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]

Carbon content (%) measurement for determination of 14C specific activity (Bq kg−1C) in environmental matrices based on thermal oxidation of the sample using pyrolyser is discussed. The carbon content in biota samples (N = 574) of the tropical region were in the range 30–45%, 28–47%, 31–46%, 32–45%, 43–49%, and 37–50% with corresponding mean values of 38 ± 3.1%, 38 ± 4.4%, 41 ± 3.1%, 41 ± 3.7%, 46 ± 1.5%, and 44 ± 5.1% respectively for wild plant leaves, vegetables, fruits, cereals, wood, and fish samples. The present study shows that carbon content within the species and category (fruit, leaves, vegetables, etc.) of the sample may differ up to ~ 20% points. [ABSTRACT FROM AUTHOR]

A method for the determination of 14 C activity in the ambient air was optimised with the development of a simple setup for the regeneration of CO 2 from carbonate sample and saturating the absorber in <45 min for direct determination of activity by liquid scintillation counting (LSC). Atmospheric CO 2 was trapped in NaOH solution and precipitated as BaCO 3 by adding BaCl 2 . The carbonate sample was taken in a newly designed regeneration system, subjected to acid hydrolysis, and the absorber (CarboSorb-E) was saturated with the CO 2 regenerated from carbonate sample. This allowed optimisation of CO 2 absorption by the absorber (up to ~ 2.3941 g of CO 2 /10 mL with an average of 2.1688 g) and a minimum detectable activity value of 14 Bq kg -1 C for a counting time of 300 min (8 Bq kg -1 C for 1000 min) was achieved with Quantulus - 1220 LSC system. The necessity of (i) the measurement of the total volume of air sampled, (ii) the determination of trapping efficiency for CO 2 in the NaOH, recovery of 14 C in chemical processing of BaCO 3 , and subsequent regeneration and absorption processes, and (iii) independent determination of carbon content in the air for expressing the results in terms of 14 C specific activity (Bq kg -1 C), are avoided in this method. The method is capable of yielding accurate results, in a considerably shorter time when compared to previously reported methods, with a deviation of <2.2% from the target value (with a relative standard deviation of 1.1%, and a relative error of 0.53%) when ambient air samples from clean air region (region not affected by local anthropogenic sources of 14 C) are analysed. Validation of the method was performed by (i) analysing BaCO 3 sample derived from ambient air by accelerator mass spectrometry, and (ii) analysing the CO 2 produced from the combustion of IAEA C3 reference material. Upon validation, the suitability of the method for determining small excess 14 C specific activity in the vicinity of a nuclear power plant was demonstrated., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Tritium in the form of tritiated water is easily incorporated into terrestrial biota as tissue free water tritium (TFWT). A part of TFWT is converted into organically bound tritium (OBT) through metabolic processes. For the computation of NE-OBT activity (expressed as Bq L -1 of combustion water) in terrestrial plants, knowledge on 'water equivalent factor (WEQ p )', defined as the volume of water produced from the combustion of 1 kg of the dry sample, is essential. On a global scenario, experimental data are not available on this parameter. This paper presents (i) a method for determination of WEQ p by combustion method using a tube furnace system, (ii) a large database (N = 294) on WEQ p parameter for samples of tropical monsoonal climate region of the Indian subcontinent, and (iii) NE-OBT activity in terrestrial biota samples (N = 186) collected from the vicinity of a PHWR nuclear power plant of India. The data generated in this study on WEQ p serves for the validation of the data compiled in IAEA (2009 and 2010), which are estimated based on the hydrogen content of protein, fat and carbohydrates, and the fractions of protein, fat and carbohydrates. The WEQ p varied in the ranges of 0.492-0.678 L kg -1 (GM = 0.569 Bq L -1 , GSD = 1.06), 0.520-0.630 L kg -1 (GM = 0.557 Bq L -1 , GSD = 1.02) 0.473-0.633 L kg -1 (GM = 0.562 Bq L -1 , GSD = 1.02) for non-leafy vegetables, leafy vegetables, and fruits, respectively. A comparison between the experimental WEQ p data with those compiled in the IAEA report revealed that the maximum deviation between the two data sets is <10%. The NE-OBT activity in the food samples collected from 2.3 to 20 km zone around NPP had a geometric mean (GM) value of 25.4 Bq L -1 (GSD = 1.6, N = 186). Variations in NE-OBT activity with different seasons of the year are discussed., (Copyright © 2020 Elsevier Ltd. All rights reserved.)