Chemistry Reference
In-Depth Information
derivatives, whose advantages include much simpler synthesis, larger solubility of
their metal solvates in the diluent, and stronger affinity for An(III) versus Ln(III).
For the extraction of Cs or/and Sr, many other extraction systems have been
reported (
457- 462
).
A variety of novel extracting systems have been developed and reported with an
increasing number of new extractants and accumulating knowledge. Although they
are not treated comprehensively here, their contribution to the progress of separation
science and technology is significant as a whole (
463-467
).
1.2.3 C
of n S of l i d a t e d
f
l of w
C
o n C e P t S
of f
a
d v a n C e d
r
e P r of C e S S i n g
Several consolidated flow concepts (CFCs) of advanced reprocessing have been pro-
posed. The overall goal of a CFC could be attained by a combination of the per-
formance of constituent elemental processes of the CFC. Technologically, it seems
inappropriate to discuss the proposed CFCs in detail, because the elemental separa-
tion technologies are still evolving and immature, and some may be replaced by others
in some cases. Three CFCs are, therefore, briefly explained here for comparison.
In the United States, variants of UREX+ flowsheets were proposed by the DOE in
the frame of the GNEP as a principal process for the next generation. The transition
from a once-through fuel cycle to a closed fuel cycle requires a staged approach. In
stage 1, reprocessing of spent fuel is restored by modifying existing aqueous-based
schemes. In stage 2, the recycling of Pu and certain MAs and the environmentally
safe disposal of other FPs are the main objectives. In stage 3, the focus is on achiev-
ing a closed fuel cycle with actinide transmutation in which all fissile and fertile
materials are recycled. Thus, in view of the accumulation of spent fuels, evolution of
Gen III (plus) reactors, limited capacity of the Yucca Mountain repository, homoge-
neous and heterogeneous recycling of all transuranics to the Gen IV (fast) reactors,
PR capability, and constraints on the progress of separation technologies, CFCs of the
UREX+ family, including UREX+1, UREX+1a, UREX+2, UREX+3, and UREX+4,
were proposed (
10
). As an example, the CFC of UREX+3 (Figure 1.7), which is sup-
posed to treat LWR spent fuels based fully on hydrometallurgical processes, separately
recovers “Pu-Np” and “Am-Cm” for heterogeneous recycling in the Gen IV (fast) reac-
tors. The CFC of UREX+3 is comprised of several processes: 30 vol % TBP-NPH
is used as an extracting solvent for U. Tc is coextracted with U and is removed by a
high-acid strip in the presence of AHA prior to recovering U. The Pu-Np recovery
is accomplished by the NPEX process after adjusting the valence state of Pu-Np to
Pu(IV)-Np(IV). The TRUEX process is applied to the extraction of Am-Cm-Lns, and
for the separation of Am-Cm from Lns, a TALSPEAK process is envisaged (
468
).
Simultaneous isolation of Cs and Sr is performed by the CCD/PEG process.
The French CEA has been developing the GANEX concept, which is an advanced
process to be applied to the homogeneous recycling of all actinides to Gen IV (fast)
reactors (
205, 469-471
). Figure 1.8 shows the CFC of GANEX, which adopts the one-
cycle “DIAMEX + SANEX.” Because the GANEX process separates Am-Cm(-Lns)
as an admixture of Pu-Np, the extraction characteristics of the mixed solvent 0.6 M
DMDOHEMA and 0.3 M HDEHP in TPH for Pu(IV) and Np(IV,V,VI) were exam-
ined.
D
(M) values and group separation of Ans from Lns were satisfactory. LOC value
