Nuclear waste tends to get much of the social attention when nuclear power is discussed. The management of this waste is safer than intuition tells us, but it is not entirely efficient. The vast majority of the energy contained in nuclear fuel is not used, which increases the volume of waste and lengthens the time it is dangerous. Fortunately, there are solutions to this problem, but they are not cheap.
Two problems: lack of fuel and excess waste.
All energy production has its advantages and disadvantages, and nuclear energy is no exception. The war in Ukraine has uncovered one of these problems, that nuclear is not a renewable source of energy. The nuclear fuel used in most plants, the isotope uranium-235 (U235), is limited and not all countries with nuclear plants have access to it.
Added to this is the problem of waste management. Although we have made great strides in managing this waste, taking care of it entails an added cost, to which we must add that the rejection it generates in the population makes its efficient management even more difficult. One more factor must be added: nuclear fuel still stores a lot of energy after being spent.
Energy waste.
Jess Gehin, laboratory director at the Idaho National Laboratory in United States, recently explained to CNBC that we only use 0.5% of the energy contained in U235 is used in the conventional reactors used today, light water reactors. Also, only 0.7% of the uranium found naturally on Earth is of this typethe rest corresponds to the isotope 238.
fast reactors.
There are ways to harness some of all this wasted energy, Gehin says. It also seems that the problem for its implementation is more economic than technological according to the expert. The key would be in the fast neutron reactors or fast reactors, so called because they do not limit the speed of these as do the conventional reactors used today.
According to the American, it would be possible to extract a substantially larger fraction of the energy from uranium by recycling the fuel with these reactors. “Fast neutron reactors can more efficiently convert uranium-238, which is predominantly what is found in spent fuel, to plutonium, so that it is fissile,” explains Gehin.
U238 is also more abundant in nature, which would facilitate the uranium enrichment process required to convert it into fissile material to fuel reactors. Taking advantage of these mechanisms would guarantee, according to the International Atomic Energy Agency (IAEA), being able to continue using nuclear energy for thousands of years. In addition, the agency continues, it would mean an improvement in the management of nuclear waste.
The origin: high demand and little fuel.
Los fast neutron reactors they were proposed in the first decades of the development of commercial nuclear power. At this time the supply of uranium was not guaranteed, so the energy efficiency of nuclear power plants was an issue that received important consideration.
This changed over the years as new uranium reserves were found, but also as hydrocarbons settled as a source of electricity production. Added to this less pressure for greater efficiency were the accidents at Three Mile Island and Chernobyl, severe blows to the social perception of this type of energy.
Types of fast reactors.
This long history, and the fact that several countries are interested in these developments, has left a diversity of types of fast reactors, especially those known as fast breeder reactors, so called because they carry out their work in two phases, with one phase using the fuel produced by the other.
Some of these types of fast reactors, in various stages of development according to the IAEAare sodium-cooled fast reactors, lead- and lead-bismuth-cooled fast reactors, molten salt fast reactors, and gas-cooled fast reactors. These “meet higher standards of safety, sustainability, economy, physical protection, and proliferation resistance.”
The technology is ready, the implementation is far away.
The main problem to implement these technologies on a commercial scale It’s economic. The increase in fuel and the existence of other non-nuclear options has kept these options at bay. This is still a paradox, since nuclear energy is already more expensive than other alternatives and increasing fuel efficiency should make it cheaper, not more expensive. This intuition would be true if the main costs of this energy were related to the purchase of fuel and the management of the fuel already used.
Fix one problem, mitigate another?
Implementing more efficient nuclear options can help keep this option in the mix even if access to fuel is limited, either due to the geopolitical situation or due to resource depletion. However, it does not seem that it will do more than mitigate the problem of nuclear waste.
Waste will continue to be produced in conventional power plants, and the current “stock” of waste, according to Gehin or the IAEA itself, is sufficient to provide energy for the next thousand years. In addition, they can work without resorting to the use of waste, feeding on low-enriched uranium such as HALEU (high-assay low-enriched uranium), uranium with a lower enrichment level (between 5 and 20% of U235, compared to 3-5% of conventional fuel than conventional fissile or enriched uranium.
This option may be cheaper than waste recycling, so in practice you may not end up realizing the recycling potential that these new technologies promise. The economy provides a double reason for skepticism in this regard.
Is this applicable in Spain?
Similar projects are not known in Spain. The Nuclear Safety Council (CSN) considers in its publications a linear cycle (as paradoxical as it sounds) of nuclear fuel. This does not prevent it from participating in the development of projects such as the Jules Horowitz European Experimental Reactor (JHR), together with other institutions such as the Center for Energy, Environmental and Technological Research (Ciemat). JHR will be an experimental, non-commercial reactor and will be located in south-eastern France.
Fusion and other alternatives.
We must not forget that we continue to advance (little by little) in fusion energy, which could also be a superior alternative to these options. Always on the horizon, it is estimated that this technology could arrive around the year 2060. That is why it is difficult to know if it will arrive before the lack of nuclear fuel sources could be a considerable problem.
Image | Idaho National Laboratory
