Assessment Of Radiation Hazards Research Articles

An assessment of natural radioactivity levels and radiation hazards in the soil of Coonoor, South India

The concentration of naturally existing primordial radionuclides (238U, 232Th and 40K) in the soil at various locations in Coonoor, South India has been determined from the gamma spectrum of soil recorded using a low-background NaI(Tl) detector coupled to 8 K multichannel analyzer system. The average concentration of 238U, 232Th and 40K radionuclides in the soil has been found to be 41.5, 78.0 and 295.6 Bq kg−1, respectively. The mean concentration of 232Th and 238U estimated in the soil of the study area is found to be 2.6 and 1.2 times the corresponding value reported as the world average. The absorbed gamma dose rate in the air at 1 m above the soil due to these radionuclides has been calculated as 78.6 nGy h−1 and it is found to be 1.54 times the world average value. The radium equivalent activity (Raeq) of soil has been calculated and it is found to be 175.9 Bq kg−1. The external hazard index (Hex) and the internal hazard index (Hin) of soil are estimated as 0.47 and 0.59, respectively. Raeq, Hex and Hin of soil in the study area are found to be less than recommended level and it is safe to live in the study area. The variation in the activity concentration of primordial radionuclides with depth is also studied. It has been found that their concentration decreases with depth. The annual outdoor and indoor effective dose equivalent is found to be 96.45 and 385.79 μSv year−1, respectively.

Assessment of Natural Radioactivity and Radiation Hazard in Soil Samples of Rajbari District of Bangladesh

Rajbari district of Bangladesh, have been studied and possible health effect were estimated. The experiment has been done by using gamma ray spectrometry system consisting of a HPGe detector coupled with MCA and associate electronics. The average natural radioactivities of 238U, 232Th and 40K have been measured as 29.03±5.67 Bq/kg, 50.91±10.17 Bq/kg and 535.32±89.19 Bq/kg respectively. To estimate health effect due to the activity of those radionuclides, the radium equivalent activity (Raeq), external hazard index (Hex), absorbed dose rate (D) and effective dose have been calculated and compared to the world average values. The results are also compared with the literature values reported for other regions of the world and found that the soil of the study area are not hazards by the radiation and does not pose any harmful effect to the environment. The outcome of this study may provide valuable information about radiation hazard and also may take part in the monitoring of environmental radioactivity. Jahangirnagar University Environmental Bulletin, Vol.2, 1-8, 2013 DOI: http://dx.doi.org/10.3329/jueb.v2i0.16324

Assessment of radiation hazards due to the concentration of natural radionuclides in the environment

A study of natural radionuclides and radon concentration of Hamirpur District of Himachal Pradesh, India is carried out using various methodologies. The activity concentration of the natural radionuclides viz. 226Ra, 232Th and 40K is measured using high-resolution-based HPGe detector. Indoor radon measurements in the dwellings of Hamirpur district is carried out using LR-115 type II cellulose nitrate films in the bare mode. The average activity concentrations of 226Ra, 232Th and 40K are 35.58, 54.95 and 580.58 Bq kg−1, respectively. The annual average indoor radon value in the study area varies from 173.90 to 198.25 Bq m−3, which is well within the recommended action level given by International Commission on Radiological Protection. The indoor radon values obtained in the present investigation are higher than the world average of 40 Bq m−3. Radon concentration in water samples is measured using RAD7, an active radon detector. The annual effective dose for stomach and lung is determined from the measured value of radon concentration in water. To assess the radiation hazard of the natural radioactivity in all samples to the people, the radium equivalent activity, external hazard index, lifetime fatality risk, absorbed dose rate and total annual effective dose is estimated. The results signify that the studied area does not possess any radiation hazards due to the presence of natural radioactivity concentration.

