Core analysis of spectral shift operated SmAHTR

Fluoride High-temperature Reactors (FHRs) are regarded for their high temperature output and passive decay heat rejection. Small Modular Advanced High Temperature Reactor (SmAHTR), a 125 MWth reactor falls under the FHR group. Along with FHRs, SmAHTR also uses multilayered, high accident tolerant TRistructural ISOtropic (TRISO) fuel kernels. Despite the reactor's benefits due to its high efficiency and safety parameters, its considerably higher fuel costs compared to traditional UO2 fuel creates a drawback. To mitigate this problem and use the fuel more efficiently, lower fraction of fuel can be loaded into the core, however the resulting cycle length may be prohibitively short. This study proposes a spectral shift scheme to improve both the discharge burnup and the cycle length simultaneously for these types of reactors. Our analyses include both the neutronic and the thermal hydraulics (T/H) assessment for the non-spatial implementation of this scheme under single- and multi-batch scheme operation. The safety performance, i.e. reactivity coefficients and T/H limits, for this concept is comparable to the original design. The results confirm that performance benefits of more than 32% compared to the original design are achievable.