ALARA (As Low As Reasonably Achievable)

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 Reduction Practices

Exposure control must include reduction to external exposure and prevention of internal contamination.

Reduction of External Exposure

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.

Prevention of Internal Contamination

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

Engineering Controls

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 Practices

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.

Personal Protective Equipment

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:

• A laboratory coat; 
• Gloves;
• Safety glasses;
• Closed-toe shoes.

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Change gloves and wash hands frequently. Remove gloves before touching any clean items that are usually touched without gloves. Do not reuse disposable gloves.

Exposure Control for Airborne Radioactive Materials

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:

• Iodine such as I-123, I-125, and I-131;
• Tritiated (Hydrogen-3) compounds in water;
• Compounds containing carbon-14;
• Radioactive gases such as krypton-85, radon-222, or chlorine-36;
• Methionine (and other amino acids) containing sulfur-35.

Storage of Radioactive Materials

Radioactive materials must be secured at all times.

This may be accomplished by any of the following:

1. Attending the materials;
2. Maintaining materials in a locked freezer or cabinet; or,
3. 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 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

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. Sealed sources that have been mutilated and damaged beyond what would reasonably be expected to occur as a result of normal use should be reported to DRS as soon as possible. 

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. 

Labeling

Clearly label all radioisotopes and calibration sources. Stock solutions of radioisotopes should be clearly labeled with the following information:

                                                      Caution: Radioactive Materials

Radionuclide

Activity and assay date

Person responsible for sample or source

This regulatory requirement does not apply to sources with an activity less than listed in the table below. However, for the safety of personnel and to guarantee proper waste disposal, all containers must be labeled with at least the identity of the radioisotope and chemical contents.

Table of quantities requiring labeling:

Limits 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

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:

• Areas in which animals are kept must be posted in accordance with the requirements of 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 Permit Holder. 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 other controlled environmental systems.
• Animal carcasses, bedding, and excreta must be disposed of properly. If excreta are mixed with bedding materials, handle in accordance with dry radioactive waste procedures. Carcasses containing hydrogen-3, carbon-14, or iodine-125 at concentrations below .05 microcuries per gram may be disposed of without regard to radioactivity, but may not be introduced into the food chain. DRS must approve disposal methods for animal carcasses before work begins.

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.

Inventory and Record Keeping

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:

• Laboratory survey records;
• Radioactive material inventory and use records;

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.

Abbreviations, Units of Measure, and Detection Efficiency

Abbreviations

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

Units of Measure

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

Detection Efficiency

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) = 179 dpm
                                            0.67

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)

Isotope Information Sheets

Tritium ³H

Radiological half-life, T_1/2……………………………………………………….12.3 years

Principle emission…………………………………………..….18.6 keV beta (maximum)

External dose rate ……………...…….minimal, see below

Annual limit on intake (ALI) by ingestion……………………………………...8x10⁴ μCi*

Biological monitoring method………………………….……………………breathe samples

Range in air…………………………………………………………………………4.7 mm

Range in water………………………………………………………………..…6x10^-3 mm

Shielding required……………………………………………………………………..none

Monitoring method for contamination…………….………wipe survey and LSC analysis

Sanitary sewer release concentration limit….................................................1x10^-2 μCi/ml

Special considerations

• The primary hazard of tritium compounds comes from internal contamination. Upon contact tritium compounds can be absorbed through the skin. Change gloves every hour when working with 50 mCi or more.
• Tritium can migrate from tritiated compounds to other molecules including water. This “creep” can cause contamination of areas of high humidity (e.g. inside refrigerators) and tritium build-up in ice inside freezers. If possible, place previously opened containers of tritiated compounds into a fume hood. If storage in a refrigerator is required, store inside a second sealed container. Monitor storage areas where large quantities of H-3 are kept.
• Bioassays are required when using >100 mCi on an open bench or >1000 mCi in a fume hood. Contact the Division of Research Safety before performing such work.
• Due to its low beta energy, tritium cannot be monitored directly, and therefore regular wipe surveys of the work areas are required.

* ALIs can vary considerably, e.g., DNA precursors such as tritiated thymidine are regarded as more toxic than tritiated water partly because the activity is concentrated in the cell nuclei.

