Previously used only in state-of-the-art military applications and other niche markets, improvements to titanium smelting techniques has seen use become more widespread in recent decades. Nuclear power plants make extensive use of titanium alloys in heat exchangers and especially valves. In fact the corrosion resistant nature of titanium means they do believe that nuclear waste storage units lasting 100,000 years could be made from it. This non-corrosive nature also means titanium alloys are widely utilised in oil refineries and marine components. Titanium is entirely non-toxic which, combined with its non-corrosive nature, means it is used for industrial scale food processing and in medical protheses. Titanium is still in high demand within the aerospace industry, with many of the most critical parts of the airframe made from these alloys in both civilian and military aircraft.