Neutron absorbing block

Powdery colemanite is molded by a compressive force of greater than 200kgf/cm2 to form a neutron absorbing block for shielding neutrons emitted from a medical neutron source or the like. Colemanite is a chemically stable mineral substance and contains a great amount of hydrogen and boron. Powdery colemanite charged in a molding die is pressed by a compressive force, for example, of about 1,000kgf/cm2 to form an appropriate shape. In addition, surface water is appropriately kept on the colemanite in the molding die for facilitating solidification. With such procedures, neutron absorbing effect can be improved and the product is made homogeneous with no detects such as cracks and an appropriate strength can be attained. Since it is solidified only by the compressive force, production is easy. Further, since no cement hydrates are not necessary, stable performance can be kept for a long period of time without causing transition or undergoing the effect of neutralization or the like. (I.N.)