Decay-in-Storage Policy and Procedure

Decay-in-storage Program

WMC-CU/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, wastes contaminated with certain short-lived radioisotopes can be stored in the laboratories generating the waste for a minimum of ten half-lives. The wastes are then rigorously surveyed, and if no activity distinguishable from background levels is found, then the wastes are 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 < 90 days. This includes radioisotopes such as P-32, P-33, S-35, Cr-51, and I-125.
  2. Wastes contaminated with short-lived radioisotopes and intended for disposal through the DIS Program must be strictly segregated in the laboratory from all other radioactive wastes. DIS wastes themselves 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 wastes that must be stored in the DIS Facilities for more than ten half-lives.
  4. Before an item is placed into a DIS solid waste container, radioactive materials labels must be removed, if possible, or thoroughly obliterated or covered. Wastes containing items with visible radioactive materials labels are not acceptable for storage in the DIS facilities.
  5. Liquid scintillation counting wastes contaminated with short-lived radioisotopes are not stored separately as DIS wastes. Due to low disposal costs for liquid scintillation counting wastes and the complexities of the DIS procedures, all liquid scintillation counting wastes, regardless of the contaminating radioisotope, are picked up and disposed of by the waste disposal service vendor.

Decay-in-storage Procedures

  1. After waste container is full:
    1. Once the container is full, gather the inner liner and tightly wrap it closed with tape.
    2. Place 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 to a waste stream.
  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 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 3 years.

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