A nuclear power cogeneration plant comprising a light water reactor and a system for capturing atmospheric CO2 or desalination of seawater, without extracting or releasing liquid water into the environment.

Abstract

The present invention relates to a nuclear cogeneration plant comprising a light water reactor (LWR) without extracting or releasing liquid water into the environment and a system for capturing atmospheric CO2 or desalination of seawater. The invention essentially consists in the combined use of a heat storage loop arranged between the primary and secondary circuits of the nuclear reactor, together with a system for capturing atmospheric CO2 or desalination of seawater in the condenser of the secondary circuit.

Description

[Technical Field]

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

[0002] The present invention relates more particularly to cogeneration facilities including such reactors. Here, and in the context of the present invention, "cogeneration" means the simultaneous or non-simultaneous production of electricity and usable heat.

[0003] In terms of providing isoservice for the production of electricity during the day, the present invention aims to make effective use of all of the heat in the primary circuit of the reactor, thereby limiting or even eliminating all of the environmental impact of the reactor (taking in liquid water from the environment and releasing liquid water back into the environment).

[0004] Although described with reference to pressurized water reactors, the invention applies to any reactor using an indirect thermodynamic cycle from the family of reactors known as Generation II, III, and IV (GEN IV) reactors, and in particular to fast neutron reactors cooled by liquid metal, in particular liquid sodium (SFRs (sodium fast reactors)), which form part of the GEN IV family of reactors. [Background technology]

[0005] In the context of the climate and energy transition, the nuclear industry has to face many future challenges. Indeed, to meet tomorrow's energy and societal challenges, - limiting the need for so-called "environmental" liquid cooling sources (rivers, tidal streams, oceans) and associated re-discharges into the environment; - be more flexible and therefore better complement other so-called renewable energies, addressing the fluctuating demand for electricity and the intermittent nature of renewable energies; - Decarbonizing methods by increasing energy efficiency and supplying heat to consuming industries (desalination, district heating networks, hydrogen, etc.); - Limiting the impact of global warming by capturing CO2 from the atmosphere and contributing to closing the carbon cycle by providing a carbon source for industrial processes. This can be achieved by increasing the economic revenue from the new services provided, without reducing the cost-effectiveness of the installation, or by significantly increasing the amount of electricity produced during the day. It would be convenient to design a reactor that would make this possible.

[0006] Pressurized water reactors (PWRs) classically use three cycles (fluid circuits), the principles of which are described below with reference to Figure 1. Temperatures and efficiencies are shown for illustrative purposes only.

[0007] The primary circuit 1 is a closed-loop fluid circuit comprising mainly the core of the reactor 2, at least one steam generator (GV) acting as the so-called primary exchanger 3, and a hydraulic pump 4 for circulating a heat transfer fluid, typically water, which in normal operation is maintained in a liquid state within the operating temperature range of the reactor, which is about 320°C to 330°C. Not described here are other equipment such as pressurizers and all systems ensuring operation under the required safety conditions.

[0008] Thus, the high-pressure water in the primary circuit receives energy in the form of heat as a result of nuclear fission of the uranium core in the core of the reactor 1.

[0009] This high temperature, high pressure water, typically 155 bar and 320°C-330°C, then enters an intermediate exchanger 3 which transfers its energy to a closed loop secondary circuit 5 which also uses pressurized water as the heat transfer fluid.

[0010] The secondary circuit 5 includes an intermediate exchanger 3, a turbine 6 having a high-pressure body 60 and a low-pressure body 61, a condenser 7, and a hydraulic pump 8 for circulating water in vapor form as a heat transfer fluid.

[0011] Thus, in this secondary circuit 5, high pressure steam water, typically around 70 bar, expands and is heated in the high pressure body of the turbine, before continuing to expand in the low pressure body 61. The turbine drives an alternator 9 which produces electricity.

[0012] The water in the secondary circuit is condensed via a condenser 7 in a third cycle, the so-called "cooling" source, the cooling cycle 10. This cycle 10 essentially consists of a wet air cooling tower 11, a hollow tower with a natural air flow that enters at the bottom and exits at the top. As it passes through, this air flow picks up the heat contained in the water in the cooling circuit and dissipates it into the atmosphere in the form of a water vapor cloud. This action is repeated continuously with the water split into fine droplets, which, on the one hand, allows for good exchange between the water and the air, thus cooling the water to a temperature close to that of the ambient air, and, on the other hand, saturates the air flow circulating upward through the tower with water vapor. Part of the water flow evaporates within the tower 11, while the rest falls as rain into a pool located below the tower, from which it is pumped back to cool the condenser 7. The evaporated water is replaced with so-called "ambient" tertiary water pumped upstream from a tidal river, stream, or sea. This can significantly increase the temperature of these streams, which can cause nuclear facility operators to reduce power levels or shut down these streams during periods of hot weather and / or low flow rates.

[0013] As FIG. 1 shows by way of example, the thermodynamic efficiency of a PWR is of the order of 33 to 34%, the temperature of the water at the inlet to the condenser 7 being of the order of 20° C. and at the outlet being of the order of 35° C.

[0014] Conventional PWR reactors can be broadly classified according to their intended use as follows: - so-called power reactors, which are dedicated solely to the production of electricity; - so-called supply reactors, which are dedicated solely to the production of heat; - so-called cogeneration reactors, which are specialized in both the production of heat and the production of electricity, either simultaneously or not.

[0015] As detailed in [1], the principle of cogeneration based on nuclear reactors is to modify the design of the energy conversion cycle so that heat is released to the cooling source at a temperature that allows its effective use. Indeed, the reduction of global warming depends on minimizing heat losses at all levels, and especially at the level of the cooling source of thermodynamic installations. This cogeneration objective is all the more relevant for nuclear reactors, in that industrial or domestic heating is often done in a conventional way by burning fossil fuels that are associated with greenhouse gas emissions.

[0016] To achieve this objective, a first configuration consists in modifying the components of the power generation system of the PWR installation in order to adjust the temperature of the water to the level of the cooling source.

[0017] However, in the classic configuration shown in Figure 1, this modification remains limited. It does not affect the high-pressure turbine 60, but only the low-pressure turbine 61, which implements the Rankine cycle. This modification is shown in Figure 2 and consists in changing the operating point P of the low-pressure turbine 61 to a pressure of the order of 1 bar instead of about 50 mbar, so that the water at the condenser outlet has a sufficiently high temperature level, typically 70°C, to be effectively utilized, for example in the district heating network 12. This modification is accompanied, first of all, by a reduction in the produced power, since the thermodynamic efficiency drops to 27%. There is also an increase in the pressure in the condenser 7.

[0018] However, this first cogeneration configuration has two major drawbacks.

[0019] First of all, as already mentioned, the efficient use of heat from the cooling source reduces the electrical efficiency of the installation, i.e. the service provided in terms of electricity is significantly degraded. In fact, as the second law of thermodynamics states, increasing the temperature of the cooling source reduces the efficiency of the conversion cycle. This phenomenon of electrical efficiency reduction due to an increase in the temperature of the cooling source is shown by the decreasing curve as a function of temperature in Figure 3, which is taken from Reference [2].

[0020] Another major drawback is that a cooling source in the form of liquid water taken from a tidal stream, river or sea is still required to supply the cooling tower 11 during periods when there is no longer a demand for heat or when the district heating network is unavailable. This also means that wastewater is released back into the environment and there are restrictions on operation related to the wastewater standards that must be complied with.

[0021] The second cogeneration configuration consists no longer in receiving heat at the level of the cooling source, but rather directly at the level of the body 60, 61 of the turbine 6 by extracting hot steam: [3], [4].

[0022] Patent document 1 also discloses a cogeneration nuclear power plant using this second configuration, in which the secondary circuit of the reactor can send a portion of the steam at the turbine outlet to a heat storage tank and / or to a heat exchanger connected to a city-type district heating network.

