Rancho Seco Nuclear Generating Station

The Rancho Seco Nuclear Generating Station is a decommissioned nuclear power plant built by the Sacramento Municipal Utility District (SMUD) in Clay Station, California.

This 2772 MWt Babcock and Wilcox pressurized water reactor (913 MWe) achieved initial criticality on 16 September 1976 and entered commercial operation on 17 April 1977. The plant operated from April 1975 to June 1989 but had a lifetime capacity average of only 39%; it was closed by public vote on 7 June 1989 (despite the fact that its operating license does not expire until 11 October 2008) after multiple referendums and the promise of ten years of subsidized power from the Diablo Canyon Power Plant. As of 2005, decommissioning activities are underway.

History

In 1966, SMUD purchased convert|2100|acre|km2|0 in southeast Sacramento County for a nuclear power plant, which was built in Clay Station, convert|25|mi|km|0 south-east of downtown Sacramento.

In the early 1970s, a small pond was expanded to a convert|160|acre|km2|1|sing=on lake to serve as an emergency backup water supply (in case of fire) for the Rancho Seco power generating station. The lake has always received its water from the Folsom South Canal and has no relationship with the power plant's daily water supply. Surrounding the lake is convert|400|acre|km2|1 of recreational area originally operated by the County of Sacramento for day-use activities.

After its closure in 1989, the plant grounds were converted into a public park, whose operations were assumed by SMUD in 1992. SMUD now uses the park-generated revenues to fund all park-related operating costs. In cooperation with the Nature Conservancy, SMUD dedicated in June 2006 the Howard Ranch Nature Trail, a seven-mile (11 km) long trail that follows riparian and marsh habitat along Rancho Seco Lake and the adjoining Howard Ranch that once belonged to the owner of the famous racehorse Seabiscuit.

The park is now also managed by the California Department of Water Resources, and the now-empty towers remain a prominent part of the local landscape. Also scattered through out the area are the still active air raid sirens that at one time would have warned people of nuclear meltdown. Additions to SMUD's Rancho Seco property have included massive solar installations and, more recently, the natural gas-fired Cosumnes Power Plant, brought online in 2006.

team generator dry-out

On 20 March 1978 a failure of power supply for the plant's non-nuclear instrumentation system led to steam generator dryout. (ref NRC LER 312/78-001). In an on-going study (ref [http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2005/secy2005-0192/attachment2.pdf NRC Commission Document SECY-05-0192 Attachment 2] [http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2005/secy2005-0192/2005-0192scy.html] ) of "precursors" that could lead to a nuclear disaster if additional failures were to have occurred, the NRC concluded (as of 24-Oct-2005) that this event at Rancho Seco was the third highest ranked occurrence (second highest if one omits the event at the Three Mile Island Nuclear Generating Station).

When the reactor was at power, a failure of the NNI power supply resulted in a loss of main feedwater, which caused a reactor trip. Because instrumentation drift falsely indicated that the steam generator contained enough water, control room operators did not take prompt action to open the EFW flow control valves to establish secondary heat removal. This resulted in steam generator dryout.

See also

*Nuclear power
*Sacramento Municipal Utility District
*S. David Freeman

References

* [http://www.nukeworker.com/nuke_facilities/North_America/usa/NRC_Facilities/Region_4/rancho_seco/index.shtml Report on Rancho Seco from nukeworker.com]
* [http://www.jbsinstruments.com/Energy/Papers/Rancho_Seco/rancho_seco.html Rancho Seco – 10 years after pulling the plug: A recharged SMUD seeing better times]