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Some remaining problems in HCDA analysis. [LMFBR]

Description: The safety assessment and licensing of liquid-metal fast breeder reactors (LMFBRs) requires an analysis on the capability of the reactor primary system to sustain the consequences of a hypothetical core-disruptive accident (HCDA). Although computational methods and computer programs developed for HCDA analyses can predict reasonably well the response of the primary containment system, and follow up the phenomena of HCDA from the start of excursion to the time of dynamic equilibrium in the system, there remain areas in the HCDA analysis that merit further analytical and experimental studies. These are the analysis of fluid impact on reactor cover, three-dimensional analysis, the treatment of the perforated plates, material properties under high strain rates and under high temperatures, the treatment of multifield flows, and the treatment of prestressed concrete reactor vessels. The purpose of this paper is to discuss the structural mechanics of HCDA analysis in these areas where improvements are needed.
Date: January 1, 1981
Creator: Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Application of containment codes to LMFBRs in the United States

Description: The application of containment codes to predict the response of the fast reactor containment and the primary piping loops to HCDAs is described. Five sample problems are given to illustrate their applications. The first problem deals with the response of the primary containment to an HCDA. The second problem deals with the coolant flow in the reactor lower plenum. The third proem concerns sodium spillage and slug impact. The fourth problem deals with the response of a piping loop. The fifth problem analyzes the response of a reactor head closure. Application of codes in parametric studies and comparison of code predictions with experiments are also discussed.
Date: January 1, 1977
Creator: Chang, Y. W.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: January 1, 1979
Creator: Chang, Y.W. & Gvildys, J.
Partner: UNT Libraries Government Documents Department

Structural dynamics in LMFBR containment analysis: a brief survey of computational methods and codes

Description: In recent years, the use of computer codes to study the response of primary containment of large, liquid-metal fast breeder reactors (LMFBR) under postulated accident conditions has been adopted by most fast reactor projects. Since the first introduction of REXCO-H containment code in 1969, a number of containment codes have evolved and been reported in the literature. The paper briefly summarizes the various numerical methods commonly used in containment analysis in computer programs. They are compared on the basis of truncation errors resulting in the numerical approximation, the method of integration, the resolution of the computed results, and the ease of programming in computer codes. The aim of the paper is to provide enough information to an analyst so that he can suitably define his choice of method, and hence his choice of programs.
Date: January 1, 1977
Creator: Chang, Y. W. & Gvildys, J.
Partner: UNT Libraries Government Documents Department

Site characteristics of Argonne National Laboratory in Illinois

Description: This report reviews the geology and topography of the Argonne National Laboratory, near Lemont, Illinois. It describes the thickness and stratigraphy of soils, glacial till, and bedrock in and adjacent to the laboratory and support facilities. Seismic surveys were also conducted through the area to help determine the values of seismic wave velocities in the glacial till which is important in determining the seismic hazard of the area. Borehole log descriptions are summarized along with information on area topography.
Date: January 1, 1995
Creator: Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Comparison of ICEPEL predictions with single elbow flexible piping system experiment

Description: The ICEPEL Code for coupled hydrodynamic-structural response analysis of piping systems is used to analyze an experiment on the response of flexible piping systems to internal pressure pulses. The piping system consisted of two flexible Nickel-200 pipes connected in series through a 90/sup 0/ thick-walled stainless steel elbow. A tailored pressure pulse generated by a calibrated pulse gun is stabilized in a long thick-walled stainless steel pipe leading to the flexible piping system which ended with a heavy blind flange. The analytical results of pressure and circumferential strain histories are discussed and compared against the experimental data obtained by Stanford Research Institute.
Date: January 1, 1978
Creator: A-Moneim, M.T. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Analysis of LMFBR containment response to an HCDA using a multifield Eulerian code. [MICE code]

