Radioactive particle analysis by digital autoradiography

Abstract

We have been exploring ways to evaluate the activity of radioactive particles that have been detected by phosphor plate digital autoradiography based on photostimulated luminescence (PSL). A PSL system with 25 μm pixel digitization has been applied to particle analysis problems, both qualitatively and quantitatively. Two data evaluation methods are currently employed: (1) bulk area signal measurement, and (2) discrete event counting which may include spectral evaluation. The first method is conventional, whereas the second method requires high spatial resolution and is presented here for the first time. The counting methods can discriminate between alpha and background counts. The unshielded background signal accumulation rate was determined by the bulk area method. Using the spectral method of evaluation for α-particle events, the mean signal intensity per recorded α-particle was measured, and the detective quantum efficiency (DQE) was found to be nominally 100%. We present a comparison to gamma-spectrometry for sub-Bq ¹³⁷Cs activities, and demonstrate an application for the qualitative assay of International Atomic Energy Agency swipe samples collected from uranium enrichment facilities.