Applications des techniques d'analyse de surface XPS/ LEIS / ToF-SIMS

National audienc

X-ray Photoelectron Spectroscopy Surface analysis technique

National audienc

Surface analysis techniques XPS / LEIS / ToF-SIMS

National audienc

Phases et sites actifs, intermédiaires réactionnels et espèces adsorbées en catalyse sur particules métalliques (analyses spectroscopiques in situ)

Une combinaison de techniques d'analyse in situ (XPS, IR et Raman) a permis de caractériser la nature de la phase active et des espèces adsorbées sur des catalyseurs à base de Pd au cours de la décomposition de NO et de sa réduction par CO. L'étude XPS montre des variations de l'état chimique du Pd, variant du Pd métallique à plusieurs formes de Pd oxydé en fonction des atmosphères et températures réactionnelles. Cette évolution de la phase active est confirmée par spectroscopie Raman de résonance qui permet la caractérisation directe de l'oxyde PdO. Différentes espèces adsorbées sur Pd0 (NOads,COads,Nads, nitro-nitrito, nitrito et nitro) et sur alumine (nitrite, nitrate et carbonate) ont été caractérisées. L'ensemble des données spectroscopiques est discuté au regard des performances catalytiques afin d'aboutir à une meilleure compréhension des mécanismes réactionnels en catalyse de post-combustion automobile. Enfin, l'oxydation de CH4 a été étudiée par spectroscopie Raman operando.LILLE1-BU (590092102) / SudocSudocFranceF

Assessment of medium-term radioactive releases in case of a severe nuclear accident on a Pressurized Water Reactor: experimental study of fission products re-vaporisation from deposits (Cs, I)

International audienc

Investigation of perovskite-based model three-way catalysts using surface analysis techniques – XPS/LEIS/ToF-SIMS

National audienc

Influence of SIC control rod material on the iodine release in case of nuclear severe accident – Chemical reactivity with fission products in thermal conditions of RCS

International audienceThe effect of Silver-Indium-Cadmiun (SIC) control rod on the transport of volatile fission products (I, Cs,Mo) in conditions of a Reactor Coolant System under NPP severe accident was investigated within threesemi-integral tests in a thermal gradient tube. The experiments addressed separately the effect of eachSIC element. Nature of transported and deposited species was investigated by ICP MS, ESEM-EDX,Raman Microspectrometry, XRD and XPS techniques.For the first time, numerous metallic molybdates involving SIC components were evidenced. The formationof such metallic molybdates competes with the formation of Cs-molybdate and may in certainconditions strongly reduce the scavenging effect of Mo towards Cs. As a result the nature of transportediodine can be strongly modified, compared to chemical systems involving only Mo, Cs and I. The dataobtained are useful to guide what species have to be added in the thermodynamic database used inthe SA simulation software

Combined ToF-SIMS and XPS characterization of 304L surface after interaction with caesium iodide under PWR severe accident conditions

International audienceIn case of a severe accident (SA) occurring in a pressurized water reactor (PWR) fission products (Cs, I) are released from the degraded fuel and transported through the reactor coolant system (RCS). A part is deposited onto surfaces of the RCS and can be subsequently chemically re-mobilized, in case the atmosphere composition changes. In order to improve our understanding on the re-mobilization processes, it is important to describe the interactions between deposited fission products and surfaces representative of RCS in SA conditions (mainly oxidized SS 304L) and to identify the species formed after remobilization. In this study CsI aerosols were deposited on the surface of 304L coupons, which have been previously oxidized. The deposits were afterwards reheated (up to 750 degrees C) in either air or steam. At every step, the 304L coupons were analysed by a combination of surface analysis techniques (XPS, ToF-SIMS), Raman spectroscopy and SEM. It has been established that the initial surface state of the 304L coupons (i.e. oxidation in air or steam) has no effect on the release of caesium or iodine. However, the composition of the carrier gas during the re-heating phase influences significantly the release of caesium. Specifically, in air a significant amount of Cs remains on the coupon and forms mixed oxides with chromium, such as Cs2CrO4 and Cs2Cr2O7. The results are then discussed and compared with literature data

Reversible Mobility of Bulk Species in Perovskite Based Three Way Catalysis by Operando/in situ Analyses

International audienc

Investigation of perovskite-based model three-way catalysts using surface analysis techniques – XPS / LEIS / ToF-SIMS

International audienc