Author(s)

P. Charp & J. Hanley

Abstract

We will discuss the evaluation of air monitoring data and deer thyroid data related to radioactive iodine releases from the Oak Ridge National Laboratory (ORNL). The radioactive iodines, estimated at 1.55 petaBecquerels (42,000 Curies) were released during chemical processing of nuclear reactor fuel rods during a procedure called RaLa. The RaLa process was designed to isolate and concentrate radioactive lanthanium used for early nuclear weapon design. The monitoring data were derived from air sampling locations in and around ORNL collected in the 1950s. Our evaluation suggests that atmospheric dispersion of Iodine-131 did not extend beyond ORNL site boundaries; thereby limiting human exposures. The dose reconstruction effort by the state of Tennessee that shows radioiodine-related thyroid doses over a 37 kilometer radius. The dose reconstruction effort was predominated by modeling efforts and includes many associated uncertainties. Among these included scrubber efficiencies, chemical forms of the iodine released, air dispersion models, and fate and transport of the iodines. Moreover, these uncertainties contribute to a typical thyroid dose 95% confidence interval covering 2 orders of magnitude. Because of these uncertainties and its potential impact on public health, the Agency for Toxic Substances and Disease Registry (ATSDR) believes that environmental soil sampling could help better identify the impacted area. In support of the soil sampling, we will discuss how the current but unknown Iodine-129 concentrations in soils can be used as a long-term retroactive surrogate for the dispersion of iodine. Keywords: soil sampling, Iodine-131, Iodine-129, air modelling, thyroid.

Keywords

soil sampling, Iodine-131, Iodine-129, air modelling, thyroid.