WO2015091222A1

WO2015091222A1 - Primary pump of a nuclear reactor

Info

Publication number: WO2015091222A1
Application number: PCT/EP2014/077454
Authority: WO
Inventors: Alexandra ITHURBIDE; Pierre Jacob
Original assignee: Societe Technique Pour L'energie Atomique Technicatome
Priority date: 2013-12-19
Filing date: 2014-12-11
Publication date: 2015-06-25
Also published as: FR3015590A1; FR3015590B1

Abstract

The invention relates to a primary pump (100) of a nuclear reactor, comprising: a through shaft (101); a first electric motor (120), referred to as primary motor, powered by a primary power supply network (10), said primary motor allowing the through shaft (101) to be set in motion; a second electric motor (130), referred to as auxiliary motor, powered by a secondary network (20), the auxiliary motor (130) making it possible to set the through shaft (101) in motion in the event of a failure of the primary power supply network (10) or the primary motor (120); said primary pump (100) being characterised in that the primary motor (10) and the auxiliary motor (20) are two electric motors formed by a rotor (122, 132) and a stator (121, 131), the rotors (122, 132) of the two motors (120, 130) being secured to the through shaft (101).

Description

PRIMARY PUMP OF A NUCLEAR REACTOR TECHNICAL FIELD OF THE INVENTION

The invention relates to a primary pump having a safety device for temporarily supplying the primary pump in case of failure of the main power supply network.

STATE OF THE PRIOR ART

The primary pumps are driven by three-phase electric motors powered by the main power grid. The loss of the main power causes the almost immediate shutdown (of the order of a few seconds) of the primary pumps. The direct consequence is the loss of the circulation of the primary fluid and thus the cooling of the reactor. In the very short term, the temperature of the primary fluid increases, which also increases the temperature of the fuel cladding. This increase in temperature is very rapid without circulation of the primary fluid and can lead to a boiling crisis and degradation of the fuel cladding.

It is however expected that the primary pumps temporarily maintain a sufficient flow in the heart to avoid excessive heating of the fuel following the phenomenon of calefaction. The decrease in heat flux is in fact lagging behind that of the primary flow rate taking into account the intervention times of the emergency stop system: instrumentation delay, drop time of the clusters, etc.

Therefore, the primary cooling pumps comprise a device allowing, in case of loss of power, to continue to ensure the circulation of the primary coolant in the reactor core, at least for a period of long enough to cover the triggering time of the safety actions.

A first solution is to store energy in the form of mechanical energy during normal operation of the primary pump through a flywheel placed on the shaft connecting the primary pump to the engine . Thus, the mass in rotation of the flywheel provides sufficient inertia to continue to ensure the circulation of the primary fluid, at least degraded manner, during the period of time corresponding to the triggering of the safety actions, generally of the order of several tens of seconds.

However, the use of these inertial groups leads to significantly increase the masses and volumes of the rotors of the primary pumps, which becomes problematic for programs constrained congestion.

These inertial groups are also noise generators and therefore constitute sources of acoustic indiscretion penalizing in certain strategic uses of these reactors, such as for example a nuclear reactor of a submarine. In addition, the integration of such flywheels is problematic in a moving vehicle, especially because of the generated Coriolis forces. Finally, the slowdown of a rotating mass is very fast in the first moments. Indeed, in a few seconds the speed, and therefore the primary flow, is divided by a factor of two, which forces during the design to define an initial speed before significant stop. Thus, in practice the flow of the primary fluid is high in part to allow this significant slowdown when the loss of the main power supplies.

Another solution consists in installing oversized pumping at nominal operating conditions, thus making it possible to cope with sudden decreases in the flow rate of the primary fluid taking into account the counter-reactions and safety actions occurring a few tens of seconds after the beginning of the spike.

