It was, and de Hevesy's suspicions were confirmed. Several days later, when the same dish was served again, he used a simple radiation detection instrument – a gold leaf electroscope – to check if the food was radioactive. To try and confirm his suspicions de Hevesy put a small amount of radioactive material into the remains of a meal. He began to suspect that some of the meals that appeared regularly might be made from leftovers from the preceding days or even weeks, but he could never be sure.

Not having much money he lived in modest accommodation and ate his meals with his landlady. At the time de Hevesy was a young student working in Manchester, studying naturally radioactive materials. The first practical application of a radioisotope was made by a Hungarian man named George de Hevesy in 1911. The attributes of naturally decaying atoms, known as ‘radioisotopes’, give such atoms several applications across many aspects of modern day life. Others are 'unstable' or radioactive since their nuclei change over time through the loss of alpha and beta particles. Some isotopes are referred to as 'stable' as they are unchanging over time. Isotopes are variants of a given chemical element that have nuclei with the same number of protons, but different numbers of neutrons. Radioisotopes, nuclear power process heat and non-stationary power reactors have essential uses across multiple sectors, including consumer products, food and agriculture, industry, medicine and scientific research, transport, and water resources and the environment.The applications of nuclear technology outside of civil electricity production in power plants are less well-known.Today most people are aware of the important contribution nuclear energy makes in providing a significant proportion of the world's low-carbon electricity. The first power station to produce electricity by using heat from the splitting of uranium atoms began operating in the 1950s.Three types of moderators are used at the MIT reactor: (1) ordinary or 'light' water that is also used to cool the reactor core, (2) deuterated or heavy water (D 20), and (3) high-purity graphite, both of which are excellent at slowing neutrons without absorbing them. Since U-235 nuclei do not readily absorb the high energy neutrons that are emitted during fission, it is necessary to slow the neutrons down with a 'moderator'. In the MIT reactor, one other group of components is essential to the maintaining and controlling a chain reaction. As fewer and fewer neutrons are absorbed, more and more neutrons are available to cause the splitting of uranium nuclei, until finally enough neutrons are available to sustain a chain reaction. To put the reactor into operation, the control blades are raised very slowly. When the control blades are fully inserted, they absorb so many neutrons from the uranium that there are not enough to allow a chain reaction to continue. Boron has the property of absorbing neutrons without re-emitting any. The rate of fissions in the uranium nuclei in the MIT reactor is controlled chiefly by six control blades of boron-stainless steel which are inserted vertically alongside the fuel elements. When it is in operation, the central active core contains a huge number of neutrons traveling in every direction at very high speeds. The MIT Research Reactor is used primarily for the production of neutrons. Hence, the possibility exists for creating a chain reaction. Each time a U-235 nucleus splits, it releases two or three neutrons. This process is known as fission (see diagram below). When a U-235 nucleus absorbs an extra neutron, it quickly breaks into two parts. The arrangement of particles within uranium-235 is somewhat unstable and the nucleus can disintegrate if it is excited by an outside source. In the nucleus of each atom of uranium-235 (U-235) are 92 protons and 143 neutrons, for a total of 235.

Examples of nuclear fission