Power plants, nuclear

In order to optimally exploit a heat source for power generation, the Carnot cycle process should work at the largest possible temperature difference. In HTGRs and in fossil- 

For the liquid metal fast breeder reactor (LMFBR), the upper temperature limit of the steam produced is approximately 500 C (505 in the Russia BN-600 reactor, 495 °C in 

In principle, all reactors are able to provide process steam and long-distance heat to bridge a distance between the locations of heat production and heat demand. Even if LWRs are not able to provide heat at a temperature level sometimes required by the industry, their temperature level could be raised by some additional conventional heating. However, only the HTGR is capable of opening the market for direct high-temperature process heat applications (Fig. 2-6) [19]. 

With regard to the heat market, a light-water reactor (LWR) of the size of the German Biblis A reactor (1200 MW(e)) has the potential to provide 10,(XX) GJ/h low-temperature heat in the CHP mode. Since hot water and process steam cannot be transported directly over long distances, nuclear power can be economically used only in areas with large heat consumption density like chemical industrial complexes, or in long-distance heating systems [4]. With respect to the latter, some of the candidate systems are operated at lower temperatures and could be used in connection with an LWR, if the catalyst conversion processes can be properly controlled [14]. 

The fact that steam generation by LWRs is limited to lower temperature steam ( 280 °C) makes the introduction of LWRs into the heat market conceivable for the chemical industry where large amounts of process steam are required as a heat carrier or as a medium used for synthesis gas and hydrogen generation. 

The secret to controlling a chain reaction is to control the neutrons. If the neutrons can be controlled, then the energy can be released in a controlled way. That s what scientists have done with nuclear power plants. 

In many respects, a nuclear power plant is similar to a conventional fossil fuel power plant. In this type of plant, a fossil fuel (coal, oil, natural gas) is burned, and the heat is used to boil water, which, in turn, is used to make steam. 

The steam is then used to turn a turbine that is attached to a generator that produces electricity. 

The big difference between a conventional power plant and a nuclear power plant is that the nuclear power plant produces heat through nuclear fission chain reactions. 

Hovl do nuclear poufer plants make electrieitff  

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Ten years passed since the biggest radioactive catastrophe in the history of humanity happened at the Chernobyl nuclear power plant. The Russian State medical dosimetric Register was founded after this catastrophe At present in the Register they keep a medical and radiation-dosimetric information about 435.276 persons. 

The development and improvement of scientific-technical level of NDT and TD means for safety issues is connected with the necessity to find additional investments that must be taken into account at the stage of new technogenic objects designing, when solving new arising problems in social, economic, ecological and medical safety. It is not accidental, that the expenses for safe nuclear power plants operation cover 50% of total sum for construction work capital investments. That is why the investments for NDT and TD have to cover 10% of total amount for development and manufacturing of any product. 

Due to the many problems concerning steam generators of nuclear power plants over the last decades, we developed our own inspection equipment and services. Next to this main activity, we provide inspections for nuclear power plants components such as thimbles, guide carts and baffle bolts. 

Recently, the inspection methodology for controlling the nuclear power plant s RCCA s (Rod Cluster Control Assemblies) has been modified to improve speed and ergonomy. 

It has developed a real time method to compare successive non-destructive inspections of the steam generator tubes in nuclear power plants. Each tube provides a safety barrier between the primary and secondary coolant circuits. Each steam generator contains several thousands of tubes whose structural integrity must be ensured through the lifetime of the plant, Therefore, Laborelec performs extensive nondestructive tests after each plant outage. 

The DART system presented in this paper will be used for inspection of welds in Swedish nuclear power plants during 1998. 

Del y for Dec y. Nuclear power plants generate radioactive xenon and krypton as products of the fission reactions. Although these products ate trapped inside the fuel elements, portions can leak out into the coolant (through fuel cladding defects) and can be released to the atmosphere with other gases through an air ejector at the main condenser. 

Krypton and Xenon from Huclear Power Plants. Both xenon and krypton are products of the fission of uranium and plutonium. These gases are present in the spent fuel rods from nuclear power plants in the ratio 1 Kr 4 Xe. Recovered krypton contains ca 6% of the radioactive isotope Kr-85, with a 10.7 year half-life, but all radioactive xenon isotopes have short half-Hves. 

Polyphenyl Ethers. These very stable organic stmctures have been synthesized in a search for lubricants to meet the needs of future jet engines, nuclear power plants, high temperature hydrauHc components, and high temperature greases (49). A typical formula is C H (—OC H ... 

Chemical-Process Vessels. Explosion-bonded products are used in the manufacture of process equipment for the chemical, petrochemical, and petroleum industries where the corrosion resistance of an expensive metal is combined with the strength and economy of another metal. AppHcations include explosion cladding of titanium tubesheet to Monel, hot fabrication of an explosion clad to form an elbow for pipes in nuclear power plants, and explosion cladding titanium and steel for use in a vessel intended for terephthaHc acid manufacture. 

