Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C1/00—Reactor types
  • G21C1/04—Thermal reactors ; Epithermal reactors
  • G21C1/06—Heterogeneous reactors, i.e. in which fuel and moderator are separated
  • G21C1/08—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being highly pressurised, e.g. boiling water reactor, integral super-heat reactor, pressurised water reactor
  • G21C1/086—Pressurised water reactors
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21D—NUCLEAR POWER PLANT
  • G21D3/00—Control of nuclear power plant
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• the present invention relates to a method for controlling a nuclear power plant.
• a nuclear power plant has a primary water circuit and a separate secondary water circuit, a nuclear reactor to heat the water circulating in the primary circuit, one or more steam generator(s) thermally coupling the primary circuit and the secondary circuit to transfer heat from the primary circuit to the secondary circuit and produce steam in the secondary circuit, and a steam turbine integrated in the secondary circuit to generate mechanical energy from the steam. This mechanical energy can then be converted into electrical energy using an electrical generator coupled to the steam turbine.
• One of the aims of the invention is to propose a method for controlling a nuclear power plant making it possible to maintain the nuclear power plant in a satisfactory operating range, preferably usable in a wide power range of the nuclear reactor.
• the invention proposes a method for controlling a pressurized water nuclear power plant implemented by an automated control system, the nuclear power plant comprising a primary circuit for the circulation of water, integrating a nuclear reactor, a secondary circuit for circulating water, and N steam generator(s), N being an integer equal to or greater than 1, each steam generator being configured to transfer thermal energy from the primary circuit to the secondary circuit with steam generation in the secondary circuit, the control method comprising:
• a primary power signal calculated as a function of the primary power and/or of at least one quantity indicative of a variation of the primary power
• a secondary power signal calculated as a function of the secondary power and/or of at least one quantity indicative of a variation of the secondary power
• a setpoint monitoring mode in which the nuclear power plant is controlled according to a setpoint operational power received by the control system so that the primary power and the secondary power follow the operational power setpoint;
• the automatic implementation of a power limitation mode comprising the calculation, by the control system, of a target equilibrium power equal to or less than the primary power and equal to or less than the secondary power, and the control of the nuclear power plant according to the target equilibrium power.
• control method includes one or more of the following optional characteristics, taken individually or according to all technically possible combinations:
• the secondary power is determined by calculating the thermal power transferred by each steam generator from the primary circuit to the secondary circuit and by calculating the sum of these thermal powers;
• the primary power signal is calculated as a function of the primary power, a filtered derivative of the primary power, an axial offset of the nuclear reactor, a filtered derivative of the axial offset of the nuclear reactor, a control rod movement signal and/or a filtered derivative of the control rod movement signal;
• the primary power signal is calculated as the sum of the primary power and one or more of the filtered derivative of the primary power multiplied by a primary power coefficient, the absolute value of the filtered derivative of the axial offset multiplied by an axial offset coefficient, and the filtered derivative of the control rod movement signal multiplied by a movement signal coefficient;
• the secondary power signal is calculated as a function of the secondary power, of a steam pressure representative of the pressure of the steam at the outlet of the steam generator(s), of a filtered derivative of the steam pressure, a feedwater temperature representative of the water temperature at the inlet of the steam generator(s), a filtered derivative of the feedwater temperature, a feedwater flow rate representative of the water flow at the inlet of the steam generator(s) and/or a filtered derivative of the feed water flow;
• the secondary power signal is calculated as the sum of the secondary power and one or more of the filtered derivative of the vapor pressure multiplied by a coefficient of vapor pressure, of the filtered derivative of the feed water temperature multiplied by a feed water temperature coefficient, and the filtered derivative of the feed water flow multiplied by a feed water flow coefficient;
• the detection of a possible imbalance comprises the comparison of a difference between the primary power signal and the secondary power signal with a lower threshold and/or an upper threshold;
• the detection of a possible imbalance comprises the generation of a rebalancing request logic signal when said difference is less than the lower threshold and/or greater than the upper threshold, controlling the switch to power limitation mode;
• the power limitation mode is activated for a power limitation duration determined from the detection of an imbalance
• the target balance power is calculated according to a maximum balance power, the target balance power being equal to or less than the maximum balance power
• the maximum equilibrium power is calculated according to the primary power reduced by a non-zero difference
• control method includes clipping in such a way that the maximum equilibrium power is lower than a determined maximum value and/or higher than a determined minimum value;
• the target balance power is determined as the minimum among the primary power, the secondary power and the maximum balance power
• control method comprises, in power limitation mode, the calculation of a primary power setpoint and a secondary power setpoint as a function of the target equilibrium power, and the control of the nuclear power plant in such so that the primary power joins the primary power setpoint and that the secondary power joins the secondary power setpoint;
• the primary power setpoint is calculated as equal to the target equilibrium power, optionally filtered, preferably by a low-pass filter, and the secondary power setpoint is calculated as equal to the power target balance, optionally filtered, preferably by a low-pass filter.
• the invention also relates to a control system for a nuclear power plant configured for the implementation of a control method as defined above.
• the invention also relates to a nuclear power plant comprising a primary circuit for the circulation of water, integrating a nuclear reactor, a secondary circuit for the circulation of water, N steam generator(s), N being an integer equal to or greater than to 1, each steam generator being configured to transfer thermal energy from the primary circuit to the secondary circuit with steam generation in the secondary circuit, the nuclear power plant comprising a control system as defined above.
