Spontaneous growth of protective oxide layer for novel Al–Gd thermal neutron absorption alloys in simulated spent nuclear fuel pool water

Novel Al-Gd thermal neutron absorbing alloys were developed to meet the demands of light weight and corrosion resistance in spent nuclear fuel wet storage. The oxide formation behavior was systematically investigated in simulated spent nuclear fuel pool water. Two parabolic stages of weight gain were identified, and the growth gradually stabilized after 3,000 h. In the early stage of immersion, micro-galvanic corrosion occurred at the low-potential Al 3 Gd particles, releasing Gd 3+ and Al 3+ ions. The Gd 3+ ions preferentially reacted with oxygen to form a Gd 2 O 3 layer on particle surfaces, whereas Al 3+ ions hydrolyzed to Al(OH) 3 , migrated through the aqueous medium, and dehydrated to nanostructured Al 2 O 3 on the matrix. With increasing immersion time, diffusion resistance suppressed further Gd 2 O 3 growth, while Al 2 O 3 gradually developed into a continuous layer that covered the Gd 2 O 3 . These findings indicate that the Al-Gd alloys can spontaneously form a protective oxide layer with excellent corrosion resistance, making them promising candidates for long-term application in the wet storage of spent nuclear fuel.