Evaluation of Potential Head-End Procedures for Graphite-Containing Fuel Elements

During the last 20 yr, several potential physical and chemical head-end procedures for graphite-containing high-temperature gas-cooled reactor (HTGR) fuel elements were investigated. In contrast to the principle that the introduction of moderator material into reprocessing should be avoided by all means, with HTGR fuel elements, which consist of ∼95 wt% graphite (moderator material), the primary objective is to remove the bulk of graphite from heavy metals and the fission products. For this purpose, the feasibility of the fluidized bed burning of crushed graphite material has been demonstrated and developed to an advanced stage. If ¹⁴C retention is necessary, the CO₂ of the burner off-gas can be converted to a solid physical state by fixation of CO₂ as CaCO₃. Because of the high carbon inventory of the ocean associated with operative dilution effects, controlled dumping of CaCO₃ on the deep sea ocean floor could represent safe ultimate disposal