Sandra K. Fiskum

Preconcentration and Analysis of Strontium-90 and Technetium-99 from Hanford Groundwater Using Solid Phase Extraction

Solid-phase extraction disks produced by 3M and Eichrom were evaluated for routine use in supporting the Hanford Groundwater Monitoring Project. Both disk formats contain Sr- or Tc-selective extractants, bound in a filter support, that act to preconcentrate and isolate the isotope of interest. The 3M Empore™ Sr Rad Disks and Tc Rad Disks were tested with respect to precision, accuracy, radiochemical yields, interferences, and volume-load variation. The Empore™ and Eichrom solid-phase extraction disks were applied to the 90Sr and/or 99Tc determination in representative Hanford groundwater samples with varying chemical and isotopic compositions. Results were compared to standard analytical methods. Both the Empore™ and Eichrom Tc extraction disks produced consistently higher radiochemical yields, lower detection limits, and greater accuracy than the standard analysis method. The Empore™ Sr extraction disks produced comparable radiochemical yields, detection limit, and accuracy relative to the standard method; however, total uncertainties were lower.

Characterization of High Phosphate Radioactive Tank Waste and Simulant Development

A sample of high-level radioactive tank waste was characterized to provide a basis for developing a waste simulant. The simulant is required for pilot-scale testing of pretreatment processes in a nonradiological facility. The waste material examined was derived from the bismuth phosphate process, which was the first industrial process implemented to separate plutonium from irradiated nuclear fuel. The bismuth phosphate process sludge is a complex mixture rich in bismuth, iron, sodium, phosphorus,silicon, and uranium.The form of phosphorus in this particular tank waste material is of specific importance because that is the primary component (other than water-soluble sodium salts) that must be removed from the high-level waste solids by pretreatment. This work shows unequivocally that the phosphorus in this waste material is not present as bismuth phosphate. Rather, the phosphorus appears to be incorporated mostly into an amorphous iron(III) phosphate phase. The bismuth in the sludge solids is best described as BiFeO3. The behavior of phosphorus during caustic leaching of the bismuth phosphate process sludge solids is also discussed.

PARTITIONING OF MERCURY FROM ACTINIDES IN THE TRUEX PROCESS

A mercury complexant, L-cysteine hydrochloride, was tested for use in separating Hg(II) from actinides during transuranic extraction (TRUEX) processing of wastes at the Idaho National Engineering and Environmental Laboratory (INEEL). Mercury, americium, plutonium, and uranyl distributions for the TRUEX solvent were characterized over a nitric acid concentration range of 0.01 to 2 M with and without cysteine. The applicability of cysteine was evaluated for selective Hg(II) complexation in an INEEL sodium-bearing waste simulant. A test was also conducted to evaluate the applicability of cysteine to separate Hg(II) from Sr in the strontium extraction (SREX) process with Sr Resin used as a stand-in for the SREX process solvent. In all cases, the use of L-cysteine HCl retained Hg in the aqueous phase while causing no or little perturbation in the actinide and Sr distribution behavior.

Characterization and Leach Testing for PUREX Cladding Waste Sludge (Group 3) and REDOX Cladding Waste Sludge (Group 4) Actual Waste Sample Composites

A testing program evaluating actual tank waste was developed in response to Task 4 from the M-12 External Flowsheet Review Team (EFRT) issue response plan.(a) The testing program was subdivided into logical increments. The bulk water-insoluble solid wastes that are anticipated to be delivered to the Waste Treatment and Immobilization Plant (WTP) were identified according to type such that the actual waste testing could be targeted to the relevant categories. Eight broad waste groupings were defined. Samples available from the 222S archive were identified and obtained for testing. The actual wastetesting program included homogenizing the samples by group, characterizing the solids and aqueous phases, and performing parametric leaching tests. Two of the eight defined groups—plutonium-uranium extraction (PUREX) cladding waste sludge (Group 3, or CWP) and reduction-oxidation (REDOX) cladding waste sludge (Group 4, or CWR)—are the subjects of this report. Both the Group 3 and 4 waste composites were anticipated to be high in gibbsite, requiring caustic leaching. Characterization of the composite Group 3 and Group 4 waste samples confirmed them to be high in gibbsite. The focus of the Group 3 and 4 testing was on determining the behavior of gibbsite during caustic leaching. The waste-type definition, archived sample conditions, homogenization activities, characterization (physical, chemical, radioisotope, and crystal habit), and caustic leaching behavior as functions of time, temperature, and hydroxide concentration are discussed in this report. Testing was conducted according to TP-RPP-WTP-467.

Boehmite Actual Waste Dissolution Studies

Abstract The U.S. Department of Energy plans to vitrify approximately 60,000 metric tons of high-level waste (HLW) sludge from underground storage tanks at the Hanford Nuclear Reservation. To reduce the volume of HLW requiring treatment, a goal has been set to remove a significant quantity of the aluminum, which comprises nearly 70 percent of the sludge. Aluminum is found in the form of gibbsite, sodium aluminate and boehmite. Gibbsite and sodium aluminate can be easily dissolved by washing the waste stream with caustic. Boehmite, which comprises nearly half of the total aluminum, is more resistant to caustic dissolution and requires higher treatment temperatures and hydroxide concentrations. Samples were taken from four Hanford tanks and homogenized in order to give a sample that is representative of REDOX (Reduction Oxidation process for Pu recovery) sludge solids. Bench scale testing was performed on the homogenized waste to study the dissolution of boehmite. Dissolution was studied at three different hydroxide concentrations, with each concentration being run at three different temperatures. Samples were taken periodically over the 170 hour runs in order to determine leaching kinetics. Results of the dissolution studies and implications for the proposed processing of these wastes will be discussed.

Characterization, Leaching, and Filtrations Testing of Ferrocyanide Tank sludge (Group 8) Actual Waste Composite

This is the final report in a series of eight reports defining characterization, leach, and filtration testing of a wide variety of Hanford tank waste sludges. The information generated from this series is intended to supplement the Waste Treatment and Immobilization Plant (WTP) project understanding of actual waste behaviors associated with tank waste sludge processing through the pretreatment portion of the WTP. The work described in this report presents information on a high-iron waste form, specifically the ferrocyanide tank waste sludge. Iron hydroxide has been shown to pose technical challenges during filtration processing; the ferrocyanide tank waste sludge represented a good source of the high-iron matrix to test the filtration processing.

Alternative TRUEX-Based Pretreatment Processing of INEEL Sodium Bearing Waste

The goals of this study were to demonstrate a selective complexant for separating mercury from the transuranic (TRU) elements in the transuranic extraction (TRUEX) process and to demonstrate alternative stripping methods to eliminate phosphorus-containing, actinide stripping agents during TRUEX processing. The work described in this report provides the basis for implementing an improved TRUEX-based flowsheet for processing INEEL sodium-bearing waste using only minor modifications to the current Idaho National Engineering and Environmental Laboratory (INEEL) flowsheet design.