Y. Wada et al., Empirical understanding of the dependency of hydrogen water chemistry effectiveness on BWR designs, J NUC SCI T, 36(2), 1999, pp. 169-178
Dependency of hydrogen water chemistry (HWC) effectiveness on plant specifi
cations and operational conditions has been studied for an empirical interp
retation. The HWC effectiveness was calculated exactly by employing a water
radiolysis model requiring results of complex flow analysis and dose distr
ibution analysis as input; in addition to the plant specifications. It was
found that decrease of oxygen concentration in the reactor water in the rea
ctor recirculation system could be taken as an exponential function of H-2
concentration added to the reactor water. Thus, the recombination factor rh
o which was the coefficient of hydrogen concentration in the exponent could
represent the recombination efficiency in the downcomer region. The rho co
rresponded to the apparent reaction rate constant of the recombination reac
tion of H2O2 with H-2, which included radical concentrations produced by ir
radiation, multiplied by the residence time in the downcomer. The dose rate
index gamma of each plant was introduced as a measure of downcomer dose ra
te. Since the recombination efficiency was known to depend on the downcomer
dose rate, functional dependence of rho on gamma was found to be linear. T
he HWC effectiveness at the reactor pressure vessel bottom region could als
o be evaluated using rho.