Neutron and Fission Fragment Damage in Zirconia

Adam, J.; Cox, B.

doi:10.1103/physrevlett.3.543

Cited by 22 publications

(4 citation statements)

References 3 publications

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“…It has also been shown that monoclinic ZrO 2 can transform to the tetragonal phase under ion irradiation [43]- [46]. This transformation was also observed under neutron irradiation in pure ZrO 2 with added impurities [47]. However, experimental evidence for increased tetragonal phase fractions in neutron irradiated commercial alloys is lacking [27].…”

Section: Introductionmentioning

confidence: 96%

Investigating the Effect of Zirconium Oxide Microstructure on Corrosion Performance: A Comparison between Neutron, Proton, and Nonirradiated Oxides

Garner

Baxter

Frankel

et al. 2018

Zirconium in the Nuclear Industry: 18th International Symposium

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Automated crystal orientation mapping in the transmission electron microscope has been used to simultaneously map the phase, orientation and grain morphology of oxides formed on Zircaloy-2 after 3 and 6 cycles in a BWR reactor in unprecedented detail. For comparison, a region of a pre-oxidised autoclave-formed oxide was also proton irradiated at the Dalton Cumbrian Facility. The proton irradiation was observed to cause additional stabilisation of the tetragonal phase, attributed to the stabilising effect of irradiation-induced defects in the oxide. In the reactor-formed oxides, no extra stabilisation of the tetragonal grains was observed under neutron irradiation, as indicated by the similar tetragonal phase fraction and transformation twin boundary distributions between the non-irradiated and reactor-formed oxides. It is suggested that the damage rate is too low in the newly formed oxide to cause significant stabilisation of the tetragonal phase. This technique also reveals the oxide formed under reactor conditions has a more heterogeneous microstructure and the growth of well-oriented columnar monoclinic grains is significantly reduced when compared to a non-irradiated oxide. High angle annular dark field scanning transmission electron microscopy (HAADF STEM) also revealed the development of extensive networks of intergranular porosity and eventually grain decohesion in the

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Section: Introductionmentioning

confidence: 96%

Investigating the Effect of Zirconium Oxide Microstructure on Corrosion Performance: A Comparison between Neutron, Proton, and Nonirradiated Oxides

Garner

Baxter

Frankel

et al. 2018

Zirconium in the Nuclear Industry: 18th International Symposium

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“…Irradiation-induced phase transformations in m-ZrO2 have been extensively reported. A monoclinic-to-tetragonal transformation under ion irradiation has been described by some authors [21][22][23][24], while others claim that the transformation is monoclinic-to-cubic [25][26][27][28],…”

Section: Phase Transformations and Stabilisation Mechanisms Under Irradiationmentioning

confidence: 99%

“…The results presented above show that nano-crystalline m-ZrO2 grains in a thin TEM are transformed into the higher symmetry cubic phase under in-situ ion irradiation, without any evidence for the formation of an intermediate tetragonal phase. The mechanisms of phase transformations between the different phases of zirconia upon deformation or thermal treatment have been widely studied [84][85][86][87], but this kind of direct transformation from the monoclinic to cubic structures has only been observed under irradiation [25][26][27][28] and is supposed to occur in a displacive manner [29,46,88]. To explore the nature of this transformation it is necessary to analyze the orientation relationship between the two phases, which was predicted to be (100) m ∥(100) c and [001] m ∥[001] c [78] and confirmed in this work.…”

