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At least 1,153 records · Page 64Linked to original sources
PubMed1983

Plutonium--its behavior in natural water systems and assimilation by man.

There are a number of factors which must be considered in establishing whether or not the inadvertent intrusion of a sizable amount of plutonium-bearing material into a natural water system may have a significant impact on the health of those individuals who use that system as a drinking water resource. These factors include the chemical form(s) and solubility of plutonium in natural waters, its behavior in relation to natural processes (geochemical and biological), its fate in water treatment systems, and its uptake by man from drinking water. From the results obtained in our investigations of the behavior in natural water systems, it appears that (1) the chemical forms of plutonium dissolved in natural waters are Pu(IV) and Pu(V), (2) the soluble plutonium in many waters is bound to the organic constituents which probably enhances plutonium solubility, (3) the natural process responsible for the removal of plutonium from water is adsorption onto sediments, and (4) in water treatment systems, soluble plutonium is oxidized to the VI state and this form is not removed. From our investigations of gastrointestinal absorption, it appears that the value for f1, the fraction transferred from the gut to blood, is surely greater than 1 X 10(-3) and may be as high as 2 X 10(-1). Consideration of these and other factors indicates that, in the event of an accident, the concentration of plutonium could, in certain small natural water systems, approach and perhaps even exceed, the MPC for plutonium. However, the impact on the health of the affected population would not be inordinately high.

Humans↗
PubMed1985

Distribution of gamma exposure rates in a reactor effluent stream flood plain system.

Ground-level gamma dosimetry surveys were conducted along the length of a radiocesium-contaminated reactor effluent stream flood plain system to determine the extent and patterns of isotope distribution over a decade after reactor releases were stopped. The maximum mean exposure rates were found at upstream locations near the source of the contamination and in a downstream sedimentary delta. Gamma exposure rates were not uniformly distributed and high exposure rates were generally restricted to small areas of the flood plain. There was little similarity in either the spatial distribution or magnitudes of maximum gamma exposure rates across flood plains along the stream. Frequency the measured exposure rates tended to be highly skewed and most closely approximated the log-normal distribution in most areas along the stream. However, the complex and changing patterns of dose distributions strongly affected the ability to predict the probability of encountering unusually high exposure rates. Complex statistical and distributional models are required to provide precise descriptions of the dosimetry environment in such complex ecosystems and different models could be required on a site-by-site basis.

Cesium Radioisotopes↗
PubMed1991

Monitoring underground radiation fields using powdered calcium sulfate thermoluminescent dosimeters.

Powered thermoluminescent dosimeters, CaSO4:Dy, were used to monitor underground radiation fields. Methods of monitoring at selected sites in Taiwan are described; exposure rates above ground at the monitoring sites are also included for comparison. Differences in exposure rates between above ground at 1 m and underground at -2 m may reach 0.516 nC kg-1 h-1. The key factor affecting exposure rates underground is the water content in soil or precipitation that may reduce the diffusion of Rn. The difference in exposure rates between rainy days and sunny days may reach 0.774 nC kg-1 h-1. An example of applying this monitoring technique at a radwaste repository is given.

Calcium Sulfate↗
PubMed1993

Impact of a 2 MWth research reactor on radioactivity in sediments.

The objective of this study was to determine the environmental impact caused by liquid effluent discharge from the University of Virginia's 2 MWth Research Reactor during the course of its first quarter-century of normal operation. Sediment samples were collected from the reactor pond (situated in a restricted area next to the Reactor Facility), the stream feeding it, and its exit stream. For a comparative study, sediment samples were taken from a nearby closed reference pond having no direct link with the reactor pond. Concentrations of long-lived alpha, beta and gamma emitting radionuclides, from natural and nuclear weapons fallout sources, were detected in pond and stream sediments. Low levels of activation product radioisotopes from the research reactor were detected in the reactor pond sediment. It was observed that both natural and artificial radionuclide concentrations were higher in the UVAR pond (with the exception of 54Mn and 65Zn) as compared to exist stream and reference sediments.

Nuclear Reactors↗
PubMed1995

Uptake of 137Cs in vegetable crops grown on a contaminated lakebed.

Mean concentrations and plant:soil concentration ratios of 137Cs were determined for six vegetable crops grown on an exposed, contaminated lakebed of a former reactor cooling reservoir in South Carolina. Each crop species was grown with or without potassium fertilizer. Selected crops were also irrigated with either reservoir water or groundwater. Subsamples of crops were prepared for human consumption before analysis to determine the extent of any loss. Plant:soil concentration ratios (dry basis) ranged from 0.22 to 6.82, values which were substantially higher than those used in generic assessment models. While there was no statistically significant effect of irrigation source or culinary preparation, the effect of potassium-fertilizer was dramatic. In many cases, concentrations of 137Cs in those plants receiving potassium were less than half of the concentrations in plants that did not receive potassium. Significant differences among species and plant parts for 137Cs concentrations were observed. Dose/risk calculations for the ingestion of these vegetables by a hypothetical 30-y resident indicates the possibility of a lifetime fatal cancer risk well-above the U.S. Environmental Protection Agency's regulatory guideline of 10(-4).

