JP6174347B2 - Container for radioactive material - Google Patents

Description

  The present invention relates to a concrete container having a storage chamber for storing a radioactive substance.

  The following Patent Document 1 discloses a concrete container main body having a substantially rectangular parallelepiped shape and a concrete post-coating on a solidified body (waste treated with a solidifying material) stored in a recess of the container main body. And a lid provided with a lid.

  Since concrete containers such as the above are known to have a radiation shielding effect, radioactive materials less than 8000 Bq / kg for which disposal is entrusted to the local government (radioactive waste and its Attempts have been made to store incinerated ash etc. in a concrete container as described above and transport it to a final disposal site, or to store it until the final disposal site is installed.

  However, when the radioactive substance is stored in the concrete container as described above, the radioactive substance adheres to the inner surface of the storage chamber, that is, the concrete surface in a state where it is difficult to decontaminate. In short, since the container after taking out the stored radioactive substance becomes a radioactive substance, the container cannot be reused.

JP-A-10-297703

  An object of the present invention is to provide a radioactive substance storage container that can be reused after the stored radioactive substance is taken out.

In order to achieve the above object, the present invention provides a concrete container having a storage chamber for storing a radioactive substance, wherein the inner surface of the storage chamber is a decontamination film mainly composed of a thermosetting plastic. The decontamination film is covered with a first decontamination film that covers the inner surface of the storage chamber, and a second decontamination film that has a higher Young's modulus than the first decontamination film and covers the inner surface of the first decontamination film. Is included .

  ADVANTAGE OF THE INVENTION According to this invention, the radioactive substance storage container which can be reused after taking out the stored radioactive substance can be provided.

  The above and other objects of the present invention, and the features and effects according to the respective objects will become apparent from the following description and the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a radioactive substance storage container (first embodiment) to which the present invention is applied. 2A is a top view of the container main body shown in FIG. 1, FIG. 2B is an enlarged vertical sectional view taken along line BB in FIG. 2A, and FIG. 2C is FIG. 2A. It is a CC line expanded vertical sectional view. 3A is a top view of the lid shown in FIG. 1, FIG. 3B is an enlarged vertical sectional view taken along line BB in FIG. 3A, and FIG. 3C is C in FIG. FIG. FIG. 4 is a longitudinal sectional view of a radioactive substance storage container (second embodiment) to which the present invention is applied. FIG. 5 is a longitudinal sectional view of a radioactive substance storage container (third embodiment) to which the present invention is applied.

[First Embodiment (FIGS. 1 to 3)]
The container shown in FIG. 1 includes a container body 11 made of concrete (see FIG. 2) and a lid 12 made of concrete (see FIG. 3) .
As shown in FIG. 1 and FIG. 2 (A) to FIG. 2 (C), the container body 11 has a recess 11a on the inside having an outer appearance of a substantially rectangular parallelepiped shape and a transverse cross-sectional shape of a substantially rectangular shape. Yes. Moreover, the inner surface (four inner side surfaces and inner bottom surface) of the recess 11a, that is, the concrete background is covered with a decontamination film 11b described in detail later. Furthermore, a grid-like reinforcing bar 11 c for increasing the strength of the container body 11 is embedded in the container body 11.

  In addition, on the upper surface of the container main body 11, a water-stop packing 11d mainly composed of a silicone resin or the like is provided so as to surround the upper surface opening of the recess 11a. Further, a step portion 11 e for filling a caulking agent 13 mainly composed of a silicone resin or the like is provided on the outer peripheral portion of the upper surface of the container body 11. Further, nuts 11f (8 in total) for fastening bolts are embedded in the upper surface of the container body 11. Furthermore, hanging metal fittings 11g (four in total) are embedded in the four corners of the upper surface of the container body 11.

  On the other hand, as shown in FIG. 1 and FIGS. 3A to 3C, the lid 12 has a substantially rectangular plate appearance, and is approximately 4 fitted into the upper surface opening of the recess 11 a of the container body 11. A fitting portion 12a having a truncated pyramid shape is provided at the center of the lower surface. Moreover, the surface (lower surface and four outer surfaces) of the fitting part 12a, ie, the concrete surface, is covered with a decontamination film 12b described in detail later. Furthermore, a lattice-like reinforcing bar 12 c for increasing the strength of the lid 12 is embedded in the lid 12.

