SPARC, an Effort to Reestablish a Horizontal Split Table Critical Facility for HALEU Experiments and Beyond

The development of nuclear technology has been accompanied by experiments using zero power reactors starting with Chicago Pile 1. These critical experiments operate at power levels insufficient to investigate irradiation effects or thermal performance but are ideal for experiments focused on nuclear physics. Many facilities of this type have been created to produce data and validation cases for criticality safety and reactor physics models, but several were decommissioned around the turn of the millennium as nuclear research waned. While some specialized critical experiment facilities and expertise remain alive, the United States has now been without a large Horizontal Split Table (HST) facility for decades. A backlog of data needs for criticality safety experiments in intermediate neutron energies, and significant momentum building toward commercialization of advanced reactors, now create the overwhelming need for a new HST capability. Compared to the current light water reactors fleet, many advanced fuel/reactor designs use higher²³⁵U enrichment (i.e., >5% and <20%), alternate coolant strategies (i.e., inert gases, liquid metals, molten salts, heat pipes), and different moderators (i.e., graphite, beryllium, metal hydrides). These new designs offer high value potential, but there are few relevant experiments to validate physics models. A new project is underway to establish the System Physics Advanced Reactor Critical facility (SPARC) by assessing the user need, selecting a site, and developing a planning bases for a large HST at the Idaho National Laboratory. This paper will present the outcomes of this assessment for SPARC alongside strategic plans to realize its vision.