Paragon reverse engineered the average power range monitor (APRM) circuit cards and power supplies for a U.S. nuclear power plant.

Our reverse engineered units have the same form, fit, and function as the originals and can be installed in the APRM pages with no modifications.

The reverse engineered units were designed to be drop-in replacements that required no field work at the power plant. The circuit boards and metalwork were all built to the original unit dimensions and they were also verified to fit inside the original APRM pages. Test jack locations were maintained in similar locations as the original so there would be no learning curve for maintenance or operations personnel.

The traces on the circuit boards were routed as close to the original design as possible to reduce and/or eliminate any EMI/RFI risks. Any deviations due to component obsolescence were documented indicating the replacement had retained the same form, fit, and function as the original component. All circuit boards were manufactured to IPC-610, Class 2 Specifications.

This project included 11 circuit cards, two system power supplies (5V and ion chamber power supply), and the meter panel. The meter panel included the meter, wiring, and subpanels.


The designs were seismically tested and qualified per the safety-related requirements of our customer. Additionally, the ion chamber power supply has also been seismically tested to another site’s response spectra. All units were functionally tested based on the critical design characteristics of that unit, developed from the original design, industry OPEX, and site procedures.

The Paragon APRM circuit cards, power supplies, and meter panels are fit, form, and functionally equivalent to the original units. They can interface directly with the existing APRM system components and operate in accordance with existing plant operating procedures.

Part Numbers

The part numbers below have been reverse engineered by Paragon and are available for manufacture. Click on each part number to link to the Paragon Catalog.

Part Number


115D6320BBG001/ATC Meter Panel
115D6320BBG003/ATC Meter Panel
135B9879G004/ATC 5V Power Supply
136B1308G007/ATC Averaging Card
136B1313G002/ATC Calibrator Card
136B2503AAG003/ATC LPRM Aux Card
136B2543AAG002/ATC LPRM Card
136B2772AAG002/ATC 15V Regulator
136B3107BBG003/ATC DC Amplifier
136B3109AAG002/ATC Flow Controlled Trip Reference
136B3118AAG002/ATC Quad Trip Unit
136B3122AAG003/ATC Trip Reference
193B1392AAG003/ATC Ion Chamber Power Supply
195B9074AAG002/ATC Thermal Trip Unit
198B6787G002/ATC Auxiliary Card
A-2036/ATC Op Amp Module (sub component)