Numerical investigation of the tritium permeation phenomenon through cooling plates in breeding blankets

摘要

Understanding and predicting tritium transport is considered a key issue for the design of safe and self-sufficient fusion power plants. Indeed, tritium generated in the breeder materials is susceptible to permeate to the blanket coolant circuits where it is harder to remove and process. Therefore, the predictive models become very important to evaluate the performance of any blanket design. In this work, 2D finite volume methods are employed to analyze in detail the tritium permeation through a cooling plate considering a set of different parameters that affect the breeding blanket (BB) performance. Different BB configurations are studied varying the geometrical parameters defining the plate: the wall thickness and the cooling channel pitch. Moreover, the analyses cover every permeation regime, from diffusion-limited to surface-limited, including intermediate situations. This way, results are applicable to every BB concept which employs cooling plates with independence of their specific materials, temperatures and tritium concentrations. Results have been compared with those of 1D models in order to define form factors that can be used to increase the precision of system level tritium transport models. A total of 91 simulations have been carried out to find correlations that allows computing the form factors in a wide variety of situations. Results show that the accuracy of 1D models and consequently the accuracy of most system level models strongly depends on the permeation regime and can be poor in some conditions. However, this study demonstrates that the use of form factors can be used for an effective increase of system level exactness.