separation and recovery of uranium and group actinide products...

Fuel Cycle Research and Development

Separation and Recovery of Uranium and Group Actinide Products from Irradiated Fast Reactor MOX Fuel via Electrolytic Reduction and Electrorefining

S. D. Herrmann, S. X. Li, B. R. WestphalPyroprocessing Technology DepartmentIdaho National Laboratory

3rd International Pyroprocessing Research ConferenceDimitrovgrad, RussiaNovember 29 – December 3, 2010

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

http://www.novapdf.com


Outline

Objectives Test Approach / Setup MOX Fuel Characteristics Electrolytic Reduction Results

– Cell response plots– Post-test observations / analyses

Electrorefining Results– Uranium electrorefining

• Cyclic voltammetry• Cell response plots• Post-test observations / analyses

– Group actinide recovery• Cyclic voltammetry• Cell response plots• Post-test observations / analyses

Summary and Conclusions




Objectives

Purpose– Demonstrate and characterize the separation

and recovery of uranium and group actinides from irradiated fast reactor MOX fuel via electrolytic reduction and electrorefining.

– Compare results with previous tests using LWR fuel.

Specific Objectives– Determine the extents of reduction of metal

oxides in spent fuel following electrolytic reduction.

– Examine the distribution of fuel constituents between the salt and fuel phases in both processes, including the purity of the actinide products from electrorefining.

– Assess the possible effect of accumulated fission products on the processes.

Hot Fuel Dissolution Apparatus (HFDA) in Hot Fuel

Examination Facility (HFEF)




Test Approach

Pt wire(1 mm dia.)

spiral woundanode

crushed(< 4mm) MOX

fuel inpermeableSST basket(cathode)

reducedfuel

basket(anode)

UO2 → UO2 (g) ↑

carbon steelcathode

rod (1/8” dia.)

Electrolytic Reduction Electrorefining

LiCl~ 1 wt%

Li2O(~ 500 ml)

650 ºC

LiClKClUCl3

(~500 ml)

500 ºC

Uimpure Urefined

interim sealed storage

FPs FPs




Test Equipment – Electrolytic Reduction

Fuel basket(cathode) Pt anode Reference

electrodecenterline

thermocoupleFuel basket(cathode) Pt anode Reference

electrodecenterline

thermocouple

Y2O3 (MOX fuel)vs.

MgO (LWR fuel)




Electrolytic Reduction Cell Configuration

IPri

ISec

VSec

basket wall potential (VBW)Pt anode potential (VPt)

Ni/NiO reference electrode

LiCl1 wt% Li2O

Pt anodecrushed oxide fuel basket (cathode)

center lead potential (VCL)

VPri




MOX Fuel Characteristics

UO2-PuO2 fuel with initial Pu to heavy metal ratio of 0.293, 81.5% U-235

Irradiated in EBR-II in two different periods between 1980 and 1984

Used 4 elements for reduction runs – 3 high burn-up (~17.7%), 1 low burn-up (~3%)

1 high burn-up element subjected to voloxidation prior to electrolytic reduction

Elements cut, crushed, separated from cladding and sieved to 0.045 – 4 mm

Fines of each fuel type (high burn-up, low burn-up, high burn-up after voloxidation) analyzed for pre-test fuel constituent concentrations

Sectioned MOX Fuel

Crushed and Sieved MOX Fuel




Results of MOX Fuel Analysis

ppm Hi b/u Hi b/u-V Lo b/u ppm Hi b/u Hi b/u-V Lo b/uNd 13700 10800 3820 Zr 14500 11600 2900Ce 7630 6200 1550 Mo 11800 8750 2400La 4430 3560 1020 Ru-total 3140 3110 999Pr 3600 3190 882 Tc-99 319 3630 412Sm 3600 2920 747 Pd-total 2092 3480 899Y 1570 1300 287 Rh-103 169 728 294

Gd 179 229 <80 Cd-total 267 392 117

ppm Hi b/u Hi b/u-V Lo b/u ppm Hi b/u Hi b/u-V Lo b/uU-total 562000 512000 598000 Cs-total 24000 7380 3740

Pu-total 169000 131000 235000 Ba 11200 6880 1910Np-237 483 414 116 Sr 2710 2160 503Am-241 1860 1470 1990 Te-total 4180 1873 695

