Nuclear waste and nuclear waste management around the world

Many countries that use nuclear energy have disposal facilities for low- and intermediate-level waste, whereas no countries have been able to commence the disposal of high-level waste. Many countries that use nuclear energy, such as Finland, are running a long-term research and development programme aimed at the implementation of high-level nuclear waste disposal.

Low and intermediate-level waste maintenance

The low- and intermediate-level nuclear waste generated in nuclear power plants remains radioactive for so long that storing it to reduce its radioactivity to a safe level is not practical. Therefore, the waste is processed and packed for disposal.

The pre-processing of waste may comprise the collection, sorting, neutralisation or other adjustment of the chemical properties of the waste or the decontamination or initial characterisation of the waste (see categorisation). The volume of liquid waste can be reduced, i.e. by means of ion-exchange, mechanical filtering, evaporation, chemical precipitation or centrifugation. The volume of solid waste, on the other hand, can be reduced by means of incineration, compression, dissection or melting. In connection with pre-processing, some of the waste may be released from monitoring to be disposed of as normal waste, as long as it has been deemed to be sufficiently low-level during the initial characterisation.

In the final processing, the waste is turned into a stable form and packed for storage, transport and final disposal. Liquid and fine waste materials are usually turned into a more stable form by solidifying them in a waste package with a suitable solidifying agent, such as concrete (at the nuclear facility in Loviisa) or bitumen (at the nuclear facility in Olkiluoto). Solid wastes are packed into containers as they are or with concrete filling.

Intermediate- and low-level wastes have been disposed around the world since the 1950s. Nowadays, there are mainly two prevalent principal disposal solutions in use: a concrete bunker in the surface layers of the earth or caves in the bedrock approximately 50–100 metres deep. Despite their ostensible differences, the isolation of radioactive substances is largely based on the same factors in each solution:

• Sustainable waste packages
• The insulating capacity of and propitious chemical environment created by concrete structures
• The low flow rate of groundwater in the vicinity of the disposal facility
• The slow transport of radionuclides in the ground or bedrock surrounding the disposal facility

The key difference between these two solution models is that a disposal facility located in the surface layers of the earth must be monitored for a few hundred years after the facility has been closed. Whereas ensuring the safety of a disposal facility located in the bedrock does not require monitoring measures after the closure of the facility.

High-level waste maintenance options

The fuel used in nuclear power plants can be managed in two alternative ways: it can be recycled to recover uranium and plutonium (the reprocessing option) or the fuel can be used only once. Both alternatives produce high-level waste, which must be isolated from nature for a very long time.

The disposal of high-level wastes in facilities built deep in the bedrock is currently the only known feasible disposal solution. Such disposal solutions have been subject to intense research and development for the last 30 years.

One temporary solution is the monitored long-term storage of wastes. The wastes are then stored for an indefinite period of time in storage facilities above or near the surface in the hope that technological development will generate better methods for waste management. However, long-term storage will largely shift the responsibility for implementing the maintenance and disposal of nuclear waste to future generations, which goes against the grain of the principles of international recommendations. Furthermore, a long-term storage is more vulnerable to a crisis or an act of terrorism than a disposal facility located deep in the bedrock.

Another alternative method that has been suggested is to separate very long-term radioactive substances from wastes and disposing of them using nuclear transformation or transmutation. Then, the radioactive source material would be transformed to make it more stable or to shorten its lifespan using powerful neutron flow produced by spallation reactions generated by a fast reactor or a particle accelerator. In addition to new types of nuclear reactors, the transmutation technology requires advanced reprocessing based on nuclide separation. Even if there were significant investments made in the development of nuclear technology, technologies such as these are not expected to be widely adopted. Furthermore, transmutation would only enable the disposal of some of the long-term radioactive substances. The quantity of disposed waste could be reduced. However, this would not render the need to store nuclear waste deep in the bedrock null and void.