Neutron radiation is essential to the working of nuclear reactors and nuclear weapons. There are two primary isotopes used for fission reactions inside of nuclear reactors. One of the nuclear reactors was damaged. Large releases of radioactivity from nuclear reactors are extremely rare. Cs is one of the long-lived fission products of uranium produced in nuclear reactors. Tritium is a radioisotope of concern in nuclear reactor waste streams. Kr is released during the reprocessing of fuel rods from nuclear reactors. Samples are exposed to neutrons in a nuclear reactor. The treaty calls for halving the number of strategic nuclear missile launchers. This makes hafnium a good material for use in the control rods for nuclear reactors. This includes physics research in support of nuclear fission and nuclear fusion energy. Lithium-7 gained interest for use in nuclear reactor coolants. It is a protection against being threatened with nuclear weapons. Estimates of Pakistan's stockpile of nuclear warheads vary. It was not restricted to those involving nuclear weapons.