The present research work was aimed to study the ambient radiation environment of the most popular sea-beaches of Bangladesh. The average activity concentrations of radioactive elements such as ²³² Th, ²³⁸ U and ⁴⁰ K of beach sand samples were measured by gamma-ray spectrometry using an HPGe detector and found to be higher than the internationally accepted values. The absorbed γ dose rate levels of the study areas are similar to other monazite sand-bearing high background radiation areas (HBRAs) of southern and southwestern coastal regions of India and of the world. The estimated values of the radiological parameters of the present study areas were also higher than the internationally accepted values. Hence, Cox's bazaar, Kuakata and Potenga sea-beach regions can be considered as HBRAs and potential zones for monazite like radioactive sand.

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After delivering X-ray beam of 15 MV energy, measurable radiation level near the treatment head of medical electron linear accelerator (LINAC) and in its surrounding is observed due to induced activity generated in target, flattening filter, monitor chamber, cooling tube, collimating jaws, etc., The radiation generated in the head of LINAC has the potential of exposing the radiotherapy staff/personnel (technologists) if he/she comes in close proximity of the machine head immediately after delivering the planned treatment. A systematic study was carried out to quantify the radiation levels near LINAC head, isocenter and 0.5 m lateral to isocenter for planned beam delivery of 50, 100, 200, 300, 400, 500 and 1000 MU (Monitor Units) for field sizes 5 cm × 5 cm, 10 cm × 10 cm, 20 cm × 20 cm, 30 cm × 30 cm and 40 cm × 40 cm. The measured maximum radiation level near LINAC head, isocenter and 0.5 m lateral to isocenter after 1 min of completion of treatment was about 10 μSv/h when the accelerator was operated for < 500 MU. However, the radiation levels at these locations after 1 min of completion of treatment were found to be > 10 μSv/h when the accelerator was operated for 800-1000 MU. It was also observed that the radiation level due to induced activity increases with increasing field size and number of monitor units and shows saturation characteristics when the field size approaches to 30 cm × 30 cm. This study indicates that the radiation dose received by the radiotherapy technologists while standing below the treatment head of the LINAC is significant even after 1 min of completion of the dose delivery when the accelerator is operated for higher number of monitor units (e.g., 1000 MU) in high energy photon mode.

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The European Radiation Dosimetry Group (EURADOS) has set-up a worldwide unique program of self-sustainable international intercomparisons for individual monitoring services (IMS). Starting in 2008, with three intercomparisons for whole body photon dosimeters every 2 ^nd year, one intercomparison in 2009 for photon and beta extremity dosimeters and in 2012, an intercomparison for neutron whole body dosimeters, the intercomparisons became fundamental for the harmonization of radiation protection and individual monitoring in Europe. With the intercomparison results, the participants can show compliance within their quality management system, compare their results with those from other participants and develop plans for improvement of their system. The costs of the exercises are covered by the participant's fees. For the whole body photon intercomparisons a the number of participating systems increased from 62 in 2008 to 88 in 2012, showing the big demand for such exercises. Some of the system types like film dosimeters showed decreasing deviations of their results in the general and subsequently increased their quality in the dosimetric performance. The calibration of the systems showed to be an important factor for the performance of all system types. The intercomparison for extremity dosimeters for photon and beta radiation revealed large deviations for quite a few of the participating systems. The intercomparison actions are planned to be continued on a regular basis; the next whole body photon intercomparison is scheduled for 2014. International intercomparisons for IMS for external radiation will bring in improvement and harmonization in individual monitoring.

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Smooth, bubble free yellow colored thick radiochromic films could be prepared by solvent casted method. The film emulsion contains gelatin, diacetylene microcrystalline particles and yellow dye. Self-standing films of 70 ± 10 micron thickness were obtained that show a distinct visual change in color from yellow to dark green on exposure to 1.25 MeV ⁶⁰ Co gamma-radiation, with intermediate shades of both the colors in the dose range between 25 cGy and 400 cGy. Optical characterization of the prepared film before and after exposure shows a change in the spectral characteristics from 10 cGy onwards.

