Fukushima Aftermath/Davis-Besse Nuclear Power Station

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The Davis-Besse NPP (NRC image)

Davis-Besse Nuclear Power Station is a nuclear power plant with a single pressurized water reactor, also referred to as a light water reactor. Template:As of, it is operated by the FirstEnergy Nuclear Operating Company subsidiary of FirstEnergy Corp. The power station is located on the southwest shore of Lake Erie about 10 miles (16 km) north of Oak Harbor, Ohio and is on the north side of Highway 2 just east of Highway 19 on a 954-acre (386 ha) site in the Carroll Township. The plant only utilizes 221 acres (89 ha), with 733 acres (297 ha) devoted to the Ottawa National Wildlife Refuge. The entrance to the Magee Marsh Wildlife Area[1] is less than a mile east of the power station. The official name according to the U.S. Energy Information Administration is the Davis-Besse Nuclear Generating Station. It is the 57th commercial power reactor to commence building in the United States of America (construction began on September 1, 1970) and the 50th to come on-line July 31, 1978.[2] The plant was originally jointly owned by Cleveland Electric Illuminating (CEI) and Toledo Edison (TE) and was named for former TE Chairman John K. Davis and former CEI Chairman Ralph M. Besse.

According to the Nuclear Regulatory Commission, Davis-Besse has been the source of two of the top five most dangerous nuclear incidents in the United States since 1979.[3]

Unit One[edit]

Unit One is an 879 MWe pressurized water reactor supplied by Babcock and Wilcox. The reactor was shut down from 2002 until early 2004 for safety repairs and upgrades, so recent operational statistics are not yet available for the unit.

The reactor head under inspection

Surrounding population[edit]

The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of 10 miles (16 km), concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about 50 miles (80 km), concerned primarily with ingestion of food and liquid contaminated by radioactivity.[4]

The 2010 U.S. population within 10 miles (16 km) of Davis-Besse was 18,635, an increase of 14.2 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within 50 miles (80 km) was 1,791,856, an increase of 1.4 percent since 2000. Cities within 50 miles include Toledo (26 miles to city center).[5]

Incident history[edit]

Over the years of its operation, the plant has experienced several incidents, none of which have resulted in exposure to dangerous levels of radiation.

First stuck-open pilot-operated relief valve[edit]

On September 24, 1977, the reactor, running at only 9% power, shut down because of a disruption in the feedwater system.[6] This caused the relief valve for the pressurizer to stick open. As of 2005, the NRC considers this to be the fourth highest ranked safety incident.[7]

Loss of feedwater event[edit]

On June 9, 1985, the main feedwater pumps, used to supply water to the reactor steam generators, shut down. A control room operator then attempted to start the auxiliary (emergency) feedwater pumps. These pumps both tripped on overspeed conditions because of operator error. This incident was originally classified an "unusual event" (the lowest classification the NRC uses) but it was later determined that it should have been classified a "site area emergency".[8]

Tornado[edit]

On June 24, 1998 the station was struck by an F2 tornado.[9] The plant's switchyard was damaged and access to external power was disabled. The plant's reactor automatically shut down at 8:43 pm and an alert (the next to lowest of four levels of severity) was declared at 9:18 pm. The plant's emergency diesel generators powered critical facility safety systems until external power could be restored.[10][11]

Erosion of the 6-inch-thick (150 mm) carbon steel reactor head, caused by a persistent leak of borated water.

Reactor head hole[edit]

