G. D. Del Cul's research while affiliated with Oak Ridge National Laboratory and other places

Publications (87)

Article
The complete recycle of used nuclear fuel (UNF) is desirable to recover the energy value from the remaining U and higher actinides; however, construction of a large-scale facility is extremely expensive. To address this issue, a hybrid process was evaluated in which UNF pretreated for tritium removal is dissolved in a tributyl phosphate (TBP) solve...
Article
The oxidation kinetics of U3O8 powder to ε-UO3 in an NO2 environment was measured by in situ x-ray diffraction (XRD). Experiments were performed at temperatures of 195, 210, 235, and 250 °C using a custom designed and fabricated sample isolation stage. Data were refined to quantify phase fractions using a newly proposed structure for the ε-UO3 poly...
Article
Thorium-based nuclear fuel cycles have received renewed attention in both research and public circles since about the year 2000. Much of the attention has been focused on nuclear fission energy production that utilizes thorium as a fertile element for producing fissionable ²³³U for recycle in thermal reactors, fast reactors, or externally driven sy...
Article
Full-text available
This study investigates the equilibrium absorption of water in various solvents and solvent-mixtures being considered for the counter-current solvent extraction of acetic acid from improved Uranium Extraction (UREX+) process solutions. It then seeks to determine if there is any correlation between the equilibrium water content of these solvents and...
Article
A novel dry treatment process for used nuclear fuel (UNF) using nitrogen dioxide is being developed to remove volatile and semi-volatile fission products and convert the monolithic fuel material to a fine powder suitable as a feed to many different separations processes. The process may be considered an advanced form of voloxidation, which was envi...
Conference Paper
With world stockpiles of used nuclear fuel increasing, the long-term remediation of used fuel is a growing concern. Many of the transuranic (TRU) actinides in nuclear spent fuel produce decay heat for long durations, resulting in significant nuclear waste management challenges. Partitioning and transmutation of the spent fuel is one possibility to...
Article
The United States inventory of used nuclear fuels contains approximately 2 to 5 wt % fission products, depending on the extent of fuel burnup during irradiation, with the greater amounts produced in higher burnup fuels. For reprocessing of used nuclear fuels, fission products are more often divided into categories according to their chemical and ra...
Article
Full-text available
The objective for this research was to employ the extended adsorption isotherm (EAI) to develop a predictive relationship between the activity of H2O (aw) and the mean ionic activity (a±) of aqueous HNO3. The EAI model is a calculative approach to the estimation of solutions for activities of highly non-ideal chemical systems and is the collective...
Article
Recycle of nitric acid in the UREX+ process requires removal of acetic acid. An analysis of the effects of acetic acid in each process step indicates no step will be significantly affected by the concentrations expected. Thus, acetic acid removal can be placed after the last salts are removed, just before the nitric acid is recycled. Two promising...
Article
Low-temperature (20 Κ-120 Κ) high-resolution luminescence spectra of UO2Cl42- doped in cubic crystals of Cs2ZrCl6 are reported. The luminescence is associated with the A1g ← Eg electronic origin transition and vibronic transitions associated with this origin. The vibronic structure is consistent with the UO2Cl42- ion having D4h symmetry. The distri...
Article
Full-text available
This study explores different technologies for removing acetic acid from a UREX + waste stream. The waste stream contains both nitric and acetic acids, and the acetic acid must be removed from the waste stream to prevent potential problems in the downstream steps as well as affecting the recycle of nitric acid. The acetic acid is formed after the U...
Article
Full-text available
In the UREX + process, acetic acid must be removed from the raffinate stream to avoid interference with the recovery and recycle of nitric acid solutions. Solvent extraction was selected to be the most promising approach to accomplish this cleanup. Acetic acid partitioning into pure diluents used in the UREX + process were found to be too low for a...
Article
The internal gelation process and a suitable broth formulation with an uranium concentration of 1.3 M was used to produce air-dried uranium trioxide dihydrate (UO3 center dot 2H(2)O) and carbon microspheres with crush strengths greater than 600 g per microsphere. The addition of carbon lowered the slow-pour densities of the air-dried microspheres b...
Article
Full-text available
Recent studies indicate that maximized recycling, where more than 95% of the components of spent nuclear fuel are reused, can be economically justified and can reduce the mass of waste products by a substantial amount. The potentially removable and reusable components include the uranium, zirconium from the cladding, structural hardware, certain no...
