JP2017090376A - Neutron shield structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutron shield structure with excellent strength that can be formed more easily without requiring management for preventing alteration or corrosion and setting of an attached facility.SOLUTION: A neutron shield structure 1A includes: a concrete part 2 (a first concrete part 5 and a second concrete part 6) surrounding a facility P, which emits neutrons; a water-containing part 4 in contact with the concrete part 2, surrounding the facility P; and a closed container 8 filled with an aqueous solution of water-soluble polymers, the aqueous solution containing water in a concentration of 98% by weight or higher and the closed container 8 being in the water-containing part 4.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a neutron shielding structure.

When neutrons are generated in a nuclear reactor or radiation utilization facility, etc., it is necessary to shield the generated neutrons so that the neutrons do not affect the operator or the general public. In order to shield neutrons, it is efficient to reduce the energy of neutrons by elastic scattering with light nuclei and capture neutrons by an absorption reaction with a shielding material provided on the outer periphery of a facility or the like. Since the hydrogen (H) nucleus consists of a single proton, the hydrogen nucleus is the lightest of all the elements, and the energy loss due to hydrogen elastic scattering is the largest. Therefore, the shielding ability of hydrogen against neutrons is the highest, and a substance containing hydrogen is optimal as a neutron shielding material. As a shielding material containing hydrogen, for example, water, polyethylene, paraffin, concrete and the like are known.
For example, in Patent Document 1, two sheets or a board-shaped sandwiching body are stacked, and a hydrous layer made of fibers or a porous body is sandwiched between the sandwiching bodies, and rubber latex and A water-containing sheet and a water-containing board impregnated with a liquid mixture of a superabsorbent resin are disclosed.

Of the above-described shielding materials, water, polyethylene and paraffin have the same ability to shield against neutrons. Since polyethylene and paraffin are weak in strength, they have a problem that they are easily damaged when subjected to a load and are expensive. Regarding water, there is a problem that it is easily deteriorated, corroded, and decayed after a long period of time. In nuclear reactors, water is used as a neutron shielding material for the core, but this water is managed to maintain high water quality by the water circulation system. Absent. However, such water quality management is not common, and it is difficult to apply it to the entire reactor or the outer periphery of a radiation utilization facility.
On the other hand, the shielding ability of concrete against neutrons is inferior to that of water, polyethylene and paraffin. However, since concrete contains a relatively large amount of moisture, is excellent in strength and stability, and is inexpensive, it is widely used as a neutron shielding material.

In order to compensate for the lack of neutron shielding ability of concrete, for example, a method of increasing the thickness of concrete can be considered, but a method of using water, polyethylene and paraffin in combination is also proposed.
For example, in Patent Document 2, formed by adding water to a casing that forms a space around a neutron generation source or a neutron passage, and a mixture of a superabsorbent resin and a neutron absorber, the casing is formed. A neutron shield having a filler filling the space is disclosed. A shield made of concrete and lead is added to the casing or the like for shielding gamma rays emitted simultaneously with neutrons.

JP 2002-162493 A JP-A-5-323066

However, in the water-containing sheet and the water-containing board described in Patent Document 1, since the porous body sandwiched between the two sandwiched bodies is not sealed, contact between the porous body and the atmosphere cannot be prevented, and the porous body There was a problem that it was not possible to prevent invasion of various bacteria into the material and oxidation of the porous material.
Further, in the water-containing sheet and the water-containing board described in Patent Document 1, it is necessary to impregnate a porous body sandwiched between two sandwiched bodies with a mixed solution of rubber latex and superabsorbent resin. Moreover, in the neutron shield described in Patent Document 2, it is necessary to add water to the mixture of the highly water-absorbent resin and the neutron water-absorbing agent. In this way, it takes time to include water in the material for holding water, and the larger the size of the nuclear reactor, radiation utilization facility, etc., that is, the larger the space for shielding neutrons, the construction of the shielding structure. There is a problem that it takes a lot of time and effort.

