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Inverted organic light-emitting diodes (inverted OLEDs) require electron injection to an organic semiconductor from a transparent oxide electrode. Polyethylenimine ethoxylated (PEIE) has attracted considerable attention as an electron injection material. An injection mechanism has been suggested; however, the barrier height of electron injection has not been determined. In this paper, we present the experimental values for the electron injection barrier height at the transparent oxide electrode/PEIE/organic semiconductor interface. Electron-only devices, consisting of indium-tin-oxide (ITO)/PEIE/tris(8hydroxyquinolinato) aluminum (Alq3)/Al, are fabricated. The temperature dependence of the current-voltage curves is measured corresponding to the electron injection of the ITO/PEIE/Alq3 interface. The current-voltage curves are found to be independent of the measurement temperature, which is explained by the tunneling model. The tunneling injection barriers height are calculated, and the experimental injection barrier height will be important for the development of inverted OLED devices.

Breeding of plutonium with light water cooling has been studied for many years, but high breeding to meet growing demand for electricity in a developed country has not been accomplished. The purpose of this study is to investigate a high breeding core of Super FBR (supercritical pressure light water cooled fast breeder reactor) with new fuel assemblies consisting of tightly packed fuel rods without gaps, which leads to low coolant to fuel volume fraction. The plant system of a Super FBR is once-through coolant cycle with high head pumps. The coolant flow rate is low due to the high enthalpy rise in the core. It is compatible with the high pressure drop of the new fuel assemblies. Both neutronic and thermal hydraulic design of the core is considered. The challenge of high breeding with light water cooling is to satisfy negative coolant void reactivity, high breeding and low enrichment simultaneously. The core with new assemblies has been designed with the average coolant density of 248 kg/m3. It is achieved by setting 380C inlet and 500C outlet temperature. For satisfying negative void reactivity, a solid moderator layer composed of zirconium hydride (ZrH) rods are adopted in some blanket assemblies. Cross sections of the blanket fuel assemblies with ZrH rods are prepared with assembly-wise calculation, because the pin-wise collision probability calculation overestimates the breeding. MOX fuel is used for seed fuel assemblies. Three types of core layouts with “radially heterogeneous”, “radiating” and “scattered” seed assemblies have been considered, and “radiating” layout shows best breeding characteristics among them. The seed assemblies in a “radiating” layout are not radially separated so that more numbers of blanket assemblies can be placed in high neutron flux region of a core. Fraction of blanket fuel assemblies with ZrH rods is selected for high breeding. Super FBR using the new fuel assemblies achieved both negative void and high plutonium breeding.

Light water cooled fast reactor with new fuel assemblies (FA) has been studied for high breeding of fissile plutonium. It achieves fissile plutonium surviving ratio (FPSR) of 1.342 (discharge/loading), 1.013 end and beginning of equilibrium cycle (EOEC/BOEC), and compound system doubling time (CSDT) of 95.9 years at the average coolant density of pressurized water reactor (PWR). It is further improved for reduced moderation boiling water reactor (BWR) (RMWR) coolant density. Fissile plutonium surviving ratio reaches 1.397 (discharge/loading), 1.030 (EOEC/BOEC) and CSDT is 37 years. The present study has shown the possibility of breeding at the PWR coolant density and meeting the growth rate of energy demand of advanced countries at the RMWR and Super FR coolant density for the first time. The new FA consist of closely packed fuel rods. The integrity of welding of fuel rods at the top and bottom ends is maintained as the conventional fuel rods. The coolant to fuel volume fraction is reduced to 0.085, onesixth of that of RMWR. The volume fraction remains unchanged with the diameter of the fuel rod. The thermal hydraulic design of the cores remains for the future study.

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