Innovative Reprocessing Techniques

Managed by UT-Battellefor the Department of Energy

Innovative Reprocessing Techniques

Global Climate & Energy ProjectStanford-MIT Fission Energy WorkshopOpportunities for Fundamental Research and Breakthrough in FissionCambridge, MassachusettsNovember 30, 2007

Emory D. CollinsOak Ridge National Laboratory

2 Managed by UT-Battellefor the Department of Energy

Outline

• What spent fuel reprocessing is

• What is done today in commercial plants

• What modifications and additions are needed


Physical Characteristics of LWR Fuel Assemblies (ORNL/TM-7431)

________________________________________________________________BWR PWR

________________________________________________________________

Overall assembly length, m 4.470 4.059

Cross section, cm 13.9 x 13.9 21.4 x 21.4

Fuel element length, m 4.064 3.851

Active fuel height, m 3.759 3.658

Fuel element OD, cm 1.252 0.950

Fuel element array 8 x 8 17 x 17

Fuel elements/assembly 63 264

Assembly total weight, kg 275.7 657.9

Uranium/assembly, kg 183.3 461.4

UO2/assembly, kg 208.0 523.4

Zircaloy/assembly, kg 99.5a 108.4b

Hardware/assembly, kg 12.4c 26.1d

Total metal/assembly, kg 111.9 134.5

Nominal volume/assembly, me 0.0864e 0.186e

_______________________________________________________________aIncludes Zircaloy fuel-element spacers and fuel channel.bIncludes Zircaloy control-rod guide thimbles.cIncludes stainless steel tie-plates, Inconel springs, and plenum springs.dIncludes stainless steel nozzles and Inconel-718 grids.eBased on overall outside dimension.


Mass Proportions of the Chemical Elements in Spent Fuel

Cm 0.1

Pu 84.6

Am 10.5

Np 4.8

Other 3.1%Fission

Products 2.4%

TRU 0.7%

U 66.4%

Zircalloy 25.1%

Hardware 5.4%

Ln 30.3%

Xe/Kr 16.7%

Mo/Ru 16.2%

Zr 11.1%

Cs/Sr 7.2%

Others 13.9%

I 0.7%

Tc 2.3%

Se/Te 1.6%

• Separation and recovery of the re-usable elements are the partitioning goals

• Each element can be chemically separated if desired

• Industrial deployment of separations processes depends on reliability, cost minimization, waste minimization, and provision of “sufficient” proliferation resistance features (engineered safeguards)


The time factor is also extremely important –especially for repository benefits

0%

20%

40%

60%

80%

100%

5 10 30 50 70 100

Cooling time (years)

Rel

ativ

e he

at o

utpu

tTRU Cs/Sr Rest


Significant Chemical Valences of the Spent Fuel Components

• Iodine I-1

• Technetium Tc+7

• Uranium U+4, U+6 UO2 (NO3)2 · 6 H2O

Uranyl nitrate hexahydrate (UNH)• Plutonium Pu+3, Pu+4, Pu+6

• Neptunium Np+4, Np+5, Np+6

• Americium Am+3, Am+5, Am+6

• Curium Cm+3, Cm+4

• Lanthanide FP’s Ln+3 (Sm, Eu, Gd, Dy, etc.)• Zirconium Zr+4, complexes• Ruthenium Ru+3, Ru+4, Ru+6

• Molybdenum Mo+6

• Strontium Sr+2

• Cesium Cs+1


Separation Processes for Spent Fuel Components• Mechanical disassembly

• Dry pyrochemical treatment – removal of volatile components– Voloxidation– Fluoride volatility

• Aqueous-based processes– Dissolution in nitric acid– Clarification via centrifugation– Liquid-liquid solvent extraction– Liquid-solid ion exchange (including chromatographic ion exchange)– Liquid-solid extraction chromatography– Crystallization/filtration– Precipitation/filtration– Product conversion (denitration) calcination– Waste solidification – calcination – vitrification

