Hydroxycalix[n]arenes possess high chemical and radiolytic stability, being promising extractants for long-lived radionuclides recovery from alkaline media. P-isononylcalix[6]arene shows the optimal combination of high extraction ability and good solubility in a paraffin diluent. During the static tests on real waste, high purification factors were achieved: 15,000 for ¹³⁷Cs and β-emitters and 100—for α-emitting radionuclides. Dynamic tests were carried out on a 16-stage test bench in countercurrent mode using model alkaline HLW. Purification factor > 500 was achieved for ¹³⁷Cs with its tenfold concentration in the re-extract. Test results confirm the possibility of using p-isononylcalix[6]arene for alkaline HLW processing.