4.2 Labeling and Storage of Radionuclides

4.2.1 Labeling

Regulations require that any containers with radioactive material in excess of the limits specified in Table 4-1 be labeled with the nuclide, activity, date, and name of user. Limits for nuclides not specified are contained in Arizona Administrative Code 12-1, Article 4 Appendix C. Containers with lesser amounts of radioactive material should be labeled when practical. Racks or boxes containing a number of samples with small amounts of radioactive material may be labeled in lieu of a label on each vial.

NUCLIDE	ACTIVITY (uCi)
14C 45Ca 57Co 60Co 51Cr 59Fe 3H 125I 22Na 32P 35S	1,000 100 100 1 1,000 10 1,000 1 10 10 100

Table 4-1 Labeling

4.2.2 Storage

All radioactive material must be stored so that radiation fields are less than those specified for a "Radiation Area" in sub-chapter 4.1, unless specific approval is obtained from the RSO. Radioactive sources must be secured against unauthorized removal at all times. This means that one of the following conditions must be met:

1. Material is attended by a responsible person authorized to work with radioactive material;
2. Material is contained in a locked container;
3. The room in which the material is stored is locked.

4.3 Contamination Control

4.3.1 General Rules for Contamination Control

1. The area within the laboratory where unsealed sources of radioactive material are used must be covered with absorbent material surrounded with yellow tape or tape with the standard radiation caution symbol. If possible, work should be conducted in a tray lined with absorbent paper and in a chemical or radionuclide fume hood.

2. Disposable gloves and lab coats must be worn at all times when handling unsealed sources of radioactive materials. Lab coats must not be taken from the lab to lunch rooms.

3. All radioactive waste must be placed in marked containers which have been approved by the ORS.

4. Never pipette solutions by mouth.

5. Use the smallest quantity of radioactivity compatible with the objective of the experiment.

6. Label containers of radioactive material clearly indicating nuclide, total activity, and date.

7. Do not eat, drink, smoke, chew gum, or apply cosmetics in spaces where unsealed sources of radioactive material are used.

8. Do not store food, drink, or personal items with radioactive material.

9. Know how to react in case of a spill or personal contamination.

10. Wear assigned dosimetry devices as required.

11. Work carefully, and regularly monitor the work area to avoid accidental contamination.

4.3.2 User Surveys for Surface Contamination

After procedures using unsealed sources of radioactive material are complete, or at the end of each day during which radioactive materials are used, the work areas must be surveyed for surface contamination.

The extent of the survey depends on the type of procedures being conducted and the amount of radioactive material.

Use of activities equal to or less than those in paragraph 4.2.1 requires a check for contamination in the immediate work area, and on the hands and feet of those handling the material.

Complicated procedures, and those involving quantities of radioactive material in excess of those listed in paragraph 4.2.1 require more extensive surveys; including checks on surfaces such as the floor, table tops, phones, doorknobs, feet, hands, and other areas where there is a potential for the spread of radioactive material.

Surveys must be documented. The individual conducting the survey must initial or sign a document indicating that the survey was conducted, and whether contamination was or was not found. The documentation may be through use of the source utilization logs, or other log provided by the user.

4.3.3 Survey Procedures (See RAM Survey)

Surveys for some nuclides may be made using a laboratory survey instrument. Surveys for other nuclides, such as H-3, require wiping surfaces with filter papers. Removable activity on the filter papers can be counted using liquid scintillation. Specific procedures for some nuclides in use at ASU are:

1. ³H: Wipe surfaces with filter paper and count by liquid scintillation for five minutes. If the count rate is more than 15 cpm above background, the surfaces should be decontaminated.

2. ¹⁴C / ³⁵S / ⁴⁵Ca / ¹²⁵I: G.M. counters with thin windows (1.2-2 mg/cm2) may be used for detecting areas of gross contamination. However, the efficiency of thin window G.M. detectors for these nuclides is such that contamination in excess of allowable limits may not be detected. A final check must be conducted using filter paper wipes as outlined for ³H.

3. ³²P and other "hard beta emitters": These nuclides are adequately detected with laboratory survey meters. The probe should be placed within a couple of millimeters of the surface, and moved very slowly. Surfaces with readings of more than 50 cpm above background should be decontaminated.

4. Laboratory survey techniques for other nuclides may be obtained from the RSO.

4.3.4 Contaminated Surfaces and Equipment

Instruments and glassware which are repeatedly used with radioactive materials may be stored in their contaminated condition if they are bagged, marked with the radiation warning symbol, and placed in a closed container such as a drawer or cupboard which also shows the radiation warning symbol.

Interior surfaces of some equipment, such as centrifuges, may contain low level contamination if the equipment is properly marked and closed so that contaminated surfaces are not exposed to the room. Measurable contamination must not be allowed to remain on equipment and laboratory surfaces other than those listed above. Exceptions to this policy must be approved by the RSO.

