Abstract
The development of the Molten salt Nuclear Battery (MsNB) has been accompanied by an evaluation of the back end of its fuel cycle. A method used for online uranium recovery of the Molten Salt Reactor Experiment [1] was adapted into a new process that not only recovers uranium but alsoother useful elements from used molten salt reactor fuel while reducing the amount of high-level waste (HLW) needing disposal. This process contains similar processes/procedures to that of the fluoride volatility processes. In order to determine the likelihood of successful treatment of the waste, the process underwent analysis of its chemical reaction and mass transport processes. This analysis was used to determine the different rates involved in the process (chemical reaction rate, gas supply rate, fluorine diffusion through the molten salt rate, and bubble rise rate) and which rate limits the treatment process. A rate is considered to limit the process when it corresponds to the greatest time required to reach the associated completion (chemical reaction, gas input, diffusion through the molten salt, or movement up through the treatment system). The limiting rate leads to the determination of the time needed to complete the treatment of the waste. The time needed for treatment was used to determine that the 3169 kg of uranium or one 400kWth MsNB core could be fluorinated within 38.5 days.
In order to evaluate the effect the fluoride present in the MsNB waste has on the transport of radionuclides through the bentonite buffer material, the KBS-3 Swedish waste repository was used as a reference. The KSB-3 bentonite pore-water composition was used to analyze the behavior of a MsNB waste package in a similar environment. The system consisting of a waste package within a bentonite buffer material was analyzed with various concentrations of aqueous fluoride and compared to the control case of 0 M aqueous fluoride. The results of the analysis lead to the conclusion that the fluoride present within the MsNB waste does not impact the transport of radionuclides through the buffer material under KSB-3 pore water conditions.