Gross Alpha Activity Measurements: Investigating the Crucial Role of Self-Absorption Correction Factors

The detection and measurement of radionuclides are indispensable processes, crucially guided by particle and photon emission mechanisms. Regulatory agencies and policymakers demand precise measurements to ensure compliance with safety standards and environmental protection mandates. To convert detection rates into meaningful activity values, certain vital parameters must be derived, necessitating validation through reference measurements, technical innovations, and proficiency testing. Gross alpha activity assessment holds particular significance in both finished products and the waste generated within naturally occurring radioactive materials (NORM) industries. The thickness of the radiation source emerges as a pivotal factor influencing gross alpha activity determination, owing to the energy losses incurred through self-absorption processes. This study endeavors to comprehensively investigate the impact of self-absorption in relation to source thickness, alongside an exploration of the associated procedural considerations. The research encompasses theoretical examinations of the range and stopping power of alpha particles as they interact with the source material itself, complemented by empirical measurements involving sources of varying thicknesses. Specifically, this study examines the influence of source thickness on the measurement of alpha activity within radioactive waste materials, originating from front-end nuclear facilities. In the context of this study, liquid wastes arise during the ore processing into uranium concentrate (sodium diuranate), subsequently conveyed to tailing ponds in slurry form. Solid wastes, on the other hand, predominantly consist of waste rock fragments produced during mining operations. A notable observation underscores the significance of self-absorption correction factors: In their absence, the measured values of alpha-specific activity experience substantial underestimation. This investigation yields self-absorption correction factors that have been quantified for varying source thicknesses. For liquid wastes, a second-degree polynomial fit, and for solid waste, a linear fit have been applied to these correction factors, facilitating improved accuracy in alpha activity measurements within radioactive samples. This research not only enhances our understanding of the intricate interplay between source thickness and self-absorption but also provides valuable insights for refining measurement methodologies in radiological assessments, especially concerning gross alpha activities in radioactive waste materials.