A Method for Concurrent and Continuous Measurement of Rn-222 and Rn-220 Using Scintillation Cells

A method is described for the continuous and simultaneous measurement of both {sup 220}Rn and {sup 222}Rn in air. Two scintillation flasks are arranged in a serial configuration and the concentrations of {sup 222}Rn and {sup 220}Rn are determined by making use of the difference between the half-lives of the two radon isotopes. The method was developed for directly measuring {sup 220}Rn in occupied areas where fuel materials containing {sup 228}Th were being used, but could also be useful for other applications. Since {sup 222}Rn is usually present from either naturally occurring materials or due to the presence of process material, the method was designed to allow measurement of the two isotopes at coincident times. The method is discussed for counting equipment using scintillation cells, but the approach would also be directly applicable for any type of pulse-counting radon monitoring equipment such as pulse-ion chambers. Although intermittent measurements with decay correction could be performed using a single detector, the use of two cells allows continuous monitoring and a higher degree of detection sensitivity. The approach makes use of isotope-independent calibration factors and could therefore easily be modified for use with a single detector when only one of the radon isotopesmore » is expected to be present.« less