Radioactive Waste Management

Because of the risks associated with the presence of radioisotopes, they cannot be discarded in the same way as normal waste. Instead, specific rules and procedures have to be followed. These procedures may vary slightly depending on national legislation, but the same basic principles have to be followed everywhere.
Processing radioactive waste is expensive, and furthermore, this cost may vary significantly depending on the physical state of the waste. Therefore, all radioactive waste must be carefully sorted into different categories, each of which have certain processing requirements.

• radioactive waste in liquid form should be separated into:
  • aqueous
  •  non-aqueous (organic solvents)
• radioactive waste in solid form should be separated into:
  • combustible (e.g. absorbing paper, plastic syringes, rubber closures)
  • non-combustible (e.g. stationary phases of chromatographic columns, glass)
• radioactive waste with different categories of non-radioactive risk should be separated into:
  • non-hazardous (e.g. paper)
  • biohazardous (biological materials, e.g. blood, animal tissues, faeces, urine)
  • glass (e.g. vials, chromatographic plates)
  • sharps (needles, broken glass)

In most departments, non-radioactive waste is also sorted according to (some or all of) the categories described above. To reduce the cost of processing, radioactive waste may also be stored on-site or in a central room that caters for the whole hospital or organisation. This is to allow the radioactivity to decay to a sufficiently low level to enable its further (much cheaper) processing as non-radioactive waste. This is especially true in the case of short-lived radionuclides such as technetium-99m (T½ = 6.1 h), iodine-123 (T½ = 13.27 h) and the PET radioisotopes carbon-11 (T½ = 20.38 min), nitrogen-13 (T½ = 9.96 min), oxygen-15 (T½ = 2.04 min) and fluorine-18 (T½ = 109.8 min). This may apply to other radioisotopes too. Local rules dictate the maximum half-life of radioactive waste that can be stored locally for decay to non-radioactive waste. Radioactive waste not falling within this category must be transported to a specialised organisation for appropriate processing. Before radioactive waste that has undergone sufficient decay may be mixed with and processed as non-radioactive waste, the safety officer or his representative must check the radioactivity level of the waste. (It may be that longer-lived radioisotopes have been accidentally discarded into the stored waste of short-lived radionuclides or that short-lived radioisotopes are contaminated with longer-lived radionuclidic impurities.)

Safety inspection: monitoring the non-radioactive waste bags.

The LAF-cabinet for the preparation of technetium-99m labelled radiopharmaceuticals is normally provided with a small shielded bin for radioactive waste (either as a built-in feature or as a freestanding container). This allows the worker to discard radioactive waste from the working area immediately when carrying out a procedure in the LAF cabinet such as the preparation of a solution for injection or the withdrawal of individual patient doses. This bin or container can be emptied into a bigger container during the cleaning up procedure or the next morning, by which time the radioactivity will have already decayed to a much lower level. Containers for radioactive waste must be well shielded – usually they are lead-lined – and stored in a well-shielded area. They must be clearly labelled to indicate which type of radioactive waste may be discarded in each of these containers.

As well as the radioactive waste bin, a container for non-radioactive waste is also present in the immediate vicinity of any LAF cabinet that is used for manipulation of radioactive materials. This allows the immediate removal of non-radioactive waste (e.g. used sterile swabs, wrapping of sterile disposable syringes and needles) from the working area whilst working at the cabinet.

Non-radioactive waste (here the sterile swab wrapper) is discarded into a non-radioactive waste container.