Synthesis and Outlook

Abstract

This book provides a comprehensive overview of Chinese activities to establish a new underground laboratory for repository research.

This book provides a comprehensive overview of Chinese activities to establish a new underground laboratory for repository research. The URL project in the Chinese province of Gansu started in 2015 with several potentially suitable sites in crystalline and clay rock. The Beishan site has proven to be the most suitable location for the construction of the underground research laboratory. A tunnel boring machine (TBM) was specially designed and constructed for the excavation of the URL tunnel. The start-up of the laboratory is planned in four years for 2027 (see Sect. 2.1).

In addition to the host rock, the geotechnical barrier plays an important role in the concept for the final disposal of radioactive waste. The so-called Gaomiaozi (GMZ) bentonite, which is available in sufficient quantities in China, is intended for this purpose. In order to investigate the thermo-hydro-mechanical-chemical (THMC) processes acting on the GMZ, a corresponding long-term laboratory experiment was carried out (GMZ Mock-Up Test) (see Chap. 2). The data from the large-scale laboratory experiment are available for process studies. To evaluate the data, the modelling teams from BRIUG, TU Clausthal and TU Freiberg joined forces and interpreted the measurement results with different models (see Chap. 4). The results are also to be published in a joint publication. Transport processes in the far field of a deep geological repository were investigated by the UFZ. This primarily involved the influence of heterogeneities in the aquifers of the framework rock. As part of the pilot project, the experimental database on the GMZ bentonite was further completed. Geomechanical, mineralogical and geochemical investigations were carried out in the laboratories of BGR, GRS, Jena University and KIT (Chap. 3). For this purpose, BRIUG provided corresponding samples of the GMZ bentonite. The results of the project have contributed both to the experimental basis and to a better understanding of the complex THMC processes in the geotechnical barrier (GZM bentonite). In addition, the cooperation between the Chinese and German scientists could be further deepened, despite the difficult conditions caused by the Corona pandemic.

With the site selection act (2014/2017) and the final report of the commission ‘Deposition of highly radioactive waste’ (2016), Germany faces the challenge of the comparative site search in the different types of host rocks: salt, clay and crystalline formations. In Germany, there is an excellent level of knowledge regarding salt rock, an advanced status with regard to clay/clay stone, but only few insights into crystalline formations, so there is a special need for research and cooperation here. The teaching and research underground laboratory ‘Reiche Zeche’ operated by TU Freiberg covers broad aspects of mining research. Since Germany does not have its own dedicated underground laboratory (URL) for repository studies in crystalline rock, individual aspects of long-term safety in granite formations have been investigated in cooperation with the Swiss NAGRA¹ (Grimsel Rock Laboratory) and the Swedish SKB² (Hard Rock Laboratory Äspö). However, these studies do not comply requirements of the above-mentioned legal acts, and they are not transferable (e.g. unlike in Germany, in Sweden no higher and longer heat-generating mixed-oxide (MOX) fuel elements are stored). China’s decision to establish a new URL in Beishan (Gansu Province) offers a unique opportunity to obtain data in its original state in an undisturbed crystalline formation (with regionally higher than average geothermal gradients). The new URL in Beishan is welcomed in the network of established URLs in crystalline rocks (Fig. 5.1) and shall play an important role also for international research in future—as a place of international collaboration in order to improve the knowledge base for safe deep geological deposition of radioactive waste in the subsurface.

Fig. 5.1

Network of URLs in crystalline rock environments