Corrosion phenomenon of stainless steel in boiling nitric acid solution using large-scale mock-up of reduced pressurized evaporator

Ueno, Fumiyoshi  ; Kato, Chiaki   ; Motooka, Takafumi; Ichikawa, Shiro*; Yamamoto, Masahiro 

For purpose of life prediction of components in spent nuclear fuel reprocessing plants, corrosion test was performed about 36,000 hours using a large scale mock-up test apparatus of a reduced pressurized thermosiphon evaporator, and a corrosion mechanism of heat transfer tube made of an ultra-low carbon type 304 stainless steel in boiling nitric acid solution was studied. As the results, the tendencies of increases of amount of corrosion and corrosion rate were saturated when intergranular penetration and grain dropping occurred in turn. This result means that a linear estimation can be applied to the life prediction for corrosion. No difference in morphologies of intergranular corrosion existed among three portions could find even though amounts of corrosion were different. The amount of corrosion was dominated by tube surface temperature and heat flux. And the largest amount of corrosion could be seen at boiling starting portion and the top where indicated highest values of tube surface temperatures.