A technique called probabiUstic safety assessment (PSA) has been developed to analy2e complex systems and to aid in assuring safe nuclear power plant operation. PSA, which had its origin in a project sponsored by the U.S. Atomic Energy Commission, is a formali2ed identification of potential events and consequences lea ding to an estimate of risk of accident. Discovery of weaknesses in the plant allows for corrective action. 

The pubhc perceives the risk of nuclear power to be much greater than that deterrnined by experts (4). Among explanations for the discrepancy are the behef in the possibiUty of a disaster and the association of reactors with weapons. Living 50 years within five miles of a nuclear power plant has been shown to be comparable in terms of risk to smoking 1.4 cigarettes during the same period (5). 

Demand. The demand for uranium in the commercial sector is primarily determined by the requirements of power reactors. At the beginning of 1993, there were 424 nuclear power plants operating worldwide, having a combined capabity of about 330 GWe. Moderate but steady growth is projected for nuclear capacity to the year 2010. The capacity in 2010 is expected to be about 446 GWe (29). 

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Water chemistry is important to the safe and reflable operation of a nuclear power plant. Improper conditions can lead to equipment and material failures which ia turn can lead to lengthy unscheduled shutdown periods for maintenance (qv) and repair operations. Water chemistry can also have an impact on the radiation levels duriag both power operations and shutdown periods. These affect the abiUty of personnel to perform plant functions. 

About half of the world s nuclear power plants are from Westinghouse Electric Corporation or its Hcensees. One Westinghouse PWR design is the... 

R. L. Loftness, Nuclear Power Plants Design, Operating Experience and Economics, D. Van Nostrand Co. Inc., Princeton, N.J., 1964. 

Strategic Plan for Building New Nuclear Power Plants, Nuclear Energy Institute Executive Committee, Washiagton, D.C., 1994 (armual update). 

The Westinghouse Pressuricyed Water Reactor Nuclear Power Plant, Westinghouse Electric Corp., Water Reactor Divisions, Pittsburgh, Pa., 1984. 

Low Level Waste Treatment. Methods of treatment for radioactive wastes produced in a nuclear power plant include (/) evaporation (qv) of cooling water to yield radioactive sludges, (2) filtration (qv) using ion-exchange (qv) resins, (J) incineration with the release of combustion gases through filters while retaining the radioactively contaminated ashes (see Incinerators), (4) compaction by presses, and (5) solidification in cement (qv) or asphalt (qv) within metal containers. 

Nucleai energy is a principal contributor to the production of the world s electricity. As shown in Table 1, many countries are strongly dependent on nuclear energy. For some countries, more than half of the electricity is generated by nuclear means (1,3). There were 424 nuclear power plants operating worldwide as of 1995. Over 100 of these plants contributed over 20% of the electricity in the United States (see also Power generation). 

Safety provisions have proven highly effective. The nuclear power industry in the Western world, ie, outside of the former Soviet Union, has made a significant contribution of electricity generation, while surpassing the safety record of any other principal industry. In addition, the environmental record has been outstanding. Nuclear power plants produce no combustion products such as sulfuric and nitrous oxides or carbon dioxide (qv), which are... 

If possible comparisons are focused on energy systems, nuclear power safety is also estimated to be superior to all electricity generation methods except for natural gas (30). Figure 3 is a plot of that comparison in terms of estimated total deaths to workers and the pubHc and includes deaths associated with secondary processes in the entire fuel cycle. The poorer safety record of the alternatives to nuclear power can be attributed to fataUties in transportation, where comparatively enormous amounts of fossil fuel transport are involved. Continuous or daily refueling of fossil fuel plants is required as compared to refueling a nuclear plant from a few tmckloads only once over a period of one to two years. This disadvantage appHes to solar and wind as well because of the necessary assumption that their backup power in periods of no or Httie wind or sun is from fossil-fuel generation. Now death or serious injury has resulted from radiation exposure from commercial nuclear power plants in the United States (31). 

The safety principles and criteria used ia the design and constmction of the faciUties which implement the nuclear fuel cycle are analogous to those which govern the nuclear power plant. The principles of multiple barriers and defense-ia-depth are appHed with rigorous self-checking and regulatory overview (17,34). However, the operational and regulatory experience is more limited. 

The sum total of risks of the nuclear fuel cycle, most of which are associated with conventional industrial safety, are greater than those associated with nuclear power plant operation (30,35—39). However, only 1% of the radiological risk is associated with the nuclear fuel cycle so that nuclear power plant operations are the dominant risk (40). Pubhc perception, however, is that the disposition of nuclear waste poses the dominant risk. 

Substantial research and development is ongoing to define the characteristics of improved lightwater-cooled nuclear power plants (62—65). The safety area is no exception. 

Nuclear power plants of the future are to be designed and operated with the objective of better fiilfiUing the role as a bulk power producer that, because of reduced vulnerabiUty to severe accidents, should be more broadly accepted and implemented. Use of these plants could help stem the tide of environmental damage caused by air pollution from fossil-fuel combustion products (64). 

Basic Safety Principles for Nuclear Power Plants, IAEA Safety Series 75, INSAG-3, IAEA, Vienna, Austria, 1988, pp. 6—8. 

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