JP2016176734A - Shield structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shield structure capable of replacing liquid for blocking neutron rays.SOLUTION: A shield structure 1 is disposed between an irradiation chamber 2 irradiated with neutron rays and an operation room 3 located outside the irradiation chamber 2, and blocks the neutron rays in the irradiation chamber 2. The shield structure 1 includes: a transparent water tank 11 that separates the irradiation chamber 2 from a space S, and stores transparent liquid E including water; a liquid supply unit 12 for supplying the liquid E into the water tank 11; a heater for heating the liquid E so as to generate upflow F of the liquid E in the water tank 11; and a liquid discharge unit 14 for discharging, from the water tank 11, the liquid E heated by the heater to be elevated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shielding structure that shields neutron beams.

  Japanese Patent Application Laid-Open No. 2011-141198 describes a radiation shield that shields alpha rays, beta rays, gamma rays, and neutron rays. This radiation shielding body includes a plurality of lead glasses and a spacer inserted between the plurality of lead glasses, and a space is formed between the plurality of lead glasses by the spacers. In this space, a shielding liquid for shielding neutron beams is accommodated. The solute of the shielding liquid is natural boron or a boron compound, or a mixture of these with a plurality of electrolytes.

  A lead plate having a two-layer structure is provided outside the radiation shield described above, and alpha, beta, gamma and neutron rays are shielded by this two-layer structure. Moreover, this radiation shielding body is provided with a viewing window in which the inside can be visually confirmed, and the above-described shielding liquid is accommodated inside the viewing window.

JP2011-141198A

  In the radiation shield described above, the neutron beam is shielded by the liquid accommodated between the two lead glasses. At this time, the substance (impurities and the like) in the liquid may be activated depending on the irradiation condition of the neutron beam and the kind of the irradiated substance. Activation is a phenomenon in which a nuclear reaction occurs upon irradiation of radiation, and a previously non-radioactive element is changed to a radioisotope. Since the liquid in which the radioactive material has accumulated needs to be purified, handling becomes complicated. Accordingly, it is required to streamline the wastewater treatment by replacing the liquid that shields neutron rays before the radioactive material accumulates.

  This invention makes it a subject to provide the shielding structure which can replace the liquid which shields a neutron beam.

  A shielding structure according to the present invention is a shielding structure that is provided between an irradiation chamber in which neutron irradiation is performed and an external space located outside the irradiation chamber, and shields neutron beams in the irradiation chamber. A transparent water tank that contains a transparent liquid containing water, a liquid supply unit that supplies the liquid into the water tank, and a liquid so as to generate an upward flow of the liquid in the water tank. A heater for heating, and a liquid discharger for discharging the liquid heated by the heater and discharged from the water tank.

  In this shielding structure, the water tank partitions the irradiation chamber and the external space located outside the irradiation chamber, and a liquid containing water is accommodated in the water tank. Therefore, the neutron beam generated in the irradiation chamber can be shielded by the liquid hydrogen atoms in the water tank. Moreover, this water tank and the liquid accommodated in a water tank are transparent. Therefore, the water tank and the liquid function as a window through which the irradiation chamber can be viewed from the external space. In this specification, “external space” refers to a space located outside the irradiation room, and this “external space” refers to an indoor space of a building such as an operation room and an outdoor space outside the building. , Including both. In addition, the liquid is heated by the heater after being supplied from the liquid supply unit into the water tank, and an upward flow of the liquid is generated in the water tank. The liquid heated and raised by the heater is discharged from the water tank to the liquid discharge portion. As described above, the liquid in the water tank can be quickly replaced by supplying the liquid from the liquid supply unit into the water tank and generating the upward flow by the heater and discharging the liquid from the water tank. Moreover, in this shielding structure, since the upward flow is generated by the heater and the liquid is discharged, the configuration for replacing the liquid in the water tank can be simplified.

  The liquid supply unit may supply the liquid uniformly to the bottom surface of the water tank. When the liquid is supplied uniformly to the bottom surface of the water tank in this way, the upward flow of the liquid in the water tank tends to be uniform. When the upward flow of the liquid is uniform, the liquid does not easily flow backward compared to the case where the liquid is not uniform, so that the liquid in the water tank can be quickly discharged before the radioactive material accumulates. Therefore, the liquid in the water tank can be replaced quickly and efficiently.

