125I Disk Source Using Charcoal Activated Polyurethane Foam Rubber Mat

Uniform 125I disk sources were prepared as a reference source to calibrate NaI (Tl) scintillation detector to measure 125I activity on a filter of air monitor in a laboratory. The base of the disk source was a charcoal activated polyurethane foam rubber mat of 75mm in diameter, 2mm in thicknes. 125I disk sources of approximate 0.5kBq, 1kBq, and 10kBq were obtained through immersing disks in ethanol solution containing Na125I of 0.5kBq/ml, 1kBq/ml and 10kBq/ml, respectively, and then drying up them. The uniformity of the distribution of 125I on the disk source was estimated by analyzing the autoradiograph of the disk source using an imaging analyzer. The radioactivity of 125I was distributed uniformly on the surface of the disk source within an uncertainty of about 10%.