The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of, concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about, concerned primarily with ingestion of food and liquid contaminated by radioactivity. The 2010 population within of Callaway was 10,092, an increase of 3.8 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 population within was 546,292, an increase of 15.0 percent since 2000. Cities within 50 miles include Fulton, Jefferson City, and Columbia. In 2014, the Nuclear Regulatory Commission tests found contaminated ground water near the site.
Power output
According to Ameren, Callaway produces about 19 percent of Ameren Missouri's power. In 2001, Callaway set a plant record by producing 101.1 percent of its rated electrical output, ranking it among the world's top reactors, according to the Energy Information Administration. The plant produces 1,279 electrical megawatts of net power. It has run continuously for over 500 days between refuelings, one of 26 U.S. reactors to do so. On November 19, 2005, its workers finished replacing all four steam generators in 63 days, 13 hours, a world record for a four-loop plant.
Cooling tower
The cooling tower at Callaway is tall. It is 430 feet wide at the base, and is constructed from reinforced concrete. It cools about of water per minute when the plant is operating at full capacity; about of water per minute are lost out the top from evaporation. Another of water are sent to the Missouri River as "blowdown" to flush solids from the cooling tower basin. All water lost through evaporation or blowdown is replaced with water from the river, located five miles from the plant. The temperature of the water going into the cooling tower is, and the tower cools it to. The tower is designed such that if it were to somehow topple over completely intact, it would not damage any of the critical plant structures.
Proposed Unit 2 and cancellation
On July 28, 2008, Ameren Missouri applied to the U.S. Nuclear Regulatory Commission for a Combined Construction and Operating License to build a 1,600-MW ArevaEvolutionary Power Reactor. "Given projections for a nearly 30 percent increase in demand for power in Missouri in the next two decades, we believe we will need to build a large generating plant to be on line in the 2018–2020 timeframe," wrote Thomas R. Voss, the company's president and chief executive officer. In April 2009, the proposal was cancelled. One stumbling block was a law that forbids utilities to charge customers for the interest accrued on a construction loan before a new plant produces electricity. The new nuclear reactor would have cost at least $6 billion. In April 2012, Ameren Missouri and Westinghouse Electric Company announced their intent to seek federal funding for a new generation of nuclear reactors to be installed at the Callaway site. The U.S. Department of Energy could provide up to $452 million in research and development funds to Westinghouse. The new reactors would be smaller and, the companies claimed, safer in design than any currently operating. Ameren Missouri would apply to license up five of the 225-megawatt reactors at the Callaway site, more than doubling its current electrical output. In August 2015, a month after Ameren had announced plans to build solar energy plants in Missouri, all plans to expand nuclear-powered electricity generation at the site were scrapped.
Seismic risk
In August 2010, the Nuclear Regulatory Commission's estimated that the annual chance that an earthquake might damage the core at Callaway was 1 in 500,000, the lowest probability of any U.S. reactor.
