Nuclear reactor problem

A. Radkowsky and R. Brodsky, A Bibliography of Available Digital Computer Codes for Nuclear Reactor Problems, AECU-3078. U.S. At. Energy Comm., Washington,... 

Repeat the previous exercise for the nuclear reactor problem in Section 1.3.6 (p. 12) ignoring the inequahty constraints. 

In addition, overseas professional practice is also informative to study e.g. the Tokyo Electric Power Company (TEPCO), which had nuclear reactor problems arising after the 2011 tsunami. A later investigation revealed that a senior field engineer, who was dismissed some years prior for whistle-blowing, had alerted TEPCO to problems with their nuclear reactors several years ago (Moret 2011). 

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

The basic requirements of a reactor are 1) fissionable material in a geometry that inhibits the escape of neutrons, 2) a high likelihood that neutron capture causes fission, 3) control of the neutron production to prevent a runaway reaction, and 4) removal of the heat generated in operation and after shutdown. The inability to completely turnoff the heat evolution when the chain reaction stops is a safety problem that distinguishes a nuclear reactor from a fossil-fuel burning power plant. 

Although the problems associated with the corrosion and protection of jointed structures have been recognised since the early days of structural fabrication, they have taken on a special significance in the past 15 years. The motivation for the increased impetus is mainly one of concern over possible costly, hazardous or environmentally unfriendly failures particularly those concerned with offshore constructions, nuclear reactors, domestic water systems, food handling, waste disposal and the like. 

Disposal of radioactive wastes from nuclear reactors has proved to he a serious political problem. The NIMBY syndrome (not in my backyard) applies here. 

If an electric current flows through a wire, ihe heat generated internally will result in a temperature distribution between the central axis and the surface of the wire. This type of problem will also arise in chemical or nuclear reactors where heat is generated internally. It is necessary to determine the temperature distribution in such a system and the maximum temperature which will occur. 

These arguments are often put forward to promote the use ofNuclear Energy. However not all is well with the Nuclear Energy. There are the questions of the waste problem so far unsolved, safety ofNuclear Reactors is not guaranteed to the extent that they are inherently safe. If we aim to construct inherently safe reactors, then the economics of a Nuclear Reactor makes it unacceptable. 

Unfortunately, stopping the development of nuclear power may do more environmental harm than good. We consider below a number of global problems - with important connections to nuclear power - that involve environmental risks of greater size and global scope than those posed by nuclear reactors or nuclear wastes. 

The effect of flow obstructions on the flow pattern transitions in horizontal two-phase flow was studied by Salcudean and Chun (1983). The practical importance of the problem is related to the use of rod spacing devices in water-cooled nuclear reactors. In general, these devices are expected to affect the flow distribu-... 

Flow instabilities are undesirable in boiling, condensing, and other two-phase flow processes for several reasons. Sustained flow oscillations may cause forced mechanical vibration of components or system control problems. Flow oscillations affect the local heat transfer characteristics and may induce boiling crisis (see Sec. 5.4.8). Flow stability becomes of particular importance in water-cooled and watermoderated nuclear reactors and steam generators. It can disturb control systems, or cause mechanical damage. Thus, the designer of such equipment must be able to predict the threshold of flow instability in order to design around it or compensate for it. 

Conventional nuclear reactors and advanced breeder reactors were America s primary energy strategy since the 1950s to resolve the fossil fuel problem but when a reactor accident occurred in 1979 at Three Mile Island in Pennsylvania, public and investor confidence in nuclear fission dropped. The accident was triggered by the failure of a feedwater pump that supplied water to the steam generators. The backup feedwater pumps were not connected to the system as required, which caused the reactor to heat up. The safety valve then failed to act which allowed a radioactive water and gas leak. This was the worst nuclear power accident in the U.S., but in this accident no one was killed and no one was directly injured. At Three Mile Island faulty instrumentation gave incorrect readings for the... 

Nuclear reactors are useful in the production of electricity, but they are not without their problems. These problems include disposal of nuclear wastes, accidents, and sabotage. The eventual answer may lie in nuclear fusion. 

The development of thorium-based nuclear power cycles still faces various problems and requires much more R D to be commercialised. As a nuclear fuel, thorium could play a more important role in the coming decades, partly as it is more abundant on Earth than uranium and also because mined thorium has the potential to be used completely in nuclear reactors, compared with the 0.7% of natural uranium. Its future use as a nuclear source of energy will, however, depend greatly on the technological developments currently investigated in various parts of the world and the availability of and access to conventional uranium resources. 

The effect of ionising radiation is described in Section 4.2. Most often, accelerated tests are carried out using gamma radiation from an isotope source or an electron beam from an accelerator. Radiation from nuclear reactors can also be used but will be a mixed radiation which may or may not be suitable for the simulation. The penetration of an electron beam is inherently limited which means that only relatively thin samples can be treated. Hence, gamma irradiation is the more versatile technique. With thin samples, such that penetration limits are not a problem, there are conversion factors to approximately equate the various radiations and energies to an equivalent gamma dose. 

The extraction of deuterium from natural water feed forms an excellent case study of the application of large scale distillation and exchange distillation to isotope separation. The principal historical demand for deuterium has been as heavy water, D20, for use in certain nuclear reactors. Deuterium is an excellent neutron moderator, and more importantly, it has a low absorption cross section for slow neutrons. Therefore a reactor moderated and cooled with D20 can be fueled with natural uranium thus avoiding the problems of uranium isotope enrichment. This was the... 

Accident analysis during melt-down of a nuclear reactor. The problem to be considered here is the erosion of concrete by liquid material during a melt-... 

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. 

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