In March 2002, plant staff discovered that the boric acid that serves as the reactor coolant had leaked from cracked control rod drive mechanisms directly above the reactor and eaten through more than six inches[12] of the carbon steel reactor pressure vessel head over an area roughly the size of a football (see photo). This significant reactor head wastage left only 3/8 inch of stainless steel cladding holding back the high-pressure (~2500 psi) reactor coolant. A breach would have resulted in a loss-of-coolant accident, in which superheated, superpressurized reactor coolant could have jetted into the reactor's containment building and resulted in emergency safety procedures to protect from core damage or meltdown. Because of the location of the reactor head damage, such a jet of reactor coolant might have damaged adjacent control rod drive mechanisms, hampering or preventing reactor shut-down. As part of the system reviews following the accident, significant safety issues were identified with other critical plant components, including the following: (1) the containment sump that allows the reactor coolant to be reclaimed and reinjected into the reactor; (2) the high pressure injection pumps that would reinject such reclaimed reactor coolant; (3) the emergency diesel generator system; (4) the containment air coolers that would remove heat from the containment building; (5) reactor coolant isolation valves; and (6) the plant's electrical distribution system.[13] Under certain scenarios, a reactor rupture would have resulted in core meltdown and/or breach of containment and release of radioactive material. The resulting corrective operational and system reviews and engineering changes took two years. Repairs and upgrades cost $600 million, and the Davis-Besse reactor was restarted in March 2004.[14] The U.S. Justice Department investigated and penalized the owner of the plant over safety and reporting violations related to the incident. The NRC determined that this incident was the fifth most dangerous nuclear incident in the United States since 1979.[3]

Criminal prosecutions[edit]

On January 20, 2006, the owner of Davis-Besse, FirstEnergy Corporation of Akron, Ohio, acknowledged a series of safety violations by former workers, and entered into a deferred prosecution agreement with the U.S. Department of Justice. The deferred prosecution agreement relates to the March 2002 incident (see above). The deferment granted by the NRC were based on letters from Davis-Besse engineers stating that previous inspections were adequate. However, those inspections were not as thorough as the company suggested, and as proved by the material deficiency discovered later. In any case, because FirstEnergy cooperated with investigators on the matter, they were able to avoid more serious penalties. Therefore, the company agreed to pay fines of $23.7 million, with an additional $4.3 million to be contributed to various groups, including the National Park Service, the U.S. Fish and Wildlife Service, Habitat for Humanity, and the University of Toledo as well as to pay some costs related to the federal investigation.

Two former employees and one former contractor were indicted for statements made in multiple documents and one videotape, over several years, for hiding evidence that the reactor pressure vessel was being corroded by boric acid. The maximum penalty for the three is 25 years in prison. The indictment mentions that other employees also provided false information to inspectors, but does not name them.[15][16]

2008 discovery tritium leak[edit]

The NRC and Ohio EPA were notified of a tritium leak accidentally discovered during an unrelated fire inspection on October 22, 2008. Preliminary indications suggest radioactive water did not infiltrate groundwater outside plant boundaries[17]

2010 Replacement reactor head problems[edit]

After the 2002 incident, Davis-Besse purchased a used replacement head from a mothballed reactor in Midland, Michigan. Davis-Besse operators replaced the original cracked reactor head before restarting in 2004. On March 12, 2010, during a scheduled refueling outage, ultrasonic examinations performed on the control rod drive mechanism nozzles penetrating the reactor vessel closure head identified that two of the nozzles inspected did not meet acceptance criteria. FirstEnergy investigators subsequently found new cracks in 24 of 69 nozzles, including one serious enough to leak boric acid. Root cause analysis is currently underway by the Department of Energy, First Energy, and the NRC to determine the cause of the premature failures.[18] [19] Crack indications required repair prior to returning the vessel head to service. Control rod drive nozzles were repaired using techniques proven at other nuclear facilities. The plant resumed operation in 2010. The existing reactor vessel head is scheduled for replacement in 2011.[20]


Future[edit]

The facility's original nuclear operating license expires on April 22, 2017. On August 11, 2006 FirstEnergy Nuclear Operating Company (FENOC) submitted a letter of intent (Adams Accession No. ML062290261).[21] The submission date for the application is August 10, 2010. This initiates a long process that results in an application approval or revocation. Public hearings[22] are a vital part of any application review and information on this process can be found on the U.S. Nuclear Regulatory Commission (NRC) website at NRC.gov. [4]. The site map contains many valuable links [23]

Seismic risk[edit]

The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Davis-Besse was 1 in 149,254, according to an NRC study published in August 2010.[24][25]


References[edit]

