Uranium emanation

Marie (NLP 1903, NLC 1911 ) and Pierre (NLP 1903 ) Curie took up further study of Becquerel s discovery. In their studies, they made use of instrumental apparatus, designed by Pierre Curie and his brother, to measure the uranium emanations based on the fact that these emanations turn air into a conductor of electricity. In 1898, they tested an ore named pitchblende from which the element uranium was extracted and found that the electric current produced by the pitchblende in their measuring instrument was much stronger than that produced by pure uranium. They then undertook the herculean task of isolating demonstrable amounts of two new radioactive elements, polonium and radium, from the pitchblende. In their publications, they first introduced the term radio-activity to describe the phenomenon originally discovered by Becquerel. After P. Curie s early death, M. Curie did recognize that radioactive decay (radioactivity) is an atomic property. Further understanding of radioactivity awaited the contributions of E. Rutherford. 

Global uranium flux calculations have typically been based on the following two assumptions (a) riverine-end member concentrations of dissolved uranium are relatively constant, and (b) no significant input or removal of uranium occurs in coastal environments. Other sources of uranium to the ocean may include mantle emanations, diffusion through pore waters of deep-sea sediments, leaching of river-borne sediments by seawater," and remobilization through reduction of a Fe-Mn carrier phase. However, there is still considerable debate... 

Barretto, P.M.C., Emanation Characteristics of Terrestrial and Lunar Materials and the Radon-222 Loss Effect on the Uranium-Lead System Discordance, Ph.D. thesis, Rice University, Houston (1973). ... 

Strong, K.P., and Levins, D.M., Effect of Moisture Content on Radon Emanation from Uranium Ore and Tailings, Health Phys. 42 27-32 (1982). 

Figure 7. Radon concentration growth in the outer volume during the first fifteen hours after closure. The exhalation can is radon-tight (y= 1). The exhalation material is dry sand mixed with 11 % ground uranium ore by weight. The diffusion length, L, is 1.4 m, the sample thickness, d, is 26 cm and the outer volume height, h, is 4.0 cm. Other parameters of the sample are as follows porosity 0.47, radium concentration 1180 Bq kg, emanation fraction 0.33, bulk density 1710 kg m 3 (experiment + theory).

Radon-222, a decay product of the naturally occuring radioactive element uranium-238, emanates from soil and masonry materials and is released from coal-fired power plants. Even though Rn-222 is an inert gas, its decay products are chemically active. Rn-222 has a a half-life of 3.825 days and undergoes four succesive alpha and/or beta decays to Po-218 (RaA), Pb-214 (RaB), Bi-214 (RaC), and Po-214 (RaC ). These four decay products have short half-lifes and thus decay to 22.3 year Pb-210 (RaD). The radioactive decays products of Rn-222 have a tendency to attach to ambient aerosol particles. The size of the resulting radioactive particle depends on the available aerosol. The attachment of these radionuclides to small, respirable particles is an important mechanism for the retention of activity in air and the transport to people. 

Depleted uranium is composed mostly of the U-238 isotope and is considered depleted because most of its U-235 component has been removed. Natural uranium is composed of approximately 0.7% U-235 and 99.3% U-238. Depleted uranium has only about half the radioactivity of the original natural element, but radiation emanating from depleted uranium can be hazardous to human health and the environment. 

Large thorium deposits have heen found in many parts of the world. It occurs in minerals thorite, ThSi04, and thorianite, Th02"U02. Thorium also is found in mineral monazite which contains between 3 to 9% Th02. Th02 is the principal source of commercial thorium. Abundance of thorium in earth s crust is estimated at about 9.6 mg/kg. Thorium and uranium are believed to have contributed much of the internal heat of the earth due to their radioactive emanations since earth s formation. 

May 14,1899 Aug. 16,1899 1899 1900 1900 Death of Nilson. Death of Bunsen. Debierne discovers actinium. Dorn discovers radon (radium emanation). Sir William Crookes discovers uranium Xj. 

A radioactive element is an element that disintegrates spontaneously with the emission of various rays and particles. Most commonly, the term denotes radioactive elements such as radium, radon (emanation), thorium, promethium, uranium, which occupy a definite place in the periodic table because of their atomic number. The term radioactive element is also applied to the various other nuclear species, (which arc produced by the disintegration of radium, uranium, etc.) including (he members of the uranium, actinium, thorium, and neptunium families of radioactive elements, which differ markedly in their stability, and are isotopes of elements from thallium (atomic number 81) to uranium (atomic number... 

Radium is chemically similar to barium it displays a characteristic optical spectrum its salts exhibit phosphorescence in the dark, a continual evolution of heat taking place sufficient in amount to raise the temperature of 100 times its own weight of water 1°C every hour and many remarkable physical and physiological changes have been produced. Radium shows radioactivity a million times greater than an equal weight of uranium and. unlike polonium, suffers no measurable loss of radioactivity over a short period of time (its half life is 1620 years). From solutions of radium salts, there is separable a radioactive gas radium emanation, radon, which is a chemically ineit gas similai to xenon and disintegrates with a half life of 3.82 days, with the simultaneous formation of another radioactive element, Radium A (polonium-218). 

The loss of the alpha particle by the emanation, 21sRn, leads to the formation of 214Po, which is identical with radium C2 of the Uranium Series the subsequent decay of the coliateral series thus becomes identical with that of the main Uranium Series at this point. 

P Decay is named for the second most ionizing rays that were found to emanate from uranium samples. The naturally occurring p rays were identified as fast moving (negative) electrons relatively easily, but it took many years to obtain a full understanding of the emission process. The difficulty lies in the fact that two particles are... 

The low helium concentrations of rocks of known ages indicate emanation efficiencies of 0.8-1 (Podosek et al., 1980 Zaikowski et al., 1987). The concentrations of uranium and thorium vary by a factor of 10 in common rocks, but knowledge of the lithologies of the main aquifer rocks can narrow the uncertainty to a factor of three or less. The rock water ratio is more difficult to assess, but reasonable values are 4-20. Local information... 

Before Rutherford left the Cavendish Laboratory he had taken active part in the many discussions over the work of Becquerel, Roentgen, and the Curies. Here was a virgin field full of possibilities. He chose it, and began working with uranium and thorium, a kindred element. By 1900, he had already noticed a peculiar phenomenon in connection with the latter substance. It gave off a minute amount of a gas very rich in radioactivity. He carried out precise experiments to determine the nature of the gas and found, to his astonishment, that it was a hitherto unknown substance. He named this gas thorium emanation. ... 

---