Article
Fluorination and structural change of highly ordered mesoporous carbons were studied. Mesoporous and fluorinated carbons with ordered cubic structure were synthesized and characterized with TEM, FTIR, adsorption, and EDX.
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Full-text available
The crush-leach process was investigated as a method to treat GEN IV TRISO-coated reactor fuels. The method retains the bulk of the carbon components in elemental form, which is favorable for achieving waste reduction goals. A literature review identified the potential problems with this technique. Leaching of simulated crushed TRISO-coated fuel an...
Article
The safe handling and storage of radioactive materials require an understanding of the effects of radiolysis on those materials. Radiolysis may result in the production of gases (e.g., corrosives) or pressures that are deleterious to storage containers. A study has been performed to address these concerns as they relate to the radiolysis of residua...
Article
Advanced High-Temperature Reactors (AHTRs) that have improved safety features and more efficient energy conversion systems constitute a new generation of nuclear power reactors. A molten-fluoride cooled version of the High Temperature Gas-cooled Reactor (HTGR) offers the benefits of high thermodynamic efficiency, additional fission product containm...
Article
It has been proposed that GaClâ can be removed by direct volatilization from a Pu-Ga alloy that is dissolved in a molten chloride salt. Although pure GaClâ is quite volatile (boiling point: 201 deg. C), the behavior of GaClâ dissolved in chloride salts is quite different because of solution effects and is critically dependent upon the composition o...
Article
The Molten Salt Reactor Experiment (MSRE) site at Oak Ridge National Laboratory is being cleaned up and remediated. The removal of ~37 kg of fissile ²³³U is the main activity. Of that inventory, ~23 kg has already been removed as UF6 from the piping system and chemisorbed in 25 NaF traps. This material is in temporary storage while it awaits conver...
Article
Full-text available
The Molten Salt Reactor Experiment (MSRE) was operated at Oak Ridge National Laboratory (ORNL) from 1965 to 1969 to test the concept of a high-temperature, homogeneous, fluid-fueled reactor. The discovery that UF6 and F2 migrated from the storage tanks into distant pipes and a charcoal bed resulted in significant activities to remove and recover th...
Article
The remediation of the Molten Salt Reactor Experiment (MSRE) site includes the removal of about 37 kg of uranium. Of that inventory, about 23 kg have already been removed from the piping system and chemisorbed in 25 NaF traps. This material is being stored in Building 3019. The planned recovery of -11 kg of uranium from the fuel salt will generate...
Article
Since the 1969 shutdown of the Molten Salt Reactor Experiment (MSRE) at Oak Ridge, radiolytically generated fluorine (F2) and 233-uranium hexafluoride (233UF6) migrated from the fuel storage tanks through gas piping to a charcoal bed. This report addresses the carbon–fluorine–uranium chemistry under conditions reproducing those found in the charcoa...
Article
This study addresses the physical-chemical processes that might naturally or inadvertently occur and that would lead to a separation of the poisoning nonfissionable actinides (Th, U) from the fissionable ones (Pu, U) by selective dissolution and redeposition over a prolonged storage of the waste. Of the various chemistries that were evaluated, carb...
Article
Remediation of the Molten Salt Reactor Experiment (MSRE) has required additional study of the radiolysis of a variety of fluorine-containing materials. Primary attention was directed at a more complete understanding of how UF{sub 6} was generated from the fuel salt during the period after reactor shutdown because the presence of this mobile specie...
Article
The complete vibrational spectra of strychnine is reported. Strychnine, a compound with medicinal value at the proper dosage, is also a potent toxin at certain concentration levels. Down to 5 ng of strychnine were detected from its spectrum using a microscope attached to a Raman spectrophotometer. The complete Raman and Fourier transform IR spectra...
Article
The preparation of CFx by elemental fluorination of charcoal was studied using solid state 13C and 19F NMR spectroscopy. 19F-13C CP/MAS NMR experiments determine the extent of fluorination vs reaction temperature. Three types of carbon species observed over the temperature range -80 to 350 °C were assigned to graphitic carbon (C), CF, and CF2 on th...
Article
Experimental trials were conducted to investigate some unresolved issues regarding the use of chlorine trifluoride (ClF{sub 3}) for removal of uranium-bearing deposits in the Molten Salt Reactor Experiment (MSRE) off-gas system. The safety and effectiveness of operation of the fixed-bed trapping system for removal of reactive gases were the primary...
