Nuclear waste and Vitrification. Estremoz 2007.pdf

1Marie Curie Summer School on Knowledge based MaterialEstremoz Portugal 2007

Nuclear waste and vitrificationin France

Dr. Etienne Y. Vernaz,

Director of Research,

CEA / Nuclear Energy Division

Marcoule

Etienne Y. Vernaz Nuclear waste and vitrification Marie Curie Summer School Estremoz Portugal 2007, 2

Summary

Nuclear Energy Fuel cycle Fuel fabrication Nuclear Reactor Spent Fuel processing Nuclear Waste

Waste treatment Vitrification of nuclear waste Waste Storage and Disposal

2Etienne Y. Vernaz Nuclear waste and vitrification Marie Curie Summer School Estremoz Portugal 2007, 3

Electricity production in FranceElectricity production in France

78% nuclear 58 Pressurized Water Reactors (PWRs) 63 GWe installed

11% hydroelectric 10% thermal


The resulting waste mass is also reduced by the same order of magnitude:

About 80% of French electricity is generated by nuclear reactors, producing 1 kg of radioactive waste per person per year, of which only 10 g consist of high-level long-lived waste.

This quantity can be compared with 10 000 kg of agricultural, industrial or household waste produced per person per year in France, about 100 kg of which are highly toxic.

In other words, the high-level waste arising from the electrical consumption of one person throughout her entire life would fit in a bottle of beer.

Specific feature of nuclear power: concentrated energySpecific feature of nuclear power: concentrated energy


Advantages and drawbacks of concentrated energyAdvantages and drawbacks of concentrated energy

Concentrated energy production favors: Competitiveness Small volumes (materials, waste, transportation, etc.) Controlled waste: insignificant release into the

environment (contrary to greenhouse gases)

But concentrated energy requires: Intrinsically safe and controlled reactors Highly processed nuclear fuel High tech waste treatment


Each year a 1 Each year a 1 GWeGWe plant requires plant requires

15 to 45 oil tankers15 to 45 oil tankersOILOIL 1 300 000 metric tons

6 semi6 semi--trailerstrailers

URANIUMURANIUM (PWR) 150 t natural U 150 t natural U (20 t U enriched to 4%)(20 t U enriched to 4%)

COAL COAL 2 000 000 metric tons600 trains600 trains

30 LNG tankers30 LNG tankers

GASGAS 1,8 billion m3


Nuclear Fuel Cycle


Uranium Resources

distributed well around theworld

Ultimate Resource ( < 130 $ / kg) estimated at about 15 millions tonsUranium 2005 : Ressources, production et demande

World consomation ~68 000 tStatic reserves evaluated at 200 years

An abondant resourceLargely spread on the earth ( 2 - 3 g/t )

Mainly two natural isotopes :238 (99,28 %) fertile material235 (0,718 %) fissile material


MiningMining andand millingmilling Uranium is usually mined by

either surface or underground mining techniques

the mined uranium ore is sent to a mill which is usually locatedclose to the mine. At the mill theore is crushed and ground to a fine slurry which is leached in sulfuric acid to allow theseparation of uranium from thewaste rock. It is then recoveredfrom solution and precipitated as uranium oxide concentrateknown as yellow cake ,

(ammonium diuranate(NH4)2 U2 O7)


Conversion Conversion andand enrichmentenrichmentThe vast majority of all nuclear power reactors in operation and underconstruction require enriched uranium fuel in which the proportion of the U-235 isotope has been raised from the natural level of 0.7% to about 3.5% or slightly more.Because all the enrichment process work with gaseous uranium , thefirst step is the conversion of yellow cake , into the uranium hexafluoride (UF6), that is a gaz.

Two processes are used in the world for uranium enrichment :Gazeous diffusion Ultracentrifugation

1 kg of enriched Uranium (3.5%)8kg of natural Uranium (0.7%)

7 kg of depleted uranium(0.25%)


1. Enriched UF6 isconverted to uranium dioxide (UO2) andpressed into small pellets fritted at1700C

2. These ceramic pellets are inserted into thintubes, of a zirconium alloy (zircalloy) to form fuel rods

3. The rods are thensealed and assembled in clusters to form fuel assemblies

Fuel fabrication

Assemblage FRAMATOME


Nuclear reactor


Coal power plant in Gardanne (France)

Nuclear power plant (LWR)

What is the difference between a nuclearor a thermal power plant ?


