Environmental Gamma Research Articles

Environmental radiation detected at Lin Shin hospital in Taichung during the Fukushima nuclear power plant accident

This work is the first evaluation of environmental gamma exposure rates by the Nuclear Medicine Department at Lin Shin Hospital (LSH) in Taichung with Thermoluminescent dosimeter (TLD-100H) during the Fukushima Nuclear Power Plant (FNPP) accident. After the 9.0 MW strong earthquake hit northern Japan on March 11, 2011, a TLD-100H was used to monitor environmental kerma rate at Taichung (2,500 km away from northern Japan) from Mar-08 to Apr-09, 2011 and evaluated kerma rate due to global fallout of the sever FNPP accidents. Exposure rates varied widely among positions close to the PET/CT facility. Observed kerma rates of up to 4.12 ± 0.62 mSv mo−1 indicated an explicit, heavy leakage of photon through the PET/CT facility. No significant contributions were detected at Taichung, Taiwan. Hence, the health effect cause by the “extra radiation” from FNPP accidents is negligible. As this was a rare case of environmental monitoring during a nuclear power plant accident, its findings are of considerable significance.

Outdoor radioactivity and health risks in Balikesir, northwestern Turkey

External irradiation from radionuclides naturally present in the environment or released from man-made practices or events is usually an important component of the exposure of human populations. These exposures derive primarily from gamma radiation arising from the decay of these radionuclides at locations outside the human body. The main objective of this study is to evaluate the radioactivity levels and health risks due to terrestrial radionuclides in the soil of Balikesir, one of the largest cities of the country, northwestern Turkey. For this purpose, activity concentrations of radionuclides in soil and outdoor gamma dose rates (terrestrial and cosmic) have been investigated in the city of Balikesir. In addition, maps for the radionuclide activity concentrations of soil and the outdoor gamma dose rate distributions have been plotted for the region. The average activities of radionuclides, (238)U, (232)Th, (40)K, (235)U and (137)Cs in the soil were determined to be 37.6 ± 10.8, 54.7 ± 15.1, 674.5 ± 203.2, 3.6 ± 1.6, 3.4 ± 2.2 Bq kg(-1), respectively, in the region. The average outdoor gamma dose rates due to terrestrial and cosmic radiations were found to be 78.5 ± 12.4 and 48.9 ± 5.8 nGy h(-1) with the total of 127.4 ± 18.9 nGy h(-1) in the region. Annual effective dose due to environmental outdoor gamma radiation exposures was determined to be 156.3 nSv. The mean estimated cancer risk values were found to be 0.063 × 10(-2) for the region using risk factors of ICRP 103. The results of the study were discussed with the studies done in other cities of Turkey and the worldwide averages.

Dating mortar by optically stimulated luminescence: A feasibility study

Quartz is the datable component in mortar. Although its luminescence properties are very well studied, the problem of mortar dating arises from a low level of optical bleaching. In order to reduce the time consuming efforts for dating lime mortar in monuments by optically stimulated luminescence, we investigated the most suitable methods of dose and dose rate determination, and we explored tests which are suitable to predict the datability of a given material. Reverting to the large number of publications on sedimentary partially bleached quartz we found linear modulation techniques especially useful, equally we also recommend the determination of the level of optical depletion before starting analyses. Single grain analysis is regarded as an ultimate but infallible tool to date very poorly bleached quartz from mortar. Dose rate measurements need to take into account the radioactive equilibrium of the uranium decay and the short range inhomogeneity of the environmental gamma radiation field: gamma spectrometry and on-site TLD measurements are best suited.

Evaluating emergency response models of radiological dispersion in complex terrain

Operational airborne releases of trace quantities of the radioactive noble gas 41Ar from the HIFAR Nuclear Research Reactor located in Sydney, Australia, are valuable for evaluating emergency response models incorporating radiological dispersion. A network of meteorological stations and GR-150 environmental gamma dose detectors are placed in the complex terrain within a 5 km radius of the site. Predictions from the model combination LSMC/RIMPUFF are evaluated using 15 min 41Ar peak observations from the detector network during 2002–2003 under a range of atmospheric stability conditions. Statistical analyses are carried out to compare the results against previous evaluations.

