9. Developments and evolutions

9.1 Development of gamma thermometers

This development was carried out in the 1980s at the instigation of EDF. An experimental installation comprising eight rods was tested on a 900 MWe unit over several cycles. No industrial applications have been developed, but it is of interest in terms of instrumentation techniques.

The basic principle is calorimetric measurement. It uses the property of gamma radiation to lose part of its energy in the materials it passes through. This energy is transformed into heat, and the temperature rise is proportional to the energy deposited. If there is no heat loss, the system behaves like an adiabatic calorimeter; if this is not the case, and if we assume that there is an equilibrium between the evacuated heat flux and the incident...