Evaluation of Effectiveness of Hydrogen Water Chemistry for Different Types of Boiling Water Reactors

Abstract

Short period tests of hydrogen water chemistry (HWC) were carried out at Tsuruga-1 and Tokai-2 Nuclear Power Plants. The effects of HWC at Tsuruga-1, a non-jet pump plant, are larger than those at Tokai-2, a jet pump plant; this is caused by the much higher recombination rate of hydrogen and oxygen at the downcomer region under suitable gamma ray irradiation for the former. The effective oxygen concentrations ([O₂]_eff=[O₂] + 1/2[H₂O₂]) in water measured at the reactor pressure vessel bottom are suppressed by HWC as effectively as those concentrations at the recirculating lines in both plants.

The effects of HWC in both plants were analyzed and compared with literature data on HWC to evaluate the differences in the effectiveness of HWC as caused by reactor type. From the evaluation, it was concluded that the effectiveness of HWC is much more affected by the power density in the core and the average dose rate at the downcomer than by the reactor type itself. The authors propose an evaluation concept for HWC effectiveness. This is the recombination factor, which is defined as a function of dose rate factor at the downcomer.

KEYWORDS:

• hydrogen water chemistry
• corrosive circumstance
• stress corrosion cracking
• BWR type reactors
• electrochemical corrosion potential