Nuclear engineering is the field of engineering that deals with the science and application of nuclear and radiation processes. That covers a lot of ground: designing reactors that generate electricity, developing medical treatments that target cancer at the cellular level, building propulsion systems for deep space travel, and ensuring radioactive materials are handled safely. Nuclear power currently supplies about 9% of the world’s electricity, but the discipline’s reach extends well beyond the power grid.
The Science Behind It
At its core, nuclear engineering is built on the physics of atomic nuclei. When heavy atoms like uranium split apart (fission) or light atoms like hydrogen combine (fusion), they release enormous amounts of energy from a tiny amount of fuel. Nuclear engineers study how to initiate, control, and sustain these reactions, then convert the released energy into something useful.
That requires pulling together several branches of science and math. Neutrons and gamma rays need to be tracked as they move through materials. The intense heat produced by nuclear reactions has to be managed through fluid flow and heat transfer systems. Materials behave differently when bombarded with radiation over time, becoming brittle or changing in ways that engineers must predict and account for. A working nuclear system is really a complex intersection of physics, chemistry, materials science, and mechanical engineering.
Power Generation: Current and Next-Generation Reactors
The most familiar application of nuclear engineering is electricity production. Most operating reactors today are light-water reactors, which use ordinary water both to slow down neutrons (making the chain reaction more efficient) and to carry heat away from the reactor core. That heat produces steam, which spins a turbine to generate electricity.
A major area of development is small modular reactors, or SMRs. These are compact reactor designs that can be factory-built and transported to a site, rather than constructed from scratch on location. Some use conventional water cooling, while others experiment with liquid metal, molten salt, or gas as coolants. The U.S. Department of Energy has invested heavily in SMR development, with light-water SMR designs currently under licensing review and expected to begin operating in the late 2020s to early 2030s. The appeal is flexibility: SMRs could serve remote communities, military bases, or industrial facilities that don’t need a full-scale power plant.
Medical Uses of Nuclear Technology
Nuclear engineering plays a direct role in modern medicine, particularly in cancer treatment and diagnostic imaging. Radioactive isotopes produced in reactors or particle accelerators are used to both find and fight disease. In diagnostic imaging, radioactive tracers are injected into the body and detected by scanners like PET machines, revealing how organs function or where tumors are growing.
On the treatment side, a technique called radiopharmaceutical therapy delivers radiation directly to cancer cells based on their biological characteristics rather than their location in the body. Some isotopes naturally concentrate in specific tissues. Radioactive iodine, for example, is absorbed by thyroid cells, making it effective against thyroid cancer. Radium-223 homes in on bone, treating bone metastases. More recently, engineered molecules carry radioactive payloads to cancer cells that display specific surface markers. One such therapy targets prostate cancer cells by binding to a protein on their surface, delivering radiation precisely where it’s needed while sparing healthy tissue. About 10 specific molecular targets are currently in clinical use or under investigation, covering cancers of the thyroid, blood, liver, prostate, and neuroendocrine system.
Space Exploration and Propulsion
Chemical rockets have taken humans to the Moon, but reaching Mars and the outer solar system efficiently will likely require nuclear propulsion. NASA’s Space Nuclear Propulsion program is developing two complementary systems. Nuclear thermal propulsion works by heating a propellant (typically hydrogen) using a fission reactor, then expelling it through a nozzle. This approach provides high thrust at roughly twice the fuel efficiency of chemical rockets, freeing up weight for cargo and supplies.
Nuclear electric propulsion takes a different path. A fission reactor generates electricity, which then ionizes a gas and accelerates it electromagnetically to produce thrust. The thrust is lower but extremely efficient over long durations, making it ideal for deep space missions. Both systems offer a critical advantage far from the Sun: they don’t depend on solar panels. A nuclear system can provide power for years with minimal refueling, enabling orbiters, landers, and sample return missions to destinations across the solar system that would be impractical with solar-dependent spacecraft. NASA selected several industry teams starting in 2021 to develop reactor and engine designs, with contract extensions continuing through 2025.
Industrial Testing and Quality Control
Nuclear engineering techniques are used across industries to inspect materials without damaging them. X-ray imaging, for instance, can reveal internal cracks or flaws in metal components, welds, and composite materials used in aerospace, defense, and power generation. Argonne National Laboratory has decades of experience developing these nondestructive evaluation methods, which include ultrasonic testing, thermal imaging, and electromagnetic sensing. These tools are used for in-service inspection of nuclear power plant components like piping, tubing, and pressure vessels, and they’re expected to play a growing role in evaluating parts for advanced reactor designs.
Safety, Shielding, and Waste
Radiation protection is a foundational concern in nuclear engineering. Different types of radiation require different barriers. Alpha particles, the least penetrating, are stopped by air. Beta particles require plastic shielding. Gamma rays and neutrons, which can pass through the human body, demand dense barriers of lead, concrete, or water. This is why spent nuclear fuel is stored underwater in pools or in thick concrete containers, and why medical X-ray patients wear lead blankets.
Containment follows a principle of keeping radioactive materials in the smallest possible space and preventing them from reaching the environment. Rooms that handle radioactive materials are maintained at lower air pressure than surrounding areas, so any air leak flows inward rather than outward. In the United States, the Nuclear Regulatory Commission oversees the handling, storage, and security of nuclear materials at commercial facilities. Internationally, the International Atomic Energy Agency conducts inspections and verifies that nuclear materials are accounted for, selecting facilities from eligible lists for audits and material accounting checks.
Education and Training
A nuclear engineering degree is math-intensive. At Purdue University, a typical undergraduate curriculum begins with three semesters of calculus, followed by courses in differential equations and linear algebra. The science foundation includes general chemistry, classical mechanics, and electricity and optics. From there, students move into thermodynamics, fluid mechanics, and structural mechanics before reaching the specialized nuclear coursework.
The nuclear-specific courses cover fission, fusion, and radioactivity fundamentals, then progress into how radiation interacts with matter, how neutrons diffuse through reactor materials, and the thermal and hydraulic systems that keep reactors operating safely. Students learn to calculate critical reactor sizes, multiplication constants (how self-sustaining a chain reaction is), and neutron behavior as particles slow down and get absorbed. It’s a curriculum that demands comfort with abstract mathematics applied to physical systems.
Career Outlook and Salary
Nuclear engineers earned a median salary of $127,520 per year as of May 2024, according to the Bureau of Labor Statistics. Employment in the field is projected to decline by about 1% from 2024 to 2034, reflecting a relatively flat traditional job market. That said, the median figure puts nuclear engineering among the higher-paying engineering specialties. Job opportunities exist at power utilities, national laboratories, the military, regulatory agencies, medical device companies, and the growing number of startups working on advanced reactor designs and space propulsion systems.