THE NATURAL RADIATION ENVIRONMENT: 8th International Symposium (NRE VIII)
1034(2008); http://dx.doi.org/10.1063/1.2991254View Description Hide Description
The naturally occurring radionuclides radium (Ra‐226) and polonium (Po‐210) have the potential to be used for criminal acts. Analysis of international incident data contained in the Database on Nuclear Smuggling, Theft and Orphan Radiation Sources (CSTO), operated at the University of Salzburg, shows that several acts of murder and terrorism with natural radionuclides have already been carried out in Europe and Russia. Five different modes of attack (T) are possible: (1) Covert irradiation of an individual in order to deliver a high individual dose; (2) Covert irradiation of a group of persons delivering a large collective dose; (3) Contamination of food or drink; (4) Generation of radioactive aerosols or solutions; (5) Combination of Ra‐226 with conventional explosives (Dirty Bomb).
This paper assesses the risk (R) of such criminal acts in terms of: (a) Probability of terrorist motivation deploying a certain attack mode T; (b) Probability of success by the terrorists for the selected attack mode T; (c) Primary damage consequence (C) to the attacked target (activity, dose); (d) Secondary damage consequence (C′) to the attacked target (psychological and socio‐economic effects); (e) Probability that the consequences (C, C′) cannot be brought under control, resulting in a failure to manage successfully the emergency situation due to logistical and/or technical deficits in implementing adequate countermeasures. Extensive computer modelling is used to determine the potential impact of such a criminal attack on directly affected victims and on the environment.
1034(2008); http://dx.doi.org/10.1063/1.2991200View Description Hide Description
In this paper, an account is given of the development, calibration and field use of a passive alpha track detector sensitive to thoron as well as to radon. No database of thoron and thoron progeny concentrations in dwellings in Ireland exists and, as a result, the level of exposure of the Irish population to thoron and its progeny is unknown. As an initial or pilot stage in establishing such a data base measurements of thoron and thoron progeny concentrations (the latter expressed in Equilibrium Equivalent Thoron Concentration (EETC)) were made in 40 randomly chosen Irish dwellings. The EETC measurements were made using a passive thoron progeny deposition rate monitor designed and supplied by NIRS (Japan). In addition standard unmodified SSI passive radon detectors were used to measure radon in these dwellings. The measured thoron concentrations ranged from below the level of detection to while the radon gas ranged from 15 to The thoron progeny EETC values for these dwellings ranged from 0.03 to An account is also given of the dosimetric implications of these measurements.
1034(2008); http://dx.doi.org/10.1063/1.2991210View Description Hide Description
In 1900, Dorn discovered the emanation in the uranium series that eventually became the well‐known gas From 1900 through 1908, it was demonstrated that is a radioactive gas found in tap water, highly condensable at low temperatures with a half‐life of approximately 3.7 days and can be collected on charcoal by adsorption. Although, radon was discovered in 1900, the effects of prolonged exposure had been suspected and noted 300 years earlier among underground miners who developed lung cancer. During the period from 1924–1932, it was suggested that radon was the cause of high lung cancer incidence. In 1951, researchers at the university of Rochester N.Y. pointed out that the lung cancer health hazard was from the alpha radiation dose delivered by the radon decay products that deposited in the respiratory tract. The findings of the BEIR Committee Report VI, which was based on epidemiological studies in different groups of mines in the 1950's and 1960's and on laboratory studies, showed that from 60,000 miners over 2,600 developed lung cancer where only 750 were expected.
Since 1998, the epidemiological study conducted in Iowa US, showed beyond any reasonable doubt that radon decay products cause lung cancer among women who lived at least twenty years in their homes. This paper will cover early radon measurements in soil, building material, ground water and in different air environments such as in the atmosphere, caves spas, underground mines and in residential indoor air environment. Radon measurements were conducted in many areas for diagnostic purposes. Radon was used as natural tracer to study air masses, vertical diffusion, and atmospheric studies, in earthquake prediction, and as a geological indicator for radium and uranium. In the early radon measurements, electroscopes, electrometers and primitive ionization chambers were used for many years. In the 1940's fast pulse ionization chambers replaced total ionization chambers. From the mid 1950's onwards a variety of radon measuring instruments were developed to assess the radon and radon decay product exposure to underground miners, workers at contaminated sites with uranium and radium tailings and to the general public in residential buildings. In the last twenty years, new instruments and methods were developed to measure radon by using grab, integrating and continuous modes of sampling. The most common are scintillation cell monitors, activated carbon collectors, electret ionization chambers, alpha track detectors, pulse and current ionization chambers and solid‐state alpha detectors.
