Norms (Naturally Occurring Radioactive Materials) in the Ethylene Plant, Revisited

Naturally occurring radioactive materials (NORMs) are an occupational health concern in the ethylene plant. NORMs (as radon) have been known to be a contaminant of natural gas for nearly 100 years but it was only in 1971 that radon was found to concentrate in the lighter natural gas liquids during processing. Historically, the presence of radioactivity has not been widely reported in the ethylene industry. However, that is now changing; a recent, non-exhaustive survey of North American ethylene plants showed that as many as 75% of these plants have detected radioactivity in towers, exchangers and deposits. The light ends towers - specifically the deethanizer and depropanizer - have the majority of cases. The full scale of this issue is not yet known because not every plant monitors for NORMs. Is this increase due to better monitoring and awareness or could the recent rapid increase in fracking be the root cause? This paper will discuss NORMs, locations, potential causes for the increase and how to monitor and handle NORMs in the ethylene plant.