How Deep Borehole R&D is Tied to Future of Advanced Reactors

By Kari Hulac

In 2022 the world saw a notable uptick in the number of countries pursuing clean nuclear energy to fight climate change and secure energy independence. In turn, more governments and next generation nuclear developers are thinking about the back end of the fuel cycle while evaluating deployment of reactors.

Among the more than a dozen contracts Deep Isolation has across three continents, our advanced reactor and small modular reactor waste disposal work includes:

*Participation in four U.S. Department of Energy (DOE) Advanced Research Projects Agency – Energy (ARPA-E) grant projects with three led by partner organizations. Deep Isolation’s scope will be to examine various aspects of how deep borehole repositories for nuclear waste can help close the nuclear fuel cycle through disposal of spent fuel and reprocessing waste streams. The total grant funding for these projects is $15.3 million, representing a significant investment from the U.S. government in support of an integrated waste management approach.

*A second contract with Fermi Energia, an energy company working on the development and deployment of small module reactors (SMRs) in Estonia. This work will build on Deep Isolation’s earlier work with Fermi Energia, a project that concluded that most of the country’s geology would be acceptable for deep borehole disposal.  This new project will research the cost effectiveness of using boreholes to dispose of waste from an SMR that would be deployed in Estonia by 2050.

Deep Isolation Head of Engineering Jesse Sloane, who is overseeing the company’s DOE grant work, funded under the ARPA-E umbrella, explains this synergy between advanced nuclear reactors and deep borehole repositories.

ARPA-E logo, Advanced Research Projects Agency – Energy
The U.S. Department of Energy’s Advanced Research Projects Agency — Energy helps fund R&D for nuclear energy and nuclear waste disposal projects such as deep boreholes repositories.

Q. We are clearly seeing more interest from the next generation nuclear reactor community in deep boreholes over the past year. What is the primary driver of this heightened consideration?

A. There are many factors contributing to the advancement of deep borehole disposal, and I think it is hard to narrow it down to only one. We are certainly seeing worldwide drivers such as the geopolitical environment and climate change concerns play key roles in the desire to find near-term solutions to the nuclear waste problem in support of carbon-neutral nuclear energy.

In the European Union, there are changes in taxonomy regulations to support investment in sustainable advanced nuclear technologies, and in the case of climate change mitigation, these are coupled with requirements to have plans for an operational disposal facility for high-level waste by 2050.  From a technical perspective, I think deep borehole disposal repository facilities are uniquely poised to be designed, licensed, constructed, and operational within that timeframe.  Borehole repositories require far less construction time than the traditional mined repositories, given they are smaller in scale, can be modular in design, and do not require workers to be underground.

In the United States, utilities that deploy advanced reactors will be required to fund the storage of the spent fuel for up to 20 years after it has been removed from the reactor.  This is a significant policy change from what is required for the existing fleet of reactors — for which the DOE is responsible for providing waste disposal services as of 1998 and is currently paying the utilities for spent fuel storage costs. Therefore, the industry seems keen to see progress in the form of innovative waste disposal technologies, including deep borehole disposal.

Q.  Of the four DOE projects, Deep Isolation is the lead on one, a $3.6 million grant in partnership with the University of California, Berkeley, Lawrence Berkeley National Laboratory and NAC International, to develop a universal canister system for advanced reactor waste streams. What are some key aspects of this project, and how does it fit into the broader picture of how deep boreholes can support advanced reactor deployments?

A. This project is funded through ARPA-E’s Optimizing Nuclear Waste and Advanced Reactor Disposal Systems (ONWARDS) program, and it specifically addresses consideration of deep borehole disposal as an alternative disposal pathway for advanced reactor waste.

There are four key parts for this project: 1.) The project team will research various advanced reactor waste forms through literature reviews, experimentation, and collaboration with other ARPA-E projects.  2.) These waste forms will be analyzed through repository performance assessments in a variety of geologic disposal configurations, including mined and borehole repositories.  3.) We will design and analyze a disposal canister that will be compatible with these waste forms and will be appropriately sized for disposal in a borehole or mined repository.  The design efforts will culminate with the fabrication of a prototype canister.  4.) We will develop generic waste acceptance criteria for waste forms to be packaged in the new canister, with differing criteria for disposal in both mined and borehole repository configurations. 

The project will provide a pathway for disposal of multiple waste forms for advanced reactor designs that have not yet been built or licensed so that a disposal pathway is identified prior to the reactors even coming online.  Future analyses can confirm if additional waste forms will be acceptable for disposal within the canister, which will allow these reactor designs to mature and progress while simultaneously planning for eventual disposal of the spent fuel.

Q. You are Deep Isolation’s Project Lead on a team that was recently selected to receive $4.9 million from the DOE ARPA-E CURIE program. The project, led by Argonne National Laboratory, is to develop and demonstrate oxide reduction technology for pyrochemical recycling of light water reactor used nuclear fuel. Deep Isolation will develop an integrated oxide reduction waste disposal plan, while simultaneously determining ideal waste acceptance parameters. Please explain the significance of this project.

A. ARPA-E’s CURIE program aims to significantly reduce the volume of light water reactor spent nuclear fuel requiring disposal by advancing various reprocessing technologies for ultimate commercial applicability.  We are partnering with Argonne National Laboratory, advanced reactor developer Oklo Inc., and Case Western Reserve University to advance oxide reduction reprocessing technology to maximize recovery of fissionable material from the existing inventory of spent nuclear fuel.  Reprocessing, whether through oxide reduction or some other means, will always result in waste forms that must be safely isolated and disposed of deep underground to protect the public from the harmful radiation emanating from those waste products.  This isolation is necessary because the waste, similar to spent nuclear fuel, contains isotopes with long half-lives (hundreds to thousands of years) that emit harmful radiation.

Deep Isolation will develop a disposal plan for the oxide reduction process waste streams. It is worth mentioning that the CURIE program has some ambitious target metrics, including a goal to maintain disposal costs in the range of 0.1¢/kWh. To reduce disposal costs, Deep Isolation will also perform an economic analysis to determine an ideal range of acceptance parameters for those waste streams. This will ensure that reprocessing technology is not only safe but economical and able to support the needs of the coming fleet of advanced reactors.

Q. In addition to the Argonne project you just discussed, describe Deep Isolation’s two other ARPA-E projects: An ONWARDS project with Oklo, Argonne National Lab and Idaho National Laboratory and a second CURIE project led by EPRI.

A. The ONWARDS project led by Oklo will develop a first-of-a-kind nuclear fuel recycling facility.  The project will advance the technical and commercial capabilities of an electrorefining facility to be deployed in support of metal-fueled advanced reactors.  Deep Isolation’s scope for the project will analyze the pyroprocessing waste streams to determine if they are suitable for deep borehole disposal.  We will also develop an integrated waste disposal plan for the project’s waste streams.

We are also fortunate to be part of another CURIE project, led by EPRI. This project, which includes an advanced reactor company, Oak Ridge National Laboratory, Southern Company, and Dominion Engineering, will develop a complete advanced reactor fuel cycle enterprise. The project will consider the use of light water reactor spent nuclear fuel as feedstock, explore optimization of various recycling processes, and will integrate with Deep Isolation’s innovative approach to efficient waste management through deep borehole disposal.

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