Long-term measurements of thoron, its airborne progeny and radon in 205 dwellings in Ireland

Abstract

Long-term (circa 3 months) simultaneous measurements of indoor concentrations of thoron gas, airborne thoron progeny and radon were made using passive alpha track detectors in 205 dwellings in Ireland during the period 2007-09. Thoron progeny concentrations were measured using passive deposition monitors designed at the National Institute of Radiological Sciences (NIRS), Japan, whereas thoron gas concentrations were measured using Raduet detectors (Radosys, Budapest). Radon concentrations were measured in these dwellings by means of NRPB/SSI type alpha track radon detectors as normally used by the Radiological Protection Institute of Ireland (RPII). The concentration of thoron gas ranged from <1 to 174 Bq m(-3) with an arithmetic mean (AM) of 22 Bq m(-3). The concentration of radon gas ranged from 4 to 767 Bq m(-3) with an AM of 75 Bq m(-3). For radon, the estimated annual doses were 0.1 (min), 19.2 (max) and 1.9 (AM) mSv y(-1). The concentration of thoron progeny ranged from <0.1 to 3.8 Bq m(-3) [equilibrium equivalent thoron concentration (EETC)] with an AM of 0.47 Bq m(-3) (EETC). The corresponding estimated annual doses were 2.9 (max) and 0.35 (mean) mSv y(-1). In 14 or 7% of the dwellings, the estimated doses from thoron progeny exceeded those from radon.

Long-term measurements of residential radon, thoron, and thoron progeny concentrations around the Chhatrapur placer deposit, a high background radiation area in Odisha, India

“…2, frequency distributions of radon, thoron and thoron progeny concentrations are shown. They do not have a normal distribution similar to reports from other surveys (e.g., Chen et al, 2011;Dwivedi et al, 2005;McLaughlin et al, 2011;UNSCEAR, 2000;Yamada et al, 2006). Further analysis based on the Shapiro-Wilk test reveals a log-normal distribution for radon and thoron concentrations during the rainy season (W-values: 0.59 and 0.13, respectively) and thoron progeny concentration during the autumn-winter and rainy seasons (W-values: 0.55 and 0.57, respectively).…”

“…The thickness of the films was adjusted to absorb the energy of alpha particles from radon, thoron and their progenies except for 212 Po (8.78 MeV). Since the Raduet and thoron progeny deposition detector are inexpensive and easy to use, they are often used in a large-scale survey (e.g., Chen et al, 2012;Janik et al, 2013;Kudo et al, 2015;McLaughlin et al, 2011;Ramola et al, 2010Ramola et al, , 2012.…”

“…According to the UNSCEAR reports (UNSCEAR, 2000(UNSCEAR, , 2010, thoron (including its progeny) typically contributes a dose of 0.1 mSv, which is 10% or less of the dose from radon. However, as measurement methods for radon and thoron concentration have been improved, the presence of thoron-prone areas has been recognized (e.g., Kudo et al, 2015;McLaughlin et al, 2011;Tokonami et al, 2004;Yamada et al, 2006). In such areas, the dose from thoron is equal to or exceeds that from radon, and it is not negligible for dose evaluation.…”

Long-term measurements of radon, thoron and their airborne progeny in 25 schools in Republic of Srpska

“…In the same study correlation between C Rn and C Tn and between C Tn and EETC was insignificant which is contrary to our results. Poor correlations between C Tn and EETC were reported for dwellings in China (R 2 ¼ 0.04), Yamada et al, 2006), Ireland (R 2 < 0.01) (McLaughlin et al, 2011) and Korea (R 2 ¼ 0.03) (Tokonami et al, 2005).…”

Monte Carlo simulation of semiconductor detector response to 222Rn and 220Rn environments

“…Thoron is considered to contribute about 4% to the annual effective dose of natural radiation (UNSCEAR, 2010), and must not be neglected (Steinh€ ausler et al, 1994;Tokonami, 2010). In fact, worldwide studies suggest that under certain conditions, the annual equivalent lung dose of thoron can even exceed that of radon (Tschiersch et al, 2007;Meisenberg and Tschiersch, 2011;Wiegand et al, 2000;Sreenath Reddy et al, 2004;Shang et al, 2008;McLaughlin et al, 2011). In contrast to radon, the gas concentration of the short lived 220 Rn isotope (half-life t 1/2 ¼ 55.6 s) is difficult to measure and advanced methods have to be applied (Nuccetelli and Bochicchio, 1998).…”