Time-invariant reliability assessment for a passive heat removal system based on FORM methodology with a new approach for finding the design point
ANNALS OF NUCLEAR ENERGY
Authors: Ebrahimian, M.; Pirouzmand, A.; Rabiee, A.
Abstract
Passive systems are widely becoming used in the nuclear industry to improve the safety level of nuclear power plants. However, the functioning parameters of the passive systems are extremely tied to uncertainty, and the reliability assessment of these systems is one of the important open issues in the passive safety system analysis area. So far, there is no common method to estimate the reliability of passive safety systems. The FORM method with the HL-RF algorithm is a popular iterative method to gain reliability index. However, when the nonlinearity of a system increases, the method may cause numerical instability. In this study, the reliability methodology for passive safety systems (RMPS) is applied to evaluate the reliability of the passive heat removal system (PHRS) of the VVER-1000 reactor. A simple and efficient reliability algorithm is proposed to overcome the numerical instabilities of the HL-RF algorithm of FORM based on the effective search direction vectors with an appropriate step size to find the design point. The accuracy of the proposed algorithm is shown through the stochastic response surface method (SRSM). Results show that the proposed algorithm is simple, reliable, fast, and can find the reliability index with high efficiency and accuracy. (C) 2020 Elsevier Ltd. All rights reserved.
Energy storage in magnetic textures driven by vorticity flow
PHYSICAL REVIEW B
Authors: Jones, Dalton; Zou, Ji; Zhang, Shu; Tserkovnyak, Yaroslav
Abstract
An experimentally feasible energy-storage concept is formulated based on vorticity (hydro)dynamics within an easy-plane insulating magnet. The free energy associated with the magnetic winding texture is built up in a circular easy-plane magnetic structure by injecting a vorticity flow in the radial direction. The latter is accomplished by electrically induced spin-transfer torque, which pumps energy into the magnetic system in proportion to the vortex flux. The resultant magnetic metastable state with a finite winding number can be maintained indefinitely because the process of its relaxation via phase slips is exponentially suppressed when the temperature is brought well below the Curie temperature. We characterize the vorticity-current interaction underlying the energy-loading mechanism through its contribution to the effective electric inductance in the rf response. Our proposal may open an avenue for naturally powering spintronic circuits and nontraditional magnet-based neuromorphic networks.