Document Detail

Uncertainty of 222Rn Concentrations in the Usepa Radiation and Indoor Environments National Laboratory Exposure Chamber.
MedLine Citation:
PMID:  23274820     Owner:  NLM     Status:  In-Data-Review    
ABSTRACT: The U.S. Environmental Protection Agency (EPA) operates an environmentally controlled chamber for purposes of exposing various radon and decay product measurement equipment to known Rn concentrations. Exposure durations range from 1 h to several months, and Rn concentrations vary between 37 and 4,440 Bq m. Radon concentrations are generated from Ra sources mounted on the chamber, but concentrations are continuously measured using equipment calibrated using Rn generated from Ra laboratory standards made from a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) and verified through an aliquot measured by the NIST. The Rn concentrations that are used to calibrate the equipment in the chamber are produced from bubbling a measured volume of air through the Ra laboratory standard solution. This paper describes the process to derive an average chamber concentration during the exposure period. This includes the generation of laboratory Ra standards from the original NIST SRM, Rn emanation into a measured volume of air and transfer to Rocky Mountain Glassworks stainless steel scintillation cells to generate individual cell calibration factors, the calibration of larger mounted flow-through scintillation cells, and the reduction of cumulative chamber scintillation cell counts over various time periods. Each step is associated with an uncertainty based on measured and estimated factors, and each step adds an additional uncertainty to the cumulative total. The methods used follow guidance in the 1993 ISO Guide to the Expression of Uncertainty in Measurement and NIST Technical Note 1297. Chamber exposures of 96 h and Rn concentrations between 150 and 2,700 Bq m are associated with a combined standard uncertainty of 4.1% (1 s). Ninety-six hour (96 h) exposures of lower Rn concentrations of between 150 - 370 Bq m are associated with a combined standard uncertainty of 5%. Results indicate that there are measures that can be taken to reduce the estimated uncertainty slightly. The calculations used in this analysis have been incorporated into the computer code used to track chamber concentrations and exposures so that estimated uncertainties can be associated with each exposure.
M Ronca-Battista; G Budd; S McLemore
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Health physics     Volume:  104     ISSN:  1538-5159     ISO Abbreviation:  Health Phys     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2012-12-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985093R     Medline TA:  Health Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  168-78     Citation Subset:  IM    
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