Characterization of Neptunium Oxide Generated Using the HB-Line Phase II Flowsheet

Effect of Precipitation Conditions on the Specific Surface Area of Neptunium Oxide

“…Neptunium oxide in a previous study that was created under similar precipitation and calcination conditions had a SSA of 5.34 m 2 /g [2,3]. This value is slightly higher than the SSA of 4.85 m 2 /g that was measured in this study.…”

“…The bounding case oxide was calcined at 625 ºC while the nominal case oxide was calcined at 600 ºC. Previous work has shown significant differences in SSA for NpO 2 calcined at 600 ºC and 650 ºC for two hours (5.34 m 2 /g and 3.68 m 2 /g, respectively) [2]. With limited data available, it is difficult to quantify the effect of calcination temperature on the rate of SSA reduction.…”

“…A glass standard with a surface area of 5.0 ± 0.3 m 2 /g was also analyzed. This instrument and method were used for SSA measurements associated with NpO 2 gas generation testing [2]. Based on previous measurements of NpO 2 SSA, the method precision has a 95% confidence interval of ± 2.2% [7].…”

“…Previous work has demonstrated that even after NpO 2 with a SSA of 5.34 m 2 /g is exposed to 75% relative humidity, hydrogen generation rates are acceptable for shipping [1]. Table 1 contains SSA measurements from previous experimental work [2]. In these studies, neptunium oxalate was precipitated under "nominal" conditions.…”

Water Sorption and Radiolysis Studies for Neptunium Oxides

“…With such precedents, we expect an identical limit will be established for the NpO 2 that is to be prepared at SRS. In light of the current moisture uptake data for the NpO 2 prepared at 650ºC, and based on similar results obtained at 75% relative humidity by the Savannah River Technology Center, 11 the storage standard limit of 0.5 wt % could never be reached in normal operating or storage conditions where humidity levels are controlled at 60-75%.…”