Use of titanium in the Tokamak Physics Experiment

Titanium alloys have been considered for structural materials in fusion energy devices since the 1970's. Austenitic stainless steels were historically selected because they could be fabricated at a lower system acquisition cost. Nickel alloys allowed higher operating temperatures and provided higher electrical resistivity for reactor performance [1]. Today, a greater emphasis has been placed on total system life cycle cost to include not only system acquisition costs but also operational life, decommissioning, and irradiated materials storage. The stainless steels and nickel alloys become irradiated after neutron bombardment and have radioactive species that must be stored for centuries before radioactivity dissipates to human safe handling levels. Titanium and specifically Ti-6Al-4V have radioactive species that would allow safe hands-on maintenance during initial operation and then eases decommissioning. This paper discusses the issues related to the use of Ti-6Al-4V for the Tokamak Physics Experiment (TPX) to be built at Princeton Plasma Physics Laboratory.