Nuclear reactors produce electricity through a process called nuclear fission, using uranium as fuel to release an immense amount of energy in the form of heat. Ceramic pellets containing low-enriched uranium are stacked in a metal cladding and assembled into what we call fuel rods. These rods are inserted into a reactor to produce electricity, then removed and replaced when they are exhausted. But this waste is not “empty” in the traditional sense of the term. Nuclear fuel rods contain about 90% of their remaining potential energy. Even though much of the unused fuel remains on site, it cannot power a nuclear reactor without being reused.
In fact, spent materials still contain around 96% of the original uranium. During use, fissionable U-235 diminishes to less than 1%, meaning it is no longer viable for powering reactors. Meanwhile, unusable waste accounts for 3%, and the final 1% is plutonium produced in the reactor. The United States disposes of this waste, sometimes called nuclear waste, at more than 70 sites across 35 states. It is transported and disposed of safely, but if it were recycled it could still be useful. Every four to six years per reactor, the rods are replaced, generating more than 2,200 tonnes of waste per year. This is a lot, enough for us to say that nuclear energy is not 100% clean.
Why let it go to waste? One of the main reasons for this is that raw uranium ore is significantly cheaper to mine and process. Reprocessing is considered by many to be too expensive and risky. However, other countries are successful in recycling nuclear waste, such as at the Orano reprocessing plant in La Hague, France. Leftover uranium and plutonium are extracted and stored in liquid form until they can be solidified to make new fuel.
Reprocessing and recycling is not a simple or straightforward task
One of the reasons we dispose of and store waste, rather than reprocessing it, is that it is expensive and not really easy to do. The US government stopped reprocessing in the late 1970s for this reason and also stopped experimenting with reprocessed fuel. Another form of recycling offered by nuclear start-up Oklo relies on a process called “pyroprocessing,” which introduces waste into molten salt. From there, the usable fuel is separated and converted into gas. It’s expensive, dangerous, and could potentially create weapons-grade materials. These concerns have significantly reduced its proliferation, especially when uranium is affordable and readily available. A 2003 MIT study, updated in 2009, went so far as to recommend the use of fresh uranium for the next 50 years, explicitly calling for it to be discarded after use instead of reused.
Another problem is that the waste must be transported to a reprocessing facility, usually a longer distance than simple disposal, sometimes even internationally. Once processed, it should return to the reactor sites. Experts say the longer transit time leaves more room for accidents or theft. Proponents, like Oklo, argue that recycled combustible materials would not be useful for making weapons; scientists are not so sure. Ultimately, the consensus is that the associated risks, costs and time may not justify the effort.
In addition, the development of nuclear reactors has advanced significantly, and the next generation of nuclear power is poised to take a big step forward. This could lead to efficient reactors that produce less waste than their predecessors, although they would still leave waste behind, just in smaller quantities.
Reprocessing facilities exist and are currently in operation
There are plans to make recycled nuclear waste viable. Oklo is working on facilities to demonstrate new reactors capable of operating with reprocessed materials as fresh fuel. It should be noted that it is planned to use pyroprocessing to recover nuclear waste. Critics say the technology has been around for a long time and its viability is not supported by verifiable research.
The French upgrading facility is a strong point, and the Orano plants in La Hague and Melox have been in operation for more than 50 years and produce a recycled nuclear waste called MOX. Japan is working on a similar facility, although it has been delayed several times since its initial construction in 1993. Before that, Japan shipped its waste to France and the United Kingdom for reprocessing via Orano. MOX fuel still produces waste, which brings us back to the original problem: even after being recycled, the waste must be disposed of and stored safely somewhere. MOX fuel cannot be reprocessed or reused, it is actually spent. What do we do with this waste?
As nuclear technologies continue to experience innovations, this appears to be a growing problem. Theoretical nuclear batteries could change everything that potentially powers devices for decades. But the next question is: what will happen to the waste? Waste can always be a concern when it comes to nuclear solutions.