• the invention also relates to a computer program product which can be recorded on a computer medium or in a computer memory and executable by a processor, said computer program product containing software code instructions for the implementation of a control method as defined above.
• FIG. 1 is a schematic view of a nuclear power plant, illustrating a primary circuit, integrating a nuclear reactor, and a secondary circuit;
• FIGS. 2 to 6 are block diagrams illustrating a process for controlling the nuclear power plant of Figure 1;
• FIG. 7 is a schematic view of a nuclear power plant according to another embodiment
• FIG. 8 is a schematic view of a nuclear power plant according to yet another embodiment.
• the nuclear power plant 2 illustrated in Figure 1 comprises a primary circuit 4 for the circulation of water and a secondary circuit 6 for the circulation of water, the primary circuit 4 and the secondary circuit 6 being separated and thermally coupled via of N steam generator(s) 8, N being an integer equal to or greater than 1.
• Each steam generator 8 is arranged between the primary circuit 4 and the secondary circuit 6 and configured for heat exchange between the water in the primary circuit 4 and the water in the secondary circuit 6.
• each steam generator 8 makes it possible to generate steam in the secondary circuit 6.
• each steam generator 8 is supplied at the input with water in the liquid state and supplies at the output water in a gaseous state, i.e. water vapour.
• the primary circuit 4 comprises a nuclear reactor 10 to heat the water circulating in the primary circuit 4.
• the nuclear power plant 2 is for example a pressurized water nuclear power plant, in which case the nuclear reactor 10 is a pressurized water nuclear reactor (or PWR for "Pressurized Water Reactor") or a boiling water nuclear power plant, in which case the nuclear reactor 10 is a boiling water nuclear reactor (or BWR for “Boiling Water Reactor”).
• the primary circuit 4 comprises for example N primary fluidic loop(s) 12, each primary loop 12 fluidically connecting the nuclear reactor 10 to a respective steam generator 8 .
• a single steam generator 8 and a single primary loop 12 are shown in Figure 1.
• the primary circuit 4 comprises several primary loops 12, for example four primary loops 12.
• the nuclear reactor 10 comprises a reactor vessel 14. Each primary loop 12 connects the reactor vessel 14 to a respective steam generator 8. Each primary loop 12 is connected to the reactor vessel 14 by an inlet pipe 14A and an outlet pipe 14B.
• the nuclear reactor 10 comprises a core 16 formed of a plurality of nuclear fuel assemblies 18 arranged side-by-side in the reactor vessel 14.
• the nuclear reactor 10 comprises control clusters 20 that can be lowered into or raised out of the reactor core 16 to control the reactivity of the nuclear reactor 10.
• Control rods 20 include, for example, control rods that can be selectively inserted into core 16 to decrease reactivity or extracted from core 16 to increase reactivity, and stop rods that can be dropped into core 16 to cause a automatic shutdown of the nuclear reactor 10.
• Each primary loop 12 includes a respective primary pump 22 to force the circulation of water inside this primary loop 12.
• the primary circuit 4 comprises a pressurizer 24 configured to maintain, in the primary circuit 4, sufficient pressure for the water circulating in the primary circuit 4 to remain in the state liquid.
• the pressurizer 24 is fluidically connected to a hot leg of a primary loop 12, i.e. a leg in which the fluid circulates from the nuclear reactor 10 to the steam generator 8 located on this primary loop 12.
• the primary circuit 4 comprises several primary loops 12
• the primary circuit 4 comprises for example a single pressurizer 24 connected to the hot leg of one of the primary loops 12.
• the secondary circuit 6 comprises for example a single secondary loop 26 supplied with steam from the steam generator 8 of each primary loop 12.
• the secondary circuit 6 comprises a respective secondary loop 26 associated with each primary loop 12 and supplied with steam from the steam generator 8 of this primary loop 12.
• the secondary circuit 6 comprises one or more turbine(s) 28, each turbine 28 being configured to convert the thermal energy contained in the steam circulating in the secondary circuit 6 into mechanical energy.
• the secondary circuit 6 comprises one or more secondary pump(s) 30 to force the circulation of water inside the secondary circuit 6.
• the secondary circuit 6 comprises one or more condenser(s) 32, each condenser 32 being arranged downstream of a turbine 28 to cool the steam leaving the turbine 28 and bring it back to the liquid state.
• Each condenser 32 is for example arranged on the secondary circuit 6 being configured for a heat exchange between the water of the secondary circuit 6 and the water circulating in a cooling circuit 34.
• the nuclear power plant 2 comprises one or more electrical generator(s) 36, each electrical generator 36 being mechanically coupled to a turbine 28 so as to generate electrical energy from the mechanical energy generated by this turbine 28
• the electrical energy is for example supplied to an electricity distribution network.
• the nuclear power plant 2 comprises a control system 40 configured for the automatic control of the nuclear power plant 2, in particular for the implementation of a method for controlling the nuclear power plant 2
• the control system 40 comprises first sensors for measuring first operating parameters of the nuclear power plant 2, relating to the operation of the primary circuit 4, and second sensors for measuring second operating parameters of the nuclear power plant 2, relating to the operating of the secondary circuit 6.
