An Automatic Flow Balancing Device for Boiling Water Reactors

A prototype device to control the exit steam quality in the individual fuel element assemblies of a boiling water reactor was designed, constructed and tested at simulated reactor operating conditions. The device consists of two Venturis and a mechanism for comparing the pressure signals from the Venturis and controlling the flow by means of a hydraulically operated valve. The device, which is completely self-contained within one channel of a boiling water reactor, held the discharge volume quality to ± 6% of the design value during transients in the heat transfer rate of up to 25%. The addition of the device to the high heat flux channels of a boiling water reactor would permit designing reactors at a higher heat flux for the same departure from nucleate boiling. The pressure across the core (header to header) is increased by ≈ 20% for a reactor of the Dresden type. Overall economic effects on reactor operations, including reactivity effects, were not evaluated.