What is nuclear fission?

The process that mainly takes place in stars to produce energy is:

Boron rods in a nuclear reactor are used as a

In the nuclear fusion reaction ${ }_1 H^2+{ }_1 H^3 \rightarrow{ }_2 He^4+n$, if the repulsive potential energy between the two nuclei is $2.07 \times 10^{-14} \,J$, then the temperature at which the gases must be heated to initiate the reaction is (Boltzmann constant $k = 1.38 \times 10^{-23} \,JK^{-1}$).

The process by which a heavy nucleus splits into light nuclei is known as

Thermal neutrons can cause fission in