Donald E. Wall

Simulation and analysis framework for cyber-physical systems

This paper describes a unified framework for the simulation and analysis of cyber physical systems (CPSs). The framework relies on the FreeBSD-based IMUNES network simulator. Components of the CPS are modeled as nodes within the IMUNES network simulator; nodes that communicate using real TCP/IP traffic. Furthermore, the simulated system can be exposed to other networks and the Internet to make it look like a real SCADA system. The frame-work has been used to simulate a TRIGA nuclear reactor. This is accomplished by creating nodes within the IMUNES network capable of running system modules simulating different CPS components. Nodes communicate using MODBUS/TCP, a widely used process control protocol. A goal of this work is to eventually integrate the simulator with a honeynet. This allows researchers to not only simulate a digital control system using real TCP/IP traffic to test control strategies and network topologies, but also to explore possible cyber attacks and mitigation strategies.

Synthesis and Crystal Structures of Volatile Neptunium(IV) β-Diketonates

Production of certified reference materials in support of domestic nuclear forensics programs require volatile precursors for introduction into electromagnetic isotopic separation instruments. β-Diketone chelates of tetravalent actinides are known for their high volatility, but previously developed synthetic approaches require starting material (NpCl4) that is prohibitively difficult and hazardous to prepare. An alternative strategy was developed here that uses controlled potential electrolysis to reduce neptunium to the tetravalent state in submolar concentrations of hydrochloric acid. Four different β-diketone ligands of varying degrees of fluorination were reacted with an aqueous solution of Np4+. Products of this reaction were characterized via X-ray diffraction and infrared spectroscopy, and were found to be neutral 8-coordinate complexes that adopt square antiprismatic crystal geometry. Synthesis of Np β-diketonates by this approach circumvents the necessity of using NpCl4 in tetravalent Np coordination compound synthesis. The volatility of the complexes was assessed using thermogravimetric analysis, where the temperature of sublimation was determined to be in the range of 180° to 205 °C. The extent of fluorination did not appreciably alter the sublimation temperature of the complex. Thermal decomposition of these compounds was not observed during sublimation. High volatility and thermal stability of Np β-diketonates make them ideal candidates for gaseous introduction into isotopic separation instruments.

Thermodynamic parameters for the complexation of technetium(IV) with EDTA

Abstract Technetium-99 is a high yield (~6% fission yield) fission product and long-lived (2.13×105 year half-life) component of nuclear waste that will be disposed of in a geological repository. Some 99Tc has been released into the environment due to nuclear fuel and weapon production activities at sites such as Hanford, WA. Strongly complexing ligands such as ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) are known to increase Tc(IV) solubility and mobility in environmental systems and an accurate quantification of the complexation of Tc(IV) with EDTA is important for predicting its behavior in a geological repository. A liquid–liquid extraction system utilizing 0.2 M TOPO in dodecane was used to measure the stability constants of Tc(IV)-EDTA in 0.50 m NaNO3 at variable temperatures (14.0±0.1, 25.0±0.1, and 32.0±0.1°C). The acid dependence of the apparent stability constants in the pCH range of 2.00–2.70 indicated the formation of TcO(EDTA)2− (logβ101=17.9±0.3, 25.0±0.1°C) and a protonated complex TcO(H)(EDTA)− (logβ111=20.5±0.1, 25.0±0.1°C). The associated thermodynamic parameters ΔrG101=−101.7±0.4 kJ·mol−1, ΔrH101=−47±9 kJ·mol−1, ΔrS101=179±36 J·mol−1·K−1, ΔrG111=−117.2±0.3 kJ·mol−1, ΔrH111=−23±5 kJ·mol−1, and ΔrS111=315±63 J·mol−1·K−1 (0.50 m NaNO3, 25.0±0.1°C) were determined by van’t Hoff analysis. The formation of each Tc(IV)–EDTA complex is exothermic and present favorable entropy terms.

Complexation of Tc(IV) with \( {\text{SO}}_{4}^{2 - } \) in NaCl Medium

This work reports the experimental determination of the stability constant for the complexation of the Tc(IV) cation by SO42-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Fission Yield Measurements from Highly Enriched Uranium Irradiated Inside a Boron Carbide Capsule

{\text{SO}}_{4}^{2 - }

A chemical separation procedure using ionic liquid extraction for 59Fe and 55Fe quantification

\end{document} at 1.0 mol·kg−1 ionic strength (NaCl) and pcH 1.51 ± 0.05, using a solvent extraction method. The data herein represent a first step in determining unknown thermodynamic parameters for the complexation of Tc(IV) by simple polyatomic anions. Radiotracer studies were carried out with 99Tc and 35S, using both HDEHP and TOPO as extractants, to characterize the mechanism of the solvent extraction and to examine the extraction of the competing species, TcO(HSO4)+ and TcOSO4, into the organic phase. The apparent stability constant log10βapp for the complexation of Tc(IV) by sulfate was found to be 1.13 ± 0.04.

Determination of tungsten in geochemical reference material basalt Columbia River 2 by radiochemical neutron activation analysis and inductively coupled plasma mass spectrometry

This work describes a radiochemical separation procedure for the determination of gold (Au), platinum (Pt), tantalum (Ta), and tungsten (W) activation in the presence of fission products. Chemical separations result in a reduction in the minimum detectable activity by a factor of 287, 207, 141, and 471 for 182Ta, 187W, 197Pt, and 198Au respectively, with greater than 90% recovery for all elements. These results represent the highest recoveries and lowest minimum detectable activities for 182Ta, 187W, 197Pt, and 198Au from mixed fission-activation product samples to date, enabling considerable refinement in the measurement uncertainties for neutron fluences in highly complex sample matrices.Graphical Abstract