Measurement of radon (222Rn) and thoron (220Rn) concentration with a single scintillation cell

. A single scintillation cell (ö 54 × 74 mm) is used for the measurement of radon and thoron. The radon and thoron laden air is filtered and forced to flow at 1 dm3/min through the scintillation cell in the period of 1 10 min. The count number from alpha radiation is registered in the periods of 3 10 min and 20 30 min. Two values of detection and deposition efficiency of alpha radiation are used for radon (at air flow and air at rest in the cell) and for thoron. Measurements of radon laden air and thoron laden air showed good agreement between the reference concentration and the measured concentration, not worse than 1% for radon and not worse than 2% for thoron. Combination of radon + thoron concentration showed also a small interference ("cross talk") not worse than 1%.