Temperature dependence of the calibration factor of radon and radium determination in water samples by SSNTD

The sensitivity of a Ra-226 determination method of water samples by SSNTD was measured as a function of storage temperature during exposure. The meth od is based on an etched track type radon monitor, which is closed into a g as permeable foil and is immersed in the water sample. The sample is sealed in a glass vessel and stored for an exposure time of 10-30 days. The sensi tivity increased more than a factor of two when the storage temperature was raised from 2 degrees C to 30 degrees C. Temperature dependence of the par tition coefficient of radon between water and air provides explanation for this dependence. For practical radio- analytical application the temperatur e dependence of the calibration factor is given by fitting the sensitivity data obtained by measuring 226Ra standard solutions (in the activity: conce ntration range of 0.1-48.5 kBq m(-3))at different storage temperatures.