Application of the TRUEX process to highly irradiated targets

The Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory processes highly irradiated targets for the Mark 42 program to separate americium, curium, and plutonium. Argonne National Laboratory (ANL) has developed the TRUEX process for the removal of transuranic elements from aqueous waste streams and a computer model that aids in the design of potential flowsheets. Because the TRUEX process is attractive for application to the large volumes of high-activity tank wastes stored at various Department of Energy sites, a test of the process on the highly irradiated Mark 42 target material would yield useful information on the performance of the process under {open_quotes}real{close_quotes} conditions. Researchers at ANL used the Generic TRUEX Model (GTM) to design a TRUEX flowsheet to process Mark 42 target material. Researchers at the REDC refurbished the Solvent Extraction Test Facility mixer-settler contactors and conducted three test runs using the TRUEX process. The results from the three demonstration tests are presented along with the predicted results from the GTM

Preparation of curium-americium oxide microspheres by resin-bead loading

Resin-bead loading and calcination techniques have been used to produce all curium and americium oxide feed material (about 2.2 kg) for HFIR targets since 1971. The process based on Dowex 50W resin has progressed from a series of test runs, through special production runs, into routine production in permanent equipment beginning in 1975. Key attributes of this process are its reliability, high yields, and ease of operation. The process is suited for remote operation in hot cells. Yields approaching 95% are routinely obtained and only one unacceptable product has been generated during routine production operations. There have been no problems in fabricating targets from this oxide or in the subsequent irradiation of these targets. The present scale of production of 150 to 250 g/y supplies the present need and is comparable with the level of other chemical process operations at TRU. Since the annual production is accomplished in two 8 to 12 day periods, there has been no reason to consider further scale-up. However, the rate of production could easily be doubled by simply adding a second set of calcination equipment

Chromatographic cation exchange separation of decigram quantities of californium and other transplutonium elements

Decigram quantities of highly radioactive transplutonium elements are routinely partitioned at TRU by chromatographic elution from cation resin using AHIB eluent. By using two high-pressure ion exchange columns, a small one for the initial loading of the feed and a large one for the elution, batch runs containing up to 200 mg of /sup 252/Cf can be made in about 5 hours (2 hours to load the feed and 3 hours for the elution). The number of effluent product fractions and the amount of actinides that must be collected in intermediate fractions are minimized by monitoring response from a flow-through alpha-detector. This process has been reliable and relatively easy to operate, and will continue to be used for partitioning transplutonium elements at TRU

Determination of O[H] and CO coverage and adsorption sites on PtRu electrodes in an operating PEM fuel cell

A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. Variations in both the coverage of O[H] (O[H] indicates O and/or OH) and CO (applying a novel ΔμL3 = μL3(V) − μL3(ref) difference technique), as well as in the geometric (EXAFS) and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the NPt-Ru coordination number increases much slower than the NPt-Pt with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the Δμ technique and reveal a drop in CO and an increase in OH coverage in the range of 65−90 mA/cm2. With increasing OH coverage, the Pt−O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell

Coprocessing solvent-extraction flowsheet studies for LWR and FBR fuels

Coprocessing solvent extraction studies using irradiated LWR and FBR fuels have indicated the need for an efficient feed clarification. A potentially useful filtration method for fulfilling this need has been demonstrated. Conditions necessary for the satisfactory use of unstabilized hydroxylamine nitrate (HAN) or nitrous acid as the reducing agent for Pu(IV) during reductive stripping operations have been defined. Both partial partitioning and total costripping operations have been demonstrated. In addition, solvent degradation product measurements have been made, and the effect of the presence of DBP during uranium-plutonium stripping operations has been determined