Effect of neptunium ions on corrosion of ultra low carbon type 304 stainless steel in nitric acid solution

Kato, Chiaki   ; Motooka, Takafumi; Numata, Masami; Endo, Shinya; Yamamoto, Masahiro 

Corrosion of a nuclear fuel reprocessing plant is also important problem in either current or an advanced nuclear fuel reprocessing system. In this process, nitric acid solution is used to dissolve spent nuclear fuels and solvent extraction method is used to separate U, Pu and actinoid elements. It will be much severer corrosive environment. In this paper, an effect of neptunium ions on corrosion of ultra low carbon Type 304 stainless steel was investigated. The corrosion tests were conducted in 9 kmol/m nitric acid solution adding neptunium ions. The results show that neptunium ions promote inter-grainier corrosion of SUS304ULC in nitric acid solution and corrosion rate in heat-transfer condition is larger than that in immersed condition. It is estimated that the oxidise potential of nitric ions increases under heat-transfer condition more than immersion condition in boiling solution. Furthermore, the effect of -ray irradiation used Co is examined. -ray irradiation decreases corrosion rates and the reason is discussed.