Radiation-Related Devices

General Considerations

Radiation producing machines are regulated by Federal and State agencies. The Food and Drug Administration (FDA) regulates manufacturers of electronic systems capable of producing X-rays. Wisconsin regulates and licenses those who use X-ray machines within the state. Wisconsin Administrative Code, Radiation Protection Chapter 157, describes regulations for machines used in the State of Wisconsin.

It is important to know that radiation-producing machines must not be used on humans except for healing arts. Exceptions to this must be secured in writing from the Department of Health Services (DHS).

All radiation-producing machines have to be registered with DHS. All machines used at the University of Wisconsin-Madison, including the Medical School, are registered by the UW-Madison Office of Radiation Safety (RSO). When you purchase a machine capable of producing X-rays or, the unit is replaced or broken, please have the person responsible for the system notify the Radiation Safety at (608) 265-5000 so the necessary changes in  registration can be accomplished.

A copy of the state X-Ray registration form can be found here.

Since electron microscopes are designed to exclude people, they are exempt from many of the regulations that apply to other X-ray devices. However, these devices must be registered with the UW-Madison Office of Radiation Safety (RSO) and DHS and have written operation and emergency procedures. These devices must follow the guidance listed in "Electron Microscope General Safety Protocol."

If you have any questions regarding regulations of radiation producing machines call the UW-Madison Department of Environment, Health & Safety 265-5000.

Cabinet and Analytical X-ray Devices

The predominant X-ray-producing equipment used in research is analytical X-ray. It produces intense beams of low-energy X-rays. Exposure to the direct beam can cause severe injury. To prevent exposures, newer instruments are designed with hood enclosures, interlocks, and beam shielding to minimize the risk of inadvertent exposures. It is possible that the radiation exposure rate from the primary beam can be up to 40,000 Roentgen per minute. With this high exposure rate, the hazard is not limited to the primary beam, but can also be related to leakage or scatter radiation. As a result, these X-ray machines shall not be modified without the authorization of the RSO.

A radiation survey shall be done whenever a new sample is placed in the beam, the beam is diffracted, experimental setup changed, or equipment is replaced. The analytical X-ray machines usually have a low energy that can be readily shielded with about one millimeter (1 mm) of lead. Due to the intensity of the primary beam, leakage and scatter may create a significant source of unwanted radiation. Use shutters and collimators, secure unused ports, reduce the beam cross-section by collimation, and whenever appropriate enclose the entire beam path or use a sufficient beam stop. Consider additional sources of X-rays from miscellaneous support equipment such as high-voltage supplies. Investigations of accidents have identified four main causes:

  1. Poor equipment configuration (e.g., unused beam ports not covered)
  2. Manipulation of equipment when energized (e.g., adjustment of samples or alignment of cameras when X-ray is energized)
  3. Equipment failure (e.g., shutter failure, warning light failure)
  4. Inadequate training or violation of procedure (e.g., incorrect use of equipment, overriding interlocks)  

Electron Microscope

X-rays are produced in the electron microscope whenever the primary electron beam or back scattered electrons strike metal parts with sufficient energy to excite continuous and/or characteristic X-radiation. In terms of X-ray hazards, two aspects are important: the composition of the parts which are struck and their efficiency as X-ray sources and the effectiveness/integrity of the shielding provided by the metal casing of the microscope around these.

The higher the voltage and atomic number of the "parts", the greater the efficiency of X-ray production.

The degree of X-ray "leakage" also depends on the shielding provided by the metal casing. A poorly designed microscope may have weak points where X-rays can escape, for example, between the gasket sealed junctions of two sections of the column.  

An electron microscope system is an X-ray system where the X-ray tube is enclosed in a structure that contains the irradiated material, provides radiation shielding, and excludes people.

Dosimetry

In most cases dosimeters are not required otherwise it will be provided by the Office of Radiation Safety.

Training

All users must be provided specific written instructions by the Permit Holder before using the equipment. These instructions include notice of radiation hazards; machine specific safe work practices; proper operating procedure; symptoms of acute exposure; procedure for reporting an emergency situation.  

