| Vanderbilt University Online Radiation Safety Policies & Procedures Manual |  |
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| Vanderbilt University Online Radiation Safety Policies & Procedures Manual | |
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Section 5: Receipt, Transfer, and Disposal of Radioactive Material > |
Section 4: Policies and General Procedures For Radioactive Material Use
A. General Safety Rules for Working with Radioactive Material
The PI has the responsibility to protect both the workers and the general public from any radioactive sources being used. The PI should be familiar with the basic principals of radiation protection and the properties of the radioactive materials being used. The PI should see that the work of the group is properly planned and that adequate instructions are provided for any operations involving radioactive material. For lengthy, repetitive procedures, the instructions should be in written form. A dry test run should precede an initial unfamiliar procedure. The PI shall see that instructions are followed and that safety rules are enforced.
B. Maximum Radiation and Contamination Levels
Radioactive contamination must not be allowed to remain above the limits given the Table 3. Items may be released for unrestricted use if they are below the contamination limits given in Table 3.
Type of Contamination Low Toxicity Radionuclide
(dpm/100 cm 2)Moderate and High Toxicity Radionuclide (dpm/100 cm2) Very High Toxicity Radionuclide
(dpm/100 cm2)Unrestricted areas and personal clothing 2,000 200 20 Restricted areas 10,000 1,000 200 Fixed contamination 10,000 1,000 200 Note: Toxicity classes for various radionuclides may be found in Appendix B "Table of Radionuclides". Toxicity classes are defined in Table 4.
"Removable contamination" means radioactivity that can be transferred from a surface to wipe test paper by rubbing with moderate pressure.
Fixed contamination levels may be measured with a survey meter calibrated to read in mR/hr. The average and maximum radiation levels associated with surface contamination by beta-gamma emitters should not exceed 0.2 mR/hr with the detector 1 cm from the surface and 1.0 mR/hr with the detector 1 cm from the surface, respectively, as measured through not more than 7 mg/cm2 of total absorber.
Table 4: Radionuclide Toxicity Class Toxicity class is based on the Annual Limit on Intake (ALI) Toxicity Class Low Moderate High Very High ALI (mCi) >5 0.500-4.999 0.005-0.499 <0.005
C. Posting and Labeling requirements
D. Sealed Sources of Radioactive Material
Surveys are performed to locate areas of increased exposure or removable contamination. Exposure surveys may identify areas with increased exposure or contamination. A wipe survey is routinely performed to determine if removable contamination is present. If the area is contaminated, see decontamination procedures in this manual or call VEHS (322-2057).
A survey is required after each use of radioactive material. If the laboratory is classified as a medium hazard laboratory a survey is required to be documented weekly.
Surveys after each use of radioactive material shall include a survey of hands, clothing, equipment, and the work areas. A GM or NaI survey meter evaluation is required unless only tritium is used, then a wipe survey should be performed. If increased readings are detected with the survey meter, a wipe survey of the area should be performed.
Documented weekly surveys shall include all work areas, preparation areas, equipment storage areas, cabinet fronts, drawer fronts, desks, and those areas classified as "clean". A GM or NaI scintillation meter for radioiodine evaluation and wipe surveys are required.
Geiger Mueller (GM) survey instruments can be used to detect beta and gamma radiation. When using a GM survey meter remove any protective caps. The thin window should not be covered, as it will decrease detection sensitivity. Check the calibration sticker to ensure the meter has been calibrated within the last year. Do not use the meter if more than a year has past since the last calibration. Check the batteries and do a performance check on the meter to ensure it is functioning properly. A performance check may include the use of a dedicated check source or a vial or tube containing a known amount of radioactive material. Verify background is within an acceptable range, typically 0.01-0.05 mR/hr. If there are any questionable results, e.g. no response, or the meter will not zero, call VEHS for guidance.
To survey, slowly move the probe over the surface with the thin window facing the surface. The probe should be 1 centimeter above the surface. A NaI survey meter is operated the same way as the GM. The only difference is the NaI is used for gamma radiation (e.g. 125I).
