MATERIALS FOR NUCLEAR APPLICATIONSCMAST (Computational MAterials Science & Technology) Virtual Lab

www.afs.enea.it/project/cmast

Computational Materials Science

Projects:• EERA, European Energy Research Alliance: Joint Programme on

Nuclear Materials (EERA-NM)

Liquid lead corrosion of iron

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%)

Iron atoms = 10745 lead atoms = 40685(123 123 123) Å3

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

A. Arkundato Z. Su'ud, M. Abdullah, W. Sutrisno (Univ. Bandung Indonesia), M. Celino (ENEA)

Mechanical properties of Tungsten and its alloys

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.

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, ENEATungsten 1 substitution

2 substitutions nearest neighbor

2 substitutions second nearest neighbor

3 substitutions nearest neighbor

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.

Ideal tensile strength Bulk modulus

Projects:• EFDA, European Fusion Development Agreement. Activity

Integrated Radiation Effects Modelling and Experimental Validation

Projects:• EURATOM-ENEA Association for the nuclear fusion development

Strain sensitivity and supercomputing properties of Nb3Sn

G. De Marzi, L. Morici, L. Muzzi, A. della Corte, ENEAM. 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-Dynesmodification 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.

Tensile tests

Experiment

Modeling

Good agreement between experiments and modeling. There is a range of of oxygen concentration in which the corrosion is at a minimum