[0023] This second configuration, shown in FIG. 4, with the outlet S between or at the two main body sections 60, 61, has the advantage of being able to achieve higher temperatures, typically exceeding 100°C, compared to the temperatures obtained when heat is received at the cooling source. These higher temperatures may be suitable for industrial applications without significantly reducing electrical efficiency if the received thermal power remains limited. However, this second configuration has the disadvantage of only allowing a limited extraction of thermal power, in order to avoid undesirably reducing electrical efficiency and limiting the need for environmental liquid water for cooling the conversion circuit. Therefore, water demand and the resulting wastewater generation remain a significant problem with this configuration.

[0024] Concepts aiming to limit the inherent deficiencies of cogeneration systems by adding energy storage facilities have already been proposed in the literature. These concepts can be classified into two broad families:

[0025] The first family concerns systems intended to improve the maneuverability of nuclear reactors, i.e., to make the production of electricity by nuclear reactors more flexible than it is today, by temporarily increasing the level of power fed into the grid to meet demand. In the literature, these systems are employed in power reactors, but they are equally applicable to cogeneration reactors: [5], patent document 2.

[0026] An example of such a system is shown diagrammatically in Figure 5. An auxiliary fluid circuit configured as a heat storage loop 13 is arranged between the primary circuit 1 and the secondary circuit 5 in which the energy conversion takes place.

[0027] This loop 13 includes an intermediate exchanger 3, two heat storage tanks, a so-called hot tank 14 and a so-called cold tank 15, a steam generator 16 that allows the exchange between the heat storage loop and the secondary circuit and thus the production of steam for turbines 60, 61, and finally two hydraulic pumps 17, 18 that are arranged respectively between the hot tank 14 and the steam generator 16 and between the cold tank 15 and the intermediate exchanger 3 to move the heat transfer fluid in this loop 13. The heat transfer fluid in this loop is advantageously a HITEC® molten salt mixture with the composition 53% KNO3, 40% NaNO2, 7% NaNO3. By way of example, the temperature of this heat transfer fluid is of the order of 310°C in the hot tank 14 and 245°C in the cold tank 15.

[0028] 5, the reactor core 2 operates at base, i.e., it delivers 100% power throughout the entire operating cycle. The power extracted by the pump 18 upstream of the intermediate exchanger 3 into the heat storage loop 13 is constant.

[0029] During periods of low demand, the pump 17 downstream of the hot tank that discharges power to the secondary circuit operates below rated capacity. The hot tank 14 is filled and the cold tank 15 is emptied. Therefore, the power transferred to the secondary circuit 5 is less than the power produced in the core 2.

[0030] At times of high demand, the pump 17 operates at a high rating and therefore the power transferred to the secondary circuit 5 is higher than the power produced in the reactor core. This system therefore has the advantage of decoupling the operation of the reactor core from the operation of the energy conversion system at the level of the secondary circuit, increasing the power supplied to the grid during periods of high demand.

[0031] Such systems nevertheless have the following major drawbacks: This does not make it possible to increase the temperature of the water at the outlet of the condenser 7 and therefore it remains at a very low temperature, typically below 40°C, and therefore it is not possible to make effective use of it. This requires a general upgrade of the conversion cycle, including the body of the low-pressure turbine 61, which must be very large, since the heat power transferred to the secondary cycle 5 during the day is high. - This also requires an upgrade of the cooling source, i.e., in fact, the latter must be adapted to drain the residual power of the secondary cycle being upgraded.

[0032] A second family of cogeneration systems that adds energy storage facilities includes facilities dedicated to improving the overall energy efficiency of the facility, i.e., making it possible to utilize part of the heat produced in addition to the electricity. An example of such an added facility is described, for example, in US Pat. No. 5,649,399.

[0033] 6 also shows a system from this second family in which the thermal output of the core is slaved to the power demanded by the grid. Here, a thermal storage tank 19 is arranged downstream of the condenser 7 to store water from the cooling source at the outlet of the condenser 7 and return it at another time. This arrangement therefore makes it possible to exploit some or all of the free heat of the reactor in addition to the power supplied to the grid, and to decouple the power supply from the heat supply in time.

[0034] Such systems nevertheless have a number of significant drawbacks: - The core cannot function as a base, and therefore the power produced by the core varies as a function of power demand. - The temperatures at which it can be effectively used remain very low, typically below 40°C, limiting its applications. If the conversion cycle of the secondary circuit 5 is modified so as to increase the temperature of the heat utilized, the electrical efficiency of the installation will be significantly reduced. The thermal storage tank 19 is directly connected to the district heating network 12 and therefore must be very large as the thermal storage is at a relatively low temperature, typically 40°C. - This requires the input of considerable amounts of water when the district heating network is not available or there is no demand for heat (summer).

[0035] In summary, all cogeneration nuclear installations identified in the literature can be: - Only a small portion of the heat is utilized in order not to significantly reduce electrical efficiency, in which case the cooling requirements remain very high and most of the power produced in the reactor core is not available for effective use. - Or, utilize a large portion of the heat from the reactor but significantly reduce the production of electricity, or in extreme cases, result in a reactor that produces only heat, which has a significant, or even unacceptable, impact on the cost-effectiveness of a given installation for the operator.

[0036] Furthermore, it has already been proposed to combine nuclear reactors with desalination plants. For example, publication [6] describes combining a heat-only nuclear reactor to perform a multi-effect distillation process.

[0037] Also, very high temperature reactors have already been proposed to produce both electricity and hydrogen.[7]

[0038] These designs are a far cry from the problems with cogeneration nuclear plants mentioned above.

[0039] Therefore, there is a need to improve cogeneration reactor installations in order to make it possible to make full effective use of the heat produced in the primary circuits of the installation's reactors in providing iso-services for the production of electricity during the day and, as a result, to limit or even eliminate all environmental impacts of the installation's reactor(s), i.e., the uptake of liquid water from the environment and the re-release of liquid water into the environment.

[0040] The need for this improvement has been identified by the Nuclear Regulatory Authority [8]. [Prior art documents] [Patent documents]

[0041] [Patent Document 1] Korean Patent Application No. 2021 / 0081846 [Patent Document 2] Japanese Patent Publication No. 2020 197468A [Patent Document 3] U.S. Patent No. 4,170,879A Summary of the Invention [Problem to be solved by the invention]

[0042] It is an object of the present invention to at least partially address this need for improvement. [Means for solving the problem]

[0043] To this end, one aspect of the present invention relates to an electronuclear cogeneration facility, comprising: - at least one nuclear reactor, in particular of the pressurized water reactor (PWR) or boiling water reactor (BWR) type, a first fluid circuit, called the primary circuit, including at least one first intermediate heat exchanger; a second fluid circuit, referred to as the secondary circuit, including at least one steam generator as a second intermediate heat exchanger, at least one turbine connected to the second heat exchanger, and a condenser connected to the turbine and the second heat exchanger to cool the steam from the turbine and convert it back to water for delivery to the second heat exchanger; at least one nuclear reactor, comprising an alternator mechanically coupled to the turbine and intended to be connected to a power grid; a third fluid circuit configured as a closed loop for storing thermal energy in which a heat transfer fluid circulates, at least one first tank, called the high-temperature tank, connected to the first intermediate heat exchanger; at least one first hydraulic pump connected to the high-temperature tank and the second intermediate heat exchanger; at least one second tank, called a cryogenic tank, connected to a second intermediate heat exchanger; a third fluid circuit comprising at least one second hydraulic pump connected to the cryogenic tank and the first intermediate heat exchanger; - at least one heat utilization system connected in a closed loop to a condenser of the secondary circuit of the reactor.

[0044] In an advantageous embodiment, the heat utilization system is an atmospheric carbon dioxide CO2 capture and / or desalination system and / or a district heating network. More generally, it may be any system using heat from the secondary circuit of a nuclear reactor employing a heat-using process, in particular for industrial purposes.

[0045] In another advantageous embodiment, the installation further comprises a dry air cooling system connected to bypass the connection to the heat utilization system.