1034(2008); http://dx.doi.org/10.1063/1.2991243View Description Hide Description
It is common practice to measure radon gas concentration as a surrogate of its decay products by using a known value of the equilibrium factor. Unfortunately a similar approach has been often used to infer the thoron gas concentration from the measurement of in spite of the fact that the concept of an equilibrium factor is no more meaningful. In order to study the profile of thoron and its decay products in the vicinity of the wall, a passive monitor consisting of a 25cm‐long diffusion tube has been used. The most difficult problem in practice is to keep this monitor‐tube perpendicular to vertical walls. This problem has been solved by using a 25cm‐long nose of a Pinocchio mask. The most important characteristic of the long‐nose‐geometry for thoron measurements is that it makes it possible to estimate the largest indoor concentrations of thoron, which occur at zero distances from the source under stagnant air conditions. When thoron measurements are carried out without the help from Pinocchio, it is important that the monitors lay adjacent to the thoron emanating surface. Different types of compact passive monitors are available which make it possible to measure thoron in the vicinity of the exhaling surfaces. In these cases, a combination of two different passive monitors is used in order to differentiate the thoron from radon. Because of the lack of correlation between thoron gas and its decay product, a correct dose estimate requires the measurement of the concentration of both radionuclides ( and ) separately. While the thoron gas should be measured in the vicinity of the exhaling surface just the opposite is true for the which should be measured tens of cm away from said surface. Passive measurements of are typically carried out by track detectors with suitable degraders of the alpha‐particles energy. Once again Pinocchio can be very helpful, since by positioning the at the tip of his nose, he can ensure the exposure of the detector always at the same distance from said exhalation surface.
Risk of Cancer in relation to Natural Radiation, including Radon: Evidence from Epidemiological Studies1034(2008); http://dx.doi.org/10.1063/1.2991264View Description Hide Description
A review of recently published epidemiological studies on populations exposed to natural background ionizing radiation is proposed. The advantages and disadvantages of different types of epidemiological studies as well as the uncertainty linked to multiple exposures are discussed. As radon is the greatest source of natural radiation, particular attention is given to quantification of risk obtained through cohort studies of uranium miners and after joint analysis of case‐control studies on lung cancer and residential radon.
1034(2008); http://dx.doi.org/10.1063/1.2991277View Description Hide Description
1034(2008); http://dx.doi.org/10.1063/1.2991281View Description Hide Description
Depleted Uranium (DU) is used in ammunition designed for armour‐piercing. DU was used in the Gulf war 1991, wars in Bosnia 1994–1995, Kosovo 1999 and Iraq 2003. The United Nations Environmental Programme (UNEP) Post‐Conflict Branch investigated sites where DU was used and evaluated health and environmental risks during missions to Kosovo, Serbia and Bosnia. During a mission to Lebanon in 2006, UNEP also sampled areas where DU was supposed to have been used but did not find any DU. Due to the grave risks to the lives of UN personnel, no UNEP mission was carried out in Iraq. UNEP has provided training for personnel engaged in decontamination of DU in Bosnia and Iraq.
1034(2008); http://dx.doi.org/10.1063/1.2991282View Description Hide Description
Low dose effects of alpha particles at the tissue level are characterized by the interaction of single alpha particles, affecting only a small fraction of the cells within that tissue. Alpha particle intersections of bronchial target cells during a given exposure period were simulated by an initiation‐promotion model, formulated in terms of cellular hits within the cycle time of the cell (dose‐rate) and then integrated over the whole exposure period (dose). For a given average number of cellular hits during the lifetime of bronchial cells, the actual number of single and multiple hits was selected from a Poisson distribution. While oncogenic transformation is interpreted as the primary initiation step, stimulated mitosis by killing adjacent cells is assumed to be the primary radiological promotion event. Analytical initiation and promotion functions were derived from experimental in vitro data on oncogenic transformation and cellular survival.
