[en] Radioactive waste is generated at all stages of the nuclear fuel cycle, including ore mining, processing and enrichment, nuclear fuel production, NPP operation, fuel processing, production of weapon materials, and decommissioning of nuclear facilities. Today, the disposal of radioactive waste in geological formations is the only option for waste isolation accepted worldwide. Here, the hard rock mass if becomes the major safety barrier for the waste containing long-lived radionuclides. For the purpose of objective safety evaluation for this isolation option, it is necessary to obtain the experience, instruments, and methods allowing a long-term prediction of changes in the rock safety properties. Underground laboratories are created for this purpose. The more monitoring is conducted in these facilities, the greater the probability is in obtaining the reliable data needed. Taking into consideration that the processes in the hard rock are moving slowly, the lifetime of a human being will not be enough to run the studies. This paper will outline the examples of investigations on physical processes in the hard rock massif using a heat source that was acting during a 40- year period of facility operation. (author)