Electronuclear cogeneration plant with light water reactor and system for capturing atmospheric co2 or for desalinating sea water without drawing liquid water therefrom or releasing same into the environment

Abstract

The invention relates to a nuclear cogeneration plant with a light water reactor (LWR) and a system for capturing atmospheric CO2 or for desalinating sea water without withdrawing liquid water therefrom or releasing same into the environment. The invention essentially consists in using, in combination, a thermal storage loop, arranged between the primary circuit and the secondary circuit of a reactor, with a system for capturing atmospheric carbon dioxide or for desalinating sea water at the condenser of the secondary circuit.

Description

TECHNICAL FIELD

[0001] The present invention concerns the field of light water nuclear reactors (LWR), notably pressurized water reactors (PWR).

[0002] The invention more particularly concerns cogeneration installations including such nuclear reactors. Here, and in the context of the invention, by “cogeneration” is meant the simultaneous or non-simultaneous production of electricity and usable heat.

[0003] With regard to rendering isoservice in terms of production of electricity during the day, the invention has for objective valorizing all of the heat in the primary circuit of a nuclear reactor and consequently limiting or even eliminating all environmental impact of the reactor (taking in liquid water from and rejecting liquid water to the environment).

[0004] Although described with reference to a pressurized water nuclear reactor, the invention applies to any nuclear reactor using an indirect thermodynamic cycle from the family of reactors known as second generation, third generation and fourth generation (GEN IV) reactors. It applies in particular to fast neutron nuclear reactors cooled by liquid metal, notably liquid sodium (SFR (sodium fast reactor)), forming part of the GEN IV family of reactors.PRIOR ART

[0005] In a context of climate and energy transition, the nuclear industry has to face up to a number of future challenges. Indeed, to address tomorrow's energy and societal challenges, it will be opportune to design nuclear reactors that make it possible:

[0006] to limit the requirement for so-called “environmental” liquid cold sources (rivers, tidal rivers, sea) and associated rejection into the environment;

[0007] to be more flexible and therefore to better complement other so-called renewable energies to address the fluctuating demand for electricity and the intermittent nature of renewable energies;

[0008] to decarbonize the methods by supplying heat to consuming industries (desalination, heating networks, hydrogen, . . . ) while increasing energy efficiency;

[0009] to capture atmospheric CO2 to limit the effects of global warming and to contribute to closing the carbon cycle by being a source of carbon for industrial processes;

[0010] without this decreasing the cost effectiveness of the installation, either by profiting economically from the new services rendered or by significantly increasing the quantity of electricity produced during the day.

[0011] A pressurized water reactor (PWR) classically uses three cycles (fluidic circuits) the normal generating operating principle of which is explained hereinafter with reference to FIG. 1. The temperatures and efficiency are indicated for illustrative purposes only.

[0012] The primary circuit 1 is a closed loop fluidic circuit comprising mainly the core of the reactor 2, at least one steam generator (GV), serving as a so-called primary exchanger 3, and a hydraulic pump 4 for circulating the heat transfer fluid, which is water maintained in the liquid state in the operating temperature range of the reactor, typically around 320° C.-330° C. in normal operation. There are not described here the other equipment, such as a pressurizer and all of the systems ensuring operation under required safety conditions.

[0013] The high-pressure water in the primary circuit therefore takes up the energy supplied in the form of heat as a result of fission of the uranium cores in the core of the reactor 1.

[0014] This high-pressure water at a high temperature, typically 155 bar and 320° C.-330° C., then enters the intermediate exchanger 3 and transmits its energy to a closed loop secondary circuit 5 also using pressurized water as a heat transfer fluid.

[0015] This secondary circuit 5 includes the 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.

[0016] Thus in this secondary circuit 5 water in the form of vapor at high pressure, typically around 70 bar, is expanded in the high-pressure body of the turbine and then heated before continuing to expand in the low-pressure body 61. The turbine drives an alternator 9 that produces electricity.

[0017] The water in the secondary circuit is then condensed via the condenser 7 in a third cycle, the cooling cycle 10, as a so-called “cold” source. This cycle 10 mainly comprises moist air cooling towers 11, which are towers hollow at the center in which is naturally created a flow of air entering at the bottom and leaving at the top. As it passes through, this flow of air takes up the heat contained in the water in the cooling circuit and disperses it into the atmosphere in the form of water vapor clouds. The operation is repeated continuously with the water divided into fine droplets, which on the one hand enables good exchange between the water and the air and therefore cools the water to a temperature close to that of the ambient air and on the other hand saturates with water vapor the flow of air circulating upward in the tower. Some of the flow of water evaporates in the tower 11, the rest dropping as rain into the pool located below the tower from which it is pumped and returned to cool the condenser 7. The evaporated water is replaced by so-called “environmental” tertiary water pumped on the upstream side from a tidal river, a river or the sea. This significantly increases the temperature of these water courses, which in periods of hot weather and / or of low flow in these water courses can cause the operator of the nuclear installation to lower its power level or even to shut it down.

[0018] 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 of condenser 7 is of the order of 20° C. and 35° C. at its outlet.

[0019] Conventional PWR type reactors are classified according to large families of use:

[0020] so-called electricity generation reactors that are dedicated exclusively to the production of electricity;

[0021] so-called heat generation reactors that are dedicated exclusively to the production of heat;

[0022] so-called cogeneration reactors, dedicated both to the production of heat and the production of electricity, simultaneously or non-simultaneously.

[0023] As described in detail in [1], the principle of cogeneration based on a nuclear reactor consists in modifying the design of the energy conversion cycle so that heat is released to the cold source at a temperature that enables its valorization. Indeed, the limitation of climatic heating relies on minimizing heat losses at all levels and in particular at the level of the cold source of a thermodynamic installation. This cogeneration objective becomes all the more pertinent for a nuclear reactor in that industrial or domestic heating is often obtained in the traditional way by burning fossil fuels responsible for the emission of greenhouse gases.

[0024] To achieve this objective a first configuration consists in modifying the components of the electricity production system of a PWR installation in order to adjust the temperature of the water at the level of the cold source.

[0025] In a classic configuration depicted in FIG. 1 this modification remains limited, however. It does not affect the high-pressure turbine 60 but only the low-pressure turbine 61 implementing the Rankine cycle. This modification is depicted in FIG. 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 around 50 mbar, so that the water at the outlet of the condenser has a sufficiently high temperature level, typically 70° C., to be valorized, for example in a heating network 12. This modification is accompanied first of all by a reduction of the electrical power produced, since the thermodynamic efficiency falls to 27%. There is also an increase in the pressure in the condenser 7.

[0026] However, this first cogeneration configuration has two major drawbacks.

[0027] First of all, as already mentioned, valorization of the heat from the cold source is to the detriment of the electrical efficiency of the installation: the service rendered in terms of electrical power is significantly degraded. Indeed, as the second law of thermodynamics states, increasing the temperature of the cold source reduces the efficiency of a conversion cycle. This phenomenon of degraded electrical efficiency stemming from the increase in the temperature of the cold source is depicted by the decreasing curve as a function of the temperature in FIG. 3, obtained from [2].

[0028] The other major drawback is that a cold source in the form of liquid water extracted from a tidal river, a river or the sea continues to be necessary for feeding the cooling towers 11 in periods in which the demand for heat no longer exists or during which the heating network is unusable. This also implies rejection of waste waters into the environment and the limitations on operation associated with the waste standards that have to be complied with.

[0029] A second cogeneration configuration consists in no longer taking up heat at the level of the cold source but rather directly at the level of the bodies 60, 61 of the turbine 6, by drawing off hot steam: [3], [4].

[0030] Patent application KR2021 / 0081846 also discloses an electrocogeneration nuclear installation using this second configuration: the secondary circuit of the reactor can send some of the steam at the outlet of the turbine to a heat storage tank and / or to a heat exchanger connected to an urban heating network.