Another solution is to use secondary or auxiliary motors, also called pony engines, which are powered by an auxiliary power source different from the main power supply. Such a solution is for example proposed in EP 001 7685. In this document, the pony engine serving as a secondary engine is connected to the primary engine by means of a mechanical clutch, the pony engine being powered by a secondary source such as, for example, batteries or a diesel generator. The mechanical clutch is a free wheel associated with an inertial mass to reduce the slowing of the pump after engagement of the clutch. Thus, the solution presented in this document does not overcome the mechanical clutch and the presence of an inertial flywheel.

SUMMARY OF THE INVENTION

In this context, the invention aims to provide a primary pump to solve the problems mentioned above and to overcome the effects of the use of a mechanical energy storage means and a mechanical clutch between different engines (main engine and pony engines).

To this end the invention relates to a primary pump of a nuclear reactor comprising:

- a crossing tree;

a first electric motor, said main motor, powered by a main supply network, said main motor enabling the movement of the traversing shaft;

- A second electric motor, said auxiliary motor powered by a secondary network, the auxiliary motor for ensuring the movement of the traversing shaft in case of failure of the main supply network or the main motor;

said primary pump being characterized in that the main motor and the auxiliary motor are two electric motors formed by a rotor and a stator, the rotors of the two motors being integral with the traversing shaft.

The term "solidaire" means that the rotors of the two motors and the traversing shaft form a single piece in motion. The two rotors are thus physically coupled to the shaft permanently and without the use of a mechanical clutch for coupling or decoupling the rotor of the auxiliary motor of the traversing shaft during normal operation of the primary pump. In other words, the main motor and the auxiliary motor share the same mechanical shaft on which the two rotors are arranged. For this purpose, the mechanical shaft advantageously has two distinct sections, a first section forming the rotor of the main motor, and a second section forming the rotor of the auxiliary motor.

Thanks to the invention, the storage of mechanical energy to provide the backup power function is minimized or completely eliminated. This makes it possible to make gains on the size, the dimensioning and the cost of the different systems (core of the reactor, primary pump, pressurization).

The invention also relates to a feed system of a primary pump characterized in that the system comprises:

a primary pump according to the invention;

a main driving device formed by a main supply network for electrically supplying the main motor of the primary pump during normal operation;

an auxiliary drive device formed by an auxiliary supply network and a variable speed drive for electrically supplying the auxiliary motor of the primary pump.

The feed system according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: - during normal operation, the auxiliary motor is fed continuously, at a minimum frequency and / or at a predetermined voltage (s) so that the movement of the shaft passing through the pump is ensured by the main motor;

- The auxiliary drive device provides power to the auxiliary motor so as to ensure the continuity of the movement of the traversing shaft in case of failure of the main motor or the main drive device;

the main drive device and / or the auxiliary drive device comprises a static energy converter; the auxiliary supply network is independent of the main supply network; the auxiliary supply network is powered by one or more sources formed by batteries or supercapacitors;

the auxiliary motor is used to recharge or maintain said sources of the auxiliary supply network when the movement of the traversing shaft is ensured by the main motor;

the auxiliary motor of the primary pump is an asynchronous motor driven by the auxiliary drive device at a predetermined frequency and voltage which are lower than those necessary to drive the primary pump when the main motor is in operation; the auxiliary motor of the primary pump is an asynchronous or synchronous or direct current motor driven in torque by the auxiliary drive device so that the movement of the traversing shaft of the primary pump carried out by the main motor in Normal operation switches to frequency or speed control when the power supply frequency of the main power supply or the speed of the main motor reaches a low threshold.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will emerge on reading the description which follows, with reference to the single appended figure which schematically illustrates a primary pump according to the invention comprising a dual motor, powered by two electrical networks. different.

DETAILED DESCRIPTION OF AN EMBODIMENT

The figure schematically illustrates a primary pump 1 00 according to the invention comprising a double motor 120, 130, powered by two different electrical networks: a main power supply network 1 0 and an emergency power supply network 20 having different sources 22 and independent of the sources (not shown) of the main supply network 10.

