MCQ Detailed View

Uranium is a naturally occurring radioactive element with the atomic number 92, meaning it has 92 protons in its nucleus. It exists in several isotopic forms, the most common being U-238 (over 99%), with smaller amounts of U-235 and U-234. Among these, the isotope Uranium-235 (U-235) is the one widely used in nuclear bombs and nuclear reactors due to its fissionable properties.

U-235 is a fissile isotope, meaning it can undergo nuclear fission when bombarded with a slow-moving neutron. In this process, the nucleus splits into two smaller nuclei, releasing a tremendous amount of energy, additional neutrons, and gamma radiation. These emitted neutrons can trigger more fission reactions, creating a self-sustaining chain reaction. If this reaction is uncontrolled, it results in a massive explosion, which is the principle behind nuclear bombs.

Other uranium isotopes:

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  U-234 is a decay product of U-238 and is found in very small amounts; it is not used for fission weapons.

  
  


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  U-233 is artificially produced from thorium and can be used as reactor fuel but is not a primary choice for bombs.

  
  


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  U-238, though abundant, is not easily fissionable with slow neutrons. It mainly serves as a fertile material that can be converted into plutonium-239 for weapons or reactors.

  
  

Weapons-grade uranium is highly enriched to contain about 90% or more U-235, far above its natural concentration of only 0.7%. This enrichment allows for a rapid chain reaction necessary for a nuclear explosion.

Thus, the isotope of uranium used in nuclear bombs is Uranium-235 (92 U 235), as it is capable of sustaining the fast, uncontrolled fission reaction required for explosive energy release.