Safeguards Analytical Laboratory
Quality Assurance and Computer Services group
Uncertainties of SAL nuclear material inspection sample analysis
MATERIAL TYPE and METHOD |
UNCERTAINTY OF ROUTINE ANALYSIS RESULT (95% CONFIDENCE INTERVAL, relative) |
| U Assay U Products (D&G titration) | ±0.07 % |
| U Assay U/Pu Products (D&G) | ±0.15 % |
| U Assay U/Pu Products (IDMS) | ±0.21 % |
| U Assay Spent Fuel ("LSD" IDMS) | ±0.14 % |
| Pu Assay U/Pu Products (McD&S) | ±0.14 % |
| Pu Assay U/Pu Products (IDMS) | ±0.26 % |
| Pu Assay Spent Fuel ("LSD" IDMS) | ±0.21 % |
| U Isotopic [wt% 235U], natural U | ±0.27 % |
| U Isotopic [wt% 235U], LEU | ±0.12 % |
| U Isotopic [wt% 235U], HEU | ±0.09 % |
| U Isotopic [wt% 235U], LEU, gamma-Spec | ±0.26 % |
| Pu Isotopic wt% 239Pu | ±0.03 % |
| Pu Isotopic wt% 240Pu | ±0.13 % |
| Pu Isotopic wt% 241Pu | ±0.75 % |
| Pu Isotopic wt% 242Pu | ±0.37 % |
| Pu Isotopic wt% 238Pu, alpha-spec | ±0.84 % |
| 241Am by HRGS/MGA | ±1.47 % |
The uncertainties are "expanded uncertainties" in the definition of the "Guide to the Expression of Uncertainty in Measurement", published in 1993 by ISO in collaboration with BIPM, IEC, IFCC, IUPAC, IUPAP, and OIML. The Student t-value for alpha=0.05 (two-sided) of the t-distribution for the effective degrees of freedom (obtained from the Welch-Satterthwaite formula) of the combined standard uncertainty, uc, has been used as "coverage factor", k, to obtain the expanded uncertainty. All known sources of uncertainty have been considered in the error propagation model, including long- and short-term random fluctuations (reproducibility and repeatability of results) and systematic errors like the uncertainties of certified values of calibration standards or uncertainties of physical constants like radioactive decay half-lifes.