Physics - Modern Physics Question with Solution | TestHub

${}_{92}{\mathrm{U}}^{235}+{}_0{n}^1\to {}_{54}{\mathrm{Xe}}^{139}+{}_{38}{\mathrm{Sr}}^{94}+2_0{n}^1$ Related Theory Moderators are used to slow down the neutrons produced from fission. This is necessary because many nuclear fuels (uranium-235, for instance) require neutrons to be slow-moving in order to absorb them. Nuclei with low mass numbers are most effective at doing so, therefore materials like water or graphite are often used. Caution In a nuclear fission, a heavy nucleus disintegrates into lighter nuclei. Large amount of energy is released during nuclear fission. Nuclear fission occurs by itself and no additional energy is required for a nuclear fission to occur.