Inner fuel element corrosion of steels CHS68 and EK164 at fast power reactor on basis of uranium dioxide
The austenitic chromium-nickel steel EK164 is perspective material of the fast nuclear reactor rod cladding. The physical-chemical compatibility of this steel with typical pellet uranium dioxide nuclear fuel is important aspect for rod efficiency. The post reactor investigations of the combined rod assembling were carried out after peak burn-up 9,1 % FIFA and damage dose 77,3 dpa. There were rod claddings on basis of CHS68 and EK164 cold-worked steels to compose that assembling. The gamma-scanning, electrical-potential scanning and optical metallography methods was applied. The perilous regions of rod corrosion strengthening are high-temperature parts. This fact was previously established on basis of gamma-scanning and electrical-potential method data. The comparative analysis of the inner fuel rod corrosion for steel CHS68 and steel EK164 was carry out along core region height. The inner corrosion depth of steel CHS68 under contact with fuel has not exceeded 15 mm at the maximum power flux area by temperature below 540 °C. The same rod corrosion of steel EK164 has come to 10 mm at the core region centre. The maximum of corrosion damage both steels has detected at the range from 600 to 650 °C. It is amount less than 20 mm by means of both frontal and intercrystalline corrosion type. Essential differences of corrosion mechanism both steels haven’t disclosed. The fact of local intension corrosion was detected near the fuel pellet joints and places of fission fragment caesium accumulation. Contrariwise the corrosion of EK164 steel was minimum within narrow gap between cladding and fuel where the caesium is absent. The peak cladding thinning of examined fuel rods have formed less than 5 % of initial thickness under fuel burn-up 9 % FIFA.
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