The radiological impact of the presence of radon, thoron and their progeny in the environment of a liquid petroleum gas bottling plant

Abstract

The seasonal variation of the activity of radon, thoron and their progeny has been measured, and the annual exposure, lifetime fatality risk and annual effective dose to the workers in a Liquid Petroleum Gas (LPG) bottling plant due to exposure from a mixed field of radon and thoron have been calculated over the four seasons of the year. The measurements were carried out using a passive time-integrated track etch technique employing LR-115 (type II) Solid State Nuclear Track Detectors (SSNTDs) in plastic twin-chamber dosimeter cups. The average value of the radon activity varied from 17.78 Bq/m³ to 49.01 Bq/m³ in different seasons. The minimum value of the radon activity was found to be 7.78 Bq/m³ in summer (April to July), whereas the maximum value was found to be 59.01 Bq/m³ in winter (October to January). The average value of the thoron activity varied from 8.16 Bq/m³ to 33.74 Bq/m³ in different seasons. The minimum value of the thoron activity was found to be 1.16 Bq/m³ in summer (April to July), whereas the maximum value was found to be 65.08 Bq/m³ in winter (October to January). The average value of the Potential Alpha Energy Concentration (PAEC) due to radon varied from 1.92 mWL to 5.30 mWL in different seasons. The minimum value of the PAEC due to radon was found to be 0.84 mWL in summer (April to July), whereas the maximum value was found to be 6.38 mWL in winter (October to January). The average value of the PAEC due to thoron varied from 0.22 mWL to 0.91 mWL in different seasons. The minimum value of the PAEC due to thoron was found to be 0.03 mWL in summer (April to July), whereas the maximum value was found to be 1.76 mWL in winter (October to January). The annual exposure due to radon and thoron daughters, collectively, varied from 0.105 WLM to 0.218 WLM with an average value of 0.168 WLM. The lifetime fatality risk varied from 0.31 × 10−4 to 0.65 × 10−4 with an average value of 0.50 × 10−4. The annual effective dose from radon and thoron (PAEC) varied from 0.40 mSv to 0.84 mSv with an average value of 0.64 mSv. The findings suggest that the bottling plants may affect doses from external irradiation, and the inhalation of radon decay products is significant from the health point of view.