Dynamic Response Characteristics of Fuel-Block Assemblies in a Horizontal, Compact HTGR

This paper investigates the dynamic response characteristics of fuel-block assemblies to be part of the reactor core in a horizontal, compact high temperature gas reactor (HC-HTGR). The assembly includes prismatic blocks of graphite forming the reflector and fuel elements. These blocks are vertically stacked in columns by means of shear keys, which provide some degree of interlocking. The columns of blocks are separated from others by finite gaps to accommodate fabrication and installation tolerances, thermal expansion, and swelling of graphite. Under earthquake ground shaking, the dynamic response of the columns of blocks is not fully understood, but will be affected by multiple factors, including the rigid-body dynamics of the blocks, friction and clearances within the shear key, kinematic constraints, design and manufacturing tolerances, uplift, disengagement of blocks from the shear key, and impact of blocks in adjacent columns. To characterize these effects, coordinated experimental and numerical simulations are being conducted as part of a DOE-funded Advanced Reactor Concept (ARC-20) project. This paper describes the earthquake-simulator experiments, provides insight into the rocking dynamics of columns of stacked graphite blocks, presents test results for different assemblies of blocks subjected to sinusoidal inputs covering a broad range of frequency, and summarizes the ongoing experimental and numerical work.