Postings

The following document should be placed near the controls of each analytical X-ray unit and readily accessible to the operator:

  • "Notice to Employees"
  • Certificate of registration
  • Specific written instructions
  • Analytical X-ray Emergency Procedure
  • Symptoms of Injury from Acute Local Exposure to Radiation
  • Radiation Hazards from Analytical X-ray Units
  • Safe Working Practices for Analytical X-ray

Labels and signage for X-ray devices can be found at an external site here.

Labels

Analytical x-ray equipment will be posted and labeled with:

  • Label bearing the words "Caution Radiation This Equipment Produces Radiation When Energized" near the tube activation switch.
  • Sign "Caution High-Intensity X-ray Beam," next to each tube-head. The sign must be clearly visible to any person operating, aligning, or adjusting the unit or handling or changing a sample.
  • Posting on the exterior side of the room's doors indicating the presence of X-ray producing equipment such that visitors to the lab will see the sign.

Indicators

All X-ray machines will contain an operational and clearly visible indicator of an active X-ray beam near the X-ray tube. In addition, there must be a shutter status indicator that unambiguously reports if the shutter is open or closed.

Interlocks and Safety Devices

Operational interlocks and safety devices will be provided to ensure that the primary X-ray beam cannot be interrupted by any portion of an individual's body or extremities or by machine equipment under any operating condition. If the beam is interrupted, this interlock will shut off the primary beam. Interlocks and safety devices may not be altered without the written authorization of the RSO. Approved temporary modifications must be terminated as soon as possible, specified in writing and posted near the X-ray machine tube and operators console. Securely close any unused tube ports to prevent accidental opening.

Analytical X-ray Emergency Procedure

If there is a suspected or actual case of accidental radiation exposure, turn off the system power and notify the RSO immediately. If required, exposed individuals should go to the UW Health Urgent Care Clinic to seek medical attention.

Biological Effects of Acute Radiation Exposures

With a properly functioning machine, there is little risk of radiation exposure. However, one should know the signs of an acute exposure to a localized area of the human body. These symptoms are shown in Table 1. Be aware that these effects can be caused by contact with the beam for only a fraction of a second. Typical primary beam exposures are 100,000 to 400,000 rad per minute. The most common effects from a large radiation exposure from an X-ray device are reddening of the skin (erythema). With a dose of a few hundred rem, the superficial layers of the skin are damaged and the skin will redden in a fashion similar but more complex than a sunburn. The erythema effect will most often reverse itself within a few weeks. It is also possible that doses on this level could damage cell division and temporarily stops hair growth and possibly causes the hair to fall out. With a low enough dose, hair growth should return. There could also be damage to the sebaceous glands that produce the skin oil, which could cause a temporary decrease in the amount of oil produced. There is other less common and less transitory responses. If a large area is exposure to a large amount of radiation, there could be changes in the skin pigmentation. This effect may not be reversible and could result in permanent skin changes. If the exposure is large, the transitory damage to the skin, skin hair, or sebaceous glands could cause skin scarring or lead to Radiation Dermatitis, Chronic Radiation Dermatitis, or radiation induced skin cancer. To protect yourself from the radiation consider the following potential sources of radiation exposure:

  1. The primary beam.
  2. Primary beam leakage from poor shielding or guide tube replacement.
  3. Beam penetration through stops and shutters.
  4. Secondary radiations from beam interaction of the primary beam with the sample or shielding.
  5. Radiation released from the diffraction of the beam.
  6. Radiation produced from support equipment such as power supplies.

Table 1. Acute Local Radiation Exposure Symptoms

Received Dose Symptoms
200 - 300 rad to the skin

Erythema (redness of the skin). The area may turn red within two to three weeks after the exposure depending upon dose. Epilation (hair loss) is possible within two to three weeks.

1000 - 5000 rad to the skin Wet or dry blisters within one to two weeks of exposure that usually break open and are subject to infection. Epilation may be permanent.
Over 5000 rad to the skin Severe trans epidermal injury that resembles intense scalding or chemical burn with the immediate onset of pain. Epilation is permanent.
Above 200 rad to the eye

There may be conjunctivitis (inflammation of the eye). It is possible that chronic exposures may lead to cataract formation.

