Method for fabricating a composite moderator

Abstract

A composite moderator medium for nuclear reactor systems and a method of fabricating a composite moderator block formed of the composite moderator medium. The composite moderator medium includes two or more moderators, such as a low moderating material and a high moderating material. The high moderating material has a higher neutron slowing down power compared to the low moderating material. The low moderating material includes a moderating matrix of silicon carbide or magnesium oxide. The high moderating material is dispersed within the moderating matrix and includes beryllium, boron, or a compound thereof. The high moderating material is encapsulated within the low moderating material such that the high moderating material is not exposed outside of the low moderating material. The method can include selecting a sintering aid and a weight percent of the sintering aid in a composite moderator mixture based on the low moderating material and spark plasma sintering.

What is claimed is: 
     
         1 . A method comprising:
 selecting two or more moderators including a low moderating material and a high moderating material to form a composite moderator medium;   selecting a sintering aid and a weight percent (w/w %) of the sintering aid in a composite moderator mixture based on the low moderating material;   mixing the two or more moderators with the selected sintering aid at the selected weight percent (w/w %) to create the composite moderator mixture; and   sintering the composite moderator mixture to fabricate a composite moderator block formed of the composite moderator medium.   
     
     
         2 . The method of  claim 1 , wherein the sintering the composite moderator mixture includes:
 pouring the composite moderator mixture in a mandrel; and   pressing a die into the mandrel to apply a processing temperature and pressure to the composite moderator mixture to fabricate the composite moderator block formed of the composite moderator medium.   
     
     
         3 . The method of  claim 1 , wherein:
 the low moderating material includes silicon carbide (SiC) or magnesium oxide (MgO); and   the high moderating material includes beryllium (Be), boron (B), or a compound thereof.   
     
     
         4 . The method of  claim 3 , wherein the high moderating material includes at least one of beryllium boride (Be 2 B, Be 4 B, BeB 2 , or BeB 6 ), beryllium carbide (Be 2 C), zirconium beryllide (ZrBe 13 ), titanium beryllide (TiBe 12 ), beryllium oxide (BeO), or boron carbide (B 4 C). 
     
     
         5 . The method of  claim 3 , wherein:
 the low moderating material includes silicon carbide (SiC); and   the sintering aid includes yttria (Y 2 O 3 ) or alumina (Al 2 O 3 ).   
     
     
         6 . The method of  claim 5 , wherein the selected weight percent (w/w %) of the sintering aid in the composite moderator mixture is 4 to 10 weight percent (w/w %) of yttria or alumina. 
     
     
         7 . The method of  claim 5 , wherein a processing temperature for sintering the composite moderator mixture is in a range between 1,400° Celsius (C) to 1,800° Celsius (C). 
     
     
         8 . The method of  claim 3 , wherein:
 the low moderating material includes magnesium oxide (MgO); and   the sintering aid includes lithium.   
     
     
         9 . The method of  claim 8 , wherein the selected weight percent (w/w %) of the sintering aid in the composite moderator mixture is 3 to 10 weight percent (w/w %) of lithium. 
     
     
         10 . The method of  claim 9 , wherein a processing temperature for sintering the composite moderator mixture is in a range between 1,300° Celsius (C) to 1,600° Celsius (C). 
     
     
         11 . A method comprising:
 selecting two or more moderators including a low moderating material and a high moderating material to form a composite moderator medium;   selecting a sintering aid and a weight percent (w/w %) of the sintering aid in a composite moderator mixture based on the low moderating material;   mixing the two or more moderators with the selected sintering aid at the selected weight percent (w/w %) to create the composite moderator mixture; and   spark plasma sintering the composite moderator mixture to fabricate a composite moderator block formed of the composite moderator medium.   
     
     
         12 . The method of  claim 11 , wherein the sparking plasma sintering the composite moderator mixture includes:
 pouring the composite moderator mixture in a mandrel; and   pressing a die into the mandrel to apply a processing temperature and pressure to the composite moderator mixture to fabricate the composite moderator block formed of the composite moderator medium.   
     
     
         13 . The method of  claim 12 , wherein:
 the low moderating material includes silicon carbide (SiC) or magnesium oxide (MgO); and   the high moderating material includes beryllium (Be), boron (B), or a compound thereof.   
     
     
         14 . The method of  claim 13 , wherein the high moderating material includes at least one of beryllium boride (Be 2 B, Be 4 B, BeB 2 , or BeB 6 ), beryllium carbide (Be 2 C), zirconium beryllide (ZrBe 13 ), titanium beryllide (TiBe 12 ), beryllium oxide (BeO), or boron carbide (B 4 C). 
     
     
         15 . The method of  claim 13 , wherein:
 the low moderating material includes silicon carbide (SiC); and   the sintering aid includes yttria (Y 2 O 3 ) or alumina (Al 2 O 3 ).   
     
     
         16 . The method of  claim 15 , wherein the selected weight percent (w/w %) of the sintering aid in the composite moderator mixture is 4 to 10 weight percent (w/w %) of yttria or alumina. 
     
     
         17 . The method of  claim 15 , wherein the processing temperature is in a range between 1,400° Celsius (C) to 1,800° Celsius (C). 
     
     
         18 . The method of  claim 13 , wherein:
 the low moderating material includes magnesium oxide (MgO); and   the sintering aid includes lithium.   
     
     
         19 . The method of  claim 18 , wherein the selected weight percent (w/w %) of the sintering aid in the composite moderator mixture is 3 to 10 weight percent (w/w %) of lithium. 
     
     
         20 . The method of  claim 19 , wherein the processing temperature is in a range between 1,300° Celsius (C) to 1,600° Celsius (C).