  The present invention has been made in view of the above circumstances, and has a neutron shielding structure that is excellent in strength and can be constructed more easily without requiring management or installation of ancillary facilities to prevent alteration, corrosion, decay, etc. provide.

  The neutron shielding structure according to claim 1 includes a concrete portion provided surrounding a facility that emits neutrons, a water-containing portion provided so as to surround the facility in contact with the concrete portion, and an aqueous solution of a water-soluble polymer. And a ratio of water in the aqueous solution is 98% by weight or more, and the sealed container is filled in the water-containing portion.

In said neutron shielding structure, the neutron beam from the facility is captured by the water contained in the concrete part and the water of the aqueous solution in the water-containing part, and neutron leakage to the outside is prevented.
Since the neutron shielding structure includes a concrete portion and a water-containing portion supported by contacting the concrete portion, the neutron shielding structure is excellent in strength. In addition to the fact that the concrete part is unlikely to be altered, corroded or spoiled, the water-containing part is filled with a water-soluble polymer aqueous solution with a high proportion of water. Invasion of germs and the like from the outside is prevented, and in the same way as in the concrete part, alteration, corrosion, rot, etc. hardly occur in the water-containing part. Therefore, it is not necessary to manage the neutron shielding structure described above and to install an accessory facility to prevent alteration, corrosion, decay and the like.
Furthermore, by preparing an aqueous solution of a water-soluble polymer in a sealed container in advance and bringing it into the construction site of the neutron shielding structure, the construction site process can be shortened and the neutron shielding structure can be constructed more easily.

  The neutron shielding structure according to claim 2, wherein the concrete part includes a first concrete part provided so as to directly surround the facility, and a second concrete part disposed outside the first concrete part, The water-containing part is provided between the first concrete part and the second concrete part.

  In the neutron shielding structure described above, the strength of the entire neutron shielding structure is increased by sandwiching and supporting the water-containing portion between the first concrete portion and the second concrete portion.

  The neutron shielding structure according to claim 3, wherein the water-containing portion contains a plurality of the sealed containers.

  In said neutron shielding structure, a construction process advances efficiently by accommodating multiple airtight containers prepared beforehand at the time of construction in a water-containing part.

  5. The neutron shielding structure according to claim 4, wherein a box is disposed in the water-containing portion, and the sealed container is accommodated in the box.

  In the neutron shielding structure described above, the sealed container is stably disposed by being accommodated inside the box. In particular, when a plurality of sealed containers are accommodated inside the box body, the stacked body of the plurality of sealed containers is positioned by each wall surface of the box body, and the construction process proceeds efficiently. Further, if a plurality of sealed containers are stored in advance in a box outside the construction site, brought into the construction site, and the box is placed at a predetermined position, the construction process can be shortened.

  The neutron shielding structure according to claim 5, wherein the box is made of iron.

In the neutron shielding structure described above, the strength of the box is increased, and the shielding ability against relatively strong energy neutron beams from the facility is also enhanced. Here, the relatively strong energy means, for example, 10 ⁶ eV = 10 MeV or more.

  The neutron shielding structure according to claim 6, wherein an iron layer is provided inside the water-containing portion.

  In the neutron shielding structure described above, particularly when the energy of the neutron beam from the facility is relatively strong, the high energy neutron beam is captured by the iron layer, and the low energy is absorbed by the water in the aqueous solution of the water-containing part placed outside the iron layer. Neutron rays are captured. Thus, even when the energy of the neutron beam from the facility is strong, the shielding ability against neutrons is enhanced, and the effect of preventing leakage of neutrons to the outside can be sufficiently obtained.

  The neutron shielding structure of the present invention is excellent in strength, and can be constructed more easily without requiring management for preventing alteration, corrosion, decay, etc., and installation of attached facilities.

