ulb 2009-2010 nuclear fuel cycle nuclear fuel reprocessing sellafield - uk

ULB 2009-2010Nuclear Fuel Cycle

Nuclear Fuel reprocessingNuclear Fuel reprocessing

Sellafield - UK


Nuclear fuel reprocessingNuclear fuel reprocessing

1. Why reprocess?

2. Basic principles

3. Description of PUREX process

4. Industrial status


Reprocessing objectivesReprocessing objectives

Recycling of fissile materials (U, Pu),

Reduction of U needs)

Reduction of high level waste volumes

Reduction of radiotoxicity and heat from the waste


The Reprocessing-RecyclingThe Reprocessing-Recycling

Note: message AREVA


Fissile materials recyclingFissile materials recycling

Spent UOX fuel (33 GWj/t, cooling 3 years)Spent UOX fuel (33 GWj/t, cooling 3 years)


Element Amount (kg/tHM) U 955 Pu 10 Minor actinides 1 Np 0.4 Am 0.3 Cm 0.03 Fission products 34 Rare gases (Kr, Xe) 5 Alkali metals (Cs,Rb) 4 Alkaline-earth metals (Ba, Sr) 2 Rare earths (Y,Ln) 10 Zirconium 4 Molybdenum 3 Noble metals (Ru,Rh,Pd) 4 Technetium 1 Chalcogenides 0.5 Halides (I,Br) 0.2

Spent fuel compositionSpent fuel composition


La radiotoxicité des déchetsLa radiotoxicité des déchets


Arguments against reprocessingArguments against reprocessing

Technological difficulty and large investments

Large, generally export, reprocessing costs

Accumulation of Pu: recycling need

Nuclear proliferation need

Transports of nuclear materials


Le retraitement du combustible irradiéLe retraitement du combustible irradié

1. Why reprocess?

2. Basic principles




Reprocessing functionsReprocessing functions

1. Separation from spent fuel of U, Pu, and Fission Products (FP)+ Minor Actinides (MA)

2. Purification of U and Pu, to be re-used

3. Concentration of FP + MA for final geological disposal


Developed by Oak Ridge National laboratory (ORNL) and Knolls Atomic Power Laboratory (KAPL) from 1949 to 1960

Solvent extraction based on TBP

Targeted for separation of U and Pu

Used on an industrial scale in Savannah River & Hanford (USA, past), La Hague (F), Sellafield (UK), Rokkashamura (J)

PUREX: Plutonium Uranium Refining by PUREX: Plutonium Uranium Refining by EXtractionEXtraction


UP3 La Hague plant


Nitric acidNitric acid

Due to various oxidation states of N, allows the change of actinides valences

Not too corrosive, formation of soluble metal nitrates

Stability in nitric acid medium:

UVI

NpV and NpVI

PuIV and PuVI

AmIII

Recycling of vapours in nitric acid

(2NO+O2 N2O4 +H2O)


U chemical propertiesU chemical properties

Electronic configuration: [Rn]5f3 6d1 7s2

6 extractible valence electrons: U metal oxidises easily in humid or hot air

Complex chemistry (5f electrons): oxidation levels III to VI

Level VI most stable (uranyle UO22+ in solution)

Uranyle nitrate solubility in various organic compounds


Plutonium chemical propertiesPlutonium chemical properties

Electronic configuration: [Rn]5f6 6d0 7s2

Reuslts from neutronic irradiation of U

Mix of several isotopes: 238, 239, 240, 241, 242

Oxydation levels III to VII

Levels III and IV in industrial processes

Final reprocessing product: PuO2


Physico-chemical aspects (1)Physico-chemical aspects (1)

Fuel rods/assemblies mechanical shearing (3-4 cm slices)

Fuel dissolution in boiling nitric acid (2h)

UO2 + 4HNO3 → UO2 (NO3)2 + 2NO2 + 2H2O

UO2 + 3HNO3 → UO2 (NO3)2 + 0,5NO2 + 0,5 NO + 1,5H2O

Nitrates: Pu (NO3)4, PF (NO3)3, MA(NO3)3

Structural materials conditioning (high activity solid waste)

Nitrous vapours treatment

Volatile and gaseous FP treatment


Physico-chemical aspects (2)Physico-chemical aspects (2)

TBP: organic compound forming complexes with metal (M) nitrates, not soluble in water

Maqx-

+ xNO3aq- + y TBPorg [M(NO3)x y TBP]org

Formation of complexe controled by concentration in ions NO3-

Increase NO3- favours extraction of M in organic phase

Decrease NO3- favours re-extraction of M in aqueous phase


(C(C44HH99))33POPO44 or PO(OC or PO(OC44HH99))33

Low solubility in aqueous phase

Affinity for U VI and Pu IV (selectivity)

