Dominic S. Peterson

Solid supports for micro analytical systems

The development of micro analytical systems requires that fluids are able to interact with the surface of the microfluidic chip in order to perform analysis such as chromatography, solid phase extraction, and enzymatic digestion. These types of analyses are more efficient if there are solid supports within the microfluidic channels. In addition, solid supports within microfluidic chips are useful in producing devices with multiple functionalities. In recent years there have been many approaches introduced for incorporating solid supports within chips. This review will explore several state of the art methods and applications of introducing solid supports into chips. These include packing chips with beads, incorporating membranes into chips, creating supports using microfabrication, and fabricating gels and polymer monoliths within microfluidic channels.

Evaluation of flow scintillation analysis for the determination of Sr-90 in bioassay samples

An automated procedure for the determination of (90)Sr was adapted from existing methods of flow scintillation analysis (FSA) for use on aqueous samples with low levels of activity (<1000 dpm per sample). This technique employs high-performance extraction chromatography (HPEC) and an on-line liquid scintillation counter to provide automated separation and subsequent detection of (90)Sr. The total analysis time is 30 min per sample. Dilute urine samples, spiked with (90)Sr, were also processed by this method to test the application of this technique for bioassay monitoring.

Developing and evaluating di(2-ethylhexyl) orthophosphoric acid (HDEHP) based polymer ligand film (PLF) for plutonium extraction

A method was developed to produce a thin Polymer Ligand Film (PLF) using di(2-ethylhexyl) orthophosphoric acid (HDEHP) ligand for rapid extraction of plutonium. Ligands were incorporated into a polystyrene matrix to generate a smooth and durable surface for analyte extraction. PLFs were prepared with varying amount of ligands to find the optimimum ratio between the ligands and polymer structure to give best plutonium recovery. Also, the plutonium extraction is dependent on the concentration of nitric solution. This dependency was examined in the manuscript. The PLF samples were counted directly using alpha spectroscopy without any further chemical process to test the plutonium recovery. The alpha spectroscopy data shows that HDEHP based PLFs were effective in extracting plutonium from nitric acid solution. The surface characterization was performed with a scanning electron microscope (SEM) and digital autoradiography for defect examination of the PLF and plutonium distribution study, respectively.

Additive Manufacturing Capabilities Applied to Inertial Confinement Fusion at Los Alamos National Laboratory

Abstract We describe the use at Los Alamos National Laboratory of additive manufacturing (AM) for a variety of jigs and coating, assembly, and radiography fixtures. Additive manufacturing has also been used to produce shipping containers of complex design that would be too costly to have fabricated using traditional techniques. The current goal for AM use in target fabrication is to increase target accuracy and rigidity. This has been realized by implementing AM into target stalk fabrication, allowing increased complexity to address target strength and the addition of features for alignment at facilities. We will describe the fabrication of these components and our plans to utilize AM in the future.

Design and Fabrication of Opacity Targets for the National Ignition Facility

Abstract Accurate models for opacity of partially ionized atoms are important for modeling and understanding stellar interiors and other high-energy-density phenomena such as inertial confinement fusion. Lawrence Livermore National Laboratory is leading a multilaboratory effort to conduct experiments on the National Ignition Facility (NIF) to try to reproduce recent opacity tests at the Sandia National Laboratory Z-facility. Since 2015, the NIF effort has evolved several hohlraum designs that consist of multiple pieces joined together. The target also has three components attached to the main stalk over a long distance with high tolerances that have resulted in several design iterations. The target has made use of rapid prototyped features to attach a capsule and collimator under the hohlraum while avoiding interference with the beams. This paper discusses the evolution of the hohlraum and overall target design and the challenges involved with fabricating and assembling these targets.

Evaluating bis(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) based polymer ligand film (PLF) for plutonium and uranium extraction

This paper describes a new analyte extraction medium called polymer ligand film (PLF) that was developed to rapidly extract radionuclides. PLF is a polymer medium with ligands incorporated in its matrix that selectively and quickly extracts analytes. The main focus of the new technique is to shorten and simplify the procedure for chemically isolating radionuclides for determination through alpha spectroscopy. The PLF system was effective for plutonium and uranium extraction. The PLF was capable of co-extracting or selectively extracting plutonium over uranium depending on the PLF composition. The PLF and electrodeposited samples had similar alpha spectra resolutions.

Alpha spectrometric characterization of process-related particle size distributions from active particle sampling at the Los Alamos National Laboratory uranium foundry

Uranium particles within the respirable size range pose a significant hazard to the health and safety of workers. Significant differences in the deposition and incorporation patterns of aerosols within the respirable range can be identified and integrated into sophisticated health physics models. Data characterizing the uranium particle size distribution resulting from specific foundry-related processes are needed. Using personal air sampling cascade impactors, particles collected from several foundry processes were sorted by activity median aerodynamic diameter onto various Marple substrates. After an initial gravimetric assessment of each impactor stage, the substrates were analyzed by alpha spectrometry to determine the uranium content of each stage. Alpha spectrometry provides rapid non-distructive isotopic data that can distinguish process uranium from natural sources and the degree of uranium contribution to the total accumulated particle load. In addition, the particle size bins utilized by the impactors provide adequate resolution to determine if a process particle size distribution is: lognormal, bimodal, or trimodal. Data on process uranium particle size values and distributions facilitate the development of more sophisticated and accurate models for internal dosimetry, resulting in an improved understanding of foundry worker health and safety.

Evaluating ligands for use in polymer ligand film (PLF) for plutonium and uranium extraction

Abstract This paper describes a new analyte extraction technique using polymer ligand film (PLF). PLFs were synthesized to perform direct sorption of analytes onto its surface for direct counting using alpha spectroscopy. The main focus of the new technique is to shorten and simplify the procedure for chemically isolating radionuclides for determination through a radiometric technique. 4′(5′)-di-t-butylcyclohexano 18-crown-6 (DtBuCH18C6) and 2-ethylhexylphosphonic acid (HEH[EHP]) were examined for plutonium extraction. Di(2-ethyl hexyl) phosphoric acid (HDEHP) were examined for plutonium and uranium extraction. DtBuCH18C6 and HEH[EHP] were not effective in plutonium extraction. HDEHP PLFs were effective for plutonium but not for uranium.

Lithographic Printing Via Two-Photon Polymerization of Engineered Foams

Abstract Understanding deuterium-tritium mix in capsules is critical to achieving fusion within inertial confined fusion experiments. One method of understanding how the mix of hydrogen fuels can be controlled is by creating various structured deuterated foams and filling the capsule with liquid tritium. Historically, these materials have been a stochastically structured gas-blown foam. Later, to improve the uniformity of this material, pore formers have been used which are then chemically removed, leaving behind a foam of monodisperse voids. However, this technique is still imperfect in that fragments of the pore templating particles may not be completely removed and the void distribution may not be uniform over the size scale of the capsule. Recently, advances in three-dimensional printing suggest that it can be used to create microlattices and capsule walls in one single print. Demonstrated here are proof-of-concept microlattices produced using two-photon polymerization with submicrometer resolution of various structures as well as a microlattice-containing capsule. With this technology, complete control of the mixing structure is possible, amenable to modeling and easily modified for tailored target design.