The effect of conditioning by permanganate on the dissolution behavior of stellite particles in organic complexing acid medium

Radioactive hotspots found either in the primary heat transport circuit or auxiliary circuits of nuclear reactors are mainly due to particles containing activated cobalt. The main source of these particles are stellite alloys that are rich in cobalt and are used in primary cooling circuits in valves, pumps, etc. Due to either mechanical erosion or erosion coupled with corrosion under flow conditions (known as tribocorrosion), these stellite particles are released into the system. They are then activated by neutron absorption in the reactor core before being deposited on out-of-core surfaces, causing radiation exposure problems. In this paper, the possibility of dissolving stellite particles by using an oxidation–complexation process has been explored. Permanganate based reagents were evaluated for their efficiency in conditioning the stellite particles for their dissolution with organic acids. Permanganic acid was found to be the superior conditioning agent. Two alloys of stellite, viz. stellites #3 and #6, were studied with respect to their dissolution behavior.