Environmental Gamma Radiation Research Articles

Quality assurance of environmental gamma radiation monitoring in Slovenia

Environmental gamma radiation monitoring established in Slovenia consists of a network of multifunctional gamma monitors (MFMs) based on pairs of Geiger-Müller counters and a network of measuring sites with high-sensitive thermoluminiscence dosemeters. The measuring points are evenly spread across Slovenia, located at the meteorological stations and more densely on additional locations around the Krsko NPP. The MFM network has a 2-fold function with one sensor used for the purpose of early warning system in near surroundings of the NPP and the other, more sensitive, for natural radiation monitoring. The paper summarises activities to establish quality assurance of the environmental gamma radiation measurements in Slovenia, with a critical view of the results in comparison with the international standards and recommendations. While the results of linearity and energy dependence tests were satisfying, on-field intercomparison showed that the inherent signal of one of the monitors (MFM) has to be taken into account in the range of environmental background radiation.

Terrestrial gamma radiation dose study to determine the baseline for environmentalradiological health practices in Melaka state, Malaysia

Environmental terrestrial gamma radiation dose rates were measured throughoutMelaka, Malaysia, over a period of two years, with the objective of establishingbaseline data on the background radiation level. Results obtained are shown intabular, graphic and cartographic form. The values of terrestrial gamma radiationdose rate vary significantly over different soil types and for different underlyinggeological characteristics present in the study area. The values ranged from54 ± 5 to378 ± 38 nGy h−1. The highest terrestrial gamma dose rates were measured over soil types of graniticorigin and in areas with underlying geological characteristics of an acid intrusive(undifferentiated) type. An isodose map of terrestrial gamma dose rate in Melaka wasdrawn by using the GIS application ‘Arc View’. This was based on data collected using aNaI(Tl) scintillation detector survey meter. The measurements were taken at 542locations. Three small ‘hot spots’ were found where the dose rates were more than350 nGy h−1. The mean dose rates in the main population areas in the mukims (parishes) ofBukit Katil, Sungai Udang, Batu Berendam, Bukit Baru and Bandar Melaka were154 ± 15,161 ± 16,160 ± 16,175 ± 18 and 176 ± 18 nGy h−1, respectively. The population-weighted mean dose rate throughout Melaka state is172 ± 17 nGy h−1. This is lower than the geographical mean dose rate of183 ± 54 nGy h−1. The lower value arises from the fact that most of the population lives in the central areaof the state where the lithology is dominated by sedimentary rocks consisting of shale,mudstone, phyllite, slate, hornfels, sandstone and schist of Devonian origin which havelower associated dose rates. The mean annual effective dose to the population from outdoorterrestrial gamma radiation was estimated to be 0.21 mSv. This value is higher than theworld average of 0.07 mSv.

GPS-based handheld device for measuring environmental gamma radiation and mapping contaminated areas

A portable GPS-based device was developed for mapping large areas with enhanced radioactivity. It is intended for use in difficultly accessible areas, typically for foot campaigns. Standard low cost components were used, such as a wireless GPS receiver, and a wireless RS-232 device connecting a handheld NaI detector to a pocket PC (PPC). The PPC is programmed to perform simple data logging, producing a file with position and dose rate in situ, which must be post processed in the office to map the contamination.

Environmental Gamma radiation measurement using TLDs around TNRC, tripoli

The outdoors absorbed dose rate in the air around the Tajoura nuclear research centre (TNRC), Tripoli has been measured. The measurements were performed using calcium fluoride dysprosium (CaF2: Dy) thermoluminescence dosimeters (TLD‐200) at 9 locations, all 1 m above the ground level. The average outdoors absorbed dose rate in air, effective dose and the collective effective dose were calculated to be 54 ± 4.6 nGyh− 1, 66.23 μSvy− 1 and 99.35 manSvy− 1, respectively, based on the analysis of thermoluminescence dosimeters data.