• Pyro electrochemical processes – Dissolution in molten salt liquid– Electrolytic oxide reduction– Electro-refining (electroplating – metal/salt extraction)– Product recovery (mechanical removal from electrodes, metal casting,

precipitation – centrifugation)– Waste solidification


The Industrialized PUREX Process

07-080

La Hague (France) 1600 MT/year (2x800)THORP (U.K.) 1200 MT/yearRokkasho (Japan) 800 MT/yearMayak, Tomsk-7, K-26 500+ MT/year

Current Commercial Reprocessing Using PUREX Process

Spent Fuel Assemblies

Receiving and Storage

Spent Fuel Assemblies

Receiving and Storage

Disassembly Cutting/Shearing

Disassembly Cutting/Shearing

Dissolution in Nitric

Acid

Dissolution in Nitric

AcidClarification

(Centrifugation)Clarification

(Centrifugation)

PUREX Solvent

Extraction1st Cycle

PUREX Solvent

Extraction1st Cycle

Plutonium Purification

Cycle

Plutonium Purification

Cycle

Plutonium Product

Conversion

Plutonium Product

Conversion

Waste Compaction

and Packaging

Waste Compaction

and Packaging

Acid Recovery

Evaporation

Acid Recovery

Evaporation

Waste Solidification (Vitrification)

Waste Solidification (Vitrification)

Uranium Purification

Cycle

Uranium Purification

Cycle

Uranium Product

Conversion

Uranium Product

Conversion

PuO2 to MOX Fuel Fab

“RU” Storage or Recycle

High Level Waste

(MAs and FPS)

Return to Process

Repository

Hardware Cladding Hulls Insoluble Materials

Off-Gas(Volatile FPs)

Repository


The Newest Plant – Rokkasho-mura Japan. Began hot operations in 2007.


Schematic separations plant operation.


Advanced Fuel Cycle Requirements

• Development of process for Am-Cm separation from chemically similar lanthanide fission products

• Development/qualification/licensing of Am-Cm transmutation target form

• Development of process for recovery of plutonium in combination with other elements to meet safeguards policy criteria of “no separated plutonium.” Combination with uranium and possibly neptunium appears to satisfy criteria

• Co-conversion of U-Pu or U-Pu-Np to mixed oxide• Improved retention of volatile radionuclides – tritium, 14C, 85Kr, 129I• Development of recovery/recycle process for zirconium from cladding• Implementation of recycle of uranium product• Possible recovery-reuse of platinum group metals – Ru, Rh, Pd• Improved waste forms• Management of decay heat from 90SrY and 137CsBa


Am-Cm Recovery – UREX+3 Process

Feed = Raffinate Stream from TBP Extraction

Am-Cm-Ln Fission Products (FPs) – Other FPs

TRUEX Solvent ExtractionSolvent: 1.4M TBP – 0.2M CMPO

In n-paraffin diluent

TALSPEAK Solvent ExtractionSolvent : 1 M HDEHP in n-paraffin diluent

Complexant: 0.05M DTPA in 1.5M Lactic AcidpH~3

Am-Cm + Ln FPs

Other FPs

Ln FPs

Am-Cm Product

~

~


New and Promising Extractants for An-LnSeparation

2,6-bis(5,6-n-propyl-1,2,4-triazin-3-yl)-pyridine (BTP)• BTP synthesis not difficult – may be

expensive

• Good Am distribution to organic phase, limited Eu extraction, good separation factors for single stage contact at usefully high acidity

• Good phase separation obtained and no precipitates

• Concerns about the stability of BTP (acidic hydrolysis and air oxidation)

• Impurities and other fission products may interfere with the actinide/lanthanide separations 0.001

