The Chemical stability of AlO FCCI barrier on oxide fuel pin of sodium fast reactor

Sasaki, Koei   

(Introduction) Candidate materials of fuel cladding for Gen-IV sodium fast reactor require to develop resistance to fuel cladding chemical interaction (FCCI) for future enhancement of burn-ups (20at.%). In this work, we propose a preventive technique of FCCI in oxide fuel pins by AlO film coating on fuel cladding inner surface as a FCCI barrier. It has been reported that fission product (FP) corrosions including Cesium, Cesium-Tellurium and Iodine corrosion, play an important role in FCCI behavior based on in-pile and out-pile test results. The AlO film coating on the cladding material surface is able to work as FCCI barrier to protect the corrosive FP elements due to the high chemical stability. (Experiment) In this work, a thin AlO film was experimentally formed on a Fe-12Cr-5Al ternary alloy during heat treatment in controlled atmosphere G = -870-550 kJ/mol at 1173 K for 30 hours. A transmission electron microscope (TEM) image and energy dispersive X-ray (EDX) mapping images of the formed AlO film are shown in Fig.1. Examinations of Cesium, Cesium-Tellurium and Iodine corrosion were performed on the AlO film in order to evaluate its chemical stability. *Cesium/Cesium-Tellurium corrosion test. The AlO coated specimen was immersed in Cesium or Cesium-Tellurium mixture in analumina crucible and was heated at 923 K for 10 or 100 hours in controlled atmosphere G = -420 kJ/mol. *Iodine corrosion test Iodine corrosion test was briefly carried out at 923 K for 10 or 100 hours in an enclosed quartstube containing the specimen and pure iodine chips. (Result) Scanning electron microscope observations and EDX analyses of the specimens after the corrosion tests showed that the corrosions of each corrosive FP element were prevented by the AlO coating on the specimens.