WO2002084670A1

WO2002084670A1 - Device for emergency power supply to auxiliary components of a nuclear power plant and use method

Info

Publication number: WO2002084670A1
Application number: PCT/FR2002/001244
Authority: WO
Inventors: Philippe Degard
Original assignee: Framatome Anp
Priority date: 2001-04-13
Filing date: 2002-04-09
Publication date: 2002-10-24
Also published as: EP1386325A1; FR2823592A1; JP2004530874A; ZA200307951B; KR20040002912A; CA2445185A1; FR2823592B1; CN1507632A

Abstract

The invention concerns a device for emergency power supply comprising a fuel cell (2) supplied with hydrogen and with air or with pure oxygen from specific hydrogen and compressed air circuits of the nuclear plant or specific oxygen circuits. It can also be provided in the form of a hybrid system comprising the fuel cell (2) and an installation of super-capacitors arranged in parallel or in series relative to the fuel cell and via an appropriate interface (chopper for example). The fuel cell can be a PEMFC type cell. The fuel cell can in particular ensure power supply of the motor of a pump injecting water into the joints of a primary pump of a pressurised water nuclear reactor. It can also be used for supplying certain monitoring and control circuits of the nuclear plant in case of loss of normal power supply of said circuits. The power of the inventive systems can reach 500 kVA.

Description

Emergency power supply device for auxiliary components of a nuclear power plant and method of operation

The invention relates to a device for emergency power supply of auxiliary components of a nuclear power station and in particular of a power station comprising a nuclear reactor cooled by pressurized water and a method for producing an emergency power supply, in the event of a failure of the main power supply to the auxiliary components of the nuclear power plant.

Many auxiliary components of a nuclear power plant used in particular for monitoring, controlling or backing up main components of the power plant must be permanently supplied with electric current in order to be able to perform their functions during all the operating phases of the nuclear power reactor. the power plant.

For example, equipment such as circuit breakers and contactors, reversing contactors for motorized valves and solenoid valves installed in the electrical rooms of the nuclear power plant must be able to be permanently supplied, to be available in all circumstances, so as to ensure satisfactory operation of the nuclear reactor.

These materials are supplied, for example, with 125 V direct current supplied by the nuclear power plant, from a 380 V AC network and from a rectifier. In the event of an incident or accident resulting in an interruption of the power supply to the nuclear power plant, it is necessary to keep the functions of the electrical equipment as defined above.

To ensure continuous operation in all circumstances of this electrical equipment, batteries are usually used such as lead or cadmium batteries which can deliver, for example, a nominal voltage of 125 V with a maximum current of 250 A.

In normal operating mode of the central unit, the batteries do not output any current except in the case of occasional peaks in current consumption resulting from the supply of a large number of components. In the event of an interruption to the normal power supply to the power plant, the batteries must alone ensure the supply of energy to the electrical equipment, such an incident or accident which may, for example, be a local failure of the equipment supply means electric. In this case, the batteries must be able to supply electrical equipment for at least one hour without the voltage at the battery terminals falling below a limit voltage of around 105 V, the nominal voltage being 125 V .

The size and mass of the batteries capable of performing this function are extremely important, in order to achieve the desired minimum autonomy of the power supply.

Nuclear reactors cooled by pressurized water have a primary circuit in which pressurized water is circulated by primary pumps comprising a pump impeller which is rotated inside the volute of the pump by a shaft connected to the pump motor.

The shaft of the primary pump crosses several series of seals between its part connected to the motor, at atmospheric pressure, and its end part connected to the pump wheel, inside the volute receiving l water under very high pressure and at very high temperature.

To ensure constant integrity of the seals, it is necessary to introduce pressurized water into the first series of seals, to avoid successive destruction of the seals, causing a leak of primary fluid outside the primary circuit. It is therefore necessary to ensure a constant supply of cold water to the joints to avoid any risk of destruction and leakage of primary water.

