OXIDATION OF MATERIALS FOR NUCLEAR WASTE CONTAINERS UNDER LONG TERM DISPOSAL

摘要

Low alloyed steels or carbon steels are considered as candidate materials for the fabrication of some nuclear waste package containers for intermediate storage. Dry oxidation is one possible degradation mode of such container materials staying typically in the 323 K-573 K temperature range. As the containers being required to remain retrievable for about a 100-year period, the understanding of the corrosion attack is the key point to guarantee the retrieval of the waste package in good safety and economical conditions. The estimation of the metal thickness loss by oxidation requires the development of models based upon short-time experimental data for predicting long term container performance. As only few data are available in the literature on dry oxidation of the materials under consideration over periods longer than a few hours in this temperature range, iron and low alloy steel oxidation tests in air with different water contents have been performed. The oxidation kinetics obtained at 573 K up to 700 hours were extended to a 100-year period for the two materials under consideration, showing a low oxide layer thickness (less than 150 mu m). It seems that dry oxidation under the tested reference conditions could lead to a very limited container damage. Nevertheless, the basis of these calculations has to be reinforced by a more mechanistic approach. Variation of water content in the tested conditions does not produce a large increase of the oxide layer thickness.