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At least 1,207 records · Page 67Linked to original sources
PubMed2003

129I in the environment of the La Hague nuclear fuel reprocessing plant--from sea to land.

In recent years, particular attention was paid to the long-lived radionuclides discharged with authorized low-level radioactive liquid and gaseous effluents by the nuclear spent fuel reprocessing plants of La Hague and Sellafield. The knowledge of (129)I (half-life=15.7 x 10(6) a) distribution in the environment is required to assess the radiological impact to the environment and population living in the area under the direct influence of La Hague NRP discharges. Measurement difficulties of (129)I in environmental matrices, where it is usually present at trace level, limited data published on (129)I activity levels in the European and more particularly in the French territory. Studies conducted to qualify a new alternative measurement method, direct gamma-X spectrometry with experimental self-absorption correction, led to test samples collected in the La Hague marine and terrestrial environment : seaweeds, lichens, grass, bovine thyroids, etc. All these results, often already published separately for analytical purposes and treated for intercomparison exercises, are presented here together in a radioecological manner. The levels of (129)I activity and (129)I/(127)I ratios in these samples show the spatial and temporal influence of the La Hague NRP in its local near-field environment as well as at the regional scale along the French Channel coast.

Absorption↗
PubMed2002

Biosorption of 241Am by Rhizopus arrihizus: preliminary investigation and evaluation.

The biosorption of 241Am from solution by a fungus-Rhizopus Arrihizus (R. arrihizus), and the effect of experimental conditions on the adsorption were investigated. The preliminary results showed that the biosorption of 241Am by R. arrihizus is very efficient. An average of more than 99% of the total 241Am was removed by R. arrihizus of 1.3 g/l (dry weight) from 241Am solutions of 5.6-111 MBq/l (44.3-877.2 microg/l) (C0), with adsorption capacities (W) of 4.2-79.4 MBq/g biomass (dry weight) (33.2-627.5 microg/g). The biosorption equilibrium was achieved within 1 h and the optimum pH ranged from 1 to 3. No significant differences in 241Am biosorption were observed at 10-45 degrees C, or in solutions containing Au3+ or Ag+, even 2,000 times above 241Am concentration. The relationship between concentrations and adsorption capacities of 241Am indicated that the 241Am biosorption by R. arrihizus obeys the Freundlich adsorption equation.

Adsorption↗
PubMed2004

14C and delta13C characteristics of organic matter and carbonate in saltmarsh sediments from south west Scotland.

The distribution of contaminant radionuclides from the Sellafield nuclear fuel reprocessing plant was used to establish chronologies for three saltmarsh sediment cores from south west Scotland. delta(13)C and (14)C analyses indicated that the cores provided a useful archive record of variations in input of organic matter and carbonate. The results imply that prior to major releases of contaminant (14)C from Sellafield, the (14)C specific activity of organic matter in Irish Sea offshore sediments was about 24 Bq kg(-1) C, while that of the carbonate component was below the limit of detection. These results provide baseline data for modelling the uptake of contaminant (14)C by the Irish Sea sediment system. The study confirmed that small(13)C analyses provide a sensitive means of apportioning the origin of saltmarsh organic matter between C(3) terrigenous plants, C(4) terrigenous plants and suspended particulate marine organic matter. For the <2 mm fraction of sediment, a clear pattern of decreasing marine organic input was observed in response to increasing elevation of the marsh surface as a result of sediment accumulation. Bulk sediment, including detrital vegetation, had a dominant input from terrigenous plants. The combined use of delta(13)C and (14)C data revealed that organic matter in the marine organic component of the <2 mm fraction of contemporary surface sediments of the saltmarshes is dominated by recycled old organic material.

Carbon Radioisotopes↗
PubMed1985

Diffusion of a contaminant in fractured porous media.

A theoretical model is developed for diffusion from a finite source of buried contaminant through a porous medium containing a fracture that reaches to the atmosphere. Important quantities are shown to be the burial depth, source width and fracture width, the soil porosity, the diffusion coefficients in the soil and the (air-filled) fracture, and the decay constant of a radioactive contaminant. The flux across the soil-air interface is calculated and shown to be greatly increased by the presence of the fracture. The flux is found to increase with fracture width and source width, to decrease with increasing soil porosity and decay constant, and to decrease with increasing ratio of soil diffusion coefficient to air diffusion coefficient.

Air Pollution, Radioactive↗
PubMed1990

Ground distribution patterns of selected radioactive, chemical, and physical contaminants from dispersion of U mill tailings.

