This Safety and Health Information Bulletin is not a standard or regulation, and it creates no new legal obligations. The Bulletin is advisory in nature, informational in content, and is intended to assist employers in providing a safe and healthful workplace. Pursuant to the Occupational Safety and Health Act, employers must comply with hazard-specific safety and health standards and regulations promulgated by OSHA or by a state with an OSHA-approved state plan. In addition, pursuant to Section 5(a)(1), the General Duty Clause of the Act, employers must provide their employees with a workplace free from recognized hazards likely to cause death or serious physical harm.
The purpose of this Safety and Health Information Bulletin is to:
A particle accelerator (or "accelerator") is a device (linear or circular) that uses electrostatic or electromagnetic fields to increase the speed (energy) of electrically charged particles (molecular, atomic, or subatomic) or electrons and to direct the charged particles to collide with each other or a target. The collision or interaction of the charged particles releases subatomic particles or produces various types of ionizing and nonionizing radiation. Examples of nonionizing radiation produced by accelerators include visible light such as the light produced by a cathode ray tube (CRT) in a television, ultraviolet light, infrared light, radio waves, and electric and magnetic fields. A type of ionizing radiation produced by accelerators includes x-rays that can be used in numerous ways. For example, when charged particles are captured on a specific target, medical-related isotopes are produced. When electrons are accelerated onto a metallic (typically tungsten) target, x-rays are produced. Both medical isotopes and x-rays are used to treat cancer and other tumors.
The information presented in this bulletin does not cover all types of particle accelerators. Instead, the content focuses on special purpose accelerators such as the research accelerators generally found at universities and Department of Energy (DOE) sites.
Accelerators come in a wide range of sizes from small and simple to very large and complex. They also vary extensively in energy levels, from low-energy tabletop medical accelerators to high-energy accelerators whose dimensions are measured in miles. There are several types of accelerators in use today including: deuterium-tritium generators, Cock croft-Walton accelerators, Van de Graaff accelerators, linear accelerators, and circular accelerators. Circular accelerators include cyclotrons, synchrotrons and betatrons.
Accelerators were once used almost exclusively for physics research. They are now commonly used for:
There are approximately 17,500 special purpose particle accelerators in use throughout the world, with about 4,000 such devices operating in the United States. They range from small and simple accelerators to very large and complex ones. Table 1, below, shows the approximate number of special purpose accelerators used in different technical applications.1
Approximate Number of Special Purpose
|CATEGORY OF ACCELERATOR||NUMBER IN USE|
|High energy accelerators (E>1 GeV)||~120|
|Synchrotron radiation sources||>100|
|Medical radioisotope production||~200|
|Research accelerators including biomedical research||~1,000|
|Accelerators for industrial processing and research||~1,500|
|Ion implanters, surface modification||>7,000|
Accelerator operations present a range of potential workplace safety and health hazards in addition to those posed by ionizing radiation. For example, electrical hazards are common because high-voltage and supporting cable tray systems are used in operating accelerators. Large accelerators frequently operate in tunnels which have restricted access and egress. The use of compressed gasses and cryogenics (very low temperatures) in the operation and maintenance of accelerators increases the likelihood of oxygen-deficient atmospheres, especially in confined spaces.
Lasers, used to align the accelerator's beam, pose nonionizing radiation hazards to the eyes and skin. Ionizing radiation hazards are associated with the active particle beam and materials in the beam's path.
Basic safety and health considerations for operating and working at accelerator facilities
The following are basic procedures for helping to ensure the safety of employees operating or working near accelerators:
Specific safety and health considerations for operating and working at accelerator facilities
Although the list below is not comprehensive, it provides examples of important considerations to help ensure the safe operation of accelerators and accelerator facilities:
Appropriate precautions include conducting detailed hazard analyses, use of appropriate personal protective equipment, (29 CFR 1910.132), strict compliance with safety and health requirements and, if necessary, implementing a permit-required confined space entry program as outlined in 29 CFR 1910.146.
