Modem nuclear power plants

The high cost of constructing a modem nuclear power plant— three to four billion dollars, in the U.S.— reflects in part the wide range of safety features needed to protect against various possible mishaps, especially those which could release to the environment any of the plant s inventory of radioactive substances. (Small special-purpose reactors, such as those used to power nuclear submarines or aircraft carriers, have different costs and technical features from the large, land-based reactors used to supply electrical grids.) Some of those features are incorporated into the reactor core itself. Eor example, all of the fuel in a reactor is sealed in a protective coating... 

Postulated initiating events (for the existing PSA and a comparable list for a modem nuclear power plant). 

At 1 23 AM, the power output seemed to be stable at 0.2 GW. The operators violated yet another regulation by disabling the emergency SCRAM, an automatic interlock designed to stop the reactor whenever the neutron flux exceeds a safe limit. (In modem nuclear power plants, it is physically impossible to disable this control.)... 

Concepts of nuclear reactors cooled with water at supercritical pressures were studied as early as the 1950s and 1960s in the US and Russia. After a 30-year break, the idea of developing nuclear reactors cooled with supercritical water (SCW) became attractive again as the ultimate development path for water cooling. This statement is based on the known history of the thermal power industry, which made a revolutionary step forward from the level of subcritical pressures (15—16 MPa) to the level of supercritical pressures (23.5—35 MPa) more than 50 years ago with the same major objective as that of supercritical water-cooled reactors (SCWRs) to increase thermal efficiency of power plants. The main objectives of using SCW in nuclear reactors are (1) to increase the thermal efficiency of modem nuclear power plants (NPPs) from 30—35% to about 45—50% and (2) to decrease capital and operational costs and, hence decrease electrical energy costs. 

The monitoring and control of systems important to safety involves a combination of automatic measurement and control functions, and monitoring and control by human operators. While automatic control and automatic actuation of safety systems are used extensively in modem nuclear power plants, the plant operators remain in overall command of the plant. 

The Electric Power Research Institute (EPRI 1981) conducted a survey of transuranic radionuclides in the terrestrial environs of nuclear power plants in the United States in 1978-1979. The plants included two pressurized water reactors (PWRs) and two BWRs that were of modem design and had been in operation at least 3 years. The 241 Am air concentrations around all of the power plants were extremely low and indistinguishable from fallout background... 

Tlie advances of modem teclmology have brought about new problems. Perliaps die most serious of these is die direat of a nuclear power plant accident known as a meltdown. In diis section several of tliis era s most infmnous accidents are examined some possible explmiations are also offered. 

AR137 Modem instrumentation and control for nuclear power plants A guidebook. No. 387, 1 September 1999. 

Design of the WWER-lOOO/V-392 power unit makes maximum use of technical solutions proven by operation experience of existing WWER-1000 power units. Such consistency improves technical characteristics of the reactor plant including also operational availability and maintenance. At the same time, a number of new technical decisions on the unit systems and equipment are applied in V-392 design to take into account operating experience of WWER-1000 units and modem requirements to nuclear power plant competitiveness. Some examples of advancements aimed to improve the operational performance and plant economical efficiency, to decrease the costs of constmction, repair and maintenance of the systems and equipment are given below. 

Radionuclides are released to the containment as gases and as aerosol particles by a variety of processes during severe accidents. Modem, mechanistic analyses of these radionuclide releases and the subsequent behaviour of aerosols and vapours under reactor accident conditions strive to be realistic. This realistic approach contrasts with the deliberate attempt to be conservative (which may not have been successful) in the definition of radionuclide behaviour for the design of nuclear power plant safety systems. A discussion of the various radionuclide release processes during severe reactor accidents is presented in Chapter II. Of primary interest in these discussions of release is the potential magnitude of radionuclide release and the radionuclides of most concern. Factors that most affect radionuclide release but can also be affected by accident management measures are discussed. 

The construction of the 790 MWgi BN-800 started in 1984 as Unit 4 at the Beloyarsk nuclear power plant (NPP), with an estimated startup planned for 1992. However, in 1986, after Chernobyl, aU nuclear plant construction was put on hold and has not resumed until 2006, once the economic situation stabilized and the design was brought to the modem safety standards (Rosenergoatom, 2015 Vasiliev et al., 2006). 

Command and control tystems are widely used for military applications, air transport, space tystems control, and ship control. Similar systems are used in nuclear power plants, chemical and petrol chemical plant. In modem practice they typically involve ... 

The UK Safely Assessment Principles for Nuclear Power Plants [8J is another example of a consistent safety policy document which is applied to both modem existing and next generation NPPs. Other regulatory activities on the development of safety approaches for future NPPs have also been pursued in some other countries. 

INTERNATIONAL ATOMIC ENERGY AGENCY, Modem Instmmentation and Control for Nuclear Power Plants A Guidebook, Technical Reports Series No. 387, IAEA, Vienna (1999). 

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