Distribution of radionuclides and radiation hazard assessment in soils of Southern Namibia, Southern Africa

The activity concentrations of (238)U, (232)Th and (40)K in soil samples taken from four major towns across southern Namibia have been determined by gamma spectroscopy and used to calculate the mean dose rate, radium equivalent activity (Raeq) and external hazard index (Hex) for each town. The average concentrations of radionuclides in the towns vary from 10.7±3.1 to 35.6±8.4 Bq kg(-1) for (238)U, 12.3±4.9 to 77.8±20.9 Bq kg(-1) for (232)Th and 248.0±35.6 to 734.6±61.4 Bq kg(-1) for (40)K. These values are within the range of concentrations reported in some countries but most of the values for (232)Th and (40)K are above the worldwide averages. However, the mean effective dose rate of 0.08±0.03 mSv y(-1) and the mean values of Raeq and Hex for the region are below their respective permissible limits, thus indicating that radiation hazard is negligible in the region.

Assessment of natural radioactivity and radiation hazard in volcanic tuff stones used as building and decoration materials in the Cappadocia region, Turkey

The concentrations of natural radionuclides in 6 different colors of volcanic tuff stones which are derived from the Cappadocia region in Turkey were determined using gamma-ray spectroscopy with a HPGe detector, and the mineralogical composition and formula of stones were determined by an X-ray powder diffractometer. The average activity concentrations of 238U, 232Th and 40K are 50.7, 58.6 and 717.6 Bq.kg–1, which are higher than the world averages of 35, 30 and 400 Bq.kg–1, respectively. The radium equivalent activities (Raeq), external hazard index (Hex), and internal hazard (Hin) associated with the natural radionuclides, alpha (Iα) and gamma indices (Iγ) were calculated to assess the radiation hazard of the natural radioactivity in the volcanic tuff stones. The average indoor annual effective dose equivalent is 0.1 mSv. All values of the indoor effective dose are lower than the exemption dose value of 0.3 mSv. The calculated radium equivalent activity values vary from 60.31 Bq.kg–1 to 281.32 Bq.kg–1 with a mean of 189.78 Bq.kg–1. All values of radium equivalent activity are lower than the world average. The average indoor absorbed dose rate (Din) for volcanic tuff stones, calculated to be 21.18 nGy.h–1, is lower than the world average of 84 nGy.h–1.

Radon exhalation and gamma radioactivity levels in soil and radiation hazard assessment in the surrounding area of National Thermal Power Corporation, Dadri (U.P.), India

In the present study soil samples were collected from the region around a National Thermal Power Corporation (NTPC) at Dadri (U.P.), India. Radon activity and radon exhalation rates were measured by using “sealed can technique” using LR 115-type II nuclear track detectors. Radon activities are found to vary from 177.5 ± 23.1 to 583.4 ± 4.9 Bq m−3 with an average value of 330.5 ± 30.4 Bq m−3. Surface exhalation rates in these samples vary from 63.9 ± 8.3 to 210.2 ± 15.1 mBq m−2 h−1 with an average value of 119.1 ± 11.1 mBq m−2 h−1, whereas mass exhalation rates vary from 2.5 ± 0.3 to 8.1 ± 0.6 mBq kg−1 h−1 with an average of 4.6 ± 0.4 mBq kg−1 h−1. Activity concentrations of naturally occurring radionuclides (226Ra, 232Th and 40K) were also measured in these soil samples using high resolution γ–ray spectroscopic system. Activity concentrations of 226Ra, 232Th, and 40K vary from 32.2 ± 6.0 to120.9 ± 4.5 Bq kg−1, 19.3 ± 0.9 to 44.6 ± 1.5 Bq kg−1 and 195.4 ± 2.8 to 505.4 ± 6.3 Bq kg−1 with overall mean values of 70.0 ± 8.9 Bq kg−1, 34.8 ± 1.2 Bq kg−1 and 436.1 ± 5.6 Bq kg−1 respectively. From the activity concentrations of 226Ra, 232Th and 40K, radium equivalent activity (Raeq) and the external hazard index (Hex) were calculated and found to vary from 73.4 to 214.7 Bq kg−1 and from 0.2 to 0.6 respectively.

