Study on cleaning solvents using activated alumina in PUREX process

The PUREX process is used to extract uranium and plutonium from dissolved solutions (spent nuclear fuel liquor). The extractant is 30% tributyl phosphate in n-dodecane, which is known to be degradable by radiation and nitric acid. Tributyl phosphate degradation products can generally be washed in alkali solutions like sodium carbonate solution; however, it is more difficult to remove n-dodecane degradation products using this method. A method of cleaning solvents using activated alumina is discussed in this study. A degradation sample of 30% TBP/n-dodecane was prepared by irradiating (1.6 MGy) with a 60Co gamma-source. The degradation products were then qualitatively analyzed using a gas chromatography-mass spectrometer (GC-MS). After being irradiated the solvents were cleaned with activated alumina, and a phase separation test with performed in evaluating the cleaned solvent. This resulted in the discovery of a procedure for the removal of n-dodecane degradation products of dodecanol and dodecanone, with about 70% of the degradation products, and the phase separation performance could be clearly improved through use of activated alumina.

Laser deposition of iron in oxygen atmosphere

Iron oxide films were produced by pulsed laser deposition (PLD) of 57Fe metal in an oxygen atmosphere and their compositions were studied by Mössbauer spectroscopy. The effects of gas-phase reactions were investigated by varying the pressure of O2 gas or an O2/Ar gas mixture. When PLD was performed in a high-pressure O2 atmosphere, the main product in the film was trivalent iron oxide particles. When the O2 pressure was reduced, hematite Fe2O3 became dominant in the film, while wüstite FeO was produced at very low O2 pressures. PLD in an O2/Ar gas mixture produced films of trivalent iron oxide particles and hematite solid, but wüstite was not produced. Increasing the substrate temperature during deposition induced annealing of the films, reducing the lattice defect density. X-ray diffraction patterns were obtained to confirm the assignments, and the surface morphologies of the films were investigated by scanning electron microscopy.

Automation of column-based radiochemical separations: a comparison of fluidic, robotic, and hybrid architectures

Two automated systems have been developed to perform column-based radiochemical separation procedures. These new systems are compared with past fluidic column separation architectures, with emphasis on using disposable components so that no sample contacts any surface that any other sample has contacted, and setting up samples and columns in parallel for subsequent automated processing. In the first new approach, a general purpose liquid handling robot has been modified and programmed to perform anion exchange separations using 2 mL bed columns in 6 mL plastic disposable column bodies. In the second new approach, a fluidic system has been developed to deliver clean reagents through disposable manual valves to six disposable columns, with a mechanized fraction collector that positions one of four rows of six vials below the columns. The samples are delivered to each column via a manual 3-port disposable valve from disposable syringes. This second approach, a hybrid of fluidic and mechanized components, is a simpler more efficient approach for performing anion exchange procedures for the recovery and purification of plutonium from samples. The automation architectures described can also be adapted to column-based extraction chromatography separations.

Sequential anion-exchange separation of trace U, Th, Pb and lanthanides in environmental samples

The sequential separation technique of U, Th, Pb, and the lanthanides with a single anion-exchange column was applied to analysis of the geochemical reference sample, JB-1. The separation technique was previously developed by the authors and reported. The sample was digested and dissolved in nitric acid. Five solutions of different volume containing 0.1–1 mg of the JB-1 were loaded on the separate columns, and the elements of interest in the solution were sequentially separated. The concentrations of the elements were measured with an ICP-MS. The elements were successfully separated and alkaline metals and alkaline earth metals were effectively eliminated from the elements. The elemental concentrations were concordant with the literature values within the deviation except for that of Th. The elemental concentrations were accurately determined in ≥500 μg of the JB-1 without subtraction of processing blanks.

Rapid environmental analysis using molten salt fusion sample preparation

For the analysis of the isotopic composition of environmental samples, including transuranic materials there are many methods that exist. This paper describes the development of a high throughput method, which involves dissolving a soil into an aqueous matrix, producing a homogenous mixture, and separating radionuclides to enable the identification of specific isotopes. A standard method was modified via changes in oxidation, chemical exchange, decomposition, or rearrangements to form constituents that are more soluble in acidic aqueous solutions. To accomplish this, a molten-salt fusion, dissolution in dilutes nitric or hydrochloric acids, with subsequent separation using ion exchange, direct deposition, and counting by alpha-spectrometry was used. This method is ideal for silicate samples, but can be modified to accommodate more complex soil samples.

Rapid separation and extraction of radioactive analytes onto filters and surfaces

This paper presents a radiochemical procedure that combines radiochemical sample preparation and analyte separation to provide a rapid sample preparation method. Extractive ligands are prepared in a polymer matrix. This system can be immobilized on a surface or on a filter. Filters allow rapid sample uptake due to the movement of the analyte through the filter material. These approaches offer fast uptake kinetics, high material loading, and good selectivity. These systems have been demonstrated for the rapid extraction of plutonium and americium from solution and their subsequent analysis by alpha spectrometry, with no additional sample preparation required, thus eliminating extensive wet chemical processes that would otherwise be necessary. We have evaluated the extraction efficiency that can be obtained and have shown that these systems can provide for alpha spectrometry peak widths near what can be obtained using traditional techniques such as electroplating. We have also demonstrated Polymer Ligand Films (PLFs) for the selective extraction of plutonium from a solution prepared from a soil digest.

