| 1. |
- Barberis, P., et al.
(författare)
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Discussion
- 2011
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Ingår i: ASTM Special Technical Publication.16th International Symposium on Zirconium in the Nuclear Industry, Chengdu, Sinchuan Province, 9-13 May 2010. - 0066-0558. - 9780803175150 ; 1529 STP, s. 647-648
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Burström, Per Gunnar, et al.
(författare)
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European Experiences of Sealants in Service, Correlation to Results from Laboratory Tests
- 1990
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Ingår i: Buildings Sealants: Materials, Properties, and Performance (STP 1069). - 0066-0558. - 0803112823 ; 1069, s. 295-302
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Various examinations of sealant joints show that there are many problems with leakage, even in fairly new buildings. Two main reasons have been that the sealant properties are overrated and that the joint design or workmanship is poor due to lack of knowledge about the basic requirements and the material properties. The failure mechanism of an elastic sealant is described. This serves as a basis for a suggested engineering approach for designing sealant joints. A methodology is described by which aging and durability properties of a sealant can be evaluated. Examples of test results for various sealants are given. Today there are sealants on the European market with excellent durability and high movement capability. The conditions are therefore good for a service life of at least 25 years for many selants. The problem is to get these sealants designed and used in the proper way.
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| 3. |
- Eriksson, Johan, 1987, et al.
(författare)
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Solute Concentrations in the Matrix of Zirconium Alloys Studied by Atom Probe Tomography
- 2023
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Ingår i: ASTM Special Technical Publication. - 0066-0558. ; STP1645, s. 149-172
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Konferensbidrag (refereegranskat)abstract
- This work indicates that the matrix content of the alloying elements iron, chromium, and nickel in as-produced commercial Zircaloy-2-type materials is lower than what has been indicated by many previous studies. Atom probe tomography in voltage pulse mode was used to study the matrix content of solutes in Zircaloy-2 of type LK3/L and a similar model alloy, called Alloy 2, of the same heat treatment. Both alloys were analyzed in the as-produced state and after reactor exposure. In the as-produced materials, the concentrations of iron, chromium, and nickel were all below the detection limits of around 10 wt. ppm. After reactor exposure, these alloying elements were observed to reside in clusters at loops, and the matrix content (including clusters) of iron had increased to about 1,200 wt. ppm in the fueled region of the rod and to about half that value in the plenum region. The chromium content in the fueled region was approximately 100 wt. ppm, and the nickel content was approximately 200 wt. ppm. In the plenum region, the content of these elements was lower. However, due to an uneven distribution of clusters, there was a wide scatter in the measured concentrations in the irradiated materials. Additionally, the matrix concentrations of solute elements in (nonirradiated) Zircaloy-2 were investigated for a series of samples subjected to a annealing at 770◦C followed by cooling at different rates. From these measurements, the solubilities at 770◦C were estimated to be around 65 wt. ppm for chromium, at least 37 wt. ppm for iron, and below 9 wt. ppm for nickel. Slow cooling resulted in virtually no iron, chromium, or nickel in the matrix. The concentration of aluminum in the matrix was observed to be between 10 and 20 wt. ppm for all a-annealed samples and for the as-produced materials of commercial heat treatment.
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| 4. |
- Lindgren, Mikaela, 1987, et al.
(författare)
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Toward a Comprehensive Mechanistic Understanding of Hydrogen Uptake in Zirconium Alloys by Combining Atom Probe Analysis With Electronic Structure Calculations
- 2015
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Ingår i: ASTM Special Technical Publication. - 0066-0558. - 9780803175297 ; STP 1543, s. 515-539
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Konferensbidrag (refereegranskat)abstract
- The ability of a zirconium alloy to resist corrosion relies on a compromise between two opposing strategies. Minimizing the hydrogen pickup fraction (HPUF) by invoking metallic electron conduction in the barrier oxide results in rapid parabolic oxide growth. On the other hand, slow sub-parabolic barrieroxide growth, as reflected in rate limiting electron transport, may result in a high HPUF. The objective of the present study is to offer mechanistic insights as to how low concentrations of different alloying elements become decisive for the overall corrosion behavior. Combining atomistic microanalysis with first principles modeling by means of density functional theory, the speciation and redox properties of Fe and Ni towards hydrogen evolution are firstly explored.Complementary atom probe microanalysis at the metal–oxide interface provides evidence for Fe and Ni segregation to grain boundaries in Zircaloy-2 that propagates into the ZrO2 scale. Descriptors for how alloying elements in ZrO2 control electron transport as well as catalytic electron-proton recombination ingrain boundaries to form H2 are determined by means of theory. The findings are generalized by further atomistic modeling, and are thus put in the context of early reports from autoclave experiments on HPUFs of zirconium with the alloying elements Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Nb. A shunting mechanism which combines inner and outer hydrogen evolution mechanisms is proposed. Properties of the transient zirconium sub-oxide are discussed. A plausible atomistic overall understanding emerges.
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| 5. |
- Tejland, Pia, 1978, et al.
