JPH0399296A - Device for preventing malfunction of control rod driving mechanism - Google Patents

Abstract

PURPOSE:To prevent faulty draw-out operation of a control rod by providing a water pressure control unit which selectively supplies cooling water sent out from a water pressure supply device to a control rod driving mechanism so that operation of insertion or draw-out of the control rod be executed. CONSTITUTION:Isolation of water pressure control units 10 is executed by closing sequentially an insertion line isolation valve 8 and a draw-out line isolation valve 9 of each of the water pressure control units 10. When the number of the water pressure control units 10 isolated thereby increase, the pressure of cooling water in a cooling water line 13 turns high. This pressure of the cooling water is detected by a cooling water pressure detector 11, an operation is made under the pressure of a stipulated value not causing a backflow from a four-way control valve 7 and a water discharge line isolation valve 17 is closed, while an alarm unit 19 issues an alarm. Since the cooling water of high pressure is shut off from a draw-out line 15, according to this constitution, a faulty draw-out operation does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a device for preventing erroneous withdrawal of a control rod by a control rod drive mechanism of a boiling water nuclear reactor.

(Prior art) The control rod drive hydraulic system in a boiling water reactor is for maintaining the drive pressure of the control rods that control the reactor's output. A water pressure supply device 5 includes a pump 2 that pressurizes the cooling water from the condensate tank 1 to a predetermined pressure and sends the water, a flow rate adjustment valve 3, and a pressure adjustment valve 4. It is selectively supplied to the control rod drive mechanism 6 for cooling the control rod drive mechanism 6 during reactor operation, and as pressurized drive water during control rod operation,
A hydraulic control unit 1 consisting of a four-way control valve 7 for inserting or withdrawing a control rod (not shown) at the tip of a control rod drive mechanism 6, an insertion line isolation valve 8, and a withdrawal line isolation valve 9.
It is composed of 0, etc.

Also, a cooling water pressure detector 1 is installed at the outlet of the water pressure supply device 5.
1 and a high pressure detection switch 12 which is activated by this output signal and issues an alarm when the pressure is high.

The control rod drive mechanism 6 and the hydraulic control unit 10 are installed in the same number, about 200 sets, in one general boiling water reactor, together with control rods (not shown).

(Problem to be solved by the invention) During regular inspection of a nuclear power plant, the control rod drive mechanism 6
Isolation work will be carried out on each hydraulic control unit lO for overhaul inspection and leakage rate test of the reactor-fireway containment vessel. Normally, this isolation of the water pressure control unit 1O is carried out after stopping the pump 2 of the water pressure supply device 5, but in some cases it is carried out with the pump 2 running in conjunction with other processes, and the water pressure is controlled in this state. As the number of isolated units IO increases, the amount of cooling water flowing into the water pressure control unit 10 decreases, so the pressure of the cooling water gradually increases. This allows the cooling water line 1
The pressure of 3 becomes high, and 4 is connected to the drainage line 14.
High pressure may flow backward through the directional control valve 7 and be applied to the withdrawal line 15, causing the control rod drive mechanism 6 to erroneously withdraw the control rod. When the cooling water pressure exceeds a specified value, the high pressure detection switch 12 issues an alarm, but if a control rod is accidentally pulled out, there is a problem in that the integrity of the reactor fuel in the reactor is impaired.

[Object of the Invention] (Means for Solving the Problems) A hydraulic control unit that selectively supplies cooling water sent from a hydraulic supply device to a control rod drive mechanism to insert or withdraw a control rod; A reactor control rod drive system consisting of a cooling water pressure detector and a high pressure detection switch installed at the outlet of the water pressure supply system (in the main system, a check valve with an orifice installed in the drainage line and the outlet of the water pressure supply system) a high pressure detection switch that is operated by an output signal from the cooling water pressure detector to open the drain line isolation valve, a high pressure detection switch that closes the valve, and a high pressure detection switch that closes the drain line isolation valve; Equipped with an accidental removal prevention device consisting of an alarm activated by a signal from a pressure detection switch.

(Function) If many water pressure control units that control the control rod drive mechanism, which is the load of the water pressure supply device, are stopped without stopping the pumps of the water pressure supply device, the pressure of the cooling water supplied will gradually rise. When the pressure of this cooling water reaches a set value, it is detected by the cooling water pressure detector, and the pressure detection switch at most will issue a signal and alarm when this pressure reaches the preset value before the start of backflow in the 4-way control valve. The equipment will issue an alarm and the drain line isolation valve will be closed. This prevents backflow from occurring from the four-way control valve in the hydraulic control unit, and high pressure is not applied to the control rod drive mechanism's withdrawal line, preventing control rods from being erroneously withdrawn, thus maintaining the integrity of the fuel in the reactor. . Further, when the pressure of the cooling water decreases to a normal value, the drain line isolation valve is opened by the operation signal of the high pressure detection switch, and the normal state is automatically restored.