It is a top view of the neutron shielding structure concerning the present invention. It is sectional drawing of the neutron shielding structure seen by the arrow GG shown in FIG. It is the schematic which shows the model at the time of calculating the neutron dose leaked from each material. It is a graph which shows the relationship between the thickness dimension of concrete, water, iron, and lead, and the neutron dose rate leaking from each material. In water or iron, it is a graph which shows the energy spectrum of the neutron irradiated to each material, Comprising: (a) is related with water and (b) is related with iron. It is a figure which shows the neutron shielding structure of 1st embodiment to which this invention is applied, and is sectional drawing corresponding to the case where it views on the GG line | wire shown in FIG. It is a figure which shows the neutron shielding structure of 2nd embodiment to which this invention is applied, and is sectional drawing corresponding to the case where it views on the GG line | wire shown in FIG. It is sectional drawing of the neutron shielding structure provided with the structure of Test Example 2 shown in Table 1. It is sectional drawing of the neutron shielding structure provided with the structure of Test Example 7 shown in Table 1. It is a graph which shows the relationship between the thickness dimension of the neutron shielding structure provided with the structure of the test example 1 to the test example 6 shown in Table 1, and the comparative example 1, and the neutron dose rate leaking from each neutron shielding structure. The relationship between the thickness dimension of the neutron shielding structure provided with the structure of Test Example 5, Test Example 7, Test Example 8, and Comparative Example 1 and Comparative Example 2 shown in Table 1 and the neutron dose rate leaking from each neutron shielding structure is shown. It is a graph. It is a graph which shows the relationship between the thickness dimension of the neutron shielding structure provided with the structure of Test Example 1, Test Example 9 to Test Example 11, and Comparative Example 1 shown in Table 1, and the neutron dose rate leaking from each neutron shielding structure.

A neutron shielding structure 1 according to the present invention surrounds a concrete part 2 provided around a facility P that emits neutrons as shown in FIG. 1 and surrounds the facility P in contact with the concrete part 2 as shown in FIG. And a water-containing part 4 provided.
The facility P is a radiation utilization facility including, for example, a neutron generation source and a nuclear reactor, and is not particularly limited as long as it is a facility that emits neutrons. Hereinafter, in the neutron shielding structure 1, a side closer to the facility P is referred to as “inside”, and a side far from the facility P is referred to as “outside”.
In addition, in FIG. 2, although the structure in which the water-containing part 4 is arrange | positioned between the inner concrete part 2 and the outer concrete part 2 is illustrated, the relative of the concrete part 2 and the water-containing part 4 is mentioned so that it may mention later. The positional relationship is not limited to the example of FIG.

  The concrete part 2 is comprised from the general concrete used for construction of a building. The weight moisture content of the concrete part 2 is, for example, 5% to 8%. However, the composition and weight moisture content of the concrete constituting the concrete part 2 are appropriately set in consideration of the structure and shape of the facility P, the strength required for the neutron shielding structure 1, and the like.

Furthermore, the neutron shielding structure 1 includes a sealed container 8 filled with an aqueous solution of a water-soluble polymer (not shown), and the sealed container 8 is filled in the water-containing portion 4.
Examples of the water-soluble polymer include carboxymethyl cellulose (CMC), sodium polyacrylate, polyvinyl pyrrolidone (PVP), and the like, which are used in cryogens and the like. Can be mentioned.
The ratio of water in the aqueous solution containing the water-soluble polymer is 98% by weight or more, and this aqueous solution often becomes a gel having high water absorption.

Here, taking concrete, water, iron and lead as examples, the thickness dimensions of each material and the neutron dose after passing through each material will be examined.
The graph of FIG. 4 shows each material of the neutron shielding structure 200 cm away from the target when a relatively high energy 235 MeV proton beam is applied to an iron target having dimensions of 14 cm long × 14 cm wide × 7 cm thick as shown in FIG. The neutron dose rate leaking from (only concrete is illustrated in FIG. 3) is calculated. The beam loss was 10 nA · min / weak. For concrete, the neutron dose rate was calculated using the physical properties of Portland cement, which is widely used.
As shown in FIG. 3, concrete, water, and iron have a higher shielding ability against neutrons (hereinafter sometimes referred to simply as “shielding ability”) than lead. However, for concrete and water, the shielding ability becomes the same as that of lead as the thickness dimension increases. For water, when the thickness dimension exceeds 180 cm, the shielding ability is lower than that of lead.
Note that the neutron multiplication effect is noticeable in heavy elements such as lead.