[0031] This second configuration, depicted in FIG. 4, with an outlet S between the two bodies 60, 61 or in the latter has the advantage of higher temperatures, typically above 100° C., compared to those obtained when the heat is taken up in the cold source. These higher temperatures are potentially compatible with industrial applications without significantly degrading the electrical efficiency if the thermal power taken up remains limited. However, this second configuration has the drawback of allowing only limited take off of thermal power in order not to degrade the electrical efficiency in an undesirable manner and not to limit the need for environmental liquid water for cooling the conversion circuit. The water demand and the associated waste remain therefore very consequential in this configuration.

[0032] Concepts aiming to limit the intrinsic defects of cogeneration systems by adding an energy storage installation have already been proposed in the literature. These concepts can be classified in two large families, as follows.

[0033] The first family concerns systems intended to improve the maneuverability of the reactor, that is to say aiming to render the production of electricity by the reactor more flexible than it is at present by temporarily increasing the level of electrical power supplied to the grid in order to adapt it to demand. In the literature, these systems are employed with reactors generating electricity but they are equally applicable to cogeneration reactors: [5], patent application JP2020197468A.

[0034] An example of such a system is schematically depicted in FIG. 5. A supplementary fluidic circuit configured as a thermal storage loop 13 is arranged between the primary circuit 1 and the secondary circuit 5 in which the energy conversion takes place.

[0035] This loop 13 includes the intermediate exchanger 3, two thermal storage tanks, a so-called hot tank 14 and a so-called cold tank 15, a steam generator 16 that enables exchange between the storage loop and the secondary circuit and therefore production of steam for the turbines 60, 61 and finally two hydraulic pumps 17, 18 respectively between the hot tank 14 and the steam generator 16 and between the cold tank 15 and the intermediate exchanger 3 to cause the heat transfer fluid in this loop 13 to move. The heat transfer fluid in this loop is advantageously a mixture of HITEC® molten salts with the composition 53% KNO3, 40% NaNO2, 7% NaNO3. By way of example, the temperature of this heat transfer fluid is 310° C. in the hot tank 14 and of the order of 245° C. in the cold tank 15.

[0036] In a system depicted in FIG. 5 the core 2 of the reactor functions as a base, that is to say at 100% power throughout the operating cycle. The power extracted to the storage loop 13 by the pump 18 on the upstream side of the intermediate exchanger 3 is constant.

[0037] In periods of low demand the pump 17 on the downstream side of the hot tank evacuating power to the secondary circuit is running at below full rating. The hot tank 14 is filled, the cold tank 15 is emptied. The power transferred to the secondary circuit 5 is therefore less than that produced in the core 2.

[0038] When demand is high the pump 17 is running at above full rating, the power transferred to the secondary circuit 5 is therefore higher than that produced in the core. This system therefore has the advantage of decorrelating the operation of the core of the reactor from that of the energy conversion system at the level of the secondary circuit, and increasing the electrical power supplied to the grid in periods of high demand.

[0039] Such a system nevertheless has a number of major drawbacks, as follows:

[0040] it does not enable raising of the temperature of the water at the outlet of the condenser 7, therefore remaining very low, typically below 40° C., and it is therefore not possible to valorize it;

[0041] it necessitates general upgrading of the conversion cycle, including the bodies of the low-pressure turbines 61 which must be very large, since the thermal power transferred to the secondary cycle 5 is higher during the day;

[0042] it also necessitates upgrading of the cold source: indeed the latter has to be adapted to evacuate the residual power of the secondary cycle that has been upgraded.

[0043] The second family of cogeneration systems adding an energy storage installation comprises installations dedicated to improving the overall energy efficiency of the installation, that is to say making it possible to valorize some of the heat produced in addition to the electricity. An example of an added installation is described for example in the patent U.S. Pat. No. 4,170,879A. FIG. 6 also depicts a system from this second family in which the thermal power of the core is slaved to the electrical power demanded by the grid. Here a thermal storage tank 19 is arranged downstream of the condenser 7. This tank 19 is for storing water from the cold source at the outlet of the condenser 7 and restoring it at another time. This configuration therefore enables valorization of some or all of the free heat of the reactor in addition to the electricity supplied to the grid, and enables temporal decorrelation of the supply of electrical power from the supply of heat.

[0044] Such a system nevertheless has a number of serious drawbacks, as follows:

[0045] the core is not able to function as a base, the power produced in the core therefore varying as a function of the electrical demand;

[0046] the valorized temperature remains very low, typically below 40° C., which limits the applications;

[0047] if the conversion cycle of the secondary circuit 5 is modified to raise the temperature of the valorized heat, the electrical efficiency of the installation is significantly degraded;

[0048] the storage tank 9 being connected directly to the heating network 12, it must be very large because storage is at a relatively low temperature, typically 40° C.;

[0049] it necessitates a considerable input of water in the event of unavailability of the heating network or the absence of demand for heat (in summer).

[0050] To summarize, all cogeneration nuclear installations identified in the literature can:

[0051] either valorize only a small proportion of the heat in order not to degrade the electrical efficiency significantly, in which case the cold source requirement remains very large and a large proportion of the power produced in the reactor core is not valorizable;

[0052] or valorize a large proportion of the heat from the reactor but significantly downgrade the production of electricity, the extreme case being a reactor for producing only heat, which considerably or even unacceptably affects the cost effectiveness of a given installation for its operator.

[0053] Furthermore, it has already been proposed to couple a nuclear reactor with a desalination installation. For example, publication [6] describes coupling a reactor that generates only heat to implement multiple effect distillation processes.

[0054] There has also already been proposed a very high temperature reactor for producing both electricity and hydrogen: [7].

[0055] These designs are far removed from cogeneration nuclear installation problems as mentioned hereinabove.

[0056] Thus there exists a need to improve cogeneration nuclear installations in order to enable, for rendering isoservice in terms of production of electricity during the day, valorization of all of the heat produced in the primary circuit of the reactors of the installations and consequently limiting or even eliminating all environmental impact of the reactor or reactors of the installations, that is to say taking in liquid water from and rejecting liquid water to the environment.

[0057] This need is confirmed by the nuclear authorities: [8].

[0058] The object of the invention is to address this need at least partially.STATEMENT OF INVENTION

[0059] To this end, one aspect of the invention concerns an electronuclear cogeneration installation including:

[0060] at least one nuclear reactor, notably of pressurized water reactor (PWR) type or boiling water (BWR) reactor type, including:

[0061] a first fluidic circuit, called the primary circuit, including at least one first intermediate heat exchanger;

[0062] a second fluidic circuit, called 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, a condenser connected to the turbine and to the second heat exchanger to cool the steam from the turbine and to convert it back into water and send it to the second heat exchanger;

[0063] an alternator mechanically coupled to the turbine and intended to be connected to a grid;

[0064] a third fluidic circuit configured in a closed loop for storing thermal energy in which circulates a heat transfer fluid, including:

[0065] at least one first tank, called the hot tank, connected to the first intermediate heat exchanger;

[0066] at least one first hydraulic pump connected to the hot tank and to the second intermediate heat exchanger;

[0067] at least one second tank, called the cold tank, connected to the second intermediate heat exchanger;

[0068] at least one second hydraulic pump connected to the cold tank and to the first intermediate heat exchanger;

[0069] at least one heat exploitation system connected in a closed loop to the condenser of the secondary circuit of the reactor.

[0070] In one advantageous embodiment the heat exploitation system is an atmospheric carbon dioxide CO2 capture and / or seawater desalination system and / or a heating network. More generally, it may be any system using heat from the secondary circuit of the reactor employing processes using the heat notably for industrial purposes.

[0071] In another advantageous embodiment the installation further includes a dry air cooling system connected to bypass a connection to the heat exploitation system.

[0072] The invention makes possible simultaneously:

[0073] operating the reactor at its design nominal operating level (Kd), also called the availability coefficient, independently of the power demand of the grid connected to the alternator;

[0074] optimal valorization of some or all of the thermal energy produced by the reactor to provide new non-energy services (capture of atmospheric CO2 and / or desalination of seawater and / or urban or industrial heating networks);

[0075] at least partially eliminating a need for liquid water as a cooling source and the associated waste to contribute to evacuation of non-valorized energy.

