Heat plant cogeneration plant

Abstract

Cogeneration installation for a thermal power plant, particularly a nuclear power plant, with partial steam admission stages via angular sectors at the inlet of the high and low pressure turbine sections of the heat-to-electricity (HTE) cycle. The invention essentially consists of a cogeneration installation with a heat-to-electricity conversion cycle that incorporates partial steam admission stages via arcs at the inlet of both the low-pressure and high-pressure turbine sections of the cycle, and with a cogeneration heat exchanger, i.e., to supply heat to the heat-harvesting system within the cycle, preferably a high-temperature electrolysis hydrogen production unit.

Description

technical field

[0001] The present invention relates to the field of cogeneration installations from a thermal power plant, in particular from a light water nuclear reactor (LWR), especially a pressurized water reactor (PWR).

[0002] "Cogeneration" here and within the framework of the invention means the simultaneous production of electricity with the production of useful heat.

[0003] For the purposes of this invention, "thermal power plant" means any power plant that generates heat for the production of electricity and that operates from a heat source according to the principle of heat engines and that includes a system for converting thermal energy from the heat source into electricity (SCE).

[0004] A thermal power plant conforming to the invention may be: a nuclear power plant including a steam turbine; a combustion power plant, known as a "flame" power plant, including a boiler (coal, fuel oil, gas or biomass) and a steam turbine; a power plant recovering pre-existing heat (solar thermal, geothermal steam, ...) including a steam turbine; a power plant with at least one storage tank, including a steam turbine; a power plant, including a steam turbine, with any other decarbonized heat source whose characteristics, in particular the temperature, allow conversion into electricity.

[0005] A nuclear power plant suitable for the purposes of this invention may consist of one or more light water reactors (LWRs), particularly pressurized water reactors (PWRs) with conversion cycle inlet temperatures of approximately 300 °C, or boiling water reactors (BWRs), or one or more Generation IV reactors (GEN IV), particularly small modular reactors (SMRs) or advanced nuclear reactors (AMRs), with conversion cycle inlet temperatures exceeding 500 °C, typically in the range of 550–700 °C. These may be liquid metal-cooled fast neutron reactors, particularly liquid sodium-cooled reactors (SFRs), which belong to the Generation IV reactor family. It can also be molten salt cooled fast neutron reactors or MSRs (English acronym for Molten Salt Reactors).

[0006] For the purposes of this invention, the term "SMR reactor" refers to its usual technological meaning: a nuclear fission reactor, smaller in size and power than conventional SLR reactors, whose steam generator is manufactured in a factory and transported to a nuclear site for installation. This compact, low-power steam generator can also be used for naval, or shipboard, applications.

[0007] More specifically, the invention relates to cogeneration plants comprising such nuclear reactors, in particular those of the integrated modular reactor type.

[0008] The main objective of the invention is to optimize the performance in flexibility of the energy conversion cycle of a thermal power plant for the production of thermal and electrical power.

[0009] Although described with reference to a pressurized water nuclear reactor, the invention applies to any nuclear reactor with indirect or direct thermodynamic cycle of the family of so-called second, third, fourth generation (GEN IV) reactors, insofar as there is a constraint on controlling their temperature.

[0010] A typical cogeneration plant is one in which a nuclear boiler is coupled, on the one hand, to the electrical grid of an energy system with a high proportion of renewable energy sources whose production is inherently variable, for example, linked to the sun's path, and, on the other hand, to a system that consumes significant amounts of heat. It can also be a mobile boiler whose output, by design, can be subject to dynamic load variations.

[0011] For the purposes of this invention, "nuclear boiler" means the reactor vessel, as well as all the components and parts of the fluidic circuit, including the reactor core which generates heat through nuclear fission reactions and is housed inside the reactor vessel.

[0012] By "with a power-generating purpose", we mean here and within the framework of the invention, a nuclear installation, a nuclear power plant or a nuclear reactor whose power is dedicated to the supply of electricity. Previous technique

[0013] In the context of climate and energy transition, the nuclear industry must meet several challenges for the future. Indeed, to address tomorrow's energy and societal challenges, it will be essential to design nuclear reactors that enable: to limit the need for so-called "environmental" liquid cold sources (rivers, streams, sea) and the associated discharges into the environment; to be more flexible and therefore more complementary to other so-called renewable energies (RE), to meet the fluctuating demand for electricity and the intermittency of RE production; to decarbonize processes by supplying heat to consuming industries (desalination, heat networks, hydrogen...) while increasing energy efficiency; This can be achieved without compromising the installation's profitability, by economically benefiting from the new services provided (for example, in terms of electrical grid stability through load and frequency following). The goal is therefore to efficiently integrate electricity and heat production into a low-carbon energy system.

[0014] In the conventional PWR sector, reactors are classified by major categories of use: so-called power-generating reactors which are dedicated solely to the production of electricity; so-called heat-generating reactors which are dedicated solely to the production of heat; so-called cogeneration reactors, dedicated both to the production of electricity simultaneously with useful heat.

[0015] As detailed in [1], the principle of cogeneration from a nuclear reactor is to modify the design of the energy conversion cycle so that the heat is used for purposes other than electricity production.

[0016] This cogeneration objective becomes all the more relevant for a nuclear reactor as industrial or domestic heat is often traditionally obtained by burning fossil fuels responsible for greenhouse gas emissions.

[0017] In general, there is a need, in order to optimize the performance in flexibility of the energy conversion cycle, for such an installation coupling the nuclear reactor to the thermal and electrical power production systems.

[0018] Performance in flexibility requires respecting criteria such as gradual modulation, maximum amplitude at least significant, dynamic stability and energy efficiency of load variations operated, which can be detailed as follows.

