An analytical model for the long-term emergency core cooling (ECC) of a boiling water nuclear reactor (BWR) has been developed. This one dimensional drift-flux model, is an extension of a previous study by Lahey and Kamath [1]. It considers both subcooled and bulk boiling in the core, allows the drift-flux parameters, C 0 and V g j , to be functions of void fraction (α), and can accommodate both broken and intact jet pump seals. The results of this analytical model compare well with data from simulated full scale BWR fuel rod bundles, and experiments in the PCE facility at RPI. It has been found that the unlikely failure of jet pump seals can have a detrimental effect on the long term cooling capabilities of a BWR/4.