CRP on Data for Erosion and Tritium Retention in Beryllium Plasma-Facing Materials (2012-2016)


Overview

There is very active interest at present in the properties of beryllium as a wall material exposed to plasma in a fusion reactor environment. The planned plasma-facing materials for nuclear operation in ITER are beryllium and tungsten: beryllium for most of the vacuum vessel and tungsten for the regions of highest heat load. A new "ITER-Like" Be-W vacuum vessel wall has been installed on the Joint European Torus (JET) experiment and plasma experiments on that machine resumed in August 2011. Beryllium has in its favour good heat conductivity, strong gettering capability, high tolerance as a plasma impurity and low nuclear activation. On the other hand, erosion and tritium retention are issues of concern. The central issues are erosion under regular heat and particle loads from the plasma, melting and ablation under extreme (pulsed) loads, tritium retention, and ways to extract trapped tritium. It must be taken into account that the material and surface properties are highly variable as a result of interaction with impurities (primarily C, N, O, Ne and Ar), implantation of H and He, redeposition of eroded Be and resolidification of melt layers.

The CRP on "Data for erosion and tritium retention in beryllium plasma-facing materials" is intended to enhance the knowledge base on fundamental particle-material interaction processes involving beryllium in the fusion plasma environment. The key processes to be studied in the CRP are physical and chemical sputtering by H, He and Be, which release beryllium impurities into the plasma, trapping and reflection of hydrogen (H, D, T) on beryllium surfaces, the transport of hydrogen in beryllium and means to extract trapped tritium. The CRP will emphasize data for the relevant mixed materials, especially Be-(H,D,T,He), Be-C, Be-N, Be-O and ternary and higher mixtures, and data for the principal plasma impurities as projectiles. The most important projectiles are therefore H, D, T, He, Be, C, N, O, Ne and Ar. The CRP will bring together experimentalists and computational theorists that are engaged in studies of plasma-material interaction with beryllium and related mixed materials and of hydrogen migration in solid beryllium.

The CRP is focussed on basic plasma-material interaction processes. The behaviour of the eroded material in the plasma belongs to our CRP on "Light Element Atom, Molecule and Radical Behaviour in the Divertor and Edge Plasma Regions". Macroscopic surface processes such as melting and ablation under intense (pulsed) heat loads are not emphasized in the proposed CRP. Materials issues such as neutron damage, fabrication and structural properties are outside the scope of the CRP.

Schedule

A Consultants' Meeting was held 30-31 May 2011 to advise about the content of the CRP. The first Research Coordination Meeting (RCM) was held Wed-Fri 26-28 September 2012. The second RCM was held Mon-Tue 18-19 August 2014. The third RCM is planned for Q1, 2016.

Consultants' Meeting on Data Needs for Erosion and Tritium Retention in Beryllium Surfaces, Vienna, Austria, 30-31 May 2011. Meeting report and presentations.

First Research Coordination Meeting, IAEA Headquarters, Vienna, Austria, 26-28 Sep 2012. Meeting report and Presentations.

Second Research Coordination Meeting, IAEA Headquarters, Vienna, Austria, 18-19 August 2014. Agenda and Presentations.

Third Research Coordination Meeting, IAEA Headquarters, Vienna, Austria, 15-17 June 2016. Agenda and Presentations.

Participants

R. Doerner and D. Nishijima, PISCES Laboratory, UCSD: "Research on Beryllium PMI using the PISCES facilities".

D. Borodin with A. Kreter, A. Huber, S. Brezinsek and A. Kirschner, Forchungszentrum Jülich: "Development of models for plasma interaction with Be surfaces on the basis of dedicated experiments".

M. Probst and A. Mauracher, University of Innsbruck: "Quantum Chemical and Molecular Dynamics Simulations on the Interaction of Fusion-Relevant Atoms with Pure and Hydrogenated Beryllium Surfaces".

S. Irle and H. Nakamura, Nagoya University: "Parameterization and Application of the Density-Functional Tight-Binding Method for Plasma-Wall Interactions on Be Surfaces".

K. Nordlund and C. Björkas, University of Helsinki: "Molecular Dynamics Simulations of D and Plasma Impurity Interactions with Be-containing Fusion Reactor Materials".

Ch. Linsmeier and W. Jacob, Max Planck Institute for Plasma Physics, Garching: "Beryllium-containing Plasma-facing Materials: Formation, Erosion, Hydrogen Retention and Release".