JPH0125439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control rod drive hydraulic device that supplies control rod drive water to a hydraulic control rod drive mechanism of a boiling water nuclear reactor.

A control rod drive hydraulic system for a boiling water nuclear reactor is, for example, as shown in FIG. That is, the insertion pipe c and the withdrawal pipe d are connected to the control rod drive mechanism b installed at the bottom of the reactor pressure vessel a,
A water pressure control unit e is connected to the insertion pipe c and the withdrawal pipe d. This water pressure control unit e is equipped with a directional control valve g that selectively pressure-feeds control rod drive water sent from a water supply source f to either the insertion pipe c or the withdrawal pipe d.
h is a drainage basin. In addition, an accumulator i for scram water pressure feeding is connected to the insertion pipe c,
Scram water for rapid control rod insertion can be pumped into insertion pipe c during scram. j,k
is a scram valve that is opened during scram, and the scram valve k on the outlet side is connected to a scram water discharge header m via a scram water discharge pipe l, and this header m is connected to a scram water discharge container n. .

In the conventional control rod drive hydraulic system configured as described above, control rod drive water is sent to the insertion pipe c when the control rod is inserted, and on the other hand, the control rod drive water is sent to the withdrawal pipe d when the control rod is withdrawn. Also, during scram, scram valves j and k are opened, and high-pressure scram water is rapidly inserted from accumulator i into pipe c.
for rapid insertion of control rods.

However, until the scram signal is released and the furnace operation is restarted, the scram valves j and k are closed.
Since the valve is in an open state, in this conventional device, if there is a problem such as damage or leakage in the pull-out pipe d, the scram water discharge header m, or the scram water discharge container n, the water in the pipe will leak. There is a risk of leakage. If such a situation occurs, it is necessary for a worker to close the manual valves p and q installed in the water pressure control unit e, but it may take time for the valves to close and the leakage may progress. There is also the issue of radiation exposure for workers. moreover,
There is also the problem that it is difficult to detect damage or leakage of the scram discharge header m or the like.

This invention was made based on the above circumstances, and its purpose is to prevent leakage from the damaged location even if the control rod drive mechanism pull-out piping, scram water discharge header, scram water discharge container, etc. are damaged. The object of the present invention is to provide a control rod-driven hydraulic device that can minimize the amount of damage and maintain safety.

That is, in this invention, an isolation valve is provided between the control rod drive mechanism and the hydraulic control unit, and this isolation valve is opened when the control rod is fully inserted.
Even in such a valve closed state, whenever a scram signal is input, the isolation valve is given top priority and automatically opened due to the generation of this scram signal.

The present invention will be explained below with reference to an embodiment shown in FIG. In the figure, 1 is a boiling water reactor pressure vessel, which houses a reactor core 2. And the pressure vessel 1
A hydraulic control rod drive mechanism 3 (only integrally shown as a representative) for inserting and removing control rods into and from the reactor core 2 is provided at the bottom of the reactor core 2 . A control rod drive hydraulic device that drives the control rods is connected to each control rod drive mechanism 3.

This control rod drive hydraulic system will be explained below. In the figure, 5 is an insertion pipe connected to the control rod drive mechanism 3, and 6 is a withdrawal pipe.These pipes 5 and 6 penetrate the reactor containment vessel wall 7 and are led out of the reactor containment vessel. , is connected to a directional control valve 9 provided in the water pressure control unit 8. This directional switching valve 9 is configured to selectively force feed the control rod drive water sent from the water supply source 10 to either the insertion pipe 5 or the withdrawal pipe 6. 1
8 is a drainage basin.

Further, the water pressure control unit 8 has an accumulator 13 having a pressurized nitrogen tank 11 and a water tank 12. This accumulator 13 is
It is connected to the insertion pipe 5 via a scram water supply pipe 15 equipped with a scram valve 14 on the inlet side.
Moreover, manual gate valves 16 and 17 are provided in the insertion pipe 5 and the withdrawal pipe 6.

