Nuclear Power Plant Safety

Alana Cook
March 9, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1: Three Mile Island, pictured in 2006. The large cooling towers are visible in the rear of the photo, and the nuclear reactors are contained within the two small dome-shaped buildings. (Source: Wikimedia Commons)

While nuclear energy continues to be a top producing, clean source of energy for the global community, its reputation as a safe and reliable energy source has been marred from multiple instances of disaster. Opponents to nuclear energy are quick to rule out the idea that nuclear reactor meltdowns such as Chernobyl are simply described by the Black Swan Theory, which describes when an event with a major impact occurs despite having a disproportionately low chance of occurrence. Proponents of nuclear energy do not agree with the notion that disasters involving nuclear energy production are anything but rare, relying on statistical data as well as increasing technological precautions to bolster their claims. [1]


While proponents of nuclear energy might conclude that it is the safest form of energy, when nuclear reactor disasters do occur, they are often extremely dangerous.

1. Chernobyl

Located in Ukraine: April 26, 1986. Perhaps the most commonly known nuclear disaster, the Chernobyl plant meltdown is considered to be one of the most devastating in history. The meltdown was ultimately caused by haphazard experimentation with one of the plant's four reactors, which lead to a power surge, ultimately causing the several ton steel lid to be exploded off of the reactor. [2] This crisis lead the Soviet government (and later, the Russian government) to evacuate nearly 115,000 people from the immediate surrounding areas, as well as 220,000 more civilians in the following years. The explosion and released of radioactive materials caused heavily-populated areas of Belarus, the Russian Federation, and Ukraine to be contaminated. Two workers were killed within the first couple hours after the reactor meltdown, though due to "non-radiological causes." The effects of the radiation released were quite severe, killing 28 of the 600 workers on site in the four months following the meltdown. An additional 106 workers were exposed to enough radiation to contract acute radiation sickness. In the following years, 200,000 workers charged with cleanup duties were exposed to doses of between 1 and 100 rem while the normal yearly dose of radiation for a U.S. civilian is closer to 0.6 rem. In total, over 600,000 workers were needed to fully clean up the explosion site. The government continues to monitor the related health effects on the workers on site and those that aided in cleanup. [3] Perhaps the most long-lasting effect of the explosion was seen in the increase in thyroid cancer in nearby citizens. Affecting youth more severely, the increase in thyroid cancer among those exposed to radiation skyrocketed from 0.03-0.05 cases to 4 cases per 100000 by 1995. [4]

2. Three Mile Island

Located in Harrisburg, Pennsylvania: March 28, 1979. (See Fig. 1.) Noted as the most significant nuclear plant accident in the United States, the accident at Three Mile Island has had lasting impacts on the American public's view of nuclear energy. [5] The series of events that lead the reactor overheat began with the plant experiencing a failure in a non-nuclear portion of the plant. This failure, either mechanical or electrical in nature, caused the main water pumps to stop sending water to the steam generators to be used to remove heat from the core of the reactor. With the increase in temperature of the steam generator and the reactor, both automatically shut down as a function precautionary protocol put in place. This trigged a relief valve to open in order to release the increasing pressure in the reactor. The valve malfunctioned and became stuck open, despite the pressure in the reactor having fallen back to an adequate level. Following this, a third instrumental failure occurred as the instruments used to display reactor function in the control room incorrectly indicated to operating personnel that the valve was closed. With this incorrect information, the operators took steps to ultimately reduce the amount of water being sent to cover the core of the reactor, thus causing its temperature to rise dramatically and the reactor to overheat. As the meltdown was well contained within the reactor, the nearly 2 million people living in the surrounding areas to the power plant were argued to have been exposed to an average radiation dose of only about 1 millirem more than their usual background dose. This is less than that received from a chest X-ray and about 100 times less than the area's natural radioactive background dose. [6] Though the ultimate human and environmental impact was low, the event marred nuclear energy's clean and safe image for many Americans moving forward, proving to be a difficult obstacle for present day nuclear energy advocates to overcome. [5]

3. Saint Laurent

Located at Loir-et-Cher, France: October 17, 1969 and March 13, 1980. At the time of the first incident, the nuclear plant's infrastructure was comprised of "two gas-cooled, graphite moderated reactors (GCR)". [7] Mishandling of uranium, the prime ingredient used in the nuclear reactant process, caused the reactors to experience a partial meltdown, rendering the plant useless for over a year. It took this long for workers to clean and refurbish the damaged reactor, working in an extremely dangerous and radioactive environment. Many surmise that this accident is what ultimately brought an end to the GCR nuclear program in France, though doing little to alter the country's further development in the area of nuclear energy. Little more than ten years later, one of the two GCRs experienced another severe meltdown, putting it out of commission for over two years for cleaning and repair. [7]


