Light water reactor (REL) electronuclear cogeneration plant with heat storage cycle connected to a heat network arranged in thermal parallel to the reactor conversion cycle

Abstract

The invention essentially consists of using a thermal storage loop (13) in thermal parallel with the secondary circuit (5) of a nuclear reactor.

Description

technical field

[0001] The present invention relates to the field of light water nuclear reactors (LWR), in particular pressurized water reactors (PWR).

[0002] More specifically, the invention relates to cogeneration plants comprising such nuclear reactors. "Cogeneration" is used here and within the scope of the invention to mean the simultaneous or separate production of electricity and useful heat.

[0003] The invention's main objective is to improve both the economics of a nuclear power plant and to contribute to the decarbonization of the heat market.

[0004] Although described with reference to a pressurized water nuclear reactor, the invention applies to any nuclear reactor with an indirect thermodynamic cycle belonging to the family of so-called second, third, and fourth generation (GEN IV) reactors. It applies in particular to fast neutron reactors cooled with liquid metal, notably liquid sodium, also known as SFRs (Sodium Fast Reactors), which are part of the GEN IV reactor family. Previous technique

[0005] In the context of climate and energy transition, the nuclear industry must meet several challenges for the future. Indeed, to address tomorrow's energy and societal challenges, it will be essential to design nuclear reactors that enable: to limit the need for so-called "environmental" liquid cold sources (rivers, streams, sea) and associated discharges into the environment; to be more flexible and therefore more complementary to other so-called renewable energies (RE), to meet fluctuating electricity demand and the intermittency of RE; to decarbonize processes by supplying heat to consuming industries (desalination, heat networks, hydrogen, chemicals, etc.) while increasing energy efficiency; to capture atmospheric CO2 to limit the effects of global warming and contribute to closing the carbon cycle as a carbon source for industrial processes; and this without degrading the profitability of the installation, either by economically benefiting from the new services provided, or by significantly increasing the amount of electricity produced during the day.

[0006] In the conventional PWR sector, reactors are classified by major categories of use: so-called power-generating reactors which are dedicated solely to the production of electricity; so-called heat-generating reactors which are dedicated solely to the production of heat; so-called cogeneration reactors, dedicated to both the production of electricity and heat, simultaneously or not.

[0007] As detailed in [1], the principle of cogeneration from a nuclear reactor involves modifying the design of the energy conversion cycle so that the heat is released at the cold source at a temperature that allows for its use. Indeed, limiting global warming requires minimizing heat losses at all levels, and in particular, at the cold source of a thermodynamic installation. This cogeneration objective becomes all the more relevant for a nuclear reactor since industrial or domestic heat is often traditionally obtained by burning fossil fuels, which are responsible for greenhouse gas emissions.

[0008] Furthermore, the economics of a nuclear reactor are very capital-intensive and therefore, mainly based on the amortization of the initial investment in the reactor.

[0009] Once the investment has been made, it is essential to try to operate the reactor with a load factor at full power approaching its maximum capacity.

[0010] Because electricity cannot be stored in large quantities, purely power-generating nuclear reactors must adapt to variations in power demand on the electrical grid. Therefore, they do not operate continuously at 100% of their capacity.

[0011] On average in France, for example, the full-power load rate of a nuclear reactor in the French fleet is 73% while its full-power availability rate is approximately 85%.

[0012] Therefore, there is an untapped production capacity of around 10 to 12% on average.

[0013] There figure 1shows a load curve of reactors in the nuclear power plant fleet in France, located on different sites (SITES 1, 2, 3) over a few days of operation highlighting the variations in load and therefore in reactor operation between 100% power and the technical minimum at approximately 20%.

[0014] There is therefore a general need to use this untapped capacity to help significantly improve the economics of nuclear reactors while contributing to the decarbonization of the energy system, particularly through cogeneration, i.e. the joint production and supply of heat in addition to electricity.

[0015] Heat is the primary energy use in France, representing 45% of final energy consumption, with 669 TWh in 2020. Decarbonizing heat production, currently 60% generated from fossil fuels, is a major challenge in decarbonizing the French energy mix: [2]. Globally, over 90% of heat is generated from carbon: [3].

[0016] The heat market can be divided into three main classes, each of which is linked to the service provided [4]: a first class, called "superheated water and steam" up to about 250 °C, this is the class of heat networks for the conditioning of buildings, industrial needs for low temperature steam or processes requiring vaporization (drying, dehydration, ...); a second class called "chemical", where the heat is mainly consumed by the enthalpy of chemical reactions; a third class called "mineral", where heat above -1000°C is used to melt solids and / or to drive chemical reactions between these solids (lime, cement, ore sintering, coke production, glassmaking and metallurgy).

[0017] Publication [5] indicates various examples of processes that may be affected depending on the level of heat required: first class: petroleum refining, shale oil and tar sands production, pulp and paper production, seawater desalination, district heating; second class: direct steel production, thermochemical hydrogen production, steam electrolysis, methane reforming, petrochemicals (ethylene, styrene); third class: glass and cement manufacturing.

