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Diablo Canyon’s Desalination Facility to Help Fight California Drought

July 3,2015-

  • PG&E enters five-year agreement with county
  • Desalinated water to fight wildfires; other uses under study
  • Integrated nuclear and desal facilities used in Japan, India and Kazakhstan

June 18, 2015—As California suffers through its fourth straight year of drought, increasingly severe shortages of water are raising alarms. The state has issued stringent water conservation measures for cities and towns as well as in the state’s vast agriculture industry.

San Luis Obispo County, on California’s Central Coast, has found an innovative way to supplement its rationed supply of fresh water. The Diablo Canyon Nuclear Power Plant has an on-site desalination facility that it uses to generate fresh water from seawater, both to cool the plant and for its employees’ drinking water needs.

Desalination at Diablo Canyon

Water from Diablo Canyon’s desalination facility will help fight wildfires
Photo: PG&E

Plant operator Pacific Gas & Electric Co. has entered into a five-year agreement to use the facility’s excess capacity to provide the county’s Office of Emergency Services with fresh water to help tackle the ever-present risk of wildfires.

PG&E characterized the agreement as an extension of Diablo Canyon’s safety mission.
“We live and work in this county, too, and ensuring its safety and well-being is our highest priority. We look forward to continue working with the county in identifying ways to provide further support during this ongoing water crisis,” Senior Vice President and Chief Nuclear Officer Ed Halpin said.

As Halpin suggests, PG&E has not ruled out other potential uses for its fresh water. Company spokesman Tom Cuddy said the utility and the county are considering a plan to connect the nuclear plant’s desalinated water supply to the county’s water system. He expects a feasibility study to be finished by the end of the summer.

Diablo Canyon’s desal facility can produce 1.5 million gallons of water per day, much less than a dedicated plant but still substantial enough to be useful. Diablo Canyon uses only about 40 percent of the facility’s full capacity, which would make available to the county 825,000 gallons a day.

Desalinating seawater to create potable water is a process used around the world. There are about 15,000 plants in operation, many of them in the Middle East and North Africa. The largest is in Saudi Arabia.

Almost two-thirds of the desalination conducted worldwide, including at Diablo Canyon, is accomplished by reverse osmosis. The process pressurizes seawater and forces it through a semi-permeable membrane to extract the salt. A different process, accounting for about a quarter of the world’s desalination capacity, uses a multi-stage process to flash the saltwater into steam and distill pure water out of it.

The agreement between PG&E and San Luis Obispo is a small but practical step forward for nuclear energy-based desalination in the United States. Because desalination uses substantial amounts of energy, tying nuclear power plants to desal facilities is an idea that has been successfully tested in other countries. Kazakhstan’s Aktau facility produced up to 135 megawatts of electricity and deposited 80,000 cubic meters of water per day into the municipal system between 1972 and 1999. India and Japan have used nuclear power plants for both electricity and fresh water production for plant use, as Diablo Canyon has done.

The major reason desalination has not been more broadly implemented in the United States has been its comparative cost. The U.S. Environmental Protection Agency estimates that tap water averages about $2 per 1,000 gallons. The Coquina Coast Seawater Desalination Project in Florida, which is fossil-fuel-based, estimates its costs at between $6.27 and $7.74 per 1,000 gallons.

However, using nuclear electricity for desalination can achieve exceptional economies of scale. Forbes’ James Conca calculates that the amount of electricity needed to desalinate seawater via nuclear energy is relatively low and that Diablo Canyon produces this electricity at “only 4 cents per kilowatt-hour, cheaper than most other energy sources in California.”

Conca says the overall cost will be about a tenth of a cent per gallon, and “monthly water bills might rise $10 or so.” PG&E’s Cuddy said San Luis Obispo County will pay $3.30 per 1,000 gallons for the Diablo Canyon water, although the current agreement will only provide it for fire protection and not potable water.

More desalination, nuclear-powered or not, may be needed sooner than expected. According to new NASA satellite data, the world’s largest underground aquifers, which supply fresh water to hundreds of millions of people, are rapidly emptying. The value of nuclear energy-based desalination could well increase as the need for fresh water escalates.

In the meantime, California is building the Carlsbad Desalination Plant near San Diego. Powered by the neighboring Encina gas-fired power station, it will produce about 50 million gallons of fresh water per day beginning in 2016, all of it committed to the San Diego Water Authority as a hedge against drought.

The Diablo Canyon desalination effort is less a full-scale demonstration of its potential as a supplier of fresh water than a civic effort writ large. If it also provides further evidence of the viability of the process, it will be a bonus.

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