The safe level isn't that important, because the gold can be put into an ETF investment vehicle, which is a substantial enough demand for gold. National reserves (the vast majority of gold demand) too are long term holders.
2t/GWhth is a huge amount. While the best case economics for fusion is 30c/kwh cost = $3m/Gwhe, that would be 3GWhth = 6T of gold. Even at $45/oz (1/100th of current value) that would be $8m/Gwhe revenue, and would likely be able to sell electricity at market rates as the "waste product", or not even bother with the expense/complexity of electricity generation.

arxiv.org: a pre-print source, this is not peer-reviewed yet. So, until other papers refer to this paper, it has low significance in the literature. The paper has references to other papers and to previous corpus of knowledge on the subject, which is good. However, this paper is based on simulations only.
The decommissioned blanket material would increase in value, and the Mercury-198 in the blanket doesn't majorly impact its effectiveness in transmuting lithium to tritium.
The "worst" gold isotope half-life is less than a year, so only a modest cool-down is needed for the output:
What strikes me here with this paper is the suggested liquid blanket, so this would be a kin of D-T Fusion MSR. We now have two proposed technologies behind being able handle hot radioactive liquids.
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