Understanding the irradiation-induced defects in oxides is of interest for a wide range of applications. ZnO is an interesting oxide with mixed ionic and covalent bonding that contains a variety of point defect structures—making it an excellent model for studying irradiation-induced defects and their impact on properties. Here, we investigate the effects of neutron irradiation on the formation of defects and on the structural, optical, and electrical properties of ZnO single crystals. We observe the formation of vacancies and voids via positron annihilation spectroscopy. Neutron irradiation led to a significant deterioration of the ZnO structure and formed a high concentration of point defects, vacancy clusters, and voids with large disparities in their structure across variable irradiation times. It also led to significant changes in the optical properties and sample color. Irradiation for 444 h induced a high concentration of Cu acceptors as well as a high concentration of Ga donors. Temperature-dependent Hall effect measurements revealed the competing production of donors and acceptors and showed an increase in the slope of the carrier freeze-out curve with increasing irradiation dose. This work demonstrates the combined effects of neutron irradiation in producing a wide range of structural defects, impurities, and dopants in oxides and their enormous impact on modifying the oxide structure and both the optical and electronic properties. It particularly emphasizes the importance of considering the production of new impurities and dopants during the neutron irradiation of oxides.

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

This work reports the experimental determination of the stability constant for the complexation of the Tc(IV) cation by SO_4^2 - at 1.0 mol·kg −1 ionic strength (NaCl) and p c H 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 99 Tc and 35 S, 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(HSO 4 ) + and TcOSO 4 , into the organic phase. The apparent stability constant log 10 β app for the complexation of Tc(IV) by sulfate was found to be 1.13 ± 0.04.

Microstructure of various oxide-dispersion-strengthened (ODS) steels with 15% chromium content was studied in term of vacancy defects presence and their accumulation after defined irradiation treatment, respectively. Studied materials originated from Kyoto University and studied via IAEA collaborative project. Samples were characterized "as received" by positron annihilation lifetime spectroscopy and their microstructure was examined by transmission electron microscopy as well. Samples were afterwards irradiated in Washington State University Nuclear Radiation Center via a strong gamma source (6TBq). Damage induced by gamma irradiation was evaluated by positron lifetime measurements in emphasis on defect accumulation in the materials. We have demonstrated strong defect production induced by gamma irradiation which results from positron measurement data.

Prior work has demonstrated the use of a natural B4C capsule for spectral-tailoring in a mixed spectrum reactor as an alternate and complementary method to critical assemblies for performing nuclear data measurements at near 235U fission-energy neutron spectrum. Previous fission product measurements showed that the neutron spectrum achievable with natural B4C was not as hard as what can be achieved with critical assemblies. New measurements performed with the Washington State University TRIGA reactor using a B4C capsule 96 % enriched in 10B resulted in a neutron spectrum very similar to a critical assembly and a pure 235U fission spectrum. Fission product yields measured following an irradiation of a sample with this new method and subsequent radiochemical separations are presented here.

A boron carbide capsule was previously designed and tested by Pacific Northwest National Laboratory (PNNL) and Washington State University (WSU) for spectral-tailoring in mixed spectrum reactors. The presented work used this B4C capsule to create a fission product sample from the irradiation of highly enriched uranium (HEU) with a fast fission neutron spectrum. An HEU foil was irradiated inside of the capsule in WSU’s 1 MW TRIGA reactor at full power for 200 min to produce 5.8 × 1013 fissions. After 3 days of cooling, the sample was shipped to PNNL for radiochemical separations and analysis by gamma and beta spectroscopy. Fission yields for products were calculated from the radiometric measurements and compared to measurements from thermal neutron induced fission (analyzed in parallel with the non-thermal sample at PNNL) and published evaluated fast-pooled and thermal nuclear data. Reactor dosimetry measurements were also completed to fully characterize the neutron spectrum and total fluence of the irradiation.

Zinc oxide single crystals were doped with copper acceptors by means of the nuclear transmutation doping method, which gives highly uniform dopant distributions and has a much higher probability of controlling the dopant locations in the lattice. The Cu doping was confirmed by the infrared absorption signature of Cu2+ at 5780 cm−1. Hall-effect measurements were performed to study the effect of CuZn on the electrical properties of ZnO. These measurements indicated that the Cu acceptor level lies 0.160 eV below the conduction-band minimum.

Washington State University’s 1 MW TRIGA reactor has a long history of utilization for neutron activation analysis (NAA). TRIGA reactors have the ability to pulse, reach supercritical (k > 1) for short bursts of time (~50 ms). At this high power and fast time the energy spectrum and neutron fluence are largely uncharacterized. The pulse neutron energy spectrum and fluence were determined by the activation of Cu, Au, Co, Fe, and Ti. These analyses were completed with and without Cd shielding to determine reproducibility between pulses. The applications and implications of the neutron energy and fluence reproducibility to the use of pulsed NAA will be discussed.

Since 2002, Washington State University has been building radiochemistry as a component of its overall chemistry program. Using an aggressive hiring strategy and leveraged funds from the state of Washington and federal agencies, six radiochemistry faculty members have been added to give a total of seven radiochemists out of a department of twenty-five faculty members. These faculty members contribute to a diverse curriculum in radiochemistry, and the Chemistry Department now enjoys a significant increase in the number of trainees, the quantity of research expenditures, and the volume and quality of peer-reviewed scientific literature generated by the radiochemistry faculty and the trainees. These three factors are essential for sustaining the radiochemistry education and research program at any academic institution.