Measurement of naturally occurring radioactive materials, 238U and 232Th: anomalies in photopeak selection

Assessment of NORMs (238U, 232Th, 40K) and radiation hazard indices in Beldih apatite mine region of Purulia district, West Bengal, India

The radiation arising from naturally occurring radioactive materials (NORMs) is the foremost contributor to the collective dose received by the global population. The present study aims to measure the natural background radiation level and the associated gamma radiation dose in air in the Beldih apatite mine region of Purulia district, India. This study is primarily focused on the determination of 238U, 232Th and 40K activities in the sub-surface soil of the study area. The measurements were carried out using a High Purity Germanium (HPGe) detector-based gamma-ray spectrometer with a relative efficiency of 80%. To achieve uniformity in exposure estimations, radium equivalent activity has been calculated. Additionally, the internal hazard index, external hazard index, radioactivity level index and gamma dose rates have been evaluated to estimate the radiation hazard levels in the study area. The comparison of obtained concentrations and hazard indices with global data (UNSCEAR. (2008). Sources, effects and risks of ionizing radiation. United nations scientific committee on the effects of atomic radiation (report to the general assembly, with Annexes).) suggests that this region lies in a relatively high background radiation zone.

Radiogenic quality assessment of ground and riverine water samples collected from Indian Sundarbans

The present study attempts to generate the first baseline data on gross α and β activities in groundwater and riverine water samples collected from different regions of Indian Sundarbans, a part of the world's largest mangrove ecosystem. Until the present, no information is available related to radioactivity measurement in water samples from this vast area. Gross alpha-beta activities were measured by liquid scintillation counting-triple to double coincidence ratio (LSC-TDCR) technique. The minimum detectable activities in present experimental condition were found to be 21 mBq L^-1 and 55 mBq L^-1 for gross α and β respectively. Gross alpha activities in all groundwater and riverine samples were found to be below the detection limit (BDL), whereas gross beta activities in groundwater and riverine samples varied from BDL to 0.46 ± 0.24 Bq L^-1 and BDL to 0.90 ± 0.26 Bq L^-1 respectively, which are below WHO recommended value 1 Bq L^-1. Annual effective doses were below 0.1 mSv. U and Th concentrations in the water samples were determined by ultrasonic-nebulizer assisted Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and found to be BDL. For assessing ³H activity, double-distilled water samples were measured by LSC-TDCR technique, which provided BDL result.

The evaluation of the 1001.03 keV gamma emission absolute intensity using fundamental parameter method

The accurate evaluation of the absolute intensity of the gamma-ray transition 1001.03 keV of ^234mPa is crucial for accurate determination of ²³⁸U in nuclear material and environmental samples. Over the last decades, a wide range of 1001.03 keV absolute intensity values were published by different researchers and ranged from 0.59 to 1.12%. Nowadays, one of the most commonly used values is 0.847 ± 0.008% that seems not accurate and would eventually lead to an overestimation of ²³⁸U activity concentration. The absolute intensity of 1001.03 keV gamma transition was re-evaluated using different fundamental parameter method (FPM) modes, uranium ore and granite samples, samples' geometries, sample-to-detectors' geometries and gamma ray spectrometers. The mean ± standard deviation of newly optimized absolute intensity value is 1.067 ± 0.084% with an average relative bias of - 20% from the commonly used value.

The re-evaluation of the 234mPa's 1001.03 keV gamma emission absolute intensity for the precise assessment of 238U

In this study the commonly used f-value for the 1001.03 keV (0.835 ± 0.004%) energy transition of the ^234mPa was re-evaluated due to an obvious consistent overestimation of the ²³⁸U activity concentration. Different calibration protocols, samples' matrices and geometries, and gamma-ray spectrometers were exploited in order to assure the accuracy of the derived data. An average positive relative bias of about 24% from the currently used f-value was estimating leading to newly adopted f-value of 1.037 ± 0.052%. This newly suggested f-value will lead to an improvement in the accurate assessment process of the ²³⁸U using gamma-ray spectrometry in both environmental and nuclear safeguard fields.