European Project “Supercritical Water Reactor Fuel Qualification Testâ€‌: Summary of General Corrosion Tests

Abstract

The main target of the EUROATOM FP7 project “Fuel Qualification Test for SCWRâ€‌ is to make significant progress toward the design, analysis, and licensing of a fuel assembly cooled with supercritical water in a research reactor. The program of dedicated Work Package (WP4)Prequalification was focused on evaluation of general corrosion resistance of three preselected austenitic stainless steels, 08Cr18Ni10Ti, AISI 347H, and AISI 316L, which should be prequalified for application as a cladding material for fuel qualification tests in supercritical water. Therefore, the experiments in support of WP4 concentrated on 2000hr corrosion exposures in 25MPa supercritical water (SCW) at two different temperatures 550آ°C and 500آ°C dosed with both 150 and 2000آ ppb of dissolved oxygen content. Moreover, the water chemistry effect was investigated by conducting tests in 550آ°C SCW with 1.5آ ppm of dissolved hydrogen content. At first, corrosion coupons were exposed for 600, 1400, and 2000آ hrs in Joint Research CentreInstitute for Energy and Transport (JRCIET), VTT Technical Research Centre of Finland Ltd. (VTT), and Shanghai Jiao Tong University (SJTU) autoclaves connected to the recirculation loop, allowing continual water chemistry control during the test. The following examination of exposed specimens consisted of weightchange calculations and detailed macroand microscopic investigation of oxide layers using scanning electron microscope (SEM) and energydispersive Xray spectroscopy (EDX). With respect to general corrosion results, all tested steels showed sufficient corrosion resistance in SCW conditions taking into account the conditions foreseen for future fuel qualification test in the research reactor in CVR Rez. When the results of weightchange calculations were compared for all three materials, it was found that the corrosion resistance increased in the following order: 316L<347H<08Cr18Ni10Ti. Results obtained in hydrogen water chemistry (HWC) did not indicate any significant beneficial effect compared to tests in SCW with 150 or 2000آ ppb dissolved oxygen content. Additional tests were dedicated to investigation of the surfacefinish effect. In these exposures, polished, sandblasted, and planemilled surfacefinish techniques were investigated. The beneficial effect of surface cold work in particular of sandblasting was clearly demonstrated.