PyroprocessingTechnology Development at...

0

Hansoo LeeIPRC 2010

29 Nov. - 3 Dec., 2010

Pyroprocessing Technology Development at KAERI

Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com)

http://www.novapdf.comhttp://www.novapdf.com

1

Outline

Spent Fuel ManagementI

Pyroprocessing Research ActivitiesII

Integrated Pyroprocessing in PRIDEIII

SummaryIV



2

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



3

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



4

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



5

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



6

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



7

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



8

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



9

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


http:http://www.novapdf.com

10

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


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


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%



11

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



12

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



13

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



14

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



15

Comparison of Lab and Eng-scale Salt Distiller


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



16

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



17

Electrowinning Process - I

CdTRU/U/RE/Cd- HM>10wt%- RE/TRU

18

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



19

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


http://www.novapdhttp://www.novapdf.com

20

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



21

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

22


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



23

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



24

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



25

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


http://www.novapdf.comhttp://www.novapdf.co

26

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



27

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


http://www.novapdf.comhttp://w

28

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



29

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



30

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



31

Process Layout in PRIDE



32

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.


PyroprocessingTechnology Development at...

Documents

Transcript of PyroprocessingTechnology Development at...