  The heater may warm the liquid uniformly in the horizontal direction. In this way, the liquid can be uniformly heated in the horizontal direction by the heater, so that the upward flow of the liquid can be made uniform. Therefore, the liquid can be quickly discharged before the radioactive material accumulates.

  Moreover, you may provide the temperature distribution acquisition means which acquires the temperature distribution in the horizontal direction of the liquid in a water tank. By acquiring the temperature distribution in the horizontal direction of the liquid with this temperature distribution acquisition means, it is possible to confirm whether or not there is a bias in the strength of the upward flow of the liquid. In addition, since it is possible to detect the occurrence of a bias in the strength of the upward flow of the liquid, it becomes possible to return the upward flow uniformly by controlling the heater or the like when the strength of the upward flow is biased.

  Moreover, you may provide the pressure control part which performs pressure control of the liquid supplied to the bottom face of a water tank. In this case, the pressure control unit can supply the liquid having a uniform pressure to the bottom surface of the water tank. Therefore, the upward flow from the bottom surface of the water tank can be made uniform, and the replacement of the liquid in the water tank can be performed more efficiently.

  According to the present invention, the liquid that shields the neutron beam can be replaced.

It is a longitudinal cross-sectional view which shows the shielding structure which concerns on embodiment. It is the cross-sectional perspective view which cut | disconnected the shielding structure of FIG. 1 vertically. It is a top view which shows arrangement | positioning of the liquid supply port and heater in the bottom face of the water tank which comprises the shielding structure of FIG. It is a longitudinal cross-sectional view which shows the shielding structure which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, the shielding structure 1 according to the present embodiment is provided in a building T such as a hospital or a research facility. The shielding structure 1 is used in a neutron capture therapy apparatus that performs cancer treatment by BNCT (boron neutron capture therapy), for example. This neutron capture therapy apparatus includes an irradiation chamber 2 in which a patient fixed on a treatment table is irradiated with a neutron beam to perform cancer treatment. The irradiation chamber 2 is a closed space covered with the shielding structure 1 and a shielding wall W made of concrete, for example.

  Conventionally, the irradiation chamber is a closed space without a window, and the irradiation chamber cannot be visually recognized from another adjacent chamber. However, in this embodiment, a part of the shielding structure 1 is transparent, and the inside of the irradiation chamber 2 can be visually recognized through the shielding structure 1 from the outside. On the side opposite to the irradiation chamber 2 in the shielding structure 1, for example, an operation chamber 3 is provided. The operation room 3 is an external space located outside the irradiation room 2. The operation room 3 is darker than the irradiation room 2. An operator M can enter the operation chamber 3, and this operator M controls the irradiation of the neutron beam in the irradiation chamber 2 by operating a device arranged in the operation chamber 3.

  The shielding structure 1 includes a water tank structure 10 that shields neutron beams from the irradiation chamber 2 and a wall structure 20 that is located on the operation chamber 3 side of the water tank structure 10. Thus, the shielding structure 1 has a double wall structure including the water tank structure 10 and the wall structure 20. The water tank structure 10 shields the neutron beam from the irradiation chamber 2 by the liquid E containing water.

  The wall body structure 20 is provided at a position separated from the water tank structure 10, and a space S is formed between the water tank structure 10 and the wall body structure 20. This space S is a part of the operation room 3, for example. The wall structure 20 shields secondary radiation generated from the water tank structure 10. The secondary radiation is a photon beam such as a gamma ray or an X-ray, for example, and is a radiation generated by irradiating a substance (such as an impurity) inside the liquid E with a neutron beam.

  As shown in FIGS. 1 and 2, the water tank structure 10 includes a water tank 11 positioned between the upper shielding wall W and the lower shielding wall W, and a liquid supply that supplies the liquid E to the inside of the water tank 11. Part 12, heater 13 that warms liquid E inside water tank 11 to generate upward flow F of liquid E, liquid discharge part 14 that discharges liquid E that has risen inside water tank 11, and temperature of liquid E And a temperature measurement unit (temperature distribution acquisition means) 15 for measuring the temperature.

  The liquid E is a transparent liquid containing hydrogen atoms. The liquid E may be water or a mixture in which other substances are mixed with water. When the liquid E is water, the cost of the liquid E can be reduced, and the procurement of the liquid E and the construction of the shielding structure 1 are facilitated on site. The liquid E may be tap water or pure water. When the liquid E is tap water, there is an advantage that the cost of the liquid E can be suppressed. On the other hand, when the liquid E is pure water, since impurities in the liquid E are reduced, activation inside the water tank 11 can be more reliably suppressed.

