RU52243U1 - SERVO ACTUATOR OF AUTOMATIC AND MANUAL CONTROL OF MOVEMENT OF ABSORBING ROD AND EMERGENCY PROTECTION OF ATOMIC REACTOR TYPE RBMK - Google Patents

Abstract

A servo-drive for automatic and manual control of the movement of the absorbing rod and emergency protection of an RBMK-type nuclear reactor refers to the control of nuclear reactions in reactors using absorbing rods. The servo drive contains an electric motor 1 with an electromagnetic brake (EMT), the shaft of which through a reduction gear 2 is connected to an electromagnetic clutch 3 having a thermistor 20, and through it and an intermediate gear 4 to a shaft 5 of the rod displacement drum, which is connected to the hydraulic brake 6, consisting from a gear pump 7 and a load control inductor 8. The shaft 5 is connected via a safety clutch 14 to a selsyn gearbox 15, selsyn 16, a cam mechanism 17 and a microswitch 18. The shaft 5 is also connected to a removable mechanism manual movement 12 of special shape. Details of the electromagnetic clutch 3 are separated from the remaining circuits of the electric motor, brake mechanism, selsyn, microswitch. The end connection with the shaft of the gear pump 7 of the hydraulic brake 6 is made in the form of a cross-shaped coupling.

Description

Technical field

The invention relates to the management of nuclear reactions in reactors using absorbing rods, and in particular, to devices for moving absorbing rods in the channels of the reactor core to control a chain reaction and to quickly shut down the reactor in emergency protection mode. The invention is intended for use in high power RBMK type reactors.

The prior art.

The challenge in building nuclear power plants is the development and manufacture of reliable control mechanisms for nuclear reactors and their emergency protection, since these mechanisms work near the reactor core, where they are affected by high pressures, humidity, high temperature, radiation, vibration and shock loads. Control and protection mechanisms should ensure reliable, movement of the absorbing rods and the safety of the reactor installation.

Reliability of drives of absorbing rods is increased by simplifying kinematic schemes, using special materials, improving manufacturing and operating technology.

An analogue of the claimed technical solution may be the device described in the work of I. Ya. Emelyanov et al. - Fundamentals of design of control mechanisms for nuclear reactors. M. Atomizdat, 1978. p. 46-47. The reactor is placed in concrete

mine. It is a cylindrical masonry 8 meters high, consisting of vertical graphite columns, in the openings of which are technological (with nuclear fuel) and special channels, as well as channels for moving the absorbing rods of the control and protection system (CPS). This system of rods should provide starting and stopping of the reactor, stable automatic maintenance of power at a given level, compensation for fuel burn-out, emergency protection. The control mechanism is installed in the channels of the control system, through which water with a temperature of 40-70 ° C circulates from top to bottom. The air temperature above the CPS channel is 60 ° С (in emergency situations it reaches 250 ° С in 1 hour), relative air humidity - 98%.

A drum is mounted on the shaft onto which a flexible rod with an absorbing rod is wound (or wound). The shaft receives rotation from the electric motor through a gearbox, to which are also connected a selsyn of control of the position of the rod and cams acting on the limit switches. The drive parts are separated from the cooling water channel by lip seals on the drum shaft. A dial with an arrow is installed on the selsyn shaft — an indicator of the position of the absorbing rods. The motor shaft is equipped with a stop for engaging with a manual drive leash, which can be used to lock or lift the absorbing rods in case of failure of the electric motor or power failure. The drive is driven by a DC motor. An electric motor transmits rotation through a gear transmission to a drum onto which a flexible rod with an absorbing rod is wound (from which it is wound). Through the aforementioned connection, the rotation of the shaft is transmitted to the synchro-sensor and the cams acting on the microswitches of the extreme upper and lower positions of the absorbing rod.

Also known is a servo drive, described in detail in the Technical Description and Operating Instructions RBM-K7 Sat.151

MOT and IE, 1983, the Bolshevik plant, Leningrad. It uses basically the same kinematic scheme as the previously described analogue, but it also has a number of important differences. This servo-drive, which provides manual and automatic control and emergency protection of an RBMK-type nuclear reactor, contains a gear reduction gearbox that is rigidly connected to the motor shaft. Its output gear is connected to the input gear of the shaft of the drum moving the absorbing rod. The gearbox is four-stage, contains cylindrical and bevel gears.

