HALF-LIFE OF SR-90 - MEASUREMENT AND CRITICAL-REVIEW

Recent evaluations of the half-life of Sr-90 have demonstrated the var iable quality of the available experimental data which has prevented t he estimation and adoption of a value that commands confidence. In an attempt to reduce the uncertainty in the half-life to an acceptable le vel, the decay of a Sr-90 source has been followed for over six years at NPL. The equipment comprised matching, re-entrant, high-pressure io nization chambers and a long-lived reference source to reduce non-rand om effects. The experimental technique is described together with the statistical procedure used to analyse the measured data. A half-life v alue was determined together with an estimate of the associated uncert ainties. A new evaluation of the Sr-90 half-life has been made, taking account of the new NPL data and other recent measurements. Particular attention has been paid to the experimental techniques used to produc e the data and the uncertainties attributed to them. An objective eval uation has been conducted to produce a new recommended half-life value of 10516 +/- 21 days.