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Radiation Safety

Radiation Protection Instruction

The information contained on this page is for individuals who work with sealed sources of radioactive material or enter areas in which radioactive material or radiation sources are present and radiation exposure is possible.

Introduction

Radiation Protection regulations require, that all individuals working with radioactive material at the University, receive training in radiation protection commensurate for the type of work performed. In addition, State and federal regulations control the use of radioactive materials at the University of Virginia. The University has been issued a license that allows the use of radioactive materials and also requires the University to control and monitor the use of these materials. The safe use of radioactive materials is best accomplished when the end user and radiation safety personnel act in cooperation.

General

The following instruction is provided for individuals who work with sealed sources of radioactive material or enter areas in which radioactive material or radiation sources are present and radiation exposure is possible. Please carefully read the following instructions and acknowledge that you have read and understood these instructions. If you have any questions about this information, please contact EHS at 2-4911.

Warning Signs & Labels

For the safety of individuals working at UVa, areas in which radiation exposure can occur are normally posted with some type of warning sign. Before entering research, hospital or other posted rooms at the University, you should read all warning signs and postings present on any doors or at any entrances through which you pass. Make certain that you understand what these signs mean and what precautions are required for entry.

Each laboratory using or storing radioactive materials at the University of Virginia is required to post warning signs such that members of the public (or students) will be aware of a radiation hazard in their vicinity. For some sources located in machines, the visual warning may be applied to the machine as opposed to the outer door of the laboratory.

All rooms or areas containing radioactive material will be posted or labeled with the following radiation symbol and caution statements:

Caution Radioactive Material
Room or area in which radioactive material may be used or stored or identifies a container which contains radioactive material.

Caution Radiation Area
Radiation levels are present which could result in an individual receiving greater than 5 mrem in 1 hour at 30 cm from the source or from a surface through which radiation penetrates.

Caution High Radiation Area
Radiation levels are present which could result in an individual receiving greater than 100 mrem in 1 hour at 30 cm from the source or from a surface through which radiation penetrates. (DO NOT ENTER THESE AREAS UNLESS AUTHORIZED BY EHS RADIATION SAFETY STAFF).

Security

All radioactive material must be secured from unauthorized removal AT ALL TIMES. Sealed sources must be locked in a secured container or secured storage area when not in use. Sources cannot be left unattended for any period of time, no matter how short. If the source is in use in a room and must be left unattended, the room must be locked. For more information regarding security requirements visit our Security of Radioactive Material - FAQ (http://ehs.virginia.edu/ehs/ehs.rs/rs.faqsecurity.html).

If sources are missing, lost, or stolen, contact EHS immediately at 2-4911.

Emergency Procedures

If a situation representing a life-threatening emergency occurs in the lab, lab personnel should call 911 from a safe telephone. If the situation is not a life-threatening emergency, EHS should be contacted at 2-4911. Radiation Safety should be notified of any emergency involving radioactive materials, including but not limited to: radioactive contamination of a laboratory, loss of a radioactive source, or overexposure of a person to radiation. Contact Radiation Safety personnel (2-4911) immediately if you suspect that you have received a significant exposure to radiation or that a radioactive source is leaking or damaged.

Precautions you can take to minimize your dose

You should be knowledgeable of:

  • the location of radiation sources in the area you will be working or visiting
  • the exposure rate associated with these sources so that you may take appropriate precautionary measures

Do not touch or move any radioactive source or item labeled with the radiation symbol unless you have been trained in the use of the source and authorized by your PI (Principle Investigator).

Use Time, Distance, and Shielding as described below, to minimize your dose.

Sealed Source Radioactive Material

Sealed sources are radioactive materials encased or "sealed" inside metal or plastic and can take many different forms, sizes and shapes. All forms share some type of encapsulation that prevents their radioactive contents from leaking or dispersing, barring tampering or a severe accident. In some forms, the radioactive material is an inherent part of the source and cannot be separated. Almost all "sealed sources" can be handled without concern that the radioactive material will rub-off or be dispersed onto hands or clothing. There is, however, reason to be concerned about exposure to the radiation emitted from the sealed source.

