Decay-In-Storage Policy & Procedure

The WCM/NYPH consolidated license permits disposal of certain radioactive materials through a decay-in-storage program, provided that various conditions are met. Under the Decay-In-Storage (DIS) program, waste contaminated with certain short-lived radioisotopes can be stored in a laboratory for a minimum of 10 half-lives. The waste is then rigorously surveyed, and if no activity distinguishable from background levels is found, then the waste is disposed of as non-radioactive medical wastes.

  1. Radioisotopes are permitted to be disposed of through the Decay-In-Storage program, but must have half-lives of less than 90 days. This includes radioisotopes such as P-32, P-33, S-35, Cr-51 and I-125.
  2. Waste contaminated with short-lived radioisotopes, and intended for disposal through the DIS program, must be strictly segregated in the laboratory from all other radioactive waste. DIS waste itself must be segregated by radioisotope to as large an extent as possible. Waste from an experiment with dual labeling, e.g., utilizing a short-lived radioisotope such as P-32 and a longer-lived radioisotope such as H-3, cannot be disposed of as DIS waste.
  3. High-activity (multi-millicurie) waste materials should be separated from lower-activity materials in the laboratory to decrease the volume of waste that must be stored in DIS facilities for more than 10 half-lives.
  4. Before an item is placed into a DIS solid waste container, radioactive material labels must be removed (if possible), thoroughly obliterated or covered. Waste containing items with visible radioactive materials labels are not acceptable for storage in the DIS facilities.
  5. Liquid scintillation counting waste contaminated with short-lived radioisotopes is not stored separately as DIS waste. Due to low disposal costs for liquid scintillation counting waste, and the complexities of the DIS procedures, all liquid scintillation counting waste, regardless of the contaminating radioisotope, are picked up and disposed of by a waste disposal service vendor.

Decay-In-Storage Procedures

  1. Once a waste container is full:
    1. Gather the inner liner and tightly wrap it closed with tape.
    2. Place a cover on the container and seal it so no one can access the contents.
    3. Completely fill out the waste log attached to the container, listing chemistry, radioisotopes, activities and dates.
    4. Record the date when the container was sealed, on the reverse side of the waste log.
    5. Radioisotopes must decay-in-storage for 10 half-lives before removal.
  2. After 10 half-lives have passed:
    1. Remove the cover of the container.
    2. Remove the inner liner.
    3. Check for any activity above background with a calibrated survey meter.
    4. Place an inner liner into the appropriate waste stream (biological, chemical, non-hazardous).
    5. Fill out the decay-in-storage record, entering disposal date, survey results, instrumentation used, and your name.
  3. The waste log/decay-in-storage record must be kept for at least three years.

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