Further, the graph of FIG. 5 shows a portion of each material up to 10 cm outward from the end surface on the target side, a portion of 100 cm to 110 cm with respect to the end surface on the target side, and 190 cm from the end surface on the target side on the side opposite to the target The energy spectrum of neutrons remaining without being captured in each part of the part between the end face and (a) is a calculation result for water, and (b) is a calculation result for iron. It is. The horizontal axis of FIG. 5 shows the energy of neutrons leaking from each material, and shows that it becomes stronger toward the right side of the graph.
As shown in FIG. 5, about water and iron, the shielding capability with respect to a neutron becomes high, so that it becomes an outer part. However, with water, shielding ability against neutrons with relatively low energy (for example, less than 10 ⁶ eV = 10 MeV) is sufficiently exhibited, but shielding against neutrons with high energy (for example, 10 ⁶ eV = 10 MeV or more). Capacity is reduced and high energy neutrons leak from the water. This tendency appears more prominently in the outer part. On the other hand, about iron, the shielding capability with respect to a high energy neutron is high, and the shielding capability with respect to a high energy neutron becomes very high, so that it becomes an outer part.

  As described above, the shielding ability of concrete, water and iron against neutrons is different from each other. Therefore, it is preferable that the neutron shielding structure 1 includes at least the concrete portion 2 and the water-containing portion 4 and further includes a structure (iron-containing portion) made of iron when the energy of the neutron from the facility P is relatively high. The arrangement and thickness dimensions of the concrete part 2 and the water-containing part 4 and the presence / absence of the iron-containing part can be appropriately changed in consideration of the shielding ability of each material as exemplified in FIGS.

  Hereinafter, embodiments of a neutron shielding structure to which the present invention is applied will be described with reference to the drawings.

(First embodiment)
As shown in FIG. 6, in the neutron shielding structure 1 </ b> A according to the first embodiment, the concrete portion 2 is spaced outside the first concrete portion 5 with the first concrete portion 5 and the first concrete portion 5 spaced from each other. It consists of the arranged second concrete part 6.
The hydrous part 4 is provided between the first concrete part 5 and the second concrete part 6. Since the shielding ability increases as the water (that is, the aqueous solution of the water-soluble polymer) filled in the water-containing portion 4 is arranged outside, the water-containing portion 4 is arranged outside the center of the neutron shielding structure 1A. It is preferable that it is disposed on the outermost side of the neutron shielding structure 1A.

A box 10 is disposed in the water-containing portion 4. Examples of the material of the box 10 include metals such as wood and iron, and are not limited when the energy of neutrons from the facility P is relatively low (for example, less than 10 ⁶ eV). In particular, when the energy of neutrons from the facility P is high (for example, 10 ⁶ eV or more), the box 10 is preferably made of iron. In such a configuration, in the process in which the neutron beam from the facility P passes through the inner wall 10a and the outer wall 10b of the box 10, neutrons are also captured by iron.

  A plurality of sealed containers 8 are accommodated in the water-containing portion 4. In the first embodiment, a plurality of sealed containers 8 are accommodated inside the box 10. In order to prevent the deterioration, corrosion, decay, etc. of the aqueous solution in the sealed container more reliably, it is preferable that an inert gas such as nitrogen is enclosed inside the water-containing portion 4, that is, inside the box body 10.

  The main body of the sealed container 8 (that is, a container filled with an aqueous solution of a water-soluble polymer (not shown)) is a small box formed in a size that can be disposed in the water-containing portion 4, such as plastic. It is composed of However, the main body of the sealed container 8 may be a bag made of nylon poly or non-woven fabric, and is not particularly limited as long as a plurality of the water-containing portions 4 can be arranged and can be filled with an aqueous solution of a water-soluble polymer.