Sealed sources are not a significant contamination hazard under normal conditions; however, they may present an external exposure hazard.

Many commonly used laboratory devices also contain sealed sources, such as gas chromatographs with Electron Capture Detectors (ECDs), Liquid Scintillation Counters (LSCs) and static eliminators. Sealed sources may have as little activity as a fraction of a microcurie (µCi) or as much as hundreds of Curies (Ci). They may be as small as a button, which can easily be lost, or contained in devices as large as a small room.

Sealed source forms include:

  • Plated sources
    • In this form, the radioactive material coats a disk or planchette. This coating may be covered, depending upon the type of radiation, by mylar, aluminum, steel, or plastic.
  • Capsules
    • In this form, a capsule usually made of metal surrounds the radioactive material. These sources are often placed onto the end of metal or plastic handling rods. Another example of a capsule is when a mixture of radioactive compounds is placed into a container and welded or sealed closed.
  • Activated metal
    • In this form, a metal wire or foil has been exposed to a neutron flux to irradiate the metal and create a radioactive isotope from the original material. This form of sealed source may have a plastic or epoxy coating to protect the activated metal. In some instances, however, the metal is not protected.

Many commonly used laboratory devices also contain sealed sources, such as gas chromatographs with electron capture detectors, liquid scintillation detectors, and static eliminators.

Authorized Use of Sealed Sources

In order to possess or use radioactive sealed sources (or devices containing sealed sources) at the University of Virginia, your Principal Investigator (P.I.) must have a radioactive materials permit approved by the UVa Radiation Safety Committee.

To obtain a permit, your P.I. must possess minimum experience and training requirements. This training document is one of those requirements. The P.I. and everyone in a laboratory must satisfactorily complete this training before they begin to work with sealed sources.

By issuing a radioactive materials permit to your P.I., the Radiation Safety Committee recognizes that your P.I. has assumed certain responsibilities, including assuring that everyone in the lab will have the training and equipment necessary to safely use the radioactive source(s).

Sealed, or encapsulated sources of radioactive materials may be listed by specific reference in the University's Radioactive Materials License, which means that the license must be amended for each additional source. Application for authorization to obtain and use a sealed source must be made using the appropriate EHS form.

Gas Chromatographs and Electron Capture Detectors

Some of the Gas Chromatographs (GCs) at the University of Colorado have Electron Capture Detectors (ECDs) which contain a small sealed source, typically 63Ni or 3H (tritium). These machines usually have a radioactive materials sticker or label, identifying the presence of the source. Dosimetry is not required for normal operation of these devices. However, Sealed Source Training is required before using these machines.

The exhaust from gas chromatographs shall be directed into a fume hood whenever detectors are in use. Detectors shall be stored in a well-ventilated and secure location whenever they are not mounted in the chromatograph unit.

Gas chromatographs using Tritium or Nickel-63 foils in electron capture detectors must be equipped with a temperature limiting device and vented to a hood or air handling system which exhausts directly to the outside. Tritium foils are to be limited to 225°C and Nickel-63 foils to 400°C. Nickel-63 sources will be leak-tested semi-annually by the Radiation Safety Officer. The source holder must be labeled with the radiation symbol. Chromatograph sources must be disposed of through EHS as radioactive waste. Any change in location or status of a gas chromatograph must be reported to EHS.

These sealed sources are inventoried and leak tested periodically by EHS staff. If a source is found to be leaking at a level equal to or exceeding 0.005 µCi, it must be taken out of service for repair or disposal.

Liquid Scintillation Counters

Many laboratories use liquid scintillation counters (LSCs) to analyze wipe smears and other samples. Machines which calculate H# (efficiency) may also contain a small sealed gamma sources, typically 137Cs or 226Ra. These internal sources are managed in the same way as other sealed sources and must be removed from the machine prior to disposal. Contact EHS at 2-4911 for assistance with disposal. Most LSCs have calibration check sources for routine use. These sources usually are 3H or 14C in sealed liquid form and should be included in your laboratory's inventory.

Portable Gauges

Soil Moisture Density Gauges and other portable gauges not in storage must be leak tested by EHS and require training of personnel working with the source. When planning to obtain or use such a device, contact EHS at 2-4911 for more information on licensing, using, and storing these items safely.

