RADON CHARACTERIZATION IN THE PENNSYLVANIAN STRATA OF SOUTHWESTERN INDIANA

Radon (²²²Rn, ²²⁰R) is a radioactive gas that results from the decay of uranium (²³⁸U) and thorium (²³²Th) in the earth’s crust. Radon is considered to be the second leading cause of lung cancer in the U.S. While the EPA characterizes the radon concentrations of Southwestern Indiana to be in the “Moderate Potential” range (2-4 pCi/L), isolated locations within this area have measured at levels far exceeding this rating. As a nuclear physicist the motivation for this work is to determine the presence and quantity of the radioactive radon gas in Southwestern Indiana and potentially correlate the findings to occurrences of lung cancer in the area. This study characterizes the presence and quantity of radon using its radioactive progeny. Cores were drilled on the campus of the University of Southern Indiana to a depth of 750 feet during exploration for coal-bed methane. Gamma logs were taken to measure gamma ray activity as a function of depth in the bore hole. Activity readings of 467, 555, and 388 GAPI were measured at depths of 505, 614 and 702 feet in three separate shale layers of the Pennsylvanian stratigraphic column. Cores from these high activity depths were studied with a large volume NaI crystal detector to look for gamma rays of specific energies. Since gamma decay energies are specific to the isotope that is decaying, these gamma rays can be used to unambiguously identify radioactive isotopes. Characteristic gamma rays from radon daughters were identified confirming the presence of radon. The quantity of daughter gamma rays is used to determine the potential of elevated radon levels in the area. Future studies using nuclear spectroscopic techniques, such as alpha-gamma coincidence measurements, will be discussed as an additional method for quantitative determination of radon in core samples.