Corrosion investigations on zircaloy-4 and titanium dissolver materials for MOX fuel dissolution in concentrated nitric acid containing fluoride ions

• Published in: Journal of nuclear materials 2016-05, Vol.473, p.157-166
• Main Authors: Jayaraj, J., Krishnaveni, P., Krishna, D. Nanda Gopala, Mallika, C., Mudali, U. Kamachi
• Format: Article
• Language: English
• Subjects: Boiling; Complexing ions; Corrosion rate; Dissolution; Dissolvers; Fluoride; Fluorides; Nitric acid; Passivation; Titanium; Titanium dioxide; Zircaloy; Zirconium; Zirconium dioxide
• ISSN: 0022-3115; 1873-4820; 1873-4820
• DOI: 10.1016/j.jnucmat.2016.02.018

Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better dissolver material than Zr-4 for extended service life in boiling 11.5 M HNO3+0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the metal and imparting high corrosion resistance. •Zr-4 and CP-Ti exhibited high corrosion rate in boiling fluorinated nitric acid.•Corrosion rate decreased in fluorinated nitric acid containing ZrO(NO3)2 and Al(NO3)3.•High inhibiting efficiency is exhibited by 0.15 M ZrO(NO3)2 when compared to Al(NO3)3.•Corrosion rates of CP-Ti were negligible in complexed fluorinated nitric acid.•XPS analysis on CP-Ti confirmed the presence of TiO2 and absence of fluoride.