Guiding criteria for instrument design at long-pulse neutron sources

6 págs.; 3 figs.; 7th Meeting of the Spanish Neutron Scattering Association (SETN); Open Access funded by Creative Commons Atribution Licence 3.0We introduce and describe general criteria which characterize long-pulse neutron sources, with a view to guiding and facilitating subsequent instrument design and optimization for specific applications. The ensuing analysis shows that a long-pulse neutron source allows for the possibility of a wide range of flexible instrument concepts with variable resolution and dynamic range, tasks which invariably require the implementation of pulse-modulation techniques in the time domain, particularly for high-resolution applications. We also consider in some detail yet-to-be-tapped opportunities in the use of shorter proton pulses, characterised by a duration commensurate with typical moderation times at spallation sources.This work would not have been possible without the support of the computing infrastructure of the i2BASQUE Academic Network and the support of the ESS-DMSC Computing Centre.Peer Reviewe

A dislocation dynamics study of the strength of stacking fault tetrahedra. Part II: interactions with mixed and edge dislocations

In this paper we present the sequel to Part I and present a comprehensive dislocation dynamics study of the strength of stacking fault tetrahedra to mixed and edge dislocation glides in fcc Cu

Tritium clouds environmental impact in air into the Western Mediterranean Basin evaluation

The paper considers short-term releases of tritium (mainly but not only tritium hydride (HT)) to the atmosphere from a potential ITER-like fusion reactor located in the Mediterranean Basin and explores if the short range legal exposure limits are exceeded (both locally and downwind). For this, a coupled Lagrangian ECMWF/FLEXPART model has been used to follow real time releases of tritium. This tool was analyzed for nominal tritium operational conditions under selected incidental conditions to determine resultant local and Western Mediterranean effects, together with hourly observations of wind, to provide a short-range approximation of tritium cloud behavior. Since our results cannot be compared with radiological station measurements of tritium in air, we use the NORMTRI Gaussian model. We demonstrate an overestimation of the sequence of tritium concentrations in the atmosphere, close to the reactor, estimated with this model when compared with ECMWF/FLEXPART results. A Gaussian “mesoscale” qualification tool has been used to validate the ECMWF/FLEXPART for winter 2010/spring 2011 with a database of the HT plumes. It is considered that NORMTRI allows evaluation of tritium-in-air-plume patterns and its contribution to doses

Neutron performance analysis for ESS target proposal

In the course of discussing different target types for their suitability in the European Spallation Source (ESS) one main focus was on neutronics' performance. Diverse concepts have been assessed baselining some preliminary engineering and geometrical details and including some optimization. With the restrictions and resulting uncertainty imposed by the lack of detailed designs optimizations at the time of compiling this paper, the conclusion drawn is basically that there is a little difference in the neutronic yield of the investigated targets. Other criteria like safety, environmental compatibility, reliability and cost will thus dominate the choice of an ESS target

Object Kinetic Monte Carlo calculations of irradiated Fe-Cr dilute alloys: The effect of the interaction radius between substitutional Cr and self-interstitial Fe

ObjectKineticMonteCarlo models allow for the study of the evolution of the damage created by irradiation to time scales that are comparable to those achieved experimentally. Therefore, the essential ObjectKineticMonteCarlo parameters can be validated through comparison with experiments. However, this validation is not trivial since a large number of parameters is necessary, including migration energies of point defects and their clusters, binding energies of point defects in clusters, as well as the interactionradii. This is particularly cumbersome when describing an alloy, such as the Fe–Cr system, which is of interest for fusion energy applications. In this work we describe an ObjectKineticMonteCarlo model for Fe–Cr alloys in the dilute limit. The parameters used in the model come either from density functional theory calculations or from empirical interatomic potentials. This model is used to reproduce isochronal resistivity recovery experiments of electron irradiateddiluteFe–Cr alloys performed by Abe and Kuramoto. The comparison between the calculated results and the experiments reveal that an important parameter is the capture radius between substitutionalCr and self-interstitialFe atoms. A parametric study is presented on the effect of the capture radius on the simulated recovery curves

The TechnoFusion Consortium of Spanish institutions and facilities towards the development of fusion materials and related technologies in Europe

