Abstract: A method of making a ceramic core for use in a casting process comprises the steps of forming a core in a mould by hot injection of a thermoplastic paste consisting of a refractory ceramic composition and an organic fraction, eliminating the organic fraction from the core by heat treatment, heat treating the core to achieve the minimum consolidation necessary to enable the core to be handled, impregnating the porous structure of the core with a solution comprising a silica or alumina based elementary oxide colloid, and eliminating the liquid from the impregnated product.

Abstract: The cover plug (4) comprises a cylindrical barrel (8), a support plate (10), a group of vertical tubes (12) for the control rods and for the instrumentation of the core, an apertured transverse plate (28) fixed to the lower end of the barrel (8) and a transverse deflection plate (32) located above the apertured plate (28). The transverse deflection plate (32) is suspended from the barrel (8) by substantially vertical elastically yieldable strips (34) evenly spaced apart on the periphery of the barrel (8). The strips (34) are welded to the barrel (8) by their upper end and to the edge of the deflection plate (32) by their lower end. They are located in the region of openings (35) in the barrel (8) which permit radial movement of the deflection plate. The deflection plate (32) is also integral with tubes (14b) receiving the control rods disposed in a single row coaxial with the barrel (8).