Direct measurement of the half-life of (223)Ra

S M Collins; A K Pearce; K M Ferreira; A J Fenwick; P H Regan; J D Keightley

doi:10.1016/j.apradiso.2015.02.003

Direct measurement of the half-life of (223)Ra

Appl Radiat Isot. 2015 May:99:46-53. doi: 10.1016/j.apradiso.2015.02.003. Epub 2015 Feb 7.

Authors

S M Collins¹, A K Pearce², K M Ferreira², A J Fenwick², P H Regan³, J D Keightley²

Affiliations

¹ National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom. Electronic address: sean.collins@npl.co.uk.
² National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom.
³ National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom; Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom.

PMID: 25699667
DOI: 10.1016/j.apradiso.2015.02.003

Abstract

Radioactive decay half-life measurements of (223)Ra, a member of the (235)U naturally occurring radioactive decay series, have been performed of a radiochemically pure solution with an ionisation chamber. The radioactive decay of (223)Ra was followed for 50 days, approximately 4.4 half-lives. The deduced half-life of (223)Ra was found to be 11.4358 (28) days, supporting the other published direct measurements. A detailed uncertainty budget is presented. A new evaluation of the published half-life values was performed, indicating significant variation across the existing published values, suggesting that further measurements of the half-life of (223)Ra are required. A new evaluated half-life has been calculated using a power moderated weighted mean of selected experimental values, with a new value of the recommended half-life for (223)Ra of 11.4354 (17) days.

Keywords: (223)Ra; Half-life; Ionisation chamber; NORM; Nuclear data; Nuclear medicine; Radioactivity.