Environmental gamma dosimetry with OSL of -Al2O3:C for in situ sediment measurements

The physical properties of alpha-Al(2)O(3):C are very similar to that of quartz, which make it an attractive dosimetric material for geological and archaeological dating applications. Storage experiments in an ultra-low-radiation underground environment (UDO at PTB) and gamma-ray spectrometry show that the optically stimulated luminescence (OSL) signal of this material does neither suffer from a significant inherent background caused by traces of radionuclides (<6 microGy a(-1)) nor from fading. After having performed a simple calibration procedure, gamma dosimetry based on alpha-Al(2)O(3):C detectors, which were exposed in a brick block and a lead castle for different periods of time, provided concordant results with dose values derived from independent gamma-ray spectrometric measurements using high-purity germanium and NaI:Tl detectors. These investigations indirectly confirm both the absence of a significant inherent background and fading of the detector material. Small doses of a few micro gray accumulated in short exposure times to environmental radiation can be accurately measured, even when doses (i.e. transport dose) much larger than the actual environmental dose have to be subtracted. It is shown that the OSL signal caused by small transport doses can be easily and reproducibly reset even under difficult field conditions by illuminating the dosemeters with the blue light from Luxeon LEDs. Summarised, alpha-Al(2)O(3):C appears to be the material of choice for dosimetric dating applications of quartz or related materials, when analysed by using OSL.

Assessment of the environmental outdoor gamma radiation levels in Sao Paulo City

Dose values from natural radiation sources in several sites of Sao Paulo City were assessed from environmental outdoor gamma radiation levels, by using CaSO4:Dy thermoluminescent dosimeters. Twelve monitoring stations were placed in different regions of the town including both urban and outskirts areas and the measurements were carried out quarterly and seasonally. The average annual effective dose, calculated according to the ICRP-60 procedures, was 1.23 ± 0.19 mSv.y−1. The result is of the same order of magnitude as the average annual background effective dose of 1.00 ± 0.18 mSv.y−1 obtained from a ten years follow-up of the IPEN – CNEN/SP Environmental Monitoring Programme. This environmental outdoor average annual effective dose is slightly higher than the UNSCEAR 2000 value of 0.9 mSv.y−1, estimated as the world average contribution from terrestrial and cosmic gamma rays.

Variation of radon concentrations in soil and groundwater and its correlation with radon exhalation rate from soil in Budhakedar, Garhwal Himalaya

Radon was measured in soil-gas and groundwater in the Budhakedar area of Tehri Garhwal, India in summer and winter to obtain the seasonal variation and its correlation with radon exhalation rate. The environmental surface gamma dose rate was also measured in the same area. The radon exhalation rate in the soil sample collected from different geological unit of Budhakedar area was measured using plastic track detector (LR-115 type II) technique. The variation in the radon concentration in soil-gas was found to vary from 1098 to 31,776 Bq.m−3 with an average of 7456 Bq.m−3 in summer season and 3501 to 42883 Bq.m−3 with an average of 17148 Bq.m−3 in winter season. In groundwater, it was found to vary from 8 to 3047 Bq.l−1 with an average value 510 Bq.l−1 in summer and 26 to 2311 Bq.l−1 with an average value 433 Bq.L−1 in winter. Surface gamma dose rate in the study area varied from 32.4 to 83.6 μR.h−1 with an overall mean of 58.7 μ-R.h−1 in summer and 34.6 to 79.3 μR.h−1 with an average value 58.2 μR.h−1 in winter. Radon exhalation rate from collected soil samples was found to vary from 0.1 × 10−5 to 5.7 × 10−5 Bq.kg−1.h−1 with an average of 1.5 × 10−5 Bq.kg−1.h−1 in summer season and 1.7 × 10−5 to 9.6 × 10−5 Bq.kg−1.h−1 with an average of 5.5 × 10−5 Bq.kg−1.h−1. A weak negative correlation was observed between radon exhalation rate from soil and radon concentration in the soil. Radon exhalation rate from the soil was also not found to be correlated with the gamma dose rate, while it shows a positive correlation with radon concentration in water in summer season. Inter-correlations among various parameters are discussed in detail.

