On the role of plutonium under the dissolution of 304 ULC stainless steel in plutonium nitrate solutions

Corrosion performance of type 304 ULC stainless steel in plutonium nitrate solution was experimentally studied. Corrosion rate of 304 ULC stainless steel was accelerated by co-existent plutonium in nitric acid solution. It is caused by trans-passive dissolution based on the shift of corrosion potential to the noble position. It is thought that potential shift is caused by increase of the cathodic current on the 304 ULC surface due to the reduction of Pu(VI) to Pu(IV). It is suggested that the Pu(IV) which is reduced on 304 ULC surface would be re-oxidated to Pu(VI) by HNO3 at bulk in the solution. Redox potentials of Pu(VI)/Pu(IV) and HNO3/HNO2 which are introduced by calculation from thermodynamic data support the possibility that reaction at high temperature.