Using xenon concentration in controlling a nuclear power plant

A method for controlling a nuclear power plant comprising a pressurized water nuclear reactor having a reactor core producing power, a primary circuit connecting the reactor core to a steam generator, one or more control rods movable into the reactor core for controlling the power of the reactor core, an injecting device for injecting boric acid and/or deionized water into the primary circuit for controlling the reactivity of the reactor core, the method comprising:

• determining an actual power of the nuclear reactor;
• determining automatically an actual Xenon concentration, an actual Iodine concentration, and an actual Xenon reactivity;
• obtaining a target power and a power gradient for a power ramp up period until a target power;
• obtaining a waiting period and/or a remaining waiting period in which the nuclear reactor works at a partial power until the nuclear reactor ramps up to a target power being higher than the partial power;
• calculating for an end of the obtained waiting period and/or remaining waiting period the Xenon reactivity and/or Xenon concentration based on the actual Xenon concentration, the actual Iodine concentration and the obtained waiting period and/or remaining waiting period;
• calculating, for an end of the power ramp up period, the Xenon reactivity and/or the Xenon concentration;
• calculating a control rod setpoint for a start of power ramp up for the one or more control rods based on the calculated Xenon reactivity and/or Xenon concentration at the end of the obtained waiting period and/or remaining waiting period and the end of the ramp up period, so that the power ramp up is performable using the control rods;
• positioning, during the obtained waiting period and/or remaining waiting period, the one or more control rods based on the obtained waiting period and/or remaining waiting period and the control rod setpoint for the start of the power ramp up, so that the one or more control rods reach the control rod setpoint for the start of power ramp up at the end of the obtained waiting period and/or remaining waiting period,
• determining that the obtained waiting period and/or remaining waiting period is greater than a first predetermined time, the first predetermined time allowing raising of the Xenon concentration to a maximal value, and responsive to the determination:
• moving the one or more control rods out of the reactor core for compensating the reactivity loss due to an increase of the Xenon concentration, and
• moving the one or more control rods into the reactor core to the control rod setpoint for the start of power ramp up before the end of the obtained waiting period and/or remaining waiting period.