The axis of the input gear of the drum moving the rod is shifted relative to the axis of the output gear of the gearbox by the sum of the radii of the gears mounted on them. Gears are located in one plane and are directly coupled. The motor shaft is connected to the shaft of the manual drive device by means of a detachable coupling consisting of two coaxial disks, one of which is rigidly connected to the motor shaft, the second to the shaft of the manual drive mechanism, the disks having opposite protrusions for mutual coupling, and one of the disks is mounted with the ability to move along the axis of the shaft.

In addition to the above, the servo drive contains a synchro sensor for connection with rod position control devices, limit and travel switches, and other elements necessary for the operation of the servo drive.

Taking into account modern requirements for the safety of a reactor installation, such a servo drive is not sufficiently reliable and durable, difficult to set up, poorly protected from failures in the manual control mode, and does not provide high performance.

A known servo-drive for automatic and manual control and protection of a RBMK-type nuclear reactor, comprising an electric motor, a power reducer, a drum with a tape, a braking device, an electromagnetic clutch and a hydraulic brake device in the form of a hydrobuffer, which is made separately from the drive and placed with the possibility of functioning only after full

the entry of the rod into the active zone of a nuclear reactor (patent application RU 2003113497/06).

Due to the constant increase in requirements for the speed of drives and the emergence of high-speed cluster rods, the speed of rotation of the gears of the gearbox is significantly increased. Gear connections of the gearbox, control systems, manual control, connections to the movement drum, at these speeds of rotation, loads and the aggressive environment in which they operate, wear out quickly. Their failures reduce the reliability of the drive during emergency protection. In addition, the moment of inertia of these elements does not allow you to quickly disperse and stop the cluster rod, and also leads to winding thrust on the drum in the opposite direction and its kink. This was manifested during tests, for example, of the second shutdown system at the 2nd block of the INPP.

Failures of the manual drive mechanism or signaling circuit of its inclusion reduce the safety of the reactor, preventing the introduction of rods into the reactor core.

The closest to the claimed technical solution in terms of technical essence and most of the essential features is a servo drive for the control and protection system of a nuclear reactor, containing an electric motor kinematically connected through a reduction gear, an electromagnetic clutch and a first intermediate gearbox shaft with a drum shaft, onto which a flexible tape is wound, at the end of which an absorbing rod is attached, a selsyn of controlling the position of the absorbing rod with a cam mechanism acting on the main switches, hydraulic brake assembly of the electric motor and manual control mechanism (patent SU 1748545, claimed 1989).

This servo, as well as the others described above, has the abovementioned disadvantages, namely:

- insufficient reliability of the drive in emergency input mode of the absorber rod,

- insufficient drive performance in emergency input mode of the absorber rod,

- the complexity of its assembly.

These disadvantages of the prototype are due to the following:

- the stop clutch is connected to the hydraulic brake by a reducer from a pair of bevel gears, and with a drum through a reducer from a pair of bevel gears and a pair of cylindrical gears. The use of additional conical pairs reduces the reliability of the drive. The magnitude of the final braking portion is determined by the position of the throttling hole on the cylinder body, which is blocked by the hydraulic brake nut and can only be changed when replacing the cylinder.

The aim of the invention is to increase reliability, speed, versatility, ensuring autonomy of braking with complete blackout of the drive, as well as providing manual control of the drive and simplifying its assembly.

This goal is achieved by the fact that the servomotor of manual and automatic control and emergency protection of an RBMK type nuclear reactor contains an electric motor kinematically connected through a reduction gear, an electromagnetic clutch and a first intermediate gear shaft with a drum shaft, onto which a flexible tape is wound, at the end of which is attached absorbing rod, selsyn of control of the position of the absorbing rod with a cam mechanism acting on the limit switches, a brake drum assembly with a tape, manual control mechanism. What is new is that the said electromagnetic clutch with external friction discs is connected to the motor shaft through a reduction gear, and internal friction discs are connected through the second shaft of the intermediate gear via a brake assembly to the cam mechanism, which is connected to selsyn via a selsyn gear. The selsyn reducer is connected via an additional safety clutch to the first shaft of the intermediate gearbox, and a non-linear thermistor is connected in series to the excitation coil circuit of the electromagnetic clutch.

The said hydraulic brake unit is placed in the total volume of the hydraulic fluid and contains a gear pump, which is connected to the second shaft of the intermediate gearbox, has a check valve and is connected via the control choke to the said cam mechanism. Such a hydraulic brake based on a gear pump with a non-linear load choke and a check valve, placed in one volume, serves to provide braking in emergency protection mode.

