Method and apparatus for controlling a nuclear reactor to minimize boron concentration adjustment during load follow operation.

摘要

A nuclear reactor is operated during load changes with minimal changes to boron concentration by maintaining gray rods fully inserted into the core during steady-state operation and by adjusting axial offset in response to changes in power. When a reduction in power demand is expected, the axial offset of the axial power distribution in the core of the reactor is adjusted downwards by approximately -10% by inserting a strong bank of axial offset control rods into the top of core and withdrawing the gray rods slightly. Reactivity of the core is preferably adjusted initially using a bank of gray rods having a worth similar to that of the gray rods kept fully inserted into the core and only when additional reactivity control is required are conventional black control rods used. The gray rods that are normally kept fully inserted into the core are also used for reactivity control and provide increased reactivity for a return to full power. Preferably, there is zero overlap between the gray rods, so that one bank is fully inserted into the core before the other bank is inserted to reduce reactivity.