In normal operation, a high-power charge pump supplies the joints with cold water. In the event of a loss of normal electrical supply, the injection of water into the first series of pump seals is ensured by a positive displacement pump driven by an electric motor which is generally supplied with three-phase 380 V alternating current. In the event of an interruption in the 380 V power supply from the nuclear power plant (main network, auxiliary network and generator sets), a backup power supply for the water injection pump motor must be provided in the primary pump seals. It has been proposed, for example, to use turbo-alternators supplied by the steam generators of the nuclear power station which are started in the event of an incident or accident resulting in an interruption of the supply of electric current to the injection pump.

The time required to start the turbo-alternators can cause an injection fault in the seals of the primary pump. In addition, turbo-alternators must be checked periodically and their maintenance can be costly.

The starting of the turbo-alternators for the production of driving current for the injection pump must be carried out within a maximum of two minutes after the loss of normal electrical supplies, which corresponds to the maximum operating time of the primary pump without supplying pressurized water to the seals. This period is defined to avoid any thermal shock on the alumina coating of the seals of the number 1 series of the primary pumps. Experience has shown that turbo-alternators driven by steam drawn from steam generators can exhibit certain start-up failures, due in particular to the presence of water in the circuits.

It is therefore desirable to have emergency power supply means for auxiliary components of a nuclear power plant which can be easily integrated into the circuits and components of the plant, which have a longer operating autonomy than that of batteries and which can be commissioned quickly and safely.

The object of the invention is therefore to propose a device for the emergency power supply of auxiliary components of a nuclear power plant which is compact, operates very safely and which has good autonomy, while requiring reduced maintenance operations. . For this purpose, the emergency power supply device according to the invention comprises at least one fuel cell supplied with gas containing hydrogen and with gas containing oxygen from at least one reserve and at least one respective circuit of hydrogen-containing gas and oxygen-containing gas.

In order to clearly understand the invention, there will now be described by way of example, with reference to the appended figures, an electrical supply device according to the invention and its use for the emergency supply of a water injection pump in the joints of a primary pump or an electrical monitoring and control panel.

FIG. 1 is a diagram showing the installation of an emergency power supply device constituted by a fuel cell, in the circuits of a nuclear power plant comprising a pressurized water nuclear reactor. Figure 2 is a schematic view showing the theoretical constitution of a fuel cell using hydrogen as fuel.

Figure 3 is a diagram showing the use of the emergency power supply device of Figure 1 for the supply of a water injection pump in the joints of a primary pump of the nuclear reactor and injection system auxiliaries in the primary pump seals.

FIG. 4 is a detailed diagram of the electrical supply of an electrical supply panel for components of a nuclear power plant.

In Figure 1, there is shown schematically an emergency power supply device according to the invention, generally designated by the reference 1 and the tanks and circuits of the nuclear reactor used to operate the power device electric using a fuel cell.

The device 1 mainly comprises several elements constituting fuel cells such as 2a and 2b placed in series and constituting several stages of production of electric current.

The device 1 also comprises different circuits intended respectively to supply hydrogen and oxygen to all of the fuel cells, to cool the cells, to recycle hydro- gene not used and the elimination of water formed or introduced into all fuel cells.

In Figure 2, there is shown, schematically, a cell of a fuel cell of the PEMFC type using hydrogen as fuel and air as oxidant.

The cell 3 shown in FIG. 2 is a unitary fuel cell cell intended to explain the operation of the fuel cell.

The cell 3 comprises a hydrogen inlet compartment 3a, an air inlet compartment 3b and between the compartments 3a and 3b, the elements of the cell constituted by a first electrode 4a (anode), a second electrode 4b (cathode) and between the electrodes 4a and 4b, a membrane 6 of polymer material impregnated with water constituting a solid electrolyte. Catalyst 4'a (or 4'b) deposited on the porous electrode 4a (or 4b) lets the gases pass through the cell 3.

The electrodes are produced by depositing on a conductive carbon fabric a mixture of platinum carbon powder. The anode 4a is supplied with hydrogen (or gas containing hydrogen) and the cathode 4b is supplied with gas containing oxygen, for example air. The fuel cell allows direct conversion into electrical energy, of the free energy of a chemical oxidation-reduction reaction using the hydrogen and oxygen introduced into the fuel cell.

