Electro-chemically active elements, such as excess oxygen, dissolved in the coolant stream can cause inter-granular stress corrosion cracking (IGSCC) in the reactor vessel and piping systems. This can result in additional outage time and increased costs for reactor internal replacements or repairs. The initiation of IGSCC can be mitigated by both injecting hydrogen to neutralize the free oxygen and by monitoring the electrochemical corrosion potential (ECP) in various locations.
GE recommends that BWRs use detectors that accurately monitor ECP when hydrogen injection is turned off, as well as when hydrogen is being injected. At present, many plants utilize a system that can monitor data from two different types of probes:
- An iron/ iron oxide ECP probe for measurements without hydrogen injection
- A platinum ECP probe for measurements during hydrogen injection
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