POLONIUM-210 IN DUSTS FROM THE ESF TUNNEL, YUCCA MOUNTAIN

Sampling and analysis for Po-210 has been conducted on dust accumulating on installations and tunnel walls of the Exploratory Studies Facility (ESF) at Yucca Mountain, Nevada. Polonium-210 is a radioactive daughter of radon gas and, being a solid, is electrostatically attracted to the surface of dust particles. Inhalation of this dust by researchers and operational staff may represent a potential health hazard as the Po-210 emits alpha-radiation in its decay to stable lead (Pb-206) and this may lead to lung tissue damage. A study in 1999 showed that, in the absence of control measures, flux from the bedrock caused Rn to attain relatively high levels in the air in the tunnel. Because of the relatively long half-life of its parent (Pb-210, 22.7 years), Po-210 will reside on dust particles for over 100 years and be a potential long-term health risk.

Analyses have been performed by digesting the dust in acid and concentrating the Po-210 onto silver foil for counting by alpha spectrometry. A Po-209 tracer was used to monitor recovery and determine specific activities of Po-210 in the dust. Polonium-210 concentrations were compared with U concentrations in the Yucca Mountain tuff and radon levels in the ESF tunnel and its importance as a potential hazard assessed.