pyroprocessingtechnology development at...
TRANSCRIPT
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Hansoo LeeIPRC 2010
29 Nov. - 3 Dec., 2010
Pyroprocessing Technology Development at KAERI
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Outline
Spent Fuel ManagementI
Pyroprocessing Research ActivitiesII
Integrated Pyroprocessing in PRIDEIII
SummaryIV
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Spent Nuclear Fuel Management
‘08 ’11 ’15 ’20 ’28’26
Gen IVSFR
System Performance
TestStandard
DesignDetailedDesign
DemoPlant
Mock-up PyroFacility(Nat. U)
10t/yr
Eng.-scale PyroFacility(Hotcell)
10t/yr
PrototypePyro Facility
100t/yr
PrototypePyro FacilityOperation
Pyro-process
Advanced Design Concept
Licensing Technology Development
Fuel Irradiation Test
Approved by AEC in 2008
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Flow Diagram of Pyroprocessing (KAERI)Diagram of Pyroprocessing (KAERI)
TRU fuelfabrication
Decladding & Voloxidation Electrolyticreduction Electrorefining
Electrowinning
Molten saltwaste treatment
Uraniumrecovery
Recycleor LLWRecycleor treatment
Cladding material
Low level waste
Off-gastreatment
Sodium-cooledfast reactor
Fission gas
Air
U3O8+(TRU+FP)oxide
(U+TRU+FP)metal
PWR spent fuel
TRU : Transuranic elementsNM : Noble metal elementsFP : Fission products
TRU fuelfabrication
Decladding & Voloxidation Electrolyticreduction Electrorefining
Electrowinning
Molten saltwaste treatment
Uraniumrecovery
Recycleor LLWRecycleor treatment
Cladding material
Low level waste
Off-gastreatment
Sodium-cooledfast reactor
Fission gas
Air
U3O8+(TRU+FP)oxide
(U+TRU+FP)metal
PWR spent fuel
TRU : Transuranic elementsNM : Noble metal elementsFP : Fission products
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R&D Issues of Pyroprocessing
Purposes Increase throughput Simple and easy remote operability Enhance interconnection between unit processes Reduce waste volume
Improvement High performance electrolytic reduction process Graphite cathode employment to recover U in electrorefining system Application of residual actinides recovery (RAR) system Crystallization method applied to recover pure salt from waste mixture
Spent Fuel Voloxidation Electroreduction Electrorefinning Electrowining Fuel Fabrication SFR
HM
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Issues of Electroreduction
Purposes Reduce oxide to metal Provide feed for the following process – electrorefining
Issues Operating condition : Li2O concentration Cathode Process : salt powder Increase surface area Pt anode Corrosion of reactor crucible
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6Electrolytic Reduction Process - I
• In 2002, electrolytic reduction concept development• 2005 – 2007, ACPF inactive tests of electrolytic
reduction (10 kg U3O8/batch) • In 2009, demonstration of high capacity electrolytic
reducer (20 kg UO2/batch)• Construction of eng-scale electrolytic reduction system
by 2011• Construction of ESPF electrolytic reduction system by
2016
Eng-scale design of electrolytic reduction, KAERI
Lab-scale electrolytic reduction,KAERI
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7Electrolytic Reduction Process - II
Pre-treatment
Electrolytic Reducer Electro-refining
Waste Salt Treatment
Cathode Processor
UO2
MS + Cs, SrMS: LiCl-Li2O molten salt
Metal U
Metal U+ MS + Cs, Sr
LiCl
Electrode Handling Apparatuses
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Electrolytic Reduction Process - III
Key Item Previous Process(Before ’08)Present Process
(After ’08) Effects
Cathode Integrated Porous Magnesia BasketMetal Basket (‘08),
Separable Cathode (‘10)
- Easy Operation- Strengthening Connectivity- Prevention of Li2O Accumulation
Anode Pt rod Pt plate,Metal shroud (‘10)- Maximization of Anode Utilization- Protection of Anode
Reference Electrode Pt Li-Pb
- Stable Reference Electrode- Measuring the Ending Point
Cooling Active Passive (‘10) - No Usage of Cooling Water- Increased Process Stability
Salt Vaporization -
Structure Modification,Heat Shield
- Suppression of Salt Vaporization- Reuse of Salt
Operation Mode Control of Current Control of Voltage - Protection of Pt Anode- Easy Operation
Current Supply Wire Bus bar (‘10) - Handling of High Current- Easy Handling
Current Density 80 mA/cm2 250 mA/cm2 - High Throughput Electrolytic Reduction
Li2O Con. 3 wt% 1 wt%- Increased Corrosion Resistance- Increased Reduction Yield
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Issues of Electrorefining
Purposes Recover U from metal Provide feed for following process – electrowinning
Issues Operating condition : voltage cut Cathode Process : salt powder Increase surface area Melting furnace without cooling water UCl3 preparation Salt transportation for electrowinning
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Time (s)
0 1000 2000 3000 4000 5000
Pote
ntia
l (V
vs.
