Nuclear reactor which produce delayed neutrons have half lives for their decay by neutron emission that range from milliseconds to as long as several minutes, and so considerable time is required to determine exactly when a reactor reaches the critical point. Keeping the reactor in the zone of chain-reactivity where delayed neutrons are "necessary" to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; otherwise the time between achievement of criticality and nuclear meltdown as a result of an exponential power surge from the normal nuclear chain reaction, would be too short
Cooling pond of up to 50 years in the area. The Columbia station in Pardeeville, Wisconsin is a coal fired power plant with a capacity of 1000 MW. A duel cooling system is used for heat rejection that consists of a cooling pond and two cooling towers. The pond and towers are connected in a parallel arrangement to help dissipate thermal energy at expedited rates. In 1994 North Korea's Yongbyon reactor was under U.S scrutiny and thus its nuclear fuel rods were taken out of the reactor and placed in the Yongbyon's cooling pond. They have since been removed. Cooling pond A