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    1. implement new storage facilities, and

    2. work toward emplacement in a repository (“geological disposition”), with the expectation that the repository eventually will be closed and sealed (“geological disposal”). See Sidebar 1.3.

The advantages and drawbacks of both alternatives (and the likelihood of other options becoming available) must be evaluated as input for the necessary societal decisions. The benefits, costs, and risks associated with the two current options are of a radically different nature, so that a phased approach may enhance the benefits of both options.

The long-term storage alternative can provide safety and security, as proven by more than 50 years of operation of such facilities. It also fulfills an ethical goal of keeping future options as open as possible. It can be extended to very long times in the future, provided that the storage is continuously monitored and maintained and periodically rebuilt. However, this option also faces societal challenges: efforts to site new storage facilities typically encounter public resistance, and storage requires a continuing commitment of resources. There is uncertainty that future societies will have the stability to maintain the strict institutional controls needed to prevent intentional misuse of nuclear materials or the will to continue to provide resources for the monitoring and maintenance needed for safety.

Geological disposal, the approach recommended in previous National Research Council (NRC) reports (NRC, 1957, 1990) and by many other national and international scientific bodies, is the only available alternative that does not require ongoing control and resource expenditures by future generations. The science supporting this alternative has been developed by intensive work over the past 25 years. The view repeatedly expressed by a large fraction of the scientific and technical community is that geological disposal, correctly managed, is a safe approach to long-term management of HLW and that it best satisfies the ethical goal of minimizing burdens on future generations. Nevertheless, uncertainties remain, and some scientists feel that it is premature to commit fully to disposal. The biggest challenges to initiating geological disposition, however, are societal: there is a clear lack of public confidence and support in many countries for proceeding with siting and construction of geological repositories.

Whether, how, and when to move toward geological disposition or disposal are societal decisions for each country, to be made following estimation of the uncertainties and risks associated with this option and with its alternatives. Given the technical and societal uncertainties, a stepwise process that allows for continuing improvement of scientific understanding is appropriate for decision making. A stepwise process, embedded within a flexible and adaptive management system, is also

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