Laboratory personnel handling radioactive material should check hands frequently for contamination with a GM meter or NaI scintillation meter. If contamination is detected, remove gloves and resurvey hands. If contamination is detected on the skin, call VEHS immediately. Before lab personnel leave an area where radioactive material is used, use a GM or NaI for radioiodine to check hands, clothing, and feet for contamination. Also, lab personnel should check hands, clothes, and feet at the end of each day that radioactive material is used.
Any area that has an elevated radiation exposure reading with a GM or NaI survey meter should have a wipe test performed. If the contamination is removable, then decontaminate the area. If the area cannot be decontaminated or assistance is required, call VEHS. If the exposure readings are high near a radioactive material storage area, try rearranging the containers of radioactive material to lower the exposure rates.
Radiation survey meters are required to be calibrated annually or after repairs. A meter should be checked when there is cause for concern in the meter's performance or when a contaminated probe is suspected. VEHS cannot repair meters but can sometimes diagnose common problems and suggest corrective actions.
VEHS is required to be notified when a new survey meter is acquired so that it can be included in the calibration schedule.
The PI is responsible for making arrangements to have their survey meters calibrated. VEHS offers a meter calibration service for a fee. In order to have a survey meter calibrated contact VEHS at 2-2057 to schedule a time to have the survey meter calibrated. VEHS will pick the survey meter up from the lab for calibration and leave a loaner survey meter with the lab until the lab's survey meter has been calibrated and returned. Survey meters that cannot be calibrated to +/- 20% may need to be returned to the manufacturer for repair.
G. Portable Radiation Meter Policy
The Radiation Safety Committee has established the following portable survey meter requirements for operations involving radiation sources. The RSC may waive some requirements of this policy if it can be demonstrated that safety would not be significantly compromised. The RSC may require that a meter be obtained when this policy does not specifically require one. The Committee may also require specific types of meters or detectors, such as scintillation detectors for 125I or ion chambers for mixed gamma/x-ray radiation fields.
- PI's with authorized possession limits that correspond to a total of 150 or more ALI's for any combination of radionuclides are required to have appropriate radiation survey meter(s) located in each laboratory room classified as a "medium hazard". The meter must be physically present at all times in these rooms.
- PI's with authorized possession limits that correspond to a total of 5 or more ALI's for any combination of radionuclides must have immediate access to appropriate radiation survey meters. This access can be accomplished by:
- Purchasing one's own meter.
- Labs can share a meter if it is immediately accessible to all labs involved. A meter is considered immediately accessible if it can be retrieved within 5 minutes any time radioactive materials are being used. Meters located in another building, on a different floor of the same building, or several corridors away are not considered immediately accessible. A meter cannot be shared if it belongs to a laboratory classified as a "medium hazard" laboratory.
If a meter is shared, a signed statement from the PI who owns the meter must be submitted with the application to use radioactive materials.- PI's with authorized possession limits corresponding to less than 5 ALI's must also perform surveys for radioactive contamination and therefore should have reasonable access to survey meters.
- Anyone who uses radiation-producing machines may be required by the RSC to have an appropriate survey meter.
H. Guidelines for Selecting Portable Radiation Survey Meters
I. Wipe Survey - testing surfaces by wipingAll meters will not detect all radionuclides. The following guidelines are designed to assist in selecting meters that are appropriate for detecting various types of radiation:
- For detecting beta emitters with a maximum beta energy greater than or equal to 150 keV such as 14C, 35S, or 32P either of the following are recommended:
- A Geiger-Mueller (GM) detector with a maximum window thickness of 1.7 mg/cm2. Pancake style GM's are recommended over thin end window GM's because pancake style GM's are generally more efficient for low energy beta emitters (14C or 35S) and the pancake's larger window surface area makes it easier to monitor large areas for contamination.
- A beta scintillator with a plastic scintillation detector. The cost of a GM is significantly lower than a beta scintillator, but the scintillator is generally more efficient.
