JPS6152439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for flushing cleaning by flowing reactor water through an in-core guide pipe of a nuclear reactor.

In a boiling water reactor, a neutron measurement tube is inserted vertically through the bottom of the reactor pressure vessel. This neutron measurement tube is supported by inserting its lower part into the in-core guide tube, but impurities such as crud that are generated inside the reactor during reactor operation may enter and accumulate between the guide tube and the neutron measurement tube. , it is possible that the neutron measurement tube becomes stuck to the guide tube. If such sticking occurs, it becomes difficult to lift out and replace the neutron measurement tube during periodic inspections, so it is necessary to flush the inside of the guide tube from time to time to remove impurities that cause sticking. This flushing work involves raising the neutron measurement tube relative to the guide tube, allowing reactor water to flow into the guide tube, and draining it through a drain pipe connected to the lower end of the guide tube, thereby removing impurities from the flow of reactor water. It is something to be removed.

However, in the past, this flushing work was performed by grasping the head of the neutron measurement tube from the fuel exchange platform side using the in-core equipment handling device, and disengaging the engagement between the locking recess in the upper grid plate and the neutron measurement tube head. Lifting with the auxiliary hoist on the fuel exchange platform
The work requires repeated hoisting and lowering, which is very time-consuming, and since the work is done from above the reactor core, it must be done with the reactor internal structures such as the evaporator dryer and steam separator removed. However, there was a problem in that the work was extremely large-scale.

This invention was made based on the above-mentioned circumstances, and its purpose is to enable the neutron guide tube to be driven up and down directly from the bottom side of the reactor pressure vessel, so that reactor water can easily flow down and flushing work can be carried out. It is an object of the present invention to provide a flushing device for an in-core guide tube that can easily carry out flushing.

The present invention will be explained below based on an illustrated embodiment. FIG. 1 shows the state before the flushing device is installed, and numeral 1 in the figure indicates the neutron measurement tube. The neutron measurement tube 1 has its lower half inserted into the in-core guide tube 2, and its upper half exposed in the core region between the core support plate 3 and the upper grid plate 4. A fuel assembly (not shown) is loaded in this core region. In addition, the head 1a of the neutron measurement tube 1
is constructed so as to be able to protrude and retract from the lower main body portion 1b, and is urged in the protruding direction by a spring 5 and is fitted and supported in the locking recess 6 of the upper lattice plate 4. Reference numerals 7 and 8 indicate large diameter guide portions provided in the middle of the neutron measurement tube 1, and these guide portions 7 and 8 are set to have an outer diameter that allows them to freely slide on the in-core guide tube 2.

Further, the lower end of the in-core guide tube 2 penetrates the bottom of the reactor pressure vessel 9 and is connected to the housing 10 at the lower end.
has been formed. A flange portion 11 is liquid-tightly fixed to the lower surface of the housing 10 by a plurality of bolts 12, for example, four bolts 12 (only two are shown). The lower part of the neutron measurement tube 1 passes through the housing 10 and the flange portion 11. Further, a male threaded portion 13 is formed on the lower outer circumferential surface of the neutron measurement tube 1 . This male threaded portion 13
During reactor operation, a tightening nut 14 is screwed into the neutron measuring tube 1 to tighten the neutron measuring tube 1 downward. Due to this tightening force, the sealing step portion 16 of the neutron measurement tube 1 comes into close contact with the tapered valve seat portion 15 formed within the flange portion 11, so that the inside of the in-core guide tube 2 can be kept watertight. It's summery. Further, a removable nose piece 17 that covers the terminal of the sensor is screwed onto the lowermost end of the neutron measuring tube 1. This nosepiece 17 is screwed on when replacing the neutron measurement tube 1, and after replacement, it is removed and a signal cable is connected to the sensor terminal.

