Effects of hydrogen water chemistry on chemical decontamination in boiling water reactors (BWR)

The oxide film that forms on the wetted surfaces of BWR process piping during normal plant operation varies widely depending on the plants method of operation and water chemistry. Early metal oxide films were primarily iron-nickel based oxides which were easily removed with the standard decontamination processes of LOMITM, CITROXTM or CANDEREMTM. With the onset of hydrogen water chemistry (HWC) and zinc injection, process piping films proved to be more tenacious and resistant to the decontamination processes. Recent enhancements to the decontamination process application as well as new process solvents have mitigated the effects of HWC and zinc injection. By applying multiple acidic permanganate steps in conjunction with the standard processes and using improved techniques for solvent destruction, chrome rich films can be overcome with minimal increase in resin wastes. The changes to the decontamination processes will be analyzed and compared with results from recent process applications. (author)