• the first sensors include for example neutron detectors 42 to measure a neutron flux in the nuclear reactor 10.
• the neutron detectors 42 include internal neutron detectors disposed inside the reactor core 16 (generally referred to as “incore” detectors) and/or external neutron detectors (not shown) disposed outside the reactor vessel.
• reactor 14 of nuclear reactor 10 in which core 16 is received generally referred to as “excore” detectors).
• the neutron detectors 42 are for example self-powered neutron detectors (also designated by the acronym SPND for “Self-Powered Neutron Detector” in English).
• the neutron detectors 42 are for example cobalt, vanadium and/or rhodium detectors.
• the measurement of the neutron flux generated in the nuclear reactor 10 at a given instant makes it possible to calculate a value representative of the instantaneous thermal power generated by the nuclear reactor 10 or hereinafter, the “primary power”.
• the second sensors comprise for example, for each steam generator 8, an outlet pressure sensor 44 to measure the pressure in the secondary circuit 6 at the outlet of the steam generator 8, a steam flow sensor 45 to measure the flow of steam in the secondary circuit 6 at the outlet of the steam generator 8, an incoming water flow sensor 46 to measure the flow of water entering in the liquid state in the steam generator 8 in the secondary circuit 6 and /or an inlet water temperature sensor 48 to measure the temperature of the water at the inlet of the steam generator 8 in the secondary circuit 6.
• the control system 40 comprises an electronic control unit 50 configured to control and command the nuclear power plant 2 by implementing the control command method.
• the electronic control unit 50 is for example configured to receive the first operating parameters and the second operating parameters, by receiving the measurement signals supplied by the first sensors and the second sensors.
• the electronic control unit 50 is for example configured to control the primary circuit 4 and the secondary circuit 6 according to the first parameters and the second parameters.
• the electronic control unit 50 is for example configured to control the control rods 20 to adjust the reactivity of the nuclear reactor and/or each primary pump 22 to adjust the flow of water in the primary circuit 4, and/or to control each secondary pump 30 to adjust the flow of water in the secondary circuit 6 and to control each turbine 28 and/or each generator 36.
• the piloting process includes:
• a primary power signal S1 calculated as a function of the primary power P1 and/or of at least one quantity indicative of a variation of the primary power P1
• a secondary power signal S2 calculated as a function of the secondary power P2 and/or of at least one quantity indicative of a variation of the secondary power P2
• a setpoint monitoring mode in which the nuclear power plant 10 is controlled according to an operational COP power setpoint received by the control system 40 so that the primary power P1 and the secondary power P2 follow the operational power setpoint COP;
• the automatic implementation of a power limitation mode comprising the calculation, by the control system 40, of a target equilibrium power PEC equal to or less than the power primary P1 and equal to or less than the secondary power P2, and the control of the nuclear power plant 2 according to the target equilibrium power PEC.
• the primary power P1 is calculated for example according to measurements of the first operating parameters of the nuclear power station 2, relating to the operation of the primary circuit 4 and measured by the first sensors, in particular according to a measurement of the neutron flux in the core 16 of nuclear reactor 10.
• the measurements of the first parameters are provided by the first sensors, for example by the neutron detectors 42 equipping the nuclear reactor 10.
• the secondary power P2 is calculated for example as a function of second operating parameters of the nuclear power plant 2, relating to the operation of the secondary circuit 6 and measured by the second sensors.
• the secondary power P2 is calculated for example by determining, respectively for each steam generator 8, the thermal power transferred from the primary circuit 4 to the secondary circuit 6 by this steam generator 8, and by calculating the secondary power P2 as the sum of the powers transferred.
• the power transferred from the primary circuit 4 to the secondary circuit 6 is calculated in a known manner, for example according to the second parameters, in particular according to the steam pressure leaving the steam generator 8 in the circuit secondary circuit 6, of the flow of steam leaving the steam generator 8 in the secondary circuit 6, of the flow of water entering the steam generator 8 in the secondary circuit 6 and/or the temperature of the water entering the steam generator 8 in the secondary circuit 6.
• the measurements of the second parameters are for example supplied respectively by the outlet pressure sensor 44, by the steam flow sensor 45, by the incoming water flow sensor 46 and/or by the incoming water temperature sensor 48 .
• the measurements of the second parameters are in another example provided respectively by the outlet pressure sensor 44, by a steam barrel pressure sensor (not shown) arranged to measure the pressure of the steam in a steam barrel of the secondary circuit, by the incoming water flow sensor 46 and by the incoming water temperature sensor 48.
• the steam barrel is a collector receiving the steam productions from the steam generators 8 and distributing the steam produced to the turbine 28.
• the electronic control unit 50 comprises for example a primary power calculation module 52 to calculate the primary power P1 generated by the nuclear reactor 10 and a secondary power calculation module 54 to calculate the power secondary P2 transferred from primary circuit 4 to secondary circuit 6.
• the primary power calculation module 52 receives, for example, the measurement signals supplied by the neutron detectors 42
• the secondary power calculation module 54 receives, for example, the measurement signals supplied by the outlet pressure sensor 44 measuring the pressure in the secondary circuit 6 at the outlet of the steam generator 8, by the steam flow sensor 45 measuring the steam flow in the secondary circuit 6 at the outlet of the steam generator 8, by the water flow sensor entering 46 measuring the flow of water entering in the liquid state into the steam generator 8 in the secondary circuit 6 and/or by the entering water temperature sensor 48 measuring the temperature of the water at the inlet of the steam generator 8 in the secondary circuit 6.