Note: A side window GM will not be approved for use as a detector for beta emitting radionuclides, since this type of probe will not detect 14C or 35S and is significantly less efficient than either thin window or pancake GM's.- For surveying radiation sources that generate x- or gamma rays with energy greater than 30 keV, a GM pancake, GM thin end window, or a GM side window is usually adequate. As mentioned above, the pancake style is preferable since it has a larger window surface area that assists in monitoring large areas for contamination. However, solid detectors (i.e. NaI) are usually much more efficient and may be more appropriate if very low levels of radiation need to be detected.
- For PI's approved for 125I or other radiation sources that generate x- or gamma rays with energies less than 30 keV, a low energy 1" x 1 mm NaI(Tl) gamma scintillation detector is recommended.
- For PI's approved for both beta and low energy gamma emitters (i.e. less than 30 keV), one of the following should be purchased: (1) two meters (one with a GM probe and one with a NaI probe), (2) two probes for one meter (a GM probe and a NaI probe), or (3) a beta-gamma sandwich scintillation detector. The beta-gamma scintillation detector is a combination of two scintillation probes previously described.
- Ion chambers are used to detect x- and gamma radiation fields. They have an energy independent response and are therefore recommended for any dose rate measurements that are made to demonstrate compliance with Vanderbilt's license and/or State regulations. Ion chambers are not practical for the detection of contamination.
Probes that are separate from the body of the meter are preferable. Built-in probes are often difficult to repair or replace without sending them back to the manufacturer. Separate probes can usually be readily replaced or repaired.
Be wary of purchasing a meter if a vendor cannot or will not provide the above information. If necessary, VEHS can provide vendor information.
Wipes should be taken for all areas that have an increased exposure reading with the GM and/or the NaI scintillation meter. Wipes are taken to determine if the contamination is removable. Wipes should also be taken on the work bench, floor, refrigerator handles, light switch, trash can lids, fume hood sill, fume hood sash, bottom of fume hood, etc. Wipe surveys should not always include exactly the same locations. Filter paper, Q-tips, or alcohol prep pads can be used for wipes, or wipes can be purchased from a vendor. A wipe should cover an area of at least 100 cm2 and should not exceed 300 cm2.
The wipes should be counted on a liquid scintillation counter (LSC) and/or a gamma counter depending on the radionuclide(s) used. If only beta emitting (i.e. 3H, 14C, or 32P) radionuclides are used, the wipes should be counted on a LSC. If only gamma emitting radionuclide(s) (i.e. 51Cr) are used the wipes can be counted on a gamma counter.
Radiation workers are responsible for conducting surveys of their work areas to (a) assure that radiation sources are adequately shielded and (b) to check for radioactive contamination. If gamma or high energy beta sources are used, radiation meter surveys should be made to check radiation levels in all work areas, storage areas, around waste containers, and in nearby uncontrolled areas. Contamination checks are made by using an appropriate survey meter to scan suspect surfaces or by wipe testing surfaces, i.e. rubbing a piece of paper or cotton-tipped applicator over the surface and then counting it for radioactivity with a suitable counter.
Radiation workers are personally responsible for checking themselves for contamination before leaving radioactive material areas.
A simple survey log is recommended to help the radiation worker maintain an awareness of changes in radiation levels that may indicate a need for a change in procedure.
Documented weekly surveys are required if a laboratory is classified as a "Medium Hazard"lab. If these surveys are not performed it will be necessary to downgrade the lab classification to "Low Hazard" by decreasing the PI's radioactive material possession limit.
Periodic inspections and surveys are performed by VEHS at a frequency commensurate with the hazard rating of the laboratory.
Table 5: Fume Hood Requirements for Radioactive Material Number of ALI's* Used Hood Requirement Volatile Radioisotopes < 1 No Hood Required 1 - 10 Standard Chemical Fume Hood > 10 Activated Charcoal Filter** Required Volatile Radioiodines < 1 Standard Chemical Fume Hood > 1 Activated Charcoal Filter** Required Non-Volatile Radioisotopes < 10 No Hood Required 10 - 100 Standard Chemical Fume Hood > 100 HEPA Filter*** Required *ALI or Annual Limit of Intake. A list of ALI's can be found in Appendix B "Table of Radionuclides"
**Activated charcoal filter for gaseous contamination
***High Efficiency Particulate Air (HEPA) filter for particulate airborne contamination
Releases to the atmosphere shall not exceed the maximum permissible concentrations in air specified in State regulations. Traps or filters may be required to ensure that environmental releases are within acceptable limits. Should either activated charcoal filter or a HEPA filter need to be used, the filters must be incorporated into the fume hood system. As an alternative to installing a filter in an existing hood, a tabletop hood equipped with one of these filters can be placed inside of an existing fume hood.