[0018] By using the heat produced by PWR reactors, typically at around 300°C, or FNR reactors, typically at around 550°C, it is therefore possible to contribute significantly to decarbonizing industrial ecosystems. However, it appears that some applications will require temperatures above 300°C. In this case, the use of nuclear heat can contribute in the form of preheating, and supplementary electricity will help meet the demand. In this scenario, the use of nuclear heat will have significantly improved overall energy efficiency.

[0019] There is therefore a need to further improve nuclear cogeneration facilities, in order to allow both the operation of the installation's reactor(s) at maximum capacity at full power, even when the electrical grid does not have as much demand as the reactor(s) can produce, and to meet the decarbonization needs of industrial heat.

[0020] The Applicant has already proposed, in patent applications WO2023 / 078825A1 and FR3128813A1, thermal storage loop solutions for nuclear installations. These solutions decouple the operation of the plant's nuclear reactor(s) from the operation of the electrical grid, which must adapt to load variations. Through this system, the combination of a thermal storage loop and the energy conversion system (Rankine cycle) shifts the thermal power produced by the nuclear reactor(s) into electrical power demanded by the grid. In other words, the thermal storage loop decouples the reactor's operation, which is designed to operate at maximum capacity, from the grid's electricity demand, which must meet load fluctuations.

[0021] We represented at the figure 2an optimal configuration according to the FR3128813A1 requirement with a pressurized water nuclear reactor (PWR).

[0022] The primary circuit 1 is a closed-loop fluid circuit comprising mainly the reactor core 2, at least one steam generator (SG) acting as a heat exchanger (referred to as the primary heat exchanger 3), and a hydraulic pump 4 to circulate the heat transfer fluid, which is water maintained in a liquid state within the reactor's operating temperature range, typically around 320°C-330°C during normal operation. Other equipment, such as a pressurizer and all the devices ensuring safe operation, is not described here.

[0023] Thus, the high-pressure water of the primary circuit extracts the energy supplied, in the form of heat, by the fission of uranium nuclei in the core of reactor 1.

[0024] Next, this water under high pressure and high temperature, typically 155 bar and 320°C-330°C, enters the intermediate exchanger 3 and transmits its energy to a secondary circuit 5, which also uses pressurized water as a heat transfer fluid in a closed loop.

[0025] This secondary circuit 5 includes the intermediate exchanger 3, a turbine 6 comprising a high-pressure body 60 and a low-pressure body 61, a condenser 7 and a hydraulic pump 8 to circulate water in the form of steam or liquid as a heat transfer fluid.

[0026] Thus, in this secondary circuit 5, water in the form of high-pressure steam, typically at about 70 bar, is expanded in the high-pressure body of the turbine, then superheated before continuing its expansion in the low-pressure bodies 61. The turbine drives an alternator 9 which produces electricity.

[0027] A thermal storage loop 13 is arranged between the primary circuit 1 and the secondary circuit 5, as well as a CO2 capture system with a dry air air cooler 20 in bypass.

[0028] The thermal storage loop 13 is a closed-loop fluidic circuit in which a heat transfer fluid circulates from the intermediate exchanger 3 of the reactor primary circuit to a hot tank 14, then into a steam generator 16 and into a cold tank 15 to return to the intermediate exchanger 3.

[0029] The circulation of the heat transfer fluid within the loop 13 is ensured by a hydraulic pump 17 downstream of the hot tank 14 and a hydraulic pump 18 downstream of the cold tank 18.

[0030] The fluid branches of loop 13 each consist of a cylindrical pipe with metal walls resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C, and insulated externally with high-temperature insulation. The diameter of each pipe is calculated to allow the dissipation of all the thermal power with a maximum permissible flow velocity of the heat transfer fluid, typically on the order of 5 to 10 m / s.

[0031] The hot storage tank 14 contains the heat transfer fluid, stores all the heat recovered from the intermediate heat exchanger 3, and supplies heat transfer fluid to the steam generator 16. The hot storage tank 14 can be cylindrical in shape, with walls made of metal resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C, and is lined with an external high-temperature insulating layer to limit heat loss. The size (usable storage volume) of the hot storage tank 14 depends on the characteristics of the heat transfer fluid used: it must allow it to store, at most, all the heat produced by the nuclear reactor over a rolling 24-hour period. For safety reasons, the hot storage tank 14 is located at a distance, typically a preliminary estimate of 60 m from the reactor containment building, with an intermediate embankment.Tank 14 can be equipped with a heat transfer fluid preheating system to ensure the fluid remains in a liquid state and / or a level measurement system with alarm reporting and / or a safety overflow connected directly to the cold tank 15.

