Borehole drilling and related activities at the Stripa mine

Drilling operations for the joint Swedish-U.S. program on radioactive waste storage in mined caverns were conducted from August, 1977 to April, 1978. At the peak of drilling, six drills were active, one on the surface and five underground. 160 boreholes were drilled with sizes ranging from 38 to 406 mm dia. Special techniques and drilling equipment were developed to drill and remove the large cores. Instrumentation and heater installations required strict drilling specifications. Detailed descriptions of the fractures and other relevant rock properties required orientation of the core as well as special recovery techniques. To assure the best possible quality of the core, a triple-tube core barrel was used to drill all boreholes 76 mm diameter and larger