Uranium 238 has a half-life of about 4.5 billion years. All the 238U now on Earth was created in stars and has been here since the formation of Earth about 4.5 billion years ago. Consider a kilogram of pure 238U present at the formation of the Earth.
Nuclear Fusion
Nuclear fusion is a type of nuclear reaction. In nuclear fusion, two or more than two lighter atomic nuclei combine to form a heavier nucleus. During this process, an enormous amount of energy is released. This energy is called nuclear energy. Nuclear fusion is the energy source of the sun and stars.
Fusion Bomb
A fusion bomb is also known as a thermonuclear bomb or hydrogen bomb which releases a large amount of explosive energy during a nuclear chain reaction when the lighter nuclei in it, combine to form heavier nuclei, and a large amount of radiation is released. It is an uncontrolled, self-sustaining nuclear chain reaction where isotopes of hydrogen combine under very high temperature to form helium. They work on the principle of operation of atomic fusion. The isotopes of Hydrogen are deuterium and tritium, where they combine their masses and have greater mass than the product nuclei, get heated at high temperatures, and releases energy.
) Uranium 238 has a half-life of about 4.5 billion years. All the 238U now on Earth was created
in stars and has been here since the formation of Earth about 4.5 billion years ago. Consider
a kilogram of pure 238U present at the formation of the Earth.
i) Calculate the activity of the kilogram at that time. Sketch a graph of the activity of the
uranium since then to the present day. Label the axes with appropriate numbers and
units. Mark on your graph the half-life and the characteristic decay time.
ii) 238U decays through a chain of thirteen very short-lived radionuclides (longest halflive only 1600 years) before reaching a stable isotope of lead. If what remains of this
uranium has for the last few million years been in a stable rock formation from which
nothing escapes, approximately what activity will the rock have now?
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