[0032] Steam generator 16 produces steam for turbines 60 and 61, which is characteristic of a Rankine cycle with the operating characteristics of a power generation cycle for the installation, and must be able to operate according to the electrical grid requirements 21. Steam generator 16 is typically sized to dissipate 1.5 times the power of the nuclear reactor. It should be noted that turbines 6, 60, and 61 are sized based on the peak steam flow rate produced by steam generator 16.

[0033] The hydraulic pump 17, like the hydraulic pump 18, is designed to operate at least at the availability coefficient Kd of the nuclear reactor and must be able to operate according to the fluctuations in the electricity demand of the electrical grid 21 to which the alternator 9 of the nuclear reactor is electrically connected. The flow rate of pump 17 or 18 must, taking into account the heat transfer fluid capacity and the sizing of the steam generator 16, supply the latter with heat transfer fluid at a flow rate sufficient to meet the power demands of the electrical grid 21. Each of the pumps 17 and 18 has metal walls resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C. Several pumps 17 or 18 can be positioned in parallel to distribute the pumping flow rate, and a redundant pump can be provided for safety reasons.

[0034] The cold storage tank 15 has approximately the same heat transfer fluid storage capacity as the hot storage tank 14, which is recovered from the steam generator 16. The cold storage tank 15 can be cylindrical in shape, with walls made of metal resistant to the chemical attack of the high-temperature heat transfer fluid, typically above 300°C, and is lined with an external high-temperature insulating layer to limit heat loss. The dimensions (usable storage volume) of the cold storage tank 15 depend on the characteristics of the heat transfer fluid used: it must allow it to store, at most, all the heat produced by the nuclear reactor over a rolling 24-hour period. For safety reasons, the cold storage tank 15 is located at a distance, typically a preliminary estimate of 60 m from the reactor containment building, with an intermediate embankment.Tank 15 can be equipped with a heat transfer fluid preheating system to ensure the fluid remains in a liquid state and / or a level measurement system with alarm reporting and / or a safety overflow connected directly to the hot tank 14.

[0035] The heat transfer fluid is a molten salt type, designed to remain in liquid phase over a temperature range of 100°C to 350°C, with a 40°C margin above the maximum operating temperature. Preferably, the salt will have the following chemical composition: 53% NaNO3, 40% NaNO2, 7% KNO3 (HITEC® salt).

[0036] The total volume of salt contained in the closed loop 13 is equal to the total volume of the cold tank 15 and the volume contained in the branches / fluidic lines of the loop 13 to avoid any overflow or pressurization during operation.

[0037] The electrical network 21, connected to the alternator 9, is designed to transport and distribute electricity to end users according to their needs. It is a high-voltage electrical network operating according to power demands related to electricity use, and it must be able to accept the peak electrical power produced by the cogeneration plant.

[0038] This cogeneration plant also includes at least one air-cooled cooling tower 20, known as a dry-air cooling tower, meaning it operates using a dry process, connected in a closed loop to the condenser 7 of the reactor's secondary circuit. This air-cooled cooling tower 20 will transfer heat from the condensed water in the condenser 7 to the ambient air.

[0039] The cooling tower 7 is sized to remove the thermal power not consumed by the turbines 6, 60, 61 by bringing the water supplied from the condenser 7 to the lowest temperature level that the ambient air can allow by heating up significantly.

[0040] Although not shown, the closed loop comprising the condenser 7 and the dry air cooling tower 20 is equipped with a pumping system to circulate the heat transfer fluid within it; this pumping system can be directly integrated into the tower 20. The operation of the installation with only this cooling tower 20 is a purely power-generating operation with the residual power not consumed by the electrical conversion system 6, 9 being dissipated by means of the dry air cooling tower 20. In this configuration, the installation is not fully energy efficient but has the significant advantage of producing more electricity during the day than a state-of-the-art PWR reactor without requiring the withdrawal or discharge of liquid water into the environment.

[0041] In an advantageous configuration, the dry air cooling tower 20 can be connected in bypass of a connection to an atmospheric CO2 capture system 22 (DAC for "Direct Air Capture") or water desalination system.

[0042] Thus, in the event of a shutdown of the atmospheric CO2 capture system, the installation operates according to the configuration using only the cooling tower 20.

[0043] The cogeneration operation with low-temperature heat supply for the atmospheric CO2 capture system 22 aims to utilize all the reactor's thermal energy not used for electricity production. The installation can be classified as having total energy efficiency.

[0044] In the event of a temporary absence of heat demand for this network, the installation returns to the operating configuration with only the cooling tower 20.

[0045] Typically, the entire cogeneration installation is configured to have, in the closed loop integrating the condenser 7 and the atmospheric CO2 capture system 22, a temperature T1 at the inlet of the condenser of at least 60°C and a temperature T2 at the outlet of the condenser 7 of at least 70°C advantageously between 70 and 100°C.

[0046] As can be seen, in this installation, all the fluid circuits of the nuclear reactor, the closed loop of thermal storage, the cooling tower and the desalination system are arranged in thermal series.