Article
Lanthanide elements are produced in relatively high yield by fission of U. Almost all the lanthanide isotopes decay to stable nonradioactive lanthanide isotopes in a relatively short time. Consequently, it is highly advantageous to separate the relatively small actinide fraction from the relatively large quantities of lanthanide isotopes.The TALSPE...
Article
Lanthanide elements are produced in relatively high yield by fission of ²³⁵U. Almost all the lanthanide isotopes decay to stable nonradioactive lanthanide isotopes in a relatively short time. Consequently, it is highly advantageous to separate the relatively small actinide fraction from the relatively large quantities of lanthanide isotopes. Th...
Article
The preparation of CFx by elemental fluorination of charcoal is studied using solid state 13C and 19F NMR spectroscopy. 19F-13C CP/MAS NMR experiments are used to determine the extent of fluorination vs. reaction temperature. Four types of carbon species are observed over the temperature range -80°C to 350°C, assigned to graphitic carbon (C), CF, C...
Article
Uranyl ion (UO22+) has been doped in silica glasses through a sol−gel process. The photochemistry of UO22+-doped glasses immersed in ethanol solution has been investigated. Our experimental results indicate that UO22+ in this system can be photochemically converted to U(IV) species, and evidence is provided for the possible formation of U(IV) speci...
Article
Green and less intense red emissions from Er3+ (4f11)-doped sol-gel silica samples (prepared from tetraethylorthosilicate at room temperature and dried at 70°C) under 488 nm excitation were monitored as a function of sample curing temperature. These green and red emission bands, centered at 550 and 660 nm, are the 4S32 → 4I152 and 4F92 → 4I152 tran...
Article
High-temperature near-IR absorption spectroscopy was used to study the dissolution of UO2 in molten MgCl2, CaCl2, and AlCl3 melts. The study reveals that UO2 is most soluble in molten AlCl3, followed by the melt of MgCl2. The solubility of UO2 in molten CaCl2 is too small to be measured with optical spectroscopy. This strong dependence of the solub...
Article
The near-IR electronic transition from ground-state of 3H4 to the excited-state of 3F2 for the UCl62− complex in three M2ZrCl6 host crystals (M = K+, Rb+, and Cs+) has been investigated experimentally and theoretically. The vibration frequency of the excited state is found to be sensitive to the alkaline ion substitution and the frequency variation...
Article
Low-temperature (20 K-120 K) high-resolution luminescence spectra of UO{sub 2}Cl{sub 4}{sup 2{minus}} doped in cubic crystals of Cs{sub 2}ZrCl{sub 6} are reported. The luminescence is associated with the A{sub lg} {l_arrow}E{sub g} electronic origin transition and vibronic transitions associated with this origin. The vibronic structure is consisten...
Article
Low-temperature (20 K-120 K) high-resolution luminescence spectra of UO2Cl42- doped in cubic crystals of Cs2ZrCl6 are reported. The luminescence is associated with the A(1g) <-- E(g) electronic origin transition and vibronic transitions associated with this origin. The vibronic structure is consistent with the UO2Cl42- ion having D-4h symmetry. The...
Article
The chemistry of molten fluorides is traced from their development as fuels in the Molten Salt Reactor Experiment with important factors in their selection being discussed. Key chemical characteristics such as solubility, redox behavior, and chemical activity are explained as they relate to the behavior of molten fluoride fuel systems. Fission pro...
Article
The blue emission from U{sup 4+}(5f{sup 2}) ion doped into a Cs{sub 2}ZrCl{sub 6} single crystal under green light (19,436 cm{sup {minus}1}) excitation has been observed and characterized. Five blue emission bands for the intra 5f{sup 1}I{sub 6} {yields} {sup 3}H{sub 4} (19,700, 20,010, and 20,280 cm{sup {minus}1}) and {sup 3}P{sub 2} {yields} {sup...
Article
Green upconversion emission from Er{sup 3+}(4f¹¹) ion doped into a sol-gel silica glass under red light (647.1 nm) excitation has been observed and characterized. Green and weak blue emission bands, centered at 550 and 410 nm, for the ⁴Sââ â ⁴Iâââ and ²Hââ â ⁴IâââEr{sup 3+} transitions, respectively, have been observed. These upconversio...
