The heat pipe reactor (HPR) is characterized by inherent safety and a compact structure, which making it widely applicable. The thermoelectric conversion system (TEC) is a key system in the HPR that converts thermal energy to electrical energy. Its form and operational principles significantly impact the accident safety characteristics and dynamic response of the HPR. A self-developed analysis code TAPIRS-D for HPR systems has already incorporated stirling cycle with semiconductor thermoelectric conversion system at the Nuclear Safety and Operations Research Laboratory of Xi'an Jiaotong University, China.

This study aims to develop a new dynamic thermoelectric conversion module suitable for open Brayton cycle on the basis of the TAPIRS-D code.

Firstly, an open Brayton TEC model was developed for code TAPIRS-D, making it capable of analyzing heat pipe reactor system coupled with different thermoelectric conversion systems, such as stirling cycle, open Brayton TEC as well as semiconductor thermoelectric conversion system. Then, maximum relative errors in temperature prediction, pressure prediction and maximum flowrate prediction were obtained by comparison between the calculated results of the newly developed open Brayton TEC model and the experimental data to confirm the rationality of the model. Finally, the upgraded TAPIRS-D were applied to evaluate the reactivity insertion accident of SAIRS-C reactor concept, and the transient performance of SAIRS-C coupling with different thermoelectric conversion system were analyzed and compared.

Comparison results show that the newly developed open Brayton TEC model has a maximum relative error of 2% in temperature prediction, a maximum relative error of 3% in pressure prediction and maximum relative error of 15% in flowrate prediction. Under the same accident conditions involving the introduction of reactivity, the calculation results indicate that the reactor using the Stirling conversion system has the smallest change in core power after an accident while the temperature rise of the Stirling machine's hot end is relatively high.

Results of this study demonstrate that the output power of open Brayton cycle and thermoelectric conversion system has a similar variation change, which are both larger than that of stirling conversion system whilst heat pipe reactor system coupling with semiconductor thermoelectric conversion system has the largest cycle efficiency gain. However, special attention should be pay on the circuit load of semiconductor thermoelectric conversion system under reactivity insertion accident.