Radon In Water
A standard boro-silicate glass VOA sample collection vial with Teflon sepa cap is used for sample collection. Minimum sample volume is 20 ml. Collect the sample from a source of fresh cold water. Allow the water to run until any holding tanks and pipes are cleared. Minimize aeration during sample collection.
One method of sample collection is to slowly fill a bowl or deep pan. Submerge the collection vial and cap open side up until they fill. While the vial is still submerged, screw the cap of the vial back on. The sample should not contain any air bubbles or have any headspace. The sample collection vial does not contain a preservative. If there are any air bubbles in the sample, collect the sample again. Return the sample to the laboratory within four days.
In the laboratory, a measured aliquot of the water sample is mixed with scintillation cocktail in a glass test vial. Radon preferentially dissolves into the cocktail over period of several hours. The vial is then placed in a shielded chamber for counting. Alpha particles emitted by the breakdown products of Radon create scintillations, or flashes of light, in the cocktail.
A photo-multiplier tube detects these scintillation's, the signal is electronically enhanced and the effect of the alpha particles are counted. Background counts are subtracted and the net counts are entered into a formula with other relevant data yielding quantitative results stated in picoCuries per Liter (pCi/L).