The Spot Radon Daughter Monitor (SRDM) is a fully automatic, microprocessor- based radiation monitoring system developed by RDS for the monitoring of the “momentary” potential alpha energy concentration (PAEC) of radon daughters in outdoor and indoor environments. The SRDM is powered by an internal battery pack (NiMH-7.2V-1000 mAh).
The SRDM adopts the Borak method for the assessment of the PAEC of radon daughters. It has an internal air sampling pump with a constant flow rate of 2 L/min. Radon-daughter aerosols are sampled by a 37 mm glass-fibre filter that is in close contact with a ZnS(Ag) scintillation detector. A 3-minute radon-daughter sampling time is followed by a 3-minute decay time, before the gross alpha activity of the radon daughters on the filter is counted for 3 minutes. When the alpha counting is finished, the measured PAEC is displayed on the LCD panel. The Lowest Limit of Detection (LLD) of the SRDM is approximately 0.015 µJ/m³.
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