  In addition, at the four corners of the lid 12, in order to expose the metal fittings 11g for hanging the container main body 11 (a total of four), notches 12d having a substantially circular shape in cross section are provided. Yes. In addition, on the upper surface of the lid 12, corresponding to the nuts 11f (total 8) of the container body 11, two-stage through holes 12e for bolt insertion (total of 8; the cross-sectional shape of the upper portion is substantially rectangular. The bottom section has a substantially circular cross section, and a perforated plate 12e1 made of stainless steel or the like is provided at the bottom of the upper section of each through hole 12e. Further, hanging metal fittings 12f (a total of four) are embedded in the upper surface of the lid 12 so that the lines connecting the respective centers form a substantially rectangular shape.

  For example, if the dimensions of the container body 11 and the lid 12 are given, the vertical and horizontal dimensions of the container body 11 in FIG. 2A are approximately 1600 mm, the vertical dimension in FIG. 1 is approximately 1450 mm, and the thickness is approximately 150 mm. 2A is approximately 1300 mm, and the vertical dimension in FIG. 1 is approximately 1300 mm. On the other hand, the vertical and horizontal dimensions of the lid 12 in FIG. 3A are about 1600 mm, the thickness (excluding the fitting portion 12a) is about 150 mm, and the thickness of the fitting portion 12a is about 20 mm.

  Here, the concrete which comprises the container main body 11 and the lid | cover 12 and the decontamination film | membrane 11b and the decontamination film | membrane 12b provided in the container main body 11 and the lid | cover 12 are explained in full detail.

  The concrete that forms the main body of the container body 11 and the lid 12 is obtained by curing and hardening a mixture of cement, water, coarse aggregate, fine aggregate, and admixture, as well as known concrete. Sand is generally used for the fine aggregate. When the thickness of the container body 11 and the lid 12 is less than 150 mm, for example, ferronickel slag or lead glass cullet is used as at least a part of the fine aggregate. When using, the radiation shielding effect is somewhat improved. Further, if the thickness of the container main body 11 and the lid 12 is about 200 mm, for example, the radiation shielding effect is slightly improved as compared with the case of about 150 mm. However, even if the thickness is made thicker than 200 mm, the radiation shielding effect is significant. Can't hope.

  On the other hand, the decontamination film 11b and the decontamination film 12b are mainly composed of thermosetting plastics such as epoxy resin, polyurethane, acrylic resin, silicone resin, unsaturated polyester, phenol resin, polyimide, Its thickness is in the range of 5-15 mm. When producing the decontamination film 11b and the decontamination film 12b, a paint containing an appropriate amount of a main agent, a curing agent, a property adjusting agent, and the like is prepared, and the paint is applied to the inner surface of the recess 11a and the surface of the fitting portion 12. This is cured by a method of room temperature curing or heat curing (baking curing).

  If the inner surface of the recess 11a and the surface of the fitting portion 12, that is, the concrete surface is rough, the inner surfaces of the decontamination film 11b and the decontamination film 12b may not be smooth. It is desirable to perform a process of first applying a cement or mortar added and curing. In addition, if the decontamination film 11b and the decontamination film 12b are produced by applying and curing the paint once, cracking may occur. In such a case, the application and curing of the paint should be performed in multiple steps. Is desirable.

  When the radioactive substance RM is stored in the container composed of the container body 11 and the lid 12, the radioactive substance RM is directly or radioactively provided in the recess 11a of the container body 11 whose inner surface is covered with the decontamination film 11b. A bag packed with the substance RM is put, and the lid 12 is placed so that the fitting portion 12a whose surface is covered with the decontamination film 12b fits into the upper surface opening of the recess 11a. Then, bolts (not shown) are inserted into the through holes 12 e of the lid 12, and the screw portions of the bolts are fastened to the nuts 11 f of the container body 11. Then, the caulking agent 13 is filled in the step portion 11 e that appears at the boundary portion between the container body 11 and the lid 12.

  In the container shown in FIG. 1, the inner surface (concrete background) of the recess 11a of the container body 11 is covered with the decontamination film 11b, and the surface (concrete background) of the fitting portion 12a of the lid 12 is decontaminated. Since it is covered with the membrane 12b, in the state where the lid 12 is attached to the container main body 11, the substantially rectangular parallelepiped storage chamber SR in which the entire inner surface is covered with the decontamination membrane 11b and the decontamination membrane 12b, that is, watertightness. In addition, a storage chamber SR having airtightness is defined, and the radioactive material RM is stored in the storage chamber SR. That is, the radioactive material RM stored in the storage chamber SR touches the decontamination film 11b and the decontamination film 12b, but does not touch the concrete background.