Ag/
AgC
l)
-3
-2
-1
0
1
2
3
Cathode Voltage (V)Anode Voltage (V)Cell Volatage (V)
Time (s)
0 1000 2000 3000 4000 5000 6000 7000
Pote
ntia
l (V
vs.
Ag/
AgC
l)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cathode Voltage (V)Anode Voltage (V)Cell Volatage (V)
Electrorefining - I
Time (s)
0 2000 4000 6000 8000 10000 12000 14000
Pote
ntia
l (V
vs.
Ag/
AgC
l)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Cathode Voltage (V)Anode Voltage (V)Cell Volatage (V)
Cell 1.0 V
Anode -0.5 V
Cathode -1.5 V
Cell 1.7 V
Anode 0.0 V
Cathode -1.7 V
Cathode -1.8 V
Anode 0.5 V
Cell 2.3 V
Salt content :
7.0%
Applied current : 100A
U deposit as a function of current density
Decrease of U crystal size & increase of salt content
Applied current : 200A Applied current : 300A
Salt content : 10.2%
Salt content : 15.1%
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Potential (V vs. Ag/AgCl)
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
Cur
rent
(A)
0
50
100
150
200
250
300
350
Cathode with 21kg U loading, 2.4% UCl3Anode with 21kg U loading, 2.4% UCl3Cathodewith 13kg U loading, 4.0% UCl3Anode with 13kg U loading, 4.0% UCl3Cathode with 32kg U loading, 3.9% UCl3Anode with 32kg U loading, 3.9% UCl3Cathode with 32kg U loading, 6.0% UCl3Anode with 32kg U loading, 6.0% UCl3
Effects of anode Loading and UCl3 concentration
Effect of UCl3 concentration As the concentration of UCl3
increased, the anodic overpotential decreased.
Effect of anode loading As the anode loading
increased, the anodic overpotential decreased due to the enlarged surface area
Effect of anodic cut-off potential KAERI: -0.5 V(Ag/AgCl) based
on Fe dissolution potential INL: 0.4 V(Ag/AgCl) based on
NM dissolution potential Additional experiments will be
performed to clarify the cut-off potential
AnodeINL
KAERI
Electrorefining - II
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Impedance spectroscopy
Ru: Uncompensated resistanceCdl: Double layer capacitanceRct: Charge transfer resistanceZW: Warburg impedance
Equivalent Circuit
3.7 3.8 3.9 4.0 4.1 4.2-0.2
-0.1
0
0.1
0.2
0.3
Experimentally measured Numerically fitted
- Im
agin
ary
Impe
danc
e, Z
'' /
cm
2
Real Impedance, Z' / cm2 Ru = 3.710 Ω cm2
Rct = 0.383 Ω cm2
RW = 0.009 Ω cm2
Fitting Results
Electrorefining - III
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Impedance spectroscopy
AnodeAnode
UTRUMAFP
UTRUMAFP
U → U 3+ + 3e
TRU → TRU 3+ + 3eMA → MA z+ + zeRE → RE z+ + ze
U → U 3+ + 3e
