Alternative High-Level Waste Treatments at the Idaho National Engineering and Environmental Laboratory (1999) / Chapter Skim
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3 Physical and Chemical Separations
3 Physical and Chemical Separations
Pages 29-42
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From page 29... ...
If the costs of separations process steps were not excessive and the risks acceptable, this strategy might reduce overall disposal costs and hazards. A full separations approach could remove all of the long-lived actinides, plus the i37Cs and He 90Sr.
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From page 30... ...
The committee believes the importance of SLS is not sufficiently recogruzed; therefore SLS has received inadequate consideration in both design and development work. To reduce the technical risk, it is recommended that serious development studies be conducted with at least two different SLS approaches using dissolver solution produced from actual aged calcine (i.e., solution derived by leaching calcine with nitric acid, as discussed in Chapter 2, to dissolve calcine components into nitrate forms)
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From page 31... ...
When multiple ion exchange load-elute cycles are used, the presence of even small amounts of solids in the feed generally causes lower raffinate DFs, lower column capacity, and increased pressure drop or slower flow, all of which degrade performance. Although some solvent extraction contactor equipment will operate physically with solids present in the feed, other contactors that may accumulate solids are more sensitive and may become inoperable.
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From page 32... ...
The same report assigns "filtration" testing a medium priority, with less than a two person-year effort, which the committee believes is inadequate. Recent reports on TRUEX processing propose to change the dissolution procedure by reducing the initial and final nitric acid concentration (Herbst et al., 1998; Brewer et al., 1997a)
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From page 33... ...
These results led to a recent decision to switch the sorbent choice back to AMP-PAN. In principle, the FS-2 sorbent can be eluted with strong nitric acid and regenerated for repeated loading cycles, thereby generating relatively little waste as spent sorbent.
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From page 34... ...
The smaller range of distribution coefficients would degrade performance with respect to column capacity, resulting in increased generation of HLW solids. Two column tests were conducted with AMP-PAN, one with actual al amine type calcine and one with a calcine simulant (Todd et al., in press)
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From page 35... ...
The current databases is not adequate to justify a selection. Certain key criteria (such as the required DF for the aqueous product, practicality of adequate elusion to permit multiple cycles, sorbent life, quantity of spent sorbent destined for the HEW fraction, and compatibility of the sorbent with the immobilization process)
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From page 36... ...
A feasibility study report (Fluor Daniel, Inc., 1997: Section 4.5.8) contains a concise description of the SREX process as applied to SBW and dissolved calcine.
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From page 37... ...
Whether expressed as "apparent separation factors" or as OF values, the numbers cited previously for Sr removal indicate stringent separations requirements to meet Class A levels. Although the committee concurs with previous review groups that SREX is a promising approach for removing 90Sr from SBW and dissolved calcine, the committee believes that the current technical status of SREX in application to INEEL calcine, and to a lesser extent Physical and Chemical Separations 37
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From page 38... ...
This requirement becomes critical when dealing with very complex feedstocks such as the dissolved INEEL calcines that contain large amounts of fluorides, aluminum salts, and zirconium compounds. The idea of simply stripping the actinides from dissolved calcine by feeding it to a TRUEX contactor cascade is an inviting concept, but the realities of malting such a process work over the wide range of chemical compositions in these complex feeds will probably lead to major difficulties, as discussed below.
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From page 39... ...
Boiling off excess ammonia would create an acidic ammonium nitrate solution for Cs ion exchange and SREX. Hydroxide precipitate dissolution in dilute nitric acid followed by fluoride precipitation would isolate the actinide and lanthanide elements as a precipitate.
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From page 40... ...
The order of progression of the various unit operations will also be critical since the sequence of steps needed to provide acceptable isolation of Cs, Sr, and TRU will affect each of the chemical operations under consideration. To reduce technical risk (and potential expense)
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From page 41... ...
The technical risk is substantially reduced as the criteria for the LLW fraction are relaxed from those of USNRC Class A limits. Thus, for example, achieving the USNRC Class C limit would require little decontamination except for TRU removal.
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From page 42... ...
42 Alternative High-Level Waste Treatments at INTEL
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