• the electronic control unit 50 comprises for example a control module 56 receiving the operational power setpoint COP, the calculated primary power P1 and the calculated secondary power P2, is configured to generate instructions intended for the functional organs of the nuclear power plant 2 to control the nuclear power plant 2.
• the control module 56 is configured for example to generate control instructions intended for the control rods 20 for each primary pump 22, for each turbine 28, for each secondary pump 30, and/or for each generator 36.
• the primary power P1 and the secondary power P2 are in principle balanced, the control of the nuclear power plant 2 being carried out to maintain the primary power P1 and the secondary power P2 each substantially equal to the operational setpoint of power COP received by the control system 40.
• the operational power setpoint COP is provided, for example, by the operator who operates nuclear power plant 2.
• it can be modified and/or modulated according to operating parameters of the electricity distribution network to which the nuclear power plant 2 is connected, for example according to variation in the frequency of the electricity distribution network.
• the power limitation mode is provided to restore a balance between the primary power P1 and the secondary power P2 while maintaining the nuclear power plant 2 in a normal operating zone, to avoid the intervention of a protection system which could s automatically activate to shut down NPP 2 if it moves out of a normal operating area.
• a target equilibrium power PEC is calculated by the control system 40, preferably independently of the operational power setpoint COP, the nuclear power plant 2 then being controlled according to the equilibrium power target PEC, and no longer according to the operational power setpoint COP.
• the target equilibrium power PEC is calculated to be equal to or less than the primary power P1 and equal to or less than the secondary power P2, so that the power limiting mode results in a drop in the primary power P1 and/or or a drop in the secondary power P2, while bringing them back to equilibrium.
• the power limitation mode is provided to be able to be implemented automatically using the control system 40 while remaining in a zone of normal operation of the nuclear power plant 2, and therefore without intervention of a protection system.
• the detection of a possible imbalance is carried out by comparing a primary power signal S1 and a secondary power signal S2.
• the primary power signal S1 is calculated so as to be representative of the primary power P1, while optionally being indicative of a change in the primary power P1.
• the secondary power signal S2 is calculated so as to be representative of the secondary power P2, while optionally being indicative of an evolution of the secondary power P2.
• the primary power signal S1 is calculated for example as a function of the primary power P1, of a filtered derivative of the primary power, of an axial offset AO of the nuclear reactor 10, of an absolute value of a filtered derivative of the axial offset of the nuclear reactor 10, of a movement signal PG indicative of a movement of control rods 20 and/or of a filtered derivative of the signal of PG movement of control rods 20.
• filtered derivative we mean a derivative function added to a filter which cuts the high-frequency variations and allows the low-frequency variations to pass (low-pass filter).
• the low-pass filter applied to the derivative makes it possible to smooth the derivative to take into account only the trend of the variation of the quantity which is indicated by the derivative, without taking into account too rapid variations which are not representative of a real signal evolution trend.
• the axial offset AO of the nuclear reactor 10 is representative of a non-uniform distribution of the neutron flux along the assemblies of the nuclear reactor 10, in particular of an imbalance of the neutron flux between a lower part of the nuclear reactor 10 and an upper part of the nuclear reactor 10.
• the axial offset AO can be determined for example using a set of neutron detectors 42 fitted to the nuclear reactor 10 and distributed vertically to be able to measure differences in the neutron flux as a function of their positions along the nuclear reactor 10.
• a variation of the axial offset AO can be the sign of an upcoming variation of the primary power P1. The taking into account of the axial offset AO, in particular of an absolute value of the filtered derivative of the axial offset AO, makes it possible to anticipate a variation of the primary power P1.
• a movement of control rods 20 can lead to a variation of the primary power P1.
• the movement signal PG and in particular a filtered derivative of the movement signal PG, makes it possible to anticipate a variation in the primary power P1 which would be due to a movement of control rods 20.
• the primary power signal S1 is calculated as equal to the primary power P1.
• the primary power signal S1 is calculated as the sum of the primary power P1 and one or more of a filtered derivative of the primary power P1 multiplied by a primary power coefficient KP1, an absolute value the filtered derivative of the axial offset AO of the nuclear reactor 10 multiplied by an axial offset coefficient KAO, the filtered derivative PG of the control rod movement signal multiplied by a control rod movement coefficient KPG.
• Each of the coefficients indicated above is preferably positive or zero.
• coefficients indicated above has its own value.
• the coefficients can have different values. In a very special case, they may possibly be equal.
• the primary power signal S1 is calculated as the sum of the primary power P1, the filtered derivative of the primary power P1 multiplied by the primary power coefficient KP1, the absolute value of the filtered derivative of the axial offset AO of the nuclear reactor 10 multiplied by the axial offset coefficient KAO and of the filtered derivative PG of the control rod movement signal multiplied by the control rod movement coefficient KPG.
• the secondary signal S2 is calculated for example as a function of the secondary power P2, of a steam pressure PV representative of the pressure of the steam at the outlet of the steam generator(s) 8, of a filtered derivative of the pressure of steam PV, of a feed water temperature TE representative of the water temperature at the inlet of the steam generator(s) 8, of a filtered derivative of the water temperature feed TE, a feed water flow DE representative of the water flow at the inlet of the steam generator(s) 8 and/or a filtered derivative DE of the feed water flow.
