In the described scenario, what happens to uranium-238 when struck by a neutron?

• A. It is split into Plutonium
• B. It becomes Lead
• C. It decays into Thorium
• D. It remains unchanged

Answer: (A)

This question hinges on what happens when a heavy nucleus encounters a neutron. When uranium-238 is struck by a neutron, it can capture that neutron and become uranium-239. That new isotope is unstable and undergoes beta decay in steps: first to neptunium-239, then to plutonium-239. So the end result is the formation of plutonium-239 from uranium-238 through neutron capture and subsequent beta decays. This isn’t a direct fission into plutonium, and it isn’t unchanged or simply decaying to lead or thorium on the spot. The key concept is transmutation via neutron capture followed by beta decay leading to plutonium-239.