Expanded uncertainty modeling of the uranium isotope dilution standards

Journal of Analytical Science and Technology

Table 1 Properties of the evaluated spike solutions from the CRM 112A (original stock) (CRM 112A-1, SP 1; CRM 112A-2, SP 2; CRM 112A-3, SP 3; CRM 112A-4, SP 4)

	CRM 112 A-1 (SP1)	CRM 112A-2 (SP2)	CRM 112A-3 (SP3)	CRM 112A-4 (SP4)	CRM 149 (SA)
C(U) (g U/g)	0.004402361	0.000880909	0.000542279	0.000130669	0.005144913
At.Wt	238.028918	238.028918	238.028918	238.028918	235.19792
c(U) (mol U/g)	1.84951E− 05	3.70085E− 06	2.27821E− 06	5.48963E− 07	2.18748E− 05
AF(235 U)	0.0072017	0.0072017	0.0072017	0.0072017	0.93257
AF(238 U)	0.9927458	0.9927458	0.9927458	0.9927458	0.053294
R(58) (at/at)	0.0072543	0.0072543	0.0072543	0.0072543	17.49859271
C(235) (mol U/g)	1.33196E− 07	2.66524E− 08	1.6407E− 08	3.95347E− 09	2.03998E− 05
C(238)(mol U/g)	1.83609E− 05	3.674E− 06	2.26168E− 06	5.44981E− 07	1.1658E− 06

See Certified Reference Material (CRM) certificates issued by NBL for major and minor isotope ratios. The presumed spike solutions (SP2, SP3, SP4) were calculated by diluting (factors of 5, 8, 33 times) the known quantities of SP1 (original spike solution weight is ca. 20 g). The relative atomic mass and the atom fractional abundances of ²³⁵U and ²³⁸U in the simulated solutions remain unchanged. SP1 Spike 1-original stock-, SP2 Spike 2, SP3 Spike 3, SP4 Spike 4, SA sample-treated as unknown-; for the abbreviations, see the Table 6