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At least 19 recordsLinked to original sources

Environmental impact of radionuclide migration in groundwater from a low-intermediate level radioactive waste repository.

The radionuclide migration from a certain Chinese repository with low-intermediate level radioactive solid waste is studied. The migration in groundwater is analyzed and computed in detail. Under presumption of normal releasing, or the bottom of the repository has been marinated for one month with precipitation reaching 600 mm once and a 6 m aerated zone exists, a prediction for 7 radionuclides is conducted. It shows that the aerated zone is the primary barrier for migration. The migration for radionuclides 60Co, 137Cs, 90Sr, 63Ni, etc. will be retarded in it within 500 years. The concentration of 239Pu will be decreased by amount of 6 order. Only 3H and 14C can migrate through the aerated zone. The radionuclides that go through the aerated zone and enter the aquifer will exist in spring, stream and sea. Based on this, the intake dose by residents in different age group resulting from drinking contaminated spring water, eating seafood is calculated. The results showed that the impact of the repository to the key resident group is lower than the limit in national repository regulation standard. This complies with the repository management target.

Air↗

Sorption of radioactive contaminants by sediment from the Kara Sea.

The purpose of this study is to quantify some of the parameters needed to perform near-field modelling of sites in the Kara Sea that were impacted by the disposal of radioactive waste. The parameters of interest are: the distribution coefficients (Kd) for several important radionuclides, the mineralogy of the sediment, and the relationship of Kd to liquid-to-solid ratio. Sediment from the Kara Sea (location: 73 degrees 00'N, 58 degrees 00'E) was sampled from a depth of 287 m on August 23/24, 1992. Analysis of the material included mineralogy, grain size and total organic carbon (TOC). Uptake kinetics were determined for 85Sr, 137Cs, 241Am, 99Tc, 1251, 232U and 210Pb and distribution coefficients (Kd) were determined for these radionuclides using batch type experiments. Sorption isotherms, developed for 137Cs, 85Sr and 99Tc, were linear in each case. Increasing the liquid-to-solid ratio strongly increased uptake of 137Cs and moderately increased uptake of 99Tc. Analysis for anthropogenic radionuclides indicated the presence only of 239/240Pu in the sediment with the highest activity (at the top section of the core) being 0.420 Bq kg(-1). Other anthropogenic radionuclides were below detection limits.

Absorption↗

Factors determining the radioactivity levels of waters in the province of Cáceres (Spain).

In an extensive study of different types of water in the province of Cáceres (Spain) in order to determine their total alpha- and total beta-radioactivity contents, several factors were found to have a decisive influence on their radioactivity levels. Thus, parameters such as total hardness and pH can be determinative according to the lithological type of the aquifer or according to the subterranean or surface origin of the hydrological resource. Waters from classic lithologies, or originating from a well, possess above-average radioactivity indices, surpassing in numerous cases the indicative levels set by current Spanish legislation. In contrast, surface waters from rivers, in practically all cases, possess below-average radioactivity indices.

Fresh Water↗

Comparison of inductively coupled plasma-mass spectrometry and radiochemical techniques for total uranium in environmental water samples.

Inductively coupled plasma-mass spectrometry (ICP-MS) method EPA 200.8 is gradually finding acceptance as an alternative to uranium analysis. A comparison of the ICP-MS with the accepted radiochemical method EPA 908.0 has been carried out based on data from laboratory control standards, national proficiency test samples, and environmental and drinking water samples from the State of Utah. The method detection limit (MDL) for ICP-MS was determined to be 0.017 microg/L or (0.011 pCi/L), and the minimum reporting limit (MRL) was 0.17 microg/L (MDL x 10) or (0.11 pCi/L). The minimum reporting limit for radiochemical 908.0 method is 1 pCi/L. Our spiked matrix recoveries, spiked blank samples, and reference materials deviate only a few percentage from the listed true values. Results demonstrate that the ICP-MS is a superior analytical tool for the determination of uranium in drinking and environmental waters at concentrations required by the United States Environmental Protection Agency.

Mass Spectrometry↗

Probabilistic risk assessment of nephrotoxic effect of uranium in drinking water.

Assessments of the health effects of pollutants generally use models in which exposure variables and model parameters are point values, often chosen as conservative estimates. A more realistic approach is to characterize the uncertainty of each variable and parameter explicitly as a probability distribution. This paper presents a probabilistic version of an established model for metabolism of ingested uranium and characterizes the parameters of the model as distributions. It then characterizes the uncertainty of the threshold level for nephrotoxic risk of uranium, and uses distributions of the heterogeneity in drinking water intake of uranium in the U.S. to assess nephrotoxic risk. It further evaluates the implications of inadequate data on the heterogeneity of dietary intake.

Humans↗

Study of the occurrence of 222Rn and 226Ra in drinking water in Spain.

