By RYAN RANDAZZO undefined
PHOENIX (AP) — The largest nuclear power plant in the United States is still searching for an alternative water source after scuttling plans to pump brackish groundwater west of Phoenix, which it had pursued for the first time in 2019.
The Palo Verde Power Plant is the only nuclear power 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) through the desert.
This water is becoming more expensive, and to keep the plant economical, Arizona Public Service Co. is exploring ways to use it more wisely, including a test project with Sandia National Laboratories in Albuquerque, New Mexico, this summer, the Arizona Republic reported.
The plant uses approximately 65 million gallons (246 million liters) of treated wastewater every day – more than 23 billion gallons (87 billion liters) per year – to generate electricity.
The contract with the cities to sell the treated wastewater to the plant runs until 2050 and becomes more expensive after 2025.
“It’s just a fact of what’s in our water contracts and it’s important for us to look at ways to operate more cost-effectively,” said Brad Berles, Palo Verde’s general manager of water resources.
Water from the 91st Avenue Wastewater Treatment Plant cost $53 per acre-foot in 2010. It will cost $300 per acre-foot in 2025. As of 2026, water rates will be set according to a tiered formula, increasing with the use of water.
One acre-foot equals about 326,000 gallons (1.2 million liters), enough water to supply three single-family households in Phoenix for a year.
APS is working with Sandia on a pilot dry cooling project that will be built at the New Mexico lab.
Nuclear fuel is used to heat the plant’s water and produce steam. After the steam from the plant spins a turbine and generates electricity, it is sent to large cooling towers outside the plant where much of it evaporates.
The Sandia project will study the cooling of the water before it arrives in these towers.
“If we send cooler water through the towers…we can reduce what we evaporate,” Berles said.
Cooling the water with fans or other mechanisms would of course consume energy. The purpose of the research is to determine if the cost of the equipment and the energy to operate it would save money by reducing water consumption.
“It’s a balance like everything we look at,” Berles said. “You have to weigh the pros and cons of this one.”
Testing is expected to begin in May or June and collect data for four to six months.
“We’re probably several years away from doing anything at the factory,” he said.
Another option being considered by APS is to add another water treatment facility to the nuclear plant.
The wastewater that Palo Verde receives is treated before being used at the plant. The water is typically recycled through the plant and cooling towers approximately 25 times before it becomes too saline for further use.
Once the water chemistry renders 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 has been used in the plant, to extend its useful life.
“There are different technologies out there right now, and new technologies are being sought by suppliers to the water industry,” Berles said. “There are a lot of ideas people have out there.”
In 2019, APS asked to pump poor quality groundwater from the Buckeye area and investigate whether it would be cost effective to treat and use this water at the plant in place of some of the treated wastewater that she buys.
But APS is no longer pursuing that plan, Berles said.
The utility originally planned to pump up to 10,000 acre-feet of water per year and mix it with the treated effluent that is sent 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 that the water APS planned to pump was already being used by others. The permit requested by APS was for water that has no other beneficial use.
The ADWR said that “despite generally poor water quality in the region, 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 later withdrew the request.
“Just looking at the overall societal benefits or impacts, as well as the financial impacts and benefits, we just took the big picture, engaged with those stakeholders, and determined it wasn’t worth no point moving forward for us at that point,” Berles says. “At Palo Verde, engaging with the community is a big deal for us.”