Rb-total 2440 970 436Eu 296 239 80

U-total incl. -234, -235, -236, -238; Pu-total incl. -239, -240, -241, -242

Ru-total incl. -101, -102, -104; Pd-total incl. -105, -106, -107, -108, -110; Cd-total incl. -111, -112, -114, -116

Cs-total incl. -133, -135, -137; Rb-total incl. -85, -87; Te-total incl. -125, -128, -130

Rare Earths (RE)

Actinides (U/TRU)

Noble Metals (NM)

Salt Soluble Fission Products (FPS)




Test Matrix for MOX Fuel

sinteredstainless steel

6.0 g 17.7% burn-up3.65 g 3% burn-up

6.09 g 17.7% burn-up(after voloxidation)15.74 g total

fines from all threefuel types5

stainless steelwire mesh

0.55 g (2.8 – 4 mm)13.70 g (1.2 – 2.8 mm)15.09 g (0.6 – 1.2 mm)23.32 g (0.045 – 0.6)

52.66 g total

17.7% burn-up(after voloxidation)4


5.77 g (1.2 – 2.8 mm)21.92 g (0.6 – 1.2 mm)28.05 g (0.045 – 0.6)

55.74 g total3% burn-up3


0.13 g (2.8 – 4 mm)13.58 g (1.2 – 2.8 mm)15.02 g (0.6 – 1.2 mm)23.94 g (0.045 – 0.6)

52.67 g total

17.7% burn-up2


0.27 g (2.8 – 4 mm)13.81 g (1.2 – 2.8 mm)15.35 g (0.6 – 1.2 mm)24.25 g (0.045 – 0.6)

53.68 g total

17.7% burn-up1

Basket TypeFuel Loading(particle size)

MOX FuelType

RunNo.


http://www


Cell Response Plots – LWR vs. MOX Fuel

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Faraday Charge (applied A-hr / theoretical total A-hr)

-10

-8

-6

-4

-2

0

2

4

6

8

curr

ent (

A)

V-Pt

V-BW

V-CL

I-sec

I-pri

volta

ge (V

) vs.

Ni/N

iO r

efer

ence

ele

ctro

de

BR3-1 MOX-3

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Faraday Charge (actual A-hr / theoretical A-hr)

-10

-8

-6

-4

-2

0

2

4

6

8

pote

ntia

l (V)

vs.

Ni/N

iO re

fere

nce

elec

trod

e

curr

ent (

A)

I-pri

I-sec

V-Pt

V-basket center

V-basket wall




Results of Post-Reduction Salt Analyses

run 1 1 2 3 4 5sample ppm pre-test post-test post-test post-test post-test post-test

FPS: Cs-total <3 535 - 540 1037 - 1093 1145 1554 - 1597 1841 - 1867Ba <3 468 - 500 940 - 1000 1020 1340 - 1400 1500 - 1510Sr <5 169 - 184 358 - 385 390 500 530 - 540

Te-total <10 54 - 60 83 - 84 95 128 - 144 157 - 161Rb-total <6 74 - 75 145 - 158 158 208 - 209 229 - 234I-127/129 3 11-15 10-11 7 7-9 10-11

Eu <60 <85 <55 <70 <80 <55U/TRU: U-total 50 30 - 36 13 - 29 17 46 - 72 33 - 41

Pu-239 <1 7.4 - 14 7.4 - 13 7.5 6.2 - 10 41 - 57Np-237 <2 <2 <2 <2 <2 <2

RE: Nd <1400 <3000 <1400 <1700 <1900 <1300Ce <460 <670 <430 <540 <600 <425La <80 <120 <80 <100 <110 <75Pr <890 <1300 <830 <1100 <1200 <820Sm <580 <830 <530 <690 <760 <530Y <10 <15 <10 <15 <15 <10

NM: Zr <70 <100 <70 <85 <95 <65Mo-95/7 <8 <8 <8 <8 31 - 75 <8Ru-101 <2 <2 <2 <2 <2 <2Tc-99 <2 <2 <2 <2 <2 <2

Pd-105/6/7 <12 <12 <12 <12 <12 <12Rh-103 <2 <2 <2 <2 <2 <2

Li2O wt% 0.58 0.76 - 1.10 0.79 - 1.12 0.86 0.65 - 1.45 1.32




Results of Post-Reduction Fuel Analyses

basketphase metal oxide metal oxideunits (wt%) (wt%) (wt%) (wt%)

