Gamma Exposure Rates Research Articles

Uranium Mine Proposed Experimental Design for Natural Background Gross Gamma Exposure Rates, Post Remediation Final Status Survey Sampling Density, and Radiological Water Quality Modeling for a Worst-case Catastrophic Failure, Coles Hill, Virginia.

Completely randomized experimental design statistical modeling techniques were employed to analyze exposure rate measurements for evaluating hypothetical natural background post uranium mill operations at Coles Hill, Virginia uranium milling processes. The proposed Coles Hill Uranium Mine is situated upstream of the Banister River. This River is nearly homogenous throughout the reach length used in analysis and feeds into the mouth of Kerr Reservoir, Lake Gaston, which serves as the main drinking water source for cities in the Hampton Roads area including Norfolk, Virginia Beach, and Chesapeake. A critical scan value (=DCGLscan) was developed to flag anomalies of surface contamination during simulated post remediation final status surveys. The natural background was critical for meeting the Multi-Agency Radiation Survey and Site Investigation Manual guidance for post remediation final status surveys. The overarching null hypothesis suggested that the selected mean natural background is equal to the survey unit's mean natural background. Using SAS Procedures Shapiro-Wilk Test, ANOVA, and CR, it was decided the exposure rate data was normal, had no extreme outliers, and no collinearity between the number of samples (=treatment) and the areas (=block). Using the q-hyper (hypergeometric) distribution, the soil sampling density was decided for a final status survey unit. The most likely worst-case catastrophic failure analysis, 500-year event, such as the1969 Hurricane Camille of 69 centimeters of rain in Nelson County, Virginia was included in the model. The model showed impact was minimal at most to the Banister River's drinking water and likely less than the Virginia's Drinking Water Standards for gross alpha, 226Ra and 228Ra, and total uranium.

Assessment of radionuclides in the soil of Bonny Local Government Area Of Rivers State, Nigeria and evaluation of radiological risk

Twenty Samples each of soil from Bonny LGA, Rivers State, Nigeria were analyzed using NaI(IT) gamma detector to estimate radiation hazard due to the anthropogenic sources. The activity concentration of 232Th was found to be in the range 18.78 – 397.13 BqKg-1, 40K in the range 43.72 – 390.62 BqKg-1 and 226Ra in the range 10.77 – 57.84 BqKg-1 all in soil. These results were used to calculate the radiological hazard parameters including the Annual Gonadal Equivalent Dose. The calculated gamma exposure rates ranged between 10.00 – 270.79 nGyh-1 while the average value of the Excess Lifetime Cancer Risk (ELCR) was found to be 0.38 x 10-3 for soil which is higher than the world average of 0.29 x 10-3.

On Weather Data-Based Prediction of Gamma Exposure Rates Using Gradient Boosting Learning for Environmental Radiation Monitoring.

Gamma radiation has been classified by the International Agency for Research on Cancer (IARC) as a carcinogenic agent with sufficient evidence in humans. Previous studies show that some weather data are cross-correlated with gamma exposure rates; hence, we hypothesize that the gamma exposure rate could be predicted with certain weather data. In this study, we collected various weather and radiation data from an automatic weather system (AWS) and environmental radiation monitoring system (ERMS) during a specific period and trained and tested two time-series learning algorithms—namely, long short-term memory (LSTM) and light gradient boosting machine (LightGBM)—with two preprocessing methods, namely, standardization and normalization. The experimental results illustrate that standardization is superior to normalization for data preprocessing with smaller deviations, and LightGBM outperforms LSTM in terms of prediction accuracy and running time. The prediction capability of LightGBM makes it possible to determine whether the increase in the gamma exposure rate is caused by a change in the weather or an actual gamma ray for environmental radiation monitoring.

A Methodology for Calculation of Internal Dose Following Exposure to Radioactive Fallout from the Detonation of a Nuclear Fission Device.

