Dynamic qualification of complex structural components of nuclear power plants

The safety requirements and the lack of accessibility for any future repair, impose the design requirement that the integrity of reactor components of nuclear power plants be assured for the lifetime of the plant. To meet this design requirement it is essential to qualify the component, i.e. prove its capability to perform the design function for the design life. In performing its design function, the component is subjected to both static and dynamic loads. The qualification for static loads is rather simple and reliable, but qualification for dynamic loads is complex and often uncertain. This is because analytical tools are often inadequate for a realistic dynamic qualification and exact structurally simulated experimental models are almost always difficult to build. In such a situation, methods using tests on simple experimental set-ups supplemented by conservative analytical back-ups must be evolved. This paper highlights the intricacies involved in the conservative dynamic qualification of the complex components by considering the example of the moderator sparger tube. This component is a perforated tube submerged in water and excited by flow. For such a case, a completely analytical or a totally experimental qualification is not possible. This paper describes a procedure by which the required dynamic characteristics such as added mass, damping and fluid forces are generated from simple experiments and the component is qualified by analysis using these data.     

Regulatory research in structural design and analysis of nuclear power plants

The paper gives a survey of research conducted or planned by the US Nuclear Regulatory Commission in the area of loading specification and structural mechanics as applied to safety analysis of nuclear power plant structures.     

Welding consumables for nuclear power plants

In nuclear power plants, submerged arc welding and covered arc welding have long been employed especially for main weld seams, including the core region of RPV.This paper investigates the mechanical properties of several welding consumables we have developed for industrial plants — that is, welding consumables which lower the phosphorus and copper content of the welded metal, those for plates possessing particularly high tensile strength and those for the narrow gap welding method.Recent data derived from irradiation embrittlement tests show that these welded metals using a non-copper coating are highly effective in minimizing shifts in the transition curve.Welding consumables for A533B C1.2, A543 C1.1 or A508 C1.4 steels have a higher tensile strength than those for A533B C1.1 or A508 C1.3.We have developed submerged arc and covered arc welding consumables to be used with these kinds of steels, and it was confirmed that these consumables possess excellent tensile strength and notch toughness.Our tests also confirmed that the narrow gap SAW and MIG welds are more efficient than the conventional ones. Moreover, the mechanical properties of the welded metals are also excellent.     

Flood hazards for nuclear power plants

Flooding hazards for nuclear power plants may be caused by various external geophysical events. In this paper the hydrologic hazards from flash floods, river floods and heavy rain at the plant site are considered. Depending on the mode of analysis, two types of hazard evaluation are identified: (a) design hazard which is the probability of flooding over an expected service period, and (b) operational hazard which deals with real-time forecasting of the probability of flooding of an incoming event. Hazard evaluation techniques using flood frequency analysis can only be used for type (a) design hazard. Evaluation techniques using rainfall-runoff simulation or multi-station correlation can be used for both types of hazard prediction.     

Offshore nuclear power plants

Offshore Power Systems, a joint enterprise of Westinghouse and Tenneco, has been formed to manufacture floating nuclear power plants. Commitments for the first two offshore plants have been received from the Public Service Electric and Gas Company. This paper describes the floating nuclear plant concept with special reference to its advantages and its novel features. The novel features are a consequence of the floating aspect and include the design of the platform, the safety analysis and also the analysis and specification of plant motions due to environmental effects such as wind, waves and earthquakes. Site-related aspects such as the breakwater and mooring systems are discussed. The nuclear power plants will be manufactured in a central facility and this manufacturing concept is described.     

Alexisismon isolation engineering for nuclear power plants

This paper reviews the special requirements regarding efficiency, licensibility (reliability) and cost which should be met to achieve an optimum base isolated nuclear power plant design. It then describes the Alexisismon-2, patented isolation system developed by the author, underlines its original properties (linearity and separation of functions) and presents a conceptual design of its application to a nuclear power plant. The great reliability of the system components is demonstrated. The efficiency of the A-2 is found to be very high: a reduction factor of the base shear induced in the plant higher than 25 is achieved for all examined real accelerograms scaled to 1 g GPA. So the isolation components, the structural system of the plant, its equipment and systems can be easily designed to remain in the elastic range of stresses and strain even for seismic input with GPA higher than 2 g.     

Inherently safe containments for nuclear power plants

Nuclear energy cannot be avoided in the near future. To regain public acceptance the safety of nuclear power plants has to be increased. Consequently, feasibility studies have been carried out for a containment proposal for future pressurized water reactors which will keep people unharmed even in the case of severe nuclear accidents under the assumption “all that can go wrong, will go wrong”. The main features of the design concept are a core melt cooling and retention device, a passively acting cooling system to remove the decay heat and a double-wall containment which is able to withstand high static and dynamic internal pressures due to hydrogen detonation. Internal structures are designed to resist extreme loadings resulting from various accident scenarios including in-vessel steam explosion and vessel failure under high system pressure.     

Unitized concept for earthquake-resistant nuclear power plants

This paper discusses a unitized concept for an earthquake-resistant nuclear power plant which can withstand major earthquake shaking and fault slips without releasing radioactive material into the atmosphere. A 1000 MWe pressurized water reactor power plant of recent design is adapted to a unitized concept, and cost studies are made for the incremental cost.     