TRU → TRU 3+ + 3eMA → MA z+ + zeRE → RE z+ + ze
U 3+ + 3e →
U
U 3+ + 3e →
U
U 3+U 3+ U 3+U 3+ U 3+U 3+
CathodeCathode
Charge transfer resistance (Rct) Warburg impedance (ZW) Uncompensated resistance (Ru)
Electrochemical cell for anodic dissolution
Electrorefining - IV
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Comparison of Lab and Eng-scale Electrorefiner
Lab-scale Eng-scale Remarks
Capacity/batch 20 kgU 50 kgU
Cathode
GraphiteФ2 x L 20 cm
GraphiteФ3 x L 28 cm Current density
24 ea(Double layer configuration)
30 ea(Double layer configuration)
~ 300 mA/cm2
Anode 50 kg reduced metal loading100 kg reduced metal loading
Sufficient surface area of anode
Amount of salt 60 kg 300 kg Withdrawing of U
deposit Screw conveyor Design modified
Electrorefining - V
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Comparison of Lab and Eng-scale Salt Distiller
Lab-scale Eng-scale Remarks
Vapor condensing Water cooled Water cooled
Heating zone 4 3 Easy maintenance
Dendrite crucible Alumina Alumina
Salt recovering bucket STS STS
Crucible loading Manual Automatic Top loading
Recovering bucket loading Manual Automatic Bottom loading
Capacity/batch 5 kg salt 15 kg salt
Dendrite transfer Open airSpecially designed container
Transfer to ingot casting process
Electrorefining - VI
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Issues of Electrowinning
Purposes Recover TRUs from salt Provide feed for SFR fuel
Issues Operating condition : rapid U growth Cathode Process : salt powder Optimum conditions for RAR Salt transportation for waste salt treatment
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Electrowinning Process - I
CdTRU/U/RE/Cd- HM>10wt%- RE/TRU
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Measurement of the reduction potentials on the Cd electrode
Glassy carbon
Reference
Cd electrode
Quartztube
Fig. Electrolytic cell
-2.4
-2.2
-2.0
-1.8
-1.6
-1.4
-1.2
Y
LiCl-KCl @ 500oC
Pote
ntia
l (V
vs. A
g/A
gCl) U
Gd
Pr Gd Ce Nd La
Am
Np Pu
U Pu Am Pr
Y
Ce La Np Nd
Cd CathodeSolid Cathode
A lot of potential data on the solid cathodes,
but inaccurate potential data on the Cd electrode
Fig. CV of a LiCl-KCl-1wt%CeCl3solution at 773K on liquid Cd electrode.
-2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
C
urre
nt(A
)
Cathode Voltage(V) vs. Ag/AgCl
LiCl-KCl(a) LiCl-KCl-CeCl
3(b)
CeCl3(c)
(a)(b)
(c)
W Cd
Ce -2.02 V - 1.547 V
Y -2.09 V -1.623 V
Table. Reduction potential data on the liquid Cd electrode at 773K.
