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Sat, May 28

Arizona nuclear plant seeking alternative source of water

The largest nuclear power plant in the U.S. – the Palo Verde Generating Station in Arizona - is still looking for an alternative water source after scuttling plans to pump brackish groundwater west of Phoenix it first pursued in 2019. (U.S. Department of Energy photo/Public domain)

The largest nuclear power plant in the U.S. – the Palo Verde Generating Station in Arizona - is still looking for an alternative water source after scuttling plans to pump brackish groundwater west of Phoenix it first pursued in 2019. (U.S. Department of Energy photo/Public domain)

PHOENIX - The largest nuclear power plant in the U.S. 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 (56 kilometers) 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 (246 million liters) of treated wastewater every day — more than 23 billion gallons (87 billion liters) 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 326000 gallons (1.2 million liters) , 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 exist currently and new technologies being pursued by vendors in the water industry,” Berles said. “There’s a lot of ideas that people have out there.”

In 2019 APS applied to pump low-quality groundwater from the Buckeye area and study whether that water would be cost-effective to treat and use at the plant in place of some of the treated wastewater it purchases.

But APS no longer is pursuing that plan, Berles said.

The utility was initially planning to pump as much as 10,000 acre-feet of water a year, and blend it with the treated effluent that is piped to the nuclear plant.

Buckeye Water Conservation and Drainage District and Buckeye Irrigation Co. opposed the APS plan.

The Arizona Department of Water Resources also rejected the idea, saying opponents of the plan showed the water APS planned to pump already was in use by others. The permit APS was seeking was for water that has no other beneficial use.

ADWR said that “despite generally poor water quality in the area, the water at issue in this application is and has been used for multiple purposes for a substantial period of time.”

APS appealed the decision, but then withdrew the application.

“Just looking at overall societal benefits or impacts, and the financial impacts and benefits, we just took a big picture look at the whole thing, engaged with those stakeholders, and determined it wasn’t worth going forward at this time for us,” Berles said. “At Palo Verde, engaging with the community is a big deal for us.”

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