JPS61173198A - 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 (Field of Industrial Application) The present invention relates to a neutron shielding material having excellent neutron shielding performance and having a silicone elastomer as a base material.

(Prior Art) Shielding materials based on silicone elastomer, which is a polymer with excellent heat resistance and flame retardance, have been known as neutron shielding materials used in nuclear reactors and the like. For example, JP-A-54-1798 discloses a silicone elastomer in which a boron compound is added for thermal neutron absorption. Therefore, the focus is on how much boron can be added, and the improvement is focused on how much boron can be added.
) is made to contain boron compounds.

By the way, silicone elastomers inherently have a low hydrogen content, so if the content of boron compounds is high, the hydrogen atom density will be low, and if the neutron energy spectrum is hard (high energy), there is a problem that the neutron shielding performance will be low. .

(Purpose of the Invention) This invention was made in order to eliminate such conventional drawbacks, and it provides a shielding material with excellent neutron shielding performance that takes advantage of the characteristics of silicone elastomer and prevents the hydrogen atom density from decreasing. This is what we provide.

(Structure of the Invention) The first aspect of the present invention is that 0.5 to 5% by weight of a boron compound is added to a silicone elastomer. The second feature is that 0.5 to 5% by weight of a boron compound is added to a silicone elastomer, and polypropylene or titanium hydride is further added.

(Example) Silicone elastomer is one of the materials with the best heat resistance and flame retardancy among hydrogen-containing polymer substances.

Furthermore, since silicone elastomers are temperature-curable and are liquid before hardening, they have the advantage of being able to be cast into complex shapes by utilizing their fluidity. Adding a boron compound to a silicone elastomer having such properties can improve its ability to absorb thermal neutrons. This boron compound is 84 C5BN.

8203, etc., and these can be added in the form of powder.

The amount of the boron compound added may be set depending on the neutron energy spectrum of the location where the shielding material is used. In order to investigate the relationship between the addition ω of a boron compound and its effect, a neutron source with the fission spectrum of uranium-235 was shielded with a 3Qcm thick carbon steel wall, and the neutron radiation rate in that state was calculated. 1, and the neutron beam M rate was calculated in a state where the outside of this carbon steel wall was further shielded with a shielding material with a thickness of 10 CIll. When the ratio of 84C added to the silicone elastomer as the above-mentioned shielding material was varied, results as shown in curve 1 in FIG. 1 were obtained. In other words, when the amount of B4C added is within the range of 0.5 to 5% by weight, the dose rate is as small as 2.9 or less;
When it exceeds 5 weight and 2%, it increases rapidly. Therefore, 84
The addition of G must be set within the range of 0.5 to 5% by weight. The same may be said of the amounts of other boron compounds added.

Further, by adding polypropylene or titanium hydride to the above-mentioned shielding material, the hydrogen atom density can be increased. For example, the hydrogen atom density of the shielding material is 5
In the case of 1022 atoms/cm3, add 30% by weight of polypropylene or 50% by weight of titanium hydride.
By adding , the hydrogen atom density becomes 6×10 aton+s
/cm3, the hydrogen atom density increases by 1120%.

The higher the amount added, the better in order to improve the hydrogen atom density, but as the amount added increases, the flame retardance decreases in the case of polypropylene, and the fluidity before curing decreases in the case of titanium hydride. Therefore, the amount to be added may be determined depending on the required characteristics of the shielding material, and both polypropylene and titanium hydride may be added in an appropriate ratio.

In Table 1, 84 for silicone elastomers.
The attenuation rates of the 12 mass ratio of shielding materials to which G is added in various proportions and to shielding materials to which polypropylene or titanium hydride is added are shown. In the same table, A is a conventional product containing 8.2% by weight of 84C, B-H are examples of the present application, and other additives include E, polypropylene, F,
G and H each contain titanium hydride.

As is clear from Table 1, the attenuation rate of the linear m ratio is 0.352 for the conventional product A, while the attenuation rate for B4C is 0.5 to 5%.
For B, C, and D added in the above range, the value is 0.355 or more, and when polypropylene or titanium hydride is added, the value is 0.386 or more, indicating that the attenuation rate is improved. Recognize.

(Effects of the Invention) As explained above, the present invention is a silicone elastomer containing 0.5 to 5% boron compound, or a silicone elastomer containing 0.5 to 5% boron compound. %, and polypropylene or titanium hydride is further added, thereby achieving improvement in neutron shielding performance while taking advantage of the characteristics of silicone elastomer.

[Brief explanation of drawings]

The drawing is a characteristic diagram showing the relationship between the amount of 84C added and the linear ω ratio. 1...Characteristic curve.

Claims (1)

[Claims] 1. The silicone elastomer contains 0.5 to 0.5 boron compounds.
A neutron shielding material containing 5% by weight. 2. Boron compound in silicone elastomer is 0.5~
A neutron shielding material containing 5% by weight of polypropylene or titanium hydride.