Using radiation risk for assessment of space radiation hazard

Radiation hazard caused by exposure during a spaceflight is characterized by radiobiological consequences at all levels of organism. These consequences have a stochastic nature. Even deterministic effects are basically random quantity having all attributes of such mathematical values. The radiation risk is defined in this case as an additional probability of health damage or as a death probability in extreme case. For the manned spaceflight additional peculiarity of a human’s exposure is added. A natural space radiation environment has a stochastic character because solar particle events and crew of a spacecraft can be exposed to dose from background level up to lethal one. The report presents a procedure of radiation risk assessment for quantitative expression of radiation hazard level during a flight and using this value for developing protection recommendations. It is emphasized that the risk value is connected specifically with the time interval of possible hazard’s existent. The form of risk representation must be chosen depending on a time scale of radiobiological processes induced by the exposure (expressing in fact the radiation hazard model). Surviving function specified for the crewmember mortality rate changed by the professional exposure must be used for risk calculation. Solar particle events determine a stochastic character of radiation environment in space that must be taken into account for a risk assessment. The reliability of radiation risk assessment can be used for this goal.

Radiation hazard assessment in Egyptian painting oxides. A comparative study

Building materials are potential sources of radiation, which represents a risk factor for human disease including cancer. In this work, the natural radioactivity due to the presence of (238)U, (226)Ra, (232)Th and (40)K in different painting oxides has been measured using gamma spectrometry with a Hyper Pure germanium detector. The concentrations of the heavy metals (Cd, Co, Mn, Pb, Ni, Sr, Rb, Cr, Cu and Zn) were determined by atomic absorption spectrometry in order to investigate their possible correlation with radioactive elements. The activity concentrations of (238)U, (226)Ra, (232)Th and (40)K ranged from 15 ± 0.75 to 126 ± 14, 2.35 ± 0.09 to 72.96 ± 1.96, 1.76 ± 0.31 to 12.88 ± 0.7 and 2.26 ± 0.09 to 200 ± 3.34 Bq kg(-1), respectively. The calculated radium-equivalents were lower than values recommended for construction materials (370 Bq kg(-1)). The absorbed dose rates due to the natural radioactivity of the investigated samples ranged from 8.11 ± 0.24 to 68.46 ± 4.20 nGy/h. Also, the results revealed that some heavy metals (Cd, Co, Mn and Rb) were correlated with (238)U, (226)Ra, (232)Th or (40)K.

Measurement of soil radioactivity levels and radiation hazard assessment in southern Rechna interfluvial region, Pakistan

Rechna interfluvial region is one of the main regions of Punjab, Pakistan. It is the area which is lying between River Ravi and River Chenab, alluvial-filled. Radioactivity levels in soil samples, collected from southern Rechna interfluvial region, Pakistan, have been estimated by using gamma-ray spectrometric technique. (226)Ra, (232)Th, the primordial radionuclide (40)K, and the artificial radionuclide (137)Cs have been measured in the soil of the study area. The mean radioactivity levels of (226)Ra, (232)Th, (40)K, and (137)Cs were found to be 50.6 +/- 1.7, 62.3 +/- 3.2, 662.2 +/- 32.1, and 3.1 +/- 0.3 Bq kg(-1), respectively. The mean radium equivalent activity (Ra(eq)), outdoor radiation hazard index (H(out)), indoor radiation hazard index (H(in)), and terrestrial absorbed dose rate for the area under study were determined as 190.8 +/- 8.7 Bq kg(-1), 0.52, 0.65, and 69.8 nGy h(-1), respectively. The annual effective dose to the general public was found to be 0.43 mSv. This value lies well below the limit of 1 mSv for general public as recommended by the International Commission on Radiological Protection. The measured values are comparable with other global radioactivity measurements and are found to be safe for the public and the environment.

Measurement of soil radioactivity levels and radiation hazard assessment in mid Rechna interfluvial region, Pakistan

Radioactivity levels in soil samples, collected from mid Rechna interfluvial region, Pakistan have been estimated by using gamma ray spectrometric technique. 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs have been measured in the soil of the study area. The mean radioactivity levels of 226Ra, 232Th, 40K and 137Cs were found to be 49.0 ± 1.6, 62.4 ± 3.2, 670.6 ± 33.9 and 3.5 ± 0.4 Bq kg−1 respectively. The mean radium equivalent activity (Raeq), outdoor radiation hazard index (H out), indoor radiation hazard index (H in) and terrestrial absorbed dose rate for the area under study were determined as 189.9 ± 8.8 Bq kg−1, 0.51, 0.65 and 70.1 nGy h−1 respectively. The annual effective dose to the public was estimated to be 0.43 mSv. The measured values are comparable with other global radioactivity measurements and are found to be safe for public and environment.