[0047] This thermal series configuration has three major drawbacks, as follows: The recovery of heat for an industrial process, at approximately 95°C for a DAC system or 70°C for a desalination system, depends on the power generation operation. The industrial process, connected in series to the Rankine cycle condenser, can only operate when the conversion cycle is producing electricity and must also operate according to the load demanded by the electrical grid. The temperature of the heat supplied to the industrial process is limited and does not allow for the delivery of heat at a very high temperature, i.e., reaching 300°C at the outlet of the primary circuit, due to the upstream conversion to electricity (passage of steam through the turbines). This limits the maximum temperature of the heat transferred to around 100°C at the condenser terminals, a temperature that depends on the condenser's operating pressure.It is therefore not possible to meet the thermal needs of industrial processes with a temperature of around 300°C; the overall power generation efficiency of the installation is reduced compared to a reference of around 33% in a purely power generation PWR reactor, due to an additional pinch of the heat exchanger generated by the interposition of the thermal storage between the reactor and the conversion cycle and a temperature level required to supply the processes at the terminals of the condenser higher than a classic temperature of a typical cold source (sea water or cooling tower water).

[0048] Therefore, there is still a need to improve nuclear cogeneration facilities, in order to allow both the reactor(s) of the facility to operate at maximum capacity at full power even when the electrical grid does not have as much demand as the reactor(s) can produce and to meet the needs of decarbonizing industrial heat, by overcoming all or part of the disadvantages of the facilities according to patent applications WO2023 / 078825A1 and FR3128813A1.

[0049] The aim of the invention is to at least partially meet this need. Description of the invention

[0050] To this end, the invention relates, in one of its aspects, to a nuclear power cogeneration plant comprising: at least one nuclear reactor, in particular a pressurized water reactor (PWR) or a boiling water reactor (BWR), comprising: a first fluid circuit, called the primary circuit, comprising at least one steam generator as the first intermediate heat exchanger, a second fluid circuit, called the secondary circuit, comprising at least one turbine connected to the first intermediate heat exchanger, a first condenser connected to the turbine and the steam generator, to cool the steam from the turbine and transform it back into water and return it to the steam generator; an alternator mechanically coupled to the turbine, intended to be connected to an electrical network; a third fluid circuit configured as a closed loop for thermal energy storage, in which a heat transfer fluid circulates, comprising: at least one second condenser, as the second intermediate heat exchanger;at least one outlet heat exchanger, connected in a closed loop to an industrial heating network; at least one first reservoir, called the hot reservoir, connected to the second condenser; at least one first hydraulic pump connected to the hot reservoir and the outlet heat exchanger; at least one second reservoir, called the cold reservoir, connected to the outlet heat exchanger; at least one second hydraulic pump connected to the cold reservoir and the second condenser; a fluidic system to thermally parallel the third fluidic circuit with the second fluidic circuit.

[0051] According to an advantageous embodiment, the fluidic system for thermally paralleling the third fluidic circuit with the second fluidic circuit comprises: a steam distribution and regulation device, connected inlet to the steam generator and outlet to both the turbine and the second condenser; a water collection tank connected inlet to both the first and second condensers and outlet to the steam generator; a third pump connected between the water collection tank and the steam generator.

[0052] According to an advantageous variant, the steam distribution and regulation device includes two motorized control valves, one of which connects the steam generator to the turbine and the other connects the steam generator to the second condenser.

[0053] Advantageously, the opening and closing of the valve connecting the steam generator to the turbine are controlled by control setpoints based on reactor load tracking, while the opening and closing of the valve connecting the steam generator to the second condenser are controlled by control setpoints based on the hot tank level.

[0054] Preferably, the water temperature within the collection tank is between 150°C and 200°C.

[0055] Advantageously, the reactor vessel and steam generator are configured as a modular SMR type reactor with at least one atmospheric CO2 carbon dioxide capture system and / or seawater desalination system connected in a closed loop to the reactor's secondary circuit condenser.

[0056] In an advantageous embodiment, the installation includes a CO2 carbon dioxide capture system and / or seawater desalination system, or any other cogeneration system with a heat requirement compatible with the temperature at the condenser terminals, connected in a closed loop to the condenser of the reactor's secondary circuit. This configuration allows for the simultaneous operation of: operate the reactor at its nominal design operating rate (Kd), also called the availability coefficient, independently of power demands from the electrical grid connected to the alternator; make the best use of all or part of the thermal energy produced by the reactor to provide new non-energy services (atmospheric CO2 capture and / or seawater desalination); reduce at least partial need for liquid water supply as a cooling source and associated discharges to contribute to the process of evacuating unused energy.

[0057] As a corollary, this makes it possible to improve the safety of the installation by providing a device contributing to the Evacuation of Residual Power (EPUR) for periods of reactor shutdown.

[0058] According to an advantageous variant, the installation also includes a dry air air cooler connected in bypass of a connection to the CO2 carbon dioxide sensor system or seawater desalination.

