JPS6046672B2 - Control rod drive hydraulic system - Google Patents

Description

[Detailed Description of the Invention] A plurality of control rods are arranged in the core of the nuclear reactor in order to control the reactor output during normal operation of the reactor and to shut down the reactor in an emergency. In order to insert and withdraw the rod, one end thereof is connected to a hydraulic piston type control rod drive mechanism (hereinafter referred to as CRD).

Furthermore, in order to control the driving water supplied to the CRD, a water pressure control unit (hereinafter referred to as HCU) corresponding to the drive water on a one-to-one basis is located outside the containment vessel. is set up. The HCU is constantly supplied with various water pressures adjusted by the control rod drive hydraulic system, and in response to signals from the central control room, the HCU supplies the necessary water pressure to the CRD and controls the reactor. There is.
This will be explained below with reference to the drawings.

FIG. 1 is a schematic system diagram showing a conventional control rod drive device, which includes a control rod drive water pump 1 connected to a water source (not shown), a master control 2 provided on the discharge side of the pump 1, and a control rod drive water pump 1 connected to a water source (not shown). , an HC that is connected to the master control 2 by piping and that switches the drive water flow path and controls the drive water.
It is connected to U3 and a control rod that moves inside the reactor core and controls core reactivity at the end, and is composed of CRD4 that drives the control rod and piping that connects these. The insertion and withdrawal operations of this control rod drive device will be explained.

When inserting a CRD, the direction control valves 5a and 5d in the HCU 3 open in response to an insertion signal from the central control room, and the drive water adjusted by the drive water pressure adjustment valve 2b in the master control 2 flows into the drive water header. 10, enters the HCU 3, acts on the piston lower surface 4a of the CRD 4 from the direction control valve 5a, and inserts the piston 4c upward. On the other hand, the water on the piston top surface 4b flows from the direction control valve 5d to the drain header 12.
, and returns to the master control 2, where the insertion operation is performed. When withdrawing, the directional control valves 5b and 5c open, and the driving water passes through the directional control valve 5c and acts on the upper surface 4b of the piston of the CRD 4, thereby inserting and lowering the piston 4c downward. The water on the lower surface of the piston 4a passes from the direction control valve 5b through the drainage header 12, returns to the master control 2, and is pulled out. During both insertion and withdrawal operations, the waste water returned to the master control 2 is sent to the reactor via the reactor return line 13 if there is a reactor return line 13, or to the cooling water pressure regulating valve if there is no reactor return line 13. 2c through the cooling water header 11 to other HCUs that are not in operation.
3 to CRD4. It is now being discharged into nuclear reactors. During insertion and withdrawal operations, especially during withdrawal after a scram, the wastewater discharged from the CRD4 is mixed with reactor water containing radioactivity, and as mentioned above, it passes through the master control 2, so the master control 2
The drawback was that the radioactivity levels gradually rose, increasing the exposure of power plant employees and workers during routine inspections.
Also, to explain the operation during an emergency stop (scram), the water pressure accumulated in the accumulator 8 in the HCU 3, which is connected to the discharge side of the control rod-driven water pump 1 as an energy source for the scram, is used as the scram signal in an emergency. CRD 4 through scram inlet valve 6 by rapidly opening scram inlet valve 6 and scram outlet valve 7 in response to
A 5-ton screw is applied to the lower surface 4a of the piston 4c, and the piston 4c is rapidly inserted, and the water on the piston upper surface 4b is passed through the scram outlet valve 7 to the scram discharge header 16, which is always at atmospheric pressure.
A scrum is created by ejecting the

The pressure in the drain header 12 is always approximately the same as the S reactor pressure.

The one-way control valves 5a to 5d can stop the flow in the forward direction (→marked direction in the figure), but cannot stop the flow in the reverse direction, and have a structure that makes them difficult to operate when a high differential pressure is applied. Therefore, if the scram is performed when the reactor pressure is high, the pressure in the withdrawal line 15 becomes almost S゜atmospheric pressure, and the water in the drain header 12 flows backward through the directional control valve 5d and flows out, lowering the reactor pressure. The drainage header 12, which is maintained at approximately the same pressure, also reaches approximately S atmospheric pressure. When the scram reset is performed here, the pressure in the drawing line 15 recovers to the reactor pressure, but the pressure in the drainage header 12 is almost equal to atmospheric pressure, and a high differential pressure is applied to the directional control valves 5b and 5d, causing them to operate. It becomes difficult to do. To prevent this, the drain check valve 2d in the master control 2 is equipped with a special valve with an orifice, and after the scram reset, water is supplied to the drain header 12 through this orifice to restore pressure to the directional control valve 5.
A high differential pressure is not applied to b and 5d. The purpose of the present invention has been made in view of the above, and is to provide a control rod drive hydraulic device that can further reduce radioactive contamination and control a nuclear reactor without returning wastewater containing reactor water to the master control 2. .

