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1.
Douglas D. Walker Björn Gylling Anders Ström Jan-Olof Selroos 《Hydrogeology Journal》2001,9(5):419-431
Safety Report 1997 (SR 97) of the Swedish Nuclear Fuel and Waste Management Company is a comprehensive performance assessment
of three hypothetical radioactive waste repositories in Sweden. It includes hydrogeologic studies (data compilation, parameter
synthesis, and groundwater flow modeling) to determine groundwater flow and the associated uncertainties for the three sites.
This report reviews and compares the hydrogeologic characterization programs, the site characteristics, and the groundwater
flow models used in the SR 97 performance assessment. Although differences in site-characterization programs tend to mask
differences in site characteristics, the sites do have notable differences that affect the results of the performance assessment.
The effects of model uncertainties evaluated by the variant cases appear to be smaller than the variability of results for
the base case (best estimate of site conditions) of each site.
Electronic Publication 相似文献
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David Hodgkinson Hakim Benabderrahmane Mark Elert Aimo Hautojärvi Jan-Olof Selroos Yasuharu Tanaka Masahiro Uchida 《Hydrogeology Journal》2009,17(5):1035-1049
An overview is presented of a 4-year study by the Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes, whose primary aim was to build a bridge between the approaches used for site characterisation (SC) and performance assessment (PA) associated with nuclear waste repositories. Eleven modelling teams representing six national radioactive waste organisations participated in eight modelling exercises whose objectives were: to assess simplifications used in PA models; to determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models; to support the design of SC programmes to assure that the results have optimal value for PA calculations; and to improve the understanding of site-specific flow and transport behaviour at different scales using SC models. The modelling tasks were concerned with flow and transport through single and multiple near-planar features on SC and PA timescales, including the diffusion of solutes into multiple immobile zones adjacent to fracture surfaces. In general, tracer tests provide only limited quantitative constraints on retention parameter values relevant to PA but nevertheless provide insight about the flow and transport processes, which is a key element of the bridge between SC and PA. 相似文献
3.
Patrik Vidstrand Sven Follin Jan-Olof Selroos Jens-Ove Näslund 《Hydrogeology Journal》2014,22(6):1251-1267
The impact of periglacial and glacial climate conditions on groundwater flow in fractured crystalline rock is studied by means of groundwater flow modeling of the Forsmark site, which was recently proposed as a repository site for the disposal of spent high-level nuclear fuel in Sweden. The employed model uses a thermal-hydraulically coupled approach for permafrost modeling and discusses changes in groundwater flow implied by the climate conditions found over northern Europe at different times during the last glacial cycle (Weichselian glaciation). It is concluded that discharge of particles released at repository depth occurs very close to the ice-sheet margin in the absence of permafrost. If permafrost is included, the greater part discharges into taliks in the periglacial area. During a glacial cycle, hydraulic gradients at repository depth reach their maximum values when the ice-sheet margin passes over the site; at this time, also, the interface between fresh and saline waters is distorted the most. The combined effect of advances and retreats during several glaciations has not been studied in the present work; however, the results indicate that hydrochemical conditions at depth in the groundwater flow model are almost restored after a single event of ice-sheet advance and retreat. 相似文献
4.
Effect of transport-pathway simplifications on projected releases of radionuclides from a nuclear waste repository (Sweden) 总被引：2，自引：1，他引：1
The Swedish Nuclear Fuel and Waste Management Company has recently submitted an application for a license to construct a final repository for spent nuclear fuel, at approximately 500?m depth in crystalline bedrock. Migration pathways through the geosphere barrier are geometrically complex, with segments in fractured rock, deformation zones, backfilled tunnels, and near-surface soils. Several simplifications of these complex migration pathways were used in the assessments of repository performance that supported the license application. Specifically, in the geosphere transport calculations, radionuclide transport in soils and tunnels was neglected, and deformation zones were assumed to have transport characteristics of fractured rock. The effects of these simplifications on the projected performance of the geosphere barrier system are addressed. Geosphere performance is shown to be sensitive to how transport characteristics of deformation zones are conceptualized and incorporated into the model. Incorporation of advective groundwater travel time within backfilled tunnels reduces radiological dose from non-sorbing radionuclides such as I-129, while sorption in near-surface soils reduces radiological doses from sorbing radionuclides such as Ra-226. These results help quantify the degree to which geosphere performance was pessimistically assessed, and provide some guidance on how future studies to reduce uncertainty in geosphere performance may be focused. 相似文献
5.
