Long-term activation and tritium generation of flowing lithium-lead under prolonged irradiation in fusion power plants

Lithium-lead is a candidate tritium-generating material in conceptual designs of magnetic fusion power plants.. Its prolonged utilization, ultimately during the entire lifetime of such a facility, has the potential to minimize amounts of active waste and improve the economic performance. Limits to a prolonged use are production of long-lived radioactive waste and depletion of lithium and reduction of the tritium production rate to levels where self-sufficiency is compromised. The methodology and calculations performed to estimate the transmutation of LiPb following its prolonged irradiation in two of the models in the European Power Plant Conceptual Study are presented. It is shown that no waste requiring permanent disposal is expected regardless of the irradiation length. Time-dependent tritium generation is discussed: Lithium replenishment seems unavoidable, but depletion rates are found to be lower than assumed in the design. The effect of the LiPb flow pattern in the irradiation history proves to be crucial in order to support these results.