Using xenon concentration in controlling a nuclear power plant

Patent metadata

Field	Value
Publication number	US-12191044-B2
Application number	US-201917784036-A
Country	US
Kind code	B2
Filing date	Dec 12, 2019
Priority date	Dec 12, 2019
Publication date	Jan 7, 2025
Grant date	Jan 7, 2025

Abstract

A method is for controlling a nuclear power plant comprising a pressurized water nuclear reactor. The method includes determining that an obtained waiting period and/or a remaining waiting period is greater than a first predetermined time allowing raising of a Xenon concentration to maximal value. The method further includes, responsive to the determination, moving 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 a control rod setpoint for the start of power ramp up before the end of the obtained waiting period and/or remaining waiting period.

First claim

What is claimed is:

1. 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.

2. The method according to claim 1 , wherein the calculation of the control rod setpoint for the start of power ramp up is further based on one or more reactivity values and/or reactivity coefficients of the nuclear reactor.

3. The method according to claim 2 , wherein the reactivity coefficients of the nuclear reactor include one or more reactivity coefficients of the one or more control rods, a reactivity coefficient of one or more L-rods, a reactivity change due to the difference of the Average Coolant Temperature between the actual power and the target power, a reactivity change due to the difference between the actual power and the target power, and/or reactivity contribution of a follow up flow of injected boric acid or deionized water in combination with the coefficient of the boric acid in the primary cooling fluid.

4. The method according to claim 1 , wherein the calculation of the control rod setpoint for the start of power ramp up is further based on a full power setpoint of the control rods and/or a full power setpoint of L-rods.

5. The method according to claim 1 , further comprising determining that the control rods reach at an upper control limit or a full load position when moving out of the reactor core, responsive to the determination adding some deionized water to maintain the reactor at partial power to compensate the reactivity loss due to the increase of the Xenon concentration to ensure the controllability of the reactor power.

6. The method according to claim 1 , further comprising:
determining a time limit for one or more control rods to move to the control rod setpoint for the start of power ramp up based on an actual control rod position, the control rod setpoint for the start of the power ramp up and an actual boric acid concentration in the primary cooling fluid;
in order to move the one or more control rods into the reactor core to the control rod setpoint for the start of power ramp up before the determined time limit by injection of deionized water into the primary circuit; and
adding deionized water to the primary circuit.

7. The method according to claim 6 , wherein the time limit is further determined based on a minimum feed in rate of the deionized water.

8. The method according to claim 1 , further comprising determining that the obtained waiting period and/or remaining waiting period is shorter than a second predetermined time, the second predetermined time being longer than the first predetermined time,
responsive to the determining that the obtained waiting period and/or remaining waiting period is shorter than the second predetermined time, the one or more control rods are moved, after the Xenon concentration has reached its maximum during the obtained waiting period and/or remaining waiting period, into the reactor core for compensating the reactivity increase due to the decrease of the Xenon concentration.

9. The method according to claim 1 , further comprising determining that the obtained waiting period and/or remaining waiting period is shorter than a second predetermined time, the second predetermined time being longer than the first predetermined time,
responsive to the determining that the obtained waiting period and/or remaining waiting period is shorter than the second predetermined time, the method further comprises determining that, during the movement into the reactor core, the control rods reach the control rod setpoint for the start of power ramp up,
responsive to the determining that the control rods reach the control rod setpoint for the start of power ramp up adding boric acid to the primary circuit and maintaining the control rods at the control rod setpoint for the start of power ramp up to ensure a shutdown reactivity.

10. The method according to claim 1 , further comprising determining that the obtained waiting period and/or remaining waiting period is longer than a second predetermined time, the second predetermined time being longer than the first predetermined time,
responsive to the determining that the obtained waiting period and/or remaining waiting period is longer than a second predetermined time, the method further comprises after the Xenon concentration has reached a maximum during the obtained waiting period and/or remaining waiting period, adding boric acid into the primary circuit for compensating the reactivity increase due to the decrease of the Xenon concentration, wherein the control rods remain at an upper control limit or a full power position until the movement of 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.

11. The method according to claim 10 , wherein the second predetermined time is between 20 h and 60 h.

12. The method according to claim 1 , wherein the first predetermined time corresponds to a time 2 h after the maximum of the Xenon concentration or 30% of the waiting time until a next maximum

Assignees

• Framatome Gmbh

Inventors

• Kuhn Andreas
• Hornung Klaus-Peter
• Heike Dreves
• Petrasch Andreas

Classifications

• G21D3/16

  Varying reactivity · CPC title

• G21C17/108

  Measuring reactor flux · CPC title

• G21C3/326

  comprising fuel elements of different composition; comprising, in addition to the fuel elements, other pin-, rod-, or tube-shaped elements, e.g. control rods, grid support rods, fertile rods, poison rods or dummy rods · CPC title

• G21D3/002

  Core design; core simulations; core optimisation · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title