Re: Bacteria in Reactors

["Vargo, George J" <vargo@pnl.gov>]

The algae colony in the TMI-2 reactor coolant system was described in an NRC
report as "a mature algae colony similar in composition to that found in the
Susquehanna River."  It was transmitted by air.

There were a number of technical approaches attempted to control the colony.
Eventually hydrogen peroxide was found to be the best compromise between
effectiveness and 1) creating mixed wastes; 2) introducing other chemicals that
could create a nuclear safety issue from either a materials degradation or fuel
deterioration standpoint.

Other techniques tried included UV filtration.  The problem with UV filtration
is that it generates "combustion" products that could include sulfates,
nitrates, and other things that can do evil things to plant materials and
promote or accelerate several stress corrosion cracking mechanisms.  If UV
filtration is used, particulate filtration and ion exchange on the downstream
side are probably necessary depending on the nature of the process system.

Several years ago at FitzPatrick, we used hydrogen peroxide to treat water in
some removable shielding tanks.  Success was highly variable and probably
depended to a great deal on the ability to achieve some reasonable mixing inside
the tanks.

George J. Vargo, Ph.D., CHP
Pacific Northwest National Laboratory
International Nuclear Safety Program
509-375-6836; -2019 (fax)
vargo@pnl.gov
INSP web site:  http://atom.pnl.gov/:2080