Risk Assessment in the Nuclear Age

This paper is presented in the spirit of the stated intentions for the Workshop on Comparative Risk Assessment; Woods Hole, Massachusetts; March 31-April 4, 1975. A brief discussion of several topics is provided in the hope of stimulating further consideration in the area of "risk assessment". Included are observations, experiences, clinical impressions, and speculative thoughts reflective of, the writer's growing interest in this relatively new field of scientific inquiry. A particular methodology for. quantifying the perceived "risk" of various environmental hazards and/or technological advances is proposed. A more detailed and comprehensive approach to many of these issues is the aim of the author after his appointment as Research Scholar with the collaborative International Institute of Applied Systems Analysis--International Atomic Energy Agency--Project (Vienna, Austria) in June, 1975

A Psychological Perspective of the Nuclear Energy Controversy

This report concerns the following: (1) the nuclear energy debate as a focal point for a wide range of societal concerns; (2) general considerations regarding the impact of technology on society and on the individual; (3) psychological determinants in the nuclear energy controversy; (4) potential symbolic constraints posed by nuclear energy; and (5) the possible role of social-behavioral researchers in the nuclear energy debate

Social Values in Risk Acceptance

Section I outlines the general structure of risk assessment, and in Section II the process of risk assessment as applied to technological systems, such as energy systems, is discussed. The research program of the Joint IAEA/IIASA Project is reported in Section III and some preliminary results are presented. Details of the Joint Project staffing and organization are presented in the Appendix