Article
Although the chemistry of uranium(IV) chloride complexes in molten chloride melts has been widely investigated, no studies of uranium(IV) oxychloride complexes in these melts have appeared, with the exception of a recent paper from this laboratory. In that paper, visible and near-IR absorption bands overlapping with those of the uranium(IV) chlorid...
Conference Paper
The chemistry of molten fluorides is traced from their development as fuels in the Molten Salt Reactor Experiment with important factors in their selection being discussed. Key chemical characteristics such as solubility,redox behavior, and chemical activity are explained as they relate to the behavior of molten fluoride fuel systems. Development r...
Article
Full-text available
Because of an increasing need for {sup 99}Tc removal from treatment solutions during waste processing and environmental cleanups, several inexpensive sorbents were investigated. Here, Packed-column experiments with iron dust of 40 to 60 mesh (Fisher I-57) showed an excellent uptake of pertechnetate ions from alkaline (pH {approximately} 8.5) high-n...
Article
Low-temperature (20 K-120 K) high-resolution luminescence spectra of UOâClâ²⁻ doped in cubic crystals of CsâZrClâ are reported. The luminescence is associated with the A{sub lg} âE{sub g} electronic origin transition and vibronic transitions associated with this origin. The vibronic structure is consistent with the UOâClâ²⁻ ion having D{sub...
Article
Ultraviolet-visible absorption spectroscopic studies of C[sub 60] vapor were carried out in the temperature range 400 [degree]C--720 [degree]C. The enthalpy of sublimation (180[plus minus]10 kJ/mol) was obtained through the use of the Clausius--Clapeyron equation.
Article
An efficient fiberoptic interface system was developed to convert a Gary 14 H spectrophotometer into a fiberoptic instrument. This new spectrophotometer can be used to study the UV-visible and near-IR absorption spectroscopy of radioactive samples and wastes in a confined environment.
Conference Paper
Full-text available
A laboratory-scale microwave heating system is used to demonstrate the feasibility of drying and then solidifying surrogate and authentic waste water treatment residuals. Depending upon the glass formers present in (or added to) the sludge sample, the resultant waste form is a brick-like ceramic, a stone-like monolith, or an amorphous glass. Compar...
Article
Full-text available
The potential hazard posed to future generations by long-lived radionuclides such as the transuranic elements (TRU) is perceived as a major problem associated with the use of nuclear power. TRU wastes have to remain isolated from the environment for ``geological`` periods of time. The costs of building, maintaining, and operating a ``geological TRU...
Article
Since high temperatures can lead to broadening of absorption spectra, ambient temperature chloride melts were used; the system used was AlClâ-1-ethyl-3-methyl-imidazolium chloride (EMIC). The uv-visible spectrum of UClâ in basic melt had many peaks with the most intense (triplet) ones around 2000 nm, similar to these at high temperature and indicat...
Article
The Stokes and anti-Stokes luminescence spectra characteristic of the trihalides of Cm3+ exhibit narrow features arising from transitions between the 5f electronic levels of the Cm3+ ion. The low background associated with anti-Stokes luminescence has allowed our Observation of emission features which are ordinarily obscured by matrix scatter and/o...
Article
The analyses of reported Raman spectra from tetragonal lanthanide oxychlorides are inconsistent. Nuclear site symmetry analysis predicts six Raman-active bands. Five peaks are consistently observed, whereas the sixth remains controversial. Also, two different sets of irreducible representations are reported: 2A1g + 3E(g) + B2g(or B1g) + 3A2u + 3E(u...
Article
Full-text available
The predominant form of technetium under oxic conditions is the pertechnetate anion (TcO4 ), which is highly soluble in water and readily mobile in the environment. Technetium-99 is of particular concern because of its persistence and mobility.Various equipment decontamination and uranium recovery operations at the Portsmouth Gaseous Diffusion Plan...
Article
We have recorded part of the UV-visible region of the electronic spectrum of EuOCl at both 292 and 77 K by diffuse reflectance spectroscopy. Illumination of the sample and collection of the reflected light was accomplished through the use of an all-quartz fiberoptic probe. Several absorption maxima were observed which result from transitions from t...
Article
The reported Raman spectra of the tetragonal [lead chlorofluoride-type structure, D-P4/nmm (ITC No. 129)] lanthanide oxychlorides are inconsistent. Nuclear site symmetry analysis predicts six Raman bands. Five peaks are consistently observed, whereas the sixth remains controversial. Also, two different sets of irreducible representations are report...
