## 3 Calculation Results
### Tritium Inventories  
The total store of tritium, as the most critical fuel component, is calculated by the FC-FNS code using estimates of the FC systems described in [6]. In [22], dependences were given for the tritium store in the FC of the DEMO-FNS facility on particle confinement time \(\tau_{p}/\tau_{E}\) for different plasma densities \(<\)\(\tau_{te}\)\(>\) for two types of beams (D + T and D). In addition to the case of natural ELMs, whose particle losses were included in the total diffuse losses, convective ELMs that are more frequent with lower stored energy were also considered. In this case, the ion losses from the plasma are expected to be much higher, which requires that its fueling be intensified and that the flows in the FC increase [8]. Note that, in a number of systems, the amount of accumulated isotopes will not change at different plasma parameters. However, in the majority of the FC components, there will be a correlation between flows in the FC and the hydrogen isotopes inventory in them. For this reason, during simulations by the FC-FNS code, for each separate set of plasma parameters, flows in FC and fuel component inventories are calculated [22]. Figure 15 shows the flows and distribution of the hydrogen isotopes inventory in the FC systems in the case of the deuterium beam. Figure 15a,c show the case with natural ELMs, in which the flows in the FC are lower than in the case of convective ELMs shown in Figure 15b,d. According to the accepted FC architecture [21; 22], increasing the particle flows across the plasma increases the loads on the PIS and NBI systems and the hydrogen isotope separation system (ISS) that supply them. At the same time, the flow in the gas injection system (GIS), on the contrary, decreases due to the increase in particle flow in the  
Figure 14: Neutron flow \(S_{natt}\) (\(10^{19}\) s\({}^{-1}\)) depending on the composition of the core plasma \(f_{core}\)\({}^{T}\) for the deuterium beam. Figure 13: Variation of fusion power \(P_{fis}\) and neutron yield \(S_{neut}\) in the working window of densities \(<\)\(\tau_{te}\)\(>\) and confinement parameters \(\tau_{p}/\tau_{E}\). vacuum vessel due to the partial penetration of pellets through the plasma (the penetration efficiency is <1). The maximum flows of particles through the pumping and cleaning systems are independent of the considered scenarios, since they are determined by the engineering parameters: the pressure in the divertor and the pumping rate [22]. Figure 15c,d show that the maximum amount of tritium is accumulated in the pipelines, the pumping system (if cryogenic pumps are used), and in the hydrogen isotope separation and the injection systems. The amount of tritium in the injection systems is determined, in the first place, by the construction of these systems. At the same time, the amounts of tritium and deuterium in the hydrogen isotope separation system are determined by the initial gas flows (from different FC components) and by the isotopic composition of these flows. It was noted in [42] that the method of estimating the amount of tritium inventories in the FC systems with a strong dependence of hydrogen isotope flows on plasma parameters determines the total store of tritium \(T_{inv}\) in the facility. In the described calculations, we use the earlier-developed specialized ISS module of the FC-FNS code to estimate the amount of tritium in the ISS [42]. The values calculated using the new ISS module for the FC-FNS code was lower than those obtained earlier [22]. The estimate of the contingency stock required during the temporary stop of the tritium reproduction systems (for repairs or maintenance) remained the same, and it is about 100 g of tritium. Without taking into account the tritium produced in the blanket of the facility and the tritium stored in the long-term storage for outside consumers, from 350 to 400 g of T\({}_{2}\) will be found at the facility site depending on the ELM scenario (taking into account the losses from radioactive decay).