[0019] Gradual modulation involves having the option to: to adapt the variation of electrical load operated to the precise need for balance of the electrical network; to have a resilient technical solution, i.e. one whose electricity / heat ratio is modular and therefore applicable to different current energy contexts or resulting from future energy scenarios; to postpone periods of unavailability of the nuclear unit or of the system(s) operating by cogeneration: this typically involves being able to switch from generator operation to cogeneration operation.

[0020] The maximum range consists of being able to: contribute significantly to the decarbonization of the energy sector by supplying substantial heat from a very low CO2 emitting nuclear source: typically, the target is to be able to deliver at least 30% of the Nominal Power (NP) in the form of heat; achieve electrical load monitoring as on the current French nuclear fleet, between 20 and 100% of NP.

[0021] Dynamic stability is that which is simultaneously: The temperature at the steam generator inlet must remain within a range defined during the design phase (this temperature, due to the thermal pinch of the component, defines the temperature at the reactor core inlet). The prescribed operating range results from an engineering compromise that takes into account, among other things, thermomechanical considerations related to the steam generator and the boiler vessel (which is a key component because it remains unchanged throughout the reactor's life, i.e., 40 to 60 years depending on the design), considerations related to the dynamic control of the neutronics-thermohydraulic coupling of the reactor, of which the steam generator is a pivotal component (it connects the boiler to the reactor control system), and considerations related to the desired compactness of the boiler block and the reactor control system.When it comes to the direct cycle of a BWR for which the steam generator component does not exist, the constraint on the temperature at the inlet of the steam generator is directly substituted by that at the core inlet; the quality of the heat supplied to the cogeneration in the form of water vapor at a temperature which must be greater than or equal to a threshold value, and finally the thermohydraulic implementation of the modulation of electrical and heat loads.

[0022] Energy efficiency can be defined as the preservation of natural resources, the reduction of the carbon footprint by optimizing the substitution of carbon-based energies, and the consideration of the economic aspect.

[0023] The aim is to find a control system that can meet the objectives just described, while the variation of electrical and heat loads leads, without proper control, to a modification, also called slippage, of pressures and temperatures at the level of the turbine expansion line of the heat-to-electricity conversion cycle.

[0024] This shift, detailed in publication [2], alters the operating pressures in two ways: of the steam generator, coupling the nuclear boiler and the Rankine cycle. In a pressurized water nuclear reactor of the French fleet, designed for power generation, this effect is countered by the complete throttling of the steam at the inlet of the high-pressure turbine casing, resulting in a significant loss of electrical efficiency; two-phase heat exchangers on which the cogeneration supply temperature and the inlet temperature of the steam generator depend. Stability criteria can therefore be violated.

[0025] The effect of slippage is all the more significant as the amplitude of the applied load variation increases. It induces an inertial effect with each modulation (start-up of the two-phase heat exchangers) and disrupts dynamic stability, thus consequently affecting several of the aforementioned criteria, namely gradual modulation and the achievable maximum amplitude.

[0026] Several solutions have already been proposed to improve the flexibility performance of the energy conversion cycle of a nuclear cogeneration plant.

[0027] The flexible control of a nuclear boiler operating in combined heat and power (CHP) mode, with a focus on modulation and maximum load amplitude, is discussed in publication [3]. Several turbine casing arrangements, to be selected according to the target range of CHP heat requirements, are proposed in this publication to assess the solution's resilience to the application's energy context. This publication does not consider the steam generator inlet temperature control criterion and does not discuss electrical load modulation. However, it does propose: For cogeneration load modulations of low maximum amplitude, less than 5% of the boiler's output, the pressure and temperature slippage effect can be countered by switching from an initial steam extraction point to a second, more upstream, and therefore hotter, one on the turbine's expansion line. This solution cannot be applied to high modulation criteria because it slows down the response dynamics and may even compromise stability due to the change in steam extractions it introduces, particularly with the switch from one steam quality to another at the preheater, which adds a start-up effect and therefore inertia.This solution, for high modulation, can also disrupt the three-dimensional flow of the turbine stages near the draw-off point, reducing their efficiency; for a higher maximum modulation amplitude, a back-pressure turbine housing dedicated to cogeneration and located on a different rotational shaft than the turbo-alternator is used. This solution requires cooling of this turbine housing when operating in purely power-generating mode.

[0028] The implementation of a back-pressure turbine body is also proposed by [4] by replacing the cold source of the cycle with a cogeneration system. This type of configuration has low performance in terms of flexibility due to the limitation of the expansion ratio providing mechanical work, which significantly degrades electrical efficiency (at the turbine outlet, the condenser pressure, which constitutes the cold source of the cycle, is in fact raised by a factor of at least 15 to correspond to the cogeneration steam supply pressure), due to the correlated limitation regarding the quality of heat supplied, and due to the electricity-heat correlation of this configuration, for which all the heat removed by the cold source is intended, in principle, to be consumed by cogeneration.

[0029] Publication [5] proposes the use of a partial arc admission stage at the inlet of the high-pressure core of a Rankine cycle turbine associated with a nuclear steam generator. This publication does not take into account the criteria for cogeneration, and therefore the associated constraint for the threshold temperature, nor the control of the steam generator inlet temperature.

[0030] Publication [6] implements a dual partial arc admission system at the inlet of the high-pressure turbine casing and an intermediate steam extraction stage. However, no coupling architecture between a nuclear boiler and a cogeneration system is discussed. Furthermore, this publication [6] does not consider control mechanisms for modulating the electricity and / or heat load, nor the possibility of a design resilient to different energy scenarios. Temperature control at the steam generator inlet is also not addressed.

[0031] Patent application WO2024 / 133496 discloses a nuclear cogeneration plant incorporating a high-pressure heater and an intermediate heat exchanger dedicated to operating a hydrogen production system, both arranged at the outlet of the turbine's high-pressure casing, to improve flexibility and control. The disclosed plant does not consider the maximum amplitude of the cogeneration heat, nor does it optimize performance in terms of flexibility, nor does it consider temperature constraints at the steam generator inlet, the latter of which becomes more complex to meet when the load variation is significant.

