The Effective Half-Life of Californium-252

The effective half-life of ²⁵²Cf has been determined as 2.638 ± 0.007 yr. The method utilized the ratio of the manganese activity induced in a manganous-sulfate bath by a ²⁵²Cf spontaneous-fission neutron source and the National Bureau of Standards photo-neutron source to measure the change in emission rate of the ²⁵²Cf source over a period of 1.77 half-lives. The data were corrected for the activity of radium (1622-yr half-life) in the photoneutron source (-0.2%) and for the competing neutron production from ²⁵⁰Cf.