Radiotoxicity of minor actinides in thermal, epithermal and fast TMSRs with very high burnup.

• MA characteristics from core start-up to equilibrium of three TMSRs are analyzed. • Mass equilibrium time strongly depends on the vanishing coefficients. • Fast MSRs produce less MA inventory and radiotoxicity for a short operation time. • Fast MSRs would loss its less-radiotoxic advantage for a long-term operation. A liquid-fueled molten salt reactor (MSR) can be flexibly designed as a thermal, epithermal or fast system. Meanwhile, available online fuel reprocessing can inherently interconnect the closed fuel cycle with the reactor, which would have a substantial impact on the MA production as well as nuclear waste management of a MSR. In this work, three thorium-based MSRs (thermal, epithermal and fast spectra) are chosen for analysis. The results indicate that the mass equilibrium time of a nuclide strongly depends on the vanishing coefficient of its dominant precursor nuclides and of itself. Owing to the low generation rate of MA caused by small vanishing coefficient, the fast TMSR shows a lower radiotoxicity over the thermal and epithermal TMSRs for a short operation time. Nevertheless, this advantage gradually losses as the operation time further progresses and so that the MA inventory in the fast reactor can also achieve equilibrium state. [ABSTRACT FROM AUTHOR]