Section: Irradiation-induced Phase Transformation and Grain Growthmentioning

confidence: 99%

In-situ TEM study of irradiation-induced damage mechanisms in monoclinic-ZrO2

Liu

Mir

et al. 2020

Acta Materialia

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We have investigated the microstructural and crystallographic evolution of nanocrystalline zirconia under heavy ion irradiation using in-situ transmission electron microscopy (TEM) and have studied the atomic configurations of defect clusters using aberration-corrected scanning transmission electron microscopy (STEM). Under heavy ion irradiation the monoclinic-ZrO2 is observed to transform into cubic phase, stabilised by the strain induced by irradiationinduced defect clusters. We suggest that the monoclinic-to-cubic transformation is martensitic in nature with an orientation relationship identified to be (100)m∥(100)c and [001]m∥[001]c. By increasing the damage dose, both the formation of voids and irradiationinduced grain growth were observed. A model for the formation of voids is proposed, taking defect interactions into consideration. The study has also demonstrated that high resolution orientation mapping by transmission Kikuchi diffraction (TKD) combined with in-situ irradiation in a TEM is a powerful method to probe the mechanisms controlling irradiationinduced processes, including grain boundary migration, phase transformations and texture evolution.

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“…Second, this could be due to the stabilising effect of increasing impurities after irradiation. An early study by Adam [66] also suggested that increasing concentrations of impurities in the oxide may be linked to higher volume fractions of the tetragonal phase. Analysis of neutron irradiated Zircaloy-4 samples [67] showed that increasing Fe contents in the oxide may contribute to stabilisation of the tetragonal phase, and in this case the Fe may arise not only from radiationinduced dissolution of Fe from the Zr-Nb-Fe SPPs but also from dissolved Fe in the water.…”

Section: Damage To the Oxidementioning

confidence: 99%

Effect of neutron and ion irradiation on the metal matrix and oxide corrosion layer on Zr-1.0Nb cladding alloys

Garner

Frankel

et al. 2019

Acta Materialia

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A detailed study has been carried out on recrystallised Zr-1.0Nb alloys corroded and irradiated under different conditions, including ex-autoclave and ex-reactor samples. After 540 days in reactor and damage around 5 dpa, the neutron irradiated sample shows no serious evidence for radiation enhanced corrosion and is still in pre-transition stage. The good corrosion resistance of the neutron irradiated Zr-1.0Nb can be related to the higher volume fraction of tetragonal phase and fewer interconnected nano porosity/ cracks in the oxide. This indicates less tetragonal to monoclinic transition, leads to more protective oxide in the neutron irradiated sample, containing little evidence for short circuit paths for the penetration of oxygen or water towards the metaloxide interface. These observations on a sample with a slow overall oxidation rate are consistent with the hypothesis that interconnected porosity can lead to early transitions and rapid oxidation. Tetragonal oxide can be either stabilised by irradiation, or stabilised by local release of impurity species from SPPs such as dissolution of Fe from Zr-Nb-Fe precipitates or radiation introduced precipitates (RIPs) which is likely to be small β-Nb clusters. The oxide consists of well-aligned columnar-equiaxed microstructure in the autoclave sample while a more complex oxide grain structure was observed in the neutron-irradiated sample. As oxide continues to grow, there are more and loops, dissolved Fe and RIPs in the metal matrix, however, the corrosion rate is low enough for the tetragonal oxide to stabilise and suboxide + Zr(Osat) phases exist for protectiveness, so there is no enhanced corrosion after radiation. In situ ion irradiation in the TEM revealed no visible defect clusters or voids in the oxide, suggesting that radiation damage to the metal matrix rather than oxide may have a stronger effect on corrosion mechanisms after neutron irradiation, however, cascade damages are not visible in this case. Neutron irradiation also seems to have little effect on promoting fast oxidation or dissolution of β-Nb precipitates into the surrounding oxide or metal during irradiation. These results are discussed in the light of the current mechanisms for corrosion of nuclear fuel cladding alloys.

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Neutron and Fission Fragment Damage in Zirconia

Cited by 22 publications

References 3 publications

Investigating the Effect of Zirconium Oxide Microstructure on Corrosion Performance: A Comparison between Neutron, Proton, and Nonirradiated Oxides

Investigating the Effect of Zirconium Oxide Microstructure on Corrosion Performance: A Comparison between Neutron, Proton, and Nonirradiated Oxides

In-situ TEM study of irradiation-induced damage mechanisms in monoclinic-ZrO2

Effect of neutron and ion irradiation on the metal matrix and oxide corrosion layer on Zr-1.0Nb cladding alloys

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