The loss of soluble cationic species by adsorption to glass vial walls is problematic for experiments performed at tracer concentrations. Silanization increases glass hydrophobicity to reduce cation sorption to glass surfaces. This work examines the efficacy of silanization in decreasing europium and thorium loss through glass sorption in aqueous and mixed aqueous/organic phases. The influence of the solution pH, ionic strength, electrolyte, metal concentration, organic diluent’s nature, and the addition of complexing extractants was investigated. Overall, results indicate that silanization effectively decreases cation loss to sorption to glass walls.

Technetium-99 (99Tc) is found in aqueous environmental systems (due to nuclear testing, reprocessing, and accidents), where it can coexist with halides. While Tc(VII) is the primary oxidation state under oxic conditions, Tc(IV) can also be present in the environment. Accurate knowledge of the complexation of Tc(IV) species with Cl– improves understanding of Tc behavior in the environment. Results of batch solvent extraction experiments indicate that a single chloride complex is formed in solution from an exothermic reaction with a negative entropy. Computational results support classifying an outer-sphere complex between the Tc(IV) species and chloride.

Di-(2-ethylhexyl)phosphoric acid, HDEHP, is a well-known extractant used for metal ion extraction in an industrial scale and for research work. Understanding metal extraction mechanisms is crucial for accurate interpretation of data obtained from solvent extraction experiments. The extraction mechanism of many metals by HDEHP has been determined. However, the mechanism for Tc(IV) extraction by HDEHP has not been specifically described in the literature and various assumptions have been made on the identity of the extracted Tc(IV) complex, without convincing demonstration. This work reports that TcO(OH)(DEHP)(HDEHP) is the Tc(IV) complex extracted by HDEHP into dodecane from an aqueous solution of 3 M NaClO4 at pH 2, with one HDEHP dimer participating in the extraction and one proton undergoing transfer from the HDEHP into the aqueous phase. The proposed mechanism agrees with other established metal hydroxide mechanisms and follow overall extraction trends for tetravalent metals with HDEHP.

This project investigated the cyber-security impacts of moving from an all analog, point-to-point, instrumentation and control (I&C) system to a digital I&C system based on Modbus and a shared communication medium. A formalism called a hybrid attack graph was expanded to support the nuclear research reactor system. The hybrid attack graph allows one to check a system for vulnerabilities, in this case cyber-security vulnerabilities, and to document the attack vectors (scenarios) causing those vulnerabilities. In parallel, a simulation of the system was developed to model both the physical reactor parameters and operations, as well as the network interconnects and communications. This simulation platform was modeled on the nuclear research reactor located at Washington State University. The simulation platform provided a sandbox to evaluate and quantify the impact of identified and proposed vulnerabilities in the system and to determine the effectiveness of countermeasures at stopping these attacks. The simulation and hybrid attack graph tools were integrated to provide a streamlined process of generating attack scenarios, playing those scenarios out in the simulation, and then analyzing the results to correlate system state to states in the hybrid attack graph. This process was used to (1) quantify the impact of attack scenarios and (2) to determine if the system moved through the hybrid attack graph as anticipated. The hybrid attack graph tool was extended and customized to produce a tool to automatically identify critical assets (CAs) and critical digital assets (CDAs) as defined by NRC Regulatory Guide 5.71. This tool was verified using the nuclear research reactor at Washington State University. Finally, a series of educational modules covering the findings of the different aspects of this research have been created.

The suitability of perrhenate (Re(VII)) to act as an analog for pertechnetate (Tc(VII)) was tested using solvent extraction and the carrier/tracer systems Tc-99(VII)/Tc-99m(VII) and Re-185/187/(186/188) Re(VII). Perrhenate is often used as a non-radioactive analogue of pertechnetate, but scarce data is available for the comparison of these metals for liquid-liquid extraction applications. Results show that neither Tc(VII) nor Re(VII) extraction is influenced by pH in the 2-8 range. The anion extractant also separates electrolyte anions, with increasing extraction following the order Cl- < NO3- << ClO4-, resulting in a decreased Tc(VII) and Re(VII) extraction in presence of salt. In particular, the extraction of Re and Tc is suppressed in presence of NaCl at concentrations higher than 1 mM. While Tc extraction is larger than that of Re in absence of electrolyte, they are statistically identical in presence of enough electrolyte. Furthermore, tetraphenylphosphonium chloride (Ph4PCl) is a stronger extractant than iodonitrotetrazolium chloride (INT).

This work reports the experimental determination of the stability constant for the complexation of the Tc(IV) cation by \( {\text{SO}}_{4}^{2 - } \) 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 log10 βapp for the complexation of Tc(IV) by sulfate was found to be 1.13 ± 0.04.