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A Compton suppression gamma spectrometry system has been commissioned at Environmental Survey Laboratory and the results of performance evaluation are presented in the paper. The Compton suppression system is used to reduce the contribution of scattered gamma rays in the gamma spectrum that originate within the HPGe detector by an assembly of NaI (Tl) guard detectors surrounding the HPGe detector. The HPGe and NaI (Tl) are operated in anticoincidence mode to filter the Compton gamma rays emitting from the HPGe and subsequently resulting in the reduction of Compton continuum. The system was evaluated for various parameters such as energy calibration and efficiency calibration, resolution and Peak to Compton ratio (P/C). The Peak to Compton ratio with point sources of ¹³⁷ Cs and ⁶⁰ Co was found to be 1085:1 and 392:1 in Compton suppression mode compared to the normal mode operation of 142:1 and 66:1, respectively. The Minimum Detectable Activity of the system for various nuclides in Compton suppression mode as well as in normal mode of operations are also evaluated and discussed in the paper. The usability of suppression mode of counting for gamma emitters of cascade emissions is also discussed.

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Radioiodine ( ¹³¹ I) is one of the radionuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. If released to the environment during an accident, ¹³¹ I may enter the grass→cow→cow milk pathway, leading to increased thyroid dose to those consuming milk, especially infants and children. The estimation of site-specific grass to milk transfer coefficient (F _m ) for iodine is essential for an accurate assessment of the radiological hazard to the population in the region surrounding a nuclear power plant. In this study, a method based on the chemical separation of iodine present in grass and cow milk, and subsequent neutron activation analysis (NAA) has been optimized for the determination of stable iodine concentration in grass and cow milk. The method involves preconcentration of iodine from the sample matrix, and determination of iodine by NAA. The detection limit of stable iodine in milk was found to be 1 ng/mL. For the validation of the result, iodine concentration in NIST reference materials was determined simultaneously. The present study has yielded a F _m value of 5.6 × 10⁻³ d/L for dairy farm cows and 6.3 × 10⁻³ d/L for local breed cows under equilibrium conditions. These results are similar to the values given in International Atomic Energy Agency report (TRS-472). To simulate a rapid deposition of iodine on grass and for the estimation of F _m value for an emergency situation, grass grown in the experimental field was sprayed with stable potassium iodide solution and fed to the adopted cows, and the milk samples were collected regularly and analyzed. The F _m value for the simulated accidental situation was found to be 3.9 × 10⁻³ d/L.

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It is common practice to use phosphate fertilizers in the soil to raise crop yield. Natural Radionuclides present in fertilizers are sources of external and internal radiation exposure. External radiation exposure is caused by gamma radiation originating from radionuclides in situ. Internal radiation exposure, mainly affecting the respiratory tract, is due to short-lived daughter products of radon which are exhaled from fertilizers. This paper describes the results of gamma spectrometric measurement of the concentration of the natural radionuclides namely ²²⁶ Ra, thorium-232 and potassium-40 in the soil samples from the fields using phosphate fertilizers. The radon concentration and exhalation rate have also been discussed. The values of outdoor annual effective dose are found to vary from 0.07 to 0.09 mSv/year in soil samples containing fertilizers, whereas the outdoor annual effective dose is 0.06 mSv/year in barren soil samples.

