|
||||||||||||||
Answer to Question #620 Submitted to "Ask the Experts"Category: Environmental and Background Radiation — Industry The following question was answered by an expert in the appropriate field: Q
We are NOT a licensed site for radioactive material, but do use a material with some activity (cerium oxide). A recent test indicated a level of about 300 to 500 microrem/hr. Our people use it every day for about 10 minutes. They also have a potential airborne exposure during that time. Is this a concern? What should I be looking for? What are the limits? Thanks in advance.
A
Cerium is a rare earth metal, a group of metals that includes those of the lanthanide series, and may include yttrium, scandium, and thorium. Naturally occurring radioactivity from the uranium or thorium decay series is possible from rare-earth mineral operations. In this case, thorium contamination in the cerium oxide is the cause of the radiation readings found. While the radiation readings are higher than the background readings, for workers handling the material for only about 10 minutes a day the total radiation dose is a fraction of annual occupational radiation dose limits established by the Occupational Safety and Health Administration. The total radiation dose from this activity is also well below the average annual radiation dose received by all individuals from other naturally occurring sources of radiation, which is typically 300 millirem per year (National Council on Radiation Protection and Measurements [NCRP] Report No. 94 "Exposure of the Population in the United States and Canada from Natural Background Radiation"). The workers are using the material as a glass-polishing agent. The powdered cerium oxide is scooped into a tank to create a slurry. Because exposure to airborne radioactivity is most likely to occur during mining, milling, and extraction operations, it is unlikely that significant exposure to airborne radioactivity occurs during the use of the final product. As a standard precaution the workers should be wearing some dust mask or filter appropriate to remove the majority of dust particulate matter. This will prevent inhalation of any particles containing the radioactive thorium. Cerium oxide polishing powders typically have a mean particle size ranging from approximately 1.0 to 3.5 microns. You should check with the manufacturer of the cerium oxide for the type of information concerning the materials you are using. Radon-220 and its subsequent daughter products are present, but should not present a significant hazard to workers handling the cerium oxide. An excellent source of information is NCRP Report No. 118, "Radiation Protection in the Mineral Extraction Industry." Information for ordering NCRP Reports can be found on the NCRP Web site. Sean Austin, CHP
Answer posted on 16 February 2001. 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.
|
||||||||||||||
| This page last updated 18 December 2009. Ask Question | Search ATE | Site Map | Privacy Statement | Disclaimer | Security Notice | Webmaster | ||||||||||||||