Electrolyte crucible : Quartz(18mmID)LCC crucible : Quartz(8mmID)Electrodes : W.E. : Cd, W(dia. 1mm)
C.E.: Glassy carbon(dia. 3mm)R.E.: 1wt% AgCl in LiCl-KCl
Solute concentrations : LiCl-KCl -1%CeCl3, LiCl-KCl -1%YCl3
Temperature : 773 K
Measurement of the reduction
potentials on the liquid Cd electrode
Electrowinning Process - II
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Automatic operation of the LCC assembly (Mesh). Electrodes : anode (U basket), reference (1wt%AgCl), cathode (Cd)
. Temperature : 490-500oC
. Salt stirring : 70 rpm
. LCC crucible : Alumina I.D. 50mm (Cd 316g)
. Mesh : Dia. 45mm, 1cycle/10 minutes
. Current density : 100 mA/cm2
. No dendrite growth
. U deposits in the Cd
. 10.2wt% in Cd
0 2 4 6 8 10 12-1.8
-1.6
-1.4
-1.2
-1.0
-0.8
Cur
rent
[A]
Pote
ntia
l [V]
A-hr
anode potential(V) cathode potential(V) current(A)
-3.0
-2.5
-2.0
-1.5
-1.0
Fig. Glove box and automatic LCC assembly
Electrowinning Process - III
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Evaluation of the non-consumable anodes. Anode (diam. 2mm): Mo/Graphite/Glassy carbon
. Cathode : Graphite (3 mm)
. Electrolysis : 100 mA/cm2
. UCl3 concentration : 2, 4 wt%
. Anode reaction : 2Cl- Cl2 + 2e-
0 10 20 30-1.8
-1.6
-1.4
-1.2
0.0
0.5
1.0
1.5
2.0
Cathodic potential
Cat
hodi
c P
oten
tial(V
)
Time (min)
(a) Mo anode
Ano
dic
pote
ntia
l (V
)
Anodic potential
0 10 20 30-1.8
-1.6
-1.4
-1.2
-1.0
0.0
0.5
1.0
1.5
2.0
Cathodic potential
Cat
hodi
c po
tent
ial(V
)
Time (min)
(b) Graphite anode
Anodic potential
Ano
dic
pote
ntia
l (V
)
0 10 20 30-1.8
-1.6
-1.4
-1.2
-1.0
0.0
0.5
1.0
1.5
2.0
Cathodic potential
Cat
hodi
c po
tent
ial(V
)
Time (min)
Anodic potential
Ano
dic
pote
ntia
l (V
)
(c) Glassy carbon anode
Most stable anode
: glassy carbon
Mo : unstable anode potential because of the Mo dissolution
Graphite : stable anode potential, but easily fragmented during the deposition
Glassy carbon : stable anode potential and solid electrode
Mo Graphite Glassy Carbon
Electrowinning Process - IV
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2La(Nd-U-Cd)+ 3CdCl2 2La(Nd)Cl3 + 3Cd
LaCl3+NdCl3
UCl3
LaCl3+NdCl3
UCl3
CdCl2
Confirm the residual concentration of U in a salt: < 100 ppm (after 4th electrolysis for
preparing the La(1)-Ce(1)-U(3)-Cd alloy)
Oxidation of U metals can be hindered by increasing the height of LCC.
LCC Electrolysis
OxidationAfter 3rd electrolysis
After 4thelectrolysis
After 2nd oxidationDuring 2ndoxidation
RAR operation test for reusing an LCC
0.39 %0.34 %530 ppm3rd
Electrolysis U Nd La
4th
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Lab-scale Eng-scale Remarks
AnodeInert GC rod
Inert GC tube(porous MgO
crucible)Electrode area
1 ea 2 ea Current distribution
Cl2 trapVent line apart from
the anodeShroud combined with the anode
Effective Cl2 removal
LCC position Side Center Current distribution
Mesh operation Up-down, manuallyUp-down and
rotation, automatically
Reference electrode
Ag/AgCl Ag/AgCl
Electrolytic Cell Alumina STS
LCC crucible Alumina Alumina
Salt stirrer 1ea 2ea (4 baffles) Mixing efficiency
Capacity/batch 0.05 kgHM 1 kgHM
Comparison of Lab-scale and Eng-scale Electrowinner
Electrowinning Process - VI
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Issues of Waste Salt Treatment
Purposes Purify the salt from ER and EWWaste solidification
Issues LiCl salt treatment LiCl-KCl salt treatment waste solidification salt distillation
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Waste Salt Treatment – I
Electrorefining (Drawdown)Electrorefining (Drawdown)
PWR Spent Fuel
VoloxidationU, TRU, FPs U, TRU, FPs
(Oxides)(Oxides)
LiCl Waste (Sr/Cs)
LiCl Recycle
U, TRU, FPs U, TRU, FPs (Metal)(Metal)
LiCl-KCl Recycle
RE Oxides
LiCl+KCl Waste (RE)
RE : Oxidation
Residual SaltCs & Sr/Ba
Disposal
Solidifying Agent High-integrity
Solidification
Waste Salt
minimization(FPs Removal &
Salt Recycle)
Electrolytic ReductionElectrolytic Reduction
Cs/Sr : Salt refining(Crystallization)
Distillation &Condensation
UU
TRUTRU
FinalWasteForm I
