In-House Alternative for Chemical Analyses of Rhenium and Sulfur in Glass
Accurate measurements of rhenium (Re) and sulfur (S) concentrations in solid samples are of critical importance for the key research activities at the Pacific Northwest National Laboratory (PNNL) Waste Form Development Laboratory (WFDL) related to Re behavior during waste glass melting process and solubility of S in glass. Southwest Research Institute (SwRI) has provided reliable services for chemical analysis needs at WFDL; however, its long turnaround time, occasionally up to 5 months, has caused some difficulties. An in-house method was developed for dissolving and fusing glass and feed samples in preparation for analyses by inductively coupled plasma-optical emission spectrometry and -mass spectrometry at a PNNL facility. Using a previously developed sodium hydroxide fusion method as a basis, four groups of samples from Hanford waste glass research were digested and fused at WFDL. The samples included 1) Enhanced low-activity waste glass correlation phase 2/3 melter glasses from the Vitreous State Laboratory at the Catholic University of America, 2) AN-102 dried feeds and glasses, 3) SS-AN-102 dried feeds and glasses, and 4) Integrated Research Project S solubility study glasses. We evaluated three different sets of solution preparation and analysis combinations, which included 1) a WFDL-prepared solution analyzed at SwRI, 2) a PNNLprepared solution analyzed at a laboratory in the Building-331at PNNL, and 3) an SwRIprepared solution analyzed at SwRI. We concluded that the PNNL in-house Re results can be used in parallel with the SwRI data based on the relative standard deviation values less than 6% from three different sets of solution preparation and analysis for all three groups of rhenium-containing samples tested. However, it was proposed that the in-house S data be used for the barium oxide-free glasses only because of the issue of barium sulfate precipitation in digestion/fusion solutions prepared from glasses containing barium oxide. In addition, higher analytical biases between the PNNL and SwRI S results are expected compared to the Re results, based on the relative standard deviation values of less than 10% from three different sets of solution preparation and analysis for two groups of S-containing samples.