing and will eventually malfunction with time in service. MAY/MCY resistors are precision, low temperature coefficient, metal foil technology resistors used in circuits where stability with time and temperature is required. The RTL module uses this style of resistor to achieve its accuracy and variable temperature effects specifications. The symptoms exhibited by faulty resistors were open circuit or changes in value in response to physical or thermal stress. Faulty resistors were sent to the manufacturer for failure analysis. Cracks were discovered in the bond wires that connected the resistor leads to the resistor chip inside the resistor package. The failure rate of resistors manufactured in 2017 and 2018 was significantly greater than resistors manufactured in earlier years. A search of the build records during that time interval resulted in three units. These three modules contain 10 kilo-ohm resistors with date codes from 2017. There are two 10 kilo-ohm resistors in an RTL module, R8 and R17, on the main circuit board assembly. Configured for an RTD input, only R8 is active. R8 sets the 1 milli-ampere excitation current for the RTD element. R17 is used in a voltage offset circuit that is only used in thermocouple and low level amplifier configurations. If the module has been in service for any significant amount of time with no problems, 12 weeks or more, then it is probable that R8, the only suspect resistor in the default configuration, is not affected by this phenomenon. However, if the module has not seen significant service, then the module should be considered suspect. Additionally, if the module has been or could in the future be reconfigured to a low level amplifier or thermocouple application, then the same situation exists with R17, which is not used in the default configuration. Affected Plant - Part Number (Serial Numbers): Beaver Valley - NUS-A135PA-1/3 (s/n: 1800083) Indian Point 3 - NUS-A138PA-3/13/W (s/n: 1800334) Ginna - NUS-A138PA-1/4 (s/n: 1800666) Contact Scientech-I&C-Repair@curtisswright.com to return these modules for further testing and rework, if necessary. Should you have any questions regarding this matter, please contact: Shanen Onken Scientech Business Segment Manager Curtiss-Wright Nuclear Division sonken@curtisswright.com Tel 208-497-3410, Cell 208-821-4054 |
| Where | |
|---|---|
| Curtiss Wright Flow Control Co. Idaho Falls, Idaho (NRC Region 4) | |
| Organization: | Curtiss Wright Flow Control Co. |
| Reporting | |
| Emergency class: | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+35.3 h1.471 days <br />0.21 weeks <br />0.0484 months <br />) | |
| Opened: | Bart Humble 17:18 Apr 21, 2020 |
| NRC Officer: | Ossy Font |
| Last Updated: | Apr 21, 2020 |
| 54674 - NRC Website | |
Curtiss Wright Flow Control Co. with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 546742020-04-20T06:00:00020 April 2020 06:00:00
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