Charge Carrier Trap Spectroscopy on Organic Hole Transport Materials

Electronic circuits comprising organic semiconductor thin-films are part of promising technologies for a renewable power generation and an energy-efficient information technology. Whereas TV and mobile phone applications of organic light emitting diodes (OLEDs) got ready for the market awhile ago, organic photovoltaics still lack in power conversion efficiencies, especially in relation to their current fabrication costs. A major reason for the low efficiencies are losses due to the large number of charge carrier traps in organic semiconductors as compared to silicon. It is the aim of this thesis to identify and quantify charge carrier traps in vacuum-deposited organic semiconductor thin-films and comprehend the reasons for the trap formation. For that, the techniques impedance spectroscopy (IS), thermally stimulated currents (TSC), and photoelectron spectroscopy are utilized. In order to assess the absolute energy of charge carrier traps, the charge carrier transport levels are computed for various hole transport materials such as MeO-TPD, pentacene, and ZnPc. Unlike inorganics, organic semiconductors possess in first-order approximation Gaussian distributed densities of states and temperaturedependent transport levels. The latter shift by up to 300 meV towards the energy gap-mid when changing from room temperature to 10 K as it is done for TSC examinations. The frequency-dependent capacitance response of charge carrier traps in organic Schottky diodes of pentacene and ZnPc are studied via impedance spectroscopy. In undoped systems, deep traps with depths of approx. 0.6 eV and densities in the order of 1016...1017 cm−3 are prevailing. For pentacene, the deep trap density is reduced when the material undergoes an additional purification step. Utilizing p-doping, the Fermi level is tuned in a way that deep traps are saturated. Vice versa, the freeze-out of p-doped ZnPc provides further insight into the influence of trap-filling, impurity saturation and reserve on the Fermi level position in organic semiconductors. Furthermore, charge carrier traps are investigated via thermally stimulated currents. It is shown that the trap depths are obtained correctly only if the dispersive transport of the released charge carriers until their extraction is considered. For the first time, the polarity of charge carrier traps in MeO-TPD, ZnPc, and m-MTDATA is identified from TSC’s differences in release time when spacer layers are introduced in the TSC samples. Simultaneously, tiny hole mobilities in the order of 10−13 cm2 Vs−1 are detected for low-temperature thin-films of the hole transporter material Spiro-TTB. It is shown for Spiro-TTB co-evaporated with the acceptor molecule F6-TCNNQ and a p-doped ZnPc:C60 absorber blend that the doping process creates shallow trap levels. Finally, various organic hole transport materials are examined upon their stability in water and oxygen atmosphere during sample fabrication and storage of the organic electronics. In case of pentacene, ZnPc, MeO-TPD, and m-MTDATA, hole traps are already present in unexposed thin-films, which increase in trap density upon oxygen exposure. A global trap level caused by oxygen impurities is found at energies of 4.7...4.8 eV that is detrimental to hole transport in organic semiconductors.Elektronische Bauelemente aus Dünnschichten organischer Halbleiter sind Teil möglicher Schlüsseltechnologien zur regenerativen Energiegewinnung und energieeffizienten Informationstechnik. Während Fernseh- und Mobilfunkanwendungen organischer Leuchtdioden (OLEDs) bereits vor einiger Zeit Marktreife erlangt haben, ist die organische Photovoltaik (OPV) noch durch zu hohe Fertigungskosten in Relation zu unzureichenden Effizienzen unrentabel. Ein wesentlicher Grund für die niedrigen Wirkungsgrade sind Verluste durch die im Vergleich zu Silizium hohe Zahl an Ladungsträgerfallen in organischen Halbleitern. Ziel dieser Arbeit ist es, mittels Impedanz-Spektroskopie (IS), thermisch stimulierten Strömen (TSC) und Photoelektronenspektroskopie methodenübergreifend Ladungsträgerfallen in vakuumverdampften organischen Dünnschichten zu identifizieren, zu quantifizieren und ihre Ursachen zu ergründen. Um die Energie von Ladungsträgerfallen absolut beziffern zu können, wird zunächst für verschiedene Lochtransportmaterialien wie z.B. MeO-TPD, Pentazen und ZnPc die Transportenergie aus den in erster Ordnung gaußförmigen Zustandsdichten berechnet. Im Gegensatz zu anorganischen Halbleitern ist die Transportenergie in organischen Halbleitern temperaturabhängig. Sie verschiebt sich beim Übergang von Raumtemperatur zu 10 K, wie für TSC Untersuchungen bedeutsam, um bis zu 300 meV in Richtung der Bandlückenmitte. Mittels Impedanz-Spektroskopie wird die frequenzabhängige Kapazitätsantwort von Ladungsträgerfallen in organischen Schottky-Dioden aus Pentazen und ZnPc untersucht. In undotierten Systemen dominieren Defekte mit Tiefen um 0.6 eV, deren Dichte in der Größenordnung von 1016...1017 cm−3 liegt, sich aber im Fall von Pentazen durch einen zusätzlichen Materialaufreinigungsschritt halbieren lässt. Über p-Dotierung wird das Fermi-Level so eingestellt, dass tiefe Fallen abgesättigt werden können. Umgekehrt liefert das Ausfrieren von p-dotiertem ZnPc weitere Belege für den Einfluss von Fallenzuständen, Störstellen-Erschöpfung und Reserve auf das Fermi-Level in dotierten organischen Halbleitern. Im Weiteren werden Ladungsträgerfallen über thermisch stimulierte Ströme untersucht. Es wird gezeigt, dass die Fallentiefen nur dann konsistent bestimmt werden, wenn der dispersive Transport von freigesetzten Ladungsträgern zur Extraktionsstelle berücksichtigt wird. Durch Einführung von ’Abstandshalterschichten’ werden erstmalig über TSC die Polaritäten von Ladungsträgerfallen in MeO-TPD, ZnPc und m-MTDATA per Laufzeitunterschied bestimmt. Gleichzeitig werden geringste Löcherbeweglichkeiten in der Größenordnung von 10−13 cm2 Vs−1 für stark gekühlte Dünnschichten des Lochtransporters Spiro-TTB gemessen. Wie für Spiro-TTB koverdampft mit dem Akzeptormolekül F6-TCNNQ und p-dotierte Mischschichten der Absorbermaterialien ZnPc und C60 gezeigt, erzeugt Dotierung relativ flache Störstellen. Abschließend werden verschiedene organische Lochtransporter-Materialien auf ihre Stabilität in Wasser- und Sauerstoffatmosphären während der Prozessierung und der Lagerung fertiger elektronischer Bauelemente untersucht. Für Pentazen, ZnPc, MeO-TPD und m-MTDATA werden Löcherfallen in intrinsischen Dünnschichten nachgewiesen. Bei Kontakt mit Sauerstoff nimmt deren Defektdichte zu. Es findet sich ein universales Fallenniveau bei rund 4.7...4.8 eV, verursacht durch Sauerstoffverunreinigungen, welches den Lochtransport in organischen Halbleitern limitiert

