JP2000082597A - Moderator vessel for neutron scattering facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moderator vessel for a neutron scattering facility for preventing generation of a recirculating flow in a bottom part area in a vessel body. SOLUTION: In a moderator vessel 5 used in a neutron scattering plant for studying various physical properties using a neutron, a moderator 13 introduced to the bottom part in the vessel body 14 through the inside of an inner tube 17 is constituted so as to be discharged through the part between an outer tube 15 and the inner tube 17 from the top part of the vessel body 14. A swirl plate 22 for forming a swirl flow around the axis of the inner tube 17 to the moderator 13, is fitted/arranged in the vicinity of the part passing through the opening 16 of the top part of the vessel body 14 in the inner tube 17, and a blowoff hole 23 is bored in the tangent direction corresponding to the swirl flow by the swirl plate 22 in the wall part of the inner tube 17 on the lower side of this siwrl plate 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention allows a moderator to be contained therein to transmit high-intensity fast neutrons generated from a target by a spallation reaction, thereby converting them into thermal neutrons or cold neutrons. The present invention relates to a moderator container for a neutron scattering facility.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a neutron scattering facility for conducting various physical property studies using neutrons. Protons emitted from a proton injector 1 are accelerated by a linear accelerator 2 with a high-frequency current and accumulated. The beam is incident on the ring 3, and the accelerating speed is increased by the high frequency current until the required energy is obtained while the orbit is bent and orbited by the magnetic field of the bending electromagnet in the cumulative ring 3,
After that, protons that have become the necessary energy are accumulated in a ring 3
From the target 4 to a liquid heavy metal such as mercury held in the target 4 to generate fast neutrons by a spallation reaction (sporation reaction). The fast neutrons generated from the target 4 are converted into liquid hydrogen (20K, 1.5MP).
By transmitting the moderator such as a) through the moderator container 5 holding the moderator therein, the moderator is converted into thermal neutrons or cold neutrons according to the purpose of the research, and is guided to the laboratory 7 through the beam line 6.

FIGS. 4 and 5 show an example of a conventional moderator container used in a neutron scattering facility as described above. This type of moderator container 5 includes a container body 8 having a flat shape in the vertical direction. An outer tube 10 which is airtightly joined to an opening 9 formed at the center of the top of the container body 8 in the width direction and stands up; and is inserted through the outer tube 10 to a position near the bottom of the container body 8 to be inserted into the lower end. An inner pipe 12 opening an outlet 11, and a moderator 13 introduced through the inner pipe 12 to the bottom of the container body 8.
Is discharged from the top of the container body 8 through the space between the outer tube 10 and the inner tube 12.

[0004] That is, when the high-intensity fast neutrons generated from the metal in the target 4 by the spallation reaction are transmitted and converted into thermal neutrons or cold neutrons, the moderator 13 receives a large amount of heat input. Therefore, the moderator 13 is always supplied to and discharged from the moderator container 5 to ensure a good flow state, thereby removing heat and thereby reducing the moderator 1 in the moderator container 5.
3, the moderator 13 can be maintained in a supercritical state.

[0005]

However, in such a conventional moderator container 5, the moderator 13 flowing downward in the inner pipe 12 and flowing out of the outlet 11 collides with the bottom surface of the container body 8. To form a flow that turns upward while spreading radially, the recirculation flow R is likely to be generated in the bottom region in the container body 8 surrounded by the flow, and such a recirculation flow R is generated. If this occurs, the moderator 13 which remains continuously in the container body 8 and is not discharged may be generated, causing a local temperature rise, and the moderator 13 may not be able to be maintained in a supercritical state.

The present invention has been made in view of the above circumstances, and has as its object to provide a moderator container for a neutron scattering facility in which a recirculation flow is not generated in a bottom region in a container body.

[0007]

SUMMARY OF THE INVENTION The present invention provides a container body having a flat shape in the vertical direction, an outer tube which is airtightly joined to an opening formed at the top of the container body, and which stands up. And an inner pipe which is inserted to the vicinity of the bottom in the container body and opens an outlet at the lower end, and the moderator introduced through the inner pipe to the bottom in the container body is connected to the outer pipe and the inner pipe from the top of the container body. A moderator material container for a neutron scattering facility configured to be discharged through a space between the moderator and a turbulent flow around the axis of the inner tube relative to the moderator near a portion passing through an opening at the top of the container body in the inner tube. The swirl plate forming the swirl plate is inserted into the inner pipe wall portion below the swirl plate, and a discharge hole is formed in a tangential direction corresponding to the swirling flow by the swirl plate. .

In this way, the moderator flowing downward in the inner pipe forms a swirling flow around the axis of the inner pipe passing through the swirl plate, and furthermore, the swirling flow of the moderator Is ejected in the tangential direction corresponding to the swirling flow from the ejection hole in the inner tube wall, so that the swirling flow flowing out from the outlet at the lower end of the inner tube and the jet flowing from the ejection hole are combined. As a result, a large upward swirling flow is formed around the inner pipe in the container body, which flows without stagnation, and the diffusion of the recirculation flow which is to be generated in the bottom region in the container body is promoted to generate the recirculation flow. Is prevented.