Measurements of environmental terrestrial gamma radiation dose rate in three mountainous locations in the western region of Saudi Arabia

This paper describes measurements of external gamma radiation dose rate from terrestrial gamma-rays 1 m above the ground in three different mountainous locations in the western region of the Kingdom of Saudi Arabia. These locations are At-Taif city, Al-Hada village, and Ash-Shafa village. CaSO 4:Dy (TLD-900) thermoluminescent dosimeters were used for the detection of terrestrial gamma radiation at 40 different places in the three locations. The values of terrestrial gamma radiation dose rate measured ranged between 14 and 279 nGy h –1 for the time interval from June 2001 to June 2002. The measured dose rate varied with the season of the year. The average gamma radiation dose rates were 468, 541, and 781 μGy y –1 for At-Taif city, Al-Hada village, and Ash-Shafa village, respectively. The corresponding average absorbed doses to the population of the three locations were 328, 379, and 547 μSv y –1, respectively. The quality factor of 0.7 Sv Gy −1 was applied in the calculations of the absorbed dose to humans.

Environmental gamma dose rates and influencing factors in buildings

Environmental gamma radiation measured in buildings in Dhaka shows a cosinusoidal variation of indoor dose rate with time mainly due to seasonally varied ventilation and air exchange rates of the houses. In connection, the nature and characteristics of the buildings were also discussed. As expected, a maximum dose rate was found in winter and a minimum in summer. The variations of indoor dose rates between buildings were observed. This study indicates that the higher air exchange rates of the houses may play an important role in providing a healthy and safe indoor environment for their inhabitants by reducing indoor exposure.

Environmental gamma radiation measurements in Bangladeshi houses

Indoor gamma dose rate in air measured using TLDs in the Dhaka district is not wide ranging and follows a normal distribution with an arithmetic mean of 1.54±0.26 mGy y −1 . The result has been compared with those found by other investigators for different locations of the world. Measurements were made on a monthly basis for a year period, and a sinusoidal variation of monthly indoor gamma radiation of the type: d=160+65 cos π/6 (m−1) , where d is the indoor dose rate ( nGy h −1) and m the month. This might be due to the seasonally varied air exchange rates of the houses. The average annual effective dose and the collective dose equivalent for the residents were estimated to be 0.86 mSv and 172.20 man -Sv, respectively, based on the indoor gamma exposure.

Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry

Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus™ has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.

The use of passive environmental TLDs in the operation of the Spanish early warning network 'REVIRA'.

As required by different international agreements, the regulatory body in Spain (Consejo de Seguridad Nuclear) implemented in 1992 a national automatic network (REVIRA) that continuously monitors radiation levels in order to give early warning of incidents having potential transboundary implications. The detector for environmental gamma-radiation dose rate is an active instrument based on a Geiger-Müller counter. However, the use of passive environmental dosemeters provides an additional low-cost dose estimate with an independent centralised calibration and even better basic features than active instruments. Since 1999, all 25 REVIRA stations have been monitored with passive TL environmental dosemeters based on LiF:Mg,Cu,P and operated according to the procedures established at Ciemat. This paper presents the obtained results and the further analysis considering differences in aspects such as photon energy response, inherent background or response to cosmic rays. The benefits of the use of passive environmental dosemeters in early warning networks are discussed.

The influence of urbanization on natural radiation levels in anomalous areas

This paper verifies the effects of urbanization on the original levels of environmental gamma radiation in an anomalous area. The fieldwork was done in the city of Guarapari, on the seacoast of the state of Espírito Santo, Brazil. This place was chosen because the whole region is naturally rich in monazite sand, which contains thorium and uranium. A similar study was also carried out in the 1960s. The measurements were done using an inorganic NaI scintillometer detector with Cu+Pb filters coupled to a scaler. The methodology of measurements used was similar to the one applied in the fieldwork carried out in the 1960s. In addition, a simulation was performed in the laboratory, to determine the attenuation of the materials used in the urbanization of the region. The results of this work clearly show that there was a reduction in the levels of external radiation in the streets and squares of Guarapari. It was concluded that the reduction was due to attenuation by the materials used in the urbanization.

Radiological impact on the workers, members of the public, and environment from the partial decommissioning of Pakistan Research Reactor-I and its associated radioactive residues.