Increased environmental gamma-ray dose rate during precipitation: a strong correlation with contributing air mass

It has long been observed that the environmental gamma-ray dose rate increases noticeably during precipitation intervals. This increase, due to the presence of radon progeny in the rain droplets (or snow flakes), can affect the reliability of the monitoring of artificial radioactivity and long term estimates of exposure to ambient natural radionuclides in surveillance network. Predicting the amplitude of the dose increase has been shown to be surprisingly challenging. In this work, standard air mass back trajectory analysis is used to show that the amplitude of the increase can be quantitatively linked to the history of the air mass where the precipitation is occurring. Furthermore, we show how back trajectory analysis, environmental gamma and rain data can be used to obtain estimations of relative radon emanation rates for locations far from the actual point of detection.

Assessment of environmental gamma dose in northern Rechna Doab in Pakistan

Environmental gamma radiation levels in northern Rechna Doab, Pakistan, were measured as a part of systematic study aimed at the establishment of the background data base of radiation and radioactivity levels. The measurements reported in this paper were made with portable radiation monitor which employed GM tube and was calibrated against secondary standard dosimetry system. The average absorbed dose rate in air was determined to vary from 86.0 nGy/h to 139.1 nGy/h with the mean value of 109.1 nGy/h. The annual effective dose remained within the range of 105.47 mSv to 170.54 mSv with its average value of 133.73 mSv. These environmental radiation doses in the area were comparable with those reported for other countries. It was concluded that the prevalent radiation levels did not pose any significant radiological health hazard to the population.

Radionuclide concentrations in soil and lifetime cancer risk due to gamma radioactivity in Kirklareli, Turkey

The objective of this study is to evaluate and map soil radionuclides' activity concentrations and environmental outdoor gamma dose rates (terrestrial and cosmic) in Kirklareli, Turkey. The excess lifetime cancer risks are also calculated. Outdoor gamma dose rates were determined in 230 sampling stations and soil samples were taken from 177 locations. The coordinates of the readings were determined by the Global Positioning System (GPS). The outdoor gamma dose rates were determined by Eberline smart portable device (ESP-2) and measurements were taken in air for two minutes at 1 m from the ground. The average outdoor gamma dose rate was 118 ± 34 nGy h −1. Annual effective gamma dose of Kirklareli was 144 μSv and the excess lifetime cancer risk of 5.0 × 10 −4. Soil samples were analyzed by gamma spectroscopy. The average 226Ra, 238U, 232Th, 137Cs, and 40K activities were 37 ± 18 Bq kg −1, 28 ± 13 Bq kg −1, 40 ± 18 Bq kg −1, 8 ± 5 Bq kg −1 and 667 ± 281 Bq kg −1, respectively. The average soil radionuclides' concentrations of Kirklareli were within the worldwide range although some extreme values had been determined. Annual effective gamma doses and the excess lifetime risks of cancer were higher than the world's average.

ラドン長距離大気輸送と降雨時空間ガンマ線線量率上昇:(2)長距離輸送ラドン濃度の鉛直分布

ラドン長距離大気輸送と降雨時空間ガンマ線線量率上昇:(2)長距離輸送ラドン濃度の鉛直分布

Environmental gamma radiation measurement in District Swat, Pakistan

External exposure to environmental gamma ray sources is an important component of exposure to the public. A survey was carried out to determine activity concentration levels and associated doses from (226)Ra, (232)Th, (40)K and (137)Cs by means of high-resolution gamma ray spectrometry in the Swat district, famous for tourism. The mean concentrations for (226)Ra, (232)Th and (40)K were found to be 50.4 +/- 0.7, 34.8 +/- 0.7 and 434.5 +/- 7.4 Bq kg(-1), respectively, in soil samples, which are slightly more than the world average values. However, (137)Cs was only found in the soil sample of Barikot with an activity concentration of 34 +/- 1.2 Bq kg(-1). Only (40)K was determined in vegetation samples with an average activity of 172.2 +/- 1.7 Bq kg(-1), whereas in water samples, all radionuclides were found below lower limits of detection. The radium equivalent activity in all soil samples is lower than the limit set in the Organisation for Economic Cooperation and Development report (370 Bq kg(-1)). The value of the external exposure dose has been determined from the content of these radionuclides in soil. The average terrestrial gamma air absorbed dose rate was observed to be 62.4 nGy h(-1), which yields an annual effective dose of 0.08 mSv. The average value of the annual effective dose lies close to the global range of outdoor radiation exposure given in United Nations Scientific Committee on the Effects of Atomic Radiation. However, the main component of the radiation dose to the population residing in the study area arises from cosmic ray due to high altitude.