[0076] As a corollary to this, the invention enables the safety of the installation to be improved by making available a system contributing to residual power evacuation for periods in which the reactor is shut down.

[0077] The invention essentially consists, in combination with the condenser of the secondary circuit, in using a thermal storage loop between the primary circuit and the secondary circuit of a reactor with a heat exploiting system that can advantageously be an atmospheric carbon dioxide capture and / or seawater desalination system and / or a heating network.

[0078] The resulting cogeneration installation is a total or almost total energy efficient system addressing the flexibility challenges of the grid linked to the massive introduction of renewable energies and what is at stake in climate change by no longer necessitating supply of water for cooling.

[0079] By coupling the circuits of a nuclear reactor with a thermal storage loop it is therefore possible to design an installation enabling 100% valorization of the energy produced in the core without downgrading the service rendered in terms of production of electricity during the day.

[0080] The invention is advantageously a combination of the following means:

[0081] a thermal storage loop installed on site between the primary circuit and the secondary circuit of a reactor, notably a PWR. This thermal storage loop makes it possible for the functioning of the reactor no longer to be slaved to the requirements of the grid. Thanks to thermal energy storage, the reactor functions at full power at all times and the energy conversion system of the secondary circuit restores it as a function of the demand of the grid (during the day), which increases the quantity of electricity fed to the grid.

[0082] The fact that the thermal power supplied during the day to the conversion system to the secondary circuit is greater than that of a prior art installation with a lower thermodynamic efficiency can imply uprating of the steam generators and the high-pressure turbine bodies, notably with a greater blade diameter.

[0083] The dimensions of the hot and cold tanks of the storage loop depend on the required temperature level. The volume of the tanks is advantageously between 10 000 m3 and 30 000 m3, the industrial feasibility of such tanks being already proven given what is done nowadays in other industrial fields;

[0084] increasing the temperature of the water at the outlet of the condenser secondary circuit on the cold source side to a valorizable temperature, typically above 100° C. for desalination or for atmospheric CO2 capture, which reduces the conversion efficiency of the Rankine thermodynamic cycle in the secondary circuit; this can advantageously imply a large reduction or even elimination of the low-pressure bodies of the turbine or turbines and modification of the design of the condenser, notably to increase its saturation pressure;

[0085] increasing the cold temperature on the cold source side of the electrical conversion cycle in the secondary circuit, that is to say at the inlet of the condenser, typically to above 40° C. so as to make accessible, in the event of momentary or longer absence of heat for an atmospheric CO2 capture and / or seawater desalination system, the dry air cooling technology replacing classic wet air cooling towers that consume large quantities of water.

[0086] These dry air cooling towers do not need any liquid water for cooling, whatever the consumer or the heat demand. It is atmospheric air that serves as coolant.

[0087] A major advantage of a system configuration according to the invention compared to an installation as shown in FIG. 5 and the patent JP2020197468A lies in the addition of a complementary component / process / network modifying the technical and functional configuration of the installation:

[0088] A / configuration: addition of a dry air cooling tower that makes it possible to dispense with a source of water for the free heat evacuation process;

[0089] C / configuration: connection to an atmospheric CO2 capture or seawater desalination system enabling valorization of all of the thermal energy from the reactor that is not used for the production of electricity; in this configuration the installation achieves total energy efficiency.

[0090] The inventors have overcome a technical prejudice that was based on considering that maximizing the production of electricity to valorize an electronuclear installation always requires the latter to be designed with the lowest possible temperature level of the cold source.

[0091] Now, by combining the addition of a thermal storage loop with upgrading the Rankine cycle the invention makes it possible to change the paradigm by demonstrating the capacity for carrying out cogeneration at very high energy efficiency.

[0092] The inventors have moreover carried out a refined analysis of the exergy of the various heat exploitation technologies, notably in atmospheric CO2 capture. It has made it apparent that adsorption technologies necessitate an input of energy in the form of heat for regeneration of the substrates with temperature levels of the order of 70 to 100° C., depending on the various technologies already used. See in particular the figures in publication [9], listing companies that have exploited and commercialized installations employing these technologies for a few years now with levels of power of the order of 1 MWth.

[0093] These technologies rely on the principle of agitation of air containing approximately 400 ppm of CO2, generally by means of fans, that passes over a substrate onto which the molecules of CO2 become fixed. Once the substrate is saturated it is regenerated by releasing the CO2 by the effect of an increase in temperature. The desorption temperature level can vary from 70 to 100° C., depending on the technology of the substrate developed, the modes of design and operation adopted by the manufacturer and the source of heat available for the process.

[0094] Capturing one ton of CO2 requires approximately 2 MW of energy divided in variable proportions between heat and electricity depending on the technologies: [9].

[0095] The invention therefore enables valorization of the heat not used by the Rankine cycle, the electrogenic efficiency of which is between 25 and 35% for a modern PWR, which corresponds to 65 to 75% of the thermal power of the core, at present not valorized, for the capture of atmospheric CO2 or desalination of seawater.

[0096] Finally, a PWR cogeneration installation according to the invention including a thermal storage loop and a CO2 capture system with a bypass dry air cooling system has numerous major advantages, with iso-service rendered from a production of electricity during the day point of view, among which there may be cited:

[0097] a very high energy efficiency since, in the configuration with a CO2 capture system in nominal operation, each MW produced in the core is valorized;

[0098] the absence of taking in liquid water from the environment or rejecting it into the environment whatever the operating regime of the installation;

[0099] the elimination of the need to build a nuclear installation on the coast or on a fast flowing tidal river;

[0100] the absence of environmental constraints linked to climate deregulation (heat waves);

[0101] in a context of a circular carbon economy, a potentially massive source of CO2, valorization by the production of synthetic fuels;

[0102] a drastic simplification of safety demonstrations;

[0103] a widened potential for deployment of installations in countries with a dry climate, having no tidal river, river or sea in their geography;

[0104] improved public acceptance.

[0105] Other and secondary advantages linked to the invention can be emphasized:

[0106] retaining a PWR as a base because the power variation is handled by the thermal storage loop;

[0107] simplified design of the primary circuit of the PWR of the installation;

[0108] simplification of the safety dossier of the installation;

[0109] high installation operation improvements;

[0110] improvement of availability, etc.;

[0111] a reduction of the volume of waste per MWh;

[0112] the possibility of evacuating the residual power from the core of the reactor during periods in which the reactor is shut down by means of the thermal storage loop, notably with a reserve content of heat transfer fluid in the cold tank. The conditions described that are associated with this functionality will be defined as a function of the expected safety level. In one advantageous embodiment the installation further includes a dry air cooling system connected to bypass a connection to the heat exploitation system.

[0113] In this advantageous embodiment the dry air cooling system is a dry air cooling tower.

[0114] 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 7° and 100° C.

[0115] The hot tank and the cold tank of the third fluidic circuit advantageously each have a volume between 10 000 m3 and 30 000 m3.

[0116] The heat transfer fluid of the thermal storage loop of the third fluidic circuit is more advantageously a molten salt or a mixture of molten salts adapted to remain in the liquid phase over a range of temperatures from 100° C. to 350° C. with a margin of 40° C. relative to the maximal operating temperature of the thermal storage loop.

[0117] The heat transfer fluid preferably has the following chemical composition: 53% NaNO3, 40% NaNO2, 7% KNO3.

[0118] Direct connection of the condenser to a heat exploitation system is satisfactory in a good number of configurations.

