Chemistry Reference
In-Depth Information
relatively low radioactivity. This plant, the Modular Caustic-Side Solvent Extraction
Unit (MCU), has been running since May 2008 (Geeting, 2008). The other plant,
which will be larger and take longer to build, will be able to remove Cs from tank
wastes that are highly radioactive. Bonnesen et al. (2000) and Leonard et al. (2001b)
describe some of the CSSX development work, formerly called the “Alkaline-Side
CSEX process.” The CSSX flowsheet was verified experimentally at Argonne using
a simulated waste feed (Leonard et al., 2003). In the final test, a 33-stage 2-cm ANL
contactor was run continuously for four days. The test was repeated at the SRS using
actual tank waste in its 2-cm ANL contactor (Campbell et al., 2001; Walker et al.,
2005). Based on the success of these tests, work was started on the two CSSX plants
at the SRS: the MCU, which is running, and the larger plant the salt waste processing
facility, which is being built.
Horwitz et al. (1985) proposed a process for cleanup and segregation of nuclear
waste. In this process, called TRUEX, the aqueous waste from the extraction section
of the PUREX process, the acidic aqueous raffinate, is processed to remove trace
amounts of transuranic elements, mainly Am and Pu. The TRUEX process was first
demonstrated at Argonne using a 10-stage batch countercurrent test (Vandegrift et
al., 1984). Following the success of this test, a continuous countercurrent test of the
TRUEX process was successfully run in a 14-stage 4-cm annular centrifugal con-
tactor (Leonard et al., 1985). Although proven at the laboratory scale, this process
has not been demonstrated in plant-scale contactors. However, based on the results
in smaller contactors, plant-scale operation of the TRUEX process should work well
and is widely accepted in many countries as standard technology.
10.4.3 o
t H e r
C
e in t r i f u g a l
C
o n t a C t o r S
While this chapter and this applications section has focused on ANL and CINC
contactors, other centrifugal contactors have been used to process nuclear materials.
Some of these contactors and the flowsheets tested using them are discussed here.
10.4.3.1 France
Since 1974, France has focused on using nuclear power as its primary source of
electrical power. As of 2004, nuclear power accounted for 79% of the electricity
generated in France. To support this industry, centrifugal contactors have been devel-
oped and used to process nuclear materials. An article in this area by workers at the
French Atomic Energy Commission (Commissariat à l'Énergie Atomique or CEA)
(Bergeonneau et al., 1979) describes a centrifugal contactor (referred to in this article
as an ECP type) where the inner cylinder of the annular mixing zone is stationary
and the outer cylinder rotates. In this unit, both the light and heavy phases enter at
the top of the unit and flow down the stationary center core. This design seems to
be the precursor to the Rousselet-Robatel (www.rousselet-robatel.com) multistage
centrifugal contactor, which has two to ten contactor stages on a single vertical shaft
(Hafez, 1983). This same reference also shows a monostage centrifugal contactor
much like the SRL unit. Instead of a paddle mixer below the rotor, the Rousselet-
Robatel contactor has a turbine mixer. The mixing zone below the rotor includes a
shroud attached to the rotor. The shroud looks like a smaller rotor with a smaller