Performance Characteristics of Newly Modified CaSO4:Dy based Indigenous Thermoluminescent Dosimeters for Environmental Radiation Monitoring

Environmental gamma radiation monitoring around the nuclear installations in India is being carried out for over three decades. This programme was essentially based on powder based Thermoluminescent Dosimeters (TLDs) using naturally occurring calcium fluoride (Fluorite) powder. Being powder based, it was labor intensive and to cater to the increasing demand for monitoring new stations, it was necessary to go for automatic TLD reader system. This was achieved by modifying the TLD cards suitably and using the automated PC based TLD badge TLD reader system indigenously developed and being used for personal dosimetry in India. This paper discusses the modifications that were carried out to make the TLDs suitable for environmental gamma monitoring using TLDs.Performance characterisation of the TLDs like accuracy, precision and energy dependence etc were carried out to see the efficacy of the system for use in the environmental gamma radiation monitoring. In addition, inter-comparison with the existing TLD system, both deployed simultaneously in the field was also carried out. It was found that the new TLD exhibit the accuracy of 89–96 % of the various delivered doses in the laboratory while the precision was observed to be within 4% for all the doses delivered. The gamma radiation levels as measured using two TLD systems were found to match very well with each other. The paper also discusses the results.

Development of Wide-energy Range X/γ-ray Survey-meter

The X-ray radiation produced from various X-ray generating machines has energies between 8 keV to 300 keV and for monitoring environmental gamma rays, the energy range to be measured is from 40 keV up to 1500 keV. We developed a wide-energy range X/γ-ray survey-meter , which can measure ambient dose equivalent H*(10), covering the energy range of 8 keV to 1500 keV by dividing the two energy ranges, from 8 to 300keV for X-ray mode and from 40 to 1500keV for γ-ray mode, both energy responses are within 25% from 10keV up to 300keV and from 50keV up to 1500keV using a 12.7mm diameter by 12.7mm thick NaI(Tl) scintillator.

Environmental Gamma Radiation Monitoring Around Nuclear Power Stations in India, an Indian Scenario

There are 17 operating nuclear power reactors in India at 6 sites with an installed capacity of approximately 4120 MWe of electricity. Apart from two reactors in Tarapur Atomic Power Station (TAPS), which use enriched uranium and are based on boiling water reactor (BWR) technology, all the other reactors at various power stations use natural uranium as fuel, are moderated and cooled by heavy water and are Pressurised Heavy Water Reactors (PHWR). Environs of all the power stations in India are monitored for gamma radiation on regular basis using Thermoluminescent Dosimeters (TLDs). The gamma radiation levels thus measured are regularly compared with the pre-operational levels. The data generated for all the stations during the past years was subjected to various analyses like comparison of the annual levels with those during the pre operational levels, distribution studies, regressions with the possible contributors etc. This paper discusses the environmental gamma radiation levels based on the analyses of all data generated for all the power stations during the years up to 2005. Comparisons of the annual radiation levels with those during the pre operational data indicates that none of the stations show any increase in the environmental gamma radiation levels.

First Report of Environmental Gamma Radiation Levels in Twenty Four Towns and Cities of Khorasan Region-Iran

Although many researchers have focused their attention to man made sources, but natural sources constitute more than 85% of human exposure to ionizing radiation. Due to the significance of natural sources, comprehensive studies have been carried out in developed countries. In Iran like many other developing countries, this subject has not been considered as a research priority. Until 1990 only Ramsar located in the south coast of Caspian sea had attracted attention of some researchers. In 1996 preparation of out-door natural radiation map of Iran was defined as a long term goal in my center. Since then environmental gamma radiation dose rate of residential area of 10 counties have been estimated. In this article only annual dose rates of Khorasan are reported.In every one city five stations were selected. A survey meter model RDS-110 was placed one meter above the ground level.Dose rates were measured for one hour in three successive days. Although average dose rates of every one of the stations were numerically different, but their differences are not significant. Out-door gamma dose rates acquired for 24 towns are within the range of 56 to 144 nGy/h.Minimum and maximum dose rates are respectively attributed to Dargaz, in the north and Gonabad in the south.

