XYLENE POWER LTD.

FNR MONITORING SYSTEM

By Charles Rhodes, P.Eng., Ph.D.

INTRODUCTION:
This web page focuses on the design of the FNR's monitoring system. The monitoring system performms an important role in initial setting and later adjustment of the actuator position settings.

For each movable fuel bundle the monitoring system continuously reports the actual movable fuel bundle insertion and the movable fuel bundle discharge temperature. Ideally the thermal load should be equally shared amongst all theactive fuel bundles.
 

MONITORING SYSTEM OVERVIEW:
The monitoring system is mounted in temperature controlled ceiling space above the sodium pool and looks down at an angle toward the tops of the indicator tubes. While the monitoring system is in use the gantry crane transverse beam is outside the monitoring system's field of view.

a) A scanning laser in the monitoring system looks down via a temperature controlled quartz window and measures the distance to the top of each indicator tube. That distance is geometrically converted into the movable fuel bundle insertion for each of the 464 movable fuel bundles. The monitoring system is in two packages that mount on either side of the transverse beam.

b) A near infrared scanner in the monitoring system determines the indicator tube temperature for of each of the 464 indicator tubes.
 

APPLICATION:
a) The main purpose of the monitoring sytem is to sense the positions of the actuators.

b) A secondary purpose of the monitoring system is automatic periodic testing of the actuator hardware to ensure that in an emergency it will follow FNR shutdown commands;

c) A third purpose of the monitoring system is reporting on FNR status after an automatic shutdown.

d) A fourth purpose of the monitoring system is characterization and compensation for long term reactor degradation mechanisms such as fuel burnup.
 

TEMPERATURE CONTROL:
A local temperature significantly above the reactor setpoint must cause a slight withdrawal of the corresponding moveable fuel bundle.
 

REQUIREMENT:
Any severe event, such as an attack on the FNR enclosure, should trigger a cold shutdown without reliance on the monitoring system. However, the monitoring system is required to restart the FNR.
 

This web page last updated December 12, 2025.