Sodium heat-transfer medium

The reaction is exothermic, and multitubular reactors are employed with indirect cooling of the reactor via a heat transfer medium. A number of heat transfer media have been proposed to carry out the reactor cooling, such as hot oil circuits, water, sulfur, mercury, etc. However, the favored heat transfer medium is usually a molten heat transfer salt which is a eutectic mixture of sodium-potassium nitrate-nitrite. 

An alloy of sodium and potassium (NaK) is used as a heat-transfer medium. Many potassium salts are of utmost importance, including the hydroxide, nitrate, carbonate, chloride, chlorate, bromide, iodide, cyanide, sulfate, chromate, and dichromate. 

Sodium is used as a heat-transfer medium in primary and secondary cooling loops of Hquid-metal fast-breeder power reactors (5,155—157). Low neutron cross section, short half-life of the radioisotopes produced, low corrosiveness, low density, low viscosity, low melting point, high boiling point, high thermal conductivity, and low pressure make sodium systems attractive for this appHcation (40). 

Traditionally, sodium dichromate dihydrate is mixed with 66° Bh (specific gravity = 1.84) sulfuric acid in a heavy-walled cast-iron or steel reactor. The mixture is heated externally, and the reactor is provided with a sweep agitator. Water is driven off and the hydrous bisulfate melts at about 160°C. As the temperature is slowly increased, the molten bisulfate provides an excellent heat-transfer medium for melting the chromic acid at 197°C without appreciable decomposition. As soon as the chromic acid melts, the agitator is stopped and the mixture separates into a heavy layer of molten chromic acid and a light layer of molten bisulfate. The chromic acid is tapped and flaked on water cooled roUs to produce the customary commercial form. The bisulfate contains dissolved CrO and soluble and insoluble chromic sulfates. Environmental considerations dictate purification and return of the bisulfate to the treating operation. 

Because sodium, which is liquid between about 100°C and 881°C, has excellent properties as a heat-transfer medium, with a viscosity comparable with that of water and superior heat conductivity , much attention has been paid to liquid sodium corrosion testing of metal and alloys. Indeed, ASTM have issued a Standard Practice which can be used for determination... 

Prandtl numbers of, 73 247 Heat transfer inks, 74 329-330 Heat-transfer medium, sodium as,... 

Heat-transfer medium -sodiumas [SODIUM AND SODIUMALLOYS] (Vol 22)... 

Among the a function s of molten sodium metal as a heat-transfer medium are (l)low density compared with other metals and combinations of... 

Sodium Nitrate production for fertilizers, explosives and as a heat transfer medium. 

Light-water cannot be used as a heat transporting agent, since the fast neutrons may not be slowed down. The preferred heat transferring medium is liquid sodium. 

Section 8.2.1 was concerned with equilibrium between a condensed phase and the vapour. It is often necessary, however, to estimate the effect of pressure on equilibria between two condensed phases. For example, the melting point of sodium at one atmosphere pressure is 97.6°C. Can it be used as a liquid heat transfer medium at 100°C, at a pressure of 100 atm, or will it solidify It is known that the liquid is less dense than the solid, and this argues that high pressures will encourage solidification. This is another aspect of Le Chatelier s work, which we can now quantify. This and similar problems may be solved by the Clapeyron equation, which we shall now derive. 

Sodium metal melts at 98°C and potassium metal melts at 63°C. When the two metals are mixed to give a solution that is 20% sodium, for example, the melting point is lowered to — 10°C.This is another example of the lowering of the freezing, or melting, pioint of solutions, which we will discuss later in the chapter. Potassium—sodium alloy is used as a heat-transfer medium in nuclear reactors. 

The heat is generated electrically, a molten salt (an eutectic mixture of sodium and potassium nitrites and nitrates) is used as a heat transfer medium. The water vapors are removed by flashing. The product of the evaporation unit is a anhydrous melt, which is then cooled and transformed to the desired final product ... 

The effect of sodium on the structural materials of interest has also been extensively studied, since sodium is proposed for use as the intermediate heat-transfer medium. Corrosion problems inherent in the utilization of sodium for heat-transfer purposes do not involve so much the deterioration of the metal surfaces as the tendency for components of the container material to be transported from hot to cold regions and to form plugs of deposited material in the cold region. As in the case of the corrosion by the salt mixture, the mass transfer in sodium-containing systems is extremely dependent on the maximum stem operating temperature. The results of... 

Intermediate system. The intermediate system, which also consists of six separate heat-transfer loops, utilizes sodium as the heat-transfer medium. All material of construction of the intermediate system, except the steam generator, is 2 % Cr-1% Mo steel. The steam generator, which is designed for high-pressure, high-temperature service, is constructed of type-304 stainless steel. The intermediate piping (12-in. schedule-30) is sized for a maximum sodium velocity of 17 fps. 

Power stations, whether conventional or nuclear, are designed to turn water into steam at as a high temperature and pressure as possible, as cheaply as possible, then to use the steam to generate electricity. Power reactors generate heat, and this heat has then to be transferred to the water in order to turn it into steam. Most British reactors used carbon dioxide or liquid sodium as the heat transfer medium. There are, however, other possibilities. 

Sodium is also used as a heat-transfer medium in nuclear reactors. Liquid sodium is especially good for this purpose because it has a low melting point, a high boiling point, and a low vapor pressure. Also, it has better thermal conductivity and a higher specific heat than do most liquid metals. Finally, its low density and low viscosity make it easy to pump. Sodium is also used in sodium vapor lamps, which are very popular for outdoor lighting. Because each lamp uses only a few milligrams of Na, however, the total quantity consumed in this application is rather small. 

The calciner originally built was heated by a heat exchanger using liquid sodium-potassium alloy as a transfer medium which was heated externally in an oil-fired furnace. Although 35,000 hr of satisfactory services were obtained vdth NaK, an in-bed combustion process was developed and installed to obtain a greater processing rate other changes noted were lower vessel wall temperatures, lower ruthenium volatility, and increased reliability. 

Use Production of sodium by electrolysis, heat transfer agents, reaction medium in chemical synthesis, heat-treatment of metals (from 350 to 2400F), solvents for the metals corresponding to their cations, nuclear power reactors. 

Liquid sodium has attractive properties for its application as a working fluid in a fast neutron reactor with the ability to breed plutonium fuel by the reaction of ura-nium with the fast neutrons. Sodium does not act as a neutron moderator, its liquid state at atmospheric pressure reaches from 97.8 °C to 892 °C, its heat transfer properties are excellent and its nuclear reactions do not cause a long lasting activation. Sodium is the medium which is able to transfer the energy generated in the high density reactor core better than any other heat transfer fluid... 

Diatomaceous earth heat resistance enhancer, polystyrene Lead phosphate, dibasic heat resistance modifier, ABS resins N-Phenylmaleimide heat stabilizer, PVC Dimethyltin dichloride heat storage medium Sodium sulfate heat transfer agent... 

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