Working with Radioisotopes
Safety Rules and Procedures for Working with Radioisotopes
- Keep the laboratory locked when not in use and keep unauthorized persons out of the laboratory.
- Do not eat, drink, smoke and apply cosmetics in the laboratory.
- Always wear appropriate personal protective equipment and avoid direct contact with radioactive materials. Never pipet solutions by mouth.
- Effectively contain radioactive materials at all stages of handling and use a fume hood whenever possible for work with open sources. Always use a fume hood for work with boiling or evaporating sources.
- Use appropriate shielding when working with radioactive materials.
- Do not use refrigerators or freezers designated for storage of radioisotopes for food storage. Glassware and other equipment used for radioactive work must not be used for other purposes.
- Clearly mark containers of radioactive materials with warning symbols indicating the nature and amount or radioactivity. Mark all other equipment that has been contaminated with radioisotopes and store in appropriately shielded locations in the radioisotope lab. This equipment must not be removed from the lab.
- Store radioactive waste and sources in a safe and secure place. Use shielding to ensure that the surface radiation does not exceed 2.5 Sv/h (0.25 mR/h).
- When work is complete, clean and/or isolate contaminated supplies and equipment; monitor and decontaminate trays and working surfaces. Floors and working surfaces should be wipe checked daily when the lab is in use.
- Wash hands, monitor clothes, shoes and hands before leaving the laboratory.
The Radioisotope Lab
Open source radioactive materials may be used and stored only in licensed locations (ie. Room 370A). This room must be locked at all times when not in use and only authorized personnel will be permitted entry. The room will be labelled with signs: Caution - Radiation Area and In case of Emergency Call... All storage areas, contaminated sites and decay cupboards, etc. Must be labelled Caution - Radioactive Materials. The room must also display the No Eating, Drinking or Smoking and Rules for Working with Radioisotopes signs.
When radioisotopes are being used, all personnel in the radiation area should be informed and precautions taken that the maximum allowable working field of 2.5 Sv/h in any direction from the source is not exceeded.
Working surfaces should be covered with an absorbent covering, such as plasticized paper or incontinence pads, to prevent contamination.
Label all material used for radioactive work with radiation stickers. Signs and labels should be removed when the equipment has been shown to be free of contamination and will no longer be used for isotope work.
The sink should be clearly labelled with a radiation sign.
If there is a possibility of producing airborne radioactivity (aerosols, dust, vapours) work should be performed in an absorbent paper-lined fume hood. The hood should be labelled clearly with a radioactive sign. All work with 125I must be performed in the fume hood. If the fume hood stops working, report it to the RSO immediately.
Store open source radioisotopes in the refrigerator marked with a radiation sign. The refrigerator will be kept locked. On a routine basis the refrigerators should be defrosted, cleaned and wipe tested. Food or beverages must not be stored in the same refrigerator with radioisotopes.
Personal protective equipment
Disposable gloves must be worn when working with open radioactive sources. Gloves should be checked frequently during the experiment to detect small punctures that may have developed, especially at the fingertips. Disposable gloves must never be worn outside the laboratory. For work with iodine, a minimum of two pairs of gloves is recommended, with the outer pair being changed frequently.
- Lab Coats
must be worn when working with radioactive materials. Button completely, with sleeves rolled down fully and the cuffs sealed with gloves. Lab coats should not be worn outside the lab and never in areas where food is consumed. Coat hooks are provided in the lab for storage of your lab coat.
It is recommended that long pants be worn to provide splash protection for the lower legs. Do not wear rings when working with open sources as contamination can become trapped under the band. It may be impossible to decontaminate a piece of jewellery, in which case it could never be worn again.
Shoes that cover the entire foot are required. Sandals or thongs do not provide adequate coverage in the event of a spill, nor do they provide protection from falling objects.
- Eye protection
Safety glasses, goggles or face guards should be worn, especially if there is any hazard of splashing material in the eyes. It is also good practice to wear glasses as shielding when working with high energy beta emitters to reduce the external radiation dose to the eyes.
- Remote handling devices
such as forceps or tongs, should be used when handling stock solution vials or other sources that produce a significant radiation field. A glove box should be used when working with dry radioactive powders.
In most cases it is preferable to shield the source of radiation rather than the individuals in the laboratory. In any case where reduction of the radiation field below the 2.5 Sv/h limit cannot be achieved, a lead apron that provides whole body coverage must be worn.
Receiving Radioisotope Sources
It is necessary to monitor packages in which radioisotopes have been shipped as these can be contaminated both internally and/or externally. Regular procedures for unpacking radioisotopes should include:
- Wear disposable gloves and a lab coat and eye protection.
- Place the package in the fume hood and wipe test the exterior.
- Remove packing slip and open outer package.
- Verify that the contents agree with the packing slip and check the activity.
- Measure radiation emitted by the inner container and shield as required.
- Check for damage, broken seals, loss of liquid, change in colour, etc.
- Wipe test the inner container.
- Remove or deface the radiation symbol on the shipping label and if the package is free of contamination dispose as regular garbage.
- Notify the RSO of any irregularities.
Following the use of radioisotopes, monitoring of all work surfaces that may have become contaminated must be performed. The method used to check for contamination depends on the radioisotope in question. A combination of wipe testing and direct reading provides the best margin of safety. Wipe tests are useful for the detection of loose contamination but will not give any indication of fixed or embedded contamination. On the other hand, the poor counting efficiency of survey meters results in underestimation of the level of contamination, especially if the levels are low or if the contaminant is a low energy beta emitter. Floors and working surfaces must be wipe checked daily when the lab. is in use.
- Wipe testing
This is the only effective method for detecting low energy beta particles such as those emitted by 3H, 14C or 35S. Wet a disc of filter paper with ethanol, rub it over the surface to be checked and count in the liquid scintillation counter.
- Direct reading
To supplement wipe testing, portable detectors or survey meters are used to detect high energy beta particles, X-rays or gamma radiation. Hold the detector approximately two centimetres above the surface to be monitored and move slowly over the area in a grid-like fashion.
Performance checks or survey meters should be performed on a regular basis. Before each use:
- check for signs of damage to the instrument - indications that it may have been dropped, breakage in the probe cable, excessive bouncing of the needle when the meter is moved.
- turn the meter to the battery check position to see if the batteries are still working.
- turn the range selection knob gently to the highest scale and let the needle stabilize, continue turning to move sensitive scales until a response is obtained; the needle will fluctuate more on the lower scales because of the random nature of the detected events.
- check the reproducibility of the meter response to a known radiation source. The readings obtained should not deviate from the mean value by more than 10%.
- have instruments calibrated annually.