The Analysis of Boiling Water Reactor Long-Term Cooling

A closed-form analytical model for the long-term cooling of a boiling water reactor (BWR) has been derived. This model, which is based on one-dimensional, drift-flux techniques, has been compared with data from simulated full-scale 49-rod BWR fuel bundles at atmospheric pressure. The analytical model was shown to agree with the experimental data, which indicated that effective cooling was maintained as long as the bundle was submerged by the two-phase mixture. The analysis indicates that core uncovery may occur as the core power level decays.