Nuclear reactors different types

A variety of nuclear reactor designs is possible using different combinations of components and process features for different purposes (see Nuclear REACTORS, reactor types). Two versions of the lightwater reactors were favored the pressurized water reactor (PWR) and the boiling water reactor (BWR). Each requites enrichment of uranium in U. To assure safety, careful control of coolant conditions is requited (see Nuclearreactors, water CHEMISTRY OF LIGHTWATER REACTORS NuCLEAR REACTORS, SAFETY IN NUCLEAR FACILITIES). 

The problem of burn-out prediction is a difficult one, and one on which a great deal of experimental work is being carried out, particularly in connection with nuclear-reactor development. Much of the earlier literature is rather confused, due to the fact that the mechanics of the burn-out were not carefully defined. Silvestri (S8) has discussed the definitions applicable to burn-out heat flux. It appears possible to define two distinctly different kinds of burn-out, one due to a transition from nucleate to film boiling, and one occurring at the liquid deficient point of the forced-convection region. The present discussion treats only the latter type of burn-out fluxes. The burn-out point in this instance is usually determined by the sudden rise in wall temperature and the corresponding drop in heat flux and heat-transfer coefficient which occur at high qualities. 

As seen in Fig. 3.23, the absorption-desorption curves for H are different from those for D. This phenomena is used in types (3) and (4). By use of this phenomena, the separation of H and D, and enrichment of H and D from mixed gas are possible. The absorption-desorption curve for T (tritium) also differs from those for H and D thus we can separate and enrich H or D or T from the mixed gases by use of the absorption-desorption curves. D and T, which are used in nuclear reactors and nuclear fusion reactors, can be very efficiently separated and enriched by this principle. 

From the early years of this century, the only type of radiation used to find long-range order in solids and short-range order in liquids was X-rays. However, neutrons can also be used to carry out diffraction experiments, and with certain advantages, as will be seen. The trouble is that while it is fairly easy (hence, economically attractive) to use an X-ray source, onehas to have a nuclear reactor handy to achieve a neutron stream. The advantages of using neutrons rather than X-rays in diffraction arise from a difference in how diffraction (i.e., interference) occurs for the two forms of radiation. 

In most cases, the purpose of a nuclear reactor is to capture the energy released from fission reactions and put it to some useful service. For example, the heat generated by a nuclear reactor in a nuclear power plant is used to boil water and make steam, which can then be used to generate electricity. The way that heat is removed from a reactor core is the basis for defining a number of different reactor types. 

Three different types of fuel cycle are commonly identified for nuclear power generation, depending on whether fuel is recycled and on the type of reactor used for electricity production. 

Research on separation of hydrogen isotopes is focused on the aspects related to safe operation of nuclear reactors and separation of tritium. Apart from separators based on palladium alloys [142-145], one can find catalytic units with different metallic membranes and various types of integrated systems with catalytic ceramic reactors [146-154]. 

There are a number of different nuclear reactor types. The most widely used is the light-water reactor, but graphitemoderated types, which are cooled with light-water or gas, are in operation, also heavy-water reactors. The graphitemoderated high temperature reactor is in a state of halted development, as are gas-cooled reactors and fast breeder reactors. 

It is obvious that the neutron energy spectrum of a reactor plays an essential role. Figure 19.4 shows the prompt (unmoderated) fission neutron spectrum with 2 MeV. In a nuclear explosive device almost all fission is caused by fast neutrons. Nuclear reactors can be designed so that fission mainly occurs with fast neutrons or with slow neutrons (by moderating the neutrons to thermal energies before they encounter fuel). This leads to two different reactor concepts - the fast reactor and the thermal reactor. The approximate neutron spectra for both reactor types are shown in Figure 19.4. Because thermal reactors are more important at present, we discuss this type of reactors first. 

Among a number of different projects, IAEA is considering floating power desalination complexes, in particular those with tiie marine nuclear reactor plant of KLT-40 type and desalination facilities of distillation and reverse-osmosis types. The appropriate distillation facilities in Russia are designed by the Sverd Nil ChimMash Institute (Ecaterinburg), while reverse-osmosis facilities are produced in particular by the Canadian firm "Candesal Inc". 

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