Rod Control System Testing


Software Developer Dan McCarter leads a training demonstration at an AMS training course.



AMS engineers review test results

Control and shutdown rods in nuclear power plants are moved in and out of the core for reactivity control. In PWRs, these rods are dropped into the reactor by gravity to shut down the plant. Typically, the rods are required to drop from the top to the bottom of the core in less than two seconds. AMS provides equipment, training, and services to measure the drop time of the control and shutdown rods. The test is performed using a multichannel data acquisition system that is set up in the plant for the test or permanently installed in the plant to measure the rod drop times whenever the plant is shut down or trips. With new AMS developments, rod drop time measurements can be performed on all rods simultaneously thereby reducing test time to less than 60 minutes compared to the 12 or more hours that it took to perform the test using the conventional testing procedures.

For plants with Digital Rod Position Indication (DRPI) systems, AMS has simplified the testing process by developing the capability to measure rod drop times without de-energizing the DRPI system. Referred to as the “power-on” rod drop time measurement, this patented AMS technology saves nuclear power plants additional time and effort in performing rod drop time measurements.

AMS also provides equipment, training, and services for testing the timing and sequencing of control rod drive mechanisms (CRDMs). As with rod drop time measurements, we can perform CRDM testing on all rods simultaneously or on one bank of rods at a time.

In addition to automated rod drop time measurements and CRDM testing, AMS provides rod control system diagnostics and troubleshooting. These technologies allow utilities to identify degradation or anomalies in the mechanical and/or electrical components of the rod control system including the rod position indication or CRDM coils, cables, connectors, and electronics.

AMS also provides timing and sequencing verification of slave cyclers in the rod control systems of PWRs. Slave cycler timing and sequencing tests are performed to verify the signal timing of the slave cycler stationary, moveable, and lift logic cards in the rod control logic cabinet.

For Combustion Engineering (CE) PWRs, AMS has developed a rod control testing and diagnostic system for the control element drive mechanisms (CEDMs) which has been implemented at Palo Verde, St. Lucie, and other CE (now Westinghouse) nuclear power plants.


Rod Control System Testing Brochures:
Click here to view brochures for our rod control system products and services.


  • Automated Rod Drop Time Measurements
  • Testing of Timing and Sequencing of CRDMs
  • Power-on Rod Drop Time Measurements (Patented)
  • Rod Control System Diagnostics and Troubleshooting
  • Slave Cycler Testing
  • CEDM Testing in CE Designed PWRs