Former President Donald Trump took a skeptical stance on nuclear energy in his recent interview with podcaster Joe Rogan, warning that the source of electricity Republican voters favor and GOP lawmakers vowed to support carries dangers and costs too much.

While the GOP nominee for president said atomic energy is very clean during his three-hour conversation with the popular comedian and sports commentator, he repeatedly cited the downsides of a technology his administration supported in the past and his campaign has now vowed to promote if hes elected again next month.

They get too big and too complex and too expensive, Trump said.

Theres a little danger to nuclear, he continued. You know, we had some really bad nuclear.

Trump then name-checked two proposed reactor projects that went bust during his presidency. Six months after Trump took office, South Carolina abandoned its $9 billion plan to expand the Virgil C. Summer nuclear station, which ultimately saw two executives jailed for lying to regulators about the viability of the project. Trump also mentioned Alabama, where, just a few months after Trump left the White House, the Tennessee Valley Authority gave up construction permits for a new reactor after 47 years.

The only two new reactors the United States has built from scratch in decades came online in Georgia earlier this year. The legendary U.S. nuclear developer Westinghouse designed the AP-1000 reactors built at the site in the early 2000s, initially billing the model as the workhorse of the nuclear renaissance planned under George W. Bushs administration.

Westinghouse had never built an AP-1000 before starting construction at utility giant Southern Companys Alvin W. Vogtle Generating Station in 2012. Yet the companies involved in the plan asked the Nuclear Regulatory Commission for permission to build and operate the new reactors under a combined license that required the reactors to stick to the submitted blueprints to qualify.

Each time the reactors design was tweaked during construction, the developers needed to go back to the NRC for approval, sending the costs skyrocketing. By the time Southern Company hooked the second of the two Westinghouse reactors up to the grid in the U.S. this summer, the project cost upward of $35 billion.

Trump said he wanted to avoid telling a story too long for the show because Rogans widely followed podcast was too valuable to talk about concrete. But he said each time the super hard variety of concrete poured at the nuclear construction site failed to meet specifications, an inspector would say you have to take down a 25-zillion-dollar wall.

These things ended up costing $25 billion, Trump said. And one of them never got opened.

He suggested a solution: building the same kind of reactor over and over again.