Advancing Molten Salts and Fuels at Sandia National Laboratories

Abstract

SAND2017-10478R SNL has a combination of experimental facilities, nuclear engineering, nuclear security, severe nuclear accidents, and nuclear safeguards expertise that can enable significant progress towards molten salts and fuels for Molten Salt Reactors (MSRs). The following areas and opportunities are discussed in more detail in this white paper.  Molten salt experiments-molten salt test loop (MSTL). This section includes a detailed discussion of molten salts applicable for MSR and solar applications. The emphasis is operation, chemistry, corrosion, and instrumentation. A description of MSTL, its capabilities, and level of effort required to restart the facility is presented, as well as innovative, potential upgrades for fluoride and chloride experiments, loop sectioning for multiple experiments, and fission surrogates. MSTL restart is estimated conservatively to cost 1/10 th the value of building a new facility. Furthermore, its large-scale operating regime continues to lead the industry.  Safety. MELCOR can already model several types of advanced reactors, including VHTRs, water-cooled SMRs, and sodium-cooled reactors. Current MSR capabilities in MELCOR are discussed. This investigation identified several useful MSR capabilities that are straightforward to implement. For the longer term, advanced MSR models and safety issues are identified.  Safeguards. An FY18 safeguards performance model for the Material Protection Accounting and Control Technologies (MPACT) program at DOE NE is described. Experiments using fission surrogates in molten salt mixtures are recommended for MSTL. A 2017 NA-241 safeguards analysis for thorium fuel indicates intense gamma radiation. However, this issue can be addressed at SNL's experimental facilities, and funding should be sought in this area as well.  Computational fluid dynamics (CFD). CFD modeling at SNL includes state-of-the-art large eddy simulation (LES) using the dynamic Smagorinsky turbulence model and the direct numerical simulation (DNS) model. It is noted that SNL has used CFD to successfully model gas-and water-cooled fuel assemblies under forced and natural circulation, as well as molten salt surfaces under natural circulation. SNL also has excellent coupled Multiphysics codes that couple CFD with heat transfer and structural analysis.  Nuclear criticality safety and neutronics. Because of its versatility and significant number of successful benchmark experiments, the Sandia Critical Experiments (SCX) facility is ideally suited to perform criticality experiments for molten salt-based fuels. SNL also has a broad-based experience in designing, performing, and analyzing critical benchmark experiments that will be invaluable assets for advancing molten salts and fuels. The above are areas where SNL could submit proposals with a higher degree of success because they have the highest degree of synergism between SNL's technical expertise and the recent paradigm at DOE and ARPA-E. These organizations have recently acquired a stronger stake in advanced nuclear reactors...