Evaluation of effectiveness of hydrogen water chemistry for different types of boiling water reactors

Short period tests of hydrogen water chemistry (HWC) were carried out at Ts uruga-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; t his 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 ( [O-2]eff =[O-2] + 1/2 [H2O2]) in wa ter measured at the reactor pressure vessel bottom are suppressed by HWC as effectively as those concentrations at the recirculating lines in both pla nts. The effects of HWC in both plants were analyzed and compared with literatur e data on HWC to evaluate the differences in the effectiveness of HWC as ca used by reactor type. From the evaluation, it was concluded that the effect iveness of HWC is much more affected by the power density in the core and t he average dose rate at the downcomer than by the reactor type itself. The authors propose an evaluation concept for HWC effectiveness. This is the re combination factor, which is defined as a function of dose rate factor at t he downcomer.