MW-RN-2020 (1)

Protocol for the Collection, Transfer and ANSI/AARST MW-RN 2020 Measurement of Radon in Water 36 12.3.1 Alpha-scintillation (Lucas) cell Following the transfer of radon into the Lucas cell, the analyst shall dark-adapt the cell a minimum of 3 hours after sample preparation before beginning measurement. Using equations in Section 11 , equations 3-4 are to be applied if applicable and the radon concentration is determi ned using equation 5 . SECTION 13.0 ELECTRET ION CHAMBER (EIC) METHOD The use of Electret Ion Chambers (EIC) for determining radon concentrations is water requires strict adherence to specific practices and calculations developed by manufacturers and successful participation in proficiency testing or laboratory intercomparison programs. Note 1— EIC Devices: EIC devices measure radon in air using an electret (i.e. dielectric material with a quasi- permanent electric charge) that is attached to a chamber where ions resulting from the decay of radon deplete the electric charge of the electret. The difference between the electret charge prior to and after a measurement period is compared for calculating a measurement of radon in air overtime period of the test. Note 2— EIC Method for Water Measurements: The currently developed method for measuring radon in water entails placing a small predetermined volume of sampled water in a larger closed containment jar that has a predetermined air volume. An EIC device is affixed within the containment jar. The EIC measurement of off- gassed radon in air that resulted within the containment jar over time is correlated with known volumes of water and air within the containment jar to achieve reportable measurements of radon in water. 13.1 Measurement Procedure—Electret method The required measurement procedure, based on current methods, includes: 1) Collect, handle and document duplicate water samples in accordance with Sec tions 3 , 4 and 5 using bottles that meet manufacture recommendations; 2) Record voltage readings for electrets as they exist prior to measurement; 3) Attach the electret to the ion chamber; 4) Working quickly, themethod entails placing the water sample and an EIC device inside a containment jar that meets manufacture recommendations: - Open the water sample bottle and place it upright as far inside the containment jar as possible. Note—There may be a snap holder affixed to the bottomof the jar to hold the collection bottle, but this is not required; - Affix or hook the EIC device to the inside of the containment jar lid; - Open the air inlet to the ion chamber; and - Close the containment jar with an airtight lid. 5) Carefully bring the glass jar to the vertical position, permitting the water in the sampling bottle to spill into the jar bottom. Assure the jar cap is tight, which may include installation of a rubber sealing collar around the cap and a clamp around the collar. Keep the jar vertical during the duration of the measurement. 13.1.1 Informative advisories For radon-in-water concentrations greater than 10,000 pCi/L (370 Bq/L), the use of a long-term electret, instead of a short-term electret, is recommended. Typically, a voltage drop of ±20 will provide good precision and keep agreement of the duplicate samples to within 10%. If a short-term electret is used for the analysis, a water sample with a very high radon concentration may result in a very large voltage drop (which has a chance to totally discharge the electret). On the other

RkJQdWJsaXNoZXIy MTgwNDgx