Operational technique for pressurised water cooled nuclear reactor - prevents damage to fuel elements by regulating output density

摘要

A pressurised water reactor having a core formed by fuel rods and fitted with monitors for determining the distribution of the output over the core, has an arrangement receiving signals from the monitors, for restricting the reactor output, if threshold values for the output density are exceeded. The reactor is operated so that the threshold value of the permissible operational density of the fuel rods is approximated to the actual reactor output density when output is falling, with a time constant of days, and when output is rising, with a speed of alteration of about 5%/h to within a distance of 50 %/cm. To prevent mechanical damage to the fuel element envelopes by changes of loading due to pellet-cladding-interaction. the technique allows the envelope to flow in the elastic zone under the action of the expanding fuel tablets, without shearing.