To increase the input speed and protect the rods from destruction, a change in the control throttle setting from the cam mechanism is used to further reduce the speed in the lower position of the absorber rod.

To increase the reliability and safety of manual control, the manual movement mechanism connected through the third shaft of the intermediate gearbox to the drum shaft on which the absorbing rod is attached is made removable, having a special shape in the docked state, which serves as a mechanical docking indicator.

Due to the high requirements for the reliability of the operation of the stop clutch, it must not be allowed that other elements are connected with it, the failure of which can lead to the failure of an emergency reset. Therefore, the secondary elements are separated from the important circuits and therefore the details of the electromagnetic clutch are separated from the remaining circuits of the electric motor, brake mechanism, selsyn, microswitch.

The end connection with the shaft of the gear pump of the hydraulic brake, made in the form of a cross-shaped coupling, provides a choice of eccentricity and ease of assembly.

SUMMARY OF THE INVENTION

The invention is illustrated by drawings, where figure 1 shows the kinematic diagram of the proposed servo.

A servomotor for manual and automatic control and emergency protection of an RBMK type nuclear reactor contains an electric motor 1 with an electromagnetic brake (EMT), the shaft of which is connected via an reducing gear 2 to the electromagnetic clutch 3, and through it the second (II) shaft of the intermediate gear 4 shaft 5 of the drum moving the rod. The shaft 5 of the rod displacement drum is connected to the hydraulic brake 6, which consists of a gear pump 7 and an integrated control throttle 8. To eliminate the inhibition of the upward movement of the absorbing rod 9, a check valve 10 is provided. The shaft 5 of the displacement rod 9 moving drum is arranged to rotate the drum 11 with a tape to which attached to the absorbing rod 9.

The shaft 5 of the drum for moving the absorbing rod 9 through the third (III) shaft of the intermediate gearbox 4 is connected to a removable mechanism for manual movement 12. The connection of the removable mechanism for manual movement 12 is controlled by an electrical signaling device 13, and the manual drive has a special shape in a docked state, which serves as a mechanical indicator the presence of a dock. For example, the manual movement mechanism 12 is removable with dimensions that do not allow the installation of protective plates when the manual drive is used on the drive.

The shaft 5 of the drum for moving the absorbing rod 9 through the first (I) shaft of the intermediate gearbox 4 and through the safety clutch 14 is connected to the syncron reducer 15. The syncron reducer 15 provides an indication of the position of the absorbing rod 9 by the synchro 16 and signaling the extreme positions of the absorbing rod 9 using a cam mechanism 17 and microswitches 18. The cam mechanism 17 also provides a change in the degree of braking of the hydraulic brake 6 when the absorbing rod 9 approaches the selected position by changing the hydraulic value Cesky integrated resistance regulating throttle 8. Servo

placed in the housing 19, with the exception of the manual movement mechanism 12.

In the circuit of the excitation coil (not shown) of the electromagnetic clutch 3, a nonlinear thermistor 20 is sequentially connected.

The intermediate gearbox 4 is three-stage, contains only cylindrical gears (to reduce the moment of kinematic inertia). The gear teeth of the intermediate gearbox 4 and the reduction gearbox 2 are straight. Due to the limited dimensions of the servo drive, the gears of the reducer, control systems, and connections to the drum 11 are made with the smallest module and tooth width, and to increase the strength and wear resistance, the gear teeth are nitrided.

The proposed servo operates as follows.

Regulation mode - (INPUT AND OUTPUT) of the absorbing rod.

The removable manual movement mechanism 12 is undocked from the drive, the signaling device 13 gives permission to the automatic control of the drive to the control circuit.

When a command is received to lift the absorbing rod 9 (command - OUTPUT), voltage is applied to the electric motor 1, the EMT is switched off. The rotational movement of the motor shaft through the gearbox 2, the electromagnetic clutch 3 is transmitted to the shaft 5 of the drum 11 of the movement of the absorbing rod 9. When the drum 11 is rotated, a tape is wound around it, leading the absorbing rod 9 out of the reactor core. In the hydraulic brake 6, the gear pump 7 receives hydraulic fluid through the check valve 10, operates without load and does not provide resistance to the movement of the absorbing rod 9. The cam mechanism 17, when the rod 9 reaches the upper position, triggers the upper limit switch 18, leading to the withdrawal of the command. When the OUTPUT command is removed, the motor 1 is turned off, its rotation and, accordingly, the lifting of the rod 9 is stopped, and the EMT is turned on.

