Cost estimates are always subject to uncertainties. No one can determine all future costs with certainty, but the uncertainties that arise are rarely taken into account consistently in the estimate.

The Association of Swiss Nuclear Power Plant Operators (swissnuclear) took on this task with us as part of the 2016 cost study for the decommissioning and dismantling of the Swiss nuclear power plants. Together we have developed a method with which the uncertainties that arise can be taken into account and propagated through the entire cost accounting in order to present them in the final result. In doing so, dependencies were also taken into account, which not only exist in the schedules for dismantling: If one trade takes longer, for example, this can have cost consequences for other trades. These dependencies increase the probability of cost overruns. Our method was extended and reapplied for the recently conducted 2021 cost study.

Knowing these uncertainties in the cost estimate can help to better plan provisions and future costs (eg which safety margin is necessary so that the provisions are sufficient). It can also be used to identify dependencies in the probability of major cost overruns and to take countermeasures at an early stage.