U-235, U-238 and Uranium: A Strategic Element Linked to Energy, Health, Technology and National Security

Adrian Mercer

Uranium is not merely a heavy metal found naturally on Earth. It is a highly strategic element connected to modern nuclear energy, radiation science, medicine, geological research, industry, national security and global power competition. When uranium is discussed, U-235 and U-238 are mentioned most frequently. Both are isotopes of uranium, but their nuclear behavior, roles in energy production, radiation characteristics and strategic significance differ considerably.

The chemical symbol for uranium is U, and its atomic number is 92. This means that the nucleus of every uranium atom contains 92 protons. However, not all uranium atoms contain the same number of neutrons. This difference creates different isotopes of uranium. Natural uranium consists mainly of U-238, U-235 and a very small amount of U-234. About 99.27 percent of natural uranium is U-238, while around 0.72 percent is U-235. U-234 exists only in trace amounts.

Why Is U-235 Special?

U-235 is one of the most important isotopes in nuclear energy science. Its key characteristic is that it can undergo fission after absorbing relatively low-energy neutrons. During fission, its atomic nucleus splits into two smaller nuclei, releasing a large amount of energy along with additional neutrons. These neutrons can then trigger reactions in other U-235 atoms, making a nuclear chain reaction possible.

Because of this property, U-235 is used as fuel in nuclear power plants. Inside a nuclear reactor, this process is conducted under highly controlled conditions. The heat generated is used to heat water, produce steam and drive turbines to generate electricity. Nuclear fuel has an extremely high energy density compared with fossil fuels, allowing a very large amount of energy to be produced from a relatively small quantity of material.

However, because natural uranium contains only a small proportion of U-235, its concentration must be increased for use in certain types of nuclear reactors. This process is called enrichment. It is important to distinguish between enriched uranium used for civilian energy production and highly enriched material that could have military applications. The technological and regulatory gap between the two is substantial. This is why uranium enrichment remains one of the most sensitive areas of international nuclear monitoring.

Why Is U-238 Even More Important?

U-238 makes up almost all naturally occurring uranium. It does not undergo fission as readily as U-235 under ordinary conditions, but that does not make it less important. Its most significant characteristic is that it is a fertile material. After absorbing neutrons, it can undergo a sequence of nuclear transformations that eventually produces plutonium-239, which is fissile.

For this reason, U-238 plays an important role in the nuclear fuel cycle, some advanced reactor systems and strategic nuclear technologies. Because of its high density, depleted uranium has also been used in certain industrial and specialized military applications. Such use, however, has generated controversy because of concerns not only about radiation but also about heavy-metal toxicity, exposure to uranium dust and environmental contamination.

The Basic Difference Between U-235 and U-238

Both are uranium, but they differ in the number of neutrons inside their nuclei. U-235 contains 92 protons and 143 neutrons, while U-238 contains 92 protons and 146 neutrons. This difference of just three neutrons creates a major change in their nuclear behavior.

The half-life of U-235 is about 700 million years, while that of U-238 is about 4.47 billion years. Half-life refers to the average time required for half of the atoms in a radioactive substance to decay. Because these half-lives are so long, natural uranium still exists in the Earth’s crust billions of years after the planet was formed.

How Dangerous Is Uranium Radiation?

Uranium primarily emits alpha radiation. Alpha particles have weak penetrating power and are largely blocked by human skin under normal conditions. Therefore, briefly touching an ordinary uranium-bearing rock from the outside does not automatically create an extreme radiation hazard.

The situation changes if uranium dust, soluble compounds or particles enter the body through breathing, contaminated water or food. Once inside the body, alpha radiation can damage nearby tissues. In addition, uranium itself is a heavy metal, and its chemical toxicity can pose a particular risk to the kidneys.

For this reason, uranium-related health risks cannot be assessed from the perspective of radiation alone. Chemical toxicity, exposure to dust, water contamination, environmental conditions around mining areas and other radioactive elements produced through the uranium decay chain must also be evaluated.

The Connection with Radon

As U-238 naturally decays, it produces a series of radioactive elements, eventually including radon gas. Radon is a colorless, odorless and tasteless radioactive gas. It can accumulate particularly in enclosed buildings, underground structures, mines and areas with uranium-bearing geology.

Long-term exposure to radon is considered an important environmental risk associated with lung cancer. Therefore, health assessments in areas with potential uranium deposits should monitor not only uranium concentrations but also radon levels, groundwater contamination and indicators of local public health.