Description: During a hypothetical core disruptive accident (HCDA), a core meltdown may cause the fuel cladding to rupture and the fuel fragments to penetrate into the sodium coolant. The heat in the molten fuel may cause the liquid sodium to boil, changing its phase. The interactions between materials are so complicated that a single-material model with homogenized material properties is not adequate. In order to analyze the above phenomena more realistically, a Multifield Implicit Continuous-Fluid Eulerian containment code (MICE) is being developed at Argonne National Laboratory (ANL) to solve the multifield fluid-flow problems in which the interpenetrations of materials, heat transfer, and phase changes are considered in the analysis. The hydrodynamics of the MICE code is based upon the implicit multifield (IMF) method developed by Harlow and Amsden. A partial donor-cell formulation is used for the calculation of the convective fluxes to minimize the truncation errors, while the Newton-Raphson method is used for the numerical iterations. An implicit treatment of the mass convection together with the equation of state for each material enables the method to be applicable to both compressible and incompressible flows. A partial implicit treatment of the momentum-exchange functions allows the coupling drag forces between two material fields to range from very weak to those strong enough to tie the fields completely. The differential equations and exchange functions used in the MICE code, and the treatment of the fluid and structure interactions as well as the numerical procedure are described. Two sample calculations are given to illustrate the present capability of the MICE code.
Date: January 1, 1977
Creator: Chu, H.Y. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Eulerian method for large-displacement fluid-structure interaction in reactor containments

Description: An Eulerian method for analyzing large-displacement fluid-structure interaction in reactor containments is presented. The emphasis is on the development of a generalized hydrodynamic scheme to treat the irregular cells created by the movement of the structure with respect to the fixed Eulerian coordinates. A relaxation equation is derived from the boundary condition at the fluid-structure interface for the solution of the pressure at the interface. By combining this with the Poisson equation a sufficient set of equations is obtained for the determination of the advanced-time pressures in the fluid region and at the fluid-structure interfaces. Sample problems are given to illustrate the analysis.
Date: January 1, 1977
Creator: Chang, Y.W. & Wang, C.Y.
Partner: UNT Libraries Government Documents Department

Gap and impact of LMR (Liquid Metal Reactor) piping systems and reactor components

Description: Because of high operation temperature, the LMR (Liquid Metal Reactor) plant is characterized by the thin-walled piping and components. Gaps are often present to allow free thermal expansion during normal plant operation. Under dynamic loadings, such as seismic excitation, if the relative displacement between the components exceeds the gap distance, impacts will occur. Since the components and piping become brittle over their design lifetime, impact is of important concern for it may lead to fractures of components and other serious effects. This paper deals with gap and impact problems in the LMR reactor components and piping systems. Emphasis is on the impacts due to seismic motion. Eight sections are contained in this paper. The gap and impact problems in LMR piping systems are described and a parametric study is performed on the effects of gap-induced support nonlinearity on the dynamics characteristics of the LMR piping systems. Gap and impact problems in the LMR reactor components are identified and their mathematical models are illustrated, and the gap and impact problems in the seismic reactor scram are discussed. The mathematical treatments of various impact models are also described. The uncertainties in the current seismic impact analyses of LMR components and structures are presented. An impact test on a 1/10-scale LMR thermal liner is described. The test results indicated that several clusters of natural modes can be excited by the impact force. The frequency content of the excited modes depends on the duration of the impact force; the shorter the duration, the higher the frequency content.
Date: January 1, 1987
Creator: Ma, D.C.; Gvildys, J. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Sloshing response of nonuniform density liquid in a laterally excited tank

