Advanced nuclear reactors offer various operational advantages over existing light water reactors but could produce types of spent nuclear fuel (SNF) with a wide variety of forms and characteristics ...depending on how many different concepts are deployed. Each advanced reactor SNF type potentially poses unique management challenges. New planning efforts will be necessary to anticipate how the management requirements of advanced reactor SNF will affect the deployment of an integrated waste management system. This paper applies a framework of high-level facility deployment milestones to a generic SNF management system, reviewing them together with the advanced reactor SNF characteristics and management requirements. This allows for the investigation of factors that influence facility and system deployment, and ultimately, the identification of challenges facing the deployment of different kinds of SNF management facilities. Here, the back end of the once-through fuel cycle is examined for four advanced reactor system technology types: sodium-cooled fast reactors, high-temperature gas-cooled reactors, liquid-fuel molten salt reactors, and lead-cooled fast reactors. It is observed that milestones earlier in the facility deployment process (e.g., siting and facility design) are more impacted by the uniqueness of advanced reactor SNF characteristics than others (e.g., construction and testing). Ultimately, none of the differences are seen as fundamentally disqualifying in a technical sense; however, they should be considered early, potentially as part of reactor design, to avoid issues in the future.
If advanced fuel cycles are to include a large number of fast reactors (FRs), what should be the transuranic (TRU) conversion ratio (CR)? The nuclear energy era started with the assumption that they ...should be breeder reactors (CR > 1), but the full range of possible CRs eventually received attention. For example, during the recent U.S. Global Nuclear Energy Partnership program, the proposal was burner reactors (CR < 1). Yet, more recently, Massachusetts Institute of Technology's "Future of the Nuclear Fuel Cycle" proposed CR approximately 1. Meanwhile, the French company EDF remains focused on breeders. At least one of the reasons for the differences of approach is different fuel cycle objectives. To clarify matters, this paper analyzes the impact of TRU CR on many parameters relevant to fuel cycle systems and therefore spans a broad range of topic areas.
The analyses are based on a FR physics parameter scan of TRU CR from 0 to approximately1.8 in a sodium-cooled metal-fueled FR (SMFR), in which the fuel from uranium-oxide-fueled light water reactors (LWRs) is recycled directly to FRs and FRs displace LWRs in the fleet. In this instance, the FRs are sodium cooled and metal fueled. Generally, it is assumed that all TRU elements are recycled, which maximizes uranium ore utilization for a given TRU CR and waste radiotoxicity reduction and is consistent with the assumption of used metal fuel separated by electrochemical means. In these analyses, the fuel burnup was constrained by imposing a neutron fluence limit to fuel cladding to the same constant value. This paper first presents static, time-independent measures of performance for the LWR right arrow FR fuel cycle, including mass, heat, gamma emission, radiotoxicity, and the two figures of merit for materials for weapon attractiveness developed by C. Bathke et al.
No new fuel cycle will achieve a static equilibrium in the foreseeable future. Therefore, additional analyses are shown with dynamic, time-dependent measures of performance including uranium usage, TRU inventory, and radiotoxicity to evaluate the complex impacts of transition from the current uranium-fueled LWR system, and other more realistic impacts that may not be intuited from the time-independent steady-state conditions of the end-state fuel cycle. These analyses were performed using the Verifiable Fuel Cycle Simulation Model VISION.
Compared with static calculations, dynamic results paint a different picture of option space and the urgency of starting a FR fleet. For example, in a static analysis, there is a sharp increase in uranium utilization as CR exceeds 1.0 (burner versus breeder). However, in dynamic analyses that examine uranium use over the next 1 to 2 centuries, behavior as CR crosses the 1.0 threshold is smooth, and other parameters such as the time required outside of reactors to recycle fuel become important.
Overall, we find that there is no unambiguously superior value of TRU CR; preferences depend on the relative importance of different fuel cycle system objectives.
Growing research shows tourism as a contributor to personality growth. In this study, 217 native Filipino adults (mean age=22.7 years) were prompted to describe experiences of wonderful happiness ...during travel and indicate the travel purpose, when and where their peak-experience occurred, its catalyst and intensity, whether they were alone, and subsequent impact on their view of life. Additionally, they were asked if travel had ever facilitated problem-solving or decision-making and how. Nearly 83% reported a peak-experience involving travel. Peaks involving interpersonal joy were most frequent, followed by nature, personal growth, serenity/mindfulness, culture/aesthetics, culinary delight, skill mastery, external achievement, and materialism. More than 70% reported very or extremely intense peak-experiences, and 92.8% reported that it impacted their view of life. Over 80% who experienced a peak affirmed that travel aided decision-making. The implications of these findings for understanding growth aspects of travel are discussed, and future avenues of research are highlighted.
Intraoperative probes and imaging probes Hoffman, E J; Tornai, M P; Janecek, M ...
