| 摘要 |
Neutron absorbing articles, such as those in plate form suitable for use in a storage rack for spent nuclear fuel and having such properties as to make them useful in such application for long periods of time, are made by an improved one-step curing method in which a mixture of boron carbide particles, powdered phenolic resin and a minor proportion of a liquid medium which boils at a temperature below 200 DEG C., preferably water, is compacted to desired article form and is cured at an elevated temperature, without simultaneous imposition of pressure in compacting or pressing means, so as to cause bonding of the irreversibly cured phenolic polymer resulting to the boron carbide particles and production of the neutron absorber in desired form. In preferred aspects of the invention the proportions of boron carbide particles, resin and water are respectively, 60 to 80, 20 to 40 and 2 to 8, the resin is a phenol formaldehyde two-stage resin containing hexamethylenetetramine in sufficient quantity to provide formaldehyde to cure it, the resin is of a molecular weight in the range of 1,200 to 10,000, e.g., 6,500, the resin and the irreversibly cured polymer resulting are substantially free of halogens, lead, mercury, sulfur, filler, plasticizer and solvent and the boron carbide particles contain no more than 2% of iron and no more than 0.5% of B2O3. The described method is also employable when a proportion of the boron carbide particles, e.g., 1/10 to 9/10, is replaced by a diluent compound, such as silicon carbide, alumina, silica, graphite, amorphous carbon or mixtures thereof.
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