Fission Products chemistry in simulated PWR fuel up to 2100°C: Experimental characterization and Thermodynamic modeling with the TAF-ID

Ernesto Geiger1

C. Guéneau2, M.H.A. Piro1, E.C Corcoran3

1Faculty of Energy Systems and Nuclear Science, Ontario Tech University, Oshawa, ON, L1G 0C5, Canada;

2C. Guéneau: Université Paris-Saclay, CEA, Service de la Corrosion et du Comportement des Matériaux dans leur Environnement, Gif-sur-Yvette, 91191, France;

3E.C Corcoran: Department of Chemistry and Chemical Engineering, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario, K7K 7B4, Canada.


The chemical state of Fission Products (FP) has important implications on the nuclear fuel performance during irradiation (FP affect the conductivity, melting point, swelling, creep, etc. of the nuclear fuel) and on the response of the reactor during off-normal conditions (FP interact with the fuel and its cladding/coatings, neutron absorbers, steel, concrete, etc.). The chemical state of FP affects their potential release in accident scenarios as well. The accurate prediction of FP chemistry and their interactions with the nuclear fuel and structural materials is one of the objectives for the development of the Thermodynamic of Advanced Fuels – International Database (TAF ID). As part the TAF-ID validation process, four Simfuel samples (UO2 doped with 11 FP: Ba, Ce, La, Mo, Nd, Pd, Rh, Ru, Sr, Y, and Zr) that are representative of PWR fuel irradiated up to 76 GWd.tU-1 were submitted to 1327°C under oxidizing conditions, and 1800, 2000, and 2100°C under reducing conditions. These samples were characterized by HR XRD and XAS, both using synchrotron radiation, and EPMA, which allowed determining the composition, crystal structure, and ratio of the different secondary phases. TAF-ID calculations have accurately reproduced experimental observations such as: (i) the dissolution of lanthanoids (La, Ce, Nd) in the UO2 matrix both in reducing and oxidizing conditions; (ii) the equilibrium between different Mo oxidation states (Mo0, Mo4+) giving place to the simultaneous presence of metallic (e.g., β-Mo) and oxide (e.g., MoO2, (Ba,Sr)(Mo,U,Zr)O3) phases in oxidizing conditions; (iii) the composition and evolution of metallic phases bearing Mo-Pd-Rh-Ru and U-Ru (e.g., the URu intermetallic) in reducing conditions; and (iv) the composition and evolution of ZrO2-UO2 solid solutions and interactions in the Ba-Sr-Zr-U system, also in reducing conditions. These results highlight the capabilities of the TAF-ID for predicting the behaviour of the FP-Nuclear Fuel system in a broad range of experimental conditions.

Event Timeslots (1)

Wednesday – 15th September 2021
Ernesto Geiger