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Residents of high background radiation areas of Ramsar have lived in these areas for many generations and received radiation doses much higher than the dose limit recommended by ICRP for radiation workers. The radioactivity of the high background radiation areas of Ramsar is reported to be due to ²²⁶ Ra and its decay products, which have been brought to the surface by the waters of hot springs. Over the past years the department has focused on different aspects of the health effects of the elevated levels of natural radiation in Ramsar. This study was aimed to perform a preliminary investigation on the bioeffects of exposure to elevated levels of natural radiation on the microbiology of surface water samples. Water samples were collected from surface water streams in Talesh Mahalleh district, Ramsar as well as a nearby area with normal levels of background radiation. Only two strains of bacteria, that is, Providencia stuartii and Shimwellia blattae, could be isolated from the water samples collected from high background radiation areas, while seven strains (Escherichia coli, Enterobacter asburiae, Klebsiella pneumoniae, Shigella dysenteriae, Buttiauxella agerstis, Tatumella punctuata and Raoultella ornithinolytica) were isolated from the water samples collected from normal background radiation areas. All the bacteria isolated from water samples of high and normal background radiation areas were sensitive to ultraviolet radiation, heat, betadine, alcohol, and deconex. Although other investigators have reported that bacteria isolated from hot springs show radioresistance, the results reported here do not reveal any adaptive response.

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An attempt has been made in the present work to estimate the neutron spectrum of a standard ²⁴¹ Am-B source using CR-39 solid polymeric track detector and an in-house image analysis program autoTRAK_n. The program works on the principle of greyscale variations in and around the recoil tracks and calculates the track parameters such as diameter, major, minor axes and estimates three dimensional parameters like recoil track depth and angular incidence. It is also capable of counting overlapping tracks without any segregation procedure. In the present study, the standard ²⁴¹ Am-B neutron spectrum generated from the recoil track parameters with the autoTRAK_n program is compared with the reported values measured using the time of flight method and found to be matching well, mainly at the characteristic peak. The total neutron fluence and dose equivalents are also determined with the program and are compared with the standard source measurements. The results obtained from autoTRAK_n are found to be in close agreement with the standard measurements with less than 5% error for both the parameters. Hence, this methodology can be used as a backup technique for neutron spectrum measurements along with other techniques considering its low cost, small size, easy irradiation, and processing.

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The neutron and gamma dose rate measurements were essential around the storage container of PuO ₂ for operational radiation protection purpose. In the present study, various types of active dose rate meters and passive dosimeters were used for the measurement of neutron and gamma dose rates in addition to the theoretical calculations. The neutron and gamma dose rate on the surface of PuO ₂ container varied from 0.42 mSv/h to 0.71 mSv/h and from 1.83 mSv/h to 2.15 mSv/h respectively which decreased with increasing distance from the surface of the container. The neutron dose rates calculated theoretically did not match with that of experimental values at shorter distances, however, at larger distance such as 20 and 50 cm the agreement between theoretical and experimental values were reasonably good. The observations also suggested that the neutrons emitted from PuO ₂ were mostly above the thermal neutron energy. The theoretical value of gamma dose rate on the surface and at distances from the bird cage matches very well with the measured values. The gamma dose rates are quite higher than the neutron dose rates for PuO ₂ container.

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Ensuring integrity of nuclear fuel clad is most important from radiation safety point of view. The paper provides introduction to experimental and theoretical methods for evaluation of rewetting velocity. Quality Assurance (QA) checks on Emergency Core Cooling System (ECCS) in Nuclear Reactors are very important to ensure accurate coolant flow introduction and minimum radiation hazard during Loss of Coolant Accident (LOCA). In-depth knowledge of acceptable rate of temperature rise of fuel subsequent to LOCA and having fully reliable method to ensure that the same will not exceed the set limit is testimony of safe reactor operation. Spread of radioactive contamination and resultant radiation exposure from above contamination in nuclear reactors depends heavily on size and shape of split or rupture in clad. [10] Suggests that a plant operating with 0.125 percent pin-hole in fuel-clad defects showed in general, upto five-fold increase in contamination level and resultant whole-body radiation exposure rates in some areas of the plant when compared to a sister plant with high-integrity fuel. The checks on ECCS will protect environment and public from radiation exposure to remarkable extent.

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