Carbon ¹⁴C

Radiological half-life, T_1/2………………………………………………………5730 years

Principle emission……………………………………………....156 keV beta (maximum)

External dose rate ……………… minimal skin penetration, see below

Annual limit on intake (ALI) by ingestion……………….……………..……….2x10³ μCi

Biological monitoring method………………………….…………breath or urine samples

Range in air………………………………………………………………………...21.8 cm

Range in water………………………………………………………………..…...0.28 mm

Shielding required……………………………….none

Monitoring method for contamination………….....………………………….. wipe survey and LSC analysis

Sanitary sewer release concentration limit…………………………………...9x10^-5 μCi/ml

Special considerations

• Carbon-14 is primarily an internal hazard. In addition, skin contact can result in high local doses.
• Exposure from external millicurie (or less) sources without contacting those materials is low due to the minimal penetration of the outer dead layer of skin.
• Be alert to the chemical properties (e.g., halogenated compounds) of various C-14 compounds that may allow absorption through the skin.
• Be aware of the chemistry occurring and determine if volatile compounds, such as carbon dioxide are formed that pose an inhalation hazard. Procedures releasing C-14 gases should be performed in a fume hood.

Phosphorus ³²P

Radiological half-life, T_1/2……………………………………………………….14.3 days

Principle emission…………………………………………..…1.71 MeV beta (maximum)

Dose rate (1 cm from a beta point source; isotropic in air, unshielded)…..350 R/h per mCi

Annual limit on intake (ALI) by ingestion……………….……………..……….6x10² μCi

Biological monitoring method…………………………………………….....urine samples

Range in air……………………………………………………………………….…..6.1 m

Range in water………………………………………………….……………..….….0.8 cm

Shielding required……………………………….1 cm acrylic glass (Plexiglas®; Lucite®)

Monitoring method for contamination………….....…………………………..GM counter

Sanitary sewer release concentration limit……………………………….....9x10^-5 μCi/ml

Special considerations

• P-32 poses an external and internal hazard.
• Users handling > 10 mCi at a time require a ring (extremity) dosimeter and whole body dosimeter.
• Do not work over open containers as the dose rate is not attenuated in air. Use proper shielding during liquid transfers and related work.
• Use acrylic glass (Plexiglas®; Lucite®) shielding. Do not use lead shielding, which can create Bremsstrahlung radiation.

Phosphorus ³³P

Radiological half-life, T_1/2……………………………………………………….25.4 days

Principle emission……………………………………………0.249 MeV beta (maximum)

Dose rate (1 cm from a beta point source, isotropic in air, unshielded). 350 R/h per mCi

Annual limit on intake (ALI) by ingestion……………….……………..……….6x10³ μCi

Biological monitoring method…………………………………………….....urine samples

Range in air……………………………………………………………………….….49 cm

Range in water………………………………………………………………..….…0.6 mm

Shielding required……………………………….1 cm acrylic glass (Plexiglas®; Lucite®)

Monitoring method for contamination………….....…………………………..GM counter

Sanitary sewer release concentration limit………………………………......8x10^-4 μCi/ml

Special considerations

• P-33 poses primarily an internal hazard. Skin contact can lead to a significant dose to the basal cells of the skin.

• External hazard to P-33 in closed containers is minimal as the container provides sufficient shielding to stop the beta particles.

• Do not work over open containers and use proper shielding during liquid transfers and related work.

Sulphur ³⁵S

Radiological half-life, T_1/2……………………………………………………….87.4 days

Principle emission……………………………………………..…167 keV beta (maximum)

Dose rate ……. minimal skin penetration, see below

Annual limit on intake (ALI) by ingestion……………….……………..……….6x10³ μCi

Biological monitoring method…………………………………………….....urine samples

Range in air……………………………………………………………………….….26 cm

Range in water………………………………………………………………….....0.32 mm

Shielding required……………………………….none

Monitoring method for contamination………….....…….. wipe survey and LSC analysis

Sanitary sewer release concentration limit…..……………………………....1x10^-3 μCi/ml

Special considerations

• Sulfur-35 is primarily an internal hazard. In addition, skin contact can result in high local doses.
• Exposure from external millicurie (or less) sources without contacting those materials is low due to the minimal penetration of the outer dead layer of skin.
• Be aware of the vapor pressure of the chemical. Some compounds such as S-35 methionine show significant evaporation upon opening of the container. Heating of S-35 compounds can pose an inhalation hazard. Such activities should be done in a fume hood.
• Surveys for gross levels of contamination may be performed using a Geiger counter. However, a Geiger counter is NOT sensitive enough for the required contamination surveys.

