Hydraulic Instability in Boiling Water Reactors

Abstract

The hydraulic instability is one of the impermissible evils in the operation of BWR. And there has been no effective way of preventing it, because its mechanism is not clarified yet. The authors made many experiments with an electrically heated natural circulation loop which has electric condenser type void meters. As a result, they conclude that the hydraulic instability is a kind of non-linear oscillation caused by the combination of the fluid kinetics in the heated section and the non-linearity of the friction loss of the two-phase flow. They also derive analytically a block diagram of the circulation loop, in which the kinetics of fluid are simulated with simple linear transfer functions except the term of friction loss. The solutions, calculated by an analog computer, coincide well with the experimental results.