Photodarkening mechanisms of Pr3+ singly doped and Pr3+/Ce3+ co-doped silicate glasses and fibers

In this work, we revealed the possible mechanisms of the photodarkening in Pr³⁺ ions singly doped and Pr³⁺/Ce³⁺ co-doped silicate glasses and fibers induced by X-ray and 488-nm laser radiations and studied the role of Ce³⁺ in increasing radiation resistance in Pr³⁺-doped silicate glasses and fibers. The absorption, emission, electron paramagnetic resonance (EPR), radiation induced attenuation spectra, and X-ray photoelectron spectroscopy (XPS) of Pr³⁺ singly doped and Pr³⁺/Ce³⁺ co-doped silicate glasses before and after X-ray radiation were measured and analyzed. The fluorescence intensity and photoinduced attenuation of Pr³⁺ singly doped and Pr³⁺/Ce³⁺ co-doped silicate fibers at visible wavelengths pumped by 488-nm laser were measured and analyzed. The influence of Ce³⁺ ions co-doping on the spectroscopic properties of Pr³⁺ ions as well as the radiation-induced defects in silicate glasses was studied. Results demonstrate that both X-ray and 488-nm laser radiations will induce photodamage in Pr³⁺ ions-doped silicate glasses and fibers. Co-doping Ce³⁺ (by up to 1 mol%) is efficient to suppress the darkening induced by both X-ray and 488-nm laser radiations without influence on the luminescence behavior of Pr³⁺ ions in silicate glasses and fibers. Our studies demonstrate the promising potential of Pr³⁺/Ce³⁺ co-doped silicate glasses for visible lasing applications.     

Attitude, knowledge, and skill competencies for practice in professional geropsychology: Implications for training and building a geropsychology workforce.

Professional geropsychology is a growing area of practice and training. To meet the mental health needs of an aging population, increasing numbers of psychologists need to develop competence to work with older adults, their families, and related care systems. The Pikes Peak model for geropsychology training (Knight, Karel, Hinrichsen, Qualls, & Duffy, 2009) delineates attitude, knowledge, and skill competencies for professional geropsychology practice and makes recommendations for training. In this paper, we define and illustrate the Pikes Peak geropsychology practice competencies through a case example. In the case, an older man with complex needs seeks care through a generalist psychologist in an outpatient setting. The attitudes, knowledge, and skills that the psychologist needs to consider, and implications for training, are reviewed. Training recommendations and resources are provided, with a focus on the training needs of psychologists who wish to expand their practices to include older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feasibility study of minor actinide transmutation in light water reactors with various Am/Cm separation efficiencies

A study was conducted to evaluate the feasibility of minor actinide (MA) transmutation in light water reactors (LWR). The purpose of this work was to provide a guide for future investigations into MA transmutation in LWR. This work considered the effects of various Am/Cm separation efficiencies as well as homogeneous and heterogeneous MA bearing fuel assemblies. The MA content was introduced into the reactor as mixed oxide plus minor actinide (MOX + MA) fuel. Three Am/Cm separation efficiencies were independently considered: 99.9%, 99.0%, and 90.0%. In order to evaluate the feasibility of MA transmutation, the fuel performance of the various assemblies and core designs, as well as their respective safety related parameters, were calculated. The reduction of the burden of high level waste (HLW) motivated the investigation of MA transmutation. It was found that the MA bearing fuel assemblies and their subsequent core designs were able to perform within the safety limits required as well as achieving similar burnups to a UO₂ core. The Am transmutation rates were ∼40% for the homogeneous assemblies and up to 68% for the MA targets in the heterogeneous assemblies after the described burnup, however, there was a significant amount of Cm produced during burnup. This Cm production was due to the more favorable neutron capture reaction over fission for Am in the thermal spectrum. Future work should examine the benefits of Am transmutation at the expense of large Cm production rates.     

Fuel cycle analysis of GFR using advanced fuels

The potential benefits of a synergistic light-water reactor (LWR) and gas-cooled fast reactor (GFR) fuel cycle were evaluated for its impact on the front-end and back-end of the fuel cycle. Comparisons were made with conventional once-through cycle (OTC) and MOX fuel cycle. Variations in the synergistic LWR/GFR fuel cycles were based on the degree of recycle in the LWR including both plutonium and reprocessed uranium with concomitant impact on used LWR fuel inventory. This provided a wide range in composition of GFR feed from low to high plutonium content with impact on transmutation/incineration within the GFR fuel cycle. Self-recycle of all actinides was modeled for the GFR with analyses demonstrating that the GFR can be sustained on and consequently accept a wide range of feed materials. Analyses were done using Monteburns along with MCNP and Origen2.2 to model a 60-year period corresponding to the anticipated lifetime of supposed contemporary LWRs and GFRs. All cycles were evaluated based on actinide total mass and isotopic inventory, radiotoxicity, heatload, and resource requirements including natural uranium and SWU. For comparison, all fuel cycles were normalized based on 1 TWHe output. Improvements in fuel cycle performance are dictated by the production and incineration of minor actinides in the GFR and their continued recycle may not be feasible due to the buildup of troublesome isotopes such as ²⁴⁴Cm and ²⁵²Cf. But where uranium and plutonium continue to be recycled beyond the 60-year period, the LWR/GFR cycles demonstrated order of magnitude reductions in used fuel inventories, heatload, and radiotoxicity on a per TWHe basis over LWR only cycles. The full details of the advanced fuel cycle methodology and results are presented.