MgF2—CaF2 binary system sintered body for radiation moderator and method for producing the same

Patent metadata

Field	Value
Publication number	US-9789335-B2
Application number	US-201514684765-A
Country	US
Kind code	B2
Filing date	Apr 13, 2015
Priority date	Sep 24, 2014
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A MgF 2 —CaF 2 binary system sintered body for a radiation moderator having a compact polycrystalline structure excellent in radiation moderation performance, especially neutron moderation performance, comprises MgF 2 containing CaF 2 from 0.2% by weight to 90% by weight inclusive, having a bulk density of 2.96 g/cm 3 or more, and a bending strength of 15 MPa or more and a Vickers hardness of 90 or more as regards mechanical strengths.

First claim

The invention claimed is:

1. A MgF 2 —CaF 2 binary system sintered body for a radiation moderator, comprising MgF 2 containing CaF 2 from 1.5% by weight to 80% by weight inclusive, having a compact polycrystalline structure with a bulk density of 2.96 g/cm 3 or more and having radiation moderation performance.

2. The MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 1 , wherein the radiation moderation performance is neutron moderation performance.

3. The MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 1 , having a bending strength of 15 MPa or more and a Vickers hardness of 90 or more as regards mechanical strengths.

4. A method for producing the MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 1 , comprising the steps of:
mixing a MgF 2 powder with a CaF 2 powder of 1.5-80% by weight and further adding 0.02-1% by weight of a sintering aid thereto to mix;
molding the raw material powder compounded in the preceding step at a molding pressure of 5 MPa or more using a press molding device;
molding the press molded article at a molding pressure of 5 MPa or more using a cold isostatic pressing (CIP) device;
conducting preliminary sintering by heating the CIP molded article in a temperature range of 600° C.-700° C. in an air atmosphere;
conducting sintering by heating in a temperature range from (Tn-100)° C. to (Tn)° C. when the starting temperature of foaming of the preliminary sintered body is (Tn)° C., in an air atmosphere or in an inert gas atmosphere; and
forming a sintered body having a compact structure by heating in a temperature range of 900° C.-1150° C. in the same atmosphere as the preceding step.

5. The method for producing a MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 4 ,
wherein the shape of a particle size distribution curve of the compound shows a sub-1-peak-type or 1-peak-type particle size distribution, the maximum particle diameter is 50 μm or less and the median diameter of the particles is 6 μm or less.

6. The method for producing a MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 4 ,
wherein the inert gas atmosphere in the sintering step comprises one kind of gas or a mixture of plural kinds of gases, selected from among nitrogen, helium, argon and neon.

7. The method for producing a MgF 2 —CaF 2 binary system sintered body for a radiation moderator according to claim 5 ,
wherein the inert gas atmosphere in the sintering step comprises one kind of gas or a mixture of plural kinds of gases, selected from among nitrogen, helium, argon and neon.

Assignees

• Univ Tsukuba
• Techno Eye Corp
• Daico Mfg Co Ltd

Inventors

• Kumada Hiroaki
• Nakamura Tetsuyuki
• Ikeda Takeshi
• Shigeoka Takuji

Classifications

• C04B2235/604

  Pressing at temperatures other than sintering temperatures · CPC title

• G21K1/00

  Arrangements for handling particles or ionising radiation, e.g. focusing or moderating · CPC title

• G21F1/00

  Shielding characterised by the composition of the materials · CPC title

• C04B2235/3206

  Magnesium oxides or oxide-forming salts thereof · CPC title

• C04B2235/6583

  Oxygen containing atmosphere, e.g. with changing oxygen pressures · CPC title