(Example) An embodiment of the present invention will be described with reference to the drawings.

Note that the same components as those in the prior art described above are designated by the same reference numerals and detailed explanations will be omitted.

As shown in the configuration diagram of FIG. 1, the present invention includes a water pressure supply device 5 comprising a pump 2 that pressurizes cooling water in a condensate tank 1 to a predetermined pressure and sends water, a flow rate adjustment valve 3, and a pressure adjustment valve 4; A four-way control well 7 and an insertion line isolation valve 8 that selectively supply pressurized driving water of cooling water sent from the water pressure supply device 5 to the control rod drive mechanism 6 to insert or withdraw a control rod (not shown). and a water pressure control unit 10 consisting of a drawing line isolation valve 9, and a cooling water pressure detector 11 and a high pressure detection switch 12 are provided at the outlet of the water pressure supply device 5. Furthermore, a drainage line isolation valve 17 provided between the outlet of the water pressure supply device 5 and the orifice-equipped check valve 1B of the drainage line 14, a maximum pressure detection switch 18 operated by a signal from the driving water pressure detector 11, and It is comprised of an erroneous extraction prevention device 20 consisting of an alarm 19 which is activated by the output signal of the pressure detection switch 18 at most.

Next, the effect of the above configuration will be explained. Isolation work of the water pressure control unit 10 performed during periodic inspections, etc. is performed by sequentially installing the insertion line isolation valve 8 of each water pressure Jil + control unit IO.
This is done by closing the withdrawal line isolation valve 9.

When the number of isolated water pressure control units 1o increases as a result, the amount of cooling water for the load decreases while the pump 2 of the water pressure supply device 5 remains in operation, so that the cooling water pressure in the cooling water line 13 increases. This cooling water pressure is detected by the cooling water pressure detector 11, and the maximum pressure detection switch 18 inputting this output signal operates at a preset pressure value that does not cause backflow from the four-way control valve 7. The output signal causes the drain line isolation valve 17 to close and the alarm 19 to issue an alarm. As a result, the high-pressure cooling water that flows backward through the four-way control valve 7 and is applied to the withdrawal line 15 is cut off, so that no erroneous withdrawal operation of the control rod occurs in the control rod drive mechanism 6.

Further, when the pressure in the cooling water line 13 decreases due to stopping of the pump 3, etc., and drops below the specified value of the high pressure detection switch 12, the high pressure detection switch 12 is activated, and this output signal is used to activate the drain line isolation valve. 7 is opened and automatically returns to the normal state to maintain the pressure in the withdrawal line 15 below a predetermined value at all times to prevent erroneous withdrawal of the control rod.

[Effects of the Invention] As described above, according to the present invention, even if the pressure of the cooling water supplied increases due to isolation of the water pressure control unit, etc., this can be safely prevented and the erroneous withdrawal of the control rod in the control rod drive mechanism can be prevented. Since manipulation is prevented, work such as periodic inspections can be carried out efficiently and safely, and since the device is simple, it can be easily installed in existing equipment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an erroneous operation prevention device for a control rod drive hydraulic system according to the present invention, and FIG. 2 is a block diagram of a conventional control rod drive hydraulic system. 5... Water pressure supply device, 6... Control rod drive mechanism,
7...4-way control valve, 8...Insertion line isolation valve, 9...Extraction line isolation valve, IO...Water pressure control unit, 11...Cooling water pressure detector, 12...High Pressure detection switch, 13...Cooling water line, 14...Drainage line,
16... Check valve with orifice, 17... Drain line isolation valve, 18... Maximum pressure detection switch, 19... Alarm, 20... Accidental withdrawal prevention device.

Claims (1)

[Claims] A water pressure control unit that selectively supplies cooling water sent from a water pressure supply device to a control rod drive mechanism to insert or withdraw a control rod, a cooling water pressure detector and a high In a nuclear reactor control rod drive hydraulic system consisting of a pressure detection switch, from a drainage line isolation valve provided between a check valve with an orifice provided in the drainage line and the outlet of the water pressure supply device, and the cooling water pressure detector. An erroneous operation prevention device for a control rod drive mechanism, comprising an erroneous withdrawal prevention device comprising an alarm and a maximum pressure detection switch that is activated by an output signal to operate the drainage line isolation valve.