JPS5845680B2 - control rod drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a control rod drive hydraulic system in a control rod drive system of a boiling water nuclear power plant.

The control rod drive system of a conventional boiling water nuclear power plant will be explained with reference to the drawings.

FIG. 1 shows a control rod drive mechanism 1 and a hydraulic control unit 2, and FIG. 2 schematically shows a control rod drive hydraulic pressure supply system.

The control rod drive mechanism 1 is of a hydraulic piston drive type and is composed of a drive piston 1a, an index tube 1b, and a locking mechanism 1c.

The drive piston 1a is attached to the lower part of the index tube 1b, has upper and lower pressure receiving surfaces, and inserts and withdraws the control rod based on the pressure difference between the upper and lower surfaces.

A locking groove is provided on the outer surface of the index tube 1b, and the locking mechanism 1c, such as a ratchet type collet finger, moves and holds the control rod by a certain stroke, thereby fixing the control rod in a predetermined position.

The control rod drive hydraulic system supplies and adjusts the water pressure and flow rate necessary for control rod operation.

This system consists of a hydraulic control unit attached to each control rod and a control rod drive hydraulic pressure supply system common to all control rods.

The control rod drive hydraulic system is a system for supplying condensate from the condensate storage tank 20 to the control rod drive mechanism, and includes pumps 21. Filter 22, flow nozzle 23 as a flow rate measuring device, flow rate adjustment valves 23a, 23b, pressure adjustment valves 24a, 24b,
It is composed of a stabilizing valve 25 and the like.

Drive water sent by a pump 21 from a condensate storage tank 20 passes through a filter 22 that removes foreign substances that may cause malfunctions of the drive mechanism, etc., and a portion flows to the rudder 26 to fill water as a scram hydraulic system.

Also, a part is a flow rate adjustment valve 23a for maintaining the filling water pressure.
, 23b, the water flows to the drive water header 27, which is a drive water pressure system that operates the control rod drive mechanism, and to the cooling water header 2B, which is a cooling water pressure system for the drive mechanism piston cool.

The stability valve 25 is two solenoid valves installed in parallel, and under normal conditions,
One stable valve flow rate is adjusted to be equal to the flow rate required for the insertion operation of the drive mechanism, and the other stable valve flow rate is adjusted to be equal to the flow rate required for withdrawal.

The water exiting the stabilizing valve 25 is circulated to the cooling water pipe.

That is, when one of the stabilizing valves is closed during the driving operation, a predetermined flow rate flows toward the driving mechanism, and the S operation can be performed while keeping the water pressure at the driving water pressure regulating valve 24a constant.

Furthermore, piping for a drainage header 29 is connected to the downstream side of the stabilizing valve, and during operation, the drainage water flowing from the driving water header 27 to the drainage header 29 through the control rod drive mechanism is sent to the cooling water header 28, and other water pressure is It is discharged into the reactor pressure vessel through the control unit 2.

During normal operation, only cooling water flows, and a steady flow of water flows to cool all drive mechanisms.

Each header further leads to each hydraulic control unit 2 with the same number of pipes as control rods.

The water pressure control unit supplies filling water, cooling water, and drive water from the drive water pressure supply system to the control rod drive mechanism, and one water pressure control unit is provided for each control rod.

In the drawing, the filling water goes from the filling water header 26 to the header 16, the driving water goes from the driving water header 27 to the header 1T, the cooling water goes from the cooling water header 28 to the header 18, and the draining water goes from the drainage header 19 to the header 29. flows.

The water pressure control unit consists of four electromagnetic selection valves 4°5.6, 7.
Two scram valves 8 and 9 are combined into a unit.

When inserting a control rod, the solenoid selection valves 5 and 7 for insertion are opened, and the water pressure applied to the drive water header 17 is transferred to the drive piston 1a.
water on the upper surface is discharged to the drainage header 19.

On the other hand, for the extraction operation, the insertion solenoid selection valve is opened for a short time, the drive mechanism is slightly raised to make it easier to unlock the collet fingers, and then the extraction selection valve 4°6 (Fig. 1) is opened and driven. Apply water pressure to the top of the piston and release water from the bottom to the drain header.

At the same time, the collet fingers are pushed apart along the guide and separated from the index tube, allowing for free withdrawal.

For scram operation, the scram valve 8.9 is opened to allow high pressure water to flow from the filling water header 16 to the lower surface of the piston, and the water on the upper surface of the piston is discharged to the scram discharge header 12 at atmospheric pressure, allowing rapid scram to be performed.

With the mechanism described above, the control rod drive system changes the position of the control rods in the reactor core in response to manual control signals, increasing or decreasing power at low power, adjusting long-term reactivity, and changing the power distribution within the reactor. Make adjustments.

The control rod drive mechanism may be isolated for maintenance and repairs.

In this case, isolation valves io and il in the pipes leading to the upper and lower surfaces of the driving piston 1a are closed.

When the number of isolated control rods increases, even if the flow rate of the drive hydraulic system is reduced, the flow rate of cooling water flowing to each unisolated control rod increases, and at the same time, the drive water pressure also increases.

Therefore, excessive water pressure is applied to the lower surface of the unisolated control rod drive piston 1a through the isolation valve 10, and the piston may be lifted to the point where the collet fingers are about to unlatch.

When attempting to isolate a control rod in such a state, if the isolation valve 10 is closed first, water pressure from the driving water header 17 is applied to the selection solenoid valve 6.

If there is a seat leak in this valve, there is a risk that the control rod may come out due to its own weight until the isolation valve 11 is closed.

