The Impact of the Actinide Removal Process (ARP) on the SB4 Projected Operating Windows

Peeler, D

Savannah River Site (S.C.)

关键词: Removal;    Sludges;    Flowsheets;    Sulfates;    Waste Forms;   

DOI  :  10.2172/890171
RP-ID  :  WSRC-TR-2005-00123
RP-ID  :  DE-AC09-96SR18500
RP-ID  :  890171

美国|英语

来源: UNT Digital Library

【 摘 要 】

The model-based assessments of nominal Sludge Batch 4 (SB4) compositions suggest that a viable frit candidate does not appear to be a limiting factor as the Closure Business Unit (CBU) considers various tank blending options for SB4 with or without the Actinide Removal Process (ARP) streams. This statement is based solely on the projected operating windows derived from model predictions and does not include experimental assessments of SO{sub 4} solubility or melt rate issues. To assess the impact of the various ARP options on the projected operating windows, the 1100 canister SB4 baseline options served as the technical baseline or reference point for the comparisons. With respect to the various ARP options being considered, the impacts to the projected operating windows were relatively consistent with the impacts being dependent upon the property limiting access to higher WLs. More specifically, for those 1100 canister SB4 systems (without ARP) which were T{sub L}-limited, the general impact was an increase in the upper WL which was classified as acceptable resulting in an overall increase in the operating window size. The anticipated negative impact of TiO{sub 2} (due to an assumed increase in T{sub L} which would further reduce the size of the operating window of such systems) was not observed. The hypothesis is that the negative impact was countered or compensated by a positive impact due to the additional Na{sub 2}O from the ARP process. The overall result was a net increase in the size of the operating window for the SB4 1100 canister options which were T{sub L}-limited. This trend was observed for all five ARP options with the only difference being the magnitude of the increase (ranging from a 1%-4% increase) which was strictly based on the specific ARP composition and blending strategy. Another general observation for all five ARP options was a negative impact with their addition to a 1100 canister system that was initially low viscosity limited or durability limited. For these systems, addition of each ARP stream resulted in a negative impact to the upper WL defining the operating window as a result of the additional Na{sub 2}O introduced which drove both viscosity and durability predictions lower at the same WL. The magnitude of the impact ranged from a 1-2% reduction for low viscosity limited systems to complete elimination of the operating windows for durability limited systems. The latter situation (i.e., complete elimination of the operating window for a given SB4 blending option with a specified frit) would require a change in frit to compositionally compensate for the ARP addition. One of the most interesting ARP options was the introduction of the ARP-K case. Model-based predictions and projected TiO{sub 2} concentrations, would require an increase in the current PCCS TiO{sub 2} limit from 1 wt% to 2 wt% (if WLs targeting 39% or greater are desired). With this increase, there appears to be some potential advantages of this ARP stream relative to the other four ARP options. One potential advantage is based on the {approx}4% increase in the upper WL defining the projected window for most of the options being considered (which were initially T{sub L} limited). Although potentially advantageous for some systems, the addition of the ARP-K stream could be devastating to other systems if compositional adjustments are not made (i.e., a frit change). Frits could be selected that are robust to the inclusion of the ARP but they may not be optimized for other properties (e.g., melt rate). Although ARP-K has potential advantages on the projected operating windows, the other ARP options evaluated should not be dismissed as other criteria (e.g., melt rate and/or CPC processing issues) should be considered prior to pursuing a particular ARP processing scenario. More specifically, based on the assessments performed in this report, there are no show-stoppers for any of the ARP options being considered--although some options could require a frit change between a ''sludge-only'' flowsheet and its ''coupled'' (sludge plus ARP) counterpart. Based on the SB4-ARP blending strategies, the additions of TiO{sub 2} and SO{sub 4} from the ARP streams could result in these oxides exceeding some critical value that would give rise to uncertainties or questions associated with the applicability of select models or exceeding individual solubility limits. In general, establishing a PCCS SO{sub 4} limit of 0.5 or 0.6 wt% (in glass) appears to be sufficient to avoid the SB4-ARP systems from being SO{sub 4} limited at the upper WLs. With respect to model applicability issues, the primary PCCS model of concern was the T{sub L} model which was developed over TiO{sub 2} concentrations ranging from 0.0-1.8549 wt% (in glass). Although the ARP-K option would require the TiO{sub 2} limit to be raised to 2.0 wt%, maximum TiO{sub 2} concentrations in glass are well below the 2 wt% limit established by Lorier and Jantzen (2003).