K. S. Pradeepkumar

Study on enhanced atmospheric dispersion of 41Ar at the Trombay site

An extensive study has been carried out within the site of Bhabha Atomic Research Centre, Trombay, for examining the atmospheric dispersion of (41)Ar released from research reactors. The release rate, release height, meteorological parameters and geographical information were used to establish correlation between theoretical estimation using Gaussian plume dispersion model (GPDM) and dose/dose rate data obtained from Gammatracers (GTs). Ten monitoring locations were selected in five sectors and at different downwind distances from the release point. Analysis of dose rate data shows that the maximum dose rate (7.19 μSv h(-1)) and the total annual dose (1051 μSv) were observed at a downwind distance of 0.36 km. Average dose rates of all monitoring locations were varying from 0.03±0.02 to 0.12±0.07 μSv h(-1). The average dose rate increases at the monitoring locations placed at N to NE sectors during monsoon, and for monitoring locations placed at SW and SSE sectors during winter. The maximum dose rates, monthly and annual doses recorded by GT, have been compared with predicted values. Most of the locations show statistically significant coherence in the case of monthly dose.

Evaluation of uncertainties in lung measurement of actinides due to non-uniform distribution of activity in lungs

Various parameters can introduce uncertainties in the lung activity measurements of actinides. In this study, uncertainties due to non-uniform distribution of activity in the lungs are evaluated. To study the effect of non-uniform distribution, lungs of ICRP male thorax voxel and resized phantoms are divided into upper and lower parts of both right and left lungs as well as into anterior and posterior lung regions. Simulation of uniform and non-uniform distribution of activity in lungs is carried out using thorax voxel phantoms in FLUKA for Phoswich and an array of three HPGe detectors for 18-238keV photons. Source sampling for non-uniform distribution of activity is carried out by selecting the source points by varying the weightage to 0.4, 0.5, 0.6 and 1 in different parts of lungs. Uncertainties in lung activity estimation at different energies are quantified in the form of scattering factors (SFs) which are geometric standard deviations. The SFs due to non-uniform distribution of activity of the order of 0.4-0.6 in different parts of the lungs are found to be ~ 1.25 for Phoswich and HPGe array detectors above 18keV.

Development and performance evaluation of HPGe detector-based shadow shield bed whole body counter

An HPGe detector-based shadow shield bed whole body counter has been developed for internal contamination monitoring of radiation workers. The system is calibrated for the measurement of internally deposited radionuclides which emits photon energies >100 keV. Its performance characteristics are compared with NaI(Tl) detector-based whole body counter. It is observed that due to superior energy resolution of the HPGe-based system, identification and quantification of internally deposited radionuclides in workers is superior than NaI(Tl) detector-based system. The 40 K contents of 15 persons were measured using this system. It is found that the total body potassium varies from 0.82 gk kg −1 to 2.6 gk kg −1 of the body weight.

Concentration of 3H in ground water and estimation of committed effective dose due to ground water ingestion in some places in the Maharashtra state, India.

The measurement of tritium in environmental samples requires highest possible sensitivity. In the present study, the authors have optimised the counting window for the analysis of (3)H in environmental samples using the recently installed Ultra Low Level Quantulus 1220 Liquid Scintillation Counting at BARC to improve the detection limit of the system. The optimised counting window corresponding to the highest figure of merit of 883.8 was found to be 20-162 channels. Different brands of packaged drinking waters were analysed to select a blank that would define the system background. The minimum detectable activity (MDA) achieved was 1.5 Bq l(-1) for a total counting time of 500 min. The concentration of tritium in well and bore well water samples collected from the villages of Pune, villages located at 1.8 km from Tarapur Atomic Power Station, Kolhapur and Ratnagiri, was analysed. The activity concentration ranged from 0.55 to 3.66 Bq l(-1). The associated age-dependant dose from water ingestion in the study area was estimated. The effective committed dose recorded for different age classes is negligible compared with World Health Organization and US Environmental Protection Agency dose guidelines.

Application of simulated standard spectra for the analysis of complex sample spectra from NaI(Tl) detectors

The most accurate method for the analysis of complex gamma ray spectra from scintillation detectors is least squares method. The major requirement of this method is individual standard spectra of all nuclides expected in the complex spectrum which is not possible and feasible for some nuclides. In the present work, an approach of using simulated standard spectrum of the radionuclides for the least squares analysis is studied. The paper describes the methodology used for the generation of simulated spectrum which is the main objective, and validation of results using standard sources in the Sodium Iodide (NaI(Tl)) based gamma ray spectrometer.

Experience during the monitoring of inactive scrap for the detection of inadvertent presence of radioactivity

Context: The paper describes about the experience gained during the radiation monitoring of inactive scrap generated at various nuclear facilities. This type surveillance is carried out to prevent the spread of radioactivity in public domain and also as requirement by regulatory authorities. Aim: The inspection and certification of scrap material from Nuclear facilities is a regulatory requirement to ensure that no radioactive material reaches public domain. This paper describes the methodology and experience in detection of radioactivity at inactive Scrap monitoring facility. Materials and Methods: Inactive scraps (metallic and non metallic) generated from various nuclear facilities of BARC, Trombay is dispatched to Trombay Village Store (TVS) for temporary storage before auction to the public. The monitoring at the facility includes visual inspection and radiation measurement before loading the scrap in the truck. An online PC based monitoring system and portable monitoring instruments in the range (nSv/h-μSv/h) are used to carry out radiation monitoring of inactive scrap loaded in a vehicle. Results: Radioactive source of high activity with potential for serious environmental hazard has not been detected, but few cases of presence of radioactive /contaminated material (MS plate/equipments with low level of Cs-137 contamination) have been detected and identified using portable gamma spectrometer. Conclusion: Implementation of strict regulatory measures and radiation monitoring at nuclear facilities can minimize the probability of radioactive material reaching the public domain. The methodology followed for monitoring of inactive scrap is found to be effective even for detection of presence of radioactivity in scrap if any.