Vol.:(0123456789) 1 3 Journal of Radioanalytical and Nuclear Chemistry https://doi.org/10.1007/s10967-020-07118-4 Validation of a method for measurement of  14 C in air and its application for estimation of  14 C levels around Tarapur nuclear site A. Baburajan 1  · S. S. Dalvi 1  · V. Sudheendran 1  · V. K. Varakhedkar 1  · I. V. Saradhi 2  · P. M. Ravi 3  · N. Karunakara 3 Received: 29 October 2019 © Akadémiai Kiadó, Budapest, Hungary 2020 Abstract A method for the determination of 14 C in air was validated with 4 N NaOH solution as absorbent medium. The chemical yield of the whole analytical process of precipitation of BaCO 3 and re-absorption of released CO 2 on acidifcation was determined by 14 C spike experiments. A mean analytical recovery of 84.2% with a standard deviation of 7.21% was achieved. The propagated relative uncertainty of the method was 11.9%. The application of the method for routine monitoring around a nuclear facility was demonstrated through extensive air sampling in the vicinity of Tarapur Atomic Power Station, India. The 14 C specifc activity ranged between < 0.25 and 0.39 Bq g −1 C with a 5 year mean of 0.28 Bq g −1 C. Keywords 14 C · Validation · Specifc activity · Tarapur environment Introduction 14 C, a low energy beta emitter (E max : 156 keV) with a long half-life of 5730 year, is a cosmogenic radionuclide pro- duced in the atmosphere due to the interaction of cosmic neutrons with nitrogen atoms in the stratosphere and in the upper troposphere. The annual production rate of 14 C in the atmosphere is estimated to be 1.5 × 10 3 TBq [1], with total atmospheric inventory of 1.4 × 10 5 TBq [2]. In atmospheric air, 14 C is generally present as CO 2 with less than 1% in the form of carbon monoxide, methane formaldehyde and other molecules. During photosynthesis, 14 CO 2 is incorporated in the organic matter [3, 4], forming its carbon frame. In addi- tion to the natural production, 14 C is also produced during nuclear explosions and in diferent type of nuclear facili- ties. In nuclear reactors, 14 C is produced mainly via neutron capture reaction of 17 O, in CANDU reactors (PHWR) and boiling water reactors (BWRs) [5]. There are other ways of production of this radionuclide, such as, 14 C resulted from 14 N (n, p) 14 C and from 13 C (n, γ) 14 C reactions, but with lower percentage contribution. The annual production rate of 14 C in light water reactor (PWR and BWR) is between 0.7 and 1.1 TBq/GWe/y and that for CANDU type reac- tors (PHWR) it is 26 TBq/GWe/y [1]. Corresponding to this production rate, the average normalized release of 14 C to the environment is estimated as 1.6 TBq/GWe/y from CANDU reactor and 0.51 TBq/GWe/y from BWR reactor [1]. The emission rate of 14 C from the reprocessing of LWR fuel range from 0.46 to 0.64 TBq/GWe/y and that from heavy water reactor fuel reprocessing was also found to be of same order [6]. The Tarapur nuclear complex, situated 100 km north of Mumbai, India has twin units of pressurized heavy water reactors (Tarapur Atomic Power Station 3 and 4, 540 MWe each), and twin units of Boiling Water Reactors (Tarapur Atomic Power Station 1 and 2, 160 MWe each). In addi- tion, some research facilities are also operating in the site. Due to the release of 14 C from nuclear facilities, there is a possibility of increase in specifc activity of 14 C in the atmospheric air. The specifc activity of 14 C in ambient air near the reactor environment depends upon release through gaseous efuent, the atmospheric dilution factor and stable carbon content in the ambient air. In order to assess the impact of the nuclear facilities, regular monitoring of the * A. Baburajan babu_aramana@yahoo.co.in 1 Environmental Survey Laboratory, Environmental Monitoring and Assessment Division, BARC, TAPS Colony, TAPP (P.O.), 401504 Palghar (Dt.), Maharashtra, India 2 Environmental Monitoring and Assessment Division, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra 400 085, India 3 Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangotri, Mangalore, Karnataka 574199, India