To investigate the shape of the lung cancer risk function at chronic, low level exposures in more detail, additional biological factors describing the tissue response and operating specifically at low doses were incorporated into the initiation‐promotion model. These mechanisms modifying the initial response at the cellular level were: adaptive response, genomic instability, induction of apoptosis by surrounding cells, and detrimental as well as protective bystander mechanisms. To quantify the effects of these mechanisms as functions of dose, analytical functions were derived from the experimental evidence presently available. Predictions of lung cancer risk, including these mechanisms, exhibit a distinct sublinear dose‐response relationship at low exposures, particularly for very low exposure rates.
1034(2008); http://dx.doi.org/10.1063/1.2991283View Description Hide Description
Calculations of cosmic‐ray propagation through the heliosphere, in the terrestrial atmosphere using a combination of a modified version of the adjoint Monte Carlo code, ATROPOS, and a suitably modified version of the deterministic transport code, PLOTINUS. ATROPOS solves the Parker heliospheric transport code in one and two dimensions in a 3‐dimensional heliosphere and provides cosmic‐ray spectra to be used by PLOTINUS to determine the radiation effects of interest. Other cosmic‐ray properties, such as the deceleration time (related to the so‐called deceleration potential) and the angular distribution of cosmic rays at earth orbit will also be described.
Aircrew Exposure To Cosmic Radiation Evaluated By Means Of Several Methods; Results Obtained In 20061034(2008); http://dx.doi.org/10.1063/1.2991284View Description Hide Description
Routine evaluation of aircraft crew exposure to cosmic radiation in the Czech Republic is performed by means of calculation method. Measurements onboard aircraft work as a control tool of the routine method, as well as a possibility of comparison of results measured by means of several methods. The following methods were used in 2006: (1) mobile dosimetry unit (MDU) type Liulin—a spectrometer of energy deposited in Si‐detector; (2) two types of LET spectrometers based on the chemically etched track detectors (TED); (3) two types of thermoluminescent detectors; and (4) two calculation methods. MDU represents currently one of the most reliable equipments for evaluation of the aircraft crew exposure to cosmic radiation. It is an active device which measures total energy depositions in the semiconductor unit, and, after appropriate calibration, is able to give a separate estimation for non‐neutron and neutron‐like components of H*(10). This contribution consists mostly of results acquired by means of this equipment; measurements with passive detectors and calculations are mentioned because of comparison. Reasonably good agreement of all data sets could be stated.
PARMA: PHITS‐based Analytical Radiation Model in the Atmosphere—Verification of Its Accuracy in Estimating Cosmic Radiation Doses1034(2008); http://dx.doi.org/10.1063/1.2991285View Description Hide Description
Estimation of cosmic‐ray spectra in the atmosphere has been an essential issue in the evaluation of the aircrew doses. We therefore developed an analytical model that can predict the terrestrial neutron, proton, He nucleus, muon, electron, positron and photon spectra at altitudes below 20 km, based on the Monte Carlo simulation results of cosmic‐ray propagation in the atmosphere performed by the PHITS code. The model was designated PARMA. In order to examine the accuracy of PARMA in terms of the neutron dose estimation, we measured the neutron dose rates at the altitudes between 20 to 10400 m, using our developed dose monitor DARWIN mounted on an aircraft. Excellent agreement was observed between the measured dose rates and the corresponding data calculated by PARMA coupled with the fluence‐to‐dose conversion coefficients, indicating the applicability of the model to be utilized in the route‐dose calculation.
1034(2008); http://dx.doi.org/10.1063/1.2991185View Description Hide Description
Radiation environment has been studied at high‐mountain observatories and onboard spacecraft. The most important contribution to this environment at high‐mountain observatories represents cosmic radiation component. We have been studied this environment in two high‐mountain observatories: one situated on the top of Lomnický Štít, High Tatras, Slovakia, and another one close to the top of Moussala, Rila, Bulgaria (Basic Environment Observatory—BEO). The studies have been performed using: an energy deposition spectrometer with a Si‐diode (MDU) developed at BAS, Sofia, permitting to estimate non‐neutron as well as neutron component of the radiation field; other active equipment designated to measure natural radiation background, and thermoluminescent detectors as passive dosimeters. Basic dosimetry characteristics of these fields are presented, analyzed, and discussed; they are also compared with the estimation of cosmic radiation component as published in the Report of UNSCEAR 2000. Measuring instruments mentioned above, together with an LET spectrometer based on chemically etched track detectors have been also used to characterize radiation environment onboard spacecraft, particularly International Space Station. They have been exposed on the surface and/or inside a phantom. Some of results obtained are presented, and discussed.
