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A thallium-activated sodium iodide gamma monitor is described which utilizes both the ac and dc components of the anode current of a multiplier phototube. The dc component serves to monitor over a range of 104 the gross gamma activity of selected points in a solvent extraction plant for the processing of spent nuclear fuel. From the ac component a gamma energy analysis is obtained over an activity range of 102. The ac component also serves as a monitor on the multiplier phototube gain adjustment. The characteristics of the gamma monitor system are discussed.