75 years ago today, the crucial experiment which led to the discovery of nuclear fission was conducted at the Kaiser-Wilhelm Institute for Chemistry in Berlin. This discovery fundamentally changed the image of atomic nuclei and heralded the beginning of a new era for nuclear physics.
During the experiment carried out by Otto Hahn, Director of the Institute, and his assistant Fritz Strassmann, a uranium sample was bombarded with slowed down, slow neutrons. The series of experiments was actually intended to generate and further research heavy elements of the periodic system beyond uranium, transuranium elements. Other research teams, led for example by the Italian physicist Enrico Fermi and the Frenchwoman Irène Joliot-Curie, were also carrying out similar tests. The Berlin experiment of 17 December 1938 was the answer to a challenge by the team led by Irène Curie in Paris. Hahn and Strassmann wanted to attribute the radioactivity which had been observed and assigned to a new element by Curie to known elements and decay processes. During their analysis of the reaction products, however, it transpired that the lighter element barium was also formed.
On 19 December, Hahn contacted Lise Meitner and addressed the possibility of a “splitting asunder” of uranium nuclei following neutron bombardment. Meitner had the greatest say on theory questions and physical understanding in the study group but was forced to go into exile in Sweden in July 1938 because she was being persecuted in Germany as a person of Jewish descent. Meitner and her nephew Otto Robert Frisch, who was also a physicist, provided a theoretical framework for the observations of Hahn and Strassmann and coined the term “nuclear fission”. In 1944, Otto Hahn was awarded the Nobel Prize for Chemistry for discovering the fission of heavy atomic nuclei.
A large number of physicists subsequently dedicated themselves to the discovery and quickly achieved advances in knowledge. When nuclear energy was first used, the focus was on the military aspect and this shaped the consciousness of the era at that time. However, with US President Dwight D. Eisenhower’s speech “Atoms for Peace” before the United Nations on 8 December 1953, the peaceful use of nuclear energy became the focus of attention for politicians and the world public. The speech founded the International Atomic Energy Organization (IAEO) which to this day promotes the peaceful use of nuclear technology in energy, medicine, research, industry and agriculture, monitors the stocks and exchange of fissile material and develops safety-related standards.
The most important area of use for nuclear technology is power generation which accounts for 11 percent of global electricity production in a climate-friendly way. In the 31 countries that use nuclear energy, it forms a significant component in the energy mix accounting for up to 78 percent of the supply. In view of the rising global demand for electricity, this will remain the case for a very long time. The assessment that all established types of energy will be needed to cover this increasing demand for electricity is also shared by the majority in Germany. In the DAtF’s current representative opinion poll, 65 percent of those asked hold this view. Go to kernenergie.de for the complete results of the survey.