Article
Full-text available
The solidification of spent ion exchange resins in a grout matrix as a means of disposing of spent organic resins produced in the nuclear fuel cycle has many advantages in terms of process simplicity and economy, but associated with the process is the potential for water/cement/resins to interact and degrade the integrity of the waste form solidifi...
Article
The anti-Stokes luminescence from six excited-state Stark manifolds of CmBr3 was observed at both 300 and 77 K by using dye laser excitation. The applicable mechanism for the production of the anti-Stokes luminescence is discussed and the crystal field splittings of the luminescence manifolds are correlated with the compound's crystal structure. Th...
Conference Paper
The leachabilities of technetium and nitrate wastes immobilized in cement-based grouts have been investigated. Factors found to affect the leachabilities include grout mix ratio, grout fluid density, dry solid blend composition, and waste concentration. 10 refs., 7 figs., 3 tabs.
Article
The Molten Salt Reactor Experiment (MSRE), at the Oak Ridge National Laboratory has been shut down since 1969 when the fuel salt was drained from the core into two Hastelloy N tanks at the reactor site. In 1995, a multiyear project was launched to remediate the potentially hazardous conditions generated by the movement of fissile material and react...
Article
Full-text available
It has been proposed that GaClâ can be removed by direct volatilization from a Pu-Ga alloy that is dissolved in a molten chloride salt. Although pure GaClâ is quite volatile (boiling point, 201 C), the behavior of GaClâ dissolved in chloride salts is different due to solution effects and is critically dependent on the composition of the solvent sal...
Article
INTRODUCTION Given the existing inventory of spent fuel and the present rate of fuel utilization, a second repository will be needed in just a few decades. The very large cost, between $31.5 billion and $42.8 billion in 2001 dollars [1], of a repository and the very difficult problem of finding a possible location offer a significant incentive to t...
Article
Full-text available
The Molten Salt Reactor Experiment was operated in the sixties at Oak Ridge National Laboratory to test the concept of a high-temperature, homogeneous, fluid-fueled reactor. The discovery that UF6 and F2 had migrated from the storage tanks into distant pipes and a charcoal bed resulted in significant multiyear activities to remove and recover the 2...
Article
The Molten Salt Reactor Experiment (MSRE) remediation requires that almost 40 kg of uranium hexafluoride (UF6) be converted to uranium oxide (UO). In the process of this conversion, six moles of hydrofluoric acid (HP) are produced for each mole of UF6 converted.
Article
The operation of an ADT system with the associated nuclear reactions has a profound effect upon the chemistry of the fuel - especially with regards to container compatibility and the chemical separations that may be required. The container can be protected by maintaining the redox chemistry within a relatively narrow, non-corrosive window. Neutron...
Article
During FY 1995 considerable progress was made toward gaining a better understanding of the chemistry and transport processes that continue to govern the behavior of the Molten Salt Reactor Experiment (MSRE). As measurements in the MSRE proceed, laboratory studies continue, and better analyses are available, our understanding of the state of the MSR...
Article
The current status of molten salt reactor development is discussed with reference to the experience from the Oak Ridge Molten Salt Reactor Experiment. Assessment of the future for this reactor system is reviewed with consideration of both advantages and disadvantages. Application of this concept to ADTT (accelerator driven transmutation technology)...
Article
The leachabilities of technetium and nitrate wastes immobilized in cement-based materials (i.e., grouts) have been investigated using ANS -- 16.1 test procedures. Factors found to affect the leachabilities include grout/mix ratio, grout fluid density, dry/solid blends (including ground blast-furnace slag), and waste concentration. 10 refs., 7 figs....
Article
Full-text available
The conversion of the uranium hexafluoride (UF{sub 6}) which is removed from the Molten Salt Reactor Experiment (MSRE), into a stable oxide for long-term storage will produce a significant amount of slightly contaminated, concentrated aqueous hydrofluoric acid (HF). Sin&the handling of this HF is complicated and dangerous, it was decided to transfo...
Article
The Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory has been shut down since December 1969, at which time the molten salt mixture of LiF-BeFâ-ZrFâ-²³³UFâ (64.5-30.3-5.0-0.13 mol%) was transferred to fuel salt drain tanks for storage. In the late 1980s, increased radiation in one of the gas lines from the drain tank was att...