Linear and Nonlinear Stability Analysis of a Self-Pressurized, Natural Circulation, Integral Reactor

2004 ◽  
Author(s):  
Pablo Zanocco ◽  
Dari´o Delmastro ◽  
Marcelo Gime´nez
Keyword(s):  
Time Domain ◽  
Amplification Factor ◽  
Natural Circulation ◽  
The Self ◽  
The Core ◽  
Non Linear ◽  
Pressure Feedback ◽  
Linear Effects ◽  
The Stability ◽  
Integral Reactor

The stability of a self-pressurized, integral reactor cooled by natural circulation is analyzed. CAREM reactor prototype is taken as reference for the present study. Because of the self-pressurization condition, the system is very close to saturation, and some boiling occurs along the hot leg - reactor core and riser -. Possible instabilities caused by this condition are analyzed in this work in the nominal pressure, with special attention to some particular issues of this design. A numerical code is developed to describe the reactor dynamics and it is briefly described. It includes the coolant with a one-dimensional scheme, steam dome and core modelling, considering the flashing phenomena, neutronic and pressure feedbacks. The code numerically solves the whole set of non-linear equations in a time-domain approach; it also includes a linearization method by numerical perturbations, then a classical frequency-domain stability analysis can be also carried out for the linearized system, by means of eigenvalues calculation. The amplification factor for the oscillation is plotted in the core power/steam dome condensation parameter-plane. A parametric study is carried out, to analyze the influence of core dynamic and the pressure feedback due to the self-pressurization. The pressure feedback has a stabilizing effect, increasing stability for smaller steam volumes. The core dynamic has a stabilizing effect when the core power and the steam dome condensation are low, and relatively destabilizing when they are higher. The stability boundary is determined, for several cases. The amplification factor is enlarged in the region where the flashing phenomenon occurs. The dynamic non-linear effects are studied by means of a time-domain approach, for selected conditions in growing and damped oscillations. The limit-cycle for the growing oscillations is determined, and the main non-linear sources are studied: the amplitude is restricted by strong non-linear effects, which appear when the boiling boundary crosses the core-riser limit, and more than one boiling point coexists at the same time, bounding the amplitude of oscillation to values that would remain un-noticed in case of being present in the reactor.

scholarly journals Effective time‐domain approach for the assessment of the stability characteristics and other non‐linear effects of RF and microwave circuits

2019 ◽  
Vol 13 (14) ◽  
pp. 2470-2479 ◽  
Author(s):  
Leonardo Pantoli ◽  
Domenico Spina ◽  
Daniele Romano ◽  
Giulio Antonini ◽  
Giorgio Leuzzi ◽  
...  
Keyword(s):  
Time Domain ◽  
Microwave Circuits ◽  
Effective Time ◽  
Non Linear ◽  
Linear Effects ◽  
The Stability

On the Stability of Fast Ferry in Damage Scenarios

2015 ◽  
Vol 157 (A3) ◽  
pp. 153-160
Keyword(s):  
Time Domain ◽  
Critical Condition ◽  
Regular Wave ◽  
Loss Of Life ◽  
Damage Scenarios ◽  
Linear Effects ◽  
Ship Grounding ◽  
The Stability ◽  
Heeling Moment ◽  
Damaged Ship

"The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios."

Numerical Investigations of the Effect of Radial Power Distribution and Inlet Orifice on the Stability Behavior of Parallel Multichannel Type Natural Circulation Boiling Water Reactor

2018 ◽  
Vol 4 (3) ◽  
Author(s):  
Sapna Singh ◽  
Garima Singal ◽  
A. K. Nayak ◽  
Umasankari Kannan
Keyword(s):  
Low Power ◽  
Radial Direction ◽  
Natural Circulation ◽  
Boiling Water ◽  
Boiling Water Reactor ◽  
Type I ◽  
Type Ii ◽  
Water Reactor ◽  
The Core ◽  
The Stability