Perception of Technological Risks: The Effect of Confrontation

The response of the individual to potentially threatening situations is based upon his perception of the hazard involved. In this pilot study, 148 subjects were asked to quantitatively rank the hazard they felt to be involved in living near seven different types of technological facility. The subjects were divided into four groups: AN, living about 500 m away from a research reactor; AF, living about 1.4 km away from this reactor; two small groups living at similar distances from a district heating facility and a control group about 10 km distant from both facilities. All groups, except AN, found the item "nuclear reactor" to be the most hazardous (total sample, 3.1 on a 4 point scale). Group AN (N = 32) found this item to be the third most hazardous, 2.88/4.0; group AF (N = 31) rated the item 3.55/4.0. The difference in this response between groups AN and AF is highly significant (Mann-Whitney U-test p <= 1%). Several explanations for this finding are discussed

A Systems Analysis Approach to Nuclear Facility Siting

In recent years there has been a growing tendency in science to conduct multi-disciplinary studies of large-scale systems. These studies include the entire spectrum of economic, technological, environmental and societal factors which characterize the complex problems of advanced industrialized societies. One of the more promising ways of addressing these problems is the broad research strategy of applied systems analysis. Basically this is a rational approach to problem-solving which attempts to identify and model interactions between the systems under study and all other systems. This results in a thorough understanding of the system being studied which may then serve as an aid in decision-making. This paper attempts to demonstrate an application of the techniques of systems analysis, which have been successful in solving a variety of problems, to the question of nuclear facility siting

The Determinants of Risk Perception: The Active-Passive Dimension

In this paper the suitability of using photographs as a testing technique for identifying additional factors as determinants of risk perception is discussed. A survey was performed, showing 30 slides to 222 respondents (90 males, 132 females). The risk situations presented were to be evaluated on a rating scale. Factor analytical treatment of data revealed two factors, where the first factor can be interpreted as a "general risk" factor. The second factor displayed a two-dimensional structure, the poles of which were designated "active" and "passive" with regard to the persons depicted in the various, situations. The "active" dimension is described by a permanent struggle with the event, whereas the "passive" dimension is characterized by a submissive ability of endurance with little influence through personal skill on the situation. Technological risk situations (i.e., interaction between man and his technical environment) are mainly located on the passive side of this bi-polar continuum. Here also statistically significant differences between male and female respondents were found

Self-heating, bistability, and thermal switching in organic semiconductors

We demonstrate electric bistability induced by the positive feedback of self-heating onto the thermally activated conductivity in a two-terminal device based on the organic semiconductor C60. The central undoped layer with a thickness of 200 nm is embedded between thinner n-doped layers adjacent to the contacts minimizing injection barriers. The observed current-voltage characteristics follow the general theory for thermistors described by an Arrhenius-like conductivity law. Our findings including hysteresis phenomena are of general relevance for the entire material class since most organic semiconductors can be described by a thermally activated conductivity

Machbarkeitsstudie Lausitz: Machbarkeitsstudie für Wasserhaushaltsberechnungen in den vom Braunkohlenbergbau betroffenen Regionen Sachsens: KliWES – Lückenschluss Bergbauregion Teil 1 „Erstellungskonzept und Benchmarking“

In der Studie wird untersucht, ob und wie der durch den Braunkohlebergbau gestörte natürliche Wasserhaushalt mit den Wasserhaushaltsmodellen ArcEGMO, HydPy und RAVEN simulierbar ist. In einem speziell konzipierten, vierstufigen Test, bestehend aus den synthetischen Basis-, Funktions- und Stresstest sowie einem Anwendungstest, wird die Geeignetheit der Wasserhaushaltsmodelle vergleichend analysiert und bewertet. Die Erkenntnisse zum Modellverhalten aus den synthetischen Teststufen tragen erheblich zur sachgerechten Interpretation der Simulationen im Anwendungstest bei. Die Studie ist für alle relevant, die in Verwaltung, Forschung und Consulting mit der Modellierung des Wasserhaushaltes allgemein sowie in Regionen mit Braunkohlebergbau beschäftigt sind. Redaktionsschluss: 09.11.202

Self-heating effects in organic semiconductor devices enhanced by positive temperature feedback

We studied the influence of heating effects in an organic device containing a layer sequence of n-doped / intrinsic / n-doped C60 between crossbar metal electrodes. A strong positive feedback between current and temperature occurs at high current densities beyond 100 A/cm2, as predicted by the extended Gaussian disorder model (EGDM) applicable to organic semiconductors. These devices give a perfect setting for studying the heat transport at high power densities because C60 can withstand temperatures above 200ʿ C. Infrared images of the device and detailed numerical simulations of the heat transport demonstrate that the electrical circuit produces a superposition of a homogeneous power dissipation in the active volume and strong heat sources localized at the contact edges ..