Enrichment Plant Research Articles

Climate change scenarios and the effect of sea-level rise for Estonia

Climate warming due to the enhanced greenhouse effect is expected to have a significant impact on natural environment and human activity in high latitudes. Mostly, it should have a positive effect on human activity. The main threats in Estonia that could be connected with sea-level rise are the flooding of coastal areas, erosion of sandy beaches and the destruction of harbour constructions. Possible climate change and its negative impacts in the coastal regions of Estonia are estimated in this paper. Climate change scenarios for Estonia were generated using a Model for the Assessment of Greenhouse-gas Induced Climate Change (MAGICC) and a regional climate change database—SCENanario GENerator (SCENGEN). Three alternative emission scenarios were combined with data from 14 general circulation model experiments. Climate change scenarios for the year 2100 indicate a significant increase in air temperature (by 2.3–4.5 °C) and precipitation (by 5–30%) in Estonia. The highest increase is expected to take place during winter and the lowest increase in summer. Due to a long coastline (3794 km) and extensive low-lying coastal areas, global climate change through sea-level rise will strongly affect the territory of Estonia. A number of valuable natural ecosystems will be in danger. These include both marine and terrestrial systems containing rare plant communities and suitable breeding places for birds. Most sandy beaches high in recreational value will disappear. However, isostatic land uplift and the location of coastal settlements at a distance from the present coastline reduce the rate of risk. Seven case study areas characterising all the shore types of Estonia have been selected for sea-level rise vulnerability and adaptation assessment. Results and estimates of vulnerability to 1.0-m sea-level rise by 2100 are presented in this paper. This is the maximum scenario according to which the actually estimated relative sea-level rise would vary from 0.9 m (SW Estonia) to 0.7 m on the north-western coast due to different velocities of land uplift in the studied areas. The longest coastline section recession (6.4 km) would occur on the western coast of the mainland where extensive areas of reed bed and flooded meadows would relocate landwards or disappear. Possible damages in Tallinn, the capital city, would be the greatest compared to the other study areas. The greatest threat to the environment of the Gulf of Finland and the whole Baltic Sea is the dumping site of the former uranium enrichment plant in Sillamäe which is situated very close to the coastline and can be easily influenced during storms.

Determination of uranium concentration and isotopic composition by means of ICP-MS in sequential extracts of sediment from the vicinity of a uranium enrichment plant

A method has been developed for the determination of the 238U/235U isotope abundance ratio in sequential extracts of freshwater sediment by means of ICP-MS. Instrument parameters were optimised, and sample pre-treatment procedures developed, to improve the quantification of 235U. Extracts prepared according to the three-stage BCR sequential extraction protocol were passed through a 2 cm column of anion exchange resin (BioRad AG1-X8), and uranium eluted with 8 mol l−1 HNO3 prior to analysis. The precision obtained for measurement of the 238U/235U ratio in solutions containing 20 ng ml−1238U and 0.2 ng ml−1235U was 0.18%. Analysis of stream sediments from the vicinity of a nuclear fuel enrichment plant revealed an enhancement in uranium levels (up to 27 µg g−1 dry weight) which decreased with distance from the effluent discharge point. The 238U/235U ratios measured in sequential extracts of the stream sediments were significantly less than 100 (cf. the natural value of 137.9), confirming that Rivacre Brook is contaminated with 235U-enriched uranium. Results of the sequential extraction also suggested that uranium is discharged from the plant in, or rapidly converted to, a relatively refractory form.

Experience in Japan in Adopting IAEA ST-1, 1996 Edition

Since Japan does not have rich energy resources, it is essential for Japan to ensure energy security in order to sustain economic growth and social activities. To secure a stable energy supply, the establishment of nuclear fuel recycling has a vital role in the use and development of nuclear power. Safe and smooth transport between the various nuclear fuel recycling facilities, enrichment plants, re-conversion plants, fuel fabrication plants, reprocessing plants, etc. is therefore essential and of increasing importance in the nuclear fuel cycle field. In the Japanese regulatory system, radioactive material is classified into radioactive isotopes and nuclear fuel material (which includes nuclear raw material). These two categories are regulated by different regulations. Radioactive material is widely utilised to improve the quality of plants, to preserve food and to make medical examinations etc. Nuclear fuel material is mainly utilised as fuel for nuclear power plant and research reactors.

Characterisation of airborne uranium and thorium contamination in Northern England through measurement of U, Th and 235U/238U in tree bark

Samples of tree bark were collected from four locations in Northern England (a typical rural site, a coal-fired power station, a uranium (isotopic) enrichment plant and a nuclear fuel fabrication facility), to assess the nature and extent of airborne uranium and thorium contamination. The U and Th concentrations of bark were determined by inductively coupled plasma mass spectrometry after conventional nebulisation of bark digests, whilst measurement of 235U/238U isotopic ratio utilised high efficiency nebulisation. Uranium concentrations varied between and within the sites (range, 0.01-12 micrograms g-1), with maximum values recorded within 1 km of the nuclear fuel fabrication plant (Springfields). In comparison, the concentration of Th in bark was low (mean, 0.018 microgram g-1) at all sites with the exception of the area affected by coal combustion (0.2-0.8 microgram g-1). The U/Th ratio varied from 0.5 to 3900 compared with the average crustal ratio of 0.3. Low values (< 2) were recorded at the 'coal' and 'rural' sites whilst Capenhurst and Springfields showed high values indicating the relative magnitude of uranium elevation. Significant enrichment of the natural 235U/238U ratio (0.00725) was observed near the nuclear installations, in particular, the enrichment plant (Capenhurst).

Monitoring large enrichment plants using thermal imagery from commercial satellites: A case study

Thermal imagery from currently operating commercial satellites is an interesting candidate technology for monitoring certain types of fissile material production sites. Potential applications include the Fissile Material Cutoff Treaty (FMCT) or a Fissile Material Production Moratorium. To help determine the capabilities and limitations of such imagery as a monitoring tool, I have examined archived LANDSAT‐5 images of the Portsmouth Gaseous Diffusion Plant, a large U.S. uranium‐enrichment facility in Ohio. My analysis indicates that large‐scale gaseous diffusion plants (GDPs) can very likely be recognized as operational with thermal imagery throughout most of the year in clear weather conditions. It may also be possible to identify certain other large‐scale changes in operations, such as the shut‐down of a single process building in a plant, by comparing rooftop temperatures of neighboring operational process buildings. However, uncertainties in the current data set prevent a definitive conclusion regarding the latter capability. This study identifies intrinsic weaknesses, including vulnerability to countermeasures, that prevent thermal imagery from satellites (at current resolutions) from being a robust stand‐alone verification tool, even for very large plants. Nonetheless, the imagery may be useful to trigger an on‐site inspection, to alert and train inspectors prior to an inspection, and to reduce the frequency of on‐site inspections required at a given site. It could have immediate utility for monitoring the two large GDPS in the United States and the French plant at Tricastin, and possibly for determining the operational status of two GDPS in China as well ‐ a total of five plants worldwide. The ease of acquisition and modest cost of thermal commercial imagery further increase its attractiveness as a verification tool.

Nuclear Power and Climate Without Proliferation

The analysis in the Policy Forum “A nuclear solution to climate change?” by W. C. Sailor, D. Bodansky, C. Braun, S. Fetter, and B. van der Zwaan ( Science 's Compass, 19 May, p. [1177][1]) is diminished by inclusion of the myth—popular in the United States—that efficient use of nuclear resources is a proliferation threat. Quite the contrary, destruction of weapons materials in spent nuclear fuel by their use for production of electricity in fast, so-called breeder reactors is an essential component of good nonproliferation practice. Depleted uranium at U.S. enrichment plants, which was used by the United States Department of Energy (DOE) to produce plutonium for weapons, would also be destroyed in fast reactors. The electricity produced from existing nuclear by-products would be equivalent to that needed by the United States, at present use rates, for hundreds of years. The nuclear solution presented by Sailor et al. would recover less than 1% of the energy from uranium. Spent fuel would be disposed of in a geologic repository. Depleted uranium—millions of tons of weapons source material—would accumulate indefinitely. International Atomic Energy Agency (IAEA) safeguards are required for plutonium-239 in spent fuel deposited in a geologic repository. However, virtually no one accepts the IAEA contention that planned satellite surveillance can be reasonably assured for 10,000 years. Moreover, the time required for significant decay of plutonium-239 is not 10,000 but 240,000 years. Since safeguards for these periods of time are not credible, spent fuel must be reprocessed to permit permanent disposal of unwanted fission products, i.e., high-level radioactive waste. Disposal of this waste is essential for viability of nuclear power and is a requirement of virtually all nations. Reprocessing only in well-designed, well-managed, and safeguarded facilities operated by nations with large nuclear power programs, and immediate fabrication of weapons materials into fuel assemblies for their destruction through production of electricity, provide the greatest assurance against a proliferation threat from nuclear power. The du Pont company completed designs for such facilities in 1978, based on its experience in reprocessing at the DOE Savannah River Plant and on the experience of others. Among many important features of these designs was the elimination of accumulations of separated plutonium. Unfortunately, these designs were rejected by leaders of the DOE in order to support national laboratory reprocessing concepts that had led to earlier problems (failures and proliferation) and poorly focused research on “proliferation-resistant” fuel cycles. During this same time period, political decisions were made that led ultimately to cancellation of U.S. fast reactor development. U.S. nuclear policies based on best science and best applications of science will result in nuclear power being used as the solution for climate change and other energy and environmental problems. [1]: /lookup/doi/10.1126/science.288.5469.1177

