Sulfide is oxidised by atmospheric oxygen and Fe(III), thus forming sulfuric acid which can leach from ores containing radionuclides and toxic heavy metals. As part of the radioactive decay series of uranium, radon-222, a radioactive noble gas, emanates from geological deposits. have a half-life Since 1945, the testing and use of nuclear weapons has also released numerous radioactive fission products.

As already discussed, the Th-232 isotope is the parent nuclide in a radioactive decay series. This series consists of eight α decays and six β decays. This type of radioactive equilibria is called “secular equilibrium.” In Fig. $$\overset{\underset{\mathrm{def}}{}}{=}$$, Summarizing Nuclear Structure and Stability, Summarizing Transmutation and Nuclear Energy, Effects of Long-term Radiation Exposure On the Human Body, Summarizing Biological Effects of Radiation, Appendix: Half-lives For Several Radioactive Isotopes, http://cnx.org/contents/85abf193-2bd2-4908-8563-90b8a7ac8df6@12.1. One example of this is uranium (atomic number 92) decaying into thorium (atomic number 90). Its half-life and decay constant are 14 billion years and 5×10−11/years, respectively, so its radioactivity is also very low and can be measured only with difficulty. Secular equilibrium: activities of the parent nuclide (A1), the daughter nuclide (A2), the total activity (A1+A2), and the activity of the daughter nuclide when not produced from the parent nuclide as a function of time.

Therefore, huge amounts of nuclides including radium are present in tailings. Contamination of soils, critical zone, surface and groundwater has to be considered as well as waste rock piles and tailings. Activities of the parent nuclide (A1), the daughter nuclide (A2), the total activity (A1+A2), and the activity of the daughter nuclide when not produced from the parent nuclide as a function of time. The other common decay method for isotopes with a high neutron to proton ratio (n/p) is beta decay, in which the nuclide changes elemental identity while keeping the same mass and lowering its n/p ratio. The most suitable for these studies is the isotope 211At (t1/2 7.21 hrs). 1.536 in lead-208). The final step is drying to ammonium diuranate, (NH4)2U2O7, which is then heated to obtain yellowcake (~ 80% U3O8 with 20% UO2 and UO3). During underground mining, this gas was released to the work space, and miners inhaled both this gas and its radioactive progeny in significant amounts. №  primarily a naturally occurring radioactive material (NORM) The half-lives are 24.1 days for 234Th and 4.5×109 years for 238U. Figure 4.3. 100–210 ka ... Legend for superscript symbols R.E.