Abstract
Tungsten and gold have been irradiated with 24 GeV and 10·8 GeV protons, resp., and the possible production of actinide nuclides by secondary reactions has been investigated. The actinide fractions were chemically separated and α-spectra taken. No α-peaks which could definitely be attributed to actinide nuclides could be found. By taking different formation mechanisms into consideration, upper limits for the cross-sections were calculated and compared with the values expected.