The strange link between samurai swords and Japan's nuclear reactors

As fears rise in Japan about nuclear disaster at the Fukushima plant, the first and best line of defense are the reactor's six inch thick steel-walled chambers, made by a company that still forges samurai swords by hand.

Japan Steel Works is the world's only volume builder of nuclear reactor vessels, the steel container that holds radioactive fuel, and in case of a meltdown, prevents that fuel from leaking and triggering a catastrophe. Founded in 1907 and rebuilt following World War II, it supplied nearly all of the vessels used in Japan's 54 nuclear power plants, including the containers at the Fukushima Daiichi plants designed by General Electric and Toshiba.

The strange link between samurai swords and Japan's nuclear reactors While those vessels were made from steel plates bolted and welded together, modern designs require Japan Steel Works to forge containers from a single ingot that can weigh up to 600 tons. It's a slow process that takes months at a time, using the company's 14,000-ton press to shape a special steel alloy that's been purified to maximize its strength. These methods also minimize seams that can give way in case of a meltdown, where nuclear fuel can reach 2,000 degrees Celsius.

Although Japan Steel Works is a major corporation with 5,000 employees, it also maintains a samurai sword blacksmith, in a small shack on a hill above the factory in Muroran, where a single craftsman still hammers steel into broadswords, as the company has done since 1917.

The strange link between samurai swords and Japan's nuclear reactors The expertly crafted swords, which sell for about 1 million yen when finished, are forged from a single 2.2-lb. lump of Tamahagane steel, the traditional material that's rarely used today.

"Samurai swords contain the essence of steelmaking technology,'' Japan Steel Works CEO Masahisa Nagata told Bloomberg in 2008.

The Fukushima disaster spawned by last week's tsunami pose the greatest challenge ever to a Japan Steel Works nuclear vessel. Unfortunately for Japan, the accident hit the nation's oldest operating nuclear reactors; the vessel in Fukushima 1 was made by JSW in 1967, based on a General Electric's Mark 1 design for boiling water reactors that has been criticized in the past for potentially being prone to failure.

Of the three reactors in crisis at the Fukushima plant, the one in the most danger of failure appears to be reactor number 2, which suffered an explosion on Monday. Japanese government officials gave conflicting statements about whether that explosion — likely caused by steam venting off the nuclear rods — damaged the vessel, although radiation levels outside the plant were falling Tuesday. Due to the damage from the explosions and overheating, none of the three reactors will ever work again.

Experts around the world also differ about the chances of disaster, but several say if Japanese officials can stabilize the reactors, the worst might be averted. Let's hope we never find out just how strong the steel of these samurai sword-forging metal craftsmen truly is.

(Photo Credits: Shutterstock; Fukushima plant, Digital Globe; others, Japan Steel Works)