Rod Drop Monitoring


The recording of control rod drop times is a regulatory requirement of the nuclear site license. To overcome the spares issues with obsolete equipment, Servelec Controls developed a new Rod Drop Monitoring system using commercially off-the-shelf hardware and software. The following solution can be easily adapted to the requirements of any nuclear power station, and has a proven install base.

EDF Energy Requirements

  • Real-time rod height display & slack switch status.
  • Automatic collection of ‘reactor trip’ data. Data window requirements:
    • Data window to start at 2 sec. pre trip condition.
    • Data window to extend for 28 sec. post trip condition
    • Data collection to include all 121 rods.
    • Data resolution: 20 msec.
  • Data to be visualised through chart display & printouts: rod height versus time.
  • System to calculate intermediate values.
  • Alarm system to include: reactor trip, power supply failure & system health status.

System Benefits

  • Automatic data processing: The previous system involved laborious manual intervention to process & print the data charts. All data processing & chart printing is fully automated in the new system.
  • Calibration facility: The system includes a calibration spreadsheet HMI to allow operators to calibrate the rod height data against actual rod height (conversion of pulse inputs into analogue rod height).
  • Resolution: The system provides increased resolution & extended windows for the data charts. This enhances the data quality for ‘post trip’ analysis work.
  • Chart Display: multi-line detailed charts showing 2secs before trip and 28secs afterwards.
  • Security: User access is based on an ‘administrator controlled’ user privileges set-up.
  • File management and archiving facility: offering user-friendly off-line storage of trip & calibration data.

Rod Drop Monitoring