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Innovative reactor concepts are being studied by several research institutions and private entities for their role against climate change and energy poverty. The Generation IV International Forum, committed for more than 20 years in support of advanced reactors, has drawn up a series of objectives for the new class of nuclear plants, among which is an improvement in safety and economy through passive safety systems for the removal of decay heat. One of the most studied technologies is the lead fast reactor (LFR), whose coolant has a high boiling point, excellent shielding capabilities, and good heat transfer in forced and natural circulation, as well as neutron properties suitable for a hard spectrum. These allow for designing systems with high simplification and wide safety margins. On the other hand, opacity, corrosion, and innovative design choices require demonstration of the technology in experimental campaigns before using it in the industrial field. In recent years, Westinghouse Electric Company has begun the conceptual study of an intermediate size LFR [~460 MW(electric)] which, by exploiting the opportunities of the technology, aims at marketability over the next decade. One of the features is a passive heat removal system that allows, through different heat exchange mechanisms including conduction, convection, and radiation, for the transfer of decay heat from the reactor block to a pool of water inside the containment. The system is designed for indefinite heat removal thanks to channels that allow outside air to replace water following complete boiling. For the geometry of the system, the size, the materials, and the heat transfer mechanisms, an experimental activity is required to validate the prediction of the calculation codes and potentially support design optimization. The UK Department for Business, Energy & Industrial Strategy has recently subsidized the design, procurement, installation, and operation of the Passive Heat Removal Facility, an experimental facility to study the innovative safety system. This paper presents the activities of scaling, design, pretesting, and installation of that facility. [ABSTRACT FROM AUTHOR]

In this study, a new model framework that couples the atmospheric chemistry transport model system Weather Research and Forecasting–European Monitoring and Evaluation Programme (WRF-EMEP) and the multimedia fugacity level III model was used to assess the environmental impact of in-air amine emissions from post-combustion carbon dioxide capture. The modelling framework was applied to a typical carbon capture plant artificially placed at Mongstad, on the west coast of Norway. The study region is characterized by high precipitation amounts, relatively few sunshine hours, predominantly westerly winds from the North Atlantic and complex topography. Mongstad can be considered as moderately polluted due to refinery activities. WRF-EMEP enables a detailed treatment of amine chemistry in addition to atmospheric transport and deposition. Deposition fluxes of WRF-EMEP simulations were used as input to the fugacity model in order to derive concentrations of nitramines and nitrosamine in lake water. Predicted concentrations of nitramines and nitrosamines in ground-level air and drinking water were found to be highly sensitive to the description of amine chemistry, especially of the night-time chemistry with the nitrate (NO3) radical. Sensitivity analysis of the fugacity model indicates that catchment characteristics and chemical degradation rates in soil and water are among the important factors controlling the fate of these compounds in lake water. The study shows that realistic emission of commonly used amines result in levels of the sum of nitrosamines and nitramines in ground-level air (0.6–10 pgm−3) and drinking water (0.04–0.25 ng L−1) below the current safety guideline for human health that is enforced by the Norwegian Environment Agency. The modelling framework developed in this study can be used to evaluate possible environmental impacts of emissions of amines from post-combustion capture in other regions of the world. [ABSTRACT FROM AUTHOR]

We conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimentation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger. [ABSTRACT FROM AUTHOR]

The 30-year record 1975-2004 of weekly samples of streamwater chemistry from Birkenes, Norway, shows 106 acid episodes below the threshold of ANC-50 μeq1-1. The frequency, severity and duration of episodes have diminished since about 1990 due to chemical recovery following reduced deposition of sulphur. In particular SO4-driven episodes in the first runoff following drought have become less intense and less frequent, whereas episodes driven by climate (wind, high flow) continue. The data show significant empirical relationships between strength of the driver, degree of chemical recovery, and severity of ANC depression. [ABSTRACT FROM AUTHOR]

We conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimantation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger. [ABSTRACT FROM AUTHOR]