[0119] In others, this can have disadvantages of at least functional limitations because such a direct connection renders interdependent the energy conversion systems and the system for exploitation of heat directly at the inlet and outlet of the condenser. The disadvantages of this direct correlation between production of electricity and production of heat can be as follows:

[0120] in terms of the specific availability level of the installation as a whole: any shutting down (whether planned or fortuitous) of the system or systems for exploitation of heat at the inlet and outlet of the condenser leads to shutting down the energy conversion system or would necessitate the addition of a back-up system of the dry air cooling tower type, which can lead to degrading the factor of use of the nuclear reactor and minimizing its cost effectiveness;

[0121] the choice of the technology of the exploitation system or systems connected to the inlet and outlet of the condenser: the service addressed by this system or systems must be compatible with the flexibility imposed by the requirements of the grid, which is generally but not systematically the highest priority. For example, systems necessitating high levels of heating over long periods are not compatible with daily operating cycles: there may be cited here high-temperature electrolysis systems for the production of H2, urban or industrial heating networks;

[0122] the technology of the system or systems connected to the inlet and outlet of the condenser must also be compatible with the flexibility kinetic of the upstream energy conversion system: the functioning of the heat exploitation system or systems must be able to track the power ramps imposed by the variations of power demand of the grid, potentially of the order of several MWth / minute;

[0123] the fact that the operation of the system or systems connected to the inlet and outlet of the condenser is non-continuous, i.e. at X hours per day only, also necessitates uprating of the system or systems in the same ratio as the energy conversion system relative to the power of the reactor, at equivalent daily production performance;

[0124] finally, in terms of operation / service characteristics addressed by the heat exploitation systems: because of the interdependence of the production of electricity that correlates with the production of heat, optimization of the cost effectiveness of a cogeneration installation cannot be maximized on both markets at the same time; there exists an optimization margin conditional on of decorrelating the production of electricity and the supply of heat.

[0125] The inventors were therefore confronted with an additional problem, that of temporal decorrelation of production of electricity and production of heat, without degrading the yield and the energy efficiency of the cogeneration installation as a whole.

[0126] To this end, in an additional embodiment the cogeneration installation according to the invention advantageously includes a fourth fluidic circuit configured in a closed loop for storage of thermal energy and distribution of heat in which a heat transfer fluid circulates, the fourth fluidic circuit including:

[0127] at least one third tank, called the hot tank, connected to the condenser,

[0128] at least one third hydraulic pump connected to the hot tank and to the at least one heat exploitation system,

[0129] at least one fourth tank, called the cold tank, connected to the condenser and to the at least one heat exploitation system,

[0130] at least one fourth hydraulic pump connected to the cold tank and to the condenser.

[0131] This therefore enables the cogeneration installation to function with temporal decorrelation of production of electricity and production of heat, while at the same time increasing:

[0132] the overall energy efficiency of the installation: the specific availability levels of the exploitation system or systems are increased, the impact of fortuitous shutting down of one of the systems on another is reduced, production by the exploitation system or systems can be continuous;

[0133] the compactness of a heat exploitation system: the dimensions of these various components are optimized to precisely what is needed;

[0134] the capacity to address simultaneously services and markets with totally separate characteristics, notably the requirements for flexibility of use, the kinetics of variations on all time scales, which de facto increases the cost effectiveness of the installation.

[0135] The levels of temperature in the cold and hot storage tanks of this fourth fluidic circuit can be adjusted as a function of the temperature levels required by the exploitation system or systems fed with the heat transfer fluid in the circuit.

[0136] The thermal storage loop with hot and cold tanks that distributes heat to various heat exploitation systems therefore advantageously enables addressing of services and markets with diverse characteristics.

[0137] The number of heat exploitation systems in parallel at the inlet and outlet of the condenser can be high. The choice of the number and type of exploitation systems is advantageously based on seeking to optimize over the sliding period of 24 hours of one day of operation of the installation at most, preferably all of the thermal power from the core of the nuclear reactor that is not converted to produce electricity. In other words, the aforementioned choice is made judiciously so as to evacuate from the reactor to the heat exploitation systems the maximum power not dedicated to the production of electricity. The parallel installation of a dry air cooling tower advantageously enables this objective to be achieved.

[0138] In this configuration with a supplementary thermal storage loop the heat exploitation system connected to the inlet and outlet of the condenser serves as the cold source of the nuclear reactor, which no longer needs an environmental cold source, either for cooling the reactor or for ejection of excess heat. All of the heat produced in the core of the nuclear reactor is valorized. The reserve of cold water upstream of the condenser can in this configuration temporarily alleviate a loss of cold source to operate the reactor.

[0139] The heat exploitation systems that can advantageously be envisaged in this thermal storage loop and heat distribution mode are:

[0140] urban or industrial low-temperature heating networks,

[0141] seawater desalination systems necessitating heat energy, for example by a multiple effect process (multi-effect distillation (MED)) or a multistage expansion distillation process (multi-stage flash distillation (MSF)),

[0142] capture of atmospheric CO2, notably to contribute to closing the carbon cycle.

[0143] Finally, this mode with the thermal storage loop and heat distribution brings a good number of supplementary advantages among which there may be cited:

[0144] the energy conversion system of the cogeneration installation can operate completely independently of the heat exploitation system or systems equally well on the hot source (reactor) side and on the cold source (condenser inlet and outlet) side and therefore makes it possible to obtain both total flexibility in terms of service to the grid or a maximal and optimized level of availability, with the consequences thereof for the economics of the nuclear reactor of the installation;

[0145] the possibility of parallel installation of different systems for exploitation of the heat from the nuclear reactor not consumed by the system for conversion of energy into electricity and therefore increasing the capacity to address energy markets and services having demand characteristics and profiles different from those of electricity;

[0146] the physical decoupling of the conversion cycle of the nuclear reactor and the exploitation system or systems by thermal storage tanks that serve as buffers, which makes it possible considerably to limit the risk of propagation of accidents / incidents on one of the sites on which a nuclear reactor is installed on that where one or the other of the exploitation systems is installed, and vice versa;

[0147] the fact that with constant daily operation not linked to the functioning of the electricity production service, uprating the heat exploitation system or systems is no longer necessary. This uprating was previously caused by the need to evacuate all the thermal power from the core of the reactor not transformed into electricity over a shorter time period (the operating time of the system for conversion of energy into electricity).

[0148] The heat transfer fluid of the thermal storage and heat distribution loop of the fourth fluidic circuit is preferably water adapted to remain in the liquid phase over a range of temperatures from 50° C. to 100° C. with a margin of 10° C. relative to the maximal operating temperature of the thermal storage and heat distribution loop. For instance, the temperature in the hot tank can be between 80 and 100° C. while that in the cold tank can be between 60 and 80° C. Other temperature levels would be possible, for example above 100° C., but would necessitate the use of other storage fluids.

[0149] In one advantageous embodiment the hot and cold tanks consist of a single layered thermal storage tank. By “layered thermal storage tank” is meant 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 can be divided into stacked thermal layers of heat transfer fluid having temperatures varying gradually from one end to the other, these stacked layers thus forming successive thermal strata.

[0150] The single layered thermal storage tank is preferably a moat, preferably at least partly underground, filled with the heat transfer fluid. For a required temperature level less than 100° C. the moat is advantageously filled with water in which thermal stratification is produced between a layer at 90° C. for example and a cold layer at 50° C.

[0151] In another advantageous embodiment the installation includes at least two temperature exploitation systems in parallel with the hot and cold tanks of the thermal storage and heat distribution loop.

[0152] The hot and cold tanks of the fourth fluidic circuit can advantageously each have a volume between 50 000 and 300 000 m3 for a power of the reactor equal to 150 MWe.

[0153] In another advantageous variant embodiment the turbine or turbines does or do not include a low-pressure body.

[0154] Other advantages and features of the invention will emerge more clearly upon reading the detailed description of embodiments of the invention given by way of non-limiting illustration with reference to the following figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0155] FIG. 1 depicts schematically a prior art configuration of a pressurized water reactor (PWR) configuration functioning only as an electricity generation reactor.

[0156] FIG. 2 is a schematic view of a prior art configuration of a pressurized water reactor (PWR) modified to function as a cogeneration reactor.

[0157] FIG. 3 depicts in the form of curves the evolution of the electrical efficiency and exergy of a prior art PWR as a function of the temperature of the cold source.

[0158] FIG. 4 is a schematic view of another configuration of a prior art pressurized water reactor (PWR) modified to function as a cogeneration reactor

[0159] FIG. 5 is a schematic view of a configuration of a prior art cogeneration installation comprising a pressurized water reactor (PWR) and a thermal storage loop.

