The Three Mile Island accident occurred on March 28th, 1979 near Middletown Pennsylvania. A failure caused the pumps that cooled the core to stop moving water, increasing the pressure in the cooling system. While the reactor and turbine shut down, the relief valve that was opened to reduce the pressure became stuck open, causing alarms to ring. However, the instruments indicated that the valve was closed and there was enough water in the core. Under these assumptions, the staff started to inadvertently uncover the core. The emergency cooling water that was being pumped into the core to keep it from overheating was cut off to stop it from filling the pressure vessel in which the reactor sat. Without cooling pumps and with the emergency system cut back, the core overheated, and small amounts of radiation were released into the surrounding environment. Following the accident, the TMI -2 reactor was shut down, decontaminated, and decommissioned. The radioactive waste from the accident was shipped to a disposal area, and TMI-2 was placed in long-term monitored storage. The actual health and environmental effects of the accident were debated heavily, with a paper even being published by the Physicians for Social Responsibility stating that there were 50 fatal cancer deaths associated with the radiation release from the accident. A committee from the United Nations later released a report predicting only one possible case of fatal cancer occurring from the accident. Put into context, the population analyzed was predicted to have around 320,000 cancer deaths from other causes. Other assessments by Columbia University have determined that despite the serious damage to the reactor, the release of radionuclides had negligible effects on individuals or the environment. The accident served as a lesson for the Nuclear Regulatory Commission (NRC), and many design changes and improvements in nuclear plants were put in place by the NRC to prevent similar disasters. More oversight and regulations were also adopted to reduce human error and catch problems before they manifested. Three Mile Island was not a catastrophic nuclear accident like some believe, and it is unfair to write off nuclear energy or ignore its benefits because of it.
The Fukushima Daiichi Accident started on March 11, 2011, after a 9.0 magnitude offshore earthquake rocked the Japanese coast. The actual shockwave did minor damage to the Fukushima reactors, which shut down automatically when it hit. The tsunami caused by the earthquake, which arrived around an hour later, posed significantly greater problems: 12 of the 13 backup generators in the facility were completely disabled after they were inundated by the 15-meter wave. The heat exchangers responsible for transferring excess heat from the reactor into the sea were also rendered inoperable. 3 reactors inside the plant were left unable to properly maintain cooling, which caused a partial meltdown. Emergency water injection into the reactors began, but the systems to do so eventually failed over the following 3 days. Fire hoses were rigged to continue the flow, but this required the steam and hydrogen (a byproduct of the zirconium cladding of the reactors and steam interacting) in the reactors to be vented. In unit 1, which suffered the most severe meltdown, the vented steam and hydrogen backfilled into a service floor at the top of the reactor building. The hydrogen mixed with air and ignited, causing a hydrogen explosion that destroyed the roof. A larger explosion happened 2 days later above unit 3, which scattered some radioactive debris outside the building. Another explosion also likely occurred in unit 2’s containment chamber, causing radiation leaks. Nitrogen was then injected into the containment vessels of each reactor to prevent more hydrogen explosions. Airborne radioactive particles constituted the majority of radioactive discharge during Fukushima. The main sources of these releases were the initial venting of the reactors and the breach in Unit 2’s containment chamber. Radioactive releases eventually reached minimal levels by December, with the reactors reaching “cold shutdown condition”. In March, when the largest portion of radioactive release occurred, a nuclear emergency was triggered and citizens within 2 kilometers were evacuated. Over the next few days, the evacuation was expanded to 10 and then 20 kilometers. Around 160,000 people were evacuated, and areas around the plant were restricted due to contamination. A study published by the UN in 2013 concluded, "No radiation-related deaths or acute diseases have been observed among the workers and general public exposed to radiation from the accident”. The restricted areas were and still are subjected to strict decontamination, and after 2012 some residents were able to return to their homes.
Fukushima taught essential lessons about accounting for natural phenomena and compensating for outdated design. While the tsunami struck the actual blow, the root cause of the disaster was, unfortunately, complacency. The Fukushima plant was initially designed to withstand a tsunami only 3.1 meters high. This was later revised but only to 5.7 meters in 2002, despite the multiple instances of over 10-meter tall tsunamis affecting the Japanese coast. There was even a prediction that a 15-meter-tall tsunami would strike the Daichi region 18 years before the disaster. There was no awareness of this likelihood when Fukushima was first designed and sited in 1960, but Tepco (the plant operator) and the government failed to act on this new information. Countermeasures against the tsunami, like moving backup generators to higher ground and sealing parts of the building, could have reduced the risk but were not put in place. After the accident, stress tests were ordered for all of Japan’s reactors and the previous regulatory commissions were overhauled into the Nuclear Regulatory Agency. The US Nuclear Regulatory Commission (USNRC) compiled a report on the accident and made recommendations for updates to US reactors like hydrogen mitigation systems, required reevaluations, and flood protection upgrades. In a vacuum, the design for the Fukushima plant does not contain flaws like Three Mile Island; it is just that it was not suitable for the location in which it was built. Luckily, the plant workers’ heroic efforts prevented the accident from worsening further, and the evacuation and decontamination prevented the nearby population from suffering adverse health effects. Fukushima demonstrates the consequences of complacency, but it ironically also shows that nuclear power is not as dangerous as it seems. Even under such dire circumstances, there were no health effects on the public, and parts of the contaminated land have been cleaned and rendered safe for humans. Nuclear power is reliable, clean, and safe; Fukushima should be an essential lesson to remember for the future, not a justification for writing off nuclear power. Climate change poses far worse consequences for the entire planet than Fukushima ever could have.
