112,152 research outputs found
Dóciles ¿o no tanto? - benévolos ¿o no tanto? : Un análisis de "No Witchcraft for Sale" de Doris Lessing
No full textFil: Chiapero Ricotti, Lelia. Instituto Superior del Profesorado Nº 2 - "Joaquín V. González".Fil: Azcoiti, Silvina Paola. Instituto Superior del Profesorado Nº 2 - "Joaquín V. González"
LONG-TERM SUMP NATURAL CIRCULATION IN A SUBMERGED SMALL MODULAR REACTOR
No full textThis work investigates the performances of the passive safety systems of a submerged and transportable Small Modular Reactor (SMR) after a Loss Of Coolant Accident (LOCA). The focus of the activity concerns the long-term period, addressing the feasibility of the “depressurized and flooded” safe state, i.e. a targeted situation where the reactor containment is flooded by the injection of water from a large safety tank. Decay heat is removed by sump natural circulation and rejected through the metal containment to the surrounding water, which acts as an infinite heat sink. Following the accidental event and the operation of the safety injection systems, the safe state is expected to provide a continuous and efficient cooling of the fuel rods, ensuring a potentially unlimited grace period with no electrical input or human intervention required. The study employs a numerical approach and simulations are performed using the 1D system code RELAP5. The nodalization process identifies three macro-components, i.e., the reactor pressure vessel, the reactor containment and the safety tank, connected by the recirculation lines. Conservative boundary and initial conditions are set to simulate the transient starting at 7h30’ after the scram of the reactor. Results assess the effectiveness of the sump natural circulation under the reference conditions. The main outcomes also show the good potentialities of the heat exchange systems, highlighting the safe operation of the passive safety systems for at least 21 days after the reactor scram. The sensitivity analysis identifies the nodalization of the reactor containment as a modeling and numerical issue, deserving further investigation.
KEYWORD
Revising the Emergency Management Requirements for new generation reactors
No full textThe paper presents the application of a new risk-informed methodology for the identification of the Emergency Management Requirements (EMR) to a Generation II, Large size Reactor and a Generation III+ Small Modular Reactor.
The results obtained in this test case demonstrate that the actual EMR is conservative, as expected, for the GenII reactor, while the new methodology could be applied for the definition of EMRs for the new generation Nuclear Power Plants, with a possible reduction of the emergency area without loss of safety level.
By adopting both probabilistic and deterministic approaches, the study addresses possible accidents and corresponding release scenarios for the two types of reactor, calculates the areas where the accidents have an impact on the population and defines the new EMR considering the health effects on the population
Thin and flexible contact/deformation sensors based on piezoelectric nanocomposites
No full textThis work aims at demonstrating the possibility of using advanced nanocomposite materials with tuned features in order to develop innovative pressure and deformation sensors suitable for a series of applications, including sensorization in narrow environments, implanted deformable devices, artificial skin and flexible multifunctional surgical instruments. By combining metal sputtering and spin-assisted deposition, we developed thin and flexible polymeric membranes made of polydimethylsiloxane doped with barium titanate nanoparticles, carbon nanotubes and boron nitride nanotubes. By exploiting their piezoelectric properties, the nanocomposites were able to transduce applied pressures and strains into electrical signals. Different combinations of nanoparticles, embedded in the polymeric matrix, were tested. We also highlighted the possibility to tune matrix stiffness, thus adding a “degree of freedom” in the development of nanocomposite sensing elements
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Small modular reactors
No full textThis chapter describes the main features of small modular reactors (SMRs). A demonstration of all the advantages and disadvantages of SMRs is provided in comparison with high-power reactors used in nuclear power plants (NPPs). Special attention is given to the activities of the International Atomic Energy Agency (IAEA) to expand international cooperation and coordination in the design, development, and commissioning of small- and medium-sized reactors. The opportunities and prospects of development offered to mankind by small energy are demonstrated. The question of various options for the placement of SMRs is also considered. Special attention is drawn to the description of the main existing and perspective projects of SMRs being developed in various countries of the world, and analysis of their basic features (design, peculiarities of operation, assignment, etc.) is conducted. Separately considered are the most advanced and already implemented projects, such as NuScale, CAREM-25, SMART, ACP100, IRIS, and RITM-200. Special attention is paid to the issue of ensuring the safety of these reactors and the basis of the principles that carries them out. It should be noted that the requirements for safety at modern nuclear power plants after the Fukushima-1 accident are very high. At the same time, the small linear dimensions of the SMRs and the small amount of stored energy make it possible to use different approaches and design solutions of the main systems, in contrast to those acceptable at nuclear power plants. Special attention is paid to passive SMRs security systems. At the end of the chapter, the issues of international cooperation and harmonization of nuclear control standards are discussed. Also addressed is the problem of licensing MMR technologies, because these reactors must provide a high level of safety; however, to achieve this goal many innovations are needed in the projects (some of which have not been tested). Another important issue is public acceptance of such technologies
Preliminary Design and Validation of an Implantable Artificial Bladder
No full textSubstituting the functionalities of natural organs with artificial devices is an ambitious bioengineering challenge. This study proposes an artificial solution for the restoration of natural bladder functionalities (e.g. upon natural bladder removal for cancer treatment). The design of the artificial bladder system (ABS) is tailored around clinical needs. On one hand, a smart structural design enables to functionalize the internal walls with proper materials and to prevent reflux with custom unidirectional valves. On the other hand, a novel magnetic sensing strategy, combined with embedded electronics for efficient powering and wireless data transfer, allows to potentially restore bladder filling sensitivity. The performances of the system were validated preliminarily on the bench, achieving relative error in volume estimation below 12%. Finally, cadaver experiments allowed to demonstrate the implantability and the overall feasibility of the proposed solution, confirming the stability of wireless connection within a 100 cm distance from the implant
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