  1. [1] - Magee Marsh Wildlife Area
  2. Energy Information Administration (November 2004). "U.S. Nuclear Reactor List - Operational" (XLS). http://www.eia.doe.gov/cneaf/nuclear/page/nuc_reactors/operational.xls. Retrieved 2006-06-14. 
  3. a b Nuclear Regulatory Commission (2004-09-16). "Davis-Besse preliminary accident sequence precursor analysis" (PDF). http://www.nrc.gov/reactors/operating/ops-experience/vessel-head-degradation/news/2004/09-16-04-ml0426005320.pdf. Retrieved 2006-06-14.  and Nuclear Regulatory Commission (2004-09-20). "NRC issues preliminary risk analysis of the combined safety issues at Davis-Besse". http://www.nrc.gov/reading-rm/doc-collections/news/2004/04-117.html. Retrieved 2006-06-14. 
  4. http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/emerg-plan-prep-nuc-power-bg.html
  5. Bill Dedman, Nuclear neighbors: Population rises near US reactors, msnbc.com, April 14, 2011 http://www.msnbc.msn.com/id/42555888/ns/us_news-life/ Accessed May 1, 2011.
  6. Walker, Samuel J. (2004) Three Mile Island: A Nuclear Crisis in Historical Perspective. Berkeley: University of California Press. p 68.
  7. Nuclear Regulatory Commission. "NRC Commission Document SECY-05-0192 Attachment 2" (PDF). http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2005/secy2005-0192/attachment2.pdf. Retrieved 2008-01-28. 
  8. Nuclear Regulatory Commission. "Information Notice 85-80". http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1985/in85080.html. Retrieved 2006-06-14. 
  9. United States Senate. "U.S. Senate Committee on Environment & Public Works Hearing Statements". http://epw.senate.gov/hearing_statements.cfm?id=248112. Retrieved 2006-07-07. 
  10. Nuclear Regulatory Commission. "News Release III-98-040". http://permanent.access.gpo.gov/lps11598/www.nrc.gov/reading-rm/doc-collections/news/1998/98-40iii.html. Retrieved 2006-07-07. 
  11. Nuclear Regulatory Commission. "News Announcement RIII-98-40a". http://permanent.access.gpo.gov/lps11598/www.nrc.gov/reading-rm/doc-collections/news/1998/98-40aiii.html. Retrieved 2006-06-14. 
  12. NRC NUREG/BR-0353, Rev 1, pg 4
  13. Cleveland Plain Dealer, Problems and solutions, July 16, 2003
  14. NRC. EA-05-071 - Davis-Besse. April 21, 2005.
  15. United States Department of Justice (2006-01-20). "Firstenergy Nuclear Operating Company to Pay $28 Million Relating to Operation of Davis–Besse Nuclear Power Station". http://www.usdoj.gov/opa/pr/2006/January/06_enrd_029.html. Retrieved 2006-06-14.  and "Deferred prosecution agreement between the United States of America and FirstEnergy Nuclear Operating Company" (PDF). 2006-01-20. http://www.corporatecrimereporter.com/documents/fenco_000.pdf. Retrieved 2006-06-14. 
  16. Toledo Blade "Ex-engineer found guilty of concealing Davis-Besse dangers"
  17. Davis-Besse radioactive leak is fixed
  18. Toledo Blade, May 15, 2010 "Meeting set to discuss Besse reactor-head flaws"
  19. Toledo Blade, May 4, 2010 "8 more nozzles at Davis-Besse found to be flawed"
  20. Funk, John (21 June 2010), "FirstEnergy to replace lid on Davis-Besse nuclear power plant", Cleveland Live, http://www.cleveland.com/business/index.ssf/2010/06/firstenergy_to_place_lid_on_da.html, retrieved 21 January 2011 
  21. [2][dead link] -FENOC letter of intent for license renewal.
  22. U.S. Nuclear Regulatory Commission - "NRC public hearings in 2010"
  23. [3] - NRC site map
  24. Bill Dedman, "What are the odds? US nuke plants ranked by quake risk," msnbc.com, March 17, 2011 http://www.msnbc.msn.com/id/42103936/ Accessed April 19, 2011.
  25. http://msnbcmedia.msn.com/i/msnbc/Sections/NEWS/quake%20nrc%20risk%20estimates.pdf

External links[edit]

Template:U.S. Nuclear Plants