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00971 Immobilization of 137Cs and 60Co in concrete matrix. Part 2: Mathematical modeling of transport phenomena
15 Environment (pollution, health protection, applications) 06•00971 Immobilization of 1arcs and 6°Co in concrete matrix, Part 2: Mathematical modeling of transport phenomena Plecas, I. and Dimovic, S. Annals qf Nuclear Energy, 2005, 32, (13), 1509 1515. There are two f u n d a m e n t a l issues that must be addressed in an a t t e m p t to isolate low-level waste in a disposal facility on land. The first is the isolation of waste from water, or hydrologic isolation. The second is prevention of radionuclide leakage from the disposal facility, or radionuclide migration. The authors have investigated here the latter modified scenario. T r a n s p o r t p h e n o m e n a involved in the leaching of a radioactive material from a c e m e n t composite matrix have been investigated using an empirical m e t h o d employing a polynomial equation. The results p r e s e n t e d in this paper are examples of the results obtained from a 25-year m o r t a r and concrete testing project, which will influence the design of the e n g i n e e r e d trench system for a future central Serbian radioactive waste storage centre.
06•00972 Kinetics models for safety studies of accelerator driven systems Rineiski, A. and Maschek, W. Annals of Nuclear Energy, 2005, 32, (12), 1348 1365. Safety analyses of accelerator driven systems (ADSs) are mainly performed by codes developed in the past for critical reactors, a pointkinetics m o d e l for computing the transient power being often employed. It is shown that this m o d e l that assumes t i m e - i n d e p e n d e n t n e u t r o n direct and adjoint flux shapes may be inaccurate in the ADS case even if it is acceptable for a similar 'critical' case. A l t h o u g h the m a t e r i a l distribution remains almost unchanged, flux (power) shape variations may be significant in the first case due to external source related effects. An option for a more refined modelling of the neutron adjoint flux in ADS analyses is discussed. This option is shown to be rather complicated in the general case: it may give rise to involvement of several adjoint flux shapes and several sets of related point-kinetics p a r a m e t e r s (reactivity, etc.). To improve the accuracy of the pointkinetics treatment, an extended point-kinetics model, which employs several flux (or power) shapes p r e - c o m p u t e d at steady-state conditions, is proposed in the paper. This approach may help to avoid the spatial kinetics t r e a t m e n t if no strong material m o v e m e n t occurs. The reactivity and other point-kinetics p a r a m e t e r s are defined similarly to a critical reactor.
06•00973 Leaching of CCBs: observations from over 25 years of research Hassett, D. J. et al. Fuel, 2005, 84, (11), 1378 1383. Leaching of coal combustion by-products (CCBs) using various batch laboratory methods has been ongoing at the Energy & E n v i r o n m e n t a l R e s e a r c h Center for over 25 years. Early on in the various investigations involving leaching it b e c a m e obvious that the methods being advocated and used were generating scientifically invalid and often misleading data. This realization came about because of the following. (1) The wrong leaching solutions were often being used. M e t h o d s such as the extraction p r o c e d u r e toxicity test and, later, the toxic characteristic leaching p r o c e d u r e used an acetic acid-containing solution that would be unlikely to contact CCBs under any conditions. (2) It was found that the formation of secondary hydrated phases such as ettringite could have a profound influence on concentrations of certain trace elements that exist as oxyanions in aqueous solution. Because of these realizations, a m e t h o d that included long-term leaching (LTL) was developed called the synthetic groundwater leaching procedure, which a d d r e s s e d many of the problems with existing methods. D a t a collected over the last 25 years will be p r e s e n t e d to d e m o n s t r a t e the need for the use of p r o p e r leaching solutions and LTL. Additionally, currently utilized and proposed methods will be discussed, including the new suite of leaching methods recently proposed by the US E n v i r o n m e n t a l Protection Agency.
with the version of the model w i t h o u t ETL. The improved m e t h o d o l o g y indicates a potential for significant reduction in c a r b o n - a b a t e m e n t cost and economic losses. The method, which is basically in favor of late actions in abatement, implicitly assumes early R & D support and learning investments in carbon-free systems to help these new technologies follow their learning curves. The e n d o g e n o u s t r e a t m e n t of learning already shows significant reductions of carbon emissions in the baseline case and indicates that low-carbon concentrations and improved e n v i r o n m e n t a l performance can be obtained w h e n policies are followed that c o m p e n s a t e for externalities related to climate change. More precisely, M E R G E - E T L gives C/B-optimal carbonemission trajectories near the 590-ppmv-concentration level. Moreover, the imposition of constraints on the rate of t e m p e r a t u r e change (e.g. 0.21:C per decade) d e m a n d s early actions in carbon mitigation.
