Low-Energy Fridays: The Return of Three Mile Island
Three Mile Island (TMI), a nuclear power plant (NPP) near Harrisburg, Pennsylvania, is slated to reopen in 2028. The plant became a focal point for the U.S. anti-nuclear movement when the “worst nuclear accident in American history” took place there in 1979. Unsurprisingly, news about its potential restart is ruffling some feathers. But a sober-minded analysis of TMI and general NPP safety issues will help determine whether the reopening should be celebrated or opposed.
Construction began on TMI in 1968. The first of its two reactors (TMI-1) was commissioned in 1974, and the second reactor (TMI-2) in 1978. On March 28, 1979, TMI-2 suffered a “partial meltdown” during which a failed valve caused a loss of coolant, leading to uranium fuel melting portions of the reactor core. TMI-2 was removed from the site, leaving only TMI-1 operational until the plant was decommissioned in 2019.
For some added cultural context, fictional disaster film The China Syndrome, in which safety cover-ups at an NPP led to a massive accident, was released March 16, 1979—a mere 12 days before the TMI incident—priming public concern. One example illustrating just how panicked people were during the TMI accident is the “general absolution” granted by local priests to residents living near TMI. This practice is reserved for life-threatening situations in which someone isn’t expected to be able to meet with a priest before their death. In a nutshell, people were very, very concerned.
However, the aftermath of TMI was far less impactful than what one might suspect given its status as a poster child of nuclear energy risks. There were no direct deaths (or even injuries) at the time of the accident. While the partial meltdown exposed an estimated 2 million people to radiation, the dose was very small.
Radiation doses are measured in rem or millirem (a thousandth of a rem). Things like the sun and the ground expose us to constant background radiation. We also get radiation from food we eat (like bananas, which give a dose of 0.01 millirem). The typical American receives a radiation dose of 620 millirem per year, about half of which comes from background radiation. It would take a resident of Atlanta, Georgia, three days to receive a 1-millirem dose of radiation; for comparison, people near TMI at the time of the accident received an average estimated dose of 1.7 millirem per person.
Whether TMI caused broader health effects to the public, such as a heightened incidence of cancer, is debated heavily. While we know conclusively that exposure to high levels of radiation is dangerous and that continuous exposure to elevated radiation levels can be hazardous, the risk presented by infrequent small doses of radiation, such as from an X-ray, is less certain. Put another way, we don’t have much reason to suspect that chest X-rays, which expose patients to a radiation dose of about 10 millirem, have any discernible long-term health impact. Tackling the potential health impact of the TMI accident is similarly complicated.
The truth of the incident’s public health impact is, of course, discernible through data. The appropriate method of analysis is to observe cancer rates in people who lived near the site at the time and compare that to expected cancer rates in the general population. There have been more than a dozen studies on this, with two general takeaways. The first is that there is “no consistent evidence” that the TMI radiation release had a statistically significant impact on the mortality of affected residents. The second is that, while some studies do show elevated incidence rates of cancer in the affected area, there isn’t any “direct correlation” between the TMI accident and those cancer rates. Generally, the official position of government authorities is that the accident had a “negligible” effect on public health—but of course, some people will be convinced this is true while others declare it false.
What we can say definitively from a policy perspective is that evidence of nuclear industry safety shows it to be far safer than most energy sources and likely to deliver public benefit. Alternative power sources like coal or gas produce their own pollution that can harm public health. One can’t look at the risks of nuclear power without considering alternatives.
We can also say that the Nuclear Regulatory Commission emphasizes nuclear safety practically to a fault, largely because of incidents like the one at TMI. It’s worth considering that in the 67 years the commercial nuclear power industry has existed in the United States, the “worst” incident was the TMI accident, which scientists cannot conclusively prove caused even one death.
Finally, we can say that rising electricity demand and public pressure to increase the share of low-carbon electricity in the United States will favor the retention or restart of NPPs, including old ones. The average age of an NPP in the United States is 42 years, and nuclear power makes up about a fifth of the country’s electricity generation. Nuclear is also the largest source of low-carbon electricity in America. Nuclear safety concerns should never be dismissed out of hand; however, given nuclear power’s substantial role in U.S. energy production, future policies must be grounded in science and data. Unless new evidence emerges identifying some previously underreported risk of NPPs, there is little reason to fear TMI’s market reentry.
News about TMI will always grab headlines. But are there data-driven, fact-based reasons to be concerned about its reopening? None that I can see.