Nuclear Energy Fundamentals: Fuel Cycle, Power, and Waste

Understanding Uranium and Nuclear Fuel

Natural uranium is composed of three isotopes: Uranium-238 (U-238), Uranium-235 (U-235), and Uranium-234 (U-234). While U-238 is fertile and can be converted to fissile material, U-235 is the primary fissionable isotope used for power generation. Natural uranium ore cannot be used directly as nuclear fuel because the concentration of U-235 is too low. Therefore, uranium needs to be enriched to achieve a U-235 concentration of more than 3%. To produce one kilogram of enriched uranium, approximately eight kilograms of natural uranium must be purified and refined.

How Nuclear Power Plants Operate

Nuclear power plants utilize uranium as their primary energy source, harnessing nuclear fission to generate electricity. Uranium is a finite energy source; at the current rate of consumption, existing reserves are estimated to last for several hundred years. The controlled fission of uranium nuclei takes place within the nuclear power reactor. Rods of fissionable fuel are interspersed with control rods made of a material that absorbs neutrons. By introducing or withdrawing these rods, neutrons are absorbed, thereby controlling the chain reaction. This allows for the regulation of nuclear fission to release energy at the desired rate.

Managing Radioactive Waste

Radioactive wastes are byproducts containing radioactive substances that are not intended for any further use. They are generated in nuclear power plants and other facilities that handle radioactive materials. These wastes must be stored in locations where their radioactivity poses no harm to people. Low- and medium-activity wastes are typically stored in underground facilities at shallow depths. High-activity wastes, which can remain hazardous for thousands of years, are stored in large, stable geological formations several hundred meters below the surface.

Challenges of Nuclear Energy

Many countries oppose the use of nuclear energy for several reasons:

• Risk of Accidents: The risk of accidents at nuclear plants, such as meltdowns, is a significant concern. Radiation released in such events can seriously affect all living beings for extended periods, even in distant areas.
• Waste Production: Radioactive waste produced in nuclear power plants requires long-term storage in special deposits. These wastes maintain a high level of radioactivity for a very long time, posing disposal challenges.
• Weapons Proliferation: There is a risk of using nuclear technology developed for energy purposes for weapons development, contributing to nuclear proliferation concerns.

Benefits of Nuclear Energy

Despite the challenges, there are compelling reasons for the continued use of nuclear energy:

• Clean Energy Source: Nuclear plants are considered clean energy sources. They do not emit nitrogen oxides or sulfur dioxide, thereby avoiding contributions to global warming or air pollution.
• Continuous Power Generation: They generate continuous power and often at lower operating costs compared to some other types of power plants.
• Energy Independence: Nuclear energy allows countries to reduce their dependence on fossil fuels like oil, enhancing energy security.
• High Safety Standards: With robust security measures and stringent regulations in place, the probability of a major accident is statistically low.

The Nuclear Fission Process

When a nucleus of Uranium-235 is struck by neutrons, the nucleus breaks into two or more smaller nuclei and releases two or three additional neutrons. These newly released neutrons then strike other uranium nuclei, causing them to fission in turn, thereby generating a chain reaction. The fission of a single uranium nucleus releases a large amount of energy. Other elements such as plutonium and thorium are also fissionable.