Science and TechEnergy


Three Mile Island's Nuclear Legacy

The partial meltdown at Three Mile Island in 1979 caused changes throughout the country's nuclear industry.
Posted at 5:23 PM, Mar 28, 2019

The most serious nuclear accident on U.S. soil took place in 1979 at the Three Mile Island nuclear station in Pennsylvania. Nobody was killed or even injured. But the averted disaster was a milestone for the industry, and we can still see its effects today.

On March 28, 1979, Three Mile's No. 2 reactor suffered a partial core meltdown after its coolant pumps failed. Luckily, its reactor shielding worked as intended, and very little radiation escaped.

Shortly after the accident, the Nuclear Regulatory Commission rolled out new oversight, new training and new design requirements for power stations. These reforms were all in the name of safety, but researchers say they also contributed to what was becoming a slower, much more expensive industry.

In the next decade, energy companies turned on 44 new power stations — but canceled plans for 67 more. Reactors now took more time and a lot more money to build.

Today, nuclear power still has some of the steepest upfront costs in the energy sector. Building a modern plant costs billions of dollars and, thanks to regulations added because of Three Mile, each reactor site must carry more than $1 billion in insurance.

The nuclear waste and debris from Three Mile was shipped to Idaho National Laboratory, where it's still cooling in what is technically temporary storage. Like all other U.S. nuclear waste and fuel, it doesn't have a permanent disposal site. The most likely candidate, Yucca Mountain, has gone in and out of regulatory limbo for decades. The necessary political support and funding have never aligned to put it into service. 

Opening a disposal site would also take time, which for some plants is already ticking down. Arranging permanent waste storage could take decades, and the average U.S. nuclear plant is now 37 years old. Most of them have almost worn out their operating licenses, which are good for 40-60 years. If they're not renewed, plants will have to shut down.

Three Mile Island will be one of the first to go, but that's not because it's unsafe or even because it's old. It simply hasn't been able to compete with cheap natural gas. Plant owner Exelon says it plans to start decommissioning as early as September 2019.