Radon Dosimetry

Inhaled radon (222Rn) progeny are the most important source of irradiation of the human respiratory tract. Epidemiological studies of underground miners of uranium and other minerals have provided reasonably firm estimates of the risk of lung cancer associated with exposure to radon progeny. It is well established that the absorbed radon dose in the lung is mainly due to radon progeny, but not the radon gas itself. Therefore, long-term measurements of the concentrations of radon progeny or the equilibrium factor F, the size distribution of radon progeny and the unattached fraction fp of the potential alpha energy concentration are needed to accurately assess the health hazards contribution from radon progeny.
Resources
Book chapter: Nikezic, D., Yu, K.N., "Computer Simulation of Radon Measurements with Nuclear Track Detectors", 2007, in Computer Physics Research Trends, Ed. S. J. Bianco, (Nova Science Publishers: New York), p. 119-150. (download pdf version) (purchase book)
Book chapter: Yu, K.N., Nikezic, D., "Long-Term Measurements of Radon Progeny Concentrations with Solid State Nuclear Track Detectors", 2009, in Nuclear Track Detectors: Design, Methods and Applications, Eds. Maksim Sidorov and Oleg Ivanov, (Nova Science Publishers: New York) p. 107-131. (download pdf version) (purchase book)
Review paper: Yu, K.N., Lau, B.M.F., Nikezic, D., “Assessment of Environmental Radon Hazard Using Human Respiratory Tract Models", 2006, Journal of Hazardous Materials, 132, 98-110. (download pdf version).

Invited talk (22 ICNTS, Barcelona 2004): Yu, K.N., Nikezic, D., Ng, F.M.F., Leung, J.K.C., "Long-term Measurements of Radon Progeny Concentrations with Solid State Nuclear Track Detectors", 2005, Radiation Measurements, 40, 560-568. (download pdf version).

Invited talk (23 ICNTS, Beijing 2006): Yu, K.N., Leung, S.Y.Y., Nikezic, D., Leung, J.K.C., "Equilibrium factor determination using SSNTDs", 2008, Radiation Measurements, 43 (Suppl. 1), S357-S363. (download pdf version).

 

Long-term Measurements of Equilibrium Factor (F) and Unattached Fraction (fp)

The effective dose in the lung is mainly due to short-lived radon progeny, i.e., 218Po, 214Pb, 214Bi and 214Po, but not the radon (222Rn) gas itself. Accordingly, long-term measurements of the concentrations of radon progeny or the equilibrium factor F, the size distribution of radon progeny and the unattached fraction fp of the potential alpha energy concentration are needed to accurately assess the health hazards contributed by radon progeny. Methods for long-term monitoring of the 222Rn gas itself are well established, such as through the use of solid-state nuclear track detectors (SSNTDs). We have now further designed methods for long-term monitoring of the F or  fp . 
Proxy equilibrium factor (Fp)

We proposed the "proxy equilibrium factor" or "Fp" method to determine F using bare LR 115 detectors. We found that the partial sensitivities ρi (with the unit m) of the LR 115 detector to 222Rn and its alpha emitting short-lived progeny, 218Po and 214Po, were equal! Equality of partial sensitivities enabled convenient measurements of Fp, which was defined as (f1 + f3) and was equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny (218Po+214Po) to the concentration of radon gas (222Rn). We found Fp = (ρ/ρitC0) – 1, where ρ (track/m2) was the total track density on the detector, and t was the exposure time and C0 (Bq/m3) was the concentration of 222Rn. Fp was found to be well correlated with F through the Jacobi room model.

Dependence of the equilibrium factor F on the proxy equilibrium factor Fp (= f1 + f3).

 
Unattached fraction
We developed the theoretical basis for long-term determination of airborne concentrations of unattached and attached radon progeny. After determination of F (from Fp or from the reduced equilibrium factor Fred), the airborne concentrations of 214Pb could be determined. Based on the airborne concentrations of 218Po, 214Pb and 214Bi, the parameters of the Jacobi room model, viz., the ventilation rate, aerosol attachment rate, deposition rate of unattached progeny , and the deposition rate of attached progeny, can be determined . With these parameters, fp could also be determined. 
  Publications
  • Nikezic, D., Ng, F.M.F., Yu, K.N., 2004. Theoretical basis for long-term measurements of equilibrium factor using LR 115 detector. Applied Radiation and Isotopes, 61, 1431-1435.
  • Yu, K.N., Nikezic, D., Ng, F.M.F., Leung, J.K.C., 2005. Long-term Measurements of Radon Progeny Concentrations with Solid State Nuclear Track Detectors. Radiation Measurements, 40, 560-568.
  • Leung, S.Y.Y., Nikezic, D., Yu, K.N., 2006. Passive monitoring of the equilibrium factor inside a radon exposure chamber using bare LR 115 SSNTDs. Nuclear Instruments and Methods in Physics Research A, 564, 319-323.
  • Ng, F.M.F., Nikezic, D., Yu, K.N., 2007. Long-term measurements of equilibrium factor with electrochemically etched CR-39 SSNTD. Nuclear Instruments and Methods in Physics Research B, 263, 279-283.
  • Yu, K.N., Leung, S.Y.Y., Nikezic, D., Leung, J.K.C., 2008. Equilibrium factor determination using SSNTDs. Radiation Measurements, 43 (Suppl. 1), S357-S363.
  • Nikezic, D., Yu, K.N., 2010. Long-term determination of airborne concentrations of unattached and attached radon progeny using stacked LR 115 detector with multi-step etching, Nuclear Instruments and Methods in Physics Research A, 613, 245-250.
  • Yu, K.N., Nikezic, D., 2011. Long-term determination of airborne radon progeny concentrations using LR 115 solid-state nuclear track detectors. Radiation Measurements 46, 1799-1802.
  • Yu, K.N., Nikezic, D., 2012. Long-term measurements of unattached radon progeny concentrations using solid-state nuclear track detectors. Applied Radiation and Isotopes, 70, 1104–1106.
 

Dosimetric Modeling

 

Microdosimetry

 

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Nuclear Radiation Unit
Department of Physics and Materials Science
City University of Hong Kong
Tat Chee Ave, Kowloon Tong, Hong Kong
Email: apnru@cityu.edu.hk

 

Page last modified on 13-Jun-2012

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