Induced radioactivity, also called artificial radioactivity or man-made radioactivity, is the process of using

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

to make a previously stable material

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

. The husband-and-wife team of Irène Joliot-Curie and

Frédéric Joliot-Curie Jean Frédéric Joliot-Curie (; ; 19 March 1900 – 14 August 1958) was a French chemist and physicist who received the 1935 Nobel Prize in Chemistry with his wife, Irène Joliot-Curie, for their discovery of induced radioactivity. They were t ...

discovered induced radioactivity in 1934, and they shared the 1935 Nobel Prize in Chemistry for this discovery. Irène Curie began her research with her parents,

Marie Curie Maria Salomea Skłodowska-Curie (; ; 7 November 1867 – 4 July 1934), known simply as Marie Curie ( ; ), was a Polish and naturalised-French physicist and chemist who conducted pioneering research on radioactivity. She was List of female ...

and

Pierre Curie Pierre Curie ( ; ; 15 May 1859 – 19 April 1906) was a French physicist, Radiochemistry, radiochemist, and a pioneer in crystallography, magnetism, piezoelectricity, and radioactivity. He shared the 1903 Nobel Prize in Physics with his wife, ...

, studying the natural radioactivity found in

radioactive isotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

s. Irene branched off from the Curies to study turning stable

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

s into radioactive isotopes by bombarding the stable material with

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

s (denoted α). The Joliot-Curies showed that when lighter elements, such as

boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, were bombarded with α-particles, the lighter elements continued to emit radiation even after the α−source was removed. They showed that this radiation consisted of particles carrying one unit positive charge with mass equal to that of an electron, now known as a

positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...

. Neutron activation is the main form of induced radioactivity. It occurs when an

atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester ...

captures one or more free

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s. This new, heavier

may be either stable or unstable (radioactive), depending on the

chemical element A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...

involved. Because neutrons disintegrate within minutes outside of an atomic nucleus, free neutrons can be obtained only from nuclear decay,

nuclear reaction In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two atomic nucleus, nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a t ...

, and high-energy interaction, such as cosmic radiation or

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

emissions. Neutrons that have been slowed through a

neutron moderator In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely ...

( thermal neutrons) are more likely to be captured by nuclei than fast neutrons. A less common form of induced radioactivity results from removing a neutron by

photodisintegration Photodisintegration (also called phototransmutation, or a photonuclear reaction) is a nuclear process in which an atomic nucleus absorbs a high-energy gamma ray, enters an excited state, and immediately decays by emitting a subatomic particle. The ...

. In this reaction, a high energy photon (a

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

) strikes a nucleus with an energy greater than the

binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...

of the nucleus, which releases a neutron. This reaction has a minimum cutoff of 2 MeV (for

deuterium Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...

) and around 10 MeV for most heavy nuclei. Many radionuclides do not produce gamma rays with energy high enough to induce this reaction. The isotopes used in food irradiation ( cobalt-60, caesium-137) both have energy peaks below this cutoff and thus cannot induce radioactivity in the food. The conditions inside certain types of

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

s with high neutron flux can induce radioactivity. The components in those reactors may become highly radioactive from the radiation to which they are exposed. Induced radioactivity increases the amount of

nuclear waste Radioactive waste is a type of hazardous waste that contains radioactive material. It is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear ...

that must eventually be disposed, but it is not referred to as

radioactive contamination Radioactive contamination, also called radiological pollution, is the deposition of, or presence of Radioactive decay, radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is uni ...

unless it is uncontrolled. Further research originally done by Irene and Frederic Joliot-Curie has led to modern techniques to treat various types of cancers.

Ștefania Mărăcineanu's work

After

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

, with support from Constantin Kirițescu, Ștefania Mărăcineanu obtained a fellowship that allowed her to travel to

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

to further her studies. In 1919 she took a course on radioactivity at the Sorbonne with

. Afterwards, she pursued research with Curie at the Radium Institute until 1926. She received her Ph.D. At the institute, Mărăcineanu researched the

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of polonium and devised methods of measuring

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...

.This work led her to believe that radioactive isotopes could be formed from atoms as a result of exposure to polonium's alpha rays, an observation which would lead to the Joliot-Curies' 1935 Nobel Prize. In 1935, Frederic and Irene Joliot-Curie (n.r.—daughter of scientists

and Marie Curie) won the Nobel Prize in Chemistry for the discovery of artificial radioactivity. Ștefania Mărăcineanu expressed her dismay at the fact that Irene Joliot-Curie had used a large part of her work observations regarding artificial radioactivity, without mentioning it. Mărăcineanu publicly claimed that she discovered artificial radioactivity during her years of research in Paris, as evidenced by her doctoral dissertation, presented more than 10 years earlier. "Mărăcineanu wrote to

Lise Meitner Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission. After completing her doctoral research in 1906, Meitner became the second woman ...

in 1936, expressing her disappointment that Irene Joliot Curie, without her knowledge, used much of her work, especially that related to artificial radioactivity, in her work," is mentioned in the book ''A devotion to their science: Pioneer women of radioactivity''. Historians, however, have thrown doubt on the claims of Mărăcineanu.

Notes

External links

PhysLink.com – Ask the Experts "Gamma ray food irradiation"
* Conference (Dec. 1935) for the Nobel prize of F. & I. Joliot-Curie (induced radioactivity), online and analyzed on
BibNum
' lick 'à télécharger' for English version/small>. {{DEFAULTSORT:Induced Radioactivity Radioactive waste Radiation effects

Ștefania Mărăcineanu's work

See also

Notes

External links