Ground concentrations of 226Ra and total alpha activity as a function of soil depth and distance from an acidic U mill tailings pile were measured, as well as soil pH, sulfate, chloride, and conductivity. Contamination decreased with increasing soil depth and distance from the source. Most of the measured parameters were indistinguishable from background after a distance of 3.3 km from the tailings impoundment. The highest concentrations of all contaminants were contained in the particles less than 0.045 mm in diameter at the soil surface (0-0.6 cm). This fraction represents only 4% to 10% of the total soil mass. Surface soil particles greater than 2.0 mm contained higher concentrations of all contaminants than the intermediate-size (0.045-2.0 mm) fraction. Aggregate formation of the greater than 2.0-mm fraction from small particles or preferential erosion and transport of the tailings sand fractions were proposed as possible explanations. The significant correlations between various measurements were soil 226Ra vs. total alpha activity, sulfate concentration, and conductivity. The latter two parameters are indicative of sulfuric acid leached tailings. The sulfate concentration appeared to be a sensitive and easily measured indicator of tailings contamination and migration into the soil profile. Furthermore, sulfate may be used to delineate acidic U tailings from other sources of contamination (U ore dust, yellowcake, naturally elevated U and Ra) in the environment. Actual site measurements for surface 226Ra concentration were approximately twice the MILDOS computer code prediction.

Chlorides↗
PubMed1995

A sensitivity study of the SCK.CEN BIOSPHERE model for performance assessment of near-surface repositories.

At SCK.CEN a model has been developed on behalf of NIRAS/ONDRAF for the performance assessment of near-surface repositories, consisting of several submodels. This article deals with the submodels BIOSPHERE, describing the transfer and accumulation of the radionuclides in the biosphere and DOSE, calculating effective individual doses to the critical group. An extensive literature review was performed in order to determine best-estimate values and uncertainty ranges (probability density functions) of biosphere parameter values, specific to conditions that may prevail at potential disposal sites in Belgium. In this paper the BIOSPHERE and DOSE models are described and default and site-specific values (probability density functions where appropriate) of the parameters involved are indicated for the radionuclides 129I, 239Pu, and 94Nb. A combined uncertainty/sensitivity analysis based on the pdf of the site-specific parameter values has been carried out. Median values and 95% confidence intervals of the site-specific doses are indicated and most influential parameters to the uncertainty identified. Site-specific median dose values are also compared with generic doses.

Air Pollutants, Radioactive↗
PubMed1999

Structure and function of occupational health services within selected Department of Energy sites.

The mission of the United States Department of Energy sites has recently changed from nuclear weapons production to site remediation. Considering the mass of radiological and chemical contaminants at these sites, ensuring the health and safety of workers is a major challenge. This study used the findings from a written survey to describe occupational health services at 10 Department of Energy sites. The study aims were to describe and compare: (1) the primary hazards associated with the site activities; (2) the occupational safety and health structure, including service providers; and (3) the occupational health and safety functions, including surveillance, training, and service provision. Although explosions and radiological agents were identified as the hazards with the greatest associated risks, workers at these sites were most likely to be exposed to physical hazards, ergonomic hazards, and/or chemicals, including asbestos. Physicians accounted for 2.4% of service providers, nurses for 5.5%, industrial hygienists for 12.2%, safety personnel for 11.8%, and health physicists for 64.9%. It was concluded that there is an imbalance between the most important hazards and the types of health and safety personnel at these sites.

Delivery of Health Care↗
PubMed2006

Report from the techa river dosimetry review workshop held on 8-10 December 2003 at The State Research Centre Institute of Biophysics, Moscow, Russia.

Large releases of fission products into the Techa River, in the Southern Urals, occurred in 1950 and 1951, during the early years of operation of the Mayak Production Association (Mayak PA), which produced plutonium for nuclear weapons. Increases of leukemia and of solid cancers with radiation dose have been noted in the population of about 30,000 people who lived in the settlements downstream of the site of the radioactive releases; that population has been studied for several decades by Russian scientists, notably in the framework of cooperation with American and European scientists. The radiation doses are currently estimated by means of the Techa River Dosimetry System-2000 (TRDS-2000). Recently, a scientist from Mayak PA has suggested in several publications that the doses calculated using TRDS-2000 might be underestimated substantially. A special international Workshop, held in Moscow on 8-10 December 2003, aimed to resolve some of the pressing issues related to the determination of the external and internal doses received by the Techa River population and to give recommendations on the further development of methodologies used for dose reconstruction. The authors of this article were selected by the organizers of the Workshop to draw the conclusions of the meeting. They express the view that, while the dose reconstruction system TRDS-2000 is basically sound, additional work is needed and the results of any epidemiological studies making use of TRDS-2000 should be qualified as preliminary, pending resolution of several issues. The most important of these issues is the re-evaluation of the activities released, using additional information that could be obtained with the help of Mayak experts. Other specific suggestions aiming to improve the dose reconstruction methodology for the Techa River cohort, i.e., continued measurements of accumulated dose in environmental samples and human tissues, validation of external dose estimates with thermoluminescence measurements of bricks and with electron paramagnetic resonance measurements of teeth, estimation of individual doses instead of group doses, detailed account of the contributions to dose of medical examinations and of other releases from the Mayak complex, and careful assessment of the uncertainties, were made by the meeting participants.

Dose-Response Relationship, Radiation↗