09-10-2012, 05:06 PM
CURRENT TRENDSINPOWER GENERATIONUSING NUCLEAR FUEL
CURRENT TRENDS.pptx (Size: 214.98 KB / Downloads: 32)
NUCLEAR FUEL TYPES
THE VAST MAJORITY OF NUCLEAR FUEL USED TODAY CONSISTS OF URANIUM DI-OXIDE PELLETS CONTAINED IN A SEALED TUBE OF ZIRCONIUM ALLOY TO MAKE A FUEL ROD.
THERE ARE MANY VARIATIONS IN THE WAY THE RODS ARE SUPPORTED IN ASSEMBLIES OR BUNDLES FOR USE IN THE REACTORS AND IMPROVEMENTS IN BOTH FUEL RODS AND ASSEMBLY STRUCTURE HAVE BEEN CONTINUOUS.
1.FISSION GAS RELEASE
THE MAIN PROBLEM FOR FUEL DESIGNERS WISHING TO INCREASE BURNUP TODAY IS THAT OF FISSION GAS RELEASE.
FISSION GAS IS GENERATED WITHIN THE FUEL DURING OPERATION,AND THE AMOUNT IS ROUGHLY PROPORTIONAL TO BURNUP.
2.FUEL FAILURE IN NORMAL OPERATION
THE IMPROVEMENT IN FUEL FAILURE RATIO HAS BEEN VERY IMPORTANT OVER THE PAST TWENTY YEARS.
FAILURE OCCURS WHEN THE CLADDING IS BREACHED,ALLOWING COOLANT TO ENTER THE FUEL ROD AND FISSION PRODUCTS TO ESCAPE.
HOWEVER FAILED FUEL DOES RELEASE RADIOACTIVE TO THE PRIMARY COOLANT CIRCUIT AND THIS CAN CAUSE OPERATOR EXPOSURE WHICH IS UNWANTED
REMEDIAL MEASURES
MANUFACTURING DEFECTS ARE REMEDIED THROUGH IMPROVED QUALITY ASSURANCE METHODS
GRID ROD FRETTING WHICH IS CAUSED BY GRID SPRINGS RUBBING AGAINST FUEL RODS AND WEARING THROUGH THE CLADDING,AND WHICH HAS BEEN REDUCED THROUGH DETAILED DESIGN CHANGES TO ASSEMBLY GRIDS.