Developing A Simulation Surrogacy Model

A Molten Salt Reactor that has operated for any reasonable length of time will have accumulated a substantial number of impurities from both fission and corrosion products. The result is a Salt whose chemistry changes over the course of the reactor lifetime. Understanding these chemical shifts is significant as it plays a part in many key safety factors such as radioactive release and criticality control.

However, this chemical behavior can be difficult to model given the limited selection of experimental data. This work is aimed to establish a methodology by which the multitude of elements found in the salt and in the reactor may be condensed to the limmited selection of elements for which we have sufficent data to be able to model behavior.

Key Considerations

A simple solution based on grouping by chemical similarity would not be difficult to achieve. However, such a simple solution will not hold in all cases. By considering several factors such as Elemental Abundance and Risk factor, we accomplish two things:

1. The development of a more robust method with suitable justification for chemical groupings as well as a reasonable intuition for what error can be expected.

2. An understanding of the impact of any expected or unexpected error, allowing us to call attention to the most important gaps.

Chemical Similarity

One thought I have had is to find a way to approximate error in results based on difference in reactivity.

• Reactivity

• Electrochemical Potential

• Valence State

• Physical Characteristics

  • Melting Point
  • Boiling Point
  • Atomic Size
  • Crystal Structure

Elemental Abundance

The Idea here is to understand the relative importance of a species based on its expected abundance in the core. The species related to pure salt are well studied and have plenty of data, it is impurities from fission products and corrosion that need to be accounted for. This portion of the study will produce (likely using orgin) a elemental heat map for a Flibe Molten Salt Fuel through out the life of a reactor. This can be used in the risk assessment. Expected corrosion products (Mostly Cr will also be considered and expected concentration taken from literature)

• Fission Products

• Corrosion Products

Risk Factor

This portion of the study will focus on the relative significance of different elements based on radiotoxicity, likelihood of release, and impact on core operations.

• Volatility Hazards

• Delayed Neutron Precursors

• Significant Neutron Absorbers