[0059] According to an advantageous embodiment feature, the dry air cooling device is a dry air cooling tower.

[0060] The invention essentially consists of using a thermal storage loop in thermal parallel with the secondary circuit of a reactor.

[0061] In other words, instead of coupling the circuits of a nuclear reactor and a series fluidic thermal storage loop as per patent applications WO2023 / 078825A1 and FR3128813A1, the thermal storage loop is put in parallel with the energy conversion system (Rankine cycle).

[0062] The sizing of the hot and cold storage tanks in the storage loop depends on the required temperature level. The tank volume is advantageously between 1000 m³ and 30,000 m³, the industrial feasibility of such tanks already being established based on current practices in other industrial sectors.

[0063] These dry air cooling towers do not require any liquid water for cooling, regardless of the consumer or heating requirement.

[0064] An installation allows us to retain the advantage of not making the operation of the reactor dependent on possible variations in load demand, as per patent applications WO2023 / 078825A1 and FR3128813A1.

[0065] In conclusion, a nuclear cogeneration plant with a PWR nuclear reactor and a thermal storage loop in parallel with the reactor's energy conversion cycle according to the invention offers numerous major advantages compared to a plant according to patent applications WO2023 / 078825A1 and FR3128813A1, among which we can mention: not to add a pinch of exchanger between the primary circuit and the energy conversion and therefore, not to impact the thermodynamic efficiency, to be able to supply heat to industrial processes independently of the needs of the electrical network, to supply heat at a much higher temperature than that available at the terminals of the condenser.

[0066] According to this method, the temperature T1 at the inlet of the condenser is preferably equal to at least 60°C and the temperature T2 at the outlet of the condenser is preferably equal to at least 70°C, advantageously between 70 and 100°C.

[0067] Advantageously, each of the hot and cold tanks has a volume between 1000 m³ and 30,000 m³ and may not be located on the site of the nuclear installation.

[0068] Even more advantageously, the heat transfer fluid of the thermal storage loop is a molten salt or a mixture of molten salts adapted to remain in liquid phase over a temperature range of 100°C to 350°C with a margin of 40°C relative to the maximum operating temperature of the thermal storage loop.

[0069] Preferably, the heat transfer fluid has the following chemical composition: 45% NaNO2, 7% KNO3, 48% Ca(NO3)2 (HITEC-XL salt).

[0070] According to an advantageous embodiment, the turbine(s) is / are free of low-pressure bodies.

[0071] Other advantages and features of the invention will become clearer upon reading the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0072] [ Fig 1 ] there figure 1 illustrates a load curve of reactors in the French nuclear power plant fleet, located at different sites (SITES 1, 2, 3) over a few days of operation. Fig 2 ] there figure 2 is a schematic view of a cogeneration plant configuration according to patent application FR3128813A1, comprising a pressurized water reactor (PWR), a thermal storage loop, an atmospheric CO2 capture system, and a dry-air operating air cooler bypassing the atmospheric CO2 capture system. Fig 3 ] there figure 3is a schematic view of a cogeneration plant configuration according to the invention, comprising a pressurized water reactor (PWR), a thermal storage loop in parallel with the reactor's thermal conversion system, an atmospheric CO2 capture system and / or a dry-air cooling device bypassing the atmospheric CO2 capture system. Fig 4 ] there figure 4 is a reactor load curve for the French nuclear power plant fleet, located at different sites (SITES 1, 2, 3), as it might appear over a few days of operation with the reactor operating according to the invention. Fig 5 ] there figure 5 is a synoptic view illustrating a mode of operation of an installation according to the figure 3 . Detailed description

[0073] Throughout this application, the terms "upstream" and "downstream" are to be understood by reference to the direction of flow of a heat transfer fluid within one of the fluid circuits of a nuclear cogeneration plant according to the invention.

[0074] THE Figures 1 And 2 The aspects relating to the state of the art have already been detailed in the preamble, so they will not be commented on below.

[0075] For the sake of clarity, the same element according to the invention and according to the prior art is designated by the same numerical reference in all of the figures 1 to 5 .

[0076] We will not detail again all the different relationships and functions of the common elements between a cogeneration plant according to the invention and a cogeneration plant with a thermal storage loop according to the state of the art, as illustrated in the figure 2 Only some of the elements are described again.

[0077] The nuclear cogeneration plant according to the invention illustrated in the figure 3 includes in addition to the usual components of a typical PWR reactor installation, a thermal storage loop 13 in thermal parallel with the secondary circuit 5 of the reactor.

[0078] The thermal storage loop 13 is a closed-loop fluid circuit in which a heat transfer fluid circulates from a condenser as an intermediate exchanger 16 to a hot reservoir 14 then into an outlet heat exchanger 19 and into a cold reservoir 15 to return to the condenser 16.

