A new method to evaluate the elution and corrosion properties of stainless materials in subcritical and supercritical water

To understand the elution properties as well as corrosion properties of stainless materials in subcritical and supercritical water is of great importance for verifying the sustainability of core materials in supercritical water cooled reactors (SCWR), and also for evaluation of a risk of increasing out-of-core radiation fields and worker dose. Although the elution properties under general reactor's conditions (below 300degC) have been intensively investigated, those above 300degC are still not recognized well. Thus, in order to investigate the elution properties at supercritical condition, a new supercritical water loop system combined with an elution detection system was developed. The approach is that, radioactive specimen (SUS304) with a known radioactivity was used as sample, and set at an autoclave vessel. By measuring gamma-ray emitted from the eluted products collected at an ion-exchange resin in outlet of the autoclave, which contains 60Co coming from radioactive SUS304 material, the amount of the elution can be quantified. In this work, following development and installation of the system, it was evaluated the elution properties of the stainless steel at elevated temperatures from 300degC up to 550degC, furthermore, at different oxidizing water chemistry conditions (dissolved O2 concentrations from < 10 ppb to 200 ppb and/or 400 ppb). (author)