Jan-Olof Drangert 《GeoJournal》1998,45(3):201-208
A brief look around the globe shows that most countries are facing sanitary problems, especially in the expanding cities in
the Southern Hemisphere. Governments and municipal councils are trying hard to improve sanitation conditions within the mind
set of piped systems. There is a need to know what is being done in other countries in order to enlarge the policy options.
Among these are the ones recirculating water and nutrients. This article focuses on excreta disposal systems which use little
or no water, and various ways to use the end products of faeces and urine. Doing away with our urine blindness will pave the
way to discover new possibilities which will save scarce resources in the future.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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7.
The story of phosphorus: Global food security and food for thought 总被引：12，自引：0，他引：12
Food production requires application of fertilizers containing phosphorus, nitrogen and potassium on agricultural fields in order to sustain crop yields. However modern agriculture is dependent on phosphorus derived from phosphate rock, which is a non-renewable resource and current global reserves may be depleted in 50–100 years. While phosphorus demand is projected to increase, the expected global peak in phosphorus production is predicted to occur around 2030. The exact timing of peak phosphorus production might be disputed, however it is widely acknowledged within the fertilizer industry that the quality of remaining phosphate rock is decreasing and production costs are increasing. Yet future access to phosphorus receives little or no international attention. This paper puts forward the case for including long-term phosphorus scarcity on the priority agenda for global food security. Opportunities for recovering phosphorus and reducing demand are also addressed together with institutional challenges. 相似文献
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Constraining performance assessment models with tracer test results: a comparison between two conceptual models 总被引：2，自引：2，他引：0
Tracer tests are conducted to ascertain solute transport parameters of a single rock feature over a 5-m transport pathway. Two different conceptualizations of double-porosity solute transport provide estimates of the tracer breakthrough curves. One of the conceptualizations (single-rate) employs a single effective diffusion coefficient in a matrix with infinite penetration depth. However, the tracer retention between different flow paths can vary as the ratio of flow-wetted surface to flow rate differs between the path lines. The other conceptualization (multirate) employs a continuous distribution of multiple diffusion rate coefficients in a matrix with variable, yet finite, capacity. Application of these two models with the parameters estimated on the tracer test breakthrough curves produces transport results that differ by orders of magnitude in peak concentration and time to peak concentration at the performance assessment (PA) time and length scales (100,000 years and 1,000 m). These differences are examined by calculating the time limits for the diffusive capacity to act as an infinite medium. These limits are compared across both conceptual models and also against characteristic times for diffusion at both the tracer test and PA scales. Additionally, the differences between the models are examined by re-estimating parameters for the multirate model from the traditional double-porosity model results at the PA scale. Results indicate that for each model the amount of the diffusive capacity that acts as an infinite medium over the specified time scale explains the differences between the model results and that tracer tests alone cannot provide reliable estimates of transport parameters for the PA scale. Results of Monte Carlo runs of the transport models with varying travel times and path lengths show consistent results between models and suggest that the variation in flow-wetted surface to flow rate along path lines is insignificant relative to variability in the amount of diffusive capacity that can be accessed along the transport pathway.