The primary pump 1 00 comprises a through shaft 1 01 connected in the lower part to the wheel of the primary pump 1 02. The twin engine of the primary pump 1 00 is formed by a main electric motor 120 and an auxiliary electric motor 1 30, the two motors sharing the same shaft, that is to say the shaft 1 01 .

The main electric motor is an electric motor powered by the main supply network 1 0. It is formed by:

A stator January 21 having a winding connected to the main supply network 10 possibly via a variable speed drive 123, and possibly a converter January 1;

A rotor 1 22 secured to the traversing shaft 1 01. The auxiliary motor 1 30 is provided to ensure sufficient circulation of the coolant in the reactor core for the period of time necessary to trigger the safety actions. Advantageously, the auxiliary electric motor (and its drive) may be dimensioned only to maintain the setting in motion of the shaft 01 of the pump 1 00 for a given period of time, in case of failure of the main network of supply 1 0, or in case of failure of the main motor 120, or in the event of failure of the variable speed drive 1 23 or the converter 1 1.

This auxiliary electric motor 1 30 is also formed by: · a stator January 31 having a coil connected to the auxiliary supply network 20 via a variable speed controller 1 33 and optionally a converter 21;

A rotor 1 32 integral with the traversing shaft 1 01.

The two electric motors 1 20, 1 30 may be for example synchronous motors, or asynchronous motors, or DC motors.

The two rotors 1 22, 1 32 are integral with the same shaft 1 01. Unlike primary pumps having two motors, the shaft 1 01 through the invention has no clutch suitable for coupling or decoupling the auxiliary motor 1 30 from the shaft 1 01 when it is driven by the main motor 120.

Thus, the traversing shaft January 01 is constituted by a first section forming the rotor 1 22 of the main motor 1 20 which allows the setting in motion of the shaft 1 01 during normal operation and a second section forming the rotor 1 32 of the auxiliary motor 1 30 which ensures the continuity of the setting in motion of the shaft 1 01 in the event of failure of the main installation (for example the main supply network 1 0, or the main motor 1 20, or the drive 1 23, or the converter 1 1). The primary pump 1 00 according to the invention therefore comprises two separate and independent drive devices: a main drive device formed by the main network 1 0, the converter 1 1, the main variable speed controller 1 23 supplying the main motor 1 20 and an auxiliary drive device formed by the auxiliary network 20, the converter 21, the auxiliary speed controller 1 33 supplying the auxiliary motor 1 30.

The main drive device of the primary pump 100 is sized (for example power) to permanently drive the pumping system of the primary pump 1 00 in so-called normal situations. The auxiliary drive device of the primary pump 1 00 can be sized (for example power or thermal) only to drive the pumping system of the pump 1 00 in case of failure of the main drive device. The auxiliary drive device can thus be of a simpler design, and more robust than the main drive device. For example, the variable speed controller 133 of the auxiliary drive device does not need to reduce the harmonics in the motor by the implementation for example of a high frequency switching device (HF) by modulation of width of pulse and filter. The variable speed drive 1 33 may, for example, simply feed the low frequency square signal to the auxiliary motor 1. Advantageously, the auxiliary motor 1 30 is continuously supplied by the auxiliary supply network 20 via the drive controller. speed 1 33 with voltage and frequency parameters so that the setting in motion of the shaft passing through the pump is provided solely by the main motor 1 20, that is to say that the driving torque of the auxiliary motor 1 30 is zero. The permanent supply of the auxiliary motor 1 30 overcomes a long phase of starting the auxiliary engine during the detection of main network failure and a further risk of failure of the auxiliary motor 1 30 during this phase starting.

During normal operation of the primary pump 1 00, only the main motor 1 20 supports the load of the pumping system. In the event of a fault, or simply in the event of a drop in the main motor control parameters (voltage, frequency), the auxiliary motor recovers the load and ensures the necessary cooling.

