Y.W. Chang

Seismic behavior of liquid-filled shells

Abstract The seismic response of shell structures containing a fluid is generally evaluated with the aid of the added-mass concept. This paper presents a study of the seismic response of elastic tanks based on an alternative approach which includes both acoustic and sloshing interaction of the fluid and structure. Numerical examples are presented to demonstrate the influence of the tank-wall flexibility on the fluid dynamic pressure and the sloshing wave height. The post-earthquake sloshing behavior is also examined.

Numerical simulation of seismic sloshing of LMR reactors

Abstract Numerical simulations of EPRI/CRIEPI sloshing experiments have been performed by Argonne National Laboratory using the ANL-developed FLUSTR computer code. The number of meshes used in the mathematical model for numerical simulation is rather small. Thus, the computing cost is relatively inexpensive. Results of numerical simulations of the sloshing responses of two test configurations (1 and 2) which were performed by CRIEPI are described in detail. Natural frequencies and sloshing wave heights and fluid pressures at locations of sensors are calculated. The predicted values are compared with the experimental data. In all comparisons, the agreement is very good. Thus, these computer codes can be used for numerical simulation of seismic sloshing.

Analysis of the primary containment response using a hydrodynamic-elastic-plastic computer code

Abstract The dynamic response of the primary reactor containment system to a hypothetical core disruptive accident (HCDA) is determined from the basic equations of mass, momentum, and energy, and the equations of state of the medium. These equations are first expressed in material coordinates and then set into finite difference form solved numerically on the computer using a hydrodynamic-elastic-plastic computer code, REXCO-HEP developed at ANL. Propagation of pressure waves, loads imposed on different parts of the reactor components, and the resulting deformations are determined at every time step throughout the sequence of the calculation. As a sample calculation, the code was applied to analyze the response of the FFTF reactor to a 150 MWsec HCDA. The mathematical model is described in detail, particularly in the areas of modeling reactor internals and extending the time range to cover the entire excursion phenomenon. Finally, the results obtained from the computer analysis are discussed in detail.

Seismic sloshing experiments of large pool-type fast breeder reactors

Abstract This paper presents the results of seismic sloshing experiments performed on large pool-type LMFBR vessels. Two types of tests were performed. The first type of test was designed to understand the basis phenomena of sloshing (limited to linear sloshing only) and evaluate the effects of the deck-mounted components (i.e., IHXs, pumps, and UIS) on sloshing wave heights using a 1 10 - scale model (diameter 2.23 m x H 1.03 m) of the LSPB 1340 MWe pool plant. The second type of test was designed to evaluate the structural integrity of the thermal baffles of the roof-deck to withstand sloshing impulsive pressures (focused on nonlinear sloshing), using a two-dimensional 1 3 - scale model (L 8 m × W 3 m × H 2.6 m) of a typical 1000 MWe pool plant. The results of the linear sloshing tests have shown that: (1) the vessel wall stiffness has no effect on the sloshing natural frequency; (2) sloshing wave heights are lowered by 30% to 50% in the presence of the deck-mounted components; and (3) damping factors of sloshing are not influenced by the wall stiffness while they are increased by the presence of the deck-mounted components. The results of the nonlinear sloshing tests are that: (1) the maximum impulsive pressure occurs when the first effective wave strikes at the roof-deck, and thereafter the impulsive pressure decreases irrespective of the impact velocity of the fluid; (2) the first effective wave refers to the case in which the height of the fluid free surface becomes nearly twice the height of the cover gas space; and (3) the structural integrity of the thermal baffles for the roof-deck against the sloshing load was confirmed. In addition to these results, two sloshing-caused problems were identified. The first one is the spillover of hot sodium into the gas-dam type thermal insulator. The second one is cover-gas entrainment into sodium which might lead to a transient overpower (TOP) incident because of the presence of gas bubbles in the reactor core. Their countermeasures have been suggested.

Seismic analysis of LMR reactor tanks

Abstract This paper deals with the methods of seismic analysis of LMR reactor tanks. Mathematical models of a reactor tank and LMR plant are given. Various methods of seismic analysis suitable for the analysis of fluid-structure interaction of LMR plants and their advantages and drawbacks are described. Emphasis is placed on efficiency of the numerical algorithm. The computer code FLUSTR-ANL, deveoped for seismic analysis of LMR components, is also described.

Hydrodynamic response of primary reactor containment to high-energy excursions☆

Abstract A numerical method for calculating the two-dimensional hydrodynamic response of a primary reactor containment system to a high-energy excursion is described. Equations of hydrodynamics and equations of state of reactor materials are expressed in Lagrangian form and then set into finite-difference equations. Shock discontinuities are eliminated by the use of the Von Neumann-Richtmyer pseudo-viscosity q . These equations, along with pressure pulse and other pertinent input data are programmed for solution on the IBM-360 computer. Propagation of shock waves, loads imposed on different parts of the reactor components, and the resulting damage are determined at every time step until the steel vessel ruptures or the force acting on the rotating shield plug exceeds the strength of the plug hold-down device. Calculated displacements and pressures at all spatial points at any instant of time also can be given in pictorial form.

Application of containment codes to LMFBRs in the united states

Abstract This paper describes the application of containment codes to predict the response of the fast reactor containment and the primary piping loops to HCDAs. 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 problem 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.

Analysis of nonlinear fluid-structure interaction in LMFBR containment

Abstract A generalized Eulerian method has been incorporated into ICECO for analyzing the nonlinear fluid-structure interaction in the primary containment of an LMFBR, consisting of complicated structural components such as the radial shield, core barrel, core-support structure, and the primary vessel. The method employs a Poisson equation to determine the hydrodynamic pressure in the fluid region, while using a relaxation equation to compute the pressure adjacent to the structure. A generalized coupling scheme is developed for treating the sliding condition at the fluid-structure interface, modeling the perforated structure, and analyzing the fluid motion at the geometrical discontinuities. Detailed formulations are given. Sample problems concerning wave propagation in a typical reactor containment are presented. It is shown from the results that this implicit, iterative method is unconditionally stable, and is especially suitable for excursions involving large material distortions.

Computer modelling of piping components for transient hydrodynamic-structural response

Abstract The paper describes three new piping components that are coupled with existing pipe and elbow models so that transient hydrodynamic-structural response analysis of general piping systems is possible. The three models are: a generalized piping component model, a tee-branching junction model, and a surge tank model. Optional interior rigid wall simulation and heat exchanger tube bundle representation in the generalized piping component model makes possible its use in modelling valves, pipe expansions and reducers, and heat exchangers. Two-dimensional implicit continuous-fluid Eulerian finite difference technique is utilized in the hydrodynamics calculations. A convected coordinates finite element method is used in the structural analysis which considers both the membrane and bending strengths of the thin axisymmetric shells representing the walls.

Comparison of icepel code predictions with straight flexible pipe experiments

Abstract Experimental results on the pressure pulse propagation along plastically deforming pipes are interpreted. The tests are also analyzed by the ICEPEL piping code and the results compared with the experimental measurements of both pressure and circumferential strain histories in the pipe.