Dose Mapping for the Uranium-233 Disposition and Medical Isotope Production Project at Oak Ridge, Tennessee
D.E. Gergely, CHP,CSP1; W.P. Riley, CHP1; and T.R. Butz, PhD2 (1Nuclear Fuel Services, Inc.; 2Duratek, Inc.)
Over 1.5 tons of total uranium, including 450 kg 233U are stored at ORNL. The goal of this 8-year project, awarded to Isotek Systems, LLC in October 2003, is to design and construct, in Building 3019A, a process to downblend weapons-capable material to a safe and stable form and to provide medical isotopes for cancer research and treatment. The processing design is tailored to the material form and includes chemically processing in a nitric acid system, removal of thorium by ion exchange, downblending, conversion to U 3O 8, and packaging for safe long-term storage. The extracted thorium will be packaged for shipment to medical isotope producers to extract 225Ac to produce 213Bi generators. In order to provide safe, secure facilities for processing, the building requires several modifications: 1) Construction of new heavily shielded hot cells with manipulators for pretreatment, dissolution, thorium extraction, purification, packaging and storage; 2) Addition of equipment and modification of an existing shielded cell for NMC&A measurement and downblending; 3) Removal of existing equipment and installation of new processing equipment; and, 4) Installation of new analytical laboratories, a process off-gas scrubber (including 220Rn treatment), liquid and solid waste handling equipment, and other support equipment. Radiological Safety has been an integral part of design since project conception. Containment, shielding, and maintainability have been incorporated into the design as essential to ensure exposures are ALARA. The 232U decay product 208Tl with its 2.6 MeV photon dominates shielding considerations. The uranium and its alpha emitting decay products require plutonium like containments. The presence of 220Rn introduces a unique challenge and the impact that chemical separation has on upsetting equilibrium conditions presented complexities that were addressed in the design. To address all these factors, detailed dose rate mapping was completed. The results of that mapping and the impact on the design are summarized. Isotek Systems, LLC will assume management and operation of the facility during FY 2005 and begin construction of the new process in early 2006.