0.010

0.100

1.000

10.000

100.000

1000.000

0.01 0.1 1 10

Nitric Acid Concentration

Dist

. Coe

ff/Se

p. F

acto

r

Avg D (Eu)Avg D (Am)Sep Factor


Background -- Head End Schematic

S N F S h e a r in g V o lo x id a t io n

D e c o n t a m in a t io n o r M e t a l R e f in in g

F u e lS e g m e n t s

R e c y c le o rL L W D is p o s a l

S c r e e n in g )

O x id eP o w d e r

C o n t in u o u sD is s o lv e r

A q u e o u sS e p a r a t io n

H u l l s

O f f - g a s T r a p p i n g a n d T r e a t m e n t

V a p o rC o n d e n s e r

Removal efficiency of target fission products depends on the voloxidation temperature and atmosphere. Based on Korean process development data, at 1250°C in oxygen atmosphere, volatile and semi-volatile fission product removals are:

Percent Removal

3H 14C 85Kr 129I Cs Tc Ru Rh Te Mo

100 100 100 100 98 100 100 80 90 80

E. H. KimKAERI Flowsheet StudyMarch 2007


• Hydroxylamine nitrate (HAN) is used as combination Pu-Np reductant – aqueous salting agent

• Excess HAN is U-Pu-Np product readily decomposed by NOx to gases and water

• No holding reductant (hydrazine) is required

UREX+ Codecon FlowsheetPartial Partitioning Contactor Bank

PUREX-TypePartitioning Contactor Bank

(Complete or partial partitioning is possible)

07-071

Multistage ContactorStrip U Backscrub

Loaded Organic Solvent (Feed)

Solvent ScrubAq. Strip

(Pu-Np Reductant)

U-Pu-NpAq. Product

U-LoadedSolvent

Multistage ContactorU-Pu-Np Stripping

Loaded OrganicSolvent (Feed)

Aq. Strip(Pu-Np Reductant)

U-Pu-NpAq. Product

U-Tc-LoadedSolvent

Multistage ContactorU-Pu-Np Stripping

Loaded OrganicSolvent (Feed)

Aq. Strip(Pu-Np Reductant)

U-Pu-NpAq. Product

U-Tc-LoadedSolvent

40

30

20

10

5

1.00.1 0.2 0.4 0.6 0.8 10

PuC

once

ntra

tion

Incr

ease

(Pro

duct

/Fee

d)

A/O Flow Ratio

SRL DP-1505

0.75 M Nitrate

0.50 M Nitrate

40

30

20

10

5

1.00.1 0.2 0.4 0.6 0.8 10

PuC

once

ntra

tion

Incr

ease

(Pro

duct

/Fee

d)

A/O Flow Ratio

SRL DP-1505

0.75 M Nitrate

0.50 M Nitrate

Recovery of “Unseparated Plutonium”


Scrubber

Condenser

PumpCondensateCollection

FeedTank

Off-gas

Rotary Kiln Furnace

Air purge

Oxide Product

Co-conversion of U-Pu-(Np)

Uranium/TRU actinides in liquid nitrate solutions are co-converted to oxide powder for use in fuel fabrication. The Modified Direct Denitration (MDD) process is used.

– Process developed at ORNL in 1980s

– Can be used for uranium product and mixed oxide products

– Produces powder that can be directly fabricated into fuel pellets


Zirconium Recovery from Cladding

Contaminated Hulls Metal Refining

Reuse

Recyclablegaseousreagent

Residues Back to SNFprocessing plant

PurifiedZirconium

• Purified zirconium will remain radioactive• 93Zr is not a significant radiological problem

• Half-life is 1.53M years• Beta emission at only 90 keV (max.)


Summary and Conclusions

• Reprocessing is a crucial step in the recycle of spent fuel components

• All chemical element components of spent fuel, including plutonium, can be separated

• The time factor is extremely important because of the radioactive decay process

• All current industrial reprocessing plants use the PUREX process

• Additional component recovery, recycle, and re-use processes are necessary for future successful, industrial-scale closure of the nuclear fuel cycle

Innovative Reprocessing Techniques

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