METHOD FOR DISMOUNTING DEFECTIVE SPENT FUEL ASSEMBLIES Russian patent published in 2006 - IPC G21C19/32 

FIELD: nuclear power engineering; handling nuclear wastes stored in dry storage depots including in those of submarine fleet.

SUBSTANCE: proposed method that can be used to dismount defective spent fuel assemblies disposed in dry storage depots of nuclear submarines and surface craft and provides for shielding environment from gamma and neutron rays in the course of handling defective fuel assemblies includes removal of safety plug, cutting and extraction of fuel assembly cans. Movable-portal frame is installed on dry-storage depot floor; at least one movable shielding pressure unit provided with video and radiation monitoring systems is mounted on portal, and safety plug is removed by means of lifting crane of floor; shielding pressure unit is installed above tube seat holding defective fuel assembly and let down on shielding cushion while tilting space suit, if necessary; can holding spent fuel assembly is cut out by means of face milling cutter, end part of mentioned assembly being held in the process by means of grip disposed in rod; can holding defective fuel assembly is extracted by means of pressure-unit handler grips; end parts of can holding defective fuel assembly are cut off by means of side mills and then they are placed in solid radioactive waste reservoir; pressure unit is displaced by means of portal within cavity accommodating shipping casks; axis of defective assembly active part is aligned with that of one of shipping casks; the latter is lifted and placed in pressure unit, active part of assembly is placed in the latter, pressure unit holding shipping cask is displaced to drying seat accommodating magazine with compartments to receive shipping casks; shipping cask is placed in one of magazine compartments; operations for extracting other defective fuel assemblies and for delivering shipping casks to magazine are repeated until magazine is filled up with shipping casks, whereupon magazine is closed with bayonet lid communicating through flexible pipeline with evacuating and dry-gas filling systems; active parts of defective fuel assemblies are dried out, then magazine holding shipping casks is loaded in shipping-and-packing set. This method provides for dismounting defective spent fuel assemblies whose deviation from vertical position exceeds permissible value.

EFFECT: enhanced efficiency and environmental friendliness, enlarged functional capabilities.

2 cl, 5 dwg