Proof-of-principle measurements for an NDA-based core discharge monitor

The feasibility of using nondestructive assay instruments as a core discharge monitor for CANDU reactors was investigated at the Ontario Hydro Bruce Nuclear Generating Station A, Unit 3, in Ontario, Canada. The measurements were made to determine if radiation signatures from discharged irradiated fuel could be measured unambiguously and used to count the number of fuel pushes from a reactor face. Detectors using the (γ,n) reaction thresholds of beryllium and deuterium collected the data, but data from shielded and unshielded ion chambers were collected as well. The detectors were placed on a fueling trolley that carried the fueling machine between the reactors and the central service area. A microprocessor-based electronics system (the GRAND-I, which also resided on the trolley) provided detector biases and preamplifier power and acquired and transferred the data. It was connected by an RS-232 serial link to a lap-top computer adjacent to the fueling control console in the main-reactor control room. The lap-top computer collected and archived the data on a 3.5-in. floppy disk. The results clearly showed such an approach to be a adaptable as a core discharge monitor. 4 refs., 8 figs