How Three Mile Island Changed the Way Nuclear Plants Operate Today

On March 28, 1979, the Three Mile Island Nuclear Generating Station in Pennsylvania became the site of the worst commercial nuclear accident in U.S. history. A series of mechanical failures, design flaws, and operator errors led to a partial meltdown of Reactor 2, releasing radioactive gas into the environment and triggering widespread public fear. The fallout wasn’t just physical—it was economic, regulatory, and psychological, fundamentally changing the way nuclear plants operate.

More than four decades later, Three Mile Island remains a symbol of nuclear energy’s risks. And now, it’s back in the news. Constellation Energy announced plans to restart the long-shuttered Unit 1 reactor under a 20-year agreement to supply Microsoft with carbon-free energy for its data centers. This decision highlights the ongoing debate about nuclear power’s role in the future of clean energy—but it also raises a critical question: has the industry truly learned from its past mistakes?

Corporate Negligence & Systemic Failures

The Three Mile Island accident was not just the result of bad luck—it was the direct consequence of systemic failures at multiple levels. One of the most critical issues was inadequate operator training. The control room staff misinterpreted key warning signals, ultimately shutting off cooling systems that could have prevented the meltdown. Their training had not prepared them to handle a crisis of this scale, leaving them without the knowledge or protocols needed to correct the situation before it spiraled out of control.

Compounding this failure was the negligence of Babcock & Wilcox, the reactor’s manufacturer. The company had been aware of similar malfunctions in other plants but failed to properly warn operators or implement necessary design corrections. This lack of transparency left the Three Mile Island staff vulnerable to the very issues that had already been observed elsewhere. Meanwhile, Metropolitan Edison, the plant’s operator, downplayed the severity of the situation. Residents were not informed of the radiation leak until nearly 24 hours after it began, delaying crucial evacuation efforts and exposing the public to unnecessary risk.

Regulatory failures also played a key role in the disaster. The Nuclear Regulatory Commission (NRC) had previously identified vulnerabilities in reactor design but failed to enforce corrective action. These oversight gaps allowed dangerous design flaws to persist, creating the conditions that made the meltdown possible. By the time the crisis was contained, a hydrogen bubble had formed in the reactor, raising fears of an explosion.

The uncertainty surrounding the potential for a catastrophic release of radiation led to widespread panic, with over 140,000 people evacuating the area in fear of what might happen next.

The Lasting Impact on Nuclear Policy

The Three Mile Island disaster led to sweeping changes in nuclear safety regulations, emergency preparedness, and industry oversight.

Among the most significant reforms included:

• Stricter Training Requirements: Operators must now undergo extensive simulation-based training to prepare for worst-case scenarios.
• Upgraded Equipment & Safety Systems: Reactor designs were improved with more reliable cooling systems, fire protection upgrades, and enhanced emergency shutdown mechanisms.
• Stronger Regulatory Oversight: The NRC expanded its on-site inspection program, assigning at least two full-time inspectors to every U.S. nuclear plant.
• Enhanced Emergency Preparedness: Plants are now required to immediately report significant incidents, and statewide emergency drills have become standard practice.

These measures have significantly reduced the risk of another Three Mile Island-style disaster, but they have not eliminated it.

The Human Cost of Three Mile Island

Though official reports concluded that radiation exposure from the accident was low, many local residents reported health issues consistent with significant radiation exposure. The psychological toll was immense. Studies found that residents who lived near the plant exhibited elevated levels of anxiety and post-traumatic stress, even decades after the event.

Radiation exposure symptoms from near the site included:

• Hair loss, nausea, and skin burns
• Higher rates of cancer and birth defects in the surrounding population
• Severe psychological distress, particularly in children

Radiation exposure can have devastating long-term effects, often appearing years or even decades after initial contact. Prolonged or high-dose exposure increases the risk of developing cancers such as leukemia, thyroid cancer, and lung cancer, as well as cardiovascular disease, immune system disorders, and genetic mutations that can affect future generations. Even lower levels of exposure can lead to chronic conditions, including persistent fatigue, cognitive decline, and organ damage.

Many survivors of nuclear accidents or radiation-related workplace exposure experience a significantly reduced quality of life, suffering from chronic pain, neurological disorders, and psychological distress such as PTSD and severe anxiety.

For victims of radiation exposure, the financial burden can be overwhelming—medical bills for cancer treatments, specialized care, and long-term disability support often reach into the millions. An experienced injury attorney can help victims and their families recover damages for medical expenses, lost wages, pain and suffering, and long-term care costs. In cases where corporate negligence led to radiation exposure, attorneys can also fight for punitive damages, holding companies accountable for failing to protect workers and the public.

No one should have to bear the cost of a company’s recklessness alone—not when legal action can provide the resources needed to rebuild a family’s future.

What People Living Near Nuclear Plants Are Owed

With the renewed push for nuclear energy—including Microsoft’s recent deal to power its AI data centers with Three Mile Island’s Unit 1—plant managers owe it to the people living near nuclear plants to have rigorous and proven safeguards in place.  

Managers of active nuclear plants need to clearly establish and publicize:

• Emergency Protocols: Every plant has a designated evacuation zone. Residents should be made familiar with routes and provided with a plan in case of emergency.
• Radiation Exposure Risks: While modern plants have more safeguards, accidents can still happen. Understanding radiation exposure levels and protective measures is crucial.
• Recent Plant Safety Violations: Many nuclear plants still face issues with maintenance and oversight. Residents should have access to NRC reports and local plant safety records.

Corporate Accountability Is Critical For Safe Nuclear Power

The real lesson of Three Mile Island isn’t just about improved regulations—it’s about accountability. The disaster was entirely preventable if corporations had prioritized safety over cost-cutting. And yet, history shows that companies only make meaningful changes when they are forced to.

This is why plaintiff trial lawyers play a critical role in nuclear safety. Regulators can pass laws, but trial lawyers hold companies accountable when they fail to follow them. Every major industry reform—from nuclear plants to oil refineries—has come only after corporations were forced to answer for their negligence in court.