• the steam pressure PV is preferably determined as the average of the steam pressures at the outlet of the steam generators 8, determined for example using the pressure sensors of steam 44.
• the nuclear power station 2 comprises a single steam generator 8
• the feed water temperature TE is preferably determined as the average of the feed water temperatures at the inlet of the steam generators 8, determined for example using water temperature sensors 46.
• the nuclear power station 2 comprises a single steam generator 8 it is determined as equal to the water temperature at the inlet of the steam generator(s) 8 of the nuclear power station 2 .
• the incoming water flow rate DE is preferably determined as the average of the water flow rates at the inlet of the steam generators 8, determined for example using the water flow sensors 48.
• the nuclear power plant 2 comprises a single steam generator 8
• the secondary power signal S2 is calculated as the sum of the secondary power P2 and one or more of the filtered derivative of the vapor pressure PV multiplied by a vapor pressure coefficient KPV which is preferably negative or zero, of the filtered derivative of the feed water temperature TE multiplied by a water temperature coefficient KTE which is preferably negative or zero, and the filtered derivative of the feed water flow DE multiplied by a coefficient feed water flow KDE which is preferably positive or zero.
• the secondary power signal S2 is calculated as the sum of the secondary power P2, the filtered derivative of the pressure of steam PV multiplied by a steam pressure coefficient KPV, the filtered derivative of the feed water temperature TE multiplied by a water temperature coefficient KTE and the filtered derivative of the feed water flow DE multiplied by a coefficient of KDE food water flow.
• the low-pass filters used to calculate the different filtered derivatives used for calculating the primary power signal S1 and the secondary power signal S2 can be identical. Alternatively, they are not all identical. At least two of these low-pass filters are then different. In one particular embodiment, they are all different.
• the electronic control unit 50 includes a detection module 62 configured to detect an imbalance by determining and comparing the primary power signal S1 and the secondary power signal S2.
• the detection module 62 comprises a primary signal module 64 and a secondary signal module 66 for respectively calculating the primary power signal S1 and the secondary power signal S2.
• the primary signal module 64 and the secondary signal module 66 each comprise one or more differentiators 68, each differentiator 68 being configured to receive a signal representative of a quantity and supply the derivative of this signal as output, optionally a absolute value module 69 for receiving the derivative of the axial offset AO and outputting the absolute value of this derivative, one or more amplifier(s) 70, each multiplier being configured to multiply a signal by a zero, positive or negative, and two adders 72 to calculate the primary power signal S1 and the secondary power signal S2 from the signals taken into account to calculate each of the primary power signal S1 and of the secondary power signal S2.
• the comparison of the primary power signal S1 and the secondary power signal S2 comprises the calculation of the difference between the primary power signal S1 and the secondary power signal S2 and comparing this difference with a lower threshold SINF and/or an upper threshold SSUP and switching from a setpoint tracking mode to the power limitation mode.
• the control method includes, for example, switching from the setpoint tracking mode to the power limitation mode when the difference between the primary power signal S1 and the secondary power signal S2 is less than the lower threshold SINF and/or greater than the threshold higher SSUP.
• the passage to the power limitation mode is for example delayed in such a way that the power limitation mode is maintained at least for a determined duration of power limitation from the moment it is activated.
• the determined duration of power limitation is for example predetermined. It is for example equal to or greater than 10 seconds (s), in particular equal to or greater than 20 seconds.
• Maintaining the power limitation mode for a certain minimum duration allows the effective reduction and rebalancing of the primary power P1 and the secondary power P2, without switching too quickly to the setpoint tracking mode even if the primary power P1 and the secondary power P2 quickly returned to a balanced situation.
• the control method comprises for example the generation of an imbalance logic signal SD indicative of the existence of an imbalance between the primary power signal S1 and the secondary power signal S2, and a time-delayed BP rebalancing request logic signal, determined as a function of the imbalance logic signal to control the switch to power limitation mode.
• the SD imbalance logic signal takes two values (e.g. 0 or 1), one indicative of the existence of a significant imbalance requiring a switch to power limitation mode, and the other indicative of the absence significant imbalance requiring a switch to setpoint tracking mode.
• the BP rebalancing request logic signal takes two values (eg 0 or 1), one corresponding to the setpoint tracking mode and the other to the power limitation mode, the BP rebalancing request logic signal being timed in such a way that when it changes to the value corresponding to the power limitation mode, this value is maintained for the determined duration of the power limitation.
• control module comprises for example a subtractor 74 arranged to determine the difference between the primary power signal S1 and the secondary power signal S2, a comparator 76 to compare the difference to the internal threshold SINF and/ or at the upper threshold SSUP and generate the imbalance logic signal SD according to the result of the comparison, and a limitation request generator 78 for generating the rebalancing request logic signal BP according to the imbalance logic signal SD.
• the target equilibrium power PEC is calculated as a function of a maximum equilibrium power PEMAX, the target equilibrium power PEC being equal to or less than the maximum equilibrium power PEMAX.
• the control method comprises the calculation of the maximum equilibrium power PEMAX as a function of the primary power P1.