Role of the periodic table in discovery of new elements

This year (2009) marks the 140th Anniversary of Mendeleev's original 1869 periodic table of the elements based on atomic weights. It also marks the 175th anniversary of his birth in Tolbosk, Siberia. The history of the development of periodic tables of the chemical elements is briefly reviewed beginning with the presentation by Dmitri Mendeleev and his associate Nikolai Menshutkin of their original 1869 table based on atomic weights. The value, as well as the sometimes negative effects, of periodic tables in guiding the discovery of new elements based on their predicted chemical properties is assessed. It is noteworthy that the element with Z=101 (mendelevium) was identified in 1955 using chemical techniques. The discoverers proposed the name mendelevium to honor the predictive power of the Mendeleev Periodic Table. Mendelevium still remains the heaviest element to have been identified first by chemical rather than nuclear or physical techniques. The question concerning whether there will be a future role for the current form of the periodic table in predicting chemical properties and aid in the identification of elements beyond those currently known is considered.

Environmental monitoring of radioactive and non-radioactive constituents in the vicinity of WIP

The Waste Isolation Pilot Plant (WIPP), a US Department of Energy (DOE) facility, is a deep geologic transuranic waste disposal site designed for the safe disposal of transuranic (TRU) wastes generated from the US defense program. Monitoring is a key component of the development and operation of any nuclear repository and is important to the WIPP performance assessment. Initial concerns over the release of radioactive and chemical contaminants from the WIPP led to various monitoring programs, including the independent, academic-based WIPP environmental monitoring (WIPP-EM) program conducted by the New Mexico State University (NMSU) Carlsbad Environmental Monitoring and Research Center (CEMRC) located in Carlsbad, NM. The mission of CEMRC is to develop and implement an independent health and environmental monitoring program in the vicinity of WIPP and make the results easily accessible to the public and all interested parties. Under the WIPP-EM program constituents monitored include: (1) selected radionuclides, elements, and ions of interest in air, soil, vegetation, drinking water, surface water and sediment from within a 100-mile radius of WIPP as well as in the air exiting the WIPP exhaust shaft, and (2) internally deposited radionuclides in the citizenry living within a 100-mile radius of WIPP. This article presents an evaluation of more than tens years of environmental monitoring data that informed the public that there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP. Such an extensive monitoring program and constant public engagement is an ideal model for all nuclear waste repositories anywhere in the world.

Nuclear field shift effect of lead in ligand exchange reaction using a crown ether

Lead isotopes were fractionated by the liquid-liquid extraction technique between an aqueous phase and a crown ether. After purification by ion-exchange chemistry, the 207Pb/206Pb and 208Pb/206Pb isotopic ratios were measured by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Isotope fractionations > 0.05‰ have been found. The conventional equilibrium mass-dependent isotope effect estimated by an ab initio calculation was smaller than the Pb isotope fractionation experimentally obtained. Conventional mass-dependent isotope fractionation is not a valuable explanation for our results. The nuclear field shift effect, which results from the isotopic change in the nuclear size and shape, was also estimated by an ab initio method combined with a finite nucleus model. The nuclear field shift effect calculated was in agreement with our experimental results. Therefore, this study reports the first nuclear field shift effect of Pb in an equilibrium ligand exchange reaction.

230Th-234U model ages of some uranium standard reference materials

The “age” of a sample of uranium is an important aspect of a nuclear forensic investigation and of the attribution of the material to a source. The 230Th- 234U chronometer can be used to determine the production date of even very recently-produced material ( 234U half life = 245250 ± 490 years; 230Th half life = 75690 ± 230 years [1]), provided that the 230Th/234U at the time of formation is known, and that there has been no Th-U fractionation in the sample since production. For most samples of uranium, ages determined with this chronometer are “model ages”, because they are based on the assumptions of a) some initial amount of 230Th in the sample, and b) closed-system behavior of the sample since production. The uranium standard reference materials originally prepared and distributed by the former US National Bureau of Standards and now distributed by New Brunswick Laboratory as certified reference materials (NBS SRM = NBL CRM) are good candidates for materials where these assumptions may be tested. The U isotopic standards have known purification and production dates and closed-system behavior in the solid form (U3O8) may be reliably assumed. In addition, these materials are widely available and can serve as informal round-robin inter-laboratory comparison samples. We determined 230Th-234U model ages for seven of these isotopic standards by isotope dilution mass spectrometry using a multi-collector ICP-MS. The standards dated for this study are U005-A, U010, U030-A, U100, U850, U900 and U970. Model ages obtained range from ∼ 30 to ∼ 52 years ago (reference date: 5-May-2009). The model age of U100 is the same as the purification date, within uncertainty. The other six standards analyzed all give model ages older than the purification dates of record. The magnitude of the discrepancy between model age and purification date does not correlate with the model age or the amount of 232Th in the samples. This indicates that excess 230Th in these six standards results from incomplete purification during production.