Safe Use of Sealed Sources

Sealed sources present an external radiation hazard as opposed to a contamination hazard. Sealed sources can emit any type of ionizing radiation, including alpha particles, beta particles, gamma rays, x-rays, or neutrons.

Do not touch electroplated sources, as this may result in the removal of the active material. Wear gloves when working with a plated or deposited source. Monitor hands and fingers after handling a plated or deposited source. Do not use handling tools in such a way as to penetrate the surface of the source. Storage containers should not have material that abrades the surface of the electroplated sources.

Sealed Sources shall not be opened under any circumstances!

Only authorized individuals shall perform the repair and cleaning of sources. The safety and handling precautions furnished by the manufacturer shall be maintained in a location that is readily available to all workers and followed.

Storage containers must be properly labeled.

The exhaust from gas chromatographs shall be directed into a fume hood whenever detectors are in use. Detectors shall be stored in a well-ventilated and secure location whenever they are not mounted in the chromatograph unit. Gas chromatographs using Tritium or Nickel-63 foils in electron capture detectors must be equipped with a temperature limiting device and vented to a hood or air handling system which exhausts directly to the outside. Tritium foils are to be limited to 225°C and Nickel-63 foils to 400°C. Nickel-63 sources will be leak-tested semi-annually by the Radiation Safety Office. The source holder must be labeled with the radiation symbol. Chromatograph sources must be disposed of through EHS as radioactive waste. Any change in location or status of a gas chromatograph must be reported to EHS.

When working with any radioactive materials, the principal concern is controlling exposure to radiation. Since any radiation exposure presumably involves some risk to the individual involved, the level of exposure received should be worth the result that is achieved. In principle, the objective of radiation protection is to balance the risks versus the benefits from activities that involve radiation. Different uses of ionizing radiation warrant consideration of different exposure guidelines or means to reduce exposure.

There are several simple ways that radiation exposure can be reduced when working in the lab. The main principles are Time, Distance, and Shielding. Each is described below.

Time

When working with radiation you should be aware that radiation exposure is directly proportional to the time spent in the field. If the time spent in a given radiation field is doubled, the workers exposure is doubled. What thought processes or actions will assist with this exposure reduction tool? These might include: not removing the source from its storage area until the last possible moment, thoroughly understanding the experiment by completing several "dry-runs" prior to introducing the source to the experiment, and understanding where the radiation beam is present, i.e.:

  • Does the radiation stream from the source in 360° or is the beam collimated in a particular direction?
  • Does the experimental apparatus include adequate "beam stops"?
  • Is the source removed from the experiment at the earliest opportunity?
  • Has everyone who might come into contact with the experiment or work in the vicinity been informed of the presence of radiation?

You can estimate the amount of dose you may receive in an area over a given time period using the following method.

Example: If the measured gamma exposure rate in the area you are working is 5 mR/hr and you will be working in this area for 2 hours, then:

5 mR/hr x 2 hr = 10 mR exposure = 10 mR total dose

Distance

In many cases this control is more important than controlling time in the radiation field. For those sources that can be treated as a "point" source (i.e. the distance between you and the source is greater than the largest diameter of the source), the dose received is inversely proportional to the SQUARE of the distance of separation. Thus the distance of separation between a person and a source has a greater relative influence on dose than does the time factor.

As an example, consider a person who is exposed to a radioactive source for 5 seconds at one meter or for 10 seconds at two meters. Which condition would provide the lowest exposure? If we consider that Exposure = (Time)/(Distance)2.

  • For the one-meter example: Exposure = 5/(1)2 = 5 units.
  • For the two-meter example: Exposure = 10/(2)2 = 2.5 units. Clearly, the two-meter distance leaves the worker with the lower radiation exposure.

What thought processes or actions will assist with this exposure reduction tool? They might include the use of handling tongs to handle sources (this should only be done, of course, when it does not jeopardize the integrity of the source or create handling problems) and standing well away from the radiation beam or source.

