Monitor for the thermal margin in reactor cores

Purpose: To enable overall estimation for the thermal margin in all of the fuel assemblies by computing each of the measured values to determine the distribution for power criticalinity ratio, comparing the calculated distribution with the distribution incorporated in a distribution comparator and displaying the result on a display. Constitution: Measured values concerning the power distribution for each of fuel assemblies, feedwater flow rate, reactor core pressure and sub-cooling at the core inlet are supplied to a process computer, where flow rate distribution is determined based on hydrodynamic data such as restrictions in the entrance and exit orifices for each of the fuel channels and the criticalinity power ratio for each of the fuel assemblies is computed according to the criticalinity thermal power calculation equations. The computed criticalinity power ratio is compared with a thermally most severe criticalinity power ratio incorporated in a distribution comparator, and the comparison result is supplied to a display to be displayed on a screen. (Sekiya, K.)