Small nuclear power plants based on ship-propulsion nuclear reactors

NIKIéT. Translated from Atomnaya énergiya, Vol. 77, No. 6, pp. 407–414, December, 1994.     

Selected safety aspects of containments for nuclear power plants with WWER-440 reactors

Considerable attention has been and continues to be focused on the design and operational features that prevent the release of radioactive materials to the environment for a spectrum of accidents for the two classes of WWER-440 reactors: the older 230 model and the more recently designed 213 models.This paper, based on published and unpublished information, aims to clarify the perceptions of the Russian WWER-440 models 230 and 213 Nuclear Power Plant containment system designs and their relevance to selected aspects of accident mitigation. It should be noted that these are unclearly and often negatively perceived, primarily because of a lack of reliable information and a poorly assembled experimental database. Conflicting statements have been made regarding the nature and the features of the plant's containment system. The paper presents a brief outline of the design of both WWER-440 models with respect to their confinement functions. Selected safety-related aspects of the accident localization systems are discussed, and the recognized shortcomings and safety merits are pointed out. The older 230 units experience high leak rates and are designed to withstand medium-size pipe breaks. The possible implications for safety are pointed out in the paper. The on going studies that concentrate on improving the system are highlighted. Some of the proposed modifications of the system, which would significantly decrease risks associated with accidents that are beyond the original design basis, are discussed. The design of the newer 213 model differs in many aspects. It incorporates the simple and original application of passive natural processes to limit the large-break loss-of-coolant accident post accident pressure. Other features of this containment design, such as complicated geometry, dependence on several mechanical devices and interlocks, and insufficient experimental evidence, lead to doubts concerning the operation of this containment under accident conditions. For the newer 213 model, current work is devoted mainly to safety assessment and verification of the containment design. Some information concerning the on-going work is provided in the paper.     

Optimal fuel utilization during decommissioning of nuclear power plants with RBMK reactors

When RBMK reactors are decommissioned successively in the same nuclear power plant, part of the fuel of the stopped reactors can be transferred to other units and additionally burned in continuing operations. The problem of minimizing the consumption of fresh fuel by optimal distribution of the additionally burned fuel over the reactors is examined. The limitations on the refueling rates, the holding time of fuel assemblies prior to transfer, the service life of fuel assemblies, and certain characteristics of reactors are taken into account. It is shown that the reuse of fuel in other units permits saving from one to almost two thousand fresh fuel assemblies and that the effect of optimizing the additional burn regime can reach several hundreds of saved fuel assemblies. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 284–290, May, 2007.     

Underground construction of nuclear power reactors

This paper summarizes the main findings of a comprehensive study of the underground siting of nuclear power plants carried out at the Swiss Federal Institute for Reactor Research. Main aim of the investigations made was to identify suitable siting variants and to evaluate the feasibility, the safety potential and the cost of the concept. Two of the layouts developed for the main siting alternatives — the rock cavity alternative and the pit siting — are briefly described. In these designs an accident mitigation system based on the pressure relief concept, meant to reduce the consequences for the public and the environment in the case of extreme hypothetical events, has been proposed and an evaluation of its performances has been made to quantify the achievable risk reduction. The safety potential — especially under accident conditions — of this type of siting and the possibility that an underground plant may be exposed to new accident initiating events have been evaluated.From the technical point of view, an underground nuclear power plant is considered feasible while the economic penalty associated with the underground siting lies between 11 and 15%, according to the considered alternative.     

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.     

Heavy water reactors and nuclear power plants in the USSR and Russia: Past, present, and future

The history of the development of heavy-water nuclear reactors and the assoiated, installations in the USSR and Russia is presented. Research reactors constructed at the ITEP and under the scientific direction of the ITEP in other countires (Yugoslavia), industrial heavy-water nuclear reactors, and the Maket zero-power reactor are described. Heavy-water gas-cooled reactors for nuclear power plants are discussed in detail: the nuclear power plant with an A-1 reactor, constructed in Czechoslovakia, and the design of maximum-safety nuclear power plant. Electronuclear neutron generators and subcritical nuclear reactors and the possibility of using the for burning weapons plutonium are examined. The electronuclear neutron generator developed at the ITEP is described. State Science Center of the Russian Federation—Institute of Theoetical and Experimental Physics. Translated from Atomanaya énergiya, Vol. 86, No. 4, pp. 310–321, April, 1999.     

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。     

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.     

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.     

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.