A proposed method for treating nuclear high level radioactive (NHLW) is to encapsulate it in a matrix made of complex oxide materials, such as pyrochlores with the general formula A2B2O7. Rare-earth hafnate pyrochlores have the potential to advance the current methods of NHLW disposal due to their robust chemical stability in radioactive environments, their high thermal stability, and their natural structural compatibility with radionuclide species. In this study, RE2Hf2O7:Eu3+ (RE = Y, La, Pr, Gd, Er, Lu) nanoparticles synthesized by a molten salt method were exposed to highly energetic gamma-ray irradiation. La2Hf2O7:Eu3+ and Lu2Hf2O7:Eu3+ underwent the order pyrochlore-disorder fluorite structural phase transition after exposure to gamma-ray irradiation. There was a change in the O-Eu charge transfer band (CTB) position as a function of gamma-ray dose. There was no change in the local symmetry of the Eu3+ dopant in Y2Hf2O7, Gd2Hf2O7 and Lu2Hf2O7, but in La2Hf2O7:Eu3+ gamma-ray dose reduced the symmetry around the Eu3+. For Y2Hf2O7:Eu3+ and La2Hf2O7:Eu3+, the lifetime and emission intensity were found to degrade possibly due to creation of gamma ray-induced defects which provides non-radiative pathways. Regarding Gd2Hf2O7:Eu3+, the concentration of oxygen vacancy defects predominated over other defects leading to enhanced emission and lifetime after gamma-ray irradiation. This study is of utmost importance for the design of a robust rare earth hafnate pyrochlore to be used as a nuclear waste host or gamma-ray based scintillator material.

Immobilization of radioiodine is an important requirement for current and future nuclear fuel cycles. Iodosodalite [Na-8(AlSiO4)(6)I-2] was synthesized hydrothermally from metakaolin, NaI, and NaOH. Dried unwashed sodalite powders were used to synthesize glass-bonded iodosodalite waste forms (glass composite materials) by heating pressed pellets at 650, 750, or 850 degrees C with two types of sodium borosilicate glass binders. These heat-treated specimens were characterized with X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, thermal analysis, porosity and density measurements, neutron activation analysis, and inductively-coupled plasma mass spectrometry. For the best waste form produced (pellets mixed with 10 mass% of glass binder and heat-treated at 750 degrees C), the maximum possible elemental iodine loading was 19.8 mass%, but only similar to 8-9 mass% waste loading of iodine was retained in the waste form after thermal processing. Other pellets with higher iodine retention either contained higher porosity or were incompletely sintered. ASTM C1308 and C1285 (product consistency test, PCT) experiments were performed to understand chemical durability under diffusive and static conditions. The C1308 test resulted in significantly higher normalized loss compared to the C1285 test, most likely because of the strong effect of neutral pH solution renewal and prevention of ion saturation in solution. Both experiments indicated that release rates of Na and Si were higher than for Al and I, probably due to a poorly durable Na-Si-O phase from the glass bonding matrix or from initial sodalite synthesis; however the C1308 test result indicated that congruent dissolution of iodosodalite occurred. The average release rates of iodine obtained from C1308 were 0.17 and 1.29 gm(-2) d(-1) for 80 or 8 m(-1), respectively, and the C1285 analysis gave a value of 2 x 10(-5) g m(-2) d(-1), which is comparable to or better than the durability of other iodine waste forms. (C) 2018 Elsevier B.V. All rights reserved.

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 pC H range of 2.00–2.70 indicated the formation of TcO(EDTA)2− (logβ 101=17.9±0.3, 25.0±0.1°C) and a protonated complex TcO(H)(EDTA)− (logβ 111=20.5±0.1, 25.0±0.1°C). The associated thermodynamic parameters Δr G 101=−101.7±0.4 kJ·mol−1, Δr H 101=−47±9 kJ·mol−1, Δr S 101=179±36 J·mol−1·K−1, Δr G 111=−117.2±0.3 kJ·mol−1, Δr H 111=−23±5 kJ·mol−1, and Δr S 111=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.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

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.

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.

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.

Determination of environmental tungsten (W) is inhibited by a lack of reference materials and practical methods to remove isobaric and radiometric interferences. We present a method that evaluates the potential use of commercially available sediment, Basalt Columbia River-2 (BCR-2), as a quality control standard for W. Tungsten concentrations determined using neutron activation analysis (NAA) and mass spectrometry are in statistical agreement at the significance level α = 0.05 (92 ± 4 ng g−1 for NAA and 100 ± 7 ng g−1 for mass spectrometry). These results indicate that BCR-2 may be suitable as a quality control standard for future studies.

Quantifying the iron (Fe) isotopes 55Fe and 59Fe radiometrically can be difficult due to emission interferences or high spectral backgrounds in the presence of other activation products or fission products. The purpose of this work was to demonstrate a separation procedure for Fe activation product analysis for complex samples that contain either activated soil components or freshly produced fission products generated from HEU. The developed procedure herein described succesfully allowed for quantitative analysis of both 59Fe (by gamma spectroscopy) and 55Fe (by low-energy photon spectroscopy) with greater than 90 % Fe recovery.

The WIPP geochemical model uses the Pitzer equations coupled to a thermodynamic database to carry out speciation and solubility calculations for the actinides in the +III, +IV, and +V oxidation states in aqueous systems composed of Na+-K+-Mg2+-Ca2+-SO42--OH--CO32--HCO3--H2O-acetate-citrate-oxalate-EDTA. The WIPP database incorporates results for actinide speciation and complexation work carried out primarily at Pacific Northwest National Laboratory, Forschungszentrum Karlsruhe (Germany) and Florida State University. Calculations are performed at Sandia National Laboratories with the code FMT, using the Harvie-Moller-Weare database, and parameters that were developed specifically for actinides in high ionic strength aqueous solutions. This paper describes derivation of the thermodynamic database, and provides normalized standard chemical potentials and Pitzer parameters for modeling An(III, IV, and V) speciation and solubility in brines. (c) 2006 American Chemical Society.