  For example, when a neutron with a maximum energy of 235 eV is emitted from the facility P, the thickness dimension t1 of the first concrete part 5 is 5% or more and 20% or less with respect to the thickness dimension of the entire neutron shielding structure 1A. The thickness dimension t2 filled with the container 8 is 5% or more and 15% or less, the thickness dimension t4 of the inner wall 10a and the outer wall 10b of the box 10 is 5% or more and 10% or less, and the thickness dimension t3 of the second concrete portion 6 is It is preferably 60% or more and 80% or less. By comprising in this way, the shielding capability of 1 A of neutron shielding structures increases.

When constructing the neutron shielding structure 1A, it is advisable to store and fill a plurality of sealed containers 8 in the box 10 in advance outside the construction site, enclose nitrogen and the like, and seal them.
At the construction site, first, after placing the formwork at a predetermined position, concrete is placed and the first concrete portion 5 is provided. Then, after arranging a formwork on the outer side of the first concrete part 5 at intervals, the concrete is placed and the second concrete part 6 is provided.
Next, between the first concrete part 5 and the second concrete part 6, the box body 10 filled with the sealed container 8 as described above is disposed. As needed, concrete is replenished between the first concrete part 5 and the box 10 or between the box 10 and the second concrete part 6.
The neutron shielding structure 1A can be constructed by the above-described steps. However, the construction process of the neutron shielding structure 1A is not limited to the above-described process. In the case where the work efficiency can be improved, for example, after the first concrete portion 5 is provided as described above, the box body 10 filled with the sealed container 8 is disposed outside the first concrete portion 5, and the box body After placing the formwork on the outside of 10, the concrete may be cast and the second concrete portion 6 may be provided.

In the neutron shielding structure 1A of the first embodiment described above, the neutron beam generated in the facility P is captured by the water contained in the first concrete part 5 and is contained in the aqueous solution of the water-soluble polymer contained in the water-containing part 4. It is also captured by water and further captured by the second concrete part 6. Thereby, the shielding capability with respect to the neutron of 1 A of neutron shielding structures is exhibited, and the leakage of the neutron to the outside can be prevented.
Moreover, 1 A of neutron shielding structures of 1st embodiment demonstrated above are equipped with the 1st concrete part 5 and the 2nd concrete part 6, and are equipped with the outstanding intensity | strength. And the water-containing part 4 can be protected by arrange | positioning the water-containing part 4 between the 1st concrete part 5 and the 2nd concrete part 6, and the intensity | strength as the neutron shielding structure 1A whole can be maintained.
Further, in the neutron shielding structure 1A of the first embodiment described above, the use of concrete wipes away the concern about corrosion and decay in the first concrete portion 5 and the second concrete portion 6, and there is concern about corrosion and decay. In addition, by sealing a stable aqueous solution having an appropriate viscosity in the sealed container 8, corrosion, decay, and the like in the water-containing portion 4 can be more reliably prevented. Therefore, management for preventing deterioration, corrosion, decay, etc. of water and installation of ancillary facilities are not required, and the enlargement of the neutron shielding structure 1A can be suppressed.
Further, in the neutron shielding structure 1A of the first embodiment described above, since the above-described aqueous solution is sealed in the sealed container 8, it is possible to facilitate handling in arrangement and transportation at a predetermined position during construction. As a result, even a large neutron shielding structure 1A can be constructed more easily.

Moreover, according to the neutron shielding structure 1A of the first embodiment, by accommodating a plurality of sealed containers 8 in the water-containing portion 4, the above-described aqueous solution can be handled for each sealed container 8, and the neutron shielding structure 1A construction process Can be made more efficient.
Furthermore, by arranging the box 10 in the water-containing portion 4 and housing the plurality of sealed containers 8 inside the box 10, the plurality of sealed containers 8 can be efficiently stacked along the wall surface of the box 10. it can. If the inside of the box body 10 is filled in advance with a plurality of sealed containers 8 outside the construction site and brought into the construction site, the box body 10 is placed at a predetermined position (that is, between the first concrete portion 5 and the second concrete portion 6). The hydrous part 4 can be installed only by arrange | positioning.