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a system diagram showing an embodiment of the control rod drive hydraulic system according to the present invention.

The present invention is a type of non-return valve in which the directional control valve in the HCU can stop the flow in the forward direction (in the figure → direction marked) but cannot stop the flow in the reverse direction when the coil is demagnetized. This was done by taking advantage of the fact that it acts as a valve. a control rod-driven water pump 1 connected to a water source (not shown);
Master control 2 provided on the discharge side of the pump 1
and an HCU 3 that is connected to the master control 2 through piping and switches the drive water flow path and controls the drive water;
It is connected to a control rod that moves within the reactor core and controls core reactivity at the end, and is composed of a CRD 4 that drives the control rod and piping that connects these.

The master control 2 includes a flow rate adjustment valve 2a1, pressure adjustment valves 2b, 2c, and a reactor return line 13 connected to a reactor pressure vessel (not shown) through these.
It consists of a stabilizing valve that is provided to bypass the pressure regulating valves 2b and 2c.

The HCU 3 stores water pressure as an energy source during control rod scram, and has an accumulator 8 connected to the CRD piston lower surface 4a via a scram inlet valve 6 and a pipe 14.
It is composed of four directional control valves 5a to 5d arranged in order to switch the flow path according to insertion and withdrawal when driving the CRD.

Two of each of the directional control valves 5a to 5d are provided in parallel, and the valves provided in series are connected to the upper and lower surfaces 4a and 4b of the CRD piston, respectively. These directional control valves 5a
, 5c inlet side is connected via a check valve to a driving water header 10 connected from the downstream side of the flow rate regulating valve 2a to a large number of HCUs 3, 3''... , the outlet side of the directional control valves 5b and 5d is connected to the drainage riser 1.
8 to the drainage header 17. A drain riser 1'' from another HCU 3'' is connected to the drain header 17, and is connected to the cooling water header 11 via a check valve 19.The accumulator 8 is connected to the control rod-driven water pump 1.
It is connected via a check valve to a filling water header 9 connected to the discharge side.

Further, the cooling water header 11 is connected to the insertion pipe 14 via a check valve.
The scram valve 6 is connected to the downstream side of the piston so that water can be transferred to the lower surface 4a of the piston. Next, its effect will be explained.

When inserting a CRD, the directional control valves 5a and 5d in the HCU 3 open in response to the insertion symbol from the central control room, and the drive water adjusted by the drive water pressure adjustment valve 2b in the master control 2 is transferred to the drive water header. 10, enters the HCU 3, acts on the piston lower surface 4a of the CRD 4 from the direction control valve 5a, and inserts the piston 4c upward. On the other hand, the water on the piston top surface 4b is drained from the directional control valve 5d to the drain riser 18.
and enters the drainage header 17. However, because of the check valve 19 provided there, the water does not flow to the cooling water header 11, but instead enters the HCU 3'' from the drain risers 18'' of the other HCUs 3'' that are not in operation, and flows to the directional control valves 5b'', 5''.
d'' can be reversed and returned to the reactor through a plurality of unoperated CRDs 4'', and the target CRD 4 can be inserted. Also, when pulling out, use the direction control valve 5 in the opposite direction.
b and 5c are opened, and the driving water passes through the direction control valve 5c and reaches the CRD.
4 and inserts the piston 4c downward.

The water on the lower surface 4a of the piston enters the drain header 17 via the drain riser 18 from the direction control valve 5b, as in the case of insertion, and enters the drain header 17. HCU3″ drainage riser 18′
The CRD 4 to be moved can be pulled out by entering the HCU 3', flowing backward through the directional control valves 5b'' and 5d'', and returning to the reactor through the plurality of CRDs 4'' that are not being operated. In other words, waste water will no longer flow into the master control 2 as in the past.Also, during an emergency stop (scram), the discharge side of the water pump 1 is constantly driven by the control rod as the energy source for the scram. By rapidly opening the scram inlet valve 6 and the scram outlet valve 7 in response to an emergency scram signal, the scram inlet valve 6 to act on the lower surface 4a of the piston of the CRD 4, the piston 4c is rapidly pushed up, and the water on the upper surface 4b of the piston is discharged through the scram outlet valve 7 to the scram discharge header 16, which is always at atmospheric pressure. This is done in the same way as before.

Even if there is a scram when the reactor pressure is high and the pressure in the drainage header 17 flows backward through the directional control valve 5d and reaches almost the same atmospheric pressure as the withdrawal line 15, the reactor is connected to the cooling water header 11 after the scram reset. Since the pressure recovery of the drainage header 17 can be measured through the check valve 19, the directional control valve 5b
, 5d, and the directional control valve operates smoothly even during the withdrawal operation after the scram. FIG. 3 is a system diagram showing another embodiment of the control rod drive hydraulic device according to the present invention.