Objective: This article reviews the incidence of arterial thromboembolism in patients with heart failure who are not receiving anticoagulants. We also examine whether more severe ventricular dysfunction increases this incidence and the efficacy and risks of anticoagulation for patients in sinus rhythm.Data Sources: English-language studies referenced in MEDLINE or EMBASE (January 1966 to September 1993) were reviewed. We used the search terms heart failure, congestive; congestive heart failure; heart failure; cardiac failure; and dilated cardiomyopathy in conjunction with the terms anticoagulation, cerebrovascular disorders, stroke, and thromboembolism.Study Selection: All studies with separate data for patients with chronic heart failure not receiving anticoagulants were included. Articles addressing valvular heart disease or heart failure secondary to acute myocardial infarction or Chagas' disease were excluded. Studies of the occurrence of left ventricular mural thrombi were also reviewed.Data Extraction and Synthesis: Inclusion and exclusion criteria, prevalence of atrial fibrillation, mean follow-up, and the occurrence of arterial thromboembolic events were extracted. If the incidence was not given, this was estimated using the proportion of patients with events divided by the mean follow-up.Conclusion: The incidence of arterial thromboembolism ranged from 0.9 to 5.5 events per 100 patient-years, with the largest studies reporting incidence of 2.0% and 2.4%. Findings regarding the relationship between ventricular function and thromboembolic events are contradictory. No controlled trial has assessed the efficacy or risks of anticoagulation for patients with heart failure and sinus rhythm, and reported efficacy in case series ranged from 0% to 100%. Until adequate studies are performed, anticoagulation should be discouraged for patients with heart failure who are in sinus rhythm. [ABSTRACT FROM AUTHOR]

A dynamic model based on a simple nonlinear relationship between adsorbed and dissolved sulfate in soils is used to examine the implied long-term control exerted on drainage water sulfate concentration by mineral soil adsorption. The model assumes reversible adsorption and does not consider biological sulfur transformations or variable adsorption arising from changes in soil organic matter or pH. The model is used to simulate the effects of more than a century of increased atmospheric sulfur deposition into low-order, mountainous catchments. The response time of simulated drainage water sulfate concentration is a function of the hydrological retention time and the amount of sulfate adsorbed on the soil. Simulated catchments with small adsorption capacity respond at essentially the hydrological response time (months to a year). Simulated catchments with large adsorption capacity respond much more slowly (decades). These response times decrease dramatically as adsorbed sulfate accumulates. There has been a tendency to classify catchments as those that respond to changes in sulfur deposition and those that do not. Our results suggest that (at least for low-order, shallow soil catchments) responses to sulfur deposition are continuous, not dichotomous, and response times will decrease under prolonged atmospheric deposition. [ABSTRACT FROM AUTHOR]

Research in recent years has led to conceptualizations of the long-term responses of catchment surface water quality to acidic deposition. That research has focused attention on certain soil processes as likely keys to catchment responses (anion retention, cation exchange, primary mineral weathering, aluminum dissolution, and CO2 solubility). We present a mathematical model which uses quantitative descriptions of these soil chemical processes to estimate the long-term chemical changes that occur in the soil, soil water, and surface waters of catchments in response to changes in atmospheric deposition. The model is applied to a small forested catchment in the Shenandoah National Park, Virginia. Historical changes in surface water quality are reconstructed for the catchment for the last 140 years. The model indicates that alkalinity of surface waters in the catchment may have been reduced by as much as 50%. Water quality is forecast for the catchment under three different scenarios of future changes in atmospheric deposition. The model indicates that all but very large reductions in deposition will result in further deterioration of the catchment water quality. The process-oriented, lumped-parameter approach used is consistent with all currently available observations of water quality in the catchment. Due to the lack of long-term records of catchment water quality, strict verification of the model estimates and an assessment of the model validity is problematic. This is the case for all models of long-terrn catchment chemical responses to acid deposition. Nonetheless, the model provides a means of integrating the results of individual process level laboratory and field studies. Used this way, the model becomes a vehicle for examining the interactions and long-term implications of our conceptualization of the acidification process. [ABSTRACT FROM AUTHOR]

Surface waters in Europe and North America have begun to recover in response to decreases in emissions of acidifying pollutants to the atmosphere. Variations in climate influence chemical and biological recovery. Part of the EU project Eurolimpacs (Integrated project to evaluate the impacts of global change on European freshwater ecosystems) focuses on the interactive effects of acid deposition and climate on freshwater ecosystems. This special issue of Hydrology and Earth System Sciences is devoted to this topic, and consists of studies conducted in 8 countries on aspects regarding episodes, nitrate, dissolved organic carbon, recovery and biological effects. [ABSTRACT FROM AUTHOR]

