Dynamic loading of containment during blowdown: review of experimental data from marviken and brunsbüttel

Abstract

This paper deals with the problem of the dynamic loading of the pressure suppression type containment due to pressure fluctuations which are induced during blowdown as a result of steam condensation in the suppression pool. It reviews the experimental data on pressure fluctuations and on the corresponding dynamic response of the structures submerged in the water charge. Two series of containment response experiments were performed on real pressure suppression systems. One series of measurements was performed within the framework of relief valve vent tests in the Brunsbüttel Power Plant (Federal Republic of Germany) in 1974. Another series of measurements was carried out within the framework of the blowdown tests performed at the Marviken Power Plant (Sweden) in 1972–1973. For the measurements of pressure fluctuations in the suppression pool strain gage-based pressure transducers were used. The dynamic response of the loaded structure was measured by strain gages or by piezoresistive (in some cases piezoelectric) accelerometers. The signal was amplified by carrier-frequency amplifiers (or loading amplifiers). The amplified signals were recorded on magnetic tape (FM recording). A two-step evaluation procedure was used. In the first step the time history plots of the variables directly measured (such as pressure, bending strain and acceleration) were plotted and interpreted. In the second evaluation step the cross-power spectral density function of different signal pairs was calculated, plotted and interpreted. For evaluation of the fluctuating pressure field in the suppression pool the combination was chosen of a reference pressure signal (measured at a fixed position called ‘reference position’) with a second pressure signal (measured at a different, arbitrary position) in most cases to perform the cross-spectra analysis. The set of cross-spectral density functions obtained by analyzing all signal combinations chosen was used to determine the power spectra, RMS amplitudes and phases of the corresponding pressure waves impinging on the structure submerged in the suppression pool. For the evaluation of pressure field—structural response relations one pressure signal was combined with one response signal (bending strain or acceleration) to give the input for cross-spectral analysis. By the combination of two response signals (bending strain—bending strain or acceleration—acceleration) for cross-spectral analysis the modal shapes of the responding structure was determined.