STANDARDIZATION AND HALF-LIFE MEASUREMENT OF FE-55

Methods for measurement of the specific activity and the KX-ray emissi on rate per Ig of a Fe-55 solution are described. The emission rate wa s determined by a pressurized proportional 4 pi-counter with an uncert ainty of 0.3% and absorption and self-absorption corrections were dete rmined experimentally for each source. The specific activity of the 55 Fe solution was determined with an uncertainty of 0.7% by the 4 pi KX- gamma-coincidence tracing method with Mn-54 as the tracer. Fe-55 to Mn -54 efficiency ratio equations were derived. The 55Fe half-life was me asured in the pressurized proportional 4 pi-counter over a period of s imilar to 2.5 half-lives. The result is 995 +/- 3 days. (C) 1998 Elsev ier Science Ltd. All rights reserved.