Electret ion chambers for passive measurement of airborne tritium: Theory and practice

Journal Article · Sun Dec 31 04:00:00 EST 1995 · Radioactivity and Radiochemistry

OSTI ID:160089

Kotrappa, P ^[1]; Hobbs, T G; Brown, D R ^[2]

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1. Rad Elec., Inc., Frederick, MD (United States)
2. National Institute of Standards and Technology, Gaithersburg, MD (United States)

Commercially-available electret ion chambers (EICs) are already in use for passive measurement of radon concentration in air. Modified versions of these are usable for the measurement of airborne tritium. Modification provides increased filtered area for rapid, passive exchange of airborne tritium or tritiated water vapor between the interior of an EIC to the outside air. Response factors are calculated from the first principles. These units are exposed to airborne tritiated water vapor inside an airtight chamber for a known period of time to deduce the experimental response factors. One-liter, vibrating-reed-electrometer tritium detectors calibrated by the National Institute of Standards and Technology (NIST) are used as reference detectors. EIC units with three different volumes (58,210, and 960 mL) and electrets of two different sensitivities ({open_quotes}short-term{close_quotes} and {open_quotes}long-term{close_quotes}) are studied. Using a {open_quotes}short-term{close_quotes} electret in a 210-mL-volume chamber, a 0.5 derived air concentration (12.5 {mu}Ci m{sup {minus}3} d) is measurable with an accuracy of about 10% in one day. Theoretically calculated and experimentally determined response factors agree fairly well, demonstrating the scientific validity of the theory. Field testing of these devices performed at Pickering Nuclear Facilities indicated satisfactory performance over a range of concentrations from 5 to 50 {mu}Ci m{sup {minus}3}. Advantages and disadvantages of using the EIC units for passive measurement of tritium are discussed.

• OSTI ID: 160089
• Journal Information: Radioactivity and Radiochemistry, Journal Name: Radioactivity and Radiochemistry Journal Issue: 2 Vol. 6; ISSN RARAE6; ISSN 1045-845X
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
54 ENVIRONMENTAL SCIENCES
AIR
DESIGN
ELECTRETS
IONIZATION CHAMBERS
MATHEMATICAL MODELS
PERFORMANCE
PICKERING SITE
RADIOECOLOGICAL CONCENTRATION
TRITIUM