The embodiment shown in FIG. 2 is a case in which a reactor return line 13 is provided, but the embodiment shown in FIG. 3 is an embodiment in a case in which this reactor return line 13 is not provided.

A control rod-driven water pump 1 connected to a water source (not shown), a master control 2 provided on the discharge side of the pump 1, and switching of a driving water flow path and driving water connected to the master control 2 through piping. HCU3 controls
It is the same as the embodiment shown in Fig. 2, and is connected to a control rod that moves inside the reactor core and controls the core reactivity at the end, and is composed of a CRD 4 that drives the control rod and piping that connects these. In addition, the configurations of the control rod-driven water pump 1, HCU 3, and CRD 4 are also the same.

The master control 2 is different from the embodiment shown in FIG. 2, and is composed of a flow rate regulating valve 2a, a pressure regulating valve 2b, and a stabilizing valve connected in series with these valves.

Two of the stabilizing valves are connected by piping in parallel, and the upstream side thereof is connected to the driving water header 10, and is connected to the directional control valves 5a to 5d of the HCU 3 via check valves. Its operation is also similar to the embodiment shown in FIG. In other words, C
When the RD is inserted, driving water flows from the control rod driving water pump 1 through the driving water header 10 and from the direction control valve 5a in the HCU 3 to the piston lower surface 4a. On the other hand, the water on the piston top surface 4b passes through the drain riser 18 and the drain header 17 from the directional control valve 5d, and flows from the drain riser 1 that is not in operation to the
Enters CU3'' and reverses direction control valves 5b'' and 5d'' C
Return to the reactor from RDC. This causes the insertion. In addition, when the CRD is pulled out, the driving water flows into the piston upper surface 4b from the direction control valve 5c and flows into the piston lower surface 4.
Water from the direction control valve 5b passes through the drain riser 18 and the drain header 17, and then flows through the direction control valves 5b'' and 5d'' of the HCU 32 from the drain riser 1'' of the other HCU 3'' that is not being operated.
flows backwards and returns to the reactor through its CRD4''.

This causes the drawing to take place. The scram transfers water pressure from the accumulator 8 to the piston bottom surface 4 from the scram inlet valve 6.
This is done by causing the water on the piston top surface 4b to flow rapidly into the scram outlet valve 7 and draining the water on the piston top surface 4b to the scram exhaust header 16.

Even in a scram at high pressure in the reactor, even if the pressure in the drain header 17 drops to almost atmospheric pressure, the pressure in the drain header 17 will be restored from the cooling water header 11 through the check valve 19 after the scram reset. , high differential pressure does not act on the directional control valves 5b, 5d, making operation easier. As is clear from the above description, the control rod drive hydraulic system according to the present invention can perform insertion and withdrawal operations without returning wastewater containing reactor water during insertion and withdrawal operations to the master control, so only clean water is always supplied to the master control. Since it flows, there is no radioactive contamination and it greatly contributes to reducing the radiation exposure of workers.

In addition, work efficiency during maintenance and inspection can be improved and man-hours can be reduced.
Furthermore, even during a scram, after a scram reset, the check valve connected to the cooling water header allows the drain header pressure to be quickly and easily restored, and a high differential pressure acts before and after the directional control valve, inhibiting its operation. Because there is nothing to do,
This will improve the reliability of the control rod drive hydraulic system and the safety of the entire reactor.

In addition, in the embodiment shown in Fig. 3, since there is no reactor return line, there is no nozzle part which is the connection part with the reactor pressure vessel, and the strength of cracks etc. is significantly improved, and the reactor pressure The probability of occurrence of pipe breakage opening into the container is also reduced, which has the effect of improving safety against coolant loss accidents.

In the above embodiments, the check valve provided at the connection between the drain header and the cooling water header may be a check valve with an orifice, and is not limited to these specific embodiments without departing from the spirit of the present invention. Of course, many changes and modifications can be made.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram showing a conventional control rod drive hydraulic device, FIG. 2 is a schematic system diagram showing an embodiment of the control rod drive hydraulic device according to the present invention, and FIG. 3 is a control rod drive system diagram according to the present invention. FIG. 3 is a schematic system diagram showing another embodiment of the drive hydraulic device. DESCRIPTION OF SYMBOLS 1... Control rod drive water pump, 2... Master control, 3... Water pressure control unit, 4... Control rod drive mechanism, 11... ...Cooling water header, 17...Drain header, 18...
Drain riser, 19... check valve.

Claims (1)

[Claims] 1. A pump connected to a water source and supplying driving water, a master control provided on the discharge side of the pump, a number of control devices connected to the master control via piping to control the control rod driving water, and the control device In a control rod drive hydraulic system consisting of a number of drive devices connected to a master control for driving control rods, the discharge water side of the control device is communicated with the discharge water side of other control devices, and the discharge water side of the control device is connected to the master control without being returned to the master control. A control rod-driven hydraulic device characterized by being connected to a cooling water header via a stop valve.