883 Matching Results

Search Results

Advanced search parameters have been applied.

Nuclear Synthesis of Element 43 (Tc)#x

Description: The following report on the nuclear synthesis of technetium is based on work performed under contract No. W-7405-eng-26 for the Atomic Energy Project at Oak Ridge National Laboratory.
Date: June 14, 1948
Creator: Motta, E. E. & Boyd, G. E.
Partner: UNT Libraries Government Documents Department

Radionuclide Retention in Concrete Wasteforms - FY13

Description: Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how wasteform performance is affected by the full range of environmental conditions within the disposal facility; the process of wasteform aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of wasteform aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the wasteforms come in contact with groundwater. Data collected throughout the course of this work will be used to quantify the efficacy of concrete wasteforms, similar to those used in the disposal of low-level waste and mixed low-level waste, for the immobilization of key radionuclides (i.e., uranium, technetium, and iodine). Data collected will also be used to quantify the physical and chemical properties of the concrete affecting radionuclide retention.
Date: October 15, 2013
Creator: Snyder, Michelle MV; Golovich, Elizabeth C.; Wellman, Dawn M.; Crum, Jarrod V.; Lapierre, Robert; Dage, Denomy C. et al.
Partner: UNT Libraries Government Documents Department

EVALUATION OF A TECHNETIUM-99 DETECTOR BASED ON LABORATORY TESTING FOR USE IN IN-SITU VADOSE ZONE APPLICATIONS

Description: This document evaluates the feasibility of in-situ detection of technetium-99 in Hanford Site vadose zone soils (the soils between the surface and groundwater) using laboratory tests. The detector system performs adequately for high technetium concentration, but more development and laboratory testing is needed before field demonstration is performed.
Date: September 11, 2009
Creator: FM, MANN & DA, MYERS
Partner: UNT Libraries Government Documents Department

Investigations Into the Nature of Alkaline Soluble, Non-Pertechnetate Technetium

Description: This report summarizes work accomplished in fiscal year (FY) 2013, exploring the chemistry of a low-valence technetium(I) species, [Tc(CO)3(H2O)3]+, a compound of interest due to its implication in the speciation of alkaline-soluble technetium in several Hanford tank waste supernatants. Various aspects of FY 2013’s work were sponsored both by Washington River Protection Solutions and the U.S. Department of Energy’s Office of River Protection; because of this commonality, both sponsors’ work is summarized in this report. There were three tasks in this FY 2013 study. The first task involved examining the speciation of [(CO)3Tc(H2O)3]+ in alkaline solution by 99Tc nuclear magnetic resonance spectroscopy. The second task involved the purchase and installation of a microcalorimeter suitable to study the binding affinity of [(CO)3Tc(H2O)3]+ with various inorganic and organic compounds relevant to Hanford tank wastes, although the actual measure of such binding affinities is scheduled to occur in future FYs. The third task involved examining the chemical reactivity of [(CO)3Tc(H2O)3]+ as relevant to the development of a [(CO)3Tc(H2O)3]+ spectroelectrochemical sensor based on fluorescence spectroscopy.
Date: November 14, 2013
Creator: Rapko, Brian M.; Bryan, Samuel A.; Chatterjee, Sayandev; Edwards, Matthew K.; Levitskaia, Tatiana G.; Peterson, James M. et al.
Partner: UNT Libraries Government Documents Department

Technetium Removal Using Tc-Goethite Coprecipitation

Description: This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, “Low temperature waste forms coupled with technetium removal using an alternative immobilization process such as Fe(II) treated-goethite precipitation” to increase our understanding of 99Tc long-term stability in goethite mineral form and the process that controls the 99Tc(VII) reduction and removal by the final Fe (oxy)hydroxide forms. The overall objectives of this task were to 1) evaluate the transformation process of Fe (oxy)hydroxide solids to the more crystalline goethite (α-FeOOH) mineral for 99Tc removal and 2) determine the mechanism that limits 99Tc(IV) reoxidation in Fe(II)-treated 99Tc-goethite mineral and 3) evaluate whether there is a long-term 99Tcoxidation state change for Tc sequestered in the iron solids.
Date: November 18, 2013
Creator: Um, Wooyong; Wang, Guohui; Jung, Hun Bok & Peterson, Reid A.
Partner: UNT Libraries Government Documents Department

Technetium chemistry

Description: Technetium chemistry is a young and developing field. Despite the limited knowledge of its chemistry, technetium is the workhorse for nuclear medicine. Technetium is also a significant environmental concern because it is formed as a byproduct of nuclear weapons production and fission-power generators. Development of new technetium radio-pharmaceuticals and effective environmental control depends strongly upon knowledge of basic technetium chemistry. The authors performed research into the basic coordination and organometallic chemistry of technetium and used this knowledge to address nuclear medicine and environmental applications. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).
Date: April 1996
Creator: Burns, C.; Bryan, J.; Cotton, F.; Ott, K.; Kubas, G.; Haefner, S. et al.
Partner: UNT Libraries Government Documents Department

Technetium getters in the near surface environment

Description: Conventional performance assessments assume that radioactive {sup 99}Tc travels as a non-sorbing component with an effective K{sub d} (distribution coefficient) of 0. This is because soil mineral surfaces commonly develop net negative surface charges and pertechnetate (TcO{sub 4}), with large ionic size and low electrical density, is not sorbed onto them. However, a variety of materials have been identified that retain Tc and may eventually lead to promising Tc getters. In assessing Tc getter performance it is important to evaluate the environment in which the getter is to function. In many contaminant plumes Tc will only leach slowly from the source of the contamination and significant dilution is likely. Thus, sub-ppb Tc concentrations are expected and normal groundwater constituents will dominate the aquifer chemistry. In this setting a variety of constituents were found to retard TcO{sub 4}: imogolite, boehmite, hydrotalcite, goethite, copper sulfide and oxide and coal. Near leaking tanks of high level nuclear waste, Tc may be present in mg/L level concentrations and groundwater chemistry will be dominated by constituents from the waste. Both bone char, and to a lesser degree, freshly precipitated Al hydroxides may be effective Tc scavengers in this environment. Thus, the search for Tc getters is far from hopeless, although much remains to be learned about the mechanisms by which these materials retain Tc.
Date: May 19, 2000
Creator: KRUMHANSL,JAMES L.; ZHANG,PENGCHU; WESTRICH,HENRY R.; BRYAN,CHARLES R. & MOLECKE,MARTIN A.
Partner: UNT Libraries Government Documents Department

Fundamental Chemistry, Characterization, and Separation of Technetium Complexes in Hanford Waste

Description: The ultimate goal of this project is to separate technetium from Hanford tank waste. Our prior work with Hanford Site tank waste indicates that the presence of complexants has produced unidentified, reduced technetium species not amenable to current separation technologies, or readily oxidized to pertechnetate. Consequently, we are synthesizing and characterizing some of the major classes of technetium complexes that may be formed under tank waste conditions. These complexes will be used as standards to characterize the nonpertechnetate species in actual wastes and to develop efficient oxidation or separation methods.
Date: June 2000
Creator: Schroeder, Norman C.; Ashley, Kenneth R. & Blanchard, David L.
Partner: UNT Libraries Government Documents Department

Prospects for baryon instability search with long-lived isotopes

Description: In this paper we consider the possibility of observation of baryon instability processes occurring inside nuclei by searching for the remnants of such processes that could have been accumulated in nature as mm long-lived isotopes. As an example, we discuss here the possible detection of traces of {sup 97}Tc, {sup 98}Tc, and {sup 99}Tc in deep-mined nonradioactive tin ores.
Date: December 31, 1996
Creator: Efremenko, Yu.; Bugg, W.; Cohn, H.; Kamyshkov, Yu.; Parker, G. & Plasil, F.
Partner: UNT Libraries Government Documents Department

Speciation of technetium in borosilicate glasses prepared in air

Description: A series of glass samples were prepared analogous to high level waste glass using either glass frit or glass precursors combined with a high level waste surrogate containing NaTcO{sub 4}. Three different technetium species were observed in these glasses depending upon the synthesis conditions. If the glasses were prepared by reducing NaTcO{sub 4} to TcO{sub 2} {center_dot} 2H{sub 2}O with hydrazine or if a large amount of organic material was present, inclusions of TcO{sub 2} were observed. If no organic material was present, technetium was incorporated as TcO{sub 4}{sup -}. If only a small amount of organic material was present, isolated Tc(IV) sites were observed in the glass. The relative technetium retention of these glasses was estimated from the Tc K-edge height, and had no correlation with the oxidation state of the technetium. Pertechnetate was well retained in these glasses.
Date: December 19, 2003
Creator: Lukens, Wayne W.; Shuh, David K.; Muller, Isabelle S. & McKeown, David A.
Partner: UNT Libraries Government Documents Department

Dissimilar behavior of technetium and rhenium in borosilicatewaste glass as determined by X-ray absorption spectroscopy

Description: Technetium-99 is an abundant, long-lived (t1/2 = 213,000 yr)fission product that creates challenges for the safe, long-term disposalof nuclear waste. While 99Tc receives attention largely due to its highenvironmental mobility, it also causes problems during its incorporationinto nuclear waste glass due to the volatility of Tc(VII) compounds. Thisvolatility decreases the amount of 99Tc stabilized in the waste glass andcauses contamination of the waste glass melter and off-gas system. Theapproach to decrease the volatility of 99Tc that has received the mostattention is reduction of the volatile Tc(VII) species to less volatileTc(IV) species in the glass melt. On engineering scale experiments,rhenium is often used as a non-radioactive surrogate for 99Tc to avoidthe radioactive contamination problems caused by volatile 99Tc compounds.However, Re(VII) is more stable towards reduction than Tc(VII), so morereducing conditions would be required in the glass melt to produceRe(IV). To better understand the redox behavior of Tc and Re in nuclearwaste glass, a series of glasses were prepared under different redoxconditions. The speciation of Tc and Re in the resulting glasses wasdetermined by X-ray absorption fine structure spectroscopy. Surprisingly,Re and Tc do not behave similarly in the glass melt. Although Tc(0),Tc(IV), and Tc(VII) were observed in these samples, only Re(0) andRe(VII) were found. In no case was Re(IV) (or Re(VI))observed.
Date: November 9, 2006
Creator: Lukens, Wayne W.; McKeown, David A.; Buechele, Andrew C.; Muller,Isabelle S.; Shuh, David K. & Pegg, Ian L.
Partner: UNT Libraries Government Documents Department

Characterization of Technetium Speciation in Cast Stone

Description: This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, “Production and Long-Term Performance of Low Temperature Waste Forms” to provide additional information on technetium (Tc) speciation characterization in the Cast Stone waste form. To support the use of Cast Stone as an alternative to vitrification for solidifying low-activity waste (LAW) and as the current baseline waste form for secondary waste streams at the Hanford Site, additional understanding of Tc speciation in Cast Stone is needed to predict the long-term Tc leachability from Cast Stone and to meet the regulatory disposal-facility performance requirements for the Integrated Disposal Facility (IDF). Characterizations of the Tc speciation within the Cast Stone after leaching under various conditions provide insights into how the Tc is retained and released. The data generated by the laboratory tests described in this report provide both empirical and more scientific information to increase our understanding of Tc speciation in Cast Stone and its release mechanism under relevant leaching processes for the purpose of filling data gaps and to support the long-term risk and performance assessments of Cast Stone in the IDF at the Hanford Site.
Date: November 11, 2013
Creator: Um, Wooyong; Jung, Hun Bok; Wang, Guohui; Westsik, Joseph H. & Peterson, Reid A.
Partner: UNT Libraries Government Documents Department

Development of a Chemistry-Based, Predictive Method for Determining the Amount of Non-Pertechnetate Technetium in the Hanford Tanks: FY 2012 Progress Report

Description: This report describes investigations directed toward understanding the extent of the presence of highly alkaline soluble, non-pertechnetate technetium (n-Tc) in the Hanford Tank supernatants. The goals of this report are to: a) present a review of the available literature relevant to the speciation of technetium in the Hanford tank supernatants, b) attempt to establish a chemically logical correlation between available Hanford tank measurements and the presence of supernatant soluble n-Tc, c) use existing measurement data to estimate the amount of n-Tc in the Hanford tank supernatants, and d) report on any likely, process-friendly methods to eventually sequester soluble n-Tc from Hanford tank supernatants.
Date: January 30, 2013
Creator: Rapko, Brian M.; Bryan, Samuel A.; Bryant, Janet L.; Chatterjee, Sayandev; Edwards, Matthew K.; Houchin, Joy Y. et al.
Partner: UNT Libraries Government Documents Department

RCRA Groundwater Quality Assessment Report for Waste Management Area S-SX (November 1997 through April 2000)

Description: This report updates a continuing groundwater quality assessment for single-shell tank Waste Management Area S-SX at the Hanford Site. This report covers November 1997 through April 2000. Major new findings include the following: groundwater contamination continues to persist in both the northern half of the Waste Management Area as well as the southern half; evaluation of changes in water table elevations indicates a gradual shift in the direction of groundwater flow from the southeast to a more easterly direction; discrete depth sampling suggests mobile tank waste contaminants are at the very top of the aquifer in downgradient wells along the southeast side of the SX tank farm.
Date: February 23, 2001
Creator: Johnson, Vernon G. & Chou, Charissa J.
Partner: UNT Libraries Government Documents Department

Molecular Mechanism of Microbial Technetium Reduction Final Report

Description: Microbial Tc(VII) reduction is an attractive alternative strategy for bioremediation of technetium-contaminated subsurface environments. Traditional ex situ remediation processes (e.g., adsorption or ion exchange) are often limited by poor extraction efficiency, inhibition by competing ions and production of large volumes of produced waste. Microbial Tc(VII) reduction provides an attractive alternative in situ remediation strategy since the reduced end-product Tc(IV) precipitates as TcO2, a highly insoluble hydrous oxide. Despite its potential benefits, the molecular mechanism of microbial Tc(VII) reduction remains poorly understood. The main goal of the proposed DOENABIR research project is to determine the molecular mechanism of microbial Tc(VII) reduction. Random mutagenesis studies in our lab have resulted in generation of a set of six Tc(VII) reduction-deficient mutants of Shewanella oneidensis. The anaerobic respiratory deficiencies of each Tc(VII) reduction-deficient mutant was determined by anaerobic growth on various combinations of three electron donors and 14 terminal electron acceptors. Results indicated that the electron transport pathways to Tc(VII), NO3 -, Mn(III) and U(VI) share common structural or regulatory components. In addition, we have recently found that wild-type Shewanella are also able to reduce Tc(IV) as electron acceptor, producing Tc(III) as an end-product. The recent genome sequencing of a variety of technetium-reducing bacteria and the anticipated release of several additional genome sequences in the coming year, provides us with an unprecedented opportunity to determine the mechanism of microbial technetium reduction across species and genus lines.
Date: April 30, 2013
Creator: DiChristina, Thomas J.
Partner: UNT Libraries Government Documents Department

Radiolysis of actinides and technetium in alkaline media

Description: The {gamma}-radiolysis of aerated alkaline aqueous solutions of Np(V), Np(VI), Pu(VI), Tc(IV), Tc(V), and TC(VII) was studied in the absence of additives and in the presence of CO{sub 3}{sup 2-}, NO{sub 3}{sup -}, NO{sub 2}{sup -}, EDTA, formate, and other organic compounds. The radiolytic reduction of Np(V), Np(VI), Pu(VI), and TC(VII) under different experimental conditions was examined in detail. The addition of EDTA, formate, and alcohols was found to considerably increase the radiation-chemical reduction yields. The formation of the Np(V) peroxo complex was observed in the {gamma}-radiolysis of alkaline aqueous solutions of Np (VI) in the presence of nitrate.
Date: July 10, 1996
Creator: Delegard, C. H.
Partner: UNT Libraries Government Documents Department

Sodium Removal from Hanford Waste Simulants Using Hydrated Antimony Pentoxide

Description: Sodium has been removed from each of the three Hanford waste simulants with Hydrated Antimony Pentoxide (HAP) to facilitate technetium measurement by ICP-MS. Technetium was successfully measured in simulants A and B with small dilutions of the simulants (10x). Matrix interference, probably due to organic components, prevented the accurate measurement of Tc in simulant C. HAP has been used for the selective removal of sodium from samples prior to radiochemical analysis.1-4 The analytical development section of SRTC has successfully used HAP to remove sodium from a simulated sample matrix of a SRS waste tank.5 This sample pretreatment method eliminated signal suppression caused by the 5 molar sodium matrix without affecting the concentration of Pt, Ru, and Re as measured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). With this initial success, we decided to investigate the use of HAP to remove sodium from the three Hanford waste matrices prior to ICP-MS analysis of technetium. The results of this investigation are summarized in this report.
Date: November 18, 1999
Creator: Tovo, L.L.
Partner: UNT Libraries Government Documents Department

Extraction of Long-Lived Radionuclides from Caustic Hanford Tank Waste Supernatants

Description: A series of polymer-based extraction systems, based on the use of polyethylene glycols (PEGs) or polypropylene glycols (PPGs), was demonstrated to be capable of selective extraction and recovery of long-lived radionuclides, such as Tc-99 and I-129, from Hanford SY-101 tank waste, neutralized current acid waste, and single-shell tank waste simulants. During the extraction process, anionic species like TcO₄⁻ and I⁻ are selectively transferred to the less dense PEG-rich aqueous phase. The partition coefficients for a wide range of inorganic cations and anions, such as sodium, potassium, aluminum, nitrate, nitrite, and carbonate, are all less than one. The partition coefficients for pertechnetate ranged from 12 to 50, depending on the choice of waste simulant and temperature. The partition coefficient for iodide was about 5, while that of iodate was about 0.25. Irradiation of the PEG phase with gamma-ray doses up to 20 Mrad had no detectable effect on the partition coefficients. The most selective extraction systems examined were those based on PPGs, which exhibited separation factors in excess of 3000 between TcO₄⁻ and NO₃⁻/NO₂⁻. An advantage of the PPG-based system is minimization of secondary waste production. These studies also highlighted the need for exercising great care in extrapolating the partitioning behavior with tank waste simulants to actual tank waste.
Date: July 1995
Creator: Chaiko, David J.; Mertz, C. J.; Vojta, Y.; Henriksen, J. L.; Neff, R. & Takeuchi, M.
Partner: UNT Libraries Government Documents Department

Molecular Engineering of Technetium and Rhenium Based Radiopharmaceuticals

Description: The research was based on the observation that despite the extraordinarily rich coordination chemistry of technetium and rhenium and several notable successes in reagent design, the extensive investigations by numerous research groups on a variety of N{sub 2}S{sub 2} and N{sub 3}S donor type ligands and on HYNIC have revealed that the chemistries of these ligands with Tc and Re are rather complex, giving rise to considerable difficulties in the development of reliable procedures for the development of radiopharmaceutical reagents.
Date: June 30, 2003
Creator: Zubieta, J.
Partner: UNT Libraries Government Documents Department

EVALUATION OF VADOSE ZONE TREATMENT TECHNOLOGIES TO IMMOBILIZE TECHNETIUM-99

Description: The Hanford Site End State Vision document (DOE/RL-2003-59) states: ''There should be an aggressive plan to develop technology for remediation of the contamination that could get to the groundwater (particularly the technetium [{sup 99}Tc])''. In addition, there is strong support from the public and regulatory agencies for the above statement, with emphasis on investigation of treatment alternatives. In July 2004, PNNL completed a preliminary evaluation of remediation technologies with respect to their effectiveness and implementability for immobilization of {sup 99}Tc beneath the BC Cribs in the 200 West Area (Truex, 2004). As a result of this evaluation, PNNL recommended treatability testing of in situ soil desiccation, because it has the least uncertainty of those technologies evaluated in July 2004 (Treatability Test Outline, September 30, 2004). In 2005, DOE-RL and Fluor Hanford convened an independent technical panel to review alternative remediation technologies, including desiccation, at a three-day workshop in Richland, Washington. The panel was composed of experts in vadose-zone transport, infiltration control, hydrology, geochemistry, environmental engineering, and geology. Their backgrounds include employment in academia, government laboratories, industry, and consulting. Their review, presented in this document, is based upon written reports from Hanford, oral presentations from Hanford staff, and each panel members' years of experience in their particular field of expertise. The purpose of this report is to document the panel's evaluation of various treatment alternatives with potential for minimizing contaminant migration in the deep vadose zone at the Department of Energy Hanford Site. The panel was tasked with assessing the most viable and practical approach and making recommendations for testing. The evaluation of vadose-zone treatment alternatives was conducted to be broadly applicable at a variety of locations at Hanford. However, because of limitations of time, the panel was asked to focus on one example, {sup 99}Tc contamination below the BC Cribs ...
Date: March 15, 2006
Creator: PETERSEN, S.W.
Partner: UNT Libraries Government Documents Department