Optimization of Dissolved Hydrogen Concentration for Control of Primary Coolant Radiolysis in Pressurized Water Reactors

Abstract

Optimization of the dissolved hydrogen concentration in primary coolant of pressurized water reactors has several potential advantages in material integrity and dose reduction. To assess the threshold value of dissolved hydrogen for reducing condition, in-pile loop experiments and radiolysis model calculations were performed. Both experiments and model calculations indicate that the threshold value of dissolved hydrogen for radiolysis is much less than the present control level in pressurized water reactors, and the in-core region is more easily affected by reduced dissolved hydrogen level than the out-of-core region. The measurement of electrochemical corrosion potential of structural material, while varying dissolved hydrogen levels, is desirable in the future to compensate for the uncertainty of the model calculation. For this purpose, electrochemical corrosion potential of stainless steel at the top-of-core, in which the reference electrode could be inserted, was estimated based on the correlation between the experiments and the modeling for the loop.