A flushing device 20 shown in FIG. 2 is attached to the flange portion 11. The configuration of this flushing device 20 will be explained below. Reference numeral 21 denotes a fixed outer tube, and a flange-shaped mounting seat 22 is attached to the upper end surface of the fixed outer tube 21. A pair of bolt insertion holes 23, 23 are formed in this mounting seat 22, and stud bolts 2 are inserted into these bolt insertion holes 23, 23, respectively.
4 and 24 are inserted. These stud bolts 24, 24 are obtained by removing two of the four flange fixing bolts 12, which are located symmetrically to each other, and implanting them in their place. It stands out in a long way. Then, the mounting seat 22 is supported by double-tightened nuts 25 and 26, and thereby the fixed outer tube 2
1 is suspended vertically from the in-core flange portion 11.

In addition, a lower end cap 2 is provided at the bottom of the fixed outer tube 21.
A cylinder 28 is attached via 7. This cylinder 28 is separated into an upper half 28a and a lower half 28b with an intermediate ring 29 in between.
are connected to each other via. Therefore, either the upper half 28a or the lower half 28b is connected with a reverse thread. 30 is a detachable handle for rotational operation. Further, the lower end of the cylinder 28 is fluid-tightly closed by a cover member 31, and a guide portion 32 extending downward is provided at the lower part of the cover member 31.

Furthermore, a connection port 34 communicating with the upper cylinder chamber 53a and a connection port 35 communicating with the lower cylinder chamber 53b are attached to the side portion of the cylinder 28. Water supply pipes 38 and 39 are connected to these connection ports 34 and 35 via detachable connectors 36 and 37, respectively. A pressure water supply device (not shown) is connected to these water supply pipes 38 and 39, so that piston driving pressure water can be taken in and out of the connection ports 34 and 35.

A movable inner tube 41 passes through the fixed outer tube 21 and the cylinder 28 so as to be movable in the axial direction. This movable inner tube 41 is connected to a piston 52 which will be described later.
The upper half part 41a is divided into an upper half part 41a and a lower lower half part 41b.A female threaded part 42 is formed on the inner surface of the upper end of the upper half part 41a. 13 and can be fixed with a locking nut 43. Then, the nose piece 17 is inserted into this upper half portion 41a. Furthermore, a first drainage flow section 44 is formed between the outer surface of the upper half portion 41a and the inner surface of the fixed outer tube 21. This first wastewater flow section 44 is
It communicates with the opening 11a of the in-core flange portion 11.

In addition, the inside of the movable inner tube 41, that is, the upper half 41
A and the lower half portion 41b have a second drainage flow portion 45 formed therein that is continuous with each other. The second waste water flow section 45 communicates with the lower side of the first waste water flow section 44 via drain holes 46 and 47 formed in the movable inner pipe 41. In addition, the movable inner tube 4
A drain pipe 4 equipped with an on-off valve 48 is provided at the lowest end of the drain pipe 4.
9 can be detachably connected. The other end of the drain pipe 49 is led to, for example, a rad groove pit of the pedestal.

Further, a scale 50 as an example of a display device is provided at the lower end of the movable inner tube 41.
By reading at the lower end of the guide part 32,
The relative position of the movable inner tube 41 in the axial direction with respect to the fixed outer tube 21 can be detected.

A piston 52 is attached to the middle of the movable inner tube 41 via a connecting fitting 51. The piston 52 is located within the cylinder 28, with an upper cylinder chamber 53a formed above the piston 52, and a lower cylinder chamber 53b formed below the piston 52. When the piston 52 is at its lowest position, its lower surface abuts against the upper surface of the intermediate ring 29, thereby regulating the lower limit position. Note that a cylinder-piston mechanism 54 is constituted by the piston 52, the cylinder 28, the connection ports 34, 35, and the like.

Next, the operation of the device of the above embodiment will be explained. During normal operation of the reactor, flushing device 2
0 has been removed from the flange portion 11 and a tightening nut 14 has been tightened onto the male threaded portion 13 instead. As a result, the sealing step portion 16 of the neutron measurement tube 1 is pressed against the valve seat portion 15, and watertightness is ensured. Further, the nose piece 17 has been removed, and a signal cable has been led out from the terminal of the sensor.

