Table 6. Geological formations for deep underground disposal of nuclear waste (GDF).
Host Rock Rock Characteristics Radionuclide Transport Mechanisms Country Granite, gneiss
Fractured, groundwater flow
in open fractures.
Advection and diffusion
Canada, China, Finland,
Russia, Sweden, UK.
Salt bedded, dome
No open fractures, no ground-
water.
Diffusion
Germany, USA (WIPP)
Volcanic tuffs and lavas
Fractures and pores, unsatu-
rated.
Percolating water
USA (Yucca Mountain). UK
(Longlands Farm)
Clays and mudrocks consol-
idated, plastic
No open fractures, stagnant
pore water.
Diffusion
Belgium, China, Hungary,
France, Russia, Switzerland
Although the NBS may be the main and most reliable barrier of a GDF, the overall
safety is achieved through a sensible balance of these functions [2,3,22]. Any GDF pro-
vides protection and safety in a completely passive manner; moreover, it is noted that,
once it has been closed, both the facility and the wastes become part of the natural envi-
ronment [22].
5. Nuclear Waste Disposal Options 5.1. Graded Approach Increased levels of hazard, which for nuclear waste are reflected by the activity con-
tent and radionuclide half-lives, require increased measures to be taken to isolate the
waste from inadvertent human intrusion and to minimise the migration of activity back
to the biosphere. Increasing depth of disposal with increasing hazard level of the waste is
a key parameter used to achieve the necessary degree of safety (Figure 8).
