Corrosion Characteristics of Studsvik R2 Al-Alloy by Hydrogen Evolution Under Simulated Repository Conditions
Paper in proceeding, 2025
Large quantities of low and intermediate level radioactive waste are produced by the dismantling of
nuclear reactors. It must be kept confined to ensure safety for extended time scales. To ensure this, the
waste can be encapsulated in concrete which makes the interim storage and repository conditions alkaline
(pH > 12). This is advantageous for some heavy-element radionuclides because it fosters their
precipitation. For reactive metals and their corrosion characteristics, however, it can be problematic. The
Swedish Studsvik R2 nuclear research reactor build contained an AlMg3.5 alloy similar to Al 5154 for its
core internals and the reactor tank. The corrosion of aluminum at alkaline conditions is known to start at
exorbitant high levels and then decrease very rapidly due to the formation of a protective oxide layer on
the surface of the sample. The formation of corrosion products leads to a potential volume expansion
which is accompanied by the evolution of hydrogen gas and the following pressure build-up. Both can
lead to cracks in the concrete which creates possible pathways for radionuclides. Unirradiated rod-shaped
samples were cut from a reference sample originating from the manufacture of the reactor vessel. Samples
were embedded in regular Portland cement concrete with an elevated water/cement ratio of 0.7 to ensure
the availability of water throughout the experiment due to increased pore water content. The embedded
samples were put into overpressure bottles alongside pressure, humidity & temperature sensors.
Corrosion rates were calculated from the evolving hydrogen pressure inside the bottle. Samples of the
same geometry, from pure aluminum (99.95 %) were also used as references. The R2 alloy had an initial
corrosion rate of 564 (± 180) µm during the first two weeks and then decreased to 434 (± 178) µm/y after
one month. The reference material had a corrosion rate of 1622 (± 283) µm/y during the first two weeks
and decreased to 606 (± 222) µm/y after one month which suggests a trend of the R2 alloy corroding
slower than pure aluminum.
nuclear reactors. It must be kept confined to ensure safety for extended time scales. To ensure this, the
waste can be encapsulated in concrete which makes the interim storage and repository conditions alkaline
(pH > 12). This is advantageous for some heavy-element radionuclides because it fosters their
precipitation. For reactive metals and their corrosion characteristics, however, it can be problematic. The
Swedish Studsvik R2 nuclear research reactor build contained an AlMg3.5 alloy similar to Al 5154 for its
core internals and the reactor tank. The corrosion of aluminum at alkaline conditions is known to start at
exorbitant high levels and then decrease very rapidly due to the formation of a protective oxide layer on
the surface of the sample. The formation of corrosion products leads to a potential volume expansion
which is accompanied by the evolution of hydrogen gas and the following pressure build-up. Both can
lead to cracks in the concrete which creates possible pathways for radionuclides. Unirradiated rod-shaped
samples were cut from a reference sample originating from the manufacture of the reactor vessel. Samples
were embedded in regular Portland cement concrete with an elevated water/cement ratio of 0.7 to ensure
the availability of water throughout the experiment due to increased pore water content. The embedded
samples were put into overpressure bottles alongside pressure, humidity & temperature sensors.
Corrosion rates were calculated from the evolving hydrogen pressure inside the bottle. Samples of the
same geometry, from pure aluminum (99.95 %) were also used as references. The R2 alloy had an initial
corrosion rate of 564 (± 180) µm during the first two weeks and then decreased to 434 (± 178) µm/y after
one month. The reference material had a corrosion rate of 1622 (± 283) µm/y during the first two weeks
and decreased to 606 (± 222) µm/y after one month which suggests a trend of the R2 alloy corroding
slower than pure aluminum.
Author
Marvin Schobel
Nuclear Chemistry and Industrial Materials Recycling
Christian Ekberg
Chalmers, Chemistry and Chemical Engineering, Energy and Material
Teodora Retegan Vollmer
Nuclear Chemistry and Industrial Materials Recycling
Anders Puranen
Chalmers, Chemistry and Chemical Engineering, Energy and Material
Waste Management Symposia
Waste Management Symposia
Phoenix, Arizona, USA,
Phoenix, Arizona, USA,
Areas of Advance
Energy
Subject Categories (SSIF 2025)
Surface- and Corrosion Engineering