The licence for the construction and operation of a repository for radioactive waste is inseparably linked to the demonstration of the long-term safety of such a nuclear facility. An essential basis for judging the safety of a repository is the determination of relevant scenarios that may lead to a radionuclide release in the post-operational phase. The identification, detailed description and choice of possible future processes (relevant scenarios) are all part of the scenario development process. A scenario describes a postulated evolution of the repository system and its safety functions which is specified by a combination of relevant factors that characterise the repository system or have an influence on it.

Different methodical approaches to scenario development are pursued internationally. In the context of the German repository programme, the development of a commonly accepted technical basis is therefore desirable. This is why the Working Group "Scenario Development" was formed as early as in 1997. The Working Group is organised and chaired by GRS.

The Working Group "Scenario Development" consists of representatives of different institutions who concentrate the technical expertise with respect to the issue of scenarios in Germany. With its constituting meeting in 1997, the Working Group has given itself the task of developing a common understanding of the different main emphases in the context of scenario development and transporting it to the experts, discussing new developments and trends, working out and publishing or otherwise publicly communicating common positions, seeking the dialog and promoting consensual agreement, but in addition also of identifying different views, opinions and procedures relating to the problems.

One of the topics which the Working Group has recently been intensively deliberating refers to the treatment of human intrusion into a repository for radioactive waste in a deep geological formation. The Working Group prepared a position paper on this issue that was published in the technical journal "atw" (atw Vol. 53 (2008) No. 8/9 – August/September).