• the maximum equilibrium power PEMAX is calculated from the primary power P1 reduced by a non-zero deviation E. This makes it possible to determine a power value strictly lower than the primary power P1, for example to then calculate power setpoints (primary power setpoint CP1 and secondary power setpoint CP2 as will be described later) allowing a reduction in power of the nuclear reactor 10.
• the value of the difference E is for example between 20% and 55% of the nominal operating power of the nuclear reactor 10, in particular between 20% and 35% of the nominal operating power of the nuclear reactor 10.
• the nominal operating power of the nuclear reactor 10 is its maximum power allowed in normal operation. This is a predetermined power for nuclear reactor 10.
• the difference E is constant. In a particular exemplary embodiment, the deviation E is chosen equal to 25% of the nominal power PN of the nuclear reactor 10.
• the difference between the primary power P1 and the deviation E is filtered using a maximum equilibrium power filter FPEMAX so that the absolute value of its derivative remains below a determined derivative threshold.
• the maximum equilibrium power filter FPEMAX is for example a low-pass filter, in particular a second-order low-pass filter. It may be another type of filter.
• the maximum balance power filter FPEMAX is configured so that the absolute value of the derivative of the difference between the primary power P1 and the deviation E remains lower than a maximum absolute value of the load following derivative, for example 5% of the rated power PN per minute.
• the signal resulting from the difference between the primary power P1 and the deviation E is clipped between a minimum value VMIN and/or a maximum value VMAX.
• the minimum value VMIN is for example equal to zero and the maximum value VMAX is for example equal to 75% of the nominal power PN of the nuclear reactor 10.
• control module 56 of the electronic control unit 50 includes for example a maximum power calculation module 80 configured to calculate the maximum target equilibrium power PEMAX.
• this maximum power calculation module 80 comprises for example a subtractor 82 to receive the primary power P1 as input and subtract the difference E from it, and, optionally, in series with the subtractor 82, a module filter 84 to apply the maximum equilibrium power filter FPEMAX to the primary power P1 minus the difference E and/or a clipping module 86 receiving as input the primary power P1 minus the difference E, possibly filtered by the filter module 84.
• the target equilibrium power PEC is determined according to the primary power P1, the secondary power P2 and the maximum target equilibrium power PEMAX, so as to be equal to or less than each of them.
• the target equilibrium power PEC is determined as the minimum among the primary power P1, the secondary power P2 and the maximum equilibrium power PEMAX.
• the control method comprises for example, in power limitation mode, the calculation of a primary power setpoint CP1 and a secondary power setpoint CP2, and the control of the nuclear power plant 2 in such a way that the primary power P1 joins the primary power setpoint CP1 (i.e. so as to limit a difference between the primary power P1 and the primary power setpoint CP1) and the secondary power P2 joins the primary power setpoint CP2 (i.e. so as to limit a difference between secondary power P2 and secondary power setpoint CP2).
• the primary power setpoint CP1 and the secondary power setpoint CP2, used for controlling nuclear power plant 2 in power limitation mode are calculated according to the target equilibrium power PEC.
• the primary power setpoint CP1 and the secondary power setpoint CP2 are calculated as equal to the power target balance power filter PEC, optionally filtered by applying a target balance power filter FPEC, which is preferably by a low pass filter.
• the control module 56 of the electronic control unit 50 comprises for example a setpoint calculation module 90 configured to calculate the primary power setpoint CP1 and the secondary power setpoint CP2.
• the setpoint calculation module 90 receives the primary power P1, the secondary power P2 and the maximum equilibrium power PEMAX as input, and supplies the primary power setpoint CP1 and the secondary power setpoint CP2 as output.
• the setpoint calculation module comprises for example a selector 92 configured to select, from among the primary power P1, the secondary power P2 and the maximum equilibrium power PEMAX, the signal which has the lowest value.
• the driver unit 50 includes a balance power filter module 94 for filtering the target balance power PEC, by applying the target balance power filter FPEC.
• control method comprises the calculation of the primary power setpoint CP1 and the calculation of the secondary power setpoint CP2 as being equal respectively to the primary power P1 and to the secondary power P2.
• the primary power setpoint CP1 and the secondary power setpoint CP2 thus calculated are not in principle used for the effective control of the nuclear power plant 2, which is carried out according to the operational power setpoint COP .
• the rebalancing request logic signal BP would not request a switch to power limitation mode, so that the primary power setpoint CP1 would be taken as equal to the primary power P1 and the secondary power setpoint CP2 would be taken as equal to the secondary power P2, so that the control system 40 would not modify the primary power P1 and the secondary power P2 despite the untimely switch to power limitation mode.
• the setpoint calculation module 90 comprises for example a switching module 96 receiving as input the primary power P1, the secondary power P2 and the target equilibrium power PEC possibly filtered, and supplying as output the primary power setpoint CP1 and the secondary power setpoint CP2, the switching module 96 being controlled by the logic signal of request for rebalancing BP, so that the primary power setpoint CP1 is equal to the primary power in setpoint tracking mode or to the target balance power PEC possibly filtered in power limitation mode, and the secondary power setpoint CP2 is equal to the secondary power in setpoint tracking mode and to the target equilibrium power PEC possibly filtered in power limitation mode.
• each module and/or each filter of the electronic control unit 50 is produced in the form of a software application comprising software code instructions which can be recorded on a computer memory or a medium and can be executed by a processor .