(författare)
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Detailed analysis of the microstructure of the metal/oxide interface region in Zircaloy-2 after autoclave corrosion testing
- 2011
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Ingår i: ASTM Special Technical Publication. 16th International Symposium on Zirconium in the Nuclear Industry, Chengdu, Sinchuan Province, 9-13 May 2010. - 0066-0558. - 9780803175150 ; 1529 STP, s. 595-617
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Konferensbidrag (refereegranskat)abstract
- Two varieties of Zircaloy-2, with different second phase particle (SPP) size distributions and different corrosion resistance, were oxidized in a steam autoclave. Transmission electron microscopy (TEM) of large thin-foil cross-sections of the oxide and the adjacent metal shows an undulating metal/oxide interface in both materials with a periodicity of slightly less than 1 μm and an amplitude of around 100 nm. The SPPs oxidize slower than the surrounding metal, and the absence of volume increase leads to void and crack formation as the SPPs become embedded in the oxide. On SPP oxidation, iron diffuses out of the particles into the surrounding oxide. A sub-oxide with an oxygen content of approximately 50 at. % and a layer thickness of about 200 nm was observed close to the metal/oxide interface. There is a 200 nm oxygen concentration gradient into the metal, from the level close to the sub-oxide of about 30 at. % down to a few atomic percent. All tin in the matrix is incorporated in the sub-oxide, and no segregation to the metal/oxide interface was found.
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| 6. |
- Tejland, Pia, 1978, et al.
(författare)
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Oxidation Mechanism in Zircaloy- 2—The Effect of SPP Size Distribution
- 2015
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Ingår i: ASTM Special Technical Publication. - 0066-0558. - 9780803175297 ; 1543, s. 373-403
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Konferensbidrag (refereegranskat)abstract
- The metal/oxide interface region in Zircaloy-2 oxidized in autoclave was studied with transmission electron microscopy (TEM) and atom probe tomography. In addition to waviness on the micrometer scale the metal/oxide interface was found to have irregularities on a finer scale, and metal islands were found especially at metal hills (delayed parts of the oxidation front). The thickness of the sub-oxide layer varies considerably along the interface in the same sample, from 100 to virtually 0 nm. The sub-oxide composition may vary on a very fine scale (down to 5nm), and it can sometimes be a mixture of sub-oxides with different oxygen content. The metal matrix in contact with the sub-oxide is saturated with up to 32 at. % oxygen, and the oxygen diffusion profile in the metal is in approximate agreement with literature data for pure Zr. However, the diffusion length appears to be somewhat larger at interface metal hills than under valleys, probably for both geometrical and stress state reasons. Hydride precipitates, hardly visible in conventional TEM, give a good image contrast when employing high angle annular dark field imaging. A model for the oxidation process is presented, where the creep deformation of the metal close to the interface and the formation of lateral cracks in the oxide are of highest importance. The effect of second phase particle (SPP) size is suggested to be twofold: Small and numerous SPPs give a stronger metal and therefore higher stress in the oxide. Small SPPs also nucleate many more lateral cracks in the oxide, which gives a weaker oxide. Together this leads to formation of large cracks associated with transition in the oxidation rate at an earlier time than for a material with larger and fewer SPPs, and thereby a higher oxidation rate.
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| 7. |
- Topping, Matthew, et al.
(författare)
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The effect of iron on dislocation evolution in model and commercial zirconium alloys
- 2018
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Ingår i: ASTM Special Technical Publication. - 0066-0558. ; STP 1597, s. 796-822
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Konferensbidrag (refereegranskat)abstract
- Although the evolution of irradiation-induced dislocation loops has been well correlated with irradiation-induced growth phenomena, the effect of alloying elements on this evolution remains elusive, especially at low fluences. To develop a more mechanistic understanding of the role iron has on loop formation, we used state-of-the-art techniques to study a proton-irradiated Zr-0.1Fe alloy and proton- and neutron-irradiated Zircaloy-2. The two alloys were irradiated with 2-MeV protons up to 7 dpa at 350°C and Zircaloy-2 up to 14.7 × 1025n • m-2, approximately 24 dpa, in a boiling water reactor at approximately 300°C. Baseline transmission electron microscopy showed that the Zr3Fe secondary-phase particles in the binary system were larger and fewer in number than the Zr (Fe, Cr)2and Zr2(Fe, Ni) particles in Zircaloy-2. An analysis of the irradiated binary alloy revealed only limited dissolution of Ze3Fe, suggesting little dispersion of iron into the matrix, while at the same time a higher 〈a〉-loop density was observed compared with Zircaloy-2 at equivalent proton dose levels. We also found that the redistribution of iron during irradiation led to the formation of iron nanoclusters. A delay in the onset of 〈c〉-loop nucleation in proton-irradiated Zircaloy-2 compared with the binary alloy was observed. The effect of iron redistributed from secondary-phase particles because of dissolution on the density and morphology of 〈a〉 and 〈c〉 loops is described. The implication this may have on irradiation-induced growth of zirconium fuel cladding is also discussed.
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