## 4 Results  
200 BUSS-R executions were performed for each burn-up step. Furthermore, decay times of 0 and 50,000 years were considered since the evolutions of left values over a time span of 1,000,000 years exhibit a global and local maximum at these time points, regardless of the BU [4; 11; 41]. Note that this is not only true for the AC + FP case presented here, but also for a AC only case (without FP) in which the left values' global maximum would be reached not at 0 but at 50,000 years of decay. The resulting neutron multiplication factors are presented in Figure 4 (Note that the PWR canister filled with fresh fuel assemblies (BU = 0 GWd/tHM) and completely flooded with pure water can be critical. This is one of the main reasons why the disposal of fresh fuel makes no sense and is by no means intended. Nevertheless, the case of fresh fuel in a pure water-filled canister sets the parameters for the most reactive (bounding) scenario and, in this context, is merely of academic interest without any practical relevance for the final disposal. Several technical and procedural solutions to prevent the unlikely event of a criticality excursion are currently under consideration. For instance, the minimum average fuel assembly BU required to ensure that the left value of the water-filled canister complies with the imposed criticality safety criterion can be given in the form of loading curves, which will be determined within the framework of the joint BUSS-R project between PSI and NAGRA. A preliminary loading curve for FAs of KKG is reported in [11]. Shown is the task eigenvalue keff, averaged over the 200 values obtained with an isotopic content corresponding to each burn-up and decay time, as well as error bars indicating the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Element** & **Isotope** & **Perturbed Reaction** & **Element** & **Isotope** & **Perturbed Reaction** \\  & **(ZAID)** & **Channels (MT)** & **Element** & **(ZAID)** & **Channels (MT)** \\ \hline  & 16034 & - & Cs & 55133 & 13, 101 \\ K & 19039 & - & Nd & 60143 & 13, 101 \\  & 19041 & 13, 101 & & 60145 & 13, 101 \\ Ca & 20040 & - & Sm & 62147 & - \\  & 20042 & - & & 62149 & 13, 101 \\  & 20044 & - & & 62150 & - \\ V & 23050 & - & & 62151 & 13, 101 \\  & 23051 & - & & 62152 & 13, 101 \\ Cr & 24050 & 13, 101 & Eu & 63151 & - \\  & 24052 & 13, 101 & & 63153 & 13, 101 \\  & 24053 & 13, 101 & Gd & 64155 & 13, 101 \\  & 24054 & - & U & 92233 & 13, 18, 101 \\ Mn & 25055 & 13, 101 & & 92234 & 13, 18, 101 \\ Fe & 26054 & 13, 101 & & 92235 & 2, 4, 16, 18, 101, 452, \\  & 26056 & 13, 101 & & 92236 & 13, 18, 101 \\  & 26057 & 13, 101 & & 92238 & 2, 4, 16, 18, 101, 452, \\  & 26058 & - & Np & 93237 & 13, 18, 101 \\ Ni & 28058 & 13, 101 & Pu & 94238 & 13, 101, 452 \\  & 28060 & 13, 101 & & 94239 & 2, 4, 16, 18, 101, 452, \\  & 28062 & - & & 454, 1018 \\  & 28064 & - & & 94240 & 13, 18, 101 \\ Cu & 29063 & - & Am & 94241 & 18, 101, 452 \\  & 29065 & - & & 95242 & - \\ Zr & 40090 & 13, 101 & & 95243 & 13, 18, 101 \\  & 40091 & 13, 101 & Cm & 96242 & 13, 101, 452 \\  & 40092 & 13, 101 & & 96243 & 13, 18, 101, 1018 \\  & 40094 & 13, 101 & & 96244 & 18, 101, 452, 1018 \\  & 40096 & 13, 101 & & 96245 & 13, 18, 101, 1018 \\ Nb & 41093 & - & & 96246 & 13, 18, 101, 452, 1018 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: \(Cont.\)lowest and the highest calculated keff values, respectively. At zero burn-up, no depletion calculations had to be carried out. Since no noticeable change in the fresh UQ2 fuel composition can take place over a decay time of 50,000 years, also no decay calculations were performed for this scenario, so that the values for 0 years of decay were simply adopted. For non-zero burnup, on the other side, keff values are lower after 50,000 years of decay than directly at discharge mainly due to 239 Pu decay (T\({}_{1/2}\approx\) 24,100 years). Subsequently, the standard deviation in the keff values is estimated based on the 200 samples each. The results of the consistent ND-UQ are represented by the black points in Figure 5b.