Good chemical resistance to radiolysis

Density: 0.973 gcm-3 ; if 30% diluted: 0.83 gcm-3

TBP = tri-butyl phosphateTBP = tri-butyl phosphate

Twin free oxigen electrons


UOUO2 2 + 2 NO+ 2 NO33 + 2TBP = UO + 2TBP = UO22(NO(NO33))22..2TBP2TBP

The The distribution coefficientdistribution coefficient (coéfficient de partage) (coéfficient de partage) DD is the ratio is the ratio of the concentration in the aqueous and organic phase: of the concentration in the aqueous and organic phase:

22

322

232

TBPNOUO

2TBP)(NOUO

K

22

3aq

orgU TBPNOK

U

U D

Distribution coefficient Distribution coefficient


Distribution coefficientDistribution coefficient


Extraction abilityExtraction ability

Class Ability to form complexes with TBP

Extraction ability

A) UO2+, PuO22+, Pu4+,

U4+, Zr4+, Ce4+, RuNO23+

Relatively high Very good to good

B) Pu3+, Y3+, Ce3+ Low Low to very low

C) Other FPs Very low to nil Almost nil


TBP

HNOHNO33

Spent fuel

U Pu

Fissionproducts

Minor actinides

Xe, Kr, IXe, Kr, I22

PUREX PrinciplePUREX Principle

TBP en solution dans hydrocarbure (30%)

EmulsionTransfert de matières

Mélange Décantation


Separation U - PuSeparation U - Pu

Pu4+ extracted with U (class A)

Pu3+ class B : low ability to form complexes

Mixing of organic phase with aqueous solution, containing a selective Pu reductor (concentration NO3

- must be sufficient to keep

U in organic phase)

During emulsion of the phases, Pu is reducted and goes in the aqueous phase

-


Purification U and PuPurification U and Pu

Impureties: FPs of class A

Extraction ability lower than U and Pu, depending on [U] and [nitric acid]

High [U]: mitigates FPextraction

High acidity: decreases Ru extractionincreases Zr, Sr extraction

Successive washing of organic phase

Concentration NO3- variable, but sufficient pour hinder the re-

extraction of U and Pu!


TBP separation basic principlesTBP separation basic principles

• Sélectivity of TBP (UVI and PUIV)

• Importance of acidity: to extract UVI and PuIV: 2-3 mol/l

• To de-extract UVI: <0,02 mol/l

• Separation U-Pu: reduction PuIV to PuIII

• Separation U-Np: adjustment of the Np oxidation state to NpV

• Am is not extracted by TBP



1. Why reprocess?

2. Basic principles




Shearing

Dissolution

Clearing

Extraction

Purification

Spent fuelSpent fuel

U Pu

Structural Structural elementselements

HullsHulls

Fission products & Fission products & MAMA

Insoluble residuesInsoluble residues

VitrificationVitrification

GasesGases

GasesGasesAtmospheric Atmospheric or sea or sea releaserelease

PUREX: Plutonium URanium EXtractionPUREX: Plutonium URanium EXtraction


http://www.ricin.com/nuke/bg/lahague.html

The La Hague reprocessing schemeThe La Hague reprocessing scheme


29

Spent fuel assemblies storage pool at Sellafield Spent fuel assemblies storage pool at Sellafield (UK)(UK)


Shearing of claddingShearing of cladding


Rotatif DissolverRotatif Dissolver


Caractéeristics of the dissolution solutionCaractéeristics of the dissolution solution

• Composition: U: 200 – 250 g/L Pu: 2 – 3 g/L FP: 80% of inventory MA: 100%

• Specific activity : 7,4 TBq/L (200Ci/L)

• Nitric acidity : 3 – 4 M

• Oxidation state of oxides: VI, PuIV, NpV, AmIII, CmIII


Extraction cycles in a reprocessing plant (example)Extraction cycles in a reprocessing plant (example)

1. Decontamination – separation cycle

M Extraction in organic phase Acid washing of the organic phase Pu Separation (reducing re-extraction) U Re-extraction in aqueous phase

2. U purification cycles (2x)

New U extraction in organic phase Washing U re-extraction in aqueous phase

3. Pu purification cycles (2x)

Solution oxidation (Pu4+) New Pu extraction in organic phase Pu re-extraction in reducing aqueous phase


Feed(aq)

Product(org)

