抄録
Radon gas is an alpha emitting nuclide often found in homes and buildings from the 238U decay chain. The USEnvironmental Protection Agency (EPA) estimates that radon and its progeny are the cause of over 21,000 annual deaths from lung cancer in the United States alone. It is known that the accuracy in radon measurements can be affected by environmental conditions such as temperature and humidity. Purdue University, together with Sagamore Adams Laboratories LLC have developed the tensioned metastable fluid detector (TMFD) sensor technology for efficient and cost-effective radon and progeny spectroscopic detection in a variety of environmental conditions. For radon detection, radon gas mixed with air is sparged through the TMFD detection fluid. This radon-bearing fluid is then placed into a tensioned metastable state. Under tailored metastable state, the fluid becomes sensitive to the recoil nuclei during alpha decay. When recoil nuclei deposit enough energy over nanometer scales into the sensitive fluid, the intermolecular bond energies are overcome resulting into a transient (microsecond) bubble growing to macroscopic dimensions; an audible-visible cavitation detection event is created and recorded. TMFDs are blind to gamma and beta radiation while operating with high (>95%) intrinsic detection efficiencies enabling alpha spectroscopy as well. TMFDs were used to measure the concentration of radon and radon progeny in air for the environmental test conditions set forth by the American Association of Radon Scientists and Technologists-National Radon Proficiency Program (AARST-NRPP) Device Evaluation Program (DEP). These test conditions include measurements from: temperatures spanning 13°C to 26°C, noncondensing relative humidity spanning 15% to 95%, atmospheric pressure spanning 70 kPa to 106 kPa, background photon radiation, nonionizing external EM fields, shock and vibration, and air movement from 0 m s-1 to 0.2 m s-1 . In most tests, measurements were taken at radon concentrations ranging from 37 Bq m-3 (1 pCi L-1 ) to 1480 Bq m-3 (40 pCi L1 ). It was found that temperature affects the radon collection process, for which, a dynamic compensation algorithm was developed - for, accurate radon measurements below and above the US EPA action level of 148 Bq m-3 (4 pCi L-1 ). Remaining AARST parametric influences were found to have small or negligible effect on the radon collection process and associated measurements. This paper will discuss details of the TMFD based spectroscopic Rn/progeny detection assessments and results, thereof.
