Measurement of radon daughters in water and in air using the detection unit 'YAPMARE' with a YAP:Ce scintillation detector

摘要

With a focus on the detection of the Rn concentration in water in extreme conditions, the detection unit YAPMARE was developed by the company CRYTUR. The main part of the detection unit is a detection probe based on the 025 x 100 mm YAP:Ce detector. The measured water covers approximately 95% of the crystal surface (the detection volume is 12 ml). Measurements of ~(222)Rn and ~(220)Rn standards for determination of individual peaks in the spectra were conducted, including an observation of the ~(222)Rn (and its daughters) behavior. For YAPMARE calibration, fresh water was taken from a drilled well in the Lounovice area (biotitic granodiorite-adamellite). The calibration was carried out with the assistance of radon in water monitor RAD1M 4. The results of the water measurements in Lounovice were as follows: detection limit was about 50 Bq/l, and calibration coefficient was 0.0011 imp/s per 1 Bq/l. The results of the fresh water and air sample measurements have demonstrated the main advantages (spectrometric results of the measurement, possibility for water or air samples evaluation) and disadvantages (large size of scintillation crystal increases gamma ray background, calibration for each water with particular composition, and detector cleaning using HC1 acid).