[0032] Publication [7] concerns the flexible control of a nuclear boiler by partial admission of steam via an angular sector (arc) at the inlet of the high-pressure turbine casing to achieve generator load following. This publication does not address cogeneration and, moreover, does not demonstrate the capacity of the disclosed installation to provide a significant amount of heat through cogeneration. The disclosed installation also fails to perform an optimization that maximizes energy efficiency while respecting temperature stability constraints.

[0033] Table 1 below summarizes the fact that none of the publications and references according to the state of the art meet all of the criteria defined above. [Table 1] State-of-the-art reference Criteria Gradual modulation in cogeneration Maximum Amplitude (significant) Dynamic stability Energy efficiency of load variations Publication [3] Yes, but a range of solutions depending on the target audience No Yes, but cogeneration only. Publication [5] Yes, but generator control only. Yes, but generator control only. Publication [6] The two criteria are not distinguished. Yes, but not quantified Patent application WO2024 / 133496 No Yes No Publication [7] Yes, but generator control only. No Yes, but generator control only.

[0034] There is therefore a need to further improve cogeneration facilities, particularly nuclear, in order to optimize the performance in flexibility of the energy conversion cycle of a thermal power plant coupling the heat source of the latter to the thermal and electrical power production systems of the installation.

[0035] The aim of the invention is to at least partially meet this need. Description of the invention

[0036] To this end, the invention relates, in one of its aspects, to a cogeneration plant, intended to produce electricity and, where applicable, heat, comprising: at least one thermal power plant, in particular a pressurized water reactor (PWR) or boiling water reactor (BWR), comprising: at least one fluid circuit: at least one turbine comprising a high-pressure casing and a low-pressure casing connected to the high-pressure casing by at least one fluid branch, a high-pressure heater connected in a closed loop to the high-pressure casing, a low-pressure heater connected on one side, by at least one fluid branch to the low-pressure casing and on the other side, by at least one fluid branch to the liquid reservoir, a condenser connected on one side, to the low-pressure casing and on the other side, in a closed loop to the low-pressure heater, a high-pressure hydraulic pump for circulating the liquid as a heat transfer fluid, a low-pressure hydraulic pump for extracting the condensate from the condenser and conveying it via the low-pressure heater;an alternator mechanically coupled to the turbine, intended to be connected to an electrical network; at least one second intermediate heat exchanger connected in a closed loop to a withdrawal tap, made in the fluid branch between the high-pressure and low-pressure turbine casings, and to the liquid reservoir and connected to at least one cogeneration system with a heat requirement compatible with the temperature at the terminals of the second intermediate heat exchanger; at least one stage arranged at the inlet of the high-pressure turbine casing and adapted to achieve partial admission of steam by angular sector into the high-pressure casing; at least one stage arranged at the inlet of the low-pressure turbine casing and adapted to achieve partial admission of steam by angular sector into the low-pressure casing;at least one steam pressure control system to control the partial admission of steam into the inlet stage of the high-pressure body and into the inlet stage of the low-pressure body.

[0037] The cogeneration system is preferably a high-temperature electrolysis (HTE) hydrogen production unit or any process requiring low-pressure steam, typically at 100°C, which, taking into account thermal pinch and a margin of overpressure to compensate for hydraulic pressure losses in the circuits, is close to 150°C.

[0038] According to an advantageous embodiment, the thermal power plant is a pressurized water reactor (PWR) comprising: a first fluidic circuit, called the primary circuit, comprising at least one first steam generator as the first intermediate heat exchanger; a second fluidic circuit, called the secondary circuit, comprising the turbine whose high-pressure body is connected to the first steam generator, the high-pressure heater also connected in a closed loop to the steam generator, to a liquid reservoir, the low-pressure heater, the condenser, the high-pressure and low-pressure hydraulic pumps.

[0039] In this mode, the liquid reservoir is called a food-grade tarpaulin.

[0040] Advantageously, the steam generator is of the single-pass type.

[0041] According to an advantageous embodiment, each inlet stage by arcs comprises, in parallel, four piloted valves, each supplying one of the four arcs constituting the stator of the inlet stage.

[0042] Preferably, the vapor pressure control system(s) is / are of the Proportional Integral (PI) type or of the model-based predictive control (MPC) type.

[0043] According to the PWR reactor embodiment, the reactor vessel and the steam generator are advantageously configured as an integrated SMR type modular reactor.

[0044] According to another advantageous embodiment, the installation includes, as a cogeneration system with a heat requirement compatible with the temperature at the terminals of the second intermediate heat exchanger, preferably a hydrogen production unit by EHT or any process requiring low-pressure steam.

[0045] The invention essentially consists of creating a cogeneration plant with a heat-to-electricity conversion cycle that integrates partial arc steam induction stages at the inlet of both the low-pressure and high-pressure turbine bodies of the cycle and with a cogeneration exchanger, i.e. to supply heat to the heat-exploiting system within the cycle, preferably a high-temperature electrolysis hydrogen production unit.

[0046] The inventors started from the observation that, in an SMR installation with a PWR reactor, the temperature setpoints at the inlet of the steam generator (SG) were close to those required at the inlet of the system operating in cogeneration, typically around 150°C, and they then took advantage of this proximity and proposed a common control (SG, cogeneration system) by partial admission of steam by angular sector to the low pressure body and further optimized by partial admission of steam by angular sector to the high pressure body.

[0047] In the end, with adequate sizing of the heat exchanger surfaces and the arc surfaces of the HP and LP inlets coupled with sequential control of the stage arcs according to the pressure to be had at the inlet of the low pressure LP body and advantageously of the high pressure HP body, a cogeneration installation according to the invention makes it possible to meet all the criteria to achieve flexible performance.

[0048] Within the framework of the invention, it is of course possible to adapt the steam production pressure so that the temperature at the inlet of the steam generator is greater than 150°C.

