METHOD FOR CHECKING FUEL ELEMENT COLUMN FOR INTEGRITY Russian patent published in 2001 - IPC

FIELD: nondestructive radiation inspections of nuclear reactor fuel elements in the course of their manufacture. SUBSTANCE: fuel element is subjected to gamma-ray examination in two relatively perpendicular directions, gamma-ray flux passed through fuel element is recorded, and detector signals are analyzed. Same procedures are made in advance with empty fuel can. Then gap lengths are calculated from formula L₃= 1/2(S₁:N₀₁+S₂:N₀₂), where L₃ is gap length, S₁ and S₂ are surface areas of gamma- quanta count rate dependencies obtained when fuel elements are gamma- rayed in two directions; N₀₁ and N₀₂ are count rates of gamma quanta passed through empty fuel can in two directions. Chips, if any, are determined by comparing L₃ with fuel element displacement distance during recording of gap length using predetermined criterion. Fault detection threshold level is determined on motionless fuel element incorporating pellets by analyzing time intervals so as time interval in which count rate level exceeds chosen detection threshold level were not longer than that within which fuel element will cover distance equal to width of collimator slot. EFFECT: enhanced gap measurement accuracy, improved validity of classifying integrities as chips and gaps. 3 dwg