Furthermore, a scram water discharge pipe 20 is connected to the drawn pipe 6. This scram water discharge piping 20 is connected to a scram water discharge header 22 via a scram valve 21 on the outlet side.
is connected to the scram water discharge container 23. Note that the scram water discharge pipe 20a of another control rod drive hydraulic device is also connected to the header 22. 24 is a scram drain valve.

An isolation valve 25 is installed in the middle of the above-mentioned drawing pipe 6.
is provided. As the isolation valve 25, an electric valve using a motor, an electromagnetic valve, or a valve operated by a cylinder mechanism, which can be opened and closed by remote control, is used. The isolation valve 25 is installed near the containment vessel wall 7 located upstream of the extraction pipe 6. During normal reactor operation, this isolation valve 25 is key-locked at the fully open position.
This prevents the valve from being closed due to erroneous operation. In addition, even if the isolation valve 25 is closed by mistake for some reason, an interlock has been set up so that when the reactor scram signal is input, the valve will always be given top priority and automatically opened when the reactor scram signal is input. be.
Therefore, during scram, the isolation valve 25 is always in the open state.

Furthermore, when the control rod is in the fully inserted state, the isolation valve 25 is automatically closed by this fully inserted position signal. This control rod fully inserted position can be detected using, for example, a permanent magnet and a reed switch provided in the control rod drive mechanism 3.

Furthermore, a temperature sensor 2 is installed in the extracted piping 6 near the control rod drive mechanism 3, for example in the reactor containment vessel.
6 is attached. This temperature sensor 26 detects the surface temperature of the drawn pipe 6, and the third
As shown in the figure, a leak warning signal is output when the temperature of the drawn pipe 6 reaches a predetermined set temperature T, for example, around 140°C.

That is, this set temperature T can be determined as follows. Generally, when water is not flowing in the drawn pipe 6 during nuclear reactor operation, the surface temperature of the drawn pipe 6 is a constant value (for example, 23° C.). However, when high-temperature reactor water and control rod drive water from the control rod drive mechanism 3 flow into the withdrawn piping 6 during a scram, etc., the withdrawn piping 6
The surface temperature of the piping begins to rise gradually, and during the time t when the scram operation ends and the flow of this high-temperature water stops, the surface temperature of the piping rises, for example, by several tens of degrees Celsius, and then the temperature rise stops. However, if there is a leak in the drawn pipe 6, the scram water discharge header 22, the scram water discharge container 23, etc., high temperature water continues to flow in the drawn pipe 6, and the pipe surface temperature also continues to rise. Therefore, the set temperature T is the temperature that exceeds the normal temperature and reaches a temperature sufficient to determine that a leak has occurred. If the set temperature T is exceeded, it is determined that a leakage accident has occurred.
A warning signal is output to the central control room.

Next, the operation of the control rod drive hydraulic system configured as described above will be explained. When the control rods are withdrawn during normal reactor operation, the drive water sent from the water supply source 10 is transferred to the withdrawal piping 5 via the directional control valve 9.
By sending the control rods to the reactor core 2, the control rods can be lowered and withdrawn from the reactor core 2. On the other hand, when inserting a control rod, the control rod can be pushed up by switching the directional switching valve 9 and forcefully feeding drive water to the insertion pipe 5. In addition, during normal reactor operation, the scram valves 14 and 21 are fully closed, and the isolation valve 25 and manual gate valve 1 are closed.
6 and 17 are open.

In this state, if a leak occurs in the drawn pipe 6, the scram valve 21, the scram water discharge header 22, etc., and the surface temperature of the drawn pipe 6 exceeds the set temperature T as described above, the temperature sensor 26 When temperature abnormality is detected, a warning signal is output to the central control room, and the isolation valve 25 is automatically closed by remote control from the central control room. Therefore, leakage of reactor water and control rod drive water flowing through these pipes and the like can be minimized. However, even in this case, the isolation valve 25 is in an interlock state so that when a scram signal is input, the isolation valve 25 can be given top priority and automatically opened in response to the scram signal.

