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Uranium-235 (235 U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nature as a primordial nuclide. Uranium-235 has a half-life of 703.8 million years.
Uranium in the environment is a global health concern, and comes from both natural and man-made sources. Beyond naturally occurring uranium, mining, phosphates in agriculture, weapons manufacturing, and nuclear power are anthropogenic sources of uranium in the environment. [1]
Uranium mining is the process of extracting uranium ore from the ground. Kazakhstan, Canada, and Australia are the top three producers and together account for 63% of world uranium production. [30] A prominent use of uranium is as fuel for nuclear power plants. The mining and milling of uranium present significant dangers to the environment. [31]
The 4n+3 chain of uranium-235 is commonly called the "actinium series" or "actinium cascade". Beginning with the naturally-occurring isotope uranium-235, this decay series includes the following elements: actinium, astatine, bismuth, francium, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least ...
Thus plutonium may decay and leave uranium-235. However, modern reactors are only moderately enriched with U-235 relative to U-238, so the U-238 continues to serve as a denaturation agent for any U-235 produced by plutonium decay. One solution to this problem is to recycle the plutonium and use it as a fuel e.g. in fast reactors.
Radium and radon are in the environment because they are decay products of uranium and thorium. The radon (222 Rn) released into the air decays to 210 Pb and other radioisotopes, and the levels of 210 Pb can be measured. The rate of deposition of this radioisotope is dependent on the weather. Below is a graph of the deposition rate observed in ...
A uranium radionuclide is a radioactive isotope. Radioactivity is natural in the environment, however uranium radionuclides can lead to radioactive decay. In the case of uranium mines, these radionuclides can leach into the water and cause the radioactivity to be carried elsewhere, as well as form precipitates that can be harmful to the ...
The actinide series is a group of chemical elements with atomic numbers ranging from 89 to 102, [note 1] including notable elements such as uranium and plutonium.The nuclides (or isotopes) thorium-232, uranium-235, and uranium-238 occur primordially, while trace quantities of actinium, protactinium, neptunium, and plutonium exist as a result of radioactive decay and (in the case of neptunium ...