Diablo Canyon Nuclear Power Plant: The WikiBook/DCPP

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Diablo Canyon Power Plant is an electricity-generating nuclear power plant at Avila Beach in San Luis Obispo County, California.

The plant has two Westinghouse-designed 4-loop pressurized-water nuclear reactors operated by Pacific Gas & Electric. The facility is located on about 750 acres in Avila Beach, California. Together, the twin 1,100 MWe reactors produce about 18,000 GW·h of electricity annually, supplying the electrical needs of more than 2.2 million people, sent along the Path 15 500-kV lines that connect to this plant.

Diablo Canyon was originally designed to withstand a 6.75 magnitude earthquake from four faults, including the nearby San Andreas and Hosgri faults,[1] but was later upgraded to withstand a 7.5 magnitude quake.[2] It has redundant seismic monitoring and a safety system designed to shut it down promptly in the event of significant ground motion.

The plant draws cooling water from the Pacific Ocean, and during heavy storms both units are throttled back by 80 percent to prevent kelp from entering the cooling water intake. The cooling water is used once and is not recirculated but rather returned to the Pacific Ocean at higher temperature.

The plant is located in Nuclear Regulatory Commission Region IV. In November 2009, PG&E applied to the Nuclear Regulatory Commission (NRC) for 20-year license renewals for both reactors.[3]


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Unit One

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Unit One is a 1,122 MWe pressurized water reactor supplied by Westinghouse. It went online on May 7, 1985 and is licensed to operate through November 2, 2024.[4] In 2006, Unit One generated 9,944,983 MW·h of electricity, at a nominal capacity factor of 101.2 percent.

Unit Two

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Unit Two is a 1,118 MWe pressurized water reactor supplied by Westinghouse. It went online on March 3, 1986 and is licensed to operate through August 20, 2025.[4] In 2006, Unit Two generated 8,520,000 MW·h of electricity, at a capacity factor of 88.2 percent.


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Pacific Gas & Electric Company went through six years of hearings, referenda and litigation to have the Diablo Canyon plant approved.[5] A principal concern about the plant is whether it can be sufficiently earthquake-proof. The site was deemed safe when construction started in 1968.

However, by the time of the plant's completion in 1973, a seismic fault, the Hosgri fault, had been discovered several miles offshore. This fault had a 7.1 magnitude quake 10 miles offshore on November 4, 1927, and thus was capable of generating forces equivalent to approximately 1/16 of those felt in the 1906 San Francisco earthquake.[6] The company updated its plans and added structural supports designed to reinforce stability in case of earthquake.

  • The Congressional Subcommittee on Energy and the Environment of the Committee on Interior and Insular Affairs conducted oversight hearings in June of 1977. [7]
  • In September 1981, PG&E discovered that a single set of blueprints was used for these structural supports; workers were supposed to have reversed the plans when switching to the second reactor, but did not.[8] According to Charles Perrow, the result of the error was that "many parts were needlessly reinforced, while others, which should have been strengthened, were left untouched." [9]
  • Nonetheless, on March 19, 1982 the Nuclear Regulatory Commission decided not to review its 1978 decision approving the plant's safety, despite these and other design errors.[10]
  • In 1986, the House Committee on Energy and Commerce Subcommittee on Energy Conservation and Power conducted additional hearings on NRC licensing of Diablo. [11]
  • In 1987, an NRC report was released to depository libraries with respect to loss of residual heat removal system [12][13]


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The Diablo Canyon Independent Safety Committee (DCISC) was established as a part of a settlement agreement entered into in June 1988 between the Division of Ratepayer Advocates of the California Public Utilities Commission (PUC), the Attorney General for the State of California, and Pacific Gas and Electric Company (PG&E).

The DCISC consists of three members, one each appointed by the Governor, the Attorney General and the Chairperson of the California Energy Commission. They serve staggered three-year terms. The committee has no authority to direct PG&E personnel.

Emergency planning

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In 1985, June Pujo, currently a professional planner with the Santa Barbara County Department of Planning, published a report [14] [15] entitled Emergency Planning: The Case of Diablo Canyon Nuclear Power Plant.June Belletto de Pujo (1985), Emergency planning, [S.l.]: Natural Hazard Research, OCLC 12034381</ref>

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

The 2010 U.S. population within 10 miles of Diablo Canyon was 26,123, an increase of 50.2 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within 50 miles was 465,521, an increase of 22.4 percent since 2000. Cities within 50 miles include San Luis Obispo (12 miles to city center) and Paso Robles (31 miles to city center).[17]

Neutrino 13 experiments

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In 2003 and 2004, seismic studies were conducted for the purpose of determining suitability of the site for nuetrino-13 experiments using the fission reaction in the reactor and an underground tunnel which would be required to blank cosmic rays which would otherwise interfere.[18] Lawrence Berkeley National Laboratory engineering staff performed the research for the proposed theta sub - 13 neutrino experiment focused on "the detector room design concept and mechanical engineering issues associated with the neutrino detector structures." [19]

Spent fuel waste storage

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Subcommittee on Energy and Power of the Committee on Energy and Commerce released a fact sheet on re-racking of spent fuel storage pools.[20]

Environmental impact on marine environment

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Diablo Canyon uses sea water for operations which entail return of water to the ocean environment at a higher temperature than intake, which creates an impact on the nearby marine environment. Also, the water taken in is rich with marine flora and fauna which is subjected to extreme stresses resulting in morbidity rates approaching 100%. The Thermal Effects Monitoring Program reports Thermal Effects Monitoring Program (TEMP) reports tell the story of PG&E research into that impact. Specific impacts investigated were intertidal and subtidal algal, invertebrate, fish, water temperature, and underwater light transmittance. These studies were conducted at more than one location, although it is likely that impacts do occur outside of the research perimeter.[21] According to a recent news account, environmental studies pursuant to NRC re-licensing have been postponed after political pressure from local political representatives. The postponement is due to the pending completion of seismic studies, under the theory that there is no point tying up staff resources to conduct an environmental impact report if, theoretically, the new seismic studies might disclose risks of such a magnitude that the plant would not be re-licensed due to safety reasons. However, the safety report is itself complete.


