Les pompes primaires à sodium de Phénix et Superphénix

Primary sodium pumps for Phénix and Super-Phénix reactors

¹ SNECMA-Hispano-Suiza, Bois-Colombes
² BERGERON S.A., Paris
³ CIRNA, Saclay

Abstract

This report shows how design experience at Hispano-Suiza (SNECMA Division), Bergeron SA and the French Atomic Energy Commission (see table in Fig. 1) has determined the hydraulic and mechanical features of the primary sodium pumps for the Phenix and Superphenix reactors, General layout and operating conditions General layout The general layout of the pumps, heat-exchangers and core of an integrated reactor is shown in Figure 1. Operating conditions Hydraulic conditions The primary pumps operate in parallel with the pressure drop across the reactor core, to which a certain degree of uncertainty is attached. Hydraulic and mechanical stability without dangerous cavitation is a basic requirement for the pumps at all steady-condition and transient operating points. Particularly critical conditions include stoppage of one or more pumps, loss of pump control, or unsymmetrical inflow if specific heat-exchangers cease to operate. Mechanical conditions The layout must be designed to allow a certain amount of differential horizontal pump displacement between the top and bottom of the reactor. Suitable supporting arrangements and reliability of the (inaccessible) lower bearing, therefore, require most careful consideration. Efficient shaft seals and individual isolation arrangements for non-available pumps are further important requirements. Hydraulic design General design Figure 3 shows a diagrammatic view of basic pump "architecture". The "erosion-safe" NPSH was given particularly close attention (Fig. 4), also pump inlet and delivery flow conditions resulting in minimal structural loads. Phenix reactor pumps These pumps were thoroughly tested in water before commissioning, and have proved entirely satisfactory in service. Superphenix reactor pumps Comprehensive model tests were carried out on these pumps. "Industrial" pump sets are to be tested at prototype water flow velocities, using fullest possible instrumentation for determining hydraulic and mechanical behaviour of the pump and surrounding structures (pump dimensions and velocities considerably exceed those of the Phenix equipment). Mechanical design General design The required freedom of differential movement is provided by upper and lower universal joint elements. The lower hydrostatic bearing is fed from the pump delivery, The shaft seals are mechanical oil-cooled designs. Special features of Phenix reactor pumps These pumps have a float shut-off valve, mechanical performance of which on site has been satisfactory since a few minor initial alterations were made. Special features of Superphenix reactor pumps All pump dimensions are appreciably larger than those of the Phenix pumps. The lower and upper universal joint elements had to be redesigned, the latter with a flexible ring. The hydrostatic bearing was tested experimentally. The pump has a cylindrical shut-off valve at the impeller exit.