Question

why are very high temperatures and pressures required for fusion to occur? to generate the neutrons that are needed to break the nuclei to overcome the repulsion between the protons in the nuclei that join to maintain the proper conditions to keep the chain reaction going to keep the uranium fuel separate from the control rods

Explanation:

Nuclear fusion involves joining atomic nuclei. Protons in nuclei are positively - charged and repel each other. High temperatures and pressures give nuclei enough energy to overcome this electrostatic repulsion and fuse.

Answer:

to overcome the repulsion between the protons in the nuclei that join