06•00975 Quantitative analysis of CO2 emissions reductions through introduction of stationary-type PEM-FC systems in Japan Nagata, Y. Energy, 2005, 30, (14), 2636 2653. While fuel-cell technology is expected to contribute to mitigating CO2 emissions in Japan, no quantitative analyses of energy consumption and accompanying CO2 emissions have been performed. This study analyses quantitatively the changes in t h e m effected by the p e n e t r a t i o n of proton exchange m e m b r a n e fuel cell ( P E M - F C ) cogeneration systems in J a p a n by taking account of the dynamic changes in the power-generation mix. The o p t i m a l generation mix model, developed by the J a p a n e s e Central R e s e a r c h Institute of the Electric Power Industry, is used for the calculations. The results show decreased and increased cases of CO2 emissions across the overall energy system, as c o m p a r e d with the reference cases. Key factors influencing these changes are the d e v e l o p m e n t of nuclear power, and technical progress in the efficiencies of P E M - F C systems and their o p e r a t i n g patterns in the future.
06/00976 Radiation effects on combustion and pollutant emissions of high-pressure opposed flow methane/air diffusion flames Zhu, X. L. and Gore, J. P. Combustion and Flame, 2005, 141, (1 2), 118 130. Numerical simulations of o n e - d i m e n s i o n a l opposed-flow laminar m e t h a n e / a i r diffusion flames with detailed gas chemistry and global soot kinetics were conducted using the Sandia O P P D I F code to u n d e r s t a n d the interactions between radiation and chemistry. The gasphase chemistry model was based on G R I - M e c h 2.11, and Lindstedt's global soot kinetics model was used for soot formation calculations. The O P P D I F code was modified to include the effects of the radiation source term and the equations for soot mass fraction and soot particle n u m b e r density based on soot kinetics. The radiation properties of the gas molecules and the soot particles, including a t r e a t m e n t for the selfabsorption of radiation, were considered. Interactions between soot and gas-phase chemistry were considered. The effects of radiation heat loss, pressure, and injection velocity were studied for m e t h a n e / a i r diffusion flames. The effects of radiation heat loss, thermophoresis, soot oxidation by Oe and O H radicals, and depletion of acetylene by soot formation were all found to be i m p o r t a n t in d e t e r m i n i n g soot concentrations, especially for high-pressure flames. Soot oxidation by O H radical d o m i n a t e s soot oxidation by Oe at atmospheric pressure. However, the O H oxidation rate decreases with increasing pressure, and becomes comparable to the Oe oxidation rate, which is very low c o m p a r e d with the overall soot formation rate at all pressures. The neglect of radiation heat loss leads to significantly higher estimates of soot and NO emissions c o m p a r e d with the estimates including radiation heat loss, particularly at high pressures. The effects of radiation, including those of self-absorption are found to be significant, particularly at lower stretch rates.
06•00974 Modeling experience curves in MERGE (model for evaluating regional and global effects Kypreos, S. Energy, 2005, 30, (14), 2721 2737. The Swiss National C e n t r e of C o m p e t e n c e in R e s e a r c h on Climate aims to explore the predictability, variability, and risk of climate change. The Paul Scherrer Institute, which is involved in this program, uses i n t e g r a t e d assessment models to simulate policies for climatechange mitigation under uncertainty. The authors report here selected results of the model for evaluating the regional and global effects ( M E R G E s ) of greenhouse-gas emissions with e n d o g e n o u s technological learning (ETL), known as M E R G E - E T L . The novelty of the approach is the application of a heuristic algorithm to solve the nonlinear and non-convex M E R G E problem where 'learning-by-doing' is a d o p t e d for a set of energy technologies. The study presents n u m e r i c a l examples showing the implications of e n d o g e n o u s - l e a r n i n g for the timing of c a r b o n - a b a t e m e n t that stabilizes carbon concentrations (e.g. at 550 ppmv), as well as the implications of this in terms of cost/benefit (C/B) analysis. The e n d o g e n o u s - l e a r n i n g formulation is contrasted
06/00977 Thermodynamic optimization of global circulation and climate Bejan, A. and Reis, A. H. International Journal of Energy Research, 2005, 29, (4), 303 316. The constructal law of generation of flow structure is used to predict the main features of global circulation and climate. The flow structure is the atmospheric and oceanic circulation. This feature is modelled as convection loops, and a d d e d to the earth model as a heat engine h e a t e d by the Sun and cooled by the background. It is shown that the dissipation of the power produced by the earth engine can be maximized by selecting the p r o p e r balance between the hot and cold zones of the Earth, and by optimizing the t h e r m a l conductance of the circulation loops. The optimized features agree with the main characteristics of global circulation and climate. The robustness of these predictions, and the place of the constructal law as a self-standing principle in thermodynamics, are discussed.