Where Is Uranium Found?

Uranium usually does not appear on the surface as a separate, shiny metal. It is distributed in varying concentrations within different rocks and minerals. Higher levels can occur in granite, pegmatite, sandstone and certain other geological formations.

Finding evidence of uranium is not the same as proving the existence of an economically viable uranium mine. A radioactive anomaly does not automatically mean that a large uranium deposit exists. To confirm a deposit scientifically, extensive geological mapping, drilling, sample testing, assessment of ore grade and quantity, depth, processing costs, environmental impact and economic feasibility are required.

For this reason, finding U-235 or U-238 in a sample from a particular area is not unusual in itself. Wherever natural uranium exists, these isotopes are generally present in predictable proportions. The real question is not simply whether they are present, but their concentration, geological continuity and whether the deposit is economically recoverable.

How Is Uranium Identified?

Geologists initially use geological surveys, radiation measurements, gamma spectrometry and sample analysis. Samples are then examined in laboratories to determine their chemical and isotopic composition.

A radioactive anomaly is only an indicator in uranium exploration. A final conclusion requires detailed scientific confirmation. This is why unusually high radiation detected by a basic instrument should not immediately be declared evidence of a uranium mine.

Nuclear Energy and the Climate Question

Nuclear power generation does not produce large direct carbon dioxide emissions in the same way as coal- or petroleum-based energy production. For this reason, many countries are again giving greater importance to nuclear power as a low-carbon energy option in the debate over climate change mitigation.

However, the challenges are also serious. Nuclear power plants are expensive to build, their safety systems are highly complex, radioactive waste must be stored securely for long periods, and although the probability of a major accident may be low, the consequences can be severe. Chernobyl and Fukushima demonstrated how critical institutional capacity is to nuclear safety.

The Role of Uranium in Medicine

Uranium itself is not a radioisotope widely used in routine medical treatment. However, nuclear technologies developed around uranium have provided an important foundation for modern nuclear medicine, the production of medical radioisotopes, cancer treatment and diagnostic technologies.

Many radioisotopes used in hospitals are produced in research reactors or through other nuclear technologies. Therefore, the contribution of uranium and nuclear science to healthcare extends beyond direct pharmaceutical use and into the wider infrastructure of modern medicine.

Uranium Mining and Public Health

The main health risks associated with uranium mining can arise from dust, radon, heavy metals, contaminated groundwater and mine waste affecting workers and nearby communities. Modern mining operations require radiation monitoring, personal protective equipment, air-quality surveillance, safe waste management and water testing.

Without adequate regulation, radioactive materials remaining in mine waste can affect the environment for decades. Uranium mining is therefore not solely an issue for the mining authorities. It is a multidisciplinary matter involving health, the environment, water resources, occupational safety, local communities and national security.

What It Means for Nepal

Studies concerning radioactive anomalies and uranium mineralization have been conducted in Nepal at different times. However, it is not scientifically valid to conclude that a large commercial uranium deposit exists simply because radioactive signals have been detected in a particular area.

For Nepal, the first requirement is not extraction but knowledge. The country needs a clear system to determine what minerals exist in which areas, what level of scientific evidence supports those findings, who controls geological data, who authorizes samples to be taken abroad, where test reports are stored and how national interests are protected.

When foreign companies, universities or government institutions are permitted to conduct research on a strategic mineral such as uranium, clear conditions are necessary regarding ownership of geological data, samples, intellectual property and laboratory results. Otherwise, valuable data could be lost before the natural resource itself is ever developed.

Balancing Security and Science

It is scientifically incorrect to assume that the word “uranium” automatically means “nuclear weapons.” The natural presence of uranium, energy production, scientific research and military applications are separate matters. At the same time, because uranium is strategically sensitive, weak regulation is also unacceptable.

Uranium policy should rest on three foundations. First, scientific evidence. Second, health and environmental safety. Third, national ownership and transparency.

Nepal should treat uranium neither as an object of fear nor as a tool of political publicity. It should be understood as a scientific and strategic resource. If a deposit is eventually proven, questions of health, environment, technology, security and sovereign ownership should come before its economic value.

Understanding the difference between U-235 and U-238 is only the first step toward understanding uranium. Its real significance begins where geology, nuclear physics, energy, medicine, the environment and national security converge.

Uranium itself is not the danger. The real dangers are poor knowledge, weak regulation and irresponsible use. With strong science, strict safety standards and a transparent state system, the same element can become an important source of energy, research and technological development.