Characterizing the seismic response of a molten salt nuclear reactor

Abstract

One Generation IV nuclear reactor, which uses a fluoride salt as a coolant, graphite reflector blocks as a moderator, and circulating buoyant TRISO pebbles as fuel is at an advanced stage of development. To characterize the seismic behavior of components of this reactor, validate numerical models for analysis, and develop recommendations for design, a set of earthquake-simulator experiments on a scaled model of the reactor vessel and its internals was executed on a sixdegree-of-freedom earthquake simulator. The model was seismically isolated at its base using two types of spherical sliding bearings. The scaled model involved representations of the prototype reactor vessel, core barrel, reflector blocks, coolant, and spherical fuel pebbles. The material and geometric properties of different test components were selected based on a dynamic similitude scaling analysis and an approximate length scale of 0.4. Four sets of three-component earthquake motions were used as inputs for testing. Instrumentation on the test specimen recorded the dynamic responses of the outer vessel, core barrel, and reflector-block assembly, the hydrodynamic responses (sloshing and hydrodynamic pressure) of the liquid coolant, pebble consolidation under earthquake shaking, and the behavior of the isolation systems. This paper describes the design of the experiments and presents key results from the tests. The dynamic responses of the outer vessel, core barrel, and the reflector blocks revealed that the components responded as a unit for the intense shaking used in the experiments. The sloshing response of the fluid in a thin annulus near the perimeter of the vessel was heavily damped. The change in the packing fraction of the pebble bed under repeated, intense 3D earthquake shaking was less than 3%. Seismically isolating the vessel substantially reduced demands on its internal components.

Earthquake response of head-mounted equipment in advanced nuclear reactors

“…The instrumentation on the vessel, base, and the earthquake simulator was very similar to that presented in Figure 8 of Mir et al (2022c) and included tri-axial accelerometers and displacement transducers at multiple locations on the test specimen. Three directional accelerations were measured on the earthquake simulator, below and above the isolation system for the base-isolated configurations, and at the top of the vessel.…”

“…Seismic inputs similar to those described by Mir et al (2022c) were used for testing and included three recorded ground motions and one synthetic motion, all triplets. The recorded motions were extracted from the PEER Ground Motion Database (http://nga-west2.berkeley.edu) and were from the 1999 Chi-Chi Earthquake (CCE), the 1940 Imperial Valley earthquake (ECE), and the 1952 Kern County earthquake (KCE).…”