Toni Karlsson

A wide variety of nuclear fuels and materials are irradiated at the Advanced Test Reactor (ATR), the world’s most powerful test reactor. However, all nuclear fuel forms at the ATR have been solid (e.g., ceramic or metallic fuels), and no safety analysis has been completed for molten salt experiments. This study reports one portion of a larger safety analysis for molten salt fuels at the ATR. Specifically, fail-safe material limits for molten salt experiments are derived through experiment and analysis. The off-normal condition of molten salt material release in the ATR primary coolant system (PCS) is simulated through salt titrations on PCS samples obtained during power operations. The ATR system response is extrapolated and fail-safe material limits that protect the ATR driver fuel are set for NaCl-UCl3 and NaF-KF-UF4. Potential effects on the PCS boundary are considered, as well as recommended monitoring of halide content. Finally, the method described in this paper can be used to set fail-safe material limits for other liquid nuclear fuels.

Metal oxide varistors (MOVs) are a type of resistor with significantly nonlinear current‐voltage characteristics commonly used in power lines to protect against overvoltages. If a proper recycling plan is developed MOVs can be an excellent source of secondary zinc because they contain over 90 weight percent zinc oxide. The oxides of antimony, bismuth, and to a lesser degree cobalt, manganese, and nickel are also present in varistors. Characterization of the MOV showed that cobalt, nickel, and manganese were not present in the varistor material at concentrations greater than one weight percent. This investigation determined whether a pH selective dissolution (leaching) process can be utilized as a starting point for hydrometallurgical recycling of the zinc in MOVs. This investigation showed it was possible to selectively leach zinc from the MOV without coleaching of bismuth and antimony by selecting a suitable pH, mainly higher than 3 for acids investigated. It was not possible to leach zinc without coleaching of manganese, cobalt, and nickel. It can be concluded from results obtained with the acids used, acetic, hydrochloric, nitric, and sulfuric, that sulfate leaching produced the most desirable results with respect to zinc leaching and it is also used extensively in industrial zinc production.