Generation Of Nuclear Power Plants Research Articles

Effects of fatty acid lubricants on metal injection moulding: Y. Kankawa et al (Kyoto Inst. of Industrial Research, Kyoto, Japan) J Japan Soc Powder and Powder Metallurgy, Vol 39, No 8, 1992, 680–684 (in Japanese)

SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both applications, there is an interest in the implantation of reactive and non-reactive ions into SiC and their effects on the properties of the SiC. In this study 360 keV Ag+, I+ and Xe+ ions were separately implanted into 6H–SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were also annealed in vacuum at temperatures ranging from 900 °C to 1600 °C for various times. In recent years, there had been significant advances in scanning electron microscopy (SEM) with the introduction of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of 6H–SiC wafers implanted with 360 keV Ag+ ions at room temperature and at 600 °C and then vacuum annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result is shown of 360 keV I+ ions implanted at 600 °C into 6H–SiC and annealed at 1600 °C. The 6H–SiC is not amorphized but remained crystalline when implanting at 600 °C. There are differences in the microstructure of 6H–SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids (bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at 350 °C does not amorphize the substrate as is the case with room temperature heavy ion bombardment. Subsequent annealing of the implanted polycrystalline samples leads to increased thermal etching effects such as grain boundary grooving. Damage due to channelling (or non-channelling) in the different crystallites resulted also in differences in thermal etching in the crystallites.

Micostructural changes during mechanical alloying (MA) of copper-titanium-boron powders: E. Yuasa et al (Musashi Inst. of Technology, Tokyo, Japan), Powder Metallurgy, Vol 35, No 3, 1992, 120–124

SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both applications, there is an interest in the implantation of reactive and non-reactive ions into SiC and their effects on the properties of the SiC. In this study 360 keV Ag+, I+ and Xe+ ions were separately implanted into 6H–SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were also annealed in vacuum at temperatures ranging from 900 °C to 1600 °C for various times. In recent years, there had been significant advances in scanning electron microscopy (SEM) with the introduction of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of 6H–SiC wafers implanted with 360 keV Ag+ ions at room temperature and at 600 °C and then vacuum annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result is shown of 360 keV I+ ions implanted at 600 °C into 6H–SiC and annealed at 1600 °C. The 6H–SiC is not amorphized but remained crystalline when implanting at 600 °C. There are differences in the microstructure of 6H–SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids (bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at 350 °C does not amorphize the substrate as is the case with room temperature heavy ion bombardment. Subsequent annealing of the implanted polycrystalline samples leads to increased thermal etching effects such as grain boundary grooving. Damage due to channelling (or non-channelling) in the different crystallites resulted also in differences in thermal etching in the crystallites.

Opportunities for Automation and Control of the Next Generation of Nuclear Power Plants

Application of automation using digital systems to control and manage nuclear power plants, along with the introduction of some of the techniques of artificial intelligence, can offer the public as...

Consideration of severe accidents in the licensing of nuclear power plants

Nuclear power plants are carefully designed to contain radioactive materials in the case of anticipated events and potential accidents. Thus, these events represent minimal risk to the public. Potential risk to the public could arise if events develop beyond those included in the design basis. In order to further reduce potential public risk, future nuclear power plants should consider an additional set of postulated events (more likely severe accidents) and should take appropriate steps to prevent the occurrence of these events, and to protect the public should such events occur. These steps should be taken despite the fact that the occurrence of these events is very unlikely. Formulation and enforcement of these new requirements will shape the design of the next generation of nuclear power plants. Regulatory authorities have a major role in this process, namely development of information needed for prudent decisionmaking; timely establishment of safety standards; and enforcement of these standards.

Rethinking the next generation of nuclear power plants [Forum

It is almost impossible to conceive of a modern industrial society three decades from now without significantly greater reliance on nuclear energy as a base source for the generation of electricity. Yet the potential for that occurring seems to become dimmer and dimmer. Theories abound as to the source of the dichotomy and the ways to remove it. They range from greater efforts to educate a supposedly ignorant public, to starting over with a completely different reactor system. Correctly or not, a broad negative judgment has been rendered of the safety implications of present generation reactor plants. What we all need - not just the utilities - is something we can demonstrate is better than we have. What I believe the utilities need for the next generation of power reactors - indeed all the nuclear industry needs - is a commitment to improved safety through markedly different, more conservative, simpler design engineering based on different nuclear engineering principles. That can be done.