  The water tank 11 has a rectangular parallelepiped shape, and a part of the water tank 11 protrudes into the space S (the operation chamber 3 side). The water tank 11 is transparent and transmits visible light. The water tank 11 is made of acrylic, for example, capable of shielding neutron rays. However, the material of the water tank 11 may not be acrylic, for example, glass. Moreover, a part of the shielding wall W located above enters the water tank 11 from above, and the lower surface 11b of the shielding wall W located at the upper part of the water tank 11 is a flat surface.

  Note that the lower surface 11b of the shielding wall W may not be a flat surface, but preferably has a shape in which the liquid E does not stay. Further, the size of the water tank 11 and the arrangement position of the water tank 11 are adjusted according to the position of the neutron beam source in the irradiation chamber 2, the neutron dose, and the energy of the neutron beam.

  The liquid supply unit 12 is provided below the water tank 11, a plurality of liquid supply ports 12 a located on the bottom surface 11 a of the water tank 11, a liquid supply path 12 b communicating with each liquid supply port 12 a below the bottom surface 11 a, and the water tank 11. And a pressure controller 12c for controlling the pressure of the liquid E supplied into the water tank 11. The liquid supply path 12b is connected to the lower part of the water tank 11 in the space S, and the lower end of the liquid supply path 12b is connected to the water supply pipe 12f. A part of the liquid supply path 12 b extends vertically in the space S, and the upper end of the part extending vertically of the liquid supply path 12 b enters the lower part of the water tank 11. Moreover, the part which entered the lower part of the water tank 11 of the liquid supply path 12b is connected to each liquid supply port 12a.

  The pressure control unit 12 c is provided in the middle part of the liquid supply path 12 b located in the space S. The pressure control unit 12c includes a pump 12d and a pressure detector 12e. The pump 12d is provided on the upstream side (lower side) of the pressure detector 12e in the liquid supply path 12b. The pump 12d is an inverter pump that transfers the liquid E to each liquid supply port 12a, for example. The pressure detector 12e detects the pressure of the liquid E inside the liquid supply path 12b.

  In the pressure controller 12c, the pressure detector 12e detects the pressure of the liquid E, and the pressure detector 12e performs feedback control for controlling the pump 12d based on this pressure. By this feedback control, the pressure control unit 12c can supply the liquid E into the water tank 11 with a managed water pressure. Further, the pressure control unit 12 c controls the pressure of the liquid E so that the pressure of the liquid E supplied into the water tank 11 is uniform. Specifically, the pressure control unit 12c allows the liquid E to be ejected onto the bottom surface 11a at a slightly higher water pressure than the water pressure applied to the bottom surface 11a of the water tank 11 depending on the amount of the liquid E in the water tank 11. Perform pressure control.

  As shown in FIGS. 2 and 3, the liquid supply ports 12 a are arranged in a lattice point pattern on the bottom surface 11 a of the water tank 11. The liquid supply ports 12a are provided at equal intervals in the vertical and horizontal directions on the bottom surface 11a. Therefore, the liquid E is uniformly supplied from the liquid supply unit 12 to the bottom surface 11 a of the water tank 11. Here, “uniformly supplying the liquid to the bottom surface” means that the liquid is evenly supplied in a plane parallel to the bottom surface of the water tank so that the liquid rises in a planar shape from the bottom surface of the water tank. In the present embodiment, since the bottom surface 11a of the water tank 11 extends in the horizontal direction, the same amount of liquid E is supplied from each liquid supply port 12a so that no deviation occurs in the horizontal direction.

  The heater 13 is provided, for example, on the bottom surface 11a of the water tank 11, and has a comb-teeth shape that passes between the two liquid supply ports 12a. The heater 13 warms the liquid E uniformly in the horizontal direction. Here, “heating the liquid uniformly in the horizontal direction” indicates that the liquid is uniformly heated so that the temperature distribution of the liquid E in the horizontal direction (hereinafter referred to as horizontal temperature distribution) is not biased. As described above, the heater 13 has a function of uniformly heating the liquid E in the water tank 11, and the liquid E heated by the heater 13 moves upward as a uniform upward flow F. At this time, the liquid E previously supplied into the water tank 11 rises in a planar shape, and the older the liquid E is, the higher the position is. Thus, the old liquid E that has moved upward reaches the upper end of the portion of the water tank 11 that protrudes toward the space S, and is always discharged from the upper end of the water tank 11 to the liquid discharge portion 14.

