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Hazards of radiation-producing equipment are classified into beam hazards (primary) and scattered radiation (secondary). Adequate shielding must be used to protect against exposure to both primary and secondary radiation.
A sealed source is radioactive material permanently bonded or fixed in a capsule or matrix designed to prevent the release and dispersal of the radioactive material under the most severe conditions likely to be encountered in normal use and handling.
Sealed sources are used as external sources of radiation. Examples of sealed sources are 137Cs irradiators and small check sources used to make sure radiation detectors are operating properly.
Sealed sources containing more than 100 μCi of beta and/or gamma emitters and greater than 10 μCi of alpha emitters must be leak tested for removable contamination on the external surfaces of the source at least every six months by EH&S.
The sealed source must be removed from use if the leak test results show greater than 0.005 μCi of removable contamination on the external surfaces of the sealed source.
All sealed sources (containing more than 100 μCi beta and/or gamma emitters and greater than 10 μCi alpha emitters) purchased or owned by investigators must be registered with EH&S. EH&S will perform the leak tests and inventory every six months.
There are many x-ray-producing machines at the Center used for various reasons. These machines include an x-ray diffraction unit used to analyze the structure of materials, a micro CT unit used to analyze mice and other small animals, a veterinary x-ray unit used to x-ray larger animals such as dogs, and a DEXA unit used in PHS studies. X-rays pose risks similar to those of gamma rays; therefore certain requirements must be met to ensure the machines are used properly and safely.
Annual inspections of x-ray equipment are required to ensure safe operation and compliance with all standards.
X-ray equipment operators must be trained in safe operating procedures for the machines they use and must be able to demonstrate competency. Additionally, all x-ray equipment operators must complete x-ray safety training provided by EHS.
Only a worker listed as an x-ray operator on an authorized PI's RMUA may operate x-ray-producing machines.
A PI who wishes to use an x-ray-producing machine must submit a RMUA or a RMUA amendment to the RSC requesting authorization for use.
Additional requirements of the x-ray safety program are detailed in the X-ray Safety Manual. Staff who wish to use x-ray-producing machines should refer to this manual. For a copy of this manual or additional information, contact the RSO.
Self-shielded irradiators within the Center are used to irradiate small samples. The irradiators each contain small sealed sources. A worker must be on a PI's RMUA, complete irradiator training, and meet access requirements prior to being allowed access to use an irradiator. For details on access requirements, contact the RSO.
The gamma radiation emitted produces ionization within the material being irradiated. The radiation does not cause or induce radioactivity; that is, the material being irradiated does not become radioactive itself.
Irradiators are adequately shielded with lead. The dose rate around the outside of the irradiators does not exceed 0.1 mR/hr at 30 cm from sides. It should be kept in mind that even a small dose rate of 0.1 mR/hr can register several thousand cpm on a portable radiation detector.
The irradiators are very easy to use. Please observe the following safety precautions:
Radiation-producing machinery includes x-ray machines, linear accelerators, irradiators, and similar devices designed to produce ionizing radiation. There are specific requirements for operating such machines, including a requirement that all safety alarms and interlocks be working correctly at all times. In the event of any malfunction in any radiation-producing device or related safety systems, the following actions must be taken:
Some types of gas chromatography equipment contain small radioactive sources. These sources are usually 3H or 63Ni electroplated onto metal inside an electron capture device.
If you own or intend to buy gas chromatography equipment containing radioactive material, notify EH&S. The equipment must be added to your RMUA and checked every six months for leakage.
Gas chromatography equipment containing 3H releases a small amount of 3H during normal use. Operating at an excessive temperature may cause large releases from both 3H and 63Ni devices. Therefore, all gas chromatography equipment containing radioactive material must be exhausted through tubing either into a chemical fume hood, out a window, or through a manufacturer's approved trap.
Dismantling these devices for cleaning could release some of the radioactive material, therefore precautions should be taken to prevent exposure.
If the GC is moved, inform the EH&S of the new location. Do not dispose or transfer the device to any other user or facility without notification of the RSO.
Electron microscopes produce x-rays internally. These x-rays are produced when scattered electrons from the primary electron beam strike metal parts within the microscope. The x-rays usually escape through weak points in the equipment, such as between the gasket-sealed junction of two sections of the column, or at the top of the scope where the electrical cables are attached to the gun. Newer electron microscopes are adequately shielded so none of these x-rays should escape the microscope.
After installing or moving an electron microscope, or after making significant modifications such as installing new detectors on ports in the specimen chamber, it is good practice to check the microscope using a radiation detector with a NaI probe.
With the radiation detector, check the gun, column and specimen chamber while the machine is operating at its highest accelerating voltage. Any radiation escaping the column or the specimen chamber must be stopped either by shielding, or preferably, by repair.
EH&S will perform these checks when requested.
Radioactive chemicals used as tracers or stains in electron microscopy are additional sources of ionizing radiation. Uranium and depleted uranium, often used as uranyl acetate, is a good stain by virtue of its heavy metal electron-scattering properties. All uranium is radioactive, but to varying degrees. Any uranium can easily be detected using a radiation detector with a NaI or a GM probe. Uranium used in electron microscopy is only a hazard if inhaled or ingested, so wear gloves and use good lab techniques when using uranyl compounds.
Some samples may contain very small levels of radioactive material used as tracers. These samples contain such small amounts of radioactive material that they do not pose an external radiation hazard. The samples may be an internal hazard if ingested or inhaled, therefore gloves and good lab techniques should be used when working with all samples.
Consult with EH&S for ways to check for contamination and to dispose of the uranium waste.