Study Of Aging And Lifetime For The Epoxy Coatings In Nuclear Power Plant

The organic coatings used in the reactor building of nuclear powerplant protect not only the structure metal from the oxidation and radiation,but also the sealing performance and metal separator and walls from thecorrosion of the radioactive particles during LOCA. Therefore a goodanti-oxidation, good adhesion, radiation absorption and the goodmechanical properties should be possessed by the coating in NPP. Theordinary conditions are50℃with the amount of radiation0.1Gy/h,while during the accident conditions the temperature maybe rise to150℃with a large number of radiation particles. So during the service of thenuclear power plant, the coatings will suffer the aging of oxidation andradiation, which maybe makes the coatings lose their safe functionsduring the accident conditions. For the moment organic coatings, such asepoxy resins, polyurethanes, rubber resins and phenolic resins, are largelyused in the nuclear power plant, due to their antioxidant properties. InChina and abroad the study of the aging and the degradation of epoxyhave been implemented for years, but also there are a lot of questions forthe mechanism of aging and degradation aspects. Additionally, the study on the lifetime of coatings was not conducted in depth.This dissertation conducted a study on the mechanism of oxidationand lifetime of the epoxy coatings, by the experimental simulation of theinternal environment in nuclear power plants, including the oxidativeaging and the radiant aging.The results of the experiments on the MMS system and the3D crosslinking system showed the same properties under the oxidation and theradiant aging. Amide and acid were detected as the main products amongthe three materials during the processes of oxidation. The results of theInfrared Spectroscopy and the Gel permeation chromatography showedthat the amide may be produced by the oxidative degradation, while thecarboxylic acid may be the result of the cut of crosslinking.The main oxidative products, carboxylic acid and amide, were alsofound by the analysis corresponding the industrial application. During theoxidation, three different systems reflected the same property.The modulus of Young and the elongation at break are two mainphysical characters of the epoxy coatings. The increase of the modulus ofYoung and the decrease of the elongation at break were found due to thedevelopment of oxidation. The performance of three systems was similar.Comparing the concentration of acid and the elongation at break, aproportional relation was found between them. The lifetime of epoxytherefore could be predicted by setting the threshold of lost functionality of epoxy coatings.