Currently, only nuclear power plants with fission reactors are in commercial operation. As fuel they use (almost always) uranium or plutonium, in which nuclear fission reactions take place. Thorium, which has some advantages, is being considered for the future.
Energy is released due to changes in the nucleus of the fuel atoms. The atomic nucleus is held together by extremely large forces – many times greater than the forces of chemical bonds that are released, for example, during classical combustion.
It follows that fissile fuel is literally overflowing with energy. Nuclear power plants typically use uranium fuel enriched to 5 percent uranium-235. As Wikipedia says, one pellet of uranium dioxide UO2 weighing 5 g will release as much energy as 850 kg of standard hard coal.
Uranium pellets are relatively safe and can be handled with gloves. After 1-2 years in the reactor, they become a life-threatening hard gamma ray emitter that can only be approached within a few meters, and that must be deep underwater.
From the reactor to the pool
Therefore, after removal from the reactor, the spent nuclear fuel is stored in the Spent Fuel Pool, where it is usually isolated from the surroundings by 12 meters of water and gradually cooled. After the radioactivity has decreased, the spent fuel is moved to intermediate storage – either wet (again, a pool) or dry, in which the storage containers are in the air.
Spent fuel pools at the Fukushima and Caorso power plants
From intermediate storage, the fuel should go to deep storage or reprocessing. But both are accompanied by considerable complications. It is necessary to build underground storage facilities, which is very problematic in populated areas – practically no one cares about a storage facility in their vicinity. Repository construction is expensive, permanently stored fuel will be radioactive for thousands of years and pose a risk throughout that time.
No wonder actually there is no permanent underground spent fuel repository in operation yet. The Onkalo repository in Finland should become the first in the foreseeable future. Some countries used to dump nuclear waste into the ocean in steel drums. According to the International Atomic Energy Agency, it is about 100,000 tons of nuclear waste on the seabed.
Fuel from waste? We have the technology
At the same time, there are a number of technologies in various stages of development that can be used to recycle used fuel. Whether for reuse in nuclear power plants or for other purposes, for example for radioisotope generators of space probes. The problem is, however, that due to the decline in nuclear energy, there may not be enough fuel for the economically acceptable operation of the already quite expensive recycling. Extracting and preparing new fuel is significantly cheaper than recycling the used one.
The handling of nuclear waste during its reprocessing is not only significantly more expensive, but also more complicated than during normal reactor operation. The fundamental problem lies in the fact that the processing of spent nuclear fuel actually originally served to obtain plutonium for the production of nuclear weapons. Therefore, nuclear fuel recycling has a long history of regulation, restrictions, bans and very careful controls.
For example, in the USA, spent nuclear fuel was first processed for a long time. President Jimmy Carter then banned commercial fuel recycling in 1977, primarily due to concerns about nuclear proliferation. In 1981, the ban was lifted by Ronald Reagan. The George W. Bush administration had big plans for the commercial processing of nuclear fuel, Barack Obama backed out again. The future remains open in this direction.
Source: Wikipedia (Spent nuclear fuel)
2023-07-05 16:46:17
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