AbstractAn analytical and experimental investigation of void distribution in internally heated boiling pools is presented. The experimental investigation involved measurement of the vertical profile of the void fraction and the average void fraction in an aqueous solution of ZnSO4. The observed void fractions were found to be adequately correlated byIf the results of this investigation are extended to a boiling pool of UO2, it is predicted that substantial voiding will occur even when only a very small fraction of nominal operating power density in nuclear reactors is consumed in internal vaporization.