An in-depth four-year investigation into corrosion of carbon steel materials in the secondary cooling piping of the 30 MW RSG GAS research reactor

• G.R. Sunaryo¹, M.I. Santoso², R. Kusumastuti³, D.S. Wisnubroto⁴ and Sriyono¹

¹ Research and Technology Center for Nuclear Reactor, Research Organization for Nuclear Energy, ORTN-BRIN, South Tangerang, Indonesia
² Sekolah Tinggi Teknik Nuklir, Yogyakarta, Indonesia
³ Research Organization for Nanotechnology and Material, ORNM-BRIN, South Tangerang, Indonesia
⁴ Research and Technology Center for Radioactive Waste and Fuel Cycle Research Center,ORTN-BRIN, South Tangerang, Indonesia

Abstract: An observational study examined carbon steel’s performance in PUSPIPTEK tap water, used as raw water for the RSG GAS secondary cooling system. Disc-shaped coupons (5 cm diameter) categorized into three series explored uniform, galvanic, and crevice corrosion processes using carbon steel and Stainless Steel 304. Coupons were immersed continuously for four years in a flow-controlled holding pond. Various methods for observing the water quality and material surface, including visual photography, microscopy, and X-ray diffractometry (XRD), were employed. Analysis revealed sulfate and calcium ions within Safety Analysis Report (SAR) limits for secondary cooling water, while chloride ions and water hardness exceeded allowable levels. pH and water conductivity remained acceptable. Carbon steel exhibited a corrosion rate of 1.19·10^–4 m per year. Visual inspection showed diverse corrosion product colors, while microscopy revealed distinct surface degradation, especially pitting. XRD detected compounds, such as FeCl₃, Fe₃O₄, Fe₂(SO₄)₃, Fe₂O₃, FeSO₄, FeCl₂, FeS, Fe(OH)₃, and FeO, indicating oxidation-reduction reactions. The corrosion process was sustained due to extended immersion and altered the metal surface structure, particularly at grain boundaries. Pitting corrosion occurred in crevices and galvanic circuits, with the uniform coupon circuit severely corroded. This underscores the necessity for corrosion inhibitors in RSG GAS secondary cooling water systems.

Keywords: corrosion, PUSPIPTEK water, carbon steel, surveillance corrosion, RSG-GAS 30MW

Int. J. Corros. Scale Inhib., 2024, 13, no. 2, 853-873
doi: 10.17675/2305-6894-2024-13-2-10

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