Analysis of Copper Specimens and Microbial Activity in Saturated Gap-fillMX-80 Bentonite Under Pressure

Abstract

The Canadian plan for the long-term management of used nuclear fuel is to dispose of the fuel in a deep geological repository (DGR) which utilizes a multiple barrier system (MBS). Two components of the MBS are a copper-coated carbon steel container and bentonite clay which will surround the containers deep underground. Bentonite clay will inhibit microbially influenced corrosion on waste containersin addition torestricting the transport of groundwater and corrosive agents to, or corrosion products away from, the containers. To replicate the conditions possible in the DGR, we will fill stainless steel pressure cells with compacted bentonite clay with embedded copper coupons. The pressure cells will then be sealed and pressurized with an aqueous solution, providing an in-situ experiment to monitor the swelling properties, moisture content, and water activity in the bentonite clay; the corrosion response of the copper and the nature of corrosion products formed; and the types and behaviours of any microorganisms present. The bentonite clay will be analysed using 16s rRNA analysis to determine which microbes are present within the clay, and the copper samples will be analysed using various surface analytical methods. Through these experiments we intend to determine the minimum dry density of compacted bentonite needed to prevent microbially induced corrosion on the used nuclear fuel container in the DGR.