title: Preparation of (228)Ra standard solution.
abstract: For the preparation of a standard solution of (228)Ra, (228)Ra was isolated from (232)Th salt. Two simple methods were developed for Th-Ra separation. Both are based on a very good solubility of thorium nitrate in organic solvents. The first one used Ra co-precipitation with Pb in the form of Pb(NO3)2 from acetic acid solution. The second method was based on solvent extraction, remaining Th in the organic phase, while Ra was concentrated in the aqueous phase. The activity of (228)Ra (up to 20kBq) in the standard solution was related to the (232)Th standard by means of gamma ray spectrometry measurement. The obtained uncertainty was less than 0.7% (k=1). The standard solution was free of (232)Th and contained the carrier in the usual concentration (1gL(-1) BaCl2, 10gL(-1) HCl).
authors.affiliation: Czech Metrology Institute, Radiová 1, 102 00 Prague, Czech Republic. Electronic address: mhavelka@cmi.cz.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Havelka
keywords: (228)Ra standard; Ra–Pb co-precipitation; Th–Ra separation