Abstract: A boiling water reactor is chemically decontaminated by circulating a decontamination solution through reactor recirculation loops and the annulus region of a reactor pressure vessel that surrounds the central core region while bypassing the central core region. The decontamination solution may also be circulated between the annulus region and a lower internals region while bypassing the central core region. The solution dissolves or breaks down metal oxide layers on the surfaces of the boiling water reactor. The metal oxide layers in the central core region and the activated metal ions contained in these layers, which do not substantially contribute to personnel exposure, are not released and, therefore, do not need to be removed from the solution.