Table 6.

Uncertainty Budget for ²²⁹Th massic activity by IDAS

Component	Comment		Type	ui%
Massic activity	Standard uncertainty of replicate IDAS measurements of 229Th massic activity		A	0.69
Weighing	Estimated relative uncertainty for potential bias in mass of IDAS solution aliquots		B	0.30
Peak tail	Estimated uncertainty of 229Th peak tail correction applied to the α count data		B	0.21
230Th spike	Combined standard uncertainty of the massic activity for SRM 4342A		B	0.20
Background	Estimated uncertainty of 229Th and 230Th background corrections		B	0.04
Relative combined standard uncertainty (uc)			0.81%
229Th massic activity (Bq g−1)		Expanded uncertainty (Bq g−1)
195.9		3.2 (Relative: 1.6%)

The uncertainty estimate for the massic activity was calculated in accordance with Taylor and Kuyatt, [20] and GUM protocols [21] using the GUM Workbench software [22]. u_i% represents the relative standard uncertainty for the listed components. The expanded uncertainty (U = k × u_c) for the massic activity value is the product of the combined standard uncertainty (u_c) and a coverage factor (k), with k = 2 to achieve an approximately 95% level of confidence