Control rods in a nuclear reactor absorb which particles?

Control rods in a nuclear reactor are designed to absorb neutrons. The primary function of control rods is to regulate the rate of the nuclear fission reaction. Neutrons are released during fission and, if left unchecked, can lead to a rapid increase in the reaction rate. By inserting control rods, which are made from materials like boron or cadmium that have a high neutron absorption cross-section, the number of free neutrons in the reactor core is reduced. This process effectively slows down the fission chain reaction, helping to maintain the desired power level and ensuring safety in the reactor operation.

In contrast, protons, electrons, and positrons do not play a significant role in controlling the fission process within a nuclear reactor. Protons are found in the nucleus of atoms but are not emitted during fission, while electrons are subatomic particles that orbit the nucleus and are not absorbed by control rods. Positrons, being the antiparticles of electrons, are also irrelevant in the context of neutron absorption in nuclear reactors. Therefore, neutrons are the correct answer to the question regarding what particles control rods absorb.