## 5 Conclusions  
A complex assay of the tritium breeding capacities of the different DEMO concepts that included various IVCs in the tokamak was carried out to assess the individual effects of each IVC included in the DEMO design. To this end, a set of the MCNP geometry models of different 22.5\({}^{\circ}\) toroidal segment configurations was developed and dedicated MCNP simulations were performed to provide corresponding nuclear responses. All the geometry models used in the computations were developed to represent fully heterogeneous breeder blanket structures corresponding to the current status of the EUROfusion breeder blanket R&D program. Therefore, this method provided a very realistic assessment of the various effects of the DEMO tritium breeding capacity introduced in the tokamak through the arrangement of the IVCs. In spite of the optional tokamak layout, the results obtained can serve as a basis for strategic decisions about the value of the required TBR (TBR\({}_{\text{req}}\)) adopted in the EUROfusion breeder blanket development program. Compared to the reference breeder blanket models developed thus far within EUROfusion R&D work, the TBR reduction due to arrangement of the different IVCs is about 10.5% for both the HCPB and WCLL concepts and \(\
eg\)9.3% for the WLCB blanket. If the TBR\({}_{\text{target}}=1.05\) remains the hard limit in the DEMO project, only HCPB could marginally satisfy this criterion; both the WCLL and the WLCB concepts failed in this \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multicolumn{3}{c}{**H Homogeneous HUCB [2]**} & \multicolumn{3}{c}{**Homogeneous WCLL [2]**} & \multicolumn{3}{c}{**Heterogeneous HCPB**} & \multicolumn{3}{c}{**Heterogeneous WCLL**} & \multicolumn{3}{c}{**Heterogeneous WCLB**} \\ \hline \multirow{3}{*}{} & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** & \(\delta\)**TBR** \\  & **Single IVC** & **Tokamak** & **Single IVC** & **Tokamak** & **Single IVC** & **Tokamak** & **Single IVC** & **Tokamak** & **Single IVC** & **Tokamak** \\ \hline
**EC** & 0.272 & 2.448 & 0.261 & 2.350 & 0.218 & 1.966 & 0.266 & 2.397 & 0.185 & 1.661 \\ \hline
**NBI** & 0.160 & 0.480 & 0.240 & 0.720 & 0.218 & 0.655 & 0.266 & 0.799 & 0.185 & 0.554 \\ \hline
**UL** & 0.612 & 4.896 & 0.499 & 3.990 & 0.517 & 4.135 & 0.440 & 3.522 & 0.503 & 4.022 \\ \hline
**IML** & & & & & 0.192 & 0.767 & 0.212 & 0.848 & 0.165 & 0.662 \\ \hline
**OML** & & & & & 0.373 & 1.492 & 0.386 & 1.544 & 0.299 & 1.196 \\ \hline
**Total in** & & **10.916** & & **10.270** & & **10.507** & & **10.653** & & **9.292** \\ \hline \end{tabular}
\end{table} 
Table 1: TBR reduction rate for single port or limiter, and entire 360\({}^{\circ}\) model (units: %). \begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{3}{c}{**Heterogeneous HCPB**} & \multicolumn{3}{c}{**Heterogeneous WCLL**} & \multicolumn{3}{c}{**Heterogeneous WCLB**} \\ \hline \multirow{3}{*}{} & \(\delta\)**Power Single** & \(\delta\)**Power 360\({}^{\circ}\)** & \(\delta\)**Power Single** & \(\delta\)**Power 360\({}^{\circ}\)** & \(\delta\)**Power Single** & \(\delta\)**Power 360\({}^{\circ}\)** \\  & **IVC** & **Tokamak** & **IVC** & **Tokamak** & **IVC** & **Tokamak** \\ \hline
**EC** & 0.135 & 1.211 & 0.118 & 1.062 & 0.112 & 1.008 \\ \hline
**NBI** & 0.135 & 0.404 & 0.118 & 0.354 & 0.112 & 0.336 \\ \hline
**UL** & 0.259 & 2.074 & 0.269 & 2.152 & 0.255 & 2.040 \\ \hline
**IML** & 0.187 & 0.748 & 0.151 & 0.604 & 0.160 & 0.640 \\ \hline
**OML** & 0.296 & 1.183 & 0.248 & 0.992 & 0.229 & 0.916 \\ \hline
**OLL** & 0.296 & 1.183 & 0.248 & 0.992 & 0.229 & 0.916 \\ \hline
**Total in tokamak** & & **6.40** & & **6.16** & & **5.86** \\ \hline \end{tabular}
\end{table} 
Table 2: Power reduction rate for single port or limiter and entire 360\({}^{\circ}\) model. (units: %). exercise.