Method for controlling a pressurized water nuclear reactor during stretchout

Patent metadata

Field	Value
Publication number	US-10847276-B2
Application number	US-201414902299-A
Country	US
Kind code	B2
Filing date	Jul 4, 2014
Priority date	Jul 4, 2013
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

A method for controlling a pressurized water nuclear reactor is provided, including core producing thermal power, sensors for acquiring the mean temperature of the primary coolant and for calculating the thermal power, actuators for controlling the axial distribution of power, the control method including:
a first control phase for controlling the reactor during normal operation by controlling the mean temperature of the primary coolant so as to make it correspond to a reference temperature profile (P ref ) dependent on the thermal power of the reactor; and a second control phase, referred to as stretchout, that occurs after normal operation of the reactor in order to control the reactor in stretchout by controlling the axial distribution of power, the mean temperature varying freely in a temperature range delimited by an upper limit and a lower limit.

First claim

The invention claimed is:

1. A method for controlling a pressurized water nuclear reactor comprising:
a core producing thermal power;
control rod clusters and a boron injection system configured to control the mean temperature of the primary coolant from the core and an axial distribution of power;
the control method comprising:
a first control phase comprising a step of controlling the reactor during normal operation by moving the control rod clusters in the core so as to make the mean temperature of the primary coolant correspond to a reference temperature profile (Pref) dependent on the thermal power of the reactor; and
a second control phase, referred to as a stretchout phase, that occurs after normal operation of the reactor, when the fuel of the core is used up such that a concentration of boron in the primary coolant is below 50 ppm when the thermal power of the nuclear reactor is 100% of nominal power, said second control phase comprising a step of controlling the reactor by movements of the control rod clusters, wherein the mean temperature of the primary coolant evolves freely in a temperature range having an upper limit and a lower limit,
wherein the upper limit of the temperature range corresponds to the reference temperature profile (Pref) during normal operation of the reactor, and
wherein the lower limit of the temperature range corresponds to the reference temperature profile (Pref) during normal operation of the reactor with a shift of −Y° C., Y being between 5 and 50, or
the lower limit corresponds to a fixed temperature equal to a reference temperature at 100% of nominal power with a shift of −Z° C., Z being between 10 and 50.

2. The method for controlling a pressurized water nuclear reactor according to claim 1 , wherein in the stretchout phase, the control of axial distribution is brought about by moving the control rod clusters situated above a mid-height of the core such that lower ends of the control rod clusters move between an upper part and the mid-height of the core.

3. The method for controlling a pressurized water nuclear reactor according to claim 1 , wherein in stretchout phase the control of the axial distribution of power is automated.

4. The method for controlling a pressurized water nuclear reactor according to claim 1 , wherein Y is between 5 and 30.

5. The method for controlling a pressurized water nuclear reactor according to claim 1 , wherein Z is between 20 and 30.

6. The method for controlling a pressurized water nuclear reactor according to claim 1 , wherein the second control phase further comprises:
a first sub-phase during which the thermal power of the reactor is kept at 100% of nominal power by increasing an opening of turbine inlet valves; and
a second sub-phase during which the turbine inlet valves are fully opened and the thermal power of the reactor decreases.

Assignees

• Areva Np

Inventors

• Grossetete Alain

Classifications

• Y02E30/30

  Nuclear fission reactors · CPC title

• G21C17/022

  for monitoring liquid coolants or moderators · CPC title

• G21D3/08 Primary

  Regulation of any parameters in the plant · CPC title

• G21D3/001

  Computer implemented control · CPC title

• G21C7/117

  Clusters of control rods; Spider construction · CPC title