recent progress in the synthesis and characterization of uranium carbide compounds. scr/csm,...
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![Page 1: Recent progress in the synthesis and characterization of uranium carbide compounds. SCR/CSM, Université de Rennes1, UMR CNRS 6226 Institut de Physique](https://reader035.vdocuments.site/reader035/viewer/2022070410/56649ea75503460f94ba974d/html5/thumbnails/1.jpg)
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
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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
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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 routes
B- sintering of carbides
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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 ,..)
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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
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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.
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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.
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Synthesis of uranium monocarbide
Arc-melting :
U + n Cg UCn n = 1
T > 2600°CEasy to meltHigh purity of the product ReproducibleFast (20 min)Ingots of 0.5 – 3g
Need to be grinded
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Rietveld analysis of a samples with nominal composition UC1.02
Detection limit below 1 wt % of a secondary phase, UC2.
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SEM observations of a UC IngotSEM observations :
- Dense materials, - Low porosity- Well crystallized sample : brittlee & easy to grind
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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
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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)
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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
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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)
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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: -0.7680
Surface 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.
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Natural sintering of UC Pellets
0 10 20 30 40 50 60 70
800
1000
1200
1400
1600
1800
Time (min.)T
em
pe
ratu
re (
°C)
0
4
8
12
16
20
0 20 40 601700
1725
1750
1775
1800
Tem
per
atu
re (
°C)
Time (min.)
Frittage au four HF d'une pastille de UC (UC1)
Po
we
r (%)
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
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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
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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%
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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
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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 materialSynthesis by carbothermic reduction Sintering of UC pellets
Sintering of uranium carbides great challenge
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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