1034(2008); http://dx.doi.org/10.1063/1.2991186View Description Hide Description
Beryllium‐7 is a natural radionuclide that enters into the ecosystems through wet and dry depositions and has numerous environmental applications in terrestrial and aquatic ecosystems. Atmospheric wet deposition of was measured in central Argentina. Rain traps were installed (1 m above ground) and individual rain events have been collected. Rain samples were filtered and analyzed by gamma spectrometry. The gamma counting was undertaken using a 40%‐efficient p‐type coaxial intrinsic high‐purity natural germanium crystal built by Princeton Gamma‐Tech. The cryostat was made from electroformed high‐purity copper using ultralow‐background technology. The detector was surrounded by 50 cm of lead bricks to provide shielding against radioactive background. The detector gamma efficiency was determined using a water solution with known amounts of chemical compounds containing long‐lived naturally occurring radioisotopes, and Due to the geometry of the sample and its position close to the detector, the efficiency points from the decay, had to be corrected for summing effects. The measured samples were 400 ml in size and were counted curing one day. The detection limit for the present measurements was as low as Thirty two rain events were sampled and analyzed (November 2006‐May 2007). The measured values show that the events corresponding to low rainfall are characterized by significantly higher activity concentrations The activity concentration of each individual event varied from 0.8 to while precipitations varied between 4 and 70 mm. The integrated activity by event of was fitted with a model that takes into account the precipitation amount and the elapsed time between two rain events. The integrated activities calculated with this model show a good agreement with experimental values.
1034(2008); http://dx.doi.org/10.1063/1.2991187View Description Hide Description
Radiation and Nuclear Safety Authority—STUK monitors the amount of airborne radioactivity with three aerosol samplers in Northern Finland. Naturally occurring radioactive nuclei and can be seen. A time series was constructed for both nuclei observed at Rovaniemi (lat 66,3° N long 25,4° E). The most consistent time series was found to be from Ivalo (lat 68,64° N long 27,57° E). The time series of and were compared and the ratio was plotted. A time series analysis was performed for Ivalo time series to find periodicities. Two periodicities longer than one year was found 4,3 years and 11 years, also 3 periodicities shorter than one years was found 1,7 months, 4 months and 6 months. The annual average activities at Rovaniemi and Ivalo were also compared with the annual galactic cosmic ray intensity observed with neutron monitor at Oulu (65.05°N, 25.47°E) by Sodankylä Geophysical Observatory.
1034(2008); http://dx.doi.org/10.1063/1.2991188View Description Hide Description
Thorium, cerium, lanthanum and other rare earths have been extracted from monazite sands for a long time due to several reasons. At the end of the XIX century monazite sands from Brazilian beaches were concentrated gravimetrically to be clandestinely transported to Europe to be used in the manufacture of fabric bags to be burned. Those bags when burning had their brightness enhanced by a mixture of thorium, lanthanum and cerium. The thorium oxide percentages found in monazite concentrates from several parts of the world range from 1 to 11%. While not burned or processed chemically monazite concentrate can be considered hazardous only due to gamma radiation and (thoron) inhalation by those who stay very close to storage piles. In old monazite plants the thoron concentration in air reached levels higher than Fortunately, the industrial hygiene improved with time and today's monazite separation plants do not present such high thoron concentrations. Old and recent data from rare earth processing plants suggest that occupational annual doses indoors may be up to two orders of magnitude higher than the worldwide average effective dose reported by the United Nations Scientific Committee on the Effects of the Atomic Radiation (UNSCEAR) due to the inhalation of thoron. Consumer products, like fabric bags used in gas or kerosene lamps have concentrations of the order of Remnants of the monazite industrial cycle can present activity concentrations as high as Piles of monazite concentrates were kept for strategic reasons during cold war times in several places of the territories of the United States and the former Soviet Union. Cleanup at those sites may be hazardous mostly due to high concentrations of thoron daughters that may be inhaled by workers. The paper will take a critical look at the naturally occurring radioactive materials (NORM) extant in the monazite cycle and its remnants.