Radioactive material labs are classified on the basis of the radionuclides and the corresponding possession limits that are approved for the PI. The toxicity of radioactive material varies considerably so it is necessary to "normalize" the approved activities for the various radionuclides. This is done by determining the number of ALIs (Annual Limit on Intake) represented by each radionuclide possession limit. Labs are then classified according to the following:
Lab Hazard Rating Approved No. of ALIs Slight 1 Low 1-150 Medium 150-100,000 High >100,000 The approved number of ALIs is the sum of all radionuclides for which the PI is approved. If a PI has more than one laboratory room, at least one of the rooms will be rated at the calculated level. Other rooms may be rated at a lower level.
Example: A PI is approved for:
3H 20 mCi (740 MBq) ALI = 80.0 mCi (2,960 MBq) # ALIs = 0.25 125I 10 mCi (370 MBq) ALI = 0.04 mCi (1.48 MBq) # ALIs = 250.00 32P 15 mCi (555 MBq) ALI = 0.40 mCi (14.8 MBq) # ALIs = 37.5 Total number of ALIs = 287.75, so the major lab classification = Medium
L. Survey Instrument Requirements
Laboratories classified as Medium or High hazard labs must have a portable survey meter that is appropriate for the type of radiation being used. Laboratories with a Low rating must have ready access to a survey instrument. Labs only using 3H or 63Ni are exempt from this requirement.
Survey instruments are required to be calibrated annually or after repairs are made to the instrument. The PI is responsible for making arrangements for having survey equipment calibrated. VEHS provides a calibration service for a fee.
M. Radiation Safety Training Requirements
Prior to handling radioactive material at Vanderbilt, each person must satisfy the following training requirements:
N. Animals Containing Radioactive Materials
O. Use of Division of Animal Care Facilities
Principal Investigators desiring to use these facilities must submit a written request to the Division of Animal Care. Use of these facilities does not relieve the investigator of the responsibilities for the use of the radioactive materials. Radioactive animals should be isolated from other animals. The investigator is responsible for changing and collecting radioactive litter and for providing all necessary monitoring. The cage must be decontaminated before being returned to Animal Care.
Radioactive animals should not be petted or groomed.
If radioactive materials are expired from the animal or are excreted in a volatile form, adequate ventilation must be provided.
Appropriate disposable gloves and a lab coat must be worn when changing litter or cleaning the cages. Any excreta or litter that is radioactive must be treated as biological waste.
All cages must be monitored for radioactive contamination after the animals are removed and decontaminated to below the criteria stated in section 4 of this manual.
All locations where radioactive animals were injected, housed, or sacrificed must be monitored for contamination. Be sure to monitor yourself after any work with radioactive animals.
Precautions should be taken to minimize dust production.
Experimental animals administered radioactive materials should not be used for human or animal consumption.
P. General Radiation Safety Enforcement Policy
For serious or flagrant radiation safety violations, the Principal Investigator's (PI) authorization to use radioactive material will be immediately suspended. Following a suspension, the PI must appear before the RSC and present an acceptable plan for corrective actions before authorization can be reinstated. For less serious violations, or a pattern that indicates an overall laxity in their radiation safety program, the PI will be given one written warning before a suspension is imposed.
Serious incidents or flagrant radiation safety violations can include, but are not limited to:
Violations for which a single written notice will be dispensed can include, but are not limited to:
Q. Radioactive Material Security
Radioactive material must be secured against unauthorized access or removal. Unattended radioactive material may be secured by the following methods:
Note:
R. Enforcement Policy for Security of Radioactive Material
Security of radioactive material must depend on the diligence and awareness of individual users and is a reflection of the safety culture of an institution. The following action will be taken if radioactive material is observed to be unsecured in a laboratory or shared departmental facility: