▪ Decontamination Factor (DF). It is defined as the ratio between initial
activity of feed (Af) and permeate activity after treatment (Ap).
DF ¼ Af
Ap
: ð1Þ
The lower the permeate activity, the higher the decontamination
factor. If the activity of the permeate decreases below discharge limit
it will be declassified as radioactive waste. Declassification involves exemption
from later management as radioactive material and management
as conventional waste according to chemical and/or biological
characteristics.
▪ Volume Reduction Factor (VRF). It is defined as the ratio between
feed volume (Vf) and concentrate volume after treatment (Vc).
The higher this factor, the lower the costs of transportation and
storage of the final concentrate waste.
VRF ¼ Vf
Vc
ð2Þ
Activity measurements were carried out with a scintillation NaI solid
detector from SILENA with an energy resolution of 7.1% (for 662 keV
137Cs line), and a multichannel analyser also from SILENA with 1024
memory channels. The detector was isolated by lead shielding to eliminate
background radiation. A solution of anti-calcitonin-125I with a
known activity was used as standard. Activity decay of samples was
considered by the following expression:
A tð Þ¼ A0 expðÞ ð −λt 3Þ
where A0 represents activity in the reference time, and A(t) the activity
in a later t time, being λ the disintegration constant of the radioisotope.