A NEW HALF-LIFE DETERMINATION OF NI-59

An enriched Ni-58 sample has been irradiated with thermal neutrons tog ether with an enriched Fe-54 target. After chemical purification of th e nickel sample, the produced radioactivities of Ni-59 and Fe-55 were measured with a silicon detector. The half-life of Ni-59 has been dedu ced to be 108,000+/-13,000 years. This half-life is larger than the co mmonly adopted half-life value of 76,000+/-5000 years but is in full a greement with Ni-59 concentration and activity measurements of the met eorite Admire. With accelerator mass spectrometry, the cross-section o f the reaction Ni-60(n,2n)Ni-59 for 14.8 MeV neutrons has been measure d to be 410+/-100 mb.