Continuous Counting of Gamma Rays from Hot Radioactive Liquids

A standard NaI (Tl) scintillation crystal is used continuously to count gamma rays from Fe⁵⁹ which is dispersed in lubricating oil at 270°F. The crystal is mounted in a water-cooled jacket which also serves as a light shield. The crystal and jacket assembly is placed in a well-type sample holder. The system may be used for counting liquids at temperatures much higher than 300°F by increasing the flow of water or by using a refrigerated coolant. Resolution is adequate for counting two gamma rays. The temperature of the electronics cabinet which contains conventional instrumentation is maintained at 105°F by Nichrome heater elements. Less than one per cent drift occurs when the temperature surrounding the cabinet varies from 70–100°F.