A new thorium-229 reference material

A new reference material was characterized for ²²⁹Th molality and thorium isotope amount ratios. This reference material is intended for use in nuclear forensic analyses as an isotope dilution mass spectrometry spike. The reference material value and expanded uncertainty (k = 2) for the ²²⁹Th molality is (1.1498 ± 0.0016) × 10^-10molg^-1 solution. The value and expanded uncertainty (k = 2) for the n(²³⁰Th)/n(²²⁹Th) ratio is (5.18 ± 0.26) × 10^-5 and the n(²³²Th)/n(²²⁹Th) ratio is (3.815 ± 0.092) × 10^-4.