1034(2008); http://dx.doi.org/10.1063/1.2991189View Description Hide Description
Radon gas measuring services in Switzerland must be approved by the Federal Office for Public Health (FOPH). The maintenance of approval includes the obligation to participate in annual intercomparison exercises performed at the radon gas reference laboratory of the Paul Scherrer Institut (PSI). In eleven intercomparison exercises since 1996 a total of 1,515 radon gas detectors was subjected to radon gas exposures between and Preparation and read‐out of electret detectors is performed by the measuring services. About one percent of these detectors were observed with false positive results. The quality of results of etched‐track detectors is determined by the quality assurance system and calibration of the supplier. In one case, a measuring service lost approval due to quality problems of the detector manufacturer. Double blind tests yielded less good results compared to the detectors of the same measuring service participating officially.
1034(2008); http://dx.doi.org/10.1063/1.2991190View Description Hide Description
The experience gained in measuring radon in homes in Ireland over the past 20 years is used to identify four key strategic decisions that need to be made in designing and implementing a successful program. These are (1) the need to address both individual and collective dose; (2) the type of radon mapping that needs to be undertaken; (3) the criteria to be considered in setting a reference level; and (4) a policy of information and advice versus enforcement. Each of these issues is discussed from a policy viewpoint and the radon situation in Ireland is used to support the arguments made.
The Measurement of Size Distribution of Indoor Natural Radioactive Aerosols by Imaging Plate Technique1034(2008); http://dx.doi.org/10.1063/1.2991191View Description Hide Description
The indoor radioactive aerosols of radon decay products are considered as a main radioactive contaminant in human environment. In this study, the particle size distribution was measured with low pressure cascade impactor and imaging plate. The temporal and spatial variations of indoor radioactive aerosols were measured at eight indoor sites of Nagoya, Japan. Effective doses were assessed using ICRP 66 and UNSCEAR 2000 approaches.
1034(2008); http://dx.doi.org/10.1063/1.2991192View Description Hide Description
According to recommended approach there are six (from total of twelve) open‐to‐public caves in Czech Republic, reaching near to an effective lung‐dose of 6mSv/year. A conservative approach for estimating the potential effective lung‐dose in caves (or underground) is based on two season's measurements, using solid state alpha track detector (Kodak in plastic diffusion chamber). The obtained dataset is converted into an annual effective dose, in agreement with the ICRP65 recommendation, using the “cave factor” 1.5. The value of “cave factor” which depends on the spectrum of aerosol particles, or on the proportional representation of the unattached/attached ratio (6.5 : 93.5 for residential places, 13.6 : 86.4 for caves due to lower concentration of free aerosols) and on the equilibrium factor. Thus conversion factor is 1.5 times higher in comparison with ICRP 65. Is this correct? Because a more precisely determined dose value would have a significant impact on radon remedies, or on restricting the time workers stay underground, a series of measurement was initiated in 2003 with the aim to specify input data, computation and errors in effective dose assessment in each one of the evaluated caves separately. The enhancement of personal dosimetry for underground work places includes a study of the given questions, from the following points of view in each cave: continual radon measurement; regular measurements of radon and its daughters to estimate the equilibrium factor and the presence of free regular indoor air flow measurements to study the location of the radon supply and its transfer among individual areas of the cave; natural radioactive element content evaluation in subsoil and in water inside/outside, a study of the radon sources in the cave; determination of the free fraction from continual unattached and attached fraction measurement (grid and filter); thoron measurement. Air flow measurements provide very interesting information about the origin of “radon pockets” with very high radon concentration, and enable study of the location of the radon supply and its transfer among individual areas of the cave. Most of the results show the equilibrium factor around and the unattached fraction around 2%–30%. One of the most important question remains: how accurately was the unattached fraction measured? Part of this project was to verify the influence of etched track detector position in the cave.