Status of beryllium development for fusion applications

Abstract

Beryllium is a leading candidate material for the neutron multiplier of tritium breeding blankets and the plasma facing component of first wall and divertor systems. Depending on the application, the fabrication methods proposed include hot-pressing, hot-isostatic-pressing, cold isostatic pressing/sintering, rotary electrode processing and plasma spraying. Product forms include blocks, tubes, pebbles, tiles and coatings. While, in general, beryllium is not a leading structural material candidate, its mechanical performance, as well its performance with regard to sputtering, heat transport, tritium retention/release, helium-induced swelling and chemical compatibility, is an important consideration in first-wall/blanket design. Differential expansion within the beryllium causes internal stresses which may result in cracking, thereby affecting the heat transport and barrier performance of the material. Overall deformation can result in loading of neighboring structural material. Thus, in assessing the performance of beryllium for fusion applications, it is important to have a good database in all of these performance areas, as well as a set of properties correlations and models for the purpose of interpolation/extrapolation. In this current work, the range of anticipated fusion operating conditions is reviewed. The thermal, mechanical, chemical compatibility, tritium retention/ release, and helium retention/swelling databases are then reviewed for fabrication methods and fusion operating conditions of interest. Properties correlations and uncertainty ranges are also discussed. In the case of the more complex phenomena of tritium retention/release and helium-induced swelling, fundamental mechanisms and models are reviewed in more detail. Areas in which additional data are needed are highlighted, along with some trends which suggest ways of optimizing the performance of beryllium for fusion applications. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Assessment of database for interaction of tritium with ITER plasma facing materials

“…Surface recombination coefficients vary over 8 orders of magnitude, and are sensitive to surface conditions.(M. C. Billone, et al 1994) Trap site characterization and effects Baldwin et al (1989) irradiated 98.26% Be rods (1.7% BeO) at T e 348 K to a fast fluence -5x1022 n/cm2, producing 24,000 appm (He) and many trapping sites.…”

“…Short-circuit grain-boundary diffusion may account for the rapid diffusion observed in polycrystalline specimens. , Billone et al 1994 Dalle Donne et al (1993b) extended the ANFIBE code to describe effects of helium bubbles and Be0 on tritium trapping. The equations described tritium concentrations in dynamical solution, in intragranular bubbles, at grain boundaries, and in chemical traps.…”

First-principles study of migration and diffusion mechanisms of helium in α-Be

“…The higher the temperature of irradiation and the beryllium porosity are, the less the helium atoms retain in beryllium. 8,33 It is interesting to notice that the self-diffusion coefficient of beryllium 32 is smaller than the helium diffusion coefficient, indicating that atomic helium diffusion is faster than the self-diffusion of beryllium atoms, as in all the metals which have been investigated so far. 6 The diffusion coefficient curves for D ∥ and D ⊥ are distinguishable below melting point.…”

“…The density of α-Be is 1.85×10 3 kg m −3 and the atom density is 1.45×10 29 atoms m −3 . 8 At 1530 K beryllium undergoes phase transform from α-phase to β-phase (bcc structure), and at 1556 K the beryllium crystal will melt. Right now, beryllium is usually used in nuclear reactors as highly effective moderators and reflectors of neutrons; 9 in future, it is considered to be the first wall material or blanket of thermonuclear reactor due to its excellent neutron-multiplication capability.…”

Low energy (10 to 700 eV) angularly resolved sputtering yields for D+on beryllium

“…When these effects are taken into account the total yield equals or exceeds that of beryllium. For these reasons, beryllium has already been installed and tested in JET for its plasma facing components [7], and it is proposed as the first wall material for ITER [8,9].…”