[0046] The present invention also provides: - The design nominal operating level (K), also known as the availability coefficient, regardless of the power demand of the grid to which the alternator is connected. d ) to operate the reactor; - Providing new non-energy services (atmospheric CO2 capture and / or seawater desalination and / or urban or industrial district heating networks) through optimal and efficient use of part or all of the thermal energy produced by the reactor; - Allows at least partial elimination of the need for liquid water as a cooling source and the associated wastewater associated with the release of unused energy.

[0047] As a corollary of this, the invention makes it possible to improve the safety of the installation by making available a system that contributes to the discharge of residual power during periods when the reactor is shut down.

[0048] The invention essentially consists in using a heat storage loop between the primary and secondary circuits of a nuclear reactor in combination with a condenser in the secondary circuit, together with a heat utilization system which may advantageously be an atmospheric carbon dioxide capture and / or desalination system and / or a district heating network.

[0049] The resulting cogeneration plant is a fully or nearly fully energy-efficient system that no longer requires a cooling water supply, solving key issues related to grid flexibility and climate change associated with the large-scale introduction of renewable energy.

[0050] Therefore, by combining the reactor circuit with a heat storage loop, it is possible to design an installation that allows 100% effective utilization of the energy produced in the core without any reduction in the service provided in terms of producing electricity during the day.

[0051] The invention is advantageously a combination of the following measures: - It is the combination of a thermal storage loop installed on-site between the primary and secondary circuits of a nuclear reactor, especially a PWR. This thermal storage loop allows the reactor's functioning to no longer be slaved to the requirements of the grid. Thanks to the thermal energy storage, the reactor always functions at full power, and the energy conversion system of the secondary circuit recovers it as a function of the grid demand (during the day), increasing the amount of electricity fed into the grid.

[0052] The fact that the thermal power delivered to the conversion system to the secondary circuit during the day is greater than that of prior art installations with lower thermodynamic efficiency can mean an increase in the capacity of the steam generator and high-pressure turbine body, especially with larger blade diameters.

[0053] The dimensions of the hot and cold tanks of the thermal storage loop depend on the required temperature level. The tank volume is advantageously 10,000 m 3 From 30,000m 3 and the industrial feasibility of such tanks has already been demonstrated given current practices in other industrial sectors. Increasing the temperature of the water at the outlet of the condenser secondary circuit on the cooling source side to a temperature that can be used effectively, typically above 100°C for seawater desalination or atmospheric CO2 capture, reduces the conversion efficiency of the Rankine thermodynamic cycle in the secondary circuit, which may advantageously imply a significant reduction or even elimination of the low-pressure body of one or more turbines and a modification of the design of the condenser, in particular to increase its saturation pressure. - By increasing the cold source side of the power conversion cycle in the secondary circuit, i.e. the low temperature at the condenser inlet, to temperatures typically above 40°C, dry air cooling technology can be used instead of classic wet air cooling towers, which consume large amounts of water, when heat is not present momentarily or for longer periods of time for atmospheric CO2 capture and / or desalination systems.

[0054] These dry air cooling towers do not require liquid water for cooling, whatever the consumer or heat demand: it is the atmosphere that acts as the coolant.

[0055] The main advantage of the system configuration according to the invention compared to an installation such as that shown in FIG. 5 and in patent document 2 is the addition of complementary components / processes / networks that modify the technical and functional configuration of the installation. - A / Configuration. Addition of a dry air cooling tower, which allows for the elimination of the need for a water source for the free heat rejection process. - C / Configuration: Connection to an airborne CO2 capture or desalination system allows for the effective use of all thermal energy from the reactor that is not used to produce electricity. In this configuration, the plant achieves total energy efficiency.

[0056] The inventors have overcome a technological preconception based on the belief that maximizing the production of electricity and efficient utilization of nuclear power plants always requires that the latter be designed so that the temperature of the cooling source is at the lowest possible level.

[0057] Now, by combining the addition of a thermal storage loop with a Rankine cycle upgrade, this invention makes it possible to change the paradigm by demonstrating the ability to perform cogeneration with very high energy efficiency.

[0058] The inventors have also carried out a detailed analysis of the exergy of various heat utilization technologies, in particular atmospheric CO2 capture technologies. This has revealed that adsorption technologies require the input of energy in the form of heat to regenerate the substrate, with temperature levels of the order of 70 to 100 °C, depending on the different technologies already used. See in particular the figure in the publication [9], which lists companies that have developed and commercialized installations employing these technologies for several years, with power levels of the order of 1 MWth.

[0059] These techniques rely on the principle of agitating air containing approximately 400 ppm CO2, typically with a fan, over a substrate on which CO2 molecules are immobilized. After the substrate is saturated, it is regenerated by releasing CO2 under the effect of increasing temperature. Desorption temperature levels can vary within the range of 70-100 °C, depending on the substrate technology developed, the design and operating mode adopted by the manufacturer, and the heat source available for the process.

[0060] Capturing one tonne of CO2 requires around 2MW of energy, split in various proportions between heat and electricity depending on the technology[9].

[0061] The invention therefore allows the effective use of heat not used by the Rankine cycle, the electromotive efficiency of which is between 25 and 35% in modern PWRs, which corresponds to 65 to 75% of the core's thermal power that is currently not being utilized for atmospheric CO2 capture or seawater desalination.

[0062] Finally, a PWR cogeneration plant according to the invention, including a CO2 capture system with a thermal storage loop and a bypass dry air cooling system, has a number of significant advantages in terms of the production of electricity during the day and is provided with iso-service, among which the following advantages may be obtained: - Highly energy efficient as each MW produced in the core is effectively utilized in the configuration with CO2 capture system at nominal operation. - The installation must not take in liquid water from or re-release it into the environment, whatever the operating regime. - Eliminate the need to build nuclear facilities on coasts or in fast-flowing tidal rivers. - Absence of environmental constraints linked to climate deregulation (heat waves). - In the context of a circular carbon economy, the effective use of potentially large sources of CO2 through the production of synthetic fuels. - Thorough simplification of safety demonstration. - Extensive potential for the deployment of equipment in countries with arid climates and geographically without tidal rivers, streams or seas. - Improved public acceptance.

[0063] Other and secondary advantages linked to the present invention may also be important: - Keeping PWR as the base as power fluctuations are handled by the thermal storage loop. - Simplified design of the primary circuit of the PWR of the installation. - Simplifying facility safety documentation. - Improved operation of high-quality equipment. - Improved availability, etc. - Less wastewater per MWh. - the possibility of venting residual power from the reactor core during reactor shutdowns using heat storage loops, in particular using reserves of heat transfer fluid in cryogenic tanks. The described conditions associated with this function are defined as a function of the expected safety level.

[0064] In an advantageous embodiment, the installation further comprises a dry air cooling system connected to bypass the connection to the heat utilization system.

[0065] In this advantageous embodiment, the dry air cooling system is a dry air cooling tower.

[0066] Also in this embodiment, 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] The hot and cold tanks of the third fluid circuit advantageously have a capacity of 10,000 m each. 3 From 30,000m 3 It has a volume between

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

[0069] The heat transfer fluid preferably has the following chemical composition: 53% NaNO3, 40% NaNO2, 7% KNO3.

[0070] Connecting the condenser directly to the heat utilization system is satisfactory in a significant number of configurations.

