In safety assessments of underground radioactive waste repositories, understanding radionuclide fate in ecosystems is necessary to determine the impacts of potential releases. Here, the reliability of two mechanistic models (the compartmental K-model and the 3D dynamic D-model) in describing the fate of radionuclides released into a Baltic Sea bay is tested. Both are based on ecosystem models that simulate the cycling of organic matter (carbon). Radionuclide transfer is linked to adsorption and flows of carbon in food chains. Accumulation of Th-230, Cs-135, and Ni-59 in biological compartments was comparable between the models and site measurements despite differences in temporal resolution, biological state variables, and partition coefficients. Both models provided confidence limits for their modeled concentration ratios, an improvement over models that only estimate means. The D-model enables estimates at high spatio-temporal resolution. The K-model, being coarser but faster, allows estimates centuries ahead. Future developments could integrate the two models to take advantage of their respective strengths.

Swedish nuclear utility companies are required to assess doses due to releases of radionuclides during normal operation. In 2001, calculation methods used earlier were updated due to new authority regulations. The isotope (14)C is of special interest in dose assessments due to the role of carbon in the metabolism of all life forms. Earlier, factors expressing the ratio between concentration of (14)C in air and in various plants were used. In order to extend the possibility to take local conditions into account, a process-oriented assessment model for uptake of carbon and doses from releases of (14)C to air was developed (POM(14)C). The model uses part of DAISY which has been developed to model the turnover of carbon in crops. [Hansen, S., Jensen, H.E., Nielsen, N.E., Svendsen, H., 1993. Description of the Soil Plant System Model DAISY, Basic Principles and Modelling Approach. Simulation Model for Transformation and Transport of Energy and Matter in the Soil Plant Atmosphere System. Jordbruksförlaget, The Royal Veterinary and Agricultural University, Copenhagen, Denmark]. The main objectives were to test model performance of the former method, and to investigate if taking site specific parameters into account to a greater degree would lead to major differences in the results. Several exposure pathways were considered: direct consumption of locally grown cereals, vegetables, and root vegetables, as well as consumption of milk and meat from cows having eaten fodder cereals and green fodder from the area around the nuclear plant. The total dose of the earlier model was compared with that of POM(14)C. The result of the former was shown to be slightly higher than the latter, but POM(14)C confirmed that the earlier results were of a reasonable magnitude. When full account of local conditions was taken, e.g. as regards solar radiation, temperature, and concentration of (14)C in air at various places in the surroundings of each nuclear plant, a difference in dose between sites of approximately one order of magnitude was found.

This paper is based on studies performed within the framework of the project Socio-Economic Research on Fusion (SERF3). Several fusion power plant designs (SEAFP Models 1–6) were compared focusing on part of the plant's life cycle: environmental impact of recycling the materials. Recycling was considered for materials replaced during normal operation, as well as materials from decommissioning of the plant. Environmental impact was assessed and expressed as external cost normalised with the total electrical energy output during plant operation. The methodology used for this study has been developed by the Commission of the European Union within the frame of the ExternE project. External costs for recycling, normalised with the energy production during plant operation, are very low compared with those for other energy sources. Results indicate that a high degree of recycling is preferable, at least when considering external costs, because external costs of manufacturing of new materials and disposal costs are higher.

This study was performed in the framework of the Socio-Economic Research on Fusion (SERF3), which is jointly conducted by Euratom and the fusion associations. Assessments of monetarized external impacts of the fusion fuel-cycle were previously performed (SERF1 and SERF2). Three different power plant designs were studied, with the main difference being the structural materials and cooling system used. In this third phase of the SERF project the external costs of three additional fusion power plant models using silicon carbide as structural material have been analysed. A comparison with other advanced generation technologies expected to be in use around 2050, when the first fusion power plant would be operative, has also been performed. These technologies include advanced fossil technologies, such as Natural Gas Combined Cycle, Pressurised Fluidised Bed Combustion and Integrated Gasification Combined Cycle with carbon sequestration technologies; fuel cells and renewable technologies including geothermal energy, wind energy and photovoltaic systems with energy storage devices. Fusion power plants using silicon carbide as structural material have higher efficiencies than plants using steel and this fact has a very positive effect on the external costs per kW h. These external costs are in the lowest range of the external costs of advanced generation technologies indicating the outstanding environmental performance of fusion power.