Fuel and Energy Abstracts
March 2006
141
06•00972 Kinetics models for safety studies of accelerator driven systems Rineiski, A. and Maschek, W. Annals of Nuclear Energy, 2005, 32, (12), 1348 1365. Safety analyses of accelerator driven systems (ADSs) are mainly performed by codes developed in the past for critical reactors, a pointkinetics m o d e l for computing the transient power being often employed. It is shown that this m o d e l that assumes t i m e - i n d e p e n d e n t n e u t r o n direct and adjoint flux shapes may be inaccurate in the ADS case even if it is acceptable for a similar 'critical' case. A l t h o u g h the m a t e r i a l distribution remains almost unchanged, flux (power) shape variations may be significant in the first case due to external source related effects. An option for a more refined modelling of the neutron adjoint flux in ADS analyses is discussed. This option is shown to be rather complicated in the general case: it may give rise to involvement of several adjoint flux shapes and several sets of related point-kinetics p a r a m e t e r s (reactivity, etc.). To improve the accuracy of the pointkinetics treatment, an extended point-kinetics model, which employs several flux (or power) shapes p r e - c o m p u t e d at steady-state conditions, is proposed in the paper. This approach may help to avoid the spatial kinetics t r e a t m e n t if no strong material m o v e m e n t occurs. The reactivity and other point-kinetics p a r a m e t e r s are defined similarly to a critical reactor.
06•00973 Leaching of CCBs: observations from over 25 years of research Hassett, D. J. et al. Fuel, 2005, 84, (11), 1378 1383. Leaching of coal combustion by-products (CCBs) using various batch laboratory methods has been ongoing at the Energy & E n v i r o n m e n t a l R e s e a r c h Center for over 25 years. Early on in the various investigations involving leaching it b e c a m e obvious that the methods being advocated and used were generating scientifically invalid and often misleading data. This realization came about because of the following. (1) The wrong leaching solutions were often being used. M e t h o d s such as the extraction p r o c e d u r e toxicity test and, later, the toxic characteristic leaching p r o c e d u r e used an acetic acid-containing solution that would be unlikely to contact CCBs under any conditions. (2) It was found that the formation of secondary hydrated phases such as ettringite could have a profound influence on concentrations of certain trace elements that exist as oxyanions in aqueous solution. Because of these realizations, a m e t h o d that included long-term leaching (LTL) was developed called the synthetic groundwater leaching procedure, which a d d r e s s e d many of the problems with existing methods. D a t a collected over the last 25 years will be p r e s e n t e d to d e m o n s t r a t e the need for the use of p r o p e r leaching solutions and LTL. Additionally, currently utilized and proposed methods will be discussed, including the new suite of leaching methods recently proposed by the US E n v i r o n m e n t a l Protection Agency.
with the version of the model w i t h o u t ETL. The improved m e t h o d o l o g y indicates a potential for significant reduction in c a r b o n - a b a t e m e n t cost and economic losses. The method, which is basically in favor of late actions in abatement, implicitly assumes early R & D support and learning investments in carbon-free systems to help these new technologies follow their learning curves. The e n d o g e n o u s t r e a t m e n t of learning already shows significant reductions of carbon emissions in the baseline case and indicates that low-carbon concentrations and improved e n v i r o n m e n t a l performance can be obtained w h e n policies are followed that c o m p e n s a t e for externalities related to climate change. More precisely, M E R G E - E T L gives C/B-optimal carbonemission trajectories near the 590-ppmv-concentration level. Moreover, the imposition of constraints on the rate of t e m p e r a t u r e change (e.g. 0.21:C per decade) d e m a n d s early actions in carbon mitigation.