Metal body burden and biological sensors as ecological indicators

AbstractMetal body burden (BB) was analyzed in three groups of organisms evaluated as sentinel monitors of metal exposure. The study site was a lotic system of moderate gradient that received effluent outfalls from an uranium enrichment plant. Metal BBs (e.g., Ag, Cd, Cr, Cu) increased in the order Cheumatopsyche spp. (caddisfly), Campostoma anomalum (central stoneroller minnow), and Stenonema spp. (mayfly). This was consistent with their classifications as metal‐tolerant, moderately tolerant, and sensitive taxa, respectively. The Ag, Cd, and Cu BBs in stoneroller minnows from upstream, effluent‐receiving, and downstream stations correlated strongly with macroinvertebrate bioassessment (BA) scores (r ≤ —0.95), numbers of taxa (r = —0.95), and the Ephemeroptera, Plecoptera, Trichoptera indices (r = —0.82 to —0.94). Proportional differences in metal BBs in the minnow were used to derive metal multipliers that were applied to total recoverable metal concentrations to calculate bioavailable metal. The bioavailable metal fractions correlated with BA scores and numbers of taxa (e.g., Ag, r ≤ —0.97; Cu, r = —0.95). When five metals (i.e., Ag, Cd, Cu, Cr, Pb) were included in an additive model, results also correlated with BA scores (r = —0.93) and numbers of taxa (r = —0.86). Metal BB in minnows was a strong indicator of ecological impact and provided a means of determining bioavailable metals. Also, we describe the development of the metal biosensor, which incorporates a reconstructed fish gill epithelium, the primary target of metal exposure. This in vitro biosensor should directly quantify bioreactive metals that cross the epithelium and react with a genetically engineered intracellular detector. This biosensor complements biotic ligand models based on surface binding of metals to gill epithelia.

Assessment of magnetic field exposures for a mortality study at a uranium enrichment plant.

A survey of workplace exposures to 60-Hz magnetic fields was carried out at a large uranium enrichment facility to assign exposures for an updated mortality study. Stratified random selection was used to choose workers for measurement in all jobs and areas, to determine whether consistent distinctions could be made between job groups based on average magnetic field exposures. A total of 252 workdays was measured with a personal monitor, and individual average magnetic field exposures ranged from 0.20 to 82.6 mG. A priori job groups showed significant differences between geometric mean exposures, which ranged from 0.80 to 3.51 mG. Most of these groups showed widely ranging exposures, so they were subdivided based on location and job title to improve the precision of the exposure assignments for the mortality study. These final assignments were made up of 26 groups having arithmetic means ranging from 0.43 to 24.9 mG, with most groups defined by location in addition to job title. In general, electrical maintenance workers did not have elevated magnetic field exposures (> 3 mG), but the exposures of the electricians in switchyard (substation) jobs were elevated. Available employment records did not allow most electricians to be distinguished based on location, so they were assigned exposures based on their plantwide average (above 7 mG). An estimated 9% of the work time of this cohort was spent at daily average exposures above 3 mG, despite the very large electric power consumption at this plant.

Assessment of Magnetic Field Exposures for a Mortality Study at a Uranium Enrichment Plant

Assessment of Magnetic Field Exposures for a Mortality Study at a Uranium Enrichment Plant

A preliminary investigation of the operational and isotopic speciation of uranium in sediments

Uranium was determined in extracts of inter-tidal sediment, obtained from a contaminated harbour, using the three-stage sequential extraction procedure recommended by BCR. The element was found mainly in association with reducible, or reducible and oxidisable, phases and the overall concentration was enhanced (up to 6.7 μg g–1 dry weight) with respect to typical, UK levels. The 238U/235U ratio has been measured in digests of stream sediments obtained from the vicinity of a uranium enrichment plant. Significant enhancement in 235U with respect to the natural 238U/235U ratio (137.88:1) was observed at some locations.