U/TRU:U-total 28 - 29 71 - 72 87 - 88 12 - 13

Pu-239/240 16 84 54 - 56 44 - 46Np-237 26 - 28 72 - 74 85 - 87 13 - 15

mass 241 11 - 12 88 - 89 29 - 32 68 - 71RE:

Nd-143/145/146 1 - 2 98 - 99 5 95Ce-140/142 1 99 5 - 6 94 - 95

La-139 1 - 2 98 - 99 5 - 6 94 - 95Pr-141 1 99 5 95

NM:Zr-90/91 4 96 24 - 27 73 - 76Mo-95/97 32 - 34 66 - 68 42 - 43 57 - 58

Ru-101/102 36 - 41 59 - 64 63 - 66 34 - 37Tc-99 72 - 75 25 - 28 69 - 74 26 - 31

Pd-105 32 - 41 59 - 68 37 - 41 59 - 63Rh-103 23 - 28 72 - 77 40 60

1 2




Results of Pt Anode Analyses and Microscopy

Section of feedstock Pt wire

Section of Pt wire after seriesof 5 MOX reduction runs

213Zr

351Ce-140/142

501Fe

792Eu

896Te

ICP-MS /ICP-OES

1140Li

Acid dissolution of a water-

washed section of Pt wire

581I-127ICP-MS

2850I-129

Ion specific electrode

250,000ClWash water from

a section of Pt wire

Inert gas diffusion11,800 – 56,800Oxygen

Water-washed sections of Pt

wire (x3)

TechniqueConcentration (ppm)

ConstituentSample

Pt anode after series of 5 MOX reduction

runs*EDS identified: O, Te, Eu, and Ce on surfaces




Test Equipment for Uranium Electrorefining

centerline thermocouple

reference electrode

alumina liner

cathode rod (rotating)

steelbottom disc

reduced MOX fuel basket (anode)




Cyclic Voltammetry

Cyclic voltammetry (25 mV/sec) on carbon steel and stainless steel working electrodes in LiCl-KCl at 500 °C with varying concentrations of UCl3.

U reduction potential was approximately -1.3 V vs. Ag/AgCl. Cut-off voltage for SST anode basket identified as -0.6 V vs. Ag/AgCl

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-2.5 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.7 -0.5 -0.3 -0.1voltage (V) vs. Ag/AgCl reference electrode

curr

ent (

A)

0 wt% U

9 wt% U

6 wt% U

3 wt% U

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-2.5 -2.3 -2.1 -1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.7 -0.5 -0.3 -0.1 0.1

voltage (V) vs. Ag/AgCl reference electrode

curr

ent (

A)

0 wt% U 3 wt% U

6 wt% U

9 wt% U

carbon steel working electrode stainless steel working electrode




Cell Response Plots –LWR vs. MOX Fuel

BR3-1 MOX-3

-1.5

-1.4

-1.3

-1.2

-1.1

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

0 5 10 15 20 25 30 35 40

run time (hr)

volta

ge (V

) vs.

Ag/

AgC

l ref

eren

ce e

lect

rode

DT1 DT2 DT3 DT4 DT5 DT6 DT7 DT8 DT9/DP1 DP2

direct transport deposition

fuel basket removed

VcathodeVanode

500 mA

500 mA

500 mA

500 mA

750 mA 750 mA500 mA

-1.8

-1.7

-1.6

-1.5

-1.4

-1.3

-1.2

-1.1

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

0 20 40 60 80 100 120 140 160

run time (hr)vo

ltage

(V) v

s. A

g/A

gCl r

efer

ence

ele

ctro

de

500 mA

500 mA

50 mA

500 mA

200 mA

450/200 mA

200 mA

450 mA

200 mA

500/200 mA

basket removed

direct transport deposition

DT4DT1 DT2 DT3 DT5 DT6 DP7 DP8 DP9 DP10

Vcathode

Vanode


http://ww


Uranium Recovery Observations

Run 1 Run 2 Run 3 Run 4 Run 5




Results of Electrorefining Salt Sample Analyses

MOX-1 MOX-1 MOX-2 MOX-3 MOX-4 MOX-5 control LCCppm salt salt salt salt salt salt salt salt

pre-test post-test post-test post-test post-test post-test post-test post-testFPS: Cs-133/135/137 <28 <34 <51 72.2 81.7 107.9 110.8 108.9

