Naturally occurring radioactivity

Conservation of Energy. Because the naturally occurring radioactive materials continued to emit particles, and thus the associated energy, without any decrease in intensity, the question of the source of this energy arose. Whereas the conservation of energy was a firmly estabUshed law of physics, the origin of the energy in the radioactivity was unknown. 

Thorium [7440-29-1], a naturally occurring radioactive element, atomic number 90, atomic mass 232.0381, is the second element of the actinide ( f) series (see Actinides AND transactinides Radioisotopes). Discovered in 1828 in a Norwegian mineral, thorium was first isolated in its oxide form. For the light actinide elements in the first half of the. series, there is a small energy difference between and 5/ 6d7 electronic configurations. Atomic spectra... 

Uranium [7440-61-17 is a naturally occurring radioactive element with atomic number 92 and atomic mass 238.03. Uranium was discovered in a pitchblende [1317-75-5] specimen ia 1789 by M. H. Klaproth (1) who named the element uranit after the planet Uranus, which had been recendy discovered. For 50 years the material discovered by Klaproth was thought to be metallic uranium. Pnligot showed that the uranit discovered by Klaproth was really uranium dioxide [1344-57-6] UO2, and obtained the tme elemental uranium as a black powder in 1841 by reduction of UCl [10026-10-5] with potassium (2). 

It is also necessary to explain the existence of naturally occurring radioactive elements whose half-lives (or those of their precursors) are substantially less than the presumed age of the universe. 

Radon (Rn) is a naturally occurring radioactive gas. Radon enters buildings from underlying soil and rocks as soil gas is drawn into buildings. 

Naturally occurring radioactive nuclei commonly decompose by—... 

Finally, P also differs from other elements in that it is overwhelmingly dominated by a single, stable isotopic form containing 15 protons and 16 neutrons. There are only two naturally occurring radioactive forms of P P and P, which are produced in the atmosphere by nuclear reactions with argon. A small amount of P is... 

Analyses of this type are correct only if all of the product nuclide comes from radioactive decay. This is not known with certainty, but when age estimates using different pairs of nuclides give the same age and samples from different locations also agree, the age estimate is likely to be accurate. Note also that 3.8 X 10 years agrees with the qualitative limits derived from naturally occurring radioactive nuclides. 

Radioactivity, Artificial—Man-made radioactivity produced by particle bombardment or nuclear fission, as opposed to naturally occurring radioactivity. 

There are seven naturally occurring radioactive elements from uranium, the elements are all unstable and were prepared artificially. This is an astonishing phenomenon. Not only did evolution produce a being that was in the position to discover the Periodic Table, it gave it the ability to produce elements that do not exist in nature. Needless to say, we shall not go any deeper into this aspect of natural philosophy. 

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. 

This very long half-life (1.25x1(r years) isotope comprises 0.0117 percent of all potassium. Thus, this isotope is present in all of us and has always been so. In addition, the materials around us, including the soil and the building materials, contain both potassium and the heavy naturally occurring radioactive elements thorium and uranium that contribute to a level of radiation to which we are all continuously exposed. Thus, there is always radiation exposure to the general public and we must understand the exposure due to radon in this context. The amount of radioactivity is described in units of activity. The activity is the number of decay events per unit time and is calculated as follows... 

This results in the transmutation of parent element X into daughter Y, which has an atomic number two less than X. The particular isotope of element Y which is formed is that with an atomic mass of four less than the original isotope of X. Note that, as in chemical reactions, these nuclear reactions must be numerically balanced on either side of the arrow. Many of the heavy elements in the three naturally occurring radioactive decay chains (see below) decay by a-emission. 

ISOTOPES There are 52 isotopes of cadmium. Forty-four are radioactive and artificially produced, ranging from Cd-96 to Cd-131. Of these 52 isotopes, there are five stable isotopes plus three naturally occurring radioactive isotopes with extremely long half-lives that are considered as contributing to the element s natural occurrence in the Earth s crust. The three naturally radioactive isotopes (Cd-106, Cd-113, and Cd-116) are the longest known beta emitters. They are two million years older than when the solar system was formed about 4.5 billion years ago. The five stable isotopes and their proportional contributions to the elemenfs existence on Earth are as follows Cd-108 = 0.89%, Cd-110 = 12.49%, Cd-111= 12.80%, Cd-112 = 24.13%, and Cd-114 = 28.73%. 

Most of the known chemistry of polonium is based on the naturally occurring radioactive isotope polonium-210, which is a natural radioactive decay by-product of the uranium decay series. Its melting point is 254°C, its boiling point is 962°C, and its density is 9.32g/cm. ... 

All naturally occurring radioactive substances (besides those specified in the... 

Table 11.2 Naturally occurring radioactive substances, a = years, d = days. Radionuclide Decay Process Half-Life Isotopic Abundance (%) Stable End-Product...

Radon is a naturally occurring radioactive decay product of uranium. A great deal of attention 222 228 centers around radon, which is the first decay product of radium. Radon and radon... 

Marie Curie discovered radium in her laboratory in Paris in 1898. The unique properties of this naturally occurring radioactive element suggested to many that it had therapeutic uses. In the early 1900s, radium therapy was accepted by the American Medical Association. Radium was thought to cure a range of illnesses including... 

According to the vendor, the technology can be used to (1) remediate water and sludges contaminated with radionuclides and heavy metals, (2) restore gronndwater from mining operations, (3) treat naturally occurring radioactive materials (NORMs) in water or scale from petroleum operations, and (4) remediate man-made radionuclides stored in tanks, pits, barrels, or other containers. 

Some cancers are caused by exposure to the sun or to naturally occurring radioactive isotopes. The estimated cancer incidence caused by these combined exposures is approximately 0.5 to 1.0 percent during a lifetime, with two-thirds of the exposure stemming from radon alone (Kocher and Hoffman 1991,1989 National Council on Radiation Protection and Measurement 1987,15,53 International Commission on Radiological Protection 1991, 188). 

There are (I) naturally occurring radioactive and (2) artificially produced radioactive elements. There are Ihree series of naturally occurring radioactive elements ... 

---