nuclear fission

nuclear fission Fission chain reactions and their control The emission of several neutrons in the fission process leads to the possibility of a chain reaction if at least one of the fission neutrons induces fission in another fissile nucleus, which in turn fissions and emits neutrons to continue the chain. If more than one neutron is effective in inducing fission in other nuclei, the chain multiplies more rapidly. The condition for a chain reaction is …

…When powered by either a long-lived, beta-emitting fission product (e.g., strontium-90, calcium-144, or promethium-147) or one that emits alpha particles (plutonium-238 or curium-244), these batteries are a particularly useful source of energy for cardiac pacemakers and for instruments employed in remote, unmanned facilities, such as those in outer space, the polar regions of the Earth, or the open seas. There are many practical uses for other radionuclides, as discussed in radioactivity: Applications of radioactivity.