Tritium retention in tungsten exposed to intense fluxes of 100 eV tritons

Abstract

Tungsten is a candidate material for ITER as well as other future magnetic fusion energy devices. Tungsten is well suited for certain hsion applications in that it has a high threshold for sputtering as well as a very high melting point. As with all materials to be used on the inside of a tokamak or similar device, there is a need to know the behavior of hydrogen isotopes embedded in the material. With this need in mind, the Tritium Plasma Experiment (TPE) has been used to examine the retention of tritium in tungsten exposed to very high fluxes of 100 eV tritons. Both tungsten and tungsten containing 1% lanthanum oxide were used in these experiments. Measurements were performed over the temperature range of 423 to 973 K. After exposure to the tritium plasma, the samples were transferred to an outgassing system containing an ionization chamber for detection of the released tritium. The samples were outgassed using linear ramps from room temperature up to 1473 K. Unlike most other materials exposed to energetic tritium, the tritium retention in tungsten reaches a maximum at intermediate temperatures with low retention at both high and low temperatures. For the very high triton fluences used (>lo25 T/m2), the fractional retention of the tritium was below 0.02% of the incident particles. This report presents not only the results of the tritium retention, but also includes the modeling of the results and the implication for ITER and other future fusion devices where tungsten is used. DISCLAIMERThis 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, m o mmendktion, 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 thosc of the United States Government or any agency thereof.

Deuterium accumulation in deposited tungsten films

“…The maximum retention was observed at temperatures of 400 -500 K, and achieved approximately 1:5 Â 10 20 D=m 2 . (This value is near to that reported by Causey et al [6]). Therefore the irradiation temperature in experiments on the samples with deposited tungsten films was chosen within this range, and was equal to 450 K.…”

First-principles study of carbon effects in a tungsten grain boundary: site preference, segregation and strengthening

“…One of them is nuclear fusion energy, which is a clean and infinite energy resource for future generations. Fusion energy is being developed internationally via the International Thermonuclear Experimental Reactor (ITER) Project [1], which aims to demonstrate the extended burn of deuterium-tritium (D-T) plasma in a fusion reaction. The final application of nuclear fusion energy is mainly dependent on the development of key materials in the thermonuclear fusion device "Tokamak", in which the choice of the plasma facing materials (PFMs) is one of the key issues.…”