The control of the auxiliary motor 1 30 can be done in direct control depending on the supply voltage (voltage of the auxiliary network 20 or power sources 22) or depending on the energy available in the sources of power. 22.

The deceleration of the speed of the auxiliary motor 1 30 is electronically controlled according to the needs and as a function of the tripping time of the safety actions.

The sources 22 of the auxiliary network 20 may be electrical energy storage systems such as batteries, or supercapacitors. Such energy storage sources 22 are less cumbersome and less burdensome than storing energy in the form of mechanical energy by using an inertial flywheel.

Advantageously, during normal operation of the primary pump 1 00, the auxiliary motor 1 30 can be used to recharge or maintain the energy storage means 22.

The invention also has the following advantages:

• The load variation of the auxiliary motor can be used as a detector of the loss or failure of the main network. • the propagation of faults in common mode between the two power supplies is decoupled by the inertia of the mechanical shaft of the pump;

• The primary pump as described is particularly suitable for use in flooded rotor.

Claims

Primary pump (100) of a nuclear reactor comprising:

a traversing shaft (101);

- a first electric motor (120), said main motor, powered by a main power supply network (10), said main motor for moving the traversing shaft (101);

- A second electric motor (130), said auxiliary motor, powered by a secondary network (20), the auxiliary motor (130) for ensuring the movement of the traversing shaft (101) in case of failure of the network main supply (10) or main motor (120);

said primary pump (100) being characterized in that the main motor (120) and the auxiliary motor (130) are two electric motors formed by a rotor (122; 132) and a stator (121, 131), the rotors (122 , 132) of the two motors (120, 130) being integral with the traversing shaft (101).

Feeding system of a primary pump characterized in that the system comprises:

- A primary pump according to one of the preceding claims;

a main driving device formed by a main supply network (10) for electrically supplying the main motor (120) of the primary pump (100) during normal operation;

an auxiliary drive device formed by an auxiliary supply network (20) and a variable speed drive (133) for electrically supplying the auxiliary motor (130) of the primary pump (100).

Primary pump supply system according to claim 2, characterized in that during normal operation the auxiliary motor (130) is continuously supplied at a predetermined frequency and / or voltage (s) so that the movement of the shaft (101) of the pump is ensured by the main motor (120). Feeding system of a primary pump according to one of claims 2 to 3 characterized in that the auxiliary drive device provides power to the auxiliary motor so as to ensure the continuity of the setting in motion of the shaft through (101) in the event of failure of the main motor (120) or the main driving device.

Feeding system of a primary pump according to one of Claims 2 to 4, characterized in that the main drive and / or the auxiliary drive comprises a static energy converter (1 1, 21). and / or a variator (123).

Feeding system of a primary pump according to one of claims 2 to 5 characterized in that the auxiliary supply network (20) is independent of the main supply network (10).

Primary pump supply system according to one of Claims 2 to 6, characterized in that the auxiliary supply network (20) is supplied by one or more sources (22) formed by batteries or supercapacitors.

Primary pump supply system according to claim 7, characterized in that the auxiliary motor (130) is used to recharge or maintain said sources (22) of the auxiliary supply network (20) when in motion of the traversing shaft (101) is provided by the main motor (120).

Primary pump supply system according to one of Claims 2 to 8, characterized in that the auxiliary motor (130) of the primary pump (100) is an asynchronous motor driven by the auxiliary drive device at a frequency and at a predetermined voltage which is less than that required to drive the primary pump (100) when the main motor (120) is in operation. Feeding system of a primary pump according to one of claims 2 to 8 characterized in that the auxiliary motor (130) of the primary pump (100) is an asynchronous or synchronous or DC motor driven in torque by the auxiliary drive device so that the movement of the main pump through shaft provided by the main motor (120) in normal operation switches to frequency or speed regulation when the mains power supply frequency power supply (10) or the speed of the main motor (120) reaches a low threshold.