Growth of oxide particles in FeCrAl- oxide dispersion strengthened steels at high temperature

Abstract

The growth of oxide particles in FeCrAl-oxide dispersion strengthened steel (ODSS) considering an accident condition of the light-water reactor at above 1500 K was studied by using a high-temperature annealing. Oxide particles grew from 9nm to more than 50nm as maximum at 1623K for 27h, with decreasing their number density in two orders of magnitude. Most of the oxide particles in 15Cr-7Al were identified as YAM or YAP, while the oxide particles in 15Cr-7Al-0.4Zr were identified trigonal Y 4 Zr 3 O 12. Zr addition to 15Cr-7Al ODSS accelerated the growth of the oxide particles, which is quite contrary to the effect of Zr addition during sintering as suggested in the literature. The kinetics of coarsening was characterized by an equation of Ostwald ripening. The diffusion activation energies obtained in the present materials were quite larger than the conventional diffusion activation energy of Y in alpha-iron. Gibbs free energy of oxides should be considered to discuss the coarsening.

Steam oxidation behavior of Y-bearing cladding tube with aluminizing coating

“…However, the reaction between Zr and steam at high temperature is accompanied by the release of large amounts of hydrogen gas [4][5][6]. According to the reports of the Fukushima Daiichi nuclear disaster, the oxidation of Zr cladding begins above 900°C and causes accelerated hydrogen generation above 1227°C [7][8][9]. For example, during the loss-of-coolant-accident (LOCA), cladding temperature will be increased up to 1200°C due to the decay heat from fuel accompanied by the evaporation of the cooling water, which results in the rapid steam-oxidation of Zr alloy and further produces significant and dangerous levels of hydrogen [10].…”

Multiscale investigations of nanoprecipitate nucleation, growth, and coarsening in annealed low-Cr oxide dispersion strengthened FeCrAl powder

“…The power law exponent that results in a slope of m=1 is that for n=6. Although extended 500 h anneals were not performed on the 1000°C or 1100°C temperatures due to material and time constraints, it is a reasonable assumption that the underlying mechanism for particle coarsening at these temperatures is identical to the 1050°C case due to the similar coarsening kinetics observed in previous works for ODS FeCr (n=5,6) and FeCrAl (n=4,5) alloys at even higher temperatures [74,[79][80][81]. Fig.…”

“…All specimens indicated the same homogeneous distribution of precipitates for each ageing condition. As has been performed for dispersion strengthened FeCr [74,79,80] and FeCrAl [81] alloys in previous studies, the long term ageing of these CrAZY powders at 1050°C are coupled with the short term ageing of the same powders at 1000 and 1100°C to provide insights into the coarsening kinetics of the smallest nanoprecipitates in these characteristic temperature regimes commonly used for alloy consolidation.…”

Model calculation of Cr dissolution behavior of ODS ferritic steel in high-temperature flowing sodium environment

“…Oxide dispersion strengthened (ODS) ferritic steel is recognized as high-strength and radiation-tolerant steel used for fast reactor fuel cladding tubes, fusion reactor material and accident tolerant fuel cladding tubes for light water reactors [1][2][3][4][5][6][7][8][9][10][11][12]. The Japan Atomic Energy Agency (JAEA) has been developing 9Cr-and 12Cr-ODS steels for the high burnup fuel cladding tubes of sodium-cooled fast reactors (SFR), which will be used up to 250 GWd/t (peak burnup) up to 700 o C (hot spot mid-wall temperature) for enhancement of SFR economy.…”

“…Results and discussions 3.1 BOR-60 fuel pin irradiation test[15] Figure10 shows the WDX line analysis results of 9Cr-and 12Cr-ODS steel cladding tubes at the top of fuel column after the second irradiation test at BOR-60. It can be seen that the surface Cr dissolution took place both in 9Cr-and 12Cr-ODS steel cladding tubes.…”