[0049] Also, depending in particular on the type and size of the thermal power plant, consideration could be given to installing one or more partial steam admission stages by angular sectors in addition to those at the inlet of the high pressure body and at the inlet of the low pressure body, insofar as this allows the temperature at the inlet of the steam generator and the temperature required for the cogeneration exchanger to be regulated in combination.

[0050] In general, a cogeneration plant according to the invention can operate at different values ​​of pressure and temperature of superheated steam, reactor power, inlet temperature setpoint of the steam generator and of the cogeneration exchanger.

[0051] Other advantages and features of the invention will become clearer upon reading the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0052] [ Fig 1 ] there figure 1 is a schematic view of a configuration of a nuclear cogeneration plant according to the invention, comprising a thermal energy-to-electricity conversion cycle with a partial steam admission stage in arc at the inlet of the high-pressure and low-pressure turbine bodies of the cycle. Fig 2 ] there figure 2 illustrates, in the form of curves, the temperature stability at the inlet of the steam generator of a configuration according to the invention, compared with a prior art configuration, in generator operating mode. [Fig 3A], [Fig 3B ] THE Figures 3A and 3Billustrate in the form of curves the control of partial admission at the inlet stages of the high-pressure and low-pressure turbine bodies respectively in a configuration according to the invention, compared with a prior art configuration, in generator operating mode. [Fig 4A], [Fig 4B ] THE Figures 4A and 4B illustrate in the form of curves the control of partial admission at the inlet stages of the high-pressure and low-pressure turbine bodies respectively in a configuration according to the invention compared with another configuration according to the invention, in generator operating mode. Fig 5 ] there figure 5 illustrates in the form of curves the electrical efficiency as a function of the electrical load delivered in the configurations according to the invention in comparison with some of the configurations according to the state of the art, in generator operating mode. [Fig 6A], [Fig 6B ], THE Figures 6A and 6BThey compare, as an illustration of the control, the sequences of opening the inlet arcs in stage B, as a function of the electrical load delivered, for Configuration No. 1 according to the invention and Configuration 6 according to the prior art, respectively, in generator operating mode. [Fig 6C], [Fig 6D ] THE figures 6C and 6D They compare, as an illustration of the control, the sequences of opening the inlet arcs in stage E, as a function of the electrical load delivered, for Configuration No. 1 according to the invention, and Configuration No. 6 according to the state of the art, respectively, in generator operating mode. Fig 7 ] there figure 7 illustrates in the form of curves the electrical efficiency as a function of the cogeneration thermal load / electrical load ratio in a configuration according to the invention compared with a prior art configuration, in electricity-heat cogeneration operating mode. Fig 8 ] there figure 8illustrates in the form of curves the electrical efficiency as a function of the thermal load / electrical load ratio of cogeneration in a configuration according to the invention compared with another configuration according to the invention, in electricity-heat cogeneration operating mode. [Fig 9A], [Fig 9B ] THE Figures 9A and 9B illustrate in the form of curves the evolution of the cogeneration temperature and that at the steam generator inlet, as a function of the ratio of cogeneration thermal load to electrical load in a configuration according to the invention, in electricity-heat cogeneration operating mode. [Fig 10A], [Fig 10B ] THE Figures 10A and 10Billustrate in the form of curves the control of the arc feed of the partial inlet ports of the high-pressure and low-pressure turbine bodies respectively, and for two power loads from the same hot source, as a function of the ratio of thermal load of cogeneration to electrical load in a configuration according to the invention, in electricity-heat cogeneration operating mode. [Fig 11A], [Fig 11B ] THE Figures 11A and 11B illustrate in the form of curves the control of the supply of arcs of partial admissions, as a function of the ratio of thermal load of cogeneration per electrical load in a configuration according to the invention, in comparison with another configuration according to the invention, in electricity-heat cogeneration operating mode. Detailed description

[0053] Throughout this application, the terms "upstream" and "downstream" are to be understood by reference to the direction of flow of a heat transfer fluid within one of the fluid circuits of a nuclear cogeneration plant according to the invention.

[0054] A nuclear cogeneration plant with a PWR reactor according to the invention is shown. The primary circuit is not described in detail but it is a closed-loop fluid circuit mainly comprising a reactor core (not shown), a heat exchanger A as a steam generator (SG), and a hydraulic pump (not shown) to circulate the heat transfer fluid which is pressurized water in liquid form (or pressurized water which undergoes a liquid-vapor transformation in the case of a BWR boiler, with direct cycle).

[0055] Steam generator A is a single-pass type. It could also be a generator using so-called recirculating technology.

[0056] Thus, the high-pressure water in the primary circuit absorbs, in the form of heat, the energy supplied by the fission of uranium nuclei in the reactor core.

[0057] Then this water, under high pressure and high temperature, enters the intermediate exchanger A and transmits its energy to a secondary circuit, which also uses pressurized water as a heat transfer fluid in a closed loop.

[0058] Other equipment, such as a pressurizer and all the devices that ensure the operation of the nuclear boiler under the required safety conditions, is not described here.

[0059] The secondary circuit is a thermal energy to electrical energy conversion (TEE) system which mainly comprises a turbine consisting of a high-pressure body C and a low-pressure body F connected to the high-pressure body C by a fluidic branch, a condenser G connected to the low-pressure body F by a fluidic branch and hydraulic pumps K and I to circulate water in liquid form as a heat transfer fluid.

[0060] Thus, in this secondary circuit, water in the form of steam is expanded in the high-pressure body C of the turbine, then superheated before continuing its expansion in the low-pressure body F. The turbine drives an alternator (not shown) which produces electricity.

[0061] The water from the secondary circuit is then condensed via condenser G, as a so-called "cold" source.

[0062] The steam generator A produces steam for the high and low pressure bodies C, F of the turbine, which is characteristic of a Rankine cycle with the operating conditions of a generator cycle of the installation and must be able to operate according to the needs of the electrical network.

