"A Versatile Gamma Scanning System"

A versatile gamma scanning system has been designed and installed for the scanning of irradiated fuels. The system traverses a fuel pin past an area-defining slit in a reproducible and accurate manner. Activity from the examined area is detected by a high resolution solid-state detector. Signals from the detector are amplified and routed to single channel analyzers or to a multichannel analyzer. The use of a four-input multichannel scalar permits storage of four specific energy groups versus position. A scan control module controls the operation of a stepping motor which moves the fuel pin axially past the collimator. Limit switches are used to define the scanned area. The control module also advances the multichannel scalar at selected intervals and determines the rate and direction of scanning. The use of a four-input multichannel scalar allows storage of data in four energy intervals from 512 consecutive points on the scanned element. For a typical pin this means that information is stored from 500 consecutive 27.5-mil increments. The unit is designed to scan fuel lengths of up to 50.2 in. in rods up to 84 in. long and from 0.2 to 1.125 in. in diameter. The collected information can be used to determine the distribution of activity in the fuel rod and to infer the relative distribution of specific isotopes. This information can be used to measure fuel burnup, fuel dimensions and power distribution. Other quantities of interest may be inferred from the obtained information.