Tritium Breeding Ratio Evaluation of Solid Breeder Concepts for the FESS-FNSF

Abstract

This paper presents a parametric study of the Fusion Energy System Studies-Fusion Nuclear Science Facility’s (FNSF’s) tritium breeding performance for several solid breeder concepts, neutron multiplying materials, and blanket materials, assuming volume fractions based on the most recent FNSF design as a realistically representative fusion facility. In this study, we initially surveyed the tritium breeding ratio (TBR) of several solid breeder concepts by employing a simplified but efficient one-dimensional (1-D) infinite cylinder reduced-order model (ROM). Parametric studies were performed with the ROMs for the full range of breeder-to-multiplier ratios to identify the optimum mixture compositions for each breeder type that would lead to a maximum TBR.

These optimized breeder-multiplier combinations were then homogenized with FNSF blanket component materials to estimate their impacts on the TBR. Subsequently, as a validation step for the optimal designs, TBR calculations were performed using a more realistic modified 1-D ROM with inner and outer breeding regions, as well as with a fully detailed 22.5-deg three-dimensional (3-D) sector of the FNSF to assess the impact of geometry details on the TBR. The differences between the two 1-D models were negligible, while the ROMs were able to correctly predict trends and identify the maximum and minimum TBR cases, as well as show consistent biases relative to the results produced by the full 3-D, 22.5-deg sector for specific breeder/multiplier combinations.

Solid breeder concepts such as $L{i}_{2}O$, $L{i}_{4}Si{O}_4$, and $L{i}_{8}Zr{O}_6$ outperformed all others in this study in terms of TBR performance when combined with all the neutron multiplier materials selected. An underlying goal of this study was to develop and improve rapid and reliable ROMs to aid designers during parametric optimizations of highly complex and computationally expensive fusion models.

Keywords:

• Fusion neutronics
• MCNP
• ceramic breeder
• tritium breeding ratio

Acknowledgments

We thank Dr. Charles E. Kessel from Oak Ridge National Laboratory for his advice and helpful discussions with our team.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the support from the U.S. Department of Energy, Office of Fusion Energy Sciences, under contract no. DE-SC0022308.