At one point in time, it was considered that disposing high-level radioactive waste in the deep-ocean trenches at subduction zones would be a good place. But, according to recent renowned research studies, it is not a good idea at all. Subduction zones are prone to various environmental calamities that might alter the earlier expected suitable disposal conditions for high-level radioactive waste. A geologist, on the other hand, might reveal that subduction is not actually secure because at comparatively shallow levels, subducting plates begin to be chemically altered, discharging a slurry of winding minerals to erupt in huge mud volcanoes on the seabed.
The main concern with the disposal of high-level radioactive waste is its longevity. Its radioactivity exposes humans and other living organisms to danger, and so must be secluded from the biosphere until it decomposes to a safe activity level. Uncertainties about the future of disposal sites mean that maintenance of these disposal sites cannot be guaranteed.
The main reason why trenches at subduction zones are not a good place for disposal is that it is vastly affected by earthquakes. The majority of the continental volcanoes are located above the subduction zones or oceanic-continental convergence areas (National Academy of Sciences (U.S.). Committee on International Security and Arms Control, 1994). These regions are also very seismically vigorous, possibly ruling them out as a likely waste site. Whereas, like earthquakes, most destruction to a waste site is caused by direct hit, a close eruption or intrusion would have significant hydro-geological outcome. In addition, the existence of a heat source would cause hydrothermal flow, which would affect the waste site. Hydrothermal would warm the groundwater and alter its chemistry, both of which could augment the rate of decomposition of the engineered barricades and speed the discharge of radionuclide. In addition, hydrothermal flow normally leads to the adjustment of the rocks it passes through, probably altering mechanical and chemical characteristics of the rock surrounding the repository (Fabbro, 2010).
In conclusion, subduction zones are not the safest places to deposit high-level radioactive waste as earlier thought. This is because earthquakes that may alter the repository conditions normally hard hit these regions. Furthermore, erosion can occur in the zones that may reach the repository level.