Upon contact with anode 4a, the hydrogen molecules transform into hydrogen ions (protons) with the release of electrons.

The hydrogen ions pass through the electrolyte as shown by the arrows 8 in FIG. 2, to reach the cathode 4b at the level of which the hydrogen ions and oxygen molecules are present. Under the effect of the catalyst contained in cathode 4b, the hydrogen ions ensure a reduction of the oxidizing oxygen of the air introduced into the fuel cell with absorption of electrons. The reaction produces water in the form of vapor, as shown by arrow 9. The electrons produced by the anodic reaction can circulate in a circuit of use 10 of the fuel cell, up to the cathode 4b. There is thus obtained a potential difference between the anode and the cathode and a current flow in the operating circuit 10 of the fuel cell. The theoretical potential of the fuel cell is 1.23 V, which corresponds to the redox potential of the O ₂ / H ₂ O couple.

As account must be taken of the losses inside the fuel cell, this voltage is in fact between 0.6 V and 0.9 V per element as shown in FIG. 2. The membrane 6 is a membrane of cationic type, so that it lets through only the hydrogen ions H ⁺ coming from the anode 4a into which the molecular hydrogen H ₂ is introduced (arrow 7'a). oxygen

0 ₂ of the air introduced into the second compartment 3b of the fuel cell

3 is introduced into the cathode 4b, as shown by the arrow 7'b. In fact, air introduced into compartment 3b passes through the entire fuel cell and entrains water vapor or water formed in the fuel cell, so that it is evacuated as well by the compartment 3a that by the compartment 3b of the fuel cell a mixture comprising water vapor or water formed in suspension in the sweeping air, as represented by the arrows 11 a and 11 b.

To obtain sufficient electrical power from the fuel cell to provide an emergency power supply, it is necessary to juxtapose a plurality of cells as shown in FIG. 2. For example, in the case of an emergency power supply for a injection pump in the primary pump seals, it is necessary to have a power of approximately 150 kW which can be obtained by juxtaposing a number of unit cells, the number of which is defined by the continuous voltage to be obtained and whose the section (surface of the electrodes) is defined by the value of the current which must be produced. For example, to obtain the power of 150 kW, one can use two hundred and fifteen PEMFC type cells as shown in FIG. 2, the section of which has a width of 420 mm and a height of 420 mm. Between two successive cells is disposed a bipolar plate 5a attached to an anode and a respective cathode of the successive cells. The bipolar plates ensure the distribution of gases (hydrogen and oxygen) between the cells 3, the collection of electrons from one cell to the next and the evacuation of the products formed by the reactions in the fuel cell (in particular the water vapor), and the evacuation of the heat of reaction produced in the cell.

Each of the unit cells comprises a bipolar plate, an anode, a membrane and a cathode, the second bipolar plate being common to two successive cells juxtaposed.

A PEMFC cell of the usual type has a thickness of the order of 10 mm, so that, taking into account the dimensions of the end compartments, the entire fuel cell has a length of approximately 2300 mm. Units such as 2a and 2b shown in FIG. 1 are therefore juxtaposed in very large numbers, to constitute a fuel cell 2 having the electrical characteristics desired for ensuring the emergency power supply.

The fuel cell is supplied with hydrogen and air, at the ends of each cell, at the level of a bipolar plate or of compartments 3a and 3b.

The hydrogen supply to compartment 3a and the bipolar plates is ensured by means of a hydrogen circuit 12 connected to an inlet nozzle 13 of compartment 3a of the fuel cell and to the bipolar plates such as 5a.

Nuclear power plants generally have their own hydrogen storage and distribution means which constitute a first part 12a of the hydrogen supply circuit 12 of the fuel cell. This part 12a of the circuit 12 comprises one or more hydrogen storage tanks 14 under high pressure (for example 197 bars), an expansion plate 15 of the hydrogen up to a distribution pressure (for example 7 bars) and a stop valve 15a for ensuring the distribution of hydrogen, for example in the volumetric and chemical control circuit of the nuclear reactor (arrow 16a) or in a circuit of use of the operator of the power station (arrow 16b).

