Prediction of fuel salt composition using fuel data libraries developed for the Molten Salt Demonstration Reactor

The interest of the scientific community in alternate nuclear fuel cycles such as that of the Molten Salt Reactors (MSRs) has grown and waned in the past. In the recent decades however, there has been a resurgence of interest in them owing to the ever-rising demand for sustainable energy and growing concerns of climate change. However, these reactors are yet to enter the stage of commercial operation. The MSR family form a broad spectrum of reactor concepts with unique fuel cycles, designs, online reprocessing options et cetera and some of these have progressed from the phase of conceptualization to deployment as experimental reactors. Since MSRs differ significantly from the traditional Light Water Reactors (LWRs), both conceptually and from an operational point of view they come with new and unique challenges. On the issue of safeguards, the main challenges arise from the lack of experience in the industry on handling bulk fuel material such as highly radioactive and corrosive molten fuel salts containing nuclear material in place of traditional fuel items like spent nuclear fuel (SNF) assemblies. There is also a marked lack of measurement techniques and instruments that could be brought into use for enforcing safeguards on molten salt systems. There are novel ideas that have been proposed to increase the proliferation resistance of the fuel cycle in MSRs and deter the misuse of fuel material.Among the key MSR designs that have been developed at the Oak Ridge National Laboratory (ORNL) in the past was the Molten Salt Demonstration Reactor (MSDR). The MSDR concept was a 750 MW successor to the much smaller Molten Salt Reactor Experiment (MSRE) that was once operated at ORNL. While the MSDR was never built, its design, operation, safety, security and safeguards-related issues were studied extensively at several national labs in the United States. In the current study, we aim to model the irradiation of fuel salt used in the MSDR. The reactor specifications are used in a Monte-Carlo particle transport code to model its operation. The key objective of the paper is to describe the creation and utility of a data library of fuel signatures such as fuel salt characteristics at different times in the fuel cycle that could be important from a safeguards verification standpoint. It is also expected that such signatures would be used as training features in a machine learning model in the future to develop safeguards approaches and verification techniques that can be used to assess whether the reactor has been operated as declared