Description: A large number of high level waste (HLW) storage tanks at various facilities contain liquid with nonuniformity density. Exploratory studies show that the dynamic response of a tank containing two liquids is quite different from that of an identical tank containing only one liquid. To design and evaluate the HLW storage tanks it is necessary to understand the sloshing response of tanks that contain liquid with nonuniform density. The system considered is a circular cylindrical tank containing a liquid whose density increases with the liquid depth. The density distribution along the depth can be of any arbitrary continuous function. In the analysis, the liquid field is divided into n layers. The thicknesses of the liquid layers can be different, but the density of each liquid layer is considered to be uniform and its value is assigned to be the value of the original liquid density at the mid-height of that layer. The problem is solved by the transfer matrix technique. The effect of the nonuniform liquid density on the sloshing response is illustrated in a numerical example in which the linear and cosine distributions of the liquid density are assumed. The response functions examined include the sloshing frequencies, surface wave height, and the associated convective hydrodynamic pressure. The results are presented in tabular and graphical forms. It is found that the natural frequencies of the sloshing motion for nonuniform density liquid are lower than those of the uniform density liquid of the same total depth contained in an identical tank. Also, it is shown that for nonuniform density liquid, the maximum sloshing wave height may increase significantly and the magnitude of the convective hydrodynamic pressure may be quite different compared with that of a uniform liquid contained in an identical tank.
Date: October 1, 1993
Creator: Tang, Y. & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Dynamic characteristics of Bridgestone low shear modulus-high damping seismic isolation bearings

Description: Bridgestone Company of Japan is one of the leading seismic bearing manufacturers in the world. Their bearings have very good performance records. It appears that Bridgestone`s high damping bearings are made of a blend of filled natural and synthetic rubbers with fillers and plastizers whereas in the United States, the high damping compound is a carbon filled natural rubber. To compare the properties of the two different kinds of high damping compounds, Argonne National Laboratory (ANL) purchased eight bearings from Bridgestone: four of which were made of high shear modulus-high damping rubber compound KL401; the other four were made of low shear modulus-high damping rubber compounds: two with KL301 elastomer and two with KL302 elastomer. Tests of the Bridgestone bearings were performed at the Earthquake Engineering Research Center. The dynamic characteristics of the high shear modulus Bridgestone bearings, KL401, are described in ANL/Shimizu Report ANL-003. This report describes the dynamic and failure characteristics of the low shear modulus Bridgestone bearings, KL301 and KL302.
Date: June 1, 1993
Creator: Chang, Y. W. & Seidensticker, R. W.
Partner: UNT Libraries Government Documents Department

Free vibration analysis of a tank containing two liquids

Description: A study of the dynamic characteristics of rigidly supported upright circular cylindrical tanks containing two different liquids is presented. The governing differential equations for the tank-two liquid system are obtained by application of the Rayleigh-Ritz procedure in combination with Lagrange`s equation. The response functions examined include the fundamental natural frequency, the associated mode of vibration and hydrodynamic pressure exerted against the tank wall. Unlike the cases of tanks containing one liquid in which the dynamic response is controlled by four parameters, the dynamic response of a tank that contains two liquids is controlled by six parameters. The numerical results are presented in tabular and graphic forms, and are compared with those of the identical tank filled with one liquid. Also, a simple approximate equation for evaluating the fundamental natural frequency for preliminary design is proposed.
Date: May 1, 1993
Creator: Tang, Yu & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Rocking response of tanks containing two liquids

Description: Liquid storage tanks are important components of industrial facilities and, when located in earthquake prone regions, should be designed to withstand the earthquakes to which they may be subjected. There are cases in which the density of the tank content is not uniform. For such cases, the dynamic responses of tanks containing liquids with different densities must be studied. A study on the dynamic response of upright circular cylindrical liquid-storage tanks containing two different liquids under a rock base motion with an arbitrary temporal variation is presented. Only rigid tanks were studied. The response quantities examined include the hydrodynamic pressure, sloshing wave height and the associated frequencies, base shear and moments. Each of these response quantities is expressed as the sum of the so-called impulsive component and convective component. Unlike the case of tanks containing one liquid, in which the response is controlled by one parameter, height-to-radius ratio, the response of tanks containing two different liquids are controlled by three parameters: height-to-radius ratio, and mass density ratio and height ratio of the two liquids. The interrelationship of the responses of the tank-liquid system to rocking and lateral base excitations is established by examining numerical results extensively. It is found that some of the response quantities for a tank-liquid system under a rocking base motion can be determined from the corresponding response quantities for an identical tank under a horizontal base motion.
Date: June 1, 1993
Creator: Tang, Yu & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

