Each spring, nearly 1,000 highly specialized technicians from across the U.S. descend on the Palo Verde Nuclear Generating Station near Phoenix, Arizona, to refuel one of the plant’s three nuclear reactors. As America’s largest nuclear or non-nuclear power plant, Palo Verde supplies power to 4 million people in the Southwest 24 hours a day. Even under normal conditions, refueling one of the reactors is a laborious process that takes months. But with the US in the midst of the coronavirus pandemic, plant operators have had to adjust their fueling plans.
Palo Verde is expected to begin fueling one of its reactors in early April — a spokesman for Arizona Public Service, the utility that operates the plant, declined to give an exact start date — but preparations began months in advance. The uranium fuel arrived at the factory last fall and was delivered in the cargo hold of an unmarked semi-truck. The fuel arrives ready for the reactor as rectangular bundles of 1,000-pound uranium rods that are 12 feet long and about 6 inches on each side.
The last batch of fuel arrived at the plant well before the coronavirus pandemic brought the world to a standstill, said Greg Cameron, director of nuclear communications at Palo Verde. The biggest change with this tank cycle, he says, is the size of the operation. “We have tried to reduce the amount of work to what is needed to ensure that we can run for the next 18 months without affecting the reliability of the plant,” said Cameron.
Each of Palo Verde’s three nuclear reactors are nestled in their own spherical concrete sarcophagus and operate almost completely independently of each other. This allows plant operators to periodically take one of the reactors offline for refueling and maintenance without completely disrupting the flow of energy to the grid. Each reactor is partially refueled every year and a half, with about a third of the fuel in the reactor core being exchanged for a new batch.
Adding new fuel to the reactor is like playing a giant game of Jenga underwater. The oldest uranium rods are moved to a storage basin, where they cool for several years before being transferred to dry storage vessels. Because the energy produced by a uranium rod decreases over time, the remaining fuel in the reactor must be shaken to distribute the heat evenly before adding the new rods. The whole process is done with a machine that is essentially a giant version of the arcade claw crane. that ensures the rods never leave the water, shielding radiation and preventing the fuel from overheating.
Refueling usually takes about a month and involves hosting hundreds of electricians, welders and other industrial workers who travel across the country to refuel nuclear plants. But not all of these contractors are needed to just top up a reactor. Many are involved in opportunistic repairs, upgrades and inspections that can only take place while the reactor is offline. In order to cope with the pandemic, the Arizona Public Service has made the decision to only make repairs that are essential to keep the reactor running until the next tank failure in the fall of 2021.
“Any work that is rescheduled will be evaluated to ensure the impact of not completing it is well understood and within guidelines,” a spokesperson for the industry’s trade group Nuclear Energy Institute wrote in an email. e-mail to WIRED. If a nuclear power plant delays maintenance, operators must demonstrate that the delay does not endanger safety and obtain final approval from the Nuclear Regulatory Commission.
By scaling back the scope of planned upgrades and repairs for their reactor, Palo Verde operators halved the number of contractors required to work there this month. Most of Palo Verde’s staff has been working remotely for weeks, but control room operators and other critical staff still have to come in to keep an eye on the nuclear reactors. For the past few weeks, medical personnel have been working in large tents outside the facility to screen everyone entering the power plant for symptoms of COVID-19. Once refueling begins, control room operators and temporary workers will use separate entrances to the facility to limit contact between the two groups.
Palo Verde is not the only nuclear power plant that will have to adapt its fueling process to cope with the pandemic. According to the Nuclear Energy Institute, nearly a third of 99 U.S. nuclear power plants have scheduled refueling by June. All but two must be fueled before the end of the year. But as one of 16 sectors identified as “critical” by the Department of Homeland Security, the nuclear industry — and the energy sector in general — is well prepared to leave the lights on during a crisis.
This story originally appeared on wired.com