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.

Abstract: A boiling water reactor having a reactor pressure vessel with two recirculation loops hydraulically connected thereto is decontaminated by installing plugs in the outlets of jet pump ram's head manifolds located within the reactor pressure vessel to isolate the recirculation loops from the reactor pressure vessel. A monitoring gas is bubbled into some of the ram's head manifolds through the plugs to monitor the process pressure within the manifolds and riser pipes connected with the manifolds. The level of the decontamination solution in the riser pipes can be determined by determining the differential pressure due to the vertical height of the decontamination solution in the loops.