  In addition, the heater 13 may be provided on the lower surface 11b of the shielding wall W located in the upper part of the water tank 11 in order to perform, for example, heat storage of the housing. Thus, the position where the heater 13 is provided is not particularly limited. In addition, a heater having a shape different from the comb-shaped heater 13 may be provided, and for example, a planar heater may be provided instead of the comb-shaped heater 13.

  The liquid discharge portion 14 includes a flange portion 14a that receives the liquid E overflowing from the upper end of the portion that protrudes into the space S of the water tank 11, and a liquid discharge path 14b that discharges the liquid E that has entered the flange portion 14a. Thus, the liquid discharge part 14 has a simple configuration for receiving the liquid E overflowed from the upper end of the water tank 11. The flange portion 14 a extends in the horizontal direction along the water tank 11 in the space S. The collar portion 14a has an L-shaped cross section when cut along a plane orthogonal to the longitudinal direction. That is, the collar part 14a is provided with the horizontal part 14c fixed to the outer surface of the water tank 11, and the vertical part 14d extended upwards from the edge part on the opposite side of the water tank 11 in the horizontal part 14c. The liquid discharge path 14b extends downward from a hole 14e formed so as to penetrate the horizontal portion 14c. In addition, about the shape and arrangement | positioning aspect of the liquid discharge part 14, it is not limited above, It can change suitably.

  The temperature measurement unit 15 acquires the horizontal temperature distribution of the liquid E in the water tank 11. The temperature measurement unit 15 is a thermo camera that displays an image of the horizontal temperature distribution of the liquid E, for example. Further, the temperature measuring unit 15 measures the deviation in the horizontal temperature distribution of the liquid E. Thus, it becomes possible to monitor whether the upward flow F of the liquid E is uniform, when the temperature measurement part 15 measures the deviation of horizontal temperature distribution.

  That is, the temperature measuring unit 15 can monitor whether the heater 13 is operating as expected. For example, when there is a rapid temperature change in the horizontal temperature distribution of the liquid E and the horizontal temperature distribution measured by the temperature measuring unit 15 is large, the strength of the upward flow F of the liquid E is not uniform. Since this state can be detected by the temperature measuring unit 15, the horizontal temperature distribution of the liquid E can be leveled by adjusting the amount of water of the liquid E to be supplied or changing or controlling the heater 13. It becomes possible to eliminate the unevenness of the upward flow F of E.

  Although FIG. 2 shows an example in which one temperature measurement unit 15 is provided, a plurality of temperature measurement units 15 may be provided. For example, a plurality of temperature measurement units 15 may be arranged along the vertical direction, and the plurality of temperature measurement units 15 may acquire a plurality of horizontal temperature distributions. Thus, when acquiring the horizontal temperature distribution of several height, the temperature of the liquid E can be managed in layers (for every height). Therefore, the horizontal temperature distribution and the upward flow F of the liquid E can be monitored more precisely. The temperature measurement unit 15 may not be a thermo camera, and may be a temperature detection sensor that acquires the horizontal temperature distribution of the liquid E as numerical data, for example.

  As shown in FIG. 1, the wall structure 20 is provided between the space S and the operation chamber 3. The wall structure 20 includes a transparent plate 21 that is a lead glass (glass containing lead) facing the water tank 11 in the horizontal direction, and a wall portion 22 provided around the transparent plate 21. The transparent plate 21 is embedded in the wall portion 22. The wall portion 22 includes a sheet member 22a that is a lead sheet positioned on the space S side, and a plaster board 22b that is positioned on the operation chamber 3 side to which the sheet member 22a is attached.

  The transparent plate 21 and the sheet member 22a contain lead which is a high specific gravity material, and have a function of shielding the secondary radiation described above. As described above, the shielding structure 1 includes the water contained in the liquid E, the transparent plate 21 containing lead, and the sheet member 22 a, and the water tank 11 is provided on the irradiation chamber 2 side of the transparent plate 21. Therefore, the neutron beam from the irradiation chamber 2 is reliably shielded by water, and the secondary radiation scattered from the water to the operation chamber 3 side is reliably shielded by the transparent plate 21 and the sheet member 22a. In addition, since the space S side of the transparent plate 21 (lead glass) is affected by moisture, such as being corroded by moisture in the water tank 11 and losing transparency, the transparent plate 21 of the transparent plate 21 is actually subjected to construction. Measures may be taken on the surface. Further, in the wall structure 20, it is possible to use a concrete wall portion instead of the wall portion 22.

