Using Radioactive Materials
Storage of Radioactive Materials
Radioactive materials must be secured at all times. This may be accomplished by any of the following:
- Attending the materials;
- Maintaining materials in a locked freezer or cabinet;
- Locking the room in which the materials are stored.
These requirements apply to all radioactive materials in the laboratory, including waste, contaminated equipment, and sealed sources.
Radioactive materials stored in occupied areas shall be shielded in accordance with the ALARA principle (i.e., radiation exposures to faculty, staff, students and the public resulting from the use of radiation sources in teaching and research shall be kept As Low As Reasonably Achievable (ALARA), which is discussed in Sections 7.8 and 7.9 of the Radiation Safety Manual.
Unbreakable containers are recommended for storing radioactive liquids. Glass or fragile bottles and other breakable 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 the express written consent from the Division of Research Safety (DRS). Sealed sources that have been mutilated and damaged beyond what would reasonably be expected to occur as a result of its normal use should be reported to DRS as soon as possible.
Radioisotopes and calibration sources shall be clearly labeled with the following information:
Caution: Radioactive Materials
Activity and assay date
Person responsible for sample or source
Labeling is not required if the activity is less than the following:
Exemptions for other radionuclides may be found in Appendix C of the Code of Federal Regulations, Title 10, Part 20. http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-appc.html
Using Radioisotopes in Animals
When radioisotopes are used in animals, the areas in which animals are kept must be posted in accordance with the requirements of Illinois Emergency Management Agency (IEMA) statutes and regulations.
Cages and pens must bear labels listing the isotope used, the quantity and date administered, measured external radiation levels, and the name of the principal investigators (PI). These cages and pens should be separated from those housing non-radioactive animals.
Ventilation should be adequate to handle the possibility of airborne radioactivity. In some instances, this may require the use of a fume hood or self-contained, controlled environmental systems.
Procedures for disposal of animal excreta must be included in the radiation permit application process. If excreta are mixed with bedding materials, handle in accordance with dry radioactive waste procedures.
DRS must approve disposal methods for animal carcasses.
Animal caretakers shall be instructed and adequately trained by the PI 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 shall be approved by DRS. DRS establishes the release criteria for the animals to the owners.
Radioisotope Use and Waste Log
Found in Appendix E of the Radiation Safety Manual.
Contamination Survey Procedures
Surveys are performed to monitor for the presence of contamination. Minimum survey frequencies are specified on the radiation permit. The surveys should be sufficiently extensive to allow confidence that there is no contamination. Common places to check for contamination are: bench tops, tools and equipment, floors, telephones, floors, door handles and drawer pulls, and computer keyboards.
Types of Contamination
Removable contamination can be readily transferred from one surface to another. Removable contamination may present an internal and external hazard because it can be picked up on the skin and ingested. Fixed contamination cannot be readily removed and generally does not present a significant hazard unless the material comes loose or is present large enough amounts to be an external hazard.
Types of Surveys
There are two types of survey methods used: 1) a direct (or meter) survey, and 2) a wipe (or smear) survey.
Direct surveys, using a Geiger-Mueller (GM) detector or scintillation probe, can identify gross contamination (total contamination consisting of both fixed and removable contamination) but will detect only certain isotopes.
Wipe surveys, using “wipes” such as cotton swabs or filter papers counted on a liquid scintillation counter or gamma counter can identify removable contamination only but will detect most isotopes used at the U of I. Wipe surveys are the most versatile and sensitive method of detecting low-level removable contamination in the laboratory.
The portable Geiger-Mueller (GM) survey meter is best used for P-32, a high-energy beta emitter, and other high-energy beta and gamma emitters, such as Co-60, Zn-65, Cs-137, and U-238. A GM meter can also be used to identify areas heavily contaminated with lower energy beta emitters, such as C-14 or S-35, for which the GM meter has a relatively low efficiency. GM meters should not be used to survey for I-125 contamination because they detect I-125 only when there are very high levels of contamination.
The portable thin crystal NaI scintillation survey meter should be used to locate I-125 contamination and to conduct surveys around low-energy X-ray sources such as X-ray diffractometers and electron microscopes.
The liquid scintillation counter, used for counting wipe tests, is the most versatile counting instrument because it has a high counting efficiency for a wide range of radionuclides. Most LSCs provide a printout of sample results that may be used as survey record.
Gamma counters are not portable and are used to count swipes of photon emitters such as Cr-51 or I-125.
