Volume reduction factor obtained in this pass was 45 (without the
dead volume). The volume of the initial waste was reduced to 1 L of
final concentrate. The treatment lasted an estimated time of 0.75 h.
In this third pass, conductivity was reduced from a value of
0.23 mS/cm to a value of 0.028 mS/cm (average removal of 87.8%).
With regard to activity removal, after the third pass of reverse osmosis
decontamination factor was 10.75, with an average activity in the
permeate of 0.0652 kBq/L (average activity removal of 90.7%). These
high values of activity removal make it worth the third pass of RO.
Otherwise, a long storage time (around a year) would be required to
achieve similar values of permeate activity. It must be highlighted that
values of activity removal of this RO pass were higher than the ones of
the second pass of experiment 1, in spite of similar values of initial activity.
This can be a consequence of different compositions of initial waste.
Since this value is relatively near discharge limit, the treatment of
experiment 2 finished with this pass. A later storage time of 120 days
(2 semi-decay periods of 125I) is estimated to achieve a value of activity
below the calculated discharge limit (Eq. (5)).