  Further, when the energy of neutrons emitted from the facility P is higher, the box 10 is made of iron in the neutron shielding structure 1A of the first embodiment, so that the water contained in the concrete part 2 and the water-containing part 4 is captured. High energy neutrons that cannot be captured can be captured by iron on the inner wall 10a and the outer wall 10b. Therefore, the shielding ability of the neutron shielding structure 1A against higher energy neutrons can be increased by configuring the box 10 with iron.

In addition, as a modification of the neutron shielding structure 1A of the first embodiment, if the energy of neutrons emitted from the facility P is low and does not interfere with the construction, the first concrete portion 5 and the second concrete are not provided without providing the box 10. A plurality of sealed containers 8 may be stacked on the water-containing portion 4 between the portions 6. Thereby, it is not necessary to prepare the large box 10, and a device such as a large crane for moving and transporting the box 10 becomes unnecessary, and the cost can be reduced.
Further, as another modification of the neutron shielding structure 1A of the first embodiment, if the energy of neutrons emitted from the facility P is low and construction does not interfere, the box 10 is treated as the sealed container 8 and the inside of the box 10 Alternatively, an aqueous solution of a water-soluble polymer may be accommodated. In this case, it is preferable that an antibacterial treatment is performed on the inner surface of the box 10 for the purpose of more reliably preventing corrosion or decay of the aqueous solution of the water-soluble polymer.

  Further, as described above, the amount of neutron that leaks from the outside of the neutron shielding structure 1A decreases as the water is arranged outside the neutron shielding structure 1A, so that the water-containing portion 4 is the center in the thickness direction of the neutron shielding structure 1A. It is preferable to arrange | position outside, and it is more preferable to arrange | position to the outermost side of 1 A of neutron shielding structures. Therefore, as another modification of the neutron shielding structure 1A of the first embodiment, if there is no problem in the construction, the second concrete portion 6 is omitted so that the thickness dimension of the first concrete portion 5 is sufficient, and the first concrete portion 5 The water-containing part 4 may be provided in contact with the outside. Thereby, the shielding capability of neutron shielding structure 1A can be improved more. Thus, when the water-containing part 4 is arranged outside the structure made of concrete (that is, the concrete part 2) and the outer wall of the water-containing part 4 is exposed, the strength of the water-containing part 4 and the neutron shielding structure 1A is reduced. For the purpose of restraining, it is preferable to use the box 10.

(Second embodiment)
Next, the neutron shielding structure 1B of the second embodiment to which the present invention is applied will be described. In addition, among the components of the neutron shielding structure 1B of the second embodiment, the same components as those of the neutron shielding structure 1A of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIG. 7, the neutron shielding structure 1B includes an iron layer 12 and a third concrete portion 7 in addition to the constituent elements of the neutron shielding structure 1A.

  The iron layer 12 is disposed between the first concrete part 5 and the second concrete part 6. The iron layer 12 may be composed of an iron block having dimensions that match the size of the neutron shielding structure 1B, the thickness dimension t5 of the iron layer 12, and the like, and a plurality of iron plates may be stacked in the thickness direction. For the purpose of preventing oxidation and deterioration of the iron layer 12, it is preferable that a side end portion of the iron layer 12 is coated with water resistance.

  The third concrete part 7 is a part of the concrete part 2, and is made of general concrete used for building a building, like the first concrete part and the second concrete part 6.

The hydrous part 4 is arranged between the second concrete part 6 and the third concrete part 7.
As can be seen from the water shielding ability shown in the graphs of FIGS. 4 and 5, like the neutron shielding structure 1A, the water-containing portion 4 is disposed outside the center in the thickness direction of the neutron shielding structure 1B. It is preferable that the neutron shielding structure 1B is disposed on the outermost side. However, from the viewpoint of increasing the strength of the neutron shielding structure 1B and facilitating the construction, it is preferable that the third concrete portion 7 is provided outside the water-containing portion 4 as shown in FIG.
Further, the lower the energy of neutrons emitted from the facility P, the smaller the distance between the iron layer 12 and the water-containing portion 4 is preferable. When the box 10 is made of iron and the inner wall 10a of the box 10 abuts against the outer wall of the iron layer 12, the iron layer 12 and the box 10 may be integrated. In that case, it is preferable that the inner wall 10a of the box 10 integrated with the iron layer 12 has a thickness dimension capable of capturing high energy neutrons well.