  The effect of the shielding structure 1 comprised as mentioned above is demonstrated. First, in the shielding structure 1, the water tank 11 partitions the irradiation chamber 2 and the operation chamber 3, and the liquid E containing water is accommodated in the water tank 11. Therefore, the neutron beam generated in the irradiation chamber 2 can be shielded by the hydrogen atoms of the liquid E. Moreover, this water tank 11 partitions the irradiation chamber 2 and the operation chamber 3, and the water tank 11 and the liquid E are transparent. Accordingly, the water tank 11 and the liquid E function as a window through which the inside of the irradiation chamber 2 can be seen. In other words, the shielding structure 1 ensures the transparency of the shielding structure 1 by utilizing the property that the water contained in the liquid E is transparent.

  The liquid E is heated by the heater 13 after being supplied from the liquid supply unit 12 into the water tank 11, and an upward flow F of the liquid E is generated in the water tank 11. Further, the liquid E heated by the heater 13 is discharged from the water tank 11 to the liquid discharge portion 14. As described above, the liquid E is supplied from the liquid supply unit 12 into the water tank 11, the upward flow F is generated by the heater 13, and the liquid E is discharged from the water tank 11, thereby replacing the liquid E in the water tank 11. Can be done at any time. And the liquid E in the water tank 11 can be replaced rapidly.

  Specifically, since the liquid E can be discharged before the radioactive material accumulates in the water tank 11, the liquid E can be drained into the general waste water without exceeding the general drainage standard. That is, since the liquid E is always replaced in the water tank 11 and the state in which there is almost no radioactive substance in the water tank 11 is maintained, the liquid E can be safely discharged. Moreover, in this shielding structure 1, since the upward flow F is generated with the heater 13 and the liquid E is discharged | emitted, the structure which replaces | exchanges the liquid E can be simplified.

  The liquid supply unit 12 supplies the liquid E uniformly to the bottom surface 11 a of the water tank 11. If the liquid E is supplied uniformly to the bottom surface 11a in this way, the upward flow F of the liquid E tends to be uniform. In the case where the upward flow F of the liquid E is uniform, the liquid E is less likely to be backflowed compared to the case where the liquid E is not uniform. Therefore, the liquid E can be quickly discharged before the radioactive material accumulates. Furthermore, the entire amount of the liquid E in the water tank 11 can be replaced, and the liquid E can be replaced quickly and efficiently.

  The heater 13 warms the liquid E uniformly in the horizontal direction. In this manner, the heater 13 uniformly warms the liquid E in the horizontal direction, so that the upward flow F of the liquid E can be made uniform. Therefore, the liquid E can be quickly discharged before the radioactive material accumulates.

  In addition, the shielding structure 1 includes a temperature measurement unit 15 that acquires the horizontal temperature distribution of the liquid E in the water tank 11. By acquiring the horizontal temperature distribution of the liquid E by the temperature measuring unit 15, it is possible to confirm whether or not there is a bias in the strength of the upward flow F of the liquid E. In addition, since it is possible to detect the occurrence of a bias in the strength of the upward flow F of the liquid E, when the strength of the upward flow F is biased, the strength of the upward flow F is uniformly returned by controlling the heater 13 or the like. Is possible.

  The shielding structure 1 includes a pressure control unit 12 c that performs pressure control of the liquid E supplied to the bottom surface 11 a of the water tank 11. By this pressure control unit 12c, the liquid E having a uniform pressure can be supplied to the bottom surface 11a of the water tank 11. Therefore, the upward flow F from the bottom surface 11a of the water tank 11 can be made uniform, and the replacement of the liquid E in the water tank 11 can be performed more efficiently.

  Furthermore, since the wall structure 20 includes the transparent plate 21 made of lead glass, the operator M can visually recognize the space S from the operation room 3. Moreover, since the water tank 11 and the liquid E are also transparent, the operator M can visually recognize the inside of the irradiation chamber 2 from the operation chamber 3 through the transparent plate 21, the water tank 11, and the liquid E. Therefore, by directly viewing the inside of the irradiation chamber 2 from the operation chamber 3, it is possible to always observe the situation of the patient receiving treatment in the irradiation chamber 2, and to improve the safety of the patient. Moreover, since the patient can see the operator M through the shielding structure 1 functioning as a transparent window, a sense of security can be obtained during treatment. Furthermore, compared with the conventional shielding structure without a window, the shielding structure 1 having a window eliminates the feeling of blockage.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It deform | transforms in the range which does not change the summary described in each claim, or applied to others It may be. That is, the present invention can be variously modified without changing the gist of each claim.

