Transcript Electrochemical Separation Methods at NRI Řež, plc M

Pulsed-Current Electrolytic Recovery of
Uranium from Molten Fluorides
L.Szatmáry, M.Straka, F.Lisý
Nuclear Research Institute Řež plc
Czech Republic
Innovative nuclear concepts – workshop Liblice, April 10 – 13, 2012
15.7.2015
1
Motivation
Partitioning processes using molten fluoride carrier salt:
Needed for reprocessing by Molten Salt Reactor
Modern fuel types treatment
Electrochemistry of Acs and Lns in molten fluorides,
deposition and dissolution of particular elements of
fisile material and fission products
Implementation into the reprocessing
flow sheets
15.7.2015
2
Principle of electroseparation methods
-
E – potential
of electrode
+
A
V
E0 – red-ox
potential of
respect ion
A z+
A0
E0  E
Bx+
E0 < E
Cy-
R
W
E
15.7.2015
C0
C
R, W, C – reference,
working and counter
electrode
3
Instrumentation
Two nitrogen glove-boxes with
built-in electrolysers sealed by
removable flange.
15.7.2015
4
Instrumentation
Electrolyser made of Ni/Ni-based
alloy (INCONEL 625) placed in a furnace
offering homogenous thermal field up to
1000°C.
15.7.2015
5
Measurements
Electrochemical measurements in FLiNaK, eutectic mixture
(46.5 – 11.5 – 42.0 mol %), M.P. 454°C
Working electrode: Ni
Counter electrode: glassy-carbon crucible
Reference electrode: Pt wire
15.7.2015
6
Measurements
System containing Uranium is studied by variety of electrochemical
methods (cyclic voltammetry, chronopotentiommetry)
Electrolytic experiments (potentiostatic, galvanostatic and pulsecurrent electrolysis) follow basic electrochemical studies
15.7.2015
7
Electrolytic deposition of uranium on nickel working
electrode by means of pulse-current electrolysis
Pulsed electrolysis
 Mentioned in 19th century
 Used for copper plating in 1940s
 Pulsed-potential electrolysis of uranium – ANL, 1987
 There is no fully accepted unified theory for pulse-current
 In general, authors agree on positive effect of modulated
input on the deposit
15.7.20
15
8
Electrolytic deposition of uranium on nickel working electrode
by means of pulse-current electrolysis
Current pulse electrolysis
• Change of the deposit morphology
• Better adhesion
• Better resolution
I (A)
t (s)
• Modulation parameters
• Inert vs. reactive electrode
15.7.2015
9
Electrolytic deposition of uranium on nickel working electrode
by means of pulse-current electrolysis
Electrode material: Ni
Modulation:
~ (-100) – (-200) mA/cm2 for C1
~ (-50) – (-75) mA/cm2 for C2
~ 50 – 75 mA/cm2 for A1
Systems: LiF-CaF2-UF4, LiF-NaF-KF-UF4,
15.7.2015
10
Results
Electrochemistry of uranium in fluoride melts
 Uranium introduced to the melts in the form of U4+ ions, two step reduction
mechanism:
FLiBe – UF4
Straka M, Korenko M, Lisý F; J Radioanal Nucl Chem, 284, 245 (2010)
15.7.2015
11
Results
Electrochemistry of uranium in fluoride melts
 Direct cathodic deposition is possible in all studied systems
 Mechanism of the uranium reduction was described by standard methods
 Alloying process detected when reactive electrode was used (Ni)
Ni-U
Ni
15.7.2015
12
Results
Electrochemistry of uranium in fluoride melts
 Electrolysis of U, on inert electrode
15.7.2015
13
Results
Electrolytic experiments
 Electrolysis of U, on inert and reactive electrodes
U deposit on Mo electrode
Unpublished results
15.7.2015
U deposit on Ni electrode
14
Results
Electrolytic experiments
 Electrolysis of U, on reactive electrode
U deposit on Ni electrode
15.7.2015
15
Summary
• Current pulse electrolysis tested in molten fluoride systems
• Compared to classic potentiostatic and galvanostatic electrolytic set-ups:
• better deposits, reproducible at certain parameters
• Optimization of its parameters will supposedly lead to further improvement
in terms of quality and quantity
15.7.2015
16
Financial support