Radioactive Hazards and Safety
Page Contents
Include: Principles of radiation protection | Safe handling and use of radioactive material | Simple Guidelines for Handling and Use of Radioactive | Internal Radiation Hazards | Dose Limits | Safety notes | Dealing with a Radioactive Spill Material
Also see:
- Safety Sheets
- Ten golden rules when working with radioactive isotopes
- Disposal of Radioactive Waste
- Protocol for use of 3-H (PDF)
- Protocol for use of 14-C and 35-S (PDF)
- Protocol for use of 32-P (PDF)
- Protocol for use of 51-C (PDF)
- Protocol for use of 125-I (PDF)
Principles of Radiation Protection
The International Commission of Radiation Protection recommends:
- Avoid unnecessary personnel radiation exposures.
- Keep occupational exposures as low as possible.
- Do not exceed dose limits.
The basic tenet is ALARA - Exposure AS LOW AS REASONABLY ACHIEVABLE.
Safe Handling and Use of Radioactive Material
A University course is run every year for those persons who have little or no experience in the safe handling of Radioactive Substances. It is recommended that all persons (staff or students) should attend if their work involves the use of Radioactive Substances.
Simple Guidelines for Handling and Use of Radioactive Material
- Familiarise yourself with the nature of the radiation emitted (alpha, beta, gamma, etc) by the isotopes and the tolerable levels of radiation permissible for both short and long term exposure. Remember distance from the radioactive source is the most effective way of reducing exposure.
- NEVER eat, drink, smoke or apply cosmetics whilst working with radioactive materials.
- NEVER mouth pipette radioactive materials up into pipettes; use a safety device.
- Work with appropriate shielding e.g. Lead blocks for primary source 125I with gamma- emitters, and perspex for ß-emitters.
- Cover working areas with Benchcote (Polythene backed absorbent paper).
- Use plastic trays (clearly labeled) to hold your radioactive samples, pipettes, glassware, etc.
- Mop up all spillage's immediately using paper towels.
- Wear disposable rubber or polythene gloves while handling isotopes.
- Wear a film badge.
- Monitor radioactivity before and after every experiment using the hand held monitor where relevant (e.g. 32P, 125I, 35S) or random swabs (e.g. 3H).
The above are to serve only as guidelines. Specific precautions may be necessary with some isotopes. If you are ever in doubt, consult your supervisor before starting your experiment.
Great care must be taken when unpacking radioactive materials. Remember - any accidental breakages during transport may result in the packaging being seriously contaminated. Any equipment used with radioactive substances with a long half-life must be permanently labelled as such.
Laboratory benches and adjacent areas should be monitored on a regular basis. Spills should be reported immediately to your supervisor or the Departmental Radiation Safety Officer.
Internal Radiation Hazards
Irradiation of internal organs and tissues can occur due to active materials entering the body by the following routes:
- DIRECT SKIN IRRADIATION
- INHALATION
Depending on the particle size the material may become lodged in different areas, e.g. large particles in the nose. Some elements concentrate in specific organs, e.g. 125I in thyroid. - INGESTION
Usually insoluble material will pass through the gut and be excreted, but soluble material will find its way to the whole body or to specific organs. - WOUNDS
This route operates in a similar way to ingestion.
Dose Limits
The Department operates in accordance with the NH&MRC Code of Practice which recommends that employers introduce measures aimed at keeping exposures below 20mSv per year, averaged over 5 years, with the continuing proviso that the effective dose should not exceed 50mSv in any single year.
Safety Notes
General: These notes apply to the following safety sheets for a number of different radionuclides.
Effective biological half-lives apply to the radionuclide in a simple inorganic form. If the nuclide is ingested in the form of an organic molecule which can become incorporated or absorbed by a metabolic process, the half-life in the body may be much longer. Consider tritium as an example; tritiated water has an effective biological half-life of 12 days whereas tritiated thymidine has a 190 day half-life.
Emission percentages quoted are in all cases percentages of the total
number of nuclear transformations.
The body burden is that quantity of the radionuclide which, when deposited
in the whole body, produces the maximum permissible dose rate to the
critical organ.
The shielding required is that quantity of the appropriate shielding needed to reduce the dose from the source by a factor of 10.
Dose rates are not given for the weak gamma-emitters 3H, 14C and 35S because such figures are negligible in most practical circumstances. Doses from these radionuclides is only important when the active material is ingested.
Dealing with a Radioactive Spill
In the event of a spill, it is essential to minimise the spread of contamination.
- Report all spillages immediately to both your supervisor and the Departmental Radiation Safety Officer.
- Cordon off the suspected area of contamination.
- Ascertain, if possible, the type of contamination, i.e. the nuclide(s) involved (as it may be necessary to use breathing apparatus, protective clothing or other equipment).
- Determine the area of contamination by monitoring after taking the necessary precautions.
- Starting from the outer edge, decontaminate the area in convenient sectors by wiping and scrubbing.
- Before moving on ensure that a sector is clean by monitoring.
Dispose of all radioactive waste according to the statutory requirements. Short-lived radionuclides, for example 32P, may be stored with suitable shielding and left to decay. After 4 half-lives less than 10% of the original activity remains, after 7 half-lives <1%, after 10 half-lives <0.1%.
For longer-lived radionuclides, for example, 3H, this is impractical and alternative disposal arrangements should be made.
To minimise the dose to the extremities, tongs or other remove handling equipment should be used where appropriate.
Note: Geiger counters can be located:
- Ludlum Measurements Model 3 Room 4.11
- Mini Monitor Series 900 Rooms 4.03, 3.07, 3.01
- Mini Monitor Type 5.40 Room 3.19
- Rotem Monitor Ramgene Room 5.10
Radiation warning signs are available from the store. Waste should be correctly stored, in lead-lined waste bins or perspex bins, in wet bags available from the store. There is a radioactive waste storage areas on the ground floor where waste is stored until it can be removed. Work only in approved rooms and areas (fume cupboards etc.). Avoid contaminating clean sites. Avoid using glass containers, e.g., centrifuge tubes, where there is a possibility of breakages.