Dresden Generating Station is the first privately financed nuclear power plant built in the United States. Dresden 1 was activated in 1960 and retired in 1978. Operating since 1970 are Dresden units 2 and 3, two General Electric BWR-3 boiling water reactors. Dresden Station is located on a site in Grundy County, Illinois, at the head of the Illinois River, near the city ofMorris. It is immediately northeast of the Morris Operation—the only de factohigh-level radioactive waste storage site in the United States. It serves Chicago and the northern quarter of the state of Illinois, capable of producing 867 megawatts of electricity from each of its two reactors, enough to power over one million average American homes. In 2004, the Nuclear Regulatory Commission renewed the operating licenses for both reactors, extending them from forty years to sixty.
Unit 1
After the Atomic Energy Act of 1954 allowed private companies to own and operate nuclear facilities, Commonwealth Edison contracted with General Electric to design, construct, and place into operation the 192 MWe Dresden Unit 1 for $45M in 1955. One-third of the contract price was shared by a consortium of eight companies comprising the Nuclear Power Group Inc. The BWR at GE's Vallecitos Nuclear Center and the AEC's BORAX experiments provided research data and operator training for Dresden. The core contained 488 fuel subassemblies, 80 control rods, and 8 instrument nozzles. Each subassembly contained 36 fuel rods in a Zircaloy-2 channel. The fuel was uranium dioxide clad in Zircaloy-2 tube. The core thermal power was 626 MWt. The reactor vessel was rated to 1015 psia and measured 12 ft. 2 in. diameter and 42 ft. tall. The reactor featured a dual cycle, with steam coming from both the stream drum and steam generators. This made for rapid response to changes in power demand. Reactor power was regulated by actuation of the secondary admission valve by the turbine's governor. Decreasing the rate of secondary steam reduces reactor power, and vice versa. Thus, the secondary pressure varies with the external load.
Cooling
The plant has three cooling modes: Direct open-cycle mode: Intake from canal leading to the Kankakee River, discharge directly to the Illinois River. The cooling canal system, cooling lake, and the supplementary cooling towers are completely bypassed in this mode of operation.
Indirect open-cycle mode: Intake from canal leading to the Kankakee River, discharge to cooling canal leading to Dresden Cooling Lake, discharged from lake through return cooling canal that eventually discharges into the Illinois River. Use of the cooling towers for supplemental cooling of canal system water is usually necessary during this mode of operation.
Closed-cycle mode: Intake from return cooling canal leading back from Dresden Cooling Lake, discharge to cooling canal leading to Dresden Cooling Lake. Use of the cooling towers for supplemental cooling of canal system water is usually not necessary during this mode of operation. It also has cooling towers
Activity
Between the 1970s and 1996, Dresden was fined $1.6 million for 25 incidents.
June 5, 1970: A minor instrumentation error on the Dresden II reactor caused the pressure to appear too high, triggering the turbine to dump steam, which in turn automatically started a SCRAM. Void collapse in the re-condensing cooling water caused the water level to drop, which triggered an automatic increase in cooling flow. However, the pumps read low suction pressure at the inlet, which caused them to turn off to avoid running dry. One pump turned back on when this signal turned off, feeding water which rapidly flowed into the now lower-pressure reactor vessel. At this point, the original spurious signal of high pressure disappeared. The dump valves closed, increasing the back pressure and slowing the inlet flow, while the cooling temperatures caused further void collapse. The core once again began to rapidly empty. This again automatically triggered the system to increase the flow rate, which worked properly and began to bring the reactor back to operating conditions. However, the indicator needle on the water depth gauge stuck in the low position, indicating a dangerous condition. The operator began increasing flow in order to raise the water level in the reactor, manually overriding the automatic system. A second gauge that showed the increasing levels was never checked. The water level rose until it was spilling out of the reactor, causing water to enter the main steam generator, a serious problem. Two minutes later, the needle unstuck, at which point the operator began reacting to the now high levels by spilling water and closing steam, causing a hydrostatic shock to form in the cooling pipes. This caused further reactions in the automated systems, and for the next 30 minutes the water levels and pressures seesawed as the operators attempted to get the reactor back to a stable level. It was not until two hours later that the reactor was finally shut down properly. The movie The China Syndrome bases its initial plot device on this event, with the needle becoming unstuck when the operator taps the gauge.
December 8, 1971: Events similar to the ones the year earlier on Dresden II occur on Dresden III.
May 15, 1996: Lowering water levels around the nuclear fuel in unit 3 reactor's core prompt a shut down at Dresden Generating Station and placement on the NRC's "watch list" that merit closer scrutiny by regulators. Dresden was on the NRC watch list six out of nine years between 1987-1996, longer than any of the 70 other operating plants in the nation.
July 15, 2011: Plant declared an Alert at 10:16 a.m after a chemical leak of sodium hypochlorite restricted access to a vital area that houses plant cooling water pumps.
Surrounding population
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 U.S. population within of Dresden was 83,049, an increase of 47.6 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within was 7,305,482, an increase of 3.5 percent since 2000. Cities within 50 miles include Chicago.
Ownership
Both currently operating units are owned and operated by Exelon, which also owns and is responsible for the decommissioning of Unit 1. Prior to August 3, 2000, all three units were owned by Commonwealth Edison.
Seismic risk
The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Dresden was 1 in 52,632, according to an NRC study published in August 2010.
