The rules for working safely with radiation require all exposures to be As Low As Reasonably Achievable (ALARA). Practices and principles implemented must control our individual dose from daily work, our collective dose through our career, and minimize amounts of radioactive waste and emissions. The Radiation and Laser Safety Committee (RLSC) and DRS established the following policies and procedures for maintaining ALARA radiation exposures through the safe handling, storage, use, transport, and disposal of radiation sources.
Exposure control must include reduction to external exposure and prevention of internal contamination.
Minimize personal exposure to external radiation by managing these three parameters: time, distance, and shielding. Plan experiments well to spend as little time as possible near the radiation source. For new procedures and new personnel, one or more trial runs beforehand with non-radioactive materials are recommended to test the effectiveness of procedures, training, and equipment.
Keep as much distance as possible, especially to sensitive parts of your body (e.g., eyes, upper body). For strong sources tongs can often be used to prevent high exposures to the hands. Use adequate shielding for high-energy beta and gamma emitters whenever possible. Beta particles are stopped by 1 cm of Plexiglass. Stopping gamma rays requires dense material such as lead. Do not use lead shielding for beta-emitting nuclides because it will produce hazardous Bremsstrahlung (x-rays). Shielded syringes are commercially available for manipulation of liquids containing high energy radioisotopes.
Reduce the chance for radioactive materials to enter the body through inhalation, ingestion, or skin contamination. Maintain a high standard of cleanliness and housekeeping and follow good hygiene practices:
• NO eating, drinking, or application of cosmetics in radioisotope areas
• NO storage of human food and drinks in research areas including lab refrigerators, freezers, or microwave ovens
Whenever possible, operations with radioactive materials should be conducted in a hood, dry box, or some other type of closed system. Operations with materials susceptible to atmospheric distribution, such as boiling, evaporating, distilling, or burning, must be done in a fume hood with adequate airflow of approximately 60-120 linear feet per minute (lfpm); some newer fume hoods are designed to be in compliance at lower rates, of approximately 60-65 lfpm. Fume hoods in radioactive material laboratories are checked periodically for airflow and the proper sash height is indicated on the fume hood. Work with radionuclides with half-lives of more than a few hours should be done within containment to prevent the spread of contamination in the event of a spill. Work with radioactive materials in powder form should be done in an enclosed system.
Work with hazardous materials on impervious benchtops and dedicate an area for work with radioisotopes. Working surfaces should be covered with absorbent paper regardless of the type of surface.
Label all areas (e.g., benchtops, sinks) and equipment (e.g., containers, waste receptacles) that may contact radioactive materials. Use tape or labels marked with the radiation symbol. Remove or permanently deface these symbols when the hazard no longer exists.
When work is completed, each user should clean up their own work area and arrange for disposal of all radioactive materials and equipment.
Vacuum pumps used in systems containing radioisotopes should be used in fume hoods with proper flow rates.
Before submitting repairs on facility infrastructure or equipment used for radioactive materials work such as sink drains and fume hoods, make sure the equipment and surrounding area are free of contamination.
Always use appropriate Personal Protective Equipment (PPE) when handling radioactive materials. PPE reduces the chance of intake and skin contact. Assess all hazards and select PPE based on your risk assessment. At a minimum, wear:
Change gloves and wash hands frequently. Remove gloves before touching any clean items that are usually touched without gloves. Do not reuse disposable gloves.
Some compounds may become airborne through volatilization, aerosolization, or metabolization when stored or used. When these compounds contain radioisotopes the risk of internal exposure through inhalation increases.
Use a chemical fume hood for all work with potential airborne radioactive compounds. Before opening packages or containers (e.g., vials) with gaseous, volatile, or pressurized (e.g., ampules) radioisotopes, place them in a fume hood.
Use activated charcoal, exchange resins, or zeolite catalysts to trap radioisotopes for decay.
Open containers, such as cell culture dishes containing radioisotopes, can be covered with carbon-impregnated paper.
Examples of radioactive isotopes that can become airborne:
Radioactive materials must be secured at all times.
This may be accomplished by any of the following:
These requirements apply to all radioactive materials in the laboratory, including waste, contaminated equipment, and sealed sources.