06•00975 Quantitative analysis of CO2 emissions reductions through introduction of stationary-type PEM-FC systems in Japan Nagata, Y. Energy, 2005, 30, (14), 2636 2653. While fuel-cell technology is expected to contribute to mitigating CO2 emissions in Japan, no quantitative analyses of energy consumption and accompanying CO2 emissions have been performed. This study analyses quantitatively the changes in t h e m effected by the p e n e t r a t i o n of proton exchange m e m b r a n e fuel cell ( P E M - F C ) cogeneration systems in J a p a n by taking account of the dynamic changes in the power-generation mix. The o p t i m a l generation mix model, developed by the J a p a n e s e Central R e s e a r c h Institute of the Electric Power Industry, is used for the calculations. The results show decreased and increased cases of CO2 emissions across the overall energy system, as c o m p a r e d with the reference cases. Key factors influencing these changes are the d e v e l o p m e n t of nuclear power, and technical progress in the efficiencies of P E M - F C systems and their o p e r a t i n g patterns in the future.
06/00976 Radiation effects on combustion and pollutant emissions of high-pressure opposed flow methane/air diffusion flames Zhu, X. L. and Gore, J. P. Combustion and Flame, 2005, 141, (1 2), 118 130. Numerical simulations of o n e - d i m e n s i o n a l opposed-flow laminar m e t h a n e / a i r diffusion flames with detailed gas chemistry and global soot kinetics were conducted using the Sandia O P P D I F code to u n d e r s t a n d the interactions between radiation and chemistry. The gasphase chemistry model was based on G R I - M e c h 2.11, and Lindstedt's global soot kinetics model was used for soot formation calculations. The O P P D I F code was modified to include the effects of the radiation source term and the equations for soot mass fraction and soot particle n u m b e r density based on soot kinetics. The radiation properties of the gas molecules and the soot particles, including a t r e a t m e n t for the selfabsorption of radiation, were considered. Interactions between soot and gas-phase chemistry were considered. The effects of radiation heat loss, pressure, and injection velocity were studied for m e t h a n e / a i r diffusion flames. The effects of radiation heat loss, thermophoresis, soot oxidation by Oe and O H radicals, and depletion of acetylene by soot formation were all found to be i m p o r t a n t in d e t e r m i n i n g soot concentrations, especially for high-pressure flames. Soot oxidation by O H radical d o m i n a t e s soot oxidation by Oe at atmospheric pressure. However, the O H oxidation rate decreases with increasing pressure, and becomes comparable to the Oe oxidation rate, which is very low c o m p a r e d with the overall soot formation rate at all pressures. The neglect of radiation heat loss leads to significantly higher estimates of soot and NO emissions c o m p a r e d with the estimates including radiation heat loss, particularly at high pressures. The effects of radiation, including those of self-absorption are found to be significant, particularly at lower stretch rates.
06•00974 Modeling experience curves in MERGE (model for evaluating regional and global effects Kypreos, S. Energy, 2005, 30, (14), 2721 2737. The Swiss National C e n t r e of C o m p e t e n c e in R e s e a r c h on Climate aims to explore the predictability, variability, and risk of climate change. The Paul Scherrer Institute, which is involved in this program, uses i n t e g r a t e d assessment models to simulate policies for climatechange mitigation under uncertainty. The authors report here selected results of the model for evaluating the regional and global effects ( M E R G E s ) of greenhouse-gas emissions with e n d o g e n o u s technological learning (ETL), known as M E R G E - E T L . The novelty of the approach is the application of a heuristic algorithm to solve the nonlinear and non-convex M E R G E problem where 'learning-by-doing' is a d o p t e d for a set of energy technologies. The study presents n u m e r i c a l examples showing the implications of e n d o g e n o u s - l e a r n i n g for the timing of c a r b o n - a b a t e m e n t that stabilizes carbon concentrations (e.g. at 550 ppmv), as well as the implications of this in terms of cost/benefit (C/B) analysis. The e n d o g e n o u s - l e a r n i n g formulation is contrasted
06/00977 Thermodynamic optimization of global circulation and climate Bejan, A. and Reis, A. H. International Journal of Energy Research, 2005, 29, (4), 303 316. The constructal law of generation of flow structure is used to predict the main features of global circulation and climate. The flow structure is the atmospheric and oceanic circulation. This feature is modelled as convection loops, and a d d e d to the earth model as a heat engine h e a t e d by the Sun and cooled by the background. It is shown that the dissipation of the power produced by the earth engine can be maximized by selecting the p r o p e r balance between the hot and cold zones of the Earth, and by optimizing the t h e r m a l conductance of the circulation loops. The optimized features agree with the main characteristics of global circulation and climate. The robustness of these predictions, and the place of the constructal law as a self-standing principle in thermodynamics, are discussed.
Fuel and Energy Abstracts
March 2006
141