What is the Difference Between Uranium 235 and Uranium 238?

The main difference between uranium-235 (U-235) and uranium-238 (U-238) lies in the number of neutrons in their atomic nuclei and their natural abundance. Here are the key differences:

• Atomic Mass: The nucleus of the U-235 atom contains 92 protons and 143 neutrons, giving an atomic mass of 235 units. On the other hand, the U-238 nucleus contains 92 protons and 146 neutrons, resulting in an atomic mass of 238 units.
• Natural Abundance: U-238 is the most abundant form of uranium found in nature, with approximately 99.3% of mined uranium consisting of U-238. In contrast, U-235 makes up only about 0.7% of natural uranium.
• Half-life: U-235 has a half-life of 700 million years, while U-238 has a much longer half-life of 4.5 billion years.
• Fissile Properties: The main fissile isotope of uranium is U-235, which is the primary source of energy in nuclear reactors. When concentrated (or "enriched") to about 3 to 5%, U-235 becomes suitable for use in nuclear reactors. U-238, on the other hand, can be used as a radiation shield or in depleted uranium for military applications.

The 1.27% difference in mass between U-235 and U-238 allows for the separation of these isotopes during the uranium enrichment process.

Comparative Table: Uranium 235 vs Uranium 238

Here is a table comparing the differences and similarities between Uranium-235 and Uranium-238:

Both Uranium-235 and Uranium-238 are isotopes of uranium, containing the same number of protons and electrons (92 each). They are also both naturally occurring radioactive isotopes with different half-lives. However, Uranium-235 is a fissile isotope and can sustain a nuclear fission chain reaction, while Uranium-238 is not fissile and does not participate in fission. The nuclear fuel used in reactors of the nuclear power plant contains both isotopes, but only Uranium-235 undergoes nuclear fission to generate necessary thermal energy.