The Pakistan Research Reactor-I (PARR-I) is a swimming pool type research reactor originally designed and built for a thermal power of 5 MW using High Enriched Uranium (HEU) fuel. In 1990-1991 the reactor was redesigned, partially decommissioned and recommissioned to operate with Low Enriched Uranium (LEU) fuel at a thermal power of 10 MW. An essential requirement, construction and commissioning of a wet spent fuel storage bay and fabrication of an irradiated fuel transfer cask were completed before actual dismantling of the reactor core. During the partial decommissioning operations, radioactive waste generated included 600 m3 low-level liquid radioactive waste and 14 m3 of solid radioactive waste with an average specific activity of 4.52 Bq ml(-1) and 2.22 kBq g(-1), respectively. External radiation doses of the workers were determined using TLD (NG 6,7) and direct reading dosimeters. The maximum individual external radiation dose received by any worker during this practice was 5 mSv, which was 25% of the annual dose limit of 20 mSv. Detection and measurement of internal contamination was carried out using bioassay techniques. During the whole operation, not a single case of internal contamination was detected. The ambient radiation levels around waste seepage pits are periodically monitored using TLD (G-2 cards) and G. M. radiation survey meters. Underground migration of radioactivity is checked by analyzing seepage water samples taken from boreholes that have been dug at different locations in the vicinity of the radioactive residues. The monitoring around disposal sites containing radioactive residues has been continued during the last 9 y and will be continued in the future. So far, no rise in the environmental gamma radiation dose level and migration of underground radionuclides has been found in the vicinity of these disposal sites. Working personal during the decommissioning of PARR-I have been found to be radiologically safe. Adherence to the ALARA principle, sound decommissioning and proper radioactive waste disposal procedures helped to protect the working personnel, members of the public, and the environment from the harmful effects of the ionizing radiations present due to the partial decommissioning of the research reactor and its radioactive residues. Experience gained during this work, along with the current international procedures, will be helpful for full restoration of the environment from radioactive residues likely to be generated in the future from any other practices in Pakistan.

Geological influence on terrestrial gamma radiation dose rate in the Malaysian State of Johore

Measurements of environmental terrestrial gamma radiation dose-rate (TGRD) have been made in Johore, Malaysia. The focus is on determining a relationship between geological type and TGRD levels. Data were compared using the one way analysis of variance (ANOVA), in some instances revealing significant differences between TGRD measurements and the underlying geological structure.

Technical Recommendations on Measurements of External Environmental Gamma Radiation Doses (A Report of EURADOS Working Group 12 'Environmental Radiation Monitoring')

These recommendations provide guidance and information on the measurement of dose rates in the environment arising from photon radiation both from natural sources and from man-made sources. During the past decade there has been significant interest in the levels of radiation to which the general public is exposed, both from natural causes but particularly, since the Three Mile Island and Chernobyl accidents, to that arising from man-made operations. The public concern following the Chemobyl accident prompted many countries to introduce very comprehensive monitoring systems which included national networks of dose rate monitoring systems. These systems are aimed at providing Governments with prompt warning of radioactive releases, and accurate assessment of the predicted doses to the public, following accidents at nuclear installations within their own country and from installations in neighbouring and very remote countries. The measurement of dose rates from photon radiation in the neighbourhood of a nuclear installation is an essential part of any environmental measurement programme that is necessary to demonstrate that members of the public are not exposed to unacceptable levels of radiation arising from the operation of the installation. Apart from the technical difficulties of measuring such low dose rates, there are also problems in assessing their significance in relation to the comparable, but variable, dose rates from natural sources. To help improve the quality and accuracy of environmental radiation measurements within Europe, the Commission of the European Communities (CEC) sponsored intercomparison experiments during the past ten years. The purpose of this Technical Report is to disseminate the considerable experience and expertise gained by the participants during these intercomparisons. Practical advice is given on all aspects of environmental photon dose monitoring. The report starts by describing the nature and variability of environmental gamma radiation within Europe and then discusses the quantities that should be used for measurements. The characteristics and performance of both passive and active detectors as well as of spectrometry systems are discussed. Type testing and calibration methods are recommended which will enable the response of the monitoring equipment to the different radiation components to be properly determined. Techniques for assessing the uncertainties associated with both calibration and measurements are described. Examples are given of the early warning systems installed within European countries. It is hoped that this report will assist in the harmonisation of environmental photon dose measurements within Europe and the rest of the world.

