TECHNICAL | DEEP DISPOSAL
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 flow would occur out of the repository rock because of the extremely low permeability. Thus, the use of the deep horizontal wellbore in these very tight rock zones is best suited for safe waste disposal.
BETTER LATE THAN NEVER There are still many who are skeptical of the deep horizontal wellbore approach. While it is true that this horizontal wellbore system has not been done before, there has never been a DGR implemented on the planet either. However, there are several hundred thousand successful horizontal wellbores in operation around the world today. We should be asking why billions have been unquestionably and unsuccessfully wasted on continued DGR efforts for decades, and why we have not yet moved on to a better solution.
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
46 | July 2023
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