What Is Spent Nuclear Fuel?

Spent fuel, also known as spent fuel ^[1] , is a nuclear fuel that has been exposed to radiation and used. It is usually produced by nuclear reactors in nuclear power plants. Nuclear fuel undergoes a neutron bombardment in the reactor to cause a nuclear reaction, and is discharged from the reactor after a certain period of time. It contains a large amount of unused proliferative material 238U or 232Th, unburned and newly generated fissile material 239Pu, 235U or 233U, and thorium, plutonium, plutonium and other transuranium elements generated during the irradiation of nuclear fuel. There are also fission elements 90Sr, 137Cs, 99Tc and so on. It is radioactive, and if not properly handled, it will seriously affect the environment and the health of people who come into contact with them.

When nuclear fuel is used in the reactor, the fuel reactivity changes due to the consumption of fissile nuclides, the generation of fission products and heavy nuclides, and eventually the reactor can no longer maintain the criticality. Therefore, the use of nuclear fuel must be replaced to a certain extent. Fuel that is unloaded after reactor radiation is also referred to as spent fuel or irradiated fuel. Because spent nuclear fuel contains a large amount of

Substances that make up 3% of their mass are

Waste fuel rods may generate plutonium after reprocessing, so they are considered to be capable of making nuclear weapons

Because long-lived nuclear waste (including spent fuel) must be permanently isolated from humans and the environment. It is widely accepted that spent fuel, high-level radioactive waste for nuclear fuel reprocessing, and plutonium waste need to be stored in well-designed sites for tens of thousands to one million years to reduce their radioactive pollution to the environment. At the same time, it must be ensured that plutonium and highly enriched uranium are not used for military purposes. A basic consensus is that it is safer to store spent fuel in a storage location hundreds of meters underground than to pile it on the ground. Therefore, it is a feasible solution to store these waste materials in artificially constructed underground storages in stable geological structures. This is the final disposal method of waste fuel, and it is also called deep geological disposal.

The final disposal of waste fuel refers to the storage place of radioactive nuclear waste excavated in stable geological structures, which is generally below 300 meters underground. Many factors such as the shape of nuclear waste, its packaging, site sealing and seepage prevention, and geological conditions determine the success of the storage site. The basic requirement for deep geological disposal is to isolate nuclear waste from the environment for a long time, while requiring little or no maintenance. The time scale of deep geological disposal is large, usually from tens of thousands to one million years. In deep geological disposal, the nuclear waste contained in a container is somehow sealed and stored in a tunnel. The outermost protective mechanism is the geological structure itself (such as rock formations).