sewer disposal

["John Zummo" <zummo@gene.com>]

Last week I posted a query on the sewer disposal of short lived aqueous
waste.  A total of 19 responses was received from:

12 universities
2 pharmaceutical companies
2 government agencies
1 hospital	
2 consultants

For short half lived isotopes:

2 facilities use sewer disposal without decay	
7 facilities use decay in storage, followed by sewer disposal
8 facilities use both sewer disposal with and without decay, depending
on the activity of the waste and their self or locally imposed limits

For long half life isotopes, 3 responders indicated that they use sewer
disposal.

One responder indicated that they did not use sewer disposal for short
lived isotopes since users might dispose of long lived isotopes the same
way.

Other responses indicated the problems of contaminated pipes and
reconcentration were the strong negatives in sewer disposal.

ALARA arguments were found on both sides of the decay before dispose
question, with comments that it was better ALARA practice to dispose of
the material before decay, as well as the opposite view.

Central disposal was also supported as a way of keeping better control
over what is disposed of, and maligned as creating the potential for
contamination accidents and causing extra personnel exposure.

Public perception and politics were also mentioned as decision
variables.

Sewer disposal of long lived isotopes or non-decayed short lived
isotopes, though allowed by law, seem to be the most controversial. 
Disposal of decayed short lived isotopes is less of an issue ("If it is
decayed, it is no longer radioactive").

We here at Genentech seem to be leaning toward sewer disposal of decayed
short lived isotopes only if we can get buy in from the local POTW and
prove that the waste stream is really not hazardous (fish bioassay,
etc.).  To clarify my situation, we are in an agreement State
(California), and plan to dispose from a central location.  We decay in
storage not to get below one curie, but so we can say that no
radioactivity goes to the sewer.

Thanks to all for your input.

John Zummo, RSO
Genentech, Inc.

zummo@gene.com