8. Use of unsealed sources
The use of unsealed radioisotopes regularly gives rise to radioactive waste, which has to be disposed of in a responsible and safe manner. The waste may include residual amounts of the original radionuclide, disposable containers (vials, pipette tips, etc.), partially decayed or surplus sealed sources, contaminated solids and radioactive animals. The disposal procedures are based on the following principles:
- Minimizing local accumulation of large quantities of waste.
- Using immediate local disposal of waste where appropriate, i.e., safe and legal.
- Using external disposal of waste unsuitable for local disposal.
- Safeguarding of both the local (laboratory) and the external environments.
- Reducing exposure for personnel involved in waste management (ALARA principle).
- Using procedures that can be followed simply and routinely.
- Protecting non-lab personnel (e.g. cleaners) from handling radioactive waste.
The Nuclear Safety and Control Act defines an "Exemption Quantity (EQ)" of a radionuclide as the minimum activity of that radionuclide that is subject to regulation. Or the Act allows possession of a quantity of a nuclear substance without a permit if the quantity does not exceed its EQ. The quantity depends on the radiotoxicity of the radionuclide concerned, which in turn depends on the nature and energy of the radiation emitted, the physical and biological half-lives, the critical organ when the radionuclide is ingested, and the chemical toxicity. Radionuclides are classified on this basis as having very high, high, medium or low toxicity and the exemption quantity varies accordingly. The exemption quantities of commonly used radionuclides are listed in Appendix K.
There are two possibilities:
- Local disposal via drains (liquid) or regular garbage (solids) of wastes below CNSC regulatory limits for radioactive waste.
- External disposal via the storage and disposal system operated by Hazardous Waste Management of McGill University.
Water miscible liquids or soluble solutions may be disposed of via drains provided that the CNSC disposal limits are respected.
Note that any label containing the word "Radioactive", or including the radiation symbol, should be fully obliterated before it is placed in the common garbage. See CNSC disposal limit table found below:
CNSC Regulatory Limits for Radioactive Waste
|Radio nuclide||EQ||ALI||Garbage (solid)||Sewer||Air|
|MBq||MBq||µCi/ kg||MBq/ kg||µCi/ yr/ Bldg||MBq/ yr/ Bldg||kBq/ m3|
The Hazardous Waste Management Department at McGill University provides a free service for collection and disposal of radioactive waste. Details on procedures are available by contacting Hazardous Waste Management at local 5066.
The Hazardous Waste Management Deaprtment supplies laboratories with different types of containers. The user must properly complete identification tags, attached to each container, prior to pick up by the Hazardous Waste Management technician. In addition, users are required to segregate radioactive waste in separate containers, according to three categories. They include:
- Liquid Scintillation Vials (LSV are disposed in the 5 gallon (20 litre) steel pails and then the letters "LSV" are written on the container lid. There is no need to empty each liquid scintillation vial. It is recommended to place a plastic bag inside to line the pails and to attach the completed identification tag.
- Solid Waste is disposed in the 5 gallon (20 litre) steel pails or cardboard boxes or in smaller containers like 4 litre white plastic or 1 litre clear plastic containers. Only solid and dry materials should be placed in these containers and the completed identification tag must be attached.
- Liquid waste other than LSV must be emptied in 4 litre white plastic or 1 litre clear plastic containers and identified with the completed identification tag.
- Animal Carcasses must be put in a double plastic bag, tied and tagged with completed identification label. Carcasses must be frozen at the time of collection.
The identification tag provided by Hazardous Waste Management, if used alone, specifies the waste as Class I under the Transport Canada Dangerous Goods Regulations, i.e. Radioactive I. The Permit Holder must therefore ensure that the dose rate at the surface of each container leaving the laboratory is less than 50 µSv/h (5 mrem/h). If this condition cannot be met, then:
- if the dose rate at the surface of the container falls within the range 50 to 100 µSv/h (5 to 10 mrem/h), a Radioactive II label must be attached to the container (in addition to the identification tag provided by Hazardous Waste Management) and the Transport Index (dose rate in mrem/h) at 1 m from the surface of the container) noted on the label; and
- if the surface dose rate lies within the range 100 µSv/h to 2 mSv/h (10 to 200 mrem/h), and the dose rate at 1 m is less than 100 µSv/h (10 mrem/h), a Radioactive III label must be attached and the Transport Index posted, as above.
Hazardous Waste Management must be notified in advance when class III containers are to be collected.
Radioactive II and III labels can be obtained from Hazardous Waste Management or Environmental Health & Safety. The Permit Holder is legally charged with the observance of the above procedures, since inadequate or false labelling of radioactive waste could lead to unnecessary exposure of personnel involved in waste management or members of the public.
See Appendix D for more information on transportation labels for packages containing radioactive materials.
As an effort to reduce the costs of radioactive waste, Hazardous Waste Management (HWM) decays the following radioisotopes:
- phosphorus-32 (P-32)
- phosphorus-33 (P-33)
- sulphur-35 (S-35), and
- iodine-125 (I-125).
These radioisotopes will be automatically set aside for decay. The same HWM containers (i.e. cardboard box or plastic jug) and identification tags will be used. However, it is very important that the containers be properly identified and no other radioisotope be mixed with them. Basically, there should be one waste container for each decayable radioisotope. Any problem with the decay program will be cited as a minor offence according to the Radiation Safety "3 Strikes" Enforcement Policy (see Section 2.2.2). This can lead to the cancellation of the Permit Holder's Internal Permit and a fine for improper waste disposal.
Radiation waste containers
4 L white plastic container, and 1 L clear plastic container, both used for liquid or for solids (no mixing of solids & liquids).
20 L blue plastic container used for liquids is being phased out.
Metal drum used for liquid scintillation vials (LSVs).
Metal pail (20 litre) used for solid and for liquid scintillation vials (LSVs).
Cardboard box (20 litre) used for solid waste