HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT DYTRAN ANALYSIS OF SEISMICALLY INDUCED FLUID STRUCTURE INTERACTION IN A HANFORD DOUBLE SHELL PRIMARY TANK

Abstract

M&D Professional Services, Inc. (M&D) is under subcontract to Pacific Northwest National Laboratories (PNNL) to perform seismic analysis of the Hanford Site Double-Shell Tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project-DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST System at Hanford in support of Tri-Party Agreement Milestone M-48-14. The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The overall seismic analysis of the DSTs is being performed with the general-purpose finite element code ANSYS'. The global model used for the seismic analysis of the DSTs includes the DST structure, the contained waste, and the surrounding soil. The seismic analysis of the DSTs must address the fluid-structure interaction behavior and sloshing response of the primary tank and contained liquid. ANSYS has demonstrated capabilities for structural analysis, but has more limited capabilities for fluid-structure interaction analysis. The purpose of this study is to demonstrate the capabilities and investigate the limitations of the finite element code MSC.Dytranz for performing a dynamic fluid-structure interaction analysis of the primary tank and contained waste. To this end, the Dytran solutions are benchmarked against theoretical solutions appearing in BNL 1995, when such theoretical solutions exist. When theoretical solutions were not available, comparisons were made to theoretical solutions to similar problems, and to the results from ANSYS simulations. Both rigid tank and flexible tank configurations were analyzed with Dytran. The response parameters of interest that are evaluated in this study are the total hydrodynamic reaction forces, the impulsive and convective mode frequencies, the waste pressures, and slosh heights. To a limited extent, primary tank stresses are also reported. The capabilities and limitations of ANSYS for performing a fluid-structure interaction analysis of the primary tank and contained waste were explored in a parallel investigation and documented in a companion report (Carpenter and Abatt [2006]). The results of this study were used in conjunction with the results of the global ANSYS analysis reported in Carpenter et al. (2006) and the parallel ANSYS fluid-structure interaction analysis to help determine if a more refined sub-model of the primary tank is necessary to capture the important fluid-structure interaction effects in the tank and if so, how to best utilize a refined sub-model of the primary tank. The results of this study demonstrate that Dytran has the capability to perform fluid-structure interaction analysis of a primary tank subjected to seismic loading. With the exception of some isolated peak pressures and to a lesser extent peak stresses, the results agreed very well with theoretical solutions. The benchmarking study documented in Carpenter and Abatt (2006) showed that the ANSYS model used in that study captured much of the fluid-structure interaction (FSI) behavior, but did have limitations for predicting the convective response of the waste. While Dytran appears to have stronger capabilities for the analysis of the FSI behavior in the primary tank, it is more practical to use ANSYS for the global evaluation of the tank. Thus, Dytran served the purpose of helping to identify limitations in the ANSYS FSI analysis so that those limitations can be addressed in the structural evaluation of the primary tank.