The purpose of this paper is to provide a methodology for the calculation of internal doses of radiation following exposure to radioactive fallout from the detonation of a nuclear fission device. Reliance is on methodology previously published in the open literature or in reports not readily available, though some new analysis is also included. Herein, we present two methodologic variations: one simpler to implement, the other more difficult but more flexible. The intention is to provide in one place a comprehensive methodology. Pathways considered are (1) the ingestion of vegetables and fruits contaminated by fallout directly, (2) the ingestion of vegetables and fruits contaminated by continuing deposition by rain- or irrigation-splash and resuspension, (3) the ingestion of vegetables and fruits contaminated by absorption of radionuclides by roots after tillage of soil, (4) the non-equilibrium transfer of short-lived radionuclides through the cow-milk and goat-milk food chains, (5) the equilibrium transfer of long lived radionuclides through milk and meat food chains, and (6) inhalation of descending fallout. Uncertainty in calculated results is considered. This is one of six companion papers that describe a comprehensive methodology for assessing both external and internal dose following exposures to fallout from a nuclear detonation. Input required to implement the dose-estimation model for any particular location consists of an estimate of the post-detonation external gamma-exposure rate and an estimate of the time of arrival of the fallout cloud. The additional data required to make such calculations are included in the six companion papers.

Quantification of radon/thoron exhalation rates of soil samples collected from district Faridabad of Southern Haryana, India

This paper describes radon mass exhalation rate ( $${J}_{m })$$ and thoron surface exhalation rate ( $${J}_{s}$$ ) of 46 soil samples of district Faridabad, Southern Haryana, India. Scintillation detector based SMART RnDuo (AQTEK System, India) coupled with exhalation chamber was used. Outdoor gamma exposure rate was measured by GM counter based survey meter. $${J}_{m }$$ of one sample and $${J}_{s}$$ of 95% samples were found higher than world average values of 57 mBq kg−1 h−1 and 3600 Bq m−2 h−1 for $${J}_{m}$$ and $${J}_{s}$$ respectively reported by UNSCEAR 2000. No significant correlation was observed between radon/thoron exhalation rates with outdoor gamma exposure rate.

TLD environmental monitoring of new scanner facilities at the Nuclear Medicine Department of the Taiwan Medical University Hospital.

OBJECTIVE: Single-photon emission computed tomography (SPECT) as well as dual energy X-ray absorptiometry (DXA) scanners were designed in July 2018 at the Nuclear Medicine Department (NM), of the Taiwan Medical University Hospital. These scanners emit substantial X-rays from the target, which are tungsten, iron. Therefore, patients undergoing SPECT and DXA diagnosis, in addition to medical personnel, are exposed to undesirable photon leakage.METHODS: Following administration of radiopharmaceuticals, patients become radioactive sources; thus, it is necessary to evaluate a possible increase in the environmental gamma exposure rates in the NM as a result of the operation of the new scanners. A three month evaluation of environmental radiation in the NM was performed using the accurate and sensitive TLD-100H approach, which gives an error rate less than 10%.RESULTS: Detected exposure radiation rates in the NM ranged from 0.12 0.02 to 1.00 0.15 mSv per month, indicating that the imaging room had significantly different radiation rates. The results were compared with previous results, and no significant contribution to the enhancement of environmental gamma radiation was detected, which remained far below the occupational dose recommended by ICRP 60. The minimum detectable dose (MDD) for environmental radiation is also discussed herein to demonstrate the reliability of TLD-100H.CONCLUSION:Recommendations were sent to the authorities of AEC-ROC to implement actions that could reduce doses at these high-dose locations to meet the ALARA principle.

RADON, THORON AND THEIR PROGENY DISTRIBUTION AND ESTIMATION OF ANNUAL EFFECTIVE DOSE AND EXCESS LIFETIME CANCER RISK IN PANATHADY, KASARAGOD DISTRICT, KERALA.

