Progress Report on Graphite-Salt Intrusion Studies

Approach to using 3D laser-induced breakdown spectroscopy (LIBS) data to explore the interaction of FLiNaK and FLiBe molten salts with nuclear-grade graphite

“…This is supported by weight gain during the FLiNaK intrusion tests, which showed samples K1 and K2 to have the lowest intrusion volumes. 29…”

“…A set of graphite samples were exposed to molten FLiNaK using a custom-built molten salt intrusion system, for which the design and operation is discussed in detail elsewhere. 29 Briefly, the molten salt intrusion system was designed to enable tests following the guidance provided in the ASTM D8091-16 procedure addressing impregnation of graphite with molten salt. All graphite samples were air-dried at 110 °C for 2 h and then heated to 1200 °C for 12 h under vacuum before the intrusion experiments.…”

“…The intrusion system enables samples to be immersed in a molten FLiNaK bath and withdrawn prior to cooling to avoid freezing the salt around the samples. The first set of samples analysed in this study were exposed to molten FLiNaK at 750 °C and 7.9 bar for 12 h. 29 An additional set of graphite samples was exposed to molten FLiBe at 750 °C for 1000 h in static capsule tests. These initial tests required less Be bearing salts to mitigate health and safety concerns while providing information on the compatibility of FLiBe and alloy materials for future system construction.…”

“…This is supported by weight gain during the FLiNaK intrusion tests, which showed samples K1 and K2 to have the lowest intrusion volumes. 29 The carbon emission signals increase as salt emission signals decrease. Interestingly, the salt-to-carbon ratios decrease appears to be consistent for different salt species for a given sample.…”

“…This study aimed to investigate the use of LIBS for exploring the interaction of molten FLiNaK (47 : 11 : 42 LiF : NaF : KF) and FLiBe (2 : 1 LiF : BeF 2 ) salts with graphite and to develop a data analysis methodology for future salt-graphite interaction studies. 29 A signicant benet of using LIBS for these studies was the ability to maintain an inert atmosphere, which prevents moisture and oxygen absorption. Standard emission line intensity analysis and an unsupervised learning approach to data analysis (i.e., principal component analysis [PCA]) were explored, separately and in combination, for evaluating the collected LIBS data.…”