JPH01114793A - Hydraulic device for driving control rod - Google Patents

Abstract

PURPOSE:To prevent the degradation in the function of a check valve and to assure water for scram in an accumulator over a long period of time at the time of pump tripping by closing a valve upon detection of the filling of the prescribed water for scram in the accumulator. CONSTITUTION:A withdrawal line 4 is connected via a scram output valve 7 to a scram discharge vessel 10 and an insertion line 3 is branched and connected via a scram inlet valve 6 to the accumulator 8 and a check valve 9. The check valve 9 is connected via a filling water line 18 and a filling water line base pipe 17 to a pump 15. A scram water filling device 50 is provided to the base pipe 17. The device 50 is constituted of a valve 50a, a differential pressure detector 50b which detects the differential pressure before and behind the valve as well as a pressure detector 50c which monitors the pressure on the accumulator side 8. The filling of the prescribed water for scram in the accumulator 8 is detected by the detector 50b which sends a shut signal to the valve 50a to shut the valve 50a. The factor to degrade the function of the check valve 9 by fluid oscillation, pulsation, etc., of the pump 15 in the ordinary time is thereby eliminated.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a control rod drive hydraulic system for a boiling water nuclear power plant, in which vibrations of fluid caused by water discharged from a pressurized source pump during normal operation. The present invention relates to a highly reliable control rod drive hydraulic system that protects check valves and the like from vibrations and pulsations, and more reliably prevents accumulator pressure drops during pump trips and the like.

(Prior art) In general, the power output of the core in the reactor pressure vessel is controlled by inserting and withdrawing the control rods into the core using a control rod g-motion mechanism provided corresponding to each control rod. It will be done.

The control rod drive mechanism is driven by a hydraulic control device provided corresponding to each control rod drive mechanism. If a nuclear reactor must be brought to an emergency shutdown for some reason, all control rods are inserted into the reactor core at once, a so-called scram operation.

In the scram operation, high-pressure water filled in an accumulator in the hydraulic control device is supplied to the lower surface of the piston of the control rod interlocking mechanism through the insertion line.

This is done by letting the water on the top of the piston escape through a withdrawal line into a scram drain container. A scram population valve and a scram outlet valve are provided in the insertion line and withdrawal line to the control rod drive mechanism, respectively, and these scram valves are kept closed by air pressure during reactor operation. Therefore, when a scram signal is generated by the reactor protection system, the air pressure acting on all the scram valves and outlet valves is released to the atmosphere all at once, causing the valves to open rapidly.

A conventional control rod drive hydraulic system is constructed as shown in FIG. 3, and a large number of control rod drive mechanisms 2 are attached to the bottom of a reactor pressure vessel 1.

An insertion line 3 and a withdrawal line 4 are connected to the control rod drive mechanism 2, respectively. The insertion line 3 communicates with the lower surface 5a of the piston 5, and the withdrawal line 4 communicates with the upper surface 5b of the piston 5. The other end of the insertion line 3 is branched via a scram inlet valve 6, and one end is connected to an accumulator 8, and the other end is connected to a filling water line 18 via a check valve 9. The other end of the drawing line 4 is connected to a scram discharge container 10 via a scram outlet valve 7. - The discharge side of the pump 15 connected to a power water source (not shown) is connected to a master control 16, and a filling water line main pipe 17 branches from between the pump 15 and the master control 16, and this filling water line The downstream side of the main pipe 17 is branched into a number of filling water lines 18 and connected to the check valve 9. Reference numeral 12 is a solenoid valve, and an air source (not shown) is connected to the primary side of the solenoid valve 12, and a communication pipe to the scram inlet valve 6 and the scram outlet valve 7 is connected to the secondary side of the solenoid valve 12. 13 is connected, and the solenoid valve 12 is set to 0N-OF by the scram signal.
It is connected to a power source (not shown) that supplies power.

In the control rod drive hydraulic system configured as described above, the solenoid valve 12 is normally turned on, and the scram inlet valve 6 and outlet valve 7 are kept fully closed by air pressure. pump 1
The water discharged from No. 5 is controlled by the master control 16 and becomes high pressure water, which pressurizes the accumulator 8 via the filling water line main pipe 17, compresses N2 gas by the piston 8a, and secures energy for scram.

(Problems to be Solved by the Invention) In the conventional control rod drive hydraulic system, if the pump 15 trips for some reason, the scram water stored in the accumulator 8 is held for a certain period of time by the check valve 9. However, if the seat leakage of the check valve 9 increases for some reason, the scram water in the accumulator 8 can only be held for a short time, and it is necessary to shut down the reactor when the scram water reaches the minimum required amount. Therefore, there was a possibility that the operating rate of nuclear power plants would be reduced.

The present invention has been made in consideration of the above-mentioned circumstances, and even if the pressurization source is lost due to a pump trip or the like, scram water is reliably secured in the accumulator for a long period of time, and unnecessary shutdown of the reactor is avoided. The purpose of the present invention is to provide a hydraulic control rod-driven hydraulic device that can control rods.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a reactor pressure vessel with a large number of control rod drive mechanisms for moving control rods in and out of the reactor core. The provided multiple hydraulic control devices and the control rod drive mechanism are connected through an insertion line and a withdrawal line, and the withdrawal line is connected to the scram discharge vessel through a scram outlet valve, and the insertion line is connected to the accumulator and the control rod drive mechanism through a scram outlet valve. The control rod-driven hydraulic system is connected to a pump via a filling water line and a filling water line main pipe, and a scram water filling device is provided in the filling water line main pipe.

