Measurements of radon concentration in soil gas by CR-39 detectors

A miniature diffusion chamber with a 25 x 4 x 0.5 mm CR-39 track etch detec tor (Pershore Moulding Ltd.), mounted on the 1.1, m long pole has been deve loped for radon gas measurements at 1 meter depth in the soil. For chemical ly etched CR-39 (7h, 70 degrees C NaOH) and automatic track analysis the lo west detection limit of the chamber was found to be 0.5 MBq h m(-3) and the useful exposure range from 2 to 20 MBq h m(-3). The typical exposure time in the soil is between 2 to 14 days. The chamber was tested against the act ive AlphaGUARD PQ-2000 (Genitron Instruments GmbH) probe. The test yielded consistent results for soils with typical values of permeability and which are not saturated with water. The pilot measurements of radon gas in soil c onducted with the miniature diffusion chambers around 48 buildings in Krako w and Silesia regions yielded an average radon concentration of 13 kBq m(-3 ). The chambers are to be applied to measure radon concentration in soil be fore constructing new houses in order to avoid high radon risk areas.