[0063] The secondary circuit also includes a circuit for heating the feedwater of steam generator A before it is injected / expanded as steam into the high-pressure body C of the turbine.

[0064] This heating circuit includes a high-pressure heater L connected in a closed loop to the high-pressure body C, to a water tank, called the feed tank J, and to the steam generator A. It also includes a low-pressure heater I connected on one side, by at least one fluid branch to the low-pressure body and on the other side, by at least one fluid branch to the feed tank J.

[0065] In this circuit, a low-pressure pump H, extracting condensate from the condenser G, conveys it to the feed tank J via the low-pressure heater I. The rotation speed of the low-pressure pump H is regulated on a pressure setpoint P8 (or flow rate).

[0066] The low-pressure heater I uses steam extracted from the low-pressure turbine body F as its heat source. The low-pressure heater I thus heats the feedwater to the steam generator A. This heater I, which is a two-phase heat exchanger, preferably includes level control.

[0067] Pump K brings this feed water from the feed tank J to the high-pressure heater L. This high-pressure pump K has its rotation speed regulated to maintain a temperature setpoint T2 at the outlet of the steam generator A.

[0068] The high-pressure heater L uses, as a heat source, the steam drawn from the high-pressure body C of the turbine.

[0069] The nuclear cogeneration plant also includes an injection coupling circuit with an intermediate heat exchanger M connected in a closed loop to a withdrawal tap, made in the fluid branch between the high pressure body C and the low pressure body F of the turbine, and to the feed tank J. More specifically, taking into account the temperature and pressure of the hot steam that we wish to withdraw, the withdrawal tap is at a point in the branch upstream of a dryer-superheater D, itself upstream of the low pressure body F of the turbine.

[0070] This tapping point is chosen at the appropriate temperature level to provide the latent heat to heat and / or vaporize the water so that it can be used by a system, not shown, operating in cogeneration with a heat requirement compatible with the temperature at the terminals of the second intermediate heat exchanger.

[0071] The tapping for the tapping can be carried out in a strictly identical manner (type of weld, where applicable characteristic diameter of pipe, etc.) to that of the tapping supplying the high-pressure heater L.

[0072] In the closed loop from the point of withdrawal, the fluidic branch allows the steam to be channeled and transferred to the exchanger M. After heat exchange, the liquid water is returned to the feed tank J.

[0073] According to the invention, installation 100 further comprises: a stage B arranged at the inlet of the high pressure body of the turbine and adapted to achieve the partial admission of steam by angular sector (arc) into the high pressure body C; a stage E arranged at the inlet of the low pressure body F of the turbine and adapted to achieve the partial admission of steam by angular sector into the low pressure body.

[0074] For control, the installation includes at least one steam pressure regulation system (P2 and P3) to jointly control the partial admission of steam into stage C at the inlet of the high-pressure chamber and into stage E at the inlet of the low-pressure chamber. Two pressure regulation systems are possible. These can be Proportional-Integral (PI) systems, controlling both stages B and E. Alternatively, they can be predictive control based on models (in English, "Model Predictive Control," or MPC). Each admission system per angular sector (arc) can advantageously include, in parallel, four pilot-operated valves, each supplying a given arc constituting the stator of admission stage B or E. These valves can thus be controlled in two different modes. These control valves allow for optimized operation and control of the coupling cycle with great flexibility.

[0075] For the construction of these floors, one can refer in particular to publication [8].

[0076] Finally, an electrical network, not shown, is connected to the alternator and aims to transport and distribute electricity to end users according to their needs. This is a high-voltage electrical network operating according to power demands related to electricity use, and it must be able to accept the peak electrical power produced by the cogeneration plant.

[0077] In this installation, typically: The single-pass steam generator, A, produces superheated steam at 45 bar and 300°C in normal reactor operation; the power of the nuclear reactor is that of an SMR close to 500 MWth; the condenser G is connected to a cold source and produces a low pressure of 70 mbar and the condensate is typically at a temperature of 39°C; the temperature setpoint at the inlet of the steam generator T1 and the cogeneration temperature threshold T15 are typically 150°C; the pump K brings this feedwater from the feed tank J to the high-pressure heater L to raise it to a temperature of around 150°C at a pressure of 50 bar in the steam generator A.

[0078] The sizing and operation of the installation can be advantageously optimized in a coupled manner.

[0079] In particular, the areas of each of the arcs of the partial admission stages B and E as well as the exchange areas of components M, L and I can be calculated optimally.

[0080] With regard to the piloting, the feeding sequence of the different arcs of the partial admission stages B and E can be optimally determined for pressures P2 and P3.

[0081] And the speed of pumps K and H can be varied as precisely as possible.

[0082] Thus, with stages B and E and the optimizations, the invention makes it possible to optimize the energy performance of the electrical and thermal power delivered by the installation 100, according to a modulating variation covering a significant amplitude, while guaranteeing operational stability.

[0083] This stability relates more particularly to the inlet temperature T1, the pressure P2 and the outlet temperature T2 of the steam generator A and the outlet temperature of the exchanger M, which guarantees the quality of the heat supplied to the system operating the cogeneration.

[0084] The inventor used numerical simulations to size all the components of the cogeneration plant, characterizing the different points of the circuits in terms of temperature and pressure.

[0085] These numerical simulations are carried out using a cycle model developed from a software, used under the name CYCLOP and a software marketed under the name "Dymola" by Dassault Systèmes implementing in part the library called "Thermosyspro" from EDF.

[0086] The use of the CYCLOP software and its relevance are described for example in [9] or

[10] .

[0087] Reference can be made to

[11] for the Thermosyspro library.

[0088] The CYCLOP software is qualified by the applicant for the steady-state thermodynamic optimization of thermodynamic conversion cycles.

