Control rod drive includes an electric drive and a toothed rack

Abstract

Systems for controlling and protesting nuclear reactors. A drive of an emergency safety rod of a nuclear reactor includes an electric drive, a reduction gear, and a rack-and-pinion gear. The electric drive contains a contactless electric motor based on permanent magnets, which is installed in the housing of the electric drive with a motor rotor position sensor, and a reduction gear for changing the rate of rotation of the electric drive. A toothed rack is installed along the axis of the rack-and-pinion gear in order to provide for the reciprocating motion of a system absorber rod connected thereto. A toothed electromagnetic clutch having a contactless current supply is installed on an inner shaft of the rack-and-pinion gear, enabling the rigid and simultaneous mechanical coupling of half-couplings, and the drive contains a reverse-motion coupling, a rack-separation spring and toothed rack position sensors.

Claims

1. A drive of an emergency safety rod of a nuclear reactor, comprising: an electric drive; a reduction gear; a rack-and-pinion gear; wherein the electric drive includes an electric motor installed in a housing of the electric drive with a motor rotor position sensor, wherein the reduction gear is operable to change a rate of rotation of the electric drive for a required speed and power performance of the electric drive; a toothed rack installed along a axis of the rack-and-pinion gear to provide for a reciprocating motion of a system absorber control and a protection rod connected thereto; a toothed electromagnetic clutch having a contactless current supply installed on an inner shaft of the rack-and-pinion gear enabling a simultaneous mechanical coupling of half-couplings; and a reverse-motion coupling that is interlocked with a rack pinion, a rack-separation spring and toothed rack position sensors; wherein a normally closed electromagnetic brake is installed on a shaft of the electric drive.

2. The drive according to claim 1, wherein the electric motor comprises a contactless electric motor including permanent magnets.

3. The drive according to claim 1, wherein the motor rotor position sensor is contactless.

4. The drive according to claim 3, wherein the motor rotor position sensor comprises a contactless synchro resolver.

5. The drive according to claim 1, wherein a magnet is installed in an upper part of the toothed rack.

6. The drive according to claim 1, wherein an axis of the electric drive is parallel to an axis of the toothed rack.

7. The drive according to claim 1, wherein an inner cavity of the electric drive is leak-tight.

8. The drive according to claim 1, wherein the electric drive is a brushless electric motor.

9. The drive according to claim 1, wherein a rack-separation spring is installed above the toothed rack.

10. The drive according to claim 9, wherein the rack-separation spring is composite.

11. The drive according to claim 1, wherein inductive or contactless sensors are used as toothed rack position sensors.

Description

LIST OF DRAWINGS

(1) FIG. 1 shows a nuclear reactor emergency safety rod drive, general sectional view.

(2) FIG. 2 shows a gearing diagram of the emergency safety rod drive from FIG. 1.

(3) FIG. 3 shows section A-A from FIG. 1.

(4) FIG. 4 shows detail B from FIG. 1.

IMPLEMENTATION OF THE INVENTION

(5) The CPS emergency safety rod drive is rack-mounted on the nuclear reactor housing. The drive includes an electric drive (1) with a motor stator (3) fixed in its housing (2), and a motor rotor (4) installed on the motor shaft (5) by means of two rotating bearings (6). A resolver rotor (7) is installed on the motor shaft; its stator (8) is fixed in the housing (2). The contactless resolver serves a motor rotor angular position sensor. An electromagnetic brake (9) and reduction gear (10) are also installed on the electric drive shaft.

(6) The rack-and-pinion gear includes a housing (11) and a toothed rack (12) installed along the housing axis. An absorber rod (13) is mounted at the end of the toothed rack (12). A magnet (14) is installed at the top of the toothed rack (12), which also serves as a toothed rack (12) guide. The magnet (14) is designed to send signals to the inductive limit switches (15) installed outside the housing case (11). The toothed rack (12) axis is parallel to the axis of the electric drive.

(7) An electromagnetic clutch (16) is installed on the shaft (17) of the rack-and-pinion gear, its housing is secured against rotation. In addition, a gear half-coupling (18), that is also an overrun clutch (19) sleeve, is mounted on the input element of the electromagnetic clutch. An overrun clutch hub (20) is fixed on the shaft.

(8) The torque is transmitted through the reduction gear (10) and clutch half-couplings (16) to the rack pinion (21).

(9) A rack-separation spring (22) is installed at the top of the toothed rack (12) with a CPS absorber rod (13). The upper end of the spring (22) rests against the cover of the rack-and-pinion gear, and the lower end rests against the magnet sleeve (14). The rack-separation spring (22) consists of several springs divided by special bushings (23). A shock absorber (24) is installed in the rack-and-pinion gear housing (11).

(10) The device operates in the following manner.

(11) When an emergency protection warning signal is generated, the CPS absorber rod (13) is inserted into the core, and the electric drive is switched to lowering operation. When the shaft rotates for lowering operation, torque is transmitted through the reduction gear (10) and half-couplings of the electromagnetic clutch (16) to the rack pinion (21) converting the rotary motion into linear. When the absorber rod (13) reaches the lower limit switch (15), the electric drive is shut down. The brake clutch is deenergized and the motor drive is slowed down preventing upward motion of the toothed rack (12) with the CPS absorber rod (13).

(12) According to an emergency protection alarm signal, the electromagnetic clutch (16) is deenergized, the moving part of the electromagnetic clutch is opened by the membrane spring built in the electromagnetic clutch housing, the drive train between the rack-and-pinion gear shaft (17) and electric drive shaft (5) is opened. As a result of the interlocked opening, the toothed rack (12) with the CPS absorber rod (13) is dropped into the reactor core by gravity and the separation spring (22). The spring is released along the full length of the absorber rod insertion, minimizing its insertion time, and the overrun clutch (19) prevents impact jumping of the absorber rod (13).

(13) The drive gearing allows to drop the absorber rod from any intermediate position.

(14) When the CPS absorber rod (13) is loaded (in case of scram during blackout) according to a signal for lifting operation from the lower position sent to the upper inductive limit switch (15), the process is as follows. Voltage is applied to the inductive limit switches (15), and the electromagnetic clutch (16). The drive train transmitting motion to the rack pinion (21) from the motor through the reduction gear (10) is closed. The electric drive is switched to lifting operation. The overrun clutch is inactive as rotation of its hub (20) and sleeve (19) is synchronized. The toothed rack (12) with the CPS absorber rod (13) moves up to the upper limit switch. Then the electric drive is switched off. In addition, the brake clutch (9) is also deenergized, the electric drive shaft (5) is slowed down, slipping of the CPS absorber rod (13) is excluded.

(15) When lifting the CPS absorber rod (13) inserted without interruption of power supply, the electromagnetic clutch (16) shall be actuated. The motion of the CPS absorber rod (13) is similar to the mode described above.

(16) The claimed design of the CPS emergency safety rod drive makes it possible to improve design reliability, reduce the time of negative reactivity insertion in case of an emergency, thus, substantially improving safety and reliability of the reactor plant as a whole.