Assessment of natural radioactivity levels and radiation hazards due to cement industry

The cement industry is considered as one of the basic industries that plays an important role in the national economy of developing countries. Activity concentrations of 226Ra, 232Th and 40K in Assiut cement and other local cement types from different Egyptian factories has been measured by using γ-ray spectrometry. From the measured γ-ray spectra, specific activities were determined. The measured activity concentrations for these natural radionuclides were compared with the reported data for other countries. The average values obtained for 226Ra, 232Th and 40K activity concentration in different types of cement are lower than the corresponding global values reported in UNSCEAR publications. The obtained results show that the averages of radiation hazard parameters for Assiut cement factory are lower than the acceptable level of 370 Bq kg −1 for radium equivalent Ra eq, 1 for level index Iγr, the external hazard index Hex ≤1 and 59 (nGy h −1) for absorbed dose rate. The manufacturing operation reduces the radiation hazard parameters. Cement does not pose a significant radiological hazard when used for construction of buildings.

Measurement of activity concentrations of 40K, 226Ra and 232Th for assessment of radiation hazards from soils of the southwestern region of Nigeria

Activity concentrations of the selected radionuclides (40)K, (226)Ra and (232)Th were measured in surface soil samples collected from 38 cities in the southwest region of Nigeria by means of gamma spectroscopy with a high-purity germanium detector. Measured activity concentration values of (40)K varied from 34.9 +/- 4.4 to 1,358.6 +/- 28.5 Bq kg(-1) (given on a dry mass (DM) basis) with a mean value of 286.5 +/- 308.5 Bq kg(-1); that of (226)Ra varied from 9.3 +/- 3.7 to 198.1 +/- 13.8 Bq kg(-1) with a mean value of 54.5 Bq kg(-1) and a standard deviation of 38.7 Bq kg(-1), while that of (232)Th varied from 5.4 +/- 1.1 to 502.0 +/- 16.5 Bq kg(-1) with a mean value of 91.1 Bq kg(-1) and standard deviation of 100.9 Bq kg(-1). The mean activity concentration values obtained for (226)Ra and (232)Th are greater than the world average values reported by the United Nations Scientific Committee on Effects of Atomic Radiation for areas of normal background radiation. Radiological indices were estimated for the radiation/health hazards of the natural radioactivity of all soil samples. Estimated absorbed dose rates in air varied from 12.42 +/- 2.25 to 451.33 +/- 19.06 nGy h(-1), annual outdoor effective dose rates from 0.015 +/- 0.003 to 0.554 +/- 0.023 mSv year(-1), internal hazard index from 0.10 +/- 0.03 to 3.02 +/- 0.16, external hazard index from 0.07 +/- 0.01 to 2.60 +/- 0.11, representative level index from 0.19 +/- 0.03 to 6.84 +/- 0.29, activity index from 0.09 +/- 0.02 to 3.42 +/- 0.15, and radium equivalent activity from 26.95 +/- 5.04 to 963.15 +/- 41.87 Bq kg(-1). Only the mean value of the representative level index exceeds the limit for areas of normal background radiation. All other indices show mean values that are lower than the recommended limits.

Assessment of radiation hazards due to natural radioactivity in some building materials used in Egyptian dwellings

Different types of Egyptian building materials from various locations in Cairo and its suburbs have been analysed for natural radioactivity using gamma ray spectrometry. Concentrations of (226)Ra, (232)Th and (40)K were in the ranges of (12 +/- 2.8-65 +/- 6.5), (5 +/- 1.8-60 +/- 6.7) and (159 +/- 3.8-920 +/- 12.7 Bq kg(-1)), respectively. The minimum concentration of (226)Ra, (232)Th and (40)K was found in gravel samples, whereas the maximum in granite samples. The results are compared with the published data of other countries and with the world average limits. The radiological hazard parameters: radium equivalent activity, gamma index, alpha index, absorbed dose rate and the annual exposure rate, were determined to assess the radiation hazards associated with Egyptian buildings. All studied samples are lower than world average limits.

