## 4 Conclusions  
The tritium fuel cycle (FC) systems have to provide the conditions for burning and heating of the plasma and for current generation (by injection of fast atom beams), provide the residual detritylation of gases and processing of waste, and also contain minimum stores of hydrogen isotopes. The particle flows in the FC are determined by the flows into the pumping system from the vacuum chamber (the divertor region) and the flows in the injection system required the maintaining the necessary parameters of the core plasma. The simulation of flows of particles in the FC systems has to be conducted consistently with the core and divertor plasma. For simultaneous simulations of the core and divertor plasma, the indirect integration of the ASTRA and SOLPS4.3 codes is used. The one-dimensional simulation of the main plasma by the ASTRA code is supplied with the boundary conditions and limitations presented in the form of scalings obtained by two-dimensional simulations of the edge plasma by the SOLPS4.3 code. Simulation of hydrogen flows in the FC systems is performed by the FC-FNS code. In the developed approach, feedback is realized between the pumping and injection systems in the form of changes to the isotopic composition of the core and divertor (edge) plasma. In the article, the further development of the approach is described that uses ions instead of electrons in the particle transport equations in the ASTRA code. This allows one to estimate the \"partial confinement times\" in plasma of ions from different sources (neutral beam injection, pellets, gas injection, and recycling) more accurately. The case was simulated of the injection of a deuterium beam into the plasma of DEMO-FNS with the isotope density ratio D:T = 1:1. In this work, calculations were carried out in the range of confinement parameters \(\tau_{p}/\tau_{E}\) = 0.75-2.5, since this range covers the experimental values \(D/\chi_{e}\) = 0.2-0.75. The calculated \"partial confinement times\" are presented for all sources. Figure 16: Total amount of tritium in the FC taking into account the natural and convective ELMs in the working window of densities \(<\)\(n_{e}\)\(>\) and confinement parameters \(\tau_{p}/\tau_{E}\). Estimates were made of the change in the particle flow through the pellet injection system that is required to compensate for the additional losses from the plasma in the case of stimulated convective ELMs. The stores of tritium in the FC systems of DEMO-FNS were estimated, including the case of convective ELMs. It was shown that the values obtained by the ion equations are lower than the values obtained earlier by parameterizing the calculation results obtained by the ASTRA code. The losses from the plasma turn out to be up to 1.5 times lower than in earlier estimates in the working window of parameters. The flows of particles from pellets into the plasma required to provide the given density are also 1-2.7 times lower than those calculated earlier (in the corresponding working points) and are 10\({}^{22}\) particles/s. The increase in the fuel flow needed to compensate for the particle losses in ELMs is 2-3 times, depending on the value of \(\alpha_{ELM}\), is 1-1.6 times lower than the earlier estimates. The value of gas injection was analyzed, taking into account the possible degassing from the vacuum vessel wall. Limitations were shown, due to the chosen engineering solutions. Under the assumption of the total flow of particles onto the wall of DEMO-FNS, an estimate was obtained of the intensity of gas injection equal to 1.6 \(\times\) 10\({}^{22}\) s\({}^{-1}\) (33 Pa m\({}^{3}\)/s), which is necessary to be able to compensate for the excessive degassing from the vessel wall under steady-state operation mode of facility. At the same time, to date, the DEMO-FNS project allows the effective pumping rate of -30 m\({}^{3}\)/s, which limits gas puffing at rates \(\leq\) 10\({}^{22}\) s\({}^{-1}\) (in the considered window of parameters).