With the aim of determining the contribution of water to the background of natural radiation in Spain, the 222Rn concentration levels were measured in domestic drinking water from a large part of the country. The water analyzed, both surface and groundwater, was collected in two areas of very distinct geological characteristics, pre-selected for the likelihood of their containing high levels of 222Rn. This water was measured using a coaxial detector of high purity Ge. The overall results demonstrate a log-normal distribution of 222Rn levels, with a geometric and arithmetic means of 10 and 381 Bq L-1, respectively, and a range between detection limit of 2 Bq L-1 and a maximum of 31,000 Bq L-1. The 222Rn concentrations measured in surface water are generally below the detection limit. Significant differences have been found depending on the geological characteristics of the area of reference, although the very distinct concentration levels of 222Rn found in samples of similar lithology imply the influence of more complex factors in the solution of 222Rn in water. Due to the relationship between radon and 226Ra, the concentration of the latter was measured in the same water using radiochemical separation and a scintillation ZnS(Ag) detector. No significant correlation between 226Ra and 222Rn concentrations has been observed unless measurements carried out in a high background radiation region are considered separately.

Geography↗

Variation of 222Rn in public drinking water supplies.

The U.S. Environmental Protection Agency has proposed regulating 222Rn in public drinking water. When implemented, the regulation will require periodic sampling to demonstrate compliance. The work reported in this paper was conducted to evaluate how reliably grab samples can be used to characterize the average 222Rn concentration in a groundwater source. Periodic samples were collected from 14 wells over sampling periods ranging from 2 to 26 mo. Samples were collected using a "slow-flow" collection method, and samples were analyzed using liquid scintillation techniques. The results reveal variation in 222Rn concentration over the study period; however, for the 1,468 samples collected from the 14 wells, approximately 97% of the measurement results were within 30% of the mean value for the well.

Geological Phenomena↗

Effective dose to the public from 226Ra in drinking water supplies of Iran.

One of the most important and prevalent isotopes of radium (Ra) in the human food chain, and especially in drinking water, is 226Ra. To determine the contribution of this radionuclide to the annual effective dose to the public in Iran, a national program for determination of this radionuclide was established. Over 500 water samples from different surface and ground water supplies including wells, rivers and springs, as well as hot springs and sea water from the Caspian Sea and Persian Gulf have been analyzed. An emanation method with a minimum detection limit of less than 2 mBq L(-1) was developed and applied in this study. Unweighted mean concentrations of 3.3 mBq L(-1) and 8.0 mBq L(-1) were determined in surface and ground drinking water supplies, respectively. Based on such values, mean unweighted annual intakes of 226Ra were found to be 0.85 Bq for an infant, 1.97 Bq for a child, and 2.82 Bq for an adult, which correspond to mean unweighted annual effective doses of 0.17 microSv y(-1), 0.39 microSv y(-1), and 0.56 microSv y(-1), respectively. The mean 226Ra concentrations in hot springs were higher with a maximum of 146.5 Bq L(-1) measured in the Ab-e-Siah hot spring in Ramsar, a town on the coast of the Caspian Sea in Iran.

Adult↗

Radon in public water supplies in Migdonia basin, Central Macedonia, Northern Greece.

The main objective of this work is the accurate measurement of radon concentration in the public water supplies of the Migdonia basin in Northern Greece. The main aim is to localize the sub-areas that present high radon concentrations in water and to inform the local authorities so that more detailed studies might be set up in these areas. About 80 samples from special bore holes and taps that supply the local population with fresh water were collected in order to obtain detailed radon measurements. For the analyses, a liquid scintillation counting system, using the Packard protocol for measuring radon in water, was employed. The results of the investigation show that radon concentrations in these public water supplies are significant. The concentrations ranged from background concentrations to 170 Bq x L(-1). The level of 50 Bq x L(-1) is exceeded in 23% of water supplies. These preliminary results with initial data interpretation and inter-comparison assessment are presented. These results of the analyses showed that elevated radon concentrations were detected in water samples from an area at the western part of the Lake Volvi, due probably to the local intense tectonism, and from a village above the Lake Koronia.

Fresh Water↗

[The sanitary status of natural waters on the territory of Moscow (according to the results of the examination of chemical and radionuclide composition)].

The paper presents the results of examination of the chemical and radionuclide composition of natural waters and snow cover in Moscow. Areas with abnormal contents of tritium are found in the underground and surface waters and snow cover. The high concentrations of strontium, boron, fluorine, and barium are ascertained to be associated with natural factors. Areas of technogenically polluted underground waters are identified. Recommendations are given for further studies. Particular emphasis is laid on that the artesian wells that are a reservoir source of water supply under emergency are to be revised.

Barium↗

Measurement of helium isotopes in soil gas as an indicator of tritium groundwater contamination.

