JPS6124960Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a neutron flux monitor housing that is installed at the bottom of a nuclear reactor pressure vessel. Relating to a bundle monitor housing.

[Technical background of the invention]

In order to keep the neutron flux distribution within the reactor in an appropriate form during the operating period of a nuclear reactor, it is necessary to monitor it by inserting a rod-shaped in-reactor neutron flux monitor between the fuels.

The neutron flux monitor housing is a relatively long and slender tube that is attached to the bottom of the reactor pressure vessel and houses the lower part of the neutron flux monitor, and has a neutron flux monitor guide tube welded to its upper end.

FIG. 1 is a sectional view schematically showing the lower part of the nuclear reactor.

Reference numeral 1 in the figure indicates a reactor pressure vessel, and the reactor pressure vessel 1 is supported by a pedestal 2.

There is a reactor core (not shown) inside the reactor pressure vessel 1.
A shroud 3 and a core support plate 4 are attached to support the reactor.

The neutron flux monitor housing 11 is inserted into the reactor pressure vessel 1 through a hole 6 bored in the bottom of the reactor pressure vessel 1 and fixed by welding.

Further, a neutron flux monitor guide tube 5 is attached to the upper end of the neutron flux monitor housing 11.
Its upper end is inserted into a hole 7 provided in the core support plate 4 and opened upward.

The in-core neutron flux monitor (not shown) is inserted between the fuel in the reactor core (not shown), which is housed and held within the neutron flux monitor housing 11 and the neutron flux monitor guide tube 5 and installed above the core support plate 4. There is.

By the way, in the reactor pressure vessel 1 during normal operation,
An internal pressure of approximately 70 kg/cm ² is applied, and a similar internal pressure is applied to the portion of the neutron flux monitor housing 11 outside the reactor pressure vessel 1 through the open upper end of the neutron flux monitor guide tube 5.

For this reason, the neutron flux monitor housing 11 requires a hydraulic test, which is normally performed as a single item before it is attached to the reactor pressure vessel 1.

FIG. 2 is a sectional view showing a conventionally used neutron flux monitor housing 11. In the figure, reference numeral 21 is a tube that is the main body of the housing. A flange 22 is connected thereto, and bolt holes 23 are formed in the flange 22.

Further, the total length A of the neutron flux monitor housing 11 is approximately 4400 mm.

As shown in Figure 1, the neutron flux monitor housing 1
1 is inserted through a hole 6 at the bottom of the reactor pressure vessel 1 and fixed by welding.

Therefore, no internal pressure acts on the upper end of the monitor housing tube body of the neutron flux monitor housing 11 disposed inside the reactor pressure vessel 1, and therefore a water pressure test is unnecessary.

The length of the unnecessary part of this water pressure test is B shown in Figure 2, which is approximately 200 mm.

FIG. 3 is a cross-sectional view showing the state when a conventional neutron flux monitor housing 11 is subjected to a water pressure test, and reference numeral 31 is a sectional view of the neutron flux monitor housing 11.
It is a lower end seal attached to the lower end of the 32
shows the top end seal attached to the top end.

33 is a lower end seal 31 and an upper end seal 3
2 to the neutron flux monitor housing 11.

Further, 34 is a nut for tightening the lower end seal 31 and the upper end seal 32 after they are attached to the shaft 33, and for this purpose, threads (not shown) are cut at both ends of the shaft 33.

When conducting a water pressure test, the shaft 33 is first inserted into the tube body 21 of the neutron flux monitor housing 11, and the lower end seal 31 and the upper end seal 32 are attached to the lower end and the upper end, respectively.

After that, screw the nuts 34 from both ends of the shaft 33 into the lower end seal 31 and upper end seal 32.
are firmly fixed to the lower and upper ends of the neutron flux monitor housing 11.

After the above operations are completed, pressurized water is injected through a hole (not shown) made in the lower end seal 31 or the upper end seal 32 to conduct a water pressure test.

At this time, the lower end seal 31 and the upper end seal 3
An O-ring or the like (not shown) is attached to 2 to prevent leakage of test water from inside the tube 21 of the neutron flux monitor housing 11.

[Problems with background technology]

By the way, during the preparation work for the water pressure test, shaft 3
3 into the tube 21 from the upper or lower end of the neutron flux monitor housing 11, the total length A of the neutron flux monitor housing 11 is approximately 4400 mm.
It requires a work space of approximately 10 meters, which is more than double the length, making it difficult to secure a work space.

