## 4 Conclusions  
In the present study, a developed computational code named ARTAP is used to analyze and compare the safety characteristics between the LBE-cooled ADS and CNES. The developed code consists of a space-time neutron diffusion equation with a spallation neutron source model and a thermal-hydraulics model with a package of thermophysical properties, which could be used for calculations of both the LBE-cooled ADS and the LBE-cooled CNES. In order to investigate differences of the safety characteristics of these two reactors, three typical accidents are carried out, including reactivity insertion, loss of flow, and loss of heat sink. In addition, the accident simulations are not only performed in the case of unprotected transient, but also in the case of protected transient, i.e., transient with interruption of accelerator beam for ADS and with insertion of shutdown rod for CNES. The transient behaviors of the reactor power and the temperatures of the fuel, cladding, and coolant are investigated during the accident sequences.  
The comparison results show the power and the temperatures of fuel pellet, cladding, and coolant of the CNES core are much higher than those of the ADS core during the reactivity insertion accident, which means ADS has a better safety advantage than CNES. However, due to the deep subcriticality of the ADS core and its low sensitivity to negative reactivity feedback, the simulation results indicate that the inherent safety characteristics of the CNES core are better than those of the ADS core under loss of flow accident, and the protection system of ADS would be quickly activated to achieve an emergency shutdown after the accident occurs. For the loss of heat sink, it is found that the peak temperatures of the cladding in the ADS and CNES reactors are lower than the safety limit, which mean these two reactors have good safety performance against loss of heat sink accident.  
Figure 13: Transient responses of protected loss of heat sink between the ADS core and the CNES core.  
**Author Contributions:** Conceptualization, R.L. and F.Z.; methodology, R.L., S.T.R. and F.Z.; software, R.L.; validation, R.L.; formal analysis, R.L.; investigation, R.L.; resources, R.L.; data curation, R.L.; writing--original draft preparation, R.L.; writing--review and editing, R.L., S.T.R. and F.Z.; visualization, R.L.; supervision, S.T.R. and F.Z.; project administration, R.L.; funding acquisition, R.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Scientific Research Foundation of the Education Department of Hunan Province, China (Grant No. 18B265); Fundamental Research Fund for Young Teachers of the University of South China (Grant No. 190 XQD064); Opening Project of Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, University of South China (Grant No. 2019 KFY20).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data is contained within the article, further inquiries can be directed to the corresponding authors.  
**Conflicts of Interest:** The authors declare no conflict of interest.