Effect of bacterial biofilm on corrosion of galvanically coupled aluminum and stainless steel alloys under conditions simulating wet storage of spentnuclear fuel

Galvanic corrosion is a concern during wet storage of spent nuclear fuels w hen aluminum alloys used as cladding for nuclear fuel rods become coupled t o stainless steel alloys used as materials for construction of fuel rod han gers and containment equipment. A larger galvanic current density was obser ved between coupled UNS A96061 and UNS S30400 electrodes submerged in as-re ceived makeup water from a spent nuclear fuel wet storage facility compared to control couples submerged in autoclave-sterilized makeup water. The dif ferences were attributed to the development of a discontinuous bacterial bi ofilm on the couples submerged in as-received makeup water, which was not e vident on the control couples that contained several orders of magnitude lo wer densities of bacteria. While pitting corrosion was observed on the UNS A96061 electrodes containing high or low densities of bacteria, maximum pit depth on the electrodes with high bacterial densities was twice that measu red on electrodes with low bacterial densities.