[en] ANL effort is divided into five areas: (1) cooperation with Argentina to demonstrate the use of LEU-foil targets in alkaline-based processes, (2) cooperation with Indonesia in converting their HEU-based Cintichem process to LEU-foil targets, (3) technical assistance to two potential U.S. domestic suppliers (MURR and BWTX), (4) responding to the National Academies Study, and (5) participation in the IAEA CRP for Indigenous Mo-99 production. This paper presents highlights of these activities. A short description of how the dose emitted by spent HEU target material compared to spent fuel is also included.

[en] Two series of MCC-1 tests were designed and conducted to describe the effects of surface finish on the corrosion behavior of titanate ceramics. These effects are important for the comparison of short-term test results from different laboratories. Test samples were prepared with 240- and 600-grit finishes. Tests, conducted for 1, 3, 7, and 14 days at 90 C, were carried out in Teflon(reg_sign) vessels. Two different ceramics were used in this study: a Hf-Ce-Ce ceramic containing pyrochlore, perovskite, rutile and a small amount of a silicate phase, and a Hf-Ce-U ceramic containing pyrochlore and rutile. This study shows no detectable difference in the results of tests with ceramics finished to 240-grit and 600-grit; therefore, tests conducted at these two surface finishes can be directly compared. Due to its broader use, we recommend that short-term tests be conducted with monoliths finished to 600-grit. Comparison of data from blank tests in Teflon(reg_sign) and stainless steel vessels shows that the background associated with Teflon(reg_sign) vessels is lower. Therefore, we recommend that short-term tests be conducted in Teflon(reg_sign) vessels

[en] The authors conducted Product Consistency Tests (PCTs) with a surrogate low-activity waste (LAW) glass to (1) evaluate the possible use of various test conditions in a specification test for LAW waste forms, (2) measure the reproducibility of the test at low temperatures, and (3) determine if the rates calculated from 7-day PCTs bound the rates measured in PCT conducted for longer durations, which represent more advanced corrosion. The effects of temperature and pH on the dissolution rate in PCTs are much less than the effects observed in dilute solutions due to the buildup of dissolved glass components in the PCTs. The precision of replicate 7-day tests at 20 and 40 degrees C was limited by the analytical uncertainty. The dissolution rates at all temperatures decreased with the test duration initially. However, the dissolution rates in tests at 70 and 90 degrees C increased when certain alteration phases formed after about 100 and 500 days, respectively; the rates in some tests exceeded that measured in a 7-day PCT. While the 7-day PCT does not provide a bounding rate for this glass at 70 or 90 degrees C, tests for longer durations are needed to determine if a 7-day test provides a bounding rate at lower temperatures

[en] A glass that has been tested to understand the corrosion behavior of waste glasses with high soda contents for immobilizing Hanford incidental wastes has been made by melting crushed glass with either TcO₂ or NaTcO₄ at 1,100--1,300 C. Incorporation of technetium in the glass was affected by solubility or kinetic effects. Metallic technetium inclusions formed in all the TcO₂-doped glasses. Inclusions also formed in glasses with added NaTcO₄ that were melted at 1,100 C, but a glass melted at 1,200 C did not contain detectable inclusions. The presence of Tc-bearing inclusions complicates the interpretation of results from dissolution tests because of the simultaneous release of technetium from more than one phase, the unknown surface areas of each phase, and the possible incorporation of technetium that is released from one phase into another phase. A glass containing about 0.15 mass % Tc dissolved in the glass is being used in dissolution tests to study the release behavior of technetium

[en] Four titanate ceramics were characterized and tested. These ceramics were similar to those proposed for Pu disposition, with Ce as a surrogate for Pu. The baseline ceramic contained Ti, U, Ca, Hf, Gd, and Ce, and was made up of only four crystalline phases: pyrochlore, zirconolite, rutile, and brannerite. The three other ceramics contained different amounts of impurities that are expected in the feed. Impurities are defined as any element other than Ti, U, Ca, Hf, Gd, and Ce. The ceramics that contained impurities contained different phases than the baseline. The addition of impurities led to the absence of brannerite and the presence of amorphous silicate, Ca-Al-Ti, and perovskite phases. The results from 3 day, 90 C MCC-1 tests with impurity ceramics were significantly different than the results from tests with the baseline ceramic. Overall, the addition of impurities to these titanate ceramics altered the phase assemblages, which in turn, affected the corrosion behavior