Here, the electromagnetic isolation valve 10 is closed first.
1 is closed first, the index tube may be damaged if a scram signal is received before the electromagnetic isolation valve 10 is closed.

The present invention has been made in consideration of the above points, and in order to prevent the control rod from being pulled out to be isolated as described above, the flow rate is controlled from the drive water pump outlet side of the control rod to the condensate storage tank. This system is designed to reduce the drive water pressure of the non-isolated control rod drive system.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a piping diagram showing a control rod drive hydraulic pressure supply system according to an embodiment of the present invention.

As mentioned above, the drive water pressure supply system is a system for supplying condensate from the condensate storage tank to the control rod drive mechanism as drive water, cooling water, and high pressure water during scram.

Water from the condensate storage tank 20 is pressurized by a drive water pump 21, passes through a filter 22 and is partially delivered to the ladder 26 for filling.

A portion of the water is also sent to the drive water header and cooling water header via the flow rate control valves 23a and 23b.

On the other hand, a pipe 30a returning to the condensate storage tank 20 from downstream of the flow nozzle 23 on the outlet side of the driving water pump is provided, and the flow rate returned is manually controlled in accordance with the difference between the reactor pressure vessel pressure and the driving water pressure. A pressure regulating valve 31 is provided.

FIG. 4 shows another embodiment of the present invention, in which the flow nozzle 23
FIG. 3 is a piping diagram illustrating an example in which piping 30b is connected from the downstream side to the suction side of the drive water pump 21.

FIG. 5 shows still another embodiment, in which the pressure difference between the furnace pressure and the drive water pressure is detected and the flow rate control valve 35 is automatically controlled based on the differential pressure signal.

Next, the operation of the drive water pressure supply system shown in FIGS. 3 to 5 will be explained.

As the number of isolated control rods increases, the water pressure of the cooling water flowing from the cooling water header to the lower part of the drive piston of the unisolated control rods increases.

In other words, the water pressure in the cooling water line 28a of the driving water pressure supply system shown in FIG. This increases the possibility that a control rod may be unintentionally pulled out as described above.

Therefore, to prevent this, the cooling water of the drive water pressure supply system,
It is sufficient to prevent the water pressure in the drive water line from rising even when the control rods are isolated.

In the embodiment shown in FIG. 3, a line 30a from the drive water pump outlet side to the condensate storage tank is used to drain excess cooling water to the flow rate control valve 23 according to changes in the pressure difference between the reactor pressure and the drive water line when the control rods are isolated. The driving water pressure can be reduced by regulating the water and returning it to the condensate storage tank.

In this case, as shown in FIG. 5, the differential pressure may be detected by the differential pressure gauge 23, and the flow rate control valve 35 may be automatically opened and closed by the valve controller 34.

As a piping line from the pump outlet side to the condensate storage tank, a minimum flow line 25 for preventing runout when starting the drive water pump is already provided.

Therefore, it seems possible to use this to lower the pressure.

However, in order to keep the cooling water flow constant, the flow control valve 2
It is necessary to draw in from a position on the downstream side of the pump outlet side flow nozzle 23 that sends the opening signal to 3a and 23b.

The outlet side of the line 30a in FIG. 4 is the directly driven water pump 21.
0 If you are returning to the entrance side, minimum flow line 25
can be used in combination to prevent cooling water from heating during long-term operation.

As mentioned above, by using the cooling water flow control piping of the control rod drive hydraulic system to return excess cooling water during control rod drive to the condensate storage tank or the inlet of the drive water pump, the excess cooling water is returned to the unisolated control rod drive mechanism. Excessive driving pressure can be removed.

Therefore, the control rod to be isolated can be prevented from being pulled out and falling.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the control rod drive mechanism and water pressure control unit of a boiling water reactor, Figure 2 is a piping diagram of the control rod drive water supply system, and Figure 3 is the storage of excess cooling water or condensate according to the present invention. Piping diagram showing the control rod drive hydraulic supply system with piping back to the tank;
Figure 4 is a piping diagram showing a control rod-driven water pressure supply system equipped with piping for returning surplus cooling water to the pump inlet side according to the present invention, and Figure 5 is a piping diagram showing surplus cooling water to a condensate storage tank according to the present invention with automatic control. FIG. 3 is a piping diagram showing a control rod drive hydraulic pressure supply system including piping for returning to the control rod. DESCRIPTION OF SYMBOLS 1... Control rod drive mechanism, 2... Water pressure control unit, 20... Condensate storage tank, 21...
... Drive water pump, 22 ... Filter,
23a, 23b...Flow rate control valve, 16, 26.
...Charging water header, 17゜27...Driving water header, 18.28...Cooling water header, 19
, 29... Drain header, 23... Flow nozzle, 25... Minimum flow line, 3
1゜35...Flow rate control valve, 30a...
Piping returning to the condensate storage tank, 30b... Piping returning to the pump suction side, 33... Differential pressure gauge, 34...
...Valve controller.

Claims (1)

[Claims] 1. In a hydraulic system for driving control rods of a boiling water reactor, a flow rate control valve downstream of a flow rate measuring device provided at the outlet side of a drive water pump and controlled by the flow rate measuring device. A control rod drive device characterized in that a pipe having a second flow rate control valve is provided from the front to the suction side of the drive water pump or to a condensate storage tank that is a water source for the drive water pump. 2. The control rod according to claim 1, wherein the second flow control valve is controlled by a valve controller operated by a pressure difference between the reactor pressure of the nuclear reactor and the water pressure of the drive water line. Drive device.