Seismic analysis of liquid-filled tanks with an eccentric core barrel

The seismic analysis of fluid-coupled concentric cylindrical shells is reviewed. A coupled fluid-structure finite element method which considers the sloshing effect is then developed for the seismic analysis of liquid-filled systems with internal components. The theoretical development of the mixed finite element formulation is also included. The resulting fluid-structure interaction algorithm has been integrated into the computer code FLUSTR II and the seismic analysis of liquid-filled tanks with an eccentric core barrel is performed. Numerical results show the method yields accurate solutions with large increases in efficiency

Evaluation of Lagrangian, Eulerian, and arbitrary Lagrangian-Eulerian methods for fluid-structure interaction problems in HCDA analysis

The analysis of fluid-structure interaction involves the calculation of both fluid transient and structure dynamics. In the structural analysis, Lagrangian meshes have been used exclusively, whereas for the fluid transient, Lagrangian, Eulerian, and arbitrary Lagrangian-Eulerian (quasi-Eulerian) meshes have been used. This paper performs an evaluation on these three types of meshes. The emphasis is placed on the applicability of the method in analyzing fluid-structure interaction problems in HCDA analysis

The Physics of RNA-Protein Binding

RNA-protein binding is important in many biological processes. These processes depend on the structural properties of the RNA, DNA and proteins involved. In this thesis we have investigated the nature of these interactions at the scale of coarse grained interactions, in atomistic detail and with analytical continuum theories. By exploring the dynamics of these biopolymers at these different scales, we hope to shed light on the important phenomena and characteristics that govern the biological processes involved. First we show that the structural flexibility of these polymers affects he binding energy measured in MD simulations and can help understand the different packaging scenarios in in-vitro viral reconstitution. Then using analytical models we show how flexibility can aid it non-specific binding given the strength of interaction compared to thermal energy between the binding of polymers.We finish this thesis by looking at coarse grained brownian dynamics simulations for the bonds in a chain to represent the non-linear viscoelastic behavior of proteins deforming under force. We see both equilibrium mechanical induced melting of the chain and a dynamical phase transition in the response of the chain under a varying drive amplitude and frequency of and AC applied force out of equilibrium. Using the model to understand the dynamics of a deformable chain under force, we explore how this model can provide insight into the binding of deformable structure forming chains that mimic biopolymers like RNA, DNA and proteins

Parameter studies to determine sensitivity of slug impact loads to properties of core surrounding structures

A sensitivity study of the HCDA slug impact response of fast reactor primary containment to properties of core surrounding structures was performed. Parameters such as the strength of the radial shield material, mass, void, and compressibility properties of the gas plenum material, mass of core material, and mass and compressibility properties of the coolant were used as variables to determine the magnitude of the slug impact loads. The response of the reactor primary containment and the partition of energy were also given. A study was also performed using water as coolant to study the difference in slug impact loads

Response of a base-isolated large liquid metal reactor plant to seismic loads

In recent years, base isolation has been applied to various civil structures such as bridges and buildings for the purpose of reducing its acceleration to below the level of ground accelerations during seismic events. The basic principal of base isolation is to introduce a soft layer of material between structure foundation to allow a degree of flexibility in horizontal motions which could reduce the seismic accelerations during earthquakes. If base isolation is properly designed, it shifts the fundamental frequency of the structure away from the damaging frequency range of earthquakes. Thus, the seismic loads transmitted to the structure can be greatly reduced. This is particularly important in Liquid Metal Reactor (LMR) plants, because the components of primary system such as reactor vessel and piping loops are designed to be thin-walled structures and have little inherent seismic resistance. Thus, the use of base isolation offers a viable and effective approach that permits the reactor structures to better withstand the seismic loading. This paper deals with the seismic response of a base isolated large-scale LMR plant. The analysis model was based on a preliminary nuclear island layout developed by EPRI during the concept development phase of the large-scale prototype breeder (LSPB) project. The nuclear island has a dimension of 184'-0'' {times} 210'-6''; the reactor vessel has an ID of 62 ft and an overall length of 70 ft. Two soil conditions have been considered in the analysis. One is a hard-soil site having a shear wave velocity of 6000 ft/s, and the other is a soft-soil site having a shear wave velocity of 2000 ft/s. For comparison purposes, the responses of a conventional plant (unisolated) was also analyzed. 3 figs., 1 tab

Comparisons of REXCO code predictions with SRI SM-2 experimental results

SRI International has performed a series of simple model (SM) experiments for the Clinch River Breeder Reactor Project (CRBR). The SM tests consisted of five experiments. The energy source used to simulate the core-disassembly accident loads was a PETN-microsphere mixture, which was well calibrated. These experiments were well instrumented and performed under carefully controlled conditions. The experimental data can be used as reliable test data for validation of computer codes, as well as the modeling technique used in the computer analysis. This paper deals with the REXCO-HEP code predictions of the SRI SM-2 test, which was a dynamic test performed on 1/20th scale model of the CRBR. Two calculations have been performed: one used the pressure history P(t) of the core detonation products as input, and the other the pressure-volume relation (P-V) of the detonation products as input. The pressure loadings and wall deformations obtained with the P(t) calculations are in better agreement with the experimental measurements than those obtained with the P-V calculations. This is because the P-V relations used in the code calculation were derived from the pressure gauge readings of the core gas, the measured surface motions of the slug and the calculated compressibility of the coolant; they may become less accurate at low pressures. Therefore, in performing code validation calculations, the pressure history of the core gas should be used in the analysis to describe the behavior of the core gas, if the P(t) values are available from the experimental data