Electricity

Steam Production

The major come of the way heat is produced to make steam.

Nuclear Reactor Heat Production


Dismantling

Solid waste

Reprocessing

Gaseous release(about 100 times less radioactivity

than a coal-fired plant of equivalent power ! ).

< 100 m3 per year of LLWILW and HLW

More than 99% of the activity generated is

confined in the spent fuel

A nuclear reactor releases extremely small amounts of radioactivity into the environment


What Nuclear material is produced in the reactor ? Nuclear fission : A slow-moving

neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons.

Nuclear captureFor instance uranium-238 can capture a neutron, transforms into uranium-239, which transform into plutonium-239by 2 disintegrations

Produce Fission Products , the main ultimum waste from nuclear energy

Produce Plutonium , and some minor actinides that can beconsider as waste or as resources !


SPENT NUCLEAR FUEL

After 4 years in the reactor, spent fuel contains:

94% uranium

1% plutonium

5% other(Fission products and minor actinides)

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1

H2

He3

Li4

Be5

B6

C7

N8

O9

F10

Ne11

Na12

Mg13

Al14

Si15

P16

S17

Cl18

A19

K20

Ca21

Sc22

Ti23

V24

Cr25

Mn26

Fe27

Co28

Ni29

Cu30

Zn31

Ga32

Ge33

As34

Se35

Br36

Kr37

Rb38

Sr39

Y40

Zr41

Nb42

Mo43

Tc44

Ru45

Rh46

Pd47

Ag48

Cd49

In50

Sn51

Sb52

Te53

I54

Xe55

Cs56

Ba Ln72

Hf73

Ta74

W75

Re76

Os77

Ir78

Pt79

Au80

Hg81

Tl82

Pb83

Bi84

Po85

At86

Rn87

Fr88

Ra An104

Rf105

Db106

Sg107

Bh108

Hs109

Mt110

Uun

LANTHANIDES

57

La58

Ce59

Pr60

Nd61

Pm62

Sm63

Eu64

Gd65

Tb66

Dy67

Ho68

Er69

Tm70

Yb71

Lu

ACTINIDES

89

Ac90

Th91

Pa92

U93

Np94

Pu95

Am96

Cm97

Bk98

Cf99

Es100

Fm101

Md102

No103

Lr

URANIUM AND TRANSURANIC ELEMENTS ACTIVATION PRODUCTS

FISSION PRODUCTS FISSION AND ACTIVATION PRODUCTS

URANIUM ET LMENTS TRANSURANIENS

PRODUITS DE FISSION

PRODUITS DACTIVATION

PRODUITS DE FISSION et DACTIVATION

Elements formed in the spent fuel (burn-up 33 GWj/t)U : 955 kg.t-1Pu : 9.6 kg.t-1AM : 0.8 kg.t-1PF : 34 kg.t-1


The Spent Fuel is store in a pool a few yearbefore processing

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Spent fuel is reprocessed in the La Hague plants

UP2: EDF fuel: 800 t/year UP3: Foreign fuel: 800 t/year


Main Main stepssteps in in reprocessingreprocessing nuclearnuclear fuelfuel

Cutting the fuel assemblies

Disolving the fuel in nitric acid

Liquide / liquide extraction by TBP .

Uranium et Plutonium recovered at 99,9 % !

dissolveurroue

godets La Hague

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Reprocessed Uranium

The 235U content ofreprocessed uranium is about the same as natural uranium.

One part is recycledin some nuclearplants

One part is storedas stratgic stock waiting to be used in fast breeder reactor


The recovered plutonium is recycled in MOX fuel

MOX fuel is a mixture of plutonium oxide and depleted uranium oxide

The MELOX plant at Marcoule

Recycling saves about 10% of the natural uranium

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Nuclear Waste conditionning


Fission products solution vitrification :a 50 years story !

The first part of the story is solidification:from a dispersible liquid to an inert solid

First processes developed in France (1957), England and USA were batch processes

The first industrial process (AVM) started in Marcoule (France) on 1978 Glass pouring in AVM

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Why to vitrify the waste ?