  For example, when neutrons with the maximum energy of 235 eV are emitted from the facility P, the thickness dimension t1 of the first concrete part 5 is 1% or more and 10% or less with respect to the thickness dimension of the entire neutron shielding structure 1B. The thickness dimension t2 with which the container 8 is filled is 5% or more and 15% or less, the thickness dimension t4 of the inner wall 10a and the outer wall 10b of the box 10 is 1% or more and 5% or less, and the thickness dimension t3 of the second concrete portion 6 is It is preferable that the thickness dimension t5 of the iron layer 12 is 10% or more and 20% or less, and the thickness dimension t6 of the third concrete part 7 is 5% or more and 10% or less. By comprising in this way, the shielding capability of the neutron shielding structure 1B increases.

According to the neutron shielding structure 1B of the second embodiment described above, the neutron beam generated in the facility P is captured by the water contained in the first concrete part 5, captured by the iron contained in the iron layer 12, and the second It is captured by the concrete part 6, captured by water in the aqueous solution of the water-soluble polymer contained in the water-containing part 4, and further captured by the third concrete part 7. Thereby, the shielding capability with respect to the neutron of 1 A of neutron shielding structures is exhibited more strongly, and the leakage of the neutron to the outside can be further prevented.
Moreover, since the neutron shielding structure 1B of the second embodiment described above includes the components of the neutron shielding structure 1A of the first embodiment, the same operational effects as the neutron shielding structure 1A can be obtained.

  Furthermore, in the neutron shielding structure 1B of the second embodiment described above, since the iron layer 12 is provided inside the water-containing portion 4, a high energy neutron of, for example, 10 MeV or more is emitted from the facility P. Even if it exists, the high shielding capability with respect to the neutron of the neutron shielding structure 1B is exhibited.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. It can be changed.
For example, the neutron shielding structure 1 can be applied not only to a side wall portion surrounding the facility P as shown in FIGS. 1, 6 and 7 but also as a ceiling or a floor surrounding the facility P as necessary. Further, the shape of the neutron shielding structure 1 may be a circle, a sphere, or the like according to the size or shape of the facility P.

Test example

  Hereinafter, test examples of the neutron shielding structure 1 according to the present invention will be described. The neutron shielding structure 1 according to the present invention is not limited to the test examples described below.

  In the setting shown in FIG. 3, the neutron shielding structure 1B of the second embodiment described above is adopted as the neutron shielding structure. However, the box 10 was omitted. The thickness dimension of the neutron shielding structure 1B is 200 cm, and the thickness dimensions of the first concrete part 5, the iron layer 12, the second concrete part 6, the water-containing part 4 and the third concrete part 7 are changed as shown in Table 1, The thickness dependence of the neutron dose rate leaking from the neutron shielding structure 1B was calculated. FIG. 8 illustrates a cross-sectional view of a neutron shielding structure having the configuration of Test Example 2 shown in Table 1. FIG. 9 illustrates a cross-sectional view of a neutron shielding structure having the configuration of Test Example 7 shown in Table 1. For comparison, a neutron shielding structure made of concrete having a thickness dimension of 200 cm is referred to as Comparative Example 1, and the first concrete part 5 having a thickness dimension t1 of 30 cm, the iron layer 12 having a thickness dimension t5 of 40 cm, the thickness is not provided. As a comparative example 2, the thickness dependence of the neutron dose rate leaking from these neutron shielding structures was also calculated using a neutron shielding structure provided with the second concrete part 6 having a dimension t3 of 130 cm. A three-dimensional Monte Carlo code PHITS2 was used as the calculation code.

