# System Studies on the Fusion-Fission Hybrid Systems and Its Fuel Cycle
## 4 Conclusions  
This research was performed as part of the Kurchatov Institute project on the development of fusion-fission hybrid reactors in Russia. This study shows that the application of fusion-fission hybrid reactors possesses a promising application potential for the transmutation of minor actinides. Calculations on neutron transport and nuclide kinetics were performed for particular reactors: demo, pilot industrial and industrial hybrid. It is shown that the capture to fission ratio is less than 1 for most actinides, which is a really positive feature for effective MA transmutation. The exceptions are Np-237 (only if H\({}_{2}\)O is used as a coolant), Am-241 and Am-243. For all of these, \(\alpha\) is slightly higher than 1. Utilization of CO\({}_{2}\) as a coolant leads to reduction in the total fuel loading, thus the potential advantages of this coolant for transmutation are neutralized. This situation could be improved via optimization of the transmutation area for this coolant. During irradiation, new actinides appear. This is an important feature for multicycle reprocessing and utilizing the fuel. Determining an equilibrium inventory for the FFHS's fuel is an objective for future research as well as analysis of the inventory evolution and its influence on the neutron spectrum during irradiation and vice versa.  
For effective MA transmutation, in terms of not only technical but also economical parameters, it is necessary to use a FFHS with a large fuel loading and high capacity factor, such as IHR, which is able to incinate more than 1 t of actinides per year and generate about 1 GW of electrical power.  
A system analysis of nuclear power in Russia, performed with the involvement of the hybrid reactors, highlights the problems associated with the absence of MA transmutation and the potential of FFHSs to reduce these hazards.  
As can be seen from the results obtained, there is a deficit of extracted MA, even for optimized development scenarios. At the same time, it is necessary to decommission the DEMO-FNS and PIHR (at least as burner reactors), and to abandon one additional IHR, which is needed due to the rate of MA accumulation in the system. It is also necessary to delay the commissioning of 2 other additional IHRs.  
For the considered scenarios, the deficit problem of extracted MA may be overcome around 2075. However, in the case of additional IHRs, the MA deficit takes place again at the moment when the second and third IHR are commissioned. This situation can be improved by the utilization of imported foreign SNF, which can be considered a service of radioactive waste management. The results obtained also indicate the need for faster commissioning the capacities of SNF reprocessing plants, to ensure the required amount of MA for FFHS fuel manufacturing.  
It follows from the analysis performed that, over the period of time considered, it is possible to decrease by 2130 the amount of MA in the system by \(\sim\)28%, in the case of just 1 IHR, and by \(\sim\)48%, in the case of two additional IHRs. If the MA loaded into the FFHS blankets are not considered to be waste, then the amount of MA excluded from the system may be increased by up \(\sim\)43% and, in the case of two additional IHRs, by up to \(\sim\)88%.  
Methodology, investigation, writing--original draft preparation and data curation, M.S.; supervision, conceptualization, writing--review & editing, B.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported by contract No 1/17518-D/ between ROSATOM and NRC \"Kurchatov Institute\".  
The authors appreciate the support from [PERSON] as scientific supervisor, [PERSON] and [PERSON] as consultants and the authors of the Universal System Model.  
The authors declare no conflict of interest.