Environmental monitoring program around Rokkasho nuclear fuel cycle facilities

Three commercial nuclear fuel cycle facilities, a reprocessing plant, an uranium enrichment plant and a low level radioactive waste disposal center, have been constructed or are in partial operation at Rokkasho-mura in Aomori prefecture, about 700 km north of Tokyo. A monitoring program has been settled on the modulation between Japan Nuclear Fuel Ltd. (JNFL) and Aomori Prefectural Govemment. The basic goal of environmental monitoring is to make sure that the dose equivalent received by the public, living around the facilities, is much lower than the annual dose equivalent limit. The target is as follows: (1) to estimate the dose equivalent received by the public, (2) to understand the accumulation of radioactive materials in the environment and (3) to estimate the influence on the environment due to unexpected release from the nuclear facilities and to make judgement for the enforcement of routine monitoring or not. This paper describes the contents of the monitoring program such as the object of nuclides, measuring/sampling point, kinds of samples etc.

Co-operative Autonomous Active Agents in Control of Complex Industrial Processes

Abstract This paper concerns problems of simulation and control of industrial plants using the ideas of autonomous agents. The considered environment is an industrial plant designed for separation processes with complex material streams with recycles. Such environment is typical for numerous processes occurring in chemical engineering, mineral processing, multistage flotation and many others. The different parts of the process are ruled by autonomous agents who co-operate with each other. We consider different methods of coordinating the agents’ action to obtain an overall plan. By way of illustration the proposed method is applied to control of a multicomponent ore enrichment plant.

Production and Use of Nitrogen-15 in German Agricultural, Biomedical and Ecological Research -A Historical Review-

Abstract The history of production and application of the stable nitrogen isotope15N in Germany is mainly part of the history of the former Institute of Stable Isotopes, later a part of the Central Institute of Isotope and Radiation Research (Zentralinstitut fur Isotopen-und Strahlenforschung) in Leipzig. In 1956, after a relatively large fractionation during isotopic exchange in the system NO/HNO3 was reported by SPINDEL and TAYLOR, the construction of an isotope enrichment plant was planned and started work in 1958 on a laboratory scale. The prodution of 15N-labelled material in the institute started in 1960, followed in 1968 by the start of a separation plant in Wolfen as a branch of industrial fertilizer production. The economy was optimized by feeding back the 15N decreased efflux to the fertilizer production line. The material produced was used for studies at home and abroad. Close contacts with the IAEA (International Atomic Energy Agency, Vienna) and the development of an easy-to-handle optical in...

Influence of flocculants on the performance of a ceramic capillary filter

Capillary filtration technology has been developed in Finland by Outokumpu Mintec Oy. Almost ten years of full scale experience of capillary filtration has shown that this type of filter is a very profitable and very economical solution to many filtration problems. The main area where capillary filters are used is in the dewatering of mineral concentrates. Both vacuum capillary as well as pressurised capillary filters are now commercially available. In the work reported here, the effect of flocculants on the capacity of Ceramec filters is studied. The titrations were made using three copper concentrates and a laboratory-scale automatic dipping machine. During the experiments no permanent plugging of ceramic filter media was observed. On the contrary, small concentrations of non-ionic or slightly anionic flocculants increased the capacity. However, too high a concentration of flocculants caused plugging of the ceramic plates. There were also remarkable differences between the copper concentrates used and their behaviour during filtration with Ceramec filters. Storage of copper concentrates changes their zeta potential very dramatically. In addition, the type of copper sample has an effect on the capacity. Clearly better capacities were achieved using a slurry sample which was brought straight from the mine, compared with using a copper sample which was first dewatered in a mining enrichment plant. The results show that these kinds of experiments should be performed in the mineral concentration plant if very accurate results are desired. A good way to predict the capacity and the cake moisture of mineral concentrates is to perform test filtrations using small, pilot-scale capillary action filters which can be directly connected to the mineral concentration process.

Investigations into speciation: Sorption and corrosion of actinides in systems of high ionic strength

It is a well known fact that Germany still favours the direct disposal of spent fuel elements in salt diapirs. Besides this spent fuel larger amounts of UO2, originating from enrichment plants as UF 6, transferred into (NH4)2UO2(CO3) 3 (AUC)and decomposed to UO 2 shall also be deposited in these salt domes: A hypothetical accident which must be taken into consideration is the intrusion of brine into these waste repositories. Therefore the corrosion of UO2 had to be investigated under various practical conditions and under the influence of a variety of parameters in order to obtain physicochemical data for modelling the dissolution and migration of the radionuclides contained in the various waste systems. Potentiostatic and potentiodynamic measurements which the corrosion rates were determined from had to be carried out not only by use of electrochemical but also by radiochemical methods in different systems at various temperatures and relevant potentials applied. Since many uranium species in the brines originating from the dissolution of the deposited material can easily be adsorbed at the corrosion products of cement, which is widely used for solidification of radioactive waste, investigations into the adsorption of these species on the cementitious materials had also to be performed.

