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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.
Soluble uranium salts are readily excreted in the urine, although some accumulation in the kidneys does occur in the case of chronic exposure. The World Health Organization has established a daily "tolerated intake" of soluble uranium salts for the general public of 0.5 μg/kg body weight (or 35 μg for a 70 kg adult): exposure at this level is ...
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 ...
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]
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.
The presence of 233 U will affect the long-term radioactive decay of the spent fuel. If compared with MOX fuel, the activity around one million years in the cycles with thorium will be higher due to the presence of the not fully decayed 233 U. For natural uranium fuel, fissile component starts at 0.7% 235 U
Also found in the aerosol particles was enriched Uranium-235. [7] The most prevalent radioactive gas detected was Radon, a noble gas that has no odor, no color, and no taste, and can also travel into the atmosphere or bodies of water. [8] Radon is also directly linked to lung cancer, and is the second leading cause of lung cancer in the ...
Enrichment processes generate uranium with a higher-than-natural concentration of lower-mass-number uranium isotopes (in particular 235 U, which is the uranium isotope supporting the fission chain reaction) with the bulk of the feed ending up as depleted uranium. Natural uranium metal contains about 0.71% 235 U, 99.28% 238 U, and about 0.0054% ...