Radon and thoron are natural radioactive gases that tend to accumulate in the indoor environment and one of their major health implications is the ability to cause lung cancer. Present study comprises the quantification of radon and thoron activity concentrations and measurement of gamma exposure rates in different types of dwellings from the endosulfan-affected area, Panathady, Kasaragod district, Kerala. It is observed that, residents of this area were more prone to various diseases and health problems including cancer. The LR-115 type II solid state nuclear track detectors with single entry pin-hole based dosemeters have been used for the measurement of 222Radon and 220Rn activity concentrations. The assessment of radiological parameters such as annual effective doses and excess lifetime cancer risk has also been done in order to understand the dose level and the associated risk. The estimated values have been compared with the limit recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and International Commission on Radiological Protection (ICRP). The average indoor radon and thoron activity concentrations observed in these dwellings were 134±30 and 111±28Bqm-3, respectively. The estimated activity concentrations, effective doses, etc. are found to be within the recommended level by the UNSCEAR or ICRP.

A study of seasonal variations of radon, thoron and their progeny levels in different types of dwellings in Faridabad district, Southern Haryana, India

Radon, thoron and their progeny are responsible for more than 50% of the total ionizing radiation dose received by human population. In the present work, radon, thoron and their progeny concentration measurements have been carried out in 150 dwellings in different villages of Faridabad district of Haryana, India. Pin-holes based twin cup dosimeter containing LR-115 type-II film (solid state nuclear track detectors) has been used for the time-integrated passive measurement of radon and thoron concentrations. The dosimeters were deployed for three seasons each having 4 months of exposure period. For measurement of radon and thoron progeny concentration (EERC/EETC), deposition based direct radon/thoron progeny sensors (DRPS/DTPS) were deployed with dosimeters. Based on the gamma exposure rate in different villages during preliminary survey and type of houses available in the regions, numbers of dwellings of different categories have been selected. Radon, thoron and their progeny concentration and total annual effective inhalation dose were calculated and compared with the recommended limits by UNSCEAR, ICRP and WHO.

Establishing Radiological Screening Levels for Defense-related Uranium Mine (DRUM) Sites on BLM Land Using a Recreational Future-use Scenario.

Thousands of former uranium mining sites in the United States, primarily in the southwestern states of Colorado, Arizona, New Mexico, Arizona, and Utah, are being identified and evaluated to assess their potential for causing public and environmental impacts. The common radiological contaminant of concern that characterizes these sites is naturally occurring uranium ore and associated wastes that may have been left behind postmining. The majority of these sites were abandoned and in general, are referred to as abandoned uranium mines, regardless of the government authority currently managing the land or in some cases, assigned responsibility for the oversight of assessment and remediation. The U.S. Department of Energy has identified over 4,000 defense-related uranium mine sites from which uranium ore was purchased by the U.S. government for nuclear defense programs prior to 1970. U.S. Department of Energy has established a program to inventory and perform environmental screening on defense-related uranium mine sites. The focus of this paper is the approximately 2,400 defense-related uranium mine sites located on federal land managed by the Bureau of Land Management and the U.S. Forest Service. This paper presents the results of an analysis to develop radiological screening criteria for U.S. Department of Energy's defense-related uranium mine sites that can be used as input to the overall ranking of these sites for prioritization of additional assessment, reclamation, or remedial actions. For these sites managed by Bureau of Land Management, public access is typically limited to short-term use, primarily for recreational purposes. This is a broad category that can cover a range of possible activities, including camping, hiking, hunting, biking, all-terrain vehicle use, and horseback riding. The radiological screening levels were developed by calculating the radiological dose to future recreational users of defense-related uranium mine sites assuming a future camper spends two weeks per year at the site engaged in recreational activities. Although a number of possible exposure pathways were included in this analysis (inhalation and ingestion of dust and soil, radon and progeny inhalation, and gamma radiation exposure from the soil), it is desirable as a practical matter to determine what gamma exposure rate would ensure that the annual acceptable exposure as determined by the regulatory authority will not be exceeded in the future. Because these sites are generally remote and located in semiarid environments, traditional exposure scenarios often applied in these types of analyses (e.g., subsistent farmers and ranchers), including exposure pathways for the ingestion of locally grown food products and water, were not considered relevant to short-term recreational use.

