Nuclear reactors sodium-cooled

Nickel-manganese-palladium brazes are resistant to attack by molten alkali metals and And applications in sodium-cooled turbine constructions. Their freedom from silver and other elements of high thermal neutron-capture cross-section allows them to be used in liquid-metal-cooled nuclear reactors. 

Peppier, W., E. G. Schlechtendhl, and G. F. Schultheiss, 1970, Investigation of the Dynamics of Boiling Events in Sodium-Cooled Reactors, Nuclear Eng. Design 14 23-42. (4)... 

Because the melting point of sodium metal is about 98° C (a bit lower than the boihng point of water), it is heated into a liquid phase and then transported in rail tank cars, where it cools and solidifies. When it arrives at its destination, heating coils in the tanks warm it back to the liquid stage, and it is then stored for use. Because sodium has a high specific heat rating, a major use is as a liquid coolant for nuclear reactors. Even though sodium (both solid and liquid) is extremely reactive with water, it has proven safe as a coolant for nuclear reactors in submarines. 

Liquid potassium, when mixed with liquid sodium (NaK), is an alloy used as a heat-exchange substance to cool nuclear reactors. 

This cycle uses solid reactants. Small dendritic copper particles are used to carry out the last reaction to make the transformation of all the solid copper to CuCl, thereby maximizing hydrogen yield. The reported efficiency of this cycle is 49% [66]. This low temperature cycle is believed to eliminate many of the engineering and materials issues associated with the other two previously discussed cycles, however this cycle is also in the initial stages of development [111]. The temperature ranges are such that lower temperature nuclear reactors, e.g. sodium-cooled fast reactors, could be used with this cycle [69]. A hybrid version of this cycle is under investigation in Argonne National Laboratory [66,112]. 

The application of this method is shown in Figure 5, where hydrogen is produced by the nuclear-heated steam methane reforming (using a sodium-cooled reactor and natural gas), and then this hydrogen is converted into electricity in the alkaline-type fuel cell. 

Sodium is used as a heat transfer agent in cooling nuclear reactors. It has a relatively high specific heat and an acceptable fiquid range for the purpose. (It melts just below 100°C.)... 

Liquid sodium is used to cool liquid-metal fast-breeder nuclear reactors. 

Chikazawa, Y., Okano, Y., Hori, T., Ohkubo, Y., Shimakawa, Y., and Tanaka, T. A feasibility study on a small sodium cooled reactor as a diversified power source. Journal of Nuclear Science and Technology, 2006, 43 (8), 829. 

Liquid metals are used when temperature requirement is so high that even the nitrate/nitrite salt mixture becomes unsuitable. The most commonly used liquid metal is a eutectic mixture of sodium and potassium (44%). This has a very broad temperature range (40-760°C) and very high thermal conductivity. Lead and lead-bismuth eutectic can be used up to 900° C. There are several disadvantages with the use of liquid metals. Special precautions must be taken while using alkali metals because they react violently with water and burn in air. Mercury, lead, and bismuth-based mixtures are highly toxic, hence their applications are restricted. One common use of liquid metals is in the cooling of nuclear reactors. 

The thermal and nuclear properties of sodium (it scatters neutrons without absorbing them) made it the heat exchange fluid of choice for fast-flux reactors in spite of its nasty chemical properties when exposed to air or water. The French Superphenix, a commercial-scale sodium cooled reactor, was beset with technical problems, but demonstrated that fast-flux reactors can produce electric power at the 1000 MW level. 

A new thermochemical and electrolytic hybrid hydrogen production system in lower temperature range has been developed by the Japan Nuclear Cycle Development Institute (JNC) to achieve the hydrogen production from water by using the heat from a sodium cooled fast reactor (SFR) [7]. 

A concept for nuclear production of hydrogen, FR-MR , which combines sodium cooled fast reactors (SFR) with the membrane reformer technology, has been studied jointly by MHI, ARTEC, TGC and NSA[15]. 

Y. Chikazawa et al., Conceptual Design of Hydrogen Production Plant with Thermochemical and Electrolytic Hybrid Method Using a Sodium Cooled Reactor , ICAPP 05-5084, 2005 International Congress on Advances in Nuclear Power Plants, Seoul (May 2005). 

In the 1980s, a new generation of nuclear fission reactors called Integral Fast Reactors was under development by the U.S. Department of Energy. This was a liquid sodium cooled reactor which was expected to be safer with minimal corrosion. It was also to be more efficient and able to use 15 to 20% of the uranium fuel instead of 1 to 2%. 

The Integral Fast Reactor would also be capable of breeding plutonium which could be used as nuclear fuel. This type of reactor was seen as the key to a nuclear future. Liquid sodium is a volatile substance that can burst into flames if it comes into contact with either air or water. An early liquid sodium-cooled breeder reactor, the Fermi I, had a melting accident when 2% of the core melted after a few days of operation. Four years later when the reactor was about to be put into operation again a small liquid sodium explosion occurred in the piping. 

Steam turbines can become more efficient with hotter primary steam. This in turn requires high-temperature furnaces, and in nuclear power stations, fuel elements that can withstand higher temperatures. Liquid sodium has been used in nuclear reactors as a primary, closed-loop, cooling medium, but the possibility of it corroding the stainless steel used to contain the uranium oxide fuel elements has caused concern. 

Because the thorium atom density is higher in thorium metal than in any thorium compound, metal is the preferred form of thorium where the hipest nuclear reactivity or hipest density is wanted. One likely nuclear application is in a sodium-cooled fast reactor where thorium would capture a neutron and be converted to... 

The industrial demand for potassium metal is much smaller than that for sodium. Potassium-sodium alloys (which are liquid at room temperature) serve as heat-exchange hquids in the cooling systems of nuclear reactors. Strong bases such as potassium amides and alkoxides are formed from the reaction of potassium with amines and alcohols, respectively. 

The basic nuclear reactor fuel materials used today are the elements uranium and thorium. Uranium has played the major role for reasons of both availability and usability. It can be used in the form of pure metal, as a constituent of an alloy, or as an oxide, carbide, or other suitable compound. Although metallic uranium was used as a fuel in early reactors, its poor mechanical properties and great susceptibility to radiation damage excludes its use for commercial power reactors today. The source material for uranium is uranium ore, which after mining is concentrated in a "mill" and shipped as an impure form of the oxide UjO (yellow cake). The material is then shipped to a materials plant where it is converted to uranium dioxide (UO2), a ceramic, which is the most common fuel material used in commercial power reactors. The UO2 is formed into pellets and clad with zircaloy (water-cooled reactors) or stainless steel (fast sodium-cooled reactors) to form fuel elements. The cladding protects the fuel from attack by the coolant, prevents the escape of fission products, and provides geometrical integrity. 

Maintaining required purity of the coolant and cover gas is a necessary condition for successful operation of any reactor facility. In case of sodium cooled reactor these requirements are determined by Specifications on sodium coolant for nuclear reactors (TV - 6 - 01 - 788 - 73) and Rules of the BN-600 reactor operation. They are most rigid for the primary circuit, since nuclear safety of the reactor is immediately concerned. 

Also, it should be noted that sodium cooled reactor is nuclear technology system, having maximum flexibility extent, i.e. it is capable of assuring the following operation modes in accordance with the user requests ... 

Thus, sodium cooled reactors as well would fully come up to the concept of development of nuclear technology systems having no enriched uranium, declared at the UN Millenium Summit. Moreover, no Pu stocks will exist outside LMFR with attached plant for fuel reprocessing and fabrication (e g. similar to that developed at the ANL for the IFR). 

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