Gamma-Ray Scanning System for Barrels Containing Plutonium Waste

A system designed to perform quantitative assay of plutonium waste material in 30 to 55 gallon barrels is described. The system uses up to eight 2 in. × 2 in. NaI(Tl) detectors to make a detailed gamma ray scan of the barrel to be assayed. Barrels of 55 gallon size containing 239Pu waste and 30 gallon barrels containing 238Pu waste (from 238PuO2 isotopic heat source production) have been scanned with this system. Experience has shown that a barrel assay can be performed in 10 to 15 minutes to an accuracy of ±10%. The sensitivity of the system is one gram or better for 239Pu or 238Pu in low to medium density waste material.