Management of Commercially Generated Radioactive Waste - U.S. ...

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6.1.5.5 Potential Impacts over the Long Term (Postemplacement)
Potential Events
Long-term impacts with the greatest potential significance are related to'glacial
phenomena that are not well understood. For example, ice dynamics and climatic variations
affecting glaciation might be altered by waste disposal activities. Regardless of whether
meltdown, anchored emplacement, or surface storage were used, potentially major modifica-
tions in the delicately balanced glacial environment could occur.
One of the major areas of uncertainty stems from our limited understanding of ice sheet
conditions. Little is known of the motion of the continental ice sheets except for surface
measurements made close to the coast (Gow et al. 1968). Three general types of flow have
been defined--sheet flow, stream flow, and ice-shelf movement (Mellor 1959). Each type of
flow appears to possess a characteristic velocity. It is also believed that ice sheets where
bottom melting conditions exist may move almost as a rigid block, by sliding over the bed-
rock. Where there is no water at the ice-bedrock interface, it is believed that the ice
sheet moves by shear displacement in a relative thin basal layer. The formation of large
bodies of water from the waste heat could affect the equilibrium of such ice sheets.
In addition, two potential problems concerning the movement of the waste are unique to an
ice sheet repository. First, the waste container would probably be crushed and breached once
it reached the ice/ground interface as a result of ice/ground interaction. Second, the waste
might be transported to the sea by ice movement.
Compared with other disposal schemes, the probability of human intrusion would be very
low because the disposal area would be located in the most remote and inaccessible part of
the world, presently with a low priority for exploration of natural resources or habitation.
The lack of human activity in these areas would markedly decrease the chance of humans dis-
turbing waste material emplaced in an ice sheet. Conversely, because of the remoteness of
these areas they are relatively unexplored. Therefore they could attract considerable future
resource exploration.
Potential Impacts
After the waste is emplaced and man's control is relinquished or lost, possible impacts
fall into two broad categories. One of these relates to the reappearance of the radioactive
waste in the environment, and the other involves the chance that the presence of waste would
trigger changes in the ice sheets that would have worldwide consequences. For options that
would place the waste within the ice or at the ice/ground interface, significant research
would be required to predict future ice movements, accumulation or depletion rates, subsur-
face water flow rates, frictional effects at the interface, and trigger mechanisms. A major
purpose of this research would be to compare the degree of sensitivity of the predicted
behavior to man's ability to forecast long-term situations such as global weather patterns,
stability of the ice sheets, and sea-level changes.