Development of a neutronics/thermal-hydraulic coupling optimization code and its application on the CFETR HCSB blanket

As one of the key components of fusion reactor, breeding blanket is of vital importance for the functions of tritium self-sufficiency and fusion energy transformation. The performances of the blanket mainly depend on the internal structural arrangement and material composition. However, if we directly adopt the actual 3D calculation model for the blanket design and optimization, not only will it cost extensive human and computer resources, but also make the computational process extremely complicated and lengthy. Considering that the radial build arrangement of the functional zones is the most important determinant for the detailed 3D design of the blanket, NTCOC, a Neutronics/Thermal-hydraulic Coupling Optimization Code, which adopts 1D neutronics and 2D thermal-hydraulic simplified models, is developed for accelerating the radial build design and optimization of the blanket in this work. This code realizes the iterative updating the temperature cross-section libraries through inner coupling, which can make the calculation more accurate. Besides, it realizes the automatic data transmission between the nuclear and thermal calculation results, which can facilitate the coupling optimization process greatly. In addition, a variable step length method is adopted for further improving both the coupling optimization efficiency and accuracy of this code, and several leading design requirements are set as the optimization criteria instead of taking all the practical engineering constrains into account. Finally, after the improvement of the algorithm of the integrated neutronics/thermal-hydraulic optimization for NTCOC, this code has been applied on optimizing the radial build arrangement of a conceptual design of Chinese Fusion Engineering Test Reactor (CFETR) helium cooled solid breeder blanket, which adopts separated Li4SiO4 and Beryllium pebble beds as tritium breeder and neutron multiplier respectively, under normal, critical and DEMO three conditions.