LEAKAGE CORRECTION ESTIMATE FOR ELECTRET ION CHAMBER DIELECTRIC MATERIAL USED FOR LONG-TERM ENVIRONMENTAL GAMMA MONITORING

The Idaho Department of Environmental Quality INL Oversight Program (DEQ-INL) operates an environmental gamma radiation detection network consisting of a series of high-pressure ion chambers to provide real-time ambient radiation measurements and a series of passive environmental electret ion chambers to increase coverage area and measure cumulative dose over a calendar quarter. DEQ-INL has identified a consistent over-response of approximately 40% by the electret ion chambers with respect to co-located high-pressure ion chambers since 1998. DEQ-INL conducted a series of three investigations to quantify this over-response. The over-response is likely attributable to a number of factors, including inherent voltage loss by the electret material not due to ionization within the chamber. One aspect of the investigation verified the manufacturer's calibration factor used to convert decrease in voltage to exposure. Additional investigations were performed that identified an average electret voltage loss of 0.2 V d(-1). When this voltage correction was applied to historical environmental data, electret ion chamber response was within 10% of the co-located high-pressure ion chamber response.

TLD environmental monitoring at the Institute of Nuclear Engineering in Brazil

Since 2003 the Institute of Nuclear Engineering in Rio de Janeiro city, Brazil, operates a new cyclotron, RDS-111, to produce 18F-Fluorodeoxyglucose to be used in nuclear medicine. Additionally, the IEN radioactive waste repository has been enlarged during the past last years, receiving a considerable amount of radioactive materials. Therefore, it became necessary to evaluate a possible increase of the environmental gamma exposure rates at the institute site due to the operation of the new accelerator and the enlargement of the institute waste repository as well. LiF:Mg,Cu,P, TLD-100H, and TL detectors were employed for environmental kerma rate evaluation and the results were compared with previous results obtained before the RDS-111 operation initialisation and the enlargement of IEN waste repository. No significant contribution for the enhancement of environmental gamma kerma rates was detected.

Background study for the pn-CCD detector of CERN Axion Solar Telescope

The CERN Axion Solar Telescope (CAST) experiment searches for axions from the Sun converted into photons with energies up to around 10 keV via the inverse Primakoff effect in the high magnetic field of a superconducting Large Hadron Collider (LHC) prototype magnet. A backside illuminated pn-CCD detector in conjunction with an X-ray mirror optics is one of the three detectors used in CAST to register the expected photon signal. Since this signal is very rare and different background components (environmental gamma radiation, cosmic rays, intrinsic radioactive impurities in the setup, etc.) entangle it, a detailed study of the detector background has been undertaken with the aim to understand and further reduce the background level of the detector. The analysis is based on measured data taken during the Phase I of CAST and on Monte Carlo simulations of different background components. This study will show that the observed background level (at a rate of (8.00 ± 0.07) × 10 −5 counts cm −2 s −1 keV −1 between 1 and 7 keV) seems to be dominated by the external gamma background due to usual activities at the experimental site, while radioactive impurities in the detector itself and cosmic neutrons could make just smaller contribution.

First tests of the active shield for a gamma ray spectrometer

The operational problems of the gamma ray spectrometer shielded passively with 12 cm of lead and actively by five 0.5 m × 0.5 m × 0.05 m plastic veto shields are described. The active shielding effect from environmental gamma ray, cosmic muons, and neutrons was investigated. Wide range of scintillator pulses, corresponding to the energy range of 150 keV–75 MeV, was used for anticoincidence gating. With the optimal set up, the integral background of 0.31 c/s was achieved for the energy region of 50–3000 keV. The detector mass-related background was 0.345 c/kg s. The 511 keV annihilation line was reduced by factor of 7 by the anticoincidence gate. It is shown that the plastic shields increase the neutron capture gamma line intensities due to neutron termalization.