REMOVABLE TOP NOZZLE OF NUCLEAR REACTOR (ALTERNATIVES) Russian patent published in 2004 - IPC

FIELD: nuclear power engineering. SUBSTANCE: top nozzle is secured on upper ends of guide channels 12 of absorbing rods and has top carrying plate 2 and locking member 3 both strutted off by means of at least one spring 4. Locking member 3 can be made in the form of two plates joined together by means of guide members, one of them supporting lower end of spring 4; lower (retaining) plate 10 has holes to pass coolant and those enclosing coupling members 9. Guide members can be made in the form of taper ring or tilted ribs. Coupling members 9 can be made in the form of collets whose drillings enclose shoulders 17 on guide channels 1. Guide bushings 6 pass through holes in top carrying plate 2 and in plates of locking member 3; they are provided with stops 7 installed (for instance, welded) above top carrying plate 2. Guide bushings 6 are joined through their inner ledges 8 to butt ends of guide channels 1 and at their bottom they have coupling members 9. Guide bushings 6 have external ridges 11 mounting supporting members 12. The latter can be made, for instance, in the form of bushing with flanges 14, axial clearances 15 being provided between these flanges and one of plates of locking member 3. Resting on supporting members 12 through their lower ends are springs 6 arranged coaxially to guide bushings 6 and used to support top carrying plate 2. Downward movement of locking member 3 under action of spring 4 is restricted by at least one stop 19 made on bottom end of coupling member 9. Provision is made to compensate for relative temperature expansion and radiation elongation of tubular components. This compensation ensures elimination of nonuniform loading and crooking of guide channels and fuel assembly as a whole in the course of operation. EFFECT: enhanced reliability of fuel assembly. 3 cl, 3 dwg