Soil radioactivity levels and radiation hazard assessment in the highlands of northern Jordan

Determination of the natural radioactivity has been carried out, by means of gamma-ray spectrometry system, in surface soil samples collected from various geological formations in urban areas of the northern highlands of Jordan. These highlands, extending from Yarmouk River in the north to Wadi Wala in the south, form the agriculturally important regions of Jordan. Soils of the study region, at which about 70% of the total population of the country are living, mainly originated from limestones that are locally used in construction materials, making the evaluation of environmental radioactivity and estimating the current radiation hazards to the population an interesting issue. The total average concentrations of radionuclides 226Ra, 238U, 232Th, and 40K were 42.5, 49.9, 26.7, and 291.1 Bq kg −1, respectively. Correlations made among these radionuclides prove the existence of secular equilibrium in the investigated soils. The total average absorbed dose rate in the study areas is found to be 51.5 nGy h −1, whereas the annual effective dose equivalent has an average value of 63.2 μSv y −1. The external and internal hazard indices, the radium equivalent activity, and the annual gonadal dose equivalent associated with the investigated soils do not exceed the permissible limits except for soils originated from phosphate rocks. Moreover, the radio-elemental concentrations of uranium, thorium and potassium, evaluated for the various geological features in the study areas were calculated to indicate whether relative depletion/enrichment of radioisotopes had occurred. The results of the present study were discussed and compared with internationally recommended values.

Determination of specific activity of 226Ra, 232Th and 40K for assessment of radiation hazards from Turkish pumice samples

The specific activity of 226Ra, 232Th and 40K in 52 Turkish pumice samples collected from 11 geographical areas located in Central Anatolia, Eastern Anatolia, Mediterranean and Aegean regions was determined by gamma-ray spectrometry with a high-purity germanium (HPGe) detector. The specific activity of 226Ra, 232Th and 40K ranged from 12.7 ± 0.5 to 256.2 ± 9.1 Bq kg −1 with a mean of 89.1 ± 65.2 Bq kg −1, 12.3 ± 1.0 to 237.9 ± 12.2 Bq kg −1 with a mean of 87.0 ± 61.4 Bq kg −1 and 300.1 ± 5.5 to 1899.0 ± 30.8 Bq kg −1 with a mean of 1211.9 ± 419.8 Bq kg −1, respectively. Elemental concentrations were determined for U (from 1.0 to 20.7 ppm with a mean of 7.2 ± 5.3 ppm), Th (from 3.0 to 58.6 ppm with a mean of 21.4 ± 15.1 ppm) and K (from 1.0 to 6.1% with a mean of 3.9 ± 1.3%). The radium equivalent activity (Ra eq), the activity index, the emanation coefficient, the 222Rn mass exhalation rate, the indoor absorbed dose rate and the effective dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated mean Ra eq value was 306.6 ± 177.7 Bq kg −1 (54.6 ± 5.5 to 737.6 ± 49.0 Bq kg −1) for all pumice samples. This value is lower than the recommended limit value of 370 Bq kg −1 for building raws and products. The emanation coefficient and the 222Rn mass exhalation rate of all samples ranged from 29.4 to 42.9% with a mean of 36.2% and from 11.0 to 196.4 μBq kg −1 s −1 with a mean of 73.5 μBq kg −1 s −1, respectively. The mean indoor absorbed dose rate and the corresponding mean effective dose rate were 274.6 ± 153.6 nGy h −1 (50.4–644.6 nGy h −1) and 1.35 ± 0.75 mSv y −1 (0.24–3.16 mSv y −1), respectively. For all pumice samples the mean indoor absorbed dose rate is about three times higher than the population-weighted average of 84 nGy h −1, while the mean effective dose rate values except for PUM 05, PUM 06, PUM 10 and PUM 15 exceed the dose criterion of 1 mSv y −1.

