Abstract
This study summarizes the seasonal experimental data on the activity concentrations of indoor 222Rn (Radon), 220Rn (Thoron) and their progeny in Mansa and Muktsar districts of Punjab (India) using LR-115 solid state nuclear track detector based time integrated pin-hole cup dosimeters and deposition based progeny sensors for the assessment of radiological dose. The indoor 222Rn concentration was observed higher in the rainy and winter seasons while 220Rn concentration was observed higher in the winter season. However, Equilibrium Equivalent Concentrations (EECs) of 222Rn and 220Rn exhibited distinct seasonal behaviour unlike their parent nuclides. The average equilibrium factors for 222Rn (FRn) and 220Rn (FTn) were found 0.47 ± 0.1 and 0.05 ± 0.01, respectively. The annual arithmetic means of unattached fractions of 222Rn ({f}_{p}^{Rn}) and 220Rn ({f}_{p}^{Tn}) were found to be 0.09 ± 0.02 and 0.10 ± 0.02, respectively. The attachment rate (XRn) and attachment rate coefficients (β) of 222Rn progeny were also calculated to understand the proper behaviour of progeny species in the region. A new alpha flux based technique has been proposed and used for the assessment of absorbed dose rate and annual effective dose rate for radiation protection purpose.
Highlights
222Rn and 220Rn are naturally occurring radionuclides formed within the decay series of 238U and 232Th, respectively
In 1993, ICRP switched to the epidemiology approach of 222Rn exposure in mines and later biokinetic model (HRTM) for 222Rn gas has been developed so that effective doses arising from the inhalation of 222Rn gas can be calculated[16,17,18]
In ICRP publication 115, the commission has concluded that 222Rn and its progeny should be treated in the same way as any other radionuclide within the system of protection and proposed that doses from 222Rn and its progeny should be calculated using ICRP biokinetic and HRTM19
Summary
The seasonal behaviour of 222Rn, 220Rn, unattached fraction and equilibrium factors of 222Rn and 220Rn have been studied in 42 villages of Mansa and Muktsar districts of Punjab (India). The months of March to mid-June as summer, Second half June to mid-October as rainy and Second half October to February as winter were taken for the seasonal estimation of 222Rn, 220Rn and their daughter products[27]. Estimation of concentration of 222Rn and 220Rn. The 222Rn and 220Rn concentrations in the air were estimated by using a pin hole-cup dosimeter (Fig. 2). The gas enters through the bottom of the dosimeters in the lower chamber (222Rn + 220Rn chamber) and diffuses to upper chamber (222Rn chamber) through four pin holes (2 mm length and 1 mm diameter). LR- 115 detector films (3 × 3 cm2) have been installed in both chambers of the dosimeter. The dosimeters were deployed in the indoor environment for different seasons of a year. The concentrations and 220Rn {C220Rn(Bq m−3)} gases were estimated by using Eqs (1) and (2) 29
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