## 3 Nuclear Analyses
### Summary of the WCLL vs. HCPB Comparison  
Figure 54 shows the neutron spectra impinging on the W-Monoblock placed in the central zone of the baffle region (position C, see Figures 7 and 9) in correspondence with the external edge of the inboard target, both with WCLL and HCPB. The different layout of the breeding blanket clearly affects the neutron spectrum distribution on the blanket first wall and divertor plasma facing components. In particular, the effect related to neutron moderation is predominant with the water cooled blanket -WCLL, and this is confirmed looking at the neutron spectra of Figure 54, highlighting a higher proportion of low energy neutrons (energy range of 10\({}^{-7}\)-1 MeV) in the divertor W-armour, than HCPB. For higher neutron energy values (1-14 MeV), the neutron spectra appear to be similar, showing comparable peak values of neutron fluxes. This clearly has an impact on the different response and behavior of the nuclear load's distribution on the DEMO divertor targets, passing from one type of blanket to another, due to the cross-section vs. neutron energy trends of the several phenomena described herein described. Photon production by means of (n,\(\gamma\)) neutron absorption reactions, generally represents the predominant contribution to nuclear heating deposition into materials, under neutron irradiation. The energy-cross sections dependence [32; 53; 54] of 180\(W\)(\(n,\gamma\))181\(W\), 182\(W\)(\(n,\gamma\))183\(W\) \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**WCLL** & \begin{tabular}{c} **MW Tot (48** \\ **Cassettes)** \\ \end{tabular} & **Distribution (\%)** & **HCPB** & \
\begin{tabular}{c} **MW Tot (48** \\ **Cassettes)** \\ \end{tabular} & **Distribution (\%)** & **WCLL/HCPB** \\ \hline PFCs & 25.14 & 14.38 & PFCs & 21.79 & 14.65 & 1.15 \\ \hline Inboard & 11.79 & 6.75 & Inboard & 10.12 & 6.80 & 1.17 \\ \hline W-Monoblocks & 9.04 & 5.17 & W-Monoblocks & 7.79 & 5.24 & 1.16 \\ Cu-Interlayers & 0.42 & 0.24 & Cu-Interlayers & 0.37 & 0.25 & 1.14 \\ CuCrZr-pipes & 0.61 & 0.35 & CuCrZr-pipes & 0.53 & 0.36 & 1.14 \\ Water-coolant & 0.79 & 0.45 & Water-coolant & 0.63 & 0.42 & 1.25 \\ Euforter-supports & 0.94 & 0.54 & Euorter-supports & 0.80 & 0.54 & 1.18 \\ \hline Outboard & 13.34 & 7.63 & Outboard & 11.67 & 7.85 & 1.14 \\ \hline W-Monoblocks & 10.21 & 5.84 & W-Monoblocks & 8.94 & 6.01 & 1.14 \\ Cu-Interlayers & 0.48 & 0.28 & Cu-Interlayers & 0.43 & 0.29 & 1.13 \\ CuCrZr-pipes & 0.69 & 0.39 & CuCrZr-pipes & 0.61 & 0.41 & 1.12 \\ Water-coolant & 0.84 & 0.48 & Water-coolant & 0.71 & 0.48 & 1.18 \\ Euforter-supports & 1.11 & 0.64 & Eurofer-supports & 0.98 & 0.66 & 1.14 \\ \hline CB + Liner and reflector plates & 149.67 & 85.62 &
\begin{tabular}{c} CB + Liner and \\ reflector plates \\ \end{tabular} & 126.89 & 85.35 & 1.18 \\ \hline TOTAL & 174.80 & 100.00 & TOTAL & 148.68 & 100.00 & 1.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparison between the total nuclear power (MW) deposited on the DEMO divertor (showing the breakdown for each single contribution) both for WCLL and HCPB blanket, considering all the 48 divertor cassettes. Figure 54: Comparison between the neutron spectra impinging on the W-Monoblock placed on the baffle region of the inboard target (position C, see Figures 7 and 9) at the external side, with WCLL and HCPB. \(183W(n,\gamma)184W\), \(184W(n,\gamma)185W\), \(186W(n,\gamma)187W\) for Tungsten, \(63 Cu(n,\gamma)64 Cu\) and \(65 Cu(n,\gamma)66 Cu\) for Copper, \(54 Fe(n,\gamma)55 Fe\), \(56 Fe(n,\gamma)57 Fe\), \(57 Fe(n,\gamma)58 Fe\) Iron, which is the principal element of Eurofer, shows increasing cross section with lower neutron energies, entailing a higher probability that these reactions occur in this energy range. The analysis suggests that the greater neutron moderation in the water cooled blanket of the WCLL concept, results in neutron spectra with a more intense level of low energy neutrons in the divertor targets, thereby enhancing the nuclear heating deposition, compared to the HCPB.