Patent Number: 
Section: abstract

The exit thermocouples of a pressurized water reactor (PWR) are calibrated by recording the thermocouple temperature measurements periodically during power ascension of the reactor together with a predicted power at the corresponding locations at the same time determined by a three-dimensional analytical nodal model of the core at the same core average power. The temperature measurements are converted to local core power values which are then divided into the corresponding predicted powers for the corresponding locations to arrive at mixing factors which are fitted to a selected function of core power. These mixing factors are recorded and subsequently applied to local power values calculated from measured exit thermocouple temperatures to adjust the three-dimensional nodal model power. Periodically, the mixing factors are adjusted by using flux map data to update the three-dimensional analytical nodal model power to generate a reference power distribution, calculating updated mixing factors using the current thermocouple temperature measurement taken at the same time and therefore the same average core power, and the reference power distribution, and then shifting the mixing factor functions of core power accordingly to pass through the updated mixing factors.