[0079] The circulation of the heat transfer fluid within the loop 13 is ensured by a hydraulic pump 17 downstream of the hot tank 14 and a hydraulic pump 18 downstream of the cold tank 15.

[0080] The fluid branches of loop 13 each consist of a cylindrical pipe with metal walls, resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C, and insulated externally with high-temperature insulation. The diameter of each pipe is calculated to allow the dissipation of all the thermal power with a maximum permissible flow velocity of the heat transfer fluid, typically on the order of 5 to 10 m / s.

[0081] The hot storage tank 14 contains the heat transfer fluid, stores all the heat recovered from the condenser 16, and supplies the condenser 16 with heat transfer fluid. The hot storage tank 14 can be cylindrical in shape, with walls made of metal resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C, and is lined with an external high-temperature insulating layer to limit heat loss. The size (usable storage volume) of the hot storage tank 14 depends on the characteristics of the heat transfer fluid used: it must allow it to store, at most, all the heat produced by the nuclear reactor over a rolling 24-hour period. For safety reasons, the hot storage tank 14 is located at a distance, typically a preliminary estimate of 60 m from the reactor containment building, with an intermediate embankment.Tank 14 can be equipped with a heat transfer fluid preheating system to ensure the fluid remains in a liquid state and / or a level measurement system with alarm reporting and / or a safety overflow connected directly to the cold tank 15.

[0082] The condenser 16 transfers the heat contained in the steam produced in the steam generator 3 to the heat transfer fluid of the loop. This intermediate heat exchanger 16 is a condenser because the steam from the steam generator 3 releases its energy by condensing.

[0083] The hydraulic pump 17, like the hydraulic pump 18, is designed to operate at least at the availability coefficient Kd of the nuclear reactor and must be able to accommodate fluctuations in the electricity demand of the electrical grid 21 to which the reactor's alternator 9 is electrically connected. The flow rate of pump 17 or 18 must, taking into account the heat capacity of the heat transfer fluid and the sizing of the steam generator 16, supply the latter with heat transfer fluid at a rate sufficient to meet the power demands of the electrical grid 21. Each of the pumps 17 and 18 has metal walls resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C. Several pumps 17 or 18 can be positioned in parallel to distribute the pumping flow rate, and a redundant pump can be provided for safety reasons.

[0084] The cold storage tank 15 has approximately the same heat transfer fluid storage capacity as the hot storage tank 14, which is recovered from the condenser 16. The cold storage tank 15 can be cylindrical in shape, with walls made of metal resistant to the chemical attack of the high-temperature heat transfer fluid, typically above 300°C, and is lined with an external high-temperature insulating layer to limit heat loss. The dimensions (usable storage volume) of the cold storage tank 15 depend on the characteristics of the heat transfer fluid used: it must allow it to store, at most, all the heat produced by the nuclear reactor over a rolling 24-hour period. For safety reasons, the cold storage tank 15 is located at a distance, typically a preliminary estimate of 60 m from the reactor containment building, with an intermediate embankment.Tank 15 can be equipped with a heat transfer fluid preheating system to ensure the fluid remains in a liquid state and / or a level measurement system with alarm reporting and / or a safety overflow connected directly to the hot tank 14.

[0085] The outlet heat exchanger 19 transfers the heat contained in the heat transfer fluid of loop 13 to the heat transfer fluid of an industrial district heating network (water) 30. If the industrial district heating network requires steam, then this component 19 acts as a steam generator. Its sizing depends on the characteristics of the heat transfer fluid used: it must allow it to transfer, at most, all of the heat produced by the nuclear reactor over a rolling 24-hour period. This duration could be adjusted on a case-by-case basis depending on the actual installation configurations and the industrial needs of the district heating network. At the outlet of the heat exchanger 19, the water or steam for the network 30 can be superheated to 240°C. The fluid conveyed can therefore be steam or superheated water, depending on the nature of the industrial requirements.

[0086] The heat transfer fluid is a molten salt type, remaining in liquid phase over a temperature range of 160°C to 350°C (with a 40°C margin from the maximum operating temperature). Preferably, the salt will have the following chemical composition: 45% NaNO2, 7% KNO3, 48% Ca(NO3)2 (HITEC-XL salt).

[0087] The total volume of salt contained in the closed loop 13 is equal to the total volume of the cold tank 15 and the volume contained in the branches / fluidic lines of the loop 13 to avoid any overflow or pressurization during operation.

[0088] The electrical network 21, connected to the alternator 9, is designed to transport and distribute electricity to end users according to their needs. It is a high-voltage electrical network operating according to power demands related to electricity use, and it must be able to accept the peak electrical power produced by the cogeneration plant.

[0089] The cogeneration plant includes at least one air-cooled tower 20, known as a dry air cooling tower, i.e. operating by dry means, connected in a closed loop to the condenser 7 of the reactor's secondary circuit.

[0090] This cooling tower 20 will transfer the heat from the condensed water at the condenser 7 to the ambient air.

