How to Manage Nuclear Waste

Key Takeaways

Nuclear waste is radioactive and dangerous for around 300,000 years, but it is relatively low in volume.
Regulators and power plant operators manage nuclear waste with extreme caution to ensure that it never presents health risks to the public.
Currently, in the United States, all nuclear waste in the form of spent fuel is kept in temporary storage in dry casks or wet pools until a longer-term solution is agreed upon.
In the future, nuclear waste may be buried deep underground or recycled as fuel in advanced reactors, significantly reducing long-term risks.

In all countries with operating nuclear reactors, nuclear reactor spent fuel and waste are highly regulated to ensure safety.

The nuclear industry handles the waste safely through well documented waste management procedures and in compliance with the regulations of the countries they operate in. In the case of the United States, those regulators include the Nuclear Regulatory Commission (NRC), the Department of Energy (DOE), and the Environmental Protection Agency (EPA).

In this article, we’ll answer frequently asked questions about nuclear waste, including what it is, how it is handled, and what its future might look like.

What Is Nuclear Waste?

Nuclear waste is designated into one of two categories: high-level waste and low-level waste.

When you think of nuclear waste, you probably picture high-level waste. High-level waste is the spent fuel that has been used in a nuclear reactor to generate electricity that is no longer capable of sustaining the nuclear reaction. It is highly radioactive and can be dangerous for very long periods.

Low-level waste is significantly less radioactive and less dangerous but is still stored in specially designed, dedicated facilities. An example of low-level waste would be the protective outerwear worn by a worker in a nuclear power plant.

How is Nuclear Reactor Waste Produced?

To comprehend what’s in high-level waste, we have to first understand the reaction that takes place inside a nuclear reactor.

Every nuclear reactor on Earth today uses a neutron chain reaction to split heavy isotopes into fragments, releasing large amounts of energy in a process called fission.

Nuclear fuel contains small concentrations of fissile isotopes — that is, isotopes that can undergo fission — the rest are more stable isotopes.

For example, most nuclear fuel contains 3-5% uranium-235, a fissile isotope, and 95-97% uranium-238, a more stable isotope. For comparison, natural uranium in the Earth’s crust contains 0.7% uranium-235 and over 99% uranium-238.

The uranium-235 concentration is increased in a process called enrichment before it is fabricated into fuel and placed in the reactor.

What’s In Nuclear Waste?

Inside the nuclear reactor, a huge number of neutrons are colliding with the fuel every moment. Neutron collisions with fissile and non-fissile isotopes produce two types of radioactive materials in high-level waste:

Fission products

Neutron collisions with uranium-235 split it and sustain the fission reaction by producing more neutrons. When uranium-235 is split, it divides into fission products.
These fragments of the uranium nucleus are unbalanced in their proton and neutron composition, making them highly radioactive.
Most fission products have short decay times, becoming stable, non-radioactive isotopes within a range of seconds to a few years.
A handful of fission products, like cesium-137 or strontium-90, have longer half-lives on the scale of years. Very few, like iodine-129, are radioactive for millions of years.

Transuranic elements

Neutron collisions with uranium-238, the more stable component of the fuel, can lead to neutron capture. The uranium-238 becomes uranium-239, which then decays to neptunium-239 and plutonium-239.
Additional neutron captures can produce even heavier isotopes, including plutonium-242, americium-241, curium-243, and many more.
These elements heavier than uranium — called transuranic elements — are considered the most radiotoxic component of nuclear waste, though this is not necessarily the best way to assess them.
Several transuranic isotopes will remain highly radioactive for hundreds of thousands or even millions of years. This makes it imperative to manage them properly.

How much nuclear waste is there?

Fortunately, there is not as much high-level waste as most people would suspect. The U.S. only generates about 2,000 metric tons of high-level waste per year.

If we gathered all the high-level waste that nuclear power has ever produced in the U.S. over 60 years of operation — about 90,000 metric tons — it would fit on a football field and rise about 10 yards high.

Though significant, this relatively low volume of waste makes disposal much easier.

How Dangerous Is Nuclear Waste?

High-level waste is dangerous because it remains highly radioactive for long periods of time. This makes isolation and safe storage essential.

The Danger of Radioactivity

Radioactivity’s danger depends significantly on its amount. Low amounts of radioactivity present no health risk, while high amounts of radiation pose significant risks. The amount of radiation that a person receives is called a dose.

The Earth is a radioactive planet, with very small amounts of radioactive materials like uranium in its crust. Every year, the average person receives a small dose of radioactivity from the environment.

Radiation is emitted in large quantities by the Sun all the time. It lights the Earth, as visible light is electromagnetic radiation we’ve evolved to see. The ultraviolet radiation emitted by the Sun can cause damage to the human body if exposed for too long. Sun burns — or radiation burns as they could be called with equal accuracy — are one of the most common ways that people will experience harm from radiation.

Even eating a banana, which contains trace amounts of radioactive potassium-40, provides a larger dose than living within 50 miles of a nuclear power plant for a year. Of course, both are harmless.

Medical procedures such as CAT scans and x-rays give humans a larger, modest dose of radioactivity, but still present virtually no health risk.

The amount of radioactivity released by high-level waste, on the other hand, is very large. Because of this, it is imperative that the used fuel is handled safely and isolated so that humans do not receive potentially lethal doses from it.

How Long Does It Take Nuclear Waste to Decay to A Safe Level?

Radioactivity decreases over time. Different isotopes take different amounts of time before decaying to stability, defined by a parameter called their half-life, which is the time required for half of a substance to decay.

The components of high-level waste with some of the longest half-lives include plutonium-242 (with a 375,000-year half-life), plutonium-239 (24,000 years), and americium-243 (7,370 years). These isotopes may present long durations of radioactivity, but importantly, they are not very mobile in the environment.

