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Radioactive Waste Guidance Tips

Here are some general guidelines for radioactive wastes:

  • Short-lived isotopes must be:
    • Separated from each other whenever possible.
    • Must be segregated from long-lived isotopes.
    • Must be held for decay in storage by the lab or EH&S.  All radioactive labels and markings must be completely defaced or removed prior to placing in the waste collection container.
  • Long-lived isotopes (ex. 3H and 14C) may be consolidated in the same collection container provided they are the same type of waste. Please consult EH&S for guidance regarding other long-lived isotopes.
  • Red bags must only be used for potentially infectious materials and not as a general liner for a radioactive waste container or for radioactive spill debris.
  • Every effort must be made to minimize the waste volume.
  • Scintillation fluids with a flash point <140oF generate potentially mixed wastes and should be avoid whenever possible.  Please contact EH&S for guidance prior to use.

Decay-in-storage guidelines:

The minimum storage time is 10 half lives of the isotope being decayed. The amount of activity remaining after ten half lives is approximately 1/1000 of the original amount. The following table shows some of the minimum storage periods for selected isotopes.

    32P                             6 months
    35S                             3 years
    125I                            2 years
    51Cr                           1 year
    3H                                N/A
    14C                              N/A

If more than one isotope is mixed in the waste, it must be stored for a minimum of 10 half lives of the slowest decaying component. After the waste has been stored for at least 10 half lives, the waste will be checked for any radioactivity using the appropriate monitoring device at the lowest scale. The reading must be the same as the background level and all results must be recorded. After decay, the waste will be disposed of as non-radioactive waste. All radioactive labels must be removed or destroyed before discarding the items.

Please refer the EH&S Health & Safety manual section 4.5 for additional information.