Shielding

A simple, yet effective, way of reducing radiation exposure in conjunction with or when the previous methods cannot be used is by placing appropriate shielding between you and the source. To properly utilize this method, it is necessary to understand what shields work best for which types of radiation. Selecting the most appropriate shielding material depends upon a number of factors including the type of radiation, the energy of the radiation and the density of the materials used as shielding. For this reason, Radiation Safety should be involved in helping your laboratory design necessary shielding for your source(s).

  • Shielding pure alpha sources is not necessary in the laboratory (keep in mind, however, that many alpha sources often have a secondary gamma or x-ray emission associated with them). Nearly all alpha radiation will be stopped by the dead layer of skin on your body.
  • Shielding beta sources is best accomplished with low atomic number materials. Less dense materials such as Plexiglas or plastic provide nominally thick shields that attenuate the beta particles and minimize the production of Bremsstrahlung x-ray radiation (a type of x-ray produced by stopping beta particles with dense materials). All but the most energetic beta sources can be adequately shielded with a centimeter or two of Plexiglas. Dense materials such as lead and steel are discouraged for use with beta sources and can actually increase your radiation exposure due to the production of the Bremsstrahlung x-rays. Beta particles can penetrate up to a centimeter into your skin and so should be considered an external radiation exposure hazard.
  • When shielding gamma or x-ray sources, the energy of the source and the density of the shielding material must be taken into consideration. For all but the most energetic sources, thin lead foil or moderately thick lead sheet can be used to shield the source. Metals such as steel or iron can also be used to shield gamma or x-ray sources. The exact design of gamma shielding can be quite complex and surveys may need to be performed to ensure the adequacy of the shield design. Gamma rays and x-rays emissions are very penetrating to the human body and are a significant external radiation exposure hazard.
  • Hydrogen-rich materials such as water or paraffin are often used to shield neutron sources. The hydrogen atoms work to absorb the energy of and thermalize (or slow down) the neutrons in order to make them less destructive to materials in their path. Many neutron sources also emit gamma or x-rays, and so the shielding design for these sources may become quite complex. Neutrons can cause serious damage to tissue as they impart their energy to the hydrogen molecules in your body.
Operator Requirements

All users of sealed sources or machines containing sealed sources are required to complete this instruction before using the radiation. Anyone working with radiation should be familiar with the experimental procedures for which radiation will be used. If you have any questions about proper operating procedures for working with radiation or if you have questions about the services provided by EHS, please refer to the Radiation Safety Notebook (http://ehs.virginia.edu/ehs/ehs.rs/rs.documents/rad_Notebook.doc) that is available in each laboratory, or call EHS at 2-4911.

Log Out / Sign Out and Other Operating Procedures

All sealed sources should be maintained within storage cabinets, safes, or at a designated location within the laboratory. Each storage location should have an inventory, provided by EHS, of the sources stored at that site. Whether or not the storage location should contain shielding material depends on the type of radiation emitted by the source(s). For many gamma or x-ray emitters, some form of shielding integral to the source holder or maintained within the storage cabinet itself will be necessary.

Each time a source is removed from its storage location, it must be documented on the Sealed Source Sign-out Log, kept near the storage location. When returning the source, you must log the source back in. Sources must be accounted for at all times. Sources are not to be removed from the authorized location of use or used in any other area/location without prior approval from EHS. All sealed sources must be purchased through EHS Radiation Safety (including exempt quantity sources). If you purchase a new source it must be entered into your inventory. If you wish to dispose of a source contact EHS. After disposal by EHS, you must remove the item from your inventory log. Sealed Sources at the University of Virginia are divided into two types: Sources requiring Leak Testing and Sources below a certain activity that do not require leak testing. Some sources must be leak-tested periodically by EHS (either every three months or every six months, depending on the source).

Sources may only be used within the rooms designated on the PI Permit. Sources should be returned to the locked cabinet when not in active use in order to lessen the risk of losing the source.

Only EHS employees may transport radioactive sources between non-contiguous buildings. As much time as possible (at least 2 days) should be given to EHS prior to the transport to allow for preparation of required paperwork and transport conditions.