The focus of this study was to define the shape and extent of tritium groundwater contamination emanating from a legacy burial ground and to identify vadose zone sources of tritium using helium isotopes (3He and 4He) in soil gas. Helium isotopes were measured in soil-gas samples collected from 70 sampling points around the perimeter and downgradient of a burial ground that contains buried radioactive solid waste. The soil-gas samples were analyzed for helium isotopes using rare gas mass spectrometry. 3He/4He ratios, reported as normalized to the air ratio (RA), were used to locate the tritium groundwater plume emanating from the burial ground. The 3He (excess) suggested that the general location of the tritium source is within the burial ground. This study clearly demonstrated the efficacy of the 3He method for application to similar sites elsewhere within the DOE weapons complex.

Environment↗

90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans--WOMARS results.

Under an IAEA's Co-ordinated Research Project "Worldwide Marine Radioactivity Studies (WOMARS)" 90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans have been investigated. The Pacific and Indian Oceans were divided into 17 latitudinal boxes according to ocean circulation, global fallout patterns and the location of nuclear weapons test sites. The present levels and time trends in radionuclide concentrations in surface water for each box were studied and the corresponding effective half-lives were estimated. For the year 2000, the estimated average 90Sr, 137Cs and (239,240)Pu concentrations in surface waters of the Pacific and Indian Oceans varied from 0.1 to 1.5 mBq/L, 0.1 to 2.8 mBq/L, and 0.1 to 5.2 microBq/L, respectively. The mean effective half-lives for 90Sr and 137Cs in surface water were 12+/-1 years for the North, 20+/-1 years for the South and 21+/-2 years for the Equatorial Pacific. For (239,240)Pu the corresponding mean effective half-lives were 7+/-1 years for the North, 12+/-4 years for the South and 10+/-2 years for the Equatorial Pacific. For the Indian Ocean the mean effective half-lives of 137Cs and (239,240)Pu were 21+/-2 years and 9+/-1 years, respectively. There is evidence that fallout removal rates before 1970 were faster than those observed during recent decades. The estimated surface water concentrations of 90Sr, 137Cs and (239,240)Pu in latitudinal belts of the Pacific and Indian Oceans for the year 2000 may be used as the average levels so that any new contribution from nuclear facilities, nuclear weapons test sites, radioactive waste dumping sites and from possible nuclear accidents can be identified.

Cesium Radioisotopes↗

Investigation of mine and industry dumps in the FRG in relation to a possible release of natural radioactive elements.

More than 350 dumps of mines and industries in two federal states of the FRG were recorded, measured radiometrically, evaluated, and some of them sampled. Most of the mine dumps belonged to old and smaller residues from lead/zinc and iron ore mining, while the largest depositions contain tailings of modern ore beneficiation or flyash disposal. All mine dumps from uranium exploration in Baden-Württemberg and Bavaria were investigated. The highest doses, up to 100 mSv/a, were found on the piles of the uranium exploration. These depositions, which are supervised and licensed, are followed, in terms of surface dose, by the old uncontrolled mine dumps of silver/cobalt mining with doses up to 20 mSv/a. The numerous porphyry and granite quarries show doses between 1 and 2 mSv/a, as do flyash and slag dumps. The lowest doses were found on the dumps of the hydrothermal Pb/Zn and iron ore deposits, while the slag piles of iron ore processing showed higher thorium values. Assays for Ra-226 and Pb-210 of the materials deposited confirmed the radiometric results. Analyses of seepage waters and gallery waters showed only very few values exceeding the derived drinking water concentrations.

Environmental Pollution↗

Radiation exposure from radionuclides in ground water: an uncertainty analysis for selected exposure scenarios.

The uncertainty of the potential radiation exposure of the general population has been estimated for a normalized contamination of ground water that is being used as drinking water for humans and animals, for irrigation of food and feed crops, and for fish production in freshwater bodies. The frequency distributions of annual effective dose equivalents were calculated assuming a normalized activity concentration in water of 1 Bq/l for each radionuclide considered. Estimated frequency distributions of the parameters were used as model input. This estimation is based on an exposure scenario which reflects the present radioecological conditions. Another important source for the uncertainty of the potential dose due to radionuclides released to the ground water is the uncertainty of the exposure scenario. Since such a contamination may not occur before some time in the far future, it is impossible to predict the exact boundary conditions. Therefore, scenarios were stimulated with modified consumption habits, more extensive farm management and different climatic conditions. The distributions of the potential doses cover in general about a factor of 10-20. The intake of drinking water, the root uptake and the contamination of fish are most important for the resulting potential radiation exposure. For nearly all radionuclides, the intake of drinking water dominates the potential exposure. In most cases radioactive daughter nuclides are of minor importance. In general, the influence of the exposure scenario on the dose is relatively small.

Animals↗