Carbon-14 emission from the pressurized heavy water reactor nuclear power plant at Kaiga, India.

This is a detailed study on oxide (CO ₂ ) and reduced (hydrocarbons, C _n H _m ) forms of ¹⁴ C releases through gaseous effluents from the Kaiga nuclear power plant (NPP), on the West Coast of India, where 4 × 220 MW(e) pressurized heavy water reactors (PHWRs) are operating. The gaseous effluent from the common stack of reactor units 3 and 4 (each of 220 MW(e)) was sampled from 2017 to 2020 for ¹⁴ C activity monitoring and analysed for ¹⁴ C activity by liquid scintillation counting. The normalized release rate corresponding to the four-year monitoring period had a geometric mean value of 0.12 TBq GW(e) ^-1 a ^-1 (geometric standard deviation = 7.4), and the arithmetic mean with associated standard deviation was 0.75 ± 1.47 TBq GW(e) ^-1 a ^-1 . The relative percentage contribution of reduced form (CH ₄ ) of ¹⁴ C species was less than 1.27% of the total release. The normalized release rate from Kaiga NPP was similar to those reported for the other PHWR NPPs of the world. The ¹⁴ C specific activity in the ambient air in the vicinity of the NPP was monitored at four locations. The maximum excess ¹⁴ C activity values in the ambient air in the vicinity of the NPP, evaluated by comparing the specific activity recorded for the clean air region at ∼300 km from the NPP, were 65.1 Bq kg ^-1 C (28.76 pMC) and 222.4 Bq kg ^-1 C (98.23 pMC) for the years 2019 and 2020 respectively. In addition, the release rates were calculated from the Gaussian plume model using site-specific atmospheric dilution factors and the excess ¹⁴ C specific activity measured at four off-site monitoring stations. The calculated values of release rates were in agreement (within a factor of ∼3) with the measured values.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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