Leak Tests & Inventory of Sources

The degree of regulatory control for sealed sources is dependent upon the type of radiation emitted and the activity of the source. Sources requiring leak testing are leak tested by EHS at certain intervals determined by regulation. Alpha emitters are leak-tested every three months, while beta and gamma emitters are leak-tested every six months.

Leak tests are accomplished by wiping a piece of filter paper ("wipe smear") across a source or source housing. Radioactive contamination leaking from the source can then be measured by analyzing the filter paper in a liquid scintillation counter or with other appropriate counting equipment.

The following limits are used for leak tests at the University of Virginia:

  • No action is taken if a leak test on a source reveals contamination below 0.001 µCi per smear.
  • If source wipes reveal contamination above 0.001 µCi per smear, but below 0.005 µCi per smear, EHS recommends that the source be removed from use.
  • If the leak test reveals contamination above 0.005 µCi per smear, the source is required to be removed from use and either repaired or disposed of appropriately. This level of contamination requires notification of NRC/State regulatory agencies.

At the same time leak tests are taken, sources are inventoried by EHS. If a source is found to be missing, EHS must be notified as soon as possible so that a search for the source can begin. The loss of most sources requires notification of NRC or State regulatory agencies. An inventory with current source activities is provided each time that EHS inventories a storage location.

The University is required to maintain accurate, timely records of the receipt, use, transfer and disposal of radiation sources in its possession. Users have this same responsibility for their sources. These records must be maintained by the PI and be readily available for periodic review by EHS and/or regulatory personnel.

Inventory of Devices, Gas Chromatographs and Liquid Scintillation Counters: Each instrument is conspicuously posted with an identification sticker designating the radiation source information. EHS must be notified if the location or status of this type of instrument changes. EHS will remove the radiation source in these instruments prior to transferring them to Surplus Property. Notify EHS prior to any changes in location, surplus, or transfer of these instruments.

Dose Limits

Allowed levels of radiation exposure to laboratory personnel using radioactive sources at the University of Virginia is governed by federal regulations.

  • The dose limit for occupationally exposed workers is 5000 mrem per year.
  • The dose limit for a member of the general public is 100 mrem per year.
  • The dose limit for occupationally exposed minors is 500 mrem per year.
  • The recommended dose limit for occupationally exposed pregnant women is 500 mrem for the entire pregnancy.

It is a policy of the University of Virginia that occupational doses and doses to members of the general public be kept As Low As is Reasonably Achievable (ALARA).

NRC/State regulations require that anyone likely to receive more than 10% of the allowable dose limit must be provided with an exposure-monitoring device (or dosimeter). At the University, this means that anyone working with radioactive materials energetic enough to penetrate through the epidermal layer of skin are provided with a dosimeter. We typically will not monitor your exposure to radiation with a dosimeter unless you can potentially receive 500 mrem/year. Sealed source users who are working with sources of higher energies may be issued dosimeters to monitor any dose the user might receive to insure that ALARA is being practiced. Wear whole body dosimeter on the outside of protective clothing at collar level and ring badges under protective gloves. Please contact EHS at 2-4911 for assistance in determining your requirement to be monitored for radiation exposure.

Whole body dosimeters are correctly worn on the front of the body, between the neck and the waist. Extremity (ring) dosimeters should be worn on the hand most likely to come into contact with radiation. The name plate should face toward the inside of the palm.

Contamination is not normally an issue when working with sealed sources. The exception may be certain types of plated or deposited sources. Do not touch an active surface of a plated or deposited source with your fingers. Wash hands after handling plated or deposited sources. If there is any reason to suspect that a source is leaking or that contamination is present in the laboratory, a wipe smear or a survey instrument (such as a Geiger counter) may be used to detect radioactive contamination. All survey instruments at the University of Virginia are calibrated every six months by EHS to ensure accurate measurements. Wipe smears are available from EHS, as are suggestions for types of survey instruments which would be appropriate for use in your laboratory.

Radiation Protection Instruction

Please read the following and sign below.
You may have a copy of the attached instruction to keep.
Please ask your instructor to provide you with a copy if you would like one.

I have read, understood and have been given the opportunity to ask questions about the attached radiation protection instruction.

Date Name Affiliation / Dept. Signature