XYLENE POWER LTD.

FNR MONITORING SYSTEM

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

INTRODUCTION:
Elsewhere on this website Fast Neutron Reactors (FNRs) have been identified as the primary source of energy for meeting mankind's future dependable power needs. This web page focuses on the design of the FNR's monitoring system. The monitoring system is not required for normal ongoing FNR operation but performms an important role in initial setting and later testing and adjustment of the actuator settings. For each movable fuel bundle the monitoring system reports the actual elevation, the discharge temperature and the gamma ray flux. Ideally the thermal load should be equally shared amongst all the fuel bundles.
 

MONITORING SYSTEM OVERVIEW:
The monitoring system is mounted in temperature controlled ceiling space above the sodium pool and looks down toward the tops of the indicator tubes. While the monitoring system is in use the gantry crane crossbar is moved out of 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 altitude for each of the 464 movable fuel bundles.

b) A near infrared scanner in the monitoring system determines the liquid sodium temperature in the core of each of the 464 indicator tubes.

C) A gamma ray camera in the monitoring system determines the relative gamma emission by each indicator tube.
 

APPLICATION:
a) The main purpose of the monitoring sytem is to aid in initial setup of the actuator

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.
 

TRENDS:
A gamma flux output significantly above the full power level must immediately trip the reactor shutdown systems. Note that the gamma flux should be roughly proportional to the reactor's thermal load.

A local temperature significantly above the reactor setpoint must cause a slight withdrawal of the corresponding moveable fuel bundle. Note that the coolant surface temperature should be almost independent of the FNR's thermal load.
 

REQUIREMENT:
Unless there is a major earthquake or othr event that might affect the geometry of the FNR fuel bundle, during normal FNR operation the monitoring system is not required and performs no role. Any severe event, such as an attack on the FNR enclosure, should trigger a cold shutdown without reliance on the monitoring system. However, then the monitoring system may be required to restart the FNR.
 

This web page last updated November 28, 2023.