Further, since the inner pipe is reinforced by the inner fitting of the swirl plate and the rigidity thereof is greatly improved, the vibration of the inner pipe which is excited due to the ejection of the jet from the ejection hole is significantly reduced. become.

Further, in the present invention, the inner pipe is narrowed so as to gradually decrease its diameter in the vicinity of the upper side of the swirl plate, and the narrowed diameter is maintained from the installation position of the swirl plate to the outlet. Is preferred.

With this configuration, the moderator flowing downward in the inner pipe is guided to the swirl plate after the flow velocity is increased near the upper side of the swirl plate, so that a swirling flow is formed by the swirl plate. The effect is greatly promoted, and it is possible to favorably form a swirling flow having a regular flow.

Further, in the present invention, a vacuum heat insulating layer is provided between a moderator introduction channel formed in the inner tube and a moderator discharge channel formed between the outer tube and the inner tube. It is good to intervene.

With this configuration, the discharge passage through which the moderator, which has been heated by the heat input resulting from the penetration of the high-intensity fast neutrons through the container body, flows, and the introduction through which the new moderator having a relatively low temperature flows. Since the flow path and the vacuum heat insulating layer are thermally isolated from each other, the temperature effect of the moderator flowing through the discharge flow path around the inner pipe is not affected by the moderator flowing through the introduction flow path inside the inner pipe. This prevents the moderator from causing unintended convection.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the present invention, in which the same reference numerals as in FIGS. 4 and 5 denote the same parts.

In the figure, reference numeral 14 denotes a container main body having a flat shape in the vertical direction, 15 denotes an outer pipe which is airtightly joined to an opening 16 formed at the center of the top of the container main body 14 in the width direction, and stands upright.
Denotes an inner pipe inserted through the outer pipe 15 to the vicinity of the bottom inside the container body 14 and opening the outlet 18 at the lower end, and a moderator introduced through the inner pipe 17 to the bottom inside the container body 14. 13 is configured to be discharged from the top of the container body 14 through the space between the outer pipe 15 and the inner pipe 17, the introduction flow path 19 of the moderator 13 formed in the inner pipe 17, the outer pipe 15, and the outer pipe 15. Discharge channel 2 for moderator 13 formed between inner tubes 17
A vacuum heat insulating layer 21 is interposed between 0 and 0.

The container body 14 in the inner pipe 17
Near the portion passing through the opening 16 at the top, there is a moderator 13
On the other hand, a swirl plate 22 that forms a swirling flow around the axis of the inner pipe 17 is fitted inside the swirl plate 22, and the swirl flow generated by the swirl plate 22 is provided on the wall of the inner pipe 17 below the swirl plate 22. A large number of ejection holes 23 are formed in corresponding tangential directions (see FIG. 2).

Further, the inner pipe 17 is a swirl plate 2
2 is formed so that the diameter is gradually reduced in the downward direction near the upper side of 2 and the narrowed diameter is maintained from the installation site of the swirl plate 22 to the outlet 18.
The outer pipe 1 is made to follow the drawing shape of the inner pipe 17.
5 also has an aperture shape.

In the illustrated example, in order to ensure the pressure resistance of the thinned container body 14 in consideration of the permeability of neutrons,
An internal reinforcing plate 24 is provided at a corner in the container body 14, and an external reinforcing frame 25 is fitted around the body of the container body 14 in a hasp shape.

In this manner, the moderator 13 flowing downward in the inner pipe 17 passes through the swirl plate 22 to form a swirling flow around the axis of the inner pipe 17. Since a part of the swirling flow of the moderator 13 is ejected from the ejection hole 23 in the wall of the inner pipe 17 in a tangential direction corresponding to the swirling flow, a swirling flow flowing out of the outlet 18 at the lower end of the inner pipe 17 is provided. When combined with the jet flow spouting from the jet holes 23, a large upward swirling flow is formed around the inner pipe 17 in the container main body 14 without any stagnant flow, and is likely to occur in the bottom region in the container main body 14. Diffusion of the circulating flow is promoted and the generation of the recirculating flow is prevented.

Therefore, according to the above embodiment, the container body 1
Since it is possible to prevent the occurrence of the recirculation flow in the bottom region in the inside 4, it is possible to reliably avoid a local temperature rise due to the continuous stay of the moderator 13 in the container body 14. In addition, the supercritical state of the moderator 13 can be favorably maintained.

Further, since the inner pipe 17 is reinforced by the inner fitting of the swirl plate 22 and the rigidity of the inner pipe 17 can be greatly improved, the inner pipe 17 is excited by the jet jet from the jet hole 23. The vibration of the tube 17 can also be significantly reduced.

Further, particularly in this embodiment, the inner pipe 17
Is formed so as to gradually reduce the diameter in the downward direction near the upper side of the swirl plate 22 and to maintain the narrowed diameter from the installation site of the swirl plate 22 to the outlet 18. The moderator 13 flowing downward can be guided to the swirl plate 22 after increasing the flow velocity near the upper side of the swirl plate 22, greatly facilitating the effect of the swirl plate 22 to form a swirling flow, and Can be satisfactorily formed.

