The HWC fuel surveillance of a BWR-6 NPP in Taiwan

The hydrogen water chemistry in BWRs is used to reduce the electrochemical corrosion potential of stainless steel and other components and mitigate the IGSCC cracking rate. It was first implemented in 1990s. The hydrogen addition was considered in 2000 and started since 2006 for both BWRs in Taiwan. There are a total of 6 fuel inspection campaigns in the BWR-6 NPP and the first two were accomplished with the LUA Surveillance Program prior to hydrogen addition. The working scope includes on-site visual examinations, oxide thickness measurements, crud sampling and hot cell analyzing on the 10x10 fuel assemblies. This paper focuses on the visual inspection and oxide thickness measurement experience and results. Examination data from fuel assemblies exposed to up to four 18-month cycles HWC operation and ∼46 GWd/MTU burnup have been obtained after completion of this program. The results indicate no accelerated corrosion or severe nodular corrosion on fuel cladding, Zirconium components and channels after hydrogen addition. Oxide measurements made before and after HWC agree with this observation. Fuel assemblies and their components retained their integrity. The crud layer deposited on the fuel rod surface seems uniform and still exhibits orange-reddish color. In conclusion, no detrimental effect resulting from the hydrogen addition in the coolant has been found and no impediment exists to continue the HWC operation at BWR-6 NPP in Taiwan. (author)