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Figure II.5 TRPO process
TRPO
solvent
Feed solution
(1-2 M HNO 3)
U, Pu, Np, An, Ln
extraction
Raffinate
HNO 3 (5.5 M)
An, Ln stripping
An + Ln solution
An/Ln
Separation
H 2C 2O 4 Pu, Np stripping Pu, Np solution
Na 2CO 3
U stripping
U solution
Used solvent
Diamide extraction (DIAMEX)
The DIAMEX (DIAMide EXtraction) process was first developed by Musikas et al. [15] at
the CEA Fontenay-aux-Roses Research Centre (France) and by C. Madic and M.J. Hudson in a joint
European research programme involving the CEA (Fontenay-aux-Roses) and the University of Reading
(UK) [16]. This process is based on the use of malonamide extractants. So far, the reference substance
developed for the definition of the first version of the DIAMEX process is
di-methyl-di-butyltetradecylmalonamide (DMDBTDMA). This reagent has up to now the most
attractive properties as actinide extractant but has to be considered as a compromise between its
behaviour as chemical extractant and its physical behaviour in extraction conditions (viscosity,
emulsion, settling time, etc.). The diamide extractant is used in solution in an aliphatic diluent. The
extracting properties of DMDBTDMA are, to some extent, similar to those exhibited by CMPO
(TRUEX process), hence the extraction-scrubbing-stripping cycle of the DIAMEX process resembles
TRUEX. DIAMEX offers the following advantages over TRUEX:
• DIAMEX degradation products are less troublesome than TRUEX products;
• no secondary solid waste is expected from the use of the solvent because it consists of
hydrogen, carbon, nitrogen and oxygen and is fully incinerable. On the contrary, in
TRUEX, the high phosphorus concentration (in TBP and CMPO) in the solvent causes the
production of secondary solid waste.
The DIAMEX process (Figure II.6) was tested successfully in 1993 on real waste at
Fontenay-aux-Roses Research Centre. The process continues to be developed as part of a European cooperation
project. Optimisation of the diamide formula is underway. Diamide extractants have also been
investigated in Japan, the UK, the US, Switzerland and India.
Since the diamide extractants are fully incinerable no solid secondary wastes are expected.
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