Gamma Thermometer

DELTA M Corporation is the world’s leading provider of Gamma Thermometers for use in nuclear reactor power monitoring and nuclear reactor coolant level monitoring applications.

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Gamma Thermometer Theory of Operation

Principle of Operation for the Gamma Thermometer

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Product Summary

Gamma Thermometers are a non-depleting source of information about the power level in a nuclear reactor. Their monolithic design allows for an expected lifetime higher than 10 years.

  • In-situ calibration allows for accurate measurements all the time.
  • Robust mechanical design allows for years of worry free operation.
  • With no fissile material to worry about, no sophisticated burnup algorithms are needed to utilize output.

For power measurement, Gamma Thermometers depend upon the heating of the instrument rod by fission and fission product gamma rays. The heat generated is proportional to the linear power of nearby fuel rods. Heat generated is permitted to escape to the coolant sink only along a closely controlled conduction path while the temperature drop is measured by a differential thermocouple. Signal is proportional to fuel power, not neutron flux! Signal is strong and constant with fuel burnup.

Use of GT as a collapsed level monitor

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Because of the nature of their design, Gamma Thermometers are excellent instruments for use in Inadequate Core Cooling Monitoring (ICC) applications.

  • As level indicator
  • As shutdown power monitors
  • As heat transfer monitors
  • To measure reactor temperature

Gamma Thermometers can be used to provide fast and accurate information about the primary coolant level in a nuclear reactor vessel. A heater inside the GT creates a signature temperature differential between the differential thermocouples when water is present on the boundary of the GT. When the rod becomes uncovered, caused by a drop in primary coolant level, the temperature difference rapidly increases and can be used to trip an emergency reactor shutdown.