Operating procedure automation to enhance safety of nuclear power plants

Use of logic statements and computer assist are explored as means for automation and improvement on design of operating procedures including those employed in abnormal and emergency situations. Operating procedures for downpower and loss of forced circulation are used for demonstration. Human-factors analysis is performed on generic emergency operating procedures for three strategies of control; manual, semi-automatic and automatic, using standard emergency operating procedures. Such preliminary analysis shows that automation of procedures is feasible provided that fault-tolerant software and hardware become available for design of the controllers. Recommendations are provided for tests to substantiate the promise of enhancement of plant safety. Adequate design of operating procedures through automation may alleviate several major operational problems of nuclear power plants. Also, automation of procedures is necessary for partial or overall automatic control of plants. Fully automatic operations are needed for space applications while supervised automation of land-based and offshore plants may become the thrust of new generation of nuclear power plants.

Non-catastrophic release requirements for the next generation of nuclear power plants

In the light of the Chernobyl disaster more restrictive advanced safety criteria (ASC), originally developed for urban siting, may help to increase public acceptance of nuclear power. The basic idea is to limit the activity release resulting from beyond-design severe accidents in such a way that off-site counter (emergency)-measures do not need to be considered for the short-term and long-term protection of the public and the financial damage can be coped with easily by the society. Conservative dose calculation principles are proposed to demonstrate compliance. Severe accidents include all event sequences which dominate risk and need to be identified by PSA.

The nuclear power industry in the united states: Status and projections

One sixth of the electricity in the United States is now being generated in nuclear power plants, a remarkable achievement for a technology whose basic nuclear reaction was not even known 50 years ago. On the other hand, many of the nation's electric utilities are experiencing great difficulties completing the construction of their nuclear plants; 41 partially constructed plants have been abandoned. Those abandoned plants plus about 110 in operation and 15 still to be completed comprise the first generation of nuclear power plants in the United States. When, and even if, there will be a second generation is much in doubt. Data are presented to show that the absence of a second generation of nuclear plants will place large demands on the fossil fuels, with attendant high energy prices and high environmental costs the expected outcome. It appears that the future will bring large economic forces to start new orders for nuclear plants. On the other hand, the opposing institutional forces appear equally strong. Among the problems creating these institutional forces are the difficulty the United States is having in finding a politically acceptable approach to nuclear waste disposal and the vulnerability of power plant builders and operators to litigation and high financial risk. At present, the issue of a second generation of nuclear plants is stalemated.

Application Experience of Large Scale Minicomputer System and Distributed Processing - Personnel Dosimetry Monitoring and Management System

In nuclear power generation plants, many computer systems are utilized for more safe, reliable power plant operation. Personnel Dosimetry Monitoring and Management System is one of them. In nuclear power plants, in order to provide protection to man from radiation exposure, very accurate, fast, and predictive management of radiation exposure dose to personnel has to be done. Therefore in conventional systems the staff had to perform the laborious and time-consuming routine work of collecting, analyzing, and evaluating large amounts of data. Because of the above trend, fully computerized personnel Dosimetry Monitoring and Management System has been developed to manage personnel exposure dose in real time and to maintain historical records of personnel exposure dose over a long time span. This system consists of a mini-computer with a large data base system and distributed terminal processors which handle data gathering and information retrieval.

Quantitative Safety Goals

An extensive heritage of quantitative safety knowledge now makes it feasible to consider quantitative safety goals for nuclear power plants. Comparative risk is the foundation for some of the deliberations, but most of the discussion is based on knowledge of probabilistic risk assessment (PRA) studies. The licensing notion of design basis accidents is retained for those families of events having mean frequencies above 10-4/reactor-year with PRA being used to screen the events. The consequence limit discussed, for individual risk, is that of no identifiable public injury for design basis accidents. This approach yields a dose limit of 5 rem at 10-4/reactor-year. A limit line is derived for the individual risk having a slope of -1.3. Societal risks are measured by latent cancers which could result from accidents. For safety policies which allow balancing of risks, more latent cancers can be tolerated because of the large and variable spontaneous cancer rate from non-nuclear causes. This may become a suitable and feasible policy for the present generation of light water reactors. If, on the other hand, safety policies were to emphasize nuclear risk in an attempt to lower it, a much smaller number of latent cancers might become an appropriate goal. A future generation of nuclear power plants might make such an approach more feasible. Risks from damage to public property are considered on a first cut basis.

Stability of a nuclear power generation plant with circulating fuel

A nuclear power plant with circulating incompressible fuel is discussed. The active zone of the reactor is idealized by a system with lumped parameters and the heat exchanger by a unit with distributed parameters. The stability of such a plant over a small region of the steady state cycle of operation is demonstrated. For the special case when the importance of delayed neutrons is negligibly small, the stability is demonstrated relative to arbitrary deviations from the equilibrium state.