The purpose of this clinical study was to evaluate the effect of denture adhesive on maxillary denture performance and patient perceptions. Private practitioners were solicited to assist in recruitment of their own patients as subjects and to administer the study. The participating clinicians recruited 194 patients (39% male, 61% female) with maxillary complete dentures. Of this population, 50.2% had a mandibular removable complete denture, 34.4% had a mandibular removable partial denture, and 15.4% had lower natural dentition and/or an implant supported prosthesis in the lower arch. The average age of the subjects was 66.6 years old, and 61.8% were currently using adhesives. The gnathometer was used to assess the subjects' anterior bite force (0 to 10 scale) to denture dislodgement before and after the application of a denture adhesive on their maxillary complete denture. Subjects were also asked to evaluate denture performance, speaking and chewing, fit and comfort, and confidence as "improved," "same," or "worse" with the adhesive versus without the adhesive. The average force of dislodgement for dentures without adhesives was 3.3 compared to 5.2 with adhesive. At least 63.4% of the subjects found an improvement in bite force with the use of the adhesive. Subjects also perceived improvement with use of adhesive as compared to without adhesive in the following areas: 79.45% in denture performance, 55.9% in speaking and chewing, 55.9% in fit and comfort, and 64.0% in confidence. Unfortunately, no data was collected on instrument reliability, and no statistical analysis was carried out on the data collected. [ABSTRACT FROM AUTHOR]

AbstractThe Westinghouse lead-cooled fast reactor (LFR) is a next-generation nuclear power plant whose primary mission is to reduce front-end capital costs and generate flexible and cost-competitive electricity for global markets, while offering mission versatility and satisfying the highest safety and sustainability standards. The LFR is an economical choice for carbon-free power generation to meet the ambitious goals of reducing carbon emissions. The plant utilizes passive safety systems for high reliability and public safety.The LFR testing program aims to fill the technology gaps in the key materials, components, and systems of the LFR plant. It provides demonstrations of LFR engineering that reduce the uncertainty of the LFR design and experimental data for the verification and validation of the modeling and simulation computer codes. With the support of the LFR phenomena identification and ranking table, the phenomena important to plant safety with insufficient states of knowledge have been identified and a Westinghouse testing plan developed to address them.The United Kingdom Advanced Modular Reactor Program Phase 2 was purposed to advance the level of design maturity toward eventual regulatory approval and deployment. Westinghouse and its partners have developed eight state-of-the-art test facilities within the program. Among them, the Passive Heat Removal Facility, Versatile Lead Facility, Lead Water Interaction Facility, and the Lead Freezing Facility are thermal-hydraulic testing facilities, with the other four facilities dedicated to testing lead corrosion and material mechanical behavior in lead.The design, development, and testing of the four thermal-hydraulic facilities are presented in this paper. A variety of computer codes ranging from system-level analysis, component-level analysis, and high-resolution computational fluid dynamics analysis, are utilized to support the development of the facilities. The analyses provide operational and accidental conditions in the LFR to identify major testing conditions and inform the facility design and testing matrix. With a significant amount of experimental data being generated with these highly instrumented test facilities, the computer codes and models will be benchmarked against the experimental results to improve their validation and verification status. [ABSTRACT FROM AUTHOR]

The South Pennines, an area of acid-sensitive geology at the center of a major industrial region, have undergone perhaps the most severe historic exposure to sulphur and nitrogen deposition in the UK. This study addresses a lack of existing research on the region by presenting the findings of a survey of 62 surface waters sampled during a 1-week period in April 1998. Results indicate that acidification in the region is acute; 27 of the sampled surface waters had a negative acidneutralizing capacity (ANC) and 28 had a pH below 5.0. Minimum recorded pH values were below 4.0. Non-marine sulphate levels were extremely high (median 222 mueq/1), and widespread high nitrate concentrations (median 41 mueq/1) suggest that soils in the region as a whole maybe at an advanced stage of nitrogen saturation. A consistent relationship was identified between site acidity and the balance between themajor weathering-derived cations, calcium and magnesium, and sulphate. This could in turn be linked to catchment soil type and land use, with the most acidic conditions occurring in peat-dominated catchments, where weathering is minimal and the influence of atmospheric deposition most pronounced. Percentage of peat in each catchment was the single best predictor of surface water acidity. Nitrate concentrations, although not a dominant control on acidity, varied significantly according to land use. Elevated concentrations were observed in catchments containing forestry, due to enhanced deposition inputs, and in catchments containing improved land, linked to fertilizer use. Ammoniumconcentrations, although low at most catchments, were a significant component of the inorganic nitrogen total in a number of surface waters draining waterlogged peat catchments. [ABSTRACT FROM AUTHOR]

