Pool Swell Research Articles

Modeling pressure suppression pool hydrodynamics in the ABWR containment

This paper focuses on the assessment of pressure suppression pool hydrodynamics in the advanced boiling water reactor (ABWR) containment under design-basis, loss-of-coolant accident (LOCA) conditions. The paper presents a mechanistic model for predicting various suppression pool hydrodynamics parameters. A phenomena identification and ranking table (PIRT) applicable to the ABWR containment pool hydrodynamics analysis is used as a basis for the development of the model. The highly ranked phenomena are represented by analytic equations or empirical correlations. The best estimate and several sensitivity calculations are performed for the ABWR containment using this model. Results of the sensitivity calculations are also presented that demonstrate the influence of key model parameters and assumptions on the pool hydrodynamics parameters. A comparison of model predictions to the results of the licensing analyses shows reasonable agreement. Comparison of the results of the proposed model to experimental data shows that the model predicted top vent clearance time, the pool swell height, and the bubble breakthrough elevation are within 10% of the data. The predicted pool surface velocity and the liquid slug thickness are within 30% of the measurements, which is considered adequate given the large uncertainties in the experimental measurements.

Evaluation of pool swell velocity during large break loss of coolant accident in boiling water reactor Mark III containment design

Abstract In boiling water reactor (BWR) design, safety scenarios such as main steam line break need to be evaluated. After the main steam line break, the steam will fill the upper dry well of the containment. It will then enter the vertical vent and eventually flow into the suppression pool via horizontal vents. The steam will create large bubbles in the suppression pool and cause the pool to swell. The impact of the pool swell on the equipment inside the pool and containment structure needed to be evaluated for licensing. GE has conducted a series of one-third scale three-vent air tests in supporting the horizontal vent pressure suppression system used in Mark III containment design for General Electric BWR plants. During the test, the air–water interface locations were tracked by conductivity probes. The pressure was measured at many locations inside the test rig as well. The purpose of the test was to provide a basis for the pool swell load definition for the Mark III containment. In this paper, a transient three-dimensional CFD model to simulate the one-third scale Mark III suppression pool swell process is illustrated. The Volume of Fluid (VOF) multiphase model is used to explicitly track the interface between the water liquid and the air. The CFD results such as flow velocity, pressure, interface locations are compared to the data from the test. Through comparisons, a technical approach to numerically model the pool swell phenomenon is established and benchmarked.

Analyses of Pool Swell Tests by Two-Dimensional Hydrodynamic Computer Code

Analyses of Pool Swell Tests by Two-Dimensional Hydrodynamic Computer Code

Analyses of pool swell tests by two-dimensional hydrodynamic computer code.

A two-dimensional hydrodynamic computer code SOLA-VOF was examined on the analytical capability for dynamic loads by pool swell in the MARK-I type BWR suppression chamber under LBLOCA (Large Break Loss of Coolant Accident) conditions. Two pool swell tests, (LLL 1/5-scale and EPRI 1/12-scale tests) were selected for this purpose and analyzed by the SOLA-VOF code modified with incorporation of a simple downcomer flow model. In these analyses, it was necessary to take account of three-dimensional effect of pool swell behavior along the chamber axis by use of a method such as spatially weighting function experimentally determined, because a simple two-dimensional calculation by the SOLA-VOF code gave too much conservative evaluation for the impact load on the ring header. Applications of this method gave a good agreement between the calculation and measurement. The vertical loads on the suppression chamber wall were well analyzed by this code. It might be because the local pressure difference caused by the nonuniform pool swelling disappeared owing to pressure integration on the surface of suppression chamber wall.

Analytical Simulation of Boiling Water Reactor Pressure Suppression Pool Swell

In a loss-of-coolant accident, the pressure suppression pool of a boiling water reactor swells as a steam/air mixture is expelled from the drywell into the pool and large gas bubbles are formed beneath the surface. Many tests have been performed to quantify pool swell loads, but analytical methods have been limited in their ability to provide accurate loading estimates. With advancement of numerical methods, it is now feasible to numerically simulate the pool swell process. A finite difference solution algorithm is used to solve the transient imcompressible equations for the liquid flow field. Boundary conditions at the fluid-gas interface are determined using a simplified gas flow model. The program is used to simulate several pool swell tests: comparison of the simulation with test data shows good agreement.

Modelling of the Mark I pool suppression system

A mathematic model of the Mark I type pool suppression system is presented, together with its computer implementation. The time-dependent compressible gas dynamics through the vent system and the bubble formation are described. The pressure, velocity and mass flow rates in the system have been determined. Scaling laws and compressibility effects are studied. The analysis forms the starting point for the determination of the pool swell and the dynamic loading of the torus shell.

Some Comparisons between Small-Scale Pool Swell Experiments and Model Predictions

Predictions from a one-dimensional pool swell model are compared with results from small-scale pool swell tests. The main elements of the model other than the geometric simplification are identical...

Reduced Scale Simulations of Boiling Water Reactor Pool Swell: Some Limitations to the Scaling Laws

Reduced Scale Simulations of Boiling Water Reactor Pool Swell: Some Limitations to the Scaling Laws

Fluid-Structure Interactions in Pressure-Suppression Pools: Small-Scale Experiments and Analysis

Experiments were conducted in a laboratory scale system to investigate fluid structure interaction effects on hydrodynamically induced boundary pressure histories. A single flexible member—a clamped circular plate—formed the base of a cylindrical water pool. Base plate thicknesses were varied to change the natural frequency of the plate pool system. The hydrodynamic transient was an air driven “pool swell” involving large liquid displacements and a complicated boundary pressure history. Pressures at various points on the pool boundary and strains on the flexible base were measured. A one-dimensional analysis of the perturbation pressure transients induced by the deflections of the flexible base is compared with the experimental results. Numerical solutions for the complete perturbed pressure histories are compared with the experiments. Ratios of the peak pressures in the flexible and rigid systems for a pressure pulse of variable duration are predicted analytically and compared with the experiments.

Note on pool swell dynamics during depressurization

A relationship between (1) formalism and kinematic wave analysis for the swelling of a saturated liquid pool during continuous pressure release, and (2) the extensive kinematic wave analysis of transient volumetric pool boiling is described. When the primary contribution to vapor generation, the liquid enthalpy, is the only contribution considered, and when the pressure release rate is essentially uniform, approximate results for depressurization are found to be obtained directly from existing volumetric boiling presentations.

An exact analytical solution of pool swell dynamics during depressurization by the method of characteristics

An exact analytical solution, based on the method of characteristics, has been obtained for the spatial and temporal variation of vapor volumetric (void) fraction in a depressurizing pool. Numerical evaluations have shown that the axial void profile is strongly dependent on the drift velocity formulation, and that wall heat flux plays only a minor role in the pool swell transient.