The Radioactive waste being generated at Columbia
University
can be categorized as: radioactive scintillation fluid, radioactive
liquid waste, and radioactive solid waste.
All radioactive waste will be collected by the Radiation Safety Office
and will be transported to the radioactive waste room.
All radioactive waste must be segregated by isotope and every effort
must be made to minimize the waste volume.
The scintillation fluid will be shipped for disposal while the
decayable (short and intermediate half lives) radioactive liquid and
solid waste will be stored for decay.
The minimum storage time is 10 half lives of the istope 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.
ISOTOPE
MINIMUM STORAGE TIME
32P
6 months
35S
3 years
125I
2 years
51Cr
1 year
3H
N/A
14C
N/A
Some of the minimum storage periods for selected
isotopes.
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.
For long half life isotopes (e.g. 3H and 14C) the solid waste will be
shipped for commercial burial. For high activity liquid waste of long
lived istopes, the waste will be solidified and treated as solid waste.
Animal carcasses containing radioactive material:
Animal carcasses containing 0.05 uCi or less of 3H or
14C per
gram of animal tissue will be disposed of as nonradioactive animal
carcasses.
For animal carcasses containing a larger amount of 3H or 14C or any
other isotope at any concentration, the animal carcasses will be treated as
radioactive.
For isotopes with half life of 90 days or less, the animal carcasses
will be stored in a freezer for decay, for a minimum duration of ten
half-lives. Subsequently, the animal carcasses will be checked and
released as non-radioactive.
For all other long lived isotopes, animal carcasses will be packaged in
special containers and shipped for commercial burial.