Biological Transport, Active↗
PubMed1996

Environmental monitoring in the vicinity of the Mayak atomic facility.

The goal of radiation monitoring in the zone influenced by the operation of the Mayak Production Association is to provide information for activities aimed at environmental preservation in that territory. The priority tasks of the radioecological monitoring system are measuring all parameters of radiation impact on the environment (which contribute up to 95% of the total population exposure dose), and estimating all parameters required to support effective decision-making. The basic methods for radioecological monitoring are: unification and standardization of field and laboratory techniques for radionuclide analysis; measurement of gamma-irradiation dose rate; measurement of 137Cs, 90Sr, and plutonium concentrations in soils; measurement of radionuclide concentration in surface and ground waters and the atmosphere; study of the pathways of horizontal and vertical migration of radionuclides in natural media; and establishment of data bases including ecological mapping. Based on the information obtained, assessment of contamination and forecasts of the future radiation situation are prepared using models.

Air Pollutants, Radioactive↗
PubMed2000

Highlights from WM2K.

Explore the source record for details and available documents.

Air Pollutants, Radioactive↗
PubMed2003

Radionuclide speciation in effluent from La Hague reprocessing plant in France.

Effluent from the La Hague nuclear fuel reprocessing plant was mixed with seawater in order to investigate the fate of the various radionuclides. Thus, a major objective of the present work is to characterize the effluent from La Hague reprocessing plant and to study how the radionuclide speciation changes with time when discharged into the marine environment. Discharges from the La Hague nuclear reprocessing plant represent an important source of artificially produced radionuclides to the North Sea. The transport, distribution, and biological uptake of radionuclides in the marine environment depends, however, on the physicochemical forms of radionuclides in the discharged effluents and on transformation processes that occur after entering the coastal waters. Information of these processes is needed to understand the transport and long-term distribution of the radionuclides. In the present work, a weekly discharged effluent from the nuclear fuel reprocessing plant at Cap La Hague in France was mixed with coastal water and fractionated with respect to particle size and charged species using ultra centrifugation and hollow fiber ultrafiltration with on line ion exchange. The size distribution pattern of gamma-emitting radionuclides was followed during a 62-h period after mixing the effluent with seawater. 54Mn was present as particulate material in the effluent, while other investigated radionuclides were discharged in a more mobile form or were mobilized after mixing with sea water (e.g., 60Co) and can be transported long distances in the sea. Sediments can act as a sink for less mobile discharged radionuclides (Skipperud et al. 2000). A kinetic model experiment was performed to provide information of the time-dependent distribution coefficients, Kd (t). The retention of the effluent radionuclides in sediments was surprisingly low (Kd 20-50), and the sediments acted as a poor sink for the released radionuclides. Due to the presence of non-reacting radionuclide species in the effluent, a major fraction of the radionuclides, such as Cs-isotopes, 106Ru and 125Sb, in the effluent will be subjected to marine transport to the Northern Seas (i.e., the North Sea, Norwegian Sea and the Barents Sea). The La Hague effluent may, therefore, contribute to enriched levels of radionuclides found in the English Channel, including 90Sr, 60Co and Pu-isotopes, and also 106Ru and 125Sb.

France↗
PubMed1999

Experiences in setting up the first centralized radiopharmacy in Spain.

The centralized radiopharmacy set up in Spain by the Cetir Medical Group allows optimal use of radiopharmaceuticals and complies with laws (Directive 89/343/EEC and Royal Decree 479/1993/Spain) governing their use. More than 220,000 individual patient doses have been supplied since the unit was established in November 1995. In this paper, we describe the infrastructure of the centralized radiopharmacy, including the operations and procedures involved, and how we believe we have achieved our original objectives.

Drug Storage↗
PubMedDate not supplied

Grid resolution study of ground water flow and transport.

Three-dimensional grids representing a heterogeneous, ground water system are generated at 10 different resolutions in support of a site-scale flow and transport modeling effort. These grids represent hydrostratigraphy near Yucca Mountain, Nevada, consisting of 18 stratigraphic units with contrasting fluid flow and transport properties. The grid generation method allows the stratigraphy to be modeled by numerical grids of different resolution so that comparison studies can be performed to test for grid quality and determine the resolution required to resolve geologic structure and physical processes such as fluid flow and solute transport. The process of generating numerical grids with appropriate property distributions from geologic conceptual models is automated, thus making the entire process easy to implement with fewer user-induced errors. The series of grids of various resolutions are used to assess the level at which increasing resolution no longer influences the flow and solute transport results. Grid resolution is found to be a critical issue for ground water flow and solute transport. The resolution required in a particular instance is a function of the feature size of the model, the intrinsic properties of materials, the specific physics of the problem, and boundary conditions. The asymptotic nature of results related to flow and transport indicate that for a hydrologic model of the heterogeneous hydrostratigraphy under Yucca Mountain, a horizontal grid spacing of 600 m and vertical grid spacing of 40 m resolve the hydrostratigraphic model with sufficient precision to accurately model the hypothetical flow and solute transport to within 5% of the value that would be obtained with much higher resolution.

Finite Element Analysis↗