[en] The Advanced Fuel Cycle Initiative (AFCI), funded by the Department of Energy, is developing proliferation-resistant technologies that allow safe and economical disposal of waste from reactors. A critical element is the separation of key radionuclides followed by either waste disposal, or conversion of long-lived isotopes to reactor fuel. A sample of Big Rock Point uranium oxide fuel was dissolved in nitric acid at elevated temperature to provide feedstock for the UREX+ demonstration. Elevated temperature led to the complete dissolution of noble metals at relatively low nitric acid concentrations. The conditions used in this study are not suitable for plant-scale application. Three products were obtained: (1) a dissolved fuel solution, (2) undissolved residue, and (3) leached cladding containing no observable undissolved fuel. Elemental analyses of the dissolved fuel, residue, and leached cladding are presented. The data show that 99% of the fuel, including the noble metals was dissolved. The small amount of residue contained primarily Zr, Mo, and Pu. While the total amount of residue is small, approximately 20% of the total Pu was found in the residue. Several proposals are made for the prevention of precipitation of the residue.

[en] The long-term performance of glasses developed for stabilizing Hanford low-level radioactive waste is being assessed using static leach tests conducted for up to one year and under conditions that accelerate Corrosion. These tests support development of durable waste-form compositions and application of performance assessment models. Static leach tests were run with crushed glass at glass surface area/solution volume ratios of 2000 and 20,000 m^-1 and temperatures of 20, 40, 70, and 90 degrees C. All tests showed sodium to be released from the glass faster than boron or silicon. These results are interpreted in terms of the glass structure, the corrosion mechanism, and the effects of time, glass surface area/leachant volume ratio and temperature. Vapor hydration tests were conducted at elevated temperatures (70-200 degrees C) using glasses containing various amounts of SiO₂, Na₂O, B₂O₃, CaO, and Al₂O₃. The response of a glass in these tests is relevant to its durability over very long disposal times. Different responses were observed in the tests: some glasses completely corroded within a few days while others were only slightly corroded. Corrosion led to the formation of analcime and gobbinsite; the corrosion rate increased significantly after these phases formed implications of these test results for the long-term glass durability are discussed

[en] Conversion from high-enriched uranium (HEU) to low-enriched uranium (LEU) targets for the Mo-99 production requires certain modifications of the target design, the digestion and the purification processes. ANL is assisting the Argentine Comision Nacional de Energia Atomica (CNEA) to overcome all the concerns caused by the conversion to LEU foil targets. A new digester with stirring system has been successfully applied for the digestion of the low burn-up U foil targets in KMnO4 alkaline media. In this paper, we report the progress on the development of the digestion procedure with stirring focusing on the minimization of the liquid radioactive waste.

[en] Currently, nearly all of the world's supply of ⁹⁹Mo is produced fiom the fissioning of ²³⁵U in targets of high-enriched uranium (HEU). Conversion of these targets to low-enriched uranium (LEU) would ease worldwide concern over the use and transport of this weapons-grade material. This paper reviews three projects: (1) the ongoing conversion of BATAN's ⁹⁹Mo production process from HEU oxide targets (Cintichem processing) to LEU foil targets (Cintichem processing), (2) demonstration of LEU foil targets and base-side processing in CNEA's facility, and (3) the evaluation of two inorganic Thermoxid sorbents for Mo recovery and purification in acidic U-bearing solutions.

[en] We report X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra for the plutonium LIII and uranium LIII edges in titanate pyrochlore ceramic. The titanate ceramics studied are of the type proposed to serve as a matrix for the immobilization of surplus fissile materials. The samples studied contain approximately 10 wt% fissile plutonium and 20 wt% natural uranium, and are representative of material within the planned production envelope. Based upon natural analogue models, it had been previously assumed that both uranium and plutonium would occupy the calcium site in the pyrochlore crystal structure. While the XANES and EXAFS signals from the plutonium LIII are consistent with this substitution into the calcium site within pyrochlore, the uranium XANES is characteristic of pentavalent uranium. Furthermore, the EXAFS signal from the uranium has a distinct oxygen coordination shell at 2.07 A and a total oxygen coordination of about 6, which is inconsistent with the calcium site. These combined EXAFS and XANES results provide the first evidence of substantial pentavalent uranium in an octahedral site in pyrochlore. This may also explain the copious nucleation of rutile (TiO₂) precipitates commonly observed in these materials as uranium displaces titanium from the octahedral sites