Safe Working Practices for Analytical X-ray Equipment

Beam Alignment

  1. A trained and qualified user should only do an alignment.
  2. If safety locks must be bypassed, first gain RSO approval and then post a sign indicating the safety switch status. Reinstate the safety switch as soon as possible.
  3. Wear a finger dosimeter (ring badge).
  4. Whenever available, use electronic alignment.
  5. Use the lowest power settings possible for beam alignment procedures.
  6. Use long handles on the fluorescent alignment screens, if applicable.

Sample Changing

  1. Ensure the X-ray beam is inactive by using a radiation detector.
  2. Use the shutter to stop X-rays. Verify shutter activation that the shutter indicator is properly reporting shutter status.

To send comments and suggestions to the Office of Radiation Safety, please e-mail radiationsafety@wisc.edu.

UW Radiation Safety works with users of high powered lasers to ensure that they are used safely.

Laser Baseline Eye Exam Instructions:

It is University Policy that baseline eye exams must be completed before use of Class 3B and/or Class 4 Lasers/Laser Systems. University Health Services (UHS) at UW-Madison provides baseline eye examinations. UHS is located at 333 East Campus Mall.

To complete a laser baseline eye examination:

  • UHS at 608-265-5610 to schedule for eye examination.
  • UHS will send the copy of eye exam report, including specific test results to ORS.
  • ORS will email a Laser Safety Certificate to users for successfully completing the training and eye exam.

Eye examinations are also required for laser workers in the event of any accidental or suspected eye exposure to laser radiation.

To reserve an irradiator, use Outlook (Office 365) to schedule a time.You will have access to Number 1, Number 2, or Number 3.

 

Detection

Calibration

Portable meters are calibrated by the Office of Radiation Safety. Your meter should have a sticker on the side detailing its calibration date, serial number, and efficiency.

Your meter will be retrieved on or around its calibration date and returned to your lab within a day or two. If your meter is acting strangely, or if your meter has not been calibrated by its due date, please do not hesitate to contact us.

When ordering a new meter, please contact us for initial calibration. If ordering a meter other than one mentioned on the "Choosing a Portable Meter" page, please contact us before ordering. If we are unable to provide calibration service for your meter, it will need to be sent to a third party annually for service.

LSC and Gamma counters are calibrated and serviced by a third party. Please contact us for more information. LSC Standards should be run every six months, and the records are kept to indicate that the instrument is working properly. If you do not have a set of standards, please contact us for information on obtaining a set.

Choosing a Portable Meter

Survey meters are typically sold in two parts -- the meter itself, and the detector. Meters can usually be calibrated to work with most styles of detectors, such that one meter could be used with a GM detector for beta use and then re-calibrated with a NaI crystal detector for low-energy gamma use.

The most popular meter is Ludlum Model 3. For beta work, the Ludlum 44-9 detector is usually fitted. For gamma work, the 44-3 crystal detector is used for gamma detection.  Consider the 44-21 NaI crystal and plastic scintillator or 44-98 with a BGO scintillator. The Model 3 is preferred for its reliability, durability, and ease of use on the bench and in hand for contamination surveys.

Ludlum Model 3 meter

Ludlum Model 3 Meter Image

Ludlum Model 44-9 detector

Ludlum Model 44-9 Detector Image

Ludlum Model 44-3 detector

Ludlum Model 44-3 Detector Image

Ludlum Model 44-21 detector

Ludlum Model 44-21 Detector Image

 

Another meter commonly used on campus is the Ludlum 2401-P, which is a combination meter and detector in one unit. Its lower cost and higher portability are useful, but it may not be as convenient for bench work since it is less readily used hands-free for area monitoring or to check for glove contamination. 

Johnson Nuclear also makes a fine meter for lab use, the GSM-115. Johnson meters are popular in the nuclear industry, and are made to high standards. Most Johnson products are geared towards much more rigorous measurement than most campus users require. 

