Chemistry Reference
In-Depth Information
10
8
6
4
2
0
0
1
2
3
[RCOOH] (g/L)
4
5
6
R = C4H9
R = C8H17
R = C7H15
R = C11H23
FIGURe 8.2
Interfacial tension of 30% TBP-
n
-dodecane in respect to 0.6 M NaOH as a
function of RCOOH concentration of organic acid. (Drawn from Nowak, Z., Nowak, M.,
Nukleonika
, 26(1): 19-26, 1981.)
- Chemical methods are used to solubilize degradation products in aqueous
phases. Alkaline solutions remove acidic products (HDBP, H
2
MBP, and
long-chain carboxylic acids) from the solvent (
36, 89, 128, 147, 148
). A reg-
ular solvent scrubbing appears to be beneficial for long-term use of PUREX
solvent, because it appears to limit the increase of high-molecular-weight
phosphates (
83
).
- A good solvent management in a PUREX plant includes diluent scrubbing
of high-level radioactive aqueous streams and optimum solvent and diluent
routing between extraction cycles (
143
). Diluent scrubbing allowed the
removal of the TBP solubilized in the aqueous phase, avoiding the progres-
sive formation of poorly soluble salts of di-
n
-butylphosphate (
149
).
- Distillation under reduced pressure allowed separation of the TBP-diluent
mixture components into three fractions: diluent, 60% TBP, and distillation
residue. The first two fractions can be reused in the process, but the residue
contains high-molecular-weight degradation products, which are not elimi-
nated by alkaline scrubbing. Distillation removes the degradation products
that are responsible for poor hydrodynamic behavior and for the retention of
radioactive products such as plutonium, zirconium, and ruthenium (
143
).
