Dependency of hydrogen water chemistry (H\VC) effectiveness on plant specifications and operational conditions has been studied for an empirical interpretation. The H\VC effectiveness was calculated exactly by employing a water radiolysis model requiring results of complex fiow analysis and dose distribution analysis as input, in addition to the plant specifications. It was found that decrease of oxygen concentration in the reactor water in the reactor recirculation system could be taken as an exponential function of H2 concentration added to the reactor water. Thus, the recombination factor p which was the coefficient of hydrogen concentration in the exponent could represent the recombination efficiency in the downcomer region. The p corresponded to the apparent reaction rate constant of the recombination reaction of H202 with H2, which included radical concentrations produced by irradiation, multiplied by the residence time in the downcomer. The dose rate index 'f of each plant was introduced as a measure of downcomer dose rate. Since the recombination efficiency was known to depend on the downcomer dose rate, functional dependence of p on ')' was found to be linear. The HWC effectiveness at the reactor pressure vessel bottom region could also be evaluated using p.
In order to determine. the effects of hydrogen peroxide on electrochemical corrosion potential (ECP) of type 304 stainless steel (SUS304), ECPs were measured using a high temperature, high pressure water loop with polytetrafluoroethylene (PTFE) inner liner at controlled hydrogen peroxide concentration. It is observed that the ECP of SUS304 exposed to hydrogen peroxide is higher than that when exposed to oxygen at the same oxidant concentration. The ECP shows a hysteresis pattern for its concentration dependency. Those results were attributed mainly from the chemical form of oxide film on stainless steel specimens. The oxide film was affected by the corrosive circumstances. Hematite (a-Fe203) was observed for the specimens exposed to hydrogen peroxide, while Fe304 was a main oxide when exposed to oxygen. The difference of the anodic polarization curves between 02 and H202 environments was caused by the difference of the stability between a-Fe203 and Fe304. Since the a-Fe20 3 is reduced to the Fe 2 + when hydrogen is added to water, the ECP decreases with decreasing oxidant concentration without showing the hysteresis that keep the ECP higher value.
Dependency of hydrogen water chemistry (H\VC) effectiveness on plant specifications and operational conditions has been studied for an empirical interpretation. The H\VC effectiveness was calculated exactly by employing a water radiolysis model requiring results of complex fiow analysis and dose distribution analysis as input, in addition to the plant specifications. It was found that decrease of oxygen concentration in the reactor water in the reactor recirculation system could be taken as an exponential function of H2 concentration added to the reactor water. Thus, the recombination factor p which was the coefficient of hydrogen concentration in the exponent could represent the recombination efficiency in the downcomer region. The p corresponded to the apparent reaction rate constant of the recombination reaction of H202 with H2, which included radical concentrations produced by irradiation, multiplied by the residence time in the downcomer. The dose rate index 'f of each plant was introduced as a measure of downcomer dose rate. Since the recombination efficiency was known to depend on the downcomer dose rate, functional dependence of p on ')' was found to be linear. The HWC effectiveness at the reactor pressure vessel bottom region could also be evaluated using p.
In order to determine. the effects of hydrogen peroxide on electrochemical corrosion potential (ECP) of type 304 stainless steel (SUS304), ECPs were measured using a high temperature, high pressure water loop with polytetrafluoroethylene (PTFE) inner liner at controlled hydrogen peroxide concentration. It is observed that the ECP of SUS304 exposed to hydrogen peroxide is higher than that when exposed to oxygen at the same oxidant concentration. The ECP shows a hysteresis pattern for its concentration dependency. Those results were attributed mainly from the chemical form of oxide film on stainless steel specimens. The oxide film was affected by the corrosive circumstances. Hematite (a-Fe203) was observed for the specimens exposed to hydrogen peroxide, while Fe304 was a main oxide when exposed to oxygen. The difference of the anodic polarization curves between 02 and H202 environments was caused by the difference of the stability between a-Fe203 and Fe304. Since the a-Fe20 3 is reduced to the Fe 2 + when hydrogen is added to water, the ECP decreases with decreasing oxidant concentration without showing the hysteresis that keep the ECP higher value.
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