8 Apr (NucNet): During the year after the February 2012 closure of California’s San Onofre nuclear power plant, the cost of generating electricity in the state increased by 15 percent and carbon dioxide emissions climbed more than nine million tonnes, the equivalent of putting two million additional cars on the road, a study says.

The study, released by the Energy Institute at UC Berkeley’s Haas School of Business, says the wholesale cost of electricity rose by 369 million US dollars (268 million euros) during the first 12 months after the reactors were shut down, although the increase was masked by a large decline in natural gas prices that year, which the study calls “a lucky coincidence.”

According to the US Nuclear Energy Institute, the study confirms previous studies that found increased prices and higher carbon emissions since the plant’s closing.

Between 2005 and 2011 the two reactors at San Onofre produced 16 million megawatt-hours of electricity annually, or eight percent of the state’s total and enough to serve 2.3 million households.

In January 2012, plant workers discovered a small leak in a tube in the recently installed steam generator at one of the reactors while the other one, which had a similar steam generator, was down for maintenance and refuelling. Tubes in both steam generators showed signs of premature wear. Testing of both reactors continued for months, and in June 2013 San Onofre owner Southern California Edison, while awaiting a decision from the Nuclear Regulatory Commission on operating one of the reactors at reduced power, decided to close the plant permanently.

The shutdown was “abrupt, permanent, and unexpected,” the study says, and “had a pronounced impact on the wholesale market, requiring large and immediate increases in generation from other sources.”

“In the months following the closure, almost all of the lost generation from San Onofre was met by natural gas plants inside California,” the study found, which led to higher costs and a large increase in carbon emissions.

The study says these benefits from keeping San Onofre open must be compared against several significant costs including “the real uncertainty” about the cost of required repairs, and even about whether San Onofre would have ever been allowed to restart.

The UC Berkeley study is online:

http://ei.haas.berkeley.edu/pdf/working_papers/WP248.pdf