FABRICATION DEFECTS OBSERVED IN PWR CORE 1 BLANKET FUEL RODS

摘要

A PWR Core 1 blanket fuel rod which operated for approximately 13,700 EFPH with a complete cladding penetration was removed from the Shippingport reactor and examined, after replacement of Seed 2, along with adjacent nondefective irradiated and nonirradiated rods. No unusual or unanticipated conditions were noted as a result of reactor operation with the cladding penetration. The defect was traced to a transverse tubing crack originating at the inside cladding surface during tube fabrication. Defects of the same type but varying in depth and number were noted in irradi¬ated and nonirradiated rods fabricated from the same lot used in the PWR Core 1 Blanket. Although these defects have little or no adverse effect on internal gas burst pressures, they do, however, reduce the average cladding ductility when the depth of the defects exceeds about 7 mils. A worst case reduction of 11% in cladding strain was noted on burst testing a rod which had a particularly large number of relatively deep defects.