As shown in FIGS. 10 and 11, the neutron dose generated by the beam loss of a relatively high energy 235 MeV proton beam outside the neutron shielding structures of Test Example 1 to Test Example 8 adopting the neutron shielding structure 1B. It can be seen that the shielding ability against neutrons is exhibited in the neutron shielding structure of each test example.
10, the neutron shielding structure of Test Example 5 in which the thickness dimension t5 of the iron layer 12 is 40 cm is the same as Test Examples 1 to 4 and Test Example 6 in which the thickness dimension t5 of the iron layer 12 is 30 cm. The shielding ability superior to each neutron shielding structure of Comparative Example 1 is exhibited. Thus, for example, in shielding of neutrons generated by beam loss of a 235 MeV proton beam, it is important to decelerate neutrons having high energy of 10 MeV or more, and the iron layer 12 contributes to this. It was confirmed that the elemental neutron shielding layer functions properly. In particular, since the transmittance of high energy neutrons of 10 MeV or higher in the concrete part 2 is high, it was confirmed that increasing the thickness dimension t5 of the iron layer 12 is useful for shielding high energy neutrons.

  Moreover, when FIG. 11 is seen, even if the thickness dimension t2 of the water-containing part 4 changes from 0 cm to 10 cm, 20 cm, and 40 cm when the first concrete part 5, the iron layer 12, and the second concrete part 6 are provided, The shielding ability in each neutron shielding structure has not changed greatly. Thereby, for example, in order to decelerate relatively low energy neutrons of 1 MeV or less, it is estimated that the thickness t2 of the water-containing portion 4 is about 10 cm.

  Moreover, when FIG. 12 is seen, the shielding ability superior to the comparative example 1 is exhibited in the test example 9 to the test example 11 which arrange | positioned the iron layer 12 inside, and has arrange | positioned the water-containing part 4 outside. . Further, the neutron shielding structure of Test Example 1 in which the water-containing portion 4 is disposed on the outermost side (that is, the thickness dimension t6 of the third concrete portion 7 is 0 cm) has a thickness dimension t6 on the outside of the water-containing portion 4 respectively. The shielding ability which was further superior to each neutron shielding structure of the test example 9 to the test example 11 provided with the 3rd concrete part 7 of 0 cm to 130 cm, 100 cm, and 30 cm is exhibited. From these results, in order to increase the shielding ability of the neutron shielding structure 1B with respect to the facility P that emits proton beams and neutron beams, the iron layer 12 is disposed on the inner side and the water-containing portion 4 is disposed on the outermost side. It was confirmed that it was preferable.

  From the test example described above, according to the neutron shielding structure 1 according to the present invention, the shielding ability against neutrons is satisfactorily exhibited, and the arrangement of the concrete part 2, the water-containing part 4 and the iron layer 12 and the thickness dimension of each component are adjusted. By doing so, it was confirmed that the shielding ability against high-energy neutrons also increased.

2 Concrete part 4 Water-containing part 5 First concrete part 6 Second concrete part 8 Sealed container 10 Box 12 Iron layer P Facility

Claims (6)

A concrete section that surrounds a facility that emits neutrons;
A water-containing part provided so as to surround the facility in contact with the concrete part;
A sealed container filled with an aqueous solution of a water-soluble polymer;
With
The proportion of water in the aqueous solution is 98% by weight or more,
A neutron shielding structure, wherein the sealed container is filled in the water-containing portion. The concrete part is composed of a first concrete part provided so as to directly surround the facility, and a second concrete part arranged outside the first concrete part,
2. The neutron shielding structure according to claim 1, wherein the water-containing portion is provided between the first concrete portion and the second concrete portion.   The neutron shielding structure according to claim 1 or 2, wherein a plurality of the sealed containers are accommodated in the water-containing portion. A box is arranged in the water-containing part,
The neutron shielding structure according to any one of claims 1 to 3, wherein the sealed container is accommodated in the box.   The neutron shielding structure according to claim 4, wherein the box is made of iron.   The neutron shielding structure according to any one of claims 1 to 5, wherein an iron layer is provided inside the water-containing portion.

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