Enlarge /. The Palo Verde nuclear power plant, the largest nuclear power plant in the country.
Jeff Topping / Getty
Every spring, nearly 1,000 highly specialized engineers from the United States come to the Palo Verde nuclear power plant near Phoenix, Arizona to fuel one of the plant's three nuclear reactors. As America's largest power plant – nuclear or otherwise – Palo Verde provides electricity to 4 million people in the southwest around the clock. Even under normal circumstances, refueling one of its reactors is a tedious, months-long process. But now that the United States is in the middle of the corona virus pandemic, plant operators have had to adjust their fueling plans.
Palo Verde is expected to begin refueling one of its reactors in early April – a spokesman for the Arizona Public Service, the energy company that operates the facility, declined to provide an exact start date – but preparations began months in advance. The uranium fuel arrived at the plant last fall and was delivered to the cargo hold of an unmarked truck. The fuel arrives ready for the reactor as a rectangular 1000-pound bundle of uranium rods that are 12 feet high and about 6 inches tall on each side.
The last shipment of fuel arrived at the facility long before the coronavirus pandemic halted the world, says Greg Cameron, director of nuclear communications at Palo Verde. The biggest change in this refueling cycle is the scope of the process. "We tried to reduce the amount of work to what was necessary to ensure that we would run for the next 18 months without compromising the reliability of the facility," said Cameron.
Each of the three Palo Verde nuclear reactors is located in its own bulbous concrete sarcophagus and works almost completely independently of one another. In this way, plant operators can regularly switch one of the reactors offline for refueling and maintenance without completely disrupting the energy flow to the network. Every reactor is partially refueled every one and a half years, 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 a giant underwater Jenga game. The oldest uranium rods are placed in a holding basin, where they cool down for several years before being transferred to dry storage drums. As the energy generated by a uranium rod decreases over time, the remaining fuel in the reactor must be mixed to distribute its 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. This ensures that the rods never leave the water, shielding the radiation and preventing the fuel from overheating.
Refueling typically takes about a month and includes the accommodation of hundreds of electricians, welders and other industrial workers who are traveling across the country to refuel nuclear power plants. However, not all of these contractors are needed to fill a reactor. Many are involved in opportunistic repairs, upgrades, and inspections that can only be done when the reactor is offline. To cope with the pandemic, the Arizona Public Service made the decision to only carry out repairs that are essential for the operation of the reactor until its next tank shutdown in fall 2021.
"Any new work planned will be evaluated to ensure that the effects of non-compliance are well understood and in line with guidelines," wrote a spokesman for the industry’s trading group, Nuclear Energy Institute, in an email to WIRED. If a nuclear power plant delays maintenance, its operators must demonstrate that the delay does not compromise safety and obtain final approval from the Nuclear Regulatory Commission.
By reducing the amount of upgrades and repairs planned for their reactor, Palo Verde operators have halved the number of contractors who will need to work there this month. Most Palo Verde employees have been working remotely for weeks, but control room operators and other critical staff have yet to be added to monitor the nuclear reactors. For the past few weeks, medical personnel have been working in large tents outside the facility, examining anyone 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 isn't the only nuclear power plant that needs to adjust its tank process to cope with the pandemic. According to the Nuclear Energy Institute, almost a third of the 99 American nuclear power plants will be filled before June. All but two must be refueled before the end of the year. As one of the 16 sectors classified by the Department of Homeland Security as “critical”, the nuclear industry – and the energy sector in a broad sense – is well prepared to keep the lights on during a crisis.
This story originally appeared on wired.com