[0071] In other configurations, this may have the disadvantage of being at least functionally limited, since such a direct connection makes the energy conversion system and the system for utilizing the heat directly at the inlet and outlet of the condenser interdependent. The disadvantages of having such a direct correlation between the production of electricity and the production of heat may be: - For a given availability level of the facility as a whole, the outage (whether planned or accidental) of one or more systems for utilizing heat at the condenser inlet and outlet could result in the outage of the energy conversion system or the need for additional backup systems of the dry air cooling tower type, thereby reducing the reactor utilization rate and compromising its cost-effectiveness. - The choice of the technology of the utilization system or systems connected to the inlet and outlet of the condenser. The services handled by this system or systems must be compatible with the flexibility imposed by the requirements of the power grid in general, but not organizationally, which is the highest priority. For example, systems that require a high level of heat supply for long periods of time are not compatible with the daily operating cycle. Here could be high-temperature electrolysis systems for the production of H2, or urban or industrial district heating networks. - The technology of the system or systems connected to the condenser inlet and outlet must also be adapted to the dynamic flexibility of the upstream energy conversion system. The functionality of the heat utilization system or systems must be able to follow power spikes caused by fluctuations in the grid's power demand, potentially of the order of several MWth / min. - Due to the fact that the operation of the system or systems connected to the inlet and outlet of the condenser is discontinuous, i.e. only for X hours per day, an equivalent daily production performance requires raising the capacity of the system or systems in the same proportion as the energy conversion system in relation to the reactor power. - Finally, due to the interdependence of heat production and the correlated electricity production in terms of the operational / service characteristics handled by the heat utilization system, the cost-effectiveness of the cogeneration plant cannot be maximized simultaneously in both markets, and there is room for optimization contingent on decoupling electricity production from heat supply.

[0072] The inventors were therefore faced with the additional problem of decoupling the production of electricity from the production of heat in time without reducing the yield and energy efficiency of the cogeneration plant as a whole.

[0073] To this end, in an additional embodiment, the cogeneration installation according to the invention advantageously comprises a fourth fluid circuit constituted by a closed loop for the storage of thermal energy and the distribution of heat, in which a heat transfer fluid circulates, the fourth fluid circuit comprising: - at least one third tank, called a high-temperature tank, connected to the condenser; - at least one third hydraulic pump connected to the high-temperature tank and to at least one heat utilization system; - at least one fourth tank, called a low-temperature tank, connected to the condenser and to at least one heat utilization system; at least one fourth hydraulic pump connected to the cryogenic tank and to the condenser.

[0074] This therefore allows the cogeneration plant to function by decoupling the production of electricity and heat in time, whilst at the same time increasing: - The overall energy efficiency of the facility, by increasing the specific availability level of one or more heat utilization systems, reducing the impact of an accidental outage of one of the systems on another, and allowing production by one or more heat utilization systems to continue. - Compactness of the heat utilization system: the dimensions of these various components are optimized to exactly what is required. - Services and markets with completely separate characteristics, in particular the requirement for flexibility of use, the ability to respond simultaneously to the dynamics of change on all time scales, which in effect increases the cost-effectiveness of the installation.

[0075] The temperature levels in the low and high temperature storage tanks of this fourth fluid circuit can be adjusted as a function of the temperature level required for one or more heat utilization systems supplied with heat transfer fluid in the circuit.

[0076] Thus, a thermal storage loop with hot and cold tanks distributing heat to various heat utilization systems advantageously allows for the addressing of services and markets with diverse characteristics.

[0077] The number of parallel heat utilization systems at the inlet and outlet of the condenser may be large. The selection of the number and type of heat utilization systems is advantageously based on an attempt to optimize, over a sliding period of up to 24 hours of daily operation of the installation, preferably all of the heat output from the reactor core that is not converted to produce electricity. In other words, the selection is made wisely so as to discharge the maximum amount of power not dedicated to the production of electricity from the reactor to the heat utilization systems. The parallel installation of dry air cooling towers advantageously allows this objective to be achieved.

[0078] In this configuration with the auxiliary heat storage loop, the heat utilization system connected to the inlet and outlet of the condenser serves as the reactor's cooling source, and no environmental cooling source is required for either reactor cooling or excess heat rejection. All of the heat produced in the reactor core is effectively utilized. In this configuration, the cold water reserve upstream of the condenser can temporarily mitigate the loss of the cooling source for operating the reactor.

[0079] A heat utilization system that can be advantageously envisaged in this heat storage loop and heat distribution mode is as follows. - Low-temperature district heating networks for urban or industrial use, - Seawater desalination systems requiring thermal energy, for example by multiple-effect processes (multiple-effect distillation (MED)) or multi-stage expansion distillation processes (multiple-stage flash distillation (MSF)), - Capture of atmospheric CO2, which in particular contributes to closing the carbon cycle.

[0080] Finally, this approach with a heat storage loop and heat distribution can bring about a number of additional advantages, among which are the following: - The energy conversion system of the cogeneration facility can equally well operate completely independently of one or more heat utilization systems on the heat source (reactor) side and on the cooling source (condenser inlet and outlet) side, thus making it possible to obtain both full flexibility or maximum and optimized levels of availability in terms of service to the grid, and consequently the reactor economy of the facility. - The possibility of parallel installation of different systems to utilize the heat from the reactor consumed by the system to convert energy into electricity, thus increasing the ability to respond to energy markets and services with different demand characteristics and profiles than electricity. - Physical decoupling of the conversion cycles of the reactor and one or more heat utilization systems by means of thermal storage tanks acting as a buffer, making it possible to significantly limit the risk of an accident / accident at one of the sites where the reactor is installed propagating to the sites where one or the other of the heat utilization systems is installed, and vice versa. - the fact that, due to the existence of a certain daily operation not linked to the function of the electricity production service, it is no longer necessary to increase the capacity of one or more heat utilization systems, which was previously done due to the need to evacuate all the thermal power from the reactor core that was not converted into electricity for a shorter period of time (the operating time of the system for converting energy into electricity).

[0081] The heat transfer fluid of the heat storage and heat distribution loop of the fourth fluid circuit is preferably water adapted to remain in liquid phase over a temperature range of 50°C to 100°C, with a margin of 10°C relative to the maximum operating temperature of the heat storage and heat distribution loop. For example, the temperature in the hot tank may be between 80 and 100°C, and the temperature in the cold tank between 60 and 80°C. Other temperature levels, for example temperatures above 100°C, are also possible, but in that case other heat storage fluids would need to be used.

[0082] In one advantageous embodiment, the hot and cold tanks consist of single-layer thermal storage tanks. "Layered thermal storage tank" means that the volume of heat transfer fluid contained in the thermal storage tank has a temperature gradient between the top and bottom of the tank. In other words, the volume of heat transfer fluid in the thermal storage tank is divided into stacked thermal layers of heat transfer fluid with gradually varying temperatures from one end to the other, and these stacked layers can form a continuous thermal layer.

[0083] The single layer thermal storage tank is a trench filled with a heat transfer fluid, preferably at least partially underground. For required temperature levels below 100°C, the trench is advantageously filled with water, which results in temperature stratification between a layer at 90°C and a lower temperature layer at 50°C, for example.

[0084] In another advantageous embodiment, the installation comprises at least two heat utilization systems in parallel with the hot and cold tanks of the heat storage and heat distribution loop.

[0085] The hot and cold tanks of the fourth fluid circuit advantageously each have a capacity of 50,000 to 300,000 m for a reactor power equal to 150 MWe. 3 The volume of the suction pipe may be 1000 vol.

[0086] In another advantageous variant, the turbine or turbines may or may not include a low pressure body.