Geant4-based radiation hazard assessment for human exploration missions

Human exploration missions in the Solar System will spend most of the time in deep space, without the shielding from the Earth’s magnetic field and hence, directly exposed to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE). Both GCR and SPE fluences have been used to calculate the dose deposited on a water slab phantom using MULASSIS, a program based on the Geant4 Monte Carlo particle transport code. Doses from several extreme SPE events and from a GCR model are calculated for different shielding materials and thicknesses using a planar slab geometry and compared to current dose limits for space operations. Cross-comparison of MULASSIS with HZETRN (a deterministic code) has also been performed for SPE and GCR environments showing an overall reasonable agreement between both codes.

LNG pool fire spectral data and calculation of emissive power

Spectral description of thermal emission from fires provides a fundamental basis on which the fire thermal radiation hazard assessment models can be developed. Several field experiments were conducted during the 1970s and 1980s to measure the thermal radiation field surrounding LNG fires. Most of these tests involved the measurement of fire thermal radiation to objects outside the fire envelope using either narrow-angle or wide-angle radiometers. Extrapolating the wide-angle radiometer data without understanding the nature of fire emission is prone to errors. Spectral emissions from LNG fires have been recorded in four test series conducted with LNG fires on different substrates and of different diameters. These include the AGA test series of LNG fires on land of diameters 1.8 and 6 m, 35 m diameter fire on an insulated concrete dike in the Montoir tests conducted by Gaz de France, a 1976 test with 13 m diameter and the 1980 tests with 10 m diameter LNG fire on water carried out at China Lake, CA. The spectral data from the Montoir test series have not been published in technical journals; only recently has some data from this series have become available. This paper presents the details of the LNG fire spectral data from, primarily, the China Lake test series, their analysis and results. Available data from other test series are also discussed. China Lake data indicate that the thermal radiation emission from 13 m diameter LNG fire is made up of band emissions of about 50% of energy by water vapor (band emission), about 25% by carbon dioxide and the remainder constituting the continuum emission by luminous soot. The emissions from the H 2O and CO 2 bands are completely absorbed by the intervening atmosphere in less than about 200 m from the fire, even in the relatively dry desert air. The effective soot radiation constitutes only about 23% during the burning period of methane and increases slightly when other higher hydrocarbon species (ethane, propane, etc.) are burning in the LNG fire. The paper discusses the procedure by which the fire spectral data are used to predict the thermal emission from large LNG fires. Unfortunately, no direct measurements of the soot density or smoke characteristics were made in the tests. These parameters have significant effect on the thermal emission from large LNG fires.

Estimation of a cosmonaut's radiation hazard during long-term space missions on the basis of a generalized dosimetric function

This paper presents a new concept of radiation hazard assessment for spacecraft crew members during long term space missions on the basis of a generalized dosimetric function. This new dosimetric function enables a complicated nature of space radiation exposure to be reduced to the conditions of a standard irradiation. It can be obtained on the basis of mean-tissue equivalent dose values calculated for each space radiation source and transmission coefficients describing the influence of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body on the radiobiological effects. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can also be accounted for. In terms of the generalized dose, it is possible to assess the nature and extent of lowering a crew working capacity, as well as radiation risk, both during a flight and post flight period.

Unique broad-spectrum neutron sensing instrument

This article reviews the design and operation of a transportable neutron spectrometer. Four of these instruments were produced and have been widely used for applications such as the assessment and classification of radiation hazards at field sites in the United Kingdom and Europe. An overview of the instrument hardware is presented, together with a description of the six sensor channels, their associated processing electronics and the host data logger computer. Spectral unfolding is also summarized and a sample spectra, which was measured from outside a fuel flask, is given.

Hybrid moment-method physical-optics formulation for modeling the electromagnetic behavior of on-board antennas

On-board antenna design involves aspects such as optimization of radiation patterns, control of electromagnetic interference and disturbance (EMC/EMI), the assessment of radiation hazards, etc. This paper describes a hybrid moment-method physical-optics (MM–PO) approach that has been shown to be an efficient and accurate tool to predict the above-mentioned electromagnetic aspects concerning antennas installed on board. Some numerical results are presented and compared with a reference MM solution in order to illustrate the accuracy and efficiency of the proposed approach. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 88–93, 2000.