In this blog post, we’ll explore power shortages and the principles of nuclear power, and examine how well we understand this important technology.
Power shortages, which frequently make headlines every summer, are a source of great distress for people. Even in the heat, public institutions are unable to turn on air conditioning, leaving many unable to escape the sweltering heat, and there is also the worry of blackouts caused by exceeding power capacity. In the midst of these circumstances, we are reminded anew of the value of electricity. Electricity is not merely a convenience in our daily lives; it is an essential foundation of modern society. From the use of smart devices to industrial production and medical systems, everything relies on electricity. Power shortages are emerging as a serious issue that goes beyond mere daily inconvenience and can significantly impact the national economy and safety.
In Korea, the primary methods of electricity generation are thermal and nuclear power, followed by hydropower, which accounts for the next largest share. However, hydropower constitutes less than 10% of the total, so reliance on it is low. Among these, nuclear power ranks second in terms of total electricity generation in South Korea, accounting for a significant 30% of the total. While nuclear power is a crucial technology that enables a stable power supply, it is also the most controversial form of power generation. Nevertheless, few people understand the principles behind nuclear power generation. In this article, I aim to provide a brief explanation of the principles of nuclear power generation.
First, power generation refers to the process of converting various forms of energy into electrical energy. Depending on the method used to obtain the fuel and energy required for generation, power plants are classified as thermal, hydroelectric, or nuclear. While it is easy to assume that these various methods produce electricity in different ways, surprisingly, almost all forms of power generation produce electricity by turning a turbine. This method has remained the core principle of power generation, unchanged from the first alternating current (AC) power plant to the present day. Therefore, the principle of nuclear power generation essentially revolves around how to use nuclear energy to turn a turbine.
The primary energy generated in nuclear power generation is the thermal energy produced by nuclear fission. Atoms, the basic units of matter, consist of a nucleus and electrons, and the atomic nucleus itself is composed of two types of particles: protons and neutrons. The number of protons and neutrons in the nucleus varies depending on the type of atom. Uranium, which is used as fuel in nuclear power generation, is a very heavy atom, with a total of 235 or 238 protons and neutrons. The uranium nucleus holds more than 200 particles, storing a great deal of energy within it, which makes it highly unstable. When a neutron is fired at high speed into such uranium, the uranium nucleus splits into smaller atoms, releasing an enormous amount of energy. This is nuclear fission. The neutrons ejected during the splitting process collide with other nuclei, and as this process repeats, a chain reaction of fission occurs, continuously generating heat.
The most critical aspect of nuclear power generation is controlling the speed and intensity of this chain reaction. If this reaction is not controlled, it can become a potential hazard capable of releasing explosive amounts of energy. To address this, the space between the fuel rods is filled with light water (ordinary water) or heavy water (water created by combining oxygen with a neutron-bound hydrogen atom), which serves as a moderator to maintain the neutrons—the key to the reaction—at an appropriate speed. If the reaction becomes too vigorous and the temperature rises above a certain level, control rods are inserted between the fuel rods to block neutrons from reaching other fuel rods, thereby controlling the fission. During this process, not only thermal energy but also byproducts such as radioactivity are generated. This is another major issue in nuclear power generation, and safely managing these byproducts is also a critical challenge.
However, the thermal energy generated by nuclear fission cannot directly drive a turbine. Water acts as the medium that converts this thermal energy into the kinetic energy needed to turn the turbine. The heat produced by nuclear fission heats the water, turning it into steam. There are two main methods for heating the water. The first is the boiling water reactor (BWR), in which the water that drives the turbine is directly exposed to the fuel rods to transfer heat. The second is the pressurized water reactor (PWR), in which water exposed to the reactor core heats the water that drives the turbine indirectly via a heat exchanger. This method offers higher safety than the BWR, which is why most nuclear power plants in South Korea have adopted this design. As large volumes of water turn into steam, the pressure increases, and this high-pressure steam is forced through pipes into the turbine, causing it to rotate. This process is nearly identical to other methods of power generation that use thermal energy, such as thermal power generation. However, the fundamentally different methods of heat generation—nuclear fission versus combustion—clearly distinguish nuclear power from thermal power.
Recently, concerns about the safety of nuclear power have grown, and fear and anxiety regarding nuclear power have spread, particularly following major accidents such as the Fukushima disaster. However, despite these risks, nuclear power is considered one of the most effective energy sources worldwide. If we gain a deeper understanding of nuclear power, accurately recognize its risks, and implement proper management and technological improvements, nuclear energy can remain a vital energy source in the future. Such understanding and management will play a crucial role in reducing fears surrounding nuclear power and maximizing the benefits of this technology.