[0160] FIG. 6 is a schematic view of a configuration of a prior art cogeneration installation including a pressurized water reactor (PWR) and a thermal storage loop.

[0161] FIG. 7 is a schematic view of a configuration of a cogeneration installation according to the invention including a pressurized water reactor (PWR), a thermal storage loop and a dry air cooling system.

[0162] FIG. 8 is a schematic view of a configuration of a cogeneration installation according to the invention including a pressurized water reactor (PWR), a thermal storage loop, an atmospheric CO2 capture system and a dry air cooling system bypassing the atmospheric CO2 capture system.

[0163] FIG. 9 is a graph depicting the curve of the power fed to a grid connected to a prior art PWR reactor.

[0164] FIG. 10 is a graph depicting the power curve of a PWR in a cogeneration installation according to the invention with a thermal storage loop.

[0165] FIG. 11 is a graph depicting the ratio between the sales of standard SMR type reactors and an installation according to the invention using an SMR type reactor and an atmospheric CO2 capture system as a function of the profit on the sale of each ton of CO2.

[0166] FIG. 12 is a schematic view of a configuration of a cogeneration installation according to one advantageous embodiment of the invention including a pressurized water reactor (PWR), a first thermal storage loop and a second thermal storage loop that distributes heat to a plurality of heat exploitation systems in parallel.

[0167] FIG. 13 is a schematic view in longitudinal section of a single layered thermal storage tank serving as both a hot tank and a cold tank of the second thermal storage loop of the FIG. 12 embodiment.

[0168] FIG. 14 is a graph depicting the power curve of a PWR type reactor in a cogeneration installation according to one advantageous embodiment of the invention with a first thermal storage loop and a second thermal storage loop that distributes heat to a plurality of heat exploitation systems in parallel.DETAILED DESCRIPTION

[0169] Throughout the present application the terms “upstream” and “downstream” are to be understood as relative to the direction of circulation of a heat transfer fluid in one of the fluidic circuits of a cogeneration nuclear installation according to the invention.

[0170] FIGS. 1 to 6 relating to the prior art have already been described in detail in the preamble and are therefore not commented on hereinafter.

[0171] For clarity, an element that is the same according to the invention and according to the prior art is designated by the same reference number in all of FIGS. 1 to 14.

[0172] There will not be described in detail again all the various relations and functions of the elements common to a cogeneration installation in accordance with the invention and a prior art cogeneration installation with a thermal storage loop as depicted in FIG. 5. Only some of these elements are described again.

[0173] The cogeneration nuclear installation according to the invention depicted in FIG. 8 includes in addition to the usual components of a standard installation with a PWR type reactor a thermal storage loop 13 between the primary circuit 1 and the secondary circuit 5 and a CO2 capture system bypassing a dry air cooling system 20.

[0174] 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 primary circuit of the reactor to a hot tank 14 and then into a steam generator 16 and into a cold tank 15 to return to the intermediate exchanger 3.

[0175] 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 18.

[0176] Each fluidic branch of the loop 13 consists of a cylindrical section pipe with metal walls resisting chemical attack by the heat transfer fluid at high temperatures, typically above 300° C., with external heat insulation by means of a high-temperature insulator. The diameter of a pipe is calculated to enable evacuation of all the thermal power with a permissible maximal limit rate of flow of the heat transfer fluid that is typically of the order of 5 to 10 m / s.

[0177] The hot tank 14 contains the heat transfer fluid, stores all the heat recovered from the intermediate exchanger 3 and feeds the heat transfer fluid to the steam generator 16. The hot tank 14 can be of cylindrical shape with the 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 thermal losses. The size (usable storage volume) of the hot tank 14 depend on the characteristics of the heat transfer fluid used: it must enable storage at most of all the heat produced by the nuclear reactor over a sliding period of 24 hours. For safety reasons, the hot tank 14 is at a distance from the enclosure of the reactor with a batter between them, typically at a distance preliminarily estimated at 60 m. The tank 14 can be equipped with a system for heating the heat transfer fluid to guarantee that the fluid remains in the liquid state and / or a level measuring system able to transmit an alarm and / or a safety overflow connected directly to the cold tank 15.

[0178] The steam generator 16 produces steam for the turbines 60, 61, which is characteristic of a Rankine cycle with the modes of operation of an electricity generating cycle of the installation and must be able to function in accordance with the demand from the grid 21. The steam generator 16 is typically rated to evacuate 1.5 times the power of the nuclear reactor. The turbines 6, 60, 61 are rated on the basis of the peak flowrate of steam produced by the steam generator 16.

[0179] Like the hydraulic pump 18, the hydraulic pump 17 is designed to function at least at the coefficient of availability Kd of the nuclear reactor and must be able to function in accordance with the fluctuating demand for electricity of the grid 21 to which the alternator 9 of the nuclear reactor is electrically connected. The flowrate of the pump 17 or 18 must make it possible, given the calorific capacity of the heat transfer fluid and the size of the steam generator 16, to feed the latter with heat transfer fluid at a flowrate enabling the power demand of the grid 21 to be addressed. Each of the pumps 17, 18 has metal walls resisting chemical attack by the heat transfer fluid at high temperatures, typically above 300° C. A plurality of pumps 17 or 18 can be connected in parallel to distribute the pumping flowrate and a redundant pump can be provided for safety reasons.

[0180] The cold tank 15 has substantially the same storage volume for heat transfer fluid recovered from the steam generator 16 as the hot tank 14. The cold tank 15 can be of cylindrical shape the walls of which are made of metal resisting chemical attack by the heat transfer fluid at high temperatures, typically above 300° C., and is coated with an external high-temperature insulating layer enabling thermal losses to be limited. The size (usable storage volume) of the cold tank 15 depend on the characteristics of the heat transfer fluid used: it must enable it to store at most all of the heat produced by the nuclear reactor over a sliding period of 24 hours. For safety reasons the cold tank 15 is at a distance, typically at a preliminarily estimated distance of 60 m, from the enclosure of the reactor with a batter between them.

[0181] The tank 15 can be equipped with a system for heating the heat transfer fluid to guarantee that the fluid is retained in the liquid state and / or a level measuring system that transmits an alarm and / or a safety overflow connected directly to the hot tank 14.

[0182] The heat transfer fluid is of the molten salt type so as to remain in the liquid phase over a range of temperatures from 100° C. to 350° C. with a margin of 40° C. relative to the maximum operating temperature. The salt will preferably have the following chemical composition: 53% NaNO3, 40% NaNO2, 7% KNO3 (HITEC® salt).

[0183] 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 fluidic branches / pipes of the loop 13 to prevent overflows and loading in operation.

[0184] The grid 21 connected to the alternator 9 is aimed at transporting and distributing electricity to end users as a function of their requirements. It is a high-tension grid functioning in accordance with a power demand linked to the uses of the electricity, and must be able to accept the peak electric power produced by the cogeneration installation.

[0185] According to the invention, the cogeneration installation includes at least one so-called dry air cooling tower 20, that is to say one functioning dry, connected in a closed loop to the condenser 7 of the secondary circuit of the reactor. This configuration, called the A / configuration hereinafter, is depicted in FIG. 7.

[0186] This cooling tower 20 transfers heat from the water condensed in the condenser 7 to the ambient air.

[0187] The cooling tower 7 is sized to evacuate the thermal power not consumed by the turbines 6, 60, 61 by bringing the water from the condenser 7 to the lowest temperature level that the ambient air can allow by being significantly heated.

[0188] Although not represented, the closed loop comprising the condenser 7 and the dry air cooling tower 20 is equipped with a pumping system to route the heat transfer fluid in it, this pumping system being adapted to be directly integrated into the tower 20. This A / configuration is aimed at purely electricity generation functioning with evacuation by means of the dry air cooling tower 20 of the residual power not consumed by the electrical conversion system 6, 9. In this A / configuration the installation is not operating at total energy efficiency but has the important advantage of producing more electricity during the day than a prior art PWR type reactor without necessitating take up or rejection of liquid water from or into the environment.