Further, since the vacuum heat insulating layer 21 is interposed between the introduction flow path 19 and the discharge flow path 20 of the moderator 13,
A discharge channel 20 through which the moderator 13 heated by the heat input caused by the high-intensity fast neutrons passing through the container body 14 flows;
Introducing channel 1 through which a new moderator 13 having a relatively low temperature flows
9 is thermally isolated by a vacuum heat insulating layer 21,
It is possible to prevent the moderator 13 from generating an unintended convection in advance.

The moderator container for a neutron scattering facility of the present invention is not limited to the above-described embodiment, and the moderator may be liquid methane or water other than liquid hydrogen. It goes without saying that various changes can be made without departing from the spirit of the present invention.

[0026]

According to the moderator container for a neutron scattering facility of the present invention described above, various excellent effects as described below can be obtained.

(I) According to the first aspect of the present invention, a swirling flow is formed by the swirl plate with respect to the moderator flowing in the inner pipe, and a part of the swirling flow is blown out from the inner pipe wall. By jetting from the hole, a large upward swirling flow can be formed around the inner tube in the container main body, which flows entirely without stagnation, thereby preventing the occurrence of a recirculating flow in the bottom region in the container main body. Therefore, it is possible to reliably avoid a local temperature increase due to the continuous stay of the moderator in the container main body, and to maintain the supercritical state of the moderator in a good condition.

(II) According to the first aspect of the present invention, the inner pipe is reinforced by the swirl plate being fitted inside, so that the rigidity of the inner pipe can be greatly improved.
Vibration of the inner tube, which is excited due to the ejection of the jet from the ejection hole, can be significantly reduced.

(III) According to the second aspect of the present invention, the moderator flowing downward in the inner pipe can be guided to the swirl plate after increasing the flow velocity near the upper side of the swirl plate. Thus, the swirl flow forming effect of the swirl plate is greatly promoted, and a well-formed swirl flow can be favorably formed.

(IV) According to the invention described in claim 3 of the present invention, a discharge channel in which a moderator whose temperature is increased by heat input due to the penetration of high-intensity fast neutrons through the container main body flows. The introduction flow path through which a new moderator having a low target temperature flows is thermally isolated by a vacuum heat insulating layer, so that unintended convection of the moderator in the inner pipe can be avoided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of an embodiment of the present invention.

FIG. 2 is a plan cross-sectional view of a position where a blowout hole of the inner tube of FIG. 1 is formed.

FIG. 3 is a schematic diagram showing an example of a general neutron scattering facility.

FIG. 4 is a front sectional view showing an example of a conventional moderator container.

FIG. 5 is a view in the direction of arrows VV in FIG. 4;

[Explanation of symbols]

 5 Moderator Container 13 Moderator 14 Container Main Body 15 Outer Pipe 16 Opening 17 Inner Pipe 18 Outlet 19 Introducing Channel 20 Draining Channel 21 Vacuum Insulating Layer 22 Swirl Plate 23 Spouting Hole

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Ryutaro Hino, 2-4, Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki Pref. Inside the Tokai Research Laboratory, Japan Atomic Energy Research Institute (72) Akira Nishikawa Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa 1st Ishi Kawashima Harima Heavy Industries, Ltd. Yokohama Engineering Center (72) Inventor Atsuhiko Terada 1st Shinnakahara-cho, Isogo-ku, Yokohama, Kanagawa Prefecture Ishikawashima Harima Heavy Industries, Ltd. Yokohama Engineering Center F-term (reference) 2G085 BD01 BD10 BE02 BE05 BE06 BE10 DA10

Claims (3)

[Claims] 1. A container body having a flat shape in a longitudinal direction, an outer tube which is airtightly joined to an opening formed at a top portion of the container body and rises, and a bottom portion in the container body passing through the outer tube. And a moderator introduced into the bottom of the container body through the inner tube and discharged from the top of the container body between the outer tube and the inner tube. A moderator material container for a neutron scattering facility configured as described above, wherein a swirl plate that forms a swirling flow around the axis of the inner tube with respect to the moderator is inserted around the portion of the inner tube passing through the opening at the top of the container body. A moderator container for a neutron scattering facility, wherein a moderator hole is provided in the inner pipe wall below the swirl plate in a tangential direction corresponding to a swirling flow generated by the swirl plate. 2. The method according to claim 1, wherein the inner pipe is formed so as to gradually reduce its diameter in the downward direction near the upper side of the swirl plate, and to maintain the narrowed diameter from the installation position of the swirl plate to the outlet. The moderator container for a neutron scattering facility according to claim 1. 3. A vacuum heat-insulating layer is interposed between a moderator introduction channel formed in the inner tube and a moderator discharge channel formed between the outer tube and the inner tube. The moderator container for a neutron scattering facility according to claim 1 or 2, wherein: