Development and operational performance of a single calibration chamber for radon detectors

This work shows the design, setup and performance of a new single radon detector calibration chamber developed at the University of Huelva (Environmental Radioactivity Group). This system is based on a certified radon source and a traceable reference radon detector, which allows radon concentrations inside the chamber radon to be obtained in steady-state conditions within a range of 400-22 000 Bq m^-3 with associated uncertainties in the range of 4%. In addition, the development of a new ad hoc calibration protocol (UHU-RC/01/06 "Rachel"), which is based on the modelling of radon concentration within the chamber, allows it to be used without the reference detector. To do that, a complete characterization and calibration of the different leakage constants and the flow meter reading have been performed. The accuracy and general performance of both working methods for the same chamber (i.e., with and without the reference detector) have been tested by means of their participation in an intercomparison exercise involving five active radon monitors.