[0089] The CYCLOP software essentially allows the modeling of an energy conversion cycle, consisting of different loops connected by thermal, mechanical, or electrical exchanges. Each loop is made up of components (heat exchangers, pumps, turbines, etc.) linked to each other by fluid circulation.

[0090] This software calculates each thermodynamic point of the complete cycle and deduces the useful energy production and therefore its efficiency. Each component is characterized by selected macroscopic quantities, but this tool can be linked to more detailed pre-sizing modules to obtain more precise characteristics of a given cycle.

[0091] The sizing can also be done using other commercial software, notably the one under the name THERMOFLEX ®< .

[0092] For numerical simulations, the validation of the installation is carried out considering the following specifications: a nominal nuclear boiler power of 540 MWth, transmitted by steam generator A. This generator produces steam at a temperature T2 of 300°C and a set pressure P2 of 45 bar; a temperature T1 at the inlet of steam generator A must be 150°C to + / - 1.5°C; a cogeneration temperature T15 must be greater than or equal to 150°C.

[0093] As detailed below, numerical simulations demonstrate the flexibility performance of the reference configuration according to the invention, designated Configuration No. 1, which implements dual arc-driven inlet control at stages B and E. Furthermore, this Configuration No. 1 according to the invention is improved, still featuring dual arc-driven inlet at stages B and E, but optimized for performance in combined heat and power (CHP) operation. This configuration is hereinafter designated Configuration No. 2.

[0094] Tables 2 and 3 below show comparative dimensional elements between configurations No. 1 and No. 2 according to the invention.

[0095] In all the tables: - ABi and AEi designate the passage surfaces of arc "i", in the admission stages respectively B and E; - AL and AM are the exchange surfaces of the heat exchangers respectively L and M. [Table 2] Configuration N°1 N°2 Surface area (m2) High-pressure turbine inlet (B) A B1 1,34E-02 5,22E-03 A B2 9,40E-03 6,74E-03 A B3 8,92E-03 1,06E-02 A B4 6,11E-03 1,56E-02 BP Turbine Admission (E) A E1 1,08E-01 6,69E-02 A E2 7,58E-02 6,30E-02 A E3 7,16E-02 6,96E-02 A E4 4,89E-02 6,74E-02 High pressure heater (L) AL 886 778 Cogeneration Heat Exchanger (M) AM 6414 5831 [Table 3] Configuration N°1 N°2 Distribution of the arc passage area (%) High-pressure turbine inlet (B) A B1 35,4 13,7 A B2 24,8 17,7 A B3 23,6 27,8 A B4 16,2 40,9 BP Turbine Admission (E) A E1 35,5 25,1 A E2 24,9 23,6 A E3 23,5 26,1 A E4 16,1 25,3

[0096] Tables 2 and 3 show that: Configuration No. 2 has overall smaller dimensions than Configuration No. 1, which is consistent with its reduced flexibility optimization target; the surface distributions of the arcs between these two Configurations No. 1 and No. 2 differ significantly.

[0097] In order to compare these configurations No. 1 and No. 2 according to the invention, the inventor simulated other configurations of piloting modes, as per the prior art, as follows: Configuration No. 3 : the admission by arc of steam into stage B of body C is controlled arc by arc, as in configuration No. 1 according to the invention, but the admission into stage E of body F is not: its arcs are all left open during load variations; Configuration No. 4 : the admission by arc of steam into stage B of body C is controlled arc by arc and the admission into stage E of body F is by complete rolling of the steam stream: the arcs are controlled simultaneously and dynamically during load variations, that is to say that the same opening is achieved at all arcs at a time t; Configuration No. 5: the admission by arc of steam into stage B of body C is controlled by complete rolling and the admission into stage E of body F is controlled arc by arc; Configuration No. 6: The admission by arc of steam into stage B of body C and the admission into stage E of body F are controlled by complete rolling.

[0098] It is recalled here that a complete throttling consists of abruptly lowering the pressure of the steam in a pipe by reducing the useful passage of the stream through a valve or diaphragm and without requiring it to produce work.

[0099] Table 4 below shows comparative dimensional elements between configurations No. 4 and No. 6, according to the state of the art. [Table 4] Configuration N°4 N°6 Power supply control (%) High-pressure turbine inlet (B) A B1 35,4 100 A B2 24,8 - A B3 23,6 - A B4 16,2 - BP Turbine Admission (E) A E1 100 100 A E2 - - A E3 - - A E4 - - Performance in generator load following

[0100] There figure 2highlights the respect for the temperature stability criterion allowed by the integration of a partial arc admission at stage E, by comparison with a control according to configuration No. 3: configuration No. 1 according to the invention manages to respect the temperature range allowed for T1, unlike configuration No. 3.

[0101] THE Figures 3A and 3B highlight the coupling of the piloting of the admission arcs of stages B and E of configuration No. 1 according to the invention, by comparison to Configurations No. 3 and 5, according to the state of the art.

[0102] More specifically, the figure 3A shows the impact on the control of the admission arcs in stage B, of the integration of a control of the admission arcs in stage E.

[0103] There figure 3B shows the impact on the control of the admission arcs in stage E, of the integration of a control of the admission arcs in stage B.

[0104] THE Figures 4A and 4B highlight the impact of the arch design on the control of partial admissions in floors B and E. Figures 4A and 4B compare the two Configurations No. 1 and No. 2 according to the invention, both operated in generator mode of electrical load following.

[0105] There figure 5 highlights the energy performance of the Configurations according to the invention over a wide range of electrical load variation, by comparison with the controls according to Configurations No. 4, No. 5 and No. 6 according to the state of the art which respect, like the invention (and contrary to configuration No. 3, as indicated above), the temperature stability criterion at the inlet of the steam generator.

