WASTE MANAGEMENT | DEEP DISPOSAL
V exception, geologists agree that these near surface rocks are fissured and fractured - it is a fact of nature. The presence of these fissures and fractures allows fluid migration to occur. Many recent studies have concluded that surface rainwater may reach these repository layers in less than 50 years, creating corrosion problems for the stored capsules. This has been technically confirmed by analysis in migrating surface rainwaters. For example, chlorine-36 is a chlorine radionuclide,
present in rainwater at certain stable and predictable concentrations. It can be used to ‘fingerprint’ water with respect to age. Chlorine-36 occurs in all rainwater trickling down to near surface mines and tunnels. The presence of this isotope in water in these near surface systems is a flashing red light. Elevated ratios of Chlorine-36 found in what is nominally called ‘modern water’ has been caused by the detonations associated with atomic bomb testing in the atmosphere in the 1950s. Those high ratios did not exist pre-1950s. It indicates that in the near surface HLW disposal systems, ‘modern water’ has reached downward into these disposal zones.
Exhaustive analysis of chlorine-36 levels, in the
interstitial waters surrounding and permeating the near-surface near layers of the earth, shows conclusively surface waters continue to migrate downward, reaching any stored HLW material. The inevitable chemical, physical, and electrolytic degradation of HLW materials stored in the repository shall occur, regardless of any subsequent artificial protective systems, such as titanium umbrella sheets. Safe disposal of high level waste must be done in very
deep formations to preclude the deleterious and disastrous effects of any possible downward fluid percolation over geologic time. No man-made protection within reach of water will be able to sustain its protection for the extraordinary period of time required for high level waste storage.
Supporters of near surface mining techniques indicate their solution to the water migration problem is the use of titanium ‘umbrellas,’ retroactively fitted to protect the capsules, and also the use of bentonite material as a repository ‘backfill’ which ‘swells’ to mitigate fluid flow in the capsule zone. It is difficult to see how these measures can maintain the required level of safety for a minimum of 10,000 years, much less than for the geological time scale needed for safe waste disposal. The better solution is to design and implement a deep
repository in a location where there is no chance of fluid flow into or out of the system. Such a system must be inside a massively impermeable rock zone, at great enough depths such that no downward migration of surface water can ever reach it. This is the key basis for the selection of the deep horizontal wellbore storage. In addition, we can also learn a lot from ongoing oilfield
fracking operations which have provided insight into the ability of rock to allow fluid migration. The ‘tight’ nature of the deep fracking zones mean they are initially non- productive. In order for fluid to enter into these zones, engineers must use ultra-high pressure pumps, with surface pressures up to 19,800 psi. Without these extremely high pressures, no fluid flows into the rock matrix. It can be inferred from the massive effort required that very little
Above: Germany’s Niedersachsen, Gorleben, a radioactive waste site in a former salt mine
Right:
Deep directional drilling is a standard technique in the oil and gas sector
42 | February 2023 |
www.neimagazine.com
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