Ba 14.1 47.6 60 76 90 113 117 114Sr <5 31.3 37.3 44 58 67 69 68Te <90 <230 <120 <75 <80 <100 <100 <95Rb-85/87 <15 <17 20.3 20.6 24.7 23.7 25.9 26.7I-129 <1 <1 1.00 1.84 1.20 3.02 2.94 3.02Eu <5 11.8 9.5 8.5 11.2 12.6 12.6 12.5

RE: Nd <90 840 1840 1940 2840 2920 2910 2840Ce <20 498 1020 1090 1510 1580 1590 1550La <15 285 590 620 871 905 910 900Pr <65 261 540 580 810 840 830 810Sm <40 213 433 457 670 700 705 700Y 6.2 870 1410 1500 1540 1550 1530 1520

U/TRU: U-total 84600 71100 37700 17400 6420 4250 4690 10800Pu-239/240 <40 9040 20000 34500 41500 42700 39600 34100Np-237 <0.4 18.1 45.4 49.7 68.7 49 46.5 40.3Am-241 0.13 125 274 417 475 490 502 428

NM: Zr <20 <45 <25 <15 <15 <20 <20 <20Mo <10 <30 <15 <10 <10 <15 <15 <15Ru <50 <120 <65 <40 <45 <50 <50 <50Tc <5 <10 <5 <5 <5 <5 <5 <5Pd-total <25 <25 <25 <25 <25 <25 <25 <25Rh-103 <5 <5 <5 <5 <5 <5 <5 <5




Rare Earth Concentrations in Electrorefining Salt

0

500

1000

1500

2000

2500

3000

0 1 2 3 4 5

run no.

fuel

con

stitu

ent c

onc.

(ppm

)

Nd-expectedNd-actualCe-expectedCe-actualLa-expectedLa-actualPr-expectedPr-actualSm-expectedSm-actual




Actinide Concentrations in Electrorefining Salt

General UCl3 depletions mechanisms:M + UCl3 → U + MClxMyOz + UCl3 → UO2 + MClxwhere M includes transuranics, rare earths, and lithium

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

0 1 2 3 4 5

run no.

conc

entra

tion

in s

alt (

ppm

) U-expectedTRU-expectedU-actualTRU-actual




Test Equipment for Group Actinide Recovery

SST anode basket – loaded with 8.28 g of DU metal to support

group actinide recovery experiment

Group actinide recovery assembly (x2)1. Control assembly (shown) – no Cd, small holes in bottom of Al2O3 tube for salt draining

2. LCC assembly – same as control assembly without drain holes and with 40 g cadmium




Cyclic Voltammetry Prior to Actinide Recovery

Cyclic voltammetry (25 mV/sec) of tantalum wire (set of curves) and liquid cadmium (single curve) working electrodes in electrolyte at 500 °C following uranium recovery, compared to that for steel (dashed curve) prior to uranium recovery.

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

-1.9 -1.7 -1.5 -1.3 -1.1 -0.9 -0.7 -0.5 -0.3 -0.1 0.1 0.3 0.5 0.7

voltage (V) vs. Ag/AgCl reference electrode

curr

ent (

A)

LCC

steel, pre-electrorefining (i.e., 9 wt% U)




Response Plots – Group Actinide Control and LCC Assemblies

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0

run time (hr)

curr

ent (

A)

0.682 A-hr(2.02 g equiv. U)

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0 1 2 3 4 5 6 7 8 9

run time (hr)

curr

ent (

A)

2.12 A-hr(6.27 g equiv. U)

Control (constant potential: -1.65V) LCC (constant potential: -1.65V)

post-testLCC




Results of ElectrorefiningFuel Sample Analyses

MOX-1 MOX-2 MOX-3 MOX-4 MOX-5 control LCCppm cathode cathode cathode cathode cathode cathode cathode

deposit deposit deposit deposit deposit deposit depositFPS: Cs-137 0.00950 0.0111 0.044 0.0098 0.014 0.17 0.040

