RE: Question on steam generator contamination

["Lieskovsky, Miro" <MLieskovsky@nbpower.com>]

In addition to the previuos postings:

At our station, CANDU 600, the main contaminants are 95Zr/Nb and 60Co.
They combine for ~90% of the gamma dose rate, their mutual ratio in the
dose rate is 2:1.  The fields are higher on the "cold" side, generally
2-5 mSv/h.  On the "hot" side the fields are 1-3 mSv/h.  Other deposited
isotopes are also activation products (51Cr, 54Mn, 59Fe, 124Sb, 140La,
etc.) We do not have fission products deposited as we have minimal fuel
failures.  

Prior to the access to these "areas" we regularly perform
decontamination using the ice-blast pellets.  Generally, the fields drop
by 25 - 50%.  

The surface contamination  (~10 - 100 kBq.cm-2) depends, primarily, on
the coolant flow and temperature, and on the material such as carbon
steel, Incoloy, Zircaloy, etc.

Miroslav Lieskovský
Health Physicist
NB POWER - PLGS - HP Dep't
PO BOX 10, Lepreau, NB, Canada, E0G 2H0
tel. (506) 659 7421, fax. (506) 659 6507
mlieskovsky@nbpower.com



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