A Calibration Method of an Ionization Chamber for Measuring 222Rn Concentration

When 222Rn concentration is measured with an ionization chamber, the conversion factor of ionization current to 222Rn concentration has been decided in individual case. A flow-type ionization chamber (the effective volume; 18l) was used for measuring 222Rn concentration in this work. The conversion factor of this ionization chamber was obtained 1.11 (Bq/m3/fA) by the use of RaDEF standard source. From the results of three other literatures and this work, the following formula to calculate the conversion factor (a) was obtained as a function of the effective volume V (m3) of ionization chamber. a=1.036×10-1/V⋅ (log V+6.908) (Bq/m3/fA)