Question

rods containing uranium
neutron - absorbing material
nuclear reactor
a power plant needs to slow down the fission reactions in its nuclear reactor. in which direction should the uranium - containing rods in the diagram be moved?
○ left
○ right
× up
○ down

Explanation:

In a nuclear reactor, uranium - containing rods (fuel rods) and neutron - absorbing material (control rods) interact. To slow down fission reactions, we need to increase the amount of neutron - absorbing material in contact with the uranium - containing rods. Looking at the diagram, if we move the uranium - containing rods up, more of the neutron - absorbing material (the red parts) will be in contact with the uranium - containing rods (the green rods). This is because moving the uranium - containing rods up will make them overlap more with the neutron - absorbing material, which absorbs more neutrons. Fission reactions are driven by neutron bombardment, so absorbing more neutrons slows down the fission process.

Answer:

up