How to Perform a Meter Survey
Prior to performing any survey, clean gloves should be worn. This prevents the possibility of personal contamination or cross-contamination.
Perform an instrument check. To check the operation of a survey instrument, do the following:
- Calibration check:
a. Check the calibration label on the instrument and ensure the instrument is within the calibration period. If the calibration due date has passed, contact DRS to have the instrument re-calibrated and find another instrument to use.
- Battery check:
a. Turn the switch on the survey meter to "BATTERY," or flip the battery switch to "ON." The needle on the meter face should move to a position within or beyond the indicated area on the meter face scale. Replace batteries if needed before using the survey meter.
- Speaker check:
a. If there is an audio switch on the survey meter, turn it to "ON." Set the survey meter to a scale of "X1." The survey meter should chirp or click. If the speaker does not function, the survey meter can be used, but the surveyor will need to check the reading on the survey meter face frequently.
- Background check:
a. Go to an area with an expected low background rate. Note the count rate when the survey meter is switched to the "X1" scale. The background rate for a GM meter should be less than 100 counts per minute; the background reading for a NaI meter should be less than 400 counts per minute. If background readings exceed these levels, investigate the area for unknown sources of radiation or detector contamination. Do not use the survey meter if it does not register a background rate.
- Instrument response check:
a. Hold the supplied check source (often a thorium lantern mantle) up to the probe window. Note the counting rate. The survey meter should respond to the check source, thus providing positive indication that the instrument is functioning properly.
Do not cover the probe surface with parafilm or other protective coating. Parafilm and similar materials will shield the low energy betas from C-14, P-33, and S-35 and may prevent the meter from detecting contamination.
Hold the probe window approximately 1 cm from the surface to be surveyed and move the probe over the surface at about 1 cm/second.
Check the most common sites for contamination, such as survey meter handle, soap/towel dispensers, drawer handles, refrigerator/freezer handles, chair edges, writing utensils, survey record books, floors, radio dials, telephone receiver/keypad, microwave oven touch pads/handles, doorknobs, light switches, and non-radioactive trash containers.
Record survey results in a survey log (see Appendix E of the Radiation Safety Manual). If survey results are equivalent to the background, log the result as ‘≤ BKG’. Generally, a surface is considered contaminated if the result is greater than the background count rate. If contamination is found, record the result and indicate the action taken.
How to Perform a Wipe Survey
Prior to performing any survey, clean gloves should be worn. This reduces the likelihood of personal contamination or cross-contamination.
Removable contamination is best identified by a wipe survey, which is performed by rubbing a filter paper (approximately 45 mm in diameter) or cotton swab over the survey area with moderate pressure. The paper or swab may be wetted with ethanol or water to increase the collection efficiency. Usually an area of 100 square centimeters (4 square inches) is surveyed. To monitor a larger area, take additional swipes.
If surveying for low-energy beta emitting isotopes such as H-3, C-14, P-33, and S-35., analyze the wipe using liquid scintillation counting.
If surveying for high-energy beta emitters (e.g., P-32), wipe samples may be counted using either liquid scintillation counting or a GM meter.
If monitoring for low-energy gamma emitters (e.g., I-125), wipe samples should be counted with a thin crystal NaI scintillation meter.
The net sample count rate is determined by subtracting the background count rate from the gross count rate.
Sample activity is determined by dividing the net sample count rate by the instrument’s efficiency for the isotope in question.
Survey results must be documented on a survey log (see Appendix E of the Radiation Safety Manual) or similar form. Results may be reported as gross count rate, net count rate, or in units of activity (usually disintegrations per minute). Ensure that the survey log accurately reflects how results are being reported.
Found in Appendix E of the Radiation Safety Manual.
Records required to be kept in the laboratory
DRS personnel make periodic audits and surveys in radiological laboratories. The following are expected to be readily available for inspection:
- Laboratory survey records;
- Radioactive material inventory and use records;
- Radioactive waste records (solid and liquid). Sewer disposal records can be kept either in the laboratory logs or in the DRS database.
If the forms in Appendix E of the Radiation Safety Manual are used and maintained, no findings of non-compliance should occur during the DRS audit process. Printouts from automatic counters such as a liquid scintillation counter may be attached and used as a survey record if the sample numbers correspond to survey locations. Records should be maintained by the PI for as long as the radiation permit is active.
DRS personnel perform independent laboratory contamination surveys and audits of laboratory records. The survey and audit results are sent to the PI via email when completed and approved.
Last Update: 3/20/2017