Long Term Corrosion Study of Waste Package Candidate Material for the YMP; Initial Results

摘要

Preliminary results of waste package candidate materials from the long term corrosion study are reported. The results are focused on three corrosion-allowance materials, two carbon steels and one low alloy steel. The steel samples have been exposed to two aqueous solutions, "simulated dilute water" (SDW), "simulated concentrated water" (SCW), the atmospheres above the waters (vapor phase), and at the waterlines. The solution pH values are in the range of 9-10 (bicarbonate) and the solution temperatures are at 60 ℃ and 90 ℃. In similar conditions, corrosion rate of same type specimens is slightly worse at 90 ℃ than at 60 ℃, except in-water specimens in SCW. Specimens having the worst corrosion are those in the atmosphere above SCWrn(～200μm/yr at 90 ℃). This is due to the higher vapor phase concentration of CO_2, that comes from the bicarbonate ion decomposition in SCW. The in-water specimens at 90 ℃rnin the SCW solution are the least corroded (12 μm/yr). The passivation by the higher concentration of anions and lower concentration of dissolved oxygen in SCW are the plausible reasons.