[0091] The cooling tower 7 is sized to remove the thermal power not consumed by the turbines 6, 60, 61 by cooling the water supplied from the condenser 7 and heating the ambient air.

[0092] Although not shown, the closed loop comprising the condenser 7 and the dry air cooling tower 20 is equipped with a pumping system to convey the heat transfer fluid within it, this pumping system being able to be directly integrated into the tower 20.

[0093] The dry air cooling tower 20 can be connected in bypass of a connection to an atmospheric CO2 capture system 22.

[0094] Typically, the entire cogeneration installation is advantageously configured to have in the closed loop integrating the condenser 7 and the atmospheric CO2 capture system 22, a temperature T1 at the inlet of the condenser of at least 60°C and a temperature T2 at the outlet of the condenser 7 of at least 70°C advantageously between 70 and 100°C.

[0095] According to the invention, a fluidic system 50 allows the secondary circuit 5 of the reactor to be put in thermal parallel with the thermal storage loop 13.

[0096] This system 50 comprises, firstly, a steam distribution and regulation device 51, connected at its inlet to the steam generator 3 and at its outlet to both the turbine 6 and the condenser 16 of the thermal storage loop. The function of this device 51 is therefore to distribute the steam produced by the steam generator 3 between the needs for electrical production (Rankine Cycle 5) and thermal production (storage loop 3 in series with the heat network 50).

[0097] Advantageously, this steam distribution and regulation device 51 includes two motorized control valves, one of which connects the steam generator 3 to the turbine 6, and the other connects the steam generator 3 to the condenser 16 of the thermal storage loop.

[0098] The system 50 also includes a water collection tank 52 connected at the inlet to both the condenser 7 of the circuit 5 and the condenser 16 of the storage loop 13 and at the outlet to the steam generator 3. This tank 52 therefore has the function of collecting water arriving from the conversion cycle 5 and from the condenser 16 of the loop 13 to return it to the steam generator 3. Preferably, this tank 52 is cylindrical in shape and pressurized to about 20 Bars to maintain the holding pressure of the circuit water of the conversion cycle 5 whose temperature is 150-200°C.

[0099] A pump 53 is installed on the circuit connecting the water collection tank 52 and the steam generator 3 to supply the latter with pressurized water. Like pumps 17 and 18, pump 53 is designed to operate at least at the availability coefficient Kd of the nuclear reactor. The flow rate of pump 53 must be sufficient, taking into account the specific heat capacity of the water heat transfer fluid and the temperature differential across the steam generator 3, to remove all the reactor's thermal power. This pump 53 has metal walls resistant to the chemical attack of the heat transfer fluid at high temperatures, typically above 300°C. Several pumps 53 can be positioned in parallel to distribute the pumping flow rate, and a redundant pump can be provided for safety reasons.

[0100] With such a system 50, the operating principle of the installation, illustrated in the figure 5 is as follows: The nuclear reactor operates nominally and only reduces power output once the hot tank 14 has reached its maximum fill level. Tanks 14 and 15 are filled according to grid load following. Various technical configurations and control modes for the installation according to the invention are possible.

[0101] There figure 5 illustrates a control method that maximizes nuclear reactor output with: priority given to the electrical network 21; a filling of the thermal storage tanks; as a condition that, as long as the tanks have not reached a sufficient filling level, which could be in a first approximation of around 80%, then there is adaptation of the reactor power level for the monitoring of electrical load.

[0102] According to this control method, the opening and closing of the valve connecting steam generator 3 to turbine 6 are controlled by setpoints based on monitoring the reactor's electrical load. The opening and closing of the valve connecting steam generator 3 to condenser 16 of loop 13 are controlled by setpoints based on the level of the hot tank 14.

[0103] The invention is not limited to the examples just described; in particular, features of the illustrated examples can be combined in unillustrated variants.

[0104] Other variants and embodiments may be considered without departing from the scope of the invention.

[0105] In the illustrated example, system 22 is a CO2 capture system. However, a seawater desalination system can also be considered in addition to or instead of the CO2 capture system.

[0106] The nuclear cogeneration plant just described in relation to a pressurized water reactor can be implemented with all indirect-cycle nuclear reactors, in which the heat production cycle is physically separated from the energy conversion cycle. This allows for the consideration of second, third, and fourth generation (GEN IV) reactors. It is particularly applicable to liquid-metal cooled fast neutron reactors, notably liquid sodium cooled reactors (SFRs), which belong to the GEN IV reactor family.

[0107] Facilities with one or more SMR-type reactors, particularly PWRs, can meet the decarbonization needs of industry. Currently, the majority of industrial sites (such as chemical plants) use fossil fuels and have committed to decarbonization and defossilization efforts.

[0108] SMRs can play a role in meeting these objectives by providing both electricity and heat at the temperature level they can serve, subject to the pinch points of the exchangers acting as barriers, i.e., around 300°C for a PWR, around 500°C for an FNR, 600°C for an MSR (English acronym for "Molten Salt Reactor") and 750°C for an HTR (English acronym for "High Temperature Reactor").

