(A) new burnable absorber and fuel assembly optimization for high-performance soluble-boron-free small modular reactor

Abstract

This dissertation pursues a novel re-optimization of fuel assembly (FA) and new innovative burnable absorber (BA) designs to design a high-performance soluble-boron-free SMR (small modular reactor), named ATOM (Autonomous transportable on-demand reactor module). A new truly optimized PWR (TOP) lattice concept has been proposed to maximize the neutron economy while providing improved safety parameters for an SBF FA design. For an SBF SMR, the 3D CSBA (Centrally-Shielded BA) technology is detailed and another innovative 3D BA called DiBA (Disk-type BA) is proposed in this study. Both CSBA and DiBA designs are characterized in terms of material, spatial self-shielding effect, and thermos-mechanical properties. Various CSBA and DiBA loading strategies are investigated to achieve SBF operation of a high-performance ATOM core adopting both the conventional and TOP FA designs. A single-batch SBF ATOM core has been designed using the CSBA or DiBA based on the conventional FA concept. In addition, a low-leakage two-batch fuel management is optimized for a TOP-based SBF ATOM core. In the two-batch ATOM core, both CSBA and DiBA are combined together to achieve a very small reactivity swing, which is < 1,000 pcm. It is shown that the small excess reactivity can be well controlled by mechanical shim rods with just marginal increase in the local power peaking. The current work also proposes a simple pseudo checker-board control rod pattern which enables a cold-zero shutdown of the SBF ATOM core.