Answer to Question #894 Submitted to "Ask the Experts"

Q

What are the specific federal radiation safety requirements/guidelines for operating electron beam welders?

A

There are no federal regulations specifically governing ionizing radiation safety aspects of the use of electron beam (E-beam) welders or melters. There is a Federal Communications Commission (FCC) regulation addressing secondary radiofrequency (nonionizing) emissions from any electrical or electronic device which would apply to E-beam welders or melters, as it does to computers, TVs, and other common devices. These are found in FCC regulations, 47 CFR, Part 15.109, Radiated Emissions Limits From Unintentional Irradiators. Modern E-beam equipment usually does not exceed these limits. There are two federal agencies that have authority in the areas of ionizing radiation from electrically generated sources: (1) Food and Drug Administration (FDA) in 21 CFR Parts 1000 through 1050. These regulations contain performance criteria for manufacturers of electronic equipment covered under the Radiation Control for Health and Safety Act of 1968; and (2) the Occupational Health and Safety Administration (OSHA) in 29 CFR 1910.1096. This latter regulation is essentially the dose limits, signage, and labeling requirements of the pre-1994 U.S. Nuclear Regulatory Commission (NRC) regulations in the old 10 CFR Part 20. The FDA regulations would not apply to the actual use of E-beam welders and melters. The Occupational Safety and Health Administration (OSHA) regulations have regulatory authority; however, from past experience, E-beam equipment does not have difficulty in meeting the short-term dose limits (2 millirem in an hour or 100 millirem in seven consecutive days) or the annual limit of 500 millirem as long as the original fittings and sources have not been modified (e.g., modifying flanges and other connectors into the vacuum chamber or increasing power to the electron gun beyond design limits). OSHA also has a very general worker protection limit for nonionizing emissions in 29 CFR 1910.97. There is a voluntary consensus standard published by the Institute of Electrical and Electronic Engineers (IEEE), C95.1-1991, Standard for Safety Levels with Respect to Human Exposure to Radiofrequency Electromagnetic Fields - 3 kHz to 300 GHz. The IEEE standard was also adopted by the American National Standards Institute (ANSI) in 1992, therefore it is also an ANSI standard (same name). OSHA is presently enforcing the IEEE/ANSI standard. Their enforcement is based on the fact that this is a national consensus standard accepted by industry. The exposure limits in the C95.1-1991 standard have also been adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) and published in their Threshold Limit Values. Like ionizing emissions, it is usually not likely that E-beam equipment will exceed the radiofrequency emission limits of the C-95.1 (29 CFR 1910.97) or as long as the original fittings and sources have not been modified. Traditionally, the regulation of machine generated ionizing radiation sources has been by the states. This means that there could be significant differences between states, especially in uncommon devices. New Jersey, for example, includes E-beam equipment in their accelerator category, with significant regulatory requirements. At the other end of the spectrum are states that have no regulations specifically addressing E-beam equipment, and generally do not consider them sources of x rays. Thus, the best advice is to contact your state radiation protection agency to determine their specific requirements. A nonradiation issue that should be considered is the potential generation of toxic materials during the welding or melting process. This is due to the fact that an E-beam welder or melter can vaporize some of the metal. Thus, there is always a potential for the creation of fume and respirable metallic dust inside the vacuum chamber. The hazard potential would depend on the composition of the metal being welded or melted. Tony LaMastra, CHP