7. Conclusion

The use of large-scale artificial caverns has become standard practice, both for energy and non-energy applications. Their advantages are considerable, but their potential is still insufficiently known, and there is no demand for them. Massive use obviously presupposes long-term planning of underground uses, in the same way as urban planning on the surface. The importance of geological and geographical conditions should make this an important element of land-use planning, as should the availability of natural sites, mineral deposits, sheltered harbours, waterfalls, windy peaks, and so on. Since the underground storage of radioactive waste has been accepted by public opinion, we must assume that the undergrounding of nuclear reactors is an essential condition for their acceptance in the decades to come, and that many other environmentally hazardous activities should also be placed underground,...