Chromium ⁵¹Cr

Radiological half-life, T_1/2……………………………………………………….27.7 days

Principle emissions………………..……....0.32 MeV gamma (9.8%), 5 keV X-ray (22%)

Exposure rate (1 cm from a point source)…………………………………..180 mR/h per mCi

Annual limit on intake (ALI) by ingestion……………….……………..……….4x10⁴ μCi

Biological monitoring method…………………………...……………...whole body count

Half-value layer…………………………………………………………………3 mm lead

Monitoring method for contamination………….………NaI or other scintillation detector

Sanitary sewer release concentration limit…..……………………………....5x10^-3 μCi/ml

Technetium ^99mTc

Radiological half-life, T_1/2……………………………………………………….6.02 hours

Principle emission……………………………………………….141 MeV gamma (89.1%)

Dose rate (1 cm from a point source)………………………………….720 mrad/h per mCi

Annual limit on intake (ALI) by ingestion…………………….……………..……….8 mCi

Biological monitoring method…………………………...…………………..urine samples

Half value layer………………………………………………………….…….0.3 mm lead

Monitoring method for contamination………….....……………………………..NaI probe

Sanitary sewer release concentration limit…..……………………………....1x10^-2 μCi/ml

Special considerations

• Tc-99m poses an external and internal hazard.
• Drying can cause airborne Tc-99m dust contamination. Rapid boiling and expelling solutions through syringe needles and pipette tips can generate airborne aerosols.
• A survey meter equipped with a 1" x 1" or a low-energy NaI scintillation probe is preferred for the detection of Tc-99m contamination. Typical counting efficiencies: [1" x 1" NaI probe (39%)] and [low-energy NaI probe (12%-18%)].
• Survey meters equipped with a G-M pancake/frisker (15.5 cm² surface area) can be used; however, they exhibit very low counting efficiencies (approximately, 1.2%) for detecting low-energy Tc-99m gamma rays. G-M probes are effective only for gross Tc-99m contamination.
• Indirect counting using a liquid scintillation counter (LSC), gamma counter, or gas proportional counter (GPC) should be used to detect removable Tc-99m contamination on smears, swabs, or swipes.

Iodine ¹²⁵I

Radiological half-life, T_1/2………………………………………………………….60 days

Principle emission……………………….35 keV gamma (7%), 27-32 keV X-rays (140%)

Exposure rate (1 cm from a point source)……………………………………..1.4 R/h per mCi

Annual limit on intake (ALI) by ingestion……………….……………..…………..40 μCi

Biological monitoring method…………………………...……………………thyroid scan

Half-value layer………………………………………………………………0.02 mm lead

Monitoring method for contamination………….………NaI or other scintillation detector

Sanitary sewer release concentration limit…..……………………………....2x10^-5 μCi/ml

Special considerations

• I-125 poses an external and internal hazard. Amounts that enter the body accumulate in the thyroid.
• Bioassays are required when handling >1 mCi carrier-free iodine on the open bench or >10 mCi carrier-free iodine in a fume hood. A thyroid scan must be performed within 24-48 hours after use and the results reported to the Division of Research Safety. Contact the Division of Research Safety before performing such work.
• Reduce unbound fractions of carrier-free iodine as soon as possible with sodium metabisulfate or thiosulfate.
• A survey meter equipped with a thin crystal (low energy) NaI scintillation probe should be used for contamination surveys.

Iodine ¹³¹I

Radiological half-life, T_1/2………………………………………………………..8.05 days

Principle emission………………………………………………..364 keV gamma (81.2%)

Exposure rate (1 cm from a point source)……………………………………..2.0 R/h per mCi

Annual limit on intake (ALI) by ingestion……………….……………..…………..30 μCi

Biological monitoring method…………………………...……………………thyroid scan

Half-value layer……………………………………………………………….0.3 cm lead

Monitoring method for contamination………….………NaI or other scintillation detector

Sanitary sewer release concentration limit…..……………………………....1x10^-5 μCi/ml

Special considerations

• I-131 poses an external and internal hazard. Amounts that enter the body accumulate in the thyroid. Emission also includes 606 keV beta that can penetrate the dead layer of skin.
• Bioassays are required when handling >1 mCi carrier-free iodine on the open bench or >10 mCi carrier-free iodine in a fume hood. A thyroid scan must be performed within 24-48 hours after use and the results reported to the Division of Research Safety. Contact the Division of Research
• Reduce unbound fractions of carrier-free iodine as soon as possible with sodium metabisulfate or thiosulfate.
• A survey meter equipped with a thick crystal (high energy) NaI scintillation probe should be used for contamination surveys.