The circuit 12 for supplying the fuel cell 2 is for example produced by adding to the part 12a of the hydrogen circuit existing on the nuclear power plant a part of the circuit 12b comprising a second plate 17 for expansion of the hydrogen (by example up to 3 bars), a stop valve 17a, a non-return valve 17b, and a pipe 18 for joining the part 12a of the circuit downstream of the valve 15a to the nozzle 13 of the fuel cell. - corn.

The hydrogen distribution circuit 12 further includes a recycling part 12c, ensuring the recovery of hydrogen not consumed in the fuel cell by means of a second nozzle 13 'of the first compartment 3a, the hydrogen recovered. being reintroduced into the pipe 18 connected to the nozzle 13 for entering the hydrogen in the first compartment 3a.

The recovery circuit 12c comprises a separator 19 making it possible to separate the excess hydrogen from the water vapor formed in the fuel cell, the water vapor being condensed and then evacuated in a recovery circuit for the purges 20 of the reactor. nuclear.

On the hydrogen recovery circuit 12c, are also placed a non-return valve 21a, a stop valve 21b and a circulation pump 22 electrically supplied by the fuel cell.

Depending on the power requested from the fuel cell, a more or less significant quantity of hydrogen is recovered which can be recycled so that the quantities of hydrogen taken from the storage reserve 14 are reduced.

It is thus possible to modulate the power operation of the emergency power supply device and optimize the consumption of hydrogen. Instead of a hydrogen supply specific to the nuclear power plant, a hydrogen circuit specific to the fuel cell could be used. The air supply to the second compartment 3b of the fuel cell and the bipolar plates supplying the oxidizing oxygen and ensuring the scanning of the fuel cell is carried out by a circuit 24 connected to a nozzle 23 of the second compartment 3b by a pipe 25. The circuit 24 comprises a reservoir 26 of compressed air which is a usual component used in a nuclear power plant. For example, a buffer tank 26 of compressed air with a capacity of 4 m ^{3 is used} , allowing the supply of air to the cell under a pressure of 3 bars.

Between the reservoir 26 and the nozzle 23 for injecting air into the fuel cell are arranged, on the pipe 25, an expansion plate for the compressed air 27 (for example up to a pressure of 3 bars) and a stop valve 27a. Instead of air, it is possible to use a pure oxygen circuit comprising pressurized reserves (P = 190 b), one or two expansion devices and shut-off valves following the same principle as the distribution of hydrogen.

The use of oxygen improves the efficiency of the fuel cell.

A circuit 28 connected to a nozzle 23 'opening into the second compartment 3b of the fuel cell makes it possible to evacuate the water vapor formed in the fuel cell in mixture with air blown into the fuel cell via circuit 24. Circuit 28 includes a separator 29 allowing the water formed in the purge recovery circuit 20 of the nuclear reactor to be removed.

The air separated from the vapor is evacuated to the atmosphere by an exhaust pipe from the circuit 28.

The fuel cell 2 heats up because part of the energy produced by the chemical reaction inside the fuel cell is released in the form of heat.

It is necessary to cool the fuel cell and for this cooling water coming from a demineralized water circuit 30 of the nuclear power plant is injected into specific conduits of the fuel cell, by means of an injection circuit 31 comprising a pump 32, supplied with current by the fuel cell, for circulating demineralized water in circuit 31 and the fuel cell. Demineralized water could also flow under the effect of gravity from a tank at a level higher than that of the fuel cell.

The water circulating in the fuel cell is recovered by a circuit 33 connected to the circuit 20 for recovering the purges of the nuclear reactor.

The recovery circuit 33 includes branches connected to the anode parts and to the cathode parts of the fuel cell 2 by means of bipolar plates. A stop valve 33a is arranged on the circuit 33, to ensure, when it is opened, the evacuation of the recovered water, in the purge circuit 20.

