Measurement of the total activity concentrations of Libyan oil scale

Twenty-three oil scale samples obtained from the Libyan oil and gas industry production facilities onshore have been measured using high-resolution gamma-ray spectrometry with a shielded HPGe detector, the work being carried out within the Environmental Radioactivity Laboratory at the University of Surrey. The main objectives of this work were to determine the extent to which the predominant radionuclides associated with the uranium and thorium natural decay chains were in secular equilibrium with their decay progeny, also to compare differences between the total activity concentrations (TAC) in secular equilibrium and disequilibrium and to evaluate the measured activities for the predominant gamma-ray emitting decay radionuclides within the ²³²Th and ²³⁸U chains. The oil scale NORM samples did not exhibit radioactive equilibrium between the decay progeny and longer-lived parent radionuclides of the ²³⁸U and ²³²Th series. - Highlights: • Activity concentration of naturally occurring radioactive materials (TENORM). • Application bounds for the various TAC formulae reviewed and critiqued. • Measurements made using TENORM scale from Libyan oil and gas fields. • Disequilibrium found following protracted periods of sealed storage.