[0106] More specifically, this figure 5 shows that Configuration No. 1 according to the invention: allows for a significant performance gain over the 20 to 80% electrical load range, with a gain of 1 to 2 points in electrical efficiency compared to a control according to Configuration No. 6 according to the state of the art and with approximately 50% of the gain being provided by the partial arc admission in stage E; allows exceeding the nominal electrical efficiency, when the electrical load is reduced to a value close to 75% of the nominal; obtains superior performance over a wide range, compared to Configuration No. 2 according to the invention.

[0107] THE Figures 6A And 6C compare, as an illustration of the control, the sequences of opening of the arcs of the admissions in stage B, as a function of the electrical load delivered, for respectively Configurations No. 1 according to the invention and No. 6 according to the state of the art.

[0108] THE figures 6Dand 6E compare, as an illustration of the control, the sequences of opening of the admission arcs in stage E, as a function of the electrical load delivered, for respectively Configurations No. 1 according to the invention, and No. 6 according to the state of the art. Performance in electricity-heat cogeneration

[0109] There figure 7 Compare Configuration No. 1 according to the invention and No. 6 according to the prior art, and we observe that: The maximum amplitude reached for the cogeneration heat load is significant: the ratio of cogeneration thermal power to electrical power is 1.6 obtained for an installation with a boiler operating at 80% of its nominal power, which corresponds in effect to a cogeneration power equal to 40% of the boiler power.This maximum amplitude does not correspond to an absolute ceiling and could be increased, for example by increasing the exchange surface of the cogeneration exchanger M; the ratio of cogeneration thermal power (exchanger M) to electrical power can be gradually modulated between a zero value (purely generator operation) and the high value; the energy performance of Configuration No. 1 is superior to that of a system using control according to Configuration No. 6: for the highest ratio of cogeneration thermal power to electrical power, equal to 1.6, the gain provided by Configuration No. 1 reaches the order of 1 point on the electrical efficiency.

[0110] There figure 8This illustrates that the energy performance of Configuration No. 1 is equivalent to that of Configuration No. 2 according to the invention. This equal performance is achieved by increasing the heat exchange surface area of ​​the cogeneration unit M by 10%. This increase demonstrates the resilience of Configuration No. 1's performance to the type of energy scenario considered. The oversizing required for Configuration No. 1 is considered negligible in terms of cost compared to that of a nuclear power plant, in comparison to the performance gain offered.

[0111] THE Figures 9A and 9B show that the stated temperature stability criteria are met for Configuration No. 1 according to the invention, since we observe: a stability of the temperature T1 of the inlet of the steam generator A, the temperature being maintained in a range of 150°C+ / - 1.5°C; a threshold of quality of the heat supplied to the system operating the cogeneration: the temperature T15 of the output stream of the cogeneration exchanger M is maintained above 150°C.

[0112] THE Figures 10A and 10B show the impact of the power of the nuclear boiler on the control of the supply of the arcs of the admissions of the stages B and E of the configuration No. 1 according to the invention, for a cogeneration operation carried out at two boiler powers, respectively equal to 80% and 95% of the nominal value.

[0113] THE Figures 11A and 11B show the impact of configuration No. 1 on the control of the supply of the arcs of the inlets of stages B and E, by comparison with the control of the supply of the arcs of the inlets of stages B and E of configuration No. 2 according to the invention.

[0114] Further analyses can be done for the criterion of dynamic qualities.

[0115] The start-up within the arc inlets in stages B and E can be considered instantaneous compared to the behavior of the rest of the installation since it is a sonic type flow.

[0116] It is preferable to avoid switching the power supply to the cogeneration heat exchanger M and the heater L by using higher pressure, and therefore hotter, draw-off points typically located within the unit C. This avoids installing these draw-off points which: disrupt the three-dimensional flow within the stages of the turbine body concerned and thus reduce its efficiency; require dedicated piping and piloting to ensure their use at the right time and with the required amount of steam; create pressure discontinuity effects for the supply of the exchangers and therefore, potential thermohydraulic instability effects and / or stronger start-up effects than with a continuous pressure program such as operated by arc admissions.

[0117] Table 5 below summarizes the positioning of Configuration No. 1 according to the invention with respect to the criteria defined above and in relation to Configurations No. 2, 3 and 6 according to the invention and that according to the state of the art. [Table 5] Reference Criteria Gradual modulation in cogeneration Maximum Amplitude (significant) Dynamic stability Energy efficiency of load variations Configuration No. 1 Yes - between 20 and 100% load variation in generator - Compliance with the steam and cogeneration generator inlet temperature guidelines across the entire load range, as opposed to operation according to Configuration No. 3 - Compared to the control system according to Configuration No. 6, there is a gain of 1 to 2 points in efficiency over the 20-80% range of nominal power in generator mode and 1 point in efficiency in cogeneration mode at 40% of boiler power - ≥ 30% of the boiler power in cogeneration - In cogeneration mode: iso-performance compared to configuration No. 2, provided that the cogeneration heat exchanger M is appropriately sized - Positive dynamic respect - 50% of this gain is due to partial admission to body F

[0118] Furthermore, compared to the prior art, configuration No. 1 according to the invention: combines performance in flexibility for generator load following operation and for electricity-heat cogeneration operation, and therefore exhibits resilience to the energy scenario considered, compared to publications [6] and [7]; surpasses full rolling control according to Configuration No. 6 in terms of performance, which can counterbalance the additional thermomechanical constraints on arc admission.

[0119] Furthermore, the integration of a partial arc admission at stage E of body F changes the control of the partial arc admission in stage B of body C, and the control of the admissions in stages B and E of Configuration No. 1 is very different from that of Configuration No. 2, whether in electrical load tracking mode or thermal load tracking of cogeneration.

[0120] Other advantages and improvements can be envisaged within the framework of the invention.

[0121] Thus, the cogeneration installation according to the invention can operate at other values ​​of pressure and temperature of superheated steam, reactor power, inlet temperature setpoint of the steam generator A and of the cogeneration exchanger M than those indicated and simulated previously.

