JPS6256998B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a control rod drive mechanism that uses hydraulic drive to perform fine adjustment operations for startup and reactivity compensation in normal times, and rapid insertion in emergencies. The present invention relates to a nuclear reactor control rod position indicating device that can continuously indicate the position.

As shown in FIG. 1, the conventional hydraulic drive control rod position instruction is performed by operating a reed switch 7a located at the center of the control rod drive mechanism using a magnet 6 linked to the movement of the control rod 3. This signal indicates the position of the control rod 3. In FIG. 1, reference numeral 5 is an operating piston of the control rod drive mechanism 4, and reference numeral 8 is a hydraulic piping.

Further, when the normal control operation of the fuel assembly 2 provided in the core part of the reactor pressure vessel 1 is performed by the electric motor 21 attached to the end of the control rod drive mechanism 4, as shown in FIG. As shown in FIG. 3, the compressive displacement of the shock absorber (spring) 15 is taken out of the reactor vessel 1 by an extension member 16, and a permanent magnet 17 attached to the end of the extension member 16 operates a reed switch 7b installed outside. A signal was obtained when the emergency insertion was completed using water pressure. In addition, the code 20
is a sealing device, and numerals 22 and 23 are a screw shaft and a nut.

However, in view of the need to further enhance the safety of nuclear reactors, it has become necessary to indicate the position of the control rods even during emergency insertion or in intermediate positions that do not reach the fully inserted position. In the conventional method shown in FIG. 1, continuous instructions cannot be given because the reed switch 7a is turned on and off, and the accurate insertion time at the intermediate position cannot be determined. In the method shown in Figure 2, it is difficult to incorporate a position pointing device that can continuously indicate the position into the control rod drive mechanism due to its structure, and it is difficult to satisfy the above requirements by simply knowing the total insertion time. It was a long way off.

The present invention solves these problems by:
The object of the present invention is to provide a device that can continuously indicate the position of a control rod during emergency insertion.

The figure will be explained in detail below. FIG. 3 shows an embodiment of the invention.

In a boiling water reactor, the thermal output of a fuel assembly 2 placed in the core of a reactor pressure vessel 1 is controlled by operating a control rod 3, and a nuclear reaction in the fuel assembly 2 causes a nuclear reaction in the reactor pressure vessel 1. The water supplied to 1 is heated, and the generated steam drives a turbine generator to generate electricity.
If continued operation becomes dangerous due to an earthquake or failure of equipment that makes up a nuclear power facility,
Control rods 3, which have the effect of suppressing nuclear reactions, are rapidly inserted into the reactor core to bring about an emergency shutdown of the reactor.

The drive mechanism 4 for the control rod 3 includes a cylinder 4a and a piston 5 connected to the control rod 3, and is driven by introducing high pressure water into the cylinder 4a. This high-pressure water for driving is supplied by connecting a gas cylinder 44 (usually using nitrogen gas) to the accumulator 40 with a gas pipe 43, pressurizing the water separated by a piston 41 in the accumulator 40, and creating a water pressure pipe. 8 to the cylinder 4a. A scram valve 38 is interposed in the hydraulic piping 8 to control the start of rapid insertion. Among the above series of control rod drive mechanisms 4, the cylinder 4
A and a part of the hydraulic piping 8 are disposed outside the reactor containment vessel 36 so as not to be exposed to relatively high temperatures during operation.

Next, a flow meter 37 as a detector is set in the water pressure piping 8, and a position indicator (not shown) for calculating and indicating the output of the flow meter 37 is provided. Alternatively, the output of the liquid level gauge 42 that measures the water level of the accumulator 40 (the upper surface of the gas or the position of the piston 41) may be calculated and input to the position indicator.

The structure is constructed as described above, and the operation is as follows.
The method of nuclear power generation and the necessity of emergency shutdown are as described above. The rapid insertion of the control rods 3 is achieved by opening the scram valve 38 in response to an emergency insertion signal from the reactor safety protection system, thereby controlling the high pressure water in the accumulator 40 pressurized with high pressure gas via the hydraulic piping 8. Supplied to the cylinder 4a of the rod drive mechanism 4,
This is done by pushing up the piston 5. A nuclear reactor is stopped by inserting control rods 3 that have the effect of suppressing nuclear reactions, but the load placed on the fuel assembly 2 during shutdown is
There is a characteristic that the shorter the insertion time, the lighter the weight, and even if the insertion time is the same, it will be smaller if inserted early in the early stage and late in the early stage. Therefore, when conducting safety evaluations, it is necessary to understand the speed characteristics during rapid insertion of control rods.

In the present invention, when driving the control rod 3, we focus on the simple proportional relationship between the insertion stroke and the amount of high-pressure water used for driving, and detect the amount of driving water. In this system, the position of the control rod 3 can be immediately known, and furthermore, the position can be continuously indicated.

As a means for measuring the amount of high-pressure driving water used, the water level of the accumulator 40 is calculated using the output of the liquid level gauge 42. In addition, the output of the flow meter set in the high pressure pipe 8 is calculated and determined. The position of the piston 5, that is, the position of the control rod 3, can be determined from the determined amount of driving water. These calculations can be performed continuously and over time using existing techniques, and therefore the position can be indicated continuously and speed changes can also be indicated simultaneously.

As described above, the present invention continuously captures the operating characteristics of rapid insertion of control rods during an emergency shutdown of a nuclear reactor by detecting the amount of high-pressure water used to drive the control rods. Improve it significantly. Furthermore, with the method in which the electric motor is installed at the end, it is difficult to provide a position indicating device (such as a reed switch) in a straight line in the control rod drive mechanism over all positions during rapid insertion, but the device according to the present invention Since it can be installed outside the control rod drive mechanism, it is not subject to such restrictions and can be secured in a place with a good environment that is less affected by heat outside the reactor containment vessel, which greatly improves reliability. . This is a unique device that is extremely effective for controlling the rapid insertion of control rods for emergency shutdown of nuclear reactors.

[Brief explanation of the drawing]

1 and 2 are layout diagrams illustrating a conventional reactor control rod position indicating device, and FIG. 3 is a configuration diagram illustrating an embodiment of the reactor control rod position indicating device of the present invention. . 1... Nuclear reactor pressure vessel, 2... Nuclear fuel assembly,
3... Control rod, 4... Control rod drive mechanism, 4a...
Cylinder, 5... Piston, 8... Pressure piping, 3
6... Reactor containment vessel, 37... Flow meter, 38...
...Scram valve, 40...Accumulator, 41...
...Piston, 42...Liquid level gauge, 43...Gas piping, 44...Gas cylinder.

Claims (1)

[Scope of Claims] 1. A control rod is connected to a drive piston in a cylinder of a control rod drive mechanism, and water pressure from an accumulator pressurized by compressed gas is introduced into the cylinder of the control rod drive mechanism to drive the control rod. A nuclear reactor control rod position indicating device that drives a nuclear reactor control rod and is provided with a detector that detects the flow rate of driving water introduced, and that continuously indicates the insertion position of the control rod. 2. Claim 1, characterized in that the detector is constituted by a flow meter inserted into the drive water line between the accumulator and the control rod drive cylinder.
Reactor control rod position indicating device as described in Section 3. 3. The reactor control rod position indicating device according to claim 1, wherein the detector is composed of a liquid level gauge provided in the accumulator, and the indication is provided by the liquid level gauge.