14 pags., 10 figs.With the objective of contributing to the European development of materials, technologies and facilities for the demonstration of the thermonuclear fusion, the construction of the unique TechnoFusión facility was planned in 2009. The TechnoFusión consortium, formed by selected Spanish research groups and laboratories located in Madrid, has jointly advanced in the search for solutions to the remaining technological issues of nuclear fusion by magnetic and inertial confinement. In addition, the foundation of the TechnoFusión partnership has been essential to create a network of collaborations, and also to expand and specialize human resources, by training scientists and technical staff in the use of high-tech tools. Supported by the TechnoFusión_Comunidad Madrid (III) regional programme, the consortium is focused on providing support for the construction of medium-­sized, relevant facilities in Madrid (Spain). Regarding magnetic and inertial fusion issues, the programme is structured in several key experiments and infrastructures, which combine the development of materials, of cutting-edge technologies and the construction of associated facilities, with the progress in simulation and application of computational neutronics:The authors acknowledge the funding by Community of Madrid, co-financed with Structural Funds (ERDF and ESF)), through the TechnoFusión (III)-CM (S2018/EMT-4437) programme. This work has also been carried out within the framework of the EUROfusion Consortium and has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement number 633053. The views and opinions expressed in this document do not necessarily reflect those of the European Commission. In particular, R. González-Arrabal acknowledges the Convenio Plurianual con la Universidad Politécnica de Madrid en la línea de actuación Programa de Excelencia para el Profesorado Universitario of the CAM (Comunidad Autónoma Madrid)

Ion beam analysis of as-received, H-implanted and post implanted annealed fusion steels

The elemental distribution for as-received (AR), H implanted (AI) and post-implanted annealed (A) Eurofer and ODS-Eurofer steels has been characterized by means of micro Particle Induced X-ray Emission (μ-PIXE), micro Elastic Recoil Detection (μ-ERD) and Secondary Ion Mass Spectrometry (SIMS). The temperature and time-induced H diffusion has been analyzed by Resonance Nuclear Reaction Analysis (RNRA), Thermal Desorption Spectroscopy (TDS), ERDA and SIMS techniques. μ-PIXE measurements point out the presence of inhomogeneities in the Y distribution for ODS-Eurofer samples. RNRA and SIMS experiments evidence that hydrogen easily outdiffuses in these steels even at room temperature. ERD data show that annealing at temperatures as low as 300 °C strongly accelerates the hydrogen diffusion process, driving out up to the 90% of the initial hydrogen

Synchronous parallel kinetic Monte Carlo for continuum diffusion-reaction systems

A novel parallel kinetic Monte Carlo (kMC) algorithm formulated on the basis of perfect time synchronicity is presented. The algorithm is intended as a generalization of the standard n-fold kMC method, and is trivially implemented in parallel architectures. In its present form, the algorithm is not rigorous in the sense that boundary conflicts are ignored. We demonstrate, however, that, in their absence, or if they were correctly accounted for, our algorithm solves the same master equation as the serial method. We test the validity and parallel performance of the method by solving several pure diffusion problems (i.e. with no particle interactions) with known analytical solution. We also study diffusion-reaction systems with known asymptotic behavior and find that, for large systems with interaction radii smaller than the typical diffusion length, boundary conflicts are negligible and do not affect the global kinetic evolution, which is seen to agree with the expected analytical behavior. Our method is a controlled approximation in the sense that the error incurred by ignoring boundary conflicts can be quantified intrinsically, during the course of a simulation, and decreased arbitrarily (controlled) by modifying a few problem-dependent simulation parameters

Conceptual design of the liquid metal laboratory of the TECHNOFUSION facility

The application of liquid metal technology in fusion devices requires R&D related to many phenomena: interaction between liquid metals and structural material as corrosion, erosion and passivation techniques; magneto-hydrodynamics; free surface fluid-dynamics and any other physical aspect that will be needed for their safe reliable operation. In particular, there is a significant shortage of experimental facilities dedicated to the development of the lithium technology. In the framework of the TECHNOFUSION project, an experimental laboratory devoted to the lithium technology development is proposed, in order to shed some light in the path to IFMIF and the design of chamber's first wall and divertors. The conceptual design foresee a development in two stages, the first one consisting on a material testing loop. The second stage proposes the construction of a mock-up of the IFMIF target that will allow to assess the behaviour of a free-surface lithium target under vacuum conditions. In this paper, such conceptual design is addressed