Rjukan

Rjukan (ˈrʉ̀ːkɑn) is a town and the administrative centre of Tinn municipality in Telemark, Norway. It is situated in Vestfjorddalen, between Møsvatn and Lake Tinn, and got its name from the Rjukan Falls west of the town. The Tinn municipality council granted township status for Rjukan in 1996. As of 2022, the town has 3,003 inhabitants. The town was essentially "built from scratch" with industrial developments by Norsk Hydro in the 1910s and 20s. At its peak, Rjukan was a significant industrial center of Telemark. It became a World Heritage Site under the name Rjukan–Notodden Industrial Heritage Site on 5 July 2015. But the town is perhaps best known for the heavy water sabotage operations at the local Vemork hydroelectric power plant during World War II. Rjukan does not get any sunlight between September and March because the low sun is blocked by the tall Gaustatoppen directly to the south. In 1906, the area which would become Rjukan consisted of only a few farmsteads, then called Saaheim, when Norsk Hydro began planning saltpeter (fertilizer) production in the area using the newly developed Birkeland–Eyde process. Rjukan was chosen because the Rjukan Falls, with a 104-meter longest single fall, provided easy means of generating the large amounts of electricity that was required. The Vemork hydroelectric power plant was built between 1907 and 1911, and was at the time the world's largest hydroelectric power plant. A similar power plant was finished in Såheim in 1915. The power plants had a combined cost of more than 200 million kroner, the equivalent of two national budgets at the time. With the factories, many houses for the factory workers also had to be built, in addition to a train station and a town hall. The town formally changed its name to Rjukan, and in 1920 reached a population of 8,350. In 1934, Norsk Hydro built a hydrogen plant next to the Vemork power plant. A by-product of hydrogen production via water electrolysis was heavy water.