9 Atomic scale containment (not a coating)9 Chemical flexibility9 Stability, Durability (leachingresistance)

Na

OSiAl

B

Zr

The mission : Create a new material with a waste

99 Volume reduction9 Organic destruction


Complexity of fission products solutionsfrom LWR reprocessing

SrZrMoRuPmAgTb

SbCsLaPrNdGdSn

RbY

NbTcPdEuInDy

SeTeBaCeRhSmCd

Fission Products = 42.33 g/l

PNiCrNaFe

Corrosion products and additives =27.33 g/l

CmPuAmNpUActinides = 3.37 g/l

SbSnPdTcRhUMoRu

Metallic Alloys = 4.69 g/l

more than 40 different chemical elements !

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Ability to accomodate the wasteSolubility (Cr, Ru, Rh, Pd, Ce, Pu, SO4, Cl)

Phase separation (Mo, SO4, Cl, P)Devitrification (Mo, P, F, Mg, )

Maximize the waste loading

Process / Technology

Elaborate a glass from waste is a compromiseHow to formulate a HLW glass

Formulation

Ease of processingMelting temperature

Viscosity, reactivity, residence time, Electrical cond., thermal cond.

Additives needed

Glass performanceProperties for storage/disposal

Thermal stabilityChemical durability

Resistance to self irradiationMechanical properties


GLASS FORMULATION MUST BETAILORED TO EACH APPLICATION

12.7 incl.U3O8 : 0.85.0 incl.

ThO2 : 3.6U3O8 : 0.62.8 incl.

U3O8 : 2.35.4ZnO : 2.5Remainder20.01.32.11ZrO2

520.55.70.3P2O571.05.114.915FP2O3 + Act

RussiaMayak

USAUKFranceR7/T7Oxide

10.712.010.94Fe2O3 + NiO + Cr2O3157.46.018.65Al2O3

0.20.74CaO

2513.28.011.98.510Na2O

10.412.90.917.214B2O31.68.73.14.02Li2O + K2O

50.341.055.347.045SiO2

HanfordAZ blendWVDPDWPF

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NaO

SiB

Al

Zr

HLW-Glass formulation The goal Solubilisation of all radionuclides in an ionic and covalent network by chemical reactions at the molten state

Glass formulation = a mix of calculations and experimental measurements of the basic properties to find the best compromise between contradictory properties : Homogeneity, Viscosity Electrical resistivity Thermal conductivity Devitrification sensitivity Melting temperature,Tg, Tl, Chemical durability, R0, Rf,

The design of an operational glass domain (for the industrial scale) is based on a statistical design approach implemented at the lab scale and checked at scale one on large pilots.


The R7T7 glass developed in France for LWR waste

Nominal Composition

SpecifiedInterval

Mass (%)min max

SiO 2 45,1 42,4 51,7B 2 O 3 13,9 12,4 16,5Al 2 O 3 4,9 3,6 6,6Na 2 O 9,8 8,1 11,0CaO 4,0 3,5 4,8

Fe 2 O 3 2,9

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Vitrification Principle

Glass Frit45% SiO218% B2O315% Na2O

Etc.

Objectif = Verre Final 45% SiO214% B2O310% Na2O15% Ox. (PF+Act.)

Etc.

Verre Final 45% SiO214% B2O310% Na2O15% Ox. (PF+Act.)

FUSION

Calcinat15% Ox. (PF+Act.)

Solution

Calcination


HT melting = RN solubilisation in a ionic and covalent network by chemical reactions at the molten state

Glass Frit Calcine

Impregnation of the Calcine

Partial dissolutionLocal saturation

Crystal precipitation

Agitation

Dilution

Crystal dissolution

Homogenization of the molten liquid

GLASS

REE silicates

(Si, Ca, Nd, La, Ce)

(Ce,Zr)O2

Spinelles (Fe, Ni, Cr, Mn)

RuO2

Pd

Chemical reactivity during melting

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Two-step calciner / hot crucible vitrification process

