Effect of Flow Conditions on the Deposition of Platinum Nanoparticles on Stainless Steel Surfaces

Stress corrosion cracking of stainless steel components in boiling water reactors can threaten their structural integrity and lead to costly maintenance operations. A low electrochemical corrosion potential can reduce the susceptibility of stainless steel to stress corrosion cracking. Injecting hydrogen into the reactor feed water lowers the ECP. The efficiency of hydrogen injection is improved in presence of catalytically active noble metals. Therefore, platinum (Pt) compounds are added to the reactor feed water and then deposit on the water-wetted surfaces. To understand the parameters affecting the application and mitigation processes, stainless steel coupons in as-received or pre-oxidized conditions were exposed in a high-temperature water loop to simulated boiling water reactor water conditions with the addition of platinum. Coupons were placed at three locations: in an autoclave with quasi-stagnant flow conditions (few mm/s), in a specimen holder with a flow velocity of 0.10 m/s, and in another with a flow velocity of 0.52 m/s. Independently of parameters such as platinum injection rate or water chemistry, coupons exposed to a transitional flow regime showed a lower platinum loading than the coupons exposed to a turbulent flow or suspended in the autoclave under quasi-stagnant flow.