Shielding device

This patent describes in a boiling water nuclear reactor having an under-vessel area with a plurality of downwardly extending control rod drives below the vessel, each control rod drive having a flange assembly that is a source of radiation and comprising a control rod drive housing flange having a base and a mating control rod drive flange having a base, with the flanges in each assembly being jointed together at their bases by connecting means, and usually having position indicating apparatus extending through the flange assemblies, with the areas beneath the flange bases each defining an underflange zone proximate the source of radiation, a shielding device capable of being mounted and demounted relative to a zone. The shielding device comprising: a structure for disposition around the flange bases; the structure being configured to substantially surround the zone in its mounted condition; attachment means associated with the structure, for mounting and demounting the structure relative to the flange assembly; an amount of shielding material sufficiently effective to substantially reduce the measured radiation dose rate emanating from the zone; and with the shielding material comprising at least a portion of the structure