Furthermore, when inserting the shaft 33, the inner surface of the tube 21 may be damaged, requiring careful operation by a large number of people, which tends to prolong the operation time.

[Purpose of invention]

Therefore, the purpose of the present invention was made in view of the above problems, and it is possible to use a test method that does not require a large working space, allows a small number of people to conduct a water pressure test in a short time, and does not cause damage to the inner surface of the pipe. An object of the present invention is to provide a neutron flux monitor housing.

[Summary of the idea]

In other words, the neutron flux monitor housing of the present invention has a groove for fitting and supporting a hydraulic test tool in the tip portion of the neutron flux monitor housing tube body inserted into the reactor pressure vessel, where the internal pressure does not act. This feature simplifies the water pressure test by adding a little extra space to the length of the housing tube body, and improves work efficiency because the jigs and tools can be made smaller.

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings, but a description of the same parts as in the conventional example will be omitted.

Figure 4 shows the neutron flux monitor housing of the present invention.
1 is provided with a groove 42 having a semicircular cross section.

Since the groove 42 is located inside the reactor pressure vessel 1, the pressure inside the reactor does not act on it, and therefore a water pressure test is not necessary.Since the groove 42 is provided within the range of dimension B, it is protected against neutrons during a water pressure test and during normal operation of the reactor. The internal pressure to which the bundle monitor housing is subjected is not a factor that reduces the necessary strength.

Next, a method for hydraulic pressure testing of a neutron flux monitor housing according to the present invention will be explained with reference to FIG.

In the figure, 51 is a blind lid attached to the lower end of the neutron flux monitor housing, and 52 is a plug attached to the upper end.

Further, 53 is a bolt for attaching the blind cover 52 using the bolt hole 23 of the flange 22, and 54 is a nut screwed into the bolt 53.

When conducting a water pressure test, the blind cover 51 is first attached to the flange 22 using bolts 53 and nuts 54.

Thereafter, the plug 52 is inserted from the upper end of the tube 21 and attached using the groove 42.

This plug 52 has a claw 56 that fits into the groove 42, and when the claw 56 is inserted from the upper end of the tube body 41, the diameter becomes smaller than the inner diameter of the tube body 41. After insertion, the claw 56 opens by external operation and fits into the groove 42. It is sufficient to have a well-known mechanism for mating.

After the above operations are completed, pressurized water is injected through a hole (not shown) made in the blind lid 51 or the stopper 52 to perform a water pressure test.

At this time, the blind lid 51 and the stopper 52 are filled with O2 (not shown).
A ring, etc. is installed to prevent test water from leaking.

[Effect of idea]

As explained above, the neutron flux monitor housing of the present invention can reduce the size of jigs and tools such as seal parts used during hydraulic tests, thereby reducing the required work space and improving operability. is expected.

It can also contribute to reducing the number of workers and shortening working hours.

In addition, since there is no need to pass a shaft or the like for connecting the upper and lower end seal parts into the neutron flux monitor housing, there is no possibility of damaging the inner surface of the neutron flux monitor housing during the water pressure test.

Note that the present invention is not limited to the above-mentioned embodiment, and the groove 42 may be formed in a spiral shape or in a plurality of discontinuous shapes, and the plurality of discontinuous grooves may penetrate through the inner and outer surfaces of the distal end portion. It is also possible to do so.

[Brief explanation of the drawing]

Figure 1 is a schematic vertical sectional view showing the lower part of the reactor, Figure 2
The figure is a vertical cross-sectional view showing a conventional neutron flux monitor housing, Figure 3 is a cross-sectional view showing the state of the water pressure test of the neutron flux monitor housing in Figure 2, and Figure 4 is a view of a neutron flux monitor housing according to the present invention. FIG. 5 is a sectional view showing the embodiment, and FIG. 5 is a sectional view showing the condition of the neutron flux monitor housing in FIG. 4 during a water pressure test. 21, 41...Neutron flux monitor housing tube body, 22...Flange, 23...Bolt hole, 42
……groove.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A groove for fitting and supporting a hydraulic test jig is provided in the tip portion of the neutron flux monitor housing tube body inserted into the reactor pressure vessel where internal pressure does not act. A neutron flux monitor housing characterized by: (2) The neutron flux monitor housing according to claim 1, wherein the groove has a spiral shape. (3) The neutron flux monitor housing according to claim 1, wherein a plurality of grooves are formed intermittently. (4) The neutron flux monitor housing according to claims 1 and 3, wherein the plurality of intermittent grooves pass through the inner and outer surfaces of the tip portion.