Artículo
Diffusion of H in Zircaloy-2 and Zr-2.5%Nb rolled plates between 250 °C and 350 °C by off-situ neutron imaging experiments
Santisteban, Javier Roberto
; Buitrago Montañez, Nayibe Lucia
; Moya Riffo, Alvaro Esteban
; Soria, Sergio Raul
; Baruj, Alberto Leonardo
; Schulz, M.; Grosse, M.; Luzin, V.; Hache, M.; Barrow, L.; Daymond, M. R.
Fecha de publicación:
01/2022
Editorial:
Elsevier Science
Revista:
Journal of Nuclear Materials
ISSN:
0022-3115
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
Zirconium alloys in nuclear power plants operate in high-pressure water at temperatures between 250 and 350 °C. Hydrogen (or deuterium) ingress due to waterside corrosion and if the solubility is exceeded H precipitates as a brittle hydride phase. Degradation mechanisms involve the accumulation of these brittle hydrides at cold spots or crack tips, as a result of H redistribution in response to thermal and stress gradients, respectively. Knowledge of H diffusion coefficients at operating temperatures is central to evaluating the rate of hydride accumulation and crack growth velocity. We determine the diffusion coefficients of H in Zircaloy-2 and Zr-2.5%Nb rolled plates at 250 °C, 300 °C and 350 °C along the rolling and normal directions by neutron imaging experiments with sensitivity of 5 wt ppm H for a spatial resolution 0.04 mm × 2 mm. These values were evaluated from H concentration profiles measured at room temperature on specimens of dimensions 10×10×4 mm3 containing a hydride layer on one face, after annealing treatments between 60 and 600 min. This allowed the identification of a transition zone of 200–300 μm between the hydride layer and the Zr alloy material, composed by large, sparsely distributed hydrides. In Zircaloy-2 plates, no substantial differences were observed in H diffusion along different directions or metallurgical conditions, and diffusion coefficients (0.6 ± 0.1 10−10 m2/s at 300 °C). By contrast, in hot rolled Zr-2.5%Nb plates the diffusion along the rolling direction (5.5 ± 0.5 × 10−10 m2/s at 300 °C) was much faster than along the normal direction (2.5 ± 0.7 10−10 m2/s at 300 °C), very likely due to H diffusing along the continuous network of β filaments. After a thermal treatment of 3 h at 860 °C the plate microstructure changed generating radically changed H diffusion coefficients, resulting in H diffusion being much faster along the normal direction (4.0 ± 0.5 10−10 m2/s at 300 °C) than along the rolling direction (1.4 ± 0.5 10−10 m2/s at 300 °C).
Palabras clave:
HYDROGEN EMBRITTLEMENT
,
NEUTRON IMAGING
,
SOLID DIFFUSION
,
ZIRCONIUM ALLOYS
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Colecciones
Articulos(CCT - PATAGONIA NORTE)
Articulos de CTRO.CIENTIFICO TECNOL.CONICET - PATAGONIA NORTE
Articulos de CTRO.CIENTIFICO TECNOL.CONICET - PATAGONIA NORTE
Citación
Santisteban, Javier Roberto; Buitrago Montañez, Nayibe Lucia; Moya Riffo, Alvaro Esteban; Soria, Sergio Raul; Baruj, Alberto Leonardo; et al.; Diffusion of H in Zircaloy-2 and Zr-2.5%Nb rolled plates between 250 °C and 350 °C by off-situ neutron imaging experiments; Elsevier Science; Journal of Nuclear Materials; 561; 1-2022; 1-15
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