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Recent progress in the synthesis and characterization of uranium carbide compounds. SCR/CSM, Université de Rennes1, UMR CNRS 6226 Institut de Physique Nucléaire, IPN-Orsay, Université Paris-Sud 11. . 40 ieme Journées des Actinides 2 nd Workshop an Actinide Targets. - PowerPoint PPT Presentation
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Recent progress in the synthesis and characterization
of uranium carbide compounds.SCR/CSM, Université de Rennes1, UMR CNRS 6226
Institut de Physique Nucléaire, IPN-Orsay, Université Paris-Sud 11.
40ieme Journées des Actinides 2nd Workshop an Actinide Targets
Genève, 27mars -01 avril
Recent progress efforts on the synthesis and characterization sintering
of uranium monocarbide compounds.SCR/CSM, Université de Rennes1, UMR CNRS 6226
Institut de Physique Nucléaire, IPN-Orsay, Université Paris-Sud 11.
40ieme Journées des Actinides 2nd Workshop an Actinide Targets
Genève, 27mars -01 avril
Outline :
Part I : Objective of the studyA- Frame of the work (GFR-He, ISOL-target) B – Aim the study
Part II : Synthesis of uranium monocarbide.A – Overview on the binary phases diagram U-C B – Melting of U and C using an arc furnaceC – Carbothermal reduction at high temperature
Part III : Sintering of dense UC pellets.A- Natural sintering B- Hot pressing of powder.
Part IV : Conclusions and future workA- Synthetic routesB- sintering of carbides
Gen-IV : Gas-Fast Neutron Reactors (Allegro)
(U, Pu, MA*)C/ SiC-SiCf
•WORKING CONDITIONS : GFR-He concept-T°: - working conditions : 500-1000°C
- incidental / accidental conditions : 1600 -2000°C for one hour, without melting
-η : - fast neutrons , fluence 1.1027 η/m2, - Cycle - 3 years
•ASSEMBLY : Needle-likeSTRUCTRAL & MATRIX MATERIALS : SiC-based meterials LINER M : W, (W-Re) alloysFUEL : (U, Pu)C solid solution, with insertion of MA*
- atomic ratio of the composition : U : Pu : MA* of 80-85 : 10-15 : 0-5.
- compromise between high densification and porosity * Minor actinides : Np, Am, Cm
Needle-like assembly
Liner : M
Improve the performance of reactors and fuel cycles with current nuclear system (security , resources sustainability , reprocessing ,..)
Targets for Isotope Separation On Line (ISOL) facilities
ISOL target of 3rd generation (SPIRAL2)INCIDENT BEAM : - Energetic light (deutons) or heavy ions or
thermal neutrons - Properly focusedREACTIONS : - spallation, fission or fragmentation mechanisms EJECTION FROM THE TARGET :- ionized, accelerated, purified WORKING CONDITIONS- T° # 2000°C under high vacuum- heavy irradiationTARGET- composition : UCx
Mixed UC / UC2 or UC2 + nC.
- Compromise between density and open porosity
Working temperature, T = 2000°C
Production of rare-isotope beams for nuclear physics
Pellets are pilled up in a graphite container
New generations of nuclear systemsGen IV – GFR-He reactors & ISOL facilities
CHALLENGES : Comprehensive study
Advanced materials working under extreme conditions (T°, η, D+, … long-time.)
Stability / Evolution (Fuel or Target) under working conditions microstructure of the pellets : grain sizes, morphology
porosity,distribution of the porosity
Identify the main parameters which controlled the microstructure of UC pellets.Prospective works on :
- synthetic routes, - microstructural parameters of the powder, - sintering mechanisms.
Binary phase diagram of U-C
UC : - congruent melting compound T°f # 2530°C
- solid solution UC-UC2 at high T°- line compound at low T°- NaCl type of structure, a =
4.9510(3)
R. Benz, C.G. Hoffmann, G.N. Rupert, High Temp. Science, 1 (1969) 342.
Synthesis of uranium monocarbide
Arc-melting :
U + n Cg UCn n = 1T > 2600°C Easy to melt
High purity of the product ReproducibleFast (20 min)Ingots of 0.5 – 3g
Need to be grinded
Rietveld analysis of a samples with nominal composition UC1.02
Detection limit below 1 wt % of a secondary phase, UC2.
