## 1 Introduction
The urgency of finding new storage solutions is emphasized when looking at current development in the nuclear energy sector. In Figure 2 the construction and shut-down of all reactors in the U.S. since 1958 can be seen. Furthermore, there is a forecast of future shutdowns, based on corporate announcements and reports by the Nuclear Regulatory Commission (NRC). As one can see the construction of new reactors came almost to a complete end after 1996 since only two new units are currently under construction (two have been abandoned recently [18]). The rate of reactor shutdowns will most probably increase rapidly during the next 17 years and will almost be complete by 2050 ([1], p. 1). The reason for this development is the loss of competitiveness of nuclear energy in the energy market as described in [PERSON] et al. ([1], p. 2) and [PERSON] [19]. Correlating with this increasing rate of reactor shutdowns is an even greater amount of HLW to be stored in independent storage installations as the reactors--this includes the storage pools--are going to be dismantled. Therefore, the problem the U.S. have with their nuclear waste tightens and the pressure of finding low-cost and permanent storage solutions increases. Figure 1: Regional distribution of high-level nuclear waste and nuclear power plants in the U.S. (source: own representation based on [2; 16; 17], and own estimations.) The DOE is responsible for the high-level nuclear waste management. Hence, the transport as well as the disposal costs of HLW are financed by the Nuclear Waste Fund and Governmental funding [21] and an optimization of this process is in the public interest. The DOE was not able to come up with disposal solutions until now and is currently paying significant amounts of money to the energy companies running the NPPs in order to compensate them for having to store the nuclear waste for such long periods of time. According to the DOE the total damage amounts to $20.8 billion if the federal government begins accepting SNF in 2020 (as presumed in the model presented in this paper), but could increase by hundreds of millions of dollars annually for any further delay of doing so ([4], p. 79). However, the DOE is working on solutions. One example is the 2012 report by the Blue Ribbon Commission (BRC) on America's Nuclear Future (The BRC was created in 2010 to conduct research and recommend a plan of action for the U.S. waste management and disposal of SNF) [4], inciting the DOE to release a strategy paper the following year. This strategy paper contains a program the Administration plans to implement in order to approach the HLW storage problem and to fulfill its obligations regarding the waste management. Among other things, the DOE plans to build a pilot interim storage facility and have it operate by 2021 with an initial focus on accepting used nuclear fuel from shut-down reactor sites. Furthermore, a larger consolidated interim storage facility (CISF) should be available by 2025 that will have a sufficient capacity of 20,000 metric tons or greater and will therefore allow for storage of enough used nuclear fuel to reduce government liabilities [22]. In addition, the CISF should reduce overall storage costs and provide flexibility and economics of scale for the waste management system. Although, the major challenge is that the DOE lacks the legal authority under the Nuclear Waste Policy Act (NWPA) from 1982 to provide it, the Congress would need to license Yuca Mountain for this first. Given the delays, a number of private companies have sought licenses for interim storage facilities as they are not bound by the rigidity of the NWPA ([3], p. 72). The overall resulting research question is how the storage of HLW in the U.S. has to develop over time in order to accumulate the waste at fewer locations while reducing costs. With respect to the current situation, we developed a model of HLW transportation and storage in the U.S.