Les contraintes de réalisation des pompes utilisées dans les centrales thermiques et nucléaires d'Electricité de France

Abstract

Power station water circuits include a large number of pumps which vary considerably as regards size, design, use, water properties (temperature, purity, corrosion, etc.) and the material of which they are made. Even pumps designed for heaviest-duty operation often give trouble, owing to the complex operation of their fixed and moving components (guide and thrust bearings, shaft seals, static seals, hydraulic balancing components, etc.), satisfactory behaviour of which may be impaired by vibration, corrosion, erosion, cavitation and other factors difficult to keep under control. Pump manufacturers have accumulated a wealth of experience since the turn of the century and, in the face of severe competition, are endeavouring to standardise their products with a view to ensuring satisfactory service at minimum cost. Standardisation so far has been confined to widely-used small pumps and specific components, i.e. guide and thrust bearings and shaft seals. On the other hand, technical development has resulted in increasingly higher equipment performance and design sophistication, as in the case of power station pumps for example, the outputs of which have risen sharply during the last thirty years or so. Here, standardisation possibilities for specific pump types are limited to individual technical stages, with the result that increasingly complex, diversified design studies are required for such purposes as definition of operating conditions, solution of metallurgy problems, determination of maintenance requirements, etc. In addition to availability, the effect of conditions appliable to construction of nuclear power plant in France has been requiring increasingly closer attention during the past tow years. These conditions are as follows : a) Wider standardisation possibilities associated with the scope of French power plant construction policy. b) Operating security specifications, for which highly reliable equipment designs are essential. c) Specifications for the protection of power plant service personnel against radiation, which imply minimal maintenance requirements and dismantling and assembly times. These factors all affect the hitherto conventional quality / cost ratio for pumps and justify the issuing by users of such equipment of from equipment meeting various security, reliability, investment cost and maintenance requirements. Such specifications are included among the mutual commitments of users and manufacturers to one another. To meet these various requirements, Electricite de France has concentrated action on the following points in relation to pumps for nuclear power plant : a) Choice of manufacturers according to their design and production facilities. b) Closer attention to detail in design studies by use of series effect. c) Definition of conditions under which equipment is to operate and relating to the service to be provided. d) Drawing-up of special design and manufacturing specifications. e) Choice and inspection of materials. f) Systematic checking and testing of prototype and industrial equipment.