(Function) This scram water filling device consists of a valve, a differential pressure detector that detects the differential pressure between the upstream and downstream sides of the valve, and a pressure detector that monitors the pressure on the accumulator side. When the upstream pressure and the downstream pressure of the accelerator are in balance, i.e., the accelerator is filled with a predetermined amount of scram water and the flow rate has disappeared, a closing signal is sent to the valve and the valve is closed. This eliminates unnecessary factors that normally cause the check valve to deteriorate due to fluid vibrations and pulsations of the pump, and also prevents backflow since the valve remains closed even when the upstream pressure decreases.

(Embodiment) Hereinafter, an embodiment of the control rod drive hydraulic device according to the present invention will be described with reference to the attached drawings.6 Fig. 1 is a system diagram showing an outline of the control rod drive hydraulic device according to the present invention. . This control rod drive hydraulic device has a large number of control rod drive mechanisms 2,
This control rod drive mechanism 2 is attached to the bottom of the reactor pressure vessel 1.

An insertion line 3 and a withdrawal line 4 are connected to the control rod drive mechanism 2, and the insertion line 3 is connected to the piston lower surface 5a.
The drawing lines 4 communicate with the piston upper surface 5b, respectively. The other end of the drawing line 4 is connected to a scram discharge container 10 via a scram outlet valve 7. The other end of the insertion line 3 is branched via a scram inlet valve 6, and one end is connected to an accumulator 8 and the other end is connected to a filling water line 18 via a check valve 9.

On the other hand, the discharge side of the pump 15 connected to a water source (not shown) is connected to the master control I6.
7 is branched, and via the scram water filling device 50,
The check valve 9 is branched into a number of filling water lines 18.
is connected to.

Further, reference numeral 12 is a solenoid valve that controls the artificial valve 6 and the outlet valve 7 of the blank 11, and the primary side of this solenoid valve 12 is an air source (
(not shown), and the secondary side is connected to the scram valve 6 and the outlet valve 7 through a communication pipe 13.

The power source of the solenoid valve 12 is connected by wiring to a power source (not shown) that turns NO' to OFF in response to a scram signal from the reactor protection system.

Next, the operation of the control rod drive hydraulic system according to the present invention will be explained. During normal operation of the boiling water reactor, the solenoid valve 12 is energized, and air pressure is supplied to the scram inlet valve 6 and the outlet valve 7 through the solenoid valve 12, and both valves are kept fully closed.

Therefore, high-pressure water pressurized by a pump 15 is supplied to the accumulator 8 through a scram water filling device 50 at a substantially constant pressure after being adjusted in pressure by a master control 16, and this high-pressure water is supplied via a piston 8a with nitrogen gas (N
2) can be compressed and stored. In this way, the accumulator 8 has sufficient water volume and pressure for scramming, and is ready for scramming at any time upon request.

Further, the structure and operation of the scram water filling device 50 will be explained with reference to FIG. The configuration of the scram water filling device 50 includes a valve 50a, a differential pressure detector 50b that detects the differential pressure between the upstream and downstream sides of the valve 50a, and a pressure detector 50c that detects the pressure downstream of the valve 50a. The opening and closing operations of the valves 50a are each performed by signals from a combination of the differential pressure detector 50b and the pressure detector 50c. This is summarized and shown in the table below.

(Leaving space below) According to the above table, during normal operation, the check valve 9 installed on the downstream side is not directly subjected to fluid vibration or pulsation due to the pump 15 because the valve 50a is closed. Even if the pump 15 trips, the valve 50a is closed and it is possible to prevent backflow from the downstream side, so even if the function of the check valve 9 deteriorates, the scram water stored in the accumulator 8 can be secured for a long time. can do. Therefore, even after a pump trip, the state in which scram is possible is maintained for a long time, and the safety of the reactor is ensured. Therefore, the cause of tripping of pump 15 can be investigated and countermeasures can be taken without stopping the reactor. It is possible to return to normal operation by starting.

〔Effect of the invention〕

As described above, the control rod-driven hydraulic system of the present invention prevents the function of check valves, etc., from deteriorating due to fluid vibrations and pulsations caused by the pump, maintains the integrity of the check valves, etc., and prevents the filling water pressure of the accumulator by pump tripping, etc. When the pressure source is lost, the outflow of the scram water stored in the accumulator can be prevented or reduced by using a double check valve, and scram water can be secured for a long time even after the pressure source is lost.

In other words, the scram function can be maintained for a long time even after the pressure source is lost, and the safety of the reactor is ensured, making it possible to investigate the cause of pump trips and take countermeasures without shutting down the reactor. As a result, it is possible to improve the operating rate and reliability of nuclear power plants.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram showing an embodiment of the control rod drive hydraulic system according to the present invention, Fig. 2 is a system diagram showing the configuration of the main parts of the present invention, and Fig. 3 is a conventional control rod drive hydraulic system. FIG. 8...Accumulator 15...Pump 18...
Filling line 50...Scrum water filling device agent Patent attorney Noriyuki Chika Yudo Ken Daishimaru

Claims (2)

[Claims] (1) In the control rod drive hydraulic system of a boiling water reactor,
The accumulator filling water line that connects the control rod-driven water pump and the accumulator of the water pressure control unit is closed when it detects that the accumulator is filled to the initial specified pressure, and then the accumulator filling pressure is constantly monitored to maintain the specified pressure. A control rod drive hydraulic system equipped with a scram water filling device that opens only when the following conditions occur. (2) The scram water filling device is composed of a valve, a differential pressure detector that detects the differential pressure between the primary side and the secondary side of the valve, and a pressure detector that detects the pressure on the secondary side, and the differential pressure 2. The control rod drive hydraulic system according to claim 1, wherein the valve is opened and closed by a combined signal from a detector and a pressure detector.