90 research outputs found
On the linearized problem for a second grade fluid around the 3-d Poiseuille flow
No full textThe linearized problem for a second grade fluid around the 3-d Poiseuille flow is studied and a stability result is given
Structure of the linearized problem for compressible parallel fluid flows
No full textWe consider the linearized compressible Navier-Stokes equation near a parallel flow in a cylindrical domain restricting our study to perturbations periodic in the generatrix direction. For any parameter values, we show that the initial value linear evolution problem is solved by the direct sum of a (strictly) contraction semi-group and an analytic semi-group. Any unbounded in time solution of this linear problem comes from isolated eigenvalues with finite multiplicities, which have non negative real part, and whose imaginary part is bounded. In addition, we precise the structure of the spectrum of the generator of the semi-group, locating the essential spectrum stricly on the left side of the complex plane. © 1997 Università degli Studi di Ferrara
Assessment of an Isolation Condenser of an Integral Reactor in View of Uncertainties in Engineering Parameters
No full textRMPS methodology is used for estimating the uncertainties in the fulfillment of a target related with the design of the isolation condenser of a “CAREM-like” integral reactor.
The passive-system assessment is made on a basis of a loss of heat sink transient. Given this scenario, the safety function is to remove the core decay heat after the actuation of the shutdown system, thus reducing the primary system pressure and leading the plant to a safe condition. The design target to evaluate is the avoidance of the RPV safety valves opening. In order to accomplish the evaluation, the following RMPS steps were followed: system identification, system modeling, characterization of TH phenomena, direct Monte Carlo simulation, sensitivity analysis, and quantitative reliability estimation.
As main outcomes, a ranking of parameters' importance and an estimate of the failure probability, from a design target point of view, were achieved by sensitivity analysis and Monte Carlo simulations based on a response surface model
Reliability Assessment of the Thermal Hydraulic Phenomena Related to a CAREM-like Passive RHR System
No full textIn this paper, RMPS methodology is used for estimating the reliability of the safety function associated to the Passive Residual Heat Removal System of a CAREM-like advanced reactor.
The passive system assessment is made on a basis of a Loss of Heat Sink transient. Given this scenario, the safety function is to remove the core decay heat after the actuation of the shut-down system, thus reducing the primary system pressure and leading the plant to a safe condition. In order to accomplish the evaluation of the functional reliability, the following RMPS steps were followed: system identification; system modeling; characterization of TH phenomena; direct Monte Carlo simulation; sensitivity analysis and quantitative reliability estimation.
As main outcome, an estimate of the functional reliability was achieved by Monte Carlo simulations based on a response surface model.JRC.F.4 - Safety of future nuclear reactor
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