Ba <5 <5 <5 <5 <5 <5 <5Sr <5 <5 <5 <5 <5 <5 <5Te <200 <220 <400 <250 <190 <290 <180Rb-85/87 <4 <4 <4 <4 <4 <4 8.55I-129 na na na na na na naEu <10 <10 <20 <10 <10 12.4 <10

RE: Nd <120 <130 <230 <150 <110 520 <110Ce <260 <290 <500 <320 <240 <370 <230La <15 <15 <25 <20 <15 68 <50Pr <120 <130 <220 <140 <110 <170 <170Sm <60 <65 <120 <70 <55 <85 <50Y <5 <10 <10 15.4 60 389 <5

U/TRU: U-total 477600 808000 771000 660000 394000 116000 13700Pu-239/240 280 740 2310 10500 64000 58500 57100Np-237 239 354 273 708 3160 13400 <100Am-241 0.114 0.385 0.781 3.2 24 100 550

NM: Zr <50 <55 <90 <55 <45 <70 <45Mo <30 <35 <60 <40 <30 <45 <30Ru <80 <90 <160 <100 <75 <120 <70Tc <30 <30 <50 <35 <25 <40 <25Pd-total na na na na na na naRh-103 <2 <2 <2 <2 <2 <2 <2




Summary and Conclusions

Electrolytic Reduction– The distribution of fuel constituents between the salt and fuel phases was

quantified.• Cs, Ba, Sr, Rb and Te diffused from the fuel and accumulated in the salt phase,

but at lower concentrations than expected.– The extent of fuel reduction was quantified for runs 1 and 2.

• U reduction was limited to 29% in run 1 and 88% in run 2• Lanthanides were predominantly in the oxide phase for both runs.• Noble metals existed in both oxide and metal phases.

– Higher concentrations of fission products in the MOX fuel appear to have adversely impacted its electrolytic reduction.

• An identical Pt anode exhibited consistently higher resistances during the MOX fuel runs than those with LWR fuel.

• Degradation of the Pt anode was observed over the course of 5 runs, i.e., ~20% material loss and fission product buildup on the surface.

• Lower extents of reduction (i.e., 29 – 88%) were observed in the MOX fuel than that (99.7%) in LWR fuel for comparable applied charges, indicating lower cell efficiencies.




Summary and Conclusions (cont.)

Electrorefining– The partitioning of fuel constituents into the salt phase was quantified.

• Essentially all of the rare earth and transuranic constituents (metal or oxide) in the electroreduced MOX fuel accumulated in the electrorefining salt, while the uranium concentration in the salt correspondingly declined.

• No noble metal fission products were detected in the salt, while minor accumulations of Cs, Ba, Sr, Rb, and I were measured – the concentrations of which were consistent with drag-out from the electrolytic reduction process.

– The purity of actinide products was determined. • Low levels of Cs-137 were detected in all actinide products; yttrium was

detected in cathode products for runs 4 and 5; minor amounts of Eu, Nd, La, and Y were detected in the group actinide control experiment, while no rare earths were detected in the LCC product.

• Transuranic elements were detected in all cathode products to varying degrees, except for Np-237 in the LCC product (which was below detection levels).

• The concentration of transuranic elements in the uranium and group actinide recovery products increased through the entire series of electrorefining and group actinide recovery runs, i.e., the transuranic to heavy metal fraction in the cathode products increased from 1.7% to 15% in runs 4 and 5 and from 38% to 81% in the group actinide recovery runs.




Summary and Conclusions (cont.)

Other noteworthy observations– Electrorefining of the reduced MOX fuel identified differing heavy metal

contents in the baskets based on applied charge prior to reaching cut-out potential on a basket.

• ~25% of the uranium in MOX-1 anodically dissolved, while essentially all of the uranium in MOX-2, -3, and -4 dissolved and ~80% in MOX-5 dissolved.

– As the electrorefining of reduced MOX fuel progressed, the cathode deposits became less likely to adhere to the cathode rods, and the deposits became less dendritic after MOX-3 run.


h


Acknowledgements

The authors acknowledge the significant contribution of INL’s Hot Fuel Examination Facility operators and Analytical Laboratory personnel.

This work was supported by the U.S. Department of Energy, Office of Nuclear Energy, Idaho Operations Office contract DE-AC07-05ID14517.



http://www.novapdf

separation and recovery of uranium and group actinide products...

Documents