MATERIALS FOR NUCLEAR APPLICATIONS

1. ComputationalMaterials Science MATERIALS FOR NUCLEAR APPLICATIONS CMAST (ComputationalMAterials Science & Technology) VirtualLab www.afs.enea.it/project/cmast Liquidleadcorrosion of iron • Projects: • EERA, European Energy ResearchAlliance: Joint Programme on Nuclear Materials (EERA-NM) A. Arkundato Z. Su'ud, M. Abdullah, W. Sutrisno (Univ. Bandung Indonesia), M. Celino (ENEA) Experiment We performed several iron-lead-oxygen simulations at the same T= 750 oC but with different oxygen contents: 340 atoms (0.0583 wt%) , 450 atoms (0.0771 wt%) 674 atoms (0.1152 wt%), 906 atoms (0.1552 wt%), 1132 atoms (0.1938 wt%) , 1348 atoms (0.2307 wt%) Surface oxidation can be used to protect the steel from dissolution (Active Oxygen Control): maintaining a low level of oxygen in the liquid lead allow the formation of a protective oxide layer on the steel surface thus eliminating the direct contact between the steel and liquid lead Active Oxygen Control was found to work at relatively low temperatures but for temperatures above 500 OC severe corrosion attack are observed both in austenitic and F/M steels with the formation of thick oxide layers, which may spall off periodically leaving the steel surface exposed to the coolant Iron atoms = 10745 lead atoms = 40685 (123 123123) Å3 Modeling Good agreement between experiments and modeling. Thereis a range of ofoxygenconcentration in which the corrosionis at a minimum Strain sensitivity and supercomputingproperties of Nb3Sn • Projects: • EURATOM-ENEA Associationfor the nuclearfusiondevelopment G. De Marzi, L. Morici, L. Muzzi, A. della Corte, ENEA M. Buongiorno Nardelli, Denton (USA) The A15 phase Nb3Sn compound1 is currently being used in a variety of large-scale scientific projects employing high field superconducting magnets (above 10 T), including ITER (the International Thermonuclear Experimental Reactor). In these high-field magnets, the mechanical loads during cooldown (due to different thermal contractions) and operation (due to Lorentz forces) can be very large, and since the superconducting properties of Nb3Sn strongly depend on strain8–11, an overall performance degradation can take place. The phonon dispersion curves and electronic band structures along different high-symmetry directions in the Brillouin zone were calculated, at different levels of applied strain, e, both on the compressive and the tensile side. Starting from the calculated averaged phonon frequencies and electron-phonon coupling, the superconducting characteristic critical temperature of the material, Tc, has been calculated by means of the Allen-Dynes modification of the McMillan formula. As a result, the characteristic bell-shaped Tc vs. e curve, with a maximum at zero intrinsic strain, and with a slight asymmetry between the tensile and compressive sides, has been obtained. These first-principle calculations thus show that the strain sensitivity of Nb3Sn has a microscopic and intrinsic origin, originating from shifts in the Nb3Sn critical surface. Mechanicalproperties of Tungsten and itsalloys • Projects: • EFDA, EuropeanFusionDevelopment Agreement. ActivityIntegratedRadiationEffectsModelling and ExperimentalValidation Crystalline Tungsten with a substitutional element Re, V and Ta (atom in red). Quantum atomic scale simulation are used to perform tensile test S. Giusepponi, M. Celino, ENEA 3 substitutions nearest neighbor 2 substitutions nearest neighbor 2 substitutions second nearest neighbor Tungsten 1 substitution Tensile tests Some parts inside the TOKAMAK, facing the plasma, are made of Tungsten. European efforts are aimed to strengthen Tungsten to reduce its fragility. This is achieved alloying Tungsten with several other metals. Modeling studies are used to test several alloying compositions to find the optimal atomic configuration. Ideal tensile strength Bulk modulus Total energy calculations to compute Lattice parameters; B bulk modulus;, Enthalpy of atomization; Formation energies of defects; Binding energies of defect clusters; Ideal tensile strength.