Deep Borehole Disposal
Hanford Site (Hanford) and untreated calcine HLW stored at Idaho National Laboratory (MacKinnon 2015, p. 7). DBD has several potential advantages over mined repositories. For example, at the planned depth of 3-5 km, “[u]nder ideal conditions, the transport of radionuclides away from HLW and SNF …would be limited by low water content, low porosity, and low permeability of crystalline basement rock” (Winterle et al. 2011, p. 1-3). In addition, the immense pressure of the overlying rock layers would contribute to “sealing” transport pathways. Along with these decreased radioactivity exposure risks, DBD could also increase security, offer more options for geologically suitable sites, and reduce the surface-level footprint for disposal compared to putting these materials in a repository. Since there would be significantly more geologically suitable sites across the U.S., DBD sites could be placed at, or near, the nuclear power plant sites where SNF is currently located. This would greatly reduce the need for transportation and, therefore, the associated risks of moving the waste from its current locations. Even four or five regional DBD sites would greatly reduce the transportation burden. With that being said, there are also several uncertainties and disadvantages to the DBD concept. For example, the BRC noted that DBD brings with it “the difficulty and cost of retrieving waste (if retrievability is desired) after a borehole is sealed, relatively high costs per volume of waste capacity, and constraints on the form or packaging of the waste to be emplaced” (BRC 2012, p. 30). Uncertainties about how boreholes would affect groundwater movement, where, and how much steel lining would be required, and long-term monitoring require much further examination, research, and development. Consideration and research into the DBD concept went into overdrive in the early 2010s, when the Obama Administration effectively ended the licensing process of a mined deep-geologic repository at Yucca Mountain in Nevada. The 15-member BRC was formed to determine paths forward for the nation’s radioactive waste. One of the BRC’s eight key recommendations was for there to be “[p]rompt efforts to develop one or more geologic disposal facilities” (BRC 2012, p. vii). Furthermore, the BRC recommended that the Environmental Protection Agency and the NRC “should also develop a new regulatory framework and standards for deep borehole disposal facilities” (BRC 2012, p. 95). This recommendation is particularly important because the NWPA, as amended, limits any possible HLW and SNF disposal to a mined geologic repository at Yucca Mountain. Additionally, “Regulations at 10 CFR [Code of Federal Regulations] Part 63, which are specific to geologic disposal at Yucca Mountain, also cannot be applied to DBD because they require a repository design that permits the option of retrieval for up to 50 years after waste emplacement is initiated” (Winterle et al. 2011, p. 1-4). In January 2013, DOE released a report called the “Strategy for the Management and Disposal of Used Nuclear Fuel and High-Level Radioactive Waste” that served as the Obama Administration’s response to, and consideration of, the recommendations of the BRC. This report stated, “In FY 2013, the Department is undertaking
Deep borehole disposal (DBD) is an alternative disposal concept for HLW and SNF that involves placing waste in a narrow hole 4,000 — 5,000 m below the ground in crystalline basement rock and backfilling the upper 3,000 m of the hole with various substances. Compared to a mined repository, DBD has the potential to decrease radioactivity exposure risks, increase security, offer greater geographical options, and reduce the size of the surface footprint. On the other hand, DBD would have relatively high costs per unit of waste disposed and limited retrievability. The Deep Borehole Field Test (DBFT) was a DOE project that sought to research, develop, and demonstrate the DBD concept. Public mistrust of DOE and the suspicion that hosting the DBFT would lead to hosting HLW and SNF disposal killed the project before any drilling could take place. Recently, a private enterprise called Deep Isolation has sought to prove the feasibility (and profitability) of the DBD concept using modern oil-drilling techniques and already existing drill holes. DBD is an alternative disposal concept for HLW and SNF that involves drilling a roughly 45 cm diameter hole into crystalline basement rock, such as granite, to a depth of about 5,000 m (16,400 ft) and lining it with steel casing. SNF and other vitrified HLW would then be emplaced in waste canisters that would be lowered to the bottom 2,000 m of the borehole shaft. The upper 3,000 m of the shaft would then be backfilled with concrete, asphalt, crushed rock, and bentonite (Winterle et al. 2011, p. 3-3). This is not an entirely new concept. The U.S. National Academy of Sciences Committee onWaste Disposal considered the DBD concept all the way back in 1957. Drilling technology at the time prevented the committee from advocating for this concept because of clogging concerns and the liquid state of the waste itself. For the rest of the 20th Century, a conventionally mined geologic repository, like the proposed Yucca Mountain site, occupied the majority of scientific research in America (ibid., p. 1-3). However, technological developments, DOE projects, and political directives since 2010 necessitate the addition of a DBD article in this updated version of the “Transportation Institutional Issues Archive.” In recent decades, the DBD concept has received fluctuating levels of interest. Advancements in drilling technology by the petroleum industry allows boreholes to be dug deeper, wider, and much more easily. Additionally, processes like vitrification have led to more stable, solid forms of radioactive waste that could withstand the long emplacement journey. Some of the most suitable waste streams for this type of disposal are DOE-managed small waste forms like cesium and strontium capsules currently stored at DOE’s
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