Corrosion research on rock bolts and steel sets for sub-surface reinforcement of the Yucca Mountain Repository

Underground nuclear waste storage repositories generally use steels and super alloys for various structural members and storage containers. These materials are susceptible to corrosion due to seepage of water. We studied rock bolt materials for reinforcing tunnels and containment materials for storing nuclear waste materials. In general, the design of underground support materials for tunnels are mainly based on mechanical behavior of the materials, but not much was known about the interaction of the seepage YM waters with the structural members under various conditions in the tunnels. The sources of water in the Yucca Mountain (YM) repository are due to rain fall (~5%), perched and pore waters associated with the tunnel that contain various levels of chlorides, nitrate, sulfate, silicates and bicarbonates. The temperature of the tunnel is expected to increase initially and subsequently decreases after closure of the YM repository due to nuclear waste radioactive decay. Our tests for corrosion were under 100C to obtain a wide range of data at different temperatures and electrolyte concentrations. The rock bolts are generally embedded 10 to 12 feet deep inside the host-rock of the tunnel and water seepage through the rock pores creates an interface between the bolt material and water making it conducive to aqueous corrosion. The issues related to corrosion of the rock bolts and other structural materials are: (1) variation in the temperature of the tunnel over the years, (2) concentration of the ions present in the YM waters, (3) combination of temperature and detrimental anions that cause structural damage