  For example, in the above embodiment, the operation chamber 3 is provided on the opposite side of the irradiation chamber 2 in the shielding structure 1. However, the room provided on the opposite side of the irradiation room in the shielding structure may not be the operation room 3, and may be an external space located outside the irradiation room, such as a waiting room or an observation room where a patient's family enters. Good.

  The external space includes both the indoor space of the building T such as the operation room 3 and the outdoor G outside the building T. For example, as shown in FIG. 4, the opposite side of the irradiation chamber 2 in the shielding structure 1 may be an outdoor G. That is, the shielding structure 1 may be installed between the irradiation chamber 2 and the outdoor G. In FIG. 4, the shielding structure 1 is shown in a simplified manner. When the shielding structure 1 is installed as shown in FIG. 4, the operator M can visually recognize the patient P through the transparent shielding structure 1, and the patient P can also see the operator M through the shielding structure 1. Since it can be visually recognized, a sense of security can be given to the operator M and the patient P. Furthermore, since the patient P can visually recognize the outdoor G through the shielding structure 1, it is possible to feel the amenity of the outdoor G.

  Moreover, in the said embodiment, the temperature measurement part 15 which acquires the horizontal temperature distribution of the liquid E was used. However, instead of the temperature measurement unit 15, for example, a temperature measurement unit that acquires a temperature distribution of the liquid E in the vertical direction may be used. In this case, it is possible to monitor whether the vertical temperature distribution acquired by the temperature measurement unit is as expected (for example, whether the upper liquid E is warmer than the lower liquid E). . Furthermore, the function and arrangement position of the temperature measurement unit are not limited to the above embodiment, and can be changed as appropriate.

  Moreover, in the said embodiment, although the space S was formed between the water tank 11 and the transparent board 21, the transparent board 21 may be affixed on the outer surface of the water tank 11 directly. Furthermore, although the wall body structure 20 includes the transparent plate 21 and the wall portion 22, the configuration of the wall body structure 20 can be changed as appropriate. Further, the shielding structure may include only a water tank, a liquid supply unit, a heater, and a liquid discharge unit, and the wall body structure 20 may be omitted.

  Moreover, in the said embodiment, although the transparent plate 21 which is lead glass was used, this transparent plate may not be lead glass, for example, glass containing selenium may be sufficient. That is, the material of the transparent plate may be a high specific gravity material such as lead or selenium. Furthermore, the material of the sheet member 22a of the wall structure 20 may be a high specific gravity material, and is not limited to lead. However, when the material of the transparent plate or the sheet member is lead, there is an advantage that it is easily available as compared with other high specific gravity materials.

DESCRIPTION OF SYMBOLS 1 ... Shielding structure, 2 ... Irradiation chamber, 3 ... Operation chamber (external space), 11 ... Water tank, 11a ... Bottom surface, 11b ... Bottom surface, 12 ... Liquid supply part, 12c ... Pressure control part, 13 ... Heater, 14 ... Liquid Discharge unit, 15 ... temperature measurement unit (temperature distribution acquisition means), E ... liquid, F ... upflow, G ... outdoor (external space), S ... space.

Claims (5)

A shielding structure for shielding the neutron beam in the irradiation chamber, provided between an irradiation chamber in which irradiation of neutron beams is performed and an external space located outside the irradiation chamber;
A transparent water tank that partitions the irradiation chamber and the external space, and stores a transparent liquid containing water;
A liquid supply section for supplying the liquid into the water tank;
A heater for warming the liquid so as to generate an upward flow of the liquid in the water tank;
A liquid discharger from which the liquid heated and raised by the heater is discharged from the water tank;
Shielding structure with The liquid supply unit uniformly supplies the liquid to the bottom surface of the water tank.
The shielding structure according to claim 1. The heater warms the liquid uniformly in a horizontal direction;
The shielding structure according to claim 1 or 2. Comprising a temperature distribution acquisition means for acquiring a temperature distribution in a horizontal direction of the liquid in the water tank,
The shielding structure as described in any one of Claims 1-3. A pressure control unit for controlling the pressure of the liquid supplied to the bottom surface of the water tank;
The shielding structure as described in any one of Claims 1-4.

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