Molten salts Energy System

SNETP. 2012. Sustainable Nuclear Energy Technology Platform Strategic Research Agenda—Annex, Molten Salt Reactor Systems. 

The metal is a source of nuclear power. There is probably more energy available for use from thorium in the minerals of the earth s crust than from both uranium and fossil fuels. Any sizable demand from thorium as a nuclear fuel is still several years in the future. Work has been done in developing thorium cycle converter-reactor systems. Several prototypes, including the HTGR (high-temperature gas-cooled reactor) and MSRE (molten salt converter reactor experiment), have operated. While the HTGR reactors are efficient, they are not expected to become important commercially for many years because of certain operating difficulties. 

Hot Corrosion. Hot corrosion is an accelerated form of oxidation that arises from the presence not only of an oxidizing gas, but also of a molten salt on the component surface. The molten salt interacts with the protective oxide so as to render the oxide nonprotective. Most commonly, hot corrosion is associated with the condensation of a thin molten film of sodium sulfate [7757-82-6], Na2S04, on superaHoys commonly used in components for gas turbines, particularly first-stage turbine blades and vanes. Other examples of hot corrosion have been identified in energy conversion systems, particularly coal gasifiers and direct coal combustors. In these cases the salt originates from alkali impurities in the coal which condense on the internal... 

Based on the results of the Solar One plant. Southern California Edison formed a consortium that included DOE and EPRI to constmct a Solar Two Project. Solar Two will convert the idle Solar One central receiver plant from a water/steam system to a molten salt system, thereby improving efficiency and operating performance. With the molten salt technology, solar energy can be collected during the day and stored in the salt to produce electricity when needed. The three-year demonstration is scheduled to begin in late 1996. 

G. J. Janz, C. B. AHen, N. P. Bansal, R. M. Murphy, and R. P. T. Tomkins, PhjsicalProperties Data Compilations Kelevantto Energy Storage. II Molten Salts Data on Single and Multi-Component Salt Systems, U.S. Department of Commerce, National Bureau of Standards, Washington, D.C., Apr. 1979, pp. 142-154. 

The molten salt electrolyte also contributes to the safety behavior of ZEBRA cells. The large amount of energy stored in a 700 g cell, which means about 30 kWh in a 300 kg battery, is not released suddenly as heat as be expected in a system with liquid electrodes such as the sodium sulfur cell. In the case of accidental destruction of ZEBRA cells, the sodium will react mainly with the molten salt, forming A1 sponge and NaCl. -The diffusion of the NaAICI ... 

Sindzinger and Gillan have calculated the thermal conductivity for NaCl and KCl melts as well as for sohds on the basis of MD simulations in Ml thermal equilibrium using the Green-Kubo relations (Table 17). In a single molten salt system, the local fluxes jz and of charge and energy... 

Reciprocal molten salt systems are those containing at least two cations and two anions. We shall deal with the simplest member of this class, that containing the ions A+, B+, X-, and Y-. The four constituents of the solution, AX, BX, AY, and BY, will be designated by 1, 2, 3, and 4 respectively. There are four ions in the system and one restriction of electroneutrality. Consequently, of the four constituents, there are only three which are independent components. In order to calculate the Helmholtz free energy of mixing conveniently, we must (arbitrarily) choose the three components. Here we choose BX, AY, and BY. This choice requires that in order to make mixtures of some compositions a negative quantity of BY must be used. This presents no difficulty in the theory and is thermodynamically self-consistent. One mole of some arbitrary composition (XA, XB, Yx, XY) can be made by mixing Arx moles of BX (component 2), XA moles of AY (component 3), and (XY — XA) moles of BY (component 4). ... 

E. J. Casey (Defense Research Establishment, Ottawa) reviewed the selection of anodes and electrolytes for high-energy density storage batteries. The present state of development of batteries by using light metal anodes in nonaqueous, molten salt and solid electrolytes was reviewed, and suggestions were made on the feasibility of novel systems. 

In a U.S.S.R. patent, Na anodes in molten salts (NaOH + NaBr) were disclosed as a source of electric power at high temperature, but no cycling data were presented (85a). A secondary battery operating at 150° with high TED and achieved energy output is described in a German patent, based on the system Na/NaAlCli /C, with a beta-Al203 separator (85b). 

Prospects for TR Electrolyte SBs. In view of the harmful effects often cited in the literature of even small traces of water on the operation of non-aqueous batteries with alkali metal anodes, it might be supposed that electrolytes of the TR composition cannot be applied in such batteries. This same idea may dominate when molten salt SBs are considered. Such a general conclusion cannot be justified. A dilute solution of water in a salt has the structure either of this salt proper or its adjacent hydrate, and the energy, properties and reactions of this water are quite different from those of pure water or of dilute solutions of various compounds in it. On the other hand, a small amount of water in the electrolyte system will decrease its melting point and increase its conductivity. Mixtures of water with such liquids as some alcohols or dioxane and other aprotic and even proton-forming substances, may open new prospects for... 

Since in the interconversion of electrical and chemical energies, electrical energy flows to or from the system in which chemical changes lake place, it is essential that the system be. in large part, conducting or consist of electrical conductors. These are of two general types—electronic and electrolytic—though some materials exhibit both types of conduction. Metals are the most common electronic conductors. Typical electrolytic conductors are molten salts and solutions of acids, bases, and salts. 

The melting behavior of fused salts is consistent with the idea that charge ordering is preserved. For example, the heats of fusion for alkali halide systems are usually <5% of the lattice energy, indicating that most of the lattice stmcture is preserved [78]. It has also been observed that nearest-neighbor distances decrease on melting for many molten salts, while ion... 

Fig. 13.51. Theoretical specific energy plotted against the equivalent weight for various batteries. The present commercial battery systems are in the lower right corner. Types of electrolytes , molten salt or ceramic o, aqueous. (Reprinted from K. Kordesch, in Comprehensive Treatise of Electrochemistry, J. O M. Bockris, B. E. Conway, E. Yeager, and R. E. White, eds., Vol. 3, p. 123, Plenum, 1981.)...

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