Chernobyl is by far the worst nuclear disaster and also happens to be shrouded in the most confusion and mystery. The Chernobyl Nuclear Power Plant is located near Pripyat, Ukraine, and was constructed in 1977 during Soviet Union rule. On April 26th, 1986, Unit 4 of the plant was destroyed while undergoing a systems test. Without a containment chamber like the ones Western reactors have, the reactor was completely exposed and began releasing massive amounts of radioactive particles into the environment, contaminating large areas of Ukraine, Belarus, and Russia. The exact effects of the contamination are hard to determine given the Soviet Union’s lack of transparency and truth manipulation. The internationally agreed-upon death toll is 31, with the UN estimating only 50 deaths directly from the accident. However, the other effects of Chernobyl are far more widespread and long-lasting. In 2005 the UN predicted around 4000 more people would die from radiation exposure associated with the disaster. However, death rates from the clean-up crew – or “liquidators” – and evacuees of Chernobyl paint a far more grim picture. In Ukraine alone, around 319,000 liquidators braved the radiation, and because of their intervention, death rates among them increased from 3.5 to 17.5 deaths per 100 people. The evacuees, which number around 200,000 have also seen similar mortality rates, with ~18 deaths per 100 people. Chernobyl reactor 4 currently sits inside “The New Safe Confinement,” a giant half-cylinder enclosing the remains of the reactor; a tragic and painful reminder of the disaster. The effects of Chernobyl were large and quite possibly affected millions, but it is also extremely unlikely a disaster like this will ever happen again. Basic safety systems that are standard on Western reactors – like the aforementioned containment chamber – were simply not present at Chernobyl. Western reactors are also designed in such a way that an accident similar to Chernobyl cannot happen in one, and they go through significantly more robust oversight and inspection. Chernobyl should not be painted as a failure of nuclear power, but rather as the failure of the dying and dysfunctional Soviet Union.
A more underlooked issue with nuclear energy is the sourcing of uranium for reactors. Currently, Asia and Africa have emerged as the primary exporters of uranium ore, mainly due to their low labor costs and lackluster safety standards. An increase in nuclear power plants would naturally increase the demand for uranium, most likely exacerbating these issues. If not managed properly, the mining and processing of uranium can create radioactive dust, which poses a threat to workers, surrounding communities, and the environment. Unfortunately, the data on mining's current effects and contamination are insufficient, so quantifying the scale of the problem is difficult. Thankfully, this is an issue that can be solved before it gets out of hand. With strict oversight by the international community and the governments of affected countries, mining companies can be held to a higher standard. Investment in local environmental research can help spot contamination before it becomes a serious threat, and input from local communities can help address potential concerns.
When the uranium inside a reactor is used up, it is converted into nuclear waste, a mix of radioactive isotopes into which the uranium has decayed. A reactor typically has to have a third of its fuel replaced every 12-24 months, and the fresh waste – which is highly radioactive – is stored inside spent fuel pools at the plant. These pools are typically around 40 feet deep and contain and cool off the waste. When the pools begin to fill up, older waste is sealed into dry casks and stored above ground at the plant. While this may seem dangerous, nuclear waste’s radioactivity actually significantly diminishes over time. The radioactivity of long-term nuclear waste is reduced to around 0.1% of the initial value after about 40-50 years. While plants typically transfer their waste to casks after around 5 to 10 years, the casks and their designs are certified for safety by the NRC, and there are no pressing reasons for changing storage protocols. The volume of this waste is also small, with high-level waste making up only around 3% of all nuclear waste produced. A big point of contention surrounding nuclear waste is that there is not a permanent disposal facility for it. The Department of Energy has attempted to build one in Yucca Mountain, Nevada, but the project was canceled in 2010. While this makes it seem like there isn't a solution for long-term nuclear waste storage, in reality, there are already viable solutions for disposal. A particularly promising option is called deep vertical borehole disposal. Essentially, a borehole is drilled into the ground, around 3-5 kilometers deep. Canisters of nuclear waste are then placed inside the borehole and sealed away. Provided the bedrock is suitable, this can even be done on-site at a plant. Simulations of this method have concluded that “deep vertical boreholes provide safe and cheap storage, and the isolation provided by them effectively removes high-level nuclear waste from the surrounding environment”. Ultimately, while nuclear waste can present a danger, it is not the insurmountable problem that many believe it to be. Current storage methods have proved sufficient in containing nuclear waste, and there are already possible options for longer-term storage if necessary.
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