Uranium is the primary material used for producing nuclear energy, which accounts for 11% of the world’s electric power today. It is only weakly radioactive, with a half-life of 4.5 billion years. Uranium is a naturally occurring element found in the earth’s crust, and is 40 times more abundant than silver. Global demand for refined uranium stands at around 60,000 tons per year. Most of this uranium goes toward energy production, though smaller amounts are used in medical research and for military purposes such as marine and submarine propulsion and weapons. Uranium is so important to nuclear energy production because its nucleus is relatively easy to split, and doing so releases massive amounts of energy.
Uranium is easier to find than other metals because its radiation signature is detectable from the air. Historically, companies have dug large mines to harvest uranium from the earth’s crust. The ore is extracted and leached with sulfuric acid to remove oxidation, then the uranium itself is chemically separated from impurities. Underground mines are still fairly common today, although a new method called "in situ leaching" has become more prevalent in the past few decades, particularly in Kazakhstan. "In situ leaching" is most effective when uranium is stuck within looser surrounding materials, such as sand or gravel. In this process, weakly acidic water is pumped into large containers of such material. Uranium dissolves into the water, which is removed, and then uranium is precipitated back out of the water in a refinery.
The French scientist Henri Becquerel first discovered the radioactive properties of uranium in 1896. In 1939, the German scientist Otto Hahn used uranium to conduct the first-ever nuclear fission. This sparked a serious search for uranium in places like Canada and the United States in the early 1940s, which culminated with the famous nuclear bombs dropped on Hiroshima and Nagasaki, Japan in 1945, effectively ending World War II. After the war, other countries around the globe also began searching and mining for uranium. Defense purposes aside, it became all the more desired after researchers first developed a means by which to use nuclear fission to generate electrical power in the 1950s. In situ leaching became popular in the 1970s, and allowed for a great expansion in the industry.
Mining uranium is a relatively safe process, since the element is only mildly radioactive. However, there are two main dangers for workers. The first is exposure to radon, a radioactive gas released into the atmosphere when uranium is mined. To combat this, countries have regulations requiring ventilation, dust control, and radiation detection equipment within underground Uranium mines. The second is exposure to "gamma rays", which are radioactive beams released when mining high-grade uranium ore. Since gamma rays are more dangerous than radon gas, most high-grade mines use remotely operated equipment to harvest the ore. Local governments also pass regulations to protect local groundwater in areas where in situ leaching is carried out. Following the 1986 Chernobyl Disaster, which devastated the Ukrainian and Belarusian economies, directly killed 31 people, and contaminated over 62,000 square miles (100,000 square kilometers) of landmass, many people all over the world have been more wary of utilizing nuclear energy, and have called for tighter regulations or even discontinuing its use altogether. However, concerns over the potential dangers of uranium and nuclear energy have only continued to rise after the 2011 Fukushima Daiichi disaster in Japan.