With accidents such as Chernobyl, Three Mile Island, and Saint Laurent, it isn't difficult to imagine why trying to establish nuclear energy as a viable fuel source on national and international scales is quite controversial. Understandably, nobody wants to live in the next potential evacuation zone. Nobody wants another Chernobyl. Despite the level of devastation that some of these nuclear accidents have caused, nuclear power plants as a whole have very little risk in releasing radioactive materials into the neighboring communities. Due to numerous varying and overlapping safety measures, increasingly well-trained reactor operators, thorough testing and maintenance, as well as the regulations put in place by the Nuclear Regulatory Commission (NRC), power plants pose little threat of catastrophic meltdown. [8]

While "no industrial activity ... is risk free," innovations in technology and understand of nuclear energy processing has made the design of power plants to be extremely safe, operating without any major effects on the "public health and safety and the environment." [8] Fuel Cladding is one safety used to ensure that the nuclear reactors run in a safe manner. This process involves "sealed metal tubes in which ceramic pellets of uranium fuel" are held. The next safety measure is an almost twelve inch thick heavy steel reactor tube in combination with a piping system for water cooling. To safely enclose all of this, nuclear plants use containment buildings which are buildings built with concrete and steel, often several feet thick encapsulating the reactor. Its sole purpose is to help lessen the effect of a nuclear accident if any nuclear material were to be released. [8]

Because many of the plant's barrier systems require electricity, nuclear plants are prepared for emergency situations with backup diesel generators to help power all necessary systems to keep the reactor running properly. In addition to this safety measure, there are regulations for appropriate operation of nuclear plants. Operators are required by law to operate the nuclear plants in a manner that is safe, following proper operation procedures, testing requirements and maintenance, as well as only operating under safe conditions. [5]

The NRC, wanting to ensure the safe practice of all United States nuclear plants, wrote a policy statements underlining the organizations ultimate goals and expectations with regard to properly operating a power plant. [8] In the policy statement, the NRC issued a statement that "the risk of cancer fatalities to the population near a nuclear power plant should not exceed 0.1% of the sum of cancer fatality risks from all other causes." [8] Overall, the NRC wanted to establish a safer future for nuclear energy by setting forth guidelines and requirements for safe operation. These included increased testing and maintenance measures, as well as increased transparency in regards to the probabilistic risk assessment of nuclear activity. [5]


While no industrial or fuel plant is guaranteed to be safe, opponents of the clean and efficient fuel source might argue that no other plant has the capacity to do harm to the public health and environment like a nuclear plant does. The NRC has made strides to establish increased and effective safety measures to ensure the bright future of nuclear energy, but for many, the question still lingers whether the next Chernobyl is an inevitability or an avoidable tragedy. Nuclear plant meltdowns have been caused by a variety of reasons throughout history, from mechanical failure to human error, leaving many to also question if nuclear energy can truly be made safe. It is also believed that increase in nuclear power plants may also lead to an increase in nuclear weapon production. These questions and concerns are both serious in nature and asked with valid concern. With that said, the efficiency, cleanness, and sustainability of nuclear power makes it difficult to imagine a better future fuel source. Nuclear power plants typically yield a very high capacity factor, which is the ratio of the electrical energy produced comparable to the electrical energy that could have been produced at full operational power. It provides a realistic alternative to displace and eventually replace our rapid use of fossil fuels. [9] Despite opposition, it seems to be the sustainable energy source of the future.

© Alana Cook. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. Krupka and C. Jones, "Black Swan Theory: Applications to Energy Market Histories and Technologies," Energy Strategy Rev. 1, 286 (2013).

[2] M. Caballero, "The Chernobyl Disaster," Physics 241, Stanford University, Winter 2016.

[3] "Chernobyl Nuclear Power Plant Accident", U.S. Nuclear Regulatory Commission, May 2013.

[4] O. Urban, "Health Consequences of the Chernobyl Accident," Physics 241, Stanford University, Winter 2016.

[5] C. Akin-David, "USA Nuclear Power Risks," Physics 241, Stanford University, Winter 2016.

[6] "Three Mile Island Accident", U.S. Nuclear Regulatory Commission, February 2013.

[7] R. Dudzinski, "Saint Laurent Nuclear Accidents and Their Implications," Physics 241, Stanford University, Winter 2017.

[8] "Nuclear Reactor Risk," U.S. Nuclear Regulatory Commission, November 2011.

[9] B. W. Brook et al., "Why Nuclear Energy is Sustainable and Has to be Part of the Mix," Sustain. Mater. Technol. 1-2, 8 (2014).