JPS59162487A - Neutron shielding material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a neutron shielding material that has both heat resistance and good thermal conductivity.

Conventionally, nitride or boron carbide has been known as a neutron shielding material, and substances containing large amounts of hydrogen, such as water, paraffin, wood, resin, and concrete, are effective as moderators to enhance neutron absorption ability. It is also known that there are However, since these water-containing materials have insufficient heat resistance and thermal conductivity, when used as a shielding material for exothermic radioactive substances, for example, there are many design restrictions on the installation of the shielding material, such as the location.

By the way, as a water-containing material, hydrogen storage alloys are preferable as moderators because they have a higher hydrogen atom content per unit volume than conventionally commonly used water, resin, liquid hydrogen, etc. However, regarding conventional hydrogen storage alloys, Research is being conducted on how to release stored hydrogen at low temperatures and low pressures. Substructure, water storage alloy height, □E1,, min
,=t,,-1 was not considered to be used at all.

In addition, boron-containing components mainly exhibit an effective shielding effect only in the thermal neutron region, and a hydrogen atom component is required as a moderator in dry-type transportation and storage containers for nuclear fuel that mainly contains fast neutrons. Generally speaking, in this case, the hydrogen atom component must have excellent heat resistance and thermal conductivity. Therefore, conventionally, it has been unavoidable to use a synthetic resin containing many hydrogen atoms mixed with aluminum or carbon to increase heat resistance as much as possible, even at the expense of heat resistance and thermal conductivity.

This invention was made based on this technical background, and utilizes a Ti-AQ alloy, which has excellent heat resistance among hydrogen storage alloys, as a moderator and as a shielding material in a high-temperature atmosphere. This is how it was done. Ti-Aρ alloys have superior heat resistance and are lightweight, and their shielding effect on gamma rays, which often coexist with neutrons, is much greater than that of conventional resins, so simultaneous effects can be expected. Because it easily turns into powder, it is an excellent material for transporting nuclear fuel and as a shielding material for storage containers. This Ti-AΩ alloy includes Ti2-An, Ti3-An2, Ti3-An
However, the Ti3-Aρ gold alloy has a particularly high hydrogen content and retains hydrogen up to about 600°C, so it is suitable. This Ti-12 alloy may be used as a moderator in combination with other neutron absorbers.

As the neutron absorbing material to be combined with the Ti-Aρ alloy, nitride or boron carbide is preferable. The transport and storage containers mentioned above are made of cast iron, cast steel, or forged steel, and the neutron absorbing material used in these containers is boron nitride or boron carbide, which has excellent thermal conductivity and can dissipate heat from the container. This is preferable because it does not interfere with They also have the advantage that they can be easily molded into various shapes by powdering or solidifying them. Then, convert this to the above Ti −Aρ
When used in combination with a series alloy, the neutron absorption ability is enhanced and it is possible to exhibit an efficient shielding effect across the entire neutron spectrum, and it has continuous heat resistance of about 500℃ for a long period of time. Moreover, a shielding material with excellent thermal conductivity can be obtained.

Next, an example in which this shielding material is applied to a transportation and storage container will be explained with reference to the drawings. In FIGS. 1 and 2, a storage container body 1 is made of cast iron, cast steel, or forged steel, and has a bottom wall 20 integrally formed on one side of a cylindrical part 2, and has an inner opening in the other opening of the cylindrical part 2. The lid 10 and the outer lid 11 are attached in sequence, and a gasket (not shown) is placed on the outer periphery of the inner lid 10 and the outer lid M11 for sealing. A basket 4 containing radioactive materials is housed within the storage container body 1. 15 and 16 are protective members.

The basket 4 is inserted into a cylindrical body 5 made of a steel plate, and a gap between the basket 4 and the basket 4 in the cylindrical body 5 is filled with a first shielding material 6. Further, a second shielding material 7 is filled between the cylindrical body 5 and the cylindrical portion 2. Fins 8 for heat radiation are formed on the outer periphery of the cylindrical portion 2, and trunnions 9 are formed near both ends of the outer periphery. The fins 8 may be arranged in the circumferential direction of the storage container body 1. Furthermore, a shielding material may be placed on the bottom wall 20 as well as on the cylindrical portion 2.

3 and 4 show another embodiment, in which only the first shielding material 6 filled inside the cylinder body 5 is arranged in the cylindrical part 2, and the second shielding material is placed on the outer periphery of the cylindrical part 2. The cylinder body 71 is arranged with the material 7
covered with In this way, the shielding material may be arranged separately inside and outside the cylindrical portion.

The first shielding material 6 can be formed by mixing and filling Ti3-An-1-1n powder and nitride or boron carbide powder to simultaneously decelerate and absorb fast neutrons and provide shielding. It is convenient because it is known to enhance the effect. The second shielding material 7 is formed by filling a predetermined space with nitride or boron carbide powder.

It mainly absorbs neutrons and produces a shielding effect.

Furthermore, these shielding materials may be sintered powders.

In this configuration, most of the neutron energy emitted from the basket 4 is absorbed by the first shielding material 6, and the remaining small amount of energy is absorbed by the second shielding material. Therefore, the cylindrical part 2
The thickness of the container can be relatively thin, and the weight of the container body can be reduced. Further, although heat is dissipated from the basket 4, the above-mentioned shielding material has excellent heat resistance A3 and thermal conductivity, and therefore does not hinder the dissipation of heat.

The sintered body may be integrally molded into a predetermined shape, or divided pieces may be combined and arranged as shown in FIG. That is, the first shielding material 60 is formed by alternately arranging blocks 6a and 6b made of sintered bodies, and the second shielding material 70 is formed by arranging sintered bodies 7a and 7b alternately. There is. In this case, the blocks 6a may be made of a sintered body of Ti3-An powder, and the blocks 6b may be made of a sintered body of nitride or boron carbide powder, and these may be arranged alternately as shown in the figure. Alternatively, both blocks may be made of the same sintered body. Block 7a.

Similarly, 7b' can be made of a sintered body made of the same material or a different material.

As explained above, the present invention utilizes a Ti-Aρ alloy/metal hydride as a neutron moderator, and also uses nitride or boron carbide as an absorber in the neutron region 31 +J. These materials have excellent heat resistance and thermal conductivity, making them exceptionally excellent materials for transporting pyrogenic radioactive substances and as shielding materials for storage containers.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional side view of a transportation container showing an example of application of the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a partial cross-sectional side view showing another example, and FIG. 4 is a cross-sectional view thereof. , FIG. 5 is a J-longitudinal sectional view showing another example of the arrangement of the shielding material. DESCRIPTION OF SYMBOLS 1... Container body, 2... Cylindrical part, 4... Basket, 5.71... Cylindrical body, 6.60... First shielding material, 7°70-... Second Shielding material, 6a, , 6b,
7a, 7b--Sintered block of shielding material.

Claims (1)

[Scope of Claims] 1. A neutron shielding material comprising a hydride of a Ti-Aρ alloy as a neutron shielding material. 2. A neutron shielding material characterized by combining a Ti-Aρ alloy hydride as a neutron moderator and nitride or boron carbide as a neutron absorber.