Overview of recent operating experience regarding plant aging

Recent, as well as past, studies of reactor trip frequencies and other types of operating experience have shown that relatively high frequencies are likely in new plants with little accumulated operating time. In order to better understand all the factors which contribute to high frequencies in new plants, the authors have made a comparison of reactor trip frequencies between plants which went into operation in the 1960's and the early 1970's and those which have gone into operation more recently. Trip frequency versus accumulated operating time for two plant groups are compared to see the extent to which design differences (e.g., capacity, thermal margin) affect trip frequency.This paper also presents a review of some recent events in which plant age has played a major role. The events which are reviewed have been identified through the normal systematic event analysis program conducted by the NRC. Information regarding these events was obtained through followup by reviews conducted by NRC Resident Inspectors as well as event reports submitted by licensees.     

Metal dusting (catastrophic carburization) of a waste heat boiler tube

A waste-heat boiler at a chemical plant suffered an unusual tube failure. The boiler is part of the partial oxidation (POx) syngas production for a 2-ethyl hexanol unit. The syngas primarily consists of H₂, CO and CO₂ with trace amounts of CH₄. Steam is also reportedly injected into the process. The syngas enters the boiler at approximately 1800°F (980°C) on the internal side of the tube and is cooled, while generating approximately 640 psi (4.41 MPa) steam at 490°F (255°C) on the outside of the tube. The internal surface of the tube contained a region of metal loss that was approximately 1 inches long by inch wide (44.5 mm by 19 mm). The metal loss was very localized with little evidence of attack elsewhere on the tube's surface. Molten salt attack, sulfidation and metal dusting were considered as possible mechanisms for the metal loss. It was determined that metal dusting, also called catastrophic carburization, was the cause of the metal loss. The cause of the metal dusting was localized overheating of the tube, which developed because of water/steam flow disruption due to contact of the tube baffle with the tube. Approximately one year after this tube failure, the boiler suffered two more tube failures, which were also attributed to metal dusting.     

The lexical nature of syntactic ambiguity resolution.

Ambiguity resolution is a central problem in language comprehension. Lexical and syntactic ambiguities are standardly assumed to involve different types of knowledge representations and be resolved by different mechanisms. An alternative account is provided in which both types of ambiguity derive from aspects of lexical representation and are resolved by the same processing mechanisms. Reinterpreting syntactic ambiguity resolution as a form of lexical ambiguity resolution obviates the need for special parsing principles to account for syntactic interpretation preferences, reconciles a number of apparently conflicting results concerning the roles of lexical and contextual information in sentence processing, explains differences among ambiguities in terms of ease of resolution, and provides a more unified account of language comprehension than was previously available. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention to arrays of multidimensional objects.

Encoding briefly displayed arrays of multidimensional objects appears to require selective attention, but this hypothesis is challenged by M. J. Nissen's (1985) finding that properties of an object are reported independently. Selective attention to some objects but not others should produce positive dependence. Theoretical analysis shows that deviations from independence would have been difficult to observe in Nissen's data because of high guessing rates and small sample sizes. Four new experiments showing strong positive dependence in property reports are described. Deviations from independence were highly significant for most Ss. Quantitative modeling shows that selective attention to subsets of objects would produce about the amount of dependence obtained. Rather than challenging attention theories, the amount of dependence in encoding multidimensional objects is consistent with selective attention to either objects or locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social change and law.

Comments on D. R. Fox's (see record 1993-27200-001) call for reexamination of legal efforts made on behalf of organized psychology to accomplish social change. The author disagrees with the claim made by Fox that organized psychology's advocacy efforts are misdirected because they promote values consistent with those found in the law. It is argued here that the law remains the primary and most powerful mechanism through which social change is accomplished. Further, until it can be empirically shown otherwise, law is a proper venue for efforts directed by organized psychology toward social change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Treatment of Posttraumatic Stress Disorder in Military and Veteran Populations.

While concerns about the psychological effects of war are not new, only recently has systematic attention been paid to such problems among past and present military personnel. There is increasing recognition that mental health has serious implications for operational performance, retention, and compensation. Although little controlled research exists with this population, preliminary evidence suggests that psychological treatments for posttraumatic stress disorder may be beneficial, albeit less so than for civilian populations. This article reviews evidence for each of several psychological treatment stages: stabilization and engagement, psychoeducation, symptom management, prolonged exposure, cognitive restructuring, and relapse prevention, with particular reference to the clinical issues raised by military personnel. Possible explanations for reduced treatment effects in this population compared with civilians are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Livsic theorems,maximizing measures and the stable norm

In this paper we consider two results motivated by Livsic's well-known theorem that, for a hyperbolic system, a Hölder continuous function is determined, up to a coboundary, by its values around closed orbits. The first result relates to negative values around orbits and the second result to values for finitely many orbits. We also present some new results on maximizing measures and the boundary of the unit ball in the stable norm for a surface.     

The federal role in injury control.

Early federal injury control programs in the 1960s and 1970s were centered first in the Division of Accident Prevention (Public Health Service) and subsequently in the National Highway Traffic Safety Administration (Department of Transportation) and the Consumer Product Safety Commission. The Centers for Disease Control (CDC) in the early 1970s also began to investigate injuries, particularly in the home and recreational environment. The field expanded in the 1970s and 1980s to include injuries that occur in many settings and both intentional injuries (violence) and unintentional injuries. After a 1985 report, Injury in America, CDC was chosen to be the national coordinating agency because of its mission of prevention. The current program also includes acute care, rehabilitation, and biomechanics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Addressing the special concerns of landfill closures: VLDPE and textured geomembranes

Landfill closures often require a somewhat different set of properties for synthetic liners than do landfill bottom liner installations. In particular, cap design usually presents the geotechnical engineer with greater concerns regarding long-term slope stability and accommodation of differential settlement. Friction between synthetic liners and materials contacting those liners, multiaxial elongation, and flexibility increase in importance. Since leachate does not contact the liners, chemical resistance becomes less important. Resistance to the components of landfill gas is, in most cases, all that is necessary.

As a result, synthetic liners with a textured surface to improve friction angles, and very low density polyethylene (VLDPE) geomembranes are becoming very attractive to geotechnical engineers. They provide considerable improvement in those areas which are important for cap installation. These materials, however, behave differently in standard index and performance testing of geomembranes, when compared with traditional polyethylene liners. These behaviors and differences are important for geotechnical engineers to understand. They are discussed in this paper.     

Reliability and stability of executive functioning in older adults.

A number of methodological questions have been raised about the reliability and validity of measuring executive functioning (EF) across multiple time points. In this study, correlational and latent-variable analyses were used to examine test-retest reliability of 5 common measures of EF and the stability of a latent EF construct. One hundred eighteen nondemented older adults were tested twice over a 4- to 8-week period. Findings demonstrated modest reliability of individual EF measures but very high stability of a latent EF construct. Relative contributions of each measure to the latent EF factor did not change across measurement trials. In addition, age-related effects on EF were similar at the 2 time points and were within the expected range. Implications for future studies of EF are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)