cea-03665940
https://cea.hal.science/cea-03665940
doi:10.3390/thermo2010003
[CEA] CEA - Commissariat à l'énergie atomique
[ENAC] Ecole Nationale de l'Aviation Civile
[OPENAIRE] OpenAIRE
[LM2N] Laboratoire des matériaux mésoscopiques et nanométriques
[DEN] Direction des énergies
[CEA-UPSAY] CEA - Université Paris-Saclay
[UNIV-PARIS-SACLAY] Université Paris-Saclay
[OPTIM] ENAC | Equipe de recherche Optimisation
[DEN-SACLAY] DES Saclay
[SORBONNE-UNIVERSITE] Sorbonne Université
[UNIVERSITE-PARIS-SACLAY] Université Paris-Saclay
[SU-TI] Sorbonne Université - Texte Intégral
[GS-ENGINEERING] Graduate School Sciences de l'Ingénierie et des Systèmes
[ALLIANCE-SU] Alliance Sorbonne Université
[MAP-CEA] MAP-contributeur
Thermodynamic modelling of the uranium-tellurium system. Estimation of the uncertainties by a Bayesian approach.
Gueneau, Christine
Lawrence, Eva
Klein, Thierry
Gamboa, Fabrice
[PHYS.PHYS.PHYS-DATA-AN] Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an]
ART
Under irradiation, the formation of fission products in the (U,Pu)O2 fuel with time has asubstantial effect on its chemistry. In particular, migration of the most volatile fission products (Cs,Te, I, Mo) from the center to the periphery of the fuel pellet is induced by the large radial thermalgradient. To predict the thermodynamic properties of the irradiated fuel, thermodynamic modelingof the complex multi-component (Cs-I-Te-Mo) (U-Pu) O system is performed using the CALPHADmethod. In this work, the thermodynamic assessment of the U Te sub-system is performed. Theliterature review reveals a lack of experimental data as well as scattering and inconsistency of someof the data. In particular, no thermodynamic data exist on the liquid. From this review, inputthermodynamic and phase diagram data are carefully selected. The Gibbs energy functions are thenadjusted by fitting these data. An overall good agreement is obtained with all the selected dataexcept for the enthalpy of formation for UTe which is underestimated by 13% by our model. Thiscould be due to an inconsistency between the enthalpy of formation and vapor pressure data. Ina second step, the uncertainties on the thermodynamic parameters and their propagation on thecalculated thermodynamic and phase diagram data are estimated using a Bayesian approach. Theanalysis shows that there are too many parameters (22) for too few data points (120 points). Theuncertainties are thus large on some of the calculated data. Moreover the inconsistency of someof the data and the lack of thermodynamic data for the liquid makes the model uncertain. Newexperimental data such as heat capacity, enthalpy of formation for the compounds, and chemicalpotentials or activities for the liquid phase would improve the reliability of our model. Measurementsof phase diagram data in the U UTe2 region are also required. However this work provides thefirst detailed uncertainty analysis of the U Te CALPHAD model. Moreover our approach, contraryto other Bayesian methods, provides an analytical posterior probability distribution and analyticalcredible intervals for the calculated thermodynamic quantities. It also speeds up the simulation ofthe uncertainty estimations on the phase diagram
2022
en
Thermo
MDPI