Date of Award

10-1985

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Nuclear Engineering

Supervisor

Dr. J. S. Chang

Abstract

The propagation of weak shock waves through a horizontal stratified two-phase system has been investigated both theoretically and experimentally to demonstrate the various facets of its interaction with the phases, fuel bundles and flow network branches. Two types of shock tubes are used: a lucite shock tube is utilized in monitoring the mechanism at the interface of the phases by high speed photography and the other one is an aluminum shock tube of 101.6 mm inner diameter with flow network branches is used in investigating the shock wave behaviour inside a pressure tube during blow-down and loss of coolant accidents.

This dissertation can be divided in to three broad categories. First, the inclusion of the interfacial roughness factor in the analysis of the shock wave propagation through a two-phase system inside a pressure tube weakens the strength of the shock waves, because of the energy loss due to frictional resistance at the interface. The interface is subjected to a combined effect of the waves propagating both in the gas and liquid phases of the system. High speed photography of the interface is considered to estimate the parameters pertaining to the generation of the ripples at the interface and the coupling of this parameter to a quasi-steady energy balance for the system can provide the values of the magnitude of the overpressures in the system.

Secondly, the interaction of weak shock waves with three different types of fuel bundles used in CANDU reactors is presented. Depending on the percentage of the flow area available, different fuel bundles produce different magnitudes of the overpressure. For the transmitted waves, the choking is markedly observed even for moderate range of the shock waves. Presence of liquid phase enhances the strengths of overpressure for the reflected and transmitted waves. Inside the fuel bundles, the shock waves cause unusual vibrational effects which may be detrimental to the life of the fuel elements.

Around the network, the two-phase propagation velocity is observed to be same as the gas phase propagation velocity is observed as the gas phase propagation velocity. Though tap and distilled water exhibit variations in the maximum overpressures, the time averaged magnitude under these two systems agree very well everywhere in the network branches. The vertical pressure profiles in the tap water has dispersive and high oscillatory nature whereas in the distilled water the rise in overpressure is dispersive, but smooth in nature. In distilled water, the pre-pulses moving under a free surface travel at the speed of sound in water and for those in tap water, this velocity is influenced by the presence of air bubbles in the tube walls.

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