Fuel Defect Detection by Radioiodine Monitoring

Abstract

In 1984, the uranium released from one defective fuel element at Gentilly increased the radioiodine levels in the coolant. The levels remain high 2% years later, possibly due to the buildup of fissile plutonium within the uranium contamination in the core. The corresponding gamma fields on the primary circuit components were significantly higher during the 1985 outage, but returned to normal levels a year later. The follow-up analysis confirms that the short-lived radioiodines, 1-134 and 1-132, provide advance warning of uranium release from fuel defects, and that 1-131 is an unreliable parameter for predicting the number of fuel defects in the core.