985 research outputs found
identification of the postulated initiating events of accidents occurring in a toroidal field magnet of the eu demo
AbstractThe design of the European Union (EU) DEMO reactor magnet system, currently ongoing within the EUROfusion consortium, will take advantage of the know-how developed during the design and manufacturing of ITER magnets; however, DEMO will suffer some new, more severe challenges, e.g., larger tritium inventory and higher neutron fluence, both having an impact on safety functions accomplished, among the other systems, also by the magnets. For these reasons, and in view of the need to demonstrate a high availability of the reactor (aimed at electricity production), a new, more systematic assessment of the system safety is required. As a contribution in this direction, the initiating events (IEs) of the most critical accident sequences in the EU DEMO magnet system (with special reference to the toroidal field magnets) are identified here, adopting first a functional analysis and then a failure mode, effects, and criticality analysis. In particular, the following are provided: (1) the EU DEMO magnet syste..
Evaluation of the gn-->pi-p differential cross sections in the Delta-isobar region
Differential cross sections for the process gn-->pi-p have been extracted
from MAMI-B measurements of gd-->pi-pp, accounting for final-state interaction
effects, using a diagrammatic technique taking into account the NN and piN
final-state interaction amplitudes. Results are compared to previous
measurements of the inverse process, pi-p--> ng, and recent multipole analyses.Comment: 6 pages, 4 figures. v2: Further clarifications and minor changes. A
new figure inserte
A 3-component extension of the Camassa-Holm hierarchy
We introduce a bi-Hamiltonian hierarchy on the loop-algebra of sl(2) endowed
with a suitable Poisson pair. It gives rise to the usual CH hierarchy by means
of a bi-Hamiltonian reduction, and its first nontrivial flow provides a
3-component extension of the CH equation.Comment: 15 pages; minor changes; to appear in Letters in Mathematical Physic
Simple two-layer dispersive models in the Hamiltonian reduction formalism
A Hamiltonian reduction approach is defined, studied, and finally used to
derive asymptotic models of internal wave propagation in density stratified
fluids in two-dimensional domains. Beginning with the general Hamiltonian
formalism of Benjamin [1] for an ideal, stably stratified Euler fluid, the
corresponding structure is systematically reduced to the setup of two
homogeneous fluids under gravity, separated by an interface and confined
between two infinite horizontal plates. A long-wave, small-amplitude
asymptotics is then used to obtain a simplified model that encapsulates most of
the known properties of the dynamics of such systems, such as bidirectional
wave propagation and maximal amplitude travelling waves in the form of fronts.
Further reductions, and in particular devising an asymptotic extension of
Dirac's theory of Hamiltonian constraints, lead to the completely integrable
evolution equations previously considered in the literature for limiting forms
of the dynamics of stratified fluids. To assess the performance of the
asymptotic models, special solutions are studied and compared with those of the
parent equations.Comment: 29 pages, 4 figure
The Sato Grassmannian and the CH hierarchy
We discuss how the Camassa-Holm hierarchy can be framed within the geometry
of the Sato Grassmannian.Comment: 10 pages, no figure
Advanced methods for loss-of-flow accident precursors identification in a superconducting magnet cryogenic cooling circuit
In nuclear fusion systems, such as ITER, Superconducting Magnets (SMs) will be employed to magnetically confine the plasma. A Superconducting Magnet Cryogenic Cooling Circuit (SMCCC) must keep the SMs at cryogenic temperature to preserve their superconductive properties. Thus, a Loss-Of-Flow Accident (LOFA) in the SMCCC is to be avoided. In this work, a three-step methodology for the prompt identification of LOFA precursors (i.e., those component failures leading to a LOFA) is developed. First, accident scenarios are randomly generated by Monte Carlo sampling of the SMCCC components failures and the corresponding transient system response is simulated by a deterministic thermal-hydraulic code. In this phase, fast-running Proper Orthogonal Decomposition (POD)based Kriging metamodels, adaptively trained to mimic the behavior of the detailed long-running code, are employed to reduce the associated computational burden. Second, the scenarios generated are grouped by a Spectral Clustering (SC) embedding the Fuzzy C-Means (FCM), in order to characterize the principal patterns of system evolution towards abnormal conditions (e.g., a LOFA). Third, an On-line Supervised Spectral Clustering (OSSC) approach is developed to assign signals measured during plant operation to one of the prototypical clusters identified, which may reveal the corresponding LOFA precursors (in terms of combinations of failed SMCCC components). The devised method is applied to the simplified model of a cryogenic cooling circuit of a single module of the ITER Central Solenoid. Results show that the approach developed timely identifies 95% of LOFA events and approximately 80% of the corresponding precursors
The Rarita--Schwinger field: renormalization and phenomenology
We discuss renormalization of propagator of interacting Rarita--Schwinger
field. Spin-3/2 contribution after renormalization takes usual resonance form.
For non-leading spin-1/2 terms we found procedure, which guarantees absence of
poles in energy plane. The obtained renormalized propagator has one free
parameter and is a straight generalization of the famous free propagator of
Moldauer and Case. Application of this propagator for production of
in \pi^{+}\particle{p}\to \pi^{+}\particle{p} leads to
good description of total cross-section and to reasonable agreement with
results of partial wave analysis.Comment: 19 pages, 3 figures, revtex4; misprints, min editorial change
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