ABSTRACT
When the high-level waste containments were designed and constructed, it was not anticipated that these structures would be required to remain in service for so long. As part of the BNL study, a systematic assessment of potential degradation of the materials was performed. So far, the waste has breached about one-third of the
containments and leaked to the soil or the annular space. Most of them are single shell structures. The common cause is stress-corrosion cracking of carbon steel containments that were not heat treated after welding for relieving stress. Cracks were observed along welds in these structures. No cracking or leakage has been detected in stress-relieved containments. General corrosion is less than one mil per year except for certain containments storing zeolite wastes where the rate could be as high as 5 mils per year. Pitting corrosion could occur but has not been observed so far. Neither have any other forms of metal degradation been observed nor are they expected to occur in the steel containments (Reference 10). Adding nitrites to the waste seems to inhibit both pitting and stress corrosion cracking.
