Outdoor thoron progeny levels in the environment of a thorium processing facility

Measurements of outdoor concentrations of thoron progeny in environment of a thorium compounds processing facility is presented. The geometric mean concentration of thoron progeny in the immediate vicinity of the plant is 32 mWL and at 100 metres away (western side) from the plant the concentration reduces to 8 mWL. The gaseous discharge through stacks is not significantly altering the environmental concentration of thoron progeny whereas the concentration is mostly due to storage of thorium hydroxide and other solid waste sources at the site including open trenches. The outdoor thoron progeny levels observed at 500 m northwestern side of the plant (residential area) are comparable to the natural background levels in the area and no significant enhancement attributable to thorium compounds processing facility is observed in the environment. The environmental levels of thoron progeny observed during monazite processing operations and thorium concentrate processing are comparable. (author)