The French Vitrification process

Dust scrubberGlass melter

Container

Calciner

Liquid waste

Additives

Glass frit

Recycling


Hot cells vitrification lines

La Hague Vitrification Plants

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Thermal Power

~ 2 kw

Glass Volume150 litres

Glass Mass400 kg

Height1,3 m

Diameter0,43 m

The Glass Container

Internationallyapproved


stockage chaud

chemine 100C

air ambiant 25C

110C 45C

40C

La Hague Glass interim storage( air cooling )

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Vitrified wasteforms are currently stored at the production site

La HagueMarcoule

Total number of glass containers produced in France > 13000 (18 000 t spent fuel)


Cold Crucible Induction Melter Technology

The Near Term Future of Radwaste VitrificationIncreasing waste loading

Increasing glass throughputsNew matrix (glass-ceramics)

Higher Temprature, Corrosives glass compositions

Cold Cap

Molten glass

CCIM

Cold glasslayer

Inductor

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Cold Crucible in Operation


Waste+

Glassprecursor

OxygenOxygen

CathodeAnode

Burned gases exhaust

HF Current

MoltenglassInductor

PlasmaMetallicCooled

walls

The Emerging processes :Plasma combustion & Vitrification

This process is a novel combination of two innovative technologies:

VITRIFICATION:

Glass melting by direct induction in a metal cold crucible

COMBUSTION:

Oxygen arc plasma transferred between two aerial torches above the molten glass.

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The EMERGING PROCESSES :PLASMA COMBUSTION & VITRIFICATION

Three Operations in one Apparatus :

Combustion/incineration.

Vitrification.

Gas postcombustion.

Waste

Gastreatment

Glass

Ar/O2 Ar/O2


The three main waste conditionningprocesses

1. Vitrification of Fission product solution

2. Compaction of cladding wastes (Hulls)

3. Cimentation oftechnological waste

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Cladding waste is compacted


Most technological waste is LLW suitable for surface disposalSome ILW is placed in interim storage at the production sites

Technological wastes are cemented

Homogeneous liquid or powdered wasteHeterogeneous solid waste

1088

974

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Ultimate reprocessing waste forms Ultimate reprocessing waste forms

The fission product solution, which also contains the minor actinides and about 0.1% U and Pu, is vitrified

The hulls and end pieces are rinsed and then compacted

Technological waste is grouted in cement

Today, the volume of reprocessing waste produced each year by a 1 GWe reactor is:

2.5 m3 HLW (glass) 5 m3 ILW (mainly compacted hulls) 12 m3 LLW (cemented)


Classification of solid nuclear waste in FranceNuclear waste are sorted over the period and the activity

C - WasteInterim storageHigh Activity (HLW)

B - waste :Interim storage Interim

storageIntermediate level

waste (ILW)

Stockage ddi ltude pour les dchets

radifres et graphitesA - Waste1Dedicated surface

disposal ( Soulaine )

Low Activity (LLW)

Mine residues1Dedicated surface disposal (Morvilliers)Very low activity

(VLLW)

Longue Live Priode > 30 ans

Short live Period < 30 ans

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Type vol% ActivityCumulative volume

(m3) until 2020

LLW 95%

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Calendar :

2015 : safety assessment deposit for a geological disposal site

2020 : starting a prototype reactor for transmutation

2025 : industrial opening of underground disposal

HLW and ILW DisposalIn France geological disposal is retained as reference solution

for the management of long life waste (ILW and HLW) ( french policy act n 2006-739 of June 29 ,2006)


An underground laboratory was built at at Bure (Northern France),at a depth of 500 m in a clay formation

The clay layer investigated here has favorable properties for radioactive waste containment:

- highly stable for the last 150 million years, unfractured- very low permeability- transport of chemical elements controlled by diffusion at an extremely low rate

Underground laboratory

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Final conclusions

We know what to do with nuclear waste !

High tech processes have been developed and optimized for each waste category

Vitrification of PF solution is a major step in this process They are available today at affordable cost for society This cost is taken into account in the price per kWh

and EDF has already constituted reserves French and international studies have demonstrated

that with suitable processing the environmental impact of nuclear waste will remain negligible, even over the long term

The CEAs considerable research potential ensures that further progress will be made in the futur.

Documents

Nuclear waste and Vitrification. Estremoz 2007.pdf