[0189] In an advantageous configuration, hereinafter called the C / configuration, depicted in FIG. 8 the dry air cooling tower 20 is connected to bypass a connection to an atmospheric CO2 capture system 22.

[0190] Thus in the event of the atmospheric CO2 capture system shutting down the installation functions in the A / configuration.

[0191] This C / configuration is aimed at operation with cogeneration supplying heat at low temperature for an atmospheric CO2 capture system. This C / configuration is therefore aimed at valorizing all of the thermal energy from the reactor not used for the production of electricity. In this C / configuration the installation has total energy efficiency.

[0192] Thus in the event of momentary absence of demand for heat by this network the installation reverts to the A / configuration.

[0193] All of the cogeneration installation is typically configured to have in the closed loop incorporating 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 7° and 100° C.

[0194] The inventors have rated the cogeneration installation depicted in FIGS. 7 and 8 for the A / and C / configurations respectively.

[0195] These ratings are based on the intra-daily power demand curve of a high-tension grid 21. To simplify the calculations the power curve can be simplified as shown in FIG. 9 with a constant demand in terms of power centered on a day with a duration of X hours, X being less than 24.

[0196] If in reality the demand is not identical to this simplification, the design of the installation according to the invention remains the same, considering that the total power sent daily to the grid is equal to the integral of the power over a sliding period of 24 hours.Comparative Configuration

[0197] In a prior art configuration of a PWR type reactor shown in FIG. 1 the water entering a wet air cooling tower 11 is at a temperature of the order of 35° C. and at the outlet is at a temperature of the order of 25° C.

[0198] In this case, the total power supplied daily to the grid by the system will be:PDaily⁢ elec⁢ grid(MWhe / j)=X⁡(h)×PReactor(MWth)×RdtRankine⁢ 25⁢°(%)(1)with, in this case, an efficiency RdtRankine 25°=33%.

[0200] A / and C / configurations according to the invention

[0201] The introduction of the storage loop 13 enables decorrelation of the operation of the reactor from the demands of the power curve of the grid 21. The total power produced by the reactor is therefore given by equation (2) below:PReactor⁢ daily(MWth)=24×PReactor(MWth)⁢%)(2)

[0202] This constant power is depicted in FIG. 10.

[0203] To be able to deliver all this power to the grid on a daily basis the energy conversion loop 5 employing a Rankine cycle must therefore be rated to evacuate all of its power during the X hours of power demand of the grid.

[0204] Its rated power is then given by equation (3):PRankine(MWhth)=2⁢4X×PReactor(MWhth)×RdtRankine(3)

[0205] It is possible to rate the elements of the thermal storage loop 13 on the basis of these daily power balances.

[0206] Given the chosen technology of the PWR type reactor, the input data giving the temperatures at the inlet and outlet of the intermediate exchanger 3 is fixed and the temperatures in the cold tank 15 and the hot tank 14 are therefore, respectively:Tcold⁢ salt=245⁢°⁢ C.Thot⁢ salt=310⁢°⁢ C.

[0207] Under these conditions, the pumping flowrate of salt by the pump 18 is given by the equation:QEI⁢ feed⁢ pump(m3 / s)=PReactor(MWth)Cpsalt×(Thot⁢ salt-Tcold⁢ salt)(4)where Cpsalt is the mass calorific capacity of the salt of the heat transfer fluid in the loop 13.

[0209] The power rating of the intermediate exchanger 3 is given by the equation:PReactor(MWth)=K×S×Δ⁢TTLn(5)where:

[0211] K is the mean surface thermal transmission coefficient,

[0212] S is the exchange surface area,

[0213] ΔTTLn is the logarithmic temperature delta at the inlet and outlet of the intermediate exchanger 3.

[0214] The usable volume of the hot tank 14 is then given by the formula:Vhot⁢ tank⁢ usable(m3)=24⁢ QEI⁢ feed⁢ pump(m3 / h)(5)

[0215] The design usable volume of the cold tank 15 is equal to the usable volume of the hot tank 14:Vcold⁢ tank⁢ usable(m3)=Vhot⁢ tank⁢ usable(m3)(6)

[0216] This rating method does not integrate the loss of volume during the hours covering functioning of the reactor and the electricity conversion cycle. It nevertheless enables a reactor shutting down kinetic in the event of failure of the energy conversion system at the least opportune time (grid demand cycle start). The total value before the cold tank overflows can be arrived at by adding a safety volume taken in a preliminary manner before safety analysis at 20% of the usable volume.

[0217] The flowrate of the pump 8 feeding the steam generator 16 is given by the following equation:QGV⁢ feed⁢ pump(m3 / h)=Vhot⁢ tank⁢ usable(m3)X⁡(h)(7)

[0218] The rating of the components of the Rankine cycle in the secondary circuit 5 is dictated by the thermal power to be converted and the temperature at the inlet and the outlet of the condenser 7.

[0219] The thermal power is given by the aforementioned equation (3).

[0220] The temperature at the inlet and outlet of the condenser 7 depends on the A / or C / configuration envisaged.

[0221] Table 1 below gives temperature values and the efficiency of the associated thermodynamic cycle as a function of the A / or C / configuration.TABLE 1ConfigurationA / C / Condenser 7 hot T° (T2) (° C.)50between 70 and 100Condenser 7 cold T° (T1) (° C.)40between 60 and 80Efficiency (%) of Rankine cycle used by3025 and 22.5secondary circuit 5

[0222] The rating of all of the components of the cycle is established using CYCLOP internal software type tested by the applicant for rating in the context of a permanent thermodynamic conversion cycle regime.

[0223] The use of this software is described in [3] or

[10] for example. Rating can equally well use some other commercial software, notably the THERMOFLEX® software.

[0224] As a preliminary to this, the rise in temperature at the inlet and the outlet of the condenser 7 reduces the number of turbines 6 or even reduces their size by eliminating the low-pressure bodies 61.

[0225] The generic input data adopted is as follows:

[0226] a PWR type pressurized water reactor of the type that currently exist in the French electronuclear field,

[0227] a reactor core power level equal to 100 MWth.

[0228] For each of the A / and C / configurations, the operating point of the energy conversion system of the secondary circuit is calculated using the CYCLOP software.

[0229] For the A / configuration the performance evaluations indicate:

[0230] a thermodynamic efficiency of 30.1%, which because the temperature of the cold source is increased to 50° C. is reduced relative to a classic PWR type reactor configuration for which the efficiency is of the order of 34%;

[0231] an electrical power of 44.61 MWe produced in the day for a 100 MWth reactor; remember that a classic PWR type reactor would produce approximately 34 MWe in the day; here the electrical power produced in the day is boosted thanks to the storage by the storage loop 13 of energy produced during the night;

[0232] a total absence of need for liquid water for cooling since the cold source requirement corresponds to a temperature of 40° C., compatible with the user of a dry air cooling tower 20; this temperature is achieved by modifying the pressure in the condenser 7 from approximately 50 mbar to approximately 160 mbar; this is accompanied by a reduction in the size of the low-pressure turbine body 61 and simplification of the design of the condenser.

[0233] For the C / configuration, the performance evaluations (C1) indicate:

[0234] a thermodynamic efficiency of 23.33%;

[0235] an electrical power produced during the day of 33.50 MWe (by a 100 MWth reactor), of which 14.4 MWe are supplied to the CO2 capture system 22 and 19.1 MWe are supplied to the grid 21;

[0236] 100% valorization of the energy produced by the reactor;

[0237] a total absence of the need for liquid water for cooling since the cold source is the CO2 capture system; in the event of a malfunction of the capture system, the cold temperature required for the reactor being 80° C., there is no need for liquid water, a dry air cooling tower 20 being sufficient.

[0238] A second case (C2) has been evaluated for the C / configuration necessitating a temperature T2 of 70° C. and yielded the following results:

[0239] a thermodynamic efficiency of 27.85%;

[0240] a total electrical power equal to 40.09 MWe;

[0241] a pressure at the condenser 7 equal to 0.387 bar.