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  1. "Energy: A Nuclear Horror". Time. February 9, 1976. http://www.time.com/time/magazine/article/0,9171,917988,00.html. Retrieved July 14, 2010. 
  2. David Sneed (August 9, 2011). "Diablo Canyon workshop to focus on earthquakes". The San Luis Obispo Tribune. http://www.sanluisobispo.com/2010/08/08/1244213/diablo-canyon-workshop-september.html. 
  3. "Diablo Canyon - License Renewal Application". Operating Reactor Licensing. Nuclear Regulatory Commission (NRC). March 12, 2011. Retrieved 2011-04-19.
  4. a b "California Nuclear Profile > Diablo Canyon Nuclear Power Plant". Energy Information Administration, U.S. Department of Energy (DOE). September 2010. Retrieved January 21, 2011.
  5. United States. Congress. House. Committee on Interior and Insular Affairs. Subcommittee on Energy and the Environment. (1983), Licensing process at Diablo Canyon nuclear powerplant, Washington: U.S. G.P.O.
  6. "Lompoc Earthquake (1927)". Southern California Earthquake Data Center. 2010. Retrieved November 2, 2010.
  7. United States. Congress. House. Committee on Interior and Insular Affairs. Subcommittee on Energy and the Environment. (1983), Licensing process at Diablo Canyon nuclear powerplant, Washington: U.S. G.P.O.
  8. Cummings, Judith (October 2, 1981). "Coast A-Plant Construction Error Tied to Missing Guide to Blueprint". The New York Times: p. 14. 
  9. Perrow, Charles, Normal Accidents (New York: Basic Books 1984) ISBN 0465051421 p. 37
  10. "U.S. Won't Review Diablo Plant Decision: Nuclear Board Upholds '78 Approval of Quake Design Standards". Los Angeles Times: p. A35. March 20, 1982. 
  11. United States. Congress. House. Committee on Energy and Commerce. Subcommittee on Energy Conservation and Power. (1986), NRC licensing of Diablo Canyon, Washington: U.S. G.P.O.
  12. http://catalogue.nla.gov.au/Record/4001370
  13. TY - BOOK PB - U.S. Nuclear Regulatory Commission, Region V TI - Loss of residual heat removal system [microform] : Diablo Canyon, Unit 2, April 10, 1987 KW - Diablo Canyon Nuclear Powerplant (Calif.) KW - Nuclear reactors - California - Cooling. KW - Nuclear reactors - California - Containment. KW - Nuclear power plants - Equipment and supplies. KW - Pressurized water reactors - Inspection. A2 - U.S. Nuclear Regulatory Commission. Office of Inspection and Enforcement. Region V CY - Walnut Creek, CA : N1 - Distributed to depository libraries in microfiche. N1 - "Date published: June 1987." N1 - "NUREG-1269." N1 - Includes bibliographical references. N1 - Augmented Inspection Team report. April 15-21, 29 & May 1, 1987. PY - 1987 M1 - Accessed from http://nla.gov.au/nla.cat-vn4001370 ER -
  14. http://www.worldcat.org/title/emergency-planning-the-case-of-diablo-canyon-nuclear-power-plant/oclc/428525170?title=&detail=&page=frame&url=http%3A%2F%2Fhdl.handle.net%2F10176%2Fco%3A5437_ucb6571051internet.pdf%26checksum%3D07012869e2e408d78c930480acd925d8&linktype=digitalObject
  15. http://www.colorado.edu/hazards/publications/wp/wp51.pdf
  16. http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/emerg-plan-prep-nuc-power-bg.html
  17. 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.
  18. TY - ELEC DB - /z-wcorg/ DP - http://worldcat.org ID - 68498508 LA - English UR - http://www.osti.gov/servlets/purl/834621-D19KMy/native/ T1 - Theta13 Neutrino Experiment at the Diablo Canyon Power Plant, LBNL Engineering Summary Report Y1 - 2004/// AB - This summary document describes the results of conceptual design and cost estimates performed by LBNL Engineering staff between October 10, 2003 and March 12, 2004 for the proposed [theta][sub 13] neutrino experiment at the Diablo Canyon Power Plant (DCPP). This document focuses on the detector room design concept and mechanical engineering issues associated with the neutrino detector structures. Every effort has been made not to duplicate information contained in the last LBNL Engineering Summary Report dated October 10, 2003. Only new or updated information is included in this document. ER -
  19. UR - http://www.osti.gov/servlets/purl/834621-D19KMy/native/ T1 - Theta13 Neutrino Experiment at the Diablo Canyon Power Plant, LBNL Engineering Summary Report
  20. United States. General Accounting Office (1988), Nuclear waste [microform] : information on the reracking of the Diablo Canyon spent fuel storage pools : fact sheet for the chairman, Subcommittee on Energy and Power, Committee on Energy and Commerce, House of Representatives / United States General Accounting Office, The Office
  21. http://www.nceas.ucsb.edu/marine/Files%20and%20Documents/Products/DiabloCanyonRefsMar2003.pdf

Further reading

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