European journal of nuclear medicine,
08/1999, Letnik:
26, Številka:
8
Journal Article
Recenzirano
Intraoperative probes have been employed to assist in the detection and removal of tumors for more than 50 years. For a period of about 40 years, essentially every detector type that could be ...miniaturized had been tested or at least suggested for use as an intraoperative probe. These detectors included basic Geiger-Müller (GM) tubes, scintillation detectors, and even state-of-the-art solid state detectors. The radiopharmaceuticals have progressed from (32)PO(4)(-) injections for brain tumors to sophisticated monoclonal antibodies labeled with iodine-125 for colorectal cancers. The early work was mostly anecdotal, primarily interdisciplinary collaborations between surgeons and physical scientists. These collaborations produced a few publications, but never seemed to result in an ongoing clinical practice. In the mid 1980s, several companies offered basic gamma-detecting intraoperative probes as products. This led to the rapid development of radioimmunoguided surgery (RIGS) and sentinel node detection as regularly practiced procedures to assist in the diagnosis and treatment of cancer. In recent years intraoperative imaging probes have been developed. These devices add the ability to see the details of the detected activity, giving the potential of using the technique in a low-contrast environment. Intraoperative probes are now established as clinical devices, they have a commercial infrastructure to support their continued use, and there is ongoing research, both commercial and academic, that would seem to ensure continued progress and renewed interest in this slowly developing field.
Humanistic psychology has pioneered in investigating travel as a contributor to personality growth. In this study, 182 native Chinese undergraduates responded to a survey inquiring if they had ever ...experienced “wonderful happiness” while engaged in tourism, and if so, to indicate the purpose of their travel, how recently and where their peak-experience occurred, whether they were alone or with others at the time, its intensity and subsequent impact on their view of life. Participants were also asked to describe the “trigger” of their peak-experience; these were coded into nine categories. A total of 86.8% (N=158) responded affirmatively, most of whom were touring within China. Peaks involving nature were reported significantly most frequently. A cluster involving interpersonal joy, serenity, and personal growth were reported second-most frequently, with relatively small frequencies relating to culture/aesthetics, culinary delight, and particularly materialism, skill mastery, and external achievement. More than 75% of participants rated their peak as “moderately” or “very” intense and 53.5% reported that it impacted their subsequent view of life. No significant gender differences emerged. The implications of these findings for understanding growth aspects of tourism among Chinese young adults are discussed, and future avenues of research are highlighted.
Fuel cycle analyses are performed to evaluate the impacts of further transmutation of spent nuclear fuel on high-level and low-level waste mass flows into repositories, on the composition and ...toxicity of the high-level waste, on the capacity of high-level waste repositories, and on the proliferation resistance of the high-level waste. Storage intact of light water reactor (LWR) spent nuclear fuel, a single recycle in a LWR of the plutonium as mixed-oxide fuel, and the repeated recycle of the transuranics in critical and subcritical fast reactors are compared with the focus on the waste management performance of these systems. Other considerations such as cost and technological challenges were beyond the scope of this study. The overall conclusion of the studies is that repeated recycling of the transuranics from spent nuclear fuel would significantly increase the capacity of high-level waste repositories per unit of nuclear energy produced, significantly increase the nuclear energy production per unit mass of uranium ore mined, significantly reduce the radiotoxicity of the waste streams per unit of nuclear energy produced, and significantly enhance the proliferation resistance of the material stored in high-level waste repositories.
A study in the United States has evaluated the attributes of the heterogeneous recycle approach for plutonium and minor actinide transmutation in fast reactor fuel cycles, with comparison to the ...homogeneous recycle approach, where pertinent. The work investigated the characteristics, advantages, and disadvantages of the approach in the overall fuel cycle, including reactor transmutation, systems and safety impacts, fuel separation and fabrication issues, and proliferation risk and transportation impacts. For this evaluation, data from previous and ongoing national studies on heterogeneous recycle were reviewed and synthesized. Where useful, information from international sources was included in the findings. The intent of the work was to provide a comprehensive assessment of the heterogeneous recycle approach at the current time.
Metaphor analysis has been found a valid way to examine the core values and flourishing of teachers in Western culture, but empirical evidence is sparse for their Far Eastern counterparts. In the ...present study, 60 teachers (mean teaching experience=6.9 years) in southeastern China responded to a structured questionnaire. It elicited their personal life-metaphor, whether they had always espoused it since youth, and if not, what had caused it to change; and how it guides their actions. Teachers were also asked to indicate which of 17 life-metaphors they most and least preferred, and to rate their happiness and life meaning from teaching. Consistent with their counterparts in Costa Rica, virtually all Chinese teachers recounted a personal life-metaphor. Similar to those recounted by Costa Rican teachers, these were predominantly active and individualistic, but differed by being affectively neutral rather than optimistic. The most preferred and least preferred life-metaphors were similar but not identical among the two nationalities of teachers. Consistent with the content of their personal metaphors, Chinese teachers reported moderate happiness and personal meaning from their work. The usefulness of metaphor analysis in aiding teacher development in China is discussed, and future avenues of research are highlighted.
Standardized tests are a component of the teacher certification process in many states and may also be used by colleges and universities to evaluate readiness for a teacher education program. While ...some agencies have developed examinations for single-state use, institutions of higher learning and licensing bodies in forty-three states, the District of Columbia, and three US territories have adopted the Praxis Series® examinations for these purposes. The Praxis Series, developed by Educational Testing Service, includes the Praxis Core Academic Skills for Educators, often referred to simply as Praxis Core, and the Praxis Subject Assessments, formerly known as Praxis II exams. Here, Hoffman details the structure of Praxis Series.
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