A new thorium-229 reference material.

A new reference material was characterized for 229 Th 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 229 Th molality is (1.1498 ± 0.0016) × 10-10 molg-1 solution. The value and expanded uncertainty (k = 2) for the n(230 Th)/n(229 Th) ratio is (5.18 ± 0.26) × 10-5 and the n(232 Th)/n(229 Th) ratio is (3.815 ± 0.092) × 10-4 .