[0087] Other advantages and characteristics of the present invention will become more clearly apparent after reading the detailed description of an embodiment of the invention, given by way of non-limiting example with reference to the following figures: [Brief explanation of the drawings]

[0088] [Figure 1] 1 is a schematic diagram of a prior art pressurized water reactor (PWR) configuration functioning solely as a power generating reactor; [Figure 2] 1 is a schematic diagram of a prior art configuration of a pressurized water reactor (PWR) modified to function as a cogeneration reactor; [Figure 3] FIG. 1 shows the evolution of electrical efficiency and exergy of a prior art PWR as a function of the temperature of the cooling source. [Figure 4] 1 is a schematic diagram of another configuration of a prior art pressurized water reactor (PWR) modified to function as a cogeneration reactor; [Figure 5] 1 is a diagram illustrating a schematic configuration of a prior art cogeneration plant including a pressurized water reactor (PWR) and a heat storage loop. [Figure 6] 1 is a diagram illustrating a schematic configuration of a prior art cogeneration plant including a pressurized water reactor (PWR) and a heat storage loop. [Figure 7] 1 is a diagram illustrating a schematic configuration of a cogeneration facility according to the present invention, including a pressurized water reactor (PWR), a heat storage loop, and a dry air cooling system. [Figure 8] 1 is a diagram showing a schematic configuration of a cogeneration facility according to the present invention, including a pressurized water reactor (PWR), a heat storage loop, an atmospheric CO2 capture system, and a dry air cooling system that bypasses the atmospheric CO2 capture system. [Figure 9] 1 is a graph showing a curve of power supplied to a power grid connected to a prior art PWR nuclear reactor. [Figure 10] 1 is a graph showing the power curve of a PWR in a cogeneration installation according to the present invention having a heat storage loop. [Figure 11] 1 is a graph showing the ratio of sales of a standard SMR reactor to sales of an installation according to the invention using an SMR reactor and an airborne CO2 capture system as a function of sales revenue per tonne of CO2. [Figure 12] 1 is a schematic diagram illustrating a cogeneration facility configuration according to an advantageous embodiment of the present invention, including a pressurized water reactor (PWR), a first heat storage loop, and a second heat storage loop that distributes heat in parallel to multiple heat utilization systems. [Figure 13] 13 is a schematic longitudinal cross-sectional view of a single layer thermal storage tank that serves as both the hot and cold tanks for the second thermal storage loop of the embodiment of FIG. 12. FIG. [Figure 14] 1 is a graph showing the power curve of a PWR reactor in a cogeneration installation according to an advantageous embodiment of the invention, having a first heat storage loop and a second heat storage loop that distributes heat in parallel to a number of heat utilization systems. DETAILED DESCRIPTION OF THE INVENTION

[0089] Throughout this application, the terms "upstream" and "downstream" are to be understood with respect to the direction of circulation of the heat transfer fluid in one of the fluid circuits of the cogeneration nuclear installation according to the invention.

[0090] 1 to 6, which relate to the prior art, have already been explained in detail in the preamble and therefore will not be commented on below.

[0091] For clarity, elements that are the same in the present invention and the prior art are designated by the same reference numerals in all of Figures 1-14.

[0092] All of the various relationships and functions of the elements common to the cogeneration plant according to the invention and to a prior art cogeneration plant with a heat storage loop such as that depicted in Figure 5 will not be described in detail again, only some of these elements will be described again.

[0093] The cogeneration nuclear plant according to the invention shown in FIG. 8 comprises, in addition to the usual components of a standard plant with a PWR reactor, a heat storage loop 13 between the primary circuit 1 and the secondary circuit 5, and a CO2 capture system that bypasses the dry air cooling system 20.

[0094] The heat storage loop 13 circulates the heat transfer fluid from the intermediate exchanger 3 in the reactor primary circuit to a hot tank 14 , then into a steam generator 16 , then into a cold tank 15 and back to the intermediate exchanger 3 .

[0095] The heat transfer fluid is circulated in the loop 13 by a hydraulic pump 17 downstream of the hot tank 14 and a hydraulic pump 18 downstream of the cold tank 15 .

[0096] Each fluid branch of the loop 13 consists of a cylindrical pipe with metal walls that can withstand chemical attack by heat transfer fluids at high temperatures, typically above 300°C, and externally insulated with high temperature insulation. The pipe diameter is calculated to allow the discharge of all heat power at the maximum allowable critical flow rate of the heat transfer fluid, which is typically on the order of 5 to 10 m / s.

[0097] The high-temperature tank 14 contains the heat transfer fluid, stores all the heat recovered from the intermediate exchanger 3, and supplies the heat transfer fluid to the steam generator 16. The high-temperature tank 14 can be cylindrical with walls made of a metal resistant to chemical attack by the heat transfer fluid at high temperatures, typically above 300°C, and is coated with an external high-temperature insulation layer to limit heat loss. The size (usable storage volume) of the high-temperature tank 14 depends on the characteristics of the heat transfer fluid used, which must be capable of storing up to all the heat produced by the reactor over a sliding 24-hour period. For safety reasons, the high-temperature tank 14 is located a certain distance from the reactor enclosure, with a batter in between, typically a preliminary estimate of 60 m. The tank 14 can be equipped with a system for heating the heat transfer fluid to ensure that the fluid remains in a liquid state, and / or a level measurement system capable of transmitting alarms and / or safety overflows connected directly to the low-temperature tank 15.

[0098] The steam generator 16 generates steam for the turbines 60, 61, which are characteristic of the Rankine cycle with the plant's power generation cycle operating mode and must be able to function on demand from the power grid 21. The steam generator 16 is typically rated to discharge 1.5 times the reactor power output. The turbines 60, 61 are rated based on the peak flow rate of steam generated by the steam generator 16.

[0099] Like the hydraulic pump 18, the hydraulic pump 17 is designed to function at least with the reactor's availability factor Kd and must be able to function according to the fluctuating power demands of the power grid 21 to which the reactor's alternator 9 is electrically connected. The flow rate of the pump 17 or 18 must be such that, given the heat capacity of the heat transfer fluid and the size of the steam generator 16, it can supply the latter with a flow rate that meets the power demands of the power grid 21. Each pump 17, 18 has a metal wall that can withstand chemical attack by the heat transfer fluid at high temperatures, typically above 300°C. Multiple pumps 17 or 18 can be connected in parallel to distribute the pumping flow, and redundant pumps can be provided for safety reasons.

[0100] The cryogenic tank 15 has substantially the same storage volume as the hot tank 14 for the heat transfer fluid recovered from the steam generator 16. The cryogenic tank 15 can be cylindrical with walls made of a metal that can withstand chemical attack by the heat transfer fluid at high temperatures, typically above 300°C, and is coated with an external high-temperature insulating layer that limits heat loss. The size (usable storage volume) of the cryogenic tank 15 depends on the characteristics of the heat transfer fluid used, which must be capable of storing up to all of the heat produced by the reactor over a sliding 24-hour period. For safety reasons, the cryogenic tank 15 is located a certain distance from the reactor enclosure, with a batter between them, typically a preliminary estimate of 60 m. The tank 15 can be equipped with a system for heating the heat transfer fluid to ensure that the fluid is maintained in a liquid state, and / or a level measurement system with alarms and / or safety overflow signals connected directly to the hot tank 14.

[0101] The heat transfer fluid is of the molten salt type so as to remain in the liquid phase over the temperature range of 100°C to 350°C with a margin of 40°C for the maximum operating temperature. The salt preferably has the chemical composition: 53% NaNO3, 40% NaNO2, 7% KNO3 (HITEC® salt).

[0102] The total amount of salt contained in the closed loop 13 is equal to the total volume of the cryogenic tank 15 and the volume contained in the fluid branches / pipes of the loop 13 to prevent overflow and loading during operation.

[0103] The power grid 21 connected to the alternator 9 aims to transmit and distribute electricity to end users according to their demand. It is a high-voltage power grid that operates according to the electricity demand linked to the electricity usage and must be able to accept the peak power produced by the cogeneration plant.

[0104] According to the invention, the cogeneration installation comprises at least one so-called dry air cooling tower 20, i.e., one that functions in dry conditions, connected in a closed loop to the condenser 7 of the secondary circuit of the reactor. This configuration will be referred to hereinafter as A / configuration and is depicted in FIG. 7.

[0105] The cooling tower 20 transfers heat from the water condensed in the condenser 7 to the ambient air.

[0106] The cooling tower 20 is sized to vent the heat power not consumed by the turbines 6, 60, 61 by bringing the water from the condenser 7 to the lowest temperature level that can be tolerated without the ambient air being significantly heated.

[0107] Although not shown, the closed loop including the condenser 7 and the dry air cooling tower 20 is equipped with a pumping system for pumping a heat transfer fluid therethrough, which is adapted to be directly integrated into the tower 20. This A / configuration is aimed at a pure power generation function, with the dry air cooling tower 20 discharging the residual power not consumed by the electrical conversion systems 6, 9. In this A / configuration, although the installation is not operating at an overall energy efficiency, it has the important advantage of producing more power during the day than prior art PWR reactors, without the need to receive or re-discharge liquid water from or into the environment.

