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Tarapur Atomic Power Station-3 is 540 MWe pressurized heavy water reactor in India, it achieved first criticality on May 5, 2006 and then operated at full power. The control of dose rates and collective dose of radiation worker is most important for the best performance of reactor. This article discusses the sudden rise in radiation levels on primary heat transport (PHT) pipelines and equipment. The radionuclide contributed to high radiation levels was Ag-110 m. Finding obtained during the route cause analysis used for the station operation and removal of Ag-110 m from PHT system using special type of resin (macroporous). The purification of the system using special type of resin has been enhanced. Ag-110 m activity in the PHT fluid has been controlled. PHT pipelines and equipment shielded for exposure control. The postirradiation examination of steam generator (SG) manhole gasket showed the presence of sulfur. The PHT fluid sample analysis revealed the presence of oil content in PHT fluid which was ingressed from buffer tank and FT D2O tank in PHT system. Oil containing sulfur was responsible for erosion of silver from SG manhole gasket in the form of silver sulfide and its ultimate transport to reactor core and neutron activation of silver.

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Measurement of natural radioactivity concentration in sand samples collected from the coastal belt of Kerala has been carried out using NaI(Tl) detector, and the radiological parameters were evaluated from the measured activities. It is well reported that in certain situation, the natural radioactivity in the environmental matrices can reach reference levels or beyond. Hence, the study has been performed to understand the distribution and enrichment of natural radionuclides in the coastal environment of Kerala, and thereby assessing dose to the inhabitants. The mean activity concentration of naturally occurring radionuclides, namely ⁴⁰K, ²²⁶Ra, and ²³²Th in the samples were 53.2, 7.0, and 101.3 Bq/kg, respectively. The radiological parameters, namely absorbed dose rate, the radium equivalent activity (Ra_eq), the annual effective dose (indoor and outdoor), and reference indices were evaluated and compared to the recommended safety limits. The present investigation indicates that the data are comparable with the reported values elsewhere and in most of the cases observed values were well within the permissible limit.

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This study was conducted to assess some important performance characteristics of the optically stimulated luminescence dosimetry system of the national individual monitoring service in Gabon, namely, reader performance tests, dose algorithm, and signal depletion. The reader performance tests demonstrated that the reader photomultiplier tube is performing self-consistently and that there is no abnormality in the counting system. Concerning the dose algorithm, it was shown that the proposed dose algorithm provides a good estimate of the dose compared with the system dose algorithm, which is not known. From the signal depletion study, the depletion rate per reading of 0.4 ± 0.09% (strong stimulation beam) was determined for field dosimeters. Depletion rates per reading of 0.3 ± 0.03% (strong beam) and 0.020 ± 0.001% (weak beam) were also determined for calibration dosimeters. All these values are comparable to those determined in other studies.

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Highly sensitive cerium-doped K₂SO₄phosphor was synthesized for optically stimulated luminescence (OSL) properties. The present study mainly investigated various kinetic parameters and correlation between the thermoluminescence and OSL (TL-OSL) processes. Continuous wave-OSL sensitivity of the phosphor is four times more than that of Al₂O₃:C (Landauer). The phosphor exhibits good TL-OSL correlation. Most of the charge carriers in K₂SO₄:Ce get depleted using optical stimulation which confirms their participation in TL as well as OSL processes. Optical bleaching also affects the order of kinetics for TL. The glow curve of K₂SO₄:Ce without illumination exactly fits with two components, whereas it is fitted with three components when optically bleached for 60 s. Bleaching also shifted the glow peaks toward higher temperature side indicating non- first-order kinetics.

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Accurate estimation of radioactivity content of various samples and effluents is essential in all stages of operation at a nuclear facility. Generally, two separate systems are used for estimation of α and gross β activity. A single counting setup with a detector probe consisting of a combination of ZnS (Ag) and plastic scintillator detectors can be applied for this purpose. This paper describes design, development, and characterization of a combination detector system for simultaneous assessment of α and β/γ radioactivity content of an electrodeposited or planchetted sample or that of a filter paper. Pulse height discrimination technique has been utilized to distinguish between α and β radiations. The β activity counts had been observed to contribute <0.7% in α activity. Counts from α activity are added up in β channel counts, and it was observed that for ²³⁹Pu source, it is about 2.5 times. Efficiency of the system for β sources was found to have varied from about 14% (¹³⁷Cs) to 23% (⁹⁰Sr/⁹⁰Y). The efficiency for ²³⁸Pu α source was found to be 13.4%.

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To ensure the reliability of the performance of the optically stimulated luminescence (OSL) dosimetry system used for individual monitoring of occupationally exposed workers in Gabon, some key performance indicators were evaluated. The performance indicators assessed included: measurement uncertainty, linearity, coefficient of variation, and photon energy and angular dependence. The results for uncertainty assessment were in very good agreement with the International Commission on Radiological Protection (ICRP) and International Atomic Energy Agency (IAEA) requirements for overall accuracy. The maximum relative overall uncertainty in absolute value in the region of the recording level was 45%. In the region beyond the recording level, the maximum relative overall uncertainty was 42% (in absolute value). The results for linearity assessment met the requirement for linearity of International Electrotechnical Commission (IEC) 62387 standard. The results for coefficient of variation assessment were within the relevant requirement of IEC 62387 for doses beyond the recording level. The results obtained for photon energy and angle of incidence were in good agreement with the IAEA and IEC 62387 corresponding requirements. The OSL dosimetry system can be relied on to provide acceptable monitoring data for the individual monitoring service in Gabon.

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Natural pollution level due to terrestrial gamma radiation was measured at about seventy different sites in and around the Loktak Lake of Manipur, India, using NaI (Tl) scintillator-based Micro-R-survey meter, and high purity germanium detector. The observed annual effective dose in this study area ranges from 0.3 to 1.2 mSvy⁻¹ with an average value of 0.7 ± 0.1 mSvy⁻¹, which is higher than world average value of about 0.4 mSy⁻¹ reported by the UNSCEAR 2000. The soil analysis for ²²⁶Ra, ²³²Th, and ⁴⁰K of this area gives an average concentration of 74.6 (38.9-126.0) Bq/kg, 112.1 (30.2–224.3) Bq/kg, and 792.9 (287.4–1194.8) Bq/kg, respectively.

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The South-west coast of Kerala is a well-reported high background radiation area. Hence, the radiological protection of the population in this region has great concern. In view of this, the study has been undertaken to understand the distribution of radon (²²²Rn) concentration in drinking water collected from the region. The seasonal variation of radon concentration in drinking water also forms part of the study. Emanometry method is used for the quantification of dissolved radon concentration in water collected from various open wells. The mean values of radon concentration obtained for pre- and post-monsoon were 0.95 Bq/l and 0.58 Bq/l, respectively. The whole-body dose ranges from 0.39 to 29.34 μSv/y for premonsoon and 1.33–18.76 μSv/y for postmonsoon. The average value of effective dose was below the recommended limit of 0.1 mSv/y suggested by WHO and EU council, and the water from the region can be safely consumed from the radiological protection point. All the results are presented and discussed in the manuscript.

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