Resumen Delimitando la eficacia de modelos de evaluación con resultados de pruebas de trazadores: una comparación entre dos modelos conceptuales.Se llevaron a cabo pruebas de trazadores para evaluar los parámetros de transporte de solutos en un rasgo rocoso a lo largo de una trayectoria de transporte de 5 m. Dos diferentes conceptualizaciones del transporte de solutos de porosidad doble aportan estimados de las curvas de avance de trazadores. Una de las conceptualizaciones (ritmo único) utiliza un coeficiente de difusión efectiva único en una matriz con profundidad de penetración infinita. Sin embargo, la retención del trazador entre diferentes trayectorias de flujo puede variar debido a que la relación entre la superficie mojada de flujo y el ritmo de flujo difiere entre las líneas de trayectoria. La otra conceptualización (multi-ritmo) utiliza una distribución continua de coeficientes de ritmos de difusión múltiple en una matriz con capacidad variable pero finita. La aplicación de los dos modelos con los parámetros estimados en base a las curvas de avance de trazadores producen resultados de transporte que difieren en varios órdenes de magnitud, tanto en concentración pico como en el tiempo en que se alcanza la concentración pico, en las escalas de evaluación de eficacia (PA) de tiempo y longitud (100,000 años y 1,000 m). Estas diferencias se examinan mediante el cálculo de límites de tiempo en que se considera que la capacidad difusiva actúa como un medio infinito. Estos límites se comparan en ambos modelos conceptuales y contra los tiempos característicos para difusión en escalas de PA y de prueba de trazador. Adicionalmente, se examinan las diferencias entre los modelos calculando de nuevo los parámetros para el modelo multi-ritmo a partir del modelo tradicional de doble porosidad a escala PA. Los resultados indican que para cada modelo la cantidad de la capacidad difusiva que actúa como un medio infinito sobre la escala de tiempo especificada explica las diferencias entre los resultados del modelo y que las pruebas de trazadores por sí solas no aportan cálculos confiables de los parámetros de transporte para la escala PA. Los resultados provenientes de corridas Monte Carlo de los modelos de transporte con distintos tiempos de viaje y diferentes longitudes de trayectorias muestran resultados consistentes entre modelos y sugieren que la variación en la relación de superficie de flujo mojada a ritmo de flujo a lo largo de las líneas de trayectoria es insignificante en relación con la variabilidad en la cantidad de capacidad difusiva que puede alcanzarse a lo largo de la trayectoria de transporte.
Résumé Contraindre le bilan des performances des modèles avec les résultats de traçages: une comparaison entre deux modèles conceptuels.Des tests de traçage sont mis en oeuvre pour étudier les paramètres de transport de soluté dune roche sur une longueur de 5 m. Deux différents modèles de transport de soluté dans un milieu à double porosité fournissent des estimation des courbes de restitution. Lune des conceptualisations (unique taux de restitution) emploie un seul coefficient effectif de diffusion dans une matrice possédant une pénétration infinie en profondeur. Par ailleurs, la rétention du traceur entre les différentes lignes découlement peut varier comme le rapport des débits aux surfaces mouillées et comme le rapport de la différence de débits entres les lignes découlement. Lautre conceptualisation (taux multiple) emploie une distribution continue de coefficients de diffusion dans une matrice à capacité variable et finit. Lapplication de ces deux modèles avec les pa! ramètres estimés grâce aux courbes de restitution produit des résultats de transport qui différent de plusieurs ordres de grandeur dans la magnitude du pic, le temps du pic de concentration, au bilan des performances (PA) et aux échelles de distance (100,000 ans et 1,000 m). Ces différences sont éxaminées par lintermédiaire des temps limites pour que la capacité diffusive équivaille à un milieu infini. Ces limites sont comparées à travers les modèles conceptuels ainsi que les temps caractéristiques de diffusion à léchelle du test de traçage et à léchelle du PA. Par ailleurs, les différences entre les modèles sont éxaminées en réestimant les paramètres pour le modèle à taux multiple à partir des résultats du modèle à double porosité à léchelle du PA. Les résultats indiquent que pour chaque modèle la valeur de la capacité diffusive dans un milieu infini sur une période de temps spécifiée explique les différences entre les modèles et le ! fait que le test de traçage seul ne permet pas de déterminer les paramètres de transport à léchelle du PA. Les résultats des simulations Monte Carlo du modèle de transport avec des temps et des distances de transport variables montrent des résultats concordances entre les différents modèles et suggère que la variation que la variation entre surface mouillée et le rapport de la différence de débits entre les lignes découlement est insignifiante, en regard de la variabilité du montant de la capacité diffusive qui peut être accessible le long de la ligne de transport.相似文献