All the damages that are not reflected in the market price are called external costs. The external costs of fusion were elaborated with the ExternE methodology. The external costs are in the range of a few mEuro/kWh depending on the plant model. The external costs are in general not dominated by the impacts due to radioactive emissions and releases. All stages of the life cycle contribute significantly to the external cost value. The external costs of fusion are in the same range as the external costs of photovoltaics and wind energy.

If measures to reduce greenhouse gas-emissions are taken and if fission will be phased out at the beginning of the 22nd century fusion has a good chance to win considerable shares of the electricity market. A detailed model of the Western-European energy system was made using the MARKAL toolkit. Scenarios were designed to understand the conditions that would make fusion a viable electricity production technique. Globally it is very likely that at least the first half of the 21st century will still be dominated by the use of fossil fuels, with a shift away from oil to natural gas. Energy and electricity demand are likely to increase over the complete 21st century.

Analysis of sensitivity and uncertainty of assessment models for external costs, which is monetarization of environmental impacts, of a commercial fusion plant were performed. The assessments covered the plant's entire life cycle, and adopted the ExternE methodology, which had been used to calculate external costs from other energy sources. Based on the SEAFP study, three different power plant designs were considered. The method developed in ExternE to estimate uncertainty gave very large ranges. A statistical error propagation method was employed for this study. Rather than as a single value, model input parameter values were given as distributions, from which random input sets of data were constructed. The models were then run with these sets, and the ensemble of output results was analysed statistically, yielding estimates of the uncertainty due to variation of the model parameteres. More information of parameter variation is needed for a more realistic estimation of model uncertainty, though. Sensitivity analyses were performed by varying all input parameters in a similar fashion. All model parameters were assumed to have a gaussian distribution with standard deviations of 10% of the mean value. The results pointed out the most essential parameters of the models. The sensitivity analyses are also useful for estimating the most effective ways to reduce the model computed external costs.

This study was performed in the framework of the Socio-Economic Research on Fusion (SERF 1999–2000), which is jointly conducted by Euratom and the fusion associations. An assessment of monetarized external impacts of the fusion fuel-cycle was previously performed applying the ExternE methodology (SERF-1), where, based on the SEAFP study, two different power plant designs were assessed, with the main difference being the structural materials and cooling system used. Although external costs values obtained were low, an improvement was achieved in the trade-off between design criteria and consequences on externalities. Structural and shielding materials in the previously studied plant models turned out to have a N-14 content that originated a significant amount of C-14 emissions. The present study includes alternative shielding materials with lower nitrogen content. With updated and improved technical and methodological inputs, a recalculation of externalities in the whole fusion fuel cycle was performed.

The radiological impact of an intense fusion economy, a 1000 GW operating capacity for a 1000 years, were investigated regarding the isotopes (14)C and tritium. Both isotopes,participate in global material cycles, the carbon and the water cycle. If a retention time of 10000 years is assumed for the stored waste, (14)C emissions from the repositories dominate the radiation impacts. While the cumulated collective doses over a long term period are rather high and according to the discount rate selected would lead to significant external costs, the individual doses are small compared with the doses associated with the natural background radiation. (C) 2001 Elsevier Science B.V. All rights reserved.

The evaluation of the external costs associated with an accident in a fusion power plant points out that the consequences of such an event, as far as health and environmental impacts are concerned, remain rather limited. This paper presents the main components of the evaluation on accident, performed in the framework of the Studies on Socio-Economic Research on Fusion SERF under the EURATOM agreement. This evaluation, limited to the health and environmental impacts, shows that the external costs of the fusion accident is in the range of 10−5–10−4 mEURO/kWh while the total external costs for fusion are estimated in the range of a few mEURO per kilowatt hour. It should be noted that even with the integration of risk aversion, the external cost associated with the accident scenario for fusion power plant still remains quite limited due to the low radiological impacts that would have to support the populations surrounding the power plant if an accident occurred, especially the absence of evacuation and relocation of the population and the very limited constraints on food products.