With the ENTER command, the electric motor 1 is de-energized and the absorbing rod 9, suspended from the tape of the drum 11, falls down, unwinding the tape by the force of its own weight and untwisting the kinematics of the servo drive. The system of electrodynamic braking by the electric motor 1 is turned on, limiting the speed of lowering the absorbing rod 9. When the absorbing rod 9 reaches a predetermined lower position or removing the ENTER command, the EMT is turned on and the lowering stops. In the hydraulic brake 5, the gear pump 7 pumps hydraulic fluid through the integrated control throttle 8. Due to the low input speed of the absorbing rod 9 in automatic mode and the low speed of the gear pump shaft 7, the flow rate through the integrated control throttle 8 is small and does not have significant resistance to input absorbing rod 9.

Upon receipt of the EMERGENCY PROTECTION command (A3), regardless of the state of the electric motor 1 and its electromagnetic brake, the electromagnetic clutch 3 is turned off, the absorbing rod 9 falls, unwinding the tape of the drum 11 by the force of its own weight and untwisting the kinematics of the servo drive. Due to the disconnected electromagnetic clutch 3, the engine 1 and gearbox 2 are not untwisted. After accelerating to a high speed of movement of the rod 9, the gear pump 7 of the hydraulic brake 6 provides a large flow rate through the integrated control throttle 8. The throttle 8, having a non-linear characteristic, provides increased resistance at the output of the gear pump 7 for hydraulic fluid, thereby providing effective braking of the absorbing rod 9 to the desired input speed. When the absorbing rod 9 reaches a predetermined position (at the bottom of the active zone), the cam mechanism 17 activates the mode of increasing the hydraulic resistance of the integrated control choke 8 to the maximum, which provides a smooth increase in braking of the absorbing rod 9 and its impactless reaching the bottom of the channel

the reactor. Reducing mechanical loads on the rod 9 increases its resource.

The response current of the electromagnetic clutch 3 is much greater than the current that is necessary for the already worked clutch in the state of compression of the friction discs (there is no air gap between the poles of the clutch solenoid). Therefore, after the operation of the electromagnetic clutch 3, the current is reduced by a thermistor 20 with a positive temperature coefficient. If even a short-term signal comes to interrupt the current in the clutch for emergency protection, then the rod will be introduced into the reactor, even if the voltage on the electromagnetic clutch 3 is restored. Since the time constant of the thermistor 20 is longer than the time the rod 9 was introduced into the reactor, it will not have time to cool down (there is no current through it) and reduce its resistance. Therefore, a non-linear thermistor 20 is sequentially included in the excitation coil circuit of the electromagnetic clutch 3.

In a coil circuit of a multi-plate electromagnetic friction clutch 3, a non-linear thermistor 20 connected in series provides a decrease in current through the coil of the electromagnetic clutch 3 after pulling its disks, thereby increasing the reliability of input of the rod 9 in mode A3 (“remembering” mode A3). The decrease in current through the electromagnetic clutch 3 reduces its resistance and temperature of the drive, which further increases the reliability of the drive.

During routine maintenance, the drive is put into manual control mode. For this, a removable manual movement mechanism 12 is connected to the servo drive. In this case, the signaling device 13 instructs the ban on the control circuit of the motor 1. Now you can completely remove power from the servo drive. Holding the absorbing rod 9, when the brake clutch 14 and the electromagnetic clutch 3 are turned off, provides a self-braking mechanism for manual movement 12. During manual operation, the operator manually rotates the shaft of the manual mechanism

moving 12, which through the gear 4 rotates the shaft 5 of the drum moving the absorbing rod 9 in the reactor.

Thus, in comparison with the prototype, there is a cumulative positive effect:

- since the electromagnetic clutch 3 is directly connected to the hydraulic brake 6 without an intermediate gearbox and connected to the drum through a gearbox of two cylindrical gears, due to the reduction in the number of parts and simplification of the drive layout, we obtain higher reliability, ease of manufacture. Due to the reduction in the number of parts, the moment of inertia of the kinematic drive circuit operating when the electromagnetic clutch 3 is disconnected is also reduced in the EMERGENCY PROTECTION mode. Due to this, a higher speed of the drive is achieved, the requirements for the amount of braking force from the hydraulic brake 6 are reduced, and the hydraulic brake 6 is more compact.