Studies on ambient gamma dose rate and enrichment of radon, thoron, and progeny concentration in various types of dwellings and outdoor environments of Kalliasseri, Kannur district, Kerala

The major contribution of natural background radiation exposure comes from radon, thoron, and their progeny. The activity concentration of these radionuclides depends on various factors, and the concentration level varies from place to place. The indoor concentration in dwellings depends mainly on the materials used for building construction and ventilation patterns. In the present study, an attempt is made to estimate the indoor and outdoor radon, thoron, and their progeny concentration in various types of dwellings and outdoor environments of Kalliasseri Panchayat, Kannur district, Kerala. 222Rn and 220Rn measurements were carried out using LR-115 type II-based pinhole cup dosimeters. Indoor and outdoor gamma exposure rate measurements were also carried out in all the dwellings using scintillation-based microradiation survey meter. The average concentrations of radon and thoron were estimated in about 40 dwellings categorized according to the construction type. The seasonal variation in the enrichment of radionuclides concentration has also been studied. The respective radon and thoron progeny levels were also estimated. The average radon concentration from the present study was well within the action level (200 Bq/m3) recommended by the International Commission of Radiological Protection (ICRP). The annual effective doses due to indoor radon and thoron were within the action level 3–10 mSv/y as suggested by the ICRP.

A study of thoron exhalation from monazite-rich beach sands of High Background Radiation Areas of Kerala and Odisha, India

Thoron exhalation from earth’s surface is the most important source of environmental thoron. The High Background Radiation Areas (HBRAs) of Kerala and Odisha in India have beaches with sands enriched with monazite, an ore of thorium, making it unique for study of thoron exhalation. In the present study, in situ measurement of thoron exhalation was carried out to map the thoron exhalation rate over complete coastline of the known HBRAs. New experimental setups for measurement of thoron surface exhalation and thoron mass emanation were developed and validated. The exhalation measurements were carried out on beaches of Chavara–Neendakara (CN) area of Kerala and Chatrapur (CH) region of Odisha. The beaches of the Kerala region showed an average thoron exhalation rate of 5.95 ± 2.98 Bq m−2s−1, which for the beaches of Chatrapur area of Odisha was 2.77 ± 0.96 Bq m−2s−1. The external gamma exposure rate was also measured at these locations, and it was observed to be well correlated with in situ thoron exhalation rate. Sand samples were collected from ten of the measurement locations and analyzed in the laboratory for a further understanding of thoron exhalation process in the beach sand. Measurement of specific thoron mass emanation rate, specific 224Ra content and thoron emanation coefficient was taken for the samples. A good correlation was found between in situ thoron exhalation rate and specific thoron mass emanation rate. The effective thoron diffusion length was determined by using the measured parameters in the UNSCEAR radon exhalation model and was found to be nearly constant with a value of 2.2 ± 0.36 cm. This study shows that in spite of very high thorium content (500–1000 times) as compared to normal fine soils, the thoron exhalation from the HBRA beach sands was only 4–12 times higher due to very low emanation coefficient, about 1000 times smaller than that for normal soils.

