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This paper describes the seismic study of a 450-MWe liquid metal reactor (LMR) under 0.3-g SSE ground excitation. Two calculations were performed using the new design configuration. They deal with the seismic response of the reactor vessel, the guard vessel and support skirt, respectively. In both calculations, the stress and displacement fields at important locations of those components are investigated. Assessments are also made on the elastic and inelastic structural capabilities for other beyond-design basis seismic loads. Results of the reactor vessel analysis reveal that the maximum equivalent stress is only about half of the material yield stress. For the guard vessel and support skirt, the stress level is very small. Regarding the analysis if inelastic structural capability, solutions of the Newmark-Hall ductility modification method show that the reactor vessel can withstand seismics with ground ZPAs ranging from 1.015 to 1.31 g, which corresponds to 3.37 to 4.37 times the basic 0.3-g SSE. Thus, the reactor vessel and guard vessel are strong enough to resist seismic loads. 4 refs., 10 figs., 5 tabs.
This paper describes the seismic analysis of a 450-MWe pool-type liquid metal reactor (LMR) under 0.3 g SSE ground excitations. It also assess the ultimate inelastic structural capabilities for other beyond-design-basis seismic events. Calculation is focused on a new design configuration where the vessel thickness is reduced considerably compared to the previous design (Ma and Gvildys, 1987). In the analysis, the stress and displacement fields at important locations of the reactor vessel, guard vessel, and support skirt are investigated. Emphasis is placed on the horizontal excitation in which large stress is generated. The possibility of impact between the reactor and guard vessels is examined. In the reactor vessel analysis, the effect of fluid-structure interaction is included. Attention is further given to the maximum horizontal acceleration of the reactor core as well as the relative displacement between the reactor core and the upper internal structure. The Argonne National Laboratory augmented three-dimensional Fluid-Structure Interaction program, FLUSTR-ANL is utilized for performing the base calculation where ground excitation is assumed to be 0.3 g SSE. The Newmark-Hall Ductility modification method was used for the beyond-design-basis seismic events. In both calculations, stress fields generated from the horizontal and vertical excitations are evaluated separately. The resultant stresses due to combined actions of these events are computed by the SRSS method. 4 refs., 5 figs., 2 tabs.
In the design of the core support system for liquid metal reactors (LMR) against earthquakes, the major concerns are directed toward the structural integrity as well as the reactivity control. This means that, in addition to the stress levels, maximum displacements and accelerations should also be within their allowable limits. This investigation studies the seismic responses of a large pool-type LMR with different design approaches to support the reactor core. Different core support designs yield different frequency ranges and responses. Responses of these designs to the given floor response spectra are required to satisfy a set of criteria which are common to all designs. 5 refs., 4 figs.
The system seismic analysis of an innovative primary system for a large pool type liquid metal fast breeder reactor (LMFBR) plant is presented. In this primary system, the reactor core is supported in a way which differs significantly from that used in previous designs. The analytical model developed for this study is a three-dimensional finite element model including one-half of the primary system cut along the plane of symmetry. The model includes the deck and deck mounted components, the reactor vessel, the core support structure, the core barrel, the radial neutron shield, the redan, and the conical support skirt. The sodium contained in the primary system is treated as a lumped mass appropriately distributed among various components. The significant seismic behavior as well as the advantages of this primary system design are discussed in detail.
Large-diameter LMR (Liquid Metal Reactor) tanks contain a large volume of sodium coolant and many in-tank components. A reactor tank of 70 ft. in diameter contains 5,000,000 of sodium coolant. Under seismic events, the sloshing wave may easily reach several feet. If sufficient free board is not provided to accommodate the wave height, several safety problems may occur such as damage to tank cover due to sloshing impact and thermal shocks due to hot sodium, etc. Therefore, the sloshing response should be properly considered in the reactor design. This paper presents the results of the sloshing analysis of a pool-type reactor tank with a diameter of 39 ft. The results of the fluid-structure interaction analysis are presented in a companion paper. Five sections are contained in this paper. The reactor system and mathematical model are described. The dominant sloshing mode and the calculated maximum wave heights are presented. The sloshing pressures and sloshing forces acting on the submerged components are described. The conclusions are given.
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'' x 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.
To safely assess the adequacy of the LMR piping, a three-dimensional piping code, SHAPS, has been developed at Argonne National Laboratory. This code was initially intended for calculating hydrodynamic-wave propagation in a complex piping network. It has salient features for treating fluid transients of fluid-structure interactions for piping with in-line components. The code also provides excellent structural capabilities of computing stresses arising from internal pressurization and 3-D flexural motion of the piping system. As part of the development effort, the SHAPS code has been further augmented recently by introducing the capabilities of calculating piping response subjected to seismic excitations. This paper describes the finite-element numerical algorithm and its applications to LMR piping under seismic excitations. A time-history analysis technique using the implicit temporal integration scheme is addressed. A 3-D pipe element is formulated which has eight degrees of freedom per node (three displacements, three rotations, one membrane displacement, and one bending rotation) to account for the hoop, flexural, rotational, and torsional modes of the piping system. Both geometric and material nonlinearities are considered. This algorithm is unconditionally stable and is particularly suited for the seismic analysis.