WorldWide Drilling Resource

11 NOVEMBER 2022 WorldWide Drilling Resource® Deep Isolation Uses HDD for Possible Nuclear Waste Solution Adapted from Information by Deep Isolation Around 540,000 tons of spent radioactive fuel is temporarily stored in pools and dry casks aboveground all over the world. None of this fuel has ever been placed in a permanent repository. Deep Isolation, a company headquartered in Berkeley, California, decided to consider alternative options to address a global issue which is growing in scope and scale. Elizabeth Muller and her father Richard A. Muller founded Deep Isolation by combining innovations of Silicon Valley with nuclear and scientific expertise prioritizing environmental protection and community partnerships. They were inspired to apply horizontal directional drilling (HDD) to aid nuclear waste management. The company plans to place nuclear waste in corrosion-resistant canisters (typically 9 to 13 inches in diameter and 14 feet long) deep into horizontal boreholes, in rock which has been stable for tens to hundreds of millions of years. The borehole begins with a vertical access section going down from a few thousand feet to a few miles, depending on the geology. It then gradually curves, over a distance of typically 1000 feet. The horizontal part is referred to as the disposal section. The horizontal section allows waste canisters to be placed end-to-end with some spacing between them. This results in a lower thermal heat load than a mined repository or vertical borehole and horizontal placement provides more support for the canisters. It also allows for less disturbed rock directly over the waste. An 18inch borehole will have approximately nine inches of disturbed rock around the hole, but the remaining thousands of feet of rock between the waste and surface will remain undisturbed. The horizontal disposal section could be up to two miles long. With sections this long, it would take 300 boreholes to dispose of 80,000 tons of fuel. The company said disposal sites could be located around the country at or near waste generation sites, or located at a regional or central repository location. Virtually all committees of scientists convened to study the disposition of nuclear waste have concluded deep geologic burial (1000 feet or more) is the best disposal solution. About one third of U.S. citizens currently live within 50 miles of an aboveground nuclear waste storage facility. According to Deep Isolation, their goal is to make this waste more secure by placing it underground. The key advantages of their method are the depth of burial and the fact waste is stored in a suitable geologic formation far below the water table, in rock saturated with brine that has no commercial value and has been virtually stagnant for millions of years. In addition, small-diameter boreholes require less disturbance of rock. Highly developed HDD technology can be implemented at a relatively low cost. It can be modular and minimize transportation concerns if disposal takes place at or near generation sites. Cost and safety are also improved because no person needs to go underground during construction. This solution was successfully tested at a commercial drilling facility where a prototype canister was lowered 2200 feet into an existing borehole using a wireline cable, then pushed over 400 feet with an underground tractor into a long horizontal storage section. The canister was released and the tractor and cable withdrawn. Several hours later, the tractor was placed back in the hole, where it latched and retrieved the canister, bringing it back to the surface. Deep Isolation, in partnership with the University of California, Berkeley, Lawrence Berkeley National Laboratory, and NAC International, has been awarded a $3.6 million grant by the U.S. Department of Energy’s Advanced Research Projects Agency-Energy to develop a universal nuclear waste disposal canister for advanced reactor waste streams. They are working on a canister design suitable for high-level waste which could work in a mined or deep borehole repository to meet U.S. and international market needs. Elizabeth Muller and Richard A. Muller. DIR A drilling specialist lowers the prototype canister into a test borehole during a technology demonstration event. Deep Isolation borehole waste repository concept.