核电站环境放射性监测

随着国家核电产业的发展,越来越多的核电厂将陆续建设,为了更好的保护环境、保护公众,判断核电厂对环境、对周围居民的影响,环境放射性监测是非常必要的。文章就核电厂环境放射性监测的目的,监测项目,监测方法等方面进行介绍。     

Work on nuclear power plants for space

Conclusions It should be noted that the space problems gave an unprecedented impetus to improving computational methods and design of reactors and shielding and the development of the latest technology. This is not surprising, since the designs required that the mass of the nuclear power plant be determined to within several kilograms. The placement of every kilogram of a satellite in orbit costs several thousands of dollars. The development of nuclear rocket motors and the first thermionic systems "Topaz" in the world was a very important achievement in space nuclear technology. Unfortunately, as sometimes happens in practice, this achievement was far ahead of its time and remains unused. Translated from Atomnaya énergiya, Vol. 80, No. 5, pp. 357–361, May, 1996.     

Development of full-scale simulators for nuclear power plants

The structure of full-scale simulators of nuclear power plants and their development are described. The special features of analytical simulators, which are economical tools for training nuclear power plant personnel because they require only a small investment of capital, are described. An industrial technology for developing simulators for nuclear power plants has been adopted and is maintained at a modern level at the All-Russia Scientific-Research Institute of Nuclear Power Plants. A change in the technical policy of the concern Rosénergoatom made it possible to solve, by and large, the problem of equipping nuclear power plants in Russia with simulators. 3 figures, 1 table, 4 references. All-Russia Scientific-Research Institute of Nuclear Power Plants. Translated from Atomnaya énergiya, Vol. 88, No. 6. pp. 407–414, June, 2000.     

Cosmic thermoemissional nuclear power plants

Translated from Atomnaya Énergiya, Vol. 69, No. 4, pp. 215–219, October, 1990.     

Risk assessment of nuclear power plants

The objective of the present work is to develop recommendations for controlling the safety of nuclear power plants on the basis of risk assessments and safety certification of nuclear power plants. The Kursk nuclear power plant is considered as an example of a nuclear power plant with an RBMK reactor. The concept of risk assessment of a nuclear power plant consists in constructing a set of scenarios of the appearance and development of possible accidents followed by an evaluation of the realization frequency and determination of the scales of the consequences of each one. The result of an analysis is an evaluation of a system of risk indicators in accordance with the requirements of the safety compliance certificate of the nuclear power plant as well as the development of recommendations for increasing plant safety. In risk assessment, the consequences are divided into categories of the seriousness of the damage, for which their probability is evaluated separately. The graphical interpretation of risk due to any dangerous object consists of frequency–consequences curves. Recommendations are developed on the basis of the results of risk analysis.     

Requirements for 21st centry nuclear power plants

The development of energy production in the 21st century will be subject to more uniform per capita and regional consumption. Among the competing sources of energy, the positive qualities of nuclear power-unlimited fuel resources, high energy intensiveness, and ecological compatibility with the possibility of the wastes being highly concentrated—predetermine the development of large-scale nuclear power. The conditions for the development of such nuclear power are its ecological effectiveness and safety (of the reactors and the fuel cycle with the production of wastes), nuclear fuel breeding with adequate characteristics, and guarantees of nonproliferation of fissioning materials. Continuity in the development of nuclear power dictates the requirements for reactor systems in the near and distant future. The acceptable level of safety is closely related to the scales of nuclear power and the applications of nuclear energy sources. However, progress in decreasing the potential danger of reactors and decreasing the cost of protective systems is unavoidable. In choosing new directions, it is important to demonstrate the new qualities in the solution of the problems facing nuclear power in the future. An adequate diversity of reactor technologies could exist in the future. The requirements that will face nuclear power plants in the future stages of development and the expected stages of this development are discussed. The jourmal variant of this report at the 10th annual conference of the Nuclear Society “From the first nuclear power plant in the world to power engineering of the twenty-first century” (June 28–July 2, 1999, Obninsk) Russian Science Center “Kurchatov Institute”. Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 3–14, January, 2000.     

Infrastructure of low-capacity nuclear power plants

Conceptual questions concerning the development of a system of low-capacity nuclear power plants are discussed. The basic properties which the nuclear power facilities of such plants must have are formulated. Questions concerning personnel training, the control characteristics of a system of low-capacity plants, decommissioning, and the requirements for physical protection are examined. The need to develop special normative documentation for low-capacity nuclear power plants is substantiated. Questions concerning the ecological effects of low-capacity power generation are touched upon.     

A trilinear base-isolator concept for nuclear power plants

A friction limited base-isolation concept for moderate seismicity areas is presented. The idea of the concept is to combine frictional damping with base-isolation. The aim of the design effort is to develop a system whose stiffness and damping characteristics are selected to optimize the operational properties of the isolator device for the given site conditions, so that most favourable combination of acceleration and displacement responses of the system is achieved.     

New seismic design spectra for nuclear power plants

Under a US Nuclear Regulatory Commission-sponsored project recommendations for seismic design ground motions for nuclear facilities are being developed. These recommendations will take several forms. Spectral shapes will be developed empirically and augmented as necessary by analytical models. Alternative methods of scaling the recommended shapes will be included that use a procedure that integrates over fragility curves to obtain approximately consistent risk at all sites. Site-specific soil effects will be taken into account by recommending site-specific analyses that can be used to modify rock hazard curves at a site. Also, a database of strong motion records will be archived for the project, along with recommendations on the development of artificial motions. This will aid the generation of motions for detailed soil- and structural-response studies.