Waste(aq)

Fresh solvent(org) Fresh solvent

Aqueous feed

Loaded solvent Loaded solvent meets most meets most

concentrated concentrated aqueous solutionaqueous solution

Fresh solvent meets Fresh solvent meets depleted aqueous depleted aqueous

solutionsolution

Counter current: maximising loading & extractionCounter current: maximising loading & extraction


FeedFeed(aq)(aq)

ProductProduct(org)(org)

WasteWaste(aq)(aq)

ccff ccpp

cw

Fresh solventFresh solvent(org)(org)

c = 0c = 0

1

i

n

orgnc

orgnc

org1c

orgic

org0c

org1-ic

org1-nc

aq0c

aq2c

aq1ic

aq1c

aqic

aqnc

Multi-stage extractionMulti-stage extraction


Solvent extraction devicesSolvent extraction devices


Laboratory scale centrifugal contactors (ITU)Laboratory scale centrifugal contactors (ITU)


Pulsed ColumnPulsed Column


Solvent extraction devicesSolvent extraction devices


Recovery rate and decontamination factorRecovery rate and decontamination factor

• Residual materials recovery rate: Pu:99,88%

• Decontamination factor: Impureties in inlet product divided by impureties in outlet product

• β, γ impurities: U: 1,5 106; Pu: 7 107

• Separation factor U-Pu: 106


42

Technological constraints of reprocessingTechnological constraints of reprocessing

• High activities

• Heat release

• Under-criticity to be guaranteed, verifications

• Corrosion resistance (stainless steels, zirconium)

• Maintenance of equipement

• Controls of materials fluxes


U and Pu conditioningU and Pu conditioning

Aqueous solution of Uranyl nitrate [UO2 (NO3)2] at 250 – 300 g U / l

Denitration and transformation into UO3 or UO2 (fabrication plant)

Aqueous solution of Pu nitrate: [Pu (NO3)2] at 50-150 g Pu / l

Oxidation of Pu in Pu 4+, mixing to oxalic acid which precipitates Pu as oxalate

Calcination and storage of PuO2 or transport to MOX plant


Plutonium Conversion : calcinationPlutonium Conversion : calcination


High decontamination factors

High selectivity for U and Pu

Low cost

Easy scale up

Room temperature process

Radiolytic degradation of organic phase

TBP not incinerable yielding solid radioactive waste

Some fission products are not (fully) soluble (Zr, noble metals particles)

Pure plutonium produced

Advantages and disadvantages of PUREXAdvantages and disadvantages of PUREX


Bitumen: e.g. for residues from evaporation or spent organic ion exchangers

Cement: for low radioactive waste

Glass: for high level liquid waste

Ceramics: alternatives for HLLW (not industrial)

Waste formsWaste forms


Borosilicate glass matrix

HLW concentrate is calcined

Mixed with glass frit and heated at 1100 oC

Liquid poured in a stainless steel canister

Canister is welded shut

Vitrification of HLWVitrification of HLW


Concentration (wt%)

R7/T7

(Cogema) Magnox (BNFL)

SiO2 47.2 47.2 B2O3 14.9 16.9 Al2O3 4.4 4.8 CaO 4.1 - MgO - 5.3 Na2O 10.6 8.4 Others 18.8 17.4

Silica is the main glass-forming component

Boron oxide reduces thermal expansion and improves chemical durability



Waste treatmentWaste treatment



1. Why reprocess?

2. Basic principles




52

Reprocessing capacities in the worldReprocessing capacities in the world

LWR fuel: France, La Hague 1700

UK, Sellafield (THORP) 900

Russia, Ozersk (Mayak) 400

Japan 14

total approx 3000

Other nuclear fuels:

UK, Sellafield 1500

India 275

total approx 1750

Total civil capacity 4750

NEA 2004NEA 2004


53

Rokkasho-Mura (Japan)Rokkasho-Mura (Japan)


AREVA La Hague Reprocessing PlantsAREVA La Hague Reprocessing Plants


55

UP3 plant in La Hague


56

Marcoule R&D


ConclusionConclusion

Reprocessing: strategic option

based on nitric dissolution, séparation by organic extraction

Reprocessing-Recycling strategy, in LWRs, but preferably in fast reactors

Technical and commercial success

3 main sites: FR, UK, JP

Thank you for your attention!

ulb 2009-2010 nuclear fuel cycle nuclear fuel reprocessing sellafield - uk

Documents

u metal

spent fuel of u

separation of u

pu no34

organic phasedecrease

puo2physicochemical

nitric acid medium

mano33structural materials