• At least one module and/or at least one filter of the electronic control unit 50 is produced in the form of a specific integrated circuit (or ASIC for “Application Specifies Integrated Circuit”) or of a logic circuit programmable, for example an in situ programmable gate array (or FPGA for “Field Programmable Gate Array”).
• ASIC Application Specifies Integrated Circuit
• FPGA Field Programmable Gate Array
• control system 40 controls the nuclear power plant 2 in setpoint tracking mode, in which the nuclear power plant 2 is controlled so that the primary power P1 and the secondary power P2 follow the operational power setpoint.
• the control system 40 switches to the power limitation mode in which the primary power P1 and the secondary power P2 are controlled as a function of a target equilibrium power PEC calculated by the control system 40 and equal to or less than each of the primary power P1 and the secondary power P2.
• the control system 40 calculates, for example, a primary power setpoint CP1 and a secondary power setpoint CP2 from the target equilibrium power PEC, and controls the nuclear power plant in such a way that the primary power P1 reaches primary power setpoint CP1 and secondary power P2 reaches secondary power setpoint CP2.
• the primary power setpoint CP1 is for example equal to the target balance power PEC possibly filtered, in particular by a low-pass filter
• the secondary power setpoint CP2 is for example equal to the target balance power PEC possibly filtered, in particular by a low-pass filter.
• the power limitation mode is maintained for the determined power limitation duration before returning to the setpoint tracking mode.
• the control system 40 calculates the primary power setpoint CP1 as equal to the primary power P1 and calculates the secondary power setpoint CP2 as equal to the secondary power P2.
• the invention it is possible to maintain the nuclear power plant 2 in a normal operating zone in the event of a power imbalance, by switching to a power limitation mode implemented by the control system 40 which already provides the control. of the nuclear power plant 2 in setpoint monitoring mode, and avoiding the intervention of a protection system, the function of which is to shut down the nuclear power plant, for example by causing the shutdown clusters to fall.
• the power limitation mode can be implemented at all power levels of the nuclear power plant, i.e. whatever the current operational power setpoint when an imbalance is detected.
• driver system 40 It can be implemented using the driver system 40. It can be activated on normal operation transients of high amplitude or on incidental transients of the nuclear power plant 2, resulting in a significant power imbalance.
• the safety report of nuclear power plant 2 is considered to be slightly impacted.
• the implementation of the particular control process does not require redoing the safety report of the nuclear power plant 2, except the resumption of chapters of the safety report specific to the transients modified by the innovation or to certain projects in which the limitation systems are considered.
• the invention is not limited to the exemplary embodiments and to the variants presented above, other exemplary embodiments and other variants being possible.
• the primary power setpoint P1 and the secondary power setpoint P2 are both calculated as the target equilibrium power PEC filtered by the same PEC target balance power filter.
• the primary power setpoint CP1 being equal to the target equilibrium power PEC filtered by the primary filter and the power setpoint secondary CP2 being equal to the target equilibrium power PEC filtered by the secondary filter.
• the primary power setpoint CP1 being equal to the filtered target equilibrium power PEC by the primary filter and the secondary power setpoint CP2 being equal to the target equilibrium power PEC filtered by the secondary filter.
• the calculation of the primary power P1 and the calculation of the secondary power P2 are not limited to the calculation examples presented above, other ways of calculating the primary power P1 and the secondary power P2 being possible.
• the first sensors comprise by example :
• each cold leg temperature sensor 100 for measuring the temperature of the water circulating in this cold leg and a cold leg flow sensor 102 for measuring the water flow circulating in this cold branch,
• a hot leg temperature sensor 104 for measuring the temperature of the water circulating in this hot leg and a hot leg flow sensor 106 for measuring the water flow circulating in this hot branch, and
• pressurizer pressure sensor 108 for measuring the pressure in the pressurizer 24.
• an average hot leg flow rate DBCM as the average of the hot leg flow rates measured by the hot leg flow sensors 106, optionally after filtering using a filter, preferably a low pass filter ; and - the calculation of the primary power P1 according to the average cold leg temperature TBFM, the average cold leg flow DBFM, the average hot leg temperature TBCM and the average hot leg flow DBCM.
• the calculation of the primary power P1, carried out by the primary power calculation module of the electronic control unit 50, comprises for example
• the average primary thermal power being calculated as the product of a calibration coefficient K and a calculation function of the primary thermal power FPTH, using as input data the average cold leg flow DBFM, the average hot leg flow DBCM, the average cold leg enthalpy HBFM, the average hot leg enthalpy HBCM, the temperature of mean cold leg TBFM, mean hot leg temperature TBCM and pressurize pressure PPR.
• the function for calculating the primary thermal power FPTH is preferably based on the thermal balance of the primary circuit 4.
• the calibration coefficient K is determined during a periodic test by secondary enthalpy balance necessary to determine the thermal power. It is used to readjust the primary thermal power.
• Such an embodiment makes it possible to determine a primary power P1 according to measurements provided by temperature sensors, flow sensors and a pressure sensor, instead of using, for example, neutron sensors 42.