[0242] Table 2 below summarizes the performance evaluations for the A / and C / configurations studied.TABLE 2Prior artPWR typeC1 / C2 / reactorA / configurationconfigurationData / performanceUnitconfigurationconfiguration(T2 = 100° C.)(T2 = 70° C.)Reactor thermal powerMWth100100100100Hours / day powerh16161616demand on grid 21Thermal power ofMWth100150150150Rankine cycle 5Condenser 7 temperature° C.355010070T2Efficiency of Rankine%3430.123.327.9cycle 5Daily electrical powerMWhe / day544722.4559.92668.4producedIncrease in electricity%N.A.33323productionDaily electrical powerMWhe / day544722.4329.91451.95produced sent to grid 21Quantity of CO2 capturedTons ofN.AN.A1150.051082.25by system 22CO2 / day

[0243] These evaluations confirm and quantify the advantages of the invention that have just been described for the A / and C / configurations, and notably:

[0244] while the system no longer needs liquid water for evacuation of the free heat the increased energy efficiency of the installation is further increased; indeed, in the A / and C / configurations the daily quantity of electricity produced is increased by 3 to 33%;

[0245] in addition to being favorable in terms of environmental impact, the invention increases the economic competitiveness of a nuclear installation;

[0246] extrapolation to a power level of 500 MWth corresponding to the power of a small modular reactor (SMR), the quantity of CO2 captured daily by a system 22 corresponds to the carbon balance of a town with a population of 125 000; this first estimate makes it possible to envisage a possible nuclear coupling role in the C / configuration studied, pending the carbon neutrality envisaged for 2050.

[0247] In an emerging context of generalization of carbon taxation the preliminary economic evaluations confirm the interest of the installation according to the invention.

[0248] The FIG. 11 graph repeats the figures from table 2 above for the C / configuration for an SMR type reactor and simulates the economic impact of CO2 capture with regard to an evolving carbon tax in order to compensate the loss linked to the sale of electricity.

[0249] This graph shows that equilibrium is situated between 15 and 30€ / ton CO2 depending on the sale price of electricity. By way of reference, the amount of the carbon tax as of June 2021 was around 50€ / ton.

[0250] For temporal decorrelation of production of electricity and production of heat without degrading the energy efficiency of the cogeneration installation 1 the inventors have thought to add a supplementary loop 30 at the inlet and outlet of the condenser 7 that plays the role of thermal storage and distribution of heat between the condenser 7 and one or more heat exploitation systems 22, 23, 24, as depicted in FIG. 12.

[0251] This configuration is called the D / configuration hereinafter.

[0252] To be more precise, the cogeneration installation 1 employs all of the elements described with reference to FIG. 12, with the addition of a fourth fluidic circuit 30 configured as a closed loop for storage of thermal energy and distribution of heat.

[0253] The thermal storage and heat distribution loop 30 is a closed loop fluidic circuit in which a heat transfer fluid circulates from the condenser 7 to a hot tank 31 and then in one or more heat exploitation systems 22, 23, 24 in parallel and in a cold reservoir 32 in order to return to the condenser 7.

[0254] 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.

[0255] The fluidic branches of the loop 30 each consist of a cylindrical section pipe with metal walls resisting chemical attack by the heat transfer fluid and thermally insulated on the outside in the branch connected to the hot tank 31. The diameter of a pipe is calculated to enable evacuation of all the thermal power stored in the hot tank 31 in 24 hours with a permissible maximum limit rate of flow of the heat transfer fluid that is typically of the order of a few m / s.

[0256] The hot tank 31 makes it possible to contain the heat transfer fluid, to store all of the heat recovered from the condenser 7 and to feed heat transfer fluid to one or the other of the heat exploitation systems 22, 23, 24. The hot tank 31 is covered with an external high-temperature insulating layer to limit thermal losses. The size (usable storage volume) of the hot tank 31 depends on the characteristics of the heat transfer fluid used: it must enable it to store at most all of the heat recovered at the condenser 7 over a sliding period of 24 hours. The tank 31 can be equipped with a level measuring system transmitting an alarm and / or a safety overflow connected directly to the cold tank 32.

[0257] Each of the heat exploitation systems 22, 23, 24 is intended to provide a service based on thermal energy in particular and consumes the thermal energy brought by the heat transfer fluid from the hot tank 31, lowering its temperature. By way of example:

[0258] the system 22 is a CO2 capture system,

[0259] the system 23 is an urban or industrial heating network,

[0260] the system 24 is a seawater desalination system.

[0261] Like the hydraulic pump 34, the hydraulic pump 33 is designed to function at least at the availability coefficient Kd of the nuclear reactor and must be able to function subject to the fluctuations of energy demand of the grid 21 to which the alternator 9 of the nuclear reactor is electrically connected. Given the calorific capacity of the heat transfer fluid and the temperature difference at the inlet and the outlet of the condenser 7 the flowrate of the pump 33 or 34 must enable evacuation of all the thermal power and feeding the systems 22, 23, 24 with heat transfer fluid at a flowrate enabling the power demand of the grid 21 to be addressed. Each of the pumps 33, 34 has metal walls resisting chemical attack by the heat transfer fluid. A plurality of pumps 33 or 34 may be used in parallel to divide the pumping flowrate and a redundant pump may be provided for safety reasons.

[0262] The cold tank 32 has substantially the same storage volume as the hot tank 31 for heat transfer fluid recovered from the condenser 7. The cold tank 32 is covered with an external high-temperature insulating layer enabling thermal losses to be limited. The cold tank 32 can be equipped with a level measuring system transmitting an alarm and / or a safety overflow connected directly to the hot tank 31.

[0263] Given the temperature levels required in the loop 30 and for economic reasons, the heat transfer fluid is water. Other types of heat transfer fluid can be envisaged.

[0264] The total volume of water contained in the closed loop 30 is equal to the total volume of the cold tank 31 and the volume contained in the fluidic branches / pipes of the loop 30 to prevent any overflow or loading in operation.

[0265] FIG. 13 shows an advantageous variant in which the hot tank 31 and the cold tank 32 consist of a single layered thermal storage tank which, given the temperature level below 100° C., is a water moat in which thermal layering occurs between a layer at 90° C. for example and a cold layer at 50° C. for example.

[0266] The inventors have arrived at ratings of the cogeneration installation depicted in FIG. 12 for the D / configuration.

[0267] Table 3 below gives temperature values and the efficiency of the thermodynamic cycle associated with the D / configuration.TABLE 3ConfigurationD / Hot T° of steam generator 16 and hot tank 14 (° C.)310Cold T° of steam generator 16 and cold tank 15 (° C.)240Hot T° (T2) of condenser 7 and hot tank 31 (° C.)90Cold T° (T1) of condenser 7 and cold tank 32 (° C.)70Efficiency (%) of Rankine cycle used by secondary circuit 525

[0268] All of the components of the cycle are rated as in the preceding configurations.

[0269] Table 4 below indicates, on the basis of a 100 MWth power nuclear reactor, the powers of the subsystems of the installation in the D / configuration as a function of the operating regime.TABLE 4RatedDaily operatingSubsystempowertimeNuclear reactor10024 h / 24 hRankine cycle used by secondary circuit 515016 h / 24 hHeat exploitation system 22, 237524 h / 24 h

[0270] Assuming a continuous heat demand for the heat exploitation systems 22, 23 that can respectively be a CO2 capture system and a heating network, the performance of the installation 1 in the D / configuration is as set out in table 5 below.TABLE 5DuringDuring16 h day8 h nightPower / subsystem(MWth / MWe)(MWth / MWe)Nuclear reactor100MWth100MWthThermal power transmitted to Rankine150MWth0cycle used by secondary circuit 5Electrical power supply to grid 2137.5MWe0Thermal power supplied to a single112.5MWth0layered thermal storage tank 31, 32Thermal power supplied to heat75MWth75MWthexploitation system 22, 23

[0271] Compared to the C / configuration in FIG. 8, the rated power of the heat exploitation system 22, 23 connected to the condenser 7 in the D / configuration from FIG. 12 has decreased by 33% (to 75 MWth instead of 112.5 MWth) for the same daily performance, which represents a considerable improvement in terms of compactness, investment and operating costs.

