JPS61274296A - Instrumentation tube guide for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to nuclear reactor instrumentation for sensing conditions within a nuclear reactor vessel.

(Prior Art) In a pressurized water reactor, in order to control the reactivity of the reactor, a simple tube o5 is installed with a sensor o4 inside it through a guide tube 03 attached to the bottom 02 of the reactor vessel o1, as shown in Fig. 5. is inserted into the fuel assembly 06 of the reactor core,
Measure nuclear reactivity.

However, at the time of fuel exchange, this simple tube 05 becomes an obstacle to fuel removal and loading, so it is pulled out to the furnace bottom 02. In order to pull out the simple tube 05, the simple tube 05 pulling device 07 is placed below the furnace vessel 01.
A method has been proposed in which the

Even at the time of fuel exchange, water remains in the reactor vessel 01 at a predetermined depth. In this system, a fixed seal is placed in front of the extraction device 07 with high-pressure water (approximately 160 K9f/craG) during furnace operation, and the water head in the reactor vessel 01 is sealed during fuel exchange (furnace shutdown). A special pressure-resistant seal 08 is provided that allows the simple tube 05 to be pulled out and seals against water at a pressure of several atmospheres.

(Problems to be Solved by the Invention) In the conventional pressure seal 08 described above, an organic sealing material is used in order to switch the seal between a fixed seal and a sliding seal. For this reason, it is necessary to replace the sealing material every few years in consideration of functional deterioration due to deterioration of the sealing material.
It was difficult to drain the reactor water to prevent it from leaking to the outside, and if it was drained, the radiation shielding function would be lost.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems.

In the present invention, a sensor for measuring the state inside the reactor vessel, such as a neutron flux measuring device, and an instrumentation tube surrounding a conductor extending from the sensor are inserted into a guide tube that is watertightly connected to the bottom of the reactor vessel. , sealed by a pressure seal at its outer end.

The guide pipe between the pressure seal and the reactor vessel is equipped with an expansion seal that expands and contracts by supplying and discharging pressurized fluid, and is expanded only when the pressure seal is disassembled or repaired, and the outer surface of the instrumentation tube is expanded. to prevent water from leaking inside the reactor. The pressure seal securely seals the instrumentation tube by tightening the adjustment member during normal operation, and further loosens the tightening when the operation is stopped, allowing the instrumentation tube to slide, that is, to be pulled out and inserted.

(Example) The present invention will be described below based on illustrated embodiments.

In FIG. 1, a valve 10, an inflatable seal 9 and a pressure seal 8 are provided in a guide tube 3 which is watertightly connected to the bottom of the reactor vessel. An instrumentation tube or simple tube 5 containing a detector (not shown) passes through the guide tube 3 and communicates with the extraction device 7.

As shown in Fig. 2, the inflator pull seal 9 is separated from the simple tube 5 and has no sealing function because it does not normally apply internal pressure.
By applying an internal pressure slightly higher than the water pressure to be sealed, the simple tube 5 is held and sealed from its surroundings as shown in FIG.

The pressure seal 8 is disassembled and pressurized air, which is slightly higher than the water pressure in the guide tube 3, is supplied to the internal organic material seal fleta pull seal 9, and the seal part 11 is expanded to hug the simple tube 5 from its surroundings. I can do it. Pressurized nitrogen gas or pressurized water may be used instead of pressurized air. At this time, the internal pressure of the inflatable seal 9 produces a tightening surface pressure that is slightly higher than the water pressure to be sealed, and the water is stopped by the roof tile, so that water does not flow toward the pressure-resistant seal 8. Inflatable seal 9 from pressure seal 8
The water already existing in between is drained into the drain tank by a drain line provided on the guide tube 3 between the pressure seal 8 and the inflatable seal 9, as shown in FIG.

When the structure of the pressure seal 8 is as shown in FIG.
It is possible to drain water into the drain tank. At this time, the above-mentioned drain line 2 is not particularly necessary. Thereafter, the pressure seal 8 can be disassembled and repaired without water. In FIG. 3, the sliding seal 13 is located at one or two locations on the circumference.
It consists of a ring seal that is cut in several places and assembled in several stages by changing the phase of the cut surfaces, and because flexibility is required, it is made of a material that contains an organic material. When using the cutting type sliding seal 13, after removing the tightening nut 14 and disassembling it, remove the main body 17 from the guide tube 3, and then tighten the packing retainer 18.
, 19 are removed and removed from the side through the cut surface of the sliding seal 13. A new sliding seal 13 to be replaced is attached to the simple tube 5 from the side through the cut surface in the same way.
Assemble by reversing the disassembly steps. After the pressure-resistant seal 8 is completely restored, the internal pressure of the inflatable seal 9 is released.