PERKIRAAN DOSIS RADIASI YANG DITERIMA PUBLIK DI PROVINSI KEPULAUAN BANGKA BELITUNG

Bangka and Belitung Islands is known to have the geological potential of mineral resources, especially tin along with its accessory minerals which are distributed in almost all land and sea regions. Besides tin, tin mining activities in Bangka Belitung produces a by-product containing radioactive substances which have a risk as one of factor that can affect on the health of publics members. A major contribution of the radiation dose to the publics health comes from natural radionuclides of 226Ra, 232Th and 40K in accessory minerals of tin core. The aim of this study was to estimate the total annual radiation dose received by the cmembers of the public in Bangka-Belitung through external and internal exposure. Estimation of external dose was based on the concentration of 226Ra, 232Th and 40K in the soil and gamma exposure rate direct measurement in public houses. While the internal dose was estimated based on intake of 226Ra, 232Th and 40K by ingestion of foodstuffs that were consummed by public of Bangka - Belitung (vegetables, seeds, tubers, fruits, fishes and drinking water). Internal dose also estimated from the inhalation of radon (222Rn) and thoron (220Rn) inside the house. The annual effective external doses of outdoor and indoor ranged between 0,05 to 11,55 mSv (mean=1,17 mSv) and 0,15 to 2,10 mSv (mean=0,69 mSv) per year respectively. The annual effective internal doses by ingestion of foodstuffs and drinking water and inhalation of radon and thoron gases were 0.20 mSv, 0,76 mSv and 2,32 respectively. So that the total annual effective doses received by the member of the public in Bangka-Belitung through external and internal exposure was 5.14 mSv. In conclusion, the members of the public in Bangka – Belitung islands received higher dose of radiation than the worldwide average value for normal areas.

Design and Development of Carborne Survey Equipment

In most nuclear and radiological emergencies involving the release of radioactive materials to environment, it is important that data on the geographic distribution of potentially hazardous radioactive materials be quickly presented to the authorities. The mobile radiation detection system makes it possible to measure radioactive materials in the environment at random places because of its easy mobility from place to place. The purpose of the work is to develop a mobile radiation detection system to measure gamma exposure rate, radioactive material on the ground and airborne radioactive particulate in the environment quickly. In this work, we have developed a carborne survey equipment system consisting of three gamma ray detectors, one airbome radioactive particulate sampler, a GPS (Global Positioning System), meteorological sensors, a data acquisition system and an operation software. Performance of the carborne survey equipment has been successfully demonstrated to measure iodine and argon release from medical isotope production facility on Serpong in western Java, Indonesia. Received: 04 October 2014; Revised:16 March 2015; Accepted: 23 March 2015

Assessment of radionuclides in the soil of residential areas of the Chittagong metropolitan city, Bangladesh and evaluation of associated radiological risk

Soil samples from the three residential hubs of Chittagong city, Bangladesh were analyzed using gamma spectrometry to estimate radiation hazard due to natural radioactive sources and anthropogenic nuclide 137Cs. The activity concentration of 226Ra was found to be in the range 11–25 Bq.kg−1, 232Th in the range 38–59 Bq.kg−1 and 40K in the range 246–414 Bq.kg−1. These results were used to calculate the radiological hazard parameters including Excess of Lifetime Cancer Risk (ELCR). The estimated outdoor gamma exposure rates were 40.6–63.8 nGy.h−1. The radiation hazard index (radium equivalent activity) ranged from 90–140 Bq.kg−1. The average value of the ELCR was found to be 0.21 × 10−3, which is lower than the world average. Sporadic fallout of 137Cs was observed with an average value of 2.0 Bq.kg−1.