A fuel cell heater 44 (shown as a coil) keeps the fuel cell at operating temperature when the fuel cell is not used for backup power . This reduces the starting time of the fuel cell, when it becomes necessary to use it. A circuit for using the electric current produced by the fuel cell is designated by 10. The circuit is connected to the cathode and anode parts of the fuel cell by means of the bipolar plates, so that a direct current flows in the use circuit 10 at a constant voltage.

The circuit for recovering the electric current produced under direct voltage by the fuel cell is connected, as shown in FIG. 3, to the components of the nuclear power plant for which continuity of the electrical supply is desired in the case of a incident or accident.

In FIG. 4, the normal and emergency supply means of an electrical panel 40 and of components using electrical current have been shown such as solenoid valve coils, motors or contactors of the nuclear power plant or else fuel cell auxiliaries (e.g. pumps), via circuits 41.

The normal supply means 42 of table 40 include in particular a supply unit connected to a supply network. alternating current of the nuclear power station and comprising a rectifier for obtaining direct current, for example at a voltage of 125 V.

The emergency supply means comprise in particular the fuel cell 2 and an installation comprising at least one super-capacitor 38, the structural and functional characteristics of which will be described below. The fuel cell 2 and the installation of supercapacitors 38 are connected in parallel to the electrical panel 40 and to the general supply line connected to the circuits 41 and placed in series on the supply line, with respect to the normal supply. 42. On the connecting branches of the normal supply 42, of the fuel cell 2 and of the super-capacitors 38, to the general supply line are placed respective circuit breakers or relays 37, 39 and 43.

When there is normal supply to the switchboard and user circuits, the circuit breakers 37 and 43 are closed and the circuit breaker 39 open. The table 40 and the user circuits 41 are supplied by the normal supply means 42.

The super-capacitor (s) 38 are kept charged.

In the event of loss of normal supply, the emergency power supply is put into service by opening the circuit breaker 37 and closing the circuit breaker 39.

The panel 40 and the user circuits 41 are supplied first by the super-capacitors 38 then by the fuel cell 2 which is started up for the production of electric current, during the discharge of the super-capacitors 38. This thus ensures perfect continuity of the power supply. The super-capacitors are dimensioned to guarantee the supply of the panel 40 during the starting of the fuel cell.

The interface between the super-capacitors 38 and a busbar of the power supply can be provided by a reversible chopper 38a which makes it possible to maintain a constant busbar voltage during the discharge of the super-capacitors. Depending on requirements, a DC or AC power supply can be produced at any voltage, for example 220V, 125V,

48 V or 30 V, using electronic conversion means which may include inverters, transformers or rectifiers or fuel cell units with suitable characteristics.

The circuit 10 of a fuel cell 2 can also supply, via an inverter (or several inverters), one or more low voltage motors, for example supplied with 690 V or 380 V three phase.

In particular, as shown in FIG. 3, the circuit 10 can be used to ensure the continuity of the water supply to the seals of at least one primary pump of the nuclear reactor, by means of the positive displacement pump 35 rotation by the electric motor 35a, in the event of an interruption of the normal electric supply to the pump 35.

The electric motor 35a for driving the pump 35 is supplied with three-phase alternating current at a voltage of 380 V, by means of a converter of the direct current supplied by the circuit 10 of the fuel cell into three-phase alternating current.

The converter 36 consists of an inverter.

Preferably, super-capacitors placed in parallel with respect to the fuel cell make it possible to achieve a faster start-up of the injection pump in the event of loss of normal supply, during start-up and ramp-up. of the fuel cell.

The emergency power supply to the auxiliary components 34 and 35 of the nuclear reactor can be ensured by the fuel cell as long as hydrogen fuel is available in the tanks of the nuclear power plant.

The duration of use of a PE FC type fuel cell can be of the order of at least 10,000 hours. Therefore, the duration of continuous use of the emergency power supply device by fuel cell is limited only by the capacity of the hydrogen reserve.

