Method and system for governing a pressurized water nuclear reactor

A governance system for governing a pressurized water nuclear reactor, the pressurized water nuclear reactor comprising a reactor core and a cooling circuit for the reactor core holding a reactor coolant, a reactor state represented by measurable state variables, and a reactor core reactivity being controlled by actuating variables, the actuating variables including at least a first actuating variable and a second actuating variable, the first actuating variable being positions of control rods and the second actuating variable being a position or positions of at least one feed pump and/or at least one control valve for controlling a boron concentration in the cooling circuit, the governance system including a computer programmed for executing the following steps:

• receiving measured current values of the measurable state variables;
• receiving a load schedule giving a future electrical power demand as a function of time;
• iteratively considering, for a future time interval of the future electrical power demand, a number of randomly varied possible trajectories of the first and second actuating variables under constraint of the received Load Schedule,
• predicting, for each possible combination of the trajectories of the first and second actuating variables, trajectories for the measurable state variables on the basis of each of the possible combinations of the trajectories of the first and second actuating variables, the measured current values of the measurable state variables, calculated poisoning values and a reactivity balance equation of the reactor core reactivity,
• wherein each of the possible combinations of the trajectories of the first and second actuating variables is assigned a figure of merit on the basis of a Value Table which contains weighting or penalty values for a number of events or adverse reactor core states of the reactor state, wherein the weighting or penalty values are based on:
• preset conditions or values of the actuating variables,
• the measurable state variables, and/or
• variables derived from the preset conditions or values of the actuating variables, and/or the measurable state variables,
• wherein a chosen combination of trajectories of the first and second actuating variables from amongst the possible combinations of the trajectories of the first and second actuating variables having a highest or lowest corresponding figure of merit is chosen by the computer;
• and
• instructing actuators of the nuclear reactor to achieve the chosen combination of the trajectories of the first and second actuating variables by moving the positions of the control rods with respect to the reactor core to change the reactivity of the core and/or moving the position or the positions of the at least one feed pump and/or the at least one control valve to change the boron concentration in the primary cooling circuit.