Then, during periodic inspections, etc., the inside of the in-core guide tube 2, the housing 10, the sealing step 16, etc.
When performing flushing, the flushing device 20 is used in the following manner. First, lift the fixed outer tube 21 vertically, and attach the mounting seat 2 at its upper end.
Insert the stud bolts 2 into the bolt insertion holes 23, 23 of 2.
4 and 24. And Natsuto 25, 26
The mounting seats 22 are supported by the lowermost ends of these stud bolts 24, 24. As a result, the fixed outer tube 21 is suspended with a wide gap formed between the mounting seat 22 and the inner-core flange portion 11, so that the work of connecting the upper end of the movable inner tube 41 described below can be performed. It becomes easier.

Then, as shown by the solid arrow in FIG. 2, pressurized water is sent into the lower cylinder chamber 53b through the lower water supply pipe 39, causing the piston 52 to rise.
As a result, the movable inner tube 41 rises, and the female threaded portion 42 at the upper end abuts against the male threaded portion 13 of the neutron measurement tube 1, thereby performing a screw connection operation between them. Then, tighten the locking nut 43 to fix it in place. Next, this time, as shown by the dotted arrow, from the upper water supply pipe 38 to the upper cylinder chamber 53a.
Pressurized water is pumped inside. Then, the fixed outer tube 21 rises relative to the movable inner tube 41, and the mounting seat 22 at the upper end also rises and comes into contact with the lower surface of the inner-core flange portion 11. Then, the nuts 25 and 26 are tightened to fix the fixed outer tube 21 to the inner flange portion 11.

After fixing the flushing device 20 to the in-core flange portion 11 as described above, pressure water is sent into the lower cylinder chamber 53b again, and the piston 52
The movable inner tube 41 is raised by applying a lifting force to the movable inner tube 41. Therefore, the neutron measurement tube 1 also rises, and the sealing step 1
6 rises from the valve seat portion 15. Therefore, the reactor water in the reactor pressure vessel flows into the valve seat part 1.
5 into the first wastewater flow section 44, and flows through the drain holes 46, 47 into the second wastewater flow section 45. Then, it is guided through the drain pipe 49 to the rad groove pit of the pedestal.

That is, the flow of this reactor water flushes the in-core guide tube 2, the inner surface of the housing 10, the sealing step 16, etc., and the impurities that cause the neutron measurement tube 1 to stick are washed away. In addition, the neutron measurement tube 1 is raised and lowered several times, and the sealing step part 16 and the valve seat part 15 are
By repeating the adhesion and separation of the reactor water, reactor water is intermittently discharged, and the turbulent flow generated at that time can effectively wash away the adhering dirt.

The above flushing work is performed on the neutron measuring tube within the range where the spring 5 shown in FIG.
By raising the head 1a, it is not necessary to disengage the head 1a from the locking recess 6 of the upper grid plate 4, making the work very easy. However, in this case, since the upper guide portion 7 remains located inside the in-core guide tube 2, the flow path is narrow and the amount of water flowing is relatively small. Therefore, if you want to increase the flow rate, grab the head 1a of the neutron measurement tube with the reactor equipment handling device from the fuel exchange platform side, and
After pushing in and disengaging from the locking recess 6, pressurized water is sent into the lower cylinder chamber 53b,
The movable inner tube 41 is raised significantly. In this way, the upper guide portion 7 can be extracted from the in-core guide tube 2, and the cross-sectional area of the flow path can be expanded to increase the amount of water discharged. Therefore, the flushing effect can be further improved. Note that the amount of rise of the movable inner tube 41 can be easily determined by reading the scale 50.

In this way, according to the flushing device 20, the neutron measurement tube 1 can be directly raised and lowered from the bottom side of the reactor pressure vessel for flushing, and as described above, the neutron measurement tube head 1a can be flushed within the permissible plunge/sink range. If so, all flushing work can be performed from the bottom side of the reactor pressure vessel. Therefore, work can be done extremely easily and efficiently.