Lakes in mountainous areas are of special interest in environmentalstudies because such takes are generally particularly sensitive to inputs of atmospheric pollution and to changes in climate. Mountain lakes provide, therefore, an early warning of more widespread environmental changes. Surveys of lake-water chemistry in mountain areas in Norway, and mountain areas elsewhere in Europe which have crystalline bedrock, clearly show that such lakes are generally very dilute with low concentrations of base cations, alkalinity and SO42-. Mountain lakes also have low concentrations of total-P and TOC. The low concentrations of inorganic and organic ions are due to several factors of which low weathering rates, thin soils, high water fluxes and sparse vegetation in the catchment are of major importance. N03- concentrations on the other hand, are often higher in mountain lakes relative to low elevation lakes in the same area, due to the lower retention capacity of atmosphericallydeposited N in mountain catchments. [ABSTRACT FROM AUTHOR]

During the last three decades the experimental manipulations of whole ecosystems have been a useful and widely-used tool for investigation of the effects of air pollution, air pollution reduction strategiesand management practices on the health and productivity of forests and the acidification of catchments and fresh waters. NITREX and EXMANprojects involve whole-ecosystem manipulations of forest ecosystems in Europe. The aims of these ecosystem experiments have been to investigate the impact of a continued or increased load of air pollutants on the ecosystems, and the possibilities of reversing the acidifying effects by soil amelioration, addition of buffer-acting substances orby removal of the air pollutants. Along with the field experiments, models have been used to predict future effects and dynamics in the ecosystems under different air pollution scenarios. The major findingsfrom those projects have been used in political decisions on reduction of sulphur emission in Europe via the sulphur protocol signed in 1994. Today work is going on to formulate a NOx protocol. NITREX and EXMAN results contribute to the scientific information basefor these protocols. Large-scale ecosystem manipulation projects have increased our understanding of ecosystem function and response to external change and created scientific evidence for political environmental decisions and legislation. In the future, controlled-ecosystem experiments clearly play an important role in new research on ecological effects of changes in the global atmosphere and climate. [ABSTRACT FROM AUTHOR]

European concern over the cause and consequences of forest decline, acidification of soils and surface waters, and the nutrient enrichment of terrestrial and aquatic ecosystems, led to the establishment of the NITREX (Nitrogen saturation experiments) and EXMAN (Experimental Manipulation of Forest Ecosystems in Europe) projects, two research networks of large-scale manipulation experiments under the auspices ofthe EU Commission of European Communities. NITREX comprises 10 experiments at 8 sites in 7 countries at which nitrogen is either added toor removed from ambient atmospheric deposition to simulate major changes in nitrogen deposition. EXMAN comprises experiments at 6 sites in 4 countries at which ambient atmospheric deposition is experimentally altered in chemical composition and/or quantity. The ultimate goalof this research is to contribute to the scientific basis required for the refinement of EU policy on atmospheric quality, and the legislation which will emanate from that policy. [ABSTRACT FROM AUTHOR]

The NITREX project entails large-scale manipulation of nitrogen deposition to whole, forested ecosystems at eight sites in Europe. Nitrogen is added at sites with low-to-intermediate ambient N deposition and removed at sites with high deposition. Changes in outputs of dissolved constituents reflect the integrated effects on ecosystem processes and changes in storage. At sites exhibiting clear symptoms of nitrogen saturation prior to treatment, the nitrate flux in leachate and runoff responded rapidly to changes in deposition. Reduced deposition gave immediate improvement in water quality. At sites with low nitrogen losses prior to treatment, the response to increased deposition was small and delayed. Together the results point to significant hysteresis in output response related to the nitrogen status of the ecosystem. The input--output budgets indicate that forest ecosystems requiremany years to adjust to changes in nitrogen deposition. [ABSTRACT FROM AUTHOR]

