Marcos Buser & Walter Wildi

Photo (W.Wildi): Old lava tunnel

Deep geological disposal of highly radioactive waste: a concept from the 20th century is being replaced

On 19 November 2024, Nagra submitted its general licence application for a deep geological repository for radioactive waste to the Federal Office of Energy. Switzerland’s low, intermediate and high-level radioactive waste is to be stored in a deep geological repository in the “North of Lägern” area, near the tri-border region of Zurich, Aargau and Germany, in the second half of the 21st century. The content of the application will not be made public immediately, however, but will first be checked for completeness by ENSI.

Now, that the search for a site for a deep geological repository has been going on for more than half a century (Nagra was founded in 1972), we would like to ask a more fundamental question: is the search for a site for a storage facility still relevant at all for all categories of radioactive waste? Has science stood still in the last half-century with the level of knowledge from 1972 and the concept of deep geological disposal? And where is the journey headed? Will people still be willing and able to justify burying the “hot”, highly radioactive waste in the deep underground forever in another 50 years?

Deep geological disposal has become the standard method of dealing with radioactive waste internationally and in Switzerland in the course of the second half of the 20th century. Accordingly, in 2000, the group of experts appointed by Federal Councillor Leuenberger, EKRA, proposed a storage concept in Switzerland that provided for monitored and, if necessary, retrievable deep geological disposal. This concept was adopted in the Nuclear Energy Act of 2003 and still forms the basis for the work of Nagra, which is to map out the path to the eventual storage of the waste and its location underground for many hundreds of thousands of years. So far, so good, only: over the last two decades, our demands in environmental issues and our understanding of possible alternative solutions to the waste issue have developed further:

· In the handling of valuable raw materials, the trend is towards a circular economy. Used raw materials should not be returned to the environment, sooner or later diffusing into it and causing environmental pollution; raw materials are to be recycled and reused.

While such recycling is generally difficult for low and intermediate level radioactive waste due to the mostly low concentrations in clearly separable material classes, it seems more feasible and worthwhile for the high concentrations of uranium and other heavy metals in highly radioactive waste.

For a long time, the transmutation of highly radioactive, long-lived substances into substances with lower radioactivity and a shorter lifespan (short half-life) was considered too costly and expensive. Thanks to new methods, this now seems to be changing. The Geneva-based company TRANSMUTEX, for example, is proposing a corresponding scientific and technological concept (https://www.transmutex.com/). This concept allows the conversion of highly radioactive, long-lived waste into waste with a lower level of activity and a shorter half-life. Other thorium reactors currently in development are also designed as so-called ‘waste-burners’ with the aim of one day using highly active waste from existing light water reactors as fuel and destroying it.

Even if such concepts do not yet provide a satisfactory answer to all questions of nuclear waste disposal, it seems clear that the development is moving towards the recycling of uranium and transuranic elements and thus towards the transmutation of highly radioactive waste. The idea of deep geological disposal for this category of waste is likely to be replaced sooner or later.

From this perspective, Nagra’s general licence application for the high-level radioactive waste category becomes obsolete. The ongoing process for the general licence can be completed as the final step in Switzerland’s site selection procedure, but knowing that the disposal of nuclear waste will take different and new paths and that deep geological disposal will one day be replaced by more sustainable solutions. The compass of technical development points clearly in the direction of a circular economy and transmutation, or a significantly better containment of non-transmutable substances. It is highly recommended that these newly emerging alternatives be seriously and conscientiously examined and, if necessary, that the legal framework and the waste management programme be adapted.