강릉 지역 공간 감마선량률과 강수량, 일조시간, 평균풍속 사이 교차 상관성 분석

본 논문은 강릉 지역에서 동일 기간에 기록된 공간 감마선량률과 강수량, 일조시간, 평균풍속 사이의 교차 상관 지수 <TEX>${\rho}_{DCCA}$</TEX>를 DCCA cross-correlation coefficient(DCCA <TEX>${\rho}$</TEX>)방법으로 구하여 교차 상관성을 분석하였다. 우리는 이 연구를 통해 다음의 사실을 알았다. 첫 번째, 공간 감마선량률과 강수량 사이 <TEX>${\rho}_{DCCA}$</TEX>는 일(4~7일), 달(30일), 계절(90일), 년(360일)에서 0.57~0.48, 0.39, 0.34, 0.26, 공간 감마선량률과 일조시간 사이 <TEX>${\rho}_{DCCA}$</TEX>는 일, 달, 계절, 년에서 -0.20~-0.23, -0.22, -0.17, -0.13, 공간 감마선량률과 평균풍속 사이의 <TEX>${\rho}_{DCCA}$</TEX>는 일, 달, 계절, 년에서 -0.10~-0.12, -0.11, -0.05, -0.05이다. 두 번째, <TEX>${\rho}_{DCCA}$</TEX>를 통하여 공간 감마선량률과 강수량은 교차 상관성이 있으며 공간 감마선량률과 일조시간, 평균풍속 사이에는 교차 상관성이 없다는 것을 확인하였다. In this study, we analyze the cross correlation between Gamma exposure rates and Rainfall, Hours of daylight, Average wind speed using cross-correlation coefficient <TEX>${\rho}_{DCCA}$</TEX> and DCCA cross-correlation coefficient(DCCA <TEX>${\rho}$</TEX>) method. Our data are measured simultaneous in Gangneung regional. First, we find the <TEX>${\rho}_{DCCA}$</TEX> between Gamma exposure rates and Rainfall is Day(3~7days) 0.57~0.48, Month(30days) 0.39, Season(90days) 0.34, Year(360days) 0.26, between Gamma exposure rates and Hours of daylight is Day -0.20~-0.23, Month -0.22, Season -0.17, Year -0.13, between Gamma exposure rates and Average wind speed is Day -0.10~-0.12, Month -0.11, Season -0.05, Year -0.05. Second, our finding is cross- correlation between Gamma exposure rates and Rainfall, is no cross-correlation between Gamma exposure rates and Hours of daylight, Average wind speed.

Design and Development of a Dual-Volume Ionization Chamber for an Accident Monitor to Detect Gamma Radiation During Emergency Conditions in a Nuclear Reactor

A Gamma Ionization Chamber was developed for the purpose of high gamma radiation detection during accident conditions in a Light Water reactor. The pre-eminence of the detector is that it was designed and developed to monitor gamma exposure rates in the wide range of 100 mR/hr to 107 R/hr. The detector has an overall diameter of 90 mm with a length of 400 mm. The response of the detector is accurate and the sensitivity is within ± 6% over gamma energies ranging from 660 KeV to 1.25 MeV. The detector operates with a DC voltage of 500V. The V0.9 voltage is about 250V for 107 R/hr. The estimated operation life of the detector is about 20 years.

강릉 지역 공간 감마선량률의 시계열 분석

본 논문은 1998년부터 2011년까지 강릉 지역의 지방 방사능 측정소에서 측정된 공간 감마선량률의 통계 적인 성질을 조사하였다. Autocorrelation Function Analysis(ACF), Rescaled Range Analysis(R/S Analysis), Detrended Fluctuation Analysis(DFA)의 방법들이 사용되었으며, 이 중 DFA는 non-stationary한 시계열의 장거리 상관성을 보여주는 좋은 방법으로 알려져 있다. 우리는 이 연구를 통해 다음의 사실을 알았다. 첫 번째, 공간 감마선량률은 두 가지 다른 경향을 갖는 크로스 오버가 나타난다. 이것은 연중 공간 감마선량률은 강한 장기 기억 특성이 나타나는데 비해 연간으로 넘어가면 상관성이 사라지는 것을 의미한다. 두 번째, 각 분석 방법들의 지수들이 있는데 이 지수들 사이의 관계식이 맞음을 확인 하였다. In this work, we investigate the statistical properties of gamma exposure rates using well-known analysis methods, such as Autocorrelation Function Analysis(ACF), Rescaled Range Analysis(R/S Analysis), and Detrended Fluctuation Analysis(DFA). Especially, DFA is an important method to reliably detect long-range correlations in non-stationary time series. Our data are measured by Gangneung regional radiation monitoring station over the period of 1998 to 2011. First, we find a crossover indicating two different governing regimes in fluctuations of gamma exposure rates. Within a year, they show a strong long-ranged memory while this property vanishes over the range of time period longer than one year. Second, our finding is very securely supported by a variety of analysis tools. Those tools yield many relevant exponents which satisfies the well known relation between them.