[0122] The dimensional values ​​and control settings shown in the illustrated example can be modified to take into account: of a choice of control of the nuclear boiler on the setpoint values ​​of the temperatures and pressure T1, T2 and P2 at the terminals of the steam generator A; of a steam withdrawal at the outlet of the steam generator A, at the end of cogeneration at the highest temperature offered by the energy conversion cycle; of the use of a more advanced control than the PI regulators of the pumps H and K, in particular to reduce the operating range of T1 or improve the dynamic response; of a possible substitution of the variable speed pumps K and H by single speed pumps and as a corollary, of the regulation of the speed of the pumps by a regulation of the opening of valves, one of which is placed at the inlet of the steam generator A. List of cited references

[0123] [1]: "Improving energy efficiency by using cogeneration in electricity production"Jean-Marie Loiseaux, Henri Safa, Bernard Tamain, Réseau Sauvons le Climat. [2]: Cooke, D. (1983). "On Prediction of Off-Design Multistage Turbine Pressures by Stodola's Ellipse". J. Eng. Gas Turbines Power. Jul 1985, 107(3): 596-606 https: / / www.doi.org / 10.1115 / 1.3239778. [3]: Muhlhauser, H.J. (1978). "Steam Turbines for District Heating in Nuclear Power Plants". Nuclear Technology 38, pp. 113-119. [4]: Safa, H. (2021). "Heat recovery from nuclear power plants. Electric Power Energy Syst" 2012:553e9. https: / / doi.org / 10.1016 / j.ijepes.2012.04.052. [5]: Liese, E. (2014). "Modeling of a steam turbine including partial arc admission for use in a process simulation software environment". Journal of Engineering for Gas Turbines and Power 136.11. ISSN: 15288919. DOI: 10.1115 / 1.4027255. [6]: https: / / www.ge.com / content / dam / gepower-new / global / en_US / downloads / gas-new-site / resources / reference / ger-3705-ge-steam-turbine-design-philosophy-techology-programs.pdf. [7]: Vescovi, G. et al. (2023a).« Partial Arc Admission in an SMR Steam Turbine to Improve Load Following: Model Benchmark, Thermal-Hydraulic Mechanism Analysis and Application Case in a Full Rankine Cycle". https: / / doi.org / 10.13182 / NURETH20-41331. [8]: Korellis, S. (2012). "Cost Benefit Evaluation of HP Turbine Admission Schemes". Tech. rep. Electric Power Research Institute (EPRI). [9]: 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.

[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.

[11] : El Hefni B., Bouskela D. (2019). "Modeling and Simulation of Thermal Power Plants with ThermoSysPro." Springer International Publishing.

Claims

1. Cogeneration plant (100), intended for the production of electricity and, where applicable, heat, comprising: - at least one thermal power plant, in particular a pressurized water reactor (PWR) or a boiling water reactor (BWR), comprising: • at least one fluid circuit, comprising: at least one turbine comprising a high-pressure casing (C) and a low-pressure casing (F) connected to the high-pressure casing by at least one fluid branch, a high-pressure heater (L) connected in a closed loop to the high-pressure casing (C), a low-pressure heater (I) connected on one side by at least one fluid branch to the low-pressure casing (F) and on the other side by at least one fluid branch to a liquid reservoir (J), a condenser (G) connected on one side to the low-pressure casing and on the other side in a closed loop to the low-pressure heater, a high-pressure hydraulic pump (K) for circulating the liquid as a heat transfer fluid,a low-pressure hydraulic pump (H) to extract the condensate from the condenser (G) and convey it via the low-pressure heater (I); - an alternator mechanically coupled to the turbine, intended to be connected to an electrical network; - at least one second intermediate heat exchanger (M) connected in a closed loop to a withdrawal tap, made in the fluid branch between the high-pressure casing (C) and the low-pressure casing (F) of the turbine,and to the liquid reservoir (J) and connected to at least one cogeneration system with a heat requirement compatible with the temperature at the terminals of the second intermediate heat exchanger; - at least one stage arranged (B) at the inlet of the high-pressure turbine casing and adapted to achieve partial steam admission by angular sector into the high-pressure casing; - at least one stage arranged (E) at the inlet of the low-pressure turbine casing and adapted to achieve partial steam admission by angular sector into the low-pressure casing; - at least one steam pressure control system to control the partial steam admission into the stage at the inlet of the high-pressure casing and into the stage at the inlet of the low-pressure casing.

2. Cogeneration plant according to claim 1, the thermal power plant being a pressurized water reactor (PWR) comprising: - a first fluid circuit, called the primary circuit, comprising at least a first steam generator (A) as the first intermediate heat exchanger; - a second fluid circuit, called the secondary circuit, comprising the turbine whose high-pressure casing is connected to the first steam generator, the high-pressure heater (L) also connected in a closed loop to the steam generator (A) and to a liquid reservoir (J), the low-pressure heater (I), the condenser (G), the high-pressure hydraulic pumps (K) and the low-pressure hydraulic pump (H).

3. Cogeneration installation according to claim 2, the liquid reservoir being called a feed tank.

4. Cogeneration installation according to claim 2 or 3, the steam generator being of the single-pass type.

5. Cogeneration installation according to any one of the preceding claims, each arc inlet stage comprising, in parallel, four pilot-operated valves, each supplying one of the four arcs constituting the stator of the inlet stage.

6. Cogeneration installation according to any one of the preceding claims, the steam pressure control system(s) being of the Proportional Integral (PI) type or of the model-based predictive control (MPC) type.

7. Cogeneration installation according to any one of claims 2 to 6, the reactor vessel and the steam generator being configured as an integrated modular reactor (100) of the SMR type.

8. Cogeneration installation according to any one of the preceding claims, comprising, as a cogeneration system with a heat requirement compatible with the temperature at the terminals of the second intermediate heat exchanger, preferably a hydrogen production unit by EHT or any system requiring low-pressure steam.

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