Durability of Online NobleChem™ During Impurity Transients in Boiling Water Reactors

Abstract

Online NobleChem™ (OLNC) applies platinum (Pt) particles on reactor vessel internal and piping surfaces periodically during power operation to catalyze the reaction of hydrogen and oxidants at surfaces to mitigate intergranular stress corrosion cracking (IGSCC). A BWR Water Chemistry Guidelines open issue was the impact of severe chemistry transients on deposited Pt.

To address this issue, a EPRI BWR Vessel and Internals Project (BWRVIP) laboratory test program evaluated the effects of chemical transients on the durability of Pt applied on pre-oxidized 304 SS specimens. Chloride and sulfate ions are known to accelerate environmentally assisted cracking of this material, and can occur from intrusions of ion exchange resins or other organic substances, sea water, river or lake water, etc. Phase 1 testing evaluated the durability of the deposited Pt after brief ultrasonication, or two days in 288°C water with 2 ppm O₂ containing 20 ppm chloride, 20 ppm sulfate, or pure water. Phase 2 added 13 ppm nitrate to the chloride and sulfate environments. Specimens were analyzed before and after exposures for Pt mass loading and imaged using high resolution Field Emission - Scanning Electron Microscopy (FE-SEM). Results show good durability of Pt deposits after exposure to simulated chemistry transients.