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20 July 2008

Answer to Question #6719 Submitted to "Ask the Experts"

Category: Industrial Radiation — Industrial Applications

The following question was answered by an expert in the appropriate field:

Several articles, including a fact sheet from the Centers for Disease Control and Prevention, state that cesium powder may glow. A reference to the Goiânia, Brazil, describes the material as glowing blue. Is this the Cerenkov effect to the air molecules or was a phosphor added to the cesium chloride to make it glow like the bad smell that is added to natural gas as a warning of a leak? I thought that radioactive material itself glowing was a myth.

The "cesium powder" in high-activity ¹³⁷Cs sources is cesium chloride, which is used to give the source a high-specific activity (activity per gram). Nonradioactive cesium chloride is a commonly used material in fluorescent screens used for making x-ray images. Thus, the cesium powder will glow or fluoresce when stimulated by self-absorption of its own beta- and gamma-radiation emissions. The reference to radioactive material glowing has to do with the early use of radium, mixed with a phosphorescent material, to paint clock and watch dials and hands.

John P. Hageman, CHP

Answer posted on 24 August 2007. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.