4.3.5 Laboratory Surveys by Radiation Protection Personnel

Personnel from the ORS enter laboratories and spaces designated for use of radioactive materials periodically to conduct surveys. Personnel conducting surveys make measurements of surface contamination and radiation levels. They also examine laboratory records and observe laboratory conditions for compliance of the sub-licensee and users of radioactive material with ARRA and ASU rules and regulations for use of radioactive material. Most spaces in which radioactive material is used are surveyed by ORS personnel once each month. Laboratories using radioactive material on an infrequent basis will be surveyed by ORS personnel annually.

4.3.6 Sealed Source Leak Checks

Sealed sources containing more than 100 uCi of beta or photon-emitting material or more than 10 uCi of alpha-emitting material are wipe tested for leakage once every 6 months by ORS personnel. Sub-licensees are contacted for access to sources as needed. Should leakage in excess of 0.005 uCi be discovered on these sources, they are removed from use and repaired or disposed of by the RSO.

4.4 Protection from External Exposure

4.4.1 ³H, ¹⁴C, and ³⁵S

External exposure to radiation emitted by these low-energy beta emitters is not a problem unless they are present as contamination on the surface of the skin. Beta particles from these nuclides travel less than 25 cm (10 inches) in air and less than 0.3 mm (0.1 inch) in tissue. Most radiation is absorbed by containers, solutions, air, clothing, and the dead layer of skin. The beta particle from tritium does not have sufficient energy to penetrate the dead layer of cells protecting the skin.

4.4.2 Limiting Time of Exposure

The external dose received is a function of the time spent working in the proximity of radioactive materials. Plan procedures in advance and examine ways of doing the job which will speed the procedure and/or limit the amount of time that exposure to radiation is necessary. Equipment which eliminates the need for direct handling of radioactive material is desirable.

Practice procedures using non-radioactive materials. These dry runs will increase worker's ability to conduct experiments quickly and carefully.

4.4.3 Maximizing Distance from Sources

For sources of radiation which are small in physical size, the intensity of the radiation field is inversely proportional to the square of the distance from the source. The importance of the so called "inverse square law" lies in the quadratic relationship between exposure rate and distance. By doubling the distance between a worker and the source, the exposure rate is decreased by a factor of four. Distance should be maximized by using remote handling instruments, such as tongs for handling vials of radioactive material, and by staying away from the source whenever possible.

4.4.4 Shielding Beta Particles

Shielding pure beta emitters is simplified by the lack of the more penetrating radiations. Beta particles have a finite range in shielding materials beyond which they cannot penetrate. The best shielding for ³²P is plastic, lucite, glass, and aluminum. Use of lead or other high atomic number shielding materials may create penetrating bremsstrahlung radiations. Lucite and plexiglass are easily worked materials for constructing beta shields. One fourth inch of these plastics will protect users working with millicurie quantities of ³²P. Beta shields in various configurations can be obtained commercially. Information on sources of these shield materials is available in the ORS.

Nuclide	Radiations Emitted	Range of b Particle in Air	1Dose Rate to Skin from 1 uCi/cm2 Skin Contamination (rad/hr)	2Annual Limit on Intake (mCi)
3H	18.6 keV b	0.5 cm	0.0	80
14C	156.5 keV b	0.2 m	1.2	2
32P	1.7 MeV b	6.2 m	8.9	0.6
35S	166.7 keV b	0.24 m	1.3	2
36Cl	709.3 keV b	1.9 m	7.2	0.2
45Ca	256.7 keV b	0.46 m	3.3	0.8
59Fe	465.6 keV b 1.1 MeV g 1.3 MeV g	1.1 m - -	4.7	0.3
125I	35 keV electrons 30 keV x-rays 35 keV g	1.5 cm - -	2x10-3	0.04
1 Dose rate estimated for basal skin cells 2 Amount of ingested or inhaled radioactive material resulting in a 5 rem effective dose equivalent. The number listed is the smallest of the inhalation and ingestion ALI.

Table 4-2 Characteristics of Nuclides in Common Use at ASU

4.4.5 Shielding of Gamma and X-Rays

Lead or other high atomic number materials are most efficient for shielding gamma and x-rays. The thickness required depends on the energy of the photon and the activity of the source. One quarter inch of lead will reduce radiation from ¹²⁵I by a factor of 100. Over two inches of lead is required for a comparable reduction in radiation from Co-60, however.

Radioactive materials should be stored in shielding such that the dose rate to people in the laboratory is less than 2 mrem/hr. Lead shielded storage pigs, lead sheet and lead bricks arecommercially available for shielding photons. The RSO should be consulted when designing or evaluating shielding.

4.5 Internal Contamination

All radioactive materials will expose tissues of the body if inhaled, ingested, injected or otherwise introduced into the body. (See Table 4.2). Prevention of internalization of material is through contamination control including clean work habits and frequent user surveys.

4.6 Skin Contamination

When nuclides are present on the surface of the skin, relatively large doses may be delivered in a short period of time. (See Table 4.2). Wear gloves at all times during use of radioactive material. If contaminated, the skin should be washed immediately. In all cases of skin contamination, ORS staff should be notified immediately.