Comparison of a continuous working level monitor for radon daughters with conventional grab-sampling

An evaluation of a radon daughter monitor was carried out under laboratory controlled conditions. The monitor operates on continuous sampling and time integrating principles and was tested in conjunction with a newly designed, large radon/thoron room calibration facility. The monitor was tested under constant and rapidly fluctuating radiation conditions. Experimental data obtained with the monitor were compared with data obtained by conventional grab-sampling and with an automated radon daughter/thoron daughter 'grab-sampler'. The Working Level used in the tests ranged from less than 0.01 WL to approximately 10 WL. The measurements were carried out under low aerosol concentration (1 x 103 - 2 x 103 cm-3, approximately) to study plate-out effects in the sampling head. Good agreement (within about 10 %) was found between the monitor, conventional grab-sampling and the automated grab-sampler. The monitor should prove quite flexible, useful and reliable for monitoring underground and surface environments in the uranium mining industry