By Beyond Nuclear staff

The disaster at Unit 2 of the Three Mile Island (TMI) nuclear power plant near Harrisburg, Pennsylvania, began on March 28, 1979. Today, 39 years later, the reality, of what really happened, and how many people it harmed, remains cloaked in mystery and misinformation. Unlike the popular catchphrase, TMI is a story of too little information.

What happened?

The two unit Three Mile Island nuclear power plant sits on an island in the middle of the Susquehanna River, just ten miles southeast of Harrisburg, Pennsylvania. TMI Unit 2 was running at full power, but had been commercially operational for just 88 days when, at 4 A.M. on Wednesday, March 28, 1979, it experienced either a mechanical or electrical failure that caused the turbine-generator and the nuclear reactor to automatically shut down.

The pressure and temperature in the reactor began to increase, but when a relief valve on top of the reactor’s primary coolant pressurizer stuck open, malfunctioning instrumentation indicated that the valve had shut. While cooling water emptied out of the reactor, operators mistakenly reduced the amount of cooling water flowing into the core, leading to the partial meltdown.

Workers deliberately and repeatedly vented radioactive gas over several days to relieve pressure and save the containment structure. Then came fears of a hydrogen explosion. But by April 1, when President Jimmy Carter arrived at the site, that crisis had been averted, and by April 27 the now destroyed reactor was put into “cold shutdown.” TMI-2 was finished. But its deadly legacy was to last decades.

How much radiation got out?

Within hours of the beginning of the nuclear disaster, onsite radiation monitors went off the scale because radiation levels exceeded their measurement capacity. There were only a few offsite radiation monitors operating that day. Subsequent examination of human blood, and of anomalies in animals and plants, suggest that significant levels of radiation were released.

The TMI misinformation campaign prompted this cartoon from Jules Feiffer, which was used on buttons.

In the days following the TMI meltdown, hundreds of local residents reported the same acute radiation exposure symptoms as victims of the Hiroshima and Nagasaki bombings — nausea and vomiting, severe fatigue, diarrhea, hair loss and graying, and a radiation-induced reddening of the skin. For example, Marie Holowka, a dairy farmer near TMI, recalled as she left the milkhouse that morning that, outside, “it was so blue, I couldn’t see ten feet ahead of myself.” There was a “copper taste” in the air. She was later treated for thyroid problems. Given the absence of monitors and the paucity of evidence, the only real radiation meters were the people of Three Mile Island.

“No one died:” The biggest lie

Given that exposure to ionizing radiation is medically understood to cause diseases like cancer which can be fatal, there is no way to definitively state that “no one died at TMI” or later developed cancers. The opposite is far more likely to be true.

Estimates can be complicated by the long latency period for illnesses caused by exposure to radiation. Sometimes exposed populations move away and cannot be tracked. Nevertheless, long after a catastrophic radiation release, disease can still manifest, both from the initial radiation exposure and from slow environmental poisoning, as the radionuclides released by the disaster are ingested or inhaled for many generations.

The only independent study that looked at the aftermath of TMI was conducted by the late Dr. Stephen Wing and his team at the University of North Carolina, Chapel Hill. They looked at radiation-specific markers in residents’ blood, called biomarkers, to assess dose rather than relying solely on industry measured (or mis-measured as the case was) radiation emissions. The team concluded that lung cancer and leukemia rates were two to 10 times higher downwind of the Three Mile Island reactor than upwind.

Harm to animals and plants

After the radiation release from Three Mile Island, a number of plants exhibited strange mutations including extra large leaves (gigantism), double-headed blossoms and other anomalies. These plant anomalies were documented over decades by Mary Osborn, a local resident who conducted meticulous plant research and is a founder of Three Mile Island Alert. (Her deformed rose is pictured at the top of this story.)

Robert Weber, a Mechanicsburg veterinarian, reported a 10% increase in stillbirths, and a marked increase in the need for Cesarean Sections among sheep, goats and pigs in 1979, 1980, and 1981 in a 15-mile area around the TMI site. Dr. Weber also reported significant increases in the cancer rate among animals with shorter life spans such as dogs and cats. These findings are consistent with research around Chernobyl.

Evacuation failure

During the licensing phase of the construction and operation of TMI, a nuclear disaster was considered unthinkable. Consequently, emergency plans were practically non-existent when TMI began its meltdown. Emergency planning officials were repeatedly misinformed by TMI owner, Metropolitan Edison, on the disaster’s progression, and kept in the dark about the need for public protective actions in the early days at TMI.

On March 30, Pennsylvania Governor Richard Thornburgh finally “advised” that pregnant women and pre-school age children voluntarily evacuate a five-mile perimeter around TMI, an anticipated target population of 3,500 people. Instead, approximately 200,000 people spontaneously evacuated from a 25-mile perimeter.

TMI demonstrated that managing human responses during a nuclear catastrophe is not realistic and provokes unique human behavior not comparable to any other hazard.

Competing loyalties between work duty and personal family caused a significant number of staffing problems for various emergency response roles. As the crisis intensified, more emergency workers reported late or not at all.

Doctors, nurses and technicians in hospitals beyond the five-mile perimeter and out to 25 miles, spontaneously evacuated emergency rooms and their patients. Pennsylvania National Guard, nuclear power plant workers, school teachers and bus drivers assigned to accompany their students, abandoned their roles for family obligations. A similar response could be expected in the same situation today.

You can find our full investigation — The Truth About Three Mile Island — on our website. It is free to download and reprint.