Journey's End: Exploring the Final Destinations of Nuclear Waste Disposal

Nuclear activities produce a variety of radioactive waste that may differ for the content of short- and long-lived radionuclides or the activity concentration. These features affect the choice of their final disposal.

Waste containing only radionuclides of very short half-lifes (VSLW), such as those coming from nuclear medicine or industrial applications, can be stored for decay over a limited period of up to a few years and subsequently cleared from regulatory control. In general, the management option of storage for decay is applied for waste containing radionuclides with half-lives of the order of 100 days or less.

Waste containing low levels of activity concentration and very limited concentrations of long-lived radionuclides (VLLW) generally does not need a high level of containment and isolation and, therefore, is suitable for disposal in surface landfill type facilities with limited regulatory control.

Waste containing short-lived radionuclides at higher levels of activity concentration and also long-lived radionuclides, but only at relatively low levels of activity concentration (LLW) requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near surface facilities.

Waste containing higher content of long lived radionuclides (ILW) requires a greater degree of containment and isolation that can be assured by disposal at greater depths, of the order of tens of metres to a few hundred metres. Such ILW needs no provision, or only limited provision, for heat dissipation during its storage and disposal.

Waste containing both short- and long-lived radionuclides at high levels of activity concentration (HLW) generates significant quantities of heat by the radioactive decay process that need to be considered in the design of a disposal facility. Spent nuclear fuel belongs to the category of HLW and it is initially stored in spent fuel pools at the reactor site, which are deep water tanks designed to store used fuel rods from nuclear reactors for at least five years. The fuel rods are stored underwater to shield the radiation emitted and remove the decay heat. Such pools are designed to prevent leaks and are constantly monitored.

After cooling, high level waste can then be stored in dry cask storage, where waste is placed into steel and concrete containers designed to withstand extreme temperatures and pressure. These containers are stored in secure above-ground facilities and monitored to ensure safety.

Due to their content of long lived radionuclides, disposal in deep, stable geological formations usually several hundred metres or more below the surface, is the generally recognized option for disposal of HLW. These facilities will provide safe and secure long-term solutions for nuclear waste disposal.