A rod with high neutron absorber content used in the case of emergency for the rapid shut down of a nuclear reactor (scram). Unlike control rods, emergency (or safety) rods are designed to terminate a fission reaction under any conditions. They contain a high neutron absorber content, and the mechanism by which they are released into the core is fail-safe. For example, they are held in place by electromagnets so that they will fall into the core due to gravity even in the case of a total loss of power. Some types of reactors drive emergency rods into the core to stop the fission reaction even faster.