Fuel matrix materials

The treatment of spent nuclear fuel by the IFR process results in two HLW forms ceramic and metal. The ceramic waste form stabilizes the active FPs (alkali, alkaline earth, and rare earths) and the metal waste consists of stainless steel cladding and, fuel matrix material... 

Constraint (3.5) is the fuel system material balance where the term represents the caloric value equivalent for each intermediate cir CB used in the fuel system at plant i I. The fuel production system can either consist of a single or combination of intermediates u,cr c r i and products The matrix (3crjfip... 

Initially, Oz diffuses through the bentonite and granitic domains, controlling the redox state of the system. Once 02 is exhausted, granitic groundwater controls the redox state of the system. The results of these calculations performed with the PHREEQC geochemical code (Parkhust Appelo 1999) clearly indicate that there is a substantial variability in pH/pe space along the temporal and spatial evolution of the near field of a repositoiy. This has clear consequences for the subsequent interactions with the Fe canister material and finally with the spent fuel matrix. 

The fluids that have evolved as a result of the bentonite-groundwater interactions will contact the canister on their travel towards the spent fuel matrix. Most of the proposed canister materials in different countries have in common the presence of Fe in the system, either as cast iron (Sweden, Finland) or as stainless steel (France, Spain). While the bentonite-groundwater processes have... 

The spent fuel matrix is a ceramic material with a fascinating chemical composition and a large degree of phase heterogeneity. The physical state and chemical composition of spent fuel largely depends on the bum-up of the fuel once it is taken out of the reactor. In Fig. 6 we indicate the dependence of the chemical composition on the bum-up for a series of PWR fuels. However, the fact that remains constant is that U02 constitutes the major component of spent fuel, ranging within a total of 95-98% in weight (see Fig. 7). 

Bruno, J., Casas, I., Cera, E., Swing, R. C., Finch, R. C. Werme, L. O. 1995. The assessment of the long-term evolution of the spent nuclear fuel matrix by kinetic, thermodynamic and spectroscopic studies of uranium minerals. Materials Research Society Symposium Proceedings, 353, 633-639. 

Phosphoric Acid Fuel Cells (PAFCs) for Utilities Electrocatalyst Crystallite Design, Carbon Support, and Matrix Materials Challenges... 

In chapter 4, Stonehart (a major authority in the field of H2 fuelcell technology and its fundamental aspects) writes, with co-author Wheeler, on the topic of Phosphoric Acid Fuel-Cells (PAFCs) for Utilities Electrocatalyst Crystallite Design, Carbon Support, and Matrix Materials Challenges. This contribution reviews, in detail, recent information on the behavior of very small Pt and other alloy electrocatalyst crystallites used as the electrode materials for phosphoric acid electrolyte fuel-cells. 

Lim and Winnick [110] examined removal of H2S from a simulated hot coal-gas stream fed to the cathode while elemental sulfur gas was evolved at the anode. This process was performed in a cell that was similar in construction to a molten carbonate fuel cell (Fig. 23). The electrolyte was a mixture of Na2S and Li2S retained in a porous inert matrix material (MgO). The cathodic reaction involved the two-electron reduction of hydrogen sulfide to hydrogen (information on the equilibrium potential for H2S reduction can be obtained from [111] ... 

P. Stonehart and D. Wheeler, Phosphoric Acid Fuel Cells (PAFCs) for vehicles Electrocatalyst Crystalite Design, Carbon Support, and Matrix Materials Challenges in Modem Aspects of Electrochemistry, Vol. 38, Ed. by B. E. Conway, Kluwer/Plenum, New York (2005) Chapter 4, 385. 

Arendt, R.H. Alternate matrix materials for molten carbonate fuel cell electrolyte structures. J. Electrochem. Soc. 1982, 129 (5), 979-983. 

Tanimoto, K. Miyazaki, Y. Yanagida, M. Tanase, S. Kojima, T. Okuyama, H. Kodama, T. Alternative matrix materials for molten carbonate fuel cell. Denki Kagaku 1990, 41 (2), 51-55. 

The graphite fuel blocks of the HTGR contain sulfur contaminant, which originates from the pitch used to form the fuel-rod matrix material. Neutron activation of the 4.22 percent S in natural sulfur results in 88-day S, according to the reaction... 

Chemical Vapor Deposition (CVD) is a technique of deposition of a solid on a heated substrate, from gaseous precursors. It has been used for many years to produce wear resistant coatings, coatings for nuclear fuels, thin films for electronic circuits ceramic fibers, etc. .. When the CVD technique is used to impregnate ratiier large amounts of matrix materials in fibrous preforms, it is called chemical vapor impregnation or infiltration... 

Barrier (against radioactive releases) Structure, set of structures or of systems which contrast the uncontrolled release of radioactive material to the outside or to the inside of a nuclear plant. For the radioactivity connected to fission products, the plant design provides the following barriers the fuel matrix, the fuel element claddings, the primary circuit(s), the containment system. 

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