Scalable Chrysopoeia via (n,2n) Neutron Multiplication Reactions in Deuterium-Tritium Fusion Blankets: A Comprehensive Technical Review of Marathon Fusion's Mercury-to-Gold Transmutation Process

This paper presents a rigorous technical analysis of scalable nuclear transmutation pathways for converting mercury-198 (^198Hg) into stable gold-197 (^197Au) via (n,2n) neutron multiplication reactions driven by 14.1 MeV fusion neutrons in deuterium-tritium (D-T) reactor breeding blankets. Building on the seminal work of Marathon Fusion (Rutkowski et al., arXiv:2507.13461), we examine the nuclear physics foundations, neutronics simulation results, engineering challenges, and techno-economic implications of this approach. Monte Carlo transport calculations demonstrate that optimized tokamak blanket configurations can produce approximately 2,000 kg of gold per gigawatt-thermal per year while maintaining tritium breeding ratios exceeding 1.19. This breakthrough addresses the millennia-old challenge of chrysopoeia through practical nuclear engineering and fundamentally transforms fusion economics by potentially doubling plant revenues. We critically evaluate isotope enrichment requirements, material compatibility issues, radiological cooling periods, regulatory frameworks, and market impacts. Our analysis concludes that fusion-driven gold transmutation represents a disruptive technology with profound implications for both fusion energy deployment and precious metal supply chains.