• the second sensors comprise for example, for each steam generator 8, a steam flow sensor 110 for measure the steam flow in the secondary circuit 6 at the outlet of the steam generator 8, a steam pressure sensor 112 to measure the pressure in the secondary circuit 6 at the outlet of the steam generator 8, a steam temperature sensor 114 to measure the temperature in the secondary circuit 6 at the outlet of the steam generator 8, a water pressure sensor 116 to measure the pressure of the water entering in the liquid state in the steam generator 8 in the circuit secondary 6 and a water temperature sensor 118 to measure the temperature of the water at the inlet of the steam generator 8 in the secondary circuit 6.
• the calculation of the primary power P2, performed by a secondary power calculation module of the electronic control unit 50 comprises for example:
• the primary power P2 is thus calculated according to the following equation: in which
• DVi is the steam flow at the outlet of steam generator 8 of index i in kilograms per second (kg/s),
• HVi is the output enthalpy of steam generator 8 of index i in joules per kilogram (J/kg), and
• HEi is the input enthalpy of steam generator 8 of index i in joules per kilogram (J/kg).
• a secondary circuit 6 having several steam generators 8 supplying the same turbine 28 comprises for example a steam barrel 120 (or “steam collector”) receiving the steam production from the steam generators 8 and distributing the steam produced to the turbine 28, and a water barrel 122 (or “water distributor”) receiving the water at the outlet of the condenser 32 and distributing this water to the various steam generators 8.
• the secondary circuit 6 comprises, for example, a secondary steam evacuation circuit by bypassing the turbine 28, subsequently designated by the acronym GCTC for “condenser steam bypass group” and associated with the reference numeral 124.
• GCTC 124 is configured to conduct steam from the outlet of steam barrel 120 to the inlet of condenser 32 bypassing turbine 28.
• the GCTC 124 comprises for example one or more control actuators 126 for controlling the flow of steam through the GCTC 124, such as valves, controlled by the control system 40 of the nuclear power plant, for example via a logic signal from lock GCTC_dev taking two values (for example 0 and 1 ), one not allowing opening and requesting the locking of the GCTC 124, and the other authorizing the opening and requesting an unlocking of the GCTC, and a signal of GCTC_com opening command requesting an opening of the GCTC 124 valves, for example in percentage of opening between a minimum opening and a maximum opening.
• control actuators 126 for controlling the flow of steam through the GCTC 124, such as valves, controlled by the control system 40 of the nuclear power plant, for example via a logic signal from lock GCTC_dev taking two values (for example 0 and 1 ), one not allowing opening and requesting the locking of the GCTC 124, and the other authorizing the opening and requesting an unlocking of the GCTC
• the nuclear power plant comprises for example one or more steam consuming devices 127.
• Each steam consuming device 127 is connected to the secondary circuit 6 to draw steam from the secondary circuit 6, preferably at the outlet of the steam barrel 120.
• a steam consuming device 127 is for example the equipment named “dryer-superheater”.
• the steam consuming devices 127 do not include the turbine 28 and the GCTC 124.
• the second sensors comprise for example:
• a turbine pressure sensor 128 configured to measure a pressure in the turbine 28, preferably to measure the pressure at the inlet of the first wheel of the turbine 28 when the turbine 28 comprises several wheels each defining a turbine stage
• a water barrel pressure sensor 140 for measuring the water pressure in the water barrel; - one or more steam withdrawal flow sensors 142, each steam withdrawal flow sensor measuring the flow of steam withdrawn from the secondary circuit 6 by a steam consumer device 127.
• the primary power P2 is for example calculated according to the following equations:
• P2 is the secondary power in W
• P1TR is the pressure measured at the inlet of the first wheel of turbine 28 in Pascal (Pa),
• F(P1TR) is a function giving the thermal power transmitted to the turbine 28 from the pressure measurement at the inlet of the first wheel of the turbine 28,
• PBVAP is the steam pressure at steam barrel 120 in Pa
• HBVAP is the steam enthalpy at steam barrel 120 in J/kg
• HBEAU is the enthalpy of water at the barrel of water 122 in J/kg
• GCTC_com is the opening command signal of the GCTC 124, expressed as a percentage of opening, 100% opening corresponding to maximum opening and 0% to minimum opening,
• KGCTC is an adjustment coefficient for the thermal power evacuated at the GCTC 124 expressed in W/(Pa x % opening of the GCTC 124),
• D j is the mass flow rate of steam consumed by the steam consumer of index j expressed in kg/s
• K j is an adjustment coefficient of the thermal power evacuated to the steam consumer of index j.
• Such a calculation of a secondary power P2 is in particular carried out using sensors arranged on the steam barrel 120 and on the water barrel 122 without it being necessary to equip each steam generator with one or several sensors at the inlet of the steam generator 8 and at the outlet of the steam generator 8.
• the number of sensors can be limited.

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• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
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• 2021
  • 2021-03-12 FR FR2102457A patent/FR3120734B1/fr active Active
• 2022
  • 2022-03-11 EP EP22713938.3A patent/EP4305646A1/fr active Pending
  • 2022-03-11 WO PCT/EP2022/056298 patent/WO2022189611A1/fr active Application Filing
  • 2022-03-11 CN CN202280033794.4A patent/CN117396986A/zh active Pending
  • 2022-03-11 JP JP2023555584A patent/JP2024510748A/ja active Pending
  • 2022-03-11 KR KR1020237031216A patent/KR20230169945A/ko unknown

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