Cleanup complete at Rancho Seco

08 October 2009

Decommissioning of the former Rancho Seco nuclear power plant in California has been completed and most of the site released for unrestricted public use, the US Nuclear Regulatory Commission (NRC) has announced.

Rancho Seco (Hajhouse)
An aerial view of Rancho Seco taken in 2007 (Image: Hajhouse)

Land covering approximately 80 acres (32.4 hectares) now falls below NRC regulatory requirements of a maximum radiation dose of 25 millirem per year from residual contamination (the average US citizen receives about 300 millirem per year from natural background radiation). Some six acres (2.4 hectares) of land, including a storage building for low-level radioactive waste and a dry-cask spent fuel storage facility, will remain under NRC licence.


Plant owner Sacramento Municipal Utility District (SMUD) will remain responsible for the security and protection of the licensed land and the facilities on it, and is required to maintain liability insurance coverage of $100 million until all radioactive material is finally removed from the site.
Rancho Seco, a 913 MWe pressurised water reactor, went critical in September 1974 but experienced reliability problems in the 1980s. In June 1989, shortly after the accident at the Chernobyl nuclear plant in Ukraine, 53.4% of voters in a local referendum called for the plant's closure. SMUD shut the plant permanently the very next day and defuelling was completed by the end of that year.
In 1995, the NRC approved a so-called Safestor decommissioning program for the plant. This would entail the long-term storage of the facility for some 40-60 years until eventual dismantling and decontamination activities could take place. SMUD subsequently decided to implement an incremental decommissioning project, dismantling and decommissioning other facilities on site until eventually only the waste storage buildings would remain. The incremental decommissioning program began in early 1997.
California today has four operating nuclear units, but the construction of new nuclear power plants has been prohibited by state law since 1976, pending the approval of a means of disposal of high-level nuclear waste. SMUD replaced Rancho Seco's capacity by moving towards more diverse power sources, such as cogeneration plants, wind power, low-cost purchased power from the Pacific Northwest and Canada. However, support for new nuclear build in the state, which suffered an acute electricity supply crisis in 2000-2001, appears to be growing.