Radioactive materials stored in occupied areas must be shielded in accordance with the ALARA principle.
Unbreakable containers are recommended for storing radioactive liquids. Glass and other fragile containers used for storage must be kept in non-breakable, leak-proof secondary containers or trays capable of containing the entire volume of liquid stored in the primary container.
Radioactive gases and volatile forms of radioisotopes should be stored in a well-ventilated area, such as a fume hood.
Sealed sources must remain in the same condition as received from the manufacturer. No modification of sealed sources is permitted without express written consent from DRS. If a sealed source is damaged, remove from use and contact DRS for leak-testing.
Sealed sources must be tracked and their location confirmed every six months as requested by DRS. This includes sources that have decayed to background levels. Turn over unused and decayed sources to DRS for storage and disposal.
Clearly label all radioisotopes and calibration sources with the radiation safety symbol, the nuclide, activity, and date. For multiple small containers such as sample vials, the information can be put on the holding container. For liquids, include information on the chemical composition.
Research with vertebrate animals must be approved by the Institutional Animal Care and Use Committee (IACUC). DRS reviews all IACUC protocols that involve the use of radiation sources to ensure that safety requirements have been addressed. This includes the following items:
Animal caretakers must be instructed and trained on handling procedures, dose levels, occupancy time limits, and applicable special conditions. Animal caretaking should be performed by trained research personnel.
Authorization to administer radioisotopes to animals must be approved by DRS. DRS establishes the criteria for releasing the animals to the owners.
Regulations require tracking of all radioactive materials from the source to disposal. Every use and waste disposal must be recorded. A Radioisotope Use and Waste Log is available on the DRS website. The online inventory is updated automatically whenever radioactive material is delivered or waste picked up by DRS. Sewer disposal must be requested in the online system for the disposed amount to be subtracted. The inventory of open materials and sealed sources must be confirmed by the laboratory every six months.
DRS personnel periodically audit radiological laboratories on campus. The following are expected to be readily available for inspection:
Printouts from automatic counters such as a liquid scintillation counter may be used as a survey record if the survey locations are clearly noted. Records must be maintained by the Permit Holder for as long as the radiation permit remains active.
ALARA – As Low As Reasonably Achievable
Bq – Becquerel (unit of radioactivity)
Ci – Curie (unit of radioactivity)
cpm – counts per minute
DRS – Division of Research Safety
dpm – disintegrations per minute
GM – Geiger-Mueller
Gy – Gray (unit of absorbed dose)
IEMA – Illinois Emergency Management Agency (formerly Illinois Department of Nuclear Safety (IDNS))
LSC – liquid scintillation count or liquid scintillation counter
mCi – millicurie (unit of radioactivity)
NaI – sodium iodide
PI – Principal Investigator
μCi – microcurie (unit of radioactivity)
R – Roentgen (unit of exposure)
Rad – radiation absorbed dose (unit of absorbed dose)
Rem – Roentgen equivalent man (equivalent absorbed dose)
RLSC – Radiation and Laser Safety Committee
RSO – Radiation Safety Officer
Sv – Sievert (equivalent absorbed dose)
U of I – University of Illinois at Urbana-Champaign
1 microcurie = 2.22 x 106 dpm
1 Bequerel = 1 disintegration per second (dps)
1 Ci = 37 GBq = 109 disintegrations per second (dps)
1 Gy = 100 rad
1 Sv = 100 rem
To calculate activity from meter or wipe survey results, use:
Activity (dpm) = (gross count rate – background count rate) / instrument efficiency
Example: The LSC count of a wipe sample was 150 cpm. The background was 30 cpm. Efficiency for H-3 is 67%.
Activity (dpm) = (150 cpm – 30 cpm) / 0.67 = 179 dpm
A survey instrument’s efficiency can be determined for an individual radionuclide using a known standard (decay-corrected, if necessary) of the radionuclide. The standard is counted in a fixed geometry and the instrument count rate observed. The efficiency is then determined by the formula:
Efficiency (%) = (gross count rate – background count rate) x 100 / Activity of standard (dpm)