## 5 Results and Discussion
### Comparison of Scenarios  
When comparing the different scenarios some interesting similarities and differences can be revealed (Table 3). First of all the overall costs (except for the Yuc_reproc scenario) lie in the range between $7.2 and $15.3 bn. The opening of a final repository in 2030 reduced costs by 30%, the opening of two repositories by 50% compared to the _BAU_ scenario. The opening in 2060 did not reduce costs that much. The overall cost composition differed only slightly between the scenarios, except for the CISF capital costs that cause the biggest difference (Figure 5). Regarding the total cost, the perfect foresight in the model resulting in a best case scenario of an omniscient central planner has to be kept in mind. Strategic behavior or unforeseen events could increase overall costs. The total cost in all scenarios were lower compared to other estimations. The DOE [22] calculates between $50 and $60 bn. of overall lifecycle cost for HLW. This difference can be explained by regarding the cost composition of our model (the model only took costs between dry cash storage at the ISFSIs and the long-term repository into account. Not considered are at-reactor costs, e.g., for spent fuel pools and filling the spent nuclear fuel SNF into dry casks as well as costs that occur at the final repository for storing the HLW there. These two sources of costs had a huge impact on the overall costs for waste disposal but are not considered in the model since they are not part of the optimization) as well as by regarding the limited time frame and the rough estimation of storage cost due to the lack of public information. However, the relative difference in cost between the different scenarios seems valid. Figure 4: Distribution of costs over time in the business as usual (BAU) scenario. Source: own representation. In every scenario with a final repository available all ISFSIs at the reactors sites could be closed by 2080 at the latest. More critical is the timing of the opening of final repositories to the construction of the CISFs. In every scenario it was cost efficient to built at least one of those, providing a capacity of 20,000 MTU. But in some scenarios up to 120,000 MTU of storage capacity in CISFs were needed \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Scenarios** & **BAU** & **Yuc\_2030** & **Yuc\_2060** & **Yuc\_2030+** & **Yuc\_2060+** & **Yuc\_reproc** \\ \hline Total costs [5B] in 80 years & 15.3 & 10.3 & 15 & 7.2 & 13.5 & 33.8 \\ \hline Number of & & & & & & \\ \begin{tabular}{l} CISF built \\ (needed \\ capacity [MTU]) \\ \end{tabular} & 6 & 3 & 6 & none & \begin{tabular}{l} 5 \\ (100,000) \\ \end{tabular} & \begin{tabular}{l} 1 \\ (20,000) \\ \end{tabular} \\ \hline Number of & & & & & & \\ \begin{tabular}{l} CISF that can \\ be shut down \\ (after how \\ many years) \\ \end{tabular} & none & none & \begin{tabular}{l} 3 \\ (65, 70, \\ 80 years) \\ \end{tabular} & none & \begin{tabular}{l} 5 \\ (45, 50, \\ 50, 55, \\ 60 years) \\ \end{tabular} & none & \begin{tabular}{l} 5 \\ (40, 50, \\ 50, 55, \\ 60 years) \\ \end{tabular} & \begin{tabular}{l} 1 \\ (80 years) \\ \end{tabular} \\ \hline Locations of & & & & & & \\ \begin{tabular}{l} CISF (see \\ Figure 6) \\ \end{tabular} & 2, 5, 6, & 7, 8, 9 & \begin{tabular}{l} 2, 5, 6, \\ 7, 8, 9 \\ \end{tabular} & none & \begin{tabular}{l} 2, 5, 6, \\ 7, 8 \\ \end{tabular} & 8 \\ \hline After how many & & & & & & \\ \begin{tabular}{l} years can the \\ last ISFSI be \\ closed? \\ \end{tabular} & never & 25 years & 60 years & 30 years & 40 years & 25 years \\ \hline Percentage of & & & & & \\ \
\begin{tabular}{l} casks that must \\ be refilled \\ \end{tabular} & 100\% & 66\% & 100\% & 59\% & 98\% & 2\% \\ \hline Overall amount & & & & & & \\
\begin{tabular}{l} of HLW \\ in 2100 [MTU] \\ \end{tabular} & 124,000 & 124,000 & 124,000 & 124,000 & 70,000 \\ \hline \hline \end{tabular} Source: own representation.  
\end{table} 
Table 3: Overview of the results of all scenarios.