The Accidents and Improvements of Nuclear Energy
When people hear the word “nuclear energy,” many think of accidents like Chernobyl or Three Mile Island, of burns and corpses, of green goo oozing from glowing yellow barrels. But are these images representative of nuclear energy as a whole?
The public’s fear of nuclear accidents may be justified since large incidents have the potential to irradiate landscapes and kill hundreds of people. However, in six decades of operation and over 18,500 cumulative years of active reactors in 36 countries, there have only been three major accidents (1).
The first incident occurred in 1979 at Three Mile Island in Pennsylvania and resulted in severe damage to the reactor but no adverse health or environmental consequences. It began with a minor malfunction in the cooling system but deficient instrumentation in the control room and improper emergency training among the employees meant that this minor issue could not be resolved. Even though the reactor had a partial meltdown, the proper shielding and containment of the power plant trapped most radiation. The average radiation dose of the citizens surrounding the reactor was equivalent to that of a chest X-ray, with the highest dosages being only one-third of that received by an average U.S. citizen annually. This was the worst nuclear incident in the history of the United States, but it led to no long-term consequences to human or environmental health (2).
The second incident, which occurred at the Chernobyl reactor, is infamous for its devastation. It occurred in 1986, in Pripyat, Ukraine. It was the worst nuclear accident in global history, and it resulted in two deaths from explosions, 28 deaths from acute radiation sickness, and thousands of patients who developed thyroid cancers due to radiation. The cause of this accident was improperly trained staff operating an inherently flawed reactor.
All Western reactors use water as both a moderator and coolant; this means that water is necessary to both maintain the reaction and cool down the reactor. When water evaporates due to the reaction’s heat, the reactor loses both some of the coolant and some of the moderator. Less coolant means the temperature rises, but less moderator means the reaction is slowed. By using water as both components, the reactor stays stable when water evaporates, which will prevent incidents similar to Chernobyl from happening in the future (4).
The reactors present at Chernobyl, called the Reaktor Bolshoy Moshchnosty Kanalny (RBMK) reactors, used water only as a coolant and graphite as a moderator. In this mechanism, when the reactor heats up, water evaporates which means that coolant is removed; this causes the reactor to heat up more, and more water to evaporate, and so forth. Even though some of the coolant is lost, the reaction continues at the same high speed. Normally, this system is kept in check by many other factors that affect the reactor’s stability. However, on the night of the accident, the reactor workers were performing a test that put the reactor at dangerous levels. Under those conditions, the dangerous cycle of heating and cooling led to the tragic accident in Chernobyl. This critical flaw has been addressed in new reactor designs, as were the other safety hazards that contributed to the Chernobyl incident such as improper training of employees or dysfunctional instrumentation (4).
The third and most recent incident occurred in 2011 at a reactor called Fukushima Daiichi in Japan. Although plant workers were exposed to radiation, it was not enough to threaten their health. Following a major earthquake, the power plant was hit by a 15-meter (50 ft) tall tsunami which disabled its power and cooling system. The Fukushima Daiichi reactor was not designed to withstand these extreme conditions. The Japanese government evacuated 100,000 people around the site, so, even in this unexpected scenario, no deaths from radiation were recorded (3).
The main cause of these accidents is human error and improper designs which have been addressed in modern designs. When properly designed and managed, nuclear reactors have a very low chance of sustaining or causing damage. Even when such incidents occur, proper shielding in the power plant can contain radiation and limit the impact on the populace. Many lessons have been learned from these accidents as scientists continue to improve the safety and function of nuclear reactors. The United States government requires that a reactor core must exceed a 1 in 100,000 years core damage frequency. This means that a reactor built within these conditions is expected to have only one serious accident every 100,000 years. However, many modern reactors exceed a 1 in 1 million years chance (1).
Excluding serious disasters, critics of nuclear energy often cite passive radiation, or radiation released during normal operation of a reactor, as a concern. However, these worries are completely unfounded. In fact, due to trace amounts of uranium and thorium in coal, coal power plants release 100 times more radiation into the environment than nuclear power plants. As long as no issues occur, living near a nuclear power plant is not hazardous (5).
While there have been serious accidents in the past, the world has learned from its mistakes and continues to develop increasingly safer nuclear reactors. Ultimately, it is the public and policymakers’ decision whether to accept the small but ever-present risk that nuclear power plants hold in exchange for their vast energy production capabilities.
Bibliography:
1. Safety of Nuclear Reactors – World Nuclear Association. (2022). World-Nuclear.org. https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/safety-of-nuclear-power-reactors.aspx#:~:text=The%20evidence%20over%20six%20decades,with%20other%20commonly%20accepted%20risks.
2. Three Mile Island | TMI 2 |Three Mile Island Accident. – World Nuclear Association. (2020). World-Nuclear.org. https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/three-mile-island-accident.aspx
3. Fukushima Daiichi Accident – World Nuclear Association. (2021). World-Nuclear.org. https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/fukushima-daiichi-accident.aspx
4. RBMK Reactors | reactor bolshoy moshchnosty kanalny | Positive void coefficient – World Nuclear Association. (2022). World-Nuclear.org. https://world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/appendices/rbmk-reactors.aspx
5. Nit, U., Teknologi, P., Bahagian, S., & Alam, T. (2010). Dewan Tun Dr. Ismail Agensi Nuklear Malaysia 26 -28 Oktober. 1, 0. https://inis.iaea.org/collection/NCLCollectionStore/_Public/43/035/43035329.pdf
Images:
- https://www.energywarden.com/what-exactly-is-nuclear-energy/
- https://en.wikipedia.org/wiki/Nuclear_reactor