Chemical and Radiochemical Composition of Thermally Stabilized Plutonium Oxide from the Plutonium Finishing Plant Considered as Alternate Feedstock for the Mixed Oxide Fuel Fabrication Facility

Abstract

Eighteen plutonium oxide samples originating from the Plutonium Finishing Plant (PFP) on the Hanford Site were analyzed to provide additional data on the suitability of PFP thermally stabilized plutonium oxides and Rocky Flats oxides as alternate feedstock to the Mixed Oxide Fuel Fabrication Facility (MFFF). Radiochemical and chemical analyses were performed on fusions, acid leaches, and water leaches of these 18 samples. The results from these destructive analyses were compared with nondestructive analyses (NDA) performed at PFP and the acceptance criteria for the alternate feedstock. The plutonium oxide materials considered as alternate feedstock at Hanford originated from several different sources, including Rocky Flats oxide, scrap from the Remote Mechanical C-Line (RMC) and the Plutonium Reclamation Facility (PRF), and materials from other plutonium conversion processes at Hanford. These materials were initially present at PFP as metals, oxides, and solutions. All of the plutonium considered as alternate feedstock was in the form of plutonium dioxide, PuO 2 (and likely also included residual plutonium tetrafluoride, PuF 4) and had undergone thermal stabilization according to DOE-STD-3013 criteria, generally achieved by heating at >950ºC for two hours in an oxidizing environment. The 18 plutonium oxide samples were grouped into four categories based on their origin. The Rocky Flats oxide was divided into two categories according to their relative chloride concentrations (three lowchloride and seven high-chloride samples). The other two categories were PRF/RMC scrap oxides (six samples), including scrap from both process lines, and oxides produced from solutions (two samples). The two solution samples came from samples that previously had been tested at Pacific Northwest National Laboratory. These samples originated at the PFP and are from relatively pure plutonium nitrate product solutions and double-pass filtrate solutions after they had been precipitated with magnesium hydroxide, filtered, and thermally stabilized according to the 3013 criteria. The remaining plutonium oxide from solutions at PFP, including those obtained by oxalic acid treatment to precipitate plutonium oxalate and subsequent oxalate calcination to produce PuO 2 , had already been processed and placed in 3013 containers by the start of the testing and thus were not available for characterization. Samples varied in appearance depending on the original source of material. Rocky Flats items were mostly dark olive green with clumps that crushed easily with a mortar and pestle. PRF/RMC items showed more variability, though most were rust colored. One sample contained white particles that were difficult to crush, and another sample was dark grey with a mixture of fines and large, hard fragments. The appearance and feel of the fragments indicated they might have contained a metallic alloy. The colors of the precipitated and thermally stabilized solution samples were indicative of the impurities they contained. The double-pass filtrate sample was ...

A calibration to predict the concentrations of impurities in plutonium oxide by prompt gamma analysis: Revision 1

“…The disparity was believed to be due to bias in the fluorine results from the Hanford 3013 standards. 12 Therefore, the calibration for fluorine was constructed with the Hanford 3013 container standards omitted to improve the overall fit. The appropriateness of the linear calibration lines for these data was evaluated using plots of the response versus fit and residuals versus fit.…”

“…11 The estimates of chloride concentration for the materials analyzed by this method showed good agreement with those obtained by analytical chemistry. 12 However, this correlation was detector specific and required that the concentration of 241 Am, a significant contributor to the alphaparticle activity, was the same for all materials. Because the age of the materials being packaged in 3013 containers varies considerably, the 241 Am concentration also varies and must be considered.…”

Ultratrace potassium determination in plutonium oxide

“…This can be particularly problematic for the type of analysis Actinide Analytical Chemistry group at Los Alamos National Laboratory (LANL) performs on plutonium oxide (PuO 2 ) materials. Analysis of PuO 2 materials is important for a number of reasons [6]. Of primary interest to LANL is the determination of impurities in PuO 2 material which is slated for use in mixed oxide (MOX) fuels.…”