Demand driven salt clean-up in a molten salt fast reactor – Defining a priority list

Abstract

The PUREX technology based on aqueous processes is currently the leading reprocessing technology in nuclear energy systems. It seems to be the most developed and established process for light water reactor fuel and the use of solid fuel. However, demand driven development of the nuclear system opens the way to liquid fuelled reactors, and disruptive technology development through the application of an integrated fuel cycle with a direct link to reactor operation. The possibilities of this new concept for innovative reprocessing technology development are analysed, the boundary conditions are discussed, and the economic as well as the neutron physical optimization parameters of the process are elucidated. Reactor physical knowledge of the influence of different elements on the neutron economy of the reactor is required. Using an innovative study approach, an element priority list for the salt clean-up is developed, which indicates that separation of Neodymium and Caesium is desirable, as they contribute almost 50% to the loss of criticality. Separating Zirconium and Samarium in addition from the fuel salt would remove nearly 80% of the loss of criticality due to fission products. The theoretical study is followed by a qualitative discussion of the different, demand driven optimization strategies which could satisfy the conflicting interests of sustainable reactor operation, efficient chemical processing for the salt clean-up, and the related economic as well as chemical engineering consequences. A new, innovative approach of balancing the throughput through salt processing based on a low number of separation process steps is developed. Next steps for the development of an economically viable salt clean-up process are identified.

A disruptive approach to eliminating weapon-grade plutonium – Pu burning in a molten salt fast reactor

“…Here, the first core configuration is just critical (no excess reactivity) and the burnt fissile material is continuously replaced by fissile material which is provided by the online feeding system. A comparable process is proposed for the salt clean-up, a small share of the salt is continuously separated from the core which is foreseen to be chemically cleaned from the fission products which prevent the reactor from long term operation [10, 38, 39]. This proposed highly innovative approach avoids any separation of fissile material and thus leads to a significant reduction of the proliferation and security concerns.…”

The Interplay between Breeding and Thermal Feedback in a Molten Chlorine Fast Reactor

“…Energies 2020, 13, 1609 9 of 15 precursor for the Pu-239 breeding was almost constant through the whole burnup period, while the selected fission products accumulated almost at an identical rate with increasing burnup. In a real, operating molten salt reactor as proposed in iMAGINE, some of these fission products, with priority to the ones causing the highest reduction in criticality, would be those given in [14]. For any kind of long-term operation, all solubility issues have to be taken into account, which will in the long term require an additional process to reduce the absolute amount of fission products in the reactor.…”

“…Achieving sufficient breeding in a molten salt system, see [13]; • Developing of a demand driven salt clean up system, see [14]; • Creating a deeper understanding of the operational behaviour of the system and potential control strategies.…”

Evaluation of the Breeding Performance of a NaCl-UCl-Based Reactor System

“…Achieving sufficient breeding in a molten salt system • Developing of a demand driven salt clean up system [14] The aim of this publication is to create an initial approach to the first point given above by:…”

“…Unfortunately, the system did not get the attention such an innovative work should have deserved. In contrast to REBUS-3700, iMAGINE will be based on a homogenous core design without breeding blanket, a demand driven salt clean-up and an optimization process between reactor physics and separation chemistry (more details are given in [14]). The homogeneous core without a blanket provides a much harder challenge to achieve sufficient breeding, but it provides a much more proliferation resistant system since no fresh, separable Plutonium will be formed in a separate system.…”