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Facility Safety and Environmental Impact
Food Irradiation
There are many industrial irradiation facilities operating worldwide; about 170 employ gamma irradiation. Many process foods, but most irradiation facilities are used for sterilizing disposable medical and pharmaceutical supplies, and for processing other non-food items. Radiation protection at all food irradiation facilities consists of several basic elements: facility design; worker training, procedures, and supervision; and regulatory oversight.
Food irradiation facilities are usually stationary facilities, however mobile electron-beam irradiation facilities have also been proposed. For all facilities, shielding of the radiation source is a key aspect of radiation protection. At stationary facilities, the treatment chamber is surrounded with as much as nine feet of concrete or some combination of concrete and earth or sand. The amount of shielding necessary depends on the strength of the radiation source. Facility designs must also include multiple safeguards to protect worker health and the community should a natural disaster like an earthquake, fire, or tornado occur.
On this page:
- What are the radiation protection issues surrounding food irradiation?
- Who regulates irradiation facilities?
- What are the potential environmental impacts of irradiators?
- Do irradiation facilities generate radioactive wastes?
- Have there been major accidents at industrial irradiation facilities?
- Could there be a "meltdown"?
- Would people be exposed to dangerous radiation during transport of radioactive materials to and from the facility?
- Do workers at irradiation facilities face dangers from regular long-term or accidental exposures to radiation?
What are the radiation protection issues surrounding food irradiation?
Radiation protection concerns include:- facility safety - irradiation sources are very large and could prove lethal should a person accidentally be exposed to the beam
- radioactive waste generation - some metals or other materials may become radioactive after extended exposures in the radiation chamber
- food safety - doses must be carefully controlled to meet FDA standards, and pathogen levels must be sufficiently reduced.
Who regulates irradiation facilities?
Facility regulation depends on the type of radiation source used. Facilities can treat food either with radiation from radioactive sources, such as cobalt-60 or cesium-137, or electrically generated x-ray or electron beams. Facilities that use radioactive sources must meet the following U.S. Nuclear Regulatory Commission (NRC) licensing requirements:- a design that incorporates multiple fail-safe measures
- extensive and well documented safety procedures
- extensive worker training.
What are the potential environmental impacts of irradiators?
Proponents claim there is no potential for environmental impact because the radioactive materials are fully enclosed and are returned to the manufacturer for recycling or disposal. Proponents also cite a good safety and regulatory record for existing irradiation facilities.Opponents are concerned about the potential for serious accidents at irradiation facilities that use nuclear materials. For example, a fire or sabotage at the facility, or a natural disaster, could cause the spread of radioactive material into surrounding communities and the environment. Transportation of radioactive materials also involves the chance that a significant accident will occur resulting in spread of contamination. Transportation safety records are very good.
If irradiation is adopted to the extent desired by its proponents, hundreds more irradiation facilities would need to be built, generally increasing the probability of a catastrophic accident.
Do irradiation facilities generate radioactive wastes?
At gamma irradiation facilities, cobalt-60, or less commonly cesium-137, produce the ionizing radiation beam. Both radionuclides eventually decay to non-radioactive isotopes. The waste produced from irradiators is the spent source. Sources are removed from the irradiator when the radioactivity falls to approximately 6% and 12% of the initial level.Cobalt-60 sources decay to 50% in about 5 years, and to 6 to 12% of their original radioactivity in about 16 to 21 years. They metallic cobalt pellets are shipped back to the manufacturer in hardened steel shipping canisters, which have undergone extensive testing to ensure their integrity in an accident. In the unlikely event of a broken canister, it would not leak or spread in the environment.
Cesium-137 sources decay to 50% in about 31 years. As a result they are replaced infrequently. When they are replaced, the old cesium sources are also shipped in hardened steel canisters. Since cesium-137 has most commonly been used in the form of a salt (cesium chloride), any material that leaked could dissolve in water and spread in the environment. This happened at a medical sterilizer facility in Decatur, Georgia in 1992, when a steel container holding the cesium cracked, and some cesium leaked into the shielding water tank.To minimize these kinds of incidents, many cesium sources are being manufactured today in the form of an insoluble ceramic.
Electron beam and X-ray facilities do not produce waste because they do not involve radioactive substances.When they are turned off, all radiation ceases.
Have there been major accidents at industrial irradiation facilities?
During the past 25 years, there have been a few accidents resulting in contamination. Some required costly cleanups. The incidents resulted when safety systems and control procedures were bypassed.Could there be a "meltdown"?
No. It is impossible for a "meltdown" to occur in an irradiation plant. An irradiator is not a nuclear reactor. It is simply a processing plant containing a shielded area within which foods or other items are exposed to a source of ionizing radiation. The radiation sources used in food irradiation cannot overheat, or explode.Would people be exposed to dangerous radiation during transport of radioactive materials to and from the facility?
Like all potentially hazardous substances, radioactive materials must be transported carefully, with appropriate safety precautions. It is highly unlikely that any exposure of the public would occur during transportation. In the United States the Nuclear Regulatory Commission (NRC) has jurisdiction over the safe storage and disposal of radioactive material as well as over the operation of facilities. The Department of Transportation (DOT) has carrier requirements for the transport of hazardous materials, including radioactive cobalt and cesium.These substances have been transported to irradiation facilities and hospitals throughout the world for many years without difficulty. The containers used for the transport of radioactive cobalt are so well shielded and damage resistant that the DOT permits them to be shipped by common carrier.
If an irradiation facility uses machine-generated radiation (x-ray or electron beam), there is no transport issue at all, because no radioactive isotopes are involved in such an operation.
Stringent rules and regulations govern shipments of cobalt-60 and other radioisotopes. Cobalt -60 is sealed in metal rods and must be shipped in reinforced, double encapsulated metal casks. These casks are designed to withstand the most severe accidents, including collisions, punctures, and exposure to fire and water depths.Do workers at irradiation facilities face dangers from regular long-term or accidental exposures to radiation?
Under normal operating conditions, workers are protected by shielding, detection systems, and safety procedures. Irradiator designs include redundant levels of monitoring and safety devices to protect personnel from radiation exposure. A system of interlocks prevents unauthorized entry into the radiation cell when the source is exposed.Worker safety is also dependent upon strict operating procedures and proper training. In most countries, regulations require periodic inspection of facilities to ensure compliance with the terms of operating licenses.
The Occupational Safety and Health Administration is responsible for regulating worker protection. The Nuclear Regulatory Commission or an appropriate state agency must license food irradiation plants that use cobalt or cesium, as their radiation source. The NRC is responsible for the safety of workers in NRC-licensed facilities. Plants in the United States that use machine-generated radiation are under the jurisdiction of the FDA, which establishes appropriate performance standards to ensure worker safety.