On the other hand, when a scram signal is input due to a reactor abnormality, etc., the scram valves 14 and 21 open, and the scram water stored in the water tank 12 of the accumulator 13 is sent to the insertion pipe 5 at high pressure, and the control rods are rapidly moved. Fully inserted and the furnace operation is stopped. At this time, the scram water discharged through the drawn pipe 6 is sent to the scram water discharge header 22 through the scram water discharge pipe 20 and stored in the scram water discharge container 23. When it is detected that the control rods have been fully inserted, the isolation valve 25 is closed. Therefore, even if the pull-out piping 6 or the scram water discharge piping 2
0, the scram water can be prevented from leaking even if the header 22 or the discharge container 23 is damaged or leaks. In particular, since the scram valve 21 is kept in the open state until the scram signal is canceled and the furnace operation is restarted, it is important to block off the downstream side of the isolation valve 25 as described above in order to prevent leakage. It is extremely effective. However, in this case isolation valve 25
is in a state where the valve can be opened preferentially by this scram signal when the scram signal is output again. Therefore, the isolation valve 25 is always open during scram, and the scram operation can always be performed reliably.

As described above, the control rod drive hydraulic system can reliably prevent leakage from piping, equipment, etc. located downstream of the isolation valve 25, and in the case of this embodiment, the leakage output from the temperature sensor 26 can be prevented. The warning signal allows the isolation valve 25 to be closed accurately when a leak occurs, which is very effective in stopping the leak at an early stage. Further, since the isolation valve 25 is provided near the reactor containment vessel wall 7, it is possible to partition off almost the entire length of the drawn pipe 6 located outside the reactor containment vessel, thereby increasing the leakage prevention effect.

Note that in the above embodiment, a temperature sensor is used to detect leakage and close the isolation valve.
Instead of relying on the temperature sensor, other leak detection means may be used, for example, when a leak is detected visually, the isolation valve may be closed by remote control from a central control room or the like.

As explained above, in this invention, an isolation valve is provided between the control rod drive mechanism and the hydraulic control unit, and this isolation valve is closed when the control rod is fully inserted. Even if a scram signal is input, the scram signal is always given top priority and the valve can be closed. Therefore, according to the present invention, after the control rods are fully inserted, the isolation valve minimizes leakage from the piping and equipment downstream of the isolation valve, such as the drawn piping, the scram water discharge header, or the scram water discharge container. Furthermore, if leakage is detected during normal operation of the nuclear reactor, leakage from these piping and equipment can be minimized by closing the isolation valve. In addition, since the isolation valve is opened with the highest priority during scram, it is possible to maintain a state in which scram operation can be performed reliably at all times, which has a great effect on improving the safety of the reactor.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a conventional control rod drive hydraulic system, Figure 2 is a schematic diagram showing a control rod drive hydraulic system according to the present invention, and Figure 3 is a characteristic diagram showing changes in surface temperature of drawn piping. be. 3... Control rod drive mechanism, 5... Insertion piping, 6... Pulling out piping, 8... Water pressure control unit, 22... Scram water discharge header, 25... Isolation valve, 26... Temperature sensor.

Claims (1)

[Claims] 1. Connected to the insertion piping and withdrawal piping of the hydraulic control rod drive mechanism, selectively pressure-feeding control rod driving water to these insertion piping or withdrawal piping, and at the time of scram, controlling rod insertion scram water. In a control rod drive hydraulic device comprising a water pressure control unit that pumps water into the insertion pipe, and a scram water discharge header that discharges scram water returned through the withdrawal pipe during scram, the water pressure control unit and the control rod drive mechanism are connected to each other. An isolation valve is installed in the middle of the drawn piping between the two, and when there is a leak in equipment or piping downstream of this isolation valve, the isolation valve is opened, and when a scram signal is input, this scram signal is given top priority. A control rod drive hydraulic system comprising isolation valve control means that opens the isolation valve and closes the isolation valve when the control rods are fully inserted. 2 The isolation valve control means closes the isolation valve in response to a signal from a temperature sensor that detects the temperature of the drawn piping between the isolation valve and the control rod drive mechanism indicating that the temperature has exceeded a predetermined temperature. A control rod drive hydraulic device according to claim 1, characterized in that: 3. The control rod drive hydraulic system according to claim 1 or 2, wherein the isolation valve is provided at a position upstream of the withdrawal pipe near the wall of the reactor containment vessel.