JPS61290400A - 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 absorption of thermal neutrons.

By the way, since silicone elastomers originally have a low hydrogen content, there is a problem that if a large amount of boron compounds is contained, the hydrogen atom density becomes low, and the neutron shielding performance decreases when the neutron energy spectrum is hard (high energy). .

(Purpose of the Invention) This invention was made to eliminate these conventional drawbacks, and improves the characteristics of silicone elastomers by using a gadolinium compound that has a higher thermal neutron absorption ability than a boron compound. The object of the present invention is to provide a shielding material with excellent neutron shielding performance that prevents the hydrogen atom density from decreasing.

(Structure of the Invention) The first gist of the invention is that a gadolinium compound is added to a silicone elastomer. The second aspect is that a gadolinium compound is added to a silicone elastomer, and BoIJ 70 helene 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 gadolinium oxide to a silicone elastomer having such properties can improve its ability to absorb thermal neutrons. Gadolinium oxide may be added in powder form.

The amount of gadolinium oxide added may be determined depending on the neutron energy spectrum of the location where the shielding material is used. In order to investigate the relationship between the addition of gadolinium oxide and its effects, a unit source of neutrons with the fission spectrum of uranium-235 was shielded with a carbon steel wall with a thickness of 3 Qcm, and the outside of this carbon steel wall was The neutron dose rate was calculated in a state in which the neutron was shielded by a shielding material with a thickness of IOC■. When the ratio of gadolinium oxide added to the silicone elastomer was varied as the above-mentioned shielding material, results as shown in curve 1 in the drawing were obtained. In other words, the amount of gadolinium oxide added is within the range of 20% or less.
'G;t Ii! ffi rate is 2.0xlO-'m
While it is small at rem/h or less, it increases rapidly when it exceeds 20%. Therefore, in this case, the amount of gadolinium oxide added needs to be set within a range of 20% or less.

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 x
1022 atoms/cm" (7), if 40% polypropylene or 30% titanium hydride is added to this, the hydrogen atom density becomes 6x1022 atoms/cm.
3, and the hydrogen atom density increases by 20%.

The above addition m is better as it increases in order to improve the hydrogen atom density, but when the addition amount increases, the flame retardance decreases in the case of polypropylene, and the fluidity before curing decreases in the case of titanium hydride. 6. : The amount of addition a is determined depending on the required characteristics of the shielding material. Alternatively, both polypropylene and titanium hydride may be added in appropriate proportions.

In Table 1, 84 for silicone elastomers.
The attenuation rate of the dose rate is shown for shielding materials to which G or gadolinium oxide is added in various proportions, and for shielding materials to which polypropylene or titanium hydride is added. In the same table,
A to C are conventional products to which 84C was added, and D to J are examples of the present application, with I adding polypropylene and J adding titanium hydride as additives.

As is clear from Table 1, the dose rate attenuation rate for conventional products A to C is 0.356 or less, whereas 8, C, and D, in which gadolinium oxide is added in a range of 20% or less, Then 0.
It is 36 or more, and when polypropylene or titanium hydride is added to this, it is 0.399 or more, which shows that the attenuation rate is improved.

(Effect of the invention) As explained above, this invention is made by adding a gadolinium compound to a silicone elastomer,
Alternatively, it is made by adding a gadolinium compound to a silicone elastomer, and further adding polypropylene or titanium hydride, thereby achieving improved neutron shielding performance while taking advantage of the characteristics of the silicone elastomer.

[Brief explanation of the drawing]

The drawing is a characteristic diagram showing the relationship between the amount of gadolinium oxide added and the dose rate. 1...Characteristic curve.

Claims (1)

[Claims] 1. A neutron shielding material made by adding a gadolinium compound to a silicone elastomer. 2. A neutron shielding material made by adding a gadolinium compound to a silicone elastomer, and further adding polypropylene or titanium hydride.