  Further, the decontamination film 11b covering the inner surface (concrete background) of the recess 11a of the container body 11 and the decontamination film 12b covering the surface of the fitting portion 12a (concrete background) of the lid 12 are both thermosetting plastics. If the radioactive material RM stored in the storage room SR adheres to the decontamination film 11b and the decontamination film 12b and adheres to the concrete ground, In comparison, the radioactive substance RM can be effectively decontaminated.

  Here, a test example related to the decontamination will be briefly introduced. Drop 0.2 mL of cesium chloride solution (15000 Bq / mL) on the concrete surface and leave it for 1 week, then wipe it with a paper wiper (Kimwipe (registered trademark) manufactured by Nippon Paper Crecia Co., Ltd.) The β-ray counts before and after the implementation when wiping was performed twice (measurement is TGS-133 manufactured by Aroka, measurement distance is 5 cm) are 5000 and 5000 (residual rate is 100%), and water Β-ray count after wiping 5 times with a paper wiper containing 100% (residual rate is 100%), and further wiping 3 times with a paper wiper containing 1 mol / L hydrochloric acid After that, the β-ray count amount was 5000 (residual rate was 100%).

  On the other hand, a 8 mm thick decontamination membrane was prepared on the concrete surface, and 0.2 mL of a cesium chloride solution (15000 Bq / mL) was dropped on the decontamination membrane and allowed to stand for 1 week. When wiping twice with a paper wiper, the β-ray counts before and after the implementation are 5000 and 1000 (remaining rate is 20.0%), and further wiping with a paper wiper containing water 5 times After that, the β ray count amount was 140 (residual rate was 2.8%), and the β ray count amount after wiping three times with a paper wiper containing 1 mol / L hydrochloric acid was 120 ( The residual rate was 2.4%).

  On the other hand, a 8 mm thick decontamination film made of polyurethane as a main component was produced on the concrete surface, and 0.2 mL of a cesium chloride solution (15000 Bq / mL) was dropped on the decontamination film and left for 1 week. When wiping twice with a paper wiper, β-ray count amounts before and after the execution were 5000 and 2800 (remaining rate was 56.0%), and further wiping was performed five times with a paper wiper containing water. The subsequent β-ray count was 1000 (residual rate was 20.0%), and the β-ray count after wiping 3 times with a paper wiper containing 1 mol / L hydrochloric acid was 580 (residual The rate was 11.6%).

  As can be seen from the above test example, even if the radioactive material RM stored in the storage chamber SR touches and adheres to the decontamination film 11b and the decontamination film 12b, the radioactive material RM adheres to the concrete background. In comparison, decontamination of the radioactive material RM can be performed by relatively simple cleaning (for example, water wiping or water jetting), and if the cleaning is performed carefully, the residual rate of the radioactive material RM can be close to zero. . That is, the container shown in FIG. 1 can be sufficiently reused by cleaning the decontamination film 11b and the decontamination film 12b after taking out the radioactive material RM stored in the storage room SR. .

  Further, the decontamination film 11b covering the inner surface (concrete background) of the recess 11a of the container body 11 and the decontamination film 12b covering the surface of the fitting portion 12a (concrete background) of the lid 12 are both thermosetting plastics. Since both are flexible compared to concrete, the impact when storing the radioactive material RM in the container is mitigated by the decontamination film 11b and the decontamination film 12b, and the container body 11 It is possible to prevent damage such as cracks from occurring on the inner surface of the recess 11a and the surface of the fitting portion 12a of the lid 12. Moreover, even if cracks leading to the decontamination film 11b and the decontamination film 12b occur over time on the outer surface of the container body 11 and the outer surface of the lid 12, the decontamination film 11b maintains the watertightness and airtightness of the storage chamber SR. Therefore, the radioactive material RM stored in the storage chamber SR can be prevented from leaking out of the container.

[Second Embodiment (FIG. 4)]
The container shown in FIG. 4 differs from the container shown in FIG. 1 (first embodiment) in structure.
The first decontamination film 11b1 covering the inner surface (concrete background) of the storage chamber 11a with the decontamination film 11b on the container body 11 side has a higher Young's modulus than the first decontamination film 11b1. The first decontamination film 12b1 covering the surface (concrete background) of the fitting portion 12a is replaced with the first decontamination film 12b on the dot / lid 12 side constituted by the second decontamination film 11b2 covering the inner surface of 11b1. The Young's modulus is higher than that of the decontamination film 12b1, and the second decontamination film 12b2 covers the inner surface of the first decontamination film 12b1.