Weapons to fuel

The economic implications of the U.S.‐Russian HEU agreement remain uncertain, and will depend on the health of the uranium market and the performance of the U.S. gaseous diffusion enrichment plants. The agreement, however, could be essential for the dismantlement of nuclear weapons in Russia. It also provides an opportunity to develop security, economic and institutional arrangements that would be useful in dealing with fissile materials from weapons in the future.

Criticality Safety Analysis of a Calciner Exit Chute

AbstractCalcination of uranyl nitrate into uranium oxide is part of normal operations of some enrichment plants. Typically, a calciner discharges uranium oxide powder (U3O8) into an exit chute that directs the powder into a receiving can located in a glove box. One possible scenario for a criticality accident is the exit chute becoming blocked with powder near its discharge. The blockage restricts the flow of powder causing the exit chute to become filled with the powder. If blockage does occur, the height of the powder could reach a level that would not be safe from a criticality point of view.In this analysis, the subcritical height limit is examined for 98% enriched U3O8 in the exit chute with full water reflection and optimal water moderation. The height limit for ensuring criticality safety during such an accumulation is 28.2 cm above the top of the discharge pipe at the bottom of the chute. Chute design variations are also evaluated with full water reflection and optimal water moderation. Subcritica...

U.S. forms uranium enrichment corporation

After almost 40 years of operation, the federal government is withdrawing from the uranium enrichment business. On July 1, the Department of Energy turned over to new government-owned entity—the U.S. Enrichment Corp. (USEC)—both the DOE enrichment plants at Paducah, Ky., and Portsmouth, Ohio, and domestic and international marketing of enriched uranium from them. Pushed by the inability of DOE's enrichment operations to meet foreign competition, Congress established USEC under the National Energy Policy Act of 1992, envisioning the new corporation as the first step to full privatization. With gross revenues of $1.5 billion in fiscal 1992, USEC would rank 275th on the Fortune 500 list of top U.S. companies. Energy Secretary Hazel R. O'Leary hails USEC as a model of President Clinton's commitments to gain for the U.S. the value of technological leadership in the global marketplace, and to do so by reinventing the role for government. She notes that USEC will have the ...

Die bepaling van die kragverspreiding in die drakabel van ’n sweefspoor

The analysis of the forces in the uniform carrying cable of a cableway, used for conveying ore to an enrichment plant, is described. For the purpose of the analysis the problem is considered as a static equilibruim problem. The elasticity of the cable, its motion relative to the pylon supports after loading with carts, the weights of the loaded ore carts, and the forces exerted by the towing rope are taken into consideration. Since the cable is pulled taut the influence of bending moments is negligible and consequently the cable may be considered as a perfectly flexible cable that may be modelled by discrete modelling. In particular, use is made of a point mass model. The analysis gives the maximum tensile force and the corresponding position of this force for different representative positions of the loaded carts along the carrying cable. This enables the computation of safety factors for different types of cables.

Starch accumulation during hydroponic growth of spinach and basil plants under carbon dioxide enrichment

The effects of CO 2 enrichment, photoperiod duration, and inorganic phosphate levels on growth and starch accumulation by spinach and basil plants were studied in a commercial hydroponic facility. During a 3-week growth period, both species exhibited increased whole-plant fresh weight as a result of an increase in atmospheric CO 2 concentration from 400 to 1500 μl/l. However, basil leaves exhibited a 1.5- to 2-fold greater increase in specific leaf weight ( SLW), and accumulated starch to much greater levels than did leaves of spinach. At 1500 μl CO 2/l, starch accounted for up to 38% of SLW with basil compared to <10% of SLW with spinach. The maximum ratio of starch/chlorophyll was 55.0 in basil leaves vs 8.0 in spinach leaves. High ratio values were associated with the appearance of chlorotic symptoms in leaves of basil grown under CO 2 enrichment ( Wallick and Zinnen (1990) Plant Disease 74, 171–173), whereas spinach did not exhibit chlorosis. Increasing inorganic phosphate concentrations from 0.7 to 1.8 mM in the hydroponic medium did not appreciably affect leaf starch accumulation in either species. Starch accumulation in basil leaves was not consistently related to the duration of the photoperiod. However, photoperiod-induced changes in leaf starch levels were much greater in basil than spinach. The results clearly indicate that different horticultural crops can show diverse responses to CO 2 enrichment, and this highlight the need to develop individual growth strategies to optimize production quality of each species.