Studies on emanation of thoron from monazite mineral and chemical compounds of thorium

Emanation characteristics of thoron from monazite mineral and different chemical compounds of thorium were studied. Thoron measurements were carried out using double filter unit and thoron cell. The matrix materials employed in the studies were monazite (mineral), monazite (powder) and chemical compounds of thorium such as the oxide, hydroxide and oxalate. The emanation from the mineral was very low at 0.06%. Emanation up to 2% was observed from finely divided monazite (50 μm size). Higher rates of emanation varying from 2 to 50% were observed from the chemical compounds. The emanation was also found to be moisture dependent. The infinite thickness of monazite bed for saturation emanation was found to be about 3 cm. The recoiling range of thoron in the monazite mineral grain was calculated to be 0.03 μm. Studies carried out using a test facility did not show appreciable concentration gradient for thoron activity up to 3 m height. (author)