A non-linear thermistor 20 is sequentially included in the coil circuit of a multi-disk electromagnetic friction clutch 3, which provides a decrease in current through the clutch coil after pulling its disks, thereby increasing the reliability of the rod input in A3 mode (“remembering” of A3 mode) and lowering the drive temperature.

In addition, in the invention, the beginning of the overlap of the regulating throttle 8 in the hydraulic brake 6 for maximum braking at the end of the stroke of the rod 9 in position in the reactor core is ensured by communication with the cam mechanism 17. The value of the final section of maximum braking is easily controlled by the restructuring of the cam mechanism 17. In the prototype, the value of the final the braking area is determined by the position of the throttle hole on the cylinder body, which is blocked by the hydraulic brake nut and can only be changed when replacing cylinder. Therefore, the invention allows the use of a servo drive for different types of absorbent rods, i.e. provides versatility of the drive.

In the invention, the used hydraulic brake 6 based on the gear pump 7 repeatedly pumps the volume of hydraulic fluid through the control throttle 8, which allows to reduce the volume of hydraulic fluid and reduce the dimensions of the hydraulic brake 6. (In the prototype, during the working stroke, the volume of hydraulic fluid is pumped once). By achieving a higher fluid velocity, the invention allows for increased cross-sections in the integrated control choke 8 and to reduce the working pressure in it, to reduce the volume of hydraulic fluid.

The increase in cross sections in the throttle provides more reliable operation in case of possible contamination of the hydraulic fluid. Reducing the working pressure allows you to reduce the size and weight of the integrated control throttle 8. A decrease in the amount of hydraulic fluid allows you to reduce the overall dimensions of the hydraulic brake 6 and simplify the layout of the drive.

To provide braking in emergency protection mode, a hydraulic brake based on a gear pump is used, which is characterized by an integrated nonlinear control and loading throttle and a non-return valve located in the same volume, which allows to simplify the manufacture and increase the reliability of the hydraulic brake and reduce the size.

A safety clutch connected between the drum with the tape and the selsyn gearbox serves to increase reliability and eliminate the influence of failures of secondary kinematic chains on the input of the rod in the EMERGENCY PROTECTION mode.

Claims (6)

1. Servo drive for automatic and manual control of the movement of the absorbing rod and emergency protection of an RBMK type nuclear reactor, comprising an electric motor with an electromagnetic brake kinematically connected through a reduction gear, an electromagnetic clutch and a first intermediate gear shaft with a drum shaft on which a flexible tape is wound, at the end which is attached to the absorbing rod, selsyn control the position of the absorbing rod with a cam mechanism acting on the limit switches, hydr drum assembly with a tape and a manual control mechanism, characterized in that said electromagnetic clutch (3) is connected to the electric motor shaft (1) by the external friction discs through the reduction gear (2) and the intermediate gear shaft through the second (II) internal gear discs (4) - with a brake unit (6) and with a cam mechanism (17), which is connected to a selsyn (16) through a selsyn reducer (15); the selsyn gearbox (15) is connected via an additionally inserted safety clutch (14) to the first (I) shaft of the intermediate gearbox (4), and a nonlinear thermistor (20) is connected in series to the excitation coil of the electromagnetic clutch (3). 2. The servo drive according to claim 1, characterized in that the hydraulic brake unit is placed in the total volume of the hydraulic fluid and contains a gear pump (7), which is connected to the second (II) shaft of the intermediate gearbox (4), has a check valve (10), and an integrated control choke (8) is connected to said cam mechanism (17). 3. A manual control servo according to claim 1, characterized in that it comprises a manual movement mechanism (12) connected via a third (III) shaft of the intermediate gearbox (4) to the shaft of the drum (5), on which an absorbing rod (9) is attached. 4. A manual control servo according to claim 3, characterized in that the manual movement mechanism (12) is removable, having a special shape in the docked state, serving as a mechanical docking indicator. 5. The servo drive according to claim 1, characterized in that the details of the electromagnetic clutch (3) are separated from the remaining circuits of the electric motor (1), brake mechanism, selsyn (16), microswitch (18). 6. The servo according to claim 1, characterized in that the end connection with the shaft of the gear pump (7) of the hydraulic brake (6) is made in the form of a cross-shaped coupling.