The exact solutions to the dynamic response of tanks containing two liquids

Description: The exact solution to the dynamic response of circular cylindrical tanks containing two liquids, considering the gravitational (g) effect at the interface of the two liquids, is presented. Only rigid tanks were studied. The solution is expressed as the superposition of the so-called impulsive and convective solutions. The results are compared with those obtained by neglecting the gravitational effect at the interface to elucidate the g effect and with those of the tanks containing only one liquid to elucidate the effect of the interaction between two liquids. The response functions examined include the hydrodynamic pressure, base shear, base moments, sloshing motions at surface and at the interface of two liquids and the associated sloshing frequencies. It is found that there are two natural frequencies associated with each sloshing mode in contrast to only one frequency associated with each sloshing mode if the g effect at the interface is neglected; also, the convective pressure has a jump at the interface of two liquids, whereas the impulsive pressure is continuous at the interface. Further, it is shown that in a tank containing two liquids the maximum sloshing wave height may increase significantly, and the fundamental frequency of the sloshing motion is lower than that of an identical tank filled with only one liquid. Additionally, the well-known mechanical model for tanks containing one liquid is generalized for tanks containing two liquids.
Date: February 1, 1993
Creator: Tang, Y. & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Free vibration analysis of partially filled liquid storage tanks

Description: A study on the free vibration analysis of partially filled liquid storage tanks is presented. The tanks considered are the upright circular cylindrical tanks that are rigidly supported at the base. The top of the tanks are either free or constrained. Two types of constraints are considered, namely, hinged and roller support. The governing differential equations for the tank-liquid system are obtained by application of the Rayleigh-Ritz procedure in combination with Lagrange`s equation. The response functions examined include the frequency of the fundamental mode of vibration of the tank-liquid system and the associated modal pressure.
Date: May 1, 1993
Creator: Tang, Yu & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Impulsive response of nonuniform density liquid in a laterally excited tank

Description: A study on the impulsive component of the dynamic response of a liquid of nonuniform density in a tank undergoing lateral base excitations is presented. The system considered is a circular cylindrical tank containing an incompressible and inviscid liquid whose density increases with the liquid depth. The density distribution along the depth can be of any arbitrary continuous or discontinuous function. In the analysis, the liquid field is divided into n layers. The thickness of the liquid layers can be different, but the density of each liquid layer is considered to be uniform and is equal to the value of the original liquid density at the mid-height of that layer. The problem is solved by the eigenfunction expansion in conjunction with the transfer matrix technique. The effect of the nonuniform liquid density on the impulsive component of the dynamic response is illustrated in a numerical example in which the linear and cosine distributions of the liquid density are assumed. The response quantities examined include the impulsive pressure, base shear and moments. The results are presented in tabular and graphical forms. It is found that the impulsive pressure distribution along the tank wall is not sensitive to the detailed distribution function of the density, and the base shear and moments for the nonuniform liquid can be estimated by assuming an equivalent uniform liquid density that preserves the total liquid weight. The effect of tank flexibility is assessed by a simple approach in which the response quantities for flexible tanks are evaluated by simplified equations.
Date: April 1, 1994
Creator: Tang, Y. & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Seismic fluid-structure interaction analysis of a large LMFBR reactor

Description: This paper describes a seismic analysis which includes fluid-structure interactions for a large LMFBR reactor with many internal components and structures. Two mathematical models were employed. An axisymmetrical model was used for the vertical excitation analysis whereas a three-dimensional model was used for the horizontal excitation analysis. In both analyses, the sodium coolant was treated by continuum fluid elements. Thus, important seismic effects such as fluid-structure interaction, free-surface sloshing, fluid coupling, etc. are included in the analysis. This study is useful to the design of future LMFBR reactors. The results of this study can be used to improve the margin of safety of LMFBR plants under seismic conditions.
Date: January 1, 1984
Creator: Ma, D.C.; Gvildys, J. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Free vibration analysis of partially filled liquid storage tanks