SEM observations of a UC IngotSEM observations :
- Dense materials, - Low porosity- Well crystallized sample : brittlee & easy to grind
Distribution of the grain size
De 0.375à 2000Nombres 100Moyenne: 1.594Médiane: 1.443D(3,2): 7.068Moyenne/Médiane: 1.105Mode: 1.204Intervalle à 95%: 0.544Intervalle à 95%: 4.671Ecart-type: 1.731Variance: 2.995C.V.: 0Skewness: 1.083Kurtosis: 1.498Surface spécifique m2.g-1 (BET) 2.4
Grinded UC ingots
Carbothermal reduction of uranium oxideReactions (1450 < T < 1900°C):
UO2 + 3 C UC + 2 CO ↑
- Reduction of U3O8 under H2 flux- Control of the stoichiometry of oxygen
!Experimental procedure :
UO2 + nC pellets ( 8, 10) Cgraphite crucible n = 2, 2.5, 3, 3.5, 4, 4.5
1450 - 1900°C (0.5- 6 hours)
300°C/h
High temperature furnace with C graphite resistor
Influence of : Temperatureinitial composition (n)
Carbothermal reduction of uranium oxide
- single phase of UC
n = 3
T = 1700°C for 3h
No significant diffrence on the XRD powder patterns between the arc-melting method and the carboreduction one
Arc-melted sample
T = 1900°C for 1h
SEM observations of a UC compact
x 100 x 1000 x 5000
Large cavities :
gas released
Grain sizes [1-5] µm
UO2 + 3C UCT = 1700°C, t = 3h
Synthesis and sintering in one step impossible (mechanical properties)
Size of the UC particules
!
De 0.375à 2000Nombres 100Moyenne: 10.7800Médiane: 12.3600D(3,2): 6.6040Moyenne/Médiane: 0.8720Mode: 34.5800Intervalle à 95%: 1.6410Intervalle à 95%: 70.7700Ecart-type: 2.6120Variance: 6.8240C.V.: 0Skewness: -0.4480Kurtosis: -0.7680Surface spécifique m2.g-1 (BET) 2.5
No significant diffrence on the grain size and specific area of the powders obtained by arc-melting and by carboreduction.
Natural sintering of UC Pellets
0 10 20 30 40 50 60 70800
1000
1200
1400
1600
1800
Time (min.)Te
mpe
ratu
re (°
C)
0
4
8
12
16
20
0 20 40 601700
1725
1750
1775
1800
Tem
pera
ture
(°C)
Time (min.)
Frittage au four HF d'une pastille de UC (UC1)
Power (%
)
Sintering in a H.F. furnace
7,5
5,85,5
7,5
V = 0.2496 cm² d measured = 10.26 g/cm3d calculated = 13,68 g/ cm3C = 75,0%
Pellet n° 2 : cold pressing 5 tonnes/ cm²
Densification about 75 % is a reproducible value over several experiments
1500 < T < 1900°C
SEM observations of a UC sintered pellet
x 200 x 500
x 5000
Large cavities :
Small single crystals # 50 µm
T Solid state diffusion favor the grain growth
T = 1900°C, 1 h
Hot press sintering of UC Pellets
Sintering in a H.P. furnace Mold of Cgraphite
Sintering conditions : 1500 °C for 2 h under rough vacuum with 80 MPa.
Raw surface
Æ= 10,3 mmh = 3,6 mm
Densification ~ 85%
SEM observations of a H.P UC pellet
x 200 x 2000
Black area : cavitiesGrain size about 5 µm
x 5000
Lamellar morphology - free carbon - UC2
Conclusion
- Preparation of single phase UC powders : NaCl type, a = 4.951(2) Å, [0-5]µm,
- arc-melting, n = 1,- carbothermic reduction, (T = 1700°C, n = 3, t =3h)
- Sintering : competition between grain growth / porosity- Temperature favors the grain growth only - Pressure may help to limit the growth of the grain
methodic procedures not easy task, refractory material
Synthesis by carbothermic reduction Sintering of UC pellets
Sintering of uranium carbides great challenge
Acknowlodgements
GROUPEMENT DE RECHERCHECNRS – CEA/DEN -EDF - ANDRA
R. ELOIRDIF. de BRUYCKERS. MORELD. MANARAE. COLINEAU
B. FOURESTN. DACHEUX
Merci de votre attention et de votre patience !
GROUPEMENT DE RECHERCHECEA CNRS EDF AREVA-NP AREVA-NC
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