  The material of the first decontamination film 11b1 and the second decontamination film 11b2 on the container body 11 side, and the material of the first decontamination film 12b1 and the second decontamination film 12b2 on the lid 12 side, consider each Young's modulus. The above can be selected as appropriate. For example, the first decontamination film 11b1 and the first decontamination film 12b1 are mainly composed of polyurethane, and the second decontamination film 11b2 and the second decontamination film 12b2 are mainly composed of an epoxy resin. Then, the condition “the Young's modulus of the first decontamination film 11b1 <the Young's modulus of the second decontamination film 11b2” on the container body 11 side and the “Young's modulus of the first decontamination film 12b1” on the lid 12 side <second. The condition of “Young's modulus of decontamination film 12b2” can be satisfied.

  In the container shown in FIG. 4, the inner surface (concrete background) of the recess 11a of the container body 11 is covered with the first decontamination film 11b1 and the second decontamination film 11b2 having a two-layer structure, and the cover 12 is fitted. Since the surface (concrete background) of the joint portion 12a is covered with the first decontamination film 12b1 and the second decontamination film 12b2 having a two-layer structure, it is stored in the storage chamber SR in the same manner as the container shown in FIG. The formed radioactive material RM touches the second decontamination film 11b2 and the second decontamination film 12b2, but does not touch the concrete background.

  The first decontamination film 11b1 and the second decontamination film 11b2 that cover the inner surface (concrete background) of the recess 11a of the container body 11 and the surface of the fitting portion 12a of the lid 12 (concrete background) are covered. Since both the decontamination film 12b1 and the second decontamination film 12b2 are mainly composed of a thermosetting plastic, the radioactive material RM stored in the storage chamber SR becomes the second decontamination film 11b2 and the second decontamination film. Even if the membrane 12b2 touches and adheres, as in the case of the container shown in FIG. 1, the radioactive material RM can be decontaminated relatively easily (for example, water) compared to the case where the radioactive material RM adheres to the concrete surface. Wiping, water jet, etc.), and if the cleaning is performed carefully, the residual ratio of the radioactive material RM can be brought close to zero. That is, the container shown in FIG. 4 is removed by cleaning the second decontamination film 11b2 and the second decontamination film 12b2 after taking out the radioactive material RM stored in the storage chamber SR. It can be used sufficiently.

  Further, the first decontamination film 11b1 and the second decontamination film 11b2 that cover the inner surface (concrete background) of the recess 11a of the container body 11 and the surface of the fitting portion 12a of the lid 12 (concrete background) are covered. Since both the decontamination film 12b1 and the second decontamination film 12b2 are mainly composed of thermosetting plastic, and both are more flexible than concrete, the impact when the radioactive material RM is stored in the container. Is relaxed by the first decontamination film 11b1, the second decontamination film 11b2, the first decontamination film 12b1 and the second decontamination film 12b2, and the inner surface of the recess 11a of the container body 11 and the fitting portion 12a of the lid 12 It is possible to prevent the occurrence of damage such as cracks on the surface of the film. Moreover, even if cracks reaching the first decontamination film 11b1 and the first decontamination film 12b1 occur over time on the outer surface of the container body 11 and the outer surface of the lid 12, the water tightness and air tightness of the storage chamber SR are maintained. Since it can be maintained by the first decontamination film 11b1, the second decontamination film 11b2, the first decontamination film 12b1 and the second decontamination film 12b2, it is possible to prevent the radioactive material RM stored in the storage chamber SR from leaking out of the container. it can.

  Furthermore, the first decontamination film 11b1 on the container body 11 side is more flexible than the second decontamination film 11b2, and the first decontamination film 12b1 on the lid 12 side is more flexible than the second decontamination film 12b2. Therefore, the occurrence of damage described in the previous paragraph can be prevented more accurately.

[Third Embodiment (FIG. 5)]
The place where the container shown in FIG. 5 differs in structure from the container (first embodiment) shown in FIG.
The outer surface (four outer surfaces and the outer bottom surface) of the container body 11 is covered with a third decontamination film 11h having a Young's modulus lower than that of the decontamination film 11b. The outer surface of the lid 12 (four outer surfaces and The outer upper surface is covered with a third decontamination film 12g having a Young's modulus lower than that of the decontamination film 12b.