[0108] In an advantageous configuration, shown in FIG. 8, hereinafter referred to as the C / configuration, the dry air cooling tower 20 is connected to bypass the connection to the atmospheric CO 2 capture system 22 .

[0109] Therefore, if the atmospheric CO2 capture system is shut down, the facility will function in the A / configuration.

[0110] This C / configuration aims to operate in cogeneration mode, supplying low-temperature heat to the atmospheric CO2 capture system. This C / configuration therefore aims to make effective use of all of the thermal energy from the reactor that is not used to produce electricity. In this C / configuration, the facility has overall energy efficiency.

[0111] Thus, if the demand for heat by this network were to momentarily disappear, the installation would revert to the A / configuration.

[0112] All cogeneration plants are typically configured in a closed loop incorporating the condenser 7 and atmospheric CO2 capture system 22 to have a condenser inlet temperature T1 of at least 60°C and a condenser 7 outlet temperature T2 of at least 70°C, which is advantageously between 70 and 100°C.

[0113] The inventors have rated the cogeneration plants shown in Figures 7 and 8 for A / and C / configurations, respectively.

[0114] These ratings are based on the intra-day power demand curve of the high voltage grid 21. To simplify the calculations, the power curve can be simplified with a constant demand for power centered around a day of duration X hours, where X is less than 24, as shown in Figure 9.

[0115] If the demand in reality is not identical to this simplification, the design of the installation according to the invention remains the same, considering that the total power fed into the grid each day is equal to the integral of the power over a sliding 24-hour period.

[0116] Comparison Configuration In the prior art configuration of a PWR reactor shown in Figure 1, the water entering the wet air cooling tower 11 is at a temperature of the order of 35°C and exiting at a temperature of the order of 25°C.

[0117] In this case, the total power delivered to the grid by the system each day is: P Daily elec grid (MWhe / j)=X(h)×P Reactor (MWth)×Rdt Rankine 25° (%) (1) However, in this case, the efficiency Rdt Rankine 25° =33%.

[0118] A / Configuration and C / Configuration according to the present invention The introduction of the thermal storage loop 13 makes it possible to decouple the operation of the reactor from the power demand curve of the power grid 21. The total power produced by the reactor is therefore given by equation (2) below: P Reactor daily (MWth)=24×P Reactor (MWth)(%) (2)

[0119] This constant power is shown in FIG.

[0120] To be able to deliver all of this power to the grid on a daily basis, the energy conversion loop 5 employing the Rankine cycle must therefore be rated to discharge all of its power during X hours of grid power demand.

[0121] Its power rating is then given by equation (3).

[0122]

number

[0123] Based on these daily power budgets, the elements of the thermal storage loop 13 can be rated.

[0124] Given the selected technology of the PWR reactor, the input data giving the inlet and outlet temperatures of the intermediate exchanger 3 are fixed, and therefore the temperatures of the cold tank 15 and the hot tank 14, respectively, are: T cold salt =245℃ T hot salt =310℃

[0125] Under these conditions, the salt pumping rate by pump 18 is given by the formula, where Cp salt is the mass heat capacity of the heat transfer fluid salt in loop 13.

[0126]

number

[0127] The power rating of the intermediate heat exchanger 3 is given by the formula P Reactor (MWth) = K × S × ΔTT Ln (5) is given by where: - K is the average surface heat transfer coefficient, - S is the surface area, - ΔTT Ln is the logarithmic temperature delta of the inlet and outlet of the intermediate exchanger 3.

[0128] The usable volume of the high temperature tank 14 is then calculated by the formula V hot tank usable (m 3 )=24 Q EI feed pump (m 3 / h) (5) is given by

[0129] The design usable volume of the low temperature tank 15 is equal to the usable volume of the high temperature tank 14. V cold tank usable (m 3 )=V hot tank usable (m 3 ) (6) is.

[0130] This rating method does not take into account the time during which the reactor is functioning and the volume losses that occur during the power conversion cycle. It nevertheless allows for dynamic shutdown of the reactor in case the energy conversion system fails at the most inopportune moment (at the beginning of the grid demand cycle). The total volume value before the cryogenic tank overflows can be reached by adding a safety volume taken as a precaution before the safety analysis, which is 20% of the available volume.

[0131] The flow rate that the pump 8 supplies to the steam generator 16 is given by the following formula:

[0132]

number

[0133] The rating of the Rankine cycle components of the secondary circuit 5 is determined by the heat output to be converted and the inlet and outlet temperatures of the condenser 7 .

[0134] The heat output is given by equation (3) above.

[0135] The temperatures at the inlet and outlet of the condenser 7 depend on the A / or C / configuration envisaged.

[0136] Table 1 below shows the temperature values ​​and the associated thermodynamic cycle efficiency as a function of A / configuration or C / configuration.

[0137] [Table 1]

[0138] All ratings of the cycle's components are established using CYCLOP internal software types that have been tested by the applicant for their ratings in the context of the configuration of a permanent thermodynamic conversion cycle.

[0139] The use of this software is described, for example, in documents [3] or

[10] . The ratings can equally well be used with any other commercially available software, in particular the THERMOVLEX® software.

[0140] Before this, if the temperatures at the inlet and outlet of the condenser 7 are high, the number of turbines 6 is reduced, or even the size is reduced by eliminating the low pressure body 61 .

[0141] The general-purpose input data used is as follows: - Pressurized water reactors (PWRs), of the type currently present in the French nuclear power sector; - Core power level equal to 100 MWth.

[0142] For each of the A / and C / configurations, the operating point of the energy conversion system of the secondary circuit is calculated using CYCLOP software.

[0143] A / Regarding the configuration, the performance evaluation is as follows: - Thermodynamic efficiency of 30.1%, which decreases with increasing coolant temperature up to 50°C with respect to the classical PWR reactor configuration, whose efficiency is of the order of 34%. - 44.61 MWe of electricity produced per day for a 100 MWth reactor. Remember that a classical PWR reactor produces about 34 MWe per day. Here, the electricity produced per day is boosted thanks to the storage of energy produced during the night in the thermal storage loop 13. The cooling requirements correspond to a temperature of 40°C, compatible with the use of a dry air cooling tower 20, so that no liquid water is required for cooling. This temperature is achieved by modifying the pressure in the condenser 7 from approximately 50 mbar to approximately 160 mbar. This involves reducing the size of the low-pressure turbine body 61 and simplifying the design of the condenser.

[0144] Regarding C / Configuration, the performance evaluation (C1) is as follows: - 23.33% thermodynamic efficiency. - 33.50 MWe of electricity produced during the day (by a 100 MWth nuclear reactor), of which 14.4 MWe goes to the CO2 capture system 22 and 19.1 MWe goes to the grid 21. - 100% efficient use of the energy produced by the reactor. - The cooling source is the CO2 capture system, so no liquid water is required for cooling. If the capture system malfunctions, the low temperature required for the reactor is 80°C, so liquid water is not required and a dry air cooling tower 20 is sufficient.

[0145] The second case (C2) was evaluated for a C / configuration requiring a temperature T2 of 70° C., with the following results: - 27.85% thermodynamic efficiency. - Total power equal to 40.09 MWe. - pressure in the condenser 7 equal to 0.387 bar.

[0146] Table 2 below summarizes the performance evaluation for the A / and C / configurations investigated.

[0147] [Table 2]

[0148] These evaluations confirm and quantify the advantages of the present invention just described for the A / Configuration and the C / Configuration, and are particularly as follows: - The system no longer requires liquid water for free heat extraction, while the installation's energy efficiency is even higher. In fact, in A / and C / configurations, the daily amount of electricity produced increases by 3 to 33%. In addition to being advantageous in terms of environmental impact, the invention increases the economic competitiveness of nuclear installations. - The extrapolation to a power level of 500 MWth corresponds to the output of a small modular reactor (SMR), and the amount of CO2 captured daily by system 22 corresponds to the carbon budget of a town with a population of 125,000. This first estimate makes it possible to plot the role of possible nuclear coupling in the investigated C / configurations, pending the realization of carbon neutrality envisaged in 2050.

