The most probable effect of EMP on a modern nuclear power plant is an unscheduled shutdown. EMP may also cause an extendeds hutdown by the unnecessary activation of some safty-related systems. In general, EMP would be a nuisance to nuclear plants, but it is not considered a serious threat to plant safety. Countermeasures to minimize the effect of EMP have been recommended. Implementation of these recommendations would also increase the protection of the plant against damage by lightning, switching and electromagnetic interference transients as well as general failures in electrical, control and instrument power.