  The material of the decontamination film 11b and the third decontamination film 11h on the container body 11 side and the material of the decontamination film 12b and the third decontamination film 12g on the lid 12 side are appropriately selected in consideration of each Young's modulus. it can. For example, if the decontamination film 11b and the decontamination film 12b are mainly composed of epoxy resin, and the third decontamination film 11h is mainly composed of polyurethane, the “decontamination film 11b1 on the container body 11 side” will be described. The Young's modulus of the third decontamination film 11b2 and the "Young's modulus of the decontamination film 12b> the Young's modulus of the third decontamination film 12g" on the lid 12 side can be satisfied.

  In the container shown in FIG. 5, the inner surface (concrete background) of the recess 11a of the container body 11 is covered with the decontamination film 11b, and the surface of the fitting portion 12a of the lid 12 (concrete background) is decontaminated. Since it is covered with the film 12b, the radioactive material RM stored in the storage room SR touches the decontamination film 11b and the decontamination film 12b as in the case of the container shown in FIG. Absent.

  Further, the decontamination film 11b covering the inner surface (concrete background) of the recess 11a of the container body 11 and the decontamination film 12b covering the surface of the fitting portion 12a (concrete background) of the lid 12 are both thermosetting plastics. Therefore, even if the radioactive material RM stored in the storage chamber SR touches and adheres to the decontamination membrane 11b and the decontamination membrane 12b, as in the container shown in FIG. Compared to the case where the radioactive substance RM adheres to the ground, the radioactive substance RM can be decontaminated by relatively simple cleaning (for example, water wiping or water jetting). If the cleaning is performed carefully, the radioactive substance RM The survival rate of can be close to zero. That is, the container shown in FIG. 5 is sufficiently reused by performing the cleaning operation on the decontamination film 11b and the decontamination film 12b after taking out the radioactive material RM stored in the storage chamber SR. I can plan.

  Further, the decontamination film 11b covering the inner surface (concrete background) of the recess 11a of the container body 11 and the decontamination film 12b covering the surface of the fitting portion 12a (concrete background) of the lid 12 are both thermosetting plastics. Since both are flexible compared to concrete, the impact when storing the radioactive material RM in the container is mitigated by the decontamination film 11b and the decontamination film 12b, and the container body 11 It is possible to prevent damage such as cracks from occurring on the inner surface of the recess 11a and the surface of the fitting portion 12a of the lid 12. Moreover, even if cracks leading to the decontamination film 11b and the decontamination film 12b occur over time on the outer surface of the container body 11 and the outer surface of the lid 12, the decontamination film 11b maintains the watertightness and airtightness of the storage chamber SR. Therefore, the radioactive material RM stored in the storage chamber SR can be prevented from leaking out of the container.

  Furthermore, since the outer surface of the container body 11 is covered with the third decontamination film 11h and the outer surface of the lid 12 is covered with the third decontamination film 12g, the outer surface of the container body 11 and the lid 12 The impact applied to the outer surface can be mitigated by the third decontamination film 11h and the third decontamination film 12g, thereby preventing the outer surface of the container body 11 and the outer surface of the lid 12 from being damaged.

  The third decontamination film 11h and the third decontamination film 12g can also be applied to the container (second embodiment) shown in FIG. That is, the outer surface (four outer surfaces and outer bottom surface) of the container main body 11 shown in FIG. 4 is covered with the third decontamination film 11h having a Young's modulus lower than that of the second decontamination film 11b2, and the outside of the lid 12 is covered. The surface (four outer surfaces and outer upper surface) may be covered with a third decontamination film 12g having a Young's modulus lower than that of the second decontamination film 12b2.

  DESCRIPTION OF SYMBOLS 11 ... Container body, 11a ... Recess, 11b ... Decontamination membrane, 12 ... Lid, 12b ... Decontamination membrane, SR ... Storage chamber, RM ... Radioactive material, 11b1, 12b1 ... First decontamination membrane, 11b2, 12b2 ... 2nd decontamination membrane, 11h, 12g ... 3rd decontamination membrane.

Claims (2)

A concrete container having a storage chamber for storing a radioactive substance, wherein an inner surface of the storage chamber is covered with a decontamination film mainly composed of a thermosetting plastic, and the decontamination film is stored in the storage A first decontamination film that covers the inner surface of the chamber, and a second decontamination film that has a higher Young's modulus than the first decontamination film and covers the inner surface of the first decontamination film ,
A radioactive substance storage container. The outer surface of the container is covered with a third decontamination film whose main component is thermosetting plastic and whose Young's modulus is lower than that of the decontamination film or the second decontamination film .
Radioactive substance storage container according to claim 1 Symbol mounting, characterized in that.

Images