Finally, RPI Corporation makes two meters, the beta-use GM-1 and the gamma use SD10. These meters have an easily readable display that is geared towards bench-top use. The drawback to this design is less portability.

Image Technology, Inc. is a supplier of instruments and may offer a discount to University of Wisconsin employees and students. They may be reached at 1-800-599-2643, or at 319-373-0944.

Ludlum 2401-P

Ludlum 2401-P Image

GSM-115M

GSM-115M Image

RPI-Corporation GM-1

RPI-Corporation GM-1 Image

RPI-Corporation SD10

RPI-Corporation SD10 Image

Not Recommended

We do not recommend Eberline or Bicron meters. They have merged with several other nuclear-related companies, their meters are being consolidated and the meter you buy may no longer be supported by the vendor.

We also do not recommend meters with digital readouts. It is better to have a dial with numbers and a needle that moves from 0 upward. This provides an instantaneous indication of the field strength and reduces confusion. Radiation emission is a random process. Meter efficiency is directly related to a variety of factors including geometry, energy, detector speed, etc. Digital meters suggest an accuracy that is not real.

Portable Devices

All authorized users of radioactive material must have a survey meter which is sensitive to (i.e. is able to detect) the type and energy of radiation emitted by the radioactive material being used. Thus, researchers working with beta-gamma emitting nuclides are required to have a meter with a thin-window GM detector. Users working with gamma emitters are required to have a scintillation detector.Ludlum Model 3 G-M Motor Image

Geiger counters are used for radiation surveys at the University because of their high sensitivity for beta particles. Nearly every beta particle that penetrates the detector will cause a discharge and produce a count. A thin-window GM (Geiger-Muller Meter) has a conducting shell with one surface covered by a thin (e.g. 1.5 - 4mg/cm2) mica or mylar cover. This "window" allows particles to enter the chamber. The shell of the detector is usually made of steel or coated glass approximately 200 mg/cm2 that does not let beta particles penetrate.Ludlum Model 3 Survey Meter Image

Low energy gamma (LEG) probes are highly efficient for low energy gamma rays in the 20 to 70 keV range. They normally use NaI crystals approximately 0.04" to 0.08" thick. Because the higher energy gamma rays are more penetrating, scintillation detectors designed to detect and measure photons with energies between 100 keV and 2 MeV are thicker, often more than 1" thick. NaI crystals produce a portable system sensitive to both low energy gamma rays and beta particles. This type of detector would be an excellent choice for a lab group that uses both beta emitting nuclides and 125I or 51Cr.

Many labs use both gamma-emitters as well as beta emitters in their research. Several detectors are on the market which combine detector elements to be capable of detecting both beta emitters and low-energy gamma emitters. The two most common type of detectors are the sandwich and the single crystal. The sandwich probe (e.g. Ludlum Model 44-21) is a NaI crystal fronted by a thing plastic scintillator (similar in function to liquid scintillation cocktail). The single crystal (e.g. Ludlum Model 44-98) uses a single BGO (bismith-germanium-oxide) that produces light when either beta or low energy gammas are absorbed in the crystal. One caution about these, and all scintillation detectors, is that the detector is fragile and shock sensitive, and is easily broken if mishandled. For that reason, we recommend labs use thin-window GM detectors unless a specialty detector is needed and lab personnel understand how to properly handle the detector to prevent damage.

Meters must be calibrated annually (at least once per year). The UW-Madison Department of Environment, Health & Safety is able to calibrate most types of meters at no charge. All meters listed on the web page are able to be calibrated by EH&S. Meters that cannot be calibrated by EH&S must be sent to an approved calibration service; the authorized user is then responsible for calibration fees and other charges.

Acceptable survey meters and pricing information are listed in the table for acceptable vendors. The meters have been divided into 3 general categories: beta detectors, beta + gamma detectors and gamma (LEG) detectors.

 

Henes, Yuliya
Health Physicist Advanced; X-Rays
Yuliya.Henes@wisc.edu
608-514-6895


Timilsina, Bindu
Assistant Radiation Safety Officer; Lasers
Bindu.Timilsina@wisc.edu
608-262-9608