HYDRODYNAMICS DESCRIBING ACOUSTIC PHENOMENA DURING REACTOR COOLANT SYSTEM BLOWDOWN

摘要

The potential consequences of a hypothetical loss-of-coolant accident have received major attention in assuring the safety of water cooled and moderated nuclear reactors. In the investigation of loss-of-coolant accidents, the study of the blowdown of pressurized water systems is a major area of investigation. The understanding of the phenomena associated with blowdown, such as the mechanism of flow initiation, is important in the field of nuclear safety technology.nAs part of the LOFT (Loss-of-Fluid Test) program, a digital computer program BURST-I (Blowdown Under a Rapid Sonic Transient) has been developed for calculating the spatial distributions of pressure, mass velocity, and enthalpy within a PWR primary-coolant system as functions of time during subcooled blowdown. This report outlines the present status of development and evaluation of BURST.nThe theoretical basis employed in BURST for calculating acoustic wave propagation and reflection phenomena in a one-dimensional system is presented. Comparisons of the calculated transmission and reflection of acoustic waves at area changes with those predicted by acoustic theory show that these phenomena are treated correctly by the BURST code. BURST calculational results are com¬pared with data from LOFT semiscale blowdown tests. In general, good agreement is shown between BURST results and these experimental data. The application of the BURST-I Digital Computer Program to the entire LOFT primary-coolant loop indicates that the LOFT core may be subjected to cyclic hydraulic loading during the initial portion of the blowdown transient. Although this presentation chiefly concerns subcooled, adiabatic, and frictionless systems, the methods employed in the BURST-I code are capable of treating both subcooled and two-phase systems with heat input and viscous dissipation.