[0149] In the new context of the generalisation of carbon taxes, a preliminary economic evaluation confirms the interest of the installation according to the invention.

[0150] The graph in Figure 11 repeats the figures from Table 2 above for the C / configuration of an SMR reactor and simulates the economic impact of CO2 capture in terms of a carbon tax developed to compensate for losses linked to the sale of electricity.

[0151] The graph shows that CO2 will balance out at between 15 and 30 euros per tonne, depending on the selling price of the electricity. For reference, the carbon tax rate as of June 2021 was around 50 euros / tonne.

[0152] In order to decouple the production of electricity and heat in time without reducing the energy efficiency of the cogeneration facility 1, the inventors considered adding auxiliary loops 30 at the inlet and outlet of the condenser 7, as shown in Figure 12, which serve to store and distribute heat between the condenser 7 and one or more heat utilization systems 22, 23, 24.

[0153] In the following, this configuration will be referred to as the D / configuration.

[0154] More precisely, the cogeneration plant 1 employs all of the elements described with reference to FIG. 12 with the addition of a fourth fluid circuit 30 configured as a closed loop for the storage of thermal energy and the distribution of heat.

[0155] The heat storage and distribution loop 30 is a closed-loop fluid circuit in which the heat transfer fluid circulates from the condenser 7 to the hot tank 31, then enters one or more heat utilization systems 22, 23, 24 in parallel, enters the cold tank 32 and returns to the condenser 7.

[0156] The heat transfer fluid is circulated in the loop 30 by a hydraulic pump 33 downstream of the hot tank 31 and a hydraulic pump 34 downstream of the cold tank 32 .

[0157] Each fluid branch of the loop 30 consists of a cylindrical section pipe with a metal wall that is resistant to chemical attack by the heat transfer fluid and is insulated on the outside in the branch that is connected to the high temperature tank 31. The diameter of the pipe is calculated to allow the discharge of all the thermal power stored in the high temperature tank 31 within 24 hours at the maximum allowable limit flow rate of the heat transfer fluid, which is typically on the order of a few m / s.

[0158] The high-temperature tank 31 contains a heat transfer fluid and stores all the heat recovered from the condenser 7, allowing the heat transfer fluid to be supplied to one or other of the heat utilization systems 22, 23, 24. The high-temperature tank 31 is covered with an external high-temperature insulating layer to limit heat loss. The size (usable storage volume) of the high-temperature tank 31 depends on the properties of the heat transfer fluid used and must be able to store up to all the heat recovered in the condenser 7 over a sliding period of 24 hours. The tank 31 can be equipped with a level measurement system with alarm and / or safety overflow signal connected directly to the low-temperature tank 32.

[0159] Each of the heat utilization systems 22, 23, 24 is intended to provide a service based on thermal energy in particular, consuming the thermal energy provided by the heat transfer fluid from the high temperature tank 31 and reducing its temperature, for example: - System 22 is a CO2 capture system. - System 23 is a district heating network for urban or industrial use. - System 24 is a seawater desalination system.

[0160] Like the hydraulic pump 34, the hydraulic pump 33 is designed to function at least with the reactor's availability factor Kd and must be able to function according to the fluctuations in the power demand of the power grid 21 to which the reactor's alternator 9 is electrically connected. Taking into account the heat capacity of the heat transfer fluid and the temperature difference between the inlet and outlet of the condenser 7, the flow rate of the pump 33 or 34 must be able to supply the heat transfer fluid to the systems 22, 23, 24 at a rate that allows all the heat output to be removed and the power demand of the power grid 21 to be met. Each pump 33 or 34 has a metal wall that is resistant to chemical attack by the heat transfer fluid. Multiple pumps 33 or 34 can be used in parallel to divide the pumping flow rate, and redundant pumps can be provided for safety reasons.

[0161] The cryogenic tank 32 has substantially the same storage volume as the hot tank 31 for the heat transfer fluid recovered from the condenser 7. The cryogenic tank 32 is covered with an external high temperature insulation layer that allows heat loss to be limited. The cryogenic tank 32 can be equipped with a level measurement system that transmits an alarm and / or safety overflow connected directly to the hot tank 31.

[0162] Considering the temperature levels required within the loop 30 and for economic reasons, the heat transfer fluid is water, although other types of heat transfer fluids may also be contemplated.

[0163] The total amount of water contained in the closed loop 30 is equal to the total volume of the cryogenic tank 32 and the volume contained in the fluid branches / pipes of the loop 30 to prevent any overflow and loading during operation.

[0164] Figure 13 shows an advantageous variant in which the hot tank 31 and the cold tank 32 consist of a single layer of thermal storage tanks, a water trench in which thermal stratification occurs between a layer of, for example, 90°C and a low temperature layer of, for example, 50°C, taking into account temperature levels below 100°C.

[0165] The inventors arrived at the rating of the cogeneration plant depicted in Figure 12 for the D / configuration.

[0166] Table 3 below shows the temperature values ​​and thermodynamic cycle efficiencies associated with the D / configurations.

[0167] [Table 3]

[0168] All of the cycle components are rated similarly to the configuration described above.

[0169] Table 4 below shows the subsystem outputs of a plant in D / configuration according to operating regime, based on a reactor with a power output of 100 MWth.

[0170] [Table 4]

[0171] Assuming a continuous heat demand for the heat utilization systems 22, 23, which may be a CO2 capture system and a district heating network, respectively, the performance of the installation 1 in the D / configuration is as shown in Table 5 below.

[0172] [Table 5]

[0173] Compared to the C / configuration of Figure 8, the rated power of the heat utilization systems 22, 23 connected to the condenser 7 in the D / configuration from Figure 12 is reduced by 33% for the same daily performance (75 MWth instead of 112.5 MWth), which is a considerable improvement in terms of compactness, investment costs and operating costs.

[0174] The purpose of the ratings given below is to evaluate the layered thermal storage volumes 31, 32 required for a small modular reactor (SMR) type reactor using PWR technology with a thermal power of 540 MWth, based on an example of a connection between a condenser 7 with inlet and outlet temperatures T1, T2 equal to 90°C and 70°C, respectively, and an atmospheric CO2 system 22.

[0175] The rating is calculated using a power profile such as that shown in FIG.

[0176] Table 6 below details the calculated ratings.

[0177] [Table 6]

[0178] Therefore, from Table 6, the layered thermal storage volume is 140,000 m 3 It can be seen that the order of

[0179] So far, the known dimensions of the water trenches used in layered thermal storage are 1 mm 3 The order is:

[0180] Therefore, the D / configuration of the facility is compatible with existing technologies with a high level of technological maturity and with the level of SMR nuclear power generation.

[0181] The invention is not limited to the examples just described, and in particular the features of the examples shown in variations not depicted can be combined with one another.

[0182] Other modifications and embodiments may be contemplated without departing from the scope of the present invention.

[0183] In the example shown, system 22 is a CO2 capture system; however, a seawater desalination system may equally well be contemplated. Generally speaking, one or more heat utilization systems may be used in parallel with the condenser of the secondary circuit of a nuclear reactor, connected in a closed loop.

[0184] The cogeneration nuclear installation just described with reference to a pressurized water reactor may be used equally well with any indirect thermodynamic cycle reactor in which the heat production cycle is physically separated from the energy conversion cycle.

[0185] Bypassing the high and low temperature thermal storage tanks at low temperatures using fluid lines for maintenance purposes can be envisaged to circulate the heat transfer fluid in a closed loop between the condenser and the heat utilization system (CO2 capture, desalination, district heating network) without temporarily storing the heat transfer fluid in said tanks.

