On the Use of Acoustic Waves in Nuclear Power Reactors to Determine Average Void Fractions

A method for estimating the average void fraction in water-moderated power reactors is presented. The method might be useful to determine departure from normal boiling conditions or nucleate boiling in boiling and pressurized water reactors, respectively. A standing acoustic wave is introduced in the core and the neutron density is measured, squared, time-averaged, and compared with the same quantity without an acoustic wave. The ratio is inversely proportional to the sixth power of the acoustic velocity; and the acoustic velocity depends on the average void fraction in the core. Consequently, this ratio is very sensitive to the average void fraction in the core.