In a natural circulation boiling water reactor (BWR), the core power varies in both axial and radial directions inside the reactor core. The variation along the axial direction is more or less constant throughout the reactor; however, there exists variation of reactor power in the radial direction. The channels located at the periphery have low power compared to the center of the core and are equipped with orifices at their inlet. This creates nonuniformity in the radial direction in the core. This study has been performed in order to understand the effect of this radial variation of power on the stability characteristics of the reactor. Four channels of a pressure tube type natural circulation BWR have been considered. The reactor has been modeled using RELAP5/MOD3.2. Before using the model, it was first benchmarked with experimental measurements and then the characteristics of both low power and high power oscillations, respectively, known as type-I and type-II instability, have been investigated. It was observed that the type-I instability shows slight destabilizing effect of increase in power variation among different channels. However, in the case of type-II instability, it was found out that the oscillations get damped with an increase in power variation among the channels. A similar effect was found for the presence of orifices at the inlet in different channels. However, the increase in number of orificed channels showed stabilizing effect for both type-I and type-II instabilities.

scholarly journals Homology sensing via non-linear amplification of sequence-dependent pausing by RecQ helicase

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Yeonee Seol ◽  
Gábor M Harami ◽  
Mihály Kovács ◽  
Keir C Neuman
Keyword(s):  
Single Molecule ◽  
Magnetic Tweezers ◽  
Dependent Manner ◽  
Linear Amplification ◽  
Recq Helicases ◽  
The Core ◽  
Sequence Dependent ◽  
Non Linear ◽  
Dna Strand ◽  
The Stability

RecQ helicases promote genomic stability through their unique ability to suppress illegitimate recombination and resolve recombination intermediates. These DNA structure-specific activities of RecQ helicases are mediated by the helicase-and-RNAseD like C-terminal (HRDC) domain, via unknown mechanisms. Here, employing single-molecule magnetic tweezers and rapid kinetic approaches we establish that the HRDC domain stabilizes intrinsic, sequence-dependent, pauses of the core helicase (lacking the HRDC) in a DNA geometry-dependent manner. We elucidate the core unwinding mechanism in which the unwinding rate depends on the stability of the duplex DNA leading to transient sequence-dependent pauses. We further demonstrate a non-linear amplification of these transient pauses by the controlled binding of the HRDC domain. The resulting DNA sequence- and geometry-dependent pausing may underlie a homology sensing mechanism that allows rapid disruption of unstable (illegitimate) and stabilization of stable (legitimate) DNA strand invasions, which suggests an intrinsic mechanism of recombination quality control by RecQ helicases.

ON THE STABILITY OF FAST FERRY IN DAMAGE SCENARIOS

2021 ◽  
Vol 157 (A3) ◽  
Author(s):  
M Acanfora ◽  
F De Luca
Keyword(s):  
Time Domain ◽  
Critical Condition ◽  
Regular Wave ◽  
Loss Of Life ◽  
Damage Scenarios ◽  
Linear Effects ◽  
Ship Grounding ◽  
The Stability ◽  
Heeling Moment ◽  
Damaged Ship

The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios.

A Higher Order Time Domain Rankine Panel Method for Linear and Weakly Non-Linear Computation

2015 ◽  
Author(s):  
Felipe Ruggeri ◽  
Rafael A. Watai ◽  
Alexandre N. Simos
Keyword(s):  
Time Domain ◽  
Domain Boundary ◽  
Higher Order ◽  
Floating Body ◽  
Wave Runup ◽  
Floating Bodies ◽  
B Splines ◽  
Non Linear ◽  
Boundary Elements Method ◽  
Linear Effects

This paper presents a higher order time domain boundary elements method based on the Rankine sources for the computation of both linear and weakly non-linear effects for both fixed and free floating bodies. The geometry is described based on surfaces in a standard iges file, considering a NURBS (Non Uniform Rational Basis-Spline) description. The potential function, velocity, free-surface elevation and other quantities are defined using b-splines of arbitrary degree and the floating body interaction is solved using the potential acceleration approach on a Runge-Kutta scheme for time evolution. The integral equation is obtained and solved considering several possibilities for the collocation points, leading to an over-determined system. The integration over the panels is performed using a mixed desingularized-numerical method over Gaussian points. The results comparison are performed with WAMIT solution for a floating sphere concerning wave runup, body motions, velocity field, mean drift components in time domain.

Sign in / Sign up

Export Citation Format

Share Document