[0186] (References) [1]: “Ameliorer l'efficacite energetique en utilisant la cogeneration dans la production d'electricite” Jean-Marie Loiseaux, Henri Safa, Bernard Tamain, Reseau Sauvons le Climat. [2]: “Heat recovery from nuclear power plants”, H. Safa, International Journal of Electrical Power & Energy Systems, Volume 42, Issue 1, November 2012, Pages 553-559 [3]: H.D. Nguyen, N. Alpy, D. Haubensack. “Insight on electrical and thermal powers mix with a Gen2 PWR: Rankine cycle performances under low to high temperature grade cogeneration.” Energy, Elsevier, 2020, 202, pp.117518. ff10.1016 / j.energy.2020.117518ff. ffcea-02569231f. [4]: “Cogeneration with District Heating and Cooling”, Henri Safa CEA Nuclear Energy Division Scientific Direction, IAEA Consultant meeting, Vienna, 19-22 December 2011. [5]: “Two-tanks heat storage for variable electricity production in SFR: preliminary architecture and transient results”, J.B. Droin, D. Haubensack, D. Barbier, L. Brissonneau, P. Dienot, P. Gauthe, ICAPP 2019 - International Congress on Advances in Nuclear Power Plants France, Juan-les-pins - 2019, May 12 │15. [6]: S WU et Al.: "Coupling of nuclear heating reactor with desalination process", DESALINATION, ELSEVIER, AMSTERDAM, NL, vol. 142, no. 2, February 2002 (2002-02-01), pages 187-193, XP004351067, ISSN: 0011-9164, DOI: 10.1016 / S0011-9164(01)00438-6. [7]: Jean-Claude GAUTHIER et Al: "2nd International Topical Meeting on HIGH TEMPERATURE REACTOR TECHNOLOGY ANTARES: The HTR / VHTR project at Framatome ANP", 1 September 2004 (2004-09-01), pages 1-13, XP055321369. [8]: “Advances in Nuclear Power Process Heat Applications”, IAEA-TECDOC-1682, INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2012. [9]: Fasihi, M.; Efimova, O.; Breyer, C. (2019): “Techno-economic assessment of CO2 direct air capture plants.” In: Journal of Cleaner Production. DOI: 10.1016 / j.jclepro.2019.03.086.

[10] : D. Haubensack et al., “The COPERNIC / CYCLOP computer tool: pre-conceptual design of generation 4 nuclear systems, HTR-2004”, 2nd International Topic Conference for the HTGR, September 22-24, 2004, Beijing, China, 2004. [Explanation of symbols]

[0187] 1 Primary circuit 2 nuclear reactor 3 Primary exchanger, intermediate exchanger 4 Hydraulic pump 5 Secondary circuit 6 Turbine 7. Condenser 8 Hydraulic Pump 9 Alternator 10 Cooling Cycle 11 Wet air cooling tower 12 District Heat Supply Network 13 Heat storage loop, third fluid circuit 14 High-Temperature Tank 15 Cryogenic Tank 16 Steam Generator 17 Hydraulic pump 18 Hydraulic pump 19 Heat storage tank 20 Dry air cooling system, dry air cooling tower 21 Power grid 22 Atmospheric CO2 capture system, heat utilization system 23 District heating network and heat utilization system 24 Seawater desalination system, heat utilization system 30 Auxiliary Loop, Fourth Fluid Circuit 31 High temperature tank, layered thermal storage volume 32 Cryogenic tank, layered thermal storage volume 33 Hydraulic pump 34 Hydraulic pump 60 High pressure main body, high pressure turbine 61 Low pressure main body, low pressure turbine

Claims

1. A cogeneration nuclear power plant, at least one nuclear reactor, in particular of the pressurized water reactor (PWR) or boiling water reactor (BWR) type, a first fluid circuit, called the primary circuit (1), which includes at least one first intermediate heat exchanger (3); a second fluid circuit, called the secondary circuit (5), including at least one steam generator (16) as a second intermediate heat exchanger, at least one turbine (6, 60) connected to said second heat exchanger, and a condenser (7) connected to said turbine and said second heat exchanger for cooling the steam from said turbine and converting it back into water for delivery to said second heat exchanger; at least one nuclear reactor, comprising an alternator (9) mechanically coupled to said turbine and intended to be connected to an electricity grid (21); a third fluid circuit (13) constituted by a closed loop for storing thermal energy in which a heat transfer fluid circulates, at least one first tank, called high temperature tank (14), connected to said first intermediate heat exchanger; at least one first hydraulic pump (17) connected to the high temperature tank and the second intermediate heat exchanger; at least one second tank, called cryogenic tank (15), connected to said second intermediate heat exchanger; a third fluid circuit (13) comprising at least one second hydraulic pump (18) connected to the cryogenic tank and the first intermediate heat exchanger; at least one heat utilization system (22, 23, 24) connected in a closed loop to the condenser of the secondary circuit of the reactor; Cogeneration nuclear power plant equipped with:

2. The heat utilization system uses atmospheric carbon dioxide CO ２ 2. The cogeneration installation according to claim 1, which is a recovery and / or desalination system (22) and / or a district heating network (23).

3. The cogeneration facility of claim 1 or 2, further comprising a dry air cooling system (20) connected to bypass the connection to the heat utilization system (22).

4. The cogeneration facility of claim 3 , wherein the dry air cooling system is a dry air cooling tower.

5. 5. Cogeneration plant according to any one of claims 1 to 4, wherein the temperature T1 at the inlet of the condenser (7) is at least equal to 60°C and the temperature T2 at the outlet of the condenser (7) is at least equal to 70°C, advantageously between 70 and 100°C.

6. The hot tank and the cold tank of the third fluid circuit each have a capacity of 10,000 m ３ 30,000m from ３ The cogeneration installation according to any one of claims 1 to 5, having a volume between

7. 7. The cogeneration installation according to claim 1, wherein the heat transfer fluid of the heat storage loop of the third fluid circuit is a molten salt or a mixture of molten salts adapted to remain in liquid phase over a temperature range from 100°C to 350°C with a margin of 40°C with respect to the maximum operating temperature of the heat storage loop (13).

8. The heat transfer fluid has the chemical composition 53% KNO ３ , 40% NaNO ２ , 7% NaNO ３ The cogeneration facility of claim 7, comprising:

9. A fourth fluid circuit (30) configured as a closed loop for storing thermal energy and distributing heat, in which a heat transfer fluid circulates, the fourth fluid circuit comprising: at least one third tank, called hot tank (31), connected to said condenser (7); at least one third hydraulic pump (33) connected to said high-temperature tank and to said at least one heat utilization system (22, 23, 24); at least one fourth tank, called low-temperature tank (32), connected to said condenser (7) and to said at least one heat utilization system (22, 23, 24); - at least one fourth hydraulic pump (34) connected to said cryogenic tank (32) and to said condenser.

10. 10. The cogeneration installation of claim 9, wherein the heat transfer fluid of the heat storage and heat distribution loop of the fourth fluid circuit is water adapted to remain in the liquid phase over a temperature range of 50°C to 100°C with a margin of 10°C relative to the maximum operating temperature of the heat storage and heat distribution loop (30).

11. 11. The cogeneration installation according to claim 9 or 10, wherein the high-temperature and low-temperature tanks of the fourth fluid circuit consist of single-layer thermal storage tanks.

12. 12. The cogeneration installation of claim 11, wherein the single layer thermal storage tank is a trench filled with the heat transfer fluid, preferably at least partially underground.

13. 13. The cogeneration installation according to any one of claims 9 to 12, comprising at least two heat utilization systems in parallel with the high and low temperature tanks of the heat storage and heat distribution loop (30).

14. The hot and cold tanks of the fourth fluid circuit each have a capacity of 50,000 to 300,000 m for a power output of the reactor equal to 150 MWe. ３ 14. The cogeneration installation according to claim 9, having a volume between

15. The cogeneration plant of claim 1 , wherein the one or more turbines do not include a low-pressure body.

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