Search

A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human–machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m−3 up to about 36 kBq m−3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h−1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h−1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement. [ABSTRACT FROM AUTHOR]

Tritium concentration was monitored in different water sources collected around Kaiga Nuclear Power plant, India. The concentration was in the ranges < 1.9–27.4 Bq L−1 (GM = 4.0 Bq L−1) for groundwater, < 1.9–42.1 Bq L−1 (GM = 3.5 Bq L−1) for surface water and in 12.4–42.0 Bq L−1 (GM = 24.07 Bq L−1) for reservoir water. The concentration values observed in this study are similar to those reported for other PHWR stations of the world. The radiation dose to the public due to ingestion of Tritium through groundwater was computed to be 0.08 μSvy−1. [ABSTRACT FROM AUTHOR]

This is a detailed study on oxide (CO 2) and reduced (hydrocarbons, C n H m) forms of 14C 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 14C activity monitoring and analysed for 14C 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 14C 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 14C specific activity in the ambient air in the vicinity of the NPP was monitored at four locations. The maximum excess 14C 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−1C (28.76 pMC) and 222.4 Bq kg−1C (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 14C 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. • 14C release in oxide and reduced forms from Kaiga PHWR NPP, India were quantified. • Mean value of the normalized release rate was 1.08 ± 1.80 TBq GW(e)−1 a−1. • 14C release in reduced form was <1.27% of the total release. • Maximum excess 14C activity in ambient air in the vicinity of the NPP was 222 Bq kg−1C 97 pMC (980.7‰). [ABSTRACT FROM AUTHOR]