Description: A study on the free vibration analysis of partially filled liquid storage tanks is presented. The tanks considered are the upright circular cylindrical tanks that are rigidly supported at the base. the top of the tanks are either free or constrained. Two types of constraints are considered, namely, hinged and roller support. The governing differential equations for the tank-liquid system are obtained by application of the Rayleigh-Ritz procedure in combination with Lagrange`s equation. The response functions examined include the frequency of the fundamental mode of vibration of the tank-liquid system and the associated modal pressure.
Date: June 1, 1994
Creator: Tang, Yu & Chang, Y. W.
Partner: UNT Libraries Government Documents Department

Dominant seismic sloshing mode in a pool-type reactor tank

Description: 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.
Date: January 1, 1987
Creator: Ma, D.C.; Gvildys, J. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Bauschinger effects and work-hardening in spheroidized steels

Description: The effects of cementite particles and subgrain boundaries on work-hardening behavior of spheroidized carbon steels were investigated by making direct measurements of residual internal stresses. These internal stresses developed due to plastic incompatibilities between elastic particles and an elastic-plastic matrix. A continuum analysis of these internal stress fields, based upon a multiple slip model, is presented and is found to be in good accord with the experiments. The internal stresses appear to saturate in the plastic strain range of 3 approx. 5% where a transition in strain-hardening behavior was observed (''double-n'' behavior), and to contribute approximately 20% to total work-hardening. The cementite-particle-pinned-subgrain-boundaries, formed during a post-quench annealing treatment, were found to lower the internal stress, thus indicating that they assisted the relaxation processes of entrapped Orowan loops by acting as sources of dislocations. The flow stress increment in dispersion hardened alloys due to work-hardening consisted of internal stress, forest stress, and source-shortening stress. The flow stress curves of spheroidized carbon steels were found to be described by a modified mean-square-root addition law of the form: sigma/sub f/ = sigma/sub epsilon/sub p/=0/ = sigma/sup i/ ((..delta..sigma/sup s/)/sup 2/ + (..delta..sigma/sup ss/)/sup 2/ + (sigma/sup f/)/sup 2/)/sup 1///sup 2/.The maximum normal interfacial stresses were estimated from the data. The maximum values occurred in the tensile direction at the poles of particles and the magnitude was found to be approximately one half of flow stress. The significance of these stresses regarding interface cavitation is discussed briefly.
Date: May 1, 1977
Creator: Chang, Y W
Partner: UNT Libraries Government Documents Department

Sloshing response of a reactor tank with internals

Description: The sloshing response of a large reactor tank with in-tank components is presented. The study indicates that the presence of the internal components can significantly change the dynamic characteristics of the sloshing motion. The sloshing frequency of a tank with internals is considerably higher than that of a tank without internal. The higher sloshing frequency reduces the sloshing wave height on the free-surface but increases the dynamic pressure in the fluid.
Date: January 1, 1984
Creator: Ma, D.C.; Gvildys, J. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department

Evaluation of fluid-modeling techniques in the seismic analysis of LMFBR reactors

Description: Fluid modeling is of great importance in the seismic analysis of the LMFBR primary system. If the fluid model used in the analysis is too simplified, the results could be very uncertain. On the other hand, if the model is too detailed, considerable difficulty might be encountered in the analysis. The objectives of this study are to examine the validity of the two commonly used fluid modeling techniques. i.e. simplified added mass method and lumped mass method and to provide some useful information on the treatment of fluid in seismic analysis. The validity of these two methods of analysis is examined by comparing the calculated seismic responses of a fluid-structure system based on these two methods with that calculated from a coupled fluid-structure interaction analysis in which the fluid is treated by continuum fluid elements.
Date: January 1, 1983
Creator: Ma, D.C.; Gvildys, J. & Chang, Y.W.
Partner: UNT Libraries Government Documents Department