The effect of oxide film on the corrosion of nuclear waste disposal copper canisters

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Kemian tekniikan korkeakoulu | Master's thesis
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Date

2023-01-24

Department

Major/Subject

Funtional Materials for Global Challenges

Mcode

CHEM3061

Degree programme

Master's Programme in Advanced Materials for Innovation and Sustainability

Language

en

Pages

71

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Abstract

Finnish nuclear power plants use copper canisters to store spent nuclear underground and keep it isolated from the environment. The corrosion performance of copper canisters has been constantly reviewed and evaluated in previous studies to ensure its functionality during its lifetime of 10000 years. This thesis focuses on the protective effect of the oxide layer on the copper surface in the first few years after deposition and examines how environmental factors affect the corrosion rate of copper. The experiments were conducted in synthetic ground water and pore water under air and nitrogen bubbling at three different temperatures. The non-oxidized samples and samples with heavy oxidation at 100°C at 7 days were used to compare the effect of oxide film. Linear Polarization Resistance method is used to monitor the corrosion rate. The results of the monitoring show that 1) The general corrosion rate reaches steady-state after few weeks and ranges from less than 1 µm/year to 20 µm/year in all tests; 2) Corrosion rate is observed to be dependent on pH, temperature and dissolved oxygen (DO) although the significance varies. The effect of the air-formed oxide film is quantified by comparing the corrosion rates of non-oxidized and oxidized samples in the same environment. The analysis indicates that the oxide film does not provide additional corrosion protection or accelerate corrosion rates. On the other hand, the passive film formed during immersion is probably more effective as a corrosion inhibitor and requires further studies

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Supervisor

Lundström, Mari

Thesis advisor

Aromaa, Jari

Keywords

corrosion, copper, LPR, nuclear waste

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https://urn.fi/URN:NBN:fi:aalto-202301291696

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[dipl] Kemian tekniikan korkeakoulu / CHEM