[0109] In other words, the implementation of an SMR operating in cogeneration of electricity / heat 300°C according to the invention would make it possible to respond to the decarbonization of all or part of a petrochemical site.

[0110] With a cogeneration plant according to the invention, it is possible to consider equipping petrochemical sites producing molecules of interest such as olefins, methanol and polymers. List of cited references

[0111] [1]: "Improving energy efficiency by using cogeneration in electricity production" Jean-Marie Loiseaux, Henri Safa, Bernard Tamain, Save the Climate Network. [2]: Carbon 4 Report - November 2022 - Renewable heat: the great forgotten element of the French energy strategy. [3]: International Energy Agency - CO2 emissions in 2022. [4]: ​​EUROPAIRS End User Requirement for Process heat applications with Innovative Reactors for Sustainable energy supply. [5]: Nuclear cogeneration: civil nuclear energy in a low-carbon future, The Royal Society UK.

Claims

1. Nuclear cogeneration plant comprising: - at least one nuclear reactor, in particular a pressurized water reactor (PWR) or a boiling water reactor (BWR), comprising: • a first fluid circuit, called the primary circuit (1), comprising at least one steam generator as the first intermediate heat exchanger (3), • a second fluid circuit, called the secondary circuit (5) comprising, at least one turbine (6, 60) connected to the first intermediate heat exchanger, a first condenser (7) connected to the turbine and the steam generator, to cool the steam from the turbine and transform it back into water and return it to the steam generator; • an alternator (9) mechanically coupled to the turbine, intended to be connected to an electrical network (21);- a third fluidic circuit configured as a closed loop for thermal energy storage (13), in which a heat transfer fluid circulates, comprising: • at least one second condenser (16) as a second intermediate heat exchanger; • at least one outlet heat exchanger (19), connected in a closed loop to an industrial heating network (30); • at least one first tank, called the hot tank (14), connected to the second condenser; • at least one first hydraulic pump (17) connected to the hot tank and the outlet heat exchanger; • at least one second tank, called the cold tank (15), connected to the outlet heat exchanger; • at least one second hydraulic pump (18) connected to the cold tank and the second condenser; - a fluidic system (50) for thermally paralleling the third fluidic circuit with the second fluidic circuit.

2. Cogeneration installation according to claim 1, the fluidic system (50) for putting the third fluidic circuit in thermal parallel with the second fluidic circuit, comprising: - a steam distribution and regulation device (51), connected inlet to the steam generator and outlet to both the turbine and the second condenser; - a water collection tank (52) connected inlet to both the first and second condensers and outlet to the steam generator; - a third pump (53) connected between the water collection tank and the steam generator.

3. Cogeneration installation according to claim 2, the steam distribution and regulation device (51) comprising two motorized control valves, one of which connects the steam generator to the turbine and the other connects the steam generator to the second condenser.

4. Cogeneration installation according to claim 3, the opening and closing of the valve connecting the steam generator to the turbine being controlled by control setpoints based on reactor load following, while the opening and closing of the valve connecting the steam generator to the second condenser are controlled by control setpoints based on the hot tank level.

5. Cogeneration installation according to any one of claims 2 to 4, the water temperature within the collection tank being between 150°C and 200°C.

6. Cogeneration installation according to any one of the preceding claims, the reactor vessel and the steam generator being configured as a modular reactor (100) of type SMR.

7. Cogeneration installation according to any one of the preceding claims, comprising at least one atmospheric CO2 carbon dioxide capture system and / or seawater desalination system (22) or any other system operating in cogeneration with a heat requirement compatible with the temperature at the terminals of the condenser, connected in a closed loop to the condenser of the secondary circuit of the reactor.

8. Cogeneration installation according to claim 7, further comprising a dry air air cooler (20) connected in bypass of a connection to the CO2 carbon dioxide capture system or seawater desalination system (22).

9. Cogeneration installation according to claim 8, the dry air cooling device being a dry air cooling tower.

10. Cogeneration installation according to any one of the preceding claims, the temperature T1 at the inlet of the condenser (7) being equal to at least 60°C and the temperature T2 at the outlet of the condenser (7) being equal to at least 70°C, advantageously between 70 and 100°C.

11. Cogeneration plant according to any one of the preceding claims, each of the hot and cold tanks having a volume between 1000 m³ 3 and 30,000 m 3 .

12. Cogeneration installation according to any one of the preceding claims, the heat transfer fluid of the thermal storage loop being a molten salt or a mixture of molten salts adapted to remain in liquid phase over a temperature range of 100°C to 350°C with a margin of 40°C relative to the maximum operating temperature of the thermal storage loop.

13. Cogeneration installation according to one of the preceding claims, the turbine(s) being free of low-pressure body(ies).

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