OSHA adopted its Ionizing Radiation standard in 1971, incorporating the radioactive materials exposure limits issued in 1969 by the Atomic Energy Commission, the predecessor to the Nuclear Regulatory Commission (NRC). NRC has revised its exposure limits several times since 1969 (910 CFR 20.113 through 20.2008).
To promote a coordinated and effective federal program for the protection of employees exposed to ionizing radiation, the Federal Radiation Protection Guidance (FRPG) was issued in 1960 and updated in 1987. The 1987 Federal Guidance document, developed collectively by 10 federal agencies including NRC and OSHA, generally incorporated recommendations on the limits for occupational exposure and the approach to radiation protection published by the International Commission on Radiation Protection (ICRP) in 1977. The ICRP updated its recommendations in 1990.
In addition, applicable national consensus standards (e.g., National Council on Radiation Protection and Measurements No. 144; Radiation Protection for Particle Accelerator Facilities) identify effective ionizing radiation controls including use of interlocks, shielding, administrative controls, warning systems, and appropriate PPE.
As explained below, OSHA has the authority to regulate the occupational safety and health hazards associated with (1) the operation of particle accelerators, and (2) incidental radioactive material produced by particle accelerators operated to produce only particle beams and not radioactive materials, to the extent these hazards are not regulated by other Federal agencies.
OSHA regulates employee exposure to ionizing radiation under authority granted by the Occupational Safety and Health Act of 1970 (OSH Act) (29 U.S.C. 651 et seq.). This includes, for example, occupational safety and health hazards associated with the operation of X-ray equipment, electron microscopes, and accelerators.
Several other Federal agencies, including NRC and DOE, also have responsibility to regulate employee exposure to ionizing radiation in certain circumstances. OSHA's Ionizing Radiation standard (29 CFR 1910.1096) covers occupational exposure to ionizing radiation sources not regulated by other Federal agencies. States with OSHA-approved occupational safety and health programs exercise parallel authority within their states. State programs must enforce standards that are at least as effective as Federal OSHA standards.
NRC has statutory authority for licensing and regulating nuclear facilities and materials as mandated by the Atomic Energy Act of 1954 (AEA), as amended, (42 U.S.C. 2011 et seq.) and other applicable statutes. This authority covers radiation hazards in NRC-licensed facilities as well as conditions in those facilities that affect the safety of radioactive materials that may present an increased radiation hazard to employees. Specifically, NRC has the authority to regulate the following nuclear materials: source, byproduct and certain special nuclear materials. The AEA defined "by-product material" to mean (1) material made radioactive incident to or yielded in the process of producing or utilizing special nuclear material, and (2) wastes or tailings produced during extraction (or concentration) of uranium or thorium from any ore that is being"processed primarily for its source material content" (42 U.S.C. 2014(e)).
The Energy Policy Act of 2005 (EP Act) expanded the definition of "byproduct material" that NRC is authorized to regulate to include, among other materials, any material that has been made radioactive by use of a particle accelerator (i.e., "accelerator-produced materials") (42 U.S.C. 2011 et seq.). On October 1, 2007, NRC issued regulations implementing the EPAct (72 FR 55864).
The NRC regulations divide particle accelerators into three groups:
The NRC regulations specify that the Agency will not regulate the "incidental radioactive material" produced by accelerators that are operated to produce only particle beams and not radioactive materials for use for a commercial, medical or research activity. In addition, the regulations clarify that the EP Act does not give NRC authority to regulate the possession or operation of particle accelerators. Accordingly, OSHA continues to retain authority to regulate the occupational safety and health hazards associated with the operation of particle accelerators and incidental radioactive material produced by particle accelerators that produce only particle beams and not radioactive materials.
1From W. Maciszewski and W. Scharf, "Particle Accelerators for Radiotherapy." Int. J. of Radiation Oncology, (2004).
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