Radioactivity of uranium

Rutherford E (1900) A radioactive substance emitted from thorinm componnds. Philosoph Mag 49 1-14 Rutherford E, Soddy F (1903) The radioactivity of uranium. Philosoph Mag 5 441-445... 

The presence of radiation in the workplace - which is an inevitable consequence of the radioactivity of uranium - requires that additional safety precautions be taken over and above those observed in other similar workplaces. There are generally three sources from which radiation exposure may occur (i) radiation emitted from uranium ore in-situ and/or during handling (ii) airborne radiation resulting from the decay of radon gas released from the ore and uranium dust and (iii) contamination by ore dust or concentrate. Radiation levels around uranium mining and milling facilities are quite low - for the most part only a few times the natural background levels - and they decrease rapidly as the distance from... 

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

The element was discovered in the pitchblende ores by the German chemist M.S. Klaproth in 1789. He named this new element uranium after the planet Uranus which had just been discovered eight years earlier in 1781. The metal was isolated first in 1841 by Pehgot by reducing the anhydrous chloride with potassium. Its radioactivity was discovered by Henry Becquerel in 1896. Then in the 1930 s and 40 s there were several revolutionary discoveries of nuclear properties of uranium. In 1934, Enrico Fermi and co-workers observed the beta radioactivity of uranium, following neutron bombardment and in 1939, Lise Meitner, Otto Hahn, and Fritz Strassmann discovered fission of uranium nucleus when bombarded with thermal neutrons to produce radioactive iso-... 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

Although physics and chemistry were responsible for the conceptual framework overall, radiochemistry defined the experimental approach and provided much of the initial data. The neutron sources then in use (usually radium or radon [a source of alpha particles] mixed with powdered beryllium) were weak, with the result that the new beta activities were not much stronger than the natural radioactivity of uranium and its decay products. In 1934, the Rome group chemically separated the new activities from uranium by co-precipitating them with manganese and rhenium compounds (both transition metals), which supported the notion that these were... 

Several methods that do not require chemical separation are available for measuring uranium in urine (in units of total mass or total activity). These methods include spectrophotometric (total mass), fluorometric (total mass), kinetic phosphorescence analysis (KPA) (total mass), and gross alpha (total activity) analyses (Wessman 1984). The most widely used methods for routine uranium analysis are a-spectrometry and liquid scintillation spectrometry. These methods utilize the natural radioactivity of uranium and are sensitive and require little sample preparation. Photometric techniques such as fluorometry and phosphorometry are less widely used, but kinetic phosphorescence analysis is becoming more widely used. Measurements of total uranium do not provide the relative isotopic abundance of the uranium isotopes, but this may only be important when converting between activity and mass when the isotopic ratios are uncertain. 

Radioactivity was discovered in 1896 in Paris by Henri Becquerel, who investigated the radiation emitted by uranium minerals. He found that photographic plates were blackened in the absence of light, if they were in contact with the minerals. Two years later (1898) similar properties were discovered for thorium by Marie Curie in France and by G. C. Schmidt in Germany. That radioactivity had not been discovered earher is due to fact that human beings, like animals, do not have sense organs for radioactive radiation. Marie Curie found differences in the radioactivity of uranium and uranium minerals and concluded that the minerals must contain still other radioactive elements. Together with her husband, Pierre Curie, she discovered polonium in 1898, and radium later in the same year. 

The radioactivity of uranium w as discovered in 1896 by Becquerel. Two years later, Madame Curie, observing that the radioactivity of pitchblende was greater than that of the element uranium, suggested that small quantities of a more active element were probably present in the mineral. This supposition led to the extraction of a chloride of the new element and to the subsequent discovery of radium. The... 

See this series, Vol. III., Part I. For Radioactivity of Uranium see this Vol, Chap. X. 

Becquerel, Henri. (1851-1908). A French physicist who shared the Nobel Prize in physics with the Curies for the discovery of the radioactivity of uranium salts. He also discovered the deflection of electrons by a magnetic field, as well as the existence and properties of "/-radiation. 

Curie, Marie (1867-1934). Discovered and isolated radium research on radioactivity of uranium. Nobel Prize 1903 (with Becquerel) in physics in chemistry 1911. 

In 1896, when 76 Lavoisier elements were known [1], the discovery of the radioactivity of uranium by Henri Becquerel (1852-1908) [the first positive result in March 1896, after a series of negative experiments by other people studying fluorescent materials, subsequent to a rather far-fetched remark in December 1895 by the mathematician Henri Poincare (1854-1912) that since X-rays induce a strong fluorescence in BaPt(CN)4- 4H2O, fluorescent solids may... 

The radiations produced by uranium and thorium were quite feeble, and difficult to work with. This situation was corrected by Mme. Curie. Investigating the radioactivity of uranium minerals, she found some samples of ore of low uranium content that were nevertheless intensely radioactive—more so than if they had been pure uranium. 

After discovery of the natural radioactivity of uranium, thorium, and radium, many other elements were found to have radioactive isotopes. All the elements heavier than bismuth (Bi, atomic number 83) and a few lighter than bismuth have natural radioactivity. While studying radium, Rutherford found that besides emitting alpha particles, radiiun was also producing radioactive... 

Soon after Becquerel s discovery of uranium s radioactivity, Marie Sklodowska Curie (1867—1934), also working in France, studied the radioactivity of thorium (Th) and began to search systematically for new radioactive elements. She showed that the radioactivity of uranium was an atomic property— that is, its radioactivity was proportional to the amount of the element present and was not related to any particular compound. Her experiments indicated that other radioactive elements were probably also present in certain uranium samples. With painstaking technique, she and her husband Pierre Curie (1859-1906) separated the element radium (Ra) from uranium ore and found that it is more than one million times more radioactive than uranium. In 1903, Marie and Pierre Curie shared the Nobel Prize in physics with Henri Becquerel for their discovery of radioactivity. After Pierre died. 

The prospecting of uranium mines is facilitated by the radioactivity of uranium and its daughter products. Uranium deposits are usually judged by their size and by the price it costs to extract a kilogram of uranium. A survey of the worldwide resources of uranium is given in O Table 57.13. 

The natural radioactivity of uranium can be summarized as the decay of to stable Pb and as the decay of to stable "Pb. The half-fives of and (4.468 X Iff and 0.7038 x 10 years, respectively) are much longer than those of their daughters. Therefore, these decay series satisfy the condition of secular equilibrium in a U-bearing mineral, which remains as a... 

BCC( Uerel, Antoine-Henri (1852-1908) French physicist who was the first to discover radioactivity. In 1896 he noticed that a uranium salt laid on a totally enclosed photographic plate caused the plate to be exposed. Becquerel concluded that the salt was emitting rays similar to the X-rays that had been discovered by Wilhelm Rontgen the year before. He then studied and described the properties of the natural radioactivity of uranium. For this work, he shared the Nobel Prize in physics with Pierre and Marie Curie in 1903. 

---