Water level indication

The possibility of measuring the water level in a PWR by studying the natural frequency of its pendular oscillation is discussed. The effect is complicated both by the complex internals and by the generation of surface waves when the vessel is partially full. For small losses of inventory the effects are measurable, but not large. The principal advantages are that the method measures the mass of water directly, and, above all, that it is noninvasive. The method is described, and the general formulae and numerical examples are given for a greatly oversimplified model. Only testing on real vessels can determine whether the technique is truly useful. (orig.)