MW-RN-2020 (1)

Protocol for the Collection, Transfer and ANSI/AARST MW-RN 2020 Measurement of Radon in Water 34 (e.g., Insta-Fluor) are applicable for measurement of radon in water, while environmentally-friendly fluids (e.g., Opti-Fluor O) are an alternative. Other organic-based fluids, such as mineral oil, are much less hazardous to handle, but shall also be disposed of properly. Typically, after the sample has been measured by liquid scintillation counting, the cocktail is poured from each vial into a larger container. Since each cocktail is typically 20 mL of volume, a 2-L container can hold the contents of approximately 100 scintillation vials. Due to the immiscibility of the water and organic fluid, two distinct layers will form in the waste container. Unless the water layer is known to contain high concentrations of 226 Ra, the water portion of the cocktail may be decanted and discarded safely down a drain. Any radioactivity from radon and its decay products that remain in the water will not present a hazard. The organic-based fluid shall be discarded through an accredited waste hauler or burned in a high-temperature incinerator. SECTION 12.0 ALPHA SCINTILLATION CELL— LABORATORY PROCESSING As described above, water is collected in glass VOC-type bottles at the sampling location and transported to the laboratory. A glass bubbler will be used to transfer the dissolved radon from the water sample to a fully evacuated alpha-scintillation cell. Due to their fragility and possible agitation (turbulence) of the encapsulated water, bubblers are not transported to a sampling location. The syringe shall have an attached tubing or needle of at least 6 inches in length in order to reach the bottom of the bubbler. 12.1 Prior to transferring the sample To avoid the loss of radon from the water sample while being placed into the bubbler, the glass bubbler shall first contain an aliquot (typically 10 mL) of distilled, or radon- and 226 Ra-free, water prior to the sample transfer. (The exact volume and method of adding this water to the bubbler are irrelevant.) Note—Follow Section 11.1 above. 12.2 Transfer procedure Syringe —Use a graduated syringe with attached tubing (or needle) of sufficient length to reach the bottom of the bubbler. Similar to that described above ( Section 11.2.1 ), extract ~5 mL of water from the collection bottle into the syringe, invert the syringe (tip up), withdraw the plunger slowly until the water in the syringe tubing (or needle) is emptied into the syringe, and then (with tip remaining up) push the plunger to expel the water from the syringe (although the tubing or needle will now be filled with water). Re-insert the intake of the syringe tubing (or needle) near the bottom of the bottle and draw at least 15 mL of water. Remove and invert the syringe and expel any excess water (retain 10 mL). Insert the syringe tubing (or needle) outlet far below the level of the distilled water in the bubbler, slowly expel the water sample into the bottom of the glass bubbler. Cap the bubbler immediately. Pipet —Draw over 15 mL of water into the pipet. The volume reading on the graduated pipet is noted prior to insertion of the pipet outlet below the surface of the water in the glass bubbler and slowly discharge 10 mL of the water. There shall be at least 5 mL of water remaining in the pipet after the transfer as a buffer/barrier between the air and the water being transferred. During transfer of radon from the water in the bubbler, the alpha-scintillation cell provides the force (vacuum) that bubbles the water, so it is important to evacuate the alpha-scintillation cell as much as possible. Inadequate vacuum will result in incomplete transfer of the radon from the water, and thus a low result. The initial vacuum of the scintillation cell shall be greater than 90% (e.g., 80 Torr or 10 kPa) and documented.