Database of meteorological and radiation measurements made in Belarus during the first three months following the Chernobyl accident

Results of all available meteorological and radiation measurements that were performed in Belarus during the first three months after the Chernobyl accident were collected from various sources and incorporated into a single database. Meteorological information such as precipitation, wind speed and direction, and temperature in localities were obtained from meteorological station facilities. Radiation measurements include gamma-exposure rate in air, daily fallout, concentration of different radionuclides in soil, grass, cow's milk and water as well as total beta-activity in cow's milk. Considerable efforts were made to evaluate the reliability of the measurements that were collected. The electronic database can be searched according to type of measurement, date, and location. The main purpose of the database is to provide reliable data that can be used in the reconstruction of thyroid doses resulting from the Chernobyl accident.

Indoor radon concentration levels, gamma dose rates and impact of geology – A case study in Kotli, State of Azad Jammu and Kashmir, sub-Himalayas, in Pakistan

Inhalation of indoor radon has been recognized as the largest contributor to the total effective dose received by human beings. Indoor radon data were collected from the dwellings lying on the sedimentary rocks (sandstones, siltstones and clays) of the Murree Formation, Nagri Formation, Dhok Pathan Formation, Mirpur conglomerate and surficial deposits of the Kotli area in Azad Jammu and Kashmir, Pakistan. Radon measurements were made using the passive time-integrated method using Kodak CN-85 Solid-State Nuclear Track Detectors. The radon concentration in dwellings varied from 13 ± 6 Bq.m-3 to 185 ± 23 B. qm-3 , with an average of 73 ± 15 Bq.m-3 .The radon concentration in the Murree Formation, Nagri Formation, river terrace and Dhok Pathan Formation were 89.7 ± 16.5, 72 ± 15, 68.5 and 69 Bq.m-3 , respectively. The average value of all the measured concentrations (73 ± 15 Bq.m-3 ) within the framework of this study is more than the world average value of 40 Bq.m-3 given by UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation, report to the General Assembly, United Nations, New York, 2000) and is within the action level of 200-600 Bq.m-3 fixed by the ICRP(International Commission on Radiological Protection, ICRP publication65, Protection against radon at home and at work, 1993). The ambient gamma dose rates both indoors and outdoors in different parts of Kotli were also measured. The average value of gamma absorbed dose rates prevailing in the indoor environment was 131.2 ± 16.6 nGy/h. The gamma exposure rates recorded outdoors were 35% lower than in the indoor environment. The measured gamma dose rates have a weak positive correlation with indoor radon concentration. The annual effective dose for inhabitants in Kotli due to radon ranged from 0.32 to 4.7 mSv.y-1 , with an average value of 1.8 mSv.y-1 . This dose is relatively higher than the world mean dose of 1.15 mSv/y. That is explained by the particular geology of the state of Azad Jammu and Kashmir, and the method of construction of the dwellings.

Residential radon exposure in some areas of Bangalore city, India

Background: Two isotopes, 222 Rn and 220 Rn of the natural radioactive gas radon are generally of radiological importance. About half of the total radiation effective dose to the general public is due to the irradiation of the lungs by alpha particles following the inhalation of radon decay products. In view of this, 222 Rn and 220 Rn measurements were carried out for a period of 1 year in about 50 dwellings belonging to different residential areas of Bangalore city. The results obtained were systematically analysed and discussed. Materials and Methods: 222 Rn and 220 Rn measurements were carried using Solid State Nuclear Track Detectors. The gamma exposure rate measurements were also carried out in all the dwellings using a G M tube based Environmental Radiation Dosimeter. Results: The concentration of 222 Rn and 220 Rn was found to be highest in the dwellings having mud flooring (Bare) and lowest in the dwellings having mosaic flooring. The geometric mean values of the concentrations of 222 Rn and 220 Rn were found to be 24.1 ± 8.3 and 24.5 ± 10.8 Bq m -3 respectively. The annual mean value of the gamma absorbed dose rate is found to be 175.8 nGy y -1 . Conclusion: The mean value of radon concentration is well within the indian average (42 Bq m -3 ) and world average (40 Bq m -3 ) values. The mean effective dose was found to be 1.19 mSv y -1 and is well within the action level as prescribed by ICRP-65.