Environmental gamma radiation indoors at Akure, Southwestern Nigeria

Exposures to environmental gamma radiation were assessed by using LiF thermoluminescent dosimeters (TLDs) placed inside family dwellings made out of stone, gravel concrete, brick etc., at Akure, the capital of Ondo State. Southwestern Nigeria for about two and a half months. The results show that houses made out of soil bricks give the least exposures to dwellers. The dosimetric implications are discussed in the text.

Environmental Gamma Radiation and Natural Radioactivity in Soils in Centro Experimental Aramar (CTMSP-BRAZIL) and Region

The experimental results are described obtained with CaF 2 :Dy thermoluminescence dosemeters (TLD-200) for the measurement of natural outdoor gamma radiation background and by the gamma spectrometry technique on soil samples to determine natural radioactivity in Centro Experimental Aramar (CTMSP-Brazil) and surroundings, from 1989 to 1997. The Centro Tecnologico da Marinha (CTMSP) is a military research organisation, located in S. Paulo city (Brazil), whose objectives are to develop nuclear and energy systems for Brazilian Naval Ship propulsion. The estimated average outdoor gamma dose rate in air is 405 ± 71 μGy.y -1 . The estimated average values obtained for radionuclides of the natural series are 44 ± 6 Bq.kg -1 for 214 Pb ( 238 U series), 58 ± 20 Bq.kg - for 228 Ac ( 232 Th series), and 131 ± 40 Bq.kg -1 for 40 K. These values are compared with background values of other places in the world, and indicate a low outdoor gamma dose rate in air and low natural radioactivity in soil samples in Centro Experimental Aramar and region.

熱ルミネッセンス線量計による環境γ線線量の測定及び環境特性

It is important to evaluate environmental gamma-ray exposure both at work and home in order to assess people's collective dosages. Environmental gamma radiation was measured for air-absorbed dose with a thermoluminescence dosemeter at various points in the workplace and Ningyoutouge, and workplace radiation characteristics were analysed. From the results, the public dose due to gamma rays generated artificially was assessed to be sufficiently lower than the annual limit. For indoor environments of the workplace, the maximum dosage rate among measured values was 97nGy/h and the minimum value was 70nGy/h, the average over one year was 83nGy/h. The average annual outdoor dosage for a year was 82nGy/h. In Ningyotoge, the maximum was 103nGy/h, minimum 60nGy/h, and average 88nGy/h. These values depend on the nature of the soil and weather factors, showing higher values in the summer than in the winter in the workplace. There was no significant difference in the dosage rate in houses and the workplace.

Estimation of environmental gamma background radiation levels in Pakistan.

For the purpose of preparing an environmental gamma radiation map of Pakistan, the geological materials exposed in the country were divided into eight different classes. Using average 238U, 232Th, and 40K content of these materials, total absorbed dose rate in these rocks was calculated. The dose rate in the environment ranged from 1 nGy h(-1) to 97 nGy h(-1) with a mean value of 59 nGy h(-1). These data are presented as a dose rate map of Pakistan. This map provides a usable regional picture of environmental gamma background radiation levels excluding cosmic radiation in Pakistan.

Environmental terrestrial gamma radiation dose and its relationship with soil type and underlying geological formations in Pontian District, Malaysia

An environmental terrestrial gamma radiation dose survey has been conducted, covering the Pontian district of Peninsular Malaysia. Results have allowed construction of a terrestrial gamma-ray isodose contour map of Pontian. Relationships between the gamma radiation dose levels measured at various locations and the soil type and underlying geology are discussed.

Dosimetric properties of natural quartz grains extracted from fired materials

The paper describes an examination of the dosimetric properties of natural quartz grains extracted from ancient fired materials. Eleven samples of different origin were tested for their TL and GLSL (green light stimulated luminescence) sensitivities within the mGy dose range. Very promising results were obtained showing the possibility of measuring the doses of around 10 mGy with 1% precision using GLSL or TL and using the single aliqout technique for natural quartz as a dosimeter. The lowest detectable dose was estimated to be lower than 500 μGy. The results obtained indicate that natural quartz grains from selected materials could be used for the dosimetry of environmental gamma radiation for the purposes of paleodosimetric dating methods as well as for accident dosimetry.

Analysis of the time variation of environmental gamma radiation due to the precipitation

Analysis of the time variation of environmental gamma radiation due to the precipitation