Ledes from the Land of Enchantment

Arizona nuclear plant seeking alternative source of water

Arizona Public Service Co. is partnering with Sandia National Laboratories on a test project for an alternative water source for the Palo Verde Generating Station. (Ross D. Franklin/Associated Press)

PHOENIX – The largest nuclear power plant in the US is still looking for an alternative water source after scuttling plans to pump brackish groundwater west of Phoenix it first pursued in 2019.

The Palo Verde Generating Station is the only nuclear plant in the world not adjacent to a large body of water to cool the plant. Instead, it uses reclaimed water piped more than 35 miles across the desert.

That water is getting more expensive, and to keep the plant economical, Arizona Public Service Co. is exploring ways to use it wiser, including a test project with Sandia National Laboratories in Albuquerque, New Mexico, this summer, the Arizona Republic reported.

The plant uses about 65 million gallons of treated wastewater every day – more than 23 billion gallons a year – to generate electricity.

The contract with cities to sell the plant the treated wastewater runs through 2050 and gets more expensive after 2025.

“That’s just a fact of what is in our water contracts and it is important to us to look for ways to operate more cost-effectively,” said Brad Berles, general manager of Palo Verde water resources.

The water from the 91st Avenue Wastewater Treatment Plant cost $53 an acre-foot in 2010. It will cost $300 an acre-foot in 2025. Starting in 2026, water rates will be set using a tiered formula, rising with water use.

One acre-foot is approximately 326,000 gallons, or enough water to supply three single-family households in Phoenix for a year.

APS is working with Sandia on a dry-cooling pilot project to be built at the New Mexico laboratory.

Nuclear fuel is used to heat water in the plant and make steam. After steam from the plant spins a turbine and makes electricity, it is sent to large cooling towers outside the plant where much of it evaporates away.

The Sandia project will study cooling the water before it goes to those towers.

“If we send cooler water to the towers … we can reduce what we evaporate off,” Berles said.

Cooling the water with fans or other mechanisms would of course use energy. The point of the research is to determine whether the cost of the equipment and energy to run it would save money by reducing water use.

“It’s a balance just like everything we look at,” Berles said. “You’ve got to evaluate the pros and cons of it.”

Testing should begin in May or June, and gather data for four to six months.

“We are probably multiple years out from when we would do anything at the plant,” he said.

Another option APS is reviewing is adding another water-treatment facility to the nuclear plant.

The wastewater that Palo Verde receives is treated before it’s used at the plant. Water is usually cycled through the plant and cooling towers about 25 times before it becomes too saline for another use.

Once the chemistry of the water makes it unusable in the plant, it is pumped to massive evaporation ponds on the property where it simply dries up.

APS is evaluating whether it would be cost-effective to treat the water again, after it’s used in the plant, to extend its useful life.

“There are different technologies that currently exist and new technologies being pursued by vendors in the water industry,” Berles said. “There’s a lot of ideas that people have out there.”

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