Work

Evaluation of long-term exposure of 310S and 800H under conditions of SCW-SMR

Year: 2025

Type: article

Abstract: Austenitic stainless steel 310S and Alloy 800H are considered promising candidates for fuel cladding in Small Modular Reactors cooled by Supercritical Water (SCW-SMR) due to their high corrosion resistance and favourable mechanical properties. To evaluate their long-term behaviour in supercritical water (SCW) environments, full-length tube samples were exposed to supercritical water at 500 °C, 25 MPa, and 150 ppb dissolved oxygen for up to 10,000 hours. Weight gain measurements revealed a decelerating oxidation rate over time, with low cumulative mass increases indicative of excellent corrosion resistance. Conservative extrapolation suggests that the wall penetration depth is projected to remain below 5 µm after 30,000 hours for both alloys, supporting the expectation of long-term structural integrity. Surface roughness measurements corroborated these trends: 310S showed a gradual increase from 0.18 µm (as-received) to 0.29 µm after 10,000 hours, whereas 800H exhibited minimal change, attributed to its initially higher surface roughness. Post-exposure characterization by SEM-EDS and TEM confirmed the formation of compact, chromium-rich oxide layers (Cr₂O₃) on both materials, with underlying Cr-depleted zones. Microstructural analysis revealed that 310S developed thicker oxide layer with larger grains and Cr-Ni-rich phases, whereas 800H exhibited finer oxide grains in a thinner layer, with occasional localized corrosion - nodules These differences underscore the role of alloy composition in oxidation behaviour under SCW conditions. Overall, both 310S and 800H demonstrate excellent oxidation resistance and microstructural stability, reinforcing their applicability as fuel cladding materials in SCW-SMR designs.

Source: Nuclear Engineering and Design

DOI: 10.1016/j.nucengdes.2025.114691

Authors: Daniela Marušáková, Jan Vít, Monika Šípová, Marek Vronka

Institutions: Research Centre Rez, FZU - Institute of Physics of the Czech Academy of Sciences

Language: English

Topic: Nuclear Materials and Properties

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: hybrid

Estimated APC paid: $2,710