The deposition of nitrogen from the atmosphere to coniferous forestsposes the risk of N saturation and disruption of the N cycle. Beginning in April 1991, we have conducted a whole-ecosystem manipulation of N deposition at a mature coniferous forested-catchment at Gardsjon,SW Sweden. We have added in weekly portions of about 40 kg NH4NO3-N ha-1 yr-1 in 5% extra water to the ambient 11 kg NH4NO3-N ha-1 yr-1 in throughfall. The Gardsjon experiment is part of the European NITREX project (Nitrogen saturation experiments). Both the annual mean concentrations and peak concentrations of nitrate in runoff increased dramatically in response to the chronic additions of N. The seasonal pattern and yearly amount of N loss changed during the 5 years of treatment. During the first years of treatment, concentrations of NO3- were low during the growing season and high during the winter; during the fourth and fifth years, elevated concentrations were present also during the summer. Ammonium concentrations, although generally much lower than NO3-, followed the same seasonal pattern. The inorganic N lost during the 5 years of treatment was 0.6%, 1.1%, 5.0%, 5.7% and 4.5% respectively, of the annual inorganic N input. In the fifth year, drought and generally very low runoff led to moderate N loss despite the highNO3- and NH4+ concentrations. Sulphate, inorganic Aln+, H+ and Na+ concentrations were significantly lower during the treatment period relative to the untreated control catchment while NO3-, NH4+, K+ and Ca2+ concentrations increased. The N concentrations in the runoff indicate incipient N saturation at the manipulated catchment. But theexperimental dramatic increase in N deposition occurred so rapidly that [ABSTRACT FROM AUTHOR]

The effect of changes in dissolved inorganic nitrogen (N) depositionon ecosystem functioning was investigated in the NITREX (NITRogen saturation EXperiments) project. Field-scale manipulation experiments were carried out over four to six years in seven coniferous forest ecosystems in northwestern Europe. At sites with low or moderate ambientN deposition, N was experimentally added to throughfall. At sites with high N deposition, N was removed from throughfall. We found that the capacity of the ecosystem to retain N was correlated to its internal N status. Some of the components of this N status like the N concentrations in foliage and forest floor are relatively easy to measure.The C/N ratio of the forest floor is especially closely related to the onset of nitrate leaching. Changes in N input may, in the long run, change the N status of an ecosystem due to for instance a decrease in C/N ratio in the forest floor. Decreased N input resulted in a rapid and large reduction in N concentration in drainage water. Significant improvement in tree nutritional status, tree growth, fine root biomass and diversity of ground vegetation and mycorrhizal fungi population were observed in one site only. The time period of four to six years of manipulated N deposition may have been too short for changes to be manifested in the other sites. [ABSTRACT FROM AUTHOR]

Since 1991 nitrogen deposition to a small forested catchment has been experimentally increased from ambient 11 to a total of 50 kg N ha-1 year-1 by sprinkling small portions of dissolved ammonium nitrate on about 30 occasions annually. Concentrations ofinorganic N in runoff (streamwater) were measured by flow-proportional sampling and during 6 shorter periods by frequent sampling and continuous monitoring. Shortly after the onset of the N additions, nitrate (NO3) began to appear in the runoff (streamwater), after 2 years in soil solution at shallow depths and after 4 years at alldepths. N concentrations in runoff were highly variable, and most ofthe N lost from the catchment occurred during a few episodes. Flux of N from the catchment in runoff was much larger than that calculatedfrom concentrations in lysimeter samples and discharge from groundwater levels. The annual inorganic N loss was only about 5% of the incoming N. Episodic behavior of NO3 in runoff was studied by monitoring discharge episodes after 2, 3, 4 and 6 years of N addition. The nature of NO3 concentrations in runoff during these episodes changed as the treatment proceeded. Factors such as season, hydrology, timing and size of N additions govern the loss of NO3 in runoff during episodes. Nitrogen saturation at this catchment may proceed first in the discharge areas near the outlet to uphillsoils on the slopes. [ABSTRACT FROM AUTHOR]