Atomic layer deposition on porous powders with in situ gravimetric monitoring in a modular fixed bed reactor setup

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Review of Scientific Instruments 88, 074102 (2017) and may be found at https://doi.org/10.1063/1.4992023.A modular setup for Atomic Layer Deposition (ALD) on high-surface powder substrates in fixed bed reactors with a gravimetric in situ monitoring was developed. The design and operation are described in detail. An integrated magnetically suspended balance records mass changes during ALD. The highly versatile setup consists of three modular main units: a dosing unit, a reactor unit, and a downstream unit. The reactor unit includes the balance, a large fixed bed reactor, and a quartz crystal microbalance. The dosing unit is equipped with a complex manifold to deliver gases and gaseous reagents including three different ALD precursors, five oxidizing or reducing agents, and two purge gas lines. The system employs reactor temperatures and pressures in the range of 25-600 °C and 10−3 to 1 bar, respectively. Typically, powder batches between 100 mg and 50 g can be coated. The capabilities of the setup are demonstrated by coating mesoporous SiO2 powder with a thin AlOx (submono) layer using three cycles with trimethylaluminium and H2O. The self-limiting nature of the deposition has been verified with the in situ gravimetric monitoring and full saturation curves are presented. The process parameters were used for a scale-up in a large fixed bed reactor. The samples were analyzed with established analytics such as X-ray diffraction, N2 adsorption, transmission electron microscopy, and inductively coupled plasma optical emission spectrometry.DFG, 53182490, EXC 314: Unifying Concepts in Catalysi

Technology Selection for Offshore Underwater Small Modular Reactors

This work examines the most viable nuclear technology options for future underwater designs that would meet high safety standards as well as good economic potential, for construction in the 2030–2040 timeframe. The top five concepts selected from a survey of 13 nuclear technologies were compared to a small modular pressurized water reactor (PWR) designed with a conventional layout. In order of smallest to largest primary system size where the reactor and all safety systems are contained, the top five designs were: (1) a lead–bismuth fast reactor based on the Russian SVBR-100; (2) a novel organic cooled reactor; (3) an innovative superheated water reactor; (4) a boiling water reactor based on Toshiba's LSBWR; and (5) an integral PWR featuring compact steam generators. A similar study on potential attractive power cycles was also performed. A condensing and recompression supercritical CO2cycle and a compact steam Rankine cycle were designed. It was found that the hull size required by the reactor, safety systems and power cycle can be significantly reduced (50–80%) with the top five designs compared to the conventional PWR. Based on the qualitative economic consideration, the organic cooled reactor and boiling water reactor designs are expected to be the most cost effective options.Naval Grou

A suggested roadmap for world-wide energy resource planning and management

In the near future, we will need an internationally based system for worldwide planning of future energy resources and their effect on the world environment. Logically, this should be a responsibility of the United Nations, which already possesses much of the infrastructure needed and is already active in this area. Because different nations have different resources, different problems and different needs, it is reasoned that a flexible and diplomatic approach is also called for. We will need to try to secure support from all nations, and the economies and cultures of many nations differ considerably. This calls for special skills in negotiation. This is complicated by the varied, uncertain and changing technological facilities, which we have at our disposal. After a brief and comparative review of these facilities, an outline of the structure of the internationally coordinating organisation is suggested, followed by examples of the different types of issues which are likely to be encountered. These are: reintroducing improved technology to a nation, which has suffered grievous environmental harm from inadequate similar technology such as the Fukushima incident; nations with especially difficult transport problems; nations with perceived overpopulation problems; using UN and other expertise for nations still undergoing development; applying persuasive pressure by peaceful means. Finally, by outlining a large-scale cooperative venture by several nations, the mode of operation of the suggested U.N coordinating body is outlined. The example used is the choice of thorium-based molten-salt reactor technology using both fast and thermal neutron spectra. This appears to be the only choice we have, as other sustainable systems cannot accommodate the size of our problems. The only exception is using the Desertec solar project, which appears to be disadvantaged by being significantly more expensive. Molten-salt reactors would give a 1000-year energy security for industrialised energy-hungry nations on the Far East/Pacific Rim, which is the example considered. This system would use modern actinide burn-up technology to make nuclear-waste disposal a more acceptable proposition. Thus, nuclear waste can become a lowlevel and disposable hazard after only about 300 years of storage. After this storage, the waste becomes a valuable resource due to production of rare transmuted elements

31 st USAEE/IAEE North American Conference Investigating the Economic Viability of Small Modular Reactors (SMRs)

There is much talk of the potential for small, modular reactors (SMRs) to become players in the field of energy provision. These small reactors, which range in size from tens to several hundreds of megawatts-‐ electric (MWe), are being developed in a dozen International Atomic Energy Agency (IAEA) member states, and encompass a range of both light water and non-‐light water designs [1]. Vendors promise that SMRs will ameliorate many of the concerns surrounding large, conventional nuclear power plants. Some non-‐light water technologies, for instance, promise increased safety, reduced proliferation risk, and innovative approaches to spent fuel stockpile management [2]. Meanwhile, vendors of light water SMRs promise to upend nuclear power’s unhealthy economics. Small, standardized reactors, these vendors suggest, can be built on an assembly line, achieving high levels of quality control while harnessing factory fabrication economies [3]. Also, small reactors will incorporate passive safety systems and allow for innovative approaches to siting that are infeasible for large reactors, such as underground construction. Perhaps most importantly, even if they cost more per unit of power, these reactors ’ small size will allow for a wider range of applications: more utilities will be able to acquire and operate nuclear plants without “betting the company”, and it may even be possible to operate them in places with challenging geographies or underdeveloped grids

Digitization of multistep organic synthesis in reactionware for on-demand pharmaceuticals

Chemical manufacturing is often done at large facilities that require a sizable capital investment and then produce key compounds for a finite period. We present an approach to the manufacturing of fine chemicals and pharmaceuticals in a self-contained plastic reactionware device. The device was designed and constructed by using a chemical to computer-automated design (ChemCAD) approach that enables the translation of traditional bench-scale synthesis into a platform-independent digital code. This in turn guides production of a three-dimensional printed device that encloses the entire synthetic route internally via simple operations. We demonstrate the approach for the γ-aminobutyric acid receptor agonist, (±)-baclofen, establishing a concept that paves the way for the local manufacture of drugs outside of specialist facilities

Economics of nuclear energy

While few people now believe that nuclear power would provide ‘power too cheap to meter’, there is still a common perception that nuclear power is a cheap source of electricity. The fact that nuclear power has not come to dominate electricity generation is seen as being due to a combination of public opposition and dealing with the safety issues raised by accidents such as those at Three Mile Island (1978), Chernobyl (1986) and Fukushima (2011). The reality is that nuclear power has seldom been the cheapest option for new power stations. Worse, the real cost of any normal successful technology goes down over time due to the effect of intuitively sensible factors such as ‘learning-by-doing’, economies of scale and general technical progress. For nuclear power, these factors do not seem to have worked and for its entire commercial history, the real cost of nuclear power has only ever gone upwards. The Fukushima disaster can only give a further twist to this upward spiral. This paper examines the determinants of the cost of a kilowatt hour (kWh) of nuclear electricity; what the latest designs of nuclear power plant can offer; how new nuclear plants might be financed; and what issues will determine whether South Africa can successfully launch a new nuclear programme