[0272] The objective of the ratings below is to evaluate, on the basis of an example of coupling between the condenser 7 with the temperatures T1, T2 at the inlet and the outlet respectively equal to 90° C. and 70° C. and an atmospheric CO2 system 22, the layered thermal storage volume 31, 32 that is necessary for a small modular reactor (SMR) type reactor using PWR technology the thermal power of which is 540 MWth.

[0273] The ratings are calculated using a power profile as shown in FIG. 14.

[0274] Table 6 below sets out the details of the ratings calculated.TABLE 6Calculation of volume of SCE cold source side storage tankReactor power540MWthSCE power810MWthEfficiency0.25Electrical power produced P202.5MWeCondenser P607.5MWthCooling of Rankine cycle used by secondary circuit 5Cp4.18kJ / kg / ° C.ΔT20°C.Flowrate26 160m3 / hOperating time16h / dayTotal volume of cold water pumped418 565m3 / dCO2 capture system 22 feedOperating time24h / dayFlowrate17 440m3 / hVolume of heat transfer fluid to store (=flowrate139 522m3difference over 16 h)

[0275] It therefore emerges from table 6 that the layered thermal storage volume is of the order of 140 000 m3.

[0276] As of now, the known dimensions of the water moats used for layered thermal storage are of the order of 1 Mm3.

[0277] The D / configuration of the installation is therefore compatible with existing technologies at a high level of technological maturity and with SMR nuclear power levels.

[0278] The invention is not limited to the examples that have just been described; in particular the features of the examples depicted in variants that are not depicted can be combined with one another.

[0279] Other variants and embodiments can be envisaged without departing from the scope of the invention.

[0280] In the example depicted the system 22 is a CO2 capture system. However, there may equally well be envisaged a seawater desalination system. Generally speaking, one or more heat exploitation systems may be used connected in a closed loop and in parallel with the condenser of the secondary circuit of the reactor.

[0281] The cogeneration nuclear installation that has just been described with reference to a pressurized water nuclear reactor may equally well be used with all indirect thermodynamic cycle nuclear reactors for which the heat production cycle is physically separate from the energy conversion cycle.

[0282] Using fluidic lines to bypass the hot and cold thermal storage tanks at low temperature for maintenance purposes may be envisaged in order to cause the heat transfer fluid to circulate in a closed loop between the condenser and the heat exploitation systems (CO2 capture, desalination, heating network) without being stored temporarily in said tanks.LIST OF REFERENCES CITED[1]: “Améliorer l'efficacité énergétique en utilisant la cogénération dans la production d'électricité” Jean-Marie Loiseaux, Henri Safa, Bernard Tamain, Réseau Sauvons le Climat.

[0284] [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

[0285] [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.

[0286] [4]: “Cogeneration with District Heating and Cooling”, Henri Safa CEA Nuclear Energy Division Scientific Direction, IAEA Consultant meeting, Vienna, 19-22 Dec. 2011.

[0287] [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.

[0288] [6]: S W U et Al.: “Coupling of nuclear heating reactor with desalination process”, DESALINATION, ELSEVIER, AMSTERDAM, NL, vol. 142, no. 2, February 2002 (Feb. 2 2001), pages 187-193, XP004351067, ISSN: 0011-9164, DOI: 10.1016 / S0011-9164 (01) 00438-6.

[0289] [7]: Jean-Claude GAUTHIER et Al: “2nd International Topical Meeting on HIGH TEMPERATURE REACTOR TECHNOLOGY ANTARES: The HTR / VHTR project at Framatome ANP”, 1 Sep. 2004 (Sep. 1, 2004), pages 1-13, XP055321369.

[0290] [8]: “Advances in Nuclear Power Process Heat Applications”, IAEA-TECDOC-1682, INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2012.

[0291] [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.

[0292]

[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, Sep. 22-24, 2004, Beijing, China, 2004.

Claims

1. An electrocogeneration nuclear installation including:at least one nuclear reactor, notably of pressurized water reactor (PWR) type or boiling water reactor (BWR) type, including;a first fluidic circuit, called the primary circuit, including at least one first intermediate heat exchanger;a second fluidic circuit, called 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, a condenser connected to the turbine and to the second heat exchanger to cool the steam from the turbine and to convert it back into water and send it to the second heat exchanger;an alternator mechanically coupled to the turbine and intended to be connected to a grid;a third fluidic circuit configured in a closed loop for storing thermal energy in which circulates a heat transfer fluid, including:at least one first tank, called the hot tank, connected to the first intermediate heat exchanger;at least one first hydraulic pump connected to the hot tank and to the second intermediate heat exchanger;at least one second tank, called the cold tank, connected to the second intermediate heat exchanger;at least one second hydraulic pump connected to the cold tank and to the first intermediate heat exchanger;at least one heat exploitation system connected in a closed loop to the condenser of the secondary circuit of the reactor.

2. The cogeneration installation as claimed in claim 1, the heat exploitation system being an atmospheric carbon dioxide CO2 capture and / or seawater desalination system and / or a heating network.

3. The cogeneration installation as claimed in claim 1, further including a dry air cooling system connected to bypass a connection to the heat exploitation system.

4. The cogeneration installation as claimed in claim 3, wherein the dry air cooling system is a dry air cooling tower.

5. The cogeneration installation as claimed in claim 1, wherein the temperature T1 at the inlet of the condenser is equal to at least 60° C. and the temperature T2 at the outlet of the condenser is equal to at least 70° C., advantageously between 70 and 100° C.

6. The cogeneration installation as claimed in claim 1, wherein the hot tank and the cold tank of the third fluidic circuit each having a volume between 10 000 m3 and 30 000 m3.

7. The cogeneration installation as claimed in claim 1, wherein the heat transfer fluid of the thermal storage loop of the third fluidic circuit is a molten salt or a mixture of molten salts adapted to remain in the liquid phase over a range of temperatures from 100° C. to 350° C. with a margin of 40° C. relative to the maximal operating temperature of the thermal storage loop.

8. The cogeneration installation as claimed in claim 7, wherein the heat transfer fluid has the following chemical composition: 53% KNO3, 40% NaNO2, 7% NaNO3.

9. The cogeneration installation as claimed in claim 1, further including a fourth fluidic circuit configured in a closed loop for storage of thermal energy and distribution of heat in which a heat transfer fluid circulates, the fourth fluidic circuit including:at least one third tank, called the hot tank, connected to the condenser,at least one third hydraulic pump connected to the hot tank and to the at least one heat exploitation system,at least one fourth tank, called the cold tank, connected to the condenser and to the at least one heat exploitation system,at least one fourth hydraulic pump connected to the cold tank and to the condenser.

10. The cogeneration installation as claimed in claim 9, wherein the heat transfer fluid of the thermal storage and heat distribution loop of the fourth fluidic circuit water adapted to remain in the liquid phase over a range of temperatures from 50° C. to 100° C. with a margin of 10° C. relative to the maximal operating temperature of the thermal storage and heat distribution loop.

11. The cogeneration installation as claimed in claim 9, wherein the hot and cold tanks of the fourth fluidic circuit consisting of a single layered thermal storage tank.

12. The cogeneration installation as claimed in claim 11, wherein the single layered thermal storage tank is a moat filled with the heat transfer fluid.

13. The cogeneration installation as claimed in claim 9, further including at least two temperature exploitation systems in parallel with the hot and cold tanks of the thermal storage and heat distribution loop.

14. The cogeneration installation as claimed in claim 9, wherein the hot and cold tanks of the fourth fluidic circuit each have volume between 50 000 and 300 000 m3 for a power of the reactor equal to 150 MWe.

15. The cogeneration installation as claimed in claim 1, wherein the turbine or turbines not including a low-pressure body.

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