Moreover, when installing the flushing device 20, the movable inner tube 41 is first raised by the cylinder piston mechanism 54, and its upper end female threaded portion 42 is screwed into the male threaded portion 13 of the neutron measuring tube 1, and then the fixed and unfixed tubes 41 are screwed together. Raise the tube 21 relatively and attach the mounting seat 22 at the upper end to the stud bolts 24, 24.
Since it can be brought into contact with the in-core flange portion 11 along the length, there is an advantage that the installation work can be efficiently carried out using mechanical force.

In addition, the reactor water flows through the first and second wastewater distribution sections 4.
Since the reactor water can be sent from the drain pipe 49 to a predetermined wastewater treatment facility through the drain pipes 4 and 45, there is no leakage of reactor water to the outside, and the amount of radiation exposure during work can be reduced.

In addition, after flushing, neutron measurement tube 1
When lifting up the flushing device and replacing it with a new one, remove the flushing device and remove the inner flange part 11.
The existing drain pipe is attached to the drain pipe and made into a standard style that allows lifting of the neutron measuring tube 1, and then a signal is sent to the refueling platform and the neutron measuring tube 1 is lifted using an auxiliary hoist. At this time, sufficient flushing has already been performed and dirt that causes sticking has been removed, so that smooth lifting is possible.

As explained above, in this invention, the movable inner tube attached to the neutron measurement tube is directly applied driving force from the bottom side of the pressure vessel by the cylinder-piston mechanism to move the neutron measurement tube up and down. Reactor water introduced into the inner core guide pipe as the pipe rises is passed through a first wastewater flow section formed between the fixed outer pipe and the movable inner pipe, and a movable inner pipe that communicates with the lower part of this wastewater flow section. It can be discharged from the drain pipe through the second drainage flow section of the pipe. Therefore, according to the present invention, flushing work can be efficiently performed from the bottom side of the reactor pressure vessel in a short time, especially when the head of the neutron measurement tube is engaged with the locking recess of the upper grid plate. It has extremely great practical effects on nuclear reactors, as it allows for flushing without reactor water, and there is no splashing of reactor water, reducing radiation exposure during operation.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal sectional view showing a neutron measurement tube together with a part of the reactor; FIG. 2 is a longitudinal sectional view showing a flushing device attached to the neutron measurement tube; FIG. 3 is a side view showing a part of the drain pipe in partial cross section. 1... Neutron measurement tube, 2... In-core guide tube,
9...Reactor pressure vessel, 11...In-core flange part, 11a...Opening part, 13...Male thread part, 2
0... Flushing device, 21... Fixed outer tube, 2
4... Stud bolt, 28... Cylinder, 41
...Movable inner tube, 42...Female threaded portion, 44...First
drainage distribution section, 45...second drainage distribution section, 48
...Opening/closing valve, 49...Drain pipe, 52...Piston, 54...Cylinder-piston mechanism.

Claims (1)

[Scope of Claims] 1. A fixed outer tube that is suspended vertically with its upper part liquid-tightly fixed to the in-core flange at the bottom of the reactor pressure vessel, and an upper end that is inserted through the fixed outer tube so as to be movable in the axial direction. The movable inner tube has a female threaded portion screwed into the male threaded portion of the lower part of the neutron measurement tube, and a cylinder piston mechanism for driving the movable inner tube up and down relative to the fixed outer tube, A first drainage flow part communicating with the opening of the inner flange part is provided between the fixed outer pipe and the movable inner pipe, and
The interior of the movable inner pipe is provided with a second wastewater flow section that communicates with the first wastewater flow section, and a drain pipe equipped with an on-off valve is connected to the second wastewater flow section. In-core guide tube flushing device. 2. The flushing device for an inner-core guide tube according to claim 1, wherein the fixed outer tube is fixed to a stud bolt that projects in an elongated manner from the lower surface side of the inner-core flange portion.