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Integrating Waste Management for Advanced Reactors: The Universal Canister System and Project UPWARDS
When the Department of Energy’s Advanced Research Projects Agency–Energy launched the Optimizing Nuclear Waste and Advanced Reactor Disposal Systems (ONWARDS) program in 2022, it posed a challenge that the nuclear industry had never seriously confronted before: how to design waste management solutions that anticipate the coming shift to advanced reactors and not merely retrofit existing systems built for an older generation of technology. The program’s objectives were ambitious—reduce disposal footprint, enable scalable pathways for unfamiliar waste streams, and build the technical foundations for future disposal—yet also tightly grounded in the realities of emerging nuclear fuel cycles. For the nuclear community, this was a timely call. Advanced reactors were accelerating toward deployment, but the waste management systems needed to support them had not kept pace.
Federico Scioscioli, Antonio Cammi, Stefano Lorenzi
Nuclear Science and Engineering | Volume 198 | Number 6 | June 2024 | Pages 1288-1307
Research Article | doi.org/10.1080/00295639.2023.2250144
Articles are hosted by Taylor and Francis Online.
A foreseen feature of the Molten Salt Fast Reactor is the adoption of a bubbling system for the removal of gaseous and metallic fission products (FPs). This mechanism injects helium bubbles into the core to remove FPs from the salt through floating and mass transfer mechanisms for metallic and gaseous FPs, respectively. The present work is aimed at analyzing this helium bubbling system, focusing on gaseous FPs. We investigate both operational and safety-related features in order to get information useful for the design and to assess the convenience of its adoption. Accordingly, our investigations split into two strands: (1) analyzing the characteristics of the bubbling system itself and (2) assessing the safety features of the reactor in its presence. In order to perform the above analyses, we add the capability to simulate production, transport, and mass transfer of an arbitrary number of gaseous FPs to a preexisting multiphysics solver, built with the OpenFOAM suite. In terms of operational characterization, our analyses quantify the removal efficiency through a characteristic removal time and estimate the poisoning effect of gaseous FPs. In addition, we evaluate the activity and decay heat of the removed gas, which is an aspect crucial for the design of the off-gas unit, and the effect of the bubbling system on the power versus the fuel mass flow rate curve, which is a possible control mechanism. Among our safety-related studies, we first evaluate the void coefficient, determining upper bounds on the helium flow rate in order to avoid prompt supercriticality in case of prompt loss of helium injection. The latter accidental scenario is also analyzed considering the thermal-hydraulic dynamics of the system. We also discuss another accident: complete loss of helium removal.