2.1.1 Linear Staging

Linear Staging is defined as a management process characterized by a single predetermined path to a selected, completely defined end point, with stages defined principally as milestones where program progress, costs, and schedules are reviewed. The path and end points are reevaluated only if compelling new evidence or other circumstances absolutely require it. That is, Linear Staging attempts to preserve the specified end point and the path to reach it.

2.1.2 Adaptive Staging

The committee applies the term “Adaptive Staging” to a process divided into phases (see Section 1.2), stages, and Decision Points2 (see Figures 2.1a, b, and c). The overarching goal of Adaptive Staging is to improve the chances of reaching repository program’s success, as defined in Section 1.2.2. The program begins with a reference framework that can be modified, if necessary, by new information.3 Decision Points mark the transition between stages of project implementation. At these points, the implementer evaluates results obtained and information acquired and decides on the optimal path to proceed (see Section 2.4). Subsequent stages are predicated on the outcomes of previous stages. No single path is therefore recognized from the outset as being fixed; flexibility, which allows adaptation of the approach toward agreed overarching goals, is maintained throughout.

This approach emphasizes continuous learning throughout program development: integration of new knowledge is anticipated in the program. Similarly, Decision Points allow the project to adapt and incorporate new information throughout the process. Stages are defined to pursue continuous program improvement until success is reached. Examples of criteria for program improvements may involve increasing safety, cost-effectiveness,4 or societal acceptance of the repository.

The committee’s terminology does not imply that Adaptive Staging and Linear Staging are new concepts, or denies that both approaches have common features, or that there may be a continuum between approaches.5

2.2 The safety case at the heart of Adaptive Staging

For radioactive waste repositories, safety is the overriding concern in all program-


The committee coined the term “Decision Point” and defines it in Section 2.4.


The specific path to achieve disposal of high-level waste in a geologic repository is not specified at the outset. At the beginning of any long-term, complex project, the details of the path to the final end point are not clear. Consequently, good cost estimates are also lacking. As the implementer advances in the process, details of the reference framework and cost estimates become better established.


Commitment to systematic learning and cost-effectiveness may appear, at first, to be incompatible. However, cost-effectiveness implies that Adaptive Staging can help avoid the cost of not gathering information and making unwise decisions.


In this report, Adaptive Staging is only briefly juxtaposed to Linear Staging to illustrate the differences between the two approaches. The committee mainly focuses on features, implementation, and impacts of Adaptive Staging.

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement