Paul Herrick Smith

Actinide Binding and Solubilization by Microbial Siderophores

Accurate predictions of actinide and fission product migration in the geosphere are critically dependent on identification of the biological, chemical and physical processes which affect actinide mobility in soil and water. Siderophores are low molecular weight iron chelators produced by microbes in response to low availability of soluble iron. Because of the similarities between iron(III) and tetravalent actinides, and the prevalence of siderophore-producing microbes in soil, there is strong likelihood that siderophores may also bind actinides, thereby influencing their mobility in the environment. In order to begin to assess the potential importance of siderophore-mediated actinide mobility, we have determined rate constants for solubilization of hydrous plutonium oxide by the siderophores enterobactin and desferrioxamine Β and selected carboxylate, amino polycarboxylate, and catecholate ligands. The measured rate constants for solubilization of insoluble actinide oxides show that siderophores are extremely effective in solubilizing actinides; on a per molecule basis, enterobactin is ~ 1 0 3 times more effective than the other chelators tested in increasing the rate of solubilization of hydrous plutonium oxide. Notably, ferric-siderophore complexes are more effective in solubilizing actinide oxides than the siderophores in the absence of iron. These results suggest that siderophores have the potential to mobilize actinides in the environment.

Crystallographic, spectroscopic and theoretical studies of an electron-deiocalized Cu(1.5)–Cu(1.5) complex

The mixed-valence complex [Cu2L]3+1[L ={N[CH2CH2N(H)CH2CH2N(H)CH2CH2]3N]} has been shown from EPR, visible Spectroscopic, and single-crystal X-ray diffraction measurements to possess an unpaired electron delocalized over a short Cu(1.5)–Cu(1.5) bond in both the hydrated nitrate [2.364(2)A] and acetate [2.415(2)A] salts: Fenske–Hall MO analysis reveals direct σ-bonding interactions between the copper centers.

Convenient method for the preparation of some polyhydroxamic acids : Michael addition of amines to acrylohydroxamic acid derivatives

Reagents 1, 2, and 3 are readily prepared by the reaction of the appropriate hydroxylamine derivatives with acryloyl chloride. They undergo Michael addition with a variety of amines to give the corresponding O-protected hydroxamate derivatives in moderate to good yields. Subsequent removal of the protecting group provides a convenient method for the preparation of a number of mono, di, tri and tetrahydroxamic acids.

Design and synthesis of actinide specific chelators: Synthesis of new cyclam tetrahydroxamate (CYTROX) and cyclam tetraacetonylacetone (CYTAC) chelators

Abstract Molecular modeling shows that two new chelators, the cyclam tetrahydroxamate, 1, and the cyclam tetraacetonylacetone derivative, 2, have potential for the binding of plutonium (IV). The synthesis of these chelators has been achieved using short sequences from readily available cyclam. Both the details of the molecular modeling and the synthetic route to these molecules are described.

Novel tetrahydroxamate chelators for actinide complexation: synthesis and binding studies

The chelators 1 and 2, members of a new class of tetrahydroxamate chelators, are readily synthesized and are shown by potentiometric studies to have high affinities for thorium(IV), iron(III) and neodymium(III).

Synthesis and Evaluation of Polyhydroxamate Chelators for Selective Actinide Ion Sequestration

The overall goal of our research program is to design, synthesize and evaluate organic chelators for the specific binding/removal of actinides in a variety of environmentally relevant situations. Such chelators would be useful to selectively remove actinide ions such as plutonium from a variety of waste forms including soils and waste streams. We have identified a new class of polyhydroxamates as potential chelating agents for actinides based on computer modeling, solubility properties and other important features including ease of synthesis. Several members of this class of tetrahydroxamate chelators have been synthesized in our laboratory and evaluated for the binding of actinides and other metal ions in solution. Some of the hydroxamate chelators that we have developed have also been evaluated for their plutonium(IV) binding and the results are very encouraging. Detailed studies of the complexation behavior of this class of chelators are currently in progress and the goal of these experiments is to develop an understanding of the efficiency and nature of the metal complexation chemistry. This in turn should allow the further modification of this class of chelators to obtain agents with higher specificity for the actinide ions.

Gap Analysis of Storage Conditions between NNSS and LANL for SAVY 4000 Use

As part of the gap analysis for utilizing the SAVY 4000® at NNSS, the hydrogen gas generation rate and the effect of atmospheric pressure changes on the maximum normal operating pressure (MNOP) of the SAVY container must be evaluated because the nuclear material characteristics and atmospheric conditions will not be the same for NNSS and LANL. This paper documents this analysis and demonstrates that the LANL SAVY Safety Analysis Report (SAR) is bounding with respect to the Nevada facilities.

Water Resistant Container Technical Basis Document for the TA-55 Criticality Safety Program

Criticality safety at TA-55 relies on nuclear material containers that are water resistant to prevent significant amounts of water from coming into contact with fissile material in the event of a fire that causes a breach of glovevbox confinement and subsequent fire water ingress. A “water tight container” is a container that will not allow more than 50ml of water ingress when fully submerged, except when under sufficient pressure to produce structural discontinuity. There are many types of containers, welded containers, hermetically sealed containers, filtered containers, etc.

Durability and field condition study of seal of SAVY-4000 storage container

Abstract The conditions of use for rubber O-rings are at least as important as their physical properties in their effect on the quality of a seal. Under normal use conditions, O-rings may be subject to wear and environmental contaminants such as hair and dirt. This study examines how these factors impact the leak tightness of a nuclear material storage container and the likelihood of the inadvertent release of radioactive material. The durability lifetime of an O-ring was explored by opening and closing four SAVY-4000 1 quart containers 100 times and periodically performing helium leak testing, though no significant change in leak rate was observed. This study also explored how the accumulation of dust or hair on the O-ring surface would affect the leak rate of the containers. A single hair crossing the seal, or a sufficient amount of particulate matter would compromise the seal, but after cleaning, the seal was re-established.

SAVY-4000 Surveillance and Life Extension Program Fiscal Year 2013 Annual Report

The Packaging Surveillance Program section of the DOE M441.1-1/sup>1, Nuclear Material Packaging Manual (DOE, 2008) requires DOE contractors to “ensure that a surveillance program is established and implemented to ensure the nuclear material storage package continues to meet its design criteria.” In order to ensure continuing safe storage of nuclear material and the maximization of risk reduction, TA-55 has established a Surveillance Program to ensure storage container integrity for operations within its specified design life. The LANL SAVY-4000 Field Surveillance Plan2 defines the near-term field surveillance plan for SAVY-4000 containers as required by the Manual. A long-term surveillance plan will be established based on the results of the first several years of surveillance and the results of the lifetime extension studies as defined in the Accelerated Aging Plan3. This report details progress in positioning the Surveillance Program for successful implementation in FY14 and status of the Design Life Extension Program in terms of its implementation and data collection for FY13.