Short answers, pulled from the story.
Zirconium alloys called zircaloys are used to clad nuclear fuel rods because zirconium has a low neutron-capture cross-section and strong corrosion resistance under normal service conditions. Hafnium, which absorbs neutrons 600 times more readily than zirconium, must be removed from the metal before it is used in reactors. The purified hafnium is then repurposed for reactor control rods.
Zirconium was first identified as a new element in 1789 by Martin Heinrich Klaproth, who analyzed a jargoon gemstone from the island of Ceylon (now Sri Lanka). Berzelius obtained zirconium metal in impure form in 1824 by heating potassium and potassium zirconium fluoride in an iron tube. Commercial-scale production became possible in 1925 with the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer.
When cooling was interrupted at reactors 1, 2, and 3 of the Fukushima I Nuclear Power Plant on the 11th of March 2011, temperatures rose above 900 degrees Celsius and zirconium alloy fuel rod cladding reacted rapidly with water, producing hydrogen gas. The hydrogen was vented into the maintenance halls, where it mixed with atmospheric oxygen and exploded, severely damaging the installations and at least one containment building.
Aluminium zirconium glycine salts function as antiperspirants and have been used in deodorant products since the early 1960s. Studies found them more effective as antiperspirants than aluminum chlorohydrate, the main ingredient they replaced. The human body contains on average 250 milligrams of zirconium and takes in approximately 4.15 milligrams daily from food and water.
The REDY system, first introduced in 1973, was a dialysate regeneration and recirculation system for kidney dialysis that used a sorbent column containing zirconium as a primary component, exploiting zirconium's ability to bind urea. More than 2,000,000 dialysis treatments were performed using that system before less expensive alternatives displaced it in the 1990s. Newer sorbent-based dialysis technologies building on the same principle have since received U.S. Food and Drug Administration approval.
Zirconium is the 18th most abundant element in the Earth's crust, at a concentration of about 130 milligrams per kilogram. The principal commercial mineral source, zircon (ZrSiO4), is found primarily in Australia, Brazil, India, Russia, South Africa, and the United States; as of 2023, Australia and South Africa together account for roughly half of global zircon production. Annual worldwide zirconium production is approximately 900,000 tonnes, most of it a byproduct of titanium and tin mining.