Swelling behavior of Cr16Ni19 steel under neutron irradiation: experimental and theoretical analysis

Abstract

This paper investigates the swelling behavior of Cr16Ni19 austenitic steel used for fuel cladding in the BN-600 reactor. Experimental investigations were conducted over doses of 0.3–48.5 dpa and temperatures of 370–410 °C using high-resolution electron microscopy, which revealed the formation of helium-vacancy bubbles (∼1.5 nm, 1–3·10²² m⁻³) and, at doses above 5 dpa, voids exceeding 10 nm in diameter. Dislocation density measurements ranged from (3.4–5)· 10¹⁴ m⁻², increasing to 7·10¹⁴ m⁻² at lower irradiation temperatures. A kinetic swelling model was then parameterized using these data, along with high-dose measurements (>50 dpa), to predict swelling behavior and compare it with that of AISI 316 steel. The model suggests that Cr16Ni19 steel exhibits enhanced swelling resistance due to a stable dislocation network and a higher concentration of interstitial clusters, likely influenced by its silicon content. Conventional approximation methods were found to underestimate the fuel element's remaining service life, highlighting the need for predictive models that incorporate real time microstructural data.