Note that when repairing the pressure seal 8, the simple tube 5 is pulled out to the furnace bottom 2, so the tightening nut 16 is removed and the connecting member 20 is moved rearward together with the simple tube 5. For this reason, the guide tube 3 of the main body 17
The separation of the strands can be done freely. In addition, if a seal without a cut part is used as the sliding seal 13,
After the connecting member 20 is removed from the simple tube 5, the replaced seal is taken out by sequentially sending the disassembled parts backward by the length of the simple tube 5 pulled out.

When installing a new seal, just assemble in the reverse order.

As mentioned above, the inflatable seal 9 is the pressure-resistant seal 8
Although it was installed for repair purposes, it can also be used as an emergency water-stop seal in the unlikely event that the pressure-resistant seal 8 malfunctions. The inflator pull seal 9 does not seal normally, but seals only when repairing the pressure seal 8, and does not slide on the simple tube 5, so it is much longer than the sliding seal 13 of the pressure seal 8 (・Can be used for a while.

However, since this also needs to be made from organic materials, it deteriorates over many years and needs to be replaced.

This exchange is performed as follows.

Pull out the tip of the simple tube 5 to the right side of the valve 1o (pressure seal 8 side in the figure), close the valve 1o to shut off the water, drain the water outside of this from the drain line 12 or 15, and then connect the inflatable seal. Replace with a new one.

However, in the method described above, the activated tip of the simple tube 5 is located at the inflatable seal 9, so in some cases it may become impossible to access it from the viewpoint of permissible exposure dose.

In this case, the simple tube 5 is reversely shaped as shown in FIG. 4, and the separately prepared connecting tube 21 is connected to the connecting member 2.
0 into the rear end of the removed simple tube 5, and pull the detachable rod 22 to push the simple tube 5 past the locked vent valve 10 and into the furnace vessel 1 side. after that,
Remove the lock on the detachable wand 220 and push the connecting tube 21 to the outside of the simple tube 5 to just behind the valve IO (then move the simple tube 5 to the valve 1).
The valve 10 left on the upstream side of the water valve 10 is closed to shut off the water. Valve 1
After draining water through the downstream drain line 12 or 15, the connecting tube 21 is completely pulled out from the rear. With this, there is no water downstream of the valve 10, so the inflatable seal 9 can be replaced. At the time of restoration, the inflatable seal 9 and the pressure-resistant seal 8 are in a complete state, but the pressure-resistant seal 8 is slightly old, with the connecting tube 21 installed in place of the simple tube 5, and the valve 10 is opened. Thereafter, the connecting tube 21 is pushed and guided by the guide 23 to join the tip of the connecting tube 21 to the rear end of the simple tube 5, and the detachable rod 22 is pulled and locked to completely connect both tubes. After pulling the connection 1 tube 21 (by pulling out the rear end of the simple tube 5 to the rear end of the pressure seal 8,
Separate the connecting tube 21 from the simple tube 5.

In this N, the role of the connecting tube 21 is not only to take the simple tube 5 in and out, but also to act as a sliding seal when the simple tube 5 is not in the pressure seal 8 by making the outer diameter the same as the simple tube 5. Insert into 13,
It plays the role of maintaining the seal function here.

The method of replacing the above-mentioned inflatable seal 9 is as follows.
To the extent that water leakage from the sliding seal 13 can be treated by the drain line 15, the pressure-resistant seal 8 is installed preventively before the seal is damaged.
When repairing the pressure seal 8, a system without the inflatable seal 9 can also be applied to the repair of the pressure seal 8.

In the pressure seal 8 shown in FIG. 3, when dealing with high-pressure water during reactor operation, the tightening nut 14 is tightened to the specified torque, and a large axial force is applied to the sliding seal 19 via the packing retainer 18. and use it as a fixed seal.

(Effects of the invention) According to the present invention, it is possible to completely seal the space between the instrumentation tube and the guide tube without using it under normal conditions. The pressure seal can be disassembled and repaired without having to do so.

Further, according to the embodiment described above, the expansion seal can be replaced by operating the valve, pulling out the instrumentation tube, etc. without draining or leaking the reactor water.

[Brief explanation of the drawing]

FIG. 1 is an overall conceptual diagram showing an embodiment of the present invention, and FIG.
a+ + (BL and FIG. 3 are partial detailed views of the aforementioned embodiment, FIG. 4 is an explanatory diagram of the operation of the aforementioned embodiment, and FIG. 5 is an overall diagram showing the conventional one. 1... Reactor vessel, 3...Guide tube, 5...Simple tube, 8...Pressure seal, 9...Inflatable seal, 13...Sliding seal layer 17

Claims (1)

[Claims] A guide tube that is watertightly connected to the bottom of the reactor vessel, an instrumentation tube that is removably inserted into the guide tube, and a pressure-resistant device that is attached to the outer end of the guide tube and provides a two-stage seal between it and the instrumentation tube. An instrumentation tube guide device for a nuclear reactor, comprising a seal and an expansion seal interposed in the middle of the guide tube.