In addition to preserving information and knowledge, long-term documentation also focuses on safeguarding the memory of the repository. The aim is to anchor knowledge about the existence of the repository in society. Future generations should also be aware of the repository's significance.

Why is it important to remember the radioactive waste?

The repository protects people and the environment from radioactive substances. It is planned in such a way that no human intervention will be necessary in the future. This will be ensured by the host rock, several technical barriers and the backfilling of the repository.

Final disposal is a matter of hundreds of thousands of years. Knowledge of the repository and the substances emplaced therein may be gradually lost over such a long period of time. Social or political upheavals or natural disasters, for example, can also cause an abrupt loss of such knowledge.

Should people then drill or dig in the vicinity of the repository without taking the necessary precautions, this could impair the protective effect of the repository. In a worst-case scenario, they might expose themselves and the environment to danger. This is referred to as "inadvertent human intrusion", i.e. unintentional human intrusion into the repository. At a depth of several hundred metres, however, the repository can only be reached with considerable technical effort and time.

The first concepts to reduce the probability of unintentional human intrusion were developed in the 1980s and 1990s. Many of these concepts relied on deterrence to keep people away from the repository site. Nowadays, the focus is on education, information and preserving the memory in society.

How can the memory of the repository be preserved?

Preserving the memory of the repository is no easy feat. Various factors could lead to the loss of knowledge regarding the existence of the repository and the materials emplaced therein. Simply marking the site on maps and in the land registry will not be enough.

Rather, the international consensus today is that a variety of measures should be taken. These should be as diverse as possible, but interlock and refer to each other. If one measure is then forgotten, there are others that can be used to preserve the memory and recover the knowledge. The aim is to anchor knowledge about the repository and the stored materials on a broad basis in society.

The OECD NEA's "Initiative for the Preservation of Records, Knowledge and Memory Across Generations" (RK&M) has significantly shaped understanding in this area. This "Initiative for the Preservation of Records, Knowledge and Memory Across Generations" was active from 2011 to 2018. A total of 35 measures, distributed across nine approaches, were compiled in a kind of "toolbox". These include, among others:

• Archives,
• special document sets for various target groups,
• museums,
• the above-ground marking of the repository site,
• co-operation with educational institutions, artists and cultural workers.

These approaches contribute to an "awareness preservation", i.e. preserving the memory or awareness of what is located underground.

Many countries and organisations around the world are looking at ways of preserving knowledge about the significance of the repository. The OECD's Nuclear Energy Agency (NEA) is therefore working on measures and sharing experiences. BASE has been actively involved in several expert groups of the follow-up project, the "Working Party on Information, Data and Knowledge Management" (WP-IDKM), since 2020.

To preserve the memory, it is also important to come to terms with one's own nuclear history.

Approaches to nuclear cultural heritage are therefore attracting increasing attention both on an international level and in Germany. These are being analysed by the ongoing NuCultAge research project, and put in relation to Germany.

The aim is to obtain an overview of existing active forms of remembrance. These include exhibitions and guided tours in decommissioned nuclear power plants, such as Unit 6 of the Lubmin nuclear power plant in Greifswald.

How can we communicate with the distant future?

The measures to preserve knowledge mentioned above also include mechanisms aimed at future generations.

The final disposal of high-level radioactive substances involves long periods of up to several hundred thousand years. During this time, the language and meaning of the signs will also undergo major changes. This could lead to messages no longer being understood after just a few centuries.

Various measures could be combined to maintain awareness of the existence of the repository in the long term:

• Multilingual warning texts could be set up at the repository site.
• The coordinates of locations providing further information could be indicated. These could be the locations of the German National Library. The geographic coordinates could be used to find the repositories and the associated documentation.

Atomic semiotics focuses on what needs to be considered when designing messages to the distant future. Semiotics is the study of signs and sign processes.

It forms the basis for many scientific disciplines that deal with communication processes in the broadest sense. In the field of nuclear waste disposal, it provides important insights, also by looking back into the past.

Atomic semiotics plays a role in various ideas for marking the repository above ground.