FinalWasteForm II
SolidificationSolidification
Characterizationof Waste FormsCharacterization
of Waste Forms
Solidifying Agent
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Lab-scale layer crystallization apparatus
Direction of crystal growth
bath size : 4 kg-salt/batch
Main components
1) Crystallizer (formation of LiCl crystal) :
Ta-Crucible, Inconel plates (3 EA)
2) Melter (recovery of purified LiCl crystal) : Ta-Crucible,
3) Cooling gas(air) supply system
Waste Salt Treatment – II
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Operating conditions
- to obtain both high FPs separation efficiency and high LiCl salt reuse rate(=high
pure LiCl crystal formation rate) in condition of short operation time
- initial stage ; pure seed formation(~610 oC)→ low crystal formation flux
- after that ; crystal growth (610~600 oC) → high crystal formation flux
Crystallization process
[time]
LiCl recover rate
[%]
Separation efficiency
[%]
Sr
2 ~ 3 70 ~ 80
92 ~ 93
Ba 91 ~ 92
FPs concentrated in salt(about 20wt%)
separation
chemical agent addition and
Distillation/condenstaion
(under study)
Waste Salt Treatment – III
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Lab-scale RE precipitation apparatus (4kg/batch)
• oxidative precipitation reactor : for RE oxidation reaction (oxygen sparging), vertical-type sparger• solid salt detachment device : detach cooled salt from Ta crucible• layer separation device : using thin metal saw → upper pure salt layer + precipitates layer
oxidative precipitation reactor and oxygen sparger
solid salt detachment
layer separation device solid LiCl particle collector
Oxidative precipitation reactor
gassparger
Solid saltdetachment
Layer separation
Waste Salt Treatment – IV
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phosphate injection process- phosphate ; Li3PO4(0.592 mol%) - K3PO4(0.408 mol%) no mole ratio change of LiCl-KCl eutectic salt during reaction process
- phosphate reaction of rare-earth with Ar sparging within one hour, 450-500 oC ; termination of phosphate reaction
sequential use of phosphate reaction and then oxygen sparging process- low operation temperature, short operation time
1 2 3 4 5 6 7 80
20
40
60
80
100
Con
vers
ion
effic
ienc
y [%
]
Time [hr]
70%-phosphate30%-oxidation
1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0
2 -T h e ta
REPOREPO44REOClREOClREOREO22 or REor RE22OO33
phosphate
oxidation
Waste Salt Treatment – V
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Capacity of 2 kg/batch
This distillation system can heat to 1100 oC and reduce the pressure to 10-3 Torr
A single-body of distillation and condensation chamber system
Closed chamber operation is possible
Four heaters are able to independently program
Cooling water is only circulated in the bottom of the salt collection bottle
Installation Schematic diagram
Cooling water
T2T3
T5
T6T7
T4
Vaporization chamber
Condensation chamberHeater 1
Heater 2
Heater 3
Heater 4
T1
Sample bottle
Salt collector
Pressuregauge Valve
FilterVacuum
pump
Waste Salt Treatment –VI
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LiCl waste : Dechlorination by SAP (SiO2-Al2O3-P2O5) & Consolidation
RE waste : Consolidation by ZIT (ZnO-TiO2-SiO2-CaO-P2O5-B2O3)
Layer crystallization Precipitation
RE phosphate/oxide
Waste Salt Treatment – VII
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Process Layout in PRIDE
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Summary
Based on the national long-term R&D program, the pyroprocessing technology will be developed to achieve the milestones.
Research on lab-scale unit processes will be continued in terms of throughput increase, remote operability enhancement, process optimization, waste minimization, and so on. 20 kg/batch scale experiments have been successfully conducted. Eng. scale unit processes have been designed based on the lab-scale research activity. KAERI welcomes international collaboration for development of pyroprocessing technology.
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