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Title: An improved sup 222 Rn canister using a two-stage charcoal system

An improved sup 222 Rn canister using a two-stage charcoal system A prototype for an improved passive {sup 222}Rn canister (R-Canister) was designed and compared to conventional charcoal canisters for its adsorptive and desorptive characteristics following exposures to {sup 222}Rn at 23{degrees}C in the presence of water vapor. The R-Canister, containing a two-stage charcoal system, minimizes the adverse effects of water vapor by maintaining the amount of adsorbed water vapor in the primary Rn adsorbent below the break-point of the charcoal. This is achieved by the placement of a desiccant charcoal cartridge 6 cm above the primary Rn adsorbent. The optimal bed depth of the primary adsorbent, determined from a diffusion study, was found to be 2.3 cm. The measured value for the effective diffusion coefficient of RN in a peat-based charcoal at 15% humidity and 25{degrees}C is 7.97 x 10(-10) m2 s-1. Exposures to 70% humidity for 7 d increased the buildup time-constant of Rn in the R-Canisters by 33% as compared to R-Canisters exposed to 15% humidity. At relative humidities ranging from 15-70%, the {sup 222}Rn buildup time-constant of the R-Canister ranged from 43-94 h, whereas the desorption time-constant ranged from 46-64 h. Typical buildup time-constants and desorption time-constants for conventional fully-opened charcoal canisters currently in field use ranged more » from 30-43 h and 17-29 h, respectively, over the same range of humidities. « less
Authors: ;
Publication Date:
OSTI Identifier:OSTI ID: 5897282
Resource Type:Journal Article
Resource Relation:Journal Name: Health Physics; (USA); Journal Volume: 60:2
Country of Publication:United States
Language:English
Subject: 54 ENVIRONMENTAL SCIENCES; RADIATION MONITORS; DESIGN; RADON 222; RADIATION MONITORING; CHARCOAL; INDOOR AIR POLLUTION; RADIOECOLOGICAL CONCENTRATION; ADSORBENTS; AIR POLLUTION; ALPHA DECAY RADIOISOTOPES; DAYS LIVING RADIOISOTOPES; ECOLOGICAL CONCENTRATION; EVEN-EVEN NUCLEI; HEAVY NUCLEI; ISOTOPES; MEASURING INSTRUMENTS; MONITORING; MONITORS; NUCLEI; POLLUTION; RADIOISOTOPES; RADON ISOTOPES 540130* -- Environment, Atmospheric-- Radioactive Materials Monitoring & Transport-- (1990-)