In a repository setting, the ability for a material to move into and through groundwater pathways is important when considering how that material could impact the environment. While the transuranic materials have long half-lives, they have very low mobility, and so do not dominate risk assessments for repositories, regardless of their radioactivity.

Nuclear waste will decay seemingly indefinitely. If left untouched, the radioactivity levels of spent fuel decay to the level of natural uranium after about 300,000 years. This might be considered a safe level since it is equal to the radioactivity of materials untouched by humans, enrichment, and nuclear reactors.

How Is Nuclear Waste Disposed Of?

An ideal nuclear waste storage solution would keep it safely isolated for at least 300,000 years. This presents a number of challenges. Primarily, humans have not engineered anything to survive this timescale in all of our species’ history. Recorded history only goes back on the order of tens of thousands of years. Our current best guess at the age of humanity only puts us at 200,000 years old, so engineering something to outlast us is certainly a challenge.

For now, waste management solutions involve placing waste in two levels of storage: temporary and permanent.

Temporary Storage

Currently, high-level waste is held in temporary storage. There are two primary solutions for this level of storage:

Cooling Ponds/Spent Fuel Pools

The used nuclear fuel is most radioactive when it is immediately removed from the reactor since many short-lived fission products are present.
These generate large amounts of heat and radiation.
The used fuel assemblies are moved out of the reactor into a cooling pond on-site at the nuclear power plant. These are sometimes called spent fuel pools.
They are stored underwater for around five years, after which the waste is significantly less radioactive and thermally hot, making it easier to handle.

Dry Casks

The sufficiently cooled nuclear waste can be transferred into large dry casks, made of thick concrete surrounding a metal canister.
Dry casks are certified by the U.S. NRC and other regulatory bodies, which ensure public safety as their top priority.
The casks are designed to be incredibly strong. Repeated tests have shown they do not release radioactive material even after extreme events like airplane crashes and missile impacts.
Though extremely durable, dry casks are solely meant for temporary storage, and if needed, they are safe enough to be moved off-site.
They passively cool high-level waste and do not release any radioactivity.
Though they are a short-term solution, it is worth noting that waste stored in dry casks presents virtually no risk to human or environmental health.

Permanent Storage

Currently, there are no operating permanent storage facilities for high-level waste produced in nuclear reactors. However, regulators and scientists have ideas as to how nuclear waste could be safely stored for millions of years.

Deep Geologic Disposal

The favored permanent storage method today is deep geologic disposal; in other words, burying the waste deep underground.
Repositories are at least 1,000 feet deep — far below the water table — and geologically stable environments are selected that would prevent radioactive material from spreading in the unlikely event of leakage.
The U.S. already uses a deep geologic repository, called the Waste Isolation Pilot Plant (WIPP), located in Carlsbad, New Mexico. This facility safely stores thousands of tons of high-level transuranic waste — however, all the waste stored at WIPP was made from weapons production, not nuclear power.
Finland has built the first repository for civilian spent nuclear fuel that is expected to start accepting waste in 2025.

Who Is In Charge of Nuclear Waste?

In the U.S., nuclear waste is regulated by the NRC. The NRC ensures safety for the nuclear industry, not just for waste disposal, but also for things like reactor design, licensing, transportation of nuclear materials, and inspections. The NRC is committed to being one of the most transparent agencies in the U.S. government, and it always keeps the safety of the public as its top priority.

The management of spent nuclear fuel, and the eventual disposal of it, is the domain of the Department of Energy (DOE) in the United States. Nuclear power plant operators have contracts with the DOE where the DOE will collect and dispose of the spent fuel after a certain amount of time. As the U.S. does not currently have a functioning repository, this function of the DOE has not been fulfilled.

The responsibilities for the regulation and management of spent fuel and radioactive waste have similar structures in most countries. While the Canadian Nuclear Safety Commission regulates the technologies in Canada, the Nuclear Waste Management Organization is responsible for designing and implementing their disposal solution. Andra in France and Svensk Kärnbränslehantering AB (SKB) in Sweden share similar roles.

What Is the Future of Nuclear Waste?

Besides storing used nuclear fuel for hundreds of thousands of years, there are alternative methods that can make it safer, sooner:

Reprocessing

A large component of used nuclear fuel is plutonium. Plutonium-239 and plutonium-241, like uranium-235, are fissile isotopes that can be used as fuel in nuclear reactors.
In France, reprocessing facilities chemically separate the plutonium from the used nuclear fuel.
The plutonium is then blended with fresh uranium and fabricated into mixed oxide (MOX) fuel, which can then be used as fuel in nuclear reactors where the plutonium is fissioned and consumed, converting it into shorter-lived fission products.
France has effectively found a way to recycle plutonium from its nuclear waste, reinserting it into the nuclear fuel cycle to significantly reduce waste timelines while generating additional electricity.
Reprocessing is not currently used in the U.S., since it is expensive and could be a proliferation risk by isolating plutonium isotopes.

Waste Burning

Nuclear scientists and engineers are currently working to design a new generation of nuclear reactor technologies, including a waste-burning fast reactor.
A waste-burning reactor uses higher energy neutrons than most operating reactors.
With these high-energy neutrons, almost all transuranic isotopes can be fissioned and used as fuel.
This means that even the long-lived transuranic components of high-level waste could be eliminated, potentially reducing decay timelines to under 500 years — a much more manageable timescale — while producing additional power.
While France has managed to recycle the plutonium from its nuclear waste, waste-burning reactors would allow virtually all spent nuclear fuel to be recycled as new fuels.

This article is one of many developed by EPRI’s Advanced Nuclear Technology program. Stay up-to-date on the newest nuclear technologies by becoming a member today.