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Harwell, United Kingdom

Ortner S.R.,Harwell Laboratory
Fatigue and Fracture of Engineering Materials and Structures | Year: 2011

Several models of fracture in ferritic steel consider matrix strain to be an indicator of the condition required for second-phase particle cracking (i.e. microcrack nucleation). Recent simulations predict that stress à - strain (W) is a better supported indicator. This paper examines the effect of replacing strain by W within the EOH fracture model. There is no improvement in the descriptions of fracture toughness and initiation site properties for eight different steels over a range of temperatures. The use of W, however, leads to the convergence of data from different steels, and permits estimates of the particle cracking criterion to be made from metallographic data, when suitable fractographic data are unavailable. Overall, experiment agrees with simulation in finding W a more appropriate parameter to use than strain alone. © 2011 Crown. Source

Ni N.,University of Oxford | Lozano-Perez S.,University of Oxford | Jenkins M.L.,University of Oxford | English C.,Harwell Laboratory | And 3 more authors.
Scripta Materialia | Year: 2010

Much work has been carried out over the past 40 years on the oxidation of zirconium alloys used for nuclear fuel cladding, but there is no consensus as to the critical factors that control kinetics, even though this is vital for the design of materials for higher burn-up regimes. One unanswered question is the role of porosity in controlling oxidation. Here we show that the nature of the nanoscale porosity can be correlated to different stages of the oxidation process. © 2009 Acta Materialia Inc. Source

Bullough R.,Harwell Laboratory
Philosophical Magazine | Year: 2013

Sir Alan Cottrell has made huge seminal contributions to our basic understanding of radiation damage processes in both fissile and non-fissile materials. Much of this ground-breaking work was accomplished in the mid-1950s when Cottrell was working at Birmingham University and later at Harwell Laboratory. It is interesting to relate the earlier progress in the 1950s to our present understanding of the phenomenon. © 2013 Taylor & Francis. Source

Sarsfield M.J.,National Nuclear Laboratory | Sims H.E.,Harwell Laboratory | Taylor R.J.,National Nuclear Laboratory
Solvent Extraction and Ion Exchange | Year: 2011

Formo- and aceto-hydroxamic acids are very effective reagents for stripping tetravalent actinide ions from a tri-butyl phosphate phase into nitric acid. A model describing the partitioning of actinide (IV) ions has been derived accounting for reactions in the aqueous and solvent phases, including complex formation with nitrate and hydroxamate ions. Predicted distribution ratios for Np(IV) are compared with experimental data in the presence of aceto-hydroxamate ions. Additionally, a value of 0.473 (±0.004) kgmol-1 for the Np(IV) ion interaction coefficient with nitrate ions (εNp4+-NO3-) was determined. © Taylor & Francis Group, LLC. Source

English C.A.,Harwell Laboratory | English C.A.,University of Oxford | Jenkins M.L.,University of Oxford
Philosophical Magazine | Year: 2010

A series of TEM experiments was carried out to systematically investigate the formation of vacancy dislocation loops in displacement cascades in molybdenum. Single-crystal foils of high-purity molybdenum were irradiated with Sb+ single ions and Sb2 + and Sb3 + molecular ions to low doses (≤1016 ions m-2). Three different ion energies were employed (60, l20 and 180 keV) in order to systematically vary the total cascade energy and the energy per atom in the molecular ion. Dislocation loop sizes and defect yields were found to be larger for molecular ions than for single ions of the same energy. In (011) foils, most loops had Burgers vectors b = a/2111 lying in the plane of the foil. However, in molecular ion irradiations, a small fraction of loops with b = a100 was also found. This fraction was higher for Sb3 + than for Sb 2 + ions and also increased with ion energy. In (001) foils, defect yields were much smaller because of the loss of glissile a/2111 loops to the surface, but a100 loops were still present in molecular ion irradiations. The habit planes of both a/2111 and a100 loops were consistent with nucleation on {110} planes by the Eyre-Bullough mechanism. These results are compared with recent molecular dynamics simulations of the effect of the mass of primary knock-on atoms on displacement cascades in iron. © 2010 Taylor & Francis. Source

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