Since fuel cells can have high power densities, they are capable of providing adequate power. tation of switchboards and circuits for extended periods of time and completely independently.

The total size of a fuel cell capable of supplying a switchboard and a set of user components is significantly smaller than the size of the batteries (in 220V, 125V, 48V or 30V) usually used, for one hour autonomy.

One can use a fuel cell (of reduced size) to supply each of the monitoring and control panels of the nuclear power plant or, on the contrary, use a fuel cell of greater power and of larger dimension to supply a set of monitoring and control panels.

Another application of fuel cells as an emergency supply means relates to the supply of the water injection pump to the joints of a primary pump as described above. A fuel cell has the other advantage of not requiring any external energy source to start or operate and thus being completely autonomous.

In addition, the starting up of the fuel cell is very rapid and the fuel cell only really works when it is necessary to supply electric current to supply the auxiliary components of the nuclear reactor, following a loss of 'power supply, which is advantageous in the case of all applications where the fuel cell is used as a backup source of electrical energy.

The invention is not limited to the embodiment which has been described. In order to improve the dynamics of the backup system, it is possible to use, as described above, an installation of super-capacitors placed in series or in parallel with the fuel cell. Such an installation makes it possible to instantly supply the power necessary to the various user components, during the increase in power of the fuel cell. The super-capacitors also make it possible to supply power, in the presence of a consumption peak. The invention can therefore implement a hybrid system consisting of a fuel cell and one or more super-capacitors. We call super-capacitors, capacitors which can provide by discharge much higher powers than conventional capacitors, with higher time constants.

The super-capacitors which can be used in the case of the invention are based on the principle of the double-layer capacity. Supercapacitors are made up of two porous electrodes, an electrolyte and a porous separator. The production of capacitors can call on various technologies. The electrodes can be made of carbon, deposited polymers or hydrated metal oxides. The electrolyte used can be aqueous or of organic type.

In general, the super-capacitors used have the advantage of having excellent charge-discharge cyclability (> 100,000), a small footprint and requiring little maintenance.

In all cases, the super-capacitors must be accompanied by circuits ensuring a charge between the phases of use.

It is possible to use, in place of a fuel cell of the PEMFC type, other types of fuel cell, for example a fuel cell of one of the following types: alkaline cell (AFC) with or without membrane, cell phosphoric acid PAFC, MCFC molten carbonate cell, SOFC solid electrolyte cell, DMFC methanol cell. Likewise, any other electrical energy storage device such as batteries can be used, in place of super-capacitors, to provide instant power to users in the event of normal power loss.

However, PEFMC type batteries which consume only hydrogen and air or pure oxygen are particularly well suited to be integrated into the circuits of a nuclear power plant.

Provision may be made to use, as fuel for the fuel cell, instead of pure hydrogen, a gas or any other substance containing hydrogen which may be available in a nuclear power plant circuit, to supply the cell fuel, either directly or through a reformer. Likewise, instead of air, pure oxygen can be used from a dedicated reserve, or any other gaseous mixture containing oxygen at various contents.

The invention however preferably uses a fuel cell which can be supplied directly with hydrogen or with oxygen-containing gas from the circuits of the nuclear power plant.

The invention is not limited to the emergency supply of water injection pumps in the joints of the primary pumps of a pressurized water nuclear reactor but can be applied to compensate for any loss of electrical supply in a nuclear power station and to ensure a continuous electrical supply of auxiliary components of the power station comprising motors or pumps of small dimensions, circuit breakers, automaton relays or any other low voltage equipment supplied with direct current or alternating current. The power of installations powered by the hybrid system, fuel cell + super-capacitor can range up to 500 kVA.

It is then possible to supply pumps for supplying emergency food water to the reactor steam generators, to cool the reactor in the event of total loss of electrical supplies. The motors of these pumps are supplied with 690 V.

Indeed, in the case of a reactor of recent design, the standby turbo-pumps are replaced by two standby motor-driven pumps which it is necessary to supply in these situations.

Two diesel-powered generators are currently being used only for back-up power. These small diesel engines could each be replaced by at least one fuel cell.

Claims

CLAIMS 1.- Emergency power supply device for auxiliary components (34, 35, 35a) of a nuclear power station, characterized in that it comprises at least one fuel cell (2) supplied with gas containing l hydrogen and oxygen-containing gas from at least one reserve and at least one respective circuit of hydrogen-containing gas and oxygen-containing gas.

2.- Device according to claim 1, characterized in that it further comprises an intermediate electrical energy storage device (38), placed in parallel or in series with respect to the fuel cell, to instantly provide emergency electric current, during a start-up and ramp-up phase of the fuel cell (2) or in the presence of consumption peaks.

3.- Device according to claim 2, characterized in that the intermediate electrical energy storage device consists of at least one super-capacitor (38).

4.- Supply device according to any one of claims 1 to 3, characterized in that the fuel cell is a cell of one of the following types: PEMFC, alkaline cell (AFC) with or without mem- brane, PAFC phosphoric acid cell, MCFC molten carbonate cell, SOFC solid electrolyte cell, DMFC methanol cell.

5.- Device according to any one of claims 1 to 4, characterized in that the fuel cell (2) is supplied with hydrogen from a supply circuit (12) comprising a first part of the circuit ( 12a) usual supply of circuits (16a, 16b) of the nuclear power plant and a second part (12b) connecting the first part (12a) to the fuel cell.

6.- Device according to claim 5, characterized in that the first circuit part (12a) comprises at least one reservoir (14) for storing hydrogen under pressure, a first hydrogen expansion plate ( 15) and a first stop valve (15a) and that the second part of the hydrogen supply circuit (12) comprises a second hydrogen expansion plate (17) and a second stop valve (17a) .

7.- Device according to any one of claims 5 and 6, characterized in that the circuit (12) for supplying hydrogen to the fuel cell (2) comprises a complementary circuit (12c) for recycling hydrogen not consumed in the fuel cell (2).

8.- Device according to any one of claims 1 to 4, characterized in that the fuel cell (2) is supplied with hydrogen by a circuit specific to the fuel cell (2).

9.- Device according to any one of claims 1 to 8, characterized in that it comprises a circuit (24) for supplying air to the fuel cell (2) comprising a buffer tank (26) for storage of compressed air from the nuclear power station connected to the fuel cell via a pipe on which is disposed a compressed air expansion plate (27) and a stop valve (27a).

10.- Device according to any one of claims 1 to 9, characterized in that it further comprises a circuit (31) for cooling the fuel cell (2) by means of demineralized water a demineralized water tank (30) from the nuclear power plant.

11.- Device according to any one of claims 1 to 10, characterized in that it comprises at least one water recovery circuit in the fuel cell connected to a purge recovery circuit (20) of the nuclear plant.

12.- Device according to any one of claims 1 to 11, characterized in that it further comprises a heating device (44) to maintain the fuel cell (2) at an operating temperature to reduce a fuel cell start-up time.

13.- Emergency power supply method for a drive motor of a water injection pump in seals of the drive shaft of a primary pump of a nuclear reactor , characterized in that, in the event of an interruption of the normal electrical supply to the injection pump (35), the motor (35a) of the water injection pump (35) is supplied ) in the joints of the primary pump via a fuel cell (2) and a converter (36) from direct current to three-phase alternating current such as an inverter.

14.- Method for emergency power supply of at least one electrical panel (40) for monitoring and controlling auxiliary components of a nuclear power plant, characterized in that the electrical panel (40) is supplied from of current produced by a fuel cell (2) and an installation of super-capacitors (38) used only for supplying the panel (34) or for supplying several